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
  • D21H17/46—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
  • D21H17/54—Synthetic macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen
  • D21H17/55—Polyamides; Polyaminoamides; Polyester-amides
• • 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

Definitions

• the present invention relates to a process for the production of a modified starch containing product, the modified starch containing product obtainable by said process as well as the use thereof in paper manufacture.
• the modified starch containing product is useful in the production of a paper of high strength (and recycling properties).
• additives for adjusting the properties of paper depending on the desired application of the paper obtained.
• additives for enhancing the strength of the paper in the dry state as well as in the wet state are known.
• a particular aspect in paper manufacture is the recyclability of the paper as well as the suitability of the paper for the production of recycled paper in a quality as high as possible.
• the wet strength of the paper should be not too high.
• the paper should have good performance characteristics, in particular sufficient dry strength.
• starch In place of starch or in addition to starch cereal flour can be used directly. Though this agent helps to increase the dry strength of paper further improvement is desirable.
• cationic starch as dry strength agent in paper manufacture.
• the cationic starch is obtained by reacting the starch with an amine containing polymer, for example a water-soluble polyaminoamide cross-linked with epichlorohydrin, by heating an aqueous solution containing 0.1 to 10 parts by weight starch and 0.5 to 10 parts by weights per 100 parts by weights of starch of polymer above the gelatinization temperature of the starch with stirring and under pressure.
• the aqueous mixture obtained is, after cooling, added directly to the paper stock.
• US Patent 6160050 discloses starch modified with a cationic polymer intended to be used in paper making.
• US Patent 3962159 discloses graft co-polymers prepared by condensing a polyamideamine substrate with starch in the presence of a condensing reagent such as epichlorohydrin. The resulting product is intended to be used in paper making.
• the present invention relates to a process for the production of a modified starch containing product and the modified starch containing product obtainable by that process, wherein said starch containing product is useful as an agent for the paper manufacture for obtaining paper with good performance characteristics.
• a process is desirable if the dry strength agent is retained within the fibers of the paper web with as small amount as possible of the agent being discharged into the paper mill effluent.
• a process for the production of a modified starch containing product comprising subjecting a starch containing product and a polyamidoamine epihalohydrin resin (PAAE) to gelatinizing conditions at a dry content of at least 50 weight%, optionally further comprising comminuting the resulting mixture.
• PAAE polyamidoamine epihalohydrin resin
• the invention relates to a modified starch containing product obtainable by said process.
• the invention relates to the use of the modified starch containing product in paper making, in particular as a dry strength agent in paper making.
• a further aspect of the invention relates to a process for the production of paper comprising adding a modified starch containing product of the invention to a stock containing cellulosic fibers and dewatering the stock to obtain paper.
• the invention relates to a paper obtainable by the use of the modified starch containing product of the present invention.
• the starting material used according to the invention can be any starch containing product, including starch as such, a starch containing flour or any combination thereof.
• the starch can be a native, cationic, anionic, amphoteric starch or any kind of modified starch.
• the starch can be isolated from a common vegetable starch source such as flour. Any vegetable flour can be used, cereal flours being, however, preferred.
• a great advantage of the present invention is that flour can be used directly without the need for isolating the starch therefrom.
• starch containing products are wheat, spelt, oat, barley, sorghum, corn, rice, rye, potatoes, tapioca and pea, particularly flour of one or more thereof, or starch obtained therefrom and any combination thereof.
• Cereal flours contain a high proportion of starch, with possible variation in the proportion and composition of the starch depending on the cereal type.
• starch containing products are rye flour or wheat flour as well as a flour having a proportion of starch and preferably composition of the starch corresponding to or being similar to that of rye flour or wheat flour.
• the flour used as starch containing product can be a commercially available flour.
• the flour can be used in combination with starch as such, which can be advantageous if a higher proportion of starch is desired, for example, in case of a flour containing a relatively low starch proportion. Also mixtures of different flours and/or starches can be used.
• the starch containing product is modified with at least one polyamidoamine epihalohydrin resin (hereinafter referred to as PAAE), preferably polyamidoamine epichlorohydrin.
• PAAE polyamidoamine epihalohydrin resin
• Polyamidoamine-epihalohydrin resins include those that have been prepared with epihalohydrin, e.g. epichlorohydrin, as a reactant, either during the polymerisation or in the modification of an existing polymer.
• epihalohydrin e.g. epichlorohydrin
• Such resins are widely used as wet strength agents in paper making and are commercially available, e.g. under the trademarks Eka WS 320, Eka WS 320 RC, Eka WS XO.
