Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H17/00—Non-fibrous material added to the pulp, characterised by its constitution; Paper-impregnating material characterised by its constitution
  • D21H17/20—Macromolecular organic compounds
  • D21H17/21—Macromolecular organic compounds of natural origin; Derivatives thereof
  • D21H17/24—Polysaccharides
  • D21H17/28—Starch
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H21/00—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties
  • D21H21/14—Non-fibrous material added to the pulp, characterised by its function, form or properties; Paper-impregnating or coating material, characterised by its function, form or properties characterised by function or properties in or on the paper
  • D21H21/18—Reinforcing agents
  • D21H21/20—Wet strength agents
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
  • D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
  • D21H23/76—Processes or apparatus for adding material to the pulp or to the paper characterised by choice of auxiliary compounds which are added separately from at least one other compound, e.g. to improve the incorporation of the latter or to obtain an enhanced combined effect

Definitions

• the invention relates to a process for making paper and to the use of starch in said process.
• the wet-end of the papermaking process refers to-the stages of the papermaking process, wherein a pulp of fibers, obtained from cellulose-based materials, such as recycled, used paper, wood, cotton, or alternative sources, is being processed.
• the term “wet-end” originates in the large amounts of water, in the presence of which the pulp is processed.
• the fibers and filler particles which are used to produce paper from, are negatively charged.
• cationic starch When cationic starch is used as a paper strengthening agent, its retention is mainly caused by the interaction between the positively charged starch and the negatively charged fibers and filler particles.
• anionic starch molecules In order to adhere anionic starch molecules onto anionic fibers and filler particles, use is made of a so-called cationic fixative.
• any cationic paper and can be used as a fixative for the anionic starch, although some lead to better results than others. Because they are cheap and hardly affected by water hardness, polyaluminum chlorides are considered very attractive fixatives.
• Other materials that have been proposed for use as a fixative in this regard are, inter alia, alum, or cationic polymers, such as polydimethyldiallylammonium chloride and polyamines.
• a disadvantage of the use of anionic starch instead of cationic starch in the wet-end of the papermaking process resides in the necessity of using a fixative. Even though some of the fixatives proposed in the art are relatively cheap, the costs of the paper that is produced may increase considerably because of the use of the fixative. Also, as the fixative is a cationic compound; it is inevitable that anionic counterions are added to the paper along with the fixative. Often, the counterions are chloride ions which are corrosive. Furthermore, the use of a fixative may lead to a hardening of the process water and to the production of salts, which may interfere with other papermaking aids.
• anionic starch as a strengthening agent in paper may be mitigated by using an anionic starch which primarily comprises amylopectin.
• 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.
• starch types consist of granules in which two types of glucose-polymers are present. These are amylose (15-35 wt. % on dry substance) and amylopectin (65-85 wt. %, on dry substance).
• Amylose consists of unbranched or slightly branched molecules having an average degree of polymerization of 1000 to 5000, depending on the starch type.
• Amylopectin consists of very large, highly branched molecules having an average degree of polymerization of 1,000,000 or more.
• the commercially most important starch types (maize starch, potato starch, wheat starch and tapioca starch) contain 15 to 30 wt. % amylose.
• starch granules nearly completely consist of amylopectin. Calculated as weight percent on dry substance, these starch granules contain more than 95%, and usually more than 98% amylopectin. The amylose content of these cereal starch granules is thus less than 5%, and usually less than 2%.
• the above cereal varieties are also referred to as waxy-cereal grains, and the amylopectin-starch granules isolated therefrom as waxy cereal starches.
• starch granules nearly exclusively consist of amylopectin are not known in nature.
• potato starch granules isolated from potato tubers usually contain about 20% amylose and 80% amylopectin (wt. % on dry substance).
• successful efforts have been made to cultivate by genetic modification potato plants which, in the potato tubers, form starch granules consisting for more than 95 wt. % (on dry substance) of amylopectin. It has even been found feasible to produce potato tubers comprising substantially only amylopectin.
• GBSS granule-bound starch synthase
• amylose granule-bound starch synthase
• the presence of the GBSS enzyme depends on the activity of genes encoding for said GBSS enzyme. Elimination or inhibition of the expression of these specific genes results in the production of the GBSS enzyme being prevented or limited.
• the elimination of these genes can be realized by genetic modification of potato plant material or by recessive mutation.
• An example thereof is the amylose-free mutant of the potato (amf) of which the starch substantially only contains amylopectin through a recessive mutation in the GBSS gene. This mutation technique is described in, inter alia, J.
• Elimination or inhibition of the expression of the GBSS gene in the potato is also possible by using so-called antisense 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.
• amylopectin-potato starch is the potato starch granules isolated from potato tubers and having an amylopectin content of at least 95 wt. % based on dry substance.
• composition and properties of root and tuber starch differ from those of the waxy cereal starches.
