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
  • 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
  • D21H17/33—Synthetic macromolecular compounds
  • D21H17/34—Synthetic macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/37—Polymers of unsaturated acids or derivatives thereof, e.g. polyacrylates
  • D21H17/375—Poly(meth)acrylamide

Definitions

• This invention relates to use of a cooked, specially-treated starch product as a paper wet-end additive for the climination of conventional surface sizing.
• wood pulp There are five different kinds of wood pulp: mechanical pulp (ground wood), semi-chemical pulp, sulfite pulp, sulfate or kraft pulp, and soda pulp. The first is prepared by purely mechanical means, the second by a combination of mechanical and chemical means, and the other three by chemical means.
• the mechanical pulp contains substantially all the wood except the bark and that lost during storage and transportation.
• Semi-chemical pulps are partially free of lignin.
• Chemical pulps are essentially cellulose, the unwanted lignin and other non- cellulosic components of the wood having been dissolved away by the cooking and bleaching treatment. Because of this, chemical pulps are much superior to mechanical and semi-chemical pulps for fine paper making. However, because of the special processing required, they are too expensive to serve as a main source of fiber for the cheaper grades of paper such as newsprint.
• the pulp fibers were the only constituents of a paper sheet, the usefulness of the paper would be very restricted because the sheet would be soft, have a yellowish color, and could not be successfully written or printed upon with ink. If the sheet were thin, it would be transparent to matter printed upon the opposite side. It is necessary, then, to add other substituents, such as sizing or coloring agents and fillers to the cellulosic fibers to produce papers suited to its many uses.
• Sizing is added to the paper, other than absorbent papers and filter paper, to impart resistance to penetration by liquids.
• Common sizing agents added to the pulp before it is formed into a sheet are wax emulsions or soaps made by the saponification of rosin with alkali. The sizes are precipitated with alum. Such sizing as described in this paragraph is known in the trade as internal sizing.
• the word sizing is also used in a second context in the paper industry. This second use is known as surface sizing. It differs from the internal sizing previously described in that it is applied to the surface of the paper where it cements the fibers to the body of the paper and deposits a more or less continuous film on the paper surface. Surface sizing is used to produce a smooth hard surface which will not catch a pen when the paper is written upon, will not pick off if the paper is printed using tacky inks and will not show feathering of the ink.
• An additional advantage of a surface size is that oil resistance of the paper is improved since the size tends to seal the pores of the paper.
• Surface sizing may be of greater importance than internal sizing for certain types of papers such as writing papers, printing papers and some wrapping papers. It is important to surface size paper that is used in an offset printing process since this prevents loosening of surface fibers when the paper is moistened with water on the press.
• a common way to add a surface size is to apply the sizing agent to both sides of the paper when the paper is passed through press rolls on the paper machine. These rolls force the size into the paper and remove excess size from the surface of the paper. Inherent in this process are various mechanical problems which make it expensive to apply and maintain a uniform layer of the size on the surface of the paper. This mechanical equipment is costly, and there is the added expense of evaporating the water added to the paper with a dilute suspension of the size.
• the size is a starch or a starch derivative such as an hydroxyethyl starch.
• Starch has long been used as an additive in the manufacture of paper to strengthen the paper sheet. See for example Whistler and Paschall, Starch: Chemistry and Technology, Academic Press Inc., New York, N.Y. Vol. 2, 1967, Chapter Vl.
• starch is added to the pulp before the paper sheet is formed.
• the starch is usually cooked in water before the mixture is added to the pulp. This procedure produces much soluble material which is not effectively retained in the paper sheet.
• An improvement in starch cooking was disclosed in U.S. Patent 2,805,966, issued September 10, 1957, wherein the starch slurry was heated in a steam injection cooker. This permitted control of the heating so that the majority of the starch granules were swollen but not ruptured.
• the temperature range over which the granules of starch swell and gelatinize is large. Even in this process only a portion of the granules can be obtained in the desired swollen state. Some starch granules may be still unswollen and hence useless as an adhesive while others are solubilized and not retained in the starch. Furthermore, many of the swollen starch granules so prepared have tendency to disintegrate and form more solubles when their slurries in water are subjected to vigorous agitation.
• GB-A-1 1 10 004 discloses the addition of starch and of a polyalkylenimine, which is a polyelectrolyte, to paper pulp.
• a further object is to provide an agent of this type to improve surface properties without interfering with the other additives and substances used in the makeup and manufacture of paper and without showing adverse effects on the chemical and physical characteristics of the finished sheet.
• Another object of the invention is to provide an additive for improving surface properties which is retained in and not washed out of the paper in the sheet forming process.
