NL8203743A - Plastic filter cloth has porous fused-fibre backing layer - with needled higher m.pt. fibre layer heat-treated in belt calender - Google Patents

Abstract

The plastic filter cloth (18) is obtd. by heat-treatment of a starting material (12) whilst holding this material such that it is subjected to controlled stretching or shrinkage. To this end, the material is passed through a treating zone comprising a rotating cylinder (6) and an endless belt (8) around part of the cylinder perimeter, the material passing between cylinder and belt whilst being heated, e.g.via heating elements (7) in the cylinder or radiation from outside. The starting material pref. consists of a first layer of plastic fibres, e.g. polyester, with higher softening temp. than a (porous) second layer of fibres, e.g. poly-propylene, which have been fused together and to which the polyester fibres have been secured, e.g. by needling. Plastic filter cloth, e.g. for use in the food industry such as filtration of milk, and other applications, and its manufacture.

Description

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825130 / vdV / kd

Short designation: Plastic material web, in. the special plastic material web with filter properties, as well as a method and device for its manufacture.

The invention relates to a plastic material web, and more in particular a plastic material web with filter properties obtained by heat treatment while retaining the starting material such that the starting material has undergone a controlled stretch or shrinkage.

Such a plastic material web, obtained by, for instance, holding a polyester foil fabric or non-woven fabric in a stretcher frame and heating it to, for example, ZOO, is known. With this heating, the material obtains such stability that it can be used at an operating temperature of up to 200 ° C without drastic shape changes or external changes.

Such a plastic material web is relatively expensive since the starting material has to be clamped in a tensioning frame, while moreover heating to the predetermined temperature forces the application of very precise treatment conditions.

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On the other hand, a web-shaped synthetic fiber fleece material is also known obtained by impregnating a synthetic fiber fleece with synthetic resin, and subsequently curing the synthetic resin with heat, which treatment is carried out on a roll calender. This known web-shaped plastic material has the drawback that the treatment must take place in a short time at a high line pressure between the rollers of the roll calender and the starting material.

Finally, when subjecting a web-shaped plastic material consisting of a laminate of two non-woven fabrics of different plastics, the disadvantage occurs that when heated to the melting temperature of the plastic fibers with the lowest melting point, these plastic fibers melt together to a very small mass, whereby all favorable properties of the web-shaped plastic material are lost.

The object of the invention is now a web-shaped plastic material which can be manufactured more easily and which furthermore has optimum properties, without the use of a clamping frame or a roll calender.

This object is achieved according to the invention in that the plastic material web is formed by passing the material through a zone formed by a roller and an endless belt encircling this roller at least partially, with supply of heat.

By applying these measures, which can be done efficiently with a belt calender, the pressure between the belt and the roller can be accurately controlled, and moreover, work with relatively low pressure forces, while the contact times can be long compared to the contact times and contact forces with a roll calender, which leads to a very good quality of the end product.

The plastic material web particularly advantageously consists of a first non-woven fabric layer of plastic fibers with a lower softening point 10 than another plastic layer connected to this non-woven fabric layer.

Such a plastic material web is suitable for many applications and when the other plastic layer is a porous plastic layer, the plastic material web lends itself particularly well as a filter material.

Particularly good filter materials are obtained when the other porous plastic layer on one surface is free from protruding plastic fibers of the first nonwoven layer and is obtained by fusing plastic fibers of a second nonwoven layer.

In particular, such a plastic material web is suitable for filtration of liquid food compositions such as milk filtration, but also for many other filtrations, due to the fact that the first fiber web retains its normal properties and, on the other hand, the other plastic layer is provided with certain pores. passage of liquid.

In particular, the web-shaped plastic material according to the invention has very controlled stretching or shrinking properties, as a result of which it can be optimally used as an industrial product for the manufacture of other products.

The invention also relates to a method for manufacturing a plastic material web, in particular a plastic material web with filter properties, by means of a. subjecting the web-like stock material to a heat treatment while retaining the stock material such that the material undergoes controlled stretching or shrinkage, the method being characterized in that the stock material is passed through a zone formed by a roller and a belt which at least partially wraps around this roller without end, with supply of heat.

This method provides a plastic material web with optimal 8203743 t% - 3 - t properties compared to the products hitherto manufactured on stretcher frames or by means of a roll calender.

