EP1102894B1 - The use of modified starch products as retention agents in the production of paper - Google Patents

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

The invention relates to the use of starch or starch derivatives with Modified polyelectrolytes based on dialkylaminoalkyl (meth) acrylamides and was digested in the presence of inorganic additives, as Retention agent for pigments, mineral fillers and fibrous fines at Papermaking.

Pigments and fillers are used as essential paper components in the Production of the pulp dispersion added and with the help of Retention aids bound in leaf formation. To improve the Retention, drainage and the strength of the paper are e.g. B. after the Information in the weekly paper for paper manufacturing 5 (1991), pp. 149 to 154, cationic mass starches as colloidal auxiliaries to a large extent used, with the use of cationic starch ethers according to Ullmann, 4. Aufl., 1979, Vol. 17, p. 581, in particular the retention of pigments and Fine substances 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-C ₁ -C ₂ alkylamino-C ₂ -C ₆ alkyl alcohols or the copolymers of acrylamide and the amides of (meth) acrylic acid with di -C ₁ -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. Furthermore, cationic polyacrylamides are also described in US-A-4753710 and WO-A-91/07543 as retention aids.

According to WO-A-86/00100 a method for paper manufacture is known, in which for Improved retention added to the paper pulp colloidal binder be based on aluminum silicate modified on the surface Silicic acid and cationic or amphoteric carbohydrates, such as preferably Starch or amylo pectin are obtained.

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

From the weekly paper for paper manufacturing 20, 1994, pp 785 to 790 are as Retention agents continue to be known microparticle systems in which the Pulp dispersion initially with cationic starch or cationic Polyacrylamides pretreated, flocked and dispersed: and then pretreated sheet formation by silica microparticle systems or by adding bentonite or aluminum salts are flocked again. The multi-stage procedure leads to improve retention values.

Furthermore, EP-B-0 227 465 describes a process for the production of paper described, in which the fibrous material and separately the mineral filler with a synthetic polyelectrolyte always the same charge and then the treated filler with a polymeric polyelectrolyte with opposite charge is treated.

Likewise, according to US-A-5,126,014 is a multi-stage process for improving the Retention known, in which a 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 after at least one shear treatment step bentonite or colloidal Silica is added

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

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 to be roasted with cationic polymers from 10 minutes to 5 hours then to be used as a paper strengthening agent.

Furthermore, the modification is described in EP-B-0 282 761, WO-A-96/05373 and WO-A-96/13525 of starch with ionic, especially cationic polyelectrolytes. According to EP-B-0 282 761, cationic polymers are used for this Diallyldimethylammonium chloride, N-vinylamine or N-vinylimidazoline with native or Already digested potato starch is heated, while according to WO-A-96/05373 cationic polymers with preferably anionic starch and after WO-A-96/13525 preferably hydrolyzed, cationic polymers of N-vinylformamide, Polyethyleneimines or polyalkylamines with all types of starch be implemented. These implementation products are just like strengths with Copolymers of (meth) acrylamide and dialkylaminoalkyl (meth) acrylamide were modified, only as a dry strength agent for papermaking recommended.

In US-A-5185206, FR-A-2396831 and US-A-4388150, cationic starch, which may have been siliconized, as a drainage aid and as a retention aid used in papermaking.

Furthermore, in US-A-4097427 the cationization of starch by digesting the Taught starch in the presence of quaternized polymers containing ammonium groups, the starch thus cationized as a filler retention agent in the Papermaking is used.

Because of the increasing processing of waste paper and wood pulp dispersions In papermaking, the proportion of fine materials, such as short cellulose fibers, and mineral fillers in the pulp dispersions. In addition, in everything Usually the proportion of inorganic fillers and pigments increased even further to obtain paper with a market appearance. But it is known that with increasing proportion of fine substances and especially mineral fillers and pigments adversely affect the strength of the paper. So u. a. from the publication by K. Ritter and H. Forkel "paper fiber technology" symposium 1997 21, page 4 shows that the tear resistance of paper as a measure of this Strength with increasing ash content, which is a measure of the mineral content Fillers and pigments in paper apply, decreases.

