RU2495972C2 - Improved optical bleaching compositions - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a compound of formula (1)

where R₁ denotes hydrogen or $${\text{SO}}_{\text{3}}^{-}$$

, R₂ denotes hydrogen or $${\text{SO}}_{\text{3}}^{-}$$

, R₃ denotes hydrogen or $${\text{CH}}_{\text{2}}{\text{CO}}_{\text{2}}^{-}$$

, R₄ denotes $${\text{CH}}_{\text{2}}{\text{CO}}_{\text{2}}^{-}$$

, $$CH\left(C{O}_2^{-}\right)C{H}_{2}C{O}_2^{-}$$

or $$CH\left(C{O}_2^{-}\right)C{H}_{2}C{H}_{2}C{O}_2^{-}$$

, and where M denotes a stoichiometric cation equivalent required to balance the anionic charge in formula (1) and is a combination of Mg²⁺ with at least 1 additional cation. The additional cations are selected from a group consisting of H⁺, a cation of an alkali metal, a cation of an alkali-earth metal other than Mg²⁺, ammonium, mono-C₁-C₄ alkyl-di-C₂-C₃-hydroxyalkylammonium, di-C₁-C₄-alkyl-mono-C₂-C₃-hydroxyalkylammonium, ammonium, which is mono-, di- or trisubstituted with a C₂-C₃ hydroxyalkyl radical, and mixtures thereof. The invention also relates to versions of the method of producing said compound and use of said compound in binding compositions for bleaching paper.

EFFECT: compound is a more efficient paper bleaching agent.

8 cl, 4 tbl, 10 ex

Description

FIELD OF THE INVENTION

The present invention relates to mixed salts of optical brighteners containing Mg ²⁺ which provide excellent optical whitening effects when applied to the surface of the paper.

State of the art

High whiteness is an essential parameter for the end consumer of paper products. The most important raw materials for the paper industry are cellulose, pulp and lignin, which naturally absorb blue light, therefore have a yellowish color and give the paper unsatisfactory visual characteristics. In the paper industry, optical brighteners are used to compensate for the absorption of blue light by absorbing UV radiation with a maximum wavelength of 350-360 nm and turning it into visible blue light with a wavelength of 440 nm.

In paper production, optical brighteners can be added either to the wet part of the paper machine, or to the surface of the paper, or both. As a rule, it is not possible to provide the high degrees of brightness that are required for high quality paper by adding bleach only to the wet part of the paper machine.

A common method for adding optical brightener to the surface of the paper is to apply an aqueous optical brightener solution on a size press with a sizing agent, usually natural starch or enzyme-modified starch, or chemically modified starch. A preformed sheet of paper is passed through a pressing zone between two rolls, the entrance to the pressing zone being filled with a sizing solution. The paper absorbs a certain amount of solution, the residue is removed in the pressing zone.

Along with starch and optical brightener, the sizing solution may contain other chemicals designed to provide specific properties. These include antifoam agents, paraffin emulsions, colorants, pigments and inorganic salts.

In order to obtain high whiteness, efforts have been made to develop new optical brighteners. See, for example, Japanese Kokai 62-106965, PCT Application WO 98/42685, US Patent 5,873,913 and European Patent 1,763,519.

British Patent 1239818 describes hexasulfonated optical brighteners derived from triazinylaminostilbenes. Examples 1-6 describe their sodium salts. Magnesium is mentioned only in the list of possible counterions for hexasulfonated optical brighteners, starch as a component of the composition for surface sizing is also mentioned only in the list of possible binding agents.

The need for more effective means to achieve high degrees of whiteness of paper is still there.

Disclosure of invention

The authors of the present invention, to their surprise, found that optical brighteners of the formula (1) when applied to a paper surface, optionally in combination with magnesium salts, as part of a sizing composition containing starch, enhance the whitening effect.

