WO2019057640A1

WO2019057640A1 - Composition

Info

Publication number: WO2019057640A1
Application number: PCT/EP2018/074949
Authority: WO
Inventors: Jonathan Hill; Siren TAN; Ronald Becker
Original assignee: Addivant Switzerland Gmbh
Priority date: 2017-09-19
Filing date: 2018-09-14
Publication date: 2019-03-28
Also published as: GB2566557A; GB2566557B; GB201715135D0

Abstract

In accordance with the present invention there is provided a stabilising composition, comprising methane fully hindered phenolic antioxidant; an organophosphite antioxidant; 1,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6- (1H,3H,5H)-trione; and zinc oxide.

Description

COMPOSITION

The present invention relates to stabilising compositions. More specifically, but not exclusively, the present invention relates to stabilising compositions for stabilising polypropylene, particularly biaxially oriented polypropylene film.

Polypropylene is used in a variety of applications, for example to form films. For many polypropylene applications, it is desirable for the polypropylene to retain certain of its properties during manufacture, storage, handling and subsequent application. More specifically, it may be desirable for the polypropylene to retain its melt flow properties, viscosity and have good colour stability, even during prolonged or repeated exposure to heat.

To aid retention of polypropylene properties, such as melt flow, viscosity and colour stability, it is known to add different types of additives to the polypropylene resin, for example phenolic antioxidants, phosphite antioxidants, acid scavengers, or combinations thereof.

In general, phenolic antioxidants are added to polymers to reduce degradation thereof. However, inevitably some degradation of the polymer will occur. This may produce acidic products which may cause acceleration of the degradative process. Catalytic residues in polymers may also be acidic and may contribute to, or cause, such degradation or the acceleration thereof. To counteract this effect, it is known to include acid scavengers in polymer compositions. Acid scavengers act to maintain a relatively high pH in the polymer. However, high pH can cause phenolic antioxidants to discolour. The inclusion of phosphite antioxidants in the polymer composition can ameliorate this effect i.e. reduce discolouration, but only to a limited extent.

WO2007136565 discloses antioxidant blends comprising the reactive trisphenol 1 ,3,5- tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1 ,3,5-triazine-2,4,6-(1 H,3H,5H)-trione which is known to be prone to discolouration.

A known additive blend for polypropylene involves a phenolic antioxidant, a phosphite antioxidant and a metal stearate, for example calcium stearate. However, where the polypropylene is used in a film application, metal stearates can cause problems as they are migratory additives which tend to migrate to the surface of a film. This is particularly problematic if the film is metallised and/or printed.

As an alternative to metal stearates, it is known to use hydrotalcites, for example DHT- 4A™. Hydrotalcites are non-migratory and thus, do not affect the metallisation or printability of a film. However, hydrotalcites when used in combination with phenolic antioxidants have poor colour stability which means they can cause yellowing of the polymer to which they are added.

Thus, there is a need in the art for a stabilising composition which overcomes the above-identified problems.

In accordance with the present invention there is provided a stabilising composition, comprising:

a fully hindered phenolic antioxidant comprising substituent hydrocarbyl groups on both positions ortho to the phenolic -OH group, each of these substituent groups being branched at the Ci and/or C2 position with respect to the aromatic ring;

an organophosphite antioxidant;

1 ,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1 ,3,5-triazine-2,4,6- (1 H,3H,5H)-trione; and

zinc oxide.

The inventors of the present invention have surprisingly found that the specific combination of additives in the stabilising composition produces a synergistic effect with respect to the colour stability of polypropylene. Colour stability can be determined using standard test method ASTM D1295.

More specifically, the inventors of the present invention have found that the specific combination of additives in the stabilising composition causes a significant improvement in the initial colour of polypropylene as well as a significant reduction in colour formation of polypropylene during prolonged or repeated heat exposure, particularly when compared to stabilising compositions involving traditional acid scavengers such as metal stearates or hydrotalcites.

This finding is particularly surprising given that 1 ,3,5-tris(4-tert-butyl-3-hydroxy-2,6- dimethylbenzyl)-1 ,3,5-triazine-2,4,6-(1 H,3H,5H)-trione is a reactive trisphenol which is known to be prone to discolouration.

Without wishing to be bound by any such theory, the inventors of the present invention believe that there is a particular synergistic effect between the organophosphite antioxidant and the zinc oxide which provides enhanced colour stability to polypropylene.

