HK1124047B - Storage stable solutions of optical brighteners - Google Patents

Description

Storage-stable solutions of optical brighteners

The present invention relates to storage-stable solutions of diaminostilbene derivative-based optical brighteners without the need for additional dissolved additives.

It is now well known that the whiteness and thus the attractiveness of paper, board, textile and non-wovens can be improved by the addition of Optical Brighteners (OBAs). The most important optical brighteners in the paper and board industry are anilino-substituted bistriazinyl derivatives of 4, 4 '-diaminostilbene-2, 2' -disulphonic acid. The anilino-substituent may contain additional sulfonic acid groups that provide greater water solubility. Optical brighteners in which the anilino-substituent does not contain sulfonic acid groups have a particularly high affinity for cellulose fibres and are particularly suitable for use in the wet end of the paper-making process. For ease of handling and metering, the paper and board industry requires that the optical brighteners be provided in liquid form, preferably in the form of concentrated aqueous solutions. In addition, the liquid form must have prolonged storage stability over a wide temperature range (typically 4-50 ℃). In the past, to provide storage stability, solubilizing aids, such as urea or ethylene glycol, have been added in amounts up to 30% by weight. These cosolvents have no affinity for cellulose but contaminate the effluent of the paper mill. Thus, there is a need for anilino-substituted bistriazinyl derivatives of 4, 4 '-diaminostilbene-2, 2' -disulfonic acid which form stable, concentrated aqueous solutions without the addition of solubilizing auxiliaries.

GB 1,243,276 discloses bis-triazinyl derivatives of 4, 4 '-diaminostilbene-2, 2' -disulfonic acid containing at least one, preferably two, acrylamide group and their use as optical brighteners for paper. It discloses a preparation method and application of a compound of formula (A).

The compound was isolated as a solid and dissolved in water at a concentration of 0.1% prior to application to an aqueous suspension of cellulose fibers.

Compound (a) is also disclosed in GB 1,247,765.

Compound (a) is also a preferred component of the liquid laundry detergent compositions of EP 376,893 a 2. The inventor states that: "the optical brighteners of the invention are used in powder form or in the form of aqueous solutions. Such solutions contain the active substance in an amount of 18-75% by weight and preferably also a hydrotrope (hydrotropic) ".

No indication of any advantage of using a counterion over sodium is made in GB 1,243,276, GB 1,247,765 or EP 376,893 a 2.

WO 02/055646 attempts to solve the problem of forming stable, concentrated aqueous solutions of disulfonated optical brighteners by providing a mixture of two or more bis (triazinylamino) stilbene derivatives. Example 1 describes the preparation of a stable aqueous solution comprising 0.2844mol/kg of a fluorescent whitening agent in the form of an equimolar mixture of compounds (B) and (C), each in the form of a mixed sodium/triethanolammonium salt.

However, the storage stability also depends on the presence of additives-see page 10 of WO 02/055646, e.g. (Fi) -which are preferably used in solutions having a concentration of from 0.2 to 3% by weight. Preferred additives (Fi) are tert-alkyl alcohol amines, particularly preferably triisopropanolamine.

WO 2005/028749 a1 discloses optical brightener compositions comprising an alkanolamine and a bis (triazinylamino) stilbene derivative. Preferred alkanolamines are 2-amino-2-methyl-1-propanol, 1-amino-2-propanol or a mixture of 2-amino-2-methyl-1-propanol and 2- (N-methylamino) -2-methyl-1-propanol.

Japanese Kokai 62-273266 discloses optical brightener compositions comprising quaternary ammonium salts of anionic bis (triazinylamino) stilbene derivatives. The preferred quaternary ammonium ion is trimethyl- β -hydroxyethylammonium ion.

EP-A-884312 discloses hydrates of bis (triazinylamino) stilbene derivatives of formulｃA (D):

wherein M and M₁Independently represent hydrogen, an alkaline earth metal or ammonium. The hydrate is said to be lowThe amount of the component adjuvant gives a stable liquid suspension.

However, paper mills preferably use the optical brightener in solution, for example for ease of handling and metering. Thus. There is still a need to provide stable, concentrated aqueous solutions of disulfonated optical brighteners without solubilizing aids.

It has now surprisingly been found that specific salt forms of anilino-substituted bistriazinyl derivatives of 4, 4 '-diaminostilbene-2, 2' -disulphonic acid form stable concentrated solutions without the addition of dissolution auxiliaries.

Accordingly, the present invention provides a compound of formula (1)

Wherein

R is hydrogen or a methyl group,

R₁is hydrogen, alkyl having 1 to 4 carbon atoms, beta-hydroxyalkyl having 2 to 4 carbon atoms, beta-alkoxyalkyl having 3 or 4 carbon atoms or CH₂CH₂CONH₂，

R₂Is hydrogen or a methyl group, or a mixture thereof,

M⁺is Li⁺、Na⁺Or K⁺And an

n is less than or equal to 1.5.

