HK1116175B - Improvements relating to optical brightening agents - Google Patents

Description

Improved fluorescent whitening agents

The present invention relates to a fluorescent whitening agent of 1, 2-diphenylethylene type which is highly soluble in water while having a superior fluorescent whitening effect when applied to the surface of paper in a size press or in a pigment coating composition, and has a reduced anionic charge.

Prior Art

1, 2-diphenylethylene type fluorescent whitening agents (OBA) of the formula

Wherein the content of the first and second substances,

m is typically an alkali metal atom, and,

n is 0, 1 or 2, and

the amino acid residue in which one hydrogen atom of the amino group of the amino acid is removed as R, as disclosed in Japanese patent laid-open Nos. 62-106965, PCT application WO 96/00221 and PCT application WO 98/42685, represents the state of the art for producing high-whiteness coated paper.

The compounds of the formula generally have good water solubility, which is advantageous for the paper industry, since in the paper industry optical brighteners are conveniently sold and used, mainly in the form of aqueous solutions.

However, the high anionic charge generated by the amino acid residues can present difficulties to paper makers wishing to recycle waste paper (i.e., to secondary pulp any paper waste produced in the paper making process), because the optical brightener can be extracted during the secondary pulping process, resulting in the build-up of anionic charge in the system, which can interfere with the cationic chemicals used (e.g., for sizing or retention and drainage purposes).

There is therefore a need for optical brighteners which have both a highly water-soluble character and a reduced anionic charge.

Description of the invention

We have surprisingly found that the compounds of formula (1) have both a reduced anionic charge and a high degree of water solubility, while having a superior fluorescent whitening effect when applied to the surface of paper in the size press or in a pigment coating composition.

The present invention provides compounds of formula (1) or mixtures thereof:

wherein the content of the first and second substances,

m is hydrogen, an alkali metal cation, ammonium or C₂-C₃Hydroxyalkyl mono-, di-or trisubstituted ammonium,

n is 0, 1 or 2,

R¹is hydrogen, straight-chain C which may be unsubstituted by hetero atoms₁-C₈Alkyl or branched C₃-C₈Alkyl, and

R²and R³Independently of one another, is a straight-chain C which may be unsubstituted by heteroatoms and may be acyclic₁-C₈Alkyl or branched C₃-C₈An alkyl group.

In one aspect of the invention, M in the above compounds is hydrogen, an alkali metal cation or ammonium; n is 1 or 2; r¹Is hydrogen, straight-chain C which may be unsubstituted by hetero atoms₁-C₄Alkyl or branched C₃-C₅Alkyl, and R²And R³Independently of one another, is a straight-chain C which may be unsubstituted by heteroatoms and may be acyclic₁-C₄Alkyl or branched C₃-C₆An alkyl group.

In another aspect of the present invention, M in the above compounds is hydrogen, sodium or potassium; n is 1 or 2; r¹Is hydrogen, methyl, ethyl, propyl or isopropyl, and R²And R³Independently of one another, methyl, ethyl or propyl, or isopropyl, isobutyl, isopentyl or isohexyl.

In still another aspect of the present invention, M in the above compound is hydrogen or sodium; n is 1 or 2; r¹Is hydrogen or methyl; and R²And R³Independently of one another, methyl or ethyl.

In yet another aspect, the invention provides an aqueous solution containing 10 to 40% by weight of a compound disclosed herein or a mixture thereof and optionally 5 to 20% by weight of polyethylene glycol.

In a further aspect of the invention there is provided a method of fluorescent whitening a finished cellulosic textile, the method comprising the steps of: a) adding to the crosslinkable finish an optical brightener as claimed in any one of claims 1 to 4 in or before the treatment bath; b) crosslinking the finish; and c) drying the treated textile.

Further objects of the present invention are a process for the preparation of the compounds of formula (1) and the use of the compounds of formula (1) as optical brighteners, especially for paper.

