MXPA99004586A - Manufacture of paper - Google Patents

Abstract

Starch is added to the thinstock in a papermaking process in the form of a coagulated slurry containing undissolved starch particles, cationic polymeric flocculant and anionic microparticulate network agglomeration aid, such as bentonite. The flocculant and agglomeration aid interact to give network flocculation in which the starch particles are trapped. Improved retention of the starch in the resulting paper is achieved.

Description

PAPER MANUFACTURE This invention relates to the production of paper that is reinforced with starch. It is well known to produce paper in a paper producing machine by providing a diluted cellulose suspension, flocculate the suspension by adding a solution of polymeric retention aid and thus form a flocculated suspension, drain the flocculated suspension through a screen in movement to form a wet sheet, and transport the sheet through a heated drying zone and thus form a dry sheet. The retention aid can dissolve cationic starch but is often a synthetic polymeric material. It is preferably of high or very high molecular weight, generally with an intrinsic viscosity above 4 dl / g. An alternative to this procedure involves additionally shearing the flocculated suspension to degrade the flocs and then adding an aqueous suspension of anionic material into microparticles, thereby reflocculating the suspension and then discharging the reflocculated suspension through the screen. It is often desirable to add starch during the process, often to the diluted cellulosic material, to improve the strength of the paper produced. This for example may be convenient in grooved media and linerboard, which are usually unfilled in a substantial manner. Increasing their strength makes them more suitable for packing as packing materials. It is also often desired to include starch in filled sheets, since the inclusion of significant amounts of filler in another way will tend to reduce the strength of the sheet. In order to maximize the resistance, it is convenient to include starch in amounts that can be as much as 5 or 10% or even more. Soluble cationic starch is reasonably substantive to cellulosic fibers in amounts of up to about 1 to 1.5% by weight of starch, based on dry weight of paper, and it is known to include this in the cellulosic suspension. If the amount of cationic starch dissolved in the suspension is significantly increased over this, there may be little or no increase in the amount of starch that is retained in the paper. On the contrary, there is simply an increase in the amount of dissolved cationic starch that is in the white water that is discharged through the sieve. This is undesirable, since it will accumulate in high concentrations when the white water is recycled and must be removed before discharge as an effluent, otherwise it can create a high demand for chemical oxygen in the effluent from the factory. It is also known to try to include insoluble starch in paper. When it is desired to include a quantity of starch greater than 1 to 1.5%, the usual technique involves applying a solution of unmodified starch in a sizing press to the end of the paper producing machine, ie after partial or complete drying of the paper. sheet. The application of a starch solution at this point may result in superior harvesting (up to 7 or 10%). However, it can result in the starch concentrating more on the surface than in the center of the sheet and has the particular disadvantage that it requires re-drying the sheet, thereby wasting thermal energy and / or slowing down the process. Another known method for providing significant loads of starch in the paper involves applying a spray or foam containing undissolved starch particles on the wet sheet before it is transported through the dryers, followed by cooking the starch during drying. This process also has the disadvantage of tending to produce a higher concentration of starch on the surface than in the center of the sheet. Its particular disadvantage is that it is very difficult to achieve uniform application of the starch when spraying or by application of foam for prolonged periods due to the tendency of the starch composition to cause blockages in the applicators of dew or foam. Attempts have been made to include insoluble particles in cold water in the suspension before discharge. Fowler describes some of this in the Paper (Document) 23, January 1978 (vol.189 No. 2, 1978), pages 74 and 93. A particular method that suggests is the inclusion of uncooked raw starch in a mud with bentonite. This is then added to the material before addition of the retention aid. We were involved with the work in its suggested system and in practice the mud was added to the diluted material. Fowler suggests that the bentonite absorbs the starch and after addition to the material and inclusion in the material of the retention aid, the bentonite is flocculated by the retention aid. Fowler also suggests that retention can be increased by including in the starch and bentonite sludge, a highly charged polymer with an opposite charge to that of the retention aid. He suggests that the flocculation of the bentonite that occurs when adding to the retention aid material is then greater. In practice, the polymers used were highly charged anionic polymers of low molecular weight and this is why flocculation occurs only by adding the retention aid to the material. We have recently investigated these systems even more. Results are set forth below in this specification. We have confirmed that the starch and bentonite sludge of course, remains unflocculated in the presence of highly charged low molecular weight anionic polymer and that the retention of starch in the system is not good. It has also been suggested in GB 2,223,038 that the reduction in concentration due to the latest addition of filler to the cellulosic suspension can be reduced by adding the filler as a filler mud, insoluble starch particles and flocculating agent. A suspending agent such as a gum, a synthetic organic polymer or a turgid clay, for example bentonite, can also be included in the sludge, preferably to reduce the net charge in the composition close to zero. Preferred systems use a nonionic flocculating agent and a nonionic suspending agent. These compositions include large amounts of filler, preferably 30 to 40%. Amounts of starch and flocculant based on filler are preferably 1 to 5% and 0.05 to 0.2%, respectively. The amount of starch in the final paper is typically said to be 0.05 to 1.5%. This system is aimed at the problem of including a large amount of filler in a paper. It seems that the starch is included in the sludge only to improve resistance and is a binder for the filling. The system has the particular disadvantage that it requires the addition of large amounts of filler immediately before the headbox, which can tend to weaken the paper. It would be convenient to provide a method for producing paper that has increased levels of starch while maintaining good starch retention during the process, in order to avoid as much as possible starch problems in the effluent. We have described in our International Publication WO95 / 33096, a method for increasing the levels of undissolved starch, which can be incorporated in the diluted material. In that system, we incorporate starch particles without dissolving part or all of the aqueous solution of the retention aid. In systems where the shearing and degradation of flocs followed by addition of microparticulate material are employed, we have also disclosed to include insoluble starch particles in part or all of the aqueous suspension of microparticulate material. When the starch particles are included with the microparticle material, this is always done at the point at which the microparticle material will be added in the absence of starch and no major components are suggested for inclusion in the starch sludge and microparticles When the starch is incorporated in the material as a component of the retention aid solution or suspension of microparticulate material, it is present in substantially dispersed form freelythat is, without flocculation. Although this system gives useful improvements in the levels of starch that can be incorporated into the paper without further increases in the level of starch in the effluent, we have found that there is still room for improvement, since the starch retention can be made more efficient. In particular, the retention of potato starch and especially wheat starch and corn starch can be difficult in some systems. It would be convenient to find a way to further increase the levels of starch that can be incorporated into the paper. It would be particularly convenient to be able to do this with maximum harvesting of starch, in such a way that minimum levels of starch are found in the white water that passes through the sieve. It would also be convenient to combine said system with one in which good discharge and total retention is also obtained. According to the invention, a process for producing paper containing starch comprises: providing a suspension of diluted cellulosic material, flocculating the suspension by adding an aqueous solution of polymeric retention aid and thus forming a flocculated suspension, optionally shearing the flocculated suspension and reflocculate the sheared suspension by adding aqueous anionic bridging coagulant and thus forming a reflocculated suspension, discharging the flocculated or reflocculated suspension through a moving screen to form a wet sheet, and transporting the sheet through a heated drying zone and thus form a dry sheet, wherein the process also comprises providing a coagulated sludge containing undissolved starch particles and which is substantially free of filler by combining undissolved starch particles and a cationic polymeric flocculant and an agglomeration assistant of anionic microparticle network in water, to give a network flocculation of the network agglomeration auxiliary where the starch particles are trapped, and to add the coagulated sludge to the cellulose suspension, and the undissolved starch particles are heated during the dried and release dissolved starch in the leaf in the presence of moisture. In this process, starch is added to the diluted cellulosic material as a component of a coagulated sludge. In this mud, we consider that the cationic polymeric flocculant flocculates the network agglomeration aid in microparticles to give a network flocculation. The undissolved starch particles present in the original sludge are thus trapped between the microparticles of the network agglomeration aid in this network flocculation. We found that this coagulated (preflocculated) sludge can be added to the cellulosic suspension at various points and give unexpectedly good starch retention in the leaf, even in the process where the flocculated suspension is subsequently sheared. The system described by Fowler in the article discussed above does not describe the achievement of said coagulated sludge and in fact, as explained above, does not achieve said coagulated sludge. In addition, Fowler does not suggest the specific selection of a cationic polymeric flocculant to achieve the unique network flosing that we achieved in the invention. In particular, it does not suggest the use of high-intrinsic cationic polymeric cationic flocculants which are preferred in the invention. The invention can be applied to any retention system for the production of paper. However, we find that it is particularly advantageous when applied to systems where the polymeric retention aid is cationic. Thus, in the majority of this specification, the invention will be discussed in the context of retention systems that require a cationic retention aid, although other types of retention aids may be employed. In the invention, it is essential to add a coagulated slurry to the suspension of diluted cellulose material, in this specification, when we refer to a "coagulated" sludge, we intend a sludge that has been agglomerated using the defined network flocculation system. The term "coagulated" does not limit the mechanism of action of the cationic polymeric flocculant that can act by the mechanism commonly known as "flocculation" or the mechanism commonly known as "coagulation". To make the sludge, undissolved starch particles are provided. The starch should be such that it is substantially undissolved in that sludge. It should also be such that it remains substantially undissolved when added to the cellulosic suspension before the suspension is subjected to heating. Any particulate starch that meets these conditions can be used. Convenient starches include potato starch, wheat starch, corn starch, Indian whitlow starch and tapioca starch. The process of the invention is particularly useful for improving retention of wheat starch and corn starch. The starch can be included in the coagulated sludge essentially in raw, uncooked form. In some systems, however, it may be useful to provide the starch in the sludge in a pre-swollen form. This can be done by treating raw undissolved starch particles in water at a temperature of 45 to 55 ° C before combining with the polymeric flocculant and network agglomeration aid.For example, raw starch particles can be contained in water when less for 5 minutes, up to about 30 minutes at a temperature of 45 to 55 ° C, preferably 50 to 55 ° C. Alternatively, the raw starch particles can be contacted with steam in a jet cooker for a very short period of time, for example less than one second, such that the particles are heated to a temperature 45 to 55"C, preferably 50 to 55" C, and absorbed in water. We find that these methods cause the raw starch particles to swell, but as long as the temperature remains below the cooking temperature of the starch used, usually around 60 ° C, the particles do not cook, burst and disperse through In this way, even when pre-swollen, they remain in the form of discrete undissolved starch particles.With the starch particles undissolved, either raw or pre-swollen, a polymeric flocculant is combined In this specification, "flocculant" is understood to mean any cationic polymer material capable of giving the desired network flocculation, regardless of whether it would be considered normal to act as a flocculant.Materials that are considered to act as coagulants may be employed and are included within of the term "flocculant." The flocculant can be any material capable of giving the desired network flocculation with the help of network agglomeration, but is generally a synthetic polymer. The cationic polymeric flocculant can be a synthetic polymer of substantially low intrinsic viscosity, for example less than 3 dl / g. However, it is often intrinsic viscosity at least 4 dl / g. It is usually provided as an aqueous solution.

