HK1173443B - Concentrated storage-stable aqueous optical brightening solutions - Google Patents

Description

Concentrated storage stable aqueous fluorescent whitening solutions

The present invention relates to concentrated aqueous solutions of specific triazinyl-stilbene based optical brighteners which have excellent storage stability without the use of solubilizing aids, separation or membrane filtration processes. The above whitening solutions provide excellent fluorescent whitening effect and exhibit reduced anionic charge when applied to the paper surface in the size press or used in pigmented coating compositions.

Prior Art

The paper industry has tended to use Optical Brighteners (OBAs) in the form of concentrated aqueous solutions which can be conveniently and accurately metered. However, it is well known that OBAs typically have low solubility in water at ambient temperatures due to the presence of inorganic salts as a by-product of the production process.

To prevent such disadvantages, Japanese laid-open patent 62-106965 discloses highly soluble triazinyl-stilbenes based on the following compounds of formula (I) OBA:

wherein

M is typically an alkali metal atom;

p is 0, 1 or 2; and is

R is an amino acid residue in which a hydrogen atom of an amino group is removed.

However, the high anionic charge generated by the amino acid residues can present difficulties for paper manufacturers wishing to recycle waste paper, i.e. repulping any waste paper produced in the paper making process, because the fluorescent whitening agent can be extracted in the repulping process, resulting in an accumulation of anionic charge in the system, which can interfere with the cationic chemicals used, e.g. for sizing, for retention and drainage purposes.

US4,466,900 describes the preparation of a storage stable aqueous solution containing a compound of formula (I) having a reduced anionic charge and wherein

M is typically an alkali metal atom;

p is 2; and is

R is especially diethylamino according to example 1;

the method is characterized in that: the reaction mixture is passed through a semipermeable membrane to remove inorganic salts. Due to this additional time-consuming and cost-consuming step, the process is economically disadvantageous.

CH-532,686 describes the preparation and isolation of compounds of formula (I) having a reduced anionic charge, and wherein

M is typically an alkali metal atom;

p is 2; and is

R is selected from dialkylamino; di-n-propylamine is mentioned in table I,

the method is characterized in that: precipitated from the reaction mixture. The solid compounds of formula (I) thus obtained are used directly for whitening paper, either in the size press or in coating compositions. However, this patent does not disclose anything about the preparation of concentrated storage stable aqueous solutions.

WO2006/000573A1 discloses storage-stable concentrated solutions of optical brighteners derived from aliphatic alkylamines having branched alkyl chains. Formula (10) discloses a hexasulfonated OBA derived from secondary amine methyl isopropylamine.

It would therefore be desirable to provide optical brighteners having a reduced anionic charge and from which concentrated storage-stable aqueous whitening solutions can be prepared without additional time-and cost-consuming steps such as membrane filtration, separation or addition of auxiliaries.

Disclosure of Invention

Surprisingly, the compounds of formula (1) combine a reduced anionic charge with high storage stability when prepared in concentrated aqueous solutions without the need for additional processing steps or solubilisers, while providing excellent fluorescent whitening effects when applied to the paper surface in the size press or in pigmented coating compositions.

The invention provides concentrated storage-stable aqueous solutions (S) comprising components (a), (b) and (c), wherein

Component (a) is at least one fluorescent whitening agent of formula (1)

Wherein the anionic charge on the whitening agent is balanced by a cationic charge consisting of one or more cations selected from the group consisting of: hydrogen, alkali metal cations, alkaline earth metal cations, ammonium, C_1-4Ammonium mono-, di-or trisubstituted by C, linear or branched alkyl_1-4Linear or branched hydroxyalkyl mono-, di-or tri-substituted ammonium, wherein the concentration of component (a) is from 0.08 to 0.3mol/kg, based on the weight of the concentrated storage-stable aqueous solution (S);

component (b) is at least one inorganic Salt (SA) in a concentration of 2 to 15% by weight, based on the total weight of the concentrated storage-stable aqueous solution (S);

and is

Component (c) is water at a concentration of 10 to 88 wt%, said wt% based on the total weight of the concentrated storage-stable aqueous solution (S).

The concentrated storage-stable aqueous solution (S) may optionally contain polyethylene glycol in an amount of from 2 to 40 wt. -%, based on the total weight of the concentrated storage-stable aqueous solution (S), to serve as a so-called carrier, thereby improving the properties of component (a).

The concentrated storage-stable aqueous solution (S) may optionally contain polyvinyl alcohol as a so-called carrier in an amount of 0.01 to 10% by weight, based on the total weight of the concentrated storage-stable aqueous solution (S), in order to improve the properties of component (a).

Preferred compounds of formula (1) are those in which the anionic charge on the whitening agent is balanced by a cationic charge consisting of one or more cations selected from the group consisting of: li⁺、Na⁺、K⁺、Ca²⁺、Mg²⁺And quilt C_1-4Linear or branched hydroxyalkyl mono-, di-or tri-substituted ammonium.

