PROCESS FOR MANUFACTURING PAPER USING CATIONIC AMYLOPECTIN STARCH
Description of the Invention The invention relates to the field of papermaking. More particularly, the invention relates to improvements in the manufacture of paper from hardwood pulps, such as eucalyptus. During the last few years, eucalyptus pulps have been important in papermaking by virtue of their fast rates of tree growth and their advantages of uniformity and sheet printing. This extends not only to the printing and writing grades of paper, but also to the white top coating board. Eucalyptus, such as E. granáis and E. globulus, is generally associated with the Iberian Peninsula and Latin America. In other regions of the world, there are compelling logistical reasons to use an indigenous species such as alder, acacia, birch and oak. All hardwoods have some structural features common to wood, especially the vessels, which branch off through the stem and act as water pipes, distributing the water from the roots to other parts of the tree. The vessels are usually much wider than the fibers, which are REF. 198412 responsible for many of the problems caused by the vessels in papermaking. The inclusion of hardwood cups in supplies has caused some serious print quality problems in many hardwood pulps, especially with eucalyptus. When these pulps were introduced for the first time in the market, the uncoated papers that used them in the supply suffered the presence of vessels on the surface of the leaf. This presence not only damaged the surface of the paper, it also accumulated in the press blankets, requiring the stopping of the washes in the middle of an execution and causing the printer to lose time. There was also the danger that the vessels caused wear on the coated grades by locally weakening the adhesion of the coating to the paper surface. Over time, paper manufacturers have made several attempts to contain the problem, often because of the improved surface dimension, and the demands of printers that the presence of cups can sometimes be reduced to tolerable levels. However, the improved surface dimension did not partially provide the cost advantage of hardwood pulps. In addition, in the four to five years before the problem has reappeared and in a more critical way while the speeds of the Offset press has increased with a new generation of presses that print five or six colors. Apart from the presence of glasses, the incidence of rejection of the ink in uncoated papers has been presented. The rejection of the ink manifests as white spots where the vessels are still clearly present when the printed paper is examined under a microscope. The presence implies the little union of the glasses to other fine fibers, but the rejection of the ink in a lithographic press Offset implies low superficial energy (little adherence) and / or a local variation in the compressibility that reduces the transfer of ink. In accordance with the invention, it has been surprisingly found that the problem of the presence of vessels can be significantly reduced by using a specific starch in the paper pulp, i.e. at the wet end. Consequently, the previous needs for more expensive and more elaborate surface dimension adaptations are obsolete. Under certain circumstances, the surface sizing may be omitted altogether, or it may be replaced by a preliminary coating operation. Also, a consequence of the invention is that larger quantities of hardwood, such as eucalyptus, can be used in the pulp without the presence of any problem of strength or presence of vessels, which can considerably reduce the cost of paper produced without affect quality These and other advantages of the invention are achieved, as mentioned using a specific starch at the wet end. The specific starch used according to the invention is a cationic amylopectin starch. The use of cationic starch in papermaking has been previously described. For example, U.S. Patent No. 2,935,436 discloses that a number of advantages are associated with the use of cationic starch instead of non-cationic starch. Examples of these advantages are increased retention of starch, fillers and pigments, increased paper strength (separation strength, resistance to breakage, resistance to bending) and lower dosage. In addition, European Patent Application 0 703 314 discloses a method for making paper wherein a cationic amylopectin potato starch is added to an aqueous solution of cellulose fibers, optionally in addition to other additives, continuous paper formation from this suspension in a conventional manner. It is disclosed that a higher amount of fillers can be incorporated into the paper by using cationic amylopectin potato starch without a negative impact on paper strength, when compared to the use of cationic potato starch having a normal amylopectin content. or a waxy corn starch. U.S. Patent No. 5,635,028 discloses a process for making the paper of soft creped fabric in which a cationic starch, a carboxymethylcellulose and a binding inhibitor are used as a creping facilitation composition. The crepe paper produced is intended to be used as a handkerchief or facial tissue, and is unsuitable for printing. The problem of the presence of vessels does not play a role in such a creased role. Also, creped paper is conventionally not subjected to surface sizing. Most types of starch consist of granules in which two types of