NO309683B1 - Low-color machining, heat and light stabilizer system for polypropylene fiber, and use of the same - Google Patents

Description

The present invention relates to stabilized polypropylene fibre, which is free or essentially free of some traditionally used phenolic antioxidants and which has improved light stability, improved long-term heat stability and especially improved gas fading resistance. This fiber formulation is stabilized with an effective amount of a mixture of a selected hindered amine, a selected hydroxylamine and a selected phosphite. The invention also relates to the use of the stabilized polypropylene fibres.

Polypropylene fiber is traditionally stabilized with a mixture of selected phenolic antioxidant, selected phosphite and selected hindered amine light stabilizer. This formulation generally provides adequate processing, heat and light stabilization performance, but does not provide sufficient gas bleach resistance necessary to maintain color properties during storage and end use. There is a long felt need in the market for a stabilizer system that can prevent this gas bleaching and color formation associated with the use of phenolic antioxidants. Gas bleaching is known in the industry as a mi sf heir, which is a result of exposure of plastic articles to an atmosphere containing oxides of nitrogen.

The components of the present stabilizer system for polypropylene fibers are generally well known as stabilizers for a host of organic and polymeric substrates. The components according to the present stabilizer system for polypropylene fibers are a specific combination of selected 2,2,6,6-tetramethylpiperidine hindered amines, phosphite or phosphonite and N,N-dialkylhydroxylamines in the absence, or substantially absence, of a phenolic antioxidant. The present stabilizer formulation provides unexpected superior gas bleach resistance, and heat and light stability performance characteristics to the polypropylene fibers which are notoriously difficult to effectively stabilize. Available phenol-free antioxidant stabilizer systems provide the best overall stabilization of polypropylene fibres. Discoloration of polypropylene fibers, when exposed to an atmosphere containing nitrogen, i.e., gas bleaching conditions, which is encountered by stabilizer systems containing phenolic antioxidants, renders such systems unacceptable in important properties even if the phenolic antioxidants providing other performance criteria are adequate.

The hindered amines are very important in class light and thermal stabilizers, based on compounds that have a 2,2,6,6-tetramethylpiperidine moiety somewhere in the molecule. These compounds have achieved great commercial success and became well known in the art.

Likewise, phosphonites or phosphites such as those described in US-A-4,360,617 have also achieved great commercial success as stabilizers.

N,N-dialkylhydroxylamines have also been known in the art as seen in US-A-4,590,231, UA-A-4,782,105, US-A-4,876,300 and US-A-5,013,510. These compounds are useful as process stabilizers for polyolefins when used alone or in combination with phenolic antioxidants and/or other coadditives, particularly as taught in US-A-4,876,300. Although US-A-4. 876. 300 generically teaches that N,N-dialkylhydroxylamines can be used in combination with phenolic antioxidants, hindered amines, phosphites, UV absorbers and other additives, there is no specific disclosure that polypropylene fibers can advantageously be stabilized with specific combinations of selected hindered amines , phosphites or phosphonites and N,N-dialkylhydroxylamines. The present invention is thus essentially a choice within the broad generic scope of US-A-4,876,300.

However, the present composition differs from the compositions according to the prior art in several important aspects listed below:

1. Hindered phenolic antioxidants plus phosphite combinations generally have poor gas bleaching resistance; 2. phosphites alone lack sufficient process and thermal stabilization efficiency; and 3. phosphites plus hindered amines lack adequate process stabilization.

The present combination of stabilizers provides all the necessary requirements such as gas bleaching resistance and process and thermal stability.

The aim of the present invention is to provide a stabilizer system for polypropylene fibres, in the presence of any traditionally used phenolic antioxidant or in the presence of only very small amounts of phenolic antioxidant, which will allow the polypropylene fibers to have improved light and long-term heat stability and especially improved gas bleaching resistance, while the maintains the process stabilization comparable to any system using phenolic antioxidants.

Another aim of the present invention is to provide a method for improving gas bleaching resistance and reducing color formation in polypropylene fibers using the present stabilizer system which is free of phenolic antioxidant.