• the polyamidoamine epihalohydrin resin is preferably in an aqueous solution that optionally further may comprise a water-miscible solvent such as methanol, ethanol or dimethyl formamide.
• a water-miscible solvent such as methanol, ethanol or dimethyl formamide.
• M w may, for example, be from about 50000 to about 1000000 or higher.
• the polyamidoamine epihalohydrin may also be a product with high solids content such as those disclosed in EP Application No. 08159404.6 .
• Epihalohydrins that can be used include epibromohydrin and epichlorohydrin, preferably epichlorohydrin.
• the polymers are produced using from about 0.5 to about 2 moles of epihalohydrin per mole of basic nitrogen in the polyamidoamine.
• the polyamidoamine is preferably a reaction product of a polycarboxylic acid or a derivative thereof, suitably a dicarboxylic acid or derivative thereof, and a polyamine.
• carboxylic acids include e.g. anhydrides, esters and half esters.
• Suitable poly-carboxylic acids include saturated or unsaturated aliphatic or aromatic dicarboxylic acids.
• the polycarboxylic acids contain less than 10 carbon atoms.
• Preferred polycarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid and derivatives and mixtures thereof, of which adipic acid is particularly preferred.
• Preferred polyamines include polyalkylene polyamines, or mixtures thereof, having the following formula: H 2 N-(CR 1 H) a -(CR 2 H) b -N(R 3 )-(CR 4 H) c -(CR 5 H) d -NH 2 (I) in which R 1 -R 5 represent hydrogen or lower alkyl, preferably up to C 3 and a-d represent integers of from 0 to 4.
• Preferred polyalkylene polyamines include diethylene triamine, tri-ethylene tetraamine, tetraethylene pentaamine, dipropylene triamine, and mixtures thereof.
• the polyamines of formula (I) can be combined with other polyamines or mixtures of other amines.
• these amines have any of the following formulae II-VII: R 7 R 8 N-(-(CH 2 ) g -CR 9 H-(CH 2 ) h N(R 10 )-) i -H (III) HR 11 N-(CH 2 ) j -CR 12 H-(CH 2 ) k -OH (IV) HNR 13 R 14 (V) H 2 N-(CH 2 ) l -COOH (VI) in which R 6 -R 14 represent hydrogen or lower alkyl, preferably up to C 3 , e-I represent integers of from 0 to 4, and m represents an integer of from 0 to 5.
• the polycarboxylic acid and the polyamine may, for example, be applied in a molar ratio from about 1:0.5 to about 1:1.5.
• polyamidoamine may also be referred to as polyaminopolyamide, polyamidopolyamine, polyamidepolyamine, basic polyamide, cationic polyamide, aminopolyamide, amidopolyamine or polyaminamide.
• a polyaminoamide epihalohydrin resin suitable for the present invention and processes for the production thereof are disclosed in European Patent EP 0589 917 B1 which is incorporated herein by reference.
• PAAE PAAE
• a single PAAE or a combination of two or more types thereof can be used.
• the amount of PAAE used for the present modified starch containing product is preferably from 1 to 20 weight%, most preferably from 1.5 to 10 weight% and particularly from 2 to 5 weight%, based on the starch containing product with its natural water content.
• Gelatinization of starch and flour on heating is a well-known phenomenon.
• the temperature and time required for gelatinization depends on the type of starch and flour, respectively.
• a starch containing product and PAAE are preferably heated to a temperature sufficient for gelatinization at a dry content of at least 50% by weight, preferably during continuous mixing.
• the temperature is preferably from 90°C to about 200°C, most preferably from 120°C to 180°C, or from 140°C to 170°C.
• the specific mechanical energy SME
• SME specific mechanical energy
• the specific mechanical energy input is preferably from 30 to 200 Wh/kg, most preferably from 60 to 120 Wh/kg (Watt •hour per kg reaction mixture).
• the mixture of starch containing product and PAAE has a dry weight content of at least 50% by weight, preferably at least 60% by weight and most preferably at least 70% by weight.
• a dry weight content of at least 50 % by weight means that in the reaction mixture the amount of solvent, usually water, is 50 % by weight or less.
• the amount of solvent based on the mixture of starch containing compound and of PAAE is generally within a range of 8 wt % to 40 wt %, preferably 10 wt % to 30 wt % and particularly preferred of from 15 wt% to about 25 wt% (inclusive the natural water content of the components).
• the dry weight content is less than 50 weight percent the effect of the energy input onto the components is reduced.