• Amylopectin-potato starch has a much lower content of lipids and proteins than the waxy cereal starches. Problems regarding odor and foaming, which, because of the lipids and/or proteins, may occur when using waxy cereal starch products (native and modified), do not occur, or occur to a much lesser degree when using corresponding amylopectin-potato starch products.
• amylopectin-potato starch contains chemically bound phosphate groups. As a result, 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 root and tuber sources on the other hand.
• cereal starches waxy maize starch has proven very suitable. In general, however, root and tuber starches are more preferred.
• root and tuber starches are more preferred.
• anionic amylopectin-potato starch and amylopectin-tapioca starch as a strengthening agent in paper has been found to lead to a particularly strong paper sheet.
• anionic starch a starch having a charge density of at least 0.03 seq/mg starch, preferably at least 0.15 ⁇ eq/mg starch.
• the charge density is defined as the amount of a cationic polymer (methyl glycol chitosan iodide, Sigma M-3150) which has to be added to a known amount of dissolved starch in order to reach the equivalence point.
• This equivalence point may be determined by measuring the electrophoretic zetapotential of the dispersion to which silicate particles are added as indicator. The zetapotential can for instance be measured by using a Malvern Zetasizer 3.
• the anionic starch which, according to the invention, is used in combination with a fixative as a strengthening agent in paper, may be prepared from the starch comprising at least 95 wt. %, based on dry substance of the starch, of amylopectin, or the derivative of said starch, on which it is based in any manner known for regular starch comprising both amylopectin and amylose.
• a fixative as a strengthening agent in paper may be prepared from the starch comprising at least 95 wt. %, based on dry substance of the starch, of amylopectin, or the derivative of said starch, on which it is based in any manner known for regular starch comprising both amylopectin and amylose.
• anionic starch may be obtained by introduction of any anionic substituents or by any oxidation process known 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 a suitable oxidation is oxidation by hypochlorite.
• a carboxymethyl of phosphated starch is used.
• the degree of substitution 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, may 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 wt. % amylopectin (based on dry substance) are starches wherein, besides an anionic substituent, also one or more non-ionic or cationic substituents may be introduced.
• non-ionic or cationic substituents may be introduced by etherifcation idem esterifcation reactions, such as methylation, ethylation, hydroxyethylation, hydroxypropylation, alkylglycidylation (wherein the length of the alkyl chain varies from 1 to 20 carbon atoms), acetylation, propylation, carba-imidation, diethylamino-ethylation, and/or trimethylammoniumhydroxypropylation.
• the starch may be crosslinked by any crosslinking known in the derivatization of starch.
• crosslinking agents examples include epichlorohydrine, dichloropropanol, sodium trimethaphosphate, phosphorousoxychloride and adipic acid anhydride of course, care should be taken that the overall charge of the starch is anionic.
• fixative when anionic starch is used in the wet-end to provide strength in paper.
• suitable fixatives are cationically charged compounds, which are capable of binding anionic starch to anionic paper fibers and filler particles.
• any cationic compound that has been proposed for use 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, e.g. comprising a quaternized nitrogen atom or polyvinyl alcohol, and combinations thereof.
• Such cationic polymers preferably should 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.
• a fixative having a high charge density is used.
• a charge density higher than 1 seq/mg. is considered a high charge density.
• the charge density of the fixative is defined as the amount of an anionic polymer (sodium polystyrenesulfonate, Aldrich cat. no. 24,305-1) which has to be added to a known amount of fixative (typically a few milliliters of the fixative in 500 ml demineralized water) in order to reach the equivalence point.
• This equivalence point may be determined by measuring the electrophoretic zetapotential of the dispersion to which silicate particles are added as indicator.
• the zetapotential can for instance be measured by using a Malvern Zetasizer 3. It has been found that the use of a fixative having a higher charge density leads to a decreased sensitivity of the papermaking process for the hardness and conductivity of the process water.
• Preferred fixatives having a high charge density are polyaluminum compounds, such as polyaluminum chloride or polyaluminum sulfate, polydimethyldiallylammonium chlorides, polyamines, and combinations thereof.
• the 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, and the fixative are added at the wet-end of the process.
• a pulp comprising fibers obtained from recycled paper or from wood and water.
• a filler compound to the pulp.
• any of the commonly used filler compounds such as clay, ground CaCO 3 , precipitated CaCO 3 , talc or titaniumdioxide, may be employed.
• the filler compound is added to the pulp prior to the addition of the anionic starch and the fixative.
• the anionic starch 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 desired paper strength. Generally, the amount will vary between 0.1 and 10 wt. %, preferably between 1 and 5 wt.-, based on (consistency) the weight-of the solids in the pulp (fibers, filler compounds, fines, and so forth).