In addition, the inventors of the present invention believe that zinc oxide not only acts as an acid scavenger but also acts as an optical brightener i.e. absorbs (near-) ultraviolet light and emits blue fluorescence, which contributes towards the improvement in initial colour of polypropylene as well as the reduction in colour formation during prolonged or repeated heat exposure.

The inventors of the present invention have surprisingly found that the specific combination of additives in the stabilising composition enhances the gas fading performance of polypropylene. Gas fading performance can be determined using standard test method AATCC 23-2005.

The inventors of the present invention have also unexpectedly found that the specific combination of additives in the stabilising composition enables retention of the melt flow properties of polypropylene, for example melt flow rate, even during prolonged or repeated heat exposure. Melt flow rate (MFR) can be determined using standard test method ASTM D1238.

The retention of melt flow properties is advantageous since in many applications polypropylene is often kept in a molten state for prolonged periods of time.

By 'prolonged heat exposure' we preferably mean exposure to a temperature of at least about 100°C, at least about 1 10°C, at least about 120°C, at least about 130°C, at least about 140°C, at least about 150°C, at least about 160°C, at least about 170°C, at least about 180°C, at least about 190°C, at least about 200°C, at least about 210°C, at least about 220°C, at least about 230°C, at least about 240°C or at least about 250°C, for at least about 1 hour, at least about 2 hours, at least about 4 hours, at least about 6 hours, at least about 12 hours, at least about 24 hours, at least about 36 hours, at least about 48 hours, at least about 3 days, at least about 4 days, at least about 5 days, at least about 6 days, at least about 7 days, at least about 10 days or at least about 14 days.

By 'repeated heat exposure' we preferably mean exposure to a temperature of at least about 100°C, at least about 150°C, at least about 200°C, at least about 250°C, or at least about 300°C, on more than one occasion, for at least about 5 seconds, at least about 10 seconds, at least about 20 seconds, at least about 30 seconds, at least about 1 minute, at least about 5 minutes, or at least about 10 minutes. Repeated heat exposure may be experienced during multiple passes through an extruder.

By 'fully hindered phenolic antioxidant' we mean that the phenolic antioxidant comprises substituent hydrocarbyl groups on both positions ortho to the phenolic -OH group, each of these substituent groups being branched at the Ci and/or C2 position, preferably at the Ci position, with respect to the aromatic ring. In one preferred embodiment of the invention one or both of the substituent hydrocarbyl groups ortho to the phenolic -OH group are selected from t-butyl or t-amyl groups.

The fully hindered phenolic antioxidant may comprise tetrakismethylene(3,5-di-tert- butyl-4-hydroxyhydrocinnamate) methane (ANOX™ 20 - CAS 6683-19-8); 2,2'thiodiethylene bis[3(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (ANOX™ 70 - CAS 41484-35-9); octadecyl 3-(3',5'-di-t-butyl-4'-hydroxyphenyl) propionate (ANOX™ PP18 - CAS 2082-79-3); 1 ,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate (ANOX™ IC14 - CAS 27676-62-6); 1 ,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4- hydroxybenzyl)benzene (ANOX™ 330 - CAS 1709-70-2); N,N'-hexamethylenebis[3- (3,5-di-t-butyl-4-hydroxyphenyl)propionamide] (LOWINOX™ HD98 - CAS 23128-74- 7); 1 ,2-bis(3,5-di-t-butyl-4-hydroxyhydrocinnamoyl)hydrazine (LOWINOX™ MD24 - CAS 32687-78-8); 2,2'-ethylidenebis[4,6-di-t-butylphenol] (ANOX™ 29 - CAS 35958- 30-6); butylated hydroxytoluene (BHT - CAS 128-37-0); and/or compatible mixtures of two or more thereof.

A particularly preferred fully hindered phenolic antioxidant comprises tetrakismethylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate) methane (ANOX™ 20 - CAS 6683-19-8).

