METHOD FOR MARKING PAPER AND APPARATUS FOR DETECTED MARKED PAPER

Abstract: The invention relates to a procedure for the marking of paper and detection of marked paper for sorting when the paper is recycled, in which procedure a chemical tracer corresponding to the number of times the pulp has been used in the papermaking process is introduced into paper to be marked, and the tracer is detected in reclaimed paper by means of a detector sensitive to the tracer to allow reclaimed paper to be sorted for recycling according to the number of times it has been used.

Description: METHOD FOR MARKING PAPER AND APPARATUS FOR DETECTED MARKED PAPER. The present invention relates to a procedure for the marking of paper and detection of marked paper for sorting when the paper is recycled. Moreover, the invention relates to an appara¬ tus for the detection of marked paper, as defined in the preamble of claim 10. In recent times, a strong trend towards more effective recycling and reuse of paper has been pre¬ vailing. For the reuse of paper, reclaimed paper is, after possible de-inking, mixed with pulp in desired proportions and used again as raw material in paper production. In this context, 'paper' means paper and cardboard sorts mainly manufactured from lignocellulo- se-based raw material by means of a paper or cardboard making machine. When paper is reused, the paper fibres become brittle and shorter. Therefore, it is of prima¬ ry importance for the paper manufacturer to know how many times the paper raw material has been used befo¬ re. If the paper raw material has been used several times before, the fibres are often so short and of such low quality that the raw material is not accep¬ table for reuse and has to be burned or destroyed in some other way. At present, the sorting of paper for reuse is done practically exclusively by a manual method, which means a substantial increase in the costs of proces¬ sing and use of reclaimed paper. The reason for this is simply that there is no usable method for the mar¬ king of waste paper and for detecting marked paper to allow mechanical sorting of waste paper in connection with recycling. The object of the present invention is to eliminate the drawbacks mentioned above. A specific object of the invention is to produce a new procedure for the marking of paper and detection of marked paper to allow it to be sorted in connection with recycling in such a way that the marking and detection of paper can be carried out mechanically by an online method without manually touching the paper. As for the features characteristic of the in¬ vention, reference is made to the claims. The invention is based on the basic idea, de¬ veloped during the investigations carried out, that a chemical tracer corresponding to the number of times the paper pulp has been used in the papermaking pro¬ cess is introduced into the paper to be marked. The tracer is detected in reclaimed paper by means of a detector sensitive to the tracer to allow reclaimed paper to be sorted for recycling according to the num¬ ber of times it has been used. In this way, the inven¬ tion makes it possible to determine the number of recycling times for each lot or even each sheet of reclaimed paper, arranged e.g. for transport on a con- veyor, on the basis of the tracer, which specifically corresponds to the number of times the paper has been recycled. Thus, the user of reclaimed paper is able to sort the reclaimed paper e.g. by means of a sorter ar¬ ranged in conjunction with and controlled by a detec- tor, according to the number of recycling times of the reclaimed paper. Usable and recyclable reclaimed paper can be passed on to a papermaking process, whereas reclaimed paper that has already been recycled many times and is of a lower quality can be passed to an energy production unit or to a dumping place or some other kind of disposal system. The invention thus ma¬ kes it possible to sort reclaimed paper in a desired manner and in accordance with desired criteria for reclaimed paper. The tracer used in the procedure of the in¬ vention preferably contains metal and/or metal com¬ pounds, e.g. lanthanide and/or a lanthanide compound. The tracer may also be e.g. an organometallic com¬ pound. Generally speaking, the tracer may consist of any tracer that can be introduced into paper during manufacture corresponding to the number of times the fibre raw material has been used and which is not dis¬ solved or otherwise removed from the paper during the paper manufacturing process. The tracer may consist of a single compound or it may contain two or more com¬ pounds, whose proportions in the tracer are constant. The chemical tracer may be added into paper or into a raw material of paper, e.g. lignocellulose pulp, paper filler, pigment or generally in any suitable way. In selecting the tracer it is important that the tracer can be detected by an easy and fast method, i.e. by an on-line method, e.g. using an emission spectrometer. A specially preferred method of detecti¬ on is to vaporize the tracer by means of a laser beam and to detect it by means of an emission spectrometer. If desired, other methods and/or devices for marking and/or detecting can also be used. In the following, the invention is described in detail by the aid of examples of its embodiments. EXAMPLE 1 For reasons of product liability, a paper ma¬ nufacturer wants to be able to identify their own pa¬ per in any circumstances. During the manufacturing process in the paper mill, lanthane in an amount of 100 μg/g of filler and samarium in an amount of 150 μg/g in nitrate form are mixed with the filler. The filler is added into the paper during the manufactu¬ ring process. The paper product is sent to a customer. Later, a reclamation claiming the paper sold by the manufacturer to have been defective is raised against the paper manufacturer. The manufacturer requests a sample of the defective product. The sample is ana¬ lysed in a laboratory. Using an ICP emission spectrograph, the lanthanide concentrations in the sample are determined. It is established that the La/Sm ratio is 3.5. Since the La/Sm ratio in marked paper is 0.67, the manufacturer is able to prove that the defective paper is not their produce. EXAMPLE 2 A paper mill which uses recycled fibre adver¬ tises in their marketing that their paper, certified to have a certain fibre composition, can be automati¬ cally identified during sorting and thus separated for a given use. Thus, paper containing e.g. 10 % recycled fibre is so marked that it will contain 100 μg of lanthane and 200 μg of samarium in nitrate form per dm . Paper containing 20 % recycled fibre again con¬ tains 100 μg of lanthane and 150 μg of samarium per dm 2 . When the paper sorter is provided with a laser- excited emission spectrograph, it can easily determine the lanthanide concentrations and their ratios in the paper. In this way, these paper sorts can be automati¬ cally separated from other, non-marked sorts and from each other. The embodiment examples are only intended to illustrate the invention without limiting it in any way.

