ANTIDEGRADANT BLEND

Abstract

The invention concerns an antidegradant blend for polymers, comprising: a. an antioxidant selected from one or more of: i. a phenolic antioxidant; ii. an organic phosphite antioxidant; and: b. an inorganic antioxidant or reducing agent; wherein the composition is absent any metal carboxylate or buffering agent having the capacity to buffer in aqueous solution at a pH range from 4 to 8.

Claims

1. An antidegradant blend, comprising: a. an antioxidant selected from one or more of: i. a phenolic antioxidant; ii. an organic phosphite antioxidant; and: b. an inorganic antioxidant or reducing agent; wherein the composition is absent any metal carboxylate or buffering agent having the capacity to buffer in aqueous solution at a pH range from 4 to 8.

2. An antidegradant blend according to claim 1 comprising both a phenolic and an organic phosphite antioxidant.

3. An antidegradant blend according to claim 1 wherein the inorganic antioxidant or reducing agent is selected from the group consisting of a metal phosphite, a metal hypophosphite, a metal thiosulphate, a metal bisulphite, a metal metabisulphite, a metal hydrosulphite, and mixtures thereof.

4. An antidegradant blend according to claim 3 wherein the inorganic antioxidant or reducing agent is a metal hypophosphite.

5. An antidegradant blend according to claim 4 wherein the metal hypophosphite is anhydrous.

6. An antidegradant blend according to claim 4 wherein the metal hypophosphite is hydrated.

7. An antidegradant blend according to claim 6 wherein the metal hypophosphite is provided in mono-hydrated form.

8. An antidegradant blend according to claim 1, wherein the antioxidant comprises an organic phosphite antioxidant.

9. An antidegradant blend according to claim 8 wherein the organic phosphite antioxidant is selected from the group consisting of bis(2,4,di-t-butylphenyl)pentaerythritol diphosphite (CAS 26741-53-7); 2,4,6-tri-tert-butylphenyl-2-butyl-2-ethyl-1,3-propanediol phosphite (CAS 161717-32-4); tris(2,4-di-t-butylphenyl)phosphite (CAS 31570-04-4); tetrakis (2,4-di-t-butylphenyl)4,4′-biphenylene diphosphonite (CAS 38613-77-3); tris(4-n-nonylphenyl)phosphite (CAS 26523-78-4); distearylpentaerythritol diphosphite (CAS 3806-34-6); bis(2,4-dicumylphenyl) pentaerythritol diphosphite (CAS 154862-43-8); CAS 939402-02-5; tris(dipropyleneglycol) phosphite, C.sub.18H.sub.39O.sub.9P (CAS 36788-39-3); poly(dipropylene glycol) phenyl phosphite (CAS 80584-86-7); diphenyl isodecyl phosphite, C.sub.22H.sub.31O.sub.3P (CAS 26544-23-0); phenyl diisodecyl phosphite (CAS 25550-98-5); heptakis (dipropyleneglycol) triphosphite (CAS 13474-96-9); bis(2,6-di-ter-butyl-4-methylphenyl)pentaerythritol diphosphite (CAS 80693-00-1); tris(2-t-butylphenyl)phosphite (CAS 31502-36-0); and compatible mixtures thereof.

