GB1597769A

GB1597769A - Method for extrusion of highly viscous thermosetting or thermoplastic material

Info

Publication number: GB1597769A
Application number: GB21560/78A
Authority: GB
Original assignee: MOSKOV KHIM TEKHNOLOG INST IM
Current assignee: MOSKOV KHIM TEKHNOLOG INST IM
Priority date: 1978-05-23
Filing date: 1978-05-23
Publication date: 1981-09-09

Description

(54) METHOD FOR EXTRUSION OF HIGHLY VISCOUS THERMOSETTING OR THERMOPLASTIC MATERIAL (71) We, MOSKOVSKY Khimiko Tekhnologichesky Institutimeni D.I.

Mendeleeva, 9 ploschad Miusskaya, Moscow, Uion of the Soviet Socialist Republics (U.S.S.R) a State Enterprise organised and existing under the laws of U.S.S.R. do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particuarly described in and by the following statement: The present invention relates to processing of polymer materials and, more specifically, it relates to processes for extrusion of a highly viscous thermosetting or a thermoplastic material.

Processing of a polymer material by the extrusion method stipulates production of either final articles or granules suitable for a further processing. This method involves melting of the material and forcing of the melt through a die. The use of polymer material in the granulated form has certain advantages. Granules enable accurate metering due to a good flowability; they also contribute to better labour conditions due to substantially reduced dusting of production premises.

At the present time granulation of thermosetting composite materials is great technical problem, despite the availability of methods for the manufacture of thermosetting granulated materials.

The method for extrusion of a thermosetting or a thermoplastic material according to the present invention comprises the extrusion of a melt of said material in the presence of substances which reduce the surface friction of the melt, to give a ratio of internal friction to surface friction values of the melt within the range of from 1.5 to 4.0 at extrudate flow rate of 20 to 300 mlmin; whilst maintaining the melt viscosity of the thermosetting material within the range of from 50 x 106 to 300 x 106 poises and the melt index of the thermoplastics material within the range of from 0.01 to 0.1 g/10 minutes.

The above method makes it possible to produce, from thermosetting materials, granules capable of being processed into artices by various conventional techniques.

The resulting articles from this granulated material have high physico-mechanical and dielectric properties.

The above method also makes it possible to manufacture, from thermoplastics materials, various shaped articles such as pipes, sheets at an increased extrusion speed whilst retaining a good quality surface.

As it has been already mentioned hereinabove, the ratio between internal and surface friction values of the melt should be within the range of from 1.5 to 4.0.

Lowering this ratio below 1.5 will result in an impaired surface quality of the extrudate due to an increased adherence of the melt to the material of the extrusion equipment.

Increasing said ratio above 4.0 necessitates the use of the very high pressures in the extrusion, i.e. forces required to push the material through the forming die. This ratio is decisive, since it allows the process to be conducted under the conditions such that melt surface slides along the inner working surfaces of the extrusion equipment.

Movement of the material in the extruder and in the forming die in this case occurs in the form of non-strained plug-flow which means that the velocity of the material movement in the region adjacent to the inner working surfaces of the extrusion equipment and the velocity of the material within its bulk are approaching each other or equal. This condition enables extrusion of said materials to be performed at increased speeds ranging from 20 to 300 m/min; moveover, at a speed below 20 m/min melt surface/wall sliding conditions cannot be ensured.

Viscosity of the initial thermosetting material should be within the range of from 50x 106 to 300x 106 poises. This viscosity range should be kept so as to maintain the above-mentioned ratio of internal to surface friction values of the melt within the specified range.

The melt index of the initial thermoplastics material should be from 0.01 to 0.1 g/10 min. This is also necessary to maintain said ratio of internal to surface friction values of the melt within the range specified hereinabove. The term "melt index" as used herein and in the claims means a mass of the polymer (grams) extruded via a standard viscometer capillary at a temperature of 190"C under a load of 2.16 kgf over a period of 10 minutes. Standard dimensions of the capillary are as follows: length 8.000+0.025 mm; diameter 2.095+0.005 mm; inner diameter of the viscometer barrel is 9.54+ 0.016 mm.

Preferably, extrusion of a thermosetting material is performed at a temperature within the range of from 90 to 1100C. At a temperature below 90"C the material is not totally melted, therefore the material is not fully homogenized which hampers the extrusion process. On the other hand, at a temperature above 1 l00C the condensation reaction is accelerated which results in transition of the material into a nonfusible state which makes extrusion impossible.

