US 5,096,634 A · Method of operating an apparatus for the production of biaxially stretched plastic tubes

Abstract

Biaxially stretched thermoplastic tubes are made in an apparatus having a plastic extruder, the output of which is controllable on an open-circuit or closed-circuit basis and which has a too head for the extrusion of a highly viscous exiting tubing, a stretching mandrel and a speed-controllable draw-off device. In the region of the run-on part there is disposed a surrounding temperature control bath for controlling the temperature of the tube to the stretching temperature while a cooling bath is disposed in the region of the draw-off part. A Raman spectrometer operating with laser waves is disposed in the zone downstream of the cooling bath. The frequency of the laser waves is adapted to the plastic used and the energy of the laser waves is so adapted to the wall thickness of the tube produced that in addition to the radiated wave scattered or reflected by the plastics, at least one wave corresponding to a Raman spectral line is radiated from the tube. The extent of axial orientation of the plastics molecules is determined from properties of the wave scattered or reflected and/or radiated from the tube.

Claims20

Dependent claims

A method of producing a biaxially stretched thermoplastic tube, comprising the steps of:

(a) extruding a thermoplastic tubing in a viscous state;
(b) running said tubing onto a cylindrical run-on portion of a stretching mandrel, passing said tubing next over a conical expanding portion of said mandrel, and drawing expanded tubing off from a cylindrical draw-off portion of said mandrel to biaxially stretch said tubing;
(c) controlling a temperature of said tubing at said run-on portion of said mandrel to bring said tubing to a stretching temperature;
(d) cooling said tubing at said draw-off portion;
(e) downstream of the cooling of said tubing, monitoring molecular orientation in the cooled tubing by:
direction a laser beam against said cooled tubing of a frequency selected in accordance with the composition of the thermoplastic and an energy selected in accordance with a wall thickness of the cooled tubing so that waves of said laser beam are scattered, reflected or radiated from said cooled tubing to an extent determined by the molecular orientation thereof, and
by Raman spectrometry detecting, as a measure of the molecular orientation, at least one wave corresponding to a Raman-effect spectral line radiated by said cooled tubing upon impingement of said laser beam thereon;
and
(f) controlling cooling of said tubing in response to the molecular orientation as monitored in step (e).

6 more elements

An apparatus for producing biaxially stretched thermoplastic tubes, comprising:

an extruder extruding a thermoplastic tubing in a viscous state;
a stretching mandrel downstream of said extruder having a cylindrical run-on portion, a conical expanding portion of said mandrel, and a cylindrical draw-off portion of said mandrel along which said viscous tubing is drawn to biaxially stretch said tubing;
a temperature control bath contacting said tubing at said run-on portion of said mandrel to being said tubing to a stretching temperature;
a cooling bath contacting said tubing at said draw-off portion for cooling said tubing;
variable-speed draw-off means engaging said tubing for drawing said tubing off said draw-off portion of said mandrel;
Raman spectrometer means downstream of the cooling bath for monitoring molecular orientation in the cooled tubing by:
directing a laser beam against said cooled tubing of a frequency selected in accordance with the composition of the thermoplastic and an energy selected in accordance with a wall thickness of the cooled tubing so that waves of said laser beam are scattered, reflected or radiated from said cooled tubing to an extent determined by the molecular orientation thereof, and
by Raman spectrometry detecting, as a measure of the molecular orientation, at least one wave corresponding to a Raman-effect spectral line radiated by said cooled tubing upon impingement of said laser beam thereon;
and
means responsive to said Raman spectrometer means for controlling the cooling of said tubing.

7 more elements

A method of operating an apparatus for producing biaxially stretched thermoplastic tubes which includes:

an extruder extruding a thermoplastic tubing in a viscous state;
a stretching mandrel downstream of said extruder having a cylindrical run-on portion, a conical expanding portion of said mandrel, and a cylindrical draw-off portion of said mandrel along which said viscous tubing is drawn to biaxially stretch said tubing;
a temperature control bath contacting said tubing at said run-on portion of said mandrel to bring said tubing to a stretching temperature;
a cooling bath contacting said tubing at said draw-off portion for cooling said tubing;
and
variable-speed draw-off means engaging said tubing for drawing said tubing off said draw-off portion of said mandrel;
said method comprising:
downstream of the cooling bath monitoring molecular orientation in the cooled tubing by:
directing a laser beam against said cooled tubing of a frequency selected in accordance with the composition of the thermoplastic and an energy selected in accordance with a wall thickness of the cooled tubing so that waves of said laser beam are scattered, reflected or radiated from said cooled tubing to an extent determined by the molecular orientation thereof, and
by Raman spectrometry detecting, as a measure of the molecular orientation, at least one wave corresponding to a Raman-effect spectral line radiated by said cooled tubing upon impingement of said laser beam thereon, and
controlling at least one of the parameters:
temperature of said mandrel,
temperature of said temperature control bath,
temperature of said cooling bath,
rate of extrusion of said viscous tubing, and
draw-off speed of said tubing from said mandrel,
in accordance with said measure of molecular orientation.

14 more elements

Dependencies are inferred from the claim text.

Method of operating an apparatus for the production of biaxially stretched plastic tubes

Life of this patent

Method of operating an apparatus for the production of biaxially stretched plastic tubes

Life of this patent

Abstract

Claims20