MXPA00012086A

MXPA00012086A - A process for making paper.

Info

Publication number: MXPA00012086A
Application number: MXPA00012086A
Authority: MX
Inventors: Jacob Terpstra
Original assignee: Avebe Coop Verkoop Prod
Priority date: 1998-06-10
Filing date: 1999-06-04
Publication date: 2003-04-22
Also published as: EP1086274A1; AU4293199A; CN1305552A; EP1086274B1; ATE226662T1; ID27649A; JP2002517637A; DE69903628D1; BR9910991B1; CA2334532C; EP1086274B9; BR9910991A; WO1999064677A1; CA2334532A1; JP4475810B2; DE69903628T2; CN1136360C; US20030145966A1

Abstract

The invention relates to a process for making paper wherein an anionic starch, which is based on a starch comprising at least 95 wt.%, based on dry substance of the starch, of amylopectin, or a derivative of said starch, is used in combination with a fixative as a strengthening agent.

Description

PROCESS FOR THE PREPARATION OF PAPER Field of Invention The invention relates to a process for the production of paper and the use of starch in said process.

Background of the Invention In order to increase the strength properties of paper, it has been common practice during the last thirty years to add cationic starch in the final wet stage of the papermaking process. The wet end of the papermaking process refers to the stages of the papermaking process, where a pulp of fibers, obtained from cellulose-based materials, such as waste paper, recycled, wool, cotton, or alternative sources, It has been processed. The term "wet end" originates in the large-quantities-of water, in the presence of which the pulp is processed.

Ref: 125487 During the last decade, there have been several trends in the papermaking process that either require more starch in the paper than is possible with cationic starch, or make the application of the cationic starch more difficult. One of these trends is the environmental demand to recycle paper. As paper is recycled, paper fibers tend to become shorter and weaker, the latter because the interactions between the fibers are reduced. As a result, increased amounts of starch are required in the wet end of papermaking in order to produce a paper that is sufficiently strong. It has been found that after the paper has been recycled a certain number of times, the loss of strength due to recycling can not be compensated by adding cationic starch, leading the paper to have a lower paper strength.

Another trend is the urgency of producing cheap paper. This can be done by incorporating large quantities of a cheap filling into the paper. However, a large filling content in the paper results in a deterioration of the paper strength which gives an increase in the demand for the addition of increased amounts of starch at the end or wet end.

Still another trend concerns the change in the devices used in the papermaking process. The press of size conventionally used is increasingly replaced by pre-measured size presses. The use of a press of pre-measured size often has the effect that the starch penetrates to a lesser degree in the paper sheet than when using conventional sized press. As a result, starch provides a small contribution to the strength of the paper. On the other hand, the use of pre-measured size presses for pigmentation decreases the internal resistance of the paper even more. Therefore, it is desired to provide an increase in the strength of the paper obtained in the wet end.

In "Anionic starch: an effective wet-end concept for enhancing paper strength", from the PITA Annual Conference, 87-91, Manchester, October 1997, J. Terpstra and R.P. Versluijs has proposed the use of anionic starch instead of cationic starch as a resistance agent in the wet end of the papermaking process, in order to make a greater internal resistance of the paper produced. This concept of using anionic starch has also been described in P. Brouwer, ochenblatt für Papierfabrikation, 19 (1997), 928-937, WO-A-93/01353 and EO-A-96/05373, and can be explained as follows.

Fibers and filler particles, which are used to produce paper, are negatively charged. When the cationic starch is used as a paper reinforcement agent, its retention is mainly caused by the interaction between the positively charged starch and the negatively charged fibers and the filler particles. In order to adhere the anionic starch molecules or anionic fibers and filler particles, use is made of a presumed cationic fixative. In principle, any auxiliary cationic paper can be used - as a fixative for anionic starch, however some give better results than others. Because they are cheap and hardly affected by hardness of water, polyaluminium chlorides are considered very attractive fixatives. Other materials that have been proposed to be used as a fixative in this regard are, among others, cationic or alum polymers, such as polydimethyldiallylammonium chloride and polyamines.