10. An antidegradant blend according to claim 1, wherein the antioxidant comprises a phenolic antioxidant.

11. An antidegradant blend according to claim 10 wherein the phenolic antioxidant is selected from the group consisting of 2 (1,1-dimethylethyl)-4,6-dimethyl-phenol (CAS 1879-09-0); 6-tert-butyl-2-methylphenol (CAS 2219-82-1); 4,6-di-tert-butyl-2-methylphenol; 2-tert-butyl-4-methylphenol; 2-tert-butyl-5-methylphenol; 2,4-di-tert-butylphenol; 2,4-di-tert-pentylphenol; triethyleneglycol-bis-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate] (CAS 36443-68-2); 1,3,5-tris(4-t-butyl-3-hydroxyl-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H, 3H, 5H)-trione; 2,2′-ethylidenebis[4,6-di-t-butylphenol] (CAS 35958-30-6); 2,2′methylenebis(6-t-butyl-4-methylphenol) (CAS 119-47-1); the butylated reaction product of p-cresol and dicyclopentadiene (CAS 68610-51-5); 2,6-xylenol; C13-C15 linear and branched alkyl esters of 3-(3′5′-di-t-butyl-4′-hydroxyphenyl) propionic acid (CAS 171090-93-0); octadecyl 3-(3′,5′-di-t-butyl-4′-hydroxyphenyl) propionate (CAS 2082-79-3); N,N′-hexamethylene bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionamide] (CAS 23128-74-7); C9-C11 linear and branched alkyl esters of 3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionic acid (CAS 125643-61-0); butylated hydroxytoluene (CAS 128-37-0); 2,6-di-tertiary-butyl-4-sec-butylphenol; 2,6-di-tertiary-butyl-4-nonylphenol; tetrakismethylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate) methane (CAS 6683-19-8); 1,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate (CAS 27676-62-6); 1,2-bis(3,5-di-t-butyl-4-hydroxyhydrocinnamoyl)hydrazine (CAS 32687-78-8); 2,2′thiodiethylene bis[3(3,5-di-t-butyl-4-hydroxyphenyl)propionate] (CAS 41484-35-9); 1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene (CAS 1709-70-2); butylated hydroxyanisole (CAS 25013-16-5); tocopherol, DL α-tocopherol, tocopherol derivatives, tocotrienol and/or tocotrienol derivatives (Vitamin E); and mixtures thereof.

12. An antidegradant blend comprising: a. a phenolic antioxidant; b. an organic phosphite antioxidant; and c. an inorganic phosphite antioxidant; wherein the composition is absent any metal carboxylate or buffering agent having the capacity to buffer in aqueous solution at a pH range from 4 to 8.

13. An antidegradant blend comprising: a. tetrakismethylene (3,5-di-t-butyl-4-hydroxyhydrocinnamate) methane (CAS 6683-19-8); b. tris(2,4-di-t-butylphenyl)phosphite (CAS 31570-04-4); and c. sodium hypophosphite; wherein the composition is absent any metal carboxylate or buffering agent having the capacity to buffer in aqueous solution at a pH range from 4 to 8.

14. An antidegradant blend according to claim 1, further comprising one or more antioxidants selected from the group consisting of sulphur-containing antioxidants, aminic antioxidants, hydroxylamines or precursors 49237432\2 thereof, lactone radical scavengers, acrylate radical scavengers, UV absorbers, and chelating agents.

15-16. (canceled)

17. A polymeric composition, comprising a polymeric base material and an antidegradant blend according to claim 1.

18. The polymeric composition of claim 17 wherein the antidegradant blend is present in an amount of from about 0.01% to about 5% by weight of the polymeric composition.

19. The polymeric composition of claim 17 wherein the polymeric base material is selected from the group consisting of a polyolefin, polystyrene, polyacrylonitrile, a polyacrylate, a polyurethane, a polyamide, a polyester, a polycarbonate, polyvinyl chloride, an elastomer, a rubber, and suitable mixtures, blends or copolymers thereof.

20. A useful article manufactured from a polymeric composition according to claim 17.

21. A polymeric composition, comprising a polymeric base material and an antidegradant blend according to claim 12.

22. A polymeric composition, comprising a polymeric base material and an antidegradant blend according to claim 13.

Description

[0123] The invention will now be more particularly described with reference to the following non-limiting Examples and Figures wherein

[0124] FIG. 1 depicts a graph showing the Yellowness Index of a polypropylene polymer to which various antidegradant blends had been added.

[0125] FIG. 2 depicts a graph showing the Yellowness Index of a polypropylene polymer to which various antidegradant blends had been added.

EXAMPLES

[0126] Preparation of the Polymeric Composition

[0127] The polymeric base material was a commercially available polypropylene homopolymer for Samples 1 to 16 and 23 to 35, and a polypropylene homopolymer with a lower MFR for Samples 17 to 22.

[0128] Numerous antidegradant blends were prepared.

[0129] Table 1 shows the different components that were used in the antidegradant blends.

