IE41985B1 - Heat treatment of a web containing fibres of thermoplastic material - Google Patents

Abstract

A method of, and apparatus for, consolidating and surface finishing a web of intermeshed fibres. At least a proportion of the fibers are of a synthetic thermoplastic material. The method comprises heating the web to a temperature above the softening point of the synthetic thermoplastic material. Subsequently cooling the web from a temperature above the softening point of the synthetic thermoplastic material to a temperature below the softening point of the synthetic thermoplastic material while the web is in contact with a forming surface. The finish of the forming surface is imparted to the surface of the web during cooling. The web is supported throughout the time it is above the softening point of the synthetic thermoplastic material. The apparatus comprises means for supporting the web and for heating the web while so supported to a temperature above the softening point of the synthetic thermoplastic material. Means for cooling the web from a temperature above the softening point of the synthetic thermoplastic material to a temperature below the softening point of the synthetic thermoplastic material while the web is supported on a forming surface having a surface finish. The surface finish is imparted to the surface of the web. The invention permits the production of a partially or wholly consolidated sheet. Further consolidation is carried out by heat rather than pressure.

Description

This invention relates to a method and apparatus for heat treatment of a paper web containing fibres of thermoplastic material. · Paper webs have traditionally been formed from cellulose fibres derived from various materials of vegetable origin, for example woodpulp. More recently, proposals have been made for the production of so-called synthetic wood pulp fibres from various polymers.

Such fibres have a gross morphology, e.g. length:diameter ratio, and diameter of the same order oi magnitude as cellulose papermaking fibres derived from woodpulp.

They are distinguished from most synthetic textile fibres by their gross morphology and diameter.

The use of synthetic fibres in papermaking affords the possibility of producing webs with novel properties.

One such possibility, provided the synthetic fibres are of a thermoplastic material, is that of heat treatment to soften the fibres, and thereby to produce a partially or wholly consolidated sheet.

It is an object of the invention to provide an improved method and apparatus for heat treatment of a paper web substantially all the fibres of which are of a synthetic thermoplastic material.

According to a first aspect of the invention, there is provided a method of continuously consolidating and surface finishing a paper web substantially all the fibres of which are of a synthetic thermoplastic material, comprising, the steps of heating the web to a temperature above the softening point of the synthetic thermoplastic material, the web being supported through the time it is above the softening point of the thermoplastic material, and subsequently cooling the web from a temperature above the softening point of the synthetic thermoplastic material to a temperature below the softening point of the synthetic thermoplastic material while the web is in contact with a forming surface, so that the finish of the forming surface is imparted to the surface of the web without subjecting the web to substantial pressure during the time it is so supported.

According to a second aspect of the invention there is provided apparatus for continuously consolidating and surface finishing a paper web substantially all the fibres of which are of a synthetic thermoplastic material, comprising means for heating the web to a temperature above the softening point of the synthetic thermoplastic material one surface only of the web being heated by contact with the surface of a heating member, and means for cooling the web from a temperature above the softening point of the synthetic thermoplastic material to a temperature below the softening point of the synthetic thermoplastic material and means for supporting the web throughout the time it is above the softening point, the supporting means including a forming surface having a surface finish which supports the web while it is above and then below its softening point temperature in such a manner that in use the finish of the forming surface is imparted to the surface of the web without subjecting the web to substantial pressure during the tims it is so supported.

It will be appreciated that the present method and apparatus consolidate the web by the action of heat rather than pressure, as it is discussed more fully hereinafter.

Preferably, the web is heated by passage round part of the circumference of a heating roll. The roll may be heated for example by hot oil or steam, · but the former is preferred as steam presents more problems of pressure sealing.

Preferably, the web is cooled by passage round part of the circumference of a cooling roll, the surface of which constitutes said forming surface.

The cooling roll is at a temperature helow the softening point of the thermoplastic material of which the fibres are made, but may be still considerably in excess of ambient temperature, or it may be at or below ambient temperature. If the cooling roll is to be chilled, air or cold water may be used. The choice of temperature for the cooling roll depends largely on the nature of the web and on process parameters, as will be discussed more fully hereafter.

