Paper making and fiber liberation – Processes and products – Non-fiber additive
Patent
1997-10-24
1999-06-22
Chin, Peter
Paper making and fiber liberation
Processes and products
Non-fiber additive
162179, 162199, 162DIG4, D21H 2102
Patent
active
059140062
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for controlling the deposition of stickies from paper stock suspensions in papermaking.
2. Discussion of the Invention
Even when paper was invented in the second century, the use of waste material, i.e. the technique of--at least partial--recycling, played a certain part. In today's world, considerable significance is attributed to recycling technology because of the increase in ecological awareness. Accordingly, questions of raw materials supply and the avoidance of waste are becoming increasingly important in the steadily increasing production of paper.
By using secondary fibres through the recycling of waste paper, savings can be now be made in regard to raw materials, waste disposal space and the energy involved in papermaking. However, this technology is attended by specific difficulties.
Thus, in the processing of wastepaper, tacky impurities known as stickies can seriously disrupt the production process and adversely affect the quality of the paper produced. Stickies enter the papermaking process when the wastepaper used contains glued bindings, adhesive tape or specially treated products, such as coated, laminated or coated papers or paperboards. In addition, however, stickies can be formed by the rosin in wood and by its interaction with paper auxiliaries.
If the stickies are present in compact form, they can be chemically removed relatively easily by means of sorting machines. In general, however, the stickies are present not only in compact form, but also in dispersed form in the pulp and are very difficult to remove in this form. Accordingly, the increasing use of wastepaper in papermaking and the closing of the water circuits has increasingly resulted in an increase in the percentage content of stickies in the circuit water.
Stickies cause numerous problems and disruptions not only in the manufacture of paper, but also in the processing of paper. On account of their tackiness, deposits are formed on machine parts, pipe walls, wires, wet felts, dry felts, drying cylinders, smoothing rollers, calender rollers and also in the finished paper, resulting in web breaks in the papermaking machine and in a deterioration in paper quality through holes, specks, marks, etc. (cf. H. L. Baumgarten, Das Papier, 1984, 38, No. 10A, pages V121-V125) According to H. L. Baumgarten, stickies in industrial and institutional publications have for years been regarded as the biggest problem of reusing wastepaper. Even minimal quantities of adhesive can cause breaks in papermaking and printing machines so that stoppages for cleaning are unavoidable. Baumgarten says that "2 g adhesive introduced at an appropriate point of the papermaking machine can result in the rejection of several hundred kg paper" (loc. cit. page V122, right-hand column).
Stickies do not come from a single source. For the most part, they emanate from the rosin in wood, papermaking auxiliaries, binders for the coating of paper and paperboard, paper processing adhesives, printing ink binders and paper processing materials. Of particular importance in the context of the problem addressed by the present invention are the stickies which emanate from the rosin in wood and from the adhesives used in paper processing.
The rosins present in chemical pulp and mechanical pulp contain approximately 1 to 5% by weight of so-called harmful resins, depending on the type wood. These resins may be present in colloidally non-bound form or may adhere to the paper fibres. According to J. Weigl et al., the difficulties caused by rosin deposits in the manufacture and processing of paper have steadily increased over recent years for various reasons (cf. J. Weigl et al., Das Papier, 1986, pages V52-V62; more particularly page V53, left-hand column).
The adhesives used in the processing of paper can be divided into three groups, namely: pressure-sensitive adhesives, dispersion adhesives and hotmelt adhesives.
The pressure-sensitive adhesives are permanently tacky products. In their cas
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Daute Peter
Hornfeck Klaus
Koester Rita
Nellessen Bernhard
Schreck Berthold
Chin Peter
Grandmaison Real J.
Henkel Kommanditgesellschaft auf Aktien
Jaeschke Wayne C.
Szoke Ernest G.
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