glucose polymers are present. These are amylose (15-35% by weight on dry substance) and amylopectin (65-85% by weight on 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 and 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 15 to 30% by weight amylose. Of some types of cereal, such as barley, corn, millet, wheat, milo, rice and sorghum, there are varieties whose starch granules consist almost entirely of amylopectin. Calculated as percent by weight on dry substance, these starch granules contain more than 95%, and generally more than 98% amylopectin. The amylose content of these cereal starch granules is therefore less than 5%, and generally less than 2%. The above cereal varieties are also designated as waxy cereal grains, and the amylopectin-starch granules isolated from them as waxy cereal starches. In contrast to the situation of different cereals, roots and. tuber varieties whose starch granules consist almost exclusively of amylopectin are not known in nature. For example, potato starch granules isolated from potato tubers generally contain about 20% amylose and 80% amylopectin (% by weight on dry substance). Dg the past 15 years, however, successful efforts have been made to grow genetically modified potato plants which, in potato tubers, form starch granules consisting of more than 95% by weight (in the dry substance) of amylopectin. It has even been found feasible to produce potato tubers that substantially comprise only amylopectin. In the formation of starch granules, various enzymes are catalytically active. Of these enzymes, granule-binding starch synthase (GBSS) is involved in the formation of amylose. The presence of the GBSS enzyme depends on the activity of the genes that encode the GBSS enzyme. The elimination or inhibition of the expression of these specific genes results in the production of the GBSS enzyme that is prevented or limited. The elimination of these genes can be observed by genetic modification of potato plant material or by recessive mutation. An example of the above is the amylose-free mutant of potato (amf) whose starch contains substantially only amylopectin through a recessive mutation in the GBSS gene. This mutation technique is described in, among others, J.H.M. Hovenkamp-Hermelink et al., "Isolation of amylose-free starch mutant of the potato (Solarium tuberosum L.)", Theor. Appl. Gent. , (1987), 75: 217-221, and E. Jacobsen et al., "Introduction of an amylose-free (amf) mutant into breeding of cultivated potato, Solarium tuberosum L., Euphytica, (1991), 53: 247 The removal or inhibition of GBSS gene expression in potato is also possible using so-called antisense inhibition This genetic modification of potato is described in RGF Visser et al., "Inhibition of the expression of the gene granule-bound starch synthase in potato by antisense constructs ", Mol. Gen. Genet., (1991), 225: 289-296 Using genetic modification, it has been found possible to grow and reproduce roots and tubers, for example potato, sweet potato , or cassava (South African patent 97/4383), whose starch granules contain little or no amylose, as referred to herein, potato amylopectin starch are potato starch granules isolated from potato tubers and has an amylopectin content of at least 95% by weight in bas e to the dry substance. With respect to the possibilities and production characteristics, there are significant differences between amylopectin potato starch on the one hand, and waxy cereal starches on the other hand. This applies in particular to waxy corn starch, which is the most important and most commercially available waxy cereal starch. The cultivation of waxy corn, suitable for the production of waxy corn starch is not commercially feasible in countries that have a cold or temperate climate, such as the Netherlands, Belgium, England, Germany, Poland, Sweden and Denmark. The climate in these countries, however, is convenient for the cultivation of potatoes. Tapioca starch, obtained from cassava, can be produced in countries that have a hot climate, for example in regions of Southeast Asia and South America. The composition and characteristics of root and tuber starch, such as amylopectin-potato starch and amylopectin tapioca starch, differ from those of waxy cereal starches. Amylopectin potato starch has a much lower content of lipids and proteins than waxy cereal starches. Problems with regard to odor and foam generation, which, due to lipids and / or proteins, can occur when using waxy cereal starch products (natural and modified), do not occur, or occur to a very low degree use corresponding amylopectin potato starch products. In contrast to waxy cereal starches, amylopectin potato starch contains chemically bound phosphate groups. Consequently, the amylopectin potato starch products in a dissolved state have a distinct polyelectrolyte character. The invention contemplates the use of cationic starch obtained from cereal and fruit sources on the one hand, and root and tuber sources on the other hand. From cereal starches, waxy corn starch has proved very convenient. Generally, however, root and tuber starches are more preferred. As indicated above, it is often advantageous to use a starch having a very low content of lipids and / or proteins. The use of cationic amylopectin potato starch and amylopectin tapioca starch as a strength agent in paper has been found to lead to a particularly