The present invention relates to stabilized polypropylene fibers free or essentially free of phenolic antioxidant, and which have improved light stability, improved long-term heat stability and improved gas bleaching resistance, whose fibers are stabilized by a mixture of: a) A hindered amine selected from the group consisting of the polycondensation product of 4, 4'-hexamethylene-bis(amino-

2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-tert-octylamino-s-triazine;

polycondensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid;

N,N<*> ,N",N'"-tetrakis[4,6-bis(butyl-(2,2,6,6-tetramethylpiperidin-4-yl)amino)-s-triazin-2-yl] -1,10-diamino-4,7-diazadecane;

the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-morpholino-s-triazine;

poly[methyl-3-(2,2,6,6-tetramethylpiperidin-4-yloxy)propyl]siloxane;

b i s(2,2,6,6-tetramethylpiperidin-4-yl)cyclohexylenedioxydimethylmalonate;

1,3,5-tris{N-cyclohexyl-N-[2-(2,2,6,6-tetramethylpiperazin-3-on-4-yl)ethyl]amino-s-triazine;

the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-cyclohexyl-mino-s-triazine; and

poly{N-[4,6-bis(butyl-(2,2,6,6-tetramethyl-piperidin-4-yl)amino)-s-triazin-2-yl]-1,4,7-triazanonane >-w-N"-[4,6-bis(butyl-(2,2,6,6-tetramethylpiperidin-4-yl)amino)-s-triazin-2-yl]amine;

b) a phosphite or phosphonite selected from the group consisting of

tris(2,4-di-tert-butylphenyl)phosphite;

3,9-di(2,4-di-tert-butylphenyl)-2,4,8,10-tetraoxa-3,9-diphospha[5.5]undecane;

2,2',2"-nitrilo-tris[ethyl(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-diyl)phosphite];

ethyl bis(2,4-di-tert-butyl-6-methylphenyl)phosphite; and tetrakis(2,4-di-tert-butylphenyl)-4,4'-bis(diphenylene)phosphonite; and

c) a hydroxylamine consisting of

The N,N-dialkylhydroxylamine product prepared by direct oxidation of N,N-di(hydrogenated tallow)amine by the process comprising oxidizing a solution of N,N-di(hydrogenated tallow)amine in a lower alkanol solvent with a molar excess of 10-70% aqueous hydrogen peroxide solution at a temperature of 40 to 65 °C;

wherein the weight ratio of compounds (a):(b):(c) is from 1:1:1 to 100:2:1; preferably 10:1:1 to 10:2:1: and most preferably 6:1:1 to 6:2:1.

The effective amount of the mixture of stabilizers is, for example, from 0.05 to 5 wt-#, preferably 0.1 to 2 wt-#, most preferably 0.15 to 1 wt-# based on the weight of the fiber.

Stabilized polypropylene fibers of particular interest are those in which component (a) is selected from the group consisting of: The polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4- dichloro-6-tert-octylamino-s-triazine;

the polycondensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid;

N, N ' ,N" ,N<*M->tetrakis[4,5-bis(butyl-(2,2,6,6-tetramethylpiperidin-4-yl)amino)-s-triazin-2-yl] -1,10-diamino-4,7-diazadecane;

the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-morpholino-s-triazine;

poly[methyl3-(2,2,6,6-tetramethylpiperidin-4-yloxy)propyl]siloxane;

bis(2,2,6,6-tetramethylpiperidin-4-yl)-cyclohexylenedioxy-dimethylmalonate; and

1,3,5-tris{N-cyclohexyl-N-[2-(2,2,6,6-tetramethylpiperazin-3-on-4-yl)ethyl]amino-s-triazine.

Stabilized polypropylene fibers which are also of particular interest are those in which component (b) is selected from the groups consisting of

tris(2,4-di-tert-butylphenyl)phosphite;

3,9-di(2,4-di-tert-butylphenyl)-1,4,8,10-tetraoxa-3,9-diphospha[5.5]undecane;

2,2•,2"-nitrilo-tris[ethyl-(3,3'-d,d'-tetra-tert-butyl-1,1'-biphenyl-2,2'-diyl)phosphite];

and

ethyl bis(2,4-di-tert-butyl-6-methylphenyl)phosphite.

Stabilized polypropylene fibers which are particularly preferred are those where component (c) is the N,N-dialkylhydroxylamine product produced by direct oxidation of N,N-di(hydrogenated tallow)amine.