Preferred cationic polymeric flocculants have intrinsic viscosity of at least 6 dl / g, for example 8 to 15 dl / g or 8 to 20 dl / g or higher. Convenient cationic polymers are copolymers of ethylenically unsaturated cationic monomer with the moiety which is another ethylenically unsaturated monomer, generally nonionic, soluble in water such as acrylamide. The amount of cationic monomer is usually at least 2 or 3 mol%. In general, it is not more than 20% in mol, but it can be up to 50% in mol or more. The cationic polymer may be amphoteric, due to the inclusion of a minor amount of anionic monomer, such as acrylic acid or other ethylenically unsaturated carboxylic monomer. The polymer can be totally soluble in water or it can be in the form of polymers that are entangled. The polymers can be made with a small amount of crosslinking agent, for example as described in EP-A-202,780. Normally, the polymer is linear. The or each polymeric flocculant preferably has a theoretical cationic charge density not greater than about 4 meq / g, often not greater than 3 or 2 meq / g.

It is common of at least about 0.1, or usually at least about 0.5 meq / g. In this specification, the theoretical cationic charge density is the charge density that is obtained by calculation from the monomeric composition that is intended to be used to form the polymer. Suitable cationic monomers include dialkylaminoalkyl (meth) acrylates and acrylamides as quaternary or acid addition salts. The alkyl groups may each contain 1 to 4 carbon atoms and the alkyl amino groups may contain 1 to 8 carbon atoms. Particularly preferred are dialkylaminoethyl (meth) acrylates or acrylamides and dialkylamino-1, 3-propyl (meth) acrylamides. In some systems, the polymeric flocculant may be a copolymer of diallyl dimethyl ammonium chloride and acrylamide having an intrinsic viscosity of at least 4 dl / g. In the especially convenient and efficient processes of the invention, the material that is used as the cationic polymeric retention aid is the same material as that used as the cationic polymeric flocculant. This is advantageous since it allows the benefit of the invention to be obtained using the materials already available for use in the paper production process.