tough sheet of paper. According to the invention, an amylopectin starch is defined as a starch obtained from, or in the form of, starch granules comprising more than 95% by weight, preferably more than 98% by weight, based on a dry substance, of amylopectin, whose starch granules are isolated from a vegetable source, such as potato tubers or cassava roots, wherein the starch granules are formed with the aforementioned amylopectin content. The methods of making cationic starch are known per se, and for example have been clarified by D. B. Solarek: Cationic Starches, in the book of O.B. Wurzburg (Ed.): Modified Starches: Properties and Uses, CRC Press Inc., Boca Raton, Florida, 1986, p. 113-130. The methods described in this book can also be used for the preparation of cationic amylopectin starch using an amylopectin starch, from a particular botanical source chosen, as raw material. According to the invention, it is preferred to use a cationic amylopectin starch containing electropositively charged quaternary ammonium groups. Before, after or during the cationization reaction the amylopectin starch can be further modified physically, chemically and / or enzymatically. The invention also comprises the use of these modified amylopectin starches. The degree of substitution (DS) of the cationic amylopectin starch to be used according to the invention is preferably between 0.005 and 0.5, and more preferably between 0.01 and 0.2. Although a wide variety of ammonium compounds, preferably quaternary, can be used in the preparation of a cationic amylopectin starch for use according to the present invention, it is preferred to prepare a cationic amylopectin starch by treating the amylopectin starch with sodium chloride. 3-chloro-2-hydroxypropyltrimethyl ammonium or 2,3-epoxypropyltrimethyl chloride-β-ammonium. The amount of cationic starch that is used will depend on the kind of pulp that is used, working conditions and desired paper properties. It is preferably used, 0.05 to 10% by weight and more preferably 0.1 to 2% by weight of cationic amylopectin starch, dry substance, calculated on paper pulp, dry substance. The cationic amylopectin starch is preferably first gelatinized in water. The resulting starch solution, optionally after further dilution, is added to the pulp mass. It is also possible, however, to mix the cold pregelatinized soluble cationic amylopectin starch with the pulp mass, as a dry product or after dissolution in water). The invention is particularly directed to the manufacture of paper wherein the presence of cups is a problem. These are the paper types that are conventionally sized superficially. A preferred paper category is flat paper, which is intended to be printed with ink containing oil in a sheet offset or roto-offset printing process. Such inks containing oil have a high adhesion (viscosity) which requires that large forces be exerted on the paper during printing. In contrast, creped papers are not suitable for printing with inks that have a high adhesion. Conventionally creped papers are not dimensioned superficially. The cationic amylopectin starch can be added at any time in the papermaking process. For example, it can be added to the pulp while it is located in the main box, Hollander, Hydropulper or powder box. If desired, in addition to the cationic amylopectin starch, an anionic starch can also be added to the pulp. As mentioned above, the problems specifically addressed by the invention are associated with the use of pulps specifically prepared from hardwood. Accordingly, it is preferred according to the invention that a pulp be used for the manufacture of paper comprising at least 5% by weight, based on the dry substance, hardwood pulp. Preferably, the pulp comprises at least 10% by weight, preferably at least 15% by weight, and more preferably at least 20% by weight, based on the dry substance, hardwood pulp. In a highly preferred embodiment, the pulp comprises between 30 and 70% by weight, based on the dry substance, hardwood pulp. Convenient sources of hardwood are oak, maple, poplar, elm, eucalyptus, aspen, American balsamic and acacia. In a preferred embodiment, the hardwood pulp is oak, eucalyptus or MTH (ie mixed tropical hardwood). In a more preferred embodiment, the hardwood pulp is eucalyptus. The rest of the pulp, if the pulp is not entirely hardwood, can be from several sources of softwood, such as spruce, pine and larch. It is one of the advantages of the invention that the surface treatments of manu reed paper can be performed to a lesser degree, or can be omitted altogether. The surface treatment of a sheet of paper, such as sizing or surface coating, has been conventionally used to increase the resistance to the presence of paper cups to be manufactured. Commonly, such surface treatments involve the use of starch. Normal dosage levels of surface treatment starch are from 5 to 10% by weight based on the weight of the sheet. A final leaf weight of 100 g / m2 means a starch presence of 2.5 to 5 g of starch on each side of the paper sheet. By using a cationic amylopectin starch at the wet end of the papermaking according to the present invention, the harvesting of starch in a surface treatment can be reduced from 10 to 40%, due to the improved resistance to the presence of watermelon vessels. paper. Therefore, the presence of starch in a surface treatment in a