Extrusion of a thermoplastics material is preferably conducted at a temperature within the range of from 140 to 1700C. At a temperature below 140"C the material has a very high viscosity, therefore its extrusion necessitates the use of high pressures.

Increasing the temperature above 170"C results in violation of the above-mentioned ratio of internal to surface friction values of the material melt.

Preferably also extrusion ot the material is performed with the addition thereinto of a compound which lowers the adhesive interaction of the surface of the melt with the surface of the extrusion equipment in an amount which ensures the above-specified ratio of internal to surface friction of the melt is maintained.

Suitable compounds for this purpose in the extrusion of thermosetting materials may be selected from zinc dialkyldithiophosphate (wherein the alkyl contains 4 to 8 carbon atoms) in an amount of from 0.5 to 2.50/, by weight; a mixture of zinc dialkydithiophosphate and epoxystearic acid 2-ethylhexylate in a ratio of 20--50:8-50 lie by weight) in an amount of from 0.5 to 2.5% by weight; a mixture of zinc dialkyldithiophosphate and polyhydroxypropylene glycol in a ratio of 30--50:700-50 (% by weight) in an amount of from 0.5 to 2.5 by weight.

In extrusion of thermoplastics materials suitable compounds for the same purpose may be selected from: barium sulphonate in an amount of from 0.5 to 2.0 X; by weight and calcium sulphonate in an amount of from 0.5 to 2.0% by weight.

The method for extrusion according to the present invention makes possible the granulation of a thermosetting material without any undesirable premature curing of the resulting granules.

This advantage of the extrusion method according to the present invention can be explained by the fact that the ratio of the present invention between internal and surface friction values substantially eliminates shear deformation of the melt layers relative to each other, therefore there is no considerable heating of the material which usually results in its premature curing. In addition, heat emission associated with external friction of the material melt surface with the surface of the moulding die is also reduced. This makes it possible to increase the extrudate speed of outflow up to 300 m/min and thus substantially increase the process productivity.

The resulting granules have a regular cylindrical shape they do not agglomerate upon storage and can be processed by any conventional method such as injectionmoulding or compression-moulding. The manufacture of granules by the method of the present invention is not accompanied by dusting, therefore the risk of explosion is minimized and labour conditions are improved.

The method according to the present invention makes it possible to perform extrusion of a thermoplastics material, whether containing an extender or not, and also partly cross-linked polymer, e.g. a thermoplastics material which has already been in use. In doing so, the final shaped articles are not substantially apt to undesirable swelling or shape deformation.

This advantage of the extrusion method according to the present invention can be explained by the fact that the ratio between internal and surface friction values of the material melt reduces the role of the shear component of the strain during out flow of the material melt and other normal stresses associated therewith which are responsible for the swelling value of the extrudate.

All this makes it possible to increase the speed of outflow of the extrudate up to 300 m/min while retaining a good quality thereof; this, in turn, provides for a higher productivity of the process with a simultaneous decrease of the processing temperature by 30--500C compared to the temperature employed in conventional extrusion methods thus substantially reducing power consumption for extrusion.

The process according to the present invention is preferably carried out in the following manner.

First the initial viscosity (in the case of a thermosetting material) and melt index (for a thermoplastics material) is measured.

Viscosity of a thermosetting material is determined by means of a rotary viscometer of the "cylinder-cylinder" type at a temperature of 120or and shear velocity of 0.014 sec-' and pressure of 300 kg/cm2.

Viscosity of the melt of the thermosetting material to be extruded must be within the range of 50x 106 to 300x 106 poises.

If the viscosity of the initial material does not lie within said range, it can be adjusted to the required value by mixing the initial material with a material having the same composition but a higher or lower viscosity.

For thermoplastics materials the melt index is determined, which must lie within the range of from 0.01 g/10 min to 0.1 g/10 min.

If the melt index of the initial polymer exceeds 0.1 g/10 min, it is adjusted by adding a filler or by additional cross-linking by either chemical or physical methods.