Also combined with the undissolved starch particles is an anionic microparticle network annealing aid. This material can be any anionic microparticle material that is flocculated by the cationic polymeric flocculant. It is usually provided as an aqueous suspension. The flocculant and agglomeration aid as a whole give network flocculation within which starch particles are trapped without dissolving. We consider that this is the mechanism that occurs in the invention, instead of flocculation or agglomeration of the same starch particles by any of the materials added to the sludge. Suitable network agglomeration aids include any of the anionic microparticle materials known to be used as anionic pentane coagulant in the process, for example bentonite and the microparticle polymers described in W096 / 16223, for example 50 to 75 wt% copolymers of ethyl acrylate and 25 to 50% by weight of metasyric acid. A preferred network agglomeration aid is bentonite. When bentonite is used as the network agglomeration aid, it is usually in the activated form that is generally used when using bentonite in a retention system. That is, it is normally activated in a conventional manner, to replace some calcium, magnesium or other polyvalent metal ions that are exposed, with potassium, sodium or other appropriate ions. It is preferred for improved convenience and efficiency that the network agglomeration aid be the same material as the bridging coagulant (when employed). This is beneficial, since again new materials are not required that are not already available to use in the paper production process. Each of the cationic polymeric flocculant and the network agglomeration aid can be constituted of more than one material that is provided separately or as a mixture. Preferably, however, each of these is provided as a single material. The three materials that must be present in the coagulated sludge can be combined in any order. Each is preferably supplied in an aqueous form (solution or sludge) but can be supplied dry, for example starch, it can be used as dry particles, although a sludge in water is preferable. Preferably, each of the flocculant and agglomeration aid is added to a? starch sludge in water, but it is also possible to add a starch slurry to a solution of the flocculant or a suspension of the microparticle agglomeration aid. Preferably, a slurry of undissolved starch particles in water is provided, to which is added an aqueous suspension of anionic microparticle network agglomeration aid before and after the cationic polymeric flocculant. We find that with certain systems, better results are obtained with a particular order of addition. In particular, we found that when the network agglomeration aid is bentonite, it may be preferred in some systems to add this to the starch sludge before addition of the cationic polymeric flocculant. In others, however, it is preferred to add the cationic polymeric flocculant to the starch sludge and subsequently add the bentonite. The amount of starch in the aqueous sludge is normally 10 to 40%, often 15 to 30%, especially around 20 or 25%. The cationic polymeric flocculant is usually added to the starch slurry in an amount of up to 1% by weight (active based on dry weight of starch) preferably up to 0.8%, often around 0.2 to 0.6%. It is usually added in an amount of at least 0.05%, preferably at least 0.08%, more preferably at least 0.5%. In general, the cationic polymeric flocculant is added in a greater total amount than that which would fuse the starch particles if the flocculant was only added to the sludge in starch. It is often added in such an amount that if the addition of flocculant to the starch sludge is initiated alone, the sludge begins to flocculate, and as the addition is continued the particles are redispersed. The anionic microparticle network agglomeration aid is added to the starch slurry in amounts up to 1.6% (dry weight based on dry weight of starch), preferably 0.1 to 0.8%, often around 0.4%. It is important in the invention that the coagulated slurry be substantially free of filler or filler, so as not to interfere with the network flocculation of the network agglomeration aid by the cationic polymeric flocculant. If loading is included in the final paper, it can be added to other points in the process in a conventional manner. Small amounts of charge that do not interfere can be included in the mud. For example, usually not more than the weight of starch in the sludge, and preferably it is less than half the weight of starch. Preferably, the sludge is totally free of charge. Advantageously, the coagulated sludge is also free of other materials and essentially consists of starch, cationic polymeric flocculant and auxiliary network agglomeration in water.

