NO302042B1 - A method of preventing the deposition of sticky materials on paper machine felt or the like, as well as mixing for use in the method - Google Patents

Description

The present invention relates to a method as stated in claim 1's preamble to prevent deposition on paper machine felt or similar equipment used to convert paper pulp into a web. The invention also relates to a mixture as stated in claims 32-45

The manufacture of paper typically involves the processing of a precisely prepared aqueous fiber suspension to produce very uniform dry paper webs. Three steps in a typical process are web forming, where the suspension is passed over a porous cloth or wire onto which the fibers are deposited while the liquid is filtered through the wire, web pressing, where the formed web passes through presses lined with porous felt to remove additional water from the web and improve the evenness of the web as well as providing surface quality to the paper, and finally paper drying, where residual water evaporates from the web. The web can then be further processed into the final product.

It is well known that evaporation of water requires energy and is therefore relatively expensive. Efficient papermaking depends on extracting water during the forming and pressing operations and avoiding web defects that make the finished web unfit for use. Felt and wires are therefore particularly important because they not only affect water removal, but also the quality of the pitch itself, due to their intimate contact with the pitch. Deposits collected on the felt or wire can cause holes in the web and can be transferred to the web and thereby form defects.

The quality of the aqueous fiber suspension used to manufacture the web depends on many factors, including the wood and water used as raw materials, the composition of any recycled material added to the process, and the additives used in the manufacture of the suspension. A variety of dissolved or suspended materials can be introduced into the manufacturing process, including both inorganic materials such as salts and clays, and materials that are organic in nature such as resins or pitch from wood, as well as printing inks, latex and adhesives from recycled paper products. A build-up of deposits containing inorganic and/or organic materials on felt and other web-forming equipment is known as a troublesome obstacle to efficient papermaking. In particular, the sticky materials associated with recycled fibers are problematic, such as glues, resins, rubbers and the like.

Methods for fast and efficient removal of deposits from track-forming equipment are of great importance to the industry. The paper machines can be shut down for cleaning, but interrupted operation due to cleaning is unacceptable due to loss of production. On-line cleaning is therefore strongly preferred where this is practically possible.

The wire belt or cylinder used in web forming is continuously cycled, as a belt, during production. The web contact portion of the cycle begins where the application of the suspension to the wire belt or cylinder begins and continues until the formed web separates from the wire-over surface, and the return portion of the cycle, the wire returns from the position where the web has been removed from its surface to the beginning of the web contact portion. With viruses such as Fourdrinier wires, on-line cleaning has generally been performed during the return stage (ie where the wire is not in contact with the formed web) by treating the returning wire with a cleaning fluid (typically water), often by spraying the wire with liquid under pressure. The sprays can be assisted by mechanical surface cleaning. The use of water sprays, with or without mechanical assistance, has not been found to be sufficiently satisfactory to prevent the accumulation of either organic compounds or inorganic deposits on the wires, and additives have been used to obtain cleaning fluids that are more effective. Predominantly fibrous or inorganic materials have been effectively removed by using water-based formulations containing either acids or bases formulated with other chemicals, such as surfactants. Where organic deposits are present, these have been removed to a certain extent by the use of organic solvents, including some formulations containing aromatic compounds with a low boiling point or chlorinated hydrocarbons. In some machines, finely perforated textile belts are now used instead of the more traditional wires.

Paper machine felt also typically circulates in a belt-like fashion between a web contact stage and a return stage. During the web contact step, water is drawn from the web usually by means of presses and/or vacuum into the pores of the felt. A clean felt, with fine pores that are relatively open, is particularly desirable for efficient papermaking, as this results in efficient removal of water from the paper web. A felt cleaning procedure should remove both organic and inorganic deposits of both a general and localized nature, maintain the felt's porosity and condition the textile without chemical or physical attack on the substrate. Mechanical removal, typically blade contact, has been used to remove deposits from the felt's surface. Cleaning fluids are also used to remove difficult deposits of organic and inorganic materials. The textile composition and design of many paper machine filters make them vulnerable to chemical degradation. The cleaning chemicals should be easy to remove when cleaning. Both continuous and shock cleaning are used in most paper machines. The chemicals used include organic solvents, often chlorinated hydrocarbons. Acid- and base-based systems are also used, but with lower concentrations than with wire cleaning. High concentrations of alkali metal hydroxides are often useless for filter cleaning, as they attack the textile itself.

Some of the more effective organic solvents are classified as hazardous to health, as carcinogens (cancer-causing) and therefore require particularly careful handling. Other solvent based products can destroy plastic and rubber components used in the paper forming process. An on-line treatment of the felt, which we know has been used for many years with some success, involves contacting the felt with aqueous solutions of cationic surfactants such as e.g. alkyl-dimethylbenzyl-ammonium chloride, where the alkyl group consists of a mixture of C12H25, C14H29 and C16H33 groups. Experience has nevertheless shown that sticky materials still stick to the felt despite treatment with these surfactants. Another felt treatment practice that has been used recently is the application of aqueous solutions of cationic polymers to the felt. This type of treatment can contribute to the build-up of materials originating from the cationic polymers themselves.

Other path-shaping equipment such as e.g. coaters, filters, screens and rollers can also become contaminated. The process problems and treatments usually correspond to the felt system, even if certain elements such as e.g. preservation of porosity and avoidance of chemical breakdown of the textile, which is important when cleaning felt and certain other finely porous components, is not so critical for this other equipment.

Natural resins or rubber in fresh wood may vary, depending on the species. Certain types of pine, especially those containing 2% or more resin by weight, are usually used in very low proportions because of the gum and resin problems it can cause. Papermaking alum or sodium aluminate has usually been used to control deposits of natural resin from the wood. These products can be added to the total pulp system to deposit the resin on the fibers. The effectiveness of this approach is limited by such factors as pH, corrosion potential, paper web formation, and the need to control the interaction with other chemicals in the pulp system. Treatments that allow unlimited use of this problematic pine wood would provide a significant economic gain for some pulp and paper producers.

The ever-increasing use of recycled fibers has contributed to a more serious build-up of sticky materials during paper production. Glues, resins, gums, etc. found in recycled secondary fiber tend to adhere to various parts of the paper machine and resist on-line spray cleaning. The materials that adhere to the felt can seriously affect drainage and paper formation. The end result of the product is holes and in some cases tearing of the web during the paper processing. It may be necessary to stop the machines frequently to wash the felt and remove sticky materials associated with recycled fiber. The benefit of recycling paper can be reduced to a certain extent by reducing the productivity of the paper machine.

Certain organic cleaning agents that were previously commonly used are undesirable for environmental reasons. There has therefore become a greater need to develop cleaning agents that remove organic deposits without representing an environmental hazard. Naturally, formulations used must not have a degrading effect on the felt and other track-forming equipment. Although certain materials have been found to perform satisfactorily under certain conditions, there is still a need for more effective deposit control agents for papermaking, particularly where recycled fiber is used as a raw material.