After determining the above values, the ratio of the internal friction of the melt is determined on a rotary viscometer of the "cylinder-cylinder" type with the use of a ribbed (internal friction) and smooth (surface friction) rotating barrels. This ratio is determined by the ratio between torque values of the ribbed and smooth barrels at 50 r.p.m. and at a temperature of 1200C for thermosetting plastics and 160"C for thermoplastics materials. Said ratio between internal and surface friction values should be within the range of from 1.5 to 4.0. If a material has this friction ratio, it is directly fed to extrusion; if a material does not satisfy this requirement, the required value of said ratio is ensured by way of addition. into the thermosetting material, of compounds which reduce adherence of its melt to the extrusion equipment surface. In the case of extrusion of thermosetting material zinc dialkyldithiophosphate is added in an amount ; from 0.5 to 2.5% by weight or a mixture of zinc dialkyldithiophosphate with epoxystearic acid 2-ethylhexylate is added in a ratio of 20--50:800-50 ("b by weight) in an amount of from 0.5 to 2.5% by weight or a mixture of zinc dialkyldithiophosphate with polyhydroxypropylene glycol is added in a ratio of 350:750 (% by weight) in an amount of from 0.5 to 2.5% by weight.

In extrusion of thermoplastic materials, barium sulphonate is added in an amount of from 0.5 to 2.0% by weight or calcium sulphonate is added in an amount of from 0.5 to 2.0% by weight.

The amount of the compound to be added is selected in accordance with viscosity or melt index of the material melt.

Said compounds may be added into the material either in the process of its preparation, or directly prior to its extrusion.

All the above-mentioned compounds are known in the art. Zinc dialkyldithiophosphate, barium and calcium sulphonates are available from petrochemical synthesis.

Polyhydroxypropylene glycol is prepared by polymerization of hydroxypropylene glycol, while epoxystearic acid 2-ethylhexylate is prepared by epoxydation of an etherification product of oleic acid and 2ethylhexanol.

After addition of the above-mentioned compound, the ratio between internal and external friction values is controlled by means of a rotary viscometer of the abovespecified "cylinder-cylinder" type within the range of from 1.5 to 4.0 in accordance with the present invention.

Extrusion can be performed both in a piston and a screw extruder.Extrusion of a thermosetting material is conducted at a temperature within the range of from 90 to 110"C, while extrusion of a thermoplastics material is conducted at a temperature of from 140 to 1700C at a speed of the extrudate outflow of from 20 to 300 m/min.

The present invention will now be illustrated by way of Example. In these Examples use is made of zinc dialkyldithiophosphate wherein the alkyl group contains from 4 to 8 carbon atoms.

Example 1 A thermosetting material consisting of a novolac type phenol-formaldehyde resin 42.8% by weight, hexamethylene tetramine 6.5% by weight, lime 0.9% by weight, stearine 0.7% by weight, china clay 4.4% by weight, nigrozin 1.5% by weight and sawdust 43.2% by weight, which material is prepared by rolling or screw plastication, is tested for viscosity in a rotary viscometer of the "cylinder-cylinder" type at a temperature of 1200C and shear rate of 0.014 sec~l. This viscosity is 300 x 106 poises.

Then, using the same instrument, there is determined the ratio of internal to surface friction values of the melt. It is equal to 1.36. From the value of viscosity of the starting material the amount of a lubricating compound is defined to ensure the required ratio between internal and surface friction values. This amount is 2.0% by weight. Then 2.0% by weight of zinc dialkyldithiophosphate is mixed with the thermosetting material in a vane-type mixer so that the ratio of internal to surface friction values is adjusted to 3.7. Then the thus-prepared material is granulated in a screw extruder at a forming die temperature of 105"C. The material is extruded through the die in the form of a strand at the speed of 20 m/min and then cut by means of rotating blades to granules with a diameter of 3 mm and length of 3-4 mm.

Substantially no dust fraction is formed therewith. The material is not cured during the granulation which is evidenced by a constant amount of the fraction extracted with acetone prior to granulation (49.6%) and after granulation (49.6%). The granules do not agglomerate upon storage.

Example 2 A thermosetting material is prepared by mixing 58.6% by weight of urea in the form of its mono- and dimethylol derivatives, 41.0% by weight of sulphite cellulose, 0.4% by weight of zinc stearate. Viscosity and the ratio between internal and surface friction values of the melt are measured in accordance with the procedure described in the foregoing Example 1. These parameters are respectively 250x 106 poises and 1.2.

