WO2000004229A1

WO2000004229A1 - The use of modified starch products as retention agents in the production of paper

Info

Publication number: WO2000004229A1
Application number: PCT/EP1999/005054
Authority: WO
Inventors: Johann Schulte; Joachim Werres; Ulrich Fischer; Hans-Georg Hartan
Original assignee: Stockhausen Gmbh & Co. Kg
Priority date: 1998-07-17
Filing date: 1999-07-15
Publication date: 2000-01-27
Also published as: DE19832241A1; NO20010286L; ATE226663T1; CA2336660A1; NO20010286D0; DE59903194D1; CN1309737A; AU5283599A; JP2002520510A; EP1102894A1; EP1102894B1; BR9912832A

Abstract

The invention relates to the use of modified starches as retention agents for pigments, inorganic fillers and fines in the production of paper. Said modified starches are obtained by decomposing starch, starch derivatives and/or breakdown products thereof in aqueous solution in the presence of at least one cationic polymer made up of at least 20 wt. % polymerised, protonised or quarternised dialkylaminoalkyl(meth)acrylic acid amide units and at least one inorganic mineral substance.

Description

Use of modified starch products as a retention aid in the

Papermaking

The invention relates to the use of starch or starch derivatives which have been modified with polyelectrolytes based on dialkylaminoalkyl (meth) acrylamides and digested in the presence of inorganic additives, as retention agents for pigments, mineral fillers and fibrous fines in papermaking.

Pigments and fillers are added as essential paper components in the manufacture of the paper pulp dispersion and bound with the help of retention aids during sheet formation. To improve the retention, drainage and strength of the paper, e.g. B. according to the information in the weekly paper for paper factories 5 (1991), pp. 149 to 154, cationic mass starches are used extensively as colloidal auxiliaries, with the use of cationic starch ethers according to Ullmann, 4th edition, 1979, vol. 17 , P. 581, in particular the retention of pigments and fines is improved.

However, the retention effect of the starch ethers is limited, so that high molecular weight, cationic polyelectrolytes with a higher charge density can also be used as retention agents. Such high molecular weight polyelectrolytes are, for example, the copolymers of acrylamide and the esters of (meth) acrylic acid with di-CrC ₂ -alkylamino-C ₂ -C ₆ -alkyl alcohols or the copolymers of acrylamide and the amides of (meth) acrylic acid with di-Cι- C ₂ - alkylamino-C ₂ -C ₆ alkylamines, each of which is present in protonated or quaternized form. Retention agents based on such α, β-unsaturated N-substituted carboxamides are described in EP-A-0 038 573.

According to WO 86/00100, a process for papermaking is known in which, to improve the retention, colloidal binders are added to the paper pulp, which binders are modified on the surface with aluminum silicate Silicic acid and cationic or amphoteric carbohydrates, such as preferably

Starch or amylopetkin are obtained.

EP-A-0 703 314 and WO 97/04168 propose the use of special cationic amylopectin starches to improve retention with the optional use of colloidal silica, anionic polyacrylamides or bentonite.

Microparticle systems are also known as retention agents from the weekly paper for paper manufacture 20, 1994, pp. 785 to 790, in which the pulp dispersion is first pretreated, flocked and dispersed with cationic starch or cationic polyacrylamides and then before the sheet is formed by silica microparticle systems or by addition be flocked again by bentonite or aluminum salts. The multi-stage procedure leads to an improvement in the retention values.

Furthermore, EP-B-0 227465 describes a process for the production of paper in which, in complex sub-steps, first the fibrous material and, separately, the mineral filler with a synthetic polyelectrolyte each have the same charge and then the treated filler with a polymeric polyelectrolyte with opposite charge is treated.

Likewise, according to US Pat. No. 5,126,014, a multi-stage process for improving the retention is known, in which the pulp suspension, before a possibly multi-stage shear treatment, calcium carbonate as filler, cationic starch, a cationic coagulant and an anionic flocculant are added and bentonite or colloidal after at least one shear treatment stage Silicic acid can be added.

The modification of starch products with cationic polyelectrolytes is also known from the prior art.