An object of the invention is a compound of formula (1),

Where

R ₁ is hydrogen or SO ₃ ^- ,

R ₂ is hydrogen or SO ₃ ^- ,

R ₃ is hydrogen, C _1-4 alkyl, C _2-3 hydroxyalkyl, CH ₂ CO ₂ ^- , CH ₂ CH ₂ CONH ₂ or CH ₂ CH ₂ CH,

R ₄ is C _1-4 alkyl, C _2-3 hydroxyalkyl, CH ₂ CO ₂ ^- , CH (CO ₂ ^- ) CH ₂ CO ₂ ^- or CH (CO ₂ ^- ) CH ₂ CH ₂ CO ₂ ^- , benzyl or

R ₃ and R ₄ together with an adjacent nitrogen atom denotes a morpholine ring, and where

M denotes the stoichiometric cationic equivalent required to balance the anionic charge in formula (1) and is a combination of Mg ⁺ together with at least 1, preferably 1, 2, 3, 4, 5 or 6, more preferably 1, 2 or 3 , even more preferably 1 or 2, with additional cations, the additional cations selected from the group consisting of H ^{+ an} alkali metal cation, an alkaline earth metal cation other than Mg ²⁺ , ammonium, mono-C ₁ -C ₄ -alkyl-di C ₂ -C ₃ -gidroksialkilammoniya, di-C ₁ -C ₄ -alkyl-topo-C ₂ -C ₃ -hydroxyalkyl ammonium, ammonium which is mono-, di or tri-substituted C ₂ -C ₃ hydroxyalkyl radical, and mixtures thereof.

The molar ratio of Mg ²⁺ to additional cation in M is preferably from 0.01 to 99.99 and from 99.99 to 0.01, more preferably from 20 to 80 and from 99.99 to 0.01, even more preferably from 50 to 50 and from 99.99 to 0.01. The alkali metal cation is preferably Li ⁺ , Na ⁺ or K ⁺ . An alkaline earth metal cation other than Mg ²⁺ is preferably Ca ²⁺ .

The additional cation in M is preferably selected from the group consisting of H ⁺ , Li ⁺ , Na ⁺ , K ⁺ , Ca ²⁺ , N-methyl-N, N-diethanolammonium, N, N-dimethyl-N-ethanolammonium, triethanolammonium, triisopropanolammonium and mixtures thereof.

Preferred compounds of formula (1) are those wherein R ₃ is hydrogen, methyl, ethyl, n-propyl, isopropyl, β-hydroxyethyl, β-hydroxypropyl, CH ₂ CO ₂ ^- , CH ₂ CH ₂ CONH ₂ or CH ₂ CH ₂ CN and R ₄ are methyl, ethyl, n-propyl, isopropyl, 2-butyl, β-hydroxyethyl, β-hydroxypropyl, CH ₂ CO ₂ ^- , CH (CO ₂ ^- ) CH ₂ CO ₂ ^- , CH (CO ₂ ^- ) CH ₂ CH ₂ CO ₂ ^- or benzyl.

Compounds of formula (2) and (3) with M as defined above, in all its preferred embodiments, are specific examples of compounds of formula (1); the compounds of formula (2) and (3), with M being a mixture of Mg ²⁺ with Na ⁺ and / or K ⁺ are further specific examples, but the invention is not limited to these specific examples.

The next object of the invention is a method for producing a compound of formula (1) according to claim 1, characterized by reaction A, followed by reaction B, followed by reaction C,

where in reaction A, a compound of formula (10) is reacted with a compound of formula (11) to give a compound of formula (12);

in reaction B, a compound of formula (12) is reacted with a compound of formula (13) to give a compound of formula (14);

and in reaction C, a compound of formula (14) is reacted with a compound of formula (15) to give a compound of formula (1), wherein

R ₁ , R ₂ , R ₃ and R _{4 are} defined above, also in all their preferred embodiments,

M1 are the same or different in formulas (13) and (14), and M1 is the stoichiometric cationic equivalent required to balance the anionic charge in these formulas and is at least 1 cation selected from the group consisting of H ⁺ , an alkali metal cation , an alkaline earth metal cation other than Mg ²⁺ , ammonium, mono-C ₁ -C ₄ -alkyl-di-C ₂ -C ₃ -hydroxyalkylammonium, di-C ₁ -C ₄ -alkyl-mono-C ₂ -C ₃ -hydroxyalkylammonium, ammonium, which is mono-, di or trisubstituted with a C ₂ -C ₃ hydroxyalkyl radical, and mixtures thereof.

M2, independently of one another in formulas (10) and (12), are the same or different, and M2 denotes the stoichiometric cationic equivalent required to balance the anionic charge in these formulas in the case when either R ₁ or R ₂ or both R ₁ and R ₂ denote SO ₃ , and is defined in the same way as M1,

with the proviso that at least one of the reactions A, B or C is carried out in the presence of a CAT cation, wherein the CAT cation is Mg ²⁺ .