More preferred compounds of formula (1) are those in which the anionic charge on the whitening agent is balanced by a cationic charge consisting of one or more cations selected from the group consisting of: na (Na)⁺、K⁺、Ca²⁺、Mg²⁺And quilt C_1-4Linear or branched hydroxyalkyl mono-, di-or tri-substituted ammonium.

Particularly preferred compounds of formula (1) are those in which the anionic charge on the whitening agent is balanced by a cationic charge consisting of one or more cations selected from the group consisting of: na (Na)⁺And K⁺。

Preferably, if the anionic charge on the whitening agent is balanced by a cationic charge consisting of more than one cation, the mixture of cations comprises 2, 3, 4 or 5, more preferably 2, 3 or 4, even more preferably 2 or 3 different cations.

In a preferred aspect of the invention, the concentrated storage-stable aqueous solution (S) contains from 0.08 to 0.2mol of component (a)/kg of concentrated storage-stable aqueous solution (S), more preferably from 0.09 to 0.18mol of component (a)/kg of concentrated storage-stable aqueous solution (S).

In another preferred aspect of the invention, the concentrated storage-stable aqueous solution (S) contains 2.5 to 14 wt. -%, more preferably 2.5 to 12 wt. -% of inorganic Salts (SA), wherein the wt. -% is based on the total weight of the concentrated aqueous solution (S). Preferably the Salt (SA) is a by-product of the production process.

Preferably, the inorganic Salts (SA) are alkali metal salts and alkaline earth metal salts, preferably lithium, sodium, potassium, calcium or magnesium salts or mixtures of said compounds.

More preferably, the inorganic Salt (SA) is a lithium, sodium or potassium halide or a mixture of said compounds.

Even more preferably the inorganic Salt (SA) is sodium chloride, potassium chloride or a mixture of said compounds.

Another subject of the present invention is a process for preparing a concentrated storage-stable aqueous solution (S) as described above and which in a preferred embodiment comprises reacting cyanuric halide with a), B) and c) stepwise in the presence of water and using a base (B):

a) an amine of formula (2) in the form of the free acid, partial salt or complete salt:

(b) a diamine of formula (3) in free acid, partial salt or full salt form:

c) di-n-propylamine of formula (4):

the solution obtained from the production process is preferably used directly for the preparation of a storage-stable aqueous solution (S), if necessary diluted to the desired final concentration. It is preferred that no further processing steps such as membrane filtration, drying etc. are employed in the preparation of the concentrated storage-stable aqueous solution (S).

As cyanuric halide there may be used fluoride, chloride or bromide. Cyanuric chloride is preferred.

Each reaction may be carried out in an aqueous medium in which the cyanuric halide is suspended in water, an aqueous/organic medium and dissolved in a solvent such as acetone. The amines can be introduced undiluted or in the form of an aqueous solution or suspension. The amine may be reacted with the cyanuric halide in any order, although it is preferred to react the aromatic amine first. The stoichiometric amount of amine means half the molar amount of cyanuric halide in the case of the diamine of formula (3) and an equimolar amount with cyanuric halide in the case of the amine of formula (2) and di-n-propylamine of formula (4). The amines may be reacted in stoichiometric or excess amounts relative to the cyanuric halide. The aromatic amine is generally reacted in stoichiometric amounts or in slight excess; the di-n-propylamine of formula (4) is usually used in an excess of 0.1 to 30% over the stoichiometric ratio.

For substitution of the first halogen atom of the cyanuric halide, it is preferred to operate at a temperature of 0-20 ℃ and under acidic to neutral pH conditions, more preferably at a pH of 2-7. For substitution of the second halogen atom of the cyanuric halide, it is preferred to operate at a temperature of 20 to 60 ℃ under weakly acidic to weakly basic conditions, more preferably at a pH of 4 to 8. For substitution of the third halogen atom of the cyanuric halide, it is preferred to operate at a temperature of 60 to 102 ℃ under weakly acidic to basic conditions, more preferably at a pH of 7 to 10.

The substitution time of the first, second and third halogen atoms of the cyanuric halide (for example, by the aromatic amines of formulae (2) and (3) and by the di-n-propylamine of formula (4)) is from 10 minutes to 24 hours, preferably from 30 minutes to 10 hours, more preferably from 1 to 5 hours.

The pH of each reaction is usually adjusted by addition of a suitable base (B), the choice of which is determined by the desired final composition of the concentrated storage-stable aqueous solution (S). Preferably, the base (B) is, for example, a hydroxide, carbonate or bicarbonate of an alkali or alkaline earth metal, such as lithium, sodium, potassium, calcium, magnesium, or an aliphatic tertiary amine, such as triethanolamine or triisopropanolamine or a combination thereof. When the base (B) is a combination of two or more different bases, the bases may be added in any order or simultaneously.

