WO2007048720A1

WO2007048720A1 - A composition for whitening paper

Info

Publication number: WO2007048720A1
Application number: PCT/EP2006/067414
Authority: WO
Inventors: Olli Juhani Jokinen; Stig-Erik Bruun; Timo Laine
Original assignee: Ciba Specialty Chemicals Holding Inc.
Priority date: 2005-10-24
Filing date: 2006-10-16
Publication date: 2007-05-03
Also published as: TW200728557A

Abstract

The invention relates to a composition for fluorescent whitening of paper comprising a) at least one fluorescent whitening agent of the formula (1), in which R1, R2 and R3, independently, are phenylamino; phenylamino substituted by C-i-Csalkyl, halogen, cyano, -COOR or -COR; -CONH-R; -SO2NH-R; -NH-COR; mono- or disulphonated phenylamino; morpholino; piperidino; pyrrolidino; -NH2; -NH(C1-C4alkyl) ; -N(C1C4alkyl)2; -NH(C2-C4hydroxyalkyl); -N(C2-C4hydroxyalkyl)2; -N(C1C4alkyl)(C2- C4hydroxyalkyl); -NHC2-C4 alkylsulphonic acid; -OC1C4alkyl or an amino acid or amino acid amide residue from which a hydrogen atom on the amino group has been removed; R is hydrogen; or C1-C3alkyl and M is H, Na, Li, K, Ca, Mg, ammonium, or ammonium that is mono-, di-, tri- or tetrasubstituted by C1C4alkyl, C2-C4hydroxyalkyl or a mixture thereof and b) an aqueous starch composition containing at least 15% by weight of a starch, whereby the starch has been subjected to a degradation process and, if necessary, to a stabilization process and the use thereof for whitening paper surfaces.

Description

A Composition for Whitening Paper

The present invention relates to a composition for fluorescent whitening of paper comprising a fluorescent whitening agent (FWA), which is a derivative of triazinylaminostilbene sulphonic acid and an aqueous starch composition and the use thereof for application to paper surfaces.

The advantages of using high solid starch compositions containing at least 15% dry matter for surface sizing of paper have been disclosed in WO 03/018638 A1. However, no indication is given that such starch compositions could be advantageously used together with fluorescent whitening agents for the whitening of paper surfaces.

It has now been found that combining high solid starch compositions containing at least 15% solid matter with certain fluorescent whitening agents results in more effective whitening of paper surfaces, especially when applied in the size press, than a combination of conventional starch solutions having a lower solids with fluorescent whitening agents.

Consequently, the invention relates to a composition for fluorescent whitening of paper comprising a) at least one fluorescent whitening agent of the formula

in which

R₁, R₂ and R3, independently, are phenylamino; phenylamino substituted by C-i-Csalkyl, halogen, cyano, -COOR or -COR; -CONH-R; -SO₂NH-R; -NH-COR; mono- or disulphonated phenylamino; morpholino; piperidino; pyrrolidino; -NH₂; -NH(Ci-C₄alkyl); -N(CrC₄alkyl)₂; -NH(C₂-C₄hydroxyalkyl); -N(C₂-C₄hydroxyalkyl)₂; -N(C_rC₄alkyl)(C₂-

C₄hydroxyalkyl); -NHC₂-C₄ alkylsulphonic acid; -OCrC₄alkyl or an amino acid or amino acid amide residue from which a hydrogen atom on the amino group has been removed;

R is hydrogen; or d-C₃alkyl and

M is H, Na, Li, K, Ca, Mg, ammonium, or ammonium that is mono-, di-, tri- or tetrasubstituted by CrC₄alkyl, C₂-C₄hydroxyalkyl or a mixture thereof and b) an aqueous starch composition in which the starch has previously been subjected to a degradation process and, if necessary, to a stabilization process, characterized in that the aqueous starch composition has a solids content of at least 15% dry weight of starch.

In the compounds of formula (1 ), the substituents Ri and R₂ are, preferably, identical. Furthermore, Ri and R₂ are, preferably, phenylamino; mono- or disulphonated phenylamino; morpholino; pyrrolidino; -NH₂; -NH(Ci-C₄alkyl); -N(Ci-C₄alkyl)₂; -NH(C₂- C₄hydroxyalkyl); -N(C₂-C₄hydroxyalkyl)₂; -N(C_rC₄alkyl)(C₂-C₄hydroxyalkyl); -NHC₂-C₄ alkylsulphonic acid; or an amino acid or amino acid amide residue from which a hydrogen atom on the amino group has been removed.