• the amount of the fixative which is added depends on the nature of the fixative and the pulp that is being used and on the amount of anionic starch that is to be incorporated into the paper. Generally, the amount of fixative is chosen such that at least 60%, preferably at least 80%, more preferably at least 90% adsorption of the anionic starch is attained. It is noted that in this regard a distinction should be made between adsorption and retention. Retention refers to the amount of starch added in the wet-end that is eventually incorporated in the paper, while adsorption refers to the amount of starch added in the wet-end that adsorbs to the paper fibers in the pulp in the wet-end.
• the skilled person will be able to adjust the amount of the fixative to the circumstances at hand. Typical values differ for inorganic and organic fixatives.
• the weight ratio of fixative to anionic starch is about 1:1 for inorganic fixatives and about 1:4 for organic fixatives.
• an amylopectin type anionic starch is used, these amounts may 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 for making paper in a process according to the invention may be any aqueous suspension of cellulose-based fibers that can be used to make paper from. After the anionic starch and the fixative have been added to the pulp, the pulp may be processed into paper in any known manner.
• the pulp was a birch sulfate pulp beaten to 35°SR (measured at 21° C.) at a consistency of 2% in tap-water using a Hollander. After beating the pulp was diluted to a consistency of 1% with tap-water.
• the pulp was divided in three separate batches.
• the conductivity of one batch was set to 3.01 mS/cm with sodium sulphate (Na 2 SO 4 .10H 2 O, Merck reinst).
• the water hardness of the second batch was increased from ca. 11 to ca. 80°GH by adding calcium chloride (CaCl 2 .2H 2 O, Merck reinst).
• the resulting conductivity of this batch was 3.01 ms/cm.
• To the third batch no salt was added.
• the conductivity and water hardness 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 are: anionic potato starch PR9510 A (commercialized as Aniofax AP25) and two anionic amylopectin potato starches: HK4017A and HK4041B.
• the latter two products were prepared as described in Examples I and II, respectively.
• the starches were cooked with life steam starting with a 10% slurry in tap-water. After cooking the starch solutions were diluted 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 substitution of phosphate in the starches were determined as described in J. Th. L. B. Rameau and J. ten Have, Chemisch Weekblad, No.
• the used fixatives are Sachtoklar (obtained from Sachtleben Chemie GmbH, Germany), Retinal 1030 (obtained from Joud, france), and PD5-8159 (obtained from Allied Colloids Ltd., UK).
• fixatives Sachtoklar and Retinal 1030 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 demineralized water was added.
• the charge density of the fixatives was determined by adding sodium polystyrenesulfonate to a known amount of fixative (typically a few milliliters of the fixative in 500 ml demineralized water). The amount necessary in order to reach the equivalence point was the charge density. This equivalence point was determined by measuring the electrophoretic zetapotential, using a Malvern Zetasizer 3, of the-dispersion to which silicate particles were added as indicator.
• the amount of starch in the filtrate was determined in an enzymatic method.
• starch is first converted into glucose with an a-amylase and an amyloglucosidase. Subsequently, the amount of glucose is determined spectroscopically using a hexokinase test method (Boehringer no. 716251). The amount of starch is calculated from the obtained amount of glucose using a correction factor for incomplete conversion of the starch into glucose by the enzymes.
• the applied enzymatic conversion factor of Aniofax AP25 is 0.78.
• A is the starch adsorption
• c s is the starch concentration in the filtrate
• V is the total volume of water
• G is the added amount of starch.
• the total amount of water is obtained by:
• V V p ⁇ ds p +V st ⁇ ds st +V fix ⁇ ds fix eq. B
• V p , V st and V fix represent the volume of the batch of pulp, the volume of the starch dosage and the volume of the fixative dosage, respectively.
• the total volume is corrected for the dry solids contents ds p , ds st , and ds fix (assuming density of dry solids is 1 g/ml).
• starch adsorption was investigated by varying three parameters: starch, fixative and pulp properties (conductivity and water hardness). The results will be discussed using the fixative dosage expressed as dry on fiber.
• fixative dosage 1.5 to 2.5 times larger in case of HK4041B and 2.5 to 5 times for PR9510A.
• increase of the dosage is a factor 2 to 2.5 for HK4041B and-2 to at least 5 for PR9510A.
• PR9510A and HK4017A A noteworthy difference between PR9510A and HK4017A is the effectivity of the organic fixatives PD5-8159 and Retinal 1030 at high water hardness. With HK4017A the starch adsorption is higher at high hardness for both fixatives, while with PR9510A the adsorption is the same or lower. Thus, with this anionic AAZM a high water hardness leads to higher starch adsorptions, not only for PACs but also for the tested organic fixatives. In case of the other anionic AAZM, HK4041B, the same effect of water hardness is observed for Retinal 1030, but not for PD5-8159.

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• 1999
  • 1999-06-04 JP JP2000553661A patent/JP4475810B2/ja not_active Expired - Fee Related
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  • 1999-06-04 AU AU42931/99A patent/AU4293199A/en not_active Abandoned
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