It has been found that, using anionic starch in combination with an appropriate fixative, it is possible to incorporate up to five times more starch on a paper sheet compared to the case where only cationic starch is used as a resistance agent. Of course, this results in a much stronger sheet of paper. At the same time, starch retention in a papermaking process is much higher when using anionic starch and a fixative in place of cationic starch. This means that a much smaller part of the starch, which is added to the pulp at the wet end of the papermaking process, is lost in the processing water. Aditionally, - using anionic starch in combination with an appropriate fixative, it has been found that the retention of fines and fillers increases substantially, and this is possible to reduce the refining, also, an increase in the speed of drainage has been observed.

A disadvantage of the use of anionic starch instead of cationic starch in the wet end of the papermaking process resides in the need to use a fixative. Although some of the fixators proposed in the art are relatively inexpensive, the costs of the paper that is produced can be increased considerably due to the use of fixators. Also, since the fixative is a cationic compound, it is inevitable that the anionic counterions will be added to the paper together with the fixative. Frequently, the counterions are chloride ions that are corrosive. Additionally, the use of a fixative can lead to the hardness of the process water and the production of salts, which can interfere with other papermaking auxiliaries.

Description of the invention Surprisingly, it has now been found that the above described disadvantages of the use of starch Anionic as an agent of resistance in the paper can be mitigated by using an anionic starch comprising primarily amylopectin.

Therefore, the invention relates to a process for making paper wherein an anionic starch, which is based on a starch comprising at least 95% by weight, based on the dry substance of the starch, of amylopectin, or a derivative of said starch, is used in combination with a fixative as a resistance agent.

The use of the specific anionic starch has been found to make it possible to use significantly smaller amounts of a fixative, when compared to the use of conventional anionic starch. On the other hand, the incorporation of an anionic starch comprising primarily amylopectin in a sheet of paper leads the paper sheet to have a superior strength.

Most starch types consist of granules in which two types of glucose polymers are present. These are amylose (15-35% by weight on the dry substance) and Amylopectin (65-85% by weight on the dry substance). Amylose consists of unbranched or slightly branched molecules that have an average degree of polymerization of 1000 to 5000, depending on the type of starch. Amylopectin consists of very large, highly branched molecules that have an average degree of polymerization of 1,000,000 or more. The most commercially important types of starch (corn starch, potato starch, wheat starch and tapioca starch) contain from 15 to 30% by weight of amylose.

Some types of cereal, such as barley, corn, milo, rice and sorghum, are varieties in which the starch granules consist almost entirely of amylopectin. Calculated as percent by weight in the dry substance, these starch granules contain more than 95%, and usually more than 98% amylopectin. The amylose content of these cereal starch granules is less than 5%, and usually less than 2%. The above cereal varieties are also referred to as waxy cereal grains, and the starch granules of amylopectin isolated from them as waxy cereal starches.

In contrast to the situation of the different cereals, the varieties of roots and tubers of which the starch granules consist almost exclusively of amylopectin are not known in nature. For example, potato starch granules isolated from potato tubers usually contain about 20% amylose and 80% amylopectin (% by weight, on the dry substance). During the past 10 years, however, successful efforts have been made to grow by genetic modification, potato plants that, in potato tubers, form starch granules that consist of more than 95% by weight (in the dry substance) of amylopectin. It has been found that it is possible to produce potato tubers that substantially comprise only amylopectin.

In the formation of the starch granules, the different enzymes are catalytically active. Of these enzymes, the starch ribbon that binds the granule (GBSS) is involved in the formation of amylose. The presence of the GBSS enzyme depends on the activity of the genes encoded for said GBSS enzyme. The elimination or inhibition of the expression of these specific genes results in the prevention or limitation of the production of the GBSS enzyme. The elimination of these genes can be done by genetic modification of the material of the potato plant or by recessive mutation. An example of this is the potato amylose free mutation (amf) in which the starch only contains substantially amylopectin through a recessive mutation in the GBSS genes. This mutation technique is described in, among others, J.H.M. Hovenkamp-Hermelink et al., "Isolation of amylose-free starch mutant of the potato." (Sol a n um t ubero s um L.) "R Theor. Appl. Gent. , (1987), 75: 217-221, and E. Jacobsen et al, "Introduction of an amylose-free (amf) mutant into breeding of cultivated potato, Sol an um t uberos um L., Euphytica, (1991), 53: 247-253.

The elimination or inhibition of GBSS gene expression in potatoes is also possible using so-called antisensitive inhibition. This genetic modification of the potato is described in R.G.F. Visser et al., "Inhibition of the expression of the gene for granule-bound starch synthase in potato by antisense constructs", Mol. Gen. Genet., (1991), 225: 289-296.