R₃ preferably represents morpholino; -NH₂; -NH(Ci-C₄alkyl); -N(Ci-C₄alkyl)₂; -NH(C₂-C₄hydroxyalkyl); -N(C₂-C₄hydroxyalkyl)₂; -N(C_rC₄alkyl)( C₂-C₄hydroxyalkyl); or an amino acid or amino acid amide residue from which a hydrogen atom on the amino group has been removed and M preferably represents hydrogen, potassium or sodium.

Where, in the compound of formula (1 ), one or more of the substituents R-i, R₂ and R₃ represents an amino acid or amino acid amide residue from which a hydrogen atom on the amino group has been removed, this residue is preferably derived from glycine, alanine, sarcosine, serine, cysteine, phenylalanine, tyrosine (4-hydroxyphenylalanine), diiodotyrosine, tryptophan (β-indolylalanine), histidine ((β-imidazolylalanine), α-amino butyric acid, methionine, valine (α-amino isovaleric acid), norvaline, leucine (α-amino isocaproic acid), isoleucine (α-amino-β-methylvaleric acid), norleucine (α-amino-n-caproic acid), arginine, ornithine (α,δ-diamino valeric acid), lysine (α,ε-diamino caproic acid), aspartic acid (amino succinic acid), glutamic acid (α-amino glutaric acid), threonine, hydroxyglutamic acid and taurine, as well as mixtures and optical isomers thereof, or from iminodiacetic acid or from N- (propionamido)-N-(2-hydroxyethyl)amine. Especially preferred residues are those derived from sarcosine, taurine, glutamic acid, aspartic acid, iminodiacetic acid or from N- (propionamido)-N-(2-hydroxyethyl)amine. Most preferred compounds of formula (1 ) are those in which R₁ and R₂ both represent a phenylamino, a phenylamino mono- or disulphonic acid residue, or a 2-hydroxyethylamino residue, R₃ represents a 2-hydroxyethylamino, an ethylamino, a bis(2-hydroxyethylamino), a bis(2-hydroxypropylamino) or an aspartic acid residue and M is hydrogen or sodium.

Where, in the compound of formula (1 ), CrC₄alkyl radicals are present, these may be branched or unbranched and are, for example, methyl, ethyl, n-propyl, isopropyl or n-butyl; isobutyl or tert. -butyl, whilst C₂-C₄hydroxyalkyl may, for example, be hydroxyethyl, hydroxypropyl or hydroxybutyl. Halogen is bromine, chlorine, fluorine or iodine, especially, chlorine.

The fluorescent whitening agents, component a) of the invention, are known compounds or may be obtained according to known procedures.

Any commercially available starch may be utilized as starting material for the preparation of the starch comprising the composition of the invention. Starch is a carbohydrate present in nature in all plants, especially plant seeds, roots and tubers. Sources of commercially available starches are, for example, cereal grains such as oats, wheat, rye, barley, millet, rice or maize, roots and tubers, such as potatoes, sweet potatoes, manioc or maranta and fruits such as chestnuts, peas, beans or bananas.

In order to produce the high solid starches employed in the composition of the invention, it is firstly necessary to degrade the starch by chemical treatment, which may be thermally assisted.

Such chemical degradation processes may involve hydrolysis which is brought about by enzyme treatment or treatment with mineral acid or oxidation.

Where degradation is performed by means of oxidation, suitable oxidizing agents are, for example hydrogen peroxide, optionally in the presence of metal, for example, copper, catalysts or by means of treatment with hypochlorite.

In the case that starch is modified by subjection, for example, to hypochlorite oxidation, the resulting starch is not only degraded, but simultaneously stabilized, since the retro reaction, resulting in increased viscosity, can no longer take place. Consequently, no separate stabilization process may be necessary, although this is generally beneficial.

Where degradation is performed by hydrolysis, this may be the result of treatment with suitable enzymes or by treatment with mineral acid such as sulphuric or hydrochloric acid, preferably, hydrochloric acid.

Usually, these degradation processes are performed to such an extent until the desired viscosity of the starch solutions are obtained, as indicated in WO 03/018638 A1 , although generally lying in the range of between 10 and 4000, preferably, 30 to 500 or even 30 to 200 mPas Brookfield viscosity for a 10% aqueous solution at 6O⁰C after stabilization.