process for manufacturing the paper according to the invention, can be as low as 0.5 to 6% by weight based on the weight of the sheet, and preferably 1 to 4% by weight based on the weight of the sheet. A reduction in the presence of starch will lead to a reduction in the final weight of the leaf. This loss in sheet weight can be compensated for by the addition of a pigment in the surface treatment formulation. Advantageously, substituting the surface treatment starch for the pigment achieves a total cost reduction. The invention will now be described by the following non-limiting examples. Example 1 In this example the following two cationic starch products, containing the quaternary ammonium substituents (substitution degree 0.035), were used as wet end additives for papermaking. A. Cationic potato starch (containing approximately 20% by weight of amylose in dry substance, Amylofax PV) B. Cationic amylopectin potato starch (according to the invention, contains about 2% by weight of amylase in dry substance, PR0602A). The cationic starch products were suspended in water, forming a suspension of starch with 10% by weight of starch. This suspension is gelatinized with steam. The starch solution obtained is diluted with water to 1% by weight of dry substance. The test pulp consists of a mixture of 38% long fibers, 28% short fibers (eucalyptus) and 34% CTMP. The calcium carbonate was added as filler to obtain a final ash content of 16% on the paper sheet. The amount of cationic starch added was 1.0% by weight (dry substance). The test pulp was made in manual sheets (sheet weight 80 g / m2) with a previous manual sheet. The hand sheets were dried to a water content of 7% by weight. The tendency of the presence of vessels was determined by performing the spinning with a dry presence test of Prufbau as described in Tappi Journal, July 1994, page 185. The test ink was a high adhesion ink (Huber 408004). The tendency of presence of vessels was determined visually. The results are shown in Figure 1. Example 2 In this example the same two cationic starch products, containing the quaternary ammonium substituents (substitution degree 0.035), were used as described in example 1. The pulp of The test consisted of a mixture of 42% long fibers, 8% short fiber (eucalyptus) and 50% CTMP. The calcium carbonate was added as filler to obtain a final ash content of 16% on the paper sheet. The amount of cationic starch added was 1.0% by weight (dry substance). The test pulp was made in manual sheets (sheet weight 80 g / m2) with a previous manual sheet. The hand sheets were dried to a water content of 7% by weight. The tendency of the presence of vessels was determined by performing the spinning with a dry presence test of Prufbau as described in Tappi Journal, July 1994, page 185. The test ink was a highly adhesive ink (Huber 408004). The tendency of presence of vessels was determined visually. The results are represented in figure 1.
Conclusion For both pulp qualities (ie example 1 and 2), a marked improvement was observed in the tendency of vessel presence when the cationic amylopectin potato starch was used in comparison to the regular cationic potato starch.
EXAMPLE 3 In this example the same two cationic starch products, containing the quaternary ammonium components (degree of substitution 0.035), were used as described in example 1. The pulp consisted of a mixture of 38% fibers long, 28% of short fibers (eucalyptus) and 34% of CTMP. The calcium carbonate was added as filler to obtain a final ash content of 10% on the paper sheet. The amount of cationic starch added was 1.0% by weight (dry substance). The pulp was made on a sheet of paper (sheet weight of 200 g / m2) with an ordinary paper machine at a production speed of 400 meters / minute. The sheets of paper thus obtained were sized superficially with a Dixon sizing press at an operating speed of 50 meters / minute. As well as the surface-sized starch, an aqueous solution of Perfectamyl A4692 (AVEBE) was applied at a concentration of 4%, 8% and 12%. The starch content of the various sheets of paper was determined by the enzymatic conversion of starch to glucose, followed by determination of glucose with the hexokinase method according to Boehringer. The tendency of presence of vessels was determined by performing the spin test with the Prufbau dry presence test as described in Tappi Journal, July 1994, page 185. The test ink was a highly adhesive ink (Huber 408004). The tendency of presence of vessels was determined visually. The results are represented in the following table.
Starch Starch Yarn content at 2 extreme dimensioned starch (%) m / sec surface moisture 1.0% PR0602A None 1.11 6 1.0% PR0602A 4% Perfecamyl 1.81 9 A4692 1.0% PR0602A 8% Perfecamyl 2.75 9 A4692 1.0% PR0602A 12% Perfecamyl 3.65 9 A4692 1.0% Amylofa None 1.11 3 PW 1.0% Amylofa 4% Perfecamyl 1.78 7 PW A4692 1.0% Amylofa 8% Perfecamyl 2.60 8 PW A4692 1.0% Amylofa 12% Perfecamyl 3.45 9 PW A4692 Yarn rating: 1 means very bad, 10 It means excellent. From the results shown in the table, it can be seen that for the cationic amylopectin potato starch only 0.7% of surface sized starch is required to obtain a very good spinning performance. For traditional cationic potato starch much more surface-sized starch is required to obtain the same spinning performance. 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.