Preferably the Salt (SA) is formed during the production process, for example by neutralising hydrogen halide with a suitable base (B), for example according to equation 1, in which equation 1 the base (B) is sodium hydroxide:

NaOH+HCl→NaCl+H₂o (Eq.1)

Preferably, the hydrogen halide is released during the three-stage substitution of the cyanuric halide, for example by the aromatic amines of formula (2) and (3) and by the di-n-propylamine of formula (4).

When it is necessary to adjust the reaction pH, an acid may be used, and examples thereof include hydrochloric acid, sulfuric acid, formic acid and acetic acid.

Therefore, another subject of the present invention is the use of the concentrated storage-stable aqueous solution (S) described above, in a preferred embodiment thereof as fluorescent whitening agent, preferably for fluorescent whitening of cellulosic substrates such as textiles, non-wovens or more preferably paper.

In addition to component (a), other optical brighteners structurally different from formula (1) may be used.

For the fluorescent whitening of textiles and nonwovens, the concentrated storage-stable aqueous solution (S) can be used, for example, in a padding process, in which the brightener concentration in the treatment bath can be kept virtually constant. In the finishing of textiles (fabrics or preferably nonwovens) with binders, in particular with synthetic resins, the concentrated storage-stable aqueous solution (S) can be added to the synthetic resin in or before the treatment bath. The optical brighteners can be fixed according to the cold-batch process or by thermal treatment, optionally after intermediate drying, and the finishes can be crosslinked according to the cold-batch process or by thermal treatment, optionally after intermediate drying. Owing to their stability to acids and salts, such as magnesium chloride and zinc chloride, the compounds of the formula (1) in the form of their concentrated, storage-stable aqueous solutions (S) are also suitable for the fluorescent whitening of cotton and for the simultaneous crease-resistant finishing. The concentrated storage-stable aqueous solution (S) may be used in an amount of 0.01-2.5 wt%, preferably 0.02-2.0 wt%, wherein the wt% is based on the weight of the dry cellulosic substrate.

The concentrated storage-stable aqueous solutions (S) are more preferably suitable for use as optical brighteners for whitening paper and nonwoven, even more preferably for whitening paper after sheet formation, or for whitening nonwoven after fabric formation.

It is particularly preferred that the concentrated storage stable aqueous solution (S) is suitable for whitening paper after sheet formation. This can be done by adding the concentrated storage-stable aqueous solution (S) to the pigmented coating composition or to the sizing solution or suspension. The paper may be fine or low grade paper, bleached or unbleached cellulose.

For the treatment of paper in the size press, a sizing solution or suspension containing 0.5-125 g/l of the sizing solution or suspension, preferably 2-100 g/l of the concentrated storage-stable aqueous solution (S), may be used. The sizing solution or suspension may also contain one or more binders in a concentration of 1 to 30 wt.%, preferably 2 to 20 wt.%, most preferably 5 to 15 wt.%, wherein the wt.% is based on the weight of the sizing solution. The pH of the sizing solution or suspension is generally from 5 to 9, preferably from 6 to 8.

The binder is selected from the group consisting of: natural starch, enzyme modified starch, chemically modified starch, and mixtures thereof. The modified starch is preferably an oxidized starch, a hydroxyethylated starch or an acetylated starch. The native starch is preferably anionic, cationic or amphoteric starch. Although the starch may be of any origin, it is preferred that the starch source is corn, wheat, potato, rice, tapioca or sago.

The sizing solution or suspension may optionally contain a divalent metal salt or a mixture of divalent salts different from the inorganic Salt (SA) contained in the concentrated storage-stable aqueous solution (S) in a concentration of 1 to 100g/l, preferably 2 to 80g/l, most preferably 5 to 70g/l, based on the sizing solution.

Preferably the divalent metal salt is selected from the group consisting of: calcium chloride, magnesium chloride, calcium bromide, magnesium bromide, calcium iodide, magnesium iodide, calcium nitrate, magnesium nitrate, calcium formate, magnesium formate, calcium acetate, magnesium acetate, calcium citrate, magnesium citrate, calcium gluconate, magnesium gluconate, calcium ascorbate, magnesium ascorbate, calcium sulfite, magnesium sulfite, calcium hydrogen sulfite, magnesium hydrogen sulfite, calcium dithionite, magnesium dithionite, calcium sulfate, magnesium sulfate, calcium thiosulfate, magnesium thiosulfate, and mixtures of the compounds.

Most preferably the divalent metal salt is selected from the group consisting of: calcium chloride, magnesium chloride, calcium bromide, magnesium bromide, calcium sulfate, magnesium sulfate, calcium thiosulfate, magnesium thiosulfate, and mixtures of the compounds.

Particularly preferred divalent metal salts are selected from the group consisting of: calcium chloride, magnesium sulfate and mixtures of said compounds.