Thereafter 1.8% by weight of a lubricating mixture consisting of 30% by weight of zinc dialkyldithiophosphate and 70% by weight of polyhydroxypropylene glycol and the mixture is blended into the thermosetting material in a vane-type mixer for 30 minutes. So that the ratio of frictions is adjusted to 2.8; at this ratio the material is extruded in a piston extruder at the temperature of the forming die of 95--100"C. The material is forced through the die in the form of a strand and cut into granules with a diameter of 3 mm and length 34 mm; the extrudate flow rate is 180 m/min. No dusting or premature curing of the material is observed. Granules do not agglomerate upon storage.

Example 3 Into a thermosetting material similar to that described in the foregoing Example 1 there are added 1.5% by weight of a mixture of 20% of zinc dialkyldithiophosphate and 80% by weight of 2 ethylhexylepoxystearate; then the viscosity and friction ratio are measured; these values are equal respectively to 50x loe poises and 1.5. Then the material is extruded following the procedure of Example 1. The extrudate outflow rate is 20 m/min. No dusting or premature curing of the material is observed during granulation.

Granules do not agglomerate upon storage.

Example 4 A thermosetting material similar to that described in the foregoing Example I is tested for viscosity and ratio between internal and surface frictions following the procedure of Example 1. Viscosity is 180 x 106 poises; friction ratio is 1.30. Then 2% of a mixture of zinc dialkyldithiophosphate (40% by weight) and polyhydroxypropylene glycol (60% by weight) is added to the thermosetting material to achieve the required ratio between the internal and surface friction values; then the mass is intermixed. The friction ratio is adjusted to 4.0. Further extrusion and cutting of the extrudate to lengths are performed following the procedure of Example 1 hereinbefore. The extrudate flow-rate speed is 25 m/min. Dusting and premature curing of the material are not observed. Granules do not agglomerate upon storage.

Example 5 A thermosetting material with the composition described in the foregoing Example 1 is tested for viscosity and ratio between internal and surface friction values following the procedure of Example 1.

Viscosity is 250x 106 poises, friction ratio is 1.5. Then zinc dialkyldithiophosphate in an amount of 2.5% by weight is added and the mass is intermixed in a ball mill for 30 minutes, so that the friction ratio is adjusted to 3.65. Thereafter the resulting material is extruded and granulated in a manner similar to that described in the foregoing Example 2 at the extrudate flow-rate of 240 m/min. No dusting or premature curing of the material is observed. Granules do not agglomerate upon storage.

Example 6 A thermosetting material with the composition described in the foregoing Example 2 is tested for viscosity and friction ratio as in Example 1 hereinbefore.

Viscosity is 120x 106 poises; friction ratio 1.1. Then 1.2% by weight of zinc dialkyldithiophosphate is added and the mass is blended. Thus the friction ratio is adjusted to 2.2. Then the thus-prepared material is extruded at the temperature of 90"C and granulated in a manner similar to that described in Example 2 at the extrudate flow-rate of 120 m/min. No dusting or premature curing of the material is observed.

Example 7 A thermosetting material comprising 58.6% by weight of urea in the form of mono- and dimethylol derivatives 41.0% by weight of sulphite cellulose, 0.4% by weight of zinc stearate, 0.4% by weight of zinc dialkyldithiophosphate and 1.1% by weight of polyoxyproylene glycol is first assayed as to its viscosity, then the ratio of the internal and surface friction of its melt is measured by following the procedure similar to that described in Example 1.

The above characteristics are 175x 106 poises and 1.7 respectively.

Since the thermosetting material meets the requirements of the herein proposed method, said material is directly extruded by following the procedure described in Example 2 at temperature of 95"C and extrudate flow-rate of 170 m/min, and granulated.

No dusting or premature curing of the material is observed. The granulate does not agglomerate into lumps on storage.

Example 8 Into a thermoplastics material consisting of 70% by weight of polyethylene and 30% by weight of sawdust and having a melt index value of 0.08 g/10 min and ratio between internal and surface friction of the melt at a temperature of 1600C of 1.14 is added 0.5% by weight of barium sulphonate to increase the friction ratio. After incorporation of barium sulphonate this ratio is increased to 1.75 and with this ratio extrusion of said composition is performed in a piston extruder at the temperature of 1600C. The extrudate flow-rate is 125 m/min; the extrudate is obtained in the shape of cylindrical strands having a smooth surface.