The organophosphite antioxidant may comprise bis(2,4,di-tert- butylphenyl)pentraerythritol diphosphite (ULTRANOX™ 626 - CAS 26741 -53-7); 2,4,6-tri-tert-butylphenyl-2-butyl-2-ethyl-1 ,3-propanediol phosphite (ULTRANOX™ 641 - CAS 161717-32-4); tris(2,4-di-t-butylphenyl)phosphite (ALKANOX™ 240 - CAS 31570-04-4); distearylpentaerythritol diphosphite (WESTON™ 618 - CAS 3806-34-6); bis(2,4-dicumylphenyl) pentaerythritol diphosphite (DOVERPHOS™ 9228 - CAS 154862-43-8); bis(2,6-di-ter-butyl-4-methylphenyl)pentaerythritol diphosphite (PEP 36 CAS 80693-00-1 ); tetrakis(2,4-di-tertbutylphenyl)[1 ,1 -biphenyl]-4,4'- diylbisphosphonite (IRGAFOS™ P-EPQ - CAS 1 19345-01 -6); and/or compatible mixtures of two or more thereof. A particularly preferred organophosphite antioxidant comprises bis(2,4,di-tert- butylphenyl)pentraerythritol diphosphite (ULTRANOX™ 626 - CAS 26741 -53-7).

1 ,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1 ,3,5-triazine-2,4,6-(1 H,3H,5H)- trione is a partially hindered phenolic antioxidant with CAS number 40601 -76-1 . For example, 1 ,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1 ,3,5-triazine-2,4,6- (1 H,3H,5H)-trione is sold under the product name LOWINOX™ 1790.

Zinc oxide has CAS number 1314-13-2.

The fully hindered phenolic antioxidant may be present in an amount of from about 10% to about 70% by weight of the stabilising composition, from about 20% to about 60% by weight of the stabilising composition, or from about 30% to about 50% by weight of the stabilising composition. Preferably, the fully hindered phenolic antioxidant is present in an amount of from about 25% to about 40% by weight of the stabilising composition.

The organophosphite may be present in an amount of from about 20% to about 80% by weight of the stabilising composition, from about 30% to about 70% by weight of the stabilising composition, or from about 40% to about 60% by weight of the stabilising composition. Preferably, the organophosphite is present in an amount of from about 35% to about 50% by weight of the stabilising composition. 1 ,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1 ,3,5-triazine-2,4,6-(1 H,3H,5H)- trione may be present in an amount of from about 1 % to about 20% by weight of the stabilising composition, or from about 5% to about 15% by weight of the stabilising composition.

Zinc oxide may be present in an amount of from about 1 % to about 30% by weight of the stabilising composition, from about 5% to about 25% by weight of the stabilising composition, or from about 10% to about 20% by weight of the stabilising composition.

The stabilising composition may be a solid composition, in which case it may have a melting point of 30°C or higher, 40°C or higher, 50°C or higher, 60°C or higher, or 70°C or higher, at atmospheric pressure i.e. 101 .325 kPa.

The stabilising composition may be provided as a powder blend, in granular form, or in the form of non-dust blend (NDB) granules, for example. The NDB granules may be formed according to the process outlined in WO 2015/124751 .

The stabilising composition may be for use in stabilising polypropylene.

A particularly preferred stabilising composition comprises:

tetrakismethylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate) methane;

bis(2,4-di-tert-butylphenyl) pentraerythritol diphosphite;

zinc oxide. Also provided in accordance with the present invention is the use of the stabilising composition as hereinbefore described to stabilise polypropylene.

Also provided in accordance with the present invention is a polypropylene composition, comprising:

a polypropylene base material; and

a stabilising composition comprising:

an organophosphite antioxidant;

1 .3.5- tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1 ,3,5-triazine-

2.4.6- (1 H,3H,5H)-trione; and

zinc oxide.

The stabilising composition may be present in the polypropylene composition in an amount of from about 10 ppm to about 10000 ppm, from about 100 ppm to about 5000 ppm, or from about 500 ppm to about 2000 ppm.

The inventors of the present invention have surprisingly found that the amount of the stabilising composition required for effective stabilisation of a polypropylene composition may be significantly less than for other industry standard stabilising compositions. This may result in significant cost savings. For example, the amount of the stabilising composition required for effective stabilisation of a polypropylene composition may be at least about 5% less, at least about 10% less, at least about 15% less, at least about 20% less, at least about 25% less, at least about 30% less, at least about 35% less, at least about 40% less, at least about 45% or at least about 50% less than for other industry standard stabilising compositions.

Without wishing to be bound by any such theory, the inventors of the present invention believe that the presence of 1 ,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)- 1 ,3,5-triazine-2,4,6-(1 H,3H,5H)-trione, a reactive trisphenol antioxidant, provides a boosting effect with regards to protection of the polypropylene against degradation.