The object of the present invention was therefore without additional Process steps, d. H. without the sub-steps mentioned above, in the known Paper production, preferably using waste paper, the retention of To improve pigments, fillers and fines without the mechanical Strength of the paper is adversely affected.

According to the invention this is achieved by using modified starch by digesting starch, starch derivatives and / or their breakdown 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, those in protonated, preferably quaternized Form are present, and with the addition of at least one particulate, to one inorganic mineral based additive before or during the Digestion has been obtained as a retention agent for pigments, inorganic fillers and fines in papermaking.

As a starch component, native starch, such as potato starch, wheat starch, Cereal flour, corn starch, tapioca starch, sago starch and starch with increased Hydrolysis content, rice starch, pea starch and / or mixtures thereof, Starch degradation products, especially dextrins or oxidized starches, such as Dialdehyde starch, starch derivatives, such as chemically modified starches, in particular anionic starches, such as carboxy starch and starch degraded by persulfate, anionic starch esters, such as. B. starch phosphoric acid mono- or diester, 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 positive by protonation with acids are charged and contain quaternized ammonium groups.

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

Cationic polymers used are homo- or copolymers of dialkylaminoalkyl (meth) acrylic acid amides which contain at least 20% by weight of polymerized units of amides of (meth) acrylic acid and / or acrylic acid and preferably di-C ₁ -C ₂ -alkylamino-C ₂ -C ₆ alkylamines contain, each in protonated or quaternized form. Their production is specified, for example, in EP-A-0 013 416 or in EP-A-0 113 038, the corresponding disclosure of these publications being introduced as a 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 with known quaternizing agents have been implemented. Examples of suitable quaternizing agents are: Dimethyl sulfate, diethyl sulfate, methyl chloride, ethyl chloride, preferably dimethyl sulfate or methyl chloride in question.

The polyelectrolytes can still further units of monounsaturated monomers, such as. B. diallyldimethylammonium chloride. Such copolymerized monomers can also be water-soluble, nonionic monomers, such as acrylamide, methacrylamide, NC ₁ -C ₂ alkylated (meth) acrylamides, N-vinylamide, vinylformamide, N-vinylacetamide, N-vinyl-N-methylacetamide, N-vinylpyrrolidone. Suitable water-soluble monomers are also N-methylolacrylamide, N-methylol methacrylamide and with monohydric C ₁ - to C ₄ -alcohols partially or fully etherified N-methylol (meth) acryl-amides.

Likewise, the copolymers can be used to a limited extent, preferably up to 10 % By weight, sparingly soluble and / or water-insoluble in water, simply ethylenic contain unsaturated monomers, such as (meth) acrylic acid alkyl esters and vinyl acetate, as far as the solubility of the copolymers is preserved 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% NaCl solution with a Brookfield RVT viscometer, spindle 1-3 / 10 Revolutions per minute at 20 ° C and resulted in> 10 mPas for use upcoming polymers.

As particulate additives based on inorganic minerals, d. H. can also consist of clay, preferably swellable, silica, preferably silica sol and / or polysilicates modified with aluminum, Polyorthosilicic acid or modified with aluminum Polyorthosilicic acid, bentonite, titanium dioxide or talc in question. Preferably these substances are present as microparticles or microgels. Is particularly preferred Bentonite, talc, titanium dioxide or silica sol used.

The starch component can be converted using the cationic homo- or Copolymers of preferably protonated or quaternized Dialkylaminoalkyl (meth) acrylic acid amides in aqueous dispersion discontinuously in a reaction vessel or in a continuous flow process, for example in the jet cooker under the influence of heat at temperatures of 70-130 ° C, preferably from 90 - 100 ° C, with the addition of the inorganic additive and if necessary, under pressure with the starch component digested. The Reaction conditions and the appropriate equipment conditions correspond the information in the weekly paper for paper 4, 1991, pp. 127-130, its disclosure is introduced as a reference.

The 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 wt.%, Based on the modified starch component, in the production the modified starch components before the starch digestion or during the Starch digestion, preferably before the modifying implementation and the Digestion with the cationic homo- or copolymer gives a Retention agent with improved effectiveness in the retention of filling and Fines.