Another approach to deposition control has been to use pulp additives such as anionic aryl sulfonic acid formaldehyde condensates or cationic dicyandiamide formaldehyde condensates. The additives can act as e.g. excipients, dispersants or surface-active compounds. In particular, it has been described that dicyandiamide formaldehyde aminoplast resins produce attachment of pitch (ie resinous material and rubbers) in the form of individual particles on the pulp fibers, so that the pitch particles are evenly distributed on the fibers themselves. The consequence of this is that the amount of pitch that accumulates in the paper machine is reduced, without causing black dots or spots of pitch in the paper product.

It has been found that the deposition of adhesive material from paper pulp on felt and other papermaking equipment used when processing a pulp slurry into paper webs can be avoided by applying to the equipment an aqueous solution containing at least approx. 2 ppm of a cationic polymer and applying to the equipment an aqueous solution containing compounds selected from the group consisting of water-soluble nonionic and cationic surfactants in an amount effective to prevent the build-up of deposits originating from the cationic polymer. Preferably, the aqueous solution containing the cationic polymer and the surfactant is free of anionic macromolecules. Preferred cationic polymers include protonated or quaternary ammonium polymers such as polymers formed by reaction of epihalohydrin with dimethylamine or diethylamine. Preferred cationic surfactants include alkyl dimethylbenzylammonium chlorides having alkyl groups of between 12 and 16 carbon atoms. The invention is particularly advantageous when it is used for the treatment of felt and similar equipment components used in the processing of pulp slurry for paper webs. The invention is characterized by what is stated in the characterizing part of claim 1, further features appear in claims 2-31.

One purpose of the invention is to produce a method which can effectively control deposits of material on paper forming equipment and thereby, among other things, improve efficiency in the production of paper with recycled or pine pulp fibers with a high content of resin.

Another object is to provide such an environmentally acceptable method and means for improving the productivity and product quality of papermaking processes.

These and other purposes and advantages of the present invention will be apparent from the following detailed description. Figure 1 is a schematic side section of the felts in a paper machine that can be processed according to the invention. Figure 2 is a schematic side section of the felts in a wadding-forming paper machine that can be processed according to the invention.

The present invention is directed to the use of aqueous solutions of certain water-soluble cationic polymers and certain water-soluble surfactants to mainly inhibit the deposition of both organic and inorganic material on the felts or other track-forming equipment, especially other fine-pored components of such equipment. The treatment, including a cationic polymer in combination with a cationic surfactant, provides surprisingly effective control of deposits on the treated equipment, even where recycled fibers form a significant part of the pulp formulation. The invention provides a particularly effective cleaning and treatment of felt for paper machines.

The invention has a wide range of application with regard to the precise type of polymer, and a considerable variety of different polymers can be used, provided they are cationic. The use of polyethenimines is considered to be within the scope of the invention, as well as the use of various polymeric materials containing amino groups, such as e.g. those prepared according to the method described in US patents 3,259,664, 3,642,572, 3,893,885 or 4,250,299, but it is generally preferred to use protonated or quaternary ammonium polymers. These preferred polymers include polymers obtained by reaction between epihalohydrin and one or more amines, and polymers obtained from ethylenically unsaturated monomers containing a quaternary ammonium group. The cationic polymers of the invention also include dicyandiamide-formaldehyde condensates. Polymers of this type are described in US patent 3,582,461. Either formic acid or ammonium salts, and most preferably both formic acid and ammonium chloride, can also be included as polymerization reactants. However, certain dicyandiamideformaldehyde condensates tend to agglomerate on filters and the like, even in the presence of cationic surfactants. A polymer of the dicyandiamide-formaldehyde type is commercially available, such as "Tinofix" from Ciba Geigy Chemical Ltd., Ontario, Canada, and contains as its active ingredient approx. 50% by weight of a polymer which is assumed to have a molecular weight in the range of approx. 20000 - 50000.

Of the quaternary ammonium polymers obtained from epihalohydrins and various amines, those obtained by reaction of epichlorohydrin with at least one amine selected from the group consisting of dimethylamine, ethylenediamine, and polyalkylenepolyamine. Triethanolamine can also be included in the reaction. Examples include those polymers obtained by reaction between a polyalkenyl polyamine and epichlorohydrin, as well as those polymers obtained by reaction between epichlorohydrin, dimethylamine and either ethylenediamine or a polyalkenyl polyamine. A typical amine that can be used is N,N,N',N'-tetramethylethenediamine and also ethenediamine used with dimethylamine and triethanolamine. Polymers of this type include those having the formula:

where A is 0 - 500, although other amines can of course also be used. The preferred cationic polymers of the invention also include those prepared by reaction of dimethylamine, diethylamine or methylethylamine, preferably either dimethylamine or diethylamine, with an epihalohydrin, preferably epichlorohydrin. Polymers of this type are described in US patent 3,738,945 and Canadian patent 1,096,070. Such polymers are commercially available as "Agefloc A-50", "Agefloc A-50HV" and "Agefloc B-50" from CSP Chemical Co., Inc., New Jersey, USA. These three products are reported to contain as their active ingredients approx. 50% by weight polymers with molecular weights of approx. 75000 - 80000, approx. 200,000 - 250,000, and approx. 20,000 - 30,000. Other commercially available products of this type are "Magnifloc 573C", which is sold by the American Cyanamid Company in New Jersey, USA, and is believed to contain as its active ingredient approx. 50% by weight of a polymer with a molecular weight of approx. 20,000 - 30,000.

Typical cationic polymers which can be used in the invention and which are obtained from ethylenically unsaturated monomers include homo- and copolymers of vinyl compounds such as vinylpyridine and vinylimidazole which can be quaternized with e.g. a C 1 -C 1 B alkyl halide, a benzyl halide, especially a chloride, or dimethyl or diethyl sulfate, or vinyl benzyl chloride such as e.g. can be quaternized with a tertiary amine with the formula NR1R2R3where Rx, R2 and R3 are independently lower alkyl, typically with 1 to 4 carbon atoms, so that one of R1#R2 and R3 can be C-L-C^-alkyl, allyl compounds such as e.g. diallyl-dimethylammonium chloride, or acrylic derivatives such as dialkylaminoethyl-(meth)acrylamide such as e.g. can be quaternized with a C 1 -C 4 alkyl halide, a benzyl halide or dimethyl or diethyl sulfate, a methacrylamidopropyl tri(C 1 -C 4 alkyl, especially methyl) ammonium salt or a (meth)acryloyloxyethyl tri-

(C 1 -C 4 alkyl, especially methyl)-ammonium salt, where the salt is a halide, especially a chloride, methosulfate, ethosulfate or 1/n of an n-valent anion. These monomers can be copolymerized with a (meth)acrylic derivative such as an acrylamide, an acrylate or methacrylate C-L-C4 alkyl ester or acrylonitrile or an alkyl vinyl ether, vinyl pyrrolidone, or vinyl acetate. Typically, such polymers will contain 10-100 mol-% repeating units of formula: and 0-90 mol-% repeating units of formula:

where R± represents hydrogen or a lower alkyl radical, typically with 1-4 C atoms, R2 represents a long-chain alkyl group, typically with 8-18 C atoms, R3, R4 and R5 independently represent hydrogen or lower alkyl groups, while X represents an anion, typically a halogen ion, a methosulfation, an ethosulfation or l/n of an n-valent anion.