Using genetic modification, it has been found that it is possible to grow and produce roots and tubers, for example potatoes, sweet potatoes, or cassava (South African Patent 97/4383), of which starch granules contain little or no amylose. . As referred to herein, amylopectin potato starch is potato starch granules isolated from potato tubers and having an amylopectin content of at least 95% by weight, based on the dry substance.

With respect to production possibilities and properties, these are significantly different between amylopectin potato starch on the one hand, and the waxy cereal starches on the other side. This applies particularly to waxy corn starch, which is commercially by far the most waxy cereal. important. The cultivation of waxy maize, suitable for the production of waxy maize starch, is not commercially possible in countries that have a climate or cold temperatures, such as The Netherlands, Belgium, England, Germany, Poland, Sweden and Denmark. The climate in these countries, however, is appropriate for growing potatoes. Tapioca starch, obtained from cassava, can be produced in countries that have a hot climate, such as those found in regions of South East Asia and South America.

The composition and properties of root and tuber starch, such as amylopectin potato starch and amylopectin tapioca starch, are different from those of waxy cereal starches. Amylopectin potato starch has a much lower content of lipids and proteins than waxy cereal starches. Problems with respect to odor and foam, which, due to lipids and / or proteins, can occur when using waxy cereal starch products (native and modified), do not occur, or occur to a much lesser degree when the corresponding starch products are used of amylopectin potato. In contrast to waxy cereal starches, amylopectin potato starch contains chemically bonded phosphate groups. As a result, the amylopectin potato starch products, in a dissolved state, have a distinct polyelectrolyte character.

The invention contemplates the use of anionic starch obtained from cereal and fruit sources on the one hand, and from sources of roots and tubers on the other side. From cereal starches, it has been proven that waxy corn starch is very appropriate. In general, however, root and tuber starches are more preferred. As indicated above, it is frequently advantageous to use a starch having a very low content of lipids and / or proteins. The use of amylopectin potato starch and amylopectin tapioca starch as a strength agent in paper has been found to lead to a particularly durable sheet of paper.

By the term "anionic starch" is meant a starch having a charge density of at least 0.03 μeg / g of starch, preferably at least 0.15 μeg / mg of starch. In the context of this invention, charge density is defined as the amount of a cationic polymer (chitosan methyl glycol iodide, Sigma M-3150) which is added to a known quantity of dissolved starch in order to reach the equivalence point . This point of equivalence can be determined by measuring the electrophoretic zetapontial of the dispersion to which the silicate particles are added as an indicator. The electrical potential can, for example, be measured using a Malver Zetasizer 3.

The anionic starch, which, according to the invention, is used in combination with a fixative as a strength agent in paper, can be prepared from starch comprising at least 95% by weight, based on the dry substance, of the starch of ami lopect ima, or the derivative of said starch, on which it is based in any known manner for regular starch comprising both amylopectin and amylose. For one description of a possible way to prepare an anionic starch, reference is made to O.B. urzburg (Ed.), "Modified Starches: Properties and Uses", CRC Press Inc., Boca Eaton, Florida, 1986.

Examples of anionic starch can be obtained by the introduction of any anionic substituent or by any known oxidation process in the derivatization of starch. Suitable examples of anionic substituents are phosphate, phosphonate, sulfonate, sulfate, (alkyl) succinate, anionic graft copolymers and combinations thereof. An example of an appropriate oxidation is oxidation by hypochlorite. Preferably, a carboxymethyl of the phosphate starch is used. The degree of substitution (DS), which is the molar ratio between the amount of substituted hydroxyl groups of a glucose unit in the starch and the amount of glucose units in the starch, can be in the range between 0.005 and 0.5, preferably between -_ 0.01, and. 0.2, more preferably between 0.01 and 0.1.

Suitable derivatives of a starch comprising at least 95% by weight of amylopectin (based on the dry substance) are starches wherein, in addition to an anionic substituent, one or more nonionic or cationic substituents can also be introduced. Suitable examples of nonionic or cationic substituents can be introduced by etherification reactions as well as by esterification, such as methylation, ethylation, hydroxyethylation, hydroxypropylation, alkyl glycidylation (wherein the length of the alkyl chain varies from 1 to 20 carbon atoms). ), acetylation, propylation, carbamidation, diethylamino-ethylation, and / or other imathalammonium hydroxypropylation. In addition, the starch may be crosslinked by any known crosslinker in the derivatization of the starch. Examples of suitable crosslinking agents include epochlorohydrin, dichloropropanol, sodium trimetaphosphate, phosphoroxychloride and adipic acid anhydride. Of course, care should be taken that the general charge of the starch is anionic.