When the divalent metal salt is a mixture of one or more calcium salts and one or more magnesium salts, the amount of calcium salt may be 0.1 to 99.9 wt% based on the total weight of added divalent metal salt.

In addition to the concentrated storage-stable aqueous solution (S), the sizing solution or suspension may also contain one or more binders, water, optionally an optical brightener which is structurally different from formula (1), and optionally one or more divalent metal salts. The sizing solution or suspension may contain by-products formed during the preparation of component (a) and other additives commonly used for treating cellulosic substrates such as textiles, nonwovens or paper.

Examples of paper additives are secondary binders, anti-freeze agents, biocides, defoamers, wax emulsions, dyes, inorganic salts, preservatives, complexing agents, thickeners, surface sizing agents, crosslinking agents, pigments, specialty resins, and the like.

The sizing composition is preferably prepared by adding a concentrated storage stable aqueous solution (S) and optionally a divalent metal salt and/or any other components to an aqueous solution of the binder, preferably at a temperature of 20-90 ℃.

The sizing composition may be applied to the surface of the paper substrate by any surface treatment method known in the art. Examples of methods of application of the sizing composition include size press application, calender sizing, vat sizing, coating application, or spray application. The preferred method of application of the sizing composition is in a size press, such as a chute (puddle) size press. The preformed sheet is passed through a two-roll nip impregnated with a sizing composition. The paper absorbs some of the composition, the remainder being removed in the nip.

The paper substrate contains a web of cellulose fibers which may be derived from any fibrous plant. Preferably, the cellulose fibers are derived from hardwood and/or softwood. The fibers may be fibrils or regenerated fibers, or any combination of fibrils and regenerated fibers.

The pigmented coating compositions are essentially aqueous compositions which comprise at least one binder and one white pigment, in particular a hiding white pigment, and may additionally comprise further additives such as dispersants and defoamers.

While coating compositions can be prepared that are free of white pigments, optimal white substrates for printing are prepared using an opaque coating composition comprising 10 to 80 weight percent white pigment, wherein weight percent is based on the total weight of the opaque coating composition. Such white pigments are generally inorganic pigments, such as aluminium silicates (such as kaolin, also known as china clay), calcium carbonates (such as chalk), titanium dioxide, aluminium hydroxide, barium carbonate, barium sulphate or calcium sulphate (such as gypsum), or mixtures thereof.

The binder in the pigmented coating composition may be any binder commonly used in the paper industry for producing coating compositions and may consist of a single binder or a mixture of a primary binder and a secondary binder. The single or primary binder is preferably a synthetic latex, typically a styrene-butadiene, vinyl acetate, styrene-acrylic, vinyl-acrylic or ethylene-vinyl acetate polymer. The secondary binder may be, for example, starch, carboxymethyl cellulose, casein, soy polymers, or polyvinyl alcohol.

The single or primary binder is generally used in an amount of 5 to 25% by weight, based on the total weight of the white pigment. The secondary binder is generally used in an amount of 0.1 to 10% by weight, based on the total weight of the white pigment; however, starch is generally used in amounts of 3 to 10% by weight, based on the total weight of the white pigment.

The concentrated storage-stable aqueous solution (S) may be used in an amount resulting in an amount of component (a) of 0.01 to 3 wt.%, preferably 0.05 to 2 wt.%, wherein the wt.% is based on the weight of the white pigment.

The concentrated storage-stable aqueous solution (S) containing the fluorescent whitening agent of formula (1) has the advantage of a lower anionic charge than the analogous compound of the above-mentioned Japanese laid-open patent No. 62-106965.

Surprisingly, the optical brighteners of formula (1) also have a higher solubility in water than similar compounds exemplified by patents CH532,686 and US4,466,900, in which the di-n-propylamino group of the compound of formula (1) is replaced by di-n-ethylamino or di-n-butylamino.

Surprisingly, the concentrated storage-stable aqueous solution (S) shows better application properties than the analogous compounds of the above-mentioned Japanese laid-open patent publication No. 62-106965.

The following examples illustrate the invention in more detail. "%" and "parts" mean% by weight and parts by weight, unless otherwise specified.

Examples

Preparation of example 1

520.2 parts of aniline-2, 5-disulfonic acid monosodium salt are added to 900 parts of water and dissolved at about 25 ℃ and a pH of about 8 to 9 with the aid of about 295.1 parts of 30% w/w aqueous sodium hydroxide solution. The solution thus formed was added over about 30 minutes to 331.9 parts of cyanuric chloride dispersed in 405 parts of water and 630 parts of ice. The temperature was kept below 5 ℃ using an ice/water bath and the pH was kept at about 4-5 using about 504.1 parts of 20% w/w aqueous sodium carbonate solution. At the end of the addition, the pH was raised to about 6 using about 35.1 parts of 20% w/w aqueous sodium carbonate solution and stirring was continued at about 0-5 ℃ until the reaction was complete. Then 151.2 parts of sodium bicarbonate were added to the reaction mixture. To the reaction mixture was added dropwise an aqueous solution obtained by dissolving 333.4 parts of 4,4 '-diamino-2, 2' -disulfonic acid in 1240 parts of water at about 45-50 ℃ and at a pH of about 8-9 with the aid of about 235.8 parts of a 30% w/w aqueous sodium hydroxide solution. The resulting mixture was stirred at about 45-50 ℃ until the reaction was complete. The resulting aqueous mixture contained the compound of formula (5) at a concentration of 0.161mol/kg of mixture.