According to EP-A-0 803 512 a method for producing cationic starch is known, according to which the starch is dry at temperatures from 60 to 200 ° C. for the duration from 10 minutes - 5 hours toasted with cationic polymers to be used as a paper strengthening agent.

Furthermore, EP-B-0 282 761, WO 96/05373 and WO 96/13525 describe the modification of starch with ionic, especially cationic, polyelectrolytes. According to EP-B-0 282 761, cationic polymers of diallyldimethylammonium chloride, N-vinylamine or N-vinylimidazoline are heated with native or already digested potato starch, while according to WO 96/05373 cationic polymers with preferably anionic starch and preferably according to WO 96/13525 are hydrolyzed , cationic polymers of N-vinylformamide, polyethyleneimines or polyalkylamines with starch of any kind are implemented. These starch products, like starches modified with copolymers of (meth) acrylamide and dialkylamioalkyl (meth) acrylamide, are only recommended as dry strength agents for papermaking.

Due to the increasing processing of waste paper and wood pulp dispersions in paper manufacture, the proportion of fine materials such as short cellulose fibers and mineral fillers in the paper pulp dispersions is increasing. In addition, as a rule, the proportion of inorganic fillers and pigments must be increased further in order to obtain paper with a customary appearance. However, it is known that the strength of the paper is adversely affected with an increasing proportion of fine substances and in particular mineral fillers and pigments. So u. a. from the publication by K. Ritter and H. Forkel "Papierstoffstofftechnik" Symposium 1997 21, page 4 that the tear resistance of paper as a measure of its strength with the ash content in the paper, which as a measure of the content of mineral fillers and pigments in Paper is considered to decrease with increasing ash content.

The object of the present invention was therefore to improve the retention of pigments, fillers and fines without additional process steps, ie without the above-mentioned substeps, in known paper production, preferably using waste paper, without adversely affecting the mechanical strength of the paper becomes. This is achieved according to the invention by using modified starch, which is obtained by digesting starch, starch derivatives and / or their degradation products in aqueous solution in the presence of at least one cationic polymer, built up from at least 20% by weight of polymerized di-alkylaminoalkyl (meth) acrylic acid amide -Units, which are present in protonated, preferably quaternized form, and with the addition of at least one particulate additive based on an inorganic mineral, obtained before, during or after digestion, as retention agents for pigments, inorganic fillers and fines in papermaking.

As a starch component, native starch, such as potato starch, wheat starch, cereal flour, maize starch, tapioca starch, sago starch and starch with an increased hydrolysis content, rice starch, pea starch and / or their mixtures, starch degradation products, in particular dextrins or oxidized starches, such as dialdehyde starch, starch derivatives, such as chemically modified derivatives Starches, especially anionic starches, such as carboxy starch and starch degraded by persulfate, anionic starch esters, such as. B. starch phosphoric acid mono- or diesters, starch acetates and starch citrates, anionic starch ethers, such as. B. carboxymethyl starch, carboxymethyl-2-hydroxyethyl starch or carboxymethyl-3-hydroxypropyl starch, or cationic starch derivatives, such as. B. N-containing starch ethers, especially starches with primary or secondary amino or imino groups and tertiary amino groups, which are positively charged by protonation with acids and contain quaternized ammonium groups.

Native starches such as potato starch, wheat starch, corn starch, rice starch, pea starch and / or mixtures thereof, and anionic starch and / or cationic N-containing starch ethers are preferably used.

Cationic polymers used are homo- or copolymers of dialkylaminoalkyl (meth) acrylic acid amides which contain at least 20% by weight polymerized units of amides of (meth) acrylic acid and / or acrylic acid and preferably di-C ₁ -C ₂ -alkylamino-C ₂ - Contain C ₆ alkylamines, each of which is present in protonated or quaternized form. Their manufacture is, for example, in EP-A-0 013416 or in EP-A-0 113 038, the corresponding

Disclosure of these publications is introduced for reference.