As indicated above, it is essential to use a fixative, where anionic starch is used at the wet end to provide strength on the paper. According to the invention, suitable fixatives are cationically charged compounds, which are capable of binding the anionic starch to the fibers of the anionic paper and filler particles. In principle, any cationic compound that has been proposed to be used as a fixative for anionic starch in the wet end of a papermaking process can be used. Examples include alum, cationic starch or derivatives thereof, polyaluminum compounds, and cationic polymers, such as polydimethyldiallylammonium chlorides, polyamines, polyvinylamines, polyethylene imines, dicyandiamide polycondensates, or other high molecular weight cationic polymers or copolymers. , for example, those comprising a quaternized nitrogen atom or polyvinyl alcohol, and combinations thereof. Such cationic polymers referrerebly have a weight average molecular weight of at least about 10,000, preferably at least about 50,000, more preferably at least 100,000 In a preferred embodiment, the cationic polymers have a weight average molecular weight in the range from about 50,000 to about 2,000,000.

Preferably, a fixative having a high charge density is used. In this regard, a high charge density, a high charge density of 1 μeg / mg is considered. The charge density of the fixative is defined as the amount of an anionic polymer (sodium polystyrene sulfonate, Aldrich catalyst, No. 24,305-1) which is added to a known amount of fixative (typically a few milliliters of the fixative in 500 ml of demineralized water) in order to reach the equivalence point. This point of equivalence can be determined by measuring the electrophoretic elective potential of the dispersion to which the silicate particles are added as an indicator. The electronic potential can, for example, be measured using a Malvern Zetasizer 3. It has been found that the use of a fixative having a high charge density leads to a reduction in the sensitivity of the papermaking process by the hardness and conductivity of the process water. Preferred fixatives having a high charge density are polyaluminium compounds, such as polyaluminium chloride or polyaluminium sulfate, polydimethyl ildialilammonium chlorides, polyamines, and combinations thereof.

In a process for making paper, the anionic starch, which is based on a starch comprising at least 95% by weight, based on the dry substance of the starch, of amylopectin, or a derivative of said starch, and the 'fixative, add to the wet end of the process. This means that they are added to the pulp comprising fibers obtained from recycled paper or formed from wood and water. It is a common practice to add a filler compound to the pulp. In accordance with the invention, any of the commonly used filler compounds, such as clay, CaC03 earth, precipitated CaCO3, talc or titanium dioxide, can be employed. Preferably, the filler compound is added to the pulp before the addition of the anionic starch and the fixative. In addition, the anionic starch It is preferably added to the pulp before the fixative is added.

The amount in which the anionic starch is added to the pulp will depend on the strength of the desired paper. Generally, the amount varies between 0.1 and 10% by weight, preferably between 1 and 5% by weight, based on (consistency) the weight of the solids in the pulp (fibers, fillers, fines, and so on).

The amount of the fixative that is added depends on the nature of the fixative and the pulp to be used and on the amount of anionic starch that is incorporated into the paper. Usually, the amount of fixative is chosen such that at least 60%, preferably at least 80%, more preferably at least 90% of the anionic starch absorption is reached. It will be noted that in this respect a distinction will be made between absorption and retention. Retention refers to the amount of added starch - in the wet end that is eventually incorporated in the paper, while the absorption refers to the amount of starch added in the wet end that absorbs to the paper fibers in the pulp at the wet end. The skilled person will be able to adjust the amount of the fixative to the circumstances presented. Typical values differ for inorganic and organic fixatives. When as is normal, the anionic starch containing amylose is used, the weight ratio of the fixative to the anionic starch is about 1: 1 for inorganic fixatives and about 1: 4 for organic fixatives. When, according to the invention, amylopectin-type anionic starch is used, these amounts can be reduced by a factor of about 8-10 for organic fixatives and a factor of about 4-6 for inorganic fixatives.