• the water content present during the modification of the starch containing product with PAAE affects the properties of the resulting modified starch containing product.
• the water content influences the gelatinization and viscosity of the starch containing product, which, in turn, influences the energy input by mechanical shearing and thereby also properties of the resulting product such as molecular weight distribution.. Consequently, even if the water content of the resulting product is subsequently adjusted, for example by drying or wetting, respectively, the respective properties such as molecular weight distribution can be no longer be changed.
• a low water content facilitates the further processing of the obtained mixing product to a solid granular end product.
• any mixing device can be used which is capable to introduce the necessary specific mechanical energy into the reaction mixture.
• extruders or kneading machines suitable for mixing mixtures of high viscosity. Most preferably an extruder is used. It has been shown that by the action of an extruder reaction mixtures according to the invention with high dry content can be advantageously processed to the desired modified starch containing product.
• the preferred time period for the mixing depends on the type of mixing device and is usually from about 5 to 120 seconds, preferably from 30 to 60 seconds. This time period usually corresponds to the time the starch containing product and PAAE are subjected to gelatinization conditions and thus also for the modification.
• One extruder which is suitable for the extrusion is a co-rotating twin-screw extruder.
• An example of a suitable twin-screw extruder is an extruder such as that marketed by the company Bühler under the product designation BCTA.
• Further examples of suitable extruders are the BCTH and DNDG, all also purchased by Bühler.
• the extrusion preferably takes place at a temperature of 90 to 200°C, especially of 140 to 170°C.
• the extrusion preferably takes place during addition of water.
• the water may be added in the liquid state or at least partially as vapour, for example via a pre-conditioner.
• the residence time of the reaction mixture within the extruder is usually from about 10 to 120 seconds, especially 15 to 60 seconds.
• the extruder may be coupled to a pre-conditioner. Pre-conditioning can take place at a temperature of up to 100°C.
• mixing is carried out at a pH-value of from 3 to 8, preferably 5 to 7.
• the pH-value can be adjusted by adding base or acid to the reaction mixture.
• base or acid there is no particular restriction as to the base or acid to be added.
• a conventional mineral base or acid such as sodium hydroxide and sulfuric acid, respectively, can be used.
• mono- and polycarboxylic acids such as formic acid, acetic acid, adipic acid or citric acid.
• the resulting modified starch containing product can be further processed in a manner known in the art to a final product desired for application.
• it can be comminuted to form a powdery product of suitable particle size.
• it may be milled to form a granulate.
• the particle size is not critical, although it for good dispersability for paper manufacturing preferably does not exceed 1 mm.
• the comminuted product comprises at least 95% (by weight) of particles with a particle size not exceeding 355 ⁇ m (on sieving with a 355 ⁇ m sieve).
• the resulting modified starch containing product as well as the comminuted or granulated product can be dried. Drying is accomplished by simple cooling of the hot reaction mixture at room temperature and/or by drying in a conventional dryer, for example at about 120°C.
• the modified starch containing product of the invention preferably has a dry content of at least 80 weight percent, especially at least 88 weight percent and particularly, preferred at least 92 weight percent, based on the content of starch containing product and polyaminoamide epihalohydrine resin, with the residual being solvent, usually water.
• Water that may be present in the modified starch containing product of the invention either originates from the natural water content in the starting product (e.g. flour or starch as such) and/or has been added in the course of the manufacturing process and not being removed during optional subsequent drying.
• starting product e.g. flour or starch as such
• the modified starch containing product of the invention may contain additives which may be desirable for paper manufacture. Said additives can be added during mixing and/or subsequent to mixing to the resulting reaction mixture.
• the modified starch containing product of the present invention in particular in granular form, is useful as ready-made product and can be stored and easily metered to the paper making stock on demand. Further, since it can be prepared and shipped as a commodity to the paper mill the entire process is simplified compared to carrying out the reaction at the paper mill.
• modified starch The exact chemical structure of the modified starch is not fully known, but it has been found that the properties are different compared to starch that have been modified with PAAE by other methods, such as in an aqueous suspension of low dry content.
• the modified starch containing product of the present invention is added to the paper making stock in a quantity sufficient to adjust the starch content of the resulting paper to the desired value. It has been shown that the modified starch containing product of the present invention has an excellent absorption to the paper-fibers yielding a paper web which has sufficient starch content required for adequate dry strength. Due to this good retention only a small amount of the modified starch containing product of the invention is found in the white water, the residual water obtained on dewatering the paper pulp, which means more efficient use of valuable raw materials as well as environmental advantages.