• An important object of the invention is to provide an additive for improving surface properties of manufactured paper which will operate on a wide variety of paper stocks, is safe to handle and will impart to the finished sheet desirable characteristics which have not heretofore been available when prior art attempts have been made to make paper without the additional separate step of applying a coating of surface size.
• a specific object of this invention is to provide a method of improving surface properties of manufactured paper by the addition of a specific additive to the wet-end which also imparts to the finished paper article improved dry strength.
• a still further object of this invention is to provide a starch additive for paper that is readily prepared, whose granules swell in hot water to the desired degree without the need to carefully control the heating conditions, and whose swollen granules do not disintegrate when subjected to vigorous agitation.
• This invention relates to a paper additive composition which comprises an aqueous suspension of a swellable starch and a polyelectrolyte, whereby the starch is a water-cooked, cross-linked starch having a cooked swollen volume (hereafter referred to as CSV) of from about 4 ml/g to about 25 ml/g.
• CSV cooked swollen volume
• Another aspect of this invention is a process for the manufacture of paper by adding the components of said paper additive composition to an aqueous suspension of cellulosic pulp and forming paper from said pulp.
• the present invention also is directed to an improved process for the manufacture of paper which comprises spraying an aqueous suspension of a cooked, cross-linked starch having a CSV of from about 4 ml/g to about 25 ml/g onto the wet web in the paper-forming process and drying such web.
• the starch reactant itself that may be used in practicing the invention may be derived from any vegetable source such as for example corn, wheat, potato, tapioca, rice, sago and grain sorghum. It may be either waxy or nonwaxy.
• the term starch is used broadly herein and encompasses unmodified starch and tailings, and as well, starch that has been modified somewhat by treatments with acids, alkalies, enzymes or oxidizing or derivatizing agents. If the starting starch is modified or derivatized in some manner, it nevertheless is useful as long as the product is still in the granular form and still contains hydroxyl groups capable of reacting with the cross-linking reagents.
• cross-linking agents used in this invention may be any of the well-known organic or inorganic polyfunctional reagents which can react with two or more starch hydroxyl groups.
• examples of such reagents that are well known in the art are phosphorous oxychloride, sodium trimetaphosphate, epichlorohydrin and acrolein.
• the cross-linked starches of this invention may be prepared by the general procedure disclosed in U.S. Patent 2,328,537, issued September 7, 1943. It is necessary to control the cross-linking carefully to obtain a suitable product. Suitable products for this invention are those which when cooked in water give a CSV of from about 4 to about 25 ml/g, preferably about 7 to about 20 ml/g. CSV is measured as follows:
• Starches with the CSV specified above give, when cooked in water, swollen granules particularly useful in the paper-making process. Use of these cross-linked starches obviates the need for carefully controlled heating of the starch slurries as was required in the prior art processes. Furthermore, it has been found that the swollen granules prepared from the cross-linked starches with the specified CSV have little or no tendency to disintegrate when subjected to vigorous agitation.
• the starch is prepared for addition to the paper pulp by cooking a suspension in water. Cooking may be accomplished in a batch cooker or a jet cooker.
• the cross-linked starch, properly cooked in water, may be added to the paper furnish at various points in the operation where there is efficient mixing.A suitable point of addition is at the suction side of the fan pump.
• the starches of the present process are effective when used at levels of about 1 % to about 20% by weight of dry solids in the mixture of starch and pulp.
• the preferred use level is from about 5% to about 10% by weight of dry solids in the mixture.
• Such polyelectrolytes may be used at a level of about 0.01 % to about 1%, preferably at a level of about 0.025% to about 0.1% by weight of the dry weight of furnish.
• the polyelectrolyte is added to the pulp at a point in the process after the cross-linked starch has been added.
• the polyelectrolytes employed in the process of this invention may be those employed by paper makers as flocculating agents or as aids to improve the tention of pigments in the paper. They may be either anionic or cationic. Examples of those which are suitable are the acrylamide-based copolymers sold by the Hercules Corporation, Wilmington, Delaware, under the Reten trademark; those sold by the Nalco Chemical Company, Oak Brook, Illinois, under the Nalco trademark; and those sold by the Betz Laboratories, Trevose, Pennsylvania, under the Betz trademark.
• the best polyelectrolyte for use in a particular paper-making system is determined by the following method:
• starches of this invention may be sprayed onto the wet web in the paper-making process.
• Papers produced by this method exhibit excellent surface properties comparable with those of surface-sized papers. This process also avoids the necessity for a separate surface sizing step with the attendant addition of moisture and the necessity of further drying of the product.
• Cross-linked starches were prepared using 400, 800 and 1600 micromoles of phosphorous oxychloride per mole of commercial corn starch. Paper handsheets were prepared incorporating these cross-linked starches by the following procedure.
