INSULATION COMPOSITION

Abstract

The present invention relates to a precursor material for an insulation composition, comprising: a crosslinkable graft polymer comprising a polyolefin component and a polyene component; and an antioxidant. The present invention also relates to an insulation composition obtained from the precursor material.

Claims

1. A precursor material for an insulation composition, comprising: a crosslinkable graft polymer comprising a polyolefin component and a polyene component; and an antioxidant.

2. The precursor material according to claim 1, wherein the polyolefin component forms a backbone and the polyene component forms one or more side chains grafted onto the backbone.

3. The precursor material according to claim 1, wherein the polyolefin component is derived from a polyolefin comprising polyethylene and/or polypropylene.

4. The precursor material according to claim 1, wherein the polyene component is derived from a polyene comprising 2 or more carbon-carbon double bonds and/or vinyl groups.

5. The precursor material according to claim 1, wherein the polyene component is derived from: a. a polyene selected from the group consisting of 1,7-octadiene; 1,9-decadiene; 1,11-dodecadiene; 1,13-tetradecadiene; 7-methyl-1,6-octadiene; 9-methyl-1,8-decadiene; and mixtures thereof; b. a polyene comprising a siloxane having the following formula:
CH.sub.2CH[Si(CH.sub.3).sub.2O].sub.nSi(CH.sub.3).sub.2CHCH.sub.2 wherein n=1 or higher. c. a polyene comprising a divinylsiloxane; d. a polyene selected from the group consisting of farnesene; squalene; limonene; dicyclopentadiene; 1,2,4-trivinylcyclohexane; vinyl norbornene; cyclooctadiene; cyclooctatriene; trans,trans,cis-1,5,9-cyclododecatriene; triallyl isocyanurate (1,3,5-Triallyl-1,3,5-triazinane-2,4,6-trione); triallyl cyanurate (2,4,6-Triallyloxy-1,3,5-triazine) and mixtures thereof.

6. The precursor material according to claim 1, wherein the antioxidant: a. comprises one or more components selected from the group consisting of: phenolic antioxidants, phosphite antioxidants, sulphur-containing antioxidants, and/or aminic antioxidants, and mixtures thereof; b. comprises a single antioxidant; or c. comprises a blend of two or more antioxidants.

7. The precursor material according to claim 1, further comprising a crosslinking agent.

8. The precursor material according to claim 1, further comprising a scorch retarder.

9. (canceled)

10. An insulation composition comprising a crosslinked precursor material according to claim 1.

11. (canceled)

12. A wire or cable comprising an electrically conductive material surrounded by the insulation composition according to claim 10.

13. (canceled)

14. A process for forming a precursor material, comprising: combining a polyolefin, a polyene and an antioxidant to form a reaction mixture; and heating the reaction mixture to form a precursor material according to claim 1.

15. A process for forming an insulation composition, comprising: combining a polyolefin, a polyene, a crosslinking agent and an antioxidant to form a reaction mixture; and heating the reaction mixture to form an insulation composition according to claim 10.

16. The precursor material according to claim 5, wherein the divinylsiloxane is ,-divinylsiloxane.

17. The precursor material according to claim 6, wherein the single antioxidant has both phenolic functionality and sulphur functionality.

18. The precursor material according to claim 6, wherein the single antioxidant is 4,4-thiobis (2-t-butyl-5-methylphenol) or 4,6-bis(octylthiomethyl)-o-cresol.

19. The precursor material according to claim 6, wherein the blend of two or more antioxidants comprises: i. at least one fully hindered phenolic antioxidant; at least one partially hindered phenolic antioxidant; and at least one sulphur-containing antioxidant; or ii. at least one low hindered phenolic antioxidant and/or at least one non-hindered phenolic antioxidant.

20. The precursor material according to claim 7, wherein the crosslinking agent is a peroxide.

21. The precursor material according to claim 20, wherein the peroxide is selected from the group consisting of dicumylperoxide; 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane; tert-butylcumylperoxide; di-tert-amylperoxide; 2,5-di(tert-butylperoxy)-2,5-dimethyl-3-hexyne; di(tert-butyl)peroxide; di(tert-butylperoxy-i sopropyl)benzene; butyl-4,4-bis(tert-butylperoxy)valerate; 1,1-bis(tert-butylperoxy)-3,3,5-trim ethylcyclohexane; tert-butylperoxybenzoate; dibenzoyl peroxide; and combinations thereof.