The coagulated sludge is added to diluted material. It is added separately from both the polymeric retention aid and the anion bridging coagulant (if used) but can be added at the same time as any of these. It can be added before the addition of the retention aid but is preferably added after it. In the preferred processes of the invention wherein the flocculated suspension is sheared and reflowed, the coagulated sludge can be added between the addition points of the retention aid and the bridging coagulant. We found that if this is added before the flocculated suspension is subjected to shear, then the formation is particularly good. Processes of this type are particularly suitable for the production of fine papers. We also find that if the coagulated sludge is added after shearing but before addition of the bridged coagulant, then the starch retention is particularly good. This contributes to the strength and thus these processes are especially suitable for the production of substantially no-load papers such as packaging materials, for example grooved media and linerboard. The coagulated sludge is added to the material diluted in an amount sufficient to give the desired level of starch. The amount of sludge that is added depends on the concentration of starch in the sludge, but it is often up to 150 or even 250 liters per ton of dry weight of the slurry, preferably 50 to 100 1 / t, for example around of 75 1 / t. Amounts of starch in the material of preference are at least 1 or 1.5% based on the dry weight of the suspension, preferably at least 3 or 5%, and can be as high as 7 or 10%. Levels of starch in the leaf will normally be at least 0.05% often at least 0.2%. In the processes of the invention, it is possible to achieve very high retention of the starch, and consequently it is possible to obtain a content of at least 2% or 3% and typically 6%, even up to 10, 12 or 15%, by weight of starch on the dry leaf. The starch particles are in undissolved form, when added to diluted material. The starch in these particles should remain substantially undissolved before the start of discharge of the suspension, since otherwise dissolved starch will likely be discharged from the suspension. For example, preferably the amount of starch dissolved in the discharge water should represent less than 20%, preferably less than 10% and more preferably less than 5% of the amount of particulate starch in the suspension after deducting the starch soluble that originates elsewhere. In most of the processes of the invention, the starch is introduced into the coagulated slurry, substantially in water-insoluble form and the conditions in the suspension are maintained such that significant solubilization does not occur before the start of discharge. In these processes, it is necessary to dissolve the starch during the discharge and drying stages. In conventional processes, discharge or drainage is completed at room temperature, and drying is conducted with the application of heat. By proper selection of the discharge and drying conditions and the degree of undissolved starch, it is possible to achieve proper dissolution during the drying step, while the sheet is still wet. It may be convenient to apply deliberate heating to the wet sheet, even before final discharge is completed, to preheat it before entry to the drying stages. For example, the wet sheet may be passed under a steam hood or heater such as Devroniser (brand) and this may facilitate complete dissolution of the starch. The act of shearing the flocculated suspension prior to reflocculation will necessarily tend to break up any flocs or aggregates of starch particles, and thus the preferred process will tend to result in the starch particles being more evenly distributed as mono-particles through the the sheet. As a result, more complete dissolution of these particles will occur than when swarms of particles are present in the sheet, and this is an important advantage of the preferred processes of the invention involving shearing and reflocculation of the flocculated suspension. The starch particles require gelatinization while there is still some moisture in the sheet in order to allow the dissolution to proceed satisfactorily and in order to allow the starch to dissolve and disperse to provide a film within the sheet. The starch will tend to migrate between the fibers to obtain a more uniform distribution of the starch in and around and between the paper fibers. The amount of moisture that must remain on the sheet when the starch dissolves can be quite low, and only needs to be sufficient to allow migration of the dissolved starch, sufficient to give adequate distribution of the starch through the leaf. To facilitate rapid gelatinization and dissolution, it may be desirable to use a starch that naturally has a low gelatinization temperature or that has been modified to reduce its gelatinization temperature, provided it remains substantially undissolved prior to discharge. In particular, it may be convenient to use pre-swollen starch particles as discussed above to reduce the time necessary for complete dissolution of the starch particles in the sheet. Pre-gelatinized or pre-cooked starch (and therefore soluble) can also be included as undissolved particles. In this way, the precooked starch solution in the sludge particles can be avoided by protecting the starch with a waterproofing matrix or shell that disintegrates during subsequent discharge or drying. Any material that provides sufficient water impermeability to prevent significant dissolution of the starch prior to discharge may be employed whenever the shell or matrix disintegrates to release the starch during discharge and / or drying. The cover or matrix does not have to provide water impermeability for a long time. For example, a slowly dissolving matrix or cover may be sufficient to protect the starch, since even if the cover partially disintegrates inside the headbox it may still be inappropriate time for the circumscribed starch particles to dissolve in the box of head The cover or matrix may be a thermoplastic material having such a melting point that it prevents premature disintegration of the shell or matrix. For example, the normal temperature of the suspension leading to the headbox is typically in the range of 40 to 50 ° C, and the ambient temperature around the discharge screen is typically in the same range. If the particles are provided with a coating or matrix having a melting temperature at about or above the temperature of the headbox, substantially no melting will occur until the headbox and the majority of the melt and substantially all of the melt dissolution. Starch does not occur until most of the discharge has been completed. Suitable thermoplastic materials that may be employed include hydrocarbon waxes. Instead of using a thermoplastic cover or matrix, a pH sensitive coating or matrix can be used. For example, the cooked starch may be encapsulated or otherwise protected by polymer that is insoluble in water, non-turgid or non-swellable at the pH of the starch slurry, and this sludge is added to the headbox which is at a pH in the which polymer cover swells or dissolves. For example, the protecting polymer may be a copolymer of a water-insoluble, water-soluble ethylenically unsaturated monomer such as methacrylic acid or other water-soluble monomer and ethylacrylate or other water-insoluble monomer. The manufacture of pH-sensitive polymers of this general type by oil-in-water emulsion polymerization is well known. Methods for incorporating an active ingredient into particles of a protective matrix or inside a cover, they are well known and can be used in the invention. For example, the mixture of starch and protective material may be spray-dried or a coacervate coating may be formed around starch particles. In the process of the invention, the suspension of diluted cellulosic material is usually flocculated by adding an aqueous solution of a cationic polymeric retention aid. The retention aid can be soluble cationic starch. However, it is generally preferred that the retention aid be a synthetic cationic polymer. The polymer may have an intrinsic viscosity less than 3 or 4 dl / g, but preferably preferred retention aids are synthetic cationic polymers having intrinsic viscosity of at least 4 dl / g and usually about 6 dl / g for example 8 to 15 dl / gu 8 to 20 dl / g or higher. In this specification, intrinsic viscosity (IV) is measured at 25 ° C in 1 M sodium chloride buffered to pH 7 using a suspended level viscometer.