Preference is given to compounds in which

R is hydrogen or a methyl group,

R₁is hydrogen, methyl, beta-hydroxyalkyl having 2 or 3 carbon atoms,

R₂is hydrogen or a methyl group, or a mixture thereof,

M⁺is Na⁺And an

n is less than or equal to 1.5.

More preferred are compounds wherein

R is a hydrogen atom or a hydrogen atom,

R₁is hydrogen, methyl or beta-hydroxyalkyl having 2 carbon atoms,

R₂is a hydrogen atom, and is,

M⁺is Na⁺And an

n is less than or equal to 1.5.

Particular preference is given to compounds in which

R is a hydrogen atom or a hydrogen atom,

R₁is-CH₂CH₂OH，

R₂Is a hydrogen atom, and is,

M⁺is Na⁺And an

n is less than or equal to 1.2.

The present invention also provides a process for preparing the above compound, characterized in that a compound of formula (2):

conversion to a mixed salt form (1) either by using 2-dimethylaminoethanol and a mineral acid (e.g. HCl or H)₂SO₄) Treating or sequentially treating with cation exchange resin and 2-dimethylaminoethanol to make at least 25% of M related to sulfonate groups⁺Ion quilt (CH)₃)₂NH⁺CH₂CH₂OH ion replacement. The compound of formula (1) is then optionally isolated and may be further separated from excess salts and alkanolamine by membrane filtration.

Preferred membrane filtration methods are ultrafiltration methods using, for example, polysulfone, polyvinylidene fluoride, cellulose acetate or membranes.

The present invention also provides aqueous solutions of one or more compounds of formula (1), which may optionally contain one or more carriers, anti-freeze agents, anti-foam agents, co-solvents, preservatives, complexing agents, etc., and organic by-products formed during the preparation of the optical brightener.

The carrier is known to provide improved whitening characteristics of pigmented coating whitener compositions and may be, for example, polyethylene glycol, polyvinyl alcohol, or carboxymethyl cellulose.

The antifreeze can be, for example, urea, diethylene glycol or triethylene glycol.

The co-solvent may be, for example, urea, triethanolamine, triisopropanolamine or 2-dimethylaminoethanol.

The compounds of formula (1) and their solutions are suitable as optical brighteners for the whiteness of textiles, paper, board and non-textiles. They are used in particular for whitening paper and board and are suitable, in particular in the form of a pigmented coating composition, for use in aqueous suspensions of pulp or on the surface of paper. They are characterized by high storage stability, yield and ease of application. They are also highly compatible with other additives conventionally used in the production of cellulosic articles, particularly paper and board.

Examples

The following examples shall demonstrate the invention in more detail. "parts" means "parts by weight" and "%" means "% by weight" if not otherwise specified. Membrane filtration was performed using G-series membrane ultrafiltration membranes supplied by GE Infrastructure Water & Process Technologies.

Example 1

At 60 ℃ 291 parts of an amine of the formula (3)

To a suspension of 824 parts of the compound of formula (4) in 7750 parts of water.

The mixture was heated to reflux and held for 4 hours while controlling the pH to 8.5-9.0 by adding sodium chloride in the form of a 30% aqueous solution. 44 parts of sodium hydroxide are added and the mixture is stirred at reflux for 10 minutes. The mixture was then cooled to 90 ℃ after which the stirring was stopped. After standing for 10 minutes, the less oily phase containing the compound of formula (a) (1990 parts) is separated from the aqueous phase containing the salts and added to 1570 parts of cold water at 80 ℃ with stirring. The resulting solution was then treated with 197 parts of a 2-dimethylaminoethanol solution in 350 parts of cold water and 197 parts of a 37% aqueous hydrochloric acid solution at 50 ℃. The mixture was stirred at 50 ℃ for 10 minutes and then cooled to 20 ℃. After standing for 1 hour, the less oily phase was separated and diluted with water to 5000 parts. Excess sodium chloride and alkanolamine were removed by membrane filtration of the aqueous solution, followed by removal of water by distillation to give 3520 parts of an aqueous solution containing 28% of the compound of formula (5).

The resulting aqueous solution is storage stable at 4 ℃ for at least 2 weeks with or without seed crystals.