The surface pressure during the treatment is particularly advantageous between 0.05 and 3 kg / cm2, preferably between 0.10 and 0.15 kg / cm2, and the temperature between 25 and 300 ° C with a contact time of 1 to 60 sec. . preferably 5 to 15 sec.

The method according to the invention also offers particularly great advantages when the heat treatment is carried out in several zones, namely a heating zone, a constant temperature zone and a cooling zone, whereby optimum properties can be obtained.

Advantageously, a layer of a release agent is applied to the starting product, to the roller and / or to one or more belts at least partially surrounding the roller in order to be able to easily remove the end product, in case the product is applied to the product without using a release agent. surfaces of the roller and / or one or more belts that at least partially wrap around the roller.

The release agent is expediently applied with a changing felt strip.

Finally, the invention relates to a device for carrying out the method according to the invention, comprising a central roller which cooperates with an endless belt which wraps at least a part of the circumference of the central roller, as well as a guide for the belt without end and a tensioning member for pressing the belt with adjustable pressure against the rolling surface, the device 25 being characterized in that it is provided with at least one heat supplying member and at least one cooling member.

A particularly advantageous device according to the invention is characterized in that the endless belt is made of a heat-conducting material and at least one heat supplying member is placed along a part of the roller circumference which is surrounded by the belt, while the roller is in the form of a coolable roller.

According to yet another advantageous embodiment, the central roller is surrounded by a plurality of belts, one of the belts being a belt with a low heat resistance, located between the central heatable roller 35 and a heat-insulating second belt without end, which belt with low heat resistance is guided by a cooling zone located outside the periphery of the central roller.

The invention will now be elucidated on the basis of an output 8203743

V

% - 4 - ring example using the drawing, in which:

Fig. 1 shows a cross section of a plastic material web according to the invention;

Fig. 2 a first embodiment of a device according to the invention and;

Fig. 3 a second embodiment of a device according to the invention.

Fig. 1 shows a plastic material web according to the invention, comprising a polyester fiber fleece 1, which is fixedly connected in another plastic layer 2 obtained by melting polyolefin fibers, in particular polypropylene fibers. This other plastic layer 2 is provided with pores 3.

As can be seen, the other plastic layer in the form of a porous polypropylene film 2 is fixedly attached to the polyester fiber web on one surface, the fibers of which are anchored in the polypropylene film 2. The other surface 4 of the web-shaped plastic material is free of protruding fibers.

Such a material lends itself particularly well as filter material for milk, but also for other filtration processes.

Fig. 2 shows a device according to the invention for containing a central roller 6 provided with heating coils 7 and / or a supply and discharge for heating medium in order to be able to bring this central roller to a predetermined temperature.

The circumference of the central roller 6 is partly enveloped by an endless felt belt 8 which is guided over guide rollers 9 and tensioning rollers 10 and 11 in order to be able to press the felt belt 8 against the central roller 6 with the desired pressure and therefore also the desired pressure. to be able to exert on a web-shaped laminate 12 of a fiber web of polyolefin fibers, in particular polypropylene fibers, which are needle-bonded with a fiber web of polyester fibers.

This laminated composite fiber web 12 is from a stock reel 13 or other unwinding mechanism.

A second endless belt or an idler belt 4 cooperates with the outer surface of the central roller 6, which has a low heat resistance 35, such as, for example, a metal foil with a thin polyester layer or a thin glass fiber teflon belt. This second belt 14 is guided over a coolable roller 17, behind which is placed a conveyor belt 15 through which the obtained plastic material web according to the invention (indicated 8203743 V * 'fc ..- 5- with reference number 18) is guided to a winding reel 16 or other winding mechanism. .

When using a composite fiber web of polypropylene fibers and a polyester fiber web bonded to it by needles, 5 has a temperature of the central roll 6 of about 180 ° C, while the contact time in the heating zone is 10 sec. amounts.

In the range where the web-shaped material according to the invention leaves the surface of the central roll 6, the final product is cooled, and finally cooled with the coolable roll 17 to a temperature below 100 ° C, for example 60 ° C. To this end, the cooled roller 17 is supplied with cooling water of, for example, 20 ° C via cooling water supply 19 and cooling water discharge 20.

