1. Process for preparing high density polyethylene in the gas phase comprising contacting ethylene or a mixture comprising ethylene and one or more alpha-olefins with a chromium oxide catalyst supported on a granular or microspherical refractory oxide in a fluidised bed reactor having a recycle gas line, under polymerisation conditions, characterised in that
(i) oxygen is introduced into the reactor in the range of about 0.03 to about 1 part by volume of oxygen per million parts by volume of ethylene;
(ii) an organoaluminium compound is introduced into the reactor in the range of 0.0001 to 0.05 mole per ton of ethylene; and
(iii) the polymerisation is carried out at a temperature in the range of 80 to 120 C.
2. Process according to claim 1 wherein the high density polyethylene is a homopolymer of ethylene or a copolymer of ethylene and 1-butene or 1-hexene.
3. Process according to any of claims 1 and 2 wherein the density of the high density polyethylene is comprised between 0.948 and 0.967 gram per cubic centimetre.
4. Process according to any of the preceding claims wherein the chromium oxide catalyst supported on a granular or microspherical refractory oxide is a titanium or aluminium modified silica supported chromium oxide catalyst.
5. Process according to any of the preceding claims wherein the organoaluminium compound is introduced into the reactor in the range of 0.001 to 0.01 mole per ton of ethylene.
6. Process according to any of the preceding claims wherein the organoaluminium compound is a trialkylaluminium, preferably triethylaluminium.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An apparatus for receiving power from a prime mover to move a punch relative to a die and thereby form a hole in a wall, the apparatus comprising:
a housing defining:
a transmission chamber:
a draw stud passageway in communication with the transmission chamber and including a keyway that extends in a longitudinal direction of the housing;
an input element rotatably supported by the housing in the transmission chamber and configured to be rotatably driven by the prime mover;
a transmission element rotatably supported by the housing in the transmission chamber and rotatably driven by the input element, the transmission element including a threaded inner surface;
a draw stud supported by the housing in the draw stud passageway and configured to support the punch proximate the die, the draw stud having a threaded outer surface connected to the threaded inner surface and a key received in the keyway, the key and the keyway inhibiting rotation of the draw stud as the transmission element rotates and the threaded inner surface threadingly driving the threaded outer surface as the transmission element rotates to cause translation of the draw stud in the longitudinal direction to thereby move the punch relative to the die to form the hole; and
wherein the draw stud is detachable from the apparatus by only driving the draw stud such that the key exits the keyway, rotating the draw stud to detach the draw stud from the transmission element, and thereafter removing the draw stud from the draw stud passageway.
2. The apparatus of claim 1, wherein the input element is a worm and the transmission element is a worm gear.
3. The apparatus of claim 1, wherein the punch is a first punch, and the draw stud includes:
a distal end configured to support the first punch; and
a proximal end opposite the distal end and configured to support a second punch having a different size than the first punch.
4. The apparatus of claim 3, wherein the distal end of the draw stud includes a first threaded inner surface configured to support the first punch, and the proximal end of the draw stud includes a second threaded inner surface configured to support the second punch.
5. The apparatus of claim 1, wherein the housing defines an access opening opposite the draw stud passageway providing access to the proximal end of the draw stud.
6. The apparatus of claim 1, wherein the draw stud includes:
a shaft having the threaded outer surface; and
a collar connected to the shaft so as to move with the shaft, the collar supporting the key and being configured to support the punch.
7. An apparatus for receiving power from a prime mover to move a punch relative to a die and thereby form a hole in a wall, the apparatus comprising:
a housing defining:
a transmission chamber:
a draw stud passageway in communication with the transmission chamber and including a keyway that extends from the transmission chamber in a longitudinal direction to a distal end of the housing configured to support the die;
an input element rotatably supported by the housing in the transmission chamber and configured to be rotatably driven by the prime mover;
a transmission element rotatably supported by the housing in the transmission chamber and rotatably driven by the input element, the transmission element including a threaded inner surface; and
a draw stud supported by the housing in the draw stud passageway and configured to support the punch proximate the die, the draw stud having a threaded outer surface connected to the threaded inner surface and a key received in the keyway, the key and the keyway inhibiting rotation of the draw stud as the transmission element rotates and the threaded inner surface threadingly driving the threaded outer surface as the transmission element rotates to cause translation of the draw stud in the longitudinal direction to thereby move the punch relative to the die to form the hole.
8. The apparatus of claim 7, wherein the input element is a worm and the transmission element is a worm gear.
9. The apparatus of claim 7, wherein the punch is a first punch, and the draw stud includes:
a distal end configured to support the first punch; and
a proximal end opposite the distal end and configured to support a second punch having a different size than the first punch.
10. The apparatus of claim 9, wherein the distal end of the draw stud includes a first threaded inner surface configured to support the first punch, and the proximal end of the draw stud includes a second threaded inner surface configured to support the second punch.
11. The apparatus of claim 9, wherein the housing defines an access opening opposite the draw stud passageway providing access to the proximal end of the draw stud.
12. The apparatus of claim 7, wherein the draw stud includes:
a shaft having the threaded outer surface; and
a collar connected to the shaft so as to move with the shaft, the collar supporting the key and being configured to support the punch.
13. The apparatus of claim 7, wherein the draw stud is detachable from the apparatus by only driving the draw stud such that the key exits the keyway, rotating the draw stud to detach the draw stud from the transmission element, and thereafter removing the draw stud from the draw stud passageway.
14. An apparatus for receiving power from a prime mover to move a punch relative to a die and thereby form a hole in a wall, the apparatus comprising:
a housing including:
a transmission section;
a grip section configured to support the die and to be grasped by an operator while using the apparatus for forming the hole in the wall, the grip section having a proximal end connected to the transmission section and a distal end opposite the proximal end, the grip section defining an internal passageway extending in a longitudinal direction between the proximal end and the distal end, and the internal passageway having a longitudinally-extending keyway extending from the proximal end to the distal end;
an input element rotatably supported by the transmission section and configured to be rotatably driven by the prime mover;
a transmission element rotatably supported by the transmission section and rotatably driven by the input element, the transmission element including a threaded inner surface; and
a draw stud supported in the internal passageway and configured to support the punch proximate the die, the draw stud having a threaded outer surface connected to the threaded inner surface and a key received in the keyway, the key and the keyway inhibiting rotation of the draw stud as the transmission element rotates and the threaded inner surface threadingly driving the threaded outer surface as the transmission element rotates to cause translation of the draw stud in the longitudinal direction to thereby move the punch relative to the die to form the hole.
15. The apparatus of claim 14, wherein the input element is a worm and the transmission element is a worm gear.
16. The apparatus of claim 14, wherein the punch is a first punch, and the draw stud includes:
a distal end configured to support the first punch; and
a proximal end opposite the distal end and configured to support a second punch having a different size than the first punch.
17. The apparatus of claim 16, wherein the distal end of the draw stud includes a first threaded inner surface configured to support the first punch, and the proximal end of the draw stud includes a second threaded inner surface configured to support the second punch.
18. The apparatus of claim 16, wherein the housing defines an access opening opposite the grip section providing access to the proximal end of the draw stud.
19. The apparatus of claim 14, wherein the draw stud includes:
a shaft having the threaded outer surface; and
a collar connected to the shaft so as to move with the shaft, the collar supporting the key and being configured to support the punch.
20. The apparatus of claim 14, wherein the draw stud is detachable from the apparatus by only driving the draw stud such that the key exits the keyway, rotating the draw stud to detach the draw stud from the transmission element, and thereafter removing the draw stud from the internal passageway.