In addition, the present invention also relates to a binary stabilized system where the stabilized polypropylene fiber is free, or mainly free, of any phenolic antioxidants, and which has improved light stability, improved long-term heat stability and improved gas bleaching resistance, whose fiber is stabilized by a mixture of: I) A hindered amine selected from the group consisting of

the polycondensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid;

N ,N ' ,N",N'"-tetrakis[4,6-bis(butyl-(2,2,6,6-tetramethylpiperidin-4-yl)amino)-s-triazin-2-yl]-1 ,10-diamino-4,7-diazadecane;

the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-morpholino-s-triazine;

poly[methyl-3-(2,2,6,6-tetramethylpiperidin-4-yloxy)-propyl]siloxane;

bis(2,2,6,6-tetramethylpiperidin-4-yl)cyclohexylenedioxydimethylmalonate;

1,3,5-tris{N-cyclohexyl-N-[2-(2,2,6,6-tetramethylpiperazin-3-on-4-yl)ethyl]amino-s-triazine; and the polycondensation product 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-cyclohexylamino-s-triazine; and

II) a hydroxylamine consisting of

the N,N-dialkylhydroxylamine product prepared by direct oxidation of N,N-di(hydrogenated tallow)amine by the process of US-A-5,013,510 or US-A-4,898,901;

where the weight ratio of the components (I): (II) is from 100:1 to 1:2; preferably 10:1 to 1:1: and most preferably 5:1 to 3:1.

Binary stabilized polypropylene fibers of particular interest are those in which component (I) is selected from the group consisting of

the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-tert-octylamino-s-triazine;

the polycondensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid; and N,N',N",N'"-tetrakis[4,6-bis(butyl-(2,2,6,6-tetramethylpiperidin-4-yl)amino)-s-triazin-2-yl]- 1,10-diamino-4,7-diazadecane.

Binary stabilized polypropylene fibers of particular interest are those in which component (II) is the N,N-dialkylhydroxylamine product prepared by direct oxidation of N,N-di(hydrogenated tallow)amine by the process of "US-A-5.013.510 or US-A-4,898,901.

The effective amount of the mixture of stabilizers is from 0.05 to 5 wt-#, preferably 0.1 to 2 wt-#, most preferably 0.15 to 1 wt-# based on the weight of the fiber.

The present invention comprises a selected mixture of stabilizers which are free, or mainly free, of any phenolic antioxidants. Some varieties of polypropylene add small amounts, usually <0.01 wt-# of phenolic antioxidant, to aid in the initial preparation of the polypropylene resin. The amount of phenolic antioxidant that remains in the resin used to make the polypropylene fiber is much less than the 0.05 wt% phenolic antioxidants used in the working examples of US-A-4,876,300. As the phrase free of, or substantially free of, phenolic antioxidant, as used within the scope of the present invention, means that 0 to 0.01 wt-# of phenolic antioxidant may be present in the present compositions. No phenolic antioxidant is intentionally added to the present compositions in order to achieve the described stabilization effects.

Another very important aspect of the present invention is the use of an effective stabilizing amount of the mixture of stabilizers described above, for improving the gas bleaching resistance and reducing the color formation in stabilized polypropylene fiber without losing any other stabilizing properties.

Another aspect of the present invention is the use of an effective stabilizing amount of the mixture of stabilizers described above to improve the resistance to degradation of polypropylene fibers due to exposure to UV radiation compared to what can be achieved using conventional stabilizers alone.

Yet another aspect of the present invention is the use of an effective stabilizing amount of a mixture of stabilized stabilizers described above to improve the thermal stability of polypropylene fiber above that which can be achieved using conventional stabilizers alone.

The cited hindered amines and phosphites are generally commercially available or can be prepared by published methods.

The N,N-dialkylhydroxylamines are prepared by methods described in US-A-4,782,105; US-A-4,898,901 and especially US-A-5,013,510 by direct oxidation of N,N-di-/hydrogenated talc)amine with hydrogen peroxide.

The polypropylene fiber may also contain other additives such as fillers and reinforcing agents such as calcium carbonate, silicates, glass fibres, asbestos, talc, kaolin, mikva, barium sulphate, metal oxides and hydroxides, carbon black, graphite and other additives, for example plasticisers, lubricants, emulsifiers miter agents, pigments, optical brighteners, flame retardants and antistatic agents.

Conventional stabilizer systems, such as phenolic antioxidant with phosphite and hindered amine stabilizer, or phosphite with hindered amine stabilizer, can provide excellent stabilization of polypropylene fibers in selected performance ranges, but it is only through the use of the present ternary combination of a selected hindered amine, selected hydroxylamine and selected phosphite that all important performance characteristics of stabilized polypropylene fibers can be optimised.