It would previously have been assumed that the presence of a reactive trisphenol would adversely affect the colour stability of the polypropylene composition. However, the inventors have surprisingly found that there is a synergistic effect between the organophosphite antioxidant, for example bis(2,4-di-tert-butylphenyl) pentraerythritol diphosphite, and zinc oxide which provides enhanced colour stability to the polypropylene composition.

The result of the above is that the amount of the stabilising composition required for effective stabilisation of a polypropylene composition may be significantly less than for other industry standard stabilising compositions.

The polypropylene base material may comprise a polypropylene homopolymer. The polypropylene homopolymer may be isotactic, syndiotactic or atactic.

Additionally or alternatively, the polypropylene base material may comprise a copolymer.

The copolymer may be a random copolymer or a block copolymer. Preferably the copolymer is a random copolymer.

The copolymer may comprise propylene and ethylene and/or butylene.

For example, the copolymer may comprise a propylene-ethylene random copolymer.

Additionally or alternatively, the polypropylene base material may comprise a polypropylene impact copolymer.

The polypropylene impact copolymer may be formed by the polymerisation of propylene and ethylene using Ziegler Natta catalyst(s), for example.

Also provided in accordance with the present invention is a polypropylene film manufactured from the polypropylene composition as hereinbefore described.

The polypropylene film may be oriented.

Preferably, the polypropylene film is biaxially oriented. For the avoidance of doubt, all features relating to the stabilising composition may apply, where appropriate, to the use of the stabilising composition, the polypropylene composition, and to the biaxially oriented polypropylene film, and vice versa.

The invention will now be more particularly described with reference to the following non-limiting examples.

EXAMPLES

1. STABILISATION OF POLYPROPYLENE COMPARED TO INDUSTRY STANDARD WITH PHENOLIC ANTIOXIDANT AND PHOSPHITE ANTIOXIDANT

Preparing the Polypropylene Compositions

Polypropylene compositions were prepared from the appropriate amounts of polypropylene homopolymer base material and stabilising composition.

Table 1 shows the different components that were used in the stabilising compositions.

TABLE 1

1 ,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-

LOWINOX™ 1790

1 ,3,5-triazine-2,4,6-(1 H,3H,5H)-trione

ULTRANOX™ 626 Bis(2,4-di-tert-butylphenyl) pentraerythritol diphosphite

ZnO Zinc oxide

Table 2 shows the stabilising compositions that were used. The ppm amounts shown in the table are ppm of the polypropylene composition. Sample 1 was in accordance with the present invention. Sample 2 represented an industry standard stabilising composition involving a phenolic antioxidant and a phosphite antioxidant, and constituted a comparative example.

TABLE 2

Each of the above-identified stabilising compositions were compounded with the polypropylene base material in an extruder at 230°C under nitrogen to form the polypropylene compositions. Colour Stability and Melt Flow Rate

Each of the polypropylene compositions was multi-passed through a Brabender single screw extruder at a speed of 60 rpm, and a temperature of 260°C under air. The discolouration of the compositions was measured in terms of Yellowness Index (Yl) using a colorimeter in accordance with standard test method ASTM D1295.

Yl values were taken prior to extrusion (pass 0) and after passes 1 , 2, 3, 4 and 5. The lower the Yl value, the less discolouration of the polypropylene composition. The results are shown in Table 3.

TABLE 3

The results are displayed graphically in Figure 1

From the results, it can be seen that the polypropylene composition stabilised with the stabilising composition in accordance with the present invention (Sample 1 ) shows significantly less discolouration following each pass through the extruder compared to the polypropylene composition stabilised with the industry standard stabilising composition (Sample 2). The melt flow rate of the polypropylene compositions was determined in accordance with standard test method ASTM D1238 using a melt flow tester (230°C, 2.16 kg). The melt flow rate was taken after passes 1 , 2, 3, 4 and 5. An increase in the melt flow rate value is indicative of degradation of the sample. The results are shown in Table 4.

TABLE 4

From the results it can be seen that the polypropylene composition stabilised with the stabilising composition according to the present invention (Sample 1 ) retained its melt flow rate comparably to the polypropylene composition stabilised with the industry standard stabilising composition (Sample 2).

Overall, the colour stability of the polypropylene composition is improved by using the stabilising composition according to the present invention, without experiencing a negative impact on the melt flow rate.

2. STABILISATION OF POLYPROPYLENE COMPARED TO VARIOUS INDUSTRY STANDARD STABILISING COMPOSITIONS Preparing the Polypropylene Compositions

Polypropylene compositions were prepared from the appropriate amounts of polypropylene base material and stabilising composition.