Example 2

Display ratio (CH)₃)₃N⁺CH₂CH₂OH counter ion (Japanese Kokai 62-27326)Claimed in 6) advantageous comparative example

Proceed as in example 1 to the point where the oil (1990 parts) was first separated from the aqueous phase containing the salt. The oil was then poured into a stirred solution of 309 parts choline chloride in 2700 parts water. The aqueous solution was subjected to membrane filtration to remove excess salts, and then water was removed by distillation to give 3520 parts of an aqueous solution containing 28% of the compound of formula (6).

The resulting aqueous solution precipitated within 4 days of storage at 4 ℃ in the presence of seed crystals.

Example 3

Display ratio (CH)₃)₂C(NH₃ ⁺)CH₂Comparative example with OH counter ion (as claimed in WO 2005/028749A 1) Excellent

The procedure is as in example 1 to the point where the oil obtained from the first phase separation (1990 parts) is diluted with water (1570 parts). The resulting solution was then treated with 196 parts of a solution of 2-amino-2-methyl-1-propanol and 197 parts of an aqueous 37% hydrochloric acid solution in 350 parts of cold water at 50 ℃. The mixture was stirred at 50 ℃ for 10 minutes and then cooled to 20 ℃. After standing for 1 hour, the less oily phase was separated and diluted with water to 5000 parts. Excess sodium chloride and alkanolamine were removed by membrane filtration of the aqueous solution, followed by removal of water by distillation to give 3520 parts of an aqueous solution containing 28% of the compound of formula (7).

The resulting aqueous solution precipitated within 4 days of storage at 4 ℃ in the presence of seed crystals.

Example 4

Display ratio H₃N⁺CH₂CH₂Comparative example with superior OH counter ion

The procedure is as in example 1 to the point where the oil obtained from the first phase separation (1990 parts) is diluted with water (1570 parts). The resulting solution was then treated with 135 parts ethanolamine solution in 350 parts cold water and 197 parts 37% aqueous hydrochloric acid at 50 ℃. The mixture was stirred at 50 ℃ for 10 minutes and then cooled to 20 ℃. After standing for 1 hour, the less oily phase was separated and diluted with water to 5000 parts. Excess sodium chloride and alkanolamine were removed by membrane filtration of the aqueous solution, followed by removal of water by distillation to give 3520 parts of an aqueous solution containing 27% of the compound of formula (8).

The resulting aqueous solution precipitated within 1 day of storage at 4 ℃ in the presence of seed crystals.

Example 5

Display ratio Na⁺Comparative example superior in counterion

The procedure is as in example 1 to the point where the oil obtained from the first phase separation (1990 parts) is diluted with water (1570 parts). Excess sodium chloride was removed by membrane filtration of the aqueous solution at 50 ℃ and then water was removed by distillation to give 3520 parts of an aqueous solution containing 26% of the compound of formula (a).

The resulting aqueous solution precipitates upon cooling to room temperature.

Example 6

Proceed as in example 1 to the point where the oil (1990 parts) was first separated from the aqueous phase containing the salt. This oil is added to a solution of 171 parts of 37% aqueous hydrochloric acid and 150 parts of 2-dimethylaminoethanol in 1582 parts of cold water, with stirring at 80 ℃. The mixture was stirred for 10 minutes and then cooled to 20 ℃. After standing for 1 hour, the less oily phase was separated and diluted with water to 5000 parts. The aqueous solution was treated by membrane filtration to remove excess sodium chloride, and then concentrated by distillation. Then 7 parts of 2-dimethylaminoethanol as a cosolvent is added. The concentration was adjusted to give 3520 parts of an aqueous solution containing 28 parts of the compound of formula (9) and 0.2% 2-dimethylaminoethanol.

The resulting aqueous solution is storage stable at 4 ℃ for at least 2 weeks with or without seed crystals.

Application example 1

The product of preparation example 1, at a concentration ranging from 0.2 to 2% by weight of dry fibres, is added to 200 parts of a 2.5% aqueous suspension of a 50: 50 mixture of bleached spruce sulphite cellulose and bleached beech sulphite cellulose beaten to a humidity of 20 ° SR by a Schopper Riegler. The suspension is stirred for 5 minutes and then diluted to 1000 parts. The suspension is then drawn through a wire mesh screen to make a paper sheet. After pressing and drying, the whiteness of the paper is measured on a MinoltaCM-700d spectrophotometer.

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TABLE 1

Concentration (%)	CIE whiteness
		0	77.9
0.2	118.7
		0.4	133.6
0.8	142.3
		1.2	146.8
1.6	148.2
		2.0	148.9

The results in the table clearly show that the compounds of the present invention have excellent whitening effect.