Other quaternary ammonium polymers obtained from unsaturated monomers include the homopolymer of diallyl-dimethylammonium chloride containing repeating units of the formula:

In this regard, it should be noted that this polymer should be considered "substantially linear", as despite containing cyclic moieties, these moieties are linked together along a linear chain and there are no cross-links.

Other polymers which may be used and which are obtained from unsaturated monomers include those having the formula:

where Z and Z' , which may be the same or different, are

-CH2-CH=CHCH2- or -CH2-CHOHCH2-, Y and Y', which may be the same or different, are either X or -NR'R", X is a halogen of atomic weight greater than 30, n is an integer from 2 to 20, and R' and R" (i) can be the same or different alkyl groups with 1 to 18 C atoms optionally substituted

with 1-2 hydroxyl groups, or (ii) when taken together with N represents a saturated or unsaturated ring of 5-7 atoms, or (ii) when taken together with N and an oxygen atom, N represents the morpholine group. A particularly preferred such polymer is poly(dimethylbutenyl)ammonium chloride bis-(tri-ethanol ammonium chloride).

Other classes of polymers which may be used and which are obtained from ethylenically unsaturated monomers include polybutadiene which has been reacted with a lower alkylamine and some of the resulting dialkylamino groups have been quaternized. In general, the polymer will therefore have repeating units with the formula:

in the mole ratios arb^^rC, respectively, where R represents a lower alkyl radical, typically methyl or ethyl radical. It should be understood that the lower alkyl radicals need not be the same. Typical quaternizing agents include methyl chloride, dimethyl sulfate, and diethyl sulfate. Varying ratios of arb-^bjrc can be used with amine amounts (b1 + b2) generally 10-90% with (a + c) from 90-10%. These polymers can be obtained by reaction of poly-butadiene with carbon monoxide and hydrogen in the presence of a suitable lower alkylamine.

Other cationic polymers that are capable of reacting with anionic macromolecules and/or sticky materials in the paper pulp can also be used within the scope of the invention. These are considered to include cationic tannin derivatives, such as e.g. those obtained by a Mannich-type reaction of tannin (a condensed polyphenolic compound) with formaldehyde and an amine, in the form of a salt, i.e. acetate, formate, hydrochloride or quaternized, as well as polyamine polymers which are cross-linked, such as e.g. polyamide-amine/polyethylene-polyamine copolymers cross-linked with e.g. epichlorohydrin. Natural gums and starches modified to contain cationic groups are also considered useful.

The molecular weight of the most useful polymers in this invention is generally between approx. 2000 - 3000000, although polymers with molecular weight below 2000 and above 3000000 can also be used with some success. Preferably, the molecular weight of the polymer used is at least approx. 10,000 and most preferably at least approx. 20,000. Preferably, the molecular weight of the polymer used is approx. 300,000 or less, and most preferably approx. 500 00 or less. The most preferred polymers have a molecular weight in the range of approx. 20000 - 50000. Mixtures of polymers can also be used.

The invention also has a general field of application with regard to the particular type of non-ionic or cationic surfactants that can be used, and a considerable variety of different surfactants can be used in combination with the polymer component, provided that they are water-soluble. Suitable nonionic surfactants include condensation products of ethylene oxide with hydrophobic molecules such as higher fatty alcohols, higher fatty acids, alkyl phenols, polyethylene glycol, esters of long chain fatty acids, polyhydric alcohols and their partial fatty acid esters, and long chain polyglycol partially esterified or etherified. A combination of these condensation products can also be used.

Cationic surfactants are generally preferred. Particularly preferred cationic surfactants suitable for use in the invention include water-soluble surfactants with molecular weights in the range of approx. 200 - 800 with general formula

where R is independently selected from the group consisting of hydrogen, polyethylene oxide groups, polypropylene oxide groups, alkyl groups with approx. 1-22 C atoms, aryl groups and

aralkyl groups where at least one of the R groups is an alkyl group with at least approx. 8 C atoms and preferably an n-alkyl group with approx. 12-16 C atoms, where X" is an anion, typically a halogen ion (e.g. chloride) or l/n of an n-valent anion. Mixtures of these compounds can also be used as surfactants in this invention.

Preferably, two of the R groups in the cationic surfactants of the formula are selected from the group consisting of methyl and ethyl, and most preferably is methyl, and preferably is a

R group selected from the aralkyl groups

CH2-, and most preferred is benzyl.

Particularly useful surfactants include dimethylbenzylammonium chloride having alkyl groups of 12-16 C atoms. A commercially available product of this type includes a mixture of alkyldimethylbenzyl ammonium chlorides where approx. 59% of the surfactant has a C14H29n-alkyl group, approx. 40% of the surfactant has a C12H2Sn-alkyl group and approx. 10% of the surfactant has a C16H33n alkyl group. This product is known for its microbiocidal effect.

The surfactants considered useful in this invention also include the group of pseudo-cationic materials having a molecular weight of about 1000 - 26000, with general formula NR1R2R3, where Rx and R2 are polyethers such as polyethylene oxide, polypropylene oxide or a combined chain or ethylene oxide and propylene oxide, and where R3 is selected from the group consisting of polyethers, alkyl groups or hydrogen. Examples of such types of surfactants are described in US patent 2,979,528.

It has been found that when the cationic polymers according to this invention are used together with non-ionic and/or cationic surfactants on filters, the felts will resist the build-up of sticky deposits. In particular, the build-up of sticky material in connection with recycled fibers is effectively controlled. In this way, the invention is particularly advantageous for paper production where large proportions are used, e.g. at least 10%, recycled fibre. Outstanding results have also been achieved with systems where the recycled material has accounted for at least 70% of the fibres, and even for systems where the pulp consists of approx. 100% recycled material. The invention is also very advantageous for controlling the deposition of resin from fibres, mainly (e.g. 5% or more) obtained from pine wood containing more than 2% by weight of resin: even the mechanism of this phenomenon is not fully understood, it is well known that additive materials associated with recycled fiber are generally hydrophobic, and it is assumed that the products formed after interactions of these hydrophobic materials with the cationic components of the invention are more easily soluble in water. The moistened adhesive materials can therefore largely lose their tendency to stick to the underlying felt surface, so that they can be easily removed from the felt. The pulp is also known to contain colloidal materials and anionic macromolecules, including synthetic anionic macromolecules which may be added as part of the manufacturing process in the same way as these natural anionic polymers, resins, soaps, surfactants and organic acids (e.g. abietic acid) which in industry is associated with "anionic waste". It is believed that the cationic components applied according to the invention can react with the anionic macromolecules and colloidal particles and form products that can be easily removed from the felt. In any case, the tendency of tacky materials to pass through the papermaking equipment instead of sticking to it is greatly improved by the treatment according to the invention.