• the starch containing product of the present invention can be advantageously added to the paper making stock at the wet end of the paper manufacturing process.
• the starch containing product of present invention is preferably dispersed in water and the resulting dispersion metered into the papermaking stock.
• the modified starch containing product can be added to the papermaking stock in a quantity of from about 0.5 wt % (as dry) to about 4 wt % (as dry), preferably from 2.5 wt % (as dry) to 3.5 wt % (as dry) per ton final paper.
• Native maize starch (C*size RG 03719, Cargil GmbH) was suspended at 3 % solids in water and mixed with a polyamidoamine epichlorohydrine resin (Eka WS 320, Eka Chemicals AB) in an amount of 3 % dry polymer on starch. The mixture was heated under vigorous stirring to 90° C and kept at this temperature for 30 minutes. A slightly turbid solution was obtained, which was further diluted for continous addition to the paper machine.
• a polyamidoamine epichlorohydrine resin (Eka WS 320, Eka Chemicals AB)
• the example is to demonstrate the superior performance of the invention as dry strength agent for paper in comparison to polyvinylamine modified starch compounds of EP 1 384 811 A1 (Reference Example 1)
• Papers of 110 g/m 2 were prepared on a pilot paper machine (speed 2 m/min) from a mixed waste furnish provided by a liner & fluting mill. Ash content was 13 %, and the sheet forming conditions at the headbox were conductivity 4000 ⁇ S/cm, zeta potential -5 to -6 mV, pH 6.3 - 6.7 and temperature 40 °C.
• a microparticle system (Compozil®, Eka Chemicals AB), consisting of a cationic polyacrylamide (Eka PL 1510, Eka Chemicals AB) and an anionic silica sol (Eka NP 320, Eka Chemicals AB) was used as retention and dewatering aid.
• modified starch containing products of examples 1 to 4 and Reference Example 1 were dissolved in water at 5 % solids and 50 °C by means of laboratory dispersing unit (Super Dispax SD 40, Ika). The resulting dispersions were further diluted and fed into the papermaking stock at the outlet of the machine chest.
• the paper on reel had a moisture content of 3 - 4 %. Sheets were stored for at least 24 hrs at 23 °C / 50 % r.h. before testing. Tensile strength in terms of breaking length was measured according to DIN ISO 1924/2 and burst strength according to DIN ISO 2758. The results are given in the table 2 as burst index and breaking length, respectively.
• the amount of dry strength agent in the white water serves as indicator of its self-retention capability. It was determined by photometric analysis of the starch/iodine complex in the supernatant of a centrifugated white water sample after the wet end system has reached equilibrium (45 minutes). The results were diminished by the starch amount found for the control trial (no dry strength product added) and recalculated to dry strength product concentration, taking into account the respective starch content. Table 2 Dry strength agent control without agent Ref. Ex. 1 Ex 1 Ex 2 Ex 3 Ex 4 Addition rate % dry on paper - 2 2 2 2 2 Product in W/W mg/l - 63 43 8 58 38 Breaking length, M/D km 3,68 4,42 4,34 4,55 4,41 4,54 rel.
• Breaking length The length of a paper stripe in meters that is just self supporting until rupture. Breaking length M/D in machine direction Breaking length C/D in cross direction. Product in W/W: agent found in white water;
• modified starch containing product of the present invention has in particular improved retention over reference example 1, that is less product found in white water. Moreover, it imparts higher strength to paper, which becomes most evident in burst strength.
• This example is to demonstrate the superior performance of the modified starch containing product according to the invention in comparison to products obtained by reacting native starch with PAAE resin in aqueous suspension in accordance to EP 972 1110 B1 .
• Papers of 100 g/m 2 where prepared in the same manner as described in example 6.
• the furnish was a mixed waste consisting of 30 % news print, 30 % magazines, 20 % OCC (old corrugated container) and 20 % CTMP (chemico-thermomechanical pulp).
• Example 5 Addition rate % dry on paper - 1 2 3 1 2 3 Product in W/W mg/l - 46 118 199 19 19 48 Breaking length, C/D km 1,70 1,86 1,98 2,11 1,94 2,09 2,08 rel. change % - +9 +16 +24 +14 +23 +22 Breaking length, M/D km 3,81 3,68 3,93 4,33 3,81 3,61 4,01 rel.

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Citations (6)

• 2008
  • 2008-07-22 EP EP08160881A patent/EP2148003A1/fr not_active Withdrawn

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