The pulp that is used to make paper in a process according to the invention can be any aqueous suspension of cellulose-based fibers that can be used to make paper of this. After the anionic starch and fixative have been added Ü, the pulp, the pulp can be processed on the paper in any known manner.

The invention will be further clarified by the following, non-restrictive, examples.

Example I A solution of 30 g of urea and 31.1 g of phosphoric acid (85%) in 85 ml of water was neutralized to a pH of 6.0 with 50% NaOH. This solution was mixed with 600 g of amylopectin potato starch (20% moisture) for 30 minutes in a Hobart mixer. The mixture was equilibrated and subsequently dried in a Retsch fluid bed dryer for 30 minutes at 60 ° C, and for 30 minutes at 90 ° C, the mixture was heated at 145 ° C in a fluid bed reactor for 30 minutes. The resulting product was HK4017A and had a charge density of 0.47 μeq / mg.

Example II A solution of 30 g of urea and 31.1 g of phosphoric acid (85%) in 85 ml of water was neutralized to a pH of 6.0 with 50% NaOH. This solution was mixed with 600 g of amylopectin potato starch (20% moisture) for 30 minutes in a Hobart mixer. The mixture was equilibrated and subsequently dried in a Retsch fluid bed dryer for 30 minutes at 60 ° C, and for 30 minutes at 90 ° C, the mixture was heated at 140 ° C in a fluid bed reactor for 30 minutes. The resulting product was HK4041B and had a charge density of 0.34 μeq / mg.

Example III The absorption of the starch in the solid components of the pulp was studied as follows. To the pulp (consistency of 1%) was added anionic starch (dose of 3% in consistency). The pulp was stirred in a bucket of buffered precipitation at 800 rpm. After 60 seconds, a fixative was added and after another 60 seconds the pulp was filtered. The starch absorption was determined by measuring the amount of starch not absorbed in the filtrate.

The pulp was a palpa of birch sulphate whipped up to 35 ° SR (measured at 21 ° C) at a consistency of 2% tap water using a Hollander After the shake, the pulp was diluted to a consistency of 1% with tap water.

The pulp was divided into three separate groups. The conductivity of one group was placed at 3.01 mS / cm with sodium sulfate (Na2SO0 10H2O, renewed by Merck). The water hardness of the second group increased from ca. 11 up to ca. 80 ° GH adding calcium chloride (CaCl2'2H20, renewed by Merck). The resulting conductivity of this group was 3.01 mS / cm. Salt was not added to the third group., The conductivity and hardness of the water was 0.51 mS / cm and ca. 11 ° GH, respectively. The conductivity of the pulp was measured with a Radiometer CDM 80 conductivity meter.

The starches used were: - PR9510 A anionic potato starch (marketed as Aniofax AP25) and two amylopectin potato starches: HK4017A and HK4041B. The last two products were prepared as described in Examples I and II, respectively. The resulting starches were cooked with vital steam starting with a 10% mix in tap water. After cooking the starch solutions, they were diluted up to 5% with hot tap water. The viscosities of the 5% solutions were determined using a Brookfield LVTDV-II at 60 rpm (see table 1). The degrees of phosphate substitution in the starches was determined as described in J. Th. LB Rameau and J. Ten Have, Chemisch Weekblad, No. 50 (1951), after the excess phosphate was removed by dialysis against a 0.05N HCl solution for 48 hours and against demineralized water for 24 hours, and a neutralization to a pH of 7-8 with 0.10 N NaOH.

Table 1: Ca ra c e tio n of the a lm ation is applied The fixatives used are Sachtoklar (obtained from Sachtleben Chemie GmbH, Germany), Retinal 1030 (obtained from Joud, France), and PD5-8159 (obtained from Allied Colloids Lyd., UK).

Before use, the Sachtoklar and Retinal 1030 fixatives were diluted by a factor of 10 with demineralized water. A solution of PD5-8159 was prepared by first dissolving 1 g of polymer in 4 g of acetone. After stirring for 30 minutes, 95 g of demineralized water was added. Some properties of fasteners are listed in table 2.

The charge density of the fixatives was determined by adding sodium polystyrene sulfonate to a known amount of fixative (typically a few milliliters of the fixative in 500 ml of demineralized water). The amount needed to reach the equivalence point was the charge density. This point of equivalence was determined by measuring the elec- trochemical potential elect roforético, using a Malvern Zetasizer 3, of the dispersion to which is added silicate particles as an indicator.