Example 9 Into a thermoplastic material consisting of 75% by weight of polyethylene and 25% by weight of sawdust and having a melt index of 0.07 g/l0 min and ratio between internal and surface friction values of the material melt of 1.4 at a temperature of 1600C is added calcium sulphonate in amount of 1% by weight to increase the above-mentioned friction ratio. After incorporation of calcium sulphonate this ratio is increased to 2.7. At this ratio extrusion of said composition is performed following the procedure of Example 7. The extrudate flowrate is 150 m/min. The extrudate is obtained in the shape of cylindrical strands having a smooth surface.

Example 10 A composition containing polyethylene partly cross linked by a chemical or physical method with a gel-fraction content of 58% by weight, and barium sulphonate in an amount of 1 Go by weight with a melt index of 0.09 g/10 min and a ratio between internal and surface friction values equal to 3 is extruded in a piston extruder provided with pipe-forming die at the temperature of 140"C. The extrudate flow rate is 80 m/min.

The extrudate shape is tubular; the thusmanufactured pipes have a smooth surface.

Example 11 A composition containing 49% of polypropylene, 50% by weight of synthetic silica and 1% by weight of calcium sulphonate with a melt index of 0.05 g/10 min and a ratio between internal and surface friction values of 3.2 is extruded in a piston extruder at a temperature of 170"C.

The extrudate flow-rate in the form of a strand is 240 m/min. The thus-produced strands have a smooth surface.

Example 12 A composition consisting of 58% by weight of polyethylene, 40% by weight of sawdust and 2% by weight of barium sulphonate with a melt index of 0.01 gllO min and a ratio between internal and surface friction values of 4.0 is extruded.

The extrusion is performed in a piston extruder at a temperature of 160"C. The extrudate flow-rate is 180 m/min. The extrudate has a hexagonal shape and a smodth surface.

Example 13 A composition containing 66% by weight of polyvinylchloride, 15% by weight of aerosil, 6% by weight of shellac, 12% by weight of synthetic rubber and 1% by weight of calcium sulphonate having a melt index of 0.1 g/10 min and a ratio between internal and surface friction values of the melt thereof of 1.8 is extruded in a piston extruder at a temperature of 140"C. The extrudate flow-rate in the shape of a pipe is 20 m/min. The thus-produced extrudate has a smooth surface.

WHAT WE CLAIM IS: 1. A method for the extrusion of a highly viscous thermosetting or a thermoplastics material comprising extrusion of a melt of said material in the presence of substances which reduce the surface friction of the melt to give a ratio of internal friction to surface friction values of the melt within the range of from 1.5 to 4.0 and at an extrudate flow-rate of 20 to 300 m/min. whilst maintaining the melt viscosity of the thermosetting material within the range of from 50x 106 to 300x 106 poises and the melt index of the thermoplastics material within the range of from 0.1 to 0.01 g/10 min. wherein the 'ratio of internal friction to surface friction' and 'melt index' have the meaning defined in the specification hereinbefore.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. mono- and dimethylol derivatives 41.0% by weight of sulphite cellulose, 0.4% by weight of zinc stearate, 0.4% by weight of zinc dialkyldithiophosphate and 1.1% by weight of polyoxyproylene glycol is first assayed as to its viscosity, then the ratio of the internal and surface friction of its melt is measured by following the procedure similar to that described in Example 1. The above characteristics are 175x 106 poises and 1.7 respectively. Since the thermosetting material meets the requirements of the herein proposed method, said material is directly extruded by following the procedure described in Example 2 at temperature of 95"C and extrudate flow-rate of 170 m/min, and granulated. No dusting or premature curing of the material is observed. The granulate does not agglomerate into lumps on storage. Example 8 Into a thermoplastics material consisting of 70% by weight of polyethylene and 30% by weight of sawdust and having a melt index value of 0.08 g/10 min and ratio between internal and surface friction of the melt at a temperature of 1600C of 1.14 is added 0.5% by weight of barium sulphonate to increase the friction ratio. After incorporation of barium sulphonate this ratio is increased to 1.75 and with this ratio extrusion of said composition is performed in a piston extruder at the temperature of 1600C. The extrudate flow-rate is 125 m/min; the extrudate is obtained in the shape of cylindrical strands having a smooth surface. Example 9 Into a thermoplastic material consisting of 75% by weight of polyethylene and 25% by weight of sawdust and having a melt index of 0.07 g/l0 min and ratio between internal and surface friction values of the material melt of 1.4 at a temperature of 1600C is added calcium sulphonate in amount of 1% by weight to increase the above-mentioned friction ratio. After incorporation of calcium sulphonate this ratio is increased to 2.7. At this ratio extrusion of said composition is performed following the procedure of Example 7. The extrudate flowrate is 150 m/min. The extrudate is obtained in the shape of cylindrical strands having a smooth surface. Example 10 A composition containing polyethylene partly cross linked by a chemical or physical method with a gel-fraction content of 58% by weight, and barium sulphonate in an amount of 1 Go by weight with a melt index of 0.09 g/10 min and a ratio between internal and surface friction values equal to 3 is extruded in a piston extruder provided with pipe-forming die at the temperature of 140"C. The extrudate flow rate is 80 m/min. The extrudate shape is tubular; the thusmanufactured pipes have a smooth surface. Example 11 A composition containing 49% of polypropylene, 50% by weight of synthetic silica and 1% by weight of calcium sulphonate with a melt index of 0.05 g/10 min and a ratio between internal and surface friction values of 3.2 is extruded in a piston extruder at a temperature of 170"C. The extrudate flow-rate in the form of a strand is 240 m/min. The thus-produced strands have a smooth surface. Example 12 A composition consisting of 58% by weight of polyethylene, 40% by weight of sawdust and 2% by weight of barium sulphonate with a melt index of 0.01 gllO min and a ratio between internal and surface friction values of 4.0 is extruded. The extrusion is performed in a piston extruder at a temperature of 160"C. The extrudate flow-rate is 180 m/min. The extrudate has a hexagonal shape and a smodth surface. Example 13 A composition containing 66% by weight of polyvinylchloride, 15% by weight of aerosil, 6% by weight of shellac, 12% by weight of synthetic rubber and 1% by weight of calcium sulphonate having a melt index of 0.1 g/10 min and a ratio between internal and surface friction values of the melt thereof of 1.8 is extruded in a piston extruder at a temperature of 140"C. The extrudate flow-rate in the shape of a pipe is 20 m/min. The thus-produced extrudate has a smooth surface. WHAT WE CLAIM IS:

