Paper making and fiber liberation – Processes and products – Non-fiber additive
Reexamination Certificate
1999-11-02
2003-06-10
Alvo, Steve (Department: 1731)
Paper making and fiber liberation
Processes and products
Non-fiber additive
C162S164600, C162S167000, C525S540000, C528S332000, C528S403000
Reexamination Certificate
active
06576086
ABSTRACT:
The present invention relates to a process for the production of paper, board and cardboard by draining a paper stock, containing interfering substances, in the presence of fixing agents.
EP-A-0 438 707 discloses a process for the production of paper, board and cardboard by draining a paper stock, containing interfering substances, in the presence of fixing agents and cationic retention aids, fixing agents used being hydrolyzed, homo- and/or copolymers of N-vinylformamide having a degree of hydrolysis of at least 60%. In the production of paper, water is used, in practice, and is at least partially or completely recycled from the paper machine. This is either clarified or unclarified white water or a mixture of such water qualities. The recycled water contains larger or smaller amounts of interfering substances, which are known to impair the efficiency of cationic retention and draining aids to a very great extent. The interfering substances may be water-soluble or colloidal substances and water-insoluble products.
Owing to the reuse of fibers from waste paper for the production of paper, board and cardboard, water-insoluble tacky impurities, ie. stickies and white pitch (binders originating from paper slips), enter the water circulation of the paper machine and thus cause production problems. The tacky impurities are preferentially deposited on wires, felts, rolls and other moving parts of the paper machine. If the procedure is carried out in the absence of fixing agents as process assistants, the presence of interfering substances may become evident in various ways. For example, defects form in the paper web, generally in the form of thin patches or even holes, which may cause tears in the paper machine or in the printing press.
In addition to resins and lignin components which are dissolved out of the wood during fiber production by boiling and mechanical processing, possible sources of interfering substances for stickies are mainly dispersions, natural colloidal systems, such as starch, casein and dextrin, and hotmelt adhesives. Specifically, these are resins, lignin residues, adhesives from the gluing of book spines, adhesives from pressure-sensitive adhesive labels and envelopes, and white pitch. The tacky impurities are in most cases removed only to an insufficient extent from the mixture during the processing of waste paper fibers. In order to reduce the tack of the undesired impurities, substances having a large surface area, eg. talc, chalk or bentonite, have long been added to the paper stock. It is intended thereby substantially to reduce the tack of the tacky impurities, cf. Tappi Press 1990, Vol. 2, pages 508 and 512. The disadvantage of this treatment of tacky impurities is the sensitivity to shearing and the limited retention of the particles treated in this manner in papermaking. Occasionally used dispersants, such as ligninsulfonates, naphthalenesulfonates, nonylphenols or alkoxylated fatty alcohols, prevent agglomeration of stickies to form particles having a size troublesome for the papermaking process, but considerable frothing of the paper stocks occasionally occurs with the use of these process assistants.
EP-A-0 649 941 discloses a process for controlling the settling of tacky impurities out of paper stock suspensions. Polymers which contain N-vinylformamide units, alkyl-substituted N-vinylcarboxamide units or the vinylamine units formed therefrom by hydrolysis are used for inhibiting the deposition of white pitch. EP-A-0 061 169 discloses that cationic polyelectrolytes, which are obtainable by reacting, for example, polyethyleneimine or polyvinylamine with benzyl chloride or styrene oxide and in which at least 10% of the aminoalkyl groups carry an aromatic substituent, are used for removing anionic substances from water circulations in papermaking.
WO-A-94/12560 discloses condensates of polyalkylenepolyamines, which are obtainable by partial amidation of polyalkyleneamines with carboxylic acids, carboxylic esters, carboxylic anhydrides or carbonyl halides and crosslinking of the partially amidated polyalkylenepolyamines with at least bifunctional crosslinking agents, from 0.001 to 10 parts by weight of a crosslinking agent being used per part by weight of the partially amidated polyalkylenepolyamines. These condensates are used as drainage aids, flocculants and retention aids and as fixing agents in the production of paper.
It is an object of the present invention to provide, for the papermaking process, fixing agents which fix both water-soluble interfering substances and colloidal interfering substances as well as water-insoluble tacky impurities to the paper fibers.
We have found that this object is achieved, according to the invention, by a process for the production of paper, board and cardboard by draining a paper stock, containing interfering substances, in the presence of fixing agents, the fixing agents used being reaction products which are obtainable by reacting amino- and/or ammonium-containing polymers selected from the group consisting of the
polymers containing vinylamine units
polyalkylenepolyamines
ethyleneimine-grafted polyamidoamines which may be crosslinked
polydiallyldimethylammonium chlorides
polymers containing dialkylaminoalkylacrylamide units or
dialkylaminomethacrylamide [sic] units and
polyallylamines and
dicyandiamide and formaldehyde condensates
with reactive sizes for paper in a weight ratio of polymer to reactive size of from 15,000:1 to 1:5.
The present invention furthermore relates to the use of reaction products which are obtainable by reacting amino- and/or ammonium-containing polymers selected from the group consisting of the
polymers containing vinylamine units
polyalkylenepolyamines
ethyleneimine-grafted polyamidoamines which may be crosslinked,
polydiallyldimethylammonium chlorides
polymers containing dialkylaminoalkylacrylamide units or
dialkylaminomethacrylamide [sic] units and
polyallylamines and
dicyandiamide/formaldehyde condensates
with reactive sizes for paper in a weight ratio of polymer to reactive size of from 15,000:1 to 1:5, as fixing agents for water-soluble and for water-insoluble interfering substances in the production of paper, board and cardboard from paper stocks containing interfering substances.
Suitable fibers for the production of the pulps are all qualities commonly used for this purpose, e.g. mechanical pulp, bleached and unbleached chemical pulp and paper stocks obtained from all annual plants. Mechanical pulp includes, for example, groundwood, thermomechanical pulp (TMP), chemothermomechanical pulp (CTMP), pressure groundwood, semi-chemical pulp, high-yield pulp and refiner mechanical pulp (RMP). Examples of suitable chemical pulps are sulfate, sulfite and soda pulps. The unbleached chemical pulps, which are also referred to as unbleached kraft pulp, are preferably used. Suitable annual plants for the production of paper stocks are, for example, rice, wheat, sugarcane and kenaf.
Waste paper alone or as a mixture with other fibers is also used for the production of the pulps. Waste paper includes coated waste, which, owing to the content of binders for coating and printing inks, gives rise to white pitch. The adhesives originating from pressure-sensitive adhesive labels and envelopes and adhesives from the glueing of book binds as well as hot melts, give rise to the formation of stickies.
The stated fibers can be used alone or as a mixture of one another. The pulps of the type described above contain varying amounts of water-soluble and water-insoluble interfering substances. Interfering substances can be quantitatively determined, for example, with the aid of the COD or with the aid of the cationic demand. For the purposes of the invention cationic demand is that amount of a cationic polymer which is necessary to bring a defined amount of the white water to the isoelectric point. Since the cationic demand depends to a very great extent on the composition of the cationic polymer used in each case for the determination, a condensate obtained according to Example 3 of D
Esser Anton
Ettl Roland
Höne Matthias
Lorenz Klaus
Mahr Norbert
Alvo Steve
BASF - Aktiengesellschaft
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