PAPER MACHINE BELT

Abstract

The invention relates to a paper machine belt, some of the threads or all of the threads being made partially or entirely of a bioplastic.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS AND CLAIM TO PRIORITY

This application is related to utility model number 20 2012 103 846.3, filed Oct. 8, 2012, in the Federal Republic of Germany, the entire disclosure of which is incorporated herein and to which priority is claimed.

FIELD OF THE INVENTION

The invention relates to a paper machine belt.

BACKGROUND OF THE INVENTION

Paper machine belts are endless textile products or textile products made endless by a seam with a large length and a large width, of which the structure and the chosen material is adapted to the specific requirements of a paper machine. The paper machine belts circulate in the paper machine and thereby supporting the sheet of paper being formed as it passes through the paper machine, thereby enabling both the paper formation and drying processes. A distinction can be made here between three basic types of paper machine belt according to their application.

In the first part of the paper machine—the forming part—single or multi-layered fabrics are used on to which the paper pulp is applied so that a strip of paper is formed. Water is removed from the latter through the forming fabric by the effect of gravity and by the effect of negative pressure applied by means of suction boxes. Forming fabrics must therefore on the one hand be highly permeable and on the other hand have good fibre retention on their outside. In the subsequent section of the paper machine—the press part—the strip of paper is transferred onto press felts and passed through roller presses, any liquid still contained within the strip of paper is pressed out by the roller nip pressure and subsequently pushed through the press felt. Press felts basically comprise a support in the form of a thread system onto which one or a number of fibre layers are needled. The thread system can be a woven or knitted fabric or a nonwoven scrim. Combinations of these thread systems are also known. The press part is followed by the drying part in which the strip of paper is passed onto dryer fabrics which help to guide the strip of paper over hot rollers. Water is removed by thermal means. Dryer fabrics are generally made of an open woven fabric or of a spiral linked belt (with regard to the genus: EP 0 171 891 A1, EP 0 472 072 A1 and EP 0 763 623 B1). As well as these, there are also other forms of paper machine belts, for example so-called shoe press belts which are produced from a support, consisting e.g. of a woven fabric or a nonwoven scrim and an impermeable polymer layer applied to the latter.

In the past, the thread systems of such paper machine belts were produced from wool or cotton. However, the mechanical properties of the latter were so restricted that they were not able to keep up with the developments being made in paper machine technology. For a number of decades, therefore, paper machine belts have been produced exclusively from plastics based on fossil raw materials such as polyethylene, polypropylene, polyimide, polyester, polyethylene terephthalate, polyether ether ketone and the like. The amount of such plastics consumed here is considerable due to the unfavourable environmental conditions in the paper machine. In addition, paper machine belts have a service life of only a few months and must be replaced frequently by new belts.

The fossil raw materials used in the production of polymeric plastics, in particular the petrochemical raw materials such as mineral oil, are becoming less abundant. Since there is still no replacement for mineral oil used in the production of fuels, there is a general need to save the existing mineral oil as far as possible and to keep it for the applications for which it is still indispensable.

SUMMARY OF THE INVENTION

The object underlying the invention is to provide alternative materials for the production of paper machine belts which are able to replace the plastics based on petrochemical raw materials used currently to manufacture paper machine belts.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

According to the invention this object is achieved by the paper machine belt being made partially or entirely from a bioplastic, in particular bioplastics which are produced using one or more renewable raw materials, especially plant raw materials. By using such plastics a contribution is made to saving the fossil based resources. Moreover, the disposal of bioplastics is less problematic and their material can to a large extent be salvaged for reuse.

Both biologically non-degradable and biologically degradable bioplastics can be used in order to achieve the object in question. In the latter case, however, degradation should only occur after the paper machine belt has become inoperative so that the paper machine belt retains its initial properties until the end of its service life. Biological degradation should only be possible some time after this.

The following biopolymers in particular are suitable for use in paper machine clothing. Bioplastics which are based on starch, in particular thermoplastic starch, can be used. The raw material for starch can be maize, wheat, potato or tapioca. A water-resistant starch plastic can be used here, as given in the examples from EP 0 596 437 A2, WO 02/051284 A2 or WO 96/19599 A1.

A further raw material is cellulose that is further processed, for example, by means of esterification. Examples of cellulose polymers are given in JP 2009-138022 A1, JP 2003-082160 A1, WO 2011/097700 A1, JP 2004-010844, JP 2004-131670 A1, JP 2003-335898 A1 and CN 101 492 837 A1.

Further appropriate bioplastics are polylactic acid (PLA), as described for example in WO 02/051284 A2 and in WO 2011/097700 A1 for the purpose of the production of fibres and textile threads, but also in JP 2003-082160 A1, JP 2008-223177A1 and JP 2008-297680 A1. Also suitable is polytrimethylene terephthalate (PTT) based on 1,3-propanediol (PDO), as given in the examples from WO 2010/078328 A2, US 2010/0168372 A1, JP 2008-223177 A1 and JP 2008-297680 A1.