• the starch was cooked by heating a stirred 5% slurry in water for 15 minutes at 95 ⁇ 100°C.
• the starch slurry was added to the paper pulp prepared from a 50/50 bleached hardwood/softwood kraft pulp.
• the pulp also contained alum in the ratio of 2% by weight of the dried pulp.
• the pH of the pulp slurry was adjusted to 4.5 with sulfuric acid before the starch was added.
• the dilute pulp slurry containing approximately 3% by weight solids was used to make paper handsheets using a Williams sheet machine for a series of 4 sheets formed continuously, pressed and dried. Blank sheets were prepared using the same pulp-alum composition without the addition of any starch. Bursting strength (Mullen points), critical was pick and K & N ink holdout tests were measured by TAPPI (Technical Association of the Pulp and Paper Industry, 360 Lexington Avenue, New York, New York 10017) Methods T403ts-63, T459su-65, UM413, respectively. The data are summarized in Table I.
• This Example shows that the addition of a cooked, cross-linked starch to paper pulp improves the dry strength, wax pick and ink holdout of the paper.
• Example II The procedure of Example I was repeated using the cross-linking agent at a level chosen to give starch with a CSV in the preferred range.
• the cross-linking agents used were eipchlorohydrin, sodium trimetaphosphate, and phosphorous oxychloride.
• the starches were used at the 10% level as in Example I. Results are given in Table ll.
• This Example shows that various cross-linking agents are equally effective in producing cross-linked starches which improve the properties of paper.
• Tests were run on a pilot paper machine using a pulp furnish that was 50% bleached hardwood kraft and 50% bleached softwood kraft mixture beaten to a 450 ml Canadian standard freeness. Fortified rosin size (1 %) and alum (2%) were added to the pulp in the beater. Starch was cooked in water using batches of 9.1 kg starch and 143 kg water. The cooked starch and pulp were mixed together in the machine chest at a 2% by dry weight of furnish consistency. The paper machine was run at a speed of 27.4 m/min using 72.6 kg/hr of pulp to make 66.6 g/m 2 basis weight paper.
• a surface-sized control paper was made using an 0.07 degree of substitution, 80-fluidity hydroxyethyl starch, applied as a surface size. This was cooked at 15% commercial moisture basis solids and diluted to 10% solids for size press application. There was 4% pickup of this starch on the paper. Results of the experiments are given in Table III.
• the IGT Printability Test was performed according to TAPPI Method T499su-64.
• the porosity and smoothness tests were performed according to TAPPI Methods T460m-49 and 479sm-48, respectively, and employed the Gurley-Hill S-P-S Tester, manufactured by Gurley Testing Instruments, Troy, New York.
• the amount of starch retained in the paper is determined as follows:
• Handsheets were prepared using 50% bleached hardwood kraft and 50% bleached softwood kraft ⁇ pulp. A POCI 3 cross-linked starch with a CSV of 14 was added at a level of 7% by dry weight of the starch pulp mixture. The furnish also contained 1% by weight dry basis of rosin and 2% by weight dry basis of alum plus a small amount of a polyelectrolyte added in dilute solution. Starch retention and handsheet properties are given in Table IV.
• Paper handsheets were prepared from a pulp furnish containing 50% bleached hardwood kraft and 50% bleached softwood kraft. A 0.25% dispersion of starch in water was sprayed on the wet handsheet web while it was still on the wire. Sufficient material was sprayed on the paper to give a total addition of 2% starch by weight on a dry solids basis. Properties of the dried sheets are given in Table V.

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• Chemical & Material Sciences (AREA)
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• 1979
  • 1979-10-30 NZ NZ191979A patent/NZ191979A/xx unknown
  • 1979-11-14 AR AR278892A patent/AR220792A1/es active
  • 1979-11-16 NO NO793717A patent/NO793717L/no unknown
  • 1979-11-16 DE DE7979104549T patent/DE2966992D1/de not_active Expired
  • 1979-11-16 EP EP79104549A patent/EP0011303B1/en not_active Expired
  • 1979-11-19 CA CA000340124A patent/CA1148688A/en not_active Expired
  • 1979-11-19 ES ES486102A patent/ES8100381A1/es not_active Expired
  • 1979-11-19 AU AU52955/79A patent/AU535015B2/en not_active Ceased
  • 1979-11-19 BR BR7907487A patent/BR7907487A/pt unknown
  • 1979-11-19 DK DK490679A patent/DK490679A/da not_active Application Discontinuation
  • 1979-11-20 JP JP14961779A patent/JPS5576200A/ja active Granted
  • 1979-11-20 FI FI793635A patent/FI63083C/fi not_active IP Right Cessation

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