The cooling roll finish, which is imparted to the web, may take various forms. For example, it may be a high gloss finish, a matt finish, obtained for example by shot-blasting, or an engraved finish.

Advantageously, the web is transferred from the heating roll to the cooling roll by means of a transfer roll running in contact with both the heating and cooling rolls. The transfer roll has a resilient covering, for example of rubber, so. that in passing between a nip formed by the transfer and cooling rolls, the roll will not be subjected to heavy pressure which prevents the achievement of the desired web properties. Although the resilient surface of the transfer roll gently presses the web against the surface of the cooling · roll, the pressure is much less than that used in conventional hot pressing processes. As a result of the gentle pressing of the web against the surface of the cooling roll, imparting of the surface finish of the cooling roll to the web is facilitated. The way in which the surface finish is imparted to the web is analogous to a casting process, in that the softened thermoplastic material flows and thereby accurately adopts the finish of the supporting surface.

Once the web has been heated to a temperature above the softening point of the thermoplastic material of which the fibres are made, the web has little coherence. Consequently, it is necessary for the web to be supported until it is again at a temperature some way below the softening point. If the web were unsupported when above or very near the softening point, it would be likely to break, stretch or be otherwise deformed.

The coherence of the softened web depends to some extent on the extent of consolidation required in the finished web.

The type of support which will suffice will be readily apparent to the skilled worker in the art.

A further consequence of the lack of coherence of the softened web is that if· the web is to be transferred from one support member to another while in a soft state, the support member from which the web is being transferred must be treated to facilitate release of the web. Desirably this is achieved by means of a release coating, preferably of polytetra10 fluoroethylene. A problem associated with release coatings is that they cannot have a high gloss finish or an engraved finish, so far as is known at present. Hence in order to achieve such a finish, the web must be transferred while still soft to a supporting surface having the desired finish, and on which the web is cooled to a temperature at which it has the coherence necessary to be drawn off the supporting surface without breaking. It might be thought that a fairly high gloss release coating could be achieved by the use of a release sleeve of the kind Sometimes used for drying cylinders on papermaking or papercoating machines. It has been found however that such a sleeve is not satisfactory on a heating roll which has to co-operate with another roil, as the sleeve is damaged by the other roll.

Advantageously, the web is pre-heated to a temperature below the softening point of the synthetic thermoplastic material before being heated in a separate heating stage to said temperature above the melting point ol the synthetic thermoplastic material. Pre-heating may for example be by means ol inra-red > heaters or preferably by hot air heating. Pre-heating has the effect of reducing the temperature gradient through the web when the web is being heated to a temperature above the softoning point of the thermoplastic material.

Although the present invention preferably employs heating, transfer and cooling rolls, the web may alternatively be heated and cooled while on the surface of either an endless belt or a single roll. Heating may for example be by means of infra-red heaters or hot air. Cooling may be by cold air, or may be unforced if this affords an adequate rate of heat loss. An endless belt or single roll is satisfactory if it is desired for long periods to make a web having a particular surface finish. However, if a variety of surface finishes are to be applied, the three roll system is preferred, since only the cooling roll need be changed.

In order to enable the invention to be more readily understood, reference will now be made to the accompanying drawings, which illustrate diagrammatically and by way of example some embodiments thereof, and in which :Fig. 1 is a schematic side view of a first embodiment of part of a consolidating apparatus Fig. 2 is a schematic side view of an embodiment of a consolidating apparatus of which part is shown in Fig. 1; Fig. 3 is a partially sectioned partially cut-away view of a heating roll forming part of the apparatus ’ shown in Figs. 1 and 2; Fig. 4 is a flow diagram of a heating Circuit for the heating roil shown in Fig. 3; Fig. 5 is a schematic side, view of a second embodiment of part of a consolidating apparatus corresponding to the part shown in Fig. 1; and Fig. 6 is a schematic side view of a third embodiment of part shown in Figs. 1 and 5.

