The present invention relates to novel hydrated compounds of the tertiary alkanolamine salts of a specific compound based on 4,4'-di- triazinylamino-2,2'-disulphostilbene, characterised by their hydration water content, their crystalline forms, the preparation process of the novel hydrates, and the use of the novel hydrates for the preparation of concentrated aqueous formulations thereof.

Prior art

The use of whitening agents to impart a higher degree of whiteness to products like paper, cardboard, fabrics and non-woven fabrics is well known. The whitening agents most commonly used in the paper and cardboard industry are derivatives of 4,4'-bis-[l ,3,5-triazinyl]-diaminostilbene-2,2'- disulphonic acid, substituted at the triazine ring with anilino and alkanolamino groups. The anilino groups can in turn contain other sulphonic groups, but as they increase the water solubility of the corresponding molecules, they reduce the affinity of said molecules for the cellulose fibres constituting paper, leading to lower performance in terms of whiteness.

For reasons of ease of processing, the industry requires said whitening agents to be supplied in the fluid liquid forms of an aqueous dispersion or, much more preferably, of aqueous solutions which are stable for at least a few months at temperatures ranging from 5 to 40°C.

As the stilbene whitening agents deriving from 4,4'-bis-[l ,3,5- triazinyl]-diaminostilbene-2,2'-disulphonic acid substituted at the triazine ring with anilino groups and alkanolamino groups which are preferred by this industry are not readily water-soluble, the production of the corresponding concentrated, stable aqueous solutions used to require the addition of significant amounts (up to 30% and over) of solubilising additives such as urea, caprolactam, ethylene glycol and polyglycols.

However, the solubilisers added do not have great affinity for cellulose, and do not contribute significantly to the performance of the product, so that at the end of the paper manufacturing process, they constitute undesirable pollutants. For example, in case of using whitening agents in solution formulated with urea, a high additional pollutant content based on nitrogenous by-products and ammonia are present in the process liquid effluents.

A further problem derives from the inevitable presence in the whitening agent solutions of inorganic chlorides such as sodium chloride, which derive from the whitening agent synthesis processes. In fact, all industrial processes for the production of stilbene whitening agents substituted with triazine involve the use of cyanuryl chloride as reagent, whose reaction in successive steps with the various necessary amino products unavoidably gives rise to large amounts of inorganic chlorides which are difficult to remove.

As the residual inorganic chlorides generate instability in the concentrated aqueous solutions of whitening agents, it has so far been essential to reduce their content significantly, inevitably using expensive osmotic separation techniques to obtain aqueous solutions which are stable over time.

US 3012971 discloses paper whitening compositions consisting of concentrated aqueous solutions of 4,4'-bis-[2-phenylamino-4-diethanolamino- l ,3,5-triazinyl]-diaminostilbene-2,2'-disulphonic acid or a salt thereof mixed with alkanolamines, wherein the weight ratio of the alkanolamines to the whitening agents ranges from 0.5: 1 to 3.0: 1. As the molecular weight of alkanolamines is much lower than that of the whitening agents, said interval reflects a great excess of alkanolamine over the whitening agent. However, such large amounts of alkanolamines, compared with the whitening power of the composition, are unacceptable from the ecological standpoint. WO2005/028749 describes aqueous compositions comprising stilbene whitening agents and alkanolamines. Said document does not describe any example of a composition containing a tertiary alkanolamine. Moreover, the problem of the effect of inorganic chlorides on the stability of the solution is not mentioned.

US2010/0159763 discloses aqueous compositions of fluorescent whitening agents, substituted at the triazine rings with propionamide amino groups, having the following formula:

[M ⁺ ] ₂ wherein at least 25% of the [M ] ions associated with the sulphone group are substituted with (CH ₃ ) ₂ NH ⁺ CH ₂ CH ₂ OH ions. However, it is necessary to reduce the inorganic salt content in said compositions with suitable osmosis processes to guarantee the stability of the formulation.

IT 1356016 discloses a fluorescent paper whitening method using substantially aqueous suspensions of the compound with the following formula:

wherein M and Mi represent hydrogen, an alkali metal, an alkaline earth metal or ammonium.

US 6153122 discloses novel hydrated compounds of M and M _t = alkali metals, alkaline earth metals or ammonium, having the following formula:

and able to produce concentrated, stable aqueous suspensions. Said compounds are unable to produce concentrated, stable aqueous solutions.