Polypropylene is used to a large extent for the production of fiber for residential houses, commercial use and cars. White and light colored fibers may suffer from discoloration due to gas bleach discoloration. Polypropylene resin as it is originally manufactured may contain very low levels of phenolic antioxidant for stability until said resin is later fabricated into fiber. In each case, some additional stabilizer must be added to the propylene resin before fabrication into fiber is possible. Hindered phenolic antioxidants are well known as a potential source of such discoloration by the formation of quinone-type chromophores as oxidation products or as the result of environmental exposure to oxides of nitrogen (known as "gas bleach" discoloration).

It is therefore desirable to remove the phenolic antioxidant component from the polypropylene fibre. Unfortunately, when this has been done in the past, other properties related to polymer stability have been adversely affected. Phenolic antioxidants protect the polymer during high temperature melt processing, extrusion and spinning operations. Phenolic antioxidants further protect the polymer pellets and resulting fiber during storage and end-use applications.

Surprisingly, it has been found that the phenolic antioxidant can be replaced with the present stabilizer system which is a ternary combination of a selected hindered amine, a selected hydroxylamine and a selected phosphite or a binary combination of a selected hindered amine and a selected hydroxylamine. Said system provides stability in excess of what was achieved with conventional stabilizer systems that have a phenolic antioxidant component without the discoloration associated with the phenolic antioxidant when the stabilized polypropylene fiber is exposed to gas bleaching conditions, i.e. in an atmosphere containing oxides of nitrogen.

The following examples are illustrative only, and are not to be construed as limiting the nature or scope of the present invention in any way.

Test Connections:

AO A = 1 , 3 , 5 -1 r i s ( 3 , 5-d i - tert-butyl-4-hydroxyben- zyl ) isocyanurate;

HALS 1 = the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-tert-octylamino-s-triazines;

HALS 2 = the polycondensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and

succinic acid;

HALS 3 = N ,N ' ,N" ,N * " - t e t r a c i s [ 4 , 6-b i s ( buty 1-2 ,2 ,6 ,6-tetramethylpiperidin-4-yl)-amino )-s-triazin- 2-yl]-1,10-diamino-4,7-diazadecane;

HALS 4 = the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-morpholino-s-triazine;

HALS 5 = poly 1y[methyl-3-(2,2,6,6-tetramethylpiperidin-4-yloxy)propyl]siloxane;

HALS 6 = bis(2,2,6,6-tetramethylpiperidin-4-yl)cyclohexylene dioxydimethylmalonate;

HALS 7 = 1 , 3 , 5-tris{N-cyclohexyl-N-[2-(2 ,2 ,6 ,6-tetramethylpiper azin-3-on-4-yl )-ethyl]amino-s-triazine ; Phos I = tris(2,4-di-tert-butylphenyl)phosphite;

Phos II = 3,9-di(2,4-di-tert-butylphenyl)-2,4,8,10-tetraoxa-3,9-diphosphate[5.5]undecane;

Phos III = 2,2',2"-nitrilo[triethyl-tris-(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-diyl)phosphite] ; Phos IV = ethyl bis(2,4-di-tert-butyl-6-methylphenyl )-phosphite; and

HA A = the N,N-dialkylhydroxylamine product prepared by direct oxidation of N,N-di(hydrogenated tallow)amine by the process according to US-A-5,013,510 or US-A-4,898,901.

All additives are listed in weight # based on the polypropylene. All formulations also contain 0.05 wt # of calcium stearate.

Example 1: Process stabilization of polypropylene fibre. Fiber grade polypropylene, containing 0.05 wt # calcium stearate, was dry blended with the test additives and then melted at 246°C into pellets. The pelletized fully formulated resin was then spun at 274°C into fiber using a Hill laboratory model fiber extruder. The spun tow of 41 filaments was stretched to a ratio of 1:3.2 to give a final denier of 615/41.

The melt flow rates of the formulated pellets before spinning and the spun fiber tow after spinning were determined according to ASTM 1238-86. The closer the melt flow rates before and after spinning, the more effective the process stabilization efficiency of the stabilizer system. Processing stability data is provided in Tables 1, 2, 3 and 4 below.

Inspection of the data given above shows that the present formulations containing selected hindered amines, phosphites and hydroxylamines provide excellent process stabilization to polypropylene that is fully comparable to stabilizer systems containing phenolic antioxidants.