The cationic polymers and surfactants according to the invention are applied in an aqueous solution directly to the equipment to be treated. A treatment with the surfactant alone has not provided the same degree of deposition control as is obtained with the combinations in the invention. On the other hand, without sufficient surfactant it will result in a build-up of deposits from the polymer itself and thus, in the case of felt, give a reduced porosity which may possibly reduce the removal of water or in other ways affect the production (i.e. by increased stickiness ). The treatment amount of polymer and surfactant should generally be adjusted to the requirements of the particular system to be treated. Preferably, the aqueous solution containing cationic polymer and surfactant should be essentially free of anionic macromolecules. These anionic materials include natural materials such as lignin from the wood, by-products from chemical digestion such as e.g. sodium lignosulfonates and synthetic materials such as e.g. polyacrylates.

The polymers and surfactants according to the invention are typically produced in the form of liquid mixtures consisting of aqueous solutions of polymer and/or surfactant. The polymer concentrations can range from relatively dilute solutions with polymer concentrations suitable for continuous application, up to the solubility or gelation limit of polymers, but generally the mixtures are relatively concentrated for practical transport and handling. The liquid mixtures can consist of other materials which further dissolve the polymers, so that more concentrated mixtures are possible. An example of these materials are alkoxyethanols such as butoxyethanol. Aqueous mixtures suitable for transport and handling will generally contain 5-50% by weight of the active cationic polymer according to the invention. While the cationic surfactants according to the invention can be used as separate mixtures alongside the polymer mixtures and then either applied to the felts separately (e.g. by using separate spray systems) or mixed before application, it is preferred that the aqueous mixtures contain both the cationic surfactant and the cationic polymer. Although other reagents may also be present in the mixtures according to the invention, useful mixtures can be produced according to the present invention which contain a pitch control agent consisting mainly of the aforementioned cationic surfactants and cationic polymers. In general, aqueous mixtures suitable for transport and handling will contain approx. 5-50% by weight in total of polymer and surfactant components. The weight ratio between surfactant and polymer in such combined mixtures is generally between approx. 50:1 and 1:50. Preferably, the surfactant/polymer weight ratio in aqueous solutions is between approx. 10:1 and 1:1, especially where oils may be present, and most preferably approx. 1:1 for general applications, although an excess of surfactant (eg a weight ratio of 1.1:1 or more) may be considered very appropriate in cases where oils are present.

An aqueous mixture particularly suitable for separate application of the polymer component in conjunction with application of the surfactant is commercially available from Dearborn Chemical Co., Ltd. Ontario, Canada and consists of approx. 17% by weight of an active polymeric condensation product of formaldehyde, ammonium chloride, dicyandiamide and formic acid which has an assumed molecular weight of approx. 20,000 - 50,000, approx. 2% by weight of an active polymer obtained by reacting epichlorohydrin with dimethylamine with an assumed molecular weight of approx. 20,000 - 30,000, and approx. 8% by weight butoxyethanol. Smaller amounts of other materials, including approx. 0.4% by weight of active alkyldimethylammonium chloride surfactant containing a mixture of C12, C14 and C16n-alkyl substituents described above is also present in this product, but is not considered decisive when added separately. In particular, the relative amount of alkyldimethylammonium chloride in this product is believed to be insufficient to activate the polymer deposition inhibiting effect of this invention. Other aqueous formulations considered particularly suitable for separate addition of polymer are also commercially available from Dearborn Chemical Co., Ltd., and consist of 17% by weight of an active poly(hydroxyalkanedimethylammonium chloride) molecular weight of about 20000. An aqueous formulation considered particularly suitable for separate addition of the surfactant in this invention is also available from Dearborn Chemical co., Ltd., and comprises about 16% by weight of active alkyldimethylbenzylammonium chloride surfactant mixture described above.

The most appropriate treatment doses depend on such system factors as the type of adhesive material and whether the cleaning is continuous or intermittent. Even liquid mixtures containing relatively high concentrations of a polymer in the invention (e.g. 50%) can be used at full strength (100% as liquid component) by e.g. spraying the undiluted liquid mixture directly onto the felt. Especially in cases where continuous application is used, the mixtures can advantageously be diluted at the treatment site with clean water or other aqueous liquids. Where it is important for a good water economy, good quality process water can be sufficient for the dilution.

The benefits of this invention can be achieved at application concentrations as low as 2 ppm polymer, especially where continuous application is used, and as described further below, sufficient surfactant to inhibit build-up of deposits from the applied cationic polymer component.

"Continuous processing" of felt as used herein means that the felt is routinely processed at least once during the cycle between the web contact step and the return step. This routine treatment is preferably used in the first part of the return step. The felt can be contacted with the web so that even the sticky material, including that which

typically associated with recycled material, is prevented from sticking to the felt and that the deposited material is easier to wash away when the aqueous wash solution is applied during the return step. In some cases, it is not practical

tic with continuous treatment, and treatment with cationic polymers and surfactants according to the invention can be periodic. For example, aqueous solutions of the polymer and the surfactant can be sprayed onto the felt until the felt is satisfactorily conditioned, and the spraying can then be interrupted until supplementary treatments are necessary to prevent further build-up of deposits on the felt.

Processing procedures are more specifically described with reference to the models of felt systems in papermaking which are schematically shown in a simplified form in figures 1 and 2. The press felt system represented generally as (10) in figure 1 comprises a top press felt (12), a bottom press felt (14), a final bottom press felt (16) and a final bottom press felt (18). The last bottom press felt is shown wound around a series of rollers (20), (21), (22), (23), (24), (25) and (26) and press rollers (29), the bottom press felt is wound around a number of rollers (30), (31), (32), (33), (34), (35) and

(36) and press rollers (37) and (38), the top press felt (12) is shown wrapped around a series of rollers (40), (41), (42), (43), (44) and (45) and press roller (47), and the last top press filter is shown wrapped around the press roller (49) and a series of rollers (60), (61), (62) and (63). Both the top press felt (12) and the bottom press felt (14) pass between the press rollers (37) and (47). The bottom press felt (14) passes between the rollers (38) and (48), and both the last bottom press felt (16) and the last top press felt (18) pass between the press rollers (29) and (49). Sprayers for washing the top press felt (12), the bottom press felt (14), the last bottom press felt (16) and the last top press felt (18) are shown at (50), (51), (52) respectively ) and (53). A track support roller is shown at (55). The press (57) comprises the press rollers (37) and (47), the press (58) comprises the press rollers (38) and (48) and the press (59) comprises the press rollers (29) and (49).

The press felt system (10) shown in Figure 1 is positioned to receive web material from a Fourdrinier wire type machine represented only in part by (64) in Figure 1, where a wire (65) is adapted to receive an aqueous pulp from an in -running box (not shown). The liquid is filtered through openings in the wire as the wire passes in the web contacting stage to a lump crusher roll (66) and a treatment roll (67) which is generally positioned to physically compact the web material and remove it from the wire (65). The wire (65) passes over a main roller (68) and returns to receive more pulp. The return is typically directed past a number of sprayers (not shown) and wash rollers as shown at (69). Other sprayers (not shown) can be placed at special components of the system, such as the lump breaker roller (66) or the main roller (68).