Description of the invention

Surprisingly, we have found novel hydrated compounds of the tertiary alkanolamine salts of formula (I):

(I)

wherein is hydrogen or the -CH ₂ CH ₂ OH group, X is an -HN ⁺ RiR ₂ R ₃ group wherein R R ₂ and R ₃ are selected from the group consisting of straight or branched Ci-C ₆ alkyl groups, C ₃ -C ₆ cycloalkyl groups, straight or branched Ci-C ₆ hydroxyalkyl groups and C ₃ -C ₆ hydroxycycloalkyl groups, and wherein at least one of R _{l 5} R ₂ and R ₃ is a straight or branched Ci-C ₆ hydroxyalkyl group, and the number of moles of hydration water n is an integer from 1 to 80.

The compounds of the invention are able to produce concentrated, stable aqueous solutions useful to improve the whiteness of a high number of substrates, including textiles and paper. They can also be easily formulated in detergents so that they impart an improved degree of whiteness to the products washed.

The solutions obtainable are stable even in the presence of significant amounts of salts, especially sodium chloride. Said solutions are stable regardless of the presence of specific stabilisers or solubilisers.

This property allows the manufacturing process to be simplified by eliminating the final steps of purification of the whitening agent from salts, such as osmosis.

The hydrates according to the present invention comprise the compounds of formula (I):

(I)

wherein R is hydrogen or the -CH ₂ CH ₂ OH group, X is an -HN ⁺ RiR ₂ R ₃ group wherein R R ₂ and R ₃ are selected from the group consisting of straight or branched Ci-C ₆ alkyl groups, C ₃ -C ₆ cycloalkyl groups, straight or branched Ci-C ₆ hydroxyalkyl groups and C ₃ -C ₆ hydroxycycloalkyl groups, and wherein at least one of R _{l 5} R ₂ and R ₃ is a straight or branched Ci-C ₆ hydroxyalkyl group, and the number of moles of hydration water n is an integer from 1 to 80.

The compounds of formula (I) are preferably those wherein R is a -CH ₂ CH ₂ OH group.

The compounds of formula (I) are preferably hydrates of salts with 2-(dimethylamino)ethanol wherein X is HN ⁺ (CH ₃ ) ₂ (CH ₂ CH ₂ OH).

n is preferably an integer from 10 to 70, more preferably from 15 to 65. Most preferably, the compounds of formula (I) are hydrates represented by the compounds of formula (II):

(II)

wherein X is HN ⁺ (CH ₃ ) ₂ (CH ₂ CH ₂ OH) and n ranges from 15 to 80.

For these compounds, stability in aqueous solution is observed at temperatures up to 40°C and in the presence of large amounts of sodium chloride, for example amounting to about 1% by weight of the total weight of the solution.

The compounds of the present invention can be prepared by reacting cyanuryl chloride with 4,4'-diamino stilbene disulphonic acid and aniline in succession in an aqueous medium, optionally combined with polar solvents such as acetone and/or methyl ethyl ketone, to obtain a compound of formula (III):

(III)

The compound of formula (III) is then reacted with at least 2 moles of diethanolamine or monoethanolamine, adjusting the pH between 9 and 12 with a suitable amount of bases such as sodium or potassium hydroxide, bicarbonate or carbonate. The reaction mixture is heterogeneous, and when heated separates the sodium or potassium salt of the fluorescent whitening agent which is treated with a solution of strong acid, preferably hydrochloric or sulphuric acid, in an at least stoichiometric amount to the sulphonic groups present. The result is the acid form of the fluorescent whitening agent.

This is then reacted with at least a stoichiometric amount of tertiary alkanolamine, preferably 2-(dimethylamino)ethanol, in the presence of water, to obtain the hydrated salts of the present invention by neutralisation.

The temperatures of said processes range from -20°C to 100°C and the pressures from 0 to 10 bars, more preferably from 0 to 3 bars.

In a further aspect, the invention relates to a concentrated aqueous solution of the hydrates of the present invention, comprising:

- 5 to 95% by weight of at least one compound of formula (I) as defined in claim 1 , or mixtures thereof;

- 5 to 95% by weight of water; and

- 0 to 1% by weight of additives.

The aqueous solution of the hydrates of the invention can also include a tertiary alkanolamine excess compared with the fluorescent whitening agent of formula (I). It is stable for a long time even in the absence of stabilising agents, and also in the presence of inorganic chlorides deriving from the manufacturing process of the stabilising agent.

However, the aqueous solutions of the hydrates of the invention can also include further ingredients such as further whitening agents, inorganic salts, surfactants, preservatives, solubilising agents or organic solvents.

Examples of optical whitening agents are optical tetra- and/or hexasulphonated stilbene brighteners.

Examples of inorganic salts are sodium chloride, sodium sulphate, ammonium chloride and potassium chloride.

Examples of surfactants are sodium polynaphthalene sulphonates and ethoxylated fatty alcohols.