It is also an object of the present invention to provide a process for the fluorescent whitening of paper, which process comprises the steps of a) adding the fluorescent whitening agent according to any of claims 1 to 4 to a pigmented coating composition or to a sizing solution or suspension, b) applying the coating composition or sizing solution or suspension to paper, c) drying the treated paper. In a preferred embodiment of the invention, the process comprises the additional step of adding 2 to 15% by weight of a binder to the sizing solution or suspension.

The compounds of formula (1) are prepared by stepwise reaction of cyanuric halide with a), b) and c)

a) Diamines of the formula (2)

b) An amine of formula (3)

To know

c) An amine of formula (4)

Cyanuric halides which may be used here are cyanuric fluoride, cyanuric chloride or cyanuric bromide. Cyanuric chloride is preferred.

The respective reactions can be carried out in an aqueous medium (cyanuric halide suspended in water) or in an aqueous/organic medium (cyanuric halide dissolved in a solvent such as acetone). The various amines may be introduced undiluted or in the form of an aqueous solution or suspension. The amines may be reacted in any order, but preferably the aromatic amine is reacted first. The various amines may be reacted in stoichiometric or excess amounts. Typically, the aromatic amine is reacted in stoichiometric or slightly excess amounts; the aliphatic amines are generally used in a 5-30% excess over the stoichiometric amount.

To replace the first halogen atom of the cyanuric halide, the reaction is preferably carried out at a temperature in the range of 0 to 20 ℃ and under acidic to neutral pH conditions, preferably at a pH in the range of 2 to 7. To substitute the second halogen atom of the cyanuric halide, the reaction is preferably carried out at a temperature in the range of 20 to 60 ℃ and under weakly acidic to weakly basic conditions, preferably at a pH in the range of 4 to 8. To replace the third halogen atom of the cyanuric halide, the reaction is preferably carried out at a temperature in the range of 60 to 102 ℃ and under weakly acidic to basic conditions, preferably at a pH in the range of 7 to 10. The pH can be adjusted by the addition of a suitable acid or base as desired, preferred acids being, for example, hydrochloric acid, sulfuric acid, formic acid or acetic acid, preferred bases being, for example, alkali metal (such as lithium, sodium or potassium) hydroxides, carbonates or bicarbonates, or aliphatic tertiary amines (such as triethanolamine or triisopropanolamine).

Examples of the aromatic amines of the formula (3) are aniline, aniline-2-sulfonic acid, aniline-3-sulfonic acid, aniline-4-sulfonic acid, aniline-2, 4-disulfonic acid and aniline-2, 5-disulfonic acid. Preferably, (3) is aniline-2, 5-disulfonic acid.

Examples of the aliphatic amine of formula (4) are isopropylamine, N-methylisopropylamine, N-ethylisopropylamine, 2-butylamine, 2-amino-3-methylbutylamine, 1-ethylpropylamine, 1, 3-dimethylbutylamine and 1, 5-dimethylhexylamine. Preferably (4) is isopropylamine, N-methylisopropylamine or 2-butylamine.

The optical brighteners of the present invention have the advantage of a low anionic charge compared to similar compounds of the prior art. Surprisingly, such optical brighteners also have higher water solubility than similar compounds in which the aliphatic amine has only one alkyl substituent on the alpha-carbon or in which the aliphatic amine is substituted with a hydroxyl group. An example of the former type of aliphatic amine is diethylamine, as described in swiss patent CH 532,686. An example of an aliphatic amine of the latter type is 2-amino-1-propanol, as described by Wilkowska and Konopski in Organika, 2001, Vol.1999-2000, pp.85-94.