Also suitable as a bioplastic is bio-based polyamide (PA), as described for example in JP 2010-222721 A1, WO 2011/094673 A2, WO 2011/066619 A1 or WO 2011/066620 A1. The same applies to polyhydroxyalkanoate (PHA), as disclosed e.g. in JP 2008-223177 A1 and JP 2008-297680, and to bio-based polyethylene (PE).

Other suitable biopolymers are polyvinyl chloride (PVC) made of bio-based ethene or ethyne, bio-based polybutylene terephthalate (PBT), mentioned e.g. in US 2010/0168371 A1 and WO 2010/078328 A2, polyphenylene sulfide (PPS), polyethylene terephthalate (PET), described e.g. in WO 2010/101698 A2, CN 101525416 A1, WO 2010/078328 A2, US 2010/0168371 A1 and WO 2009/120457 A2, polyethylene-co-isosorbide terephthalate polymer (PEIT), polyester based on 1,3-propane diol, mentioned e.g. in US 2010/0168371 A1, WO 2010/078328 A2 and WO 2008/088501 A1, and polyurethane (PUR), that is based on bio-based polyols and bio-based isocyanates.

The full content of the previously cited prior art documents is included in the content of the present description, and are incorporated herein by reference in their entirety. This applies in particular to the production processes described in the publications and also to the combinations respectively with other materials and raw materials. It goes without saying that the previously specified bioplastics and raw materials—also with one another or as required—can—as far as possible—be mixed with the known mineral oil-based plastics such as to form e.g. compounds or blends.

If the paper machine belt has a thread system with threads or is made of the latter, some of the threads or all of the threads should be made partially or entirely of the bioplastic. This thread system can be in the form of a woven or knitted fabric or a non-woven layer of threads, or also of a spiral link band and be formed from combinations of the latter. In the thread system there can be threads which are in the form of monofilaments—also wires—and/or of multifilaments or twisted yarns. Both fibres made of bioplastics and fibres made of mineral oil-based plastics can be used as multifilaments.

The thread system can also have a number of layers, at least one layer containing threads or consisting of threads which are partially or entirely made of a bioplastic. Here too combinations of bioplastic and petrochemical plastics are possible, for example by the one layer being produced from a bioplastic and the other layer being produced from a petrochemical plastic, or both layers from a combination of both types of plastic. If the environmental conditions in the paper machine allow it, both layers should be produced from a respective bioplastic suitable for this purpose so as to be able to dispense as far as possible with petrochemical plastics.

As in known paper machine belts, one layer of the thread system can be in the form of a woven or knitted fabric and a further layer a non-woven layer in which the threads are laid one over the other and are not woven or knitted together.

As already mentioned, there can be threads within the thread system which are partially made of the bioplastic and partially of a petrochemical plastic, both plastics being mixed as a compound or blend and/or some of the threads being produced from bioplastic and others being produced from petrochemical plastic. This can for example take place in a form such that the threads are in the form of core/sheath threads and that the core is produced from the bioplastic and the jacket is produced from the petrochemical plastic or vice versa. However, there may also be threads which are in the form of multifilament threads and/or twisted yarns, some of the filaments possibly being made of the bioplastic and some of the filaments being made of the petrochemical plastic.

In particular, the paper machine belt can be in the form of a forming fabric that is to be used in the forming section to form the strip of paper. Here the threads, which are made partially or entirely of the bioplastic, should have properties within the following ranges:

• thread diameter: 0.08-0.5 mm;
• tensile force: 2-110 N;
• thread extension upon breakage: 10-32%;
• thread elasticity modulus: 80-9250 N/mm².

In a further configuration of the invention provision is made such that the paper machine belt is provided with a coating and the coating is made partially or entirely of a bioplastic, for example one of the bioplastics identified in more detail above. Independently of this, the paper machine belt can also be provided with a fibre layer, the fibre layer being made partially or entirely of a bioplastic.

The paper machine belt described above can preferably be in the form of a forming fabric, a press felt or a dryer fabric.

In an embodiment of the invention, the paper machine belt as described herein is installed in any or all of the forming part, press part and drying part of the paper making machine. Those skilled in the art will understand that separate belts are installed in each of these parts. The paper machine belt is supported by and moves along and on typically driven rollers for thereby moving the paper web as it is being formed from one part of the paper making machine to the next successive part. The paper machine belts as herein described will be adapted for the part of the machine in which the belt is to be located. The belt in each part thus has different specifications and requirements as compared with the belts in the other parts of the paper making machine.

It will be apparent to one of ordinary skill in the art that various modifications and variations can be made in construction or configuration of the present invention without departing from the scope or spirit of the invention. Thus, it is intended that the present invention cover all such modifications and variations, and as may be applied to the central features set forth above.