1. A method for the extrusion of a highly viscous thermosetting or a thermoplastics material comprising extrusion of a melt of said material in the presence of substances which reduce the surface friction of the melt to give a ratio of internal friction to surface friction values of the melt within the range of from 1.5 to 4.0 and at an extrudate flow-rate of 20 to 300 m/min. whilst maintaining the melt viscosity of the thermosetting material within the range of from 50x 106 to 300x 106 poises and the melt index of the thermoplastics material within the range of from 0.1 to 0.01 g/10 min. wherein the 'ratio of internal friction to surface friction' and 'melt index' have the meaning defined in the specification hereinbefore.

2. A method according to claim 1,

wherein extrusion of a thermosetting material is performed with an addition thereinto of zinc dialkydithiophosphate in an amount of from 0.5 to 2.5% by weight.

3. A method according to claim 1, wherein extrusion of a thermosetting material is conducted with an addition thereinto of a mixture of zinc dialkydithiophosphate and epoxystearic acid 2-ethylhexylate in a ratio of from 2050 to 8050 (% by weight) and in an amount of from 0.5 to 2.5% by weight.

4. A method according to claim 1 wherein extrusion of a thermosetting material is conducted with an addition thereinto of a mixture of zinc dialkyldiothiophosphate and polyhydroxypropylene glycol in a ratio of from 30-50 to 70-50 (% by weight) in an amount of from 0.5 to 2.5% by weight.

5. A method according to Claim 1, wherein extrusion of a thermoplastic material is performed with an addition thereinto of barium sulphonate in an amount of from 0.5 to 2.0% by weight.

6. A method according to Claim 1, wherein extrusion of a thermoplastics material is conducted with an addition thereinto of calcium sulphonate in an amount of from 0.5 to 2.0% by weight.

7. A method according to Claim 1, wherein extrusion of a thermosetting material is conducted at a temperature within the range of from 90 to 1100C.

8. A method according to Claim 1, wherein extrusion of a thermoplastic material is conducted at a temperature within the range of from 140 to 1700C.

9. A method of extruding a thermosetting material substantially as described in the foregoing Examples 1 to 7.

10. A method of extruding a thermoplastics material substantially as described in the foregoing Examples 8 to 13.