Claims: CLAIMS 1. Procedure for the marking of paper and de¬ tection of marked paper for sorting when the paper is recycled, c h a r a c t e r i z e d in that a chemical tracer corresponding to the number of times the pulp has been used in a papermaking process is introduced into paper to be marked, and that the tracer is detec¬ ted in reclaimed paper by means of a detector sensiti¬ ve to the tracer to allow reclaimed paper to be sorted for recycling according to the number of times it has been used. 2. Procedure as defined in claim 1, c h a ¬ r a c t e r i z e d in that the tracer contains metal and/or a metal compound. 3. Procedure as defined in claim 1 or 2, c h a r a c t e r i z e d in that the tracer contains lanthanide or a lanthanide compound. . Procedure as defined in any one of claims 1 - 3, c h a r a c t e r i z e d in that the tracer con- tains an organometallic compound. 5. Procedure as defined in any one of claims 1 - 4, c h a r a c t e r i z e d in that the tracer con¬ tains at least two lanthanides, lanthanide compounds, metals, metal compounds and/or organometallic co - pounds, whose ratio in the tracer is constant. 6. Procedure as defined in any one of claims 1 - 5, c h a r a c t e r i z e d in that the tracer is substantially indissoluble in the waste paper process conditions. 7. Procedure as defined in any one of claims 1 - 7, c h a r a c t e r i z e d in that the tracer is vaporized by laser and detected by means of an emissi¬ on spectrometer. 9. Procedure as defined in any one of claims 1 - 8, c h a r a c t e r i z e d in that the paper is marked using two tracers whose ratio is substantially constant, and each tracer is detected in used paper and their ratio is determined. 10. Apparatus for the detection of a tracer in marked reclaimed paper to determine the number of times the paper has been recycled, c h a r a c t e r i ¬ z e d in that the apparatus comprises a detector (1) for determining the concentration and/or amount of tracer in the paper pulp. 11. Apparatus as defined in claim 10, c h a - r a c t e r i z e d in that the detector (1) comprises an emission spectrometer (2) . 12. Apparatus as defined in claim 10 or 11, c h a r a c t e r i z e d in that the apparatus comprises a laser vaporizer (3) . 13. Apparatus as defined in any one of claims 10 - 12, c h a r a c t e r i z e d in that the apparatus comprises at least one monochromator (4) . 14. Apparatus as defined in any one of claims 10 - 13, c h a r a c t e r i z e d in that the apparatus comprises a sorter (5) disposed in conjunction with a paper conveyor (6) and controlled by the detector (1) to sort the waste paper conveyed by the conveyor by means of the sorter according to the number of times the paper has been recycled.

Inventors: ROSENBERG ROLF, ROSENBERG, ROLF
Applicants: ROSENBERG ROLF, VALTION TEKNILLINEN, ROSENBERG, ROLF, VALTION TEKNILLINEN TUTKIMUSKESKUS
Application year: 1997
Main classification: D21H21
IPC codes: D21B1, D21C5, D21H17, D21H21, D21H23