The polypropylene base material was Moplen™ 501 N homopolypropylene powder (MFR = 10 g/10min).

Table 5 shows the different components that were used in the stabilising compositions.

TABLE 5

Table 6 shows the stabilising compositions that were used. The ppm amounts shown in the table are ppm of the polypropylene composition. Samples 3, 4, 5 and 6 represented industry standard stabilising compositions. Sample 7 was in accordance with the present invention.

TABLE 6

*Sample 4 and Sample 5 have the same general composition, however some of the components were provided by different suppliers

Each of the above-identified stabilising compositions were pre-mixed for 25 minutes with the polypropylene base material and then compounded in an extruder at a speed of 60 rpm, and a temperature of 230°C under nitrogen, to form polypropylene compositions.

Colour Stability and Melt Flow Rate

Each of the polypropylene compositions was multi-passed through a Brabender KE19 single screw extruder (4:1 screw ratio) at a speed of 90 rpm, and a temperature of 260°C under air. The discolouration of the compositions was measured in terms of Yellowness Index (Yl) using a colorimeter in accordance with standard test method ASTM D1295.

Yl values were taken prior to extrusion (pass 0) and after passes 1 , 3 and 5. The lower the Yl value, the less discolouration of the polypropylene composition. The results are shown in Table 7.

TABLE 7

3 (Comp) -0.74 0.24 1 .52 2.77

4 (Comp) -0.72 0.17 1 .43 2.85

5 (Comp) -1 .16 -0.02 1 .1 2.26

6 (Comp) -0.55 1 .03 2.12 2.83

7 -1 .71 -0.73 0.61 1 .56

The results are displayed graphically in Figure 2.

From the results, it can be seen that the polypropylene composition stabilised with the stabilising composition in accordance with the present invention (Sample 7) shows significantly less discolouration following each pass through the extruder compared to the polypropylene compositions stabilised with the industry standard stabilising compositions.

The melt flow rate of the polypropylene compositions was determined in accordance with standard test method ASTM D1238 using a using a melt flow tester (230°C, 2.16 kg). The melt flow rate was taken prior to extrusion (pass 0) and after pass 5. An increase in the melt flow rate value is indicative of degradation of the sample. The results are shown in Table 8.

TABLE 8

3 (Comp) 9.12 12.96

4 (Comp) 10.02 16.78

5 (Comp) 9.96 14.90

6 (Comp) 9.92 13.24

7 8.88 12.64

The results are displayed graphically in Figure 3.

From the results, it can be seen that the polypropylene composition stabilised with the stabilising composition according to the present invention (Sample 7) provides equivalent or superior melt flow stability compared to the polypropylene compositions stabilised with the industry standard stabilising compositions.

Overall, the colour stability of the polypropylene composition is improved by using the stabilising composition according to the present invention, with equal or better retention of melt flow stability.

Gas Fading Performance

A sample of each of the polypropylene compositions (following compounding) was exposed to NOx gases at a temperature of 60°C in accordance with standard test method AATCC Test Method 23-2005. Gas fading was measured in terms of Yellowness Index (Yl) using a colorimeter in accordance with standard test method ASTM D1295. Measurements were taken every 24 hours from 0 hours up to 168 hours. The results are shown in Table 9. TABLE 9

The results are displayed graphically in Figure 4.

From the results, it can be seen that the polypropylene composition stabilised with the stabilising composition according to the present invention (Sample 7) exhibited significantly less yellowing during gas fading compared to the industry standard stabilising compositions.

3. STABILISATION OF POLYPROPYLENE WITH REDUCED AMOUNT OF ANTIOXIDANT IN THE STABILISING COMPOSITION

Preparing the Polypropylene Compositions Polypropylene compositions were prepared from the appropriate amounts of polypropylene base material and stabilising composition.

Table 10 shows the different components that were used in the stabilising compositions.

TABLE 10

Table 1 1 shows the stabilising compositions that were used. The ppm amounts shown in the table are ppm of the polypropylene composition. Samples 8, 9, 10 and 1 1 represented industry standard stabilising compositions. Sample 12 was in accordance with the present invention.

TABLE 11

*Sample 9 and Sample 10 have the same general composition, however some of the components were provided by different suppliers

For Sample 12, the amount of the stabilising composition was reduced by 30% to 700 ppm.