If desired, the synthesized compound of formula (1) can be isolated by a conventional method such as salting out or precipitation with an acid, followed by filtration, washing and drying. If desired, the solution of the synthetic compound may be desalted and optionally concentrated (e.g., by ultrafiltration or membrane filtration). Alternatively, the filtered, washed and optionally dried compound can also be redissolved in water, and the solution thus formed can be desalted and optionally concentrated. If desired, the desalted aqueous solution of the compound may be dried. The liquid or dry compounds can be used as such or, if desired, mixed with conventional conditioners, for example, solubilizing aids or hydrotropes, such as urea or mono-, di-or triethanolamine, or other additives such as polyethylene glycol or polyvinyl alcohol. In a preferred aspect of the invention, the compounds of formula (1) are used in the form of concentrated aqueous solutions, e.g. in concentrations of 5 to 55% by weight, preferably in concentrations of 10 to 40% by weight. In a further preferred aspect of the invention, the concentrated aqueous solution of the compound of formula (1) contains 2 to 40% by weight, preferably 5 to 20% by weight, of polyethylene glycol.

The compounds of formula (1) are suitable for use as fluorescent whitening agents, in particular for the fluorescent whitening of cellulosic substrates such as textiles, non-wovens or paper.

For the fluorescent whitening of textiles and non-wovens, the compounds of formula (1) can be used, for example, in pad dyeing processes, in which the concentration of the whitening agent in the treatment bath can be kept substantially constant. In the finishing of textiles (fabrics or preferably non-woven fabrics) with binders, in particular synthetic resins, the optical brighteners can be added to the synthetic resin in the treatment bath or before. The brightener can be fixed and the finish crosslinked either in 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) are also suitable for the fluorescent whitening and simultaneous crease-resistant finishing of cotton. It can be used in a concentration of 0.01-2.5%, preferably 0.03-1.0% of the dry matrix.

The compounds of formula (1) are particularly suitable for use as optical brighteners for the whitening of paper and non-woven fabrics, more particularly preferably for the optical whitening of paper after sheet formation or of non-woven fabrics after web formation.

More preferably, the compounds of formula (1) are suitable for whitening paper after sheet formation. This can be achieved by adding the optical brightener to the pigmented coating composition or to the sizing solution or suspension. The paper may be fine or coarse paper, the cellulose of which may or may not be bleached.

For the treatment of paper in the size press, a sizing solution or suspension containing 0.2 to 30, preferably 1 to 15, g/l of the optical brightener may be used. The sizing solution or suspension also contains a binder in a concentration preferably ranging from 2 to 15% by weight. The pH is generally in the range from 5 to 9, preferably from 6 to 8.

The binder or sizing agent is typically an enzymatically or chemically modified starch, such as oxidized starch, hydroxyethylated starch or acetylated starch.

The pigmented coating compositions are essentially aqueous compositions comprising at least one binder and a white pigment, in particular an opaque white pigment, and may additionally contain other additives such as dispersants and defoamers.

Although coating compositions can be produced that do not contain white pigments, the best white substrates for printing are made from opaque coating compositions containing 10-70% by weight of white pigment. Such white pigments are generally inorganic pigments, such as aluminium silicates (kaolin, otherwise known as china clay), calcium carbonate (chalk), titanium dioxide, aluminium hydroxide, barium carbonate, barium sulphate or calcium sulphate (gypsum).

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

The amount of the single or primary binder is generally in the range of 5 to 25% by weight of the white pigment. The co-binder is generally used in an amount ranging from 0.1 to 2% by weight of the white pigment; the amount of starch used is generally in the range of 5 to 10% by weight of the white pigment.

The fluorescent whitening agents of formula (1) are generally used in amounts in the range from 0.01 to 1% by weight of the white pigment, preferably in the range from 0.05 to 0.5% by weight of the white pigment.

The following examples will describe the present invention in more detail. Unless otherwise indicated, "%" and "parts" are by weight.

Examples

Preparation of example 1

A solution of 26.6 parts of aniline-2, 5-disulfonic acid and 8.4 parts of sodium hydroxide in 40 parts of water is added to a stirred suspension of 19.4 parts of cyanuric chloride in 60 parts of ice water. The pH was maintained at 6 by dropwise addition of 30% sodium hydroxide. The mixture was stirred at 10 ℃ until no more primary arylamine groups could be detected with the diazotization reaction. A solution of 18.5 parts of 4, 4 '-diamino-1, 2-stilbene-2, 2' -disulfonic acid and 4.0 parts of sodium hydroxide in 25 parts of water is then added, the pH is adjusted to between 6.5 and 7.5 with 30% sodium hydroxide and the mixture is stirred at 30 ℃ until the diazotization reaction proceeds in the negative direction. 8.4 parts of 2-butylamine are added, the mixture is heated to reflux for 2 hours, and the pH is maintained between 8 and 9 with 30% sodium hydroxide. The product was diluted with water to 400 parts to give an aqueous solution containing 16.3% of (5) in the form of the hexasodium salt and 4.4% of sodium chloride.