When operating the felt system shown in Figure 1, the web material is removed from the wire (65) after the treatment roller (67), passed between the rollers (45) and (36) and pressed between the top press felt (12) and the bottom press felt (14) at the press rollers (37) and (47) in press (57). The web material moves with the bottom press felt (14) to the press (58) where it is pressed between the bottom press felt and the press roller (48) by means of the press roller (38). The web material is then removed from the bottom press felt (14) and moves to press (59) where it is pressed between the last bottom press felt (16) and the last top press felt (18) by the press rolls (29) and (49) in the press (59). The web material is then removed from the last press felt (16) and passed over the guide roller (55) and on to other processing equipment such as dryers (not shown). In the press felt system (10) of Figure 1, the web contact step with the top press felt (12) is from the roller (45) or a point between the roller (45) and the press (57) to a point after the press (57); the web contact step with the bottom press felt (14) lasts from a point between the roller (36) and the press (57) to a point after the press (58), the web contact step with the last bottom press felt

(16) lasts from the roller (26) to a point after the press (59) and the web contact step with the last top press felt (18) lasts from a point between the roller (63) and the press (59) to a point after the press (59) .

It will be clear that other equipment such as various presses, rollers, syringes, conductors, vacuum equipment and stretching equipment can be included in the felt system 10. Special twist presses can be used to press moisture from the felt itself. Furthermore, some of the equipment shown, such as e.g. the press (58) and the last top press felt (18) are omitted from the felt system. It will further be clear to a person skilled in the art that the felt systems are highly variable with respect to the number of filters used and the design of the felt circulation system.

Felt systems are also used in conjunction with papermaking processes that do not use Fourdrinier wire formers. One such alternative system for the production of heavier track materials uses vessel formers. The initial steps in the vessel forming system are generally shown in Figure 2. The system (70) comprises a series of wire cylinders (72) and (73) which rotate so that one end of the cylinder is brought into contact with the pulp and rotated to deposit a layer of paper web on a lower treatment felt (75). In addition to the lower treatment felt (75), the system (70) comprises a first upper treatment felt (76) and a second upper treatment felt (77). The treatment rollers (78) and (79) are positioned to assist in transferring web material from the tubs (72) and

(73) respectively on the lower bottom felt (75). The lower treatment felt (75) is shown wound around treatment rollers (78) and (79), rollers (80), suction roller (81) and press rollers (83), (84), (85) and (86). The first upper treatment felt is shown wound around the rollers (88), (89) and (90) and the suction drum (91), and the second upper treatment felt is shown wound around the press rollers (93), (94), (95) and ( 96) and the rollers (97), (98), (99) and (100). Both the lower treatment felt (75) and the first upper treatment felt (76) pass between the suction roller (81) and the suction roller treatment roller (91) which sucks water from the felt and the fiber cloth. Both the lower processing felt (75) and the second upper processing felt (77) pass through the press rollers (83) and (93), between the press rollers (84) and (94), between the press rollers (85) and (95) and between the press rollers (86) ) and

(96). The press (103) comprises the press rollers (83) and (93), the press (104) comprises the press rollers (84) and (94), the press

(105) comprises the press rollers (85) and (95) and the press (106) comprises the press rollers (86) and (96) .

Syringes for washing the lower treatment felt (75), the first upper treatment felt (76) and the second upper treatment felt (77) are respectively shown at (107), (108) and (109).

When operating the felts shown in figure 2, the web material removed from the vessels (72) and (73) is fed onto the lower treatment felt (75) above the suction roller and pressed between the lower treatment felt and the second upper treatment felt (77) at each of the presses ( 103), (104), (105) and (106). The track material is then separated from the treatment felts (75) and (77) and passed on to other treatment equipment such as the felt system (10) shown in Figure 1.

In the system shown in Figure 2, the web contact step with the lower treatment felt (75) lasts from the tub (72) to just after the press roller (86), the web contact step with the first upper treatment felt is at the suction roller-treatment roller, and the web contact step with the second upper treatment felt lasts from the roller (100) to right after the press roller (96). It will appear that more equipment in the form of vessels, presses, rollers, syringes, conductors, vacuum equipment and stretching equipment can be included in the system (70). Furthermore, certain components shown may be omitted from a vessel forming equipment. It will be clear to one skilled in the art that vessel forming systems are very different with regard to the number of filters used and the design of the felt circulation systems.

Each felt (12), (14), (16), (18), (75), (76) and (77) in the systems shown in Figures 1 and 2 can be treated continuously according to this invention by applying an aqueous solution of a suitable cationic polymer and surfactant on the felt anywhere along its return stage (ie from the point where the felt is not in contact with the web material to the point where it is again brought into contact with the web material).

Preferably, the solution is sprayed onto the felt early in the return step, so that sticky material that has been transferred from the web to the felt can be processed quickly. The location of the treatment is often limited by the design of the felt system. Syringes as shown at (50), (51), (52), (53), (107), (108) and (109) in Figures 1 and 2 can be used for treatment purposes. In cases where the applied solution has a higher concentration than is necessary for continuous treatment, the application can be interrupted and resumed as needed. When syringes such as shown at (50), (51), (52), (53), (107), (108) and (109) are used to apply solution, they can be activated intermittently and shut down according to system requirements. Equipment other than the felts may be treated in a similar manner consistent with their process operation.

In typical papermaking processes, especially those using significant amounts of recycled fiber, the cationic polymer is generally applied in amounts of at least about 0.002 g/m<2>/min, preferably approx. 0.01 g/m<2>/min or more when continuous treatment is used, and preferably approx. 0.02 g/m<2>/min or more when treatment is intermittent. Preferably, polymer application rates of 0.5 g/m<2>/min or less are used to minimize the possibility of felt plugging. For standard paper machines with foot widths of 2 to 7 meters and felt lengths of 10 to 40, an application quantity is used which is usually approx. 0.02 to 20 grams of polymer per minute per meter width (i.e. g/m/min), more commonly between approx. 0.05 to 12.6 g/m/min. One technique involves applying 1 g/m/min or more initially, until the felt is conditioned. Once the conditioning is achieved, the amount applied can be reduced, or as described above, the application can be periodically discontinuous. The surfactant is applied to the felt in an amount that effectively inhibits the build-up of deposits from the applied polymer and is therefore important for controlling felt plugging. Consequently, the weight ratio of surfactant to polymer is usually kept between approx. 50:1 and 1:50. Preferably, in order to provide sufficient surfactant to control the build-up of deposits from the polymer and provide protection from accidental amounts of impurities and oily materials from the pulp, the surfactant to polymer weight ratio is about 1:1 or more, and to avoid applying an excess of surfactant, the weight ratio of surfactant to polymer is preferably approx. 10:1 or less. The most preferred ratio between these two components is approx. 1:1. In all cases, it is preferred to apply the surfactant in a concentration of at least approx. 1 ppm. Other equipment such as wires, screens, filters, rollers and suction boxes, and materials such as metals, granite, rubber and ceramics can also be advantageously treated according to the invention. The invention is particularly applicable in connection with the treatment of felt and similar equipment with pores that are suitable for attracting water (ie relatively fine pores) where the build-up of large amounts of deposits from the polymer is undesirable, in contrast to other equipment such as e.g. metals and plastic wires with relatively large pores for draining water through them, where a certain build-up of deposits does not seem to cause unwanted problems.