Example 2: Process stabilization of polypropylene fibre

The melt flow differences resulting from insufficient processing stability can become even more apparent when the polypropylene is spun under more stringent manufacturing conditions. In Example 1, the polypropylene was spun at 274°C. However, it is not unusual for polypropylene to be spun at a much higher temperature, such as at 302°C. The melt flow values of polypropylene spun at such high temperatures are shown in tables 5, 6, 7 or 8 below.

The data in Tables 5, 6, 7 and 8 clearly show that in a conventional stabilizer system a combination of phenolic antioxidant and phosphite provides good processing stability. The removal of phenolic antioxidant in the presence or absence of a hindered amine results in a significant loss of processing stability. However, the substitution of a hydroxylamine in place of the phenolic antioxidant provides processing stability that is fully comparable to that afforded by the phenolic antioxidant-phosphate system.

As seen in Example 5, however, the presence of phenolic antioxidant in the stabilizer system has an adverse effect on gas bleach resistance.

Example 3: Light stabilization of polypropylene fibre.

The fibers are also exposed to UV light and to long-term thermal aging under standard conditions.

Stockings knitted from stabilized polypropylene fibers were exposed in an Atlas Xenon-Arc-WeatherOmeter using SAE J1885 Interior Automotive conditions at 89°C, 0.55 kW/cm<2 >at 340 nm without any spray cycle. Failure in this test was determined by observing physical failure of the stocking when "scratched" with a blunt glass rod. The longer it takes for catastrophic failure to occur, the more effective the stabilizer system is. The days before failure are given in Tables 9, 10, 11 and 12 below for each of the stabilizer systems.

Example 4: Long-term thermal stability of polypropylene fibre.

In long-term heat aging at 120°C, other knitted socks of the stabilized polypropylene fiber were exposed to a forced flow oven equipped with a rotating carousel. Again, failure was determined as described above. The longer it takes for catastrophic failure to occur, the more effective the stabilizer system is. The test data is given in

tables 13, 14 and 15 below.

Examples 5-6 show that, as far as bleach resistance is concerned, the present stabilization mixture is superior as measured according to delta E values where low numbers indicate lower color. The numerical differences shown are significant, and the examples can easily be differentiated visually.

Example 5: Gas bleach resistance or color stability of polypropylene fibre.

Other knitted socks of stabilized polypropylene fiber were exposed to oxides of nitrogen in an exposure chamber using AATCC test method in 23-1988, "Colorfastness to Burnt Gas Furnes" for 3 and 7 "cycles". The test samples were removed from the chamber and the color change measured (delta E color scale) on an Applied Color system model CS-5 colorimeter (D65 illuminant, 2° observer). Low delta E values indicate lower color and better stabilization. Test data are given in tables 16, 17, 18, 19, 20, 21 and 22 below.

Example 6: Gas bleaching resistance or color stability of polypropylene fibres

Other knitted socks of the stabilized polypropylene fiber were exposed to oxides of nitrogen in an exposure chamber using AATCC Test Method 23-1988, "Clolorfastness to Burnt Gas Furnes" for 3 "cycles". The test samples were removed from the chamber and color change measured (delta E color scale) on an Applied Color system model CS-5 colorimeter (D65 illuminant, 2° observed). The test data are given in Tables 23, 24 and 25 below. Low delta E values indicate less color and better stabilization.

Inspection of the data shown above shows that the present

in

formulations containing other selected hindered amines, other phosphites and hydroxylamines, provide excellent gas-i

bleaching resistance and color stability of polypropylene fibers which are superior to the stabilized systems containing a phenolic antioxidant.

Example 7: Gas bleach resistance or color stability to

in polypropylene fiber

Following the procedure of Example 6, the gas bleach resistance or color stability of the polypropylene fiber was measured when said fiber was protected by a binary system of stabilizers comprising a hindered amine and a hydroxylamine without the presence of any phosphite compared to fiber further containing a phenolic antioxidant. The test data are given in Tables 26, 27 and 28 below. Low delta E values

in

indicates less color and better stabilization.

in

Inspection of the data given above shows that the present binary formulations containing selected hindered amines and hydroxylamines provide excellent gas bleach resistance and colorfastness.

in

bility to polypropylene which is superior to the stabilizer systems containing a phenolic antioxidant.

Example 8: Process stabilization of polypropylene fiber The melt flow differences that result from insufficient processing stability are very clear when the polypropylene was spun under harsh processing conditions. This is particularly evident when polypropylene is spun at 302°C. The lower the melt flow rates, the more effective the processing stability efficiency of the stabilizer system (see also Example 1). The melt flow values of polypropylene spun at that temperature are shown in Tables 29, 30 and 31 below.