The CAT cation can be introduced into reactions A, B and / or C via M1 in the formula (13) containing Mg ²⁺ and / or M2 in the formula (10) containing Mg ²⁺ , or by adding the magnesium salt MS1 as an additional component to reaction A, B and / or C. The magnesium salt MS 1 is preferably selected from the group consisting of magnesium acetate, magnesium bromide, magnesium chloride, magnesium formate, magnesium iodide, magnesium nitrate, magnesium sulfates, magnesium thiosulfate, magnesium hydroxide, carbonate magnesium, magnesium bicarbonate and mixtures thereof; more preferably, the magnesium salt MS1 is magnesium hydroxide, magnesium chloride, magnesium sulfate or magnesium thiosulfate. Even more preferably, the MS1 magnesium salt is magnesium hydroxide, magnesium chloride or magnesium thiosulfate.

One, two or all three reactions A, B and C can be carried out in the presence of the magnesium salt MS1.

Preferably, if M1 and M2, independently of each other, are selected from the group consisting of H ⁺ , Li ⁺ Na ⁺ , K ⁺ , Ca ²⁺ Mg ²⁺ , N-methyl-N, N-diethanolammonium, N, N-dimethyl- N-ethanolammonium, triethanolammonium, triisopropanoammonium and mixtures thereof; more preferably, if M1 and M2, independently from each other, are selected from the group consisting of H ⁺ , Na ⁺ K ⁺ and Mg ²⁺ , even more preferably, if M1 and M2, independently from each other, are selected from the group consisting of Na ⁺ , K ⁺ and Mg ²⁺ .

Each reaction A, B and C is preferably carried out in water or in a mixture of water and a non-aqueous organic solvent. The compound of formula (11) is preferably suspended in water or the compound of formula (11) is dissolved in a solvent.

A preferred solvent is acetone.

The compound of formula (11) is preferably used as a suspension in water.

Each compound of formulas (10), (13) and (15) can be used with or without dilution, in case of dilution, the compounds of formulas (10), (13) or (15) are preferably used in the form of an aqueous solution or suspension.

The compound of formula (10) is preferably reacted in a 0-10% (mol) excess with respect to the compound of formula (11). One molar equivalent of a compound of formula (13) is reacted with two molar equivalents of a compound of formula (12), preferably in a 0-10% mol% excess with respect to a compound of formula (12). Two equivalents of the compound of formula (15) are reacted with one molar equivalent of the compound of formula (14). The compound of formula (15) is preferably reacted in a 0-30% (mol) excess with respect to the compound of formula (14).

Any reaction A, B and C is preferably carried out at atmospheric pressure to 10 bar, more preferably at atmospheric pressure.

In reaction A, the reaction temperature is preferably from −10 to 20 ° C.

In reaction B, the reaction temperature is preferably from 20 to 60 ° C.

In reaction C, the reaction temperature is preferably from 60 to 102 ° C.

Reaction A is preferably carried out under acidic or neutral pH conditions, more preferably at a pH of 2 to 7.

Reaction B is preferably carried out under conditions of slightly acidic to slightly alkaline, more preferably at a pH of from 4 to 8.

Reaction C is preferably carried out under conditions of slightly acid to alkaline, more preferably at a pH of from 5 to 11.

In each of the reactions A, B and C, the pH is usually adjusted by adding a suitable base, and the choice of base is usually dictated by the desired composition of the products. Preferred bases are selected from the group consisting of aliphatic tertiary amines and hydroxides, carbonates and bicarbonates of alkali and / or alkaline earth metals and mixtures thereof. Preferred alkali and alkaline earth metals are selected from the group consisting of lithium, sodium, potassium, calcium, magnesium. Preferred aliphatic tertiary amines are N-methyl-N, N-diethanolamine, N-dimethyl-N-ethanolamine, triethanolamine and triisopropanolamine. When a combination of two or more different bases is used, the bases can be added in any order or simultaneously. More preferably, a basic magnesium salt is used to adjust the pH. The basic magnesium salt is preferably selected from the group consisting of magnesium hydroxide, magnesium carbonate, magnesium hydrogen carbonate and mixtures thereof; more preferably, the basic magnesium salt is magnesium hydroxide.