In any case, the concentration of cationic polymer and aqueous solution applied to the felt or other equipment should be at least approx. 0.0002% by weight. In order to achieve an even distribution of polymer, a spray system according to the invention is preferably used with an aqueous spray solution with between approx.

0.0002 wt% and 0.02 wt% cationic polymer.

Application of the invention will further be apparent from the following examples.

EXAMPLE I

The experiment in this example was carried out on a paper machine with a Fourdrinier wire former. The machine had a first top press felt, a first bottom press felt, a second top press felt and a second bottom press felt, similar to the top press felt (12), the bottom press felt (14), the last top press felt (18) and last bottom press felt (16) shown in figure 1. Each of the felts had syringes. The first press felt received web material from a Fourdrinier wire located in a similar manner to unit (64) in Figure 1, and produced corrugated paper from a stock containing approx. 20 secondary (recycled) fibers and approx. 80 new hardwood fibers.

The web material formed on the wire was separated therefrom and taken to a first press, similar to the press (57) in Figure 1, where it was pressed between the first top press felt and the first bottom press felt. The web was then separated from the first press felts and taken to a second press, similar to press (59) in Figure 1, where it was pressed between the second top press felt and the second bottom press felt.

The machine had previously been exposed to deposits on the press felts, especially on the second top press felt. The deposit was due to pitch and sticky materials from the pulp and recycled material and was picked up from the fiber web in contact with the felts. Lane breakage at the second press had been a continuous problem, and happened on individual occasions as often as once per year. 8 hour shifts. Periodic stoppages were therefore necessary to reduce the number of lane breaks. The second top press felt was approx. 6 meters wide and approx. 20 meters long (ie the second top press filter had a treatment area of approx. 114.3 m2).

The second top press felt was treated according to the invention by mixing into the spray water of an existing high-pressure sprayer, similar to the sprayer (53) in figure 1, a trial product containing approx. 7.5% by weight of the alkyldimethylbenzylammonium chloride mixture described above, which contains C12, C14 and C16n-alkyl substituents and approx. 7.5% by weight of a polymer with a molecular weight of approx. 2,000 0 which is obtained from dimethylamine and epichlorohydrin, and approx. 85% solvent (which mainly consisted of water with smaller amounts of materials such as ethanol mixed in the commercial mixture of surfactant and/or polymer). The initial dosage was approx. 0.06 g/min/m<2> of each component, and the dosage was then reduced after four hours to approx. 0.02 to 0.03 g/min/m<2>.

The effect of the treatment was monitored with a Huyck & Smith porosity meter and by the number of fractures that occurred in the second press section. The felt's porosity is a measure of its ability to absorb water from the pitch. A felt with high porosity

(ie with open pores) is desirable for good dewatering of the track.

The relative porosity of the second top press felt was followed over a 21 day trial period using a Huyck&Smith procedure which gives a relative porosity number (H.S. number) ranging from 100% for non-porous or plugged filters to lower percentages for more porous filters . The H.S. figure for the second top press felt was maintained at approx. 3 5% in the first days of the trial. The supply of treatment product was accidentally stopped for 24 hours. An increase in the H.S. figure was observed to approx. 50%, which was attributed to the cessation of treatment. The felt was cleaned and the experiment was resumed. The H.S. number decreased to approx. 45%, where it remained for several days. The dosage of each treatment component was then halved due to pump failure and an increase in the H.S. number to 53% was observed. The dosage was regulated to the previous level and the HS number remained at approx. 53% the rest of the experiment.

The porosity measurements during the experiment showed that when the polymer and the surfactant were applied according to the invention, a certain porosity was maintained. When the supply stopped, plugging increased by approx. 15 to 40%. In addition, web breakage caused by the second top press felt was completely eliminated during the 30 day trial period.

Accordingly, it was concluded that the treatment according to the invention prevented breaks and interruptions attributable to deposits on the second press, that the treatment prevented collection on the treated felt and that felt plugging of fibers was significantly reduced during the treatment.

EXAMPLE II

The experiment in this example was carried out on a tub-former type (instead of a Fourdrinier) paper machine. The machine had a primary bottom felt, a suction roller treatment felt and a primary top felt corresponding respectively to the lower treatment felt (75), the first upper treatment felt (76) and the second upper treatment felt (77) shown in Figure 2. The machine also had a secondary top felt, a secondary bottom felt and a final felt corresponding respectively to the top press felt (12), the bottom press felt (14) and the last bottom press felt (16) shown in Figure 1 (i.e. there was no felt corresponding to the last top press felt ( 18). Each of the blankets had syringes. The machine had 7 wire cylinders (i.e. tubs) placed in series partly corresponding to the two tubs (72) and (73) shown in fig. 2, and manufactured cardboard (i.e. straw board, sleeve board, box board, etc.) from 100% recycled weight.

The paper web formed on the cylinders and separated from the cylinders is attached to the underside of a primary bottom felt. While the web was on the primary bottom felt, it was pressed between the primary bottom felt and the suction roller treatment felt and then passed through approx. four others press between the primary bottom felt and the primary top felt. The web was then separated from the primary bottom felt and taken to a second press, somewhat corresponding to the press (57) in fig. 2, where it was pressed between the secondary top felt and the secondary bottom felt. The web was then separated from the secondary press felts and transferred onto a final felt, where it was again pressed in a press corresponding to the press (59) in fig. 1, using a top press roll without felt.

For the experiment with the combination of cationic polymer and cationic surfactant, the primary bottom felt, the suction roller treatment felt, the primary top felt and the secondary top felt were pretreated in the usual manner with alkyldimethylbenzylammonium chloride product containing the mixture of C12, C14 and C16n alkyl substituents described above, at to use syringes located corresponding to the syringes (107),

(108), (109) and (50) in figures 1 and 2 respectively. In the experiment, a test product containing approx. 7.5% by weight alkyldimethylbenzylammonium chloride mixture, 7.5% by weight of a polymer with a molecular weight of approx. 20,000, obtained from dimethylamine and epichlorohydrin, and approx. 85% by weight solvent (ie the same product used in example 1) diluted in the spray water to an assumed concentration of approx. 2.6 ppm of both the surfactant and the polymer and applied to the same four felts.