Preparation of example 2a

To 1234.5 parts of an aqueous mixture containing the compound of formula (5) obtained according to preparation example 1, 42.5 parts of di-n-propylamine were added. The mixture was stirred at reflux for 2 hours and the pH was maintained at 8-9 by the addition of 30% w/w aqueous sodium hydroxide. The aqueous solution thus formed was cooled to 60-65 ℃ and filtered. Water was added to the filtrate or removed by distillation to obtain a concentrated storage stable aqueous solution 2a comprising the compound of formula (6) (20.4 wt% based on the total weight of the final concentrated storage stable aqueous fluorescent whitening solution 2 a) at a concentration of 0.150mol/kg of the final concentrated storage stable aqueous fluorescent whitening solution 2a and about 5.3 wt% sodium chloride (wt% based on the total weight of the final concentrated storage stable aqueous fluorescent whitening solution 2 a). The concentrated storage stable aqueous solution of fluorescent whitening 2a thus formed has a pH of 8-9 and shows no precipitation after 2 weeks at 5 ℃.

Preparation of example 2b

The concentrated storage stable aqueous fluorescent whitening solution 2b was prepared by the following procedure: the concentrated aqueous fluorescent whitening solution comprising the compound of formula (6) prepared according to preparation example 2a was stirred with polyethylene glycol having an average molecular weight of 1500 while heating to 90-95 ℃. The parts of the components are selected so as to obtain a final concentrated aqueous storage stable fluorescent whitening solution 2b comprising the compound of formula (6) at a concentration of 0.150mol/kg of the final concentrated aqueous storage stable fluorescent whitening solution 2b and 6 wt.% polyethylene glycol 1500 (wt.% based on the final concentrated aqueous storage stable fluorescent whitening solution 2 b). To obtain the desired concentration of the components in the final concentrated storage stable whitening aqueous solution 2b, water is added or removed by distillation. The concentrated aqueous storage stable fluorescent whitening solution 2b has a pH of 8-9 and comprises about 5.3 wt% (wt% based on the final concentrated aqueous storage stable fluorescent whitening solution 2b) sodium chloride. The concentrated storage stable aqueous fluorescent whitening solution 2b obtained according to this procedure showed no sign of precipitation after 2 weeks at 5 ℃.

Comparative example 2c

The compound of formula (6a) is obtained in powder form according to the same procedure as in example 6 of CH532686, wherein the anionic charge on the optical brightener is Na-capped⁺And/or K⁺Cation balance:

in addition to the compound of formula (6a), the powder comprises 1.9 wt.% sodium cations, 7.5 wt.% potassium cations, 5.1 wt.% chloride anions and 1.3 wt.% water (wt.% based on the total weight of the finally obtained powder).

An aqueous mixture comprising the compound of formula (6a) in a concentration of 0.150mol/kg is obtained by adding a powder comprising the compound of formula (6a) obtained as in example 6 of CH532686 to water and stirring for 1 hour. (see FIG. 1).

Comparative example 3

An aqueous fluorescent whitening solution 3 comprising a compound of formula (7) at a concentration of 0.150mol/kg of the final aqueous fluorescent whitening solution 3 (19.6% by weight based on the total weight of the final aqueous fluorescent whitening solution 3) and about 5.3% by weight sodium chloride (% by weight based on the total weight of the final aqueous fluorescent whitening solution 3) was obtained following the same procedure as preparation example 2a, with the only difference that 30.7 parts diethylamine was used instead of 42.5 parts di-n-propylamine. The aqueous fluorescent whitening solution 3 thus formed has a pH of 8 to 9 and shows precipitation at 5 ℃ within 0 to 4 days.

Comparative example 4

An aqueous fluorescent whitening solution 4 comprising a compound of formula (8) at a concentration of 0.150mol/kg of the final aqueous fluorescent whitening solution 4 (21.3% by weight based on the total weight of the final aqueous fluorescent whitening solution 4) and about 5.3% by weight sodium chloride (% by weight based on the total weight of the final aqueous fluorescent whitening solution 4) was prepared following the same procedure as preparation example 2a, with the only difference that 54.3 parts of di-n-butylamine were used instead of 42.5 parts of di-n-propylamine. The aqueous fluorescent whitening solution 4 thus formed has a pH of 8 to 9 and shows precipitation at 5 ℃ within 0 to 4 days.