Preferably, when the basic magnesium salt is used to adjust the pH in one of reactions A and / or B, then in subsequent reactions B and C or in subsequent reaction C, respectively, the base for regulation is also a basic magnesium salt, more preferably, when it the same basic magnesium salt that was first used in reaction A and / or B. When it is necessary to adjust the pH of the reaction with an acid, the preferred acids are selected from the group consisting of hydrochloric acid, sulfuric acid, formic acid and acetic acid.

Solutions containing one or more compounds of the general formula (1) may optionally be desalted by filtration through a membrane.

The membrane filtration method is preferably ultrafiltration. Thin film membranes are preferably used. The membrane is preferably made from polysulfone, polyvinylidene fluoride or cellulose acetate.

The next object of the invention is a method for producing a compound of formula (1), characterized by mixing a compound of formula (20) with component b), which is a magnesium salt of MS2, in an aqueous medium;

Where

R ₁ , R ₂ , R ₃ and R _{4 are} defined as described above, also in all their preferred embodiments of the invention;

and where

T balances the anionic charge and denotes the desired stoichiometric equivalent of a cation selected from the group consisting of H ⁺ cations of an alkali metal, ammonium, mono-C ₁ -C ₄ -alkyl-di-C ₂ -C ₃ -hydroxyalkylammonium, di-C ₁ - C ₄ -alkyl-topo-C ₂ -C ₃ hydroxyalkylammonium, ammonium, which is mono-, di or trisubstituted with a C ₂ -C ₃ hydroxyalkyl radical, and mixtures thereof.

Mixing is preferably carried out in an aqueous solution.

Preferably, T balances the anionic charge and denotes a cation selected from the group consisting of H ⁺ , Na ⁺ , K ⁺ , ammonium, N-methyl-N, N-diethanolammonium, N, N-dimethyl-N-ethanolammonium, triethanolammonium, triisopropanolammonium and mixtures thereof.

Compounds of formula (21) and (22) are specific examples of compounds of formula (20), but the invention is not limited to these specific examples.

The MS2 magnesium salt is selected from the group consisting of magnesium acetate, magnesium bromide, magnesium chloride, magnesium formate, magnesium iodide, magnesium nitrate, magnesium sulfate and magnesium thiosulfate.

The mixing temperature is preferably from 0 to 100 ° C.

Mixing is preferably carried out at atmospheric pressure.

Preferably, the magnesium salt is magnesium chloride, magnesium sulfate, or magnesium thiosulfate. The most preferred magnesium salt is magnesium chloride or thiosulfate.

The mixing time is preferably from 5 seconds to 24 hours.

Preferably, in addition to water, additional organic solvents may be present, more preferably, the organic solvents are selected from the group consisting of C ₁ -C ₄ alcohols and acetone.

For mixing, the compound of formula (20) is preferably used in a concentration of from 0.01 g / l to 20 g / l.

Preferably, in an aqueous medium, 0.1-50, more preferably 0.1-45, even more preferably 0.1-40, mainly 0.1-15, mainly 0, 15-10 parts of component (b).

A further object of the invention is the use of a compound of formula (20) for the preparation of a compound of formula (1).

A further object of the invention is the use of a compound of formula (1) in sizing compositions for bleaching paper, preferably in a size press. The sizing composition is preferably an aqueous composition.

For processing paper in a size press, sizing compositions containing 0.2-30, preferably 1-15 grams of the compound of formula (1) per liter can be used.

The sizing composition also contains one or more binders, preferably 1, 2, 3, 4 or 5 binders, more preferably 1, 2 or 3, even more preferably 1 or 2 binders.

The sizing composition preferably contains a binder in a concentration of preferably 2-15% by weight, based on the total weight of the sizing composition. Typically, the pH is in the range of 5-9, preferably 6-8.

The binder is preferably selected from the group consisting of starch, gelatin, alkali metal alginates, casein, coarse glue, protein, cellulose derivatives, e.g. and mixtures thereof. More preferably, the binder is starch, polyvinyl alcohol, carbomethyl cellulose, or mixtures thereof.

An even more preferred binder or adhesive is starch. More preferably, the starch is selected from the group consisting of natural starch, enzyme modified starch, and chemically modified starch. Modified starches are preferably oxidized starch, hydroxyethylated starch or acetylated starch. Natural starch is preferably anionic starch, cationic starch or amphoteric starch. Although the source of starch can be any, the preferred sources of starch are corn, wheat, potatoes, rice, tapioca or sago. Polyvinyl alcohol and / or carboxymethyl cellulose are preferably used as the second binder. In addition to the compound of formula (1), a binder, and usually water, the sizing composition may contain by-products formed during the preparation of the compound of formula (1) as well as other conventional paper additives. Examples of such additives are antifreezes, biocides, antifoam agents, paraffin emulsions, colorants, inorganic salts, solubilizers, crosslinking agents, pigments, special resins, and the like. and mixtures thereof.