TABLE-US-00001 TABLE 1 Component Shorthand Type Sodium hypophosphite Na Hyp Inorganic phosphite antioxidant 1:1 NaH2PO4:Na2HPO4 Na P Buffering Agent* Dihydrotalcite DHT-4V Inorganic Acid Scavenger Calcium Stearate CaSt Organic Acid Scavenger* ALKANOX ™ 240 A240 Organic phosphite antioxidant Tris(2-t- TOTBP Organic phosphite antioxidant butylphenyl)phosphite ULTRANOX ™ 626 U626 Organic phosphite antioxidant ANOX ™ 20 A20 Phenolic antioxidant LOWINOX ™ CA22 CA22 Phenolic antioxidant LOWINOX ™ 1790 1790 Phenolic antioxidant Butylated hydroxytoluene BHT Phenolic antioxidant Butylated hydroxyanisole BHA Phenolic antioxidant DL-α-tocopherol VitE Phenolic antioxidant *These are examples of materials which are metal carboxylates or buffering agents having the capacity to buffer in aqueous solution at a pH range from 4 to 8. Examples containing these materials are therefore comparative examples.

[0130] Tables 2, 3 and 4 show the various antidegradant blends that were prepared. The (Y0 amounts shown in the table are % by weight of the overall polymeric composition.

TABLE-US-00002 TABLE 2 Na Hyp A240 A20 CaSt DHT-4V Total Sample (%) (%) (%) (%) (%) (%) 1 (Comp)* — 0.08 0.04 — — 0.12 2 (Comp)*.sup.∧ — 0.08 0.04 0.03 — 0.15 3 (Comp)* — 0.08 0.04 — 0.018 0.138 4 0.015 0.08 0.04 — — 0.135 5 0.08 0.08 0.04 — — 0.20 6 0.01 0.04 0.04 — — 0.09 *Samples 1 to 3 contain no inorganic antioxidant or reducing agent and are therefore comparative examples .sup.∧Sample 2 contains calcium stearate which is an example of a material which has the capacity to buffer in aqueous solution at a pH range from 4 to 8. Sample 2 is, therefore comparative for that reason also.

[0131] Samples 1, 2, and 3 are comparative examples which represent industry standard antidegradant blends. Each of the above-identified antidegradant blends was compounded and dry blended with the polypropylene base material in an extruder at a temperature of 230° C. under nitrogen in the absence of solvent to form a polymeric composition.

TABLE-US-00003 TABLE 3 Na Hyp Na Hyp Anhyd Hyd A240 A20 CaSt Na P Total Sample (%) (%) (%) (%) (%) (%) (%)  7* — — 0.08 0.04 — — 0.12 (Comp)  8.sup.∧ — — 0.08 0.04 0.03 — 0.15 (Comp) 9 0.015 — 0.08 0.04 — — 0.135 10  — 0.018 0.08 0.04 — — 0.138 11.sup.∧ 0.015 — 0.08 0.04 — 0.015 0.15 (Comp) 12.sup.∧ — 0.018 0.08 0.04 — 0.015 0.153 (Comp) 13.sup.∧ 0.015 — 0.08 0.04 0.03 — 0.165 (Comp) 14.sup.∧ — 0.018 0.08 0.04 0.03 — 0.165 (Comp) *Sample 7 contains no inorganic antioxidant or reducing agent and is therefore comparative .sup.∧Samples 8, 11 and 12-14 each contain a metal carboxylate or buffering agent having the capacity to buffer in aqueous solution at a pH range from 4 to 8 and are therefore comparative.

TABLE-US-00004 TABLE 4 Na Hyp A240 TOTBP A20 DHT- Total Sample (%) (%) (%) (%) 4V (%) (%) 15 (Comp)* — — 0.0611 0.04 0.018 0.1191 16 0.015 — 0.0611 0.04 — 0.1161 17 (Comp)* — 0.12 — 0.06 — 0.18 18 (Comp)* — 0.12 — 0.06 0.035 0.215 19 0.035 0.12 — 0.06 — 0.215 20 0.025 0.12 — 0.06 — 0.205 21 0.015 0.12 — 0.06 — 0.195 22 0.03 0.0925 — 0.0925 — 0.215 *Samples 15, 17 and 18 contain no inorganic antioxidant or reducing agent and are therefore comparative examples.