Referring first to Fig, 1, part of a heat consolidating apparatus comprises a heating roll 1 having a release coating 2. The release coating is preferably of polytetrafluoroethylene, but may alternatively be of a silicone material or a ceramic material. A rubber covered feed roll 8 is mounted to co—operate with the roll 1 to form a low pressure guiding nip 9 into which a web 10 to be consolidated is fed. The roll 8 need not be positioned so as to define a nip with the roll 1, It may instead be spaced from the roll 1, provided it serves satisfactorily to guide the web on to the surface of the roll 1. The rubber covering on the roll 8 and on other rolls to be described subsequently is shown in this and in other Figures to be described subsequently by hatching around the periphery of the roll. A rubber covered transfer roll 5 is also mounted to co-operate with the roll 1 so as to define a nip 6.

The ϊόΙΙ 5 is positioned such that the web 10 passes round a major proportion of the circumference of the roll 1 before being transferred.

A cooling roll 3 is mounted to co-operate with the transfer roll 5, so as to define a nip 7 into which the web 10 is fed. Further rolls (not shown) are provided to guide the web from the roll 3 after it has passed round slightly more than half the circumference of the roll 3. The surface 4 of the roll 3 is selected in accordance with the surface characteristics it is desired to impart to the roll. Means (not shown) are provided to pre-heat the web before it reaches the feed roll 8 and heating roll 1. The rolls 1 and 3 are arranged to be positively driven by means (not shown) to maintain tension in the web.

In a modification of the apparatus shown in Fig, 1, the roll 5 is omitted and the roll 3 co-operates with the roll 1. In use, the web 10 is then transferred from the roll 1 to the roll 3..

Referring now to Fig. 2, there is shown a complete consolidating apparatus including the rolls 1, 3, 5 and 8 just described with reference to Fig. 1. The web 10 is also shown. There is also shown an unwind reel 11 on a stand 11 a, a pre-heating tunnel generally designated 12, a frame 13 supporting the tunnel 12 and in which the rolls 1, 3, 5 and 8 are journalled (the journals not being shown), and a conventional type of reel-up assembly comprising a rubber-covered roll 14, and a reel 15 supported on an arm 16 arranged to pivot at 17. The equipment ior controlling pivotal movement οϊ the arm 16 and for driving the reel-up assembly is not shown, for the sake of clarity.

The pre-heating tunnel 12 is divided by a horizontal partition 18 into upper and lower ducts 19 and 20 respectively. A vertical partition 21 depending from the partition 18 defines a vertical duct 22 which connects the ducts 19 and 20. An inlet port 24 is provided for introducing hot air into the duct 19. An outlet port 23 is provided for exhaust air. Six guide rolls 25 are disposed in the duct 20, so as to define a roughly arcuate path for passage of the web 10 through the tunnel. The web 10 enters and leaves the tunnel through slots (not shown) in the base of the tunnel. A duct floor 34 the shape of which generally conforms to the web path is disposed above the rolls 25* Respective elongate nozzles 35 are directed at the rolls 25.

Rolls 26, 27 and 28 are provided for guiding the web 10 from the reel 11 to the tunnel 12. The rolls 26 and 27 are guide rolls and are journalled in parts of the frame 13 which are not shown for the sake of clarity. The roll 28 is a skew roll positioned in a stand 29 and its position in the stand 29 is controllable in conventional manner by a hand wheel 30 to ensure that the web tension is even across the width of the web. The degree of tension in the web is controlled by conventional means (not shown), for example a pneumatic 419 8 5 or electrical controller, associated with the reel 11' and the roll 27.

Guide rolls 31, 32 and 33 are provided ior . guiding the web 10 from the roll 3 to the reel-up assembly already described. During this stage, the web is cooled to around ambient temperature.

In use of the apparatus shown in Figs. 1 and 2, the web 10 is unwound from the reel li and the web tension is suitably adjusted. The web is then pre-heated in the tunnel 12, as it passes over the guide rolls 25. Heating is by means of hot air passing through the inlet port 24, along the duct 20, through the nozzle 35 so as to impinge on the web, up the duct 22, back along the duct 19 and out through the port 23.

The pre-heated web then passes out of the tunnel 12 and round the feed roll 8 on to the heating roll 1 through the nip 9. The heating roll is heated internally by means of hot oil circulation. After passage round the roll 1, the temperature of the web is above the softening point of the synthetic fibres in the web. The softened web is then transferred to the roll 5, transfer being facilitated by the release coating on the roll 1. While on the roll 5, the web cools slightly, before passing into the nip 7 between the rolls 5 and 3.