Suitable cationic polymers are copolymers of ethylenically unsaturated cationic monomer, with the moiety being another ethylenically unsaturated monomer, generally nonionic, soluble in water such as acrylamide. The amount of cationic monomer is usually at least 2 or 3 mol%. In general, it is not more than 20% in mol, but it can be up to 50% in mol or more. The polymer can be totally soluble in water or can be in the form of polymers as described in EP-A-202,780. The or each high molecular weight cationic polymeric retention aid has a theoretical cationic cache density not greater than about 4 meq / g, often not more than about 3 or 2 meq / g. In general it is at least about 0.1 or usually at least about 0.5 meq / g. Suitable cationic monomers include dialkylaminoalkyl (meth) acrylates and acrylamides as quaternary or acid addition salts. The alkyl groups may each contain 1 to 4 carbon atoms and the amino alkyl group may contain 1 to 8 carbon atoms. Particularly preferred are dialkylaminoethyl (meth) acrylates or acrylamides and dialkylamino-1, 3, propyl (meth) acrylamides. In some cases, it may be convenient to use a copolymer of diallyl dimethyl ammonium chloride and acrylamide as the retention aid and having an intrinsic viscosity of at least 4 dl / g. The cationic polymeric retention aid can be rendered amphoteric by the inclusion of a minor amount of anionic monomer such as acrylic acid or other ethylenically unsaturated carboxylic monomer. In the process of the invention, it is possible to use more than one type of retention aid. However, it is preferred to use only one type of retention aid. The total amount of polymer retention aid is usually 0.01 to 1%, generally 0.02 to 0.3% (200 to 3,000 g / ton dry weight suspension). When the process involves shearing and reflocculation with an anion bridge coagulant, the amount of retention aid is generally in the range of 0.01 to 0.2 or 0.3% but when the process is conducted simply with flocculation followed by discharge, ie without shearing and reflocculation, the amount is usually in the range of 0.04 to 0.16%, often 0.06 to 0.15%. The type and amount of retention aid used in the process is such that they give good retention of fiber fines (and filler, if present). The selection of the retention aid and its quantity can be conducted in a conventional manner by carrying out the process in the absence of the coagulated sludge using different amounts of different retention aids to select an effective combination of retention aid and quantity for the particular cellulosic suspension that it is about. Naturally, this test should be conducted with the subsequent addition of anionic bridge coagulant when the total process involves the use of that material. When the initial cellulosic suspension includes anionic trash, it may be convenient to treat the suspension initially with a cationic coagulant (such as a high molecular weight low density charge polymer or an inorganic coagulant such as alum) and / or bentonite to reduce the amount of polymeric retention aid required. The amount of retention aid will usually be greater than the amount required to precipitate or interact with soluble anionic material in the cellulosic suspension. If the retention performance is plotted against a dose of retention aide in a typical combination, it will be seen that as the dose increases, the retention will be deficient and will only increase gradually at low values, but then increase significantly over a relatively small dosage range. , and then it will not increase more in any significant proportion. The dose at which retention is markedly improved is an indication of the demand for that suspension for that retention aid and in the invention, the total amount of that retention aid must be in or on the amount in which the retention has increased significantly. Accordingly, this amount is about the stoichiometric amount required to react with any anionic polymeric material in the cellulosic suspension and any pulp from which it is formed. In general, the suspension is made without deliberate addition of anionic polymeric materials. By saying that the cellulosic suspension is flocculated after the addition of the cationic polymeric retention aid, we intend it to have the state that is typical of a cellulosic suspension that has been treated with an effective high molecular weight retention aid in an effective amount. In the invention, it is also possible to use anionic polymeric retention aid and use nonionic polymeric retention aid. Suitable non-ionic retention aids are described in our patent publications EP-A-608,986 and O95 / 02088. Other suitable non-ionic retention aids are described in AU-A-63977/86. Suitable retention systems that can be employed are described in EP-A-017,353 and in US Pat. No. 4,305,781, wherein a substantially non-ionic polymer is added after addition of bentonite to the material. Suitable anionic retention aids are described, for example, in EP-A-308,752. Systems in which the invention may be employed include systems that have been marketed under the trade name Positek. Additional retention systems to which the invention can be applied are described in publications W095 / 21296 and W095 / 21295. In the process of the invention, the flocculated suspension can be directly discharged and dried to form a dry sheet. In preferred processes of the invention, the flocculated suspension is sheared. By shear is meant any treatment or force that is effective in degrading the flocs formed in the suspension. The shear can be provided by passing the flocculated suspension through a centriscreen or other high shear apparatus. Alternatively, in some processes simply subjecting the flocculated suspension to turbulent flow will provide enough shear to degrade the flocs in an adequate proportion. After shearing to degrade flocs, the suspension is reflowed by the addition of an anionic bridge coagulant. An anionic bridge coagulant is any material that is effective to refloculate the degraded flocs in a proportion that provides sufficient strength so that the suspension can be discharged through a moving screen to form a moisture sheet. That is, it is an anionic retention aid and can be an anionic colloidal material. The use of an anionic bridge coagulant is particularly preferred when the polymeric retention aid is cationic. Materials that have been found to be particularly effective are anionic microparticle materials. These may be inorganic, for example colloidal silica (as described in U.S. Patent No. 4,643,801), polysilicate microgel (such as described in EP-A-359,552), polysilicic acid microgel (as described in US Pat. EP-A-348, 366), versions modified with aluminum of any of these or preferably bentonite. In particular, systems may be employed as described in U.S. Pat. Nos. 4,927,498, 4,954,220, 5,176,891 and 5,279,807 and sold under the trade name Particol of Allied Colloids and Dupont. Materials in organic anionic microparticles can also be used. For example, anionic organic polymer emulsions are suitable. The emulsified polymer particles may be insoluble due to being formed of a copolymer for example of a water-soluble anionic monomer and one or more insoluble monomers such as ethyl acrylate, but preferably the polymer emulsion is an entangled microemulsion of the monomeric material soluble in water, for example as described in U.S. Pat. Nos. 5,167,766 and 5,274,055 and marketed under the trade name Polyflex. The particle size of the microparticle material in general is less than 2 μm, preferably 1 μm and more preferably less than 0.1 μm. The preferred anionic microparticle material for use as the anion bridge coagulant is bentonite. The amount of anion bridge coagulant (dry weight based on the dry weight of the cellulose suspension) in general is at least 0.03% and usually at least 0.1%. It can be up to 1.6 or 2% for example but in general it is less than 1%. The selection and quantity of the anionic bridge coagulant should be such as to cause what is commonly referred to as "supercoagulation". The anionic bridge coagulant is preferably added to the suspension after the last high shear point for example in the headbox, and the suspension can then be discharged in conventional manner.

In preferred processes of the invention the system is optimized by type and amount of polymeric retention aid and anion bridge coagulant, if employed, in the absence of the sludge containing coagulated starch. The coagulated sludge is then included in the process of the desired quantity without significant changes to the levels and optimum types previously found. The diluted cellulosic material can be formed from any convenient pulp or mixture of pulps. It may have been formed in any convenient way. For example, it may have been made from ground wood, mechanical or thermomechanical pulp and diluted material or the thick material from which it is formed. It may have been treated with bentonite before adding the retention aid. In the process of the invention, initial selection of suitable materials can be made based on tests with conventional laboratory apparatus such as a Britt vessel and a hand-laminate technique, but commercial operation of the process is performed on a paper production machine . In these processes, the diluted cellulosic material is provided in conventional manner, generally by dilution of thick material with white water, and is fed through the headbox through a convenient apparatus such as a fan pump and centriscreen, and It is discharged from headbox in a moving sieve. The screen can travel at conventional screen speeds that typically exceed 100 meters per minute and are typically in a range of 700 to 1,500 meters per minute. The process of the invention can be used to produce any desired type of paper, by which term we include cardboard. Convenient papers can be loaded and thin papers. Alternatively, the paper may be substantially unloaded. In particular, it can be a packaging material such as ribbed media or linerboard. The following are some examples of the invention. Examples Preparation of Material Composition of raw materials: 60% of newspaper 30% of cardboard 10% of magazines The previous raw material disintegrated to high consistency for 2,000 revolutions. The material is then diluted to 1 and 3% consistency, using tap water and allowed to condition overnight.

Preparation of Starch Solution The amount of deionized water required to produce a starch slurry is weighed into a glass flask, stirred thoroughly and starch added. Aliquots of 25 g of the sludge were then weighed in plastic flasks. Raw potato starch is used throughout the experiment. Optimization of Coagulated Mud Components A flask is completely stirred to produce a suspension of aqueous starch, followed by the addition of an annotated amount of aqueous bentonite suspension (1% solids) as a network agglomeration aid. The flask is shaken several times and dosed with polymer flocculant (0.5% solids) and again stirred. The remaining flasks are dosed with fixed amounts of bentonite and a range of polymer additions to obtain the optimum polymer addition level. (The level that produces the largest flocs). The optimum bentonite level is similarly found by varying the level of bentonite addition and using the optimal polymer dose. The degree of flocculation is estimated visually. The procedure is carried out using the following polymers: Polymer A (Cationic): Copolymer of 20% by weight of dimethyl amino-ethyl acrylate quaternized with methyl chloride (DMAEAqMeCl) with 80% by weight of acrylamide (ACM), IV around 9 to 11 dl / g. Polymer B (Cationic): Copolymer of 20% by weight of MDAEAqMeCl and 80% by weight of ACM IV around 9 to 11 dl / g. Comparative Polymer D (Anionic): Copolymer of 40% by weight of sodium acrylate and 60% by weight of ACM, IV over 10 dl / g. Comparative Polymer E (Non-ionic): ACM homopolymer containing less than 1% acrylate by weight.