In order to prevent an increase in viscosity, for example, on cooling, subsequent to the degradation process, it may be necessary to stabilize the resulting degraded starch. Suitable processes for stabilization are, for example, esterification and/or etherification, such as acetylation and/or hydroxyalkylation, cross-linking process with bifunctional derivatives such as adipic acid or by cationisation, whereby a combination of these stabilization processes may also be employed, for example, cross-linking with adipic acid in conjunction with acetylation with acetic anhydride, as is also described in WO 03/018638 A1. Alternatively, in the case of, for example, enzymatic degredation, stabilization may advantageously carried out prior to degredation.

Assessment as to whether "stabilization" of a modified starch has succeeded is performed by firstly heating a granular starch with water until solution results and then allowing the starch solution to cool to room temperature, whereby, at 6O⁰C the Brookfield viscosity is measured. After standing fpr 24 hours at room temperature, the temperature is raised to 6O⁰C and the viscosity remeasured. Providing the difference in the 2 measurements lies within the range of ±10%, the starch is considered to be stable.

The term cationisation is intended to mean the introduction of cationic groups into the degraded starch matrix. Thus, for example, the degraded starch may be cationised by treatment with a chemical substance prepared from epichlorohydrin and trimethylamine and at least one substance selected from the group comprising monomethylamine, dimethylamine and N,N,N',N'-tetramethylethylenediamine. In certain circumstances it may be desirable to cationise the starch not only subsequent to, but also prior to degradation.

The composition of the invention is prepared by simple mixing of the starch solution containing at least 15%, possibly 40%, preferably between 15 and 30%, by weight of dried matter with the required amount of fluorescent whitening agent, resulting in a composition suitable for use for fluorescent whitening of paper surfaces.

In one especially preferred aspect of the invention, the composition contains a fluorescent whitening agent of formula (1 ) in which R₁ and R ₂ both represent an aniline sulphonic acid residue, R3 represents bis(2-hydroxy)ethylamino or bis(2-hydroxypropylamino), M represents sodium and the starch comprises an 18% solution of barley starch which has been oxidized with sodium hypochlorite and further stabilized by treatment with acetic anhydride and adipic acid, having a viscosity of 20-70 mPas at 6O⁰C.

Application of the composition to the paper surface may be performed by any suitable method, whereby the amounts of the components may vary over wide ranges depending upon requirements. The coat weight of starch amounts to between 0.5 and 5.0g/m²/side, preferably between 0.8 and 2.5g/m²/side, as dry weight, whilst the FWA is applied within a range of from 0.5 to 40, preferably from 1 to 15 kg/tonne of paper.

In one preferred method, the composition of the invention is applied to the paper surface in the size press, metering size press or film press. Suitable devices for this application include, for example, Metso Paper Inc.'s OptiSizer (SymSizer) and Voith Paper GmbH's SpeedSizer.

In one further preferred method, the composition of the invention is applied to the paper surface by means of coating using any type of coating equipment such as a blade coater, roll coater etc., whereby the composition is then applied in the form of a coating colour containing a filler pigment such as calcium carbonate or kaolin.

Additionally, the whitening composition may, if desired, contain further additives typical for coating or size press applications and also blue or violet shading dyes or pigments. In this case, the composition of the invention is particularly advantageous, since lower quantities of shading dyes are required to achieve a desired degree of whiteness than when starch compositions of lower concentrations.

Similaraly, also in the absence of shading dyes, higher degrees of whiteness are obtained or less amounts of FWA to achieve a predetermined whiteness are required than in the case of compositions containing lower concentrations of starches.

The resulting paper which has been treated with the disclosed composition constitutes one further aspect of the invention.

The following Examples illustrate the invention, without intending to be restrictive in nature; parts and percentages are by weight, unless otherwise indicated.

Examples

The following Table 1 summarizes the fluorescent whitening agents (FW A's) of formula (1 ) and also their content as aqueous formulations, which are utilized for the size press application.

Table 1

The starch binder is produced from cereal starch as follows:

100Og of barley starch (88%) are slurried in 1 138g of water and the mixture warmed to 3O⁰C. The starch is then cationised by addition of 26.7g of a mixture consisting of 2,3- epoxypropyltrimethylammonium chloride (73%), 3-chloro-2-hydroxypropyltrimethylammonium chloride (1.2%) and water (23%), followed by 124g of 10% aqueous sodium hydroxide solution. The temperature is then raised to 35⁰C and the reaction mixture stirred for 15 hours at this temperature, after which time the cationisation is complete. The pH is then adjusted to 9.0 with sulphuric acid and 97.8g of commercial sodium hypochlorite solution (chlorine activity of sodium hypochlorite 180g/kg) are added over 1 hour. After the addition, the slurry is stirred for a further 2 hours at 35⁰C, the pH being maintained at 8.5-9.0 by addition of 10% aqueous sodium hydroxide solution. The pH is then adjusted to 8.0 and 50.Og of a solution prepared by dissolving 2.Og of adipic acid in 100ml of glacial acetic acid added with stirring over 4 hours at 35⁰C, the pH being maintained at 7.0-8.0 by addition of 10% aqueous sodium hydroxide solution. Following the addition, stirring is continued for a further 2 hours at 35⁰C and the solids filtered through a 200 micron wire. The filter cake is reslurried in 100Og of water, the solids again filtered off, air dried and ground, to yield 1068g of modified starch with a dry solids content of 88.3% and a nitrogen content of 0.16%. The Brookfield viscosity of an aqueous solution having 10% solids content is 70±20mPas at 6O⁰C.