The next object of the invention is a method of optical paper bleaching, comprising the steps of

a) applying a composition for sizing containing a compound of formula (1) on paper,

b) drying the processed paper.

Defoamers, paraffin emulsions, dyes and / or pigments and inorganic salts are preferably added to the sizing composition.

The implementation of the invention

Examples

The cation content is determined by capillary electrophoresis.

The following examples explain in more detail the invention currently being considered, without limiting the claimed scope of the invention. Unless otherwise indicated, the terms “%” and “parts” are intended to mean the bulk “%” and “parts”.

Example 1

Sizing compositions are prepared by adding an optical brightener of formula (21) in such an amount as to achieve final concentrations of optical brightener in the range from 2.5 to 12.5 g / l to a stirred aqueous solution of magnesium chloride (final concentration is 8 g / l) and anionic oxidized potato starch (Perfectarnyl A4692 from AVEBE B.A.) (final concentration of 50 g / l) at 60 ° C.

The sizing solution was allowed to cool, then poured onto the moving rollers of the laboratory size press and applied to a commercial size 75 g / m ² AKD (alkyl ketene dimer), a bleached sheet of base paper, glued. The treated paper is dried for 5 minutes at 70 ° C. in a flat-plate dryer. The dried paper was conditioned, then CIE whiteness was measured on a calibrated Eirepho spectrophotometer.

The example is repeated in the absence of magnesium chloride, i.e. in the presence of only sodium salt of optical brightener, and replacing magnesium chloride with an equivalent amount of calcium chloride.

The results are summarized in table 1 and convincingly demonstrate the advantages of using magnesium chloride compared with the use of calcium chloride and the use of only sodium salt of optical brightener to achieve high degrees of whiteness.

The non-obvious nature of the present invention is further illustrated by the evidence that chloride ions of other Group II metals, such as calcium chloride, even have a negative effect on the whitening effect of optical brightener.

Table 1 The compound of formula (21) (g / l) Magnesium Chloride (g / l) Calcium Chloride (g / l) CIE White 0 0 0 104.6 0 8 0 104.7 0 0 8 104.8 2,5 0 0 122.3 2,5 8 0 126.7 2,5 0 8 123,4 5,0 0 0 128.3 5,0 8 0 133.1 5,0 0 8 128.0 7.5 0 0 129.8 7.5 8 0 133.7 7.5 0 8 128.6 10.0 0 0 131.1 10.0 8 0 134.5 10.0 0 8 128.2 12.5 0 0 130.6 12.5 8 0 134.2 12.5 0 8 127.3

Example 2

Sizing solutions are prepared by adding an optical brightener of formula (22) in such an amount as to achieve final concentrations of optical brightener in the range from 2.0 to 10.0 g / l to a stirred aqueous solution of magnesium chloride (final concentration is 8 g / l ) and anionic oxidized potato starch (Perfectamyi A4692 from AVEBE B.A.) (final concentration is 50 g / l) at 60 ° C.

The sizing solution was allowed to cool, then poured onto the moving rollers of the laboratory size press and applied to a commercial size 75 g / m ² AKD (alkyl ketene dimer), a bleached sheet of base paper, glued. The treated paper is dried for 5 minutes at 70 ° C. in a flat-plate dryer. The dried paper was conditioned, then CIE whiteness was measured on a calibrated Eirepho spectrophotometer.

The example is repeated, and in the absence of magnesium chloride, i.e. in the presence of only sodium salt of optical brightener, and replacing magnesium chloride with an equivalent amount of calcium chloride.