Comparative example 5a

An aqueous fluorescent whitening solution 5a comprising a compound of formula (9) at a concentration of 0.150mol/kg of the final aqueous fluorescent whitening solution 5a (22.7% by weight, based on the total weight of the final aqueous fluorescent whitening solution 5 a) and about 5.3% by weight (% by weight, based on the total weight of the final aqueous fluorescent whitening solution 5 a) of sodium chloride was obtained following the same procedure as preparation example 2a, with the only difference that 55.9 parts of L-aspartic acid was used instead of 42.5 parts of di-n-propylamine. The aqueous fluorescent whitening solution 5a thus formed had a pH of 8-9 and showed no sign of precipitation after 2 weeks at 5 ℃.

Comparative example 5b

The aqueous fluorescent whitening solution 5b was prepared by stirring together an aqueous solution containing the compound of formula (9) prepared according to comparative example 5a and polyethylene glycol having an average molecular weight of 1500 while heating to 90-95 ℃. The parts of the components are selected so as to obtain a final aqueous fluorescence-whitening solution 5b comprising the compound of formula (9) in a concentration of 0.150mol/kg of said final aqueous fluorescence-whitening solution 5b and 6% by weight of polyethylene glycol 1500 (weight% based on the total weight of said final aqueous fluorescence-whitening solution 5 b). To obtain the desired concentrations of the components in the final aqueous fluorescent whitening solution 5b, water is added or removed by distillation. The aqueous fluorescent whitening solution 5b has a pH of 8-9 and comprises about 5.3 wt% (wt% based on the final aqueous fluorescent whitening solution 5b) of sodium chloride. The aqueous fluorescent whitening solution 5b obtained according to this procedure showed no sign of precipitation after 2 weeks at 5 ℃.

Comparative example 6a

An aqueous fluorescence-whitening solution 6a comprising the compound of formula (10) disclosed in WO2006/000573a1 in a concentration of 0.150mol/kg of the final aqueous fluorescence-whitening solution 6a (19.6% by weight, based on the total weight of the final aqueous fluorescence-whitening solution 6a) and about 5.3% by weight (based on the total weight of the final aqueous fluorescence-whitening solution 6a) of sodium chloride was prepared following the same procedure as preparation example 2a, with the only difference that 30.7 parts of N-methyl-N-isopropylamine was used instead of 42.5 parts of di-N-propylamine. The aqueous fluorescent whitening solution 6a thus formed had a pH of 8 to 9 and showed precipitation at 5 ℃ for 1 to 5 days.

Comparative example 6b

The aqueous fluorescent whitening solution 6b was prepared by stirring an aqueous solution containing the compound of formula (10) prepared according to comparative example 6a with polyethylene glycol having an average molecular weight of 1500 while heating to 90-95 ℃. The parts of the components are selected so as to obtain a final aqueous fluorescence-whitening solution 6b comprising the compound of formula (10) at a concentration of 0.150mol/kg of final aqueous fluorescence-whitening solution 6b and 6 wt.% of polyethylene glycol 1500 (wt.% based on the total weight of the final aqueous fluorescence-whitening solution 6 b). To obtain the desired concentration of the components in the final aqueous fluorescent whitening solution 6b, water is added or removed by distillation. The aqueous fluorescent whitening solution 6b has a pH of 8-9 and comprises about 5.3 wt.% (wt.% based on the total weight of the final aqueous fluorescent whitening solution 6 b) sodium chloride. The aqueous fluorescent whitening solution 6b obtained according to this procedure showed precipitation at 5 ℃ within 1 week.

Application example 2a and comparative application example 5a

Prepared by adding one of an aqueous fluorescent whitening solution comprising the compound of formula (6) prepared according to preparation example 2a and an aqueous fluorescent whitening solution comprising the compound of formula (9) prepared according to comparative example 5a, in a concentration of 0 to 80g/l (0 to about 20g/l based on dry fluorescent whitening agent) to a stirred aqueous solution at 60 ℃ and comprising calcium chloride (30g/l) and anionic potato starch (50g/l) (Perfectamyl A4692 of AVEBE B.A.), respectivelyA sizing solution. The sizing solution was cooled, then poured between the moving rolls of a laboratory size press and applied to a commercial 75g/m²AKD (alkyl ketene dimer) sized bleached paper base sheet. The treated paper was dried in a flat bed dryer at 70 ℃ for 5 minutes. The dried paper was conditioned and then measured for CIE whiteness and a on a calibrated Auto Elrepho spectrophotometer^＊And b^＊The value is obtained. The results are shown in table 1 and table 2, respectively, and clearly indicate that the present invention provides an excellent whiteness accumulation effect and an improved color development (shade) effect.