To an 18% aqueous solution of the starch prepared as described above, the appropriate quantities (calculated in kg of aqueous formulation/tonne of paper) of the respective fluorescent whitening agents are added (see Table 2) and the solution applied to a coated unsized and FWA-free base paper from StraEnso/Varkaus having a base weight of 59 g/m² by means of a metering size press (OptiSizer) with a running speed of 700m/min such that the starch coat weight after drying amounts to 1.5 g/m²/side. After drying and conditioning, the ISO-Fluorescence (F|_So) and degree of whiteness (W_CIE) of the resulting sheets are measured using a Datacolor Elrepho 3000 spectrophotometer.

In a parallel series of experiments, the composition as described above was replaced by a composition comprising a commercial starch solution, Raisamyl® 23252 with a solids content of 1 1 % and identical quantities of the respective fluorescent whitening agents.

The results of the measurements are summarized in the following Table 2 below, whereby the Examples referring to the composition of the invention are designated with the letter "a", whilst those referring to the comparative experiments using a commercial starch composition are designated with the letter "b".

Table 2

As is apparent from the above results, in almost all cases, superior whitening effects are demonstrated by the composition of the invention in comparison to that containing a commercial starch with lower solids content.

In a second series of experiments, paper web having a base weight of 76g/m² is produced from 100% eucalyptus fibre on a fourdrinier paper machine running at a speed of 785m/min and, thereafter, on-line surface sized with a film transfer unit on both sides to an extent of 2.2g/m² with the respective starch/FWA compositions.

Tests are performed with an 18% solution of barley starch, previously degraded with sodium hypochlorite (test series a) and with a 13% solution of enzyme converted potato starch as reference (test series b), whereby the viscosity level of both starch solutions is 40-50mPas at 50-55⁰C.

An amount corresponding to 10.5kg/ton of paper of the FWA of formula (103) is added to the surface size and, by way of the controle loop of the paper machine, sufficient of violet (Irgalite® Violet M) and blue (Irgalite® Blue R-L) shading dyes dosed in order to achieve a degree of whiteness, W_CIE, of 168 and L^*, a^* and B^* colour coordinates of 94.6, 4.1 and -18.3, respectively.

The results indicating the requisite quantities of shading dyes and measured iso-fluorescence (F iso) of the experiments are summarized in the following Table 3: Table 3

The results clearly show that, in the case of the composition of the invention, lower quantities of shading dyes are required in order to attain a predetermined level of whiteness. Furthermore, the increased fluorescence of the paper treated with the composition of the invention indicates that, alternatively, it would have been possible to reduce the dosage of FWA by at least 10% to achieve the target whiteness, should the amounts of shading dyes have been maintained constant.

In a third series of experiments, low whiteness base paper (W_CIE 137) having a base weight of 80g/m² is surface sized on a pilot surface sizing machine running at 800m/min on both sides with a film transfer unit to a dry weight coating of 3.5g/m².

Three test series are performed: a) using an 18% solution of barley starch degraded with sodium hypochlorite and having a Brookfield viscosity of 20-30mPas for a 10% solution at 6O⁰C; b) using an 18% barley starch solution prepared as described above (following Table 1 ) and c) using a 10% solution of enzyme converted native potato starch as reference.

To each of these starch solutions is added an amount of the FWA of formula (102) corresponding to 1.8kg/ton of paper.

After drying, the degrees of whiteness (W_CIE) of the coated papers are measured, whereby the designations a), b) and c) correspond to the above starch compositions. The results are summarized in the following Table 4:

Table 4

The compositions of the invention clearly in improved degrees of whiteness as demonstrated by the higher W_CIE values.

In a fourth series of experiments, medium white base paper (W_CIE 153) having a base weight of 80g/m² is surface sized on a pilot surface sizing machine running at 800m/min on both sides with a film transfer unit to a dry weight coating of 3.0g/m².