Such polymerized units are preferably derived from protonated or quaternized N-dialkyl-substituted (meth) acrylic acid amides, such as, for example, dimethylaminoethyl acrylamide or methacrylamide, dimethylaminopropyl acrylamide or methacrylamide, diethylaminopropyl acrylamide or methacrylamide, diethylaminoethyl acrylamide or methacrylamide, diethylaminomethyl acrylamide or methacrylamide and N ', N', dimethylamino-2,2-dimethylpropyl acrylamide or methacrylamide or mixtures thereof, which have been reacted with known quaternizing agents. Examples of suitable quaternizing agents are dimethyl sulfate, diethyl sulfate, methyl chloride, ethyl chloride, preferably dimethyl sulfate or methyl chloride.

The polyelectrolytes can still further units of monounsaturated monomers, such as. B. diallyldimethylammonium chloride. Such polymerized monomers can also be water-soluble, nonionic monomers such as acrylamide, methacrylamide, NC ₁ -C ₂ alkylated (meth) acrylamides, N-vinylamide, vinylformamide, N-vinyl acetamide, N-vinyl-N-methylacetamide, N-vinyl pyrrolidone. Suitable water-soluble monomers are also N-methylolacrylamide, N-methylol-methacrylamide and the N-methylol (meth) acrylic amides which are partially or fully etherified with monohydric d to C alcohols.

Likewise, the copolymers can contain to a limited extent, preferably up to 10% by weight, sparingly water-soluble and / or water-insoluble, simply ethylenically unsaturated monomers, such as (meth) acrylic acid alkyl esters and vinyl acetate, provided the solubility of the copolymers is retained in water.

The polymers to be used according to the invention preferably have a molecular weight MG (g / mol) in the range from 1.0 × 10 ⁵ to 40 × 10 ⁶ , particularly preferably in the range from 2.0 × 10 ⁶ to 15 × 10 ⁶ and very particularly preferably from 5 x 10 ⁶ to 15 x 10 ⁶ . The viscosity was determined using a 1% polymer solution in one

10% NaCI solution with a Brookfield RVT viscometer, spindle 1-3 / 10 revolutions per minute at 20 ° C and gave> 10 mPas for the polymers used.

As particulate additives based on inorganic minerals, d. H. can also consist of clay, preferably swellable, silica, preferably silica sol and / or with aluminum-modified polysilicates, polyorthosilicic acid, with aluminum-modified polysilicates or polyorthosilicic acid, bentonite, titanium dioxide or talc. These substances are preferably in the form of microparticles or microgels. Bentonite, talc, titanium dioxide or silica sol is particularly preferably used.

The starch component can be reacted with the cationic homopolymers or copolymers of preferably protonated or quaternized dialkylaminoalkyl (meth) acrylic acid amides in aqueous dispersion batchwise in a reaction vessel or in a continuous flow process, for example in a jet cooker under the action of heat at temperatures of 70-130 ° C. , preferably from 90 - 100 ° C, with the addition of the inorganic additive and optionally under pressure with the starch component being digested. The reaction conditions and the suitable apparatus conditions correspond to the information in the weekly paper for paper 4, 1991, pp. 127-130, the disclosure of which is introduced as a reference.

Addition of additives based on inorganic minerals in amounts of 0.1 to 15% by weight, preferably 3 to 15% by weight, particularly preferably 5 to 13% by weight, based on the modified starch component, before the preparation of the modified starch components the starch digestion or during the starch digestion, preferably before the modifying reaction and the digestion with the cationic homo- or copolymer, results in a retention agent with improved effectiveness in the retention capacity of fillers and fines. ?

The aqueous dispersion of the starch component which has not yet been digested and used for the modification preferably has a content of 0.5 to 20% by weight, preferably 0.5 to 10% by weight and particularly preferably 2.0 to 10% by weight of the starch component . The aqueous solution of the polyelectrolyte used for the modification has a content of 0.1 to 2.0% by weight, preferably 0.1 to 0.5% by weight and particularly preferably 0.1 to 0.3% by weight, of cationic homo - or copolymers. The weight ratio of starch component to cationic polyelectrolyte in the modification is in the range from 4: 1 to 25: 1, preferably in the range from 10: 1 to 25: 1 and particularly preferably in the range from 14: 1 to 20: 1.

The modified starch products together with the inorganic additives can, preferably in the form of an aqueous solution, be used as retention agents in the production of all types of paper and cardboard. They are preferably suitable for use in the production of paper on sulfite or sulfate pulp in the bleached or unbleached state, where this fiber material can consist of up to 100% by weight of wood pulp and / or waste paper, and for this reason alone a high proportion of mineral fillers, Has pigments and fibrous fines.