Table 1: CIE whiteness

Table 2: CIELAB a^＊And b^＊Value of

Application example 2b and comparative application example 5b

A sizing solution was prepared by adding one of the aqueous fluorescent whitening solutions comprising the compound of formula (6) prepared according to preparative example 2b and the aqueous fluorescent whitening solution comprising the compound of formula (9) prepared according to comparative example 5b, in a concentration of 0 to 80g/l (0 to about 20g/l based on dry fluorescent whitening agent), respectively, to a stirred aqueous solution at 60 ℃ and comprising calcium chloride (30g/l) and anionic potato starch (50g/l) (percectamyl a4692 of AVEBE b.a.). The sizing solution was cooled, then poured between the moving rolls of a laboratory size press and applied to a commercial 75g/m²AKD (alkyl ketene dimer) sized bleached paper base sheet. The treated paper was dried in a flat bed dryer at 70 ℃ for 5 minutes. The dried paper was conditioned and then measured for CIE whiteness and a on a calibrated Auto Elrepho spectrophotometer^＊And b^＊The value is obtained.The results are shown in table 3 and table 4, respectively, which clearly indicate that the present invention provides excellent whiteness accumulation effect and improved color rendering effect.

Table 3: CIE whiteness

Table 4: CIELAB a^＊And b^＊Value of

Application example 3

A coating composition was prepared comprising: 70 parts chalk (commercially available from OMYA under the trade name Hydrocarb 90), 30 parts clay (commercially available from IMERYS under the trade name Kaolin SPS), 42.8 parts water, 0.6 part dispersant (sodium salt of polyacrylic acid, commercially available from BASF under the trade name Polysalz S), 20 parts of 50% latex (styrene-butadiene copolymer, commercially available from Dow under the trade name DL 921), 8 parts of a 10% by weight aqueous polyvinyl alcohol solution (0.8 parts dry polyvinyl alcohol) having a degree of hydrolysis of 98-99% and a Brookfield viscosity of 4.0-5.0 mPa.s (20 ℃, 4% aqueous solution). The solids content of the coating composition was adjusted to about 65% by adding water and the pH was adjusted to 8-9 with sodium hydroxide.

Aqueous fluorescent whitening solutions 2a, 2b, 5a and 5b prepared according to preparation examples 2a and 2b and comparative examples 5a and 5b, respectively, were added to the stirred coating composition at a concentration of 0.8-2.0 wt.% dry solids. The whitened coating composition was then applied to a commercial 75gsm neutral sized white paper-based sheet using an automatic wire wound rod coater with a standard rate setting and standard rod loading. The coated paper was then dried in a stream of hot air for 2 minutes. The dried paper was conditioned and then measured for CIE whiteness and CIELAB a on a calibrated Auto Elrepho spectrophotometer^＊And b^＊The value is obtained. The results are shown in tables 5 and 6, respectively, which clearly indicate that the present invention provides excellent whiteness accumulation effect and improved color rendering effect.

Table 5: CIE whiteness

Table 6: CIELAB a^＊And b^＊Value of

Application example 4

A sizing solution was prepared by adding one of the aqueous fluorescent whitening solution comprising the compound of formula (6a) prepared according to comparative example 2C and the aqueous fluorescent whitening solution comprising the compound of formula (6) prepared according to preparation example 2a in a concentration of 0 to 60g/l (0 to about 20g/l based on dry fluorescent whitening agent) to a stirred aqueous solution at 60 ℃ and comprising anionic potato starch (50g/l) (percectamyl a4692 of AVEBE b.a.). The sizing solution was cooled, then poured between the moving rolls of a laboratory size press and applied to a commercial 75g/m²AKD (alkyl ketene dimer) sized bleached paper base sheet. The treated paper was dried in a flat bed dryer at 70 ℃ for 5 minutes. The dried paper was conditioned and then measured for CIE whiteness on a calibrated Auto Elrepho spectrophotometer. The results are shown in table 7, which clearly show that the present invention provides excellent whiteness build up.

Table 3: CIE whiteness

Claims (26)

1. A concentrated storage-stable aqueous solution comprising components (a), (b) and (c),

wherein

Component (a) is at least one fluorescent whitening agent of formula (1)

Wherein the anionic charge on the whitening agent is balanced by a cationic charge consisting of one or more cations selected from the group consisting of: hydrogenAlkali metal cations, alkaline earth metal cations, ammonium, by C_1-4Ammonium mono-, di-or trisubstituted by C, linear or branched alkyl_1-4Linear or branched hydroxyalkyl mono-, di-or tri-substituted ammonium, and

the concentration of component (a) is from 0.08 to 0.3mol/kg, based on the total weight of the concentrated storage-stable aqueous solution;

component (b) is at least one inorganic salt having a concentration of 2 to 15 weight percent based on the total weight of the concentrated storage stable aqueous solution;

and is

Component (c) is water at a concentration of 10 to 88 weight percent based on the total weight of the concentrated storage stable aqueous solution.