Three test series are performed: a) using an 18% solution of barley starch degraded with sodium hypochlorite and having a Brookfield viscosity of 20-30mPas for a 10% solution at 6O⁰C; b) using an 18% barley starch solution prepared as described above (following Table 1 ) and c) using a 9% solution of enzyme converted native potatoe starch as reference.

To each of these starch solutions is added a sufficient amount of the FWA of formula (102) to achieve a CIE-whiteness value of 163.

The following Table 5 indicates the quqntities of FWA required for the various compositions:

Table 5

Again, the experiments demonstrate the superior whitening effect of the compositions of the invention.

Claims

1. A composition for fluorescent whitening of paper comprising a) at least one fluorescent whitening agent of the formula

in which

R₁, R₂ and R3, independently, are phenylamino; phenylamino substituted by C-i-Csalkyl, halogen, cyano, -COOR or -COR; -CONH-R; -SO₂NH-R; -NH-COR; mono- or disulphonated phenylamino; morpholino; piperidino; pyrrolidino; -NH₂; -NH(Ci-C₄alkyl) ; -N(CrC₄alkyl)₂; -NH(C₂-C₄hydroxyalkyl); -N(C₂-C₄hydroxyalkyl)₂; -N(C_rC₄alkyl)(C₂-

R is hydrogen; or d-C₃alkyl and M is H, Na, Li, K, Ca, Mg, ammonium, or ammonium that is mono-, di-, tri- or tetrasubstituted by CrC₄alkyl, C₂-C₄hydroxyalkyl or a mixture thereof and b) an aqueous starch composition in which the starch has previously been subjected to a degradation process and, optionally, to a stabilization process, characterized in that the aqueous starch composition has a solids content of at least 15% dry weight of starch.

2. A composition according to claim 1 , wherein, in the compound of formula (1 ),

R₁ and R₂ are identical and represent phenylamino; mono- or disulphonated phenylamino; morpholino; pyrrolidino; -NH₂; -NH(C_rC₄alkyl); -N(C_rC₄alkyl)₂; -NH(C₂-C₄hydroxyalkyl);

-N(C₂-C₄hydroxyalkyl)₂; -N(C_rC₄alkyl)( C₂-C₄hydroxyalkyl); -NHC₂-C₄ alkylsulphonic acid; or an amino acid or amino acid amide residue from which a hydrogen atom on the amino group has been removed; R₃ represents morpholino; -NH₂; -NH(C_rC₄alkyl); -N(C_rC₄alkyl)₂; -NH(C₂-C₄hydroxyalkyl); -N(C₂-C₄hydroxyalkyl)₂; -N(CrC₄alkyl)( C₂-C₄hydroxyalkyl); or an amino acid or amino acid amide residue from which a hydrogen atom on the amino group has been removed and

M represents hydrogen, potassium or sodium.

3. A composition according to claim 1 or claim 2, in which, in the compound of formula (1 ), an amino acid or amino acid amide residue from which a hydrogen atom on the amino group has been removed is derived from glycine, alanine, sarcosine, serine, cysteine, phenylalanine, tyrosine (4-hydroxyphenylalanine), diiodotyrosine, tryptophan (β-indolylalanine), histidine ((β- imidazolylalanine), α-amino butyric acid, methionine, valine (α-amino isovaleric acid), norvaline, leucine (α-amino isocaproic acid), isoleucine (α-amino-β-methylvaleric acid), norleucine (α-amino-n-caproic acid), arginine, ornithine (α,δ-diamino valeric acid), lysine (α,ε- diamino caproic acid), aspartic acid (amino succinic acid), glutamic acid (α-amino glutaric acid), threonine, hydroxyglutamic acid and taurine, as well as mixtures and optical isomers thereof, or from iminodiacetic acid or from N-(propionamido)-N-(2-hydroxyethyl)amine.

4. A composition according to any one of claims 1 to 3, in which the starch has been subjected to degradation by means of oxidation, enzymes or treatment with mineral acid.

5. A composition according to any one of claims 1 to 4, in which the starch is stabilized by etherification, esterification, cross-linking or cationisation or a combination thereof.

6. Use of the composition according to any one of the preceding claims for fluorescent whitening of paper surfaces.

7. Use, according to claim 6, wherein the composition is applied to the paper in the size press, metering size press or film press.

8. Use, according to claim 6, wherein the composition is applied to the paper by means of coating.

9. Paper, which has been treated with a composition according to any one of claims 1 to 5.