Preparation of example 2

A solution of 26.6 parts of aniline-2, 5-disulfonic acid and 8.4 parts of sodium hydroxide in 40 parts of water is added to a stirred suspension of 19.4 parts of cyanuric chloride in 60 parts of ice water. The pH was maintained at 6 by dropwise addition of 30% sodium hydroxide. The mixture was stirred at 10 ℃ until no more primary arylamine groups could be detected with the diazotization reaction. A solution of 18.5 parts of 4, 4 '-diamino-1, 2-stilbene-2, 2' -disulfonic acid and 4.0 parts of sodium hydroxide in 25 parts of water is then added, the pH is adjusted to between 6.5 and 7.5 with 30% sodium hydroxide and the mixture is stirred at 30 ℃ until the diazotization reaction proceeds in the negative direction. 8.4 parts of 2-butylamine are added, the mixture is heated to reflux for 2 hours, and the pH is maintained between 8 and 9 with 30% sodium hydroxide. The resulting aqueous solution was cooled to 80 ℃ and treated with 20 parts of polyethylene glycol having an average molecular weight of 1500. The solution was refluxed for 10 minutes again and then diluted to 400 parts with water. The resulting aqueous solution comprising 16.3% of (5) in the form of the hexasodium salt, 5% of polyethylene glycol 1500 and 4.4% of sodium chloride had an anionic charge of 0.75 μ eq/g (Lasertrim particle charge Analyzer) and showed no sign of precipitation after storage for 2 weeks at 5 ℃.

Comparative example 2A

Preparation example 2 was repeated using 15.3 parts of iminodiacetic acid instead of 8.4 parts of 2-butylamine to give an aqueous solution containing 18.9% of (6) in the form of the decasodium salt, 5% of polyethylene glycol 1500 and 4.4% of sodium chloride. The anionic charge of this solution was 1.35. mu. eq/g (Lasertrim particle Charge Analyzer).

Comparative example 2B

Preparation example 2 was repeated using 8.4 parts of diethylamine instead of 8.4 parts of 2-butylamine, to obtain an aqueous solution containing 16.3% of (7) in the form of the hexasodium salt, 5% of polyethylene glycol 1500 and 4.4% of sodium chloride. The solution precipitated within 6 days at 5 ℃.

Comparative example 2C

Preparation example 2 was repeated using 8.6 parts of DL-2-amino-1-propanol instead of 8.4 parts of 2-butylamine to obtain an aqueous solution containing 16.4% of (8) in the form of the hexasodium salt, 5% of polyethylene glycol 1500 and 4.4% of sodium chloride. The solution precipitated within 6 days at 5 ℃.

Preparation of example 3

Preparative example 2 was repeated until the reaction with 2-butylamine was completed. The resulting aqueous solution was desalted by membrane filtration and concentrated to a solution containing up to 40% of (5) in the form of the hexasodium salt. The solution was heated to 80 ℃ and treated with 10 parts of polyethylene glycol having an average molecular weight of 1500. The solution was refluxed for 10 minutes again and then diluted to 200 parts with water. The resulting aqueous solution has a viscosity of 0.02 to 0.03Pa.s at 20 ℃ and contains 32.6% of (5) in the form of the hexasodium salt, 5% of polyethylene glycol 1500 and 0.1% of sodium chloride.

Preparation of example 4

Preparation example 2 was repeated using 6.8 parts of isopropylamine instead of 8.4 parts of 2-butylamine, to give an aqueous solution containing 16.0% of (9) in the form of the hexasodium salt, 5% of polyethylene glycol 1500 and 4.4% of sodium chloride.