After the felts showed no signs of plugging as a result of the polymer addition during the first treatment period, the concentration of surfactant and polymer was increased 50% (to an estimated level of about 4 ppm). Treatment continued at this level for the remainder of the trial period. Each of the components was applied to each field in an amount of approx. 1.5 g/min at the beginning of the experiment and approx. 2.25 g/min for the remainder of the experiment. The primary bottom felt, suction roller treatment felt, primary top felt and secondary top felt were all approx. 2.3 m wide and respectively approx. 31.2 m, 18.6 m, 19.8 m and 12.6 m long (ie the treatment surface was 74.9 m<2>, 44.7 m<2>, 47.5 m<2> and 30 0 m2). During the experiment, the relative porosity was measured as vacuum (mm Hg) along the width of the treated felts and also across the untreated secondary bottom felt. A significant increase in the vacuum will represent destruction of the felt, The results are shown in Tables I to V.

It will be clear from Tables I to V that cationic polymer can be supplied to paper machine filters according to the invention without plugging the felts and destroying their porosity. The press load (i.e. the pressure applied by the press rollers in the six presses in the paper machine) remained unchanged during the trial and the vacuum pressures (i.e. the suction pressure applied to remove liquid from the felts), measured at 13 points on the primary bottom felt , the suction roller processing felt, the primary top felt, the secondary top felt and the secondary bottom felt, remained unchanged over the trial period. The treatment vacuum remained unchanged during the experiment. Various track characteristics were also measured during the experiment and are summarized in table VI.

the tub was approx. 38°C. The weight consistency was approx. 0.37% for cylinders 1 and 7, and approx. 0.40% for cylinders 2, 3, 4, 5 and 6. The paper grade remained unchanged during the experiment. Optimum humidity was assumed to be approx. 5% and optimal thickness was assumed to be approx. 800.

It will appear from table VI that an advantageous web moisture was maintained throughout the experiment and that the high speed could be maintained during and after treatment of the felts according to the invention.

EXAMPLE III

The experiment in this example was carried out on a single wire Fourdrinier paper machine with a pick-up felt and a series of presses and filters leading to a Yankee cylinder. The machine typically processed pulp with a significant proportion (ie between 40 and 100%) of de-inked recycled pulp. The pulp was typically kept at a pH of 6.0-6.5 and a temperature of about 40°C, and the amount produced was about 50 tonnes per day and night.

Before the experiment, the felt needed up to 15 washings per day with organic solvent and/or mixtures of organic solvent with detergent. Up to 19 liters were used per wash (ie up to approx. 284 liters of solution per day). Washing with the solution was determined by the track quality. Significant quantities of paper could not be sold due to poor quality. The de-inked recycled pulp, which was relatively inexpensive and therefore desirable in large proportions, was considered to cause production problems which in turn could result in poor quality and/or web failure. For practical reasons, the quantity of recycled de-blackened pulp was typically limited to approx. 60%.

Before the experiment, a new pick-up felt with approx. 2.7 meters wide and 16.2 meters long. Two lubrication syringes for the pick-up felt were placed. Filters of this type typically had a lifetime of approx. 50 days. A new low-pressure fan sprayer was installed for trials on the lane side of the felt approx. 1 meter before the suction box. The sprayer used fresh water and had 13 nozzles, each of 7.6 liters per minute.

During the experiment, an experimental product containing approx. 7.5% by weight alkyldimethylbenzylammonium chloride mixture, approx. 7.5% by weight polymer with a molecular weight of approx. 20,000 obtained from dimethylamine and epichlorohydrin, and approx. 85% by weight solvent (ie the same product as in examples I and II) diluted in fresh spray water in the new low-pressure sprayer to an estimated concentration of approx. 34 ppm of each of the surfactant and the polymer, and applied to the felt in an amount of approx. 0.09 g/m<2>/min each of surfactant and polymer.

Although the felt porosity was not monitored in this machine, it was clear that after several hours after the start of the experiment, the cleaning frequency could be reduced. Furthermore, the content of de-blackened weight was increased to approx. 100% The washing was reduced to 5 to 12 washings per day for five days, and the solution used for each wash was reduced to approx. 11.3 liters per wash, which resulted in a reduction of daily solution consumption of approx. half that (i.e. approx. 13 6 liters per day).

The low-pressure sprayer was moved to a new position after the suction box. Washing was further reduced to approx. 3 times per day and night. The new injection position was thought to represent an improvement.

The pulp composition was changed to 60% de-blackened pulp/ 40% new fibres. For this quality, washing was reduced to 1 wash per day and night.

Even from this initial attempt which lasted approx. 18 days it was clear that processing the felt on this machine in accordance with the invention would result in significant cost savings by enabling the use of pulp with a high content of de-blackened pulp without this causing significant operational problems, by reducing the number of necessary washings which are necessary for efficient production and the volume of solution used for washing, and by reducing the amount of finished paper of unacceptable quality.

Claims (45)