Examples of preservatives are glutaraldehyde, isothiazolinones and 2-bromo-2-nitropropano- 1 ,3-diol.

Examples of solubilising agents are polyethylene glycols, urea and caprolactam.

Examples of organic solvents are ethylene and propylene glycols.

The solutions containing the hydrates of the invention are obtained by dissolving the fluorescent agent of formula (I) and preferably the compound of formula (II) in water or a mixture of water and another solvent miscible with water, optionally subjecting the solution to heating and stirring.

The solutions of the hydrates of the invention can be used to whiten natural, semisynthetic or synthetic fibres or paper.

The solutions containing the hydrates of the invention are particularly effective in pulp slurry or mass treatment and surface treatment of paper and cardboard (size press and coating).

The hydrates of the invention can also be used in the formulation of detergents able to improve the whiteness of textiles and other products.

The invention will be illustrated by reference to the following examples. The number of moles of hydration water "n" in formulae (I) and (II) of the compounds of the invention was determined by subtracting the value of the water content that freezes, obtainable with differential scanning calorimetry measurements, from the value of the total water content, obtainable by calculating the weight difference after drying, or by the Karl Fischer method.

The specific extinction El l of the hydrated compounds of the invention and the solutions thereof were determined with a UV-VIS Perkin-Elmer Lambda 35 spectrophotometer in 1 cm cells.

The CIE whiteness (D65/10 ⁰ ) of products treated with the hydrates of the invention was determined with an Elrepho LWE450-X Datacolor reflectometer according to standard ISO 1 1475.

Example 1

62.8 g of 4,4'-bis-[2-phenylamino-4-diethanolamino- l ,3,5-triazinyl]- diaminostilbene-2,2'-disulphonic acid was dispersed in a solution of 20.5 g of dimethylaminoethanol (pH>8) in 325.2 g of water at 80-90°C.

The compound completely dissolved.

7 g of NaCl was added to the solution to cause phase separation.

The temperature was maintained at 80-85 °C under stirring until the solid was transformed into an oily organic phase.

Stirring was then stopped, the mixture was cooled to 10- 15°C, and the two phases were separated to obtain 170 g of a stable oil phase with El l amounting to 286.4, consisting of the hydrate corresponding to the compound of formula (II) with n = 24 (SAMPLE 1 A).

Demineralised water was added to the oil to give an El 1 of 1 16, and the mixture was clarified on clarcel to obtain a stable solution of hydrate of formula (II) with n = 46 (SAMPLE IB). Example 2

161.2 g of 4,4'-bis-[2-phenylamino-4-monoethanolamino-l ,3,5- triazinyl]-diaminostilbene-2,2'-disulphonic acid was dispersed in a solution of 51.5 g of dimethylaminoethanol (pH>8) in 754.8 g of water at 80-90°C.

The compound completely dissolved.

20 g of NaCl was added to the solution to cause phase separation.

The temperature was maintained at 80-85 °C under stirring until the solid was transformed to an oily organic phase.

Stirring was then stopped, the mixture was cooled to 10- 15°C, and the two phases were separated to obtain 320 g of oil with El 1 amounting to 299.2, consisting of the hydrate corresponding to the formula (I) wherein R=H and with n = 21 (SAMPLE 2 A).

Demineralised water was added to the oil to give an El 1 of 1 16, and the mixture was clarified on clarcel to obtain a stable hydrate of formula (I) with R=H and n = 35 (SAMPLE 2B).

Application tests

The aqueous solutions of the hydrates of examples 1 and 2 were evaluated applicatively on paper in pulp slurry, coating and size press and in a detergent, and compared with the results obtained with the same system in the absence of the compounds according to the present invention. In all cases the whiteness of the products obtained with the treatments in the presence of the hydrated compounds according to the present invention was much greater.

Application example of evaluation of the hydrated compounds in pulp slurry

A fibrous mixture was prepared according to the following recipe:

20% by weight of precipitated calcium carbonate (PCC) was added to 50% short-fibre bleached cellulose, with a dry fibre content of 3%, pH 6.8 and Schopper-Riegler refinement of 35°SR. The fibrous dispersion thus obtained was divided into 5 parts.

One portion was left as is (ie. unchanged for reference), while the other portions were mixed respectively with:

0.30% by weight of the dry matter of the fibre of sample 1A

0.90% by weight of the dry matter of the fibre of sample IB

0.30% by weight of the dry matter of the fibre of sample 2A

0.90% by weight of the dry matter of the fibre of sample 2B

These doses were calculated to give the same extinction value.

After 15 minutes' stirring, laboratory sheets were prepared with a Rapid-Koethen sheet former and dryer, on which the whiteness was tested.