[0132] Samples 15, 17 and 18 are comparative examples which represent industry standard antidegradant blends. Each of the above-identified antidegradant blends was compounded and dry blended with the polypropylene base material in an extruder at a temperature of 230° C. under nitrogen in the absence of solvent to form a polymeric composition.

TABLE-US-00005 TABLE 5 NaHyp A240 A20 CA2 U626 1790 BHT BHA VitE DHT-4V Total Sample (%) (%) (%) 2 (%) (%) (%) (%) (%) (%) (%) (%) 23 (Comp)* — 0.08 0.04 — — — — — — — 0.12 24 (Comp)* — 0.08 — — — 0.04 — — — 0.03 0.15 25 0.03 0.08 — — — 0.04 — — — — 0.15 26 (Comp)* — — 0.04 — 0.04 — — — — 0.03 0.11 27 0.03 — 0.04 — 0.04 — — — — — 0.11 28 (Comp)* — 0.08 — 0.04 — — — — — 0.03 0.15 29 0.03 0.08 — 0.04 — — — — — — 0.15 30 (Comp)* — 0.08 — — — — 0.04 — — 0.03 0.15 31 0.03 0.08 — — — — 0.04 — — — 0.15 32 (Comp)* 0.08 — — — — — 0.04 — 0.03 0.15 33 0.03 0.08 — — — — — 0.04 — — 0.15 34 (Comp)* 0.08 — — — — — — 0.04 0.03 0.15 35 0.03 0.08 — — — — — — 0.04 — 0.15 *Samples 23, 24, 26, 28, 30, 32 and 34 contain no inorganic antioxidant or reducing agent and are therefore comparative examples.

[0133] Sample 23 is a comparative example which represent an industry standard antidegradant blend. Each of the above-identified antidegradant blends was compounded and dry blended with the polypropylene base material in an extruder at a temperature of 230° C. under nitrogen in the absence of solvent to form a polymeric composition.

[0134] Colour Stability

[0135] Each of the polymeric compositions referenced in Tables 2 to 5 were multi-passed through an extruder at 260° C. under air. Extrusion experiments were performed on a 25 mm SS Brabender™ Extruder. After each pass through the extruder the polymer sample is cooled in a water bath, dried and chipped to give pellets which were analysed and subjected to the same procedure again. The discolouration of the compositions was measured in terms of Yellowness Index (YI) using a colorimeter (X-rite™ Color i7) according to YI ASTM D1925. Each YI measurement is the average of 4 measured values. YI values were taken following compounding (pass 0) and after passes 1, 3, and 5. The lower the YI value, the less discolouration of the composition. The results are shown in Table 6 as far as samples 1 to 6 and 15 to 35 are concerned, and in FIGS. 1 and 2 as far as samples 7 to 14 are concerned.

TABLE-US-00006 TABLE 6 YI Value Sample Pass 0 Pass 1 Pass 3 Pass 5  1 (Comp) 0.08 0.96 3.00 3.90  2 (Comp) −0.16 0.68 1.96 2.61  3 (Comp) −0.28 1.43 3.23 4.51  4 0.01 0.32 1.01 1.60  5 0.11 0.18 0.79 1.48  6 0.14 0.79 1.73 2.19  7 (Comp) 0.08 1.44 3.85 8.61  8 (Comp) 0.14 1.80 3.90 5.56  9 −0.21 0.60 2.92 4.35 10 −0.25 0.63 1.95 3.05 11 (Comp) 0.43 1.92 3.33 5.65 12 (Comp) −0.06 1.50 2.86 4.08 13 (Comp) 0.08 1.61 3.38 4.10 14 (Comp) 0.12 1.81 2.77 3.93 15 (Comp) −0.03 0.99 2.94 4.48 16 −0.29 0.78 2.18 2.68 17 (Comp) −0.34 0.51 2.64 4.33 18 (Comp) 0.05 1.69 4.55 6.96 19 −0.55 0.25 1.32 1.85 20 −0.48 0.56 1.50 2.15 21 −0.64 0.47 1.82 2.47 22 −0.23 1.29 2.47 3.10 23 (Comp) −0.68 0.99 3.17 4.41 24 (Comp) 3.77 7.69 10.69 12.38 25 2.38 3.95 5.20 5.35 26 (Comp) −0.99 0.01 0.79 1.36 27 −0.96 −0.41 −0.23 −0.04 28 (Comp) −0.31 1.44 3.44 5.20 29 −0.83 0.09 1.36 1.97 30 (Comp) −0.85 0.38 1.8 2.75 31 −1.50 −1.15 −0.40 −0.39 32 (Comp) 0.53 1.96 4.26 5.25 33 −0.65 0.72 1.84 2.49 34 (Comp) 0.95 4.46 8.23 10.69 35 −0.75 1.26 3.88 5.47