The rubber coating on the roll 5 prevents the web being subjected to substantial pressure in the nips 6 and 7, and ensures that such pressure as there is is oven across the width of the web, It will be appreciated that the nip pressure produced by the rubber coating is much less than would be produced by a steel transfer roll. Whereas a steel roll would be in substantially linear contact with the roll 3, the rubber coating deforms so as to wrap around the roll slightly, so that the force in the nip is spread oyer a large area, i.e. there is a lower nip pressure. As discussed previously, it is important to avoid high pressure on the web, since it prevents the resultant product having the desired properties, Although the roll 3 is referred to as a cooling roll, it must be emphasised that the expression cooling is used in relation to the temperature of the web arriving at the roll. The cooling roll may still be very hot compared with ambient temperature, but still he cooler than the web. Alternatively, the cooling roll may be maintained at or below ambient temperatures, e.g. by air or water cooling. The temperatures chosen for the rolls 1 and 3 will he discussed more fully hereafter.

On the first part of the cooling roll, the web is still soft. This is important, since the surface of the web in contact with the roll 3 can then flow such that the surface finish of the roll is cast on to the surface of the web in contact with the roll.

The surface finish may for example be a high gloss finish, a matt finish, or an engraved finish.

The gentle pressing action of the rubber covered roll 5 in the nip 7 assists the softened web material to'flow into close contact with the roll 3, whereby the finish of the roll 3 is cast on to the web.

By the time the web leaves the cooling roll, it has cooled to an extent such that it has sufficient coherence to be unsupported. The coherence is such that there is no need for a release coating on the roll 3, which as discussed previously would prevent the casting of a high gloss or engraved finish on to the web.

On leaving the roll 3, the web passes over guide rolls 31, 32 and 33 to the reel-up assembly 14, 15, 16, The temperatures chosen for the rolls 1 and 3 depend on the web speed and substance, the diameters of the rolls, the proportion of the circumference of the rolls contacted by the web, the extent of pre-heating, and the surface and other characteristics required in the finished product, The heat supplied to the web by the time it leaves the roll 1 should be such that the web is at a temperature slightly above the softening point of the thermoplastic material of which the synthetic fibres are made. This normally requires the roll to be considerably hotter than the final web temperature desired. A high roll temperature is needed for a fast web speed, for a small roll diameter, and for a small proportion of roll surface in contact with the web. A lower roll temperature will suffice if pre-heating is increased or web substance decreased. ο By way of example, for a 75 g/m web made wholly of polyethylene fibres and travelling at 50 ft/min, with an 8-inch diameter roll, 270° of the circumference of which is in contact with the web, a web temperature of 180°C is suitable.

The web should cool after leaving the roll 1 and while on the roll 3 to a temperature below the softening point of the thermoplastic material. The rate of heat loss required for this depends partly on the substance of the Web and partly on the web speed.

If cooling is too fast, the web may not have time before solidifying to adopt closely the finish of the cooling roll. For a low substance web running at low speed, the cooling roll must be fairly hot if over-cooling is not to occur. For a high substance web running at high speed, the rate of heat loss.must be greater, and hence the cooling roll must be cooler.

In certain cases, the roll 3 may not need to be heated at all. By way of example, for the web described in the preceding paragraph, and which has been heated as described in the preceding paragraph, the cooling roll temperature can be in the range 90 to 120°C, depending to some extent on the surface finish which it is desired to impart to the web.

The construction of the heating roll is important.

An oil filled roll arranged to be heated by electric immersion heaters may be used. However, it is normally necessary to strengthen such a roll by internal radial metal webbing. This may lead to two disadvantages. Firstly, the webbing, being of metal, has a better heat conductivity than the oil, and hence hot spots are produced on the surface of the roll opposite the points of contact of the webbing and the roll cylinder. Secondly, the webbing may expand and lead to the formation of bumps on the roll surface. It has therefore been found desirable to use a roll construction as will now be described with reference to Fig. 3.