The retention agent according to the invention is added to the aqueous paper pulp dispersion in an amount of 0.1 to 10% by weight solids, preferably 0.5 to 5% by weight and particularly preferably 1.0 to 3% by weight, based on the dry matter or Pulp, added before the headbox of the paper machine, preferably as an aqueous solution with stirring. It is added to the aqueous dispersion, which already contains or has been added as fillers calcium carbonate, kaolin, aluminum silicate and oxide hydrates, satin white, talc, gypsum, barite, calcium silicate and lithopone, diatomaceous earth and synthetic, organic fillers from the recycling material.

The retention agent according to the invention is advantageously added to the material dispersion in the machine chest, before the vertical classifier and before or after the material pump before the sheet formation. The retention agent according to the invention based on modified starch and inorganic additives achieves excellent retention of the fillers and surprisingly prevents the strength values from being impaired despite the increase in the filler and thus the ash content of the paper. This applies in particular to the use of paper pulp dispersions which contain or consist of portions of waste paper or wood pulps such as wood pulp and thermomechanical material (TMP).

It was also found that the use of the retention aid according to the invention does not impair the effect of optical brighteners which are added to the paper stock to improve the whiteness.

The following examples further illustrate the invention:

Examples 1 to 4:

A 250 g of an aqueous, 4.0% by weight dispersion of native potato starch, product name C ^* Gel 30002, from Cerestar Holding BV, were stirred into a heated vessel with 250 g of a 0.25% by weight solution of a mixed water-soluble cationic polymer, provided with different amounts of bentonite or with the addition of talc and heated to a temperature of 95 to 100 ° C. In Comparative Example 1, no mineral was added. The mixture was held in this temperature range for 15 to 20 minutes, then cooled and used as a retention aid. Copolymers of trimethylammonium propylacrylamide chloride and acrylamide with a quaternized monomer content of 70% by weight were used as water-soluble cationic polymers.

B After dilution with water to a content of 1% by weight, the 4.0% by weight pulp suspension made from 100% by weight of waste paper pulp was mixed with the retention aid prepared according to A, which was in an amount of 2.125% by weight solids , based on the dry content of the stock suspension, was added.

C With the stock suspension obtained according to B, test sheets with a basis weight of approx. 100 g / m ² were produced in the laboratory according to the Rapid Koethen method in accordance with DIN 54358 with the sheet forming device model 20-12 MC from Haage. The leaves were dried and overnight under normal conditions at 23 ° C and 50% rel. Humidity stored.

After the papers had been weighed out, basis weight, ash content according to DIN 54373 and burst pressure according to DIN 63141 were determined.

The total retention gives the ratio of the amount of dry substance used for paper production to that remaining in the finished paper Amount of substance again. This can be determined by weighing the respective quantities of substance.

The ash retention represents the ratio of the ash content of the (dry) amount of material used for paper production to the ash content of the finished paper. This is determined by determining the respective ash content.

The fines retention shows the ratio of the fines content of the (dry) amount of paper used for paper production to the fines content of the finished paper.

The corresponding fines content is determined using a Britt Dynamic Drainage Jar as follows:

An aqueous paper stock suspension with 0.5 g dry paper stock, from which the paper is made, (StWG) is diluted to approx. 1% by weight with tap water. This suspension is stirred at 750 rpm for a few seconds, then dewatered with stirring. The residue is mixed again with 500 ml of water, stirred and drained. The process is repeated 4-5 times until the filtrate is completely clear, i. H. fine fibers can no longer be washed out. The residue on the sieve is passed through a tared filter and determined gravimetrically (drying at 110 ° C.).

Calculation of the fine fraction: fine fraction = 100 - coarse fraction (%)

The coarse fraction corresponds to the amount of fiber that is on the filter.

Coarse fraction in g

Fine fraction = 100 - (%)

0.5 gx 1 wt% ii

The corresponding values from Comparative Example 1 or Examples 1 to 4 are given in Table 1.