Generally, the surface pressure between felt belt 8 and second or trailing belt 14 is chosen between 0.05 and 3 kg / cm2 and preferably between 0.10 and 0.15 kg / cm2. Preferably, the temperature is between 25 and 300 ° C for a total contact time between trailing tape 14 and felt tape 8 from 1 to 60 seconds, preferably 5 to 15 seconds.

In Fig. 3 a still further embodiment is shown comprising a cooled central roller 6 ", provided with a central inlet 21 for supplying cooling water, so that the peripheral surface of the central roller 6" is cooled to, for instance, room temperature.

The composite nonwoven fabric 12, also supplied from a supply reel 13, consisting of a fiber web of polyester fibers and fiber web of polypropylene fibers interconnected by needles, is pressed against the surface of the cooled central roll 61 by means of a first endless belt 8 '. For supplying the heat required for the heat treatment, the device is provided with a heating member 22, which is placed opposite the peripheral surface of the central roller 6 *, but such that the heat supply of the heating member 22 takes place over a part of the encircled portion of the 50 central roll 6 '. After passing the active area of the heating member 22, the heat-treated composite nonwoven material whose fibers of the polypropylene nonwoven are fused, cooling occurs, therefore in the area indicated by arrows 23, 231.

After leaving the central roller 61, the obtained porous 55 polypropylene film 2 with polyester fiber web 5 connected thereto is passed over conveyor 15 to take-up reel 16.

In order to prevent adhesion of the composite nonwoven product 18 to the central roller 6 'or endless heat-conducting first belt 8', it may be advisable to use a release agent applicator 23, for example, in the form of a varying apply felt-strip release agent to these surfaces.

It is, of course, also possible to apply release agent directly to both surfaces of the starting material using release agent applicators 23 'as shown in Figure 3.

It is of course also possible to apply a release agent with the aid of release agents 23 to the second endless belt 14, and to the felt belt 8.

In fig. 4 the starting product is schematically shown comprising a fiber web 1 of polyester fibers and a fiber web 2 of polypropylene fibers which are joined together by needle-working.

During the heat treatment in the device according to Figure 2, the polypropylene fiber web 2 'is guided such that it abuts against the second endless belt or an idler tape '14.

In FIG. 3, on the other hand, the polypropylene fiber web 2 'is guided against the polyester-coated metal foil tape 8'.

The endless tape 8 'may also consist of a silicone paper 20 or a Teflon film, of course the smoothness of the surface of the laminated polypropylene layer 2 depends partly on the smoothness of the endless tape 81.

In the embodiment according to Fig. 2, the central roller 6 has a surface temperature of at least 190 ° C, but in any case the temperature must be below 225 ° C, since at this temperature the polyester shows a melting point.

The above has discussed the application of a release agent by means of a changing felt strip, but it is of course also possible to apply the release agent by spraying or by means of an application roller.

The invention will now be elucidated on the basis of a number of exemplary embodiments.

EXAMPLE I

To a belt calender according to Fig. 3, a composite nonwoven layer consisting of 20% by weight of a polypropylene fiber nonwoven layer and 80% of its weight by a polyester fiber nonwoven layer, the two layers of which are bonded together, is fed.

In order to obtain a filter material in which the polypropylene 8203743 '' ..- 7- has melted into a smooth porous layer, while the polyester fiber-fleece is attached to it as a voluminous filter layer, the composite starting non-woven web is heated by means of the heating element 22 at a temperature of 180 ° C. A copper foil thermally conductive tape 58 'which is in contact with the polypropylene fiber nonwoven layer is used; the side is provided with a polyester coating.

The contact time in the heating zone deformed by heating element 22 is 10 seconds, while it is subsequently cooled by means of the cooled central roller 6 'to a temperature of 80 ° C. The obtained web-shaped material according to the invention then passes through conveyor belt 18 to take-up reel 16.

The obtained plastic material web consists of a polyester fiber fleece, the polyester fibers of which are anchored in a pore-containing polypropylene layer, formed by fusing the polypropylene fibers of the polypropylene fiber fleece 2 '.

The pore structure in the layer 2 is such that any detachable polyester fibers are retained by the polypropylene filter 2 during use of the sheet material according to the invention. EXAMPLE IX

A composite nonwoven web according to Example I is treated in a felt belt calender according to Fig. 2.

