High speed cross-linking of grafted plastomers

Abstract

The present invention discloses a process for providing a cross-linked composition, the process comprising the steps of (a) providing an ethylene-?-olefin plastomer havinga density of from 850 kg/m.sup.3 to 900 kg/m.sup.3; andan melt flow rate (ISO 1133, 2.16 kg, 190? C.) of 0.3 to 50 g/10 min; (b) grafting the ethylene-?-olefin plastomer with silane crosslinker such that the content of silane crosslinker is in the range of 0.1 to 10.0 wt. % with respect to the grafted ethylene-?-olefin plastomer; (c) contacting said grafted ethylene-?-olefin plastomer with 2 to 8 wt. % of a tin-free silane crosslinking catalyst with respect to the resulting mixture of grafted ethylene-?-olefin plastomer and tin-freesilane crosslinking catalyst, wherein said tin-free catalyst comprises a Br?nsted acid at 23? C. and 50% relative humidity for at least 15 minutes thus forming a cross-linked composition, wherein gel content of said cross-linked composition after 15 min is at least 60%.

Claims

1. A process for providing a cross-linked composition, the process comprising the steps of (a) providing an ethylene-?-olefin plastomer which is a copolymer of ethylene and 1-octene and providing no other polymer, the ethylene-?-olefin plastomer having a density of from 850 kg/m.sup.3 to 900 kg/m.sup.3; and a melt flow rate (ISO 1133, 2.16 kg, 190? C.) of 0.3 to 50 g/10 min; (b) grafting the ethylene-?-olefin plastomer from step (a) with a silane crosslinker such that the content of the silane crosslinker is in the range of 0.1 to 10.0 wt. % with respect to the resulting grafted ethylene-?-olefin plastomer; and (c) contacting said grafted ethylene-?-olefin plastomer from step (b) with 2 to 8 wt. % of a tin-free silane crosslinking catalyst with respect to the resulting mixture of grafted ethylene-?-olefin plastomer and tin-free silane crosslinking catalyst to form an intermediate composition, which in turn forms a cross-linked composition having a gel content of at least 60% when subjected to 23? C. and 50% humidity for 15 minutes, and wherein said tin-free catalyst comprises a sulfonic acid; wherein step c) is carried out: in an extruder; and/or at a temperature 120 to 210? C.

2. The process according to claim 1, wherein the ethylene-?-olefin plastomer has a density of from 865 to 895 kg/m.sup.3; and a melt flow rate (ISO 1133, 2.16 kg, 190? C.) of 0.40 to 2 g/10min.

3. The process according to claim 1, wherein the ethylene content of the ethylene-a-olefin plastomer is from 60.0 to 95.0 wt %.

4. The process according to claim 1, wherein the 1-octane content of the ethylene-?-olefin plastomer is up to 40.0 wt %.

5. The process according to claim 1, wherein a gel content of said cross-linked composition after 15 min of contacting is at least 70%.

6. The process according to claim 1, wherein step b) takes place in an extruder; and/or at a temperature 120 to 210? C.

7. The process according to claim 1, wherein step b) is initiated by a free radical forming agent.

8. The process according to claim 1, wherein the grafted ethylene-?-olefin plastomer is formed into pellets.

Description

EXAMPLES

(1) Inventive Examples IE1-IE3 and Comparative Examples CE1 and CE2 were treated with silane crosslinking catalyst Ambicat LE4476 under the conditions given below.

(2) TABLE-US-00001 TABLE 1 Base resin Gel content after crosslinking MFR Density VTMS Ambicat 15 min after 48 h Example Name (g/10 min) (kg/m.sup.3) % LE4476 extrusion at RT IE1 P1 0.5 863 2.0 5% 81% 96% IE2 P2 1 857 1.8 5% 87% 96% IE3 P3 0.5 861 1.7 5% 60% 96% CE1 R1 1 922 1.4 5% 0 70 CE2 R2 16 944 1.3 5% 0 40

(3) As may be seen, polymerized silane resins R1 and R2 resulted in 0% gel content after tape extrusion and 70 and 40% respectively after 48 h.

(4) However, when using plastomers P1-P3, which have been VTMS grafted, a surprising increase in cross-linking speed was observed (60 to 87% gel content after tape extrusion). Therefore, an instant crosslinking completion is achieved after extruding the tapes, since many customers consider a good level of crosslinking degree at 70% gel content. In all cases finish surface looks acceptable.