Claims

1. A paper machine belt, characterised in that some of the threads or all of the threads are made partially or entirely of a bioplastic.

2. The paper machine belt according to claim 1, characterised in that the bioplastic is produced using one or more renewable raw materials, in particular plant raw materials.

3. The paper machine belt according to claim 1, characterised in that the bioplastic is not biologically degradable.

4. The paper machine belt according to claim 1, characterised in that the bioplastic is created such that it does not degrade or only degrades biologically after the paper machine belt has become inoperative under the environmental conditions in a paper machine.

5. The paper machine belt according to claim 1, characterised in that the bioplastic or its raw material is chosen from a group that consists of starch, cellulose polymer, polylactic acid (PLA), polytrimethylene terephthalate (PTT) made of bio-based 1,3-propanediol (PDO), bio-based polyamide (PA), polyhydroxyalkanoate (PHA), bio-based polyethylene (PE), polyvinyl chloride (PVC) made of bio-based ethene or ethyne, bio-based polybutylene terephthalate (PBT), bio-based polyphenylene sulfide (PPS), bio-based polyethylene terephthalate (PET), bio-based polyethylene-co-isosorbide terephthalate polymer (PEIT), polyurethane (PUR) made of bio-based polyol and/or bio-based isocyanate.

6. The paper machine belt according to claim 1, characterised in that the paper machine belt has a thread system with threads or is made of the latter, some of the threads or all of the threads being made partially or entirely of a bioplastic.

7. The paper machine belt according to claim 6, characterised in that the thread system forms one or more woven or knitted fabrics or non-woven yarn layers or combinations of the latter and/or a spiral link band.

8. The paper machine belt according to claim 6, characterised in that there are threads in the thread system which are in the form of monofilaments and/or multifilaments.

9. The paper machine belt according to claim 6, characterised in that the thread system has a number of layers and that at least one layer contains threads or consists of threads which are made partially or entirely of a bioplastic.

10. The paper machine belt according to claim 6, characterised in that the thread system has a number of layers and that at least one layer contains threads which are made partially or entirely of a petrochemical plastic.

11. The paper machine belt according to claim 9, characterised in that one layer of the thread system is in the form of a woven fabric and a further layer is in the form of a non-woven layer.

12. The paper machine belt according to claim 6, characterised in that there are threads within the thread system which are partially made of the bioplastic and partially of a petrochemical plastic.

13. The paper machine belt according to claim 12, characterised in that the threads are in the form of core/sheath threads and that the core is made of the bioplastic and the core of the petrochemical plastic or vice versa.

14. The paper machine belt according to claim 12, characterised in that there are threads in the thread system which are in the form of multifilament threads or yarns, some of the filaments being made of the bioplastic and some of the filaments being made of the petrochemical plastic.

15. The paper machine belt according to claim 6, characterised in that the paper machine belt is in the form of a forming fabric and the threads which are made partially or entirely of the bioplastic have properties within the following ranges:

thread diameter: 0.08-0.5 mm;

tensile force: 2-110 N;

thread extension upon breakage: 10-32%;

thread elasticity modulus: 80-9250 N/mm2.

16. The paper machine belt according to claim 1, characterised in that the paper machine belt is provided with a coating and the coating is made partially or entirely of a bioplastic.

17. The paper machine belt according to claim 1, characterised in that the paper machine belt is provided with a fibre layer and the fibre layer is made partially or entirely of a bioplastic.

18. The paper machine belt according to claim 2, characterised in that the bioplastic is not biologically degradable.

19. The paper machine belt according to claim 2, characterised in that the bioplastic is created such that it does not degrade or only degrades biologically after the paper machine belt has become inoperative under the environmental conditions in a paper machine.

20. The paper machine belt according to claim 3, characterised in that the bioplastic is created such that it does not degrade or only degrades biologically after the paper machine belt has become inoperative under the environmental conditions in a paper machine.

21. A paper making machine, comprising: a forming part, a press part and a drying part, each of the parts having positioned and movable therein a paper machine belt, at least one of the paper machine belts is manufactured from a bioplastic selected from the group consisting of starch, cellulose polymer, polylactic acid (PLA), polytrimethylene terephthalate (PTT) made of bio-based 1,3-propanediol (PDO), bio-based polyamide (PA), polyhydroxyalkanoate (PHA), bio-based polyethylene (PE), polyvinyl chloride (PVC) made of bio-based ethene or ethyne, bio-based polybutylene terephthalate (PBT), bio-based polyphenylene sulfide (PPS), bio-based polyethylene terephthalate (PET), bio-based polyethylene-co-isosorbide terephthalate polymer (PEIT), polyurethane (PUR) made of bio-based polyol and/or bio-based isocyanate.