Table 2: Ca r c e tting of the fixed fi xers.

The amount of starch in the filtrate was determined in an enzymatic method. In accordance with this method, the starch is first converted to glucose with an α-amylase and an amyloglucosidase. Subsequently, the amount of glucose is determined spectroscopically using a hex-kinase test method (Boehringer No. 716251) The amount of starch is calculated from the amount of glucose obtained using a correction factor for the incomplete conversion of the glucose. starch in glucose by enzymes. The applied enzymatic conversion factor of Aniofax AP25 is 0.78. The starch absorption was calculated enzymatically by determining the concentration of starch in the filtrate using the following expression: Cs x V A = 1 eq. where A is the absorption of starch, Cs is the concentration of starch in the filtrate, V is the total volume of water and G is the aggregate amount of starch. The total amount of water is obtained by: V = Vp-dsp + Va t -dss t + Vfíx-dsfix eq. B where Vp, Vs and Vflx represent the volume of the pulp group, the volume of the dose of starch and the volume of the fixative dose, respectively. The total volume is corrected for the dry solids content dsp, dsst and dsflx (the assumed density of dry solids is 1 g / ml).

The starch absorption was investigated by varying three parameters: starch, fixative and pulp properties (conductivity and water hardness). The results are discussed using the fixative doses expressed as dry in the fiber.

A summary of the doses of fixatives necessary for a starch absorption of at least 90% is given in Table 3 for each starch and each experimental condition The smallest amounts of the fixative for the absorption of the starch from > 90% are necessary in case of HK4017A. For PD5-8159 the fixative dose is 1.5 to 2.5 times larger in case of HK4041B and 2.5 to 5 times larger for PR9510A. For Retinal 1030, the dose increase is a factor of 2 to 2.5 for HK4041B and up to at least 5 for PR9510A.

Also for the PAC Sachtoklar, the best results are obtained, from I05 amylopectin starches. In the case of PR9510A, the PAC dose is 1.5 to more than 3.5 times higher than in the case of HK4017A.

A notable difference between PR9510A and HK4017A is the effectiveness of organic fixatives PD5-8159 and Retinal 1030 at high water hardness. With HK4017A, starch absorption is greater than altsa hardness for both fixatives, while with PR9510A the absorption is the same or less. In this way, with this anionic AAZM, a higher water hardness leads to higher starch absorptions, not only for PACs but also for the tested organic fixatives. In the case of another anionic AAZM, HK4041B, the same effect of water hardness is observed for Retinal 1030, but not for PD5-8159.

These results confirm that the applied organic fixatives are more effective in absorbing amylopectin molecules than absorbing amylose molecules.

Table 3: Data for the comparison of starches. The listed dose of fixatives is the lowest dose so that a starch absorption of 90% is obtained. The fixator dose ratio is the amount of fixative needed with the HK4041B or the PR9510A divided by the amount needed for the HK4017A.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, the content of the following is claimed as property.

Claims

1. A process for making paper, characterized in that an anionic starch, which is based on a starch comprising at least 95% by weight, based on the dry substance of the starch, of amylopectin, or a derivative of the starch, is used in combination with a fixative as a resistance agent.

2. The process according to claim 1, characterized in that the starch is a root or tuber starch.

3. The process according to claim 2, characterized in that the starch is a potato or tapioca starch.

4. The process according to any of claims 1-3, characterized in that the starch derivative is obtained by a de-etherification or esterification reaction, or a combination thereof.

5. The process according to any of the preceding claims, characterized in that the fixative is a cationic compound having a charge density of at least 1 μeq / mg.

6. The process according to any of the preceding claims, characterized in that the fixative is selected from the group of polyaluminium compounds, alum, cationic starch or a derivative thereof, polydimethyldiallylammonium chlorides, polyamines, polyvinylamines, polyethylene imines, and polycondensate dicyandiamides. .

7. A paper that is obtained by a process according to any of the preceding claims.

8. The use of an anionic starch, which is based on a starch comprising at least 95% by weight, based on the dry substance of the starch, of amylopectin, or a derivative of the starch, as an agent of resistance in the paper.

9. The use of an anionic starch, which is based on a starch comprising at least 95% by weight, based on the dry substance of the starch, of amylopectin, or a derivative of the starch, to reduce the amount of a fixative in a process for making paper, where the anionic starch is used as a resistance agent.