Classifications

• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/1026—Other features in bleaching processes
  • D21C9/1036—Use of compounds accelerating or improving the efficiency of the processes
• • D—TEXTILES; PAPER
  • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
  • D21C—PRODUCTION OF CELLULOSE BY REMOVING NON-CELLULOSE SUBSTANCES FROM CELLULOSE-CONTAINING MATERIALS; REGENERATION OF PULPING LIQUORS; APPARATUS THEREFOR
  • D21C9/00—After-treatment of cellulose pulp, e.g. of wood pulp, or cotton linters ; Treatment of dilute or dewatered pulp or process improvement taking place after obtaining the raw cellulosic material and not provided for elsewhere
  • D21C9/10—Bleaching ; Apparatus therefor
  • D21C9/16—Bleaching ; Apparatus therefor with per compounds
  • D21C9/163—Bleaching ; Apparatus therefor with per compounds with peroxides

Definitions

• the present invention refers to compositions comprising hydrogen peroxide and a polydiallyldialkylammonium salt, and their use as additives in the paper and cellulose industry.
• compositions according to the invention allows to keep constant the degree of whiteness of the paper produced from cellulose, substantially independently from the amounts of lignin it contains.
• cellulose is obtained almost exclusively from wood, which is mainly composed of lignin, a brown non-fibrous substance, and cellulose.
• the procedures essentially consist in the separation of these two components and in the subsequent, more or less drastic purification of the cellulose thus obtained.
• the common feature of the different procedures is the digestion of wood in a solution of an agent (e.g. sodium hydroxide, sodium sulphite) capable of dissolving lignin by transforming it into one of its water-soluble derivatives in order to separate it from cellulose in the form of an aqueous solution.
• an agent e.g. sodium hydroxide, sodium sulphite
• the cellulose which is left undissolved and separated, is subsequently washed to remove most of the residual foreign substances among which, as an example, the compounds resulting from the degradation of lignin.
• the cellulose thus obtained still contains more or less significant residues of lignin; hence, it must be further purified before being employed in the production of paper suitable for most uses.
• the residual lignin is removed or transformed into colorless compounds through “bleaching" procedures.
• Bleaching is an oxidation reaction and can be performed according to two different methods, by employing, as the oxidizer, chlorine, generally in the form of sodium or calcium hypochlorite, or oxygen, which can also be in the form of ozone or, generally, hydrogen peroxide.
• the amount of lignin in wood varies within sufficiently wide limits.
• some residual lignin always remains, as such or in the form of a corresponding salt, the amount of which varies depending on the type of wood and the purification procedure (generally, from about 10 to about 800 ppm).
• a retentive agent is added to the cellulose suspension, generally a cationic polymer.
• the residual lignin present in the cellulose generally as a soluble sulfonate, forms with the cationic polymer a water-insoluble polymeric salt and hence, it precipitates, at least partially, in the form of a yellow solid.
• This solid being mixed with the cellulose during the formation of the sheet, makes it more or less yellow, depending on its amount and the precipitated portion.
• any lignin that is present in the cellulose suspension is not quantitatively precipitated and, as a consequence, a portion remains undissolved in the waste waters.
• the latter are always recycled, possibly after a simple clarification process, and, therefore, the dissolved lignin adds to that contained in the following cellulose charge; in view of this, in extreme cases, lignin can continue to accumulate and, as a consequence, a continuous lowering of the degree of whiteness is observed.
• the whiteness degree might also improve if the subsequent charges of cellulose contained considerably lower amounts of lignin, but even any possible increase in the whiteness degree, being a variation, would consitute a problem for the production as well.
• compositions according to the invention are solutions, dispersions or suspensions of hydrogen peroxide and a polydiallyldialkylammonium salt in a liquid vehicle, in which the reciprocal weight ratios hydrogen peroxide : polydiallyldialkylammonium salt are comprise between about 5:1 and about 70:1.
• the total amount of the hydrogen peroxide and the polydiallyldialkylammonium salt represents from about 1% to about 65% of the weight of the composition and, preferably, from about 10% to about 50%.
• the liquid vehicle is water and the compositions are solutions of hydrogen peroxide and of a polydiallyldialkylammonium salt, in which the reciprocal weight ratios hydrogen peroxide : polydiallyldialkylammonium salt are as above indicated, and the polydiallyldialkylammonium salt is polydiallyldimethylammonium chloride.
• the type and the amount of composition of the invention which is added to the cellulose suspension depends on the nature of the wood which is employed for the preparation of said suspension and the way the pulp is worked for removing most of lignin.
• a further object of the present invention is represented by suspensions of cellulose added with the compositions of the invention.
• these suspensions are added with the compositions according to the invention so as to have in the suspension a total amount of hydrogen peroxide and the selected polydiallyldialkylammonium salt varying from about 0.01% to about 5% of the weight of the cellulose suspension.
• Another object of the present invention is represented by a process for the preparation of the above mentioned cellulose suspensions, which comprises the addition of a composition of the invention to a cellulose suspension containing sulfonated lignin in amounts comprised between about 10 and about 800 part per million (ppm), so as to obtain a suspension in which the total amount of hydrogen peroxide and the polydiallyldialkylammonium salt varies from about 0.01% and about 5% of the weight of the suspension.
• ppm part per million
• the composistion can also be prepared in situ by separately adding to the cellulose suspension, in whichever order, hydrogen peroxide and the selected polydiallyldialkylammonium salt or the solutions, suspensions or dispersions of hydrogen peroxide and the selected polydiallyldialkylammonium salt, respectively.
• compositions of the present invention to keep constant the degree of whiteness of the paper during its production is new and surprising.
• polydiallyldialkylammonium salts are commercial products. They can also be prepared as desribed in US Patent 3,288,770. Polydiallyldimethylammonium chloride is commercially available as CONDITIONER P6 (3V SIGMA, Bergamo, Italy).
• sheets are prepared from a suspension of cellulose containing different amounts of sodium ligninsulfonate (LSS) therein dissolved. Then, the degree of whiteness of the sheets is measured by means of an ELREPHO® 2000 reflection spectrophotometer (Datacolor).
• LSS sodium ligninsulfonate

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Wood Science & Technology (AREA)
• Paper (AREA)
• Cosmetics (AREA)

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Family Applications (1)

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Citations (7)

• 1997
  • 1997-03-13 IT IT97MI000565A patent/IT1290070B1/it active IP Right Grant
• 1998
  • 1998-03-10 EP EP98104260A patent/EP0866095A1/en not_active Withdrawn

Patent Citations (7)

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