The roll, generally designated 1, comprises a cylinder 40 fitted with end caps 41 and 42. Within the roll 1 is a closed inner drum 43. The roll 1 and the drum 43 are mounted on common trunnions 44 arranged to be mounted in bearings (not shown). An axial bore 45, 46 is formed in each trunnion and communicates with the interior of the roll 1 through radially disposed bores 47, 48. Two helically disposed fins 49, 50 are mounted on the cylindrical surface of the drum 43 to define two helical races about the drum.

Thus any reinforcing necessary is carried in the inner drum 43 the fins being sufficient without any additional reinforcing over this part of the cylinder.

In use, hot oil is pumped in the direction of the arrow through the channel 45, from whence it passes into the interior of the roll 1 through the channels 47. The oil then passes along the races defined by the fins 49, 50, heating the cylinder 40 as it does so. On emerging from the races, the oil passes through the bores 48 and out of the roll along the bore 46, as indicated by the arrow.

A preferred oil flow and heating circuit will now be described with reference to Fig. 4. By way of example, it will be assumed that the heating roll, shown as 1 in . Fig. 4, is to be supplied with oil at a temperature of 180°C.

The circuit comprises a heater 60 for heating oil to a temperature considerably greater than is desired for the roll 1, for example 300°C and 180°C respectively.

A main pump 61 is provided for pumping the heated oil arouhd a closed main circuit 62 and back to heater 60.

A take off pipe 63 leads to a subsidiary circuit 64 for • heating the roll 1. The subsidiary circuit includes a subsidiary pump 65. A three-way valve 66 is provided at the junction of the pipe 63 and the circuit 64. A return pipe 67 in which is a one-way valve 68 connects the subsidiary circuit 64 with the main circuit 62» The valve 68 is arranged to permit oil flow only from the subsidiary circuit 64 to the main circuit 62. An infrared temperature sensor 69 is provided adjacent the roll 1 to sense its temperature. The sensor is connected to a controller 70 for the valve 66. The controller may for example be pneumatically or electrically controlled. The sensing and controlling connections are shown by the dotted lines in Fig. 4.

In use, oil at 300°C is pumped continually round the closed circuit 62, as shown by the thick lines in Fig. 4.

When the temperature of the roll drops below 180°0, the ' sensor 69 sends a signal to the controller 70, which in turn causes the Valve 66 to open to admit hot oil from the circuit 62 along the pipe 63, and into the piping 64. The hot oil is then circulated by the pump 65 through the roll 1, the one-way valve 68, and the piping 67 back to the circuit 62.

When the roll 1 reaches the desired temperature, the sensor G9 signals the controller 70 accordingly.

The valve 66 is then altered to cut off flow of hot oil from the pipe 63, and instead to permit circulation of oil at 180°C round the closed circuit 64, by means of the pump 65. This is indicated by the thin dashed lines in Fig.4. When the temperature next drops below 180°C, the procedure just described is repeated.

Xf precise temperature control of the roll 1 is not needed, the subsidiary circuit can be dispersed with, and the roll simply installed in the main circuit. It has been found however that such an arrangement only permits temperature control within about - 3°C. The arrangement just described permits control to within about - i°C.

If it is desired to heat the cooling roll 3 to a high temperature, for example 90 to 120°C, a further subsidiary circuit can be installed, in parallel with the circuit 64. The equipment required, and its operation are as described with reference to the circuit 64.

Referring now to Fig.5, there is shown an alternative embodiment of the part of the apparatus shown in Fig.l.

The remaining part of the apparatus is as shown in Fig.2. The apparatus comprises an endless belt 70 arranged to run around three triangularly disposed rolls 71, 72 and 73. The roll 71 is a heating roll, and may be as described previously with reference to the heating roll 1. A feed roll 74 is provided for guiding a web 10 on to the roll 71 and has the function described previously for the roll 8. 419 8 5 Λ rubber-covered take-off roll 75 is provided above the roll 72, and forms a gentle nip with the roll 72. Means (not shown) are provided for pre-heating the web (arrows . donoted H(), for pre-heating the belt 70 (arrows denoted Hg) and for cooling the belt (arrows denoted C). The heating means may be infra-red heaters and the cooling means may be cool air jets. Depending on the extent of cooling required, it may be possible to dispense with special cooling means, in that ordinary unforced heat less from the web may result in adequate temperature loss.