[0136] From the results, it can be seen that the polymeric compositions stabilised with the antidegradant blends in accordance with the present invention (Samples 4 to 6, 9, 10, 16 and 19 to 22) show significantly less discolouration than the polymeric compositions stabilised with the industry standard antidegradant blends (Samples 1 to 3, 7, 8, 11 to 15, 17, 18 and 23).

[0137] It can also be seen that the polymeric composition stabilised with the antidegradent blends in accordance with the present invention (Samples 25, 27, 29, 31, 33 and 35) show significantly less discolouration than the polymeric compositions stabilised with DHT-4V (Samples 24, 26, 28, 30, 32 and 34).

[0138] Turning to FIG. 1 there is shown a comparative chart of YI in which:

[0139] Sample 7 is a comparative additive blend comprising A240 and A20.

[0140] Sample 8 is a comparative additive blend comprising A240 A20 and Ca Stearate.

[0141] Sample 9 is an example of the invention corresponding to comparative blend 7 additionally comprising anhydrous sodium hypophosphite.

[0142] Sample 10 is an example of the invention corresponding to comparative blend 7 additionally comprising mono-hydrated sodium hypophosphite.

[0143] Sample 11 is the additive blend 7 additionally comprising anhydrous sodium hypophosphite and a phosphate buffer as disclosed in the unpublished GB1707120.0.

[0144] Sample 12 is the additive blend 7 additionally comprising mono-hydrated sodium hypophosphite and a phosphate buffer as disclosed in the unpublished GB1707120.0.

[0145] It will be seen from the results that the additive blend comprising only sodium hypophosphite (whether anhydrous or hydrated) performs better than the corresponding blend including also a phosphate buffer according to the unpublished GB1707120.0. It is also observed that, with or without phosphate buffer, hydrated hypophosphite performs better than the anhydrous version. It is suspected that this may be to do to an interaction effect between the hypophosphite and the phosphite antioxidant, possibly because the hydrated hypophosphite is able at least partially hydrolyse the phosphite antioxidant, making it more reactive.

[0146] Turning to FIG. 2 there is shown a comparative chart of YI in which:

[0147] Sample 8 is an additive blend comprising A240 and A20 and CaSt.

[0148] Sample 13 is an additive blend comprising A240 A20 and CaSt and anhydrous sodium hypophosphite.

[0149] Sample 14 is an additive blend comprising A240 A20 and CaSt and mono-hydrated sodium hypophosphite.

[0150] It will be seen from the results that the additive blend comprising only sodium hypophosphite (whether anhydrous or hydrated) performs better than the corresponding blend including CaSt. The hydrated hypophosphite performs better than the anhydrous.

[0151] Melt Flow Rate

[0152] The melt flow rate of the polymeric composition of Samples 1 to 5 and 7 to 35 were determined following compounding (pass 0) and after pass 5, using a CEAST™ 7026 Melt Flow Tester according to standard test method ASTM D1238L with a temperature of 230° C., a 2.16 kg weight and a 2.095 mm die. An increase in the melt flow rate is indicative of unfavourable degradation of the sample. The results are shown in Table 7.