The results are summarized in table 2 and convincingly demonstrate the advantages of using magnesium chloride to achieve high degrees of whiteness in comparison with the use of optical brightener only in the form of sodium salt.

table 2 The compound of formula (22) (g / l) Magnesium Chloride (g / l) Calcium Chloride (g / l) CIE White 0 0 0 104.6 0 8 0 104.7 0 0 8 104.8 2.0 0 0 119.2 2.0 8 0 122.5 2.0 0 8 121.5 4.0 0 0 127.2 4.0 8 0 131.1 4.0 0 8 127.9 6.0 0 0 131.1 6.0 8 0 135.4 6.0 0 8 131.6 8.0 0 0 133.7 8.0 8 0 138.1 8.0 0 8 133.5 10.0 0 0 136.0 10.0 8 0 139.7 10.0 0 8 134.7

Example 3

Sizing compositions are prepared by adding an optical brightener of formula (22) in such an amount as to achieve final concentrations of optical brightener in the range from 0 to 12.5 g / l, to stirred aqueous solutions of magnesium chloride (final concentration is 6, 25 and 12, 5 g / l) and anionic oxidized corn starch (Penford Starch 260) (final concentration 50 g / l) at 60 ° C.

Each sizing solution was allowed to cool, then poured onto moving rollers of a laboratory size press and applied to a commercial size 75 g / m ² AKD (alkyl ketene dimer), a bleached sheet of base paper, glued. The treated paper is dried for 5 minutes at 70 ° C. in a flat-plate dryer. The dried paper is brought to a condition, then the CIE whiteness is measured on a calibrated Auto Eirepho spectrophotometer.

The results are shown in table 3.

Example 4

Sizing compositions are prepared by adding an optical brightener of the formula (22) in such an amount as to achieve final concentrations of optical brightener in the range from 0 to 12.5 g / l to stirred aqueous solutions of magnesium thiosulfate hexahydrate (final concentration is 10 and 20 g / l) and anionic oxidized corn starch (final concentration is 50 g / l) (Penford Starch 260) at 60 ° C. The sizing solution was allowed to cool, then poured onto the moving rollers of the laboratory size press and applied to a commercial size 75 g / m ² AKD (alkyl ketene dimer), a bleached sheet of base paper, glued. The treated paper is dried for 5 minutes at 70 ° C. in a flat-plate dryer. The dried paper was conditioned, then CIE whiteness was measured on a calibrated Eirepho spectrophotometer.

The results are shown in table 3.

Table 3 CIE White The compound of formula (22) (g / l) There is no Mg salt, i.e. only Na salt Magnesium Salt Added Magnesium Chloride (g / l) (Example 3) Magnesium thiosulfate hexahydrate (g / l) (example 4) 6.25 12.5 10.0 20,0 0 102.8 102.9 103.5 102,2 102.7 2,5 119.6 122,4 125.5 125.1 123.6 5,0 128.9 131.1 132.5 132.9 132.7 7.5 135.1 136.3 137.9 137.7 137.9 10.0 139.2 140.9 141.4 141.1 141.0 12.5 141.1 142.3 142.8 142.4 142.4

The results convincingly demonstrate the benefits of using magnesium chloride or magnesium thiosulfate to achieve high degrees of whiteness compared to using optical brightener only in the form of sodium salt.

Example 5

Aniline-2.5 disulfonic acid monosodium salt (115.6 parts) is added to 74.5 parts of cyanuric acid chloride in 400 parts of ice and 300 parts of water.

The reaction mixture was maintained at a pH of about 4-5 by dropwise adding a 30% aqueous NaOH solution, while at the same time, the temperature was kept below 10 ° C using an ice / water bath. After completion of the reaction, the temperature was gradually raised to 30 ° C. using an external heating system, and 74.1 parts of 4,4′-diaminostilbene-2,2′-disulfonic acid were added. The resulting mixture was heated to 50-60 ° C, maintaining a pH of approximately 5-7 by adding dropwise 30% aqueous NaOH solution until the reaction was completed. Then 63.8 parts of aspartic acid are added, then 89.8 parts of magnesium hydroxide are added and the resulting suspension is heated at 90-95 ° C. until the reaction is complete. The temperature is gradually reduced to room temperature and insoluble matters are filtered off. The final concentration is adjusted to 0.125 mol of the compound of formula (3) per kg of solution, for this purpose either water is added or water is removed by distillation. In this case, M consists of a mixture of sodium and magnesium cations.