2. The concentrated storage stable aqueous solution of claim 1 further comprising polyethylene glycol in an amount of 2 to 40 weight percent based on the total weight of the concentrated storage stable aqueous solution.

3. The concentrated storage stable aqueous solution of claim 1 or 2 further comprising polyvinyl alcohol in an amount of 0.01 to 10 weight percent based on the total weight of the concentrated storage stable aqueous solution.

4. A concentrated storage stable aqueous solution according to claim 1 or 2 wherein the anionic charge on the whitening agent of formula (1) is balanced by a cationic charge consisting of one or more cations selected from the group consisting of: li⁺、Na⁺、K⁺、Ca²⁺、Mg²⁺And quilt C_1-4Linear or branched hydroxyalkyl mono-, di-or tri-substituted ammonium.

5. A concentrated storage stable aqueous solution according to claim 1 or 2 characterized in that the concentration of component (a) is 0.08-0.2mol/kg concentrated storage stable aqueous solution.

6. A concentrated storage stable aqueous solution according to claim 1 or 2 characterized in that the concentration of component (a) is 0.09 to 0.18mol/kg of concentrated storage stable aqueous solution.

7. The concentrated storage stable aqueous solution of claim 1 or 2 wherein the concentration of the inorganic salt/component (b) is from 2.5 to 14 weight percent based on the total weight of the concentrated aqueous solution and the salt is a by-product of the manufacturing process.

8. The concentrated storage stable aqueous solution of claim 1 or 2 wherein the concentration of the inorganic salt/component (b) is from 2.5 to 12 weight percent based on the total weight of the concentrated aqueous solution and the salt is a by-product of the manufacturing process.

9. The concentrated storage stable aqueous solution of claim 1 or 2 wherein the inorganic salt is an alkali metal salt and an alkaline earth metal salt, or a mixture of said compounds.

10. The concentrated storage stable aqueous solution of claim 1 or 2 wherein the inorganic salt is a lithium, sodium, potassium, calcium or magnesium salt, or a mixture of said compounds.

11. A process for preparing a concentrated storage-stable aqueous solution as claimed in claim 1 by reacting cyanuric halide with

a) An amine of formula (2) in the form of the free acid, partial salt or complete salt:

(b) a diamine of formula (3) in free acid, partial salt or full salt form:

and

c) di-n-propylamine of formula (4):

the reaction is carried out in the presence of water and in stages using a base.

12. A process according to claim 11 wherein the cyanuric halide is used in the form of cyanuric fluoride, cyanuric chloride or cyanuric bromide.

13. A process according to claim 11 or 12 wherein the cyanuric halide is suspended in water or an aqueous/organic medium.

14. The process as claimed in claim 11 or 12, wherein the aromatic amines (2) and (3) are reacted in stoichiometric ratio or in slight excess and the di-n-propylamine (4) is used in excess of the stoichiometric ratio by from 0.1 to 30%.

15. The method of claim 11 or 12, wherein the first reaction step is performed at a temperature in the range of from 0 to 20 ℃, the second reaction step is performed at a temperature in the range of from 20 to 60 ℃, and the third reaction step is performed at a temperature in the range of from 60 to 102 ℃.

16. The method of claim 11 or 12, wherein the first reaction step is performed under acidic to neutral conditions, the second reaction step is performed under weakly acidic to weakly basic conditions, and the third reaction step is performed under weakly acidic to basic conditions.

17. The process of claim 11 or 12, wherein the base is an alkali or alkaline earth metal hydroxide, carbonate or bicarbonate, or an aliphatic tertiary amine or a combination thereof.

18. Use of a concentrated storage stable aqueous solution according to any one of claims 1 to 10 as a fluorescent whitening agent to whiten cellulosic substrates, textiles or non-woven materials.

19. The method of claim 18, wherein the solution is used in an amount of 0.01-2.5 wt% based on the weight of the cellulosic material when used to fluorescent whiten textiles and nonwovens.

20. A method as claimed in claim 18 or 19, wherein the solution is used for treating paper in a size press, the concentration of the solution in the sizing solution or suspension being from 0.5 to 125 grams per litre of sizing solution or suspension.

21. A sizing solution or suspension for treating paper comprising a concentrated storage-stable aqueous solution as claimed in any of claims 1 to 10.

22. The sizing solution or suspension of claim 21, wherein the solution is included at a concentration of 0.5 to 125 grams per liter of the sizing solution or suspension.

23. The sizing solution of claim 21 or 22, additionally comprising one or more binders selected from the group consisting of: native starch, enzymatically modified starch, chemically modified starch, or mixtures thereof.

24. The sizing solution of claim 21 or 22, further comprising a divalent metal salt or a mixture of divalent metal salts different from the salt.

25. The sizing solution of claim 21 or 22, further comprising one or more binders, water and optionally other optical brighteners structurally different from formula (1).

26. A pigmented coating composition comprising the concentrated storage stable aqueous solution of any one of claims 1-10.