Application example 2

A coating composition was prepared comprising 500 parts chalk (commercially available from OMYA under the trade name Hydrocarb 90), 500 parts clay (commercially available from IMERYS under the trade name Kaolin SPS), 470 parts water, 6 parts dispersant (a sodium polyacrylate salt commercially available from BASF under the trade name Polysalz S), 200 parts latex (an acrylate copolymer commercially available from BASF under the trade name Acronal S320D), 40 parts aqueous solution of 10% polyvinyl alcohol (commercially available from Kuraray under the trade name Mowiol 4-98) and 50 parts aqueous solution of 10% carboxymethylcellulose (commercially available from Noviant under the trade name Finnfix 5.0). The solids content was adjusted to 60% by adding water and the pH was adjusted to 8-9 with sodium hydroxide.

The product of preparation example 1 was added to the stirred coating composition at concentrations of 0.5, 1.0 and 1.5%. The whitening coating composition was then applied to a commercial 75gsm medium size white paper substrate using an automatic wire-wound rod applicator set at standard speed and standard load on the rod. The coated paper was then dried under a stream of hot air for 5 minutes. The dried paper was allowed to meet the requirements and then measured for CIE whiteness on a calibrated Elrepho spectrophotometer.

TABLE 2

Concentration (%)	CIE whiteness
		0	90.2
0.5	105.2
		1.0	108.9
1.5	109.6

The results in the table clearly show that the compounds of the present invention provide excellent whitening effect.

Claims (14)

1. A compound of formula (1):

wherein

R is hydrogen or a methyl group,

R₁is hydrogen, alkyl having 1 to 4 carbon atoms, beta-hydroxyalkyl having 2 to 4 carbon atoms, beta-alkoxyalkyl having 3 or 4 carbon atoms or CH₂CH₂CONH₂，

R₂Is hydrogen or a methyl group, or a mixture thereof,

M⁺is Li⁺、Na⁺Or K⁺And an

n is less than or equal to 1.5.

2. A compound according to claim 1, wherein

R is hydrogen or a methyl group,

R₁is hydrogen, methyl or beta-hydroxyalkyl having 2 or 3 carbon atoms,

R₂is hydrogen or a methyl group, or a mixture thereof,

M⁺is Na⁺And an

n is less than or equal to 1.5.

3. The compound of claim 1, wherein

R is a hydrogen atom or a hydrogen atom,

R₁is hydrogen, methyl or beta-hydroxyalkyl having 2 carbon atoms,

R₂is a hydrogen atom, and is,

M⁺is Na⁺And an

n is less than or equal to 1.5.

4. The compound of claim 1 wherein

R is a hydrogen atom or a hydrogen atom,

R₁is-CH₂CH₂OH，

R₂Is a hydrogen atom, and is,

M⁺is Na⁺And an

n is less than or equal to 1.2.

5. An aqueous solution containing 20 to 40% by weight of at least one compound of formula (1) according to any one of claims 1 to 4 as active substance.

6. Aqueous solution according to claim 5, wherein the concentration of the active substance is between 25 and 35% by weight.

7. The aqueous solution according to claim 5 or 6, further comprising one or more carriers, antifreezes, defoamers, co-solvents, preservatives, complexing agents and organic by-products formed during the preparation of the optical brightener.

8. A process for the preparation of a compound of formula (1) according to any one of claims 1 to 4, wherein the compound of formula (2) is in the form of an aqueous solution:

is converted to mixed salt form (1) wherein at least 25% M bound to the sulfonate group⁺The ions are either treated with 2-dimethylaminoethanol and mineral acid or sequentially with cation exchange resin and 2-dimethylaminoethanol₃)₂NH⁺CH₂CH₂OH ion replacement.

9. The process according to claim 8, wherein the compound of formula (1) is isolated and further separated from excess salts and alkanolamine by membrane filtration.

10. A process for the preparation of a solution according to claim 7, wherein further ingredients selected from one or more of carriers, anti-freeze agents, anti-foaming agents, co-solvents, preservatives and complexing agents are added to the aqueous solution obtained from the preparation of the compound of formula (1).

11. Use of a compound of formula (1) according to any one of claims 1 to 4 or an aqueous solution according to any one of claims 5 to 7 for the fluorescent whitening of textiles, paper, board and non-wovens.

12. Use according to claim 11, which is an aqueous suspension for pulp.

13. A method of whitening paper comprising the main steps of:

-providing a pulp suspension,

-adding 0.01-2% by weight, based on dry fibre, of an aqueous solution according to any one of claims 5-7,

-producing paper from the pulp suspension,

-pressing and drying the paper.

14. A method of whitening paper comprising the main steps of:

-preparing an aqueous coating composition by mixing together chalk or other white pigments, one or more dispersants, a primary latex binder and optionally a secondary binder and optionally further additives,

-adding 0.01-3% by weight, based on dry pigment, of an aqueous solution according to any one of claims 5-7,

-applying the coating composition to paper,

-drying the coated paper.