The low heat resistance band 14 of copper foil transports the obtained sheet material 18 to the cooling roll 17 which is cooled by water, such that the composite web material has a temperature of 80 ° C. After that, the plastic material web according to the invention is wound up. 1 8203743

Claims (21)

1. Plastic material web, in particular plastic material web with filtering properties, obtained by heat treatment while holding the starting material such that the starting material has undergone a controlled stretch or shrinkage, characterized in that the sheet material is formed by passing the starting material through a zone formed by a roller and an endless belt, which at least partially wraps around this roller, under application of heat. 2. Plastic material web according to claim 1, characterized in that the sheet-like material consists of a first non-woven layer of plastic fibers with a higher softening point than another plastic layer connected to this non-woven layer. Plastic material web according to claim 1 or 2, characterized in that the other plastic layer is a porous plastic layer. Plastic material web according to claim 3, characterized in that the porous plastic layer on one surface is free from protruding plastic fibers of the first nonwoven layer. Plastic material web according to claims 2 to 4, characterized in that the other plastic layer is obtained by fusing plastic fibers of a second nonwoven layer. Plastic material web according to claims 1 to 5, characterized in that the other porous plastic layer is formed by fusing a second nonwoven layer of polyolefin fibers, preferably polypropylene fibers, and the first nonwoven layer consists of polyester fibers. * 7. A method of manufacturing a plastics material web by heat-treating sheet-like stock material while holding the stock material such that the stock material undergoes controlled stretching or shrinkage, characterized in that the stock material is passed through a zone between a roller ( 6) and an endless belt (6), (8 '), which at least partially wraps around this roller (6), under the supply of heat. Method according to claim 7, characterized in that the starting material consists of a first nonwoven layer of synthetic fibers with a higher softening point than a synthetic material web with filter properties 8203743 with this nonwoven nonwoven layer *. e »- 9 - bandages other plastic layer. Method according to claim 7 or 8, characterized in that the other plastic layer is formed into a porous plastic layer. 10. Method according to claims 7 to 9, characterized in that the porous other plastic layer is formed in such a way that a surface is free of protruding plastic fibers of the first nonwoven layer. 11. Method according to claims 7 to 10, characterized in that the synthetic fibers of a second nonwoven layer are fused into another porous synthetic layer. Method according to one or more of the preceding claims, characterized in that the other porous plastic layer is formed by fusing a second nonwoven layer of polyolefin fibers, preferably polypropylene fibers, and the first nonwoven layer consists of polyester needle-working fibers, the starting layers being be one / 15 connected. Method according to claims 7 to 12, characterized in that the surface pressure during the heat treatment is between 0.05 and 3 kg / cm2, preferably 0.10 to 0.15 kg / cm2, and the temperature between 25 and 300 ° C at contact times from 1 to 60 sec., Preferably 5 to 20 sec. Method according to claims 7 to 13, characterized in that the heat treatment takes place in several zones, which are located on or near the periphery of the central roller (é, 6'j. 15. A method according to claim 14, characterized in that the starting material is passed through a heating zone, a constant temperature zone and a cooling zone. 16. Method as claimed in one or more of the foregoing claims, characterized in that a layer of a release agent is applied to the starting product, to the central roller and / or to one or more walls which at least partly encircle the roller. Method according to claim 16, characterized in that the release product is applied continuously by means of a changing felt strip. 18. Device for carrying out the method according to one or more. of the preceding claims, comprising a central roller (δ, 6 ') co-operating with an endless belt (8, 8'J which wraps at least a portion of the circumference of the central roller, as well as guide rollers 8203743-10-V-ft (9) and pressure adjusting rollers (10,11) for pressing the belt (8, 8 ') with adjustable pressure against the surface of the central roller (6, 6'), characterized in that the device is provided with at least a heat supply member (22, 6) and of at least one cooling member (6 ', 17). Device according to claim 18, characterized in that the belt is made of a heat-conducting material and a heating element (22) is placed along a part of the circumferential circumference of the central roller (6 *), which central roller (6 ') is designed as a coolable roller (6'). Device according to claim 18, characterized in that the central roller (6 ') is surrounded by two belts, one of the belts (14) being a belt with low heat resistance, located between the heated central roller (6) and a heat insulating second belt without end (8), which belt with low heat resistance (14) is guided along a cooling member (17). Device according to claim 20, characterized in that the cooling zone is designed as a cooling roller. 20 8203743