In use, the web 10 passes round the feed roll 74 after having been pre-heated, and on to the surface of the helt 70. During passage over the roll 71, the web is heated to a temperature sufficient to soften the synthetic fibres in the web. The web then passes on the belt to the gentle nip between the rolls 75 and 72 and is then taken off the belt 70. The rolls 74 and 75 together hold the web firmly against the belt. The surface finish of the belt is therefore imparted to the surface of the web while the web is in a softened state.

It will be noted that the web remains on the same support, i.e. the belt, throughout the process. There is thus no need for the belt to have a release coating. By the time the web is removed from the belt, the web has cooled sufficiently to have acquired sufficient coherence to be pulled from the belt without breaking.

Referring now to Fig.6, there is shown another embodiment of part of a consolidating apparatus corresponding to that shown in Fig.l. The remainder of the apparatus is as shown in Fig.2. The apparatus comprises a drivably rotatable roll 80 which is divided internally into compartments 81, 82 by a nonrotatabie barrier 83, which makes sealed contact with ' I the inside of the roll 80. A rubber-covered feed roll 84, constructed and functioning in the same way as the roll 8, shown in Fig.l, is provided to guide a web 10 on to the·external surface of the roll 80.

A rubber-covered take-off roll 85 is provided to guide tho web away from the roll 80 after the web has been treated. The rolls 84 and 85 are disposed such that the web contacts a major proportion of the circumference of the roll 80, The compartment 82 is arranged to be heated by hot oil. The compartment 81 is arranged to be heated, or cooled, by a suitable fluid, for example oil, steam, water or air. Means (not shown),e.g. infra-red heaters,may be provided for heating the web externally, (as shown by arrows denoted II). Means (also not shown) e.g. air jets, may be provided for cooling the web externally, as shown by the arrows denoted C) depending on the extent of cooling required.

In use, the web 10 is pre-heated and passed round the roll.84 onto the surface of the heated part of the drum. The synthetic fibres in the web are thereby softened. On passing beyond the barrier 83, the web is cooled.

While the web is still soft, the surface finish of the roll 80 is imparted to the web, since the web is held firmly against the roll 80 by means of the rolls 84 and 85.

After cooling, the web is guided away from the roll 80 by the roll 85.

Since the web is on the surface of the roll 80 throughout the process, there is no need for the roll 80 to carry a release coating. This is because by the time the web is taken off the roll 80, it has cooled to an extent adequate to give the web the necessary coherence to prevent breaking of the web.

It may not be necessary for the web to be heated both from within and without the roll. Only heating from within may be Used if sufficient heat can be supplied to the web in that way.

If it is desired to impart particular Surface finsihes to both surfaces of the web, two sets of apparatus as described herein may be used, positioned in line so as to treat first one surface and then the other. Alternatively, the one apparatus may contain means for heating and surface finishing the web first on one side and then on the other. It is also possible to surface finish both sides simultaneously between two cooling rolls, provided these are mounted so as not to apply substantial pressure to the web.

Claims (22)

CLAIMS:

1. A method of continubusly consolidating and surface finishing a paper web substantially all the fibres of which are of a synthetic thermoplastic material, comprising the steps of heating the web to a temperature above the softening point of the synthetic thermoplastic material, the web being supported throughout the time it is above the softening point of the thermoplastic material, and subsequently cooling the web from a temperature above the softening point of the synthetic 10 thermoplastic material while the web is in contact with a forming surface, so that the finish of the forming surface is imparted to the surface of the web without subjecting the web to substantial pressure during the time it is so supported.

2. A method as claimed in claim 1, wherein the web is heated 15 by passage round part of the circumference of a heating roll.

3. A method as claimed in claim 1 or claim 2 wherein the web is cooled by passage round part of the circumference of a cooling roll the surface of which constitutes said forming surface. 20

4. A method as claimed in claims 2 and 3 wherein the web is transferred from the heating roll to the cooling roll by a passage round part of the circumference of a transfer roll having a resilient covering, the transfer roll running in co-operation with both the heating and cooling rolls and defining a nip : ’5 with the cooling roll serving to press the web gently against the surface of the cooling roll while the web is still soft, whereby the surface finish of the cooling roll is imparted to the web. - 21 41985

5. A method as claimed in ciaim 3 or claim 4 wherein the cooling roll is at a temperature slightly below the softening point of the thermoplastic material of which the fibres are made but which is considerably in excess of ambient temperature.