Colour Stability and Melt Flow Rate

Yl values were taken prior to extrusion (pass 0) and after passes 1 , 3 and 5. The lower the Yl value, the less discolouration of the polypropylene composition. The results are shown in Table 12.

TABLE 12 Yl Value

Sample

Pass 0 Pass 1 Pass 3 Pass 5

8 (Comp) -0.74 0.24 1 .52 2.77

9 (Comp) -0.72 0.17 1 .43 2.85

10 (Comp) -1 .16 -0.02 1 .1 2.26

11 (Comp) -0.55 1 .03 2.12 2.83

12 -1 .77 -0.80 0.99 1 .96

The results are displayed graphically in Figure 5.

From the results, it can be seen that the polypropylene composition stabilised with the stabilising composition in accordance with the present invention (Sample 12) maintained its colour stability performance at a 30% lower dosage. In fact, Sample 12 outperforms the industry standard stabilising compositions despite having a 30% lower dosage.

The melt flow rate of the polypropylene compositions was determined in accordance with standard test method ASTM D1238 using a using a melt flow tester (230°C, 2.16 kg). The melt flow rate was taken prior to extrusion (pass 0) and after pass 5. An increase in the melt flow rate value is indicative of degradation of the sample. The results are shown in Table 13.

TABLE 13 Melt Flow Rate (g/10min)

Sample

Pass 0 Pass 5

8 (Comp) 9.12 12.96

9 (Comp) 10.02 16.78

10 (Comp) 9.96 14.90

11 (Comp) 9.92 13.24

12 9.06 13.22

The results are displayed graphically in Figure 6.

From the results, it can be seen that the polypropylene composition stabilised with the lower dosage stabilising composition according to the present invention (Sample 12) retained its melt flow rate either comparably to or superior to the polypropylene compositions stabilised with the industry standard stabilising compositions.

Gas Fading Performance

A sample of each of the polypropylene compositions (following compounding) was exposed to NOx gases at a temperature of 60°C in accordance with standard test method AATCC Test Method 23-2005. Gas fading was measured in terms of Yellowness Index (Yl) using a colorimeter. Measurements were taken every 24 hours from 0 hours up to 168 hours. The results are shown in Table 14.

TABLE 14 Yl Yl Yl Yl Yl Yl Yl Yl

Sample

0 hr 24 hr 48 hr 72 hr 96 hr 120 hr 144 hr 168 hr

8

-0.02 5.23 6.72 7.44 8.54 9.94 12.86 14.7

(Comp)

9

0.14 6.91 10.50 12.73 14.44 15.45 15.97 16.44

(Comp)

10

-0.14 6.41 8.57 10.9 1 1 .28 12.55 13.58 15.12 (Comp)

11

0.37 2.59 3.41 4.07 5.52 6.59 9.62 1 1 .12 (Comp)

12 -1 .3 1 .89 3.13 3.89 5.14 7.36 8.95 9.57

The results are displayed graphically in Figure 7.

From the results, it can be seen that the polypropylene composition stabilised with the stabilising composition in accordance with the present invention (Sample 12) maintained its gas fading performance at a 30% lower dosage. In fact, Sample 12 outperforms the majority of the industry standard stabilising compositions despite having a 30% lower dosage.

4. STABILISATION OF POLYPROPYLENE COMPARED TO INDUSTRY STANDARD STABILISING COMPOSITION WITH AND WITHOUT DHT-4V

Preparing the Polypropylene Compositions

Polypropylene compositions were prepared from the appropriate amounts of polypropylene homopolymer base material and stabilising composition. The polypropylene base material was Buplen™ 6531 homopolypropylene powder (MFR = 3 - 5 g/10min).

Table 15 shows the stabilising compositions that were used. The % amounts shown in the table are % by weight of the stabilising composition. Sample 13 was a stabilising composition in accordance with the present invention. Sample 15 was a stabilising composition in accordance with the present invention with the addition of 90 ppm DHT- 4V. Sample 14 represented an industry standard stabilising composition involving a phenolic antioxidant and a phosphite antioxidant, and constituted a comparative example. Sample 16 represented an industry standard stabilising composition with the addition of 90 ppm DHT-4V.

TABLE 15

ULTRANOX™ 626 42.5

ZnO 15.0

DHT-4V -

ANOX™ 20 70.0

16 (Comp) NDB452 + DHT ULTRANOX™ 626 30.0

DHT-4V -

Each of the above-identified stabilising compositions were pre-mixed in a turbula mixer in an amount of 1200 ppm, 900 ppm and 600 ppm, for 25 minutes with the polypropylene base material. They were then compounded in an extruder at a speed of 60 rpm, and a temperature of 230°C under nitrogen, to form polypropylene compositions.