Preparation of example 5

Preparation example 2 was repeated using 8.4 parts of N-methylisopropylamine instead of 8.4 parts of 2-butylamine to obtain an aqueous solution containing 16.3% of (10) in the form of the hexasodium salt, 5% of polyethylene glycol 1500 and 4.4% of sodium chloride.

Preparation of example 6

Preparation example 2 was repeated using 10.0 parts of 1, 2-dimethylpropylamine in place of 8.4 parts of 2-butylamine to obtain an aqueous solution containing 16.7% of (11) in the form of the hexasodium salt, 5% of polyethylene glycol 1500 and 4.4% of sodium chloride.

Preparation of example 7

Preparation example 2 was repeated using 11.6 parts of 1, 3-dimethylbutylamine instead of 8.4 parts of 2-butylamine, to obtain an aqueous solution containing 17.0% of (12) in the form of the hexasodium salt, 5% of polyethylene glycol 1500 and 4.4% of sodium chloride.

Preparation of example 8

Preparation example 2 was repeated using 14.9 parts of 1, 5-dimethylhexylamine instead of 8.4 parts of 2-butylamine to obtain an aqueous solution containing 17.7% of (13) in the form of the hexasodium salt, 5% of polyethylene glycol 1500 and 4.4% of sodium chloride.

Preparation of example 9

A solution of 18.2 parts of aniline-4-sulfonic acid and 4.2 parts of sodium hydroxide in 20 parts of water is added to a stirred suspension of 19.4 parts of cyanuric chloride in 60 parts of ice water. The pH was maintained at 6 by dropwise addition of 30% sodium hydroxide. The mixture was stirred at 10 ℃ until no more primary arylamine groups could be detected with the diazotization reaction. A solution of 18.5 parts of 4, 4 '-diamino-1, 2-stilbene-2, 2' -disulfonic acid and 4.0 parts of sodium hydroxide in 25 parts of water is then added, the pH is adjusted to between 6.5 and 7.5 with 30% sodium hydroxide and the mixture is stirred at 30 ℃ until the diazotization reaction proceeds in the negative direction. 8.4 parts of 2-butylamine are added, the mixture is heated under reflux for 2 hours, and the pH is maintained between 8 and 9 with 30% sodium hydroxide. The resulting aqueous solution was cooled to 80 ℃ and treated with 20 parts of polyethylene glycol having an average molecular weight of 1500 and 80 parts of urea. The solution was refluxed for 10 minutes again and then diluted to 400 parts with water. The resulting aqueous solution contained 13.8% of (14) in the form of the tetrasodium salt, 5% of polyethylene glycol 1500, 20% of urea and 4.4% of sodium chloride.

Application example 1

To an aqueous solution of anionic potato starch (Perfectamyl A4692 from AVEBE B.A.) stirred at 60 ℃ was added a solution of brightener (5) in the form of the sodium salt, prepared as described in preparation example 2, in a concentration range of 10-80g/l to prepare a sizing solution. The solution was diluted with water to a starch content of 5% and cooled.

The sizing solution was poured between the moving rolls of a laboratory size press and coated onto a commercial 75g/m²On a paper base sheet sized with AKD (alkyl ketene dimer) and bleached. 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 Elrepho spectrophotometer. The measurements show a surprising whiteness.

OBA concentration (g/l)	CIE whiteness using the brightener from example 2
		0	95.5
10	108.7
		20	115.0
40	122.9
		60	126.9
80	129.1

The results are also given in graph form in fig. 1.

Application example 2

A coating composition was prepared comprising 500 parts chalk (available from OMYA under the trade name Hydrocarb 90), 500 parts clay (available from IMERYS under the trade name Kaolin SPS), 470 parts water, 6 parts dispersant (sodium salt of polyacrylic acid, available from BASF under the trade name Polysalz S), 200 parts latex (acrylate copolymer, available from BASF under the trade name Acronal S320D), and 400 parts of a 20% aqueous solution of an anionic oxidized potato starch (available from ave under the trade name perfectamyl a 4692). Water was added to adjust the solids content to 65% and the pH was adjusted to 8-9 with sodium hydroxide.