The values obtained are set out in table 1 below:

Table 1

The application yield of the whitening agents is quantifiable as the increase in the whiteness of the paper compared with the reference whiteness.

Application example of evaluation of the hydrated compounds in a coating The coated specimens were obtained by applying an even layer of a coating prepared according to the following recipe to "Fabriano 2 smooth" paper with a weight of 1 10 g/m ² :

90 parts of calcium carbonate Hydrocarb 90 AV

10 parts of Hydrafine kaolin clay

10 parts of Acronal S728 synthetic binder

0.8 parts of Mowiol 4-98 polyvinyl alcohol Sodium hydroxide in solution (NaOH 10%) up to pH ~9

Demineralised water up to a final dry residue of 70%.

The coating thus prepared was divided into 5 parts: one portion was left as is (ie. unchanged for reference, with the dose of optical whitening agent =

0), while the other portions were mixed respectively with:

0.40% by weight of the dry matter of the formulation of sample 1 A 1.20% by weight of the dry matter of the formulation of sample IB 0.40% by weight of the dry matter of the formulation of sample 2A 1.20% by weight of the dry matter of the formulation of sample 2B These doses were calculated to give the same degree of extinction.

After 10 minutes' stirring, each sample was applied to the backing paper with a laboratory doctor blade; at the end of the application the specimens were dried at ambient temperature for one hour.

The CIE whiteness values (D65/10 ⁰ ) found on the samples coated in the laboratory are set out in table 2 below.

Table 2

Once again, the application yield of the whitening agents is quantifiable by the increase in the whiteness of the paper compared with the reference whiteness.

Application example of evaluation of the hvdrated compounds in a size press

A solution for surface treatment of paper in a size press, consisting of a C*Film 0731 1 corn starch paste with dry final residue of 5.0%, was divided into 3 parts:

one portion was left as is (ie. unchanged for reference, with the dose of optical whitening agent = 0), while the other portions were mixed respectively with:

1.5 grams of sample IB / litre of formulation

3.5 grams of sample 2B / litre of formulation.

After 5 minutes' stirring, each sample was applied to the "Fabriano 2 smooth 1 10 g/m ² " backing paper with a laboratory doctor blade; at the end of the application the specimens were dried at ambient temperature for one hour.

The CIE whiteness values (D65/10 ⁰ ) found on the laboratory samples are set out in table 3 below.

Table 3

Once again in this application an increase in the whiteness of the paper was visible compared with the reference whiteness.

Application example of evaluation of the hydrated compounds in a detergent

The sample of Example IB was formulated at the concentration of 0.52% (specific extinction 1 16) in a liquid detergent (heavy-duty liquid, table 4) designed for washing fabrics. Table 4: composition of heavy-duty liquid

The detergent formulation was evaluated for whitening power conducting repeated washes on two different types of standard fabric:

1) Empa 21 1 cotton fabric, bleached chemically and without fluorescent whitening agent

2) Empa 213 polyester/cotton fabric, in the ratio of 65/35, bleached chemically and without optical whitening agent.

Experimentally, the fabrics were repeatedly washed with the same formulation, assessing the degree of whitening power by reading the surface of the fabric on the colorimeter. The colorimeter reading was performed before washing and after 3 and 5 consecutive washes. Whitening power was expressed on the Berger scale.

As reference, the same fabrics were washed with the detergent described in table 4 to which the fluorescent stilbene whitening agent was not added, the formula being made up to 100% with water.

The experimental conditions are set out below. Washing machine Linitest

Hardness of water ± 20° (French)

Washing cycle 10 minutes

Number of washes (cycles) 5

Detergent concentration 5 g/L

Fabric/washing water weight 10: 1

ratio

Fabrics tested - Empa 21 1 cotton fabric, whitened chemically and without optical whitening agent

- Empa 213 polyester/cotton fabric in the ratio of 65/35, whitened chemically and without optical whitening agent.

Washing temperature 25°C

Drying conditions 1 minute at 90°C in a Benz Dryer

Measuring instrument Zeiss Elrepho 2000 colorimeter

Expression of whiteness Berger scale

The whiteness results are shown in table 5.

Table 5

Before

3rd wash 5th wash washing

Fabric Formulation (Berger (Berger

(Berger

degrees) degrees) degrees)

Fluorescent

whitening

80.93 122.50 132.69 agent,

example IB

EMPA 211

Without

fluorescent

80.93 81.10 79.69 whitening

agent

Fluorescent

whitening

78.40 1 1 1.23 1 19.63 agent,

example IB

EMPA 213

Without

fluorescent

78.40 78.25 76.40 whitening

agent