Colour Stability and Melt Flow Rate

Each of the polypropylene compositions was multi-passed through a Brabender extruder at a speed of 90 rpm, and a temperature of 260°C under air.

The discolouration of the compositions was measured in terms of Yellowness Index (Yl) using a colorimeter in accordance with standard test method ASTM D1295. Yl values were taken prior to extrusion (pass 0) and after passes 1 , 3 and 5. The lower the Yl value, the less discolouration of the polypropylene composition.

The results are displayed graphically in Figures 8 and 9. From Figure 8 it can be seen that Sample 13 (DVS161 ) provides superior protection against yellowing compared to the industry standard stabilising composition (Sample 14).

From Figure 9 it can be seen that Sample 15 (DVS161 + DHT) provides superior protection against yellowing compared to the industry standard stabilising composition (Sample 16) when antacid additive DHT-4V is included in the polypropylene composition.

The melt flow rate of the polypropylene compositions was determined in accordance with standard test method ASTM D1238 using a melt flow tester (230°C, 2.16 kg). The melt flow rate was taken prior to extrusion (pass 0) and after pass 5. An increase in the melt flow rate value is indicative of degradation of the sample.

The results are displayed graphically in Figures 10 and 1 1 .

From Figure 10 it can be seen that Sample 13 (DVS161 ) provides superior melt flow stability compared to the industry standard stabilising composition (Sample 14).

From Figure 1 1 it can be seen that Sample 15 (DVS161 + DHT) provides superior melt flow stability compared to the industry standard stabilising composition (Sample 16) when antacid additive DHT-4V is included in the polypropylene composition.

Gas Fading Performance A sample of each of the '900 ppm' polypropylene compositions (following compounding) was exposed to NOx gases at a temperature of 60°C in accordance with standard test method AATCC Test Method 23-2005 in a Lawler Gas Fume Chamber. Gas fading was measured in terms of Yellowness Index (Yl) using a colorimeter in accordance with standard test method ASTM D1295. Measurements were taken every 24 hours from 0 hours up to 168 hours.

The results are displayed graphically in Figure 12.

From Figure 12 it can be seen that the stabilising composition in accordance with the present invention (Sample 13 and Sample 15) provides superior protection against discolouration under gas fading conditions compared to the industry standard stabilising compositions, with and without antacid additive DHT-4V in the polypropylene composition.

Filter Pressure Test

A 10 micron screen pack assembly was placed in th Die of a Brabender 16 mm single screw extruder. The extruder was set to a speed of 60 rpm and a temperature of 230°C. A pressure transducer was connected to measure the pressure behind the screen pack. A new screen pack was used for each sample.

The two stabilising compositions tested are shown in Table 16.

TABLE 16 Sample Shorthand Component Amount (%)

ANOX™ 20 34.5

LOWINOX™ 1790 8.0

17 DVS161

ULTRANOX™ 626 42.5

ZnO 15.0

ANOX™ 20 70.0

18 (Comp) Benchmark ULTRANOX™ 626 30.0

DHT-4V -

Sample 17 was present in an amount of 1000 ppm.

Sample 18 was present in an amount of 1000 ppm with 250 ppm DHT-4V.

The results are displayed graphically in Figure 13.

From Figure 13 it can be seen that the stabilising composition in accordance with the present invention (Sample 17) has a lower melt pressure i.e. improved performance, which may help to reduce production downtime when compared to the industry standard stabilising composition (Sample 18).

Claims

1 . A stabilising composition, comprising:

an organophosphite antioxidant;

1 .3.5- tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1 ,3,5-triazine-

2.4.6- (1 H,3H,5H)-trione; and

zinc oxide.

2. The stabilising composition according to Claim 1 , wherein the fully hindered phenolic antioxidant comprises tetrakismethylene(3,5-di-tert-butyl-4- hydroxyhydrocinnamate) methane; 2,2'thiodiethylene bis[3(3,5-di-t-butyl-4- hydroxyphenyl)propionate]; octadecyl 3-(3',5'-di-t-butyl-4'-hydroxyphenyl) propionate; 1 ,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate; 1 ,3,5- trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene; Ν,Ν'- hexamethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide]; 1 ,2- bis(3,5-di-t-butyl-4-hydroxyhydrocinnamoyl)hydrazine; 2,2'-ethylidenebis[4,6- di-t-butylphenol]; butylated hydroxytoluene; and/or compatible mixtures of two or more thereof.