Comparative Polymer F (Anionic): Copolymer of 40% by weight of sodium acrylate and 60% by weight of ACM, IV on 10 dl / g. The results are illustrated in Table 1 below. The observations are coded as follows: 1. Massively defined flocs and a clear supernatant were formed. 2. Large, well-defined flocs are formed and a clear supernatant. 3. Defined medium flocs and a clear supernatant were formed. 4. Well-defined, small florets and a clear supernatant were formed. 5. Very small, well-defined flocs and a clear supernatant were formed. 6. Small flocs and a cloudy supernatant were produced. 7. Very small flocs and a cloudy supernatant were produced. 8. The sludge was very slightly flocculated and a cloudy supernatant is produced. 9. Without flocs. Table 1 Flocculant Addition of Polymeric Bentonite Employed Addition (g / t of ia / t starch Observation B 400 4000 9 B 800 4000 5 B 1200 4000 4 B 1500 4000 3 B 1800 4000 2 Table 1 (cont.) Flocculant Addition of Polymeric Bentonite Employee Addition (g / t of (/ t) starch) Observation B 2100 4000 1 B 2400 4000 1 B 2700 4000 2 B 2800 8000 1 B 8000 4000 3 B 8000 8000 3 B 4000 2000 3 A 400 4000 9 A 800 4000 8 A 1200 4000 4 A 4000 4000 2 A 4000 8000 3 A 4000 2000 3 A 8000 4000 3 A 2000 4000 3 A 8000 8000 3 A 4000 4000 1 A 3000 4000 1 A 2000 4000 1 A 1000 4000 4 Table 1 (continued Flocculant Addition of Polymeric Bentonite Employee Addition (g / t of (a / t) starch1 Observation A 1500 4000 4 A 2000 3000 1 (Flocs do not form well) A 8000 4000 1 The above shows the flocculation effect produced in the sludge using a cationic retention aid and a network agglomeration aid, according to the invention The results in Table 2 below are given for Comparative Polymers D, E and F, which are not cationic and do not give these remarkable flocculation effects Table 2 Flocculant Addition of Polymeric Bentonite Employee Addition (g / t of (g / t) starch) Observation F 400 4000 9 F 800 4000 9 F 1200 4000 7 F 2000 4000 7 Table 2 (Cont.) Flocculant Addition of Polymeric Bentonite Employee Addition (g / t of (cr / t starch) Remark F 4000 4000 7 F 4000 8000 7 F 4000 2000 7 F 8000 8000 7 D 400 4000 9 D 800 4000 9 D 1200 4000 9 D 2000 4000 9 D 4000 4000 9 D 4000 8000 9 D 8000 8000 9 D 2000 2000 9 E 400 4000 8 E 800 4000 8 E 1200 4000 9 E 2000 4000 8 E 4000 4000 9 E 4000 8000 6 E 4000 2000 9 E 8000 8000 6 Table 2 (Cont.) Flocculant Addition of Polymeric Bentonite Employee Addition (g / t of (g / t) starch ') Observation E 8000 16000 6 Additional tests were carried out to observe the effects of using anionic polymers of low molecular weight of the type used by Fowler in the article in Paper, mentioned above. One flask was stirred thoroughly to produce a suspension of aqueous starch, followed by the addition of a note amount of aqueous bentonite suspension (1% solids) as a network agglomeration aid. The flask was stirred several times and dosed with anionic polymer (0.5% solids) as polymer flocculant and again stirred. The remaining flasks were dosed with a range of addition levels of polymer and bentonite in an attempt to obtain starch flocculation. The above procedure is carried out using the following polymers, which are all acrylic acid polymers (neutralized in sodium acrylate): Comparative Polymer G: Molecular Weight of about 30,000, as measured by gel permeation chromatography (GPC) Comparative Polymer H: Approximately 250,000, by GPC Comparative Polymer J: Approximately 2.5 million, by calculation of IV Comparative Polymer K: Approximately 5 million by calculation of IV The results are illustrated in Table 3 below. Table 3 Addition of Bentonite Polymer Employed Addition (g / t of (g / t of starch) starch) Observation Comparative Polymer H 400 4000 Comparative polymer H 800 4000 Comparative polymer H 1200 4000 Comparative polymer H 2500 4000 Comparative polymer H 4000 4000 Comparative polymer H 4000 8000 Table 3 (Cont.) Addition of Polymer Bentonite Employee Addition (g / t of (g / t of starch) starch) Observation Comparative polymer H 4000 1600 Comparative polymer H 4000 3000 Comparative polymer H 800 2000 Comparative polymer H 800 1000 Comparative polymer H 400 4000 Comparative polymer J 800 4000 Comparative polymer J 1200 4000 Comparative polymer J 2500 4000 Comparative polymer J 4000 4000 Comparative polymer J 4000 8000 Table 3 (Cont.) Addition of Polymer Bentonite Employee Addition (g / t of (g / t starch) starch) Observation Comparative polymer J 8000 8000 Comparative polymer J 4000 3000 Comparative polymer J 800 2000 Comparative polymer J 200 4000 Comparative polymer J 400 4000 Comparative polymer G 800 4000 Comparative polymer G 1200 4000 Comparative polymer G 2500 4000 Comparative polymer G 4000 4000 Comparative polymer G 4000 8000 Table 3 (Cont.) Addition of Polymer Bentonite Employee Addition (g / t of (g / t starch) starch) Observation Comparative polymer G 4000 160000 Comparative polymer G 8000 32000 Comparative polymer G 2500 2000 Comparative polymer K 400 4000 Comparative polymer K 800 4000 Comparative polymer K 1200 4000 Comparative polymer K 2500 4000 Comparative polymer K 4000 4000 Comparative polymer K 4000 800 Comparative polymer K 4000 16000 Table 3 (Cont.) Addition of Bentonite Polymer Employed Addition (g / t of (g / t of starch) starch) Observation Comparative polymer K 4000 3200 Comparative polymer K 800 2000 Comparative polymer K 800 1 00 The above results show that none of the low molecular weight anionic polymers give some flocculation effect in the starch sludge in the presence of bentonite. Use of the Retention / Discharge System Two systems were optimized. System 1 requires addition of Polymer A as a cationic polymeric retention aid and bentonite as anionic bridge coagulant. System 2 uses only addition of cationic polymeric retention aid (Polymer C, a cationic copolymer of 20% by weight of DMAEAqMeCl and 80% by weight of ACM, IV 6 to 7 dl / g), without shearing and reflocculation of the suspension flocculated This is used to test the anionic polymers (G, H, J and K), since a system of this type is used by Fowler in the experiments referring to his article in Paper, in the previous document. The tests were carried out in the system, with and without coagulated sludge, as described below. In System 1, the high shear system involves adding coagulated sludge when the material is subjected to high shear and the low shear system involves adding coagulated sludge when the material is subjected to low shear. Preform Retention (1) i. The Heidolph adjusts to 1500 rpm and turns on, ii. 500 mol of 1% material is emptied into the Britt vessel with deflector and the timer is simultaneously started. iii. After a period of 35 seconds of agitation, the rpm is reduced to 800. IV. 5 seconds later, the lid of the Britt container is opened. v- The recovery water discharged in the initial 5 seconds is discarded and the next 30 seconds of recovery water are collected in a flask. Control (1) i. The Heidolph adjusts to 1500 rpm and turns on, ii. 500 mol of 1% material is emptied into the Britt container with deflector and the timer is started simultaneously. iii. The material is stirred for 5 seconds, after which the addition of starch sludge is performed.