Example 6

Aniline-2.5 disulfonic acid monosodium salt (115.6 parts) is added to 74.5 parts of cyanuric acid chloride in 400 parts of ice and 300 parts of water. 26.8 parts of magnesium hydroxide are added while maintaining the temperature at 10 ° C. with an ice / water bath. After completion of the reaction, the temperature is gradually increased to 30 ° C using an external heating system. 25.7 parts of magnesium hydroxide are added, then 74.1 parts of 4,4'-diaminostilbene-2,2'-disulfonic acid are added. The resulting mixture is heated to 50-60 ° C until completion of the reaction. Then 63.8 parts of aspartic acid and 100 parts of water are added, then 89.8 parts of magnesium hydroxyl are added, and the resulting suspension is heated at 90-95 ° C. until completion of the reaction. The temperature is gradually reduced to room temperature and insoluble matters are filtered off. The final concentration was adjusted to 0.125 mol of the compound of formula (3) per kg of solution using UV spectroscopy. In this case, M consists of a mixture of sodium and magnesium cations.

Reference Example 7

A comparative solution 7 for optical whitening is prepared by dissolving a compound of formula (22) in water to a final concentration of 0.125 mol / kg.

Example 8

Sizing compositions are prepared by adding an aqueous solution of optical brightener obtained according to example 5 in such an amount as to achieve final concentrations of optical brightener in the range from 0 to 80 g / l in an aqueous solution obtained according to the procedure of example 5 to a stirred aqueous solution of anionic oxidized potato starch (Perfectamyi A4692 from AVEBE B.A.) (final concentration of 50 g / l) at 60 ° C. Each sizing solution was allowed to cool, then poured onto moving rollers of a laboratory size press and applied to a commercial size 75 g / m ² AKD (alkyl ketene dimer), a bleached sheet of base paper, glued. The treated paper is dried for 5 minutes at 70 ° C. in a flat-plate dryer.

The dried paper is brought to a condition, then the CIE whiteness is measured on a calibrated Auto Eirepho spectrophotometer.

The results are shown in table 4.

Example 9

Sizing compositions are prepared by adding an aqueous solution of optical brightener obtained according to the procedure of Example 6 in such an amount as to achieve final concentrations of optical brightener in the range from 0 to 80 g / l in the aqueous solution obtained according to the method of Example 6 to a stirred aqueous solution anionic oxidized potato starch (Perfectamyi A4692 from AVEBE B.A.) (final concentration of 50 g / l) at 60 ° C. Each sizing solution was allowed to cool, then poured onto moving rollers of a laboratory size press and applied to a commercial size 75 g / m ² AKD (alkyl ketene dimer), a bleached sheet of base paper, glued. The treated paper is dried for 5 minutes at 70 ° C. in a flat-plate dryer.

The dried paper is brought to a condition, then the CIE whiteness is measured on a calibrated Auto Eirepho spectrophotometer.

The results are shown in table 4.

Reference Example 10

Sizing compositions are prepared by adding an aqueous solution of optical brightener obtained according to the procedure of Example 7 in such an amount as to achieve final concentrations of optical brightener in the range from 0 to 80 g / l in the aqueous solution obtained according to the method of Example 7 to a stirred aqueous solution anionic oxidized potato starch (Perfectamyi A4692 from AVEBE B.A.) (final concentration of 50 g / l) at 60 ° C. Each sizing solution was allowed to cool, then poured onto moving rollers of a laboratory size press and applied to a commercial size 75 g / m ² AKD (alkyl ketene dimer), a bleached sheet of base paper, glued. The treated paper is dried for 5 minutes at 70 ° C. in a flat-plate dryer.

The dried paper is brought to a condition, then the CIE whiteness is measured on a calibrated Auto Eirepho spectrophotometer.

The results are shown in table 4.

Table 4 C1E whiteness The concentration of the solution for optical whitening (g / l) Example 8 Example 9 Reference Example 10 0 101.5 101.5 101.5 10 119.5 119.6 119.2 twenty 127.4 128.4 126.7 40 133.6 135.0 132.6 60 137.1 138.6 135.8 80 138.2 140.2 136.8

The results convincingly demonstrate the advantage of using a mixed salt of optical brightener containing a magnesium cation.