22. The precursor material according to claim 8, wherein the scorch retarder is 2,4-diphenyl-4-methyl-1-pentene.

Description

EXAMPLES

Preparation of Examples 1 to 3

[0135] An antioxidant and a crosslinking agent as shown in Table 1 were combined in the appropriate ratio in a conical flask, and the mixture was warmed in a water bath at 85 C. This mixture was then added in the appropriate amount to low density polyethylene (LDPE) pellets having a density of 0.920 g/cm.sup.3 and a melt flow rate of 2.0 at 190 C., 2.16 kg (manufactured by BASF-YPC Company Limited), in a rotary evaporator flask. The mixture was agitated and heated using a water bath at 85 C. until the LDPE pellets had absorbed the liquid, which took approximately 20 minutes.

[0136] Examples 1 to 3 are comparative examples.

Preparation of Examples 4 to 13

[0137] An antioxidant, polyene, scorch retarder and crosslinking agent as shown in Table 1 were combined in the appropriate ratio in a conical flask, and the mixture was warmed in a water bath at 85 C. This mixture was then added in the appropriate amount to low density polyethylene (LDPE) pellets having a density of 0.920 g/cm.sup.3 and a melt flow rate of 2.0 at 190 C., 2.16 kg (manufactured by BASF-YPC Company Limited), in a rotary evaporator flask. The mixture was agitated and heated using a water bath at 85 C. until the LDPE pellets had absorbed the liquid, which took approximately 20 minutes.

[0138] Examples 4 to 13 are in accordance with the present invention.

[0139] The resulting LDPE pellets for each of examples 1 to 13 were compounded using the Farrel Twin Roll Mill at 120 C. for 2 minutes to produce calendered sheets.

TABLE-US-00001 TABLE 1 Antioxidant Polyene Scorch Retarder Crosslinking Agent % % % % Example Identity Loading* Identity Loading Identity Loading Identity Loading 1 BLEND 0.24 Dicumylperoxide 1.8 (Comp) 1** 2 BLEND 1 0.24 Dicumylperoxide 1.35 (Comp) 3 BLEND 1 0.24 Dicumylperoxide 1.48 (Comp) 4 BLEND 1 0.24 1,2,4- 1.0 2,4-diphenyl-4- 0.3 Dicumylperoxide 1.48 trivinylcyclohexane methyl-1-pentene 5 BLEND 1 0.24 Farnesene 1.0 2,4-diphenyl-4- 0.3 Dicumylperoxide 1.48 methyl-1-pentene 6 BLEND 1 0.24 trans,trans,cis- 1.0 2,4-diphenyl-4- 0.3 Dicumylperoxide 1.48 1,5,9- methyl-1-pentene cyclododecatriene 7 BLEND 1 0.24 1,2,4- 1.0 2,4-diphenyl-4- 0.3 Dicumylperoxide 1.34 trivinylcyclohexane methyl-1-pentene 8 BLEND 1 0.20 1,2,4- 1.0 2,4-diphenyl-4- 0.3 Dicumylperoxide 1.30 trivinylcyclohexane methyl-1-pentene 9 BLEND 1 0.22 1,2,4- 1.0 2,4-diphenyl-4- 0.3 Dicumylperoxide 1.30 trivinylcyclohexane methyl-1-pentene 10 BLEND 1 0.22 1,2,4- 1.0 2,4-diphenyl-4- 0.3 Dicumylperoxide 1.19 trivinylcyclohexane methyl-1-pentene 11 BLEND 1 0.22 1,2,4- 1.0 2,4-diphenyl-4- 0.3 Dicumylperoxide 1.29 trivinylcyclohexane methyl-1-pentene 12 BLEND 1 0.24 1,2,4- 1.0 2,4-diphenyl-4- 0.3 Dicumylperoxide 1.19 trivinylcyclohexane methyl-1-pentene 13 BLEND 1 0.24 1,2,4- 1.0 2,4-diphenyl-4- 0.3 Dicumylperoxide 1.29 trivinylcyclohexane methyl-1-pentene *% Loading is the amount of the component by weight of the low density polyethylene **BLEND 1 57 wt. % ditridecylthiodipropionate (NAUGARD DTDTDP (liquid) CAS-10595-72-9) 29 wt. % C13-C15 linear and branched alkyl esters of 3-(35-di-t-butyl-4-hydroxyphenyl) propionic acid (ANOX 1315-CAS 171090-93-0) 14 wt. % 6-tert-butyl-2-methylphenol (CAS 2219-82-1)