The aqueous dispersion of the modification used, not yet digested starch component preferably has a content of 0.5 to 20% by weight, preferably from 0.5 to 10% by weight and particularly preferably from 2.0 up to 10% by weight of the starch component. The aqueous solution for modification polyelectrolyte used 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 cationic homo- or copolymers. The weight ratio of Starch component to cationic polyelectrolyte lies in the modification Range from 4: 1 to 25: 1, preferably in the range from 10: 1 to 25: 1 and especially 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, as a retention agent in the Production of all types of paper and cardboard can be used. Preferably they are suitable for use in the manufacture of paper on sulfite or Sulphate pulp in the bleached or unbleached state, this Fiber material can consist of up to 100% by weight of ground wood and / or waste paper, and therefore a high proportion of mineral fillers, pigments and fibrous fines.

The retention aid according to the invention becomes aqueous according to the invention Pulp dispersion in an amount of 0.1 to 10 wt.% Solid, preferably from 0.5 to 5% by weight and particularly preferably 1.0 to 3% by weight, based on the Dry matter or pulp, before the headbox of the paper machine, preferably added as an aqueous solution with stirring. The addition is made to the aqueous dispersion, which already contains 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 Recycled material may or may have been added.

The retention agent according to the invention is advantageously added to the Dispersion of material in the machine chest, before the vertical classifier and before or after Feed pump before sheet formation.

By means of the retention agent according to the invention based on modified starch and inorganic additives will have an excellent retention of the fillers reached and an impairment of the strength values despite the increase in Filler and thus the ash content of the paper surprisingly avoided. This applies in particular when using pulp dispersions, the proportions of Waste paper or wood materials, such as sanded wood and thermomechanical material (TMP) contain or consist of.

It has also been found that by using the invention Retention agent the effect of optical brighteners, which improve the Whiteness added to the paper stock is not affected.

The following examples further illustrate the invention:

Examples 1 to 4:

A 250 g of an aqueous 4.0% by weight solution were placed in a heatable vessel Dispersion of native potato starch, product name C * Gel 30002, Fa. Cerestar Holding B.V., with stirring, with 250 g of a 0.25% by weight solution of a water-soluble cationic polymer mixed 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 in for 15 to 20 minutes kept in this temperature range, then cooled and as Retention agent used. As water-soluble cationic polymers were copolymers of trimethylammonium propylacrylamide chloride and Acrylamide with a quaternized monomer content of 70% by weight used.

B A 4.0% by weight stock suspension made from 100% by weight waste paper stock was used dilution with water to a content of 1% by weight with stirring added to the retention aid prepared according to A, 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 according to 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 and ash content were reduced DIN 54373 and burst pressure determined according to DIN 63141.

The total retention gives the relationship to the paper production amount of dry substance used to the remaining in the finished paper Amount of substance again. This is done by weighing the respective amounts of substance determinable.

The ash retention gives the ratio of the ash content to the Paper production used (dry) amount of substance to the ash content of the finished paper again. This is determined by determining each Ash content determined.

The retention of fines indicates the ratio of the fines content to the Paper production used (dry) amount of substance to the proportion of fines of the finished paper again.

The appropriate proportion of fines is determined using a Britt Dynamic Drainage Jar determined 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, ie 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. Fine fraction = 100 - Coarse fraction in g 0.5 gx 0.01 (%)

The corresponding values from Comparative Example 1 or Examples 1 to 4 are given in Table 1. Comparative example
1/
Examples 1 to 4 Ash retention% by weight Total retention% by weight Burst pressure kPa mod. Starch without added minerals 93.3 89.1 95 mod. Starch 9.7 bentonite 0.3 95.3 90.7 104 mod. Strength 9.5 bentonite 0.5 95.2 92.1 106 mod. Starch 9.0 bentonite 1.0 97.6 96.7 92 mod. Starch 9.0 talc 1.0 95.3 94.0 -

Comparative Example 2

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

The corresponding values are given in Table 2. Comparative Example cation. Proportion in the copolymer% by weight Ash retention% by weight Total retention% by weight Burst pressure kPa 2 70 0 44.8 60

Claims (16)