(Sufficient to give a level in the material of 5% starch in dry fibers). iv. After a period of 30 seconds of agitation, the rpm is reduced to 800 rpm. v 5 seconds later, the container lid opens Britt. vi Recovery water discharged in the initial 5 seconds is discarded and the next 30 seconds of recovery water is collected in a flask. Retention in System 1 (High shear) i. A coagulated sludge containing 25% starch is prepared as above using the optimum addition levels of bentonite (network agglomeration aid) and polymer A (cationic polymer flocculant) found above, which were 4000 g / t of starch and 3000 g / t of starch respectively. ii. The Heidolph adjusts to 1500 rpm and turns on. iii. 500 mis of material 1% are emptied into the container Brítt with Deflector and the stopwatch is started simultaneously. iv. The material is stirred for 5 seconds after which an addition of polymer A is effected. v. 15 seconds later an addition of the coagulated sludge is made (5% of starch in dry fibers), vi. After a period of 15 seconds of agitation the rpm is reduced to 800 and a simultaneous addition of bentonite is effected. vii. 5 seconds later the container stage Britt opens. viii. The replenishment water discharged in the initial 5 seconds is discarded and the next 30 seconds of replenishment water are collected. ix. The above procedure is repeated using a range of levels of addition of retention aid.

Retention in System 1 (Low shears) i. A coagulated sludge containing 25% starch is prepared as above, using the optimum addition levels of bentonite and polymer A found above, which were 4000 g / t of starch and 3000 g / t of starch respectively, ii. The Heidolph adjusts to 1500 rpm and turns on. iii. 500 ml of material 1% is emptied into the Britt container with deflector and the timer is started simultaneously. iv. The material is stirred for 5 seconds after which an addition of polymer A is effected. v. After a period of 30 seconds of agitation the rpm is reduced to 800 and an addition of coagulated sludge is made simultaneously (to give a level in the material of 5% starch in dry fibers). saw. 15 seconds later the material is dosed with bentonite. vii. After 5 seconds of stirring, the container stage Britt opens. viii. The replenishment water discharged in the initial 5 seconds is discarded and the next 30 seconds of replenishment water are collected. System 2 i. Coagulated sludge containing 25% starch was prepared containing a range of bentonite levels and addition of low molecular weight anioniso polymer. A range of levels of addition is used because optimal doses could not be found (mud not flocculated). ii. 166.7 grams of diluted material (3% consistency) is placed in a Britt vessel that is adjusted to 1500 rpm. iii. The required addition of the coagulated sludge is carried out (5% starch in dry fibers) and the material is stirred for 30 seconds. iv. The treated material is then transferred to a measuring cylinder, dosed with polymer C and mixed by reversing the measuring cylinder four times, v. The Heidolph adjusts to 800 rpm and turns on. saw. The flocculated material is then emptied into the Britt container with deflector and a stopwatch is started simultaneously. vii. After 5 seconds of agitation the lid of the container Britt opens. viii. The replenishment water discharged in the initial 5 seconds is discarded and the next 30 seconds of replenishment water are collected in a flask. Control (2) i. 166.7 grams of thick material (3% consistency) are placed in a Britt reagent set at 1500 rpm. ii. An addition of 25% starch sludge is made and the material is stirred for 30 seconds. iii. The agitator speed is reduced to 800 rpm. iv. Five seconds later the container lid Britt opens, v. The replenishment water discharged in the initial 5 seconds is discarded and the next 30 seconds of replenishment water are collected in a flask.