[0140] Moving Die Rheometer Analysis

[0141] Discs having a 35 mm diameter and 4 g weight were punched from the calendered sheets for each of examples 1 to 13. The crosslinking profile of the discs was characterised by measuring the maximum torque and the maximum crosslinking speed, using a MDR3000 Basic from MonTech at 180 C. and 0.5 torsion at 1.66 Hz, in accordance with standard test method ASTM D5289.

[0142] The maximum torque acts as a measure of the degree of crosslinking i.e. the polymer strength. The maximum crosslinking speed is the maximum rate of increase in crosslinking during heating.

[0143] The results are shown in Table 2.

TABLE-US-00002 TABLE 2 Maximum Torque Maximum Speed Example (dNm) (dNm/min) 1 (Comp) 3.46 1.88 2 (Comp) 2.33 1.32 3 (Comp) 2.66 1.51 4 3.26 1.60 5 2.51 1.24 6 1.78 0.62 7 2.62 1.12 8 2.62 1.19 9 2.52 1.14 10 2.32 1.00 11 2.55 1.18 12 2.21 0.96 13 2.54 1.12

[0144] Comparative examples 1 to 3 clearly show that as the amount of peroxide crosslinking agent is increased, the maximum torque increases i.e. the degree of crosslinking increases, and the maximum crosslinking speed increases.

[0145] A comparison of the results for examples 3 and 4 shows that by adding a polyene to the initial mixture (which subsequently forms a graft polymer with the LDPE) in accordance with the present invention, both the maximum torque and the maximum crosslinking speed increases.

[0146] A comparison of the results for examples 3, 7, 8, 9, 10, 11, 12 and 13 shows that by adding a polyene to the initial mixture a similar crosslinking performance i.e. a similar maximum torque, can be achieved with a much lower amount of peroxide crosslinking agent. More specifically, in Example 8 the amount of peroxide crosslinking agent used is roughly 12% less than the amount used in Example 3. This is expected to result in roughly a 12% reduction in degassing time to remove flammable by-products.

[0147] The thermal aging properties of the formulations 8 to 13 were also measured. The method used was to take the calendared sheet samples described above and prepare from them crosslinked plaques of thickness 1.5 mm by compression molding at 120 C. increasing the pressure from 50 to 200 bar over 5 minutes. The cooled plaques were then transferred to a second mold and heated for a further 15 mins at 180 C. under 200 bar. The cooled plaques were then used to punch tensile bars (DIN 53-504-82) whose tensile properties were analysed before and after aging at 135 C. for 7 days and 150 C. for 10 days according to ASTM D638 using an Instron 3340 with 5 kN load cell. The results are shown table 3 and indicate an excellent aging performance.

TABLE-US-00003 TABLE 3 Aged 7 Aged 10 days Initial Tensile days @135 C @150 C. Tensile Elonga- TS Elong TS Elong Strength tion Retention Retention Retention Retention Example MPa % % % % % 8 20.9 665.5 92.8 98.1 90.6 95.5 9 20.7 663.3 95.2 100.2 94.1 98.1 10 19.2 645.3 93.7 94.4 85.3 88.6 11 19.8 646.4 89.9 91.7 86.8 89.3 12 19.4 655.6 97.9 97.4 86.6 86.8 13 20.0 658.9 91.1 91.3 90.1 91.7