6. A method as claimed ih claim 3 or claim 4 wherein the cooling roll is at or near ambient temperature.

7. A method as claimed in claim 1 wherein the web is heated and cooled while on the surface of an endless belt,

8. A method as claimed in Claim 1 wherein the web is heated and cooled while on the surface of a single roll.

9. A method as claimed in any preceding claim wherein the web is pre-heated to a temperature below the softening point of the synthetic thermoplastic material before being heated in a separate heating stage to said temperature above the softening point of the synthetic thermoplastic material.

10. Apparatus for continuously Consolidating and surface finishing a paper web substantially all the fibres of which are of a synthetic thermoplastic material, comprising means for heating the web to a temperature above the softening point of the synthetic thermoplastic material one surface only of the web being heated by contact with the surface of a heating member, and means for cooling the web from a temperature above the softening point of the synthetic thermoplastic material to a temperature below the softening point of the synthetic thermoplastic material and means for supporting the web throughout the time it is above the softening point, the supporting means including a forming surface having a surface finish which supports the web while it is above and then below the softening point temperature in such a manner that in use the finish of the forming surface is imparted to the surface of the web without subjecting the web to substantial pressure during the time it is so supported.

11. Apparatus as claimed in Claim 10 whei'ein said means ior heating tho web comprises an internally heatable roll for heating the web, while the web is supported on·the surface of the roll, said surface being provided with a release coating.

12. Apparatus as claimed in Claim 10 or Claim 11 wherein said means for cooling the web comprises an internally heatable or coolable roll the surface of which constitutes said forming surface.

13. Apparatus as claimed in Claims 11 and 12 wherein a transfer roll having a resilient covering is provided for transferring the web from the heating roll to the cooling roll, tho transfer roll being arranged to run in co-operation with both the heating and cooling rolls and to define a gentle nip with the cooling roll for pressing the soft web gently against the surface of the cooling roll, whereby in use the surface finish of the cooling roll is imparted to the web.

14. Apparatus as claimed in Claim 10 comprising an endless belt, said heating and cooling means being arranged to heat and cool the web while on the said belt.

15. Apparatus as claimed in Claim 10 comprising a roll, said heating and cooling means being arranged to heat and cool the web while on said roll.

16. Apparatus as claimed in any one of Claims 10 to 15 comprising means for pre-heating the web to a temperature below the softening point of the synthetic thermoplastic material before the web passes to said means for heating the web to a temperature above the softening point of the thermoplastic material.

17. A consolidated surface finished web produced by a method as claimed in any one of Claims 1 to 9.

18. A method of consolidating and surface finishing a paper web substantially all the fibres of which are of a synthetic thermoplastic material, substantially as hereinbefore described with reference 5 to Figs. 1 and 2 of the accompanying drawings, or substantially as hereinbefore described with reference to Fig. 2 when modified as described with reference to Fig. 5 or Fig, 6 of the accompanying drawings,

19. A method pf consolidating and surface finishing a 10 paper web substantially all the fibres of which are of a synthetic thermoplastic material, substantially as hereinbefore described with reference to Figs. 1 to 4 of the accompanying drawings,

20. Apparatus for consolidating and surface finishing lb a paper web substantially all the fibres of which are of a synthetic thexmofl as tic xaa.teria.1, substantially as hereinbefore described with reference to, and as illustrated in, Figs. 1 and 2 of the accompanying drawings, or substantially as hereinbefore 20 described with reference to and as illustrated in Fig. 2 when modified as described with referenpe to Fig. 5 or Fig. 6 of the accompanying drawings.

21. Apparatus for consolidating and surface finishing a paper web substantially all the fibres of 25 which are of a synthetic thermoplastic material,substantially as hereinbefore described with reference to and as illustrated in Figs. 1 to 4 of the accompanying drawings.

22. A consolidated surface finished web produced by a method as claimed in Claim 18 or Claim 19.