TABLE-US-00007 TABLE 7 Melt Flow Rate (g/10 min) Sample Pass 0 Pass 5  1 (Comp) 7.20 12.27  2 (Comp) 6.92 13.74  3 (Comp) 6.98 13.64  4 7.43 13.46  5 6.93 12.87  7 (Comp) 7.57 12.95  8 (Comp) 7.17 12.97  9 7.42 12.75 10 7.43 13.06 11 (Comp) 7.74 12.50 12 (Comp) 6.83 13.04 13 (Comp) 7.01 13.73 14 (Comp) 7.04 14.31 15 (Comp) 7.38 17.35 16 7.78 15.59 17 (Comp) 2.54 4.83 18 (Comp) 2.55 4.76 19 2.46 4.50 20 2.70 4.69 21 2.73 4.20 22 2.34 4.52 23 (Comp) 9.16 16.63 24 (Comp) 8.22 12.22 25 8.39 12.18 26 (Comp) 8.35 12.85 27 9.03 14.49 28 (Comp) 8.13 17.19 29 8.31 15.88 30 (Comp) 9.29 13.56 31 9.52 13.38 32 (Comp) 8.27 13.86 33 8.31 12.44 34 (Comp) 8.10 12.06 35 8.04 12.02

[0153] From the results it can be seen that the polymeric compositions stabilised using the antidegradant blends according to the present invention (Samples 4, 5, 9, 10, 16 and 19 to 22) retained melt flow rate similarly to the polymeric compositions stabilised using the industry standard or otherwise comparative antidegradant blends (Samples 1 to 3, 7, 8, 11 to 15, 17, 18 and 23).

[0154] It can also be seen that the polymeric composition stabilised using the antidegradent blends according to the present invention (Samples 25, 27, 29, 31, 33 and 35) retained melt flow rate comparably relative to the polymeric compositions stabilised using DHT-4V (Samples 24, 26, 28, 30, 32 and 34).

[0155] Polymer Corrosivity

[0156] The corrosivity of a polymer and additives is determined on a semi-quantitative basis by compression moulding the compounded polymer against a mild steel coupon at high temperature for 15 minutes. After cooling, the coupon is removed from the polymer and aged in a humidity chamber. The aged coupons are examined for corrosion and rated for severity.

[0157] The metal coupons are cold rolled low carbon steel SAE1008/1010 supplied by Q-LAB with designation QD-36 and one side is sanded, cleaned with solvent and dried. Onto this surface the compounded polymer is pressed at 260° C. for 15 mins at high pressure (200 bar). After cooling the polymer is removed from the coupon before exposing the coupon to 85% relative humidity at 42° C. in a test chamber. The coupon is inspected after 4 hrs and 24 hrs for the level of corrosion and discolouration and rated according to the scale below; [0158] None=Corrosion is not detected without magnification. [0159] Light=Corrosion/discolouration is just detectable without magnification and requires magnification to confirm. [0160] Moderate=Corroded surface is visible from any angle in standard illumination. It has a characteristic rust colour. No magnification is required to confirm corrosion. [0161] Severe=Corroded surface is clear with a rich colour and uneven surface. Magnification is not required to see the corrosion.

[0162] Tables 2 and 4 show the various antidegradant blends that were prepared. The % amounts shown in the table are % by weight of the overall polymeric composition. The results of the corrosion tests are shown in Table 8.

TABLE-US-00008 TABLE 8 Corrosion Test Assessment Sample 4 hrs 24 hrs  1 (Comp) Moderate Severe  2 (Comp) None None  3 (Comp) None None  4 None None 18 (Comp) None None 19 None None 21 None None

[0163] From the results it can be seen that the polymeric composition stabilised using the antidegradant blend according to the present invention (Samples 4, 19, and 21) exhibited corrosion protection that was equal to that shown by the state of the art acid scavenger containing formulations (Samples 2, 3, and 18). The control (Sample 1) without any acid scavenger additive shows clear evidence of corrosion.

[0164] This data using a commercially available polypropylene homopolymer shows that using hydrated sodium hypophosphite at equal phosphorus loading has no detrimental effect on performance on the multipass colour test in the CaSt and non-CaSt recipes. There was also no evidence for bubbles of gas in the extruded polymer produced from the hydrated hypophosphite. Bubbles are undesirable in the extruded polymer and so a lack of bubbles is important. It was thought that the water of hydration might result in bubbles in the extruded polymer, but this was found to not be the case.