The data in Tables 29, 30 and 31 clearly show that in a conventional stabilizer system a combination of phenolic antioxidant, hindered amine and phosphite provides good processing stability. The removal of the phenolic antioxidant resulted in a significant loss in processing stability. However, the substitution of a hydroxylamine 1 in place of the phenolic antioxidant provided process stabilization that was fully comparable to that provided by the phenolic antioxidant-phosphite system both in the presence and absence of the phosphite component. The binary stabilizer system of hindered amine plus hydroxylamine thus provides excellent thermal processing stabilization of the polypropylene fiber.

TRIAL REPORT 1

Test Compounds:

HALS A = the polycondensation product of 4,4'-hexamethylene- bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4- dichloro-6-tert-octylamino-s-triazine.

HA A = the N,N-dialkylhydroxylamine product prepared by direct oxidation of N,N-di(hydrogenated

tallow)amine by the method according to US-A-5,013

510 or US-A-4 898 901 or example 9 according to EP-A-0 323 409.

HA 5 = N,N-dialkylhydroxylamine with the formula T1T2N0H

where Ti and Tg are the alkyl mixture found in hydrogenated tallow, as shown in EP-A-0 323 409. Example 15.

Experimental procedure: The experimental procedure corresponds to example 22 in EP-A-0 323 409.

Fiber grade polypropylene containing 0.1 wt # of calcium stearate is compounded for 1.5 minutes at 220°C to incorporate the test stabilizers listed below. It

in

The kbmpounded polymer is then spun at 270°C with a 3 minute dwell time for the polymer in the spinneret into a fiber rope with 37 filaments. The spun rope is stretched at an eh ratio of 1:3.2 to give a final rope with a dezitex of 114. The fibers are exposed in a Xenotest 1200 (Fa. Heraeus)

xenon-arc weatherometer. The exposure time required for the initial tensile strength of the fiber rope to drop to half of its original value is the criterion used to assess failure in this test. The longer it takes for this catastrophic failure to occur, the more effective the stabilizer system is. The results are summarized in table 32.

It is clear from these data that fibers stabilized by HA A, the hydroxylamine prepared by direct oxidation of hydrogenated tallow amine according to US-A-5 013 510 or US-A-4 898 901 or Example 9 of EP-A-0 323 409 , in the presence of HALS A are more stable than when hydroxylamine HA 5 described in EP-A-0 323 409, example 15, is used.

Conclusion. ion:

While both hydroxylamines are effective stabilizers for polypropylene fibers containing a hindered amine, the hydroxylamine prepared by the direct oxidation of hydrogenated tallow amine according to US-A-5,013,510 or US-A-4,898,901 or Example 9 of EP-A -0 323 409 surprisingly good stabilization efficiency which could not be predicted from the prior art.

EOR SEARCH REPORT 2

Test Connections:

HALS 1 = the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4- dichloro-6-tert-octylamino-s-triazines.

HALS 2 = the polycondensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and

succinic acid.

BALS 3 = N,N' ,N" ,N' "-1 e t r a c i s [ 4 , 6-b i s (butyl-2 , 2,6,6-tetramethylpiperidin-4-yl )-amino )-s-triazin- 2-yl]-1,10-diamino-4,7-diazadecane.

HiALS 4 = the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-j dichloro-6-morpholino-s-triazine.

HALS 5 = poly[methyl-3-(2,2,6,6-tetramethylpiperidin-4-yloxy)propyl]siloxane.

HALS 6 = bis(2,2,6,6-tetramethylpiperidin-4-yl)cyclohexylenedioxydimethylmalonate.

HALS 7 = 1,3,5-tris{N-cyclohexyl-N-[2-(2,2,6,6-tetramethylpiperazin-3-on-4-yl)-ethyl]amino-s-triazine. HALS 9 = polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-cyclohexylamino-s-triazine.

HA A = the N,N-dialkylhydroxylamine product prepared by direct oxidation of N,N-di(hydrogenated tallow)amine by the method of US-A-5,013,510 or US-A-4,898,901 or Example 9

according to EP-A-0 323 409.

HA B = N,N-dialkylhydroxylamine according to the formula T1T2N0H

where T-1 and T2 are the alkyl mixture found in hydrogenated tallow, as shown in example 15 in EP-A-0 323 409.