Claims (8)

1. The compound of formula (1)

where R ₁ denotes hydrogen or $${\text{SO}}_{\text{3}}^{-}$$

,
R ₂ is hydrogen or $${\text{SO}}_{\text{3}}^{-}$$

,
R ₃ is hydrogen or $${\text{CH}}_{\text{2}}{\text{CO}}_{\text{2}}^{-}$$

,
R ₄ is $${\text{CH}}_{\text{2}}{\text{CO}}_{\text{2}}^{-}$$

, $$\text{CH}\left({\text{CO}}_{\text{2}}^{\text{-}}\right){\text{CH}}_{\text{2}}{\text{CO}}_{\text{2}}^{-}$$

or $$\text{CH}\left({\text{CO}}_{\text{2}}^{\text{-}}\right){\text{CH}}_{\text{2}}{\text{CH}}_{\text{2}}{\text{CO}}_{\text{2}}^{-}$$

, and where
M denotes the stoichiometric cationic equivalent required to balance the anionic charge in the formula (1) and is a combination of Mg ²⁺ together with at least 1, preferably 1, 2, 3, 4, 5 or 6, more preferably 1, 2 or 3 , even more preferably 1 or 2, additional cations, the additional cations selected from the group consisting of H ⁺ , an alkali metal cation, an alkaline earth metal cation other than Mg ²⁺ , ammonium, mono-C ₁ -C ₄ -alkyl di -C ₂ -C ₃ -hydroxyalkylammonium, di-C ₁ -C ₄ -alkyl-mono-C ₂ -C ₃ -hydroxyalkyl Lammonium, ammonium, which is mono-, di- or trisubstituted with a C ₂ -C ₃ hydroxyalkyl radical, and mixtures thereof. 2. The method of obtaining the compounds of formula (1), as defined in claim 1, characterized by reaction A, followed by reaction B, followed by reaction C,
where in reaction A, a compound of formula (10) is reacted with a compound of formula (11) to obtain a compound of formula (12)

in reaction B, a compound of formula (12) is reacted with a compound of formula (13) to give a compound of formula (14)

and in reaction C, a compound of formula (14) is reacted with a compound of formula (15) to give a compound of formula (1)

where R ₁ , R ₂ , R ₃ and R _{4 are} defined in claim 1;
M1 are the same or different in formulas (13) and (14), and M1 is the stoichiometric cationic equivalent required to balance the anionic charge in these formulas, and is at least 1 cation selected from the group consisting of H ⁺ , alkali metal cation, alkaline earth metal cation other than Mg ²⁺ , ammonium, mono-C ₁ -C ₄ -alkyl-di-C ₂ -C ₃ -hydroxyalkylammonium, di-C ₁ -C ₄ -alkyl-mono-C ₂ -C ₃ -hydroxyalkylammonium, ammonium, which is mono-, di- or trisubstituted by a C ₂ -C ₃ hydroxyalkyl radical, and mixtures thereof.
M2 independently of one another can be the same or different in formulas (10) and (12), and M2 is the stoichiometric cationic equivalent required to balance the anionic charge in these formulas in the case when either R ₁ or R ₂ , or as R ₁ and R ₂ are SO ₃ , and is defined as M1,
with the proviso that at least one of reactions A, B or C is carried out in the presence of a CAT cation, wherein the CAT cation is Mg ²⁺ . 3. A method of obtaining a compound of formula (1) as defined in claim 1, characterized in mixing a compound of formula (20) with component b), which is a magnesium salt of MS2, in an aqueous medium,

where R ₁ , R ₂ , R ₃ and R _{4 are} defined in claim 1;
T balances the anionic charge and denotes the desired stoichiometric equivalent of a cation selected from the group consisting of H ⁺ , an alkali metal cation, ammonium, mono-C ₁ -C ₄ -alkyl-di-C ₂ -C ₃ -hydroxyalkylammonium, di-C ₁ -C ₄ -alkyl-mono-C ₂ -C ₃ -hydroxyalkylammonium, ammonium, which is mono-, di- or trisubstituted by a C ₂ -C ₃ hydroxyalkyl radical, and mixtures thereof. 4. The method according to claim 3, where the MS2 magnesium salt is selected from the group consisting of magnesium acetate, magnesium bromide, magnesium chloride, magnesium formate, magnesium iodide, magnesium nitrate, magnesium sulfate and magnesium thiosulfate. 5. The method according to claim 3 or 4, where the mixing is carried out in an aqueous solution. 6. The use of the compounds of formula (20) as defined in claim 3 to obtain the compounds of formula (1) as defined in claim 1. 7. The use of the compounds of formula (1) as defined in claim 1 in the sizing compositions for bleaching paper. 8. The method of optical paper whitening, comprising stages
a) applying a composition for sizing containing a compound of formula (1) according to claim 1, on paper,
b) drying the processed paper.