A solution (concentration range 0.1-0.6%) of brightener (5) in the form of the sodium salt prepared as described in preparative example 2 was added to the stirred coating composition. The whitened coating composition was then coated onto a commercial 75gsm neutral sized white paper base sheet using an automatic wire wound rod coater using a standard speed setting and standard rod loading. The coated paper was then dried in a stream of hot air for 5 minutes. The dried paper was conditioned and then measured for CIE whiteness on a calibrated Elrepho spectrophotometer.

OBA concentration (%)	CIE whiteness using the brightener from example 2
		0	88.3
0.4	96.6
		0.8	101.1
1.2	105.2
		1.6	107.8
2.0	110.7
		3.0	115.3

The results are also given in graph form in fig. 2.

Claims (10)

1. A compound of formula (1)

Wherein the content of the first and second substances,

m is hydrogen, an alkali metal cation, ammonium or C₂-C₃Hydroxyalkyl mono-, di-or trisubstituted ammonium,

n is 1 or 2, and n is a hydrogen atom,

R¹is hydrogen, not taken by a hetero atomLinear chain of generations C₁-C₈Alkyl or branched C₃-C₈Alkyl, and

R²and R³Independently of one another, is a linear C chain which is unsubstituted by heteroatoms and is acyclic₁-C₈Alkyl or branched C₃-C₈An alkyl group.

2. The compound of claim 1, wherein

M is hydrogen, an alkali metal cation or ammonium,

n is 1 or 2, and n is a hydrogen atom,

R¹is hydrogen, straight-chain C not substituted by hetero atoms₁-C₄Alkyl or branched C₃-C₅Alkyl, and

R²and R³Independently of one another, is a linear C chain which is unsubstituted by heteroatoms and is acyclic₁-C₄Alkyl or branched C₃-C₆An alkyl group.

3. The compound of claim 2, wherein

M is hydrogen, sodium or potassium,

n is 1 or 2, and n is a hydrogen atom,

R¹is hydrogen, methyl, ethyl, propyl or isopropyl, and

R²and R³Independently of one another, methyl, ethyl or propyl, or isopropyl, isobutyl, isopentyl or isohexyl.

4. The compound of claim 3, wherein

M is hydrogen or sodium, and M is hydrogen or sodium,

n is 1 or 2, and n is a hydrogen atom,

R¹is hydrogen or methyl, and

R²and R³Independently of one another, methyl or ethyl.

5. An aqueous solution containing 10 to 40% by weight of a compound according to any one of claims 1 to 4 or a mixture thereof and optionally 5 to 20% by weight of polyethylene glycol.

6. A process for the preparation of a compound of claim 1, said process comprising the step-wise reaction of a cyanuric halide with a), b) and c):

a) diamines of the formula (2)

b) An amine of formula (3)

And c) an amine of the formula (4)

Wherein M, n and the group R¹、R²And R³Has the meaning as defined in claim 1.

7. The process of claim 6 wherein the aromatic amine of formula (3) is aniline-2, 5-disulfonic acid and the aliphatic amine of formula (4) is isopropylamine, N-methylisopropylamine, or 2-butylamine.

8. A method of fluorescent whitening a finished cellulosic textile, the method comprising the steps of:

a) adding to the crosslinkable finish an optical brightener as claimed in any of claims 1 to 4 in or before the treatment bath,

b) crosslinking the finish, and

c) drying the treated textile.

9. A method of fluorescent whitening paper, said method comprising the steps of

a) Adding to the pigmented coating composition or to the sizing solution or suspension the fluorescent whitening agent according to any of claims 1 to 4,

b) applying the coating composition or sizing solution or suspension to paper,

c) the treated paper is dried.

10. The method of claim 9, comprising the additional step of adding 2-15% by weight of a binder to said sizing solution or suspension.