Experimental Procedures:

The test compounds are incorporated into polypropylene containing 0.05 wt # of calcium stearate and spun into fiber at 274°C, as described in Example 1 of the present description. Knitted sticks of said fibers are exposed in a Xenon arc weatherometer at 89°C according to the SAE J1885 test method. Expose-none continues until the logs no longer pass "scratching" with a blunt glass rod. The longer it takes for this catastrophic failure to occur, the more effective the stabilizer system is. The results are summarized in tables 33 and 34.

It is clear from these data that a fiber stabilized on HA A, the hydroxylamine produced by the direct oxidation of hydrogenated tallow according to US-A-5 013 510, US-A-4 898 901 or Example 9 of EP-A-0 323 409, in presence of a wide variety of hindered amines are more stable in each case than when hydroxylamine HA B pitched in example 15 according to EP-A-0 323 409 is used.

Conclusion:

While both hydroxylamines are effective stabilizers for polypropylene fibers containing hindered amine, the hydroxylamine prepared by the direct oxidation of hydrogenated tallow amine according to US-A-5,013,510, US-A-4,898,901 or Example 9 of EP-A-0 323,409 surprisingly better stabilization efficiency than could be predicted from the prior art.

Claims (14)

1. Stabilized polypropylene fiber, free or substantially free of<1> any phenolic antioxidant, and having improved light(stability, improved long-term heat stability and improved gas bleach resistance, wherein the fiber is stabilized by a mixture of a) jet hindered amine selected from the group consisting of the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-tert-octylamino-s-triazine; ; the polycondensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid; N,N' ,N" ,N ' "-tetrakis[4,6-bis(butyl-(2,2,6,6-tetramethylpiperidin-4-yl)amino)-s-triazin-2-yl]-1 ,10-diamino-4,7-j diazadecane; the polycondensation product of 4,4'-hexamethylene-bis(amino-i 2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-morpholino-s-triazine; ' poly [methy 1 - 3- (2,2,6, 6-te tramethylpiperidin-4-yloxy )pro- pyl]siloxane; in bis(2 , 2 , 6 , 6-tetramethylpiperidin-4-yl)cyclohexylenedioxy- dimethyl malonate; 1,3, 5-tris(N-cyclohexyl-N-[2-(2 ,2,6 ,6-tetramethylpipera- zin-3-on-4-yl)ethyl]amino-s-triazine; the polycondensation product of 4,4'-hexamethylene-bis(amino- 2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-cyclohexyl-amino-s-triazine; and poly{N-[4,6-bis(butyl-(2,2,6,6-tetramethyl-piperidin-4-yl)amino)-s-triazin-2-yl]-1,4,7- triiazanonan}-u-N"-[4,6-bis(butyl-(2,2,6,6-tetramethylpiperidin-4-yl)amino)-s-triazin-2-yl]amine; b) a phosphite or phosphonite selected from the group consisting of tris(2,4-di-tert-butylphenyl)phosphite; 3,9-di(2,4-di-tert-butylphenyl)-2,4,8,1O-tetraoxa-3,9-diphospha[5.5]undecane; 2,2',2"-nitrilo-tris[ethyl(3,3',5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-diyl)phosphite]; ethyl bis(2,4-di-tert-butyl-6-methylphenyl)phosphite; and tetrakis(2,4-di-tert-butylphenyl)-4,4'-bis(diphenylene)phosphonite; and c) a hydroxylamine, characterized in that the hydroxylamine consists of The N,N-dialkylhydroxylamine product prepared by direct oxidation of N,N-di(hydrogenated tallow)amine by the process comprising oxidizing a solution of N,N-di(hydrogenated tallow)amine in a lower alkanol solvent with a molar excess of 10-70$ aqueous hydrogen peroxide solution at a temperature of 40 to 65"C; where the weight ratio between the compounds (a):(b):(c) is from 1:1:1 to 100:2:1. 2. Stabilized fiber according to claim 1, characterized in that component (a) is selected from the group consisting of the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-tert-octylamino-s-triazine; the polycondensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid; N ,N ' ,N" ,N ' "-tetrakis[4,6-bis(butyl-(2,2,6,6-tetramethylpiperidin-4-yl)amino)-s-triazin-2-yl]-1 ,10-diamino-4,7-diazadecane; the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-morpholino-s-triazine; poly[methyl 3-(2,2,6,6,-tetramethylpiperidin-4-yloxy)propyl]siloxane; b i s (2,2,6,6-tetramethylpiperidin-4-yl)cyclohexylenedioxydimethylmalonate; and 1,3,5-tris{N-cyclohexyl-N-[2-(2,2,6,6-tetramethylpiperazin-3-on-4-yl)ethyl]amino-s-triazine. 