? Preform (2) This is carried out for control (2) with an alteration since no addition of starch is made. Results for total retention (given as fiber retention) and level of starch in the replenishment water are given in the tables below. Table 4 Details of Coagulated Mud System Addition of additive of starch addition (% in polymer A Bentonite dry fibers) flocculant (g / t) (g / t) in in dry starch dry starch Preform (l) - Control (1) 5 System 1 - System 1 - - - System 1 - System 1 - System 1 - System 1 High Shear 5 3000 43D System 1 of High Shear 5 3000 4X0 System 1 High Shear 5 3000 43QD Table 4 (Cont.) Details of ___ Coagulated Mud System Addition Adding Adding Starch (% polymer A Bentonite dry fibers) flocculant (g / t) (g / t) in starch Dry dry starch System 1 of High Shear 5 3000 4Q0 System 1 of High Shear 5 3000 43D System 1 of High Shear 5 3000 4JD System 1 High Shear 5 3000 43D CONTINUED TABLE 4 Details of System 1 System Addition of Addition of% of Retention of Auxiliary level of bentonite starch Retention (g / t) in Average (ppm in (g / t) in fiber water of fibers dry dry replenishment) Preform (1) - - 79 2.42 Control (1) - - 72 465.87 System 1 800 4000 80 0.15 System 1 1400 4000 88 _ CONTINUE TABLE 4 Details of System 1 System Addition of Addition of% of Retention- Level of Auxiliary of bentonite starch Retention (g / t) in Average (ppm in (g / t) in fiber water of fibers dry dry replenishment) System 1 1600 4000 92 - System 1 1800 4000 93 - System 1 2000 4000 95 - System 1 High Shear 1200 4000 83 244.33 CONTINUE TABLE 4 Details of System l System Addition of Addition of% of Retention- Level of AUXÍ3 .iar bentonite starch Retention (g / t) in Average (ppm in (g / t) fiber dry water fiber dry replenishment) System l High Shear 1400 4000 85 171.63 System 1 of High Shear 1800 4000 92 184.71 System 1 of High CÍ2: alla 2000 4000 94 166.70 CONTINUE TABLE 4 Details of System 1 System Addition of Addition of% of Retention- Level of Auxiliary of bentonite starch Retention (g / t) in Average (ppm in (g / t) fiber dry water dry fibers replenishment) System 1 of High Shear 1600 4000 92 System 1 of High Shear 1800 4000 91 213.24 System 1 High Shear 2000 4000 94 164.98 CONTINUE TABLE 4 Details of .__ Coagulated mud System Addition of Addition Type Addition of Starch (% Polymeric Bentonite Polymer in g / t fiber as dry auxiliary) in starch Hold dry ( g / t on dry fibers) Preform (2) Control (2) CONTINUOUS TABLE 4 Details of coagulated mud System Addition of Addition Type Addition of Starch (% Polymer Bentonite in L fiber g / t as a dry auxiliary) almi- of retention dry don (g / t in dry fibers) System 2 - - - - System 2 - - - - System 2 - - - - System 2 - - - - System 2 5 G 3000 4000 System 2 5 G 10000 2000 System 2 5 G 30000 4000 System 2 5 G 1000 2000 System 2 5 K 3000 4000 System 2 5 K 10000 20000 System 2 5 K 30000 40000 System 2 5 K 1000 2000 CONTINUE TABLE 4 Details Polymer Retention Level of C (g / t of fibers Starch System in starch Average Dry average) (%) (ppm in retention water) Preform (2) - 70 0 Control - 65 502.75 (2) 700 84 0 System 2 900 86 0 System 2 1100 87 0 System 2 1300 89 0 System 2 1500 92 0 System 2 1500 87 541.79 System 2 1500 87 577.82 System 2 1500 88 611.92 System 2 1500 90 492.03 System 2 1500 86 450.96 System 2 1500 86 533.21 System 2 1500 88 615.35 System 2 1500 87 377.73 The above results show the significant improvement in starch levels in replenishment water using system 1 with a coagulated slurry according to the invention in comparison with use of a non-coagulated sludge, despite the fact that widely similar total retention results are obtained.

Claims (16)

1. CLAIMS 1. A process for producing a paper-containing starch, characterized in that it comprises: providing a suspension of diluted cellulosic material, flocculating the suspension by adding an aqueous solution of polymeric retention aid and thus forming a flocculated suspension, optionally shearing the Flocculated suspension and reflocculate the sheared suspension by adding aqueous anionic bridge coagulant and thus form a reflocculated suspension, discharge the flocculated or reflocculated suspension through a moving screen to form a wet sheet, and transport the sheet through an area of heated drying and thus forming a dry sheet, wherein the process also comprises providing a coagulated slurry containing undissolved starch particles and which is substantially free of charge by combining undissolved starch particles and a cationic polymeric flocculant and a auxiliary agglomeration of anionic microparticle network to give network flocculation of the network agglomeration auxiliary where the starch particles are trapped and the coagulated sludge is added to the cellulose suspension and the undissolved starch particles are heated during the drying and release the dissolved starch on the leaf in the presence of moisture.
2. 2. A process according to claim 1, characterized in that the polymeric retention aid is a cationic polymeric retention aid selected from dissolved cationic starch and cationic synthetic polymers having intrinsic viscosity of at least 4 dl / g.
3. A process according to any of claims 1 or 2, characterized in that it comprises shearing the flocculated suspension and reflocculating the sheared suspension, by adding anionic bridge coagulant and in this way forming a reflocculated suspension which is discharged through a sieve in movement to form the wet leaf.
4. 4. A process according to claim 3, characterized in that the anionic bridge coagulant is a suspension of anionic microparticle material selected from bentonite, colloidal silica, polysilicate microgel, polysilicic acid microgel and intertwined microemulsions of monomeric material soluble in water and preferably, it is bentonite.
5. 5. A method according to any preceding claim, characterized in that the polymeric retention aid is a synthetic cationic polymer having an intrinsic viscosity of at least 4 dl / g.
6. 6. A process according to any preceding claim, characterized in that the anionic microparticle network agglomeration aid is bentonite.
7. 7. A process according to any preceding claim, characterized in that the polymeric flocculant is a synthetic cationic polymer having an intrinsic viscosity of at least 4 dl / g.
8. 8. A process according to claim 3, characterized in that the polymeric flocculant is the same material as the polymeric retention aid and the anionic network agglomeration auxiliary is the same material as the anionic bridging coagulant.
9. 9. A process according to any of the preceding claims, characterized in that the coagulated slurry is added to the suspension of diluted cellulose material after addition of the aqueous solution of polymeric retention aid.
10. 10. A process according to claim 3, characterized in that the coagulated sludge is added to the flocculated suspension before shearing.
11. 11. A process according to claim 3, characterized in that the coagulated slurry is added to the suspension after shearing and before addition of anionic bridge coagulant.
12. 12. A process according to any preceding claim, characterized in that the polymeric flocculant has a charge density of not more than 3 meq / g and an intrinsic viscosity of at least 4 dl / g.
13. 13. Procedure according to any preceding claim, characterized in that the starch particles are pre-swollen before the addition of polymeric flocculant and network agglomeration aid, by heating raw starch particles at a temperature of 45 to 55 ° C in the presence of water.
14. A process according to any preceding claim wherein the amount of polymeric flocculant in the coagulated sludge is up to 10 kg / t dry solids based on dry starch solids and the amount of network agglomeration aid is up to 16 kg / t dry solids based on dried starch solids.
15. 15. A process according to any preceding claim wherein the coagulated slurry is formed by adding to a slurry of starch particles, an aqueous suspension of the network agglomeration aid and an aqueous solution of the polymeric flocculant.
16. 16. A method according to any preceding claim, wherein the paper is substantially unloaded and preferably is a packaging material.