3. The stabilising composition according to Claim 1 or Claim 2, wherein the fully hindered phenolic antioxidant comprises tetrakismethylene(3,5-di-tert-butyl-4- hydroxyhydrocinnamate) methane.

4. The stabilising composition according to any one of claims 1 to 3, wherein the organophosphite antioxidant comprises bis(2,4,di-tert- butylphenyl)pentraerythritol diphosphite; 2,4,6-tri-tert-butylphenyl-2-butyl-2- ethyl-1 ,3-propanediol phosphite; tris(2,4-di-t-butylphenyl)phosphite; distearylpentaerythritol diphosphite; bis(2,4-dicumylphenyl) pentaerythritol diphosphite; bis(2,6-di-ter-butyl-4-methylphenyl)pentaerythritol diphosphite; tetrakis(2,4-di-tertbutylphenyl)[1 ,1 -biphenyl]-4,4'-diylbisphosphonite; and/or compatible mixtures of two or more thereof.

5. The stabilising composition according to any one of claims 1 to 4, wherein the organophosphite comprises bis(2,4,di-tert-butylphenyl)pentraerythritol diphosphite.

6. The stabilising composition according to any one of claims 1 to 5, wherein the fully hindered phenolic antioxidant is present in an amount of from about 10% to about 70% by weight of the stabilising composition, from about 20% to about 60% by weight of the stabilising composition, from about 30% to about 50% by weight of the stabilising composition, or from about 25% to about 40% by weight of the stabilising composition.

7. The stabilising composition according to any one of claims 1 to 6, wherein the organophosphite antioxidant is present in an amount of from about 20% to about 80% by weight of the stabilising composition, from about 30% to about 70% by weight of the stabilising composition, from about 40% to about 60% by weight of the stabilising composition, or from about 35% to about 50% by weight of the stabilising composition.

8. The stabilising composition according to any one of claims 1 to 7, wherein 1 ,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1 ,3,5-triazine-2,4,6-

(1 H,3H,5H)-trione is present in an amount of from about 1 % to about 20% by weight of the stabilising composition, or from about 5% to about 15% by weight of the stabilising composition.

9. The stabilising composition according to any one of claims 1 to 8, wherein the zinc oxide is present in an amount of from about 1 % to about 30% by weight of the stabilising composition, from about 5% to about 25% by weight of the stabilising composition, or from about 10% to about 20% by weight of the stabilising composition.

10. The stabilising composition according to any one of claims 1 to 9, wherein the stabilising composition is a solid composition with a melting point of 30°C or higher, 40°C or higher, 50°C or higher, 60°C or higher, or 70°C or higher, at atmospheric pressure i.e. 101 .325 kPa.

1 1 . Use of the stabilising composition according to any one of claims 1 to 10 to stabilise polypropylene.

12. A polypropylene composition, comprising:

a polypropylene base material; and

a stabilising composition comprising:

a fully hindered phenolic antioxidant;

an organophosphite antioxidant;

1 ,3,5-tris(4-tert-butyl-3-hydroxy-2,6-dimethylbenzyl)-1 ,3,5- triazine-2,4,6-(1 H,3H,5H)-trione; and

zinc oxide.

13. The polypropylene composition according to Claim 12, wherein the stabilising composition is present in the polypropylene composition in an amount of from about 10 ppm to about 10000 ppm, from about 100 ppm to about 5000 ppm, or from about 500 ppm to about 2000 ppm.

14. The polypropylene composition according to Claim 12 or Claim 13, wherein the polypropylene base material comprises a polypropylene homopolymer.

15. The polypropylene composition according to any one of claims 12 to 14, wherein the polypropylene base material comprises a copolymer, optionally a random copolymer.

16. The polypropylene composition according to Claim 15, wherein the copolymer comprises propylene and ethylene and/or butylene.

17. The polypropylene composition according to Claim 15 or Claim 16, wherein the copolymer comprises a propylene-ethylene random copolymer.

18. The polypropylene composition according to any one of claims 12 to 17, wherein the polypropylene base material comprises a polypropylene impact copolymer.

19. A polypropylene film manufactured from the polypropylene composition according to any one of claims 12 to 18.

20. The polypropylene film according to Claim 19, wherein the polypropylene film is biaxially oriented.