3. Stabilized fiber according to claim 1, characterized in that component (b) is selected from the group consisting of tris(2,4-di-tert-butylphenyl)phosphite; 3,9-di(2,4-di-tert-butylphenyl)-2,4,8,10-tetraoxa-3,9-diphospha[5.5]undecane; 2,2*,2"-nitr i lo-tri is[ethyl-(3,3' ,5,5'-tetra-tert-butyl-1,1'-biphenyl-2,2'-diyl)phosphite ]; and ethyl bis(2,4-di-tert-butyl-6-methylphenyl)phosphite. 4. Stabilized fiber according to claim 1, characterized in that the weight ratio of the components (a):(b):-(c) is from 10:1:1 to 10:2:1. 5 . Stabilized fiber according to claim 1, characterized in that the amount of stabilizers is from 0.05 to 5 weight-$ based on the weight of the fiber. 6. Use of a mixture of stabilizers according to claim 1, for improving gas bleaching resistance and reducing color formation in stabilized polypropylene fibres, without loss of any other stabilizing properties. 7. Use of a mixture of stabilizers according to claim 1, for improving the resistance to degradation of polypropylene fiber due to exposure to UV radiation beyond what can be achieved by using conventional stabilizers alone. 8. Provision of a mixture of stabilizers according to claim 1, for improving the thermal stability of polypropylene fiber, beyond what can be achieved by using conventional stabilizers alone. 9 . Stabilized polypropylene fiber free, or substantially free, of any phenolic antioxidant, and having improved light stability, improved long-term heat stability and improved gas bleach resistance, wherein the fibers are stabilized by a mixture of I) a hindered amine selected from the group consisting of the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-tert-octylamino-s-triazine; the polycondensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid; N , N ' ,N",N"M-tetrakis[4,6-bis(butyl-(2,2,6,6-tetramethylpiperidin-4-yl)amino)-s-triazin-2-yl]-1 ,10-diamino-4,7-diazadecane; the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-morpholino-s-triazine; poly[methyl-3-(2,2,6,6-tetramethylpiperidin-4-yloxy)-propyl]siloxane; bis (2,2,6,6-tetramethylpiperidin-4-yl)cyclohexylenedioxydimethylmalonate; 1 , 3 , 5-tris(N-cyclohexyl-N-[2-(2,2,6,6-tetramethylpiperazin-3-on-4-yl)ethyl]amino-s-triazine; and the polycondensation product 4 ,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-cyclohexylamino-s-triazine; characterized in that the mixture also consists of II) the N,N-dialkylhydroxylamine product produced by direct oxidation of N,N-di(hydrogenated tallow)amine by the method which comprises oxidizing a solution of N,N-di(hydrogenated tallow)amine in a lower alkanol solvent with a molar excess of 10-70% aqueous hydrogen peroxide solution at a temperature of 40 to 65°C; where the weight ratio between the components (I): (II) is from 100:1 to 1:2. 10. Stabilized fiber according to claim 9, characterized in that component (I) is selected from the group consisting of the polycondensation product of 4,4'-hexamethylene-bis(amino-2,2,6,6-tetramethylpiperidine) and 2,4-dichloro-6-tert-octylamino-s-triazine; the polycondensation product of 1-(2-hydroxyethyl)-2,2,6,6-tetramethyl-4-hydroxypiperidine and succinic acid; and N,N',N",N'"-tetrakis[4,6-bis(butyl-(2,2,6,6-tetramethylpiperidin-4-yl)amino)-s-triazin-2-yl]- 1,10-diamine-4,7-diazadecane. 11. Stabilized fiber according to claim 9, characterized in that the weight ratio of the components (I): (II) is from 10:1 to 1:1. 12. Stabilized fiber according to claim 9, characterized in that the amount of the mixture of stabilizers is from 0.05 to 5 weight-$ based on the weight of the fiber. 13. Preparation of a mixture of stabilizers according to claim 9, for improving the gas bleaching resistance and reducing the color formation in stabilized polypropylene fiber, without loss of any other stabilizer property. 14 . Use of a mixture of stabilizers according to claim 9, for improving the resistance to degradation of polypropylene fiber due to exposure to UV radiation beyond what can be achieved by using conventional stabilizers alone.