Table 1

Comparative Example 2

The procedures A, B and C of Examples 1 to 4 were retained, but the cationic polymer mentioned in A of Examples 1 to 4 was tested as such as a retention aid in sheet formation.

The corresponding values are given in Table 2. \ Z

Table 2

without starch component

Claims

claims

1. Use of modified starch by digesting starch, starch derivatives and / or their degradation products in aqueous solution in the presence of at least one cationic polymer, composed of at least 20% by weight of polymerized dialkylaminoalkyl (meth) acrylic acid amide units, and under Addition of at least one particulate additive based on an inorganic mineral was obtained as a retention agent for pigments, inorganic fillers and fines in paper production.

2. Use according to claim 1, characterized in that the protonated or quaternized units of di-CrC ₂ alkylamino-C ₂ -C ₆ alkyl (meth) acrylamide units are present as dialkylaminoalkyl (meth) acrylic acid amide units.

3. Use according to claim 1 or 2, characterized in that the quaternized, polymerized units of dimethylaminoethyl acrylamide or methacrylate as the quaternized di-C ₁ -C ₂ -alkylamino-C ₂ -C ₆ alkyl (meth) acrylamide units, Diethylaminopropyl-acrylamids or -methacrylamids, diethylaminoethyl-acrylamids or -methacrylamids, diethylaminomethyl-acrylamids or -methacrylamids, dimethylaminopropylacrylamids or -methacrylamids, dimethylaminomethylacrylamids or -methacrylamids, N, N-dimethylamino or 2,2-methacrylamides or mixtures thereof.

4. Use according to claim 3, characterized in that the units have been reacted with dimethyl sulfate or methyl chloride as quaternizing compounds.

5. Use according to one or more claims 1 to 4, characterized in that trimethylammonium-propylacrylamide chloride units are present as quaternized di-alkylaminoalkylacrylic acid amide units.

6. Use according to one or more claims 1 or 5, characterized in that the cationic polymers further polymerized units of water-soluble, unsaturated monomers, preferably of α, β-unsaturated amides, N-vinyl amides, N-hydroxyalkyl amides, which if necessary are partially or completely etherified, have N-vinylpyrrolidone and / or dialkyldimethylammonium chloride.

7. Use according to claim 6, characterized in that the amide units are derived from acrylamide or methacrylamide, preferably from acrylamide.

8. Use according to one or more of claims 1 to 7, characterized in that the cationic polymers contain up to 10% by weight of units of α, β-unsaturated monomers which are sparingly soluble or insoluble in water, preferably of (meth) acrylic acid alkyl ester or vinyl acetate .

9. Use according to one or more claims 1 to 8, characterized in that the cationic polymer has a molecular weight MG (g / mol) of 0.1 to 20 million.

10. Use according to one or more claims 1 to 9, characterized in that native starch, preferably potato starch, cereal flour, wheat starch, corn starch, rice starch, pea starch and / or mixtures thereof, anionic starch or cationic N-containing starch ethers are used as starch.

11. Use according to one or more claims 1 to 10, characterized in that the digestion of the starch component in the presence of microparticles of at least one additive based on an inorganic mineral, preferably clay, optionally modified with aluminum, optionally modified with aluminum Polysilicates or polyorthosilicic acid, bentonite, titanium dioxide or talc was carried out.

12. Use according to one or more of claims 1 to 11, characterized in that the inorganic additive was used in amounts of 0.1 to 15% by weight, based on the modified starch component.

13. Use according to one or more claims 1 to 12, characterized in that the weight ratio of starch component to the cationic homo- or copolymer is in the range from 4: 1 to 25: 1, preferably in the range from 10: 1 to 25: 1, particularly preferably 14: 1 to 20: 1, in the modification.

14. Use according to one or more claims 1 to 13, characterized in that the starch component is digested at temperatures from 70 to 150 ° C, preferably from 90 to 100 ° C.

15. Use according to one or more claims 1 to 14, characterized in that the retention agent is added to the pulp suspension before sheet formation.

16. Use according to one or more claims 1 to 15, characterized in that the retention agent is added in amounts of 0.1 to 10% by weight, preferably 0.5 to 5% by weight, of solids, based on the pulp.

17. Use according to one or more claims 1 to 16, characterized in that waste paper is used in papermaking.