1. Method for preventing the deposition of sticky material on paper machine felt or similar equipment components used to convert paper pulp into a web, characterized in that it comprises a) applying to these equipment components an aqueous solution containing at least 2 ppm of a cationic polymer, and b) applying to the equipment components an aqueous solution of at least one compound selected from the group consisting of water-soluble, non-ionic or cationic surfactants, which is applied in an amount effective to prevent the build-up of such sticky deposits. 2. Method according to claim 1, characterized in that the cationic polymer is a dicyandiamide-formaldehyde condensate polymer optionally containing at least one compound selected from the group consisting of formic acid and ammonium salts as polymerization reactants. 3. Method according to claim 2, characterized in that the cationic polymer is obtained by reaction between formaldehyde, dicyandiamide, formic acid and ammonium chloride. 4. Process according to claim 1, characterized in that the cationic polymer is obtained by reaction between an epihalohydrin and one or more amines, or is obtained from ethylenically unsaturated monomers containing quaternary ammonium groups. 5. Method according to claim 1, characterized in that the cationic polymers are protonated or contain quaternary ammonium groups. 6. Method according to claim 1, characterized in that the cationic polymer is obtained by reacting an epihalohydrin with at least one compound selected from the group consisting of diethylamine, dimethylamine and methylethylamine. 7. Method according to claim 6, characterized in that the cationic polymer is prepared by reacting epichlorohydrin with dimethylamine. 8. Method according to claim 6, characterized in that the cationic polymer is prepared by reacting epichlorohydrin with diethylamine. 9. Method according to claim 1, characterized in that the concentration of the cationic polymer in the aqueous solution is between 0.0002 and 0.02% by weight and the weight ratio between surfactant applied to the felt and polymer applied to the felt is between 50:1 and 1:50. 10. Method for controlling the deposition of material on a paper machine felt circulating between a web contact step and a return step according to claim 1, characterized in that the surfactant and the cationic polymer are applied to the paper machine felt in the same aqueous solution during its return step in a weight ratio between surfactant and polymer between 50:1 and 1:50. 11. Method according to claim 10, characterized in that the aqueous solution is essentially free of anionic macromolecules. 12. Procedure according to claim 10, characterized in that the cationic polymer is applied in an amount of at least 0.002 g/m<2>/min. 13. Method according to claim 10, characterized in that the deposits on the felt that receives web material from the vessels in a vessel forming machine are checked. 14. Method according to claim 10, characterized in that the deposits on the felts that receive track material from the wire of a Fourdri nine wire forms are checked. 15. Method according to claim 10, characterized in that continuous treatment of the felt with the aqueous solution is used. 16. Method according to claim 15, characterized in that the cationic polymer is applied in an amount of at least 0.01 g/m<2>/min. 17. Method according to claim 10, characterized in that the treatment of the felt with an aqueous solution is intermittent. 18. Method according to claim 17, characterized in that the cationic polymer is applied in an amount of at least 0.02 g/m<2>/min during the application period. 19. Method according to claim 1, characterized in that at least 10% of the fibers in the paper pulp are obtained from recycled material. 20. Method according to claim 1, characterized in that the fibers in the pulp are obtained approx. 100% from recycled material. 21. Method according to claim 1, characterized in that the paper machine pulp is mainly obtained from pine wood containing 2% by weight or more resin. 22. Method according to claim 1, characterized in that the aqueous solution containing the surfactant contains at least 1 ppm surfactant. 23. Method according to claim 1, characterized in that the applied surface-active agent is selected from the surface-active agents that have a molecular weight of between 200 and 800 and with a general formula where each R is independently selected from the group consisting of hydrogen, polyethylene oxide groups, polypropylene oxide groups, alkyl groups with between 1 and 22 carbon atoms, aryl groups, and aralkyl groups, where at least one of the R groups is an alkyl group with at least 8 carbon atoms and in which X "is an anion, or l/n of an n-valent anion. 24. Method according to claim 23, characterized in that at least one R-group in the surfactant is an n-alkyl group with 12 - 16 carbon atoms. 25. Method according to claim 24, characterized in that two of the R groups in the 26. Method according to claim 24, characterized in that the surfactant is an alkyldimethylammonium chloride or a mixture of alkyldimethylammonium chlorides. 27. Method according to claim 1 when treating paper machine felt that circulates between a web contact stage and a return stage, characterized in that it comprises the steps: applying to the felt during the return step an aqueous solution containing (i) at least 2 ppm of a cationic polymer with a molecular weight between 10,000 and 300,000, and (ii) a water-soluble surfactant with a molecular weight between 200 and 800 of general formula where each R is independently selected from the group consisting of hydrogen, polyethylene oxide groups, polypropylene oxide groups, alkyl groups with 1 to 22 carbon atoms, aryl groups, and aralkyl groups, where at least one R group is an alkyl group with at least 8 carbon atoms, and wherein X" is an anion or l/n of an n-valent anion, wherein the surfactant is applied to the felt in an amount effective to prevent build-up of deposits from the cationic polymer, and the cationic polymer is applied in amounts between 0.002 and 0.5 g/m<2> /my. 28. Method according to claim 27, characterized in that the felt is routinely treated at least once during the cycle between the web contact step and the return step and in which the cationic polymer is applied in an amount of at least 0.01 g/min/m<2>felt. 29. Method according to claim 27, characterized in that the aqueous solution is sprayed onto the felt in an amount of at least 0.02 g of cationic polymer per min per m<2>felt until a satisfactory treatment has been achieved and after which the spraying is interrupted until new treatments are necessary to further inhibit the build-up of deposits on the felt. 30. Method according to claim 1 for controlling deposits of adhesive materials on paper machine felt in a papermaking system, where recycled fibers account for at least 10% of the fibers in the system, and where the felt moves between a contact stage and a return stage, where the pulp contains both anionic macromolecules and adhesive materials for webs, characterized in that the method comprises the following steps: contacting the felt during the return step with an aqueous solution which is essentially free of anionic macromolecules and contains (i) at least 2 ppm of a cationic polymer having a molecular weight between 10,000 and 3,000,000 and (ii) a water-soluble surfactant with a molecular mass between 200 and 800 with general formula: where each R is independently selected from the group consisting of hydrogen, polyethylene oxide groups, polypropylene oxide groups, alkyl groups with 1 to 22 carbon atoms, aryl groups and aralkyl groups, where at least one R group is an alkyl group with at least 8 carbon atoms, and where X" is an anion or l /n of an n-valent anion, said surfactant is applied to the felt in an amount effective to prevent the build-up of deposits obtained from the cationic polymer and the cationic polymer, and the surfactant is applied in a ratio by weight of surfactant to polymer of 10 :1 to 1:1, and reacts with the anionic macromolecules and adhesive materials to form products that can be easily removed from the felt. 31. Method according to claim 30, characterized in that recycled fibers account for at least 70% of the fibers in the system, and where the cationic polymer is applied to the felt in an amount of at least 0.002 g per minute per m<2>felt. 32. Mixture for use in the method according to claims 1-31, characterized in that it comprises: (a) a cationic polymer, and (b) a water-soluble surfactant with a molecular weight between 200 and 800 with general formula: where each R is independently selected from the group consisting of hydrogen, polyethylene oxide groups, polypropylene oxide groups, alkyl groups with 1-22 carbon atoms, aryl groups and aralkyl groups, where at least one R group is an alkyl group with at least 8 carbon atoms, X" is an anion or l/n of an n-valent anion, and the surfactant to cationic polymer weight ratio is 50:1 to 1:1. 33. Mixture according to claim 32, characterized in that the molecular weight of the cationic polymer is between 10,000 and 3,000,000. 34. Mixture according to claim 33, characterized in that the cationic polymer ren is a dicyandiamide formaldehyde condensation polymer optionally including at least one group selected from the group consisting of formic acid and ammonium salts as polymerization reactants. 35. Mixture according to claim 33, characterized in that the cationic polymer is obtained from a reaction between formaldehyde, dicyandiamide, formic acid and ammonium chloride. 36. Mixture according to claim 33, characterized in that the cationic polymer is obtained by reaction between an epihalohydrin and one or more amines, or is obtained from ethylenically unsaturated monomers containing a quaternary ammonium group. 37. Mixture according to claim 33, characterized in that the cationic polymer has a molecular weight of 3,000,000 or less and is either protonated or contains quaternary ammonium groups. 38. Mixture according to claim 33, characterized in that the cationic polymer is obtained by reaction between an epihalohydrin and at least one compound selected from the group consisting of diethylamine, dimethylamine and methylethylamine. 39. Mixture according to claim 33, characterized in that at least one R group in the surfactant is an n-alkyl group with 12 - 16 carbon atoms. 40. Mixture according to claim 39, characterized in that two of the R groups in it 41. Mixture according to claim 39, characterized in that the surfactant is an alkyldimethylammonium chloride or a mixture of alkyldimethylammonium chlorides. 42. Mixture according to claim 41, characterized in that the cationic polymer is obtained from dimethylamine and epichlorohydrin and has a molecular weight of 20,000. 43. Mixture according to claim 33, characterized in that the mixture is an aqueous solution containing 5-50% by weight in total of the polymer and the surfactant. 44. Mixture according to claim 33, characterized in that the weight ratio of surfactant to cationic polymer is between 10:1 to 1:1. 45 . Mixture according to claim 44, characterized in that the weight ratio of surfactant to cationic polymer is 1.1:1 or more.