1. Use of modified starch as retention agent for pigments, inorganic fillers and fines in paper manufacturing, said modified starch being obtained by pulping starch, starch derivatives and/or degradation products thereof in aqueous solution and in the presence of at least one cationic polymer constituted of at least 20 wt.-% of polymerized dialkylaminoalkyl(meth)acrylic acid amide moieties and with addition of at least one particulate additive prior to or during pulping which is based on an inorganic mineral substance.
2. The use according to claim 1, characterized in that protonated or quaternized di(C₁-C₂)alkylamino(C₂-C₆)alkyl(meth)acrylamide moieties are present as dialkylaminoalkyl(meth)acrylic acid amide moieties.
3. The use according to claim 1 or 2, characterized in that quaternized moieties of dimethylaminoethylacrylamide or -methacrylamide, diethylaminopropylacrylamide or -methacrylamide, diethylaminoethylacrylamide or -methacrylamide, diethylaminomethylacrylamide or -methacrylamide, dimethylaminopropylacrylamide or -methacrylamide, dimethylaminomethylacrylamide or -methacrylamide, N,N-dimethylamino-2,2-dimethylpropylacrylamide or -methacrylamide or mixtures thereof are present as quaternized di(C₁-C₂)-alkylamino(C₂-C₆)alkyl(meth)acrylamide moieties.
4. The use according to claim 3, characterized in that the moieties have been reacted with dimethyl sulfate or methyl chloride as quaternizing compounds.
5. The use according to one or more of claims 1 to 4, characterized in that trimethylammoniumpropylacrylamide chloride moieties are present as quaternized dialkylaminoalkylacrylic acid amide moieties.
6. The use according to one or more of claims 1 to 5, characterized in that the cationic polymers include additional polymerized moieties of water-soluble, unsaturated monomers, preferably of α,β-unsaturated amides, N-vinyl-amides, N-hydroxyalkylamides optionally etherified partially or completely, N-vinylpyrrolidone and/or dialkyldimethylammonium chloride.
7. The use according to claim 6, characterized in that the amide moieties are derived from acrylamide or methacrylamide, preferably from acrylamide.
8. The use according to one or more of claims 1 to 7, characterized in that the cationic polymers include up to 10 wt.-% of moieties of α,β-unsaturated monomers sparingly soluble or insoluble in water, preferably of (meth)acrylic acid alkyl ester or vinyl acetate.
9. The use according to one or more of claims 1 to 8, characterized in that the cationic polymer has a molecular weight m.w. (g/mol) of from 0.1 to 20 millions.
10. The use according to one or more of claims 1 to 9, characterized in that native starches, preferably potato starch, cereal flour, wheat starch, corn starch, rice starch, pea starch, and/or mixtures thereof, anionic starches, preferably starch mono- or diphosphates, anionic starch ethers, preferably carboxymethylstarch, or cationic starch derivatives, preferably N-containing starch ethers, are used as starch.
11. The use according to one or more of claims 1 to 10, characterized in that the starch component is pulped in the presence of microparticles or microgels of at least one additive based on an inorganic mineral substance, preferably clay, silica sol, silica optionally modified with aluminum, polysilicates optionally modified with aluminum, or polyorthosilicic acid, bentonite, titanium dioxide, or talc.
12. The use according to one or more of claims 1 to 11, characterized in that the inorganic additive is employed in amounts of from 0.1 to 15 wt.-%, preferably from 3 to 15 wt.-%, relative to the modified starch component.
13. The use according to one or more of claims 1 to 12, characterized in that the weight ratio of starch component to cationic homo- or copolymer ranges from 4:1 to 25:1, preferably from 10:1 to 25:1, more preferably from 14:1 to 20:1 when performing the modification.
14. The use according to one or more of claims 1 to 13, characterized in that the starch component has been pulped at temperatures of from 70 to 150° C, preferably from 90 to 100°C.
15. The use according to one or more of claims 1 to 14, characterized in that the retention agent is added in amounts of from 0.1 to 10 wt.-%, preferably from 0.5 to 5 wt.-% solids, relative to the paper pulp.
16. The use according to one or more of claims 1 to 15, characterized in that waste paper is used in paper manufacturing.