MXPA99006606A - Tint for pa - Google Patents

Abstract

The present invention relates to a dye having the formula (I), wherein each M is a hydrogen ion, an alkali metal ion or RaRbRcRdN + (wherein Ra, Rb, Rc and Rd are independently hydrogen, C1-C6 alkyl or C1-C6 hydroxyalkyl). This invention also relates to the use of tin

Description

Paper Dye BACKGROUND OF THE INVENTION This invention relates to a bleachable dye useful for the manufacture of brown kraft paper shades and other substrates of the style. Azo dyes and fluorescent brighteners derived from diaminostilbenodisulfonic acids are known. For example, H. Zollinger, Color Chemistry (VCH Verlagsgessellschaft, 1991), pages 164 and 257. German Patent Application Publication 4,139,302 describes dyes of disazostilbene having the formula wherein R1 and R2 can be hydrogen, halogen, N02, OH, NH2 or C? -C6 alkyl. Although the R1 and R2 groups may be located in any vacant position of the ring in the terminal benzene rings, the hydroxyl groups must always be located for the azo groups. Compare European Patent Application 739,747 and Japanese Patent 52/55625. U.S. Pat. No. 5,495,003 discloses dyesthoestilbene dyes of the following general formula wherein Ri to R5 represent several substituents and M represents several cations. In one such compound, each Rx is a hydroxyl group located ortho to an azo group. See Example 58. All of those compounds, however, must have substituted triazine groups located for azo groups. Compare European Patent Application 739,747 and Japanese Patent 52/55625, which also require functional groups other than the ortho-hydroxyl and meta-methyl groups of the present invention. It has now been seen that the disazostilbene dye of the present invention, wherein each terminal benzene ring is substituted with a hydroxyl group in an ortho position to an azo group and a methyl group in a meta position to an azo group, can be used in solution as a dye for paper that imparts a dull yellow color, commonly referred to as a "kraft-toasted" color. The dye of the present invention not only provides this distinctive color without being mixed with other dyes, but also exhibits a minimum sensitivity of hue to changes in pH in the typical range of papermaking and, therefore, can be used even to dye paper with alkaline sizing, for which known dyes, such as CI Direct Yellow 4, they are inadequate. The dye of the invention is also stable when stored in solution and exhibits excellent bleachability in chlorine-containing bleaching agents, such as those used in the recovery of waste paper. This unique combination of properties could not be previously achieved with the known dyes.

COMPENDIUM OF THE INVENTION This invention relates to a dye having the formula (I) wherein each M is a hydrogen ion, an alkali metal ion (preferably, potassium ion) or RaRbRcRdN + (where Ra, Rb, Rc and Rd are independently hydrogen, C?-C6 alkyl or C?-C6 hydroxyalkyl). This invention is further related to the use of this dye to color paper and other substrates of this type.

DETAILED DESCRIPTION OF THE INVENTION The dye of the present invention can be prepared as free acid (ie, where each M is a hydrogen ion) or as various alkali metal or ammonium salts (wherein one or more M is an alkali metal or ammonium ion) . Suitable salts of alkali metals include the lithium, sodium and potassium salts, preferably where the four M's are all potassium ions. The term "C?-C6 alkyl", as used in the description of Ra, Rb, Rc and Rd, refers to straight or branched chain aliphatic hydrocarbon groups having from 1 to 6 carbon atoms. Examples of C6-C6 alkyl are methyl, ethyl, propyl, butyl, pentyl, hexyl and their isomeric forms. The term "C2-C6 hydroxyalkyl" refers to straight or branched chain aliphatic hydrocarbon groups having from 2 to 6 carbon atoms and substituted with a hydroxy group. Examples of C2-C6 hydroxyalkyl hydroxyethyl, hydroxypropyl, hydroxybutyl, hydroxypentyl, hydroxyhexyl and their isomeric forms are examples.

The dye of the present invention can be prepared by known methods of azo coupling. In a preferred method, the diazonium salt of flavonic acid, having the formula (II) is coupled with p-cresol, having the formula (III) The diazonium salt of formula (II) can be prepared using known diazotization methods from the corresponding diamine, flavonic acid. In a particularly useful diazotization method, flavonic acid is diazotized in water containing a nitrite salt (preferably, an alkali metal nitrite, such as sodium nitrite) and a mineral acid (preferably, hydrochloric acid). Diazotizations according to this preferred method are typically carried out at temperatures of less than about 40 ° C (preferably, from about 5 ° C to about 40 ° C), although it is possible to use temperatures somewhat outside this range. The resulting diazonium salt is then coupled in aqueous medium with p-cresol in the presence of a suitable base. Although phenols ordinarily react in a position to the hydroxyl group (for example, as described in German Patent Application Publication 4,139,302), p-cresol has a methyl group in the para position and, therefore, , reacts instead in a position ortho to the hydroxyl group. Suitable bases for coupling are those which provide a basic environment, but which, moreover, do not react with the reactive species of the coupling reaction. The preferred base is an alkali metal hydroxide, more preferably potassium hydroxide. If an ammonium salt is to be prepared, the base is typically an amine (such as RaRbRcN, where Ra, Rb and Rc are defined as above) or a quaternary ammonium hydroxide (such as RaRbRcRdN + OH ", where Ra, Rb, Rc and Rd are defined as above.) The azo coupling reaction is preferably carried out at temperatures of less than about 30 ° C (preferably, from about 10 C to 30 ° C), although it is also possible, but less preferred, to use temperatures. Something outside this range When using an alkali metal hydroxide, a tertiary amine of the formula RaRbRcN, or a quaternary ammonium hydroxide of the formula RaRbRRdN + OH "as a base, the resulting solution can be used directly or can still be processed, for example, by concentration or dilution, before being used as a dye. Other bases (such as other inorganic metal hydroxides) can be used, but are less preferred, since the resulting solution must still be processed, for example, by exchange of the cations or by derivatization, to obtain the desired amine salts. The dye of the present invention can be used to impart color to a variety of substrates, but is particularly useful for dyeing and printing paper, paperboard and cardboard, as well as other cellulosics for which a "kraft-toasted" color is desired. Particularly suitable substrates include, for example, bleached, sizing or unprepared lignin-free paper, for which the starting material can be bleached, semi-milled or unbleached pulp, and recycled and de-inked fibers. Other cellulosic fibers can also be colored by means of the dye of the present invention. The dye can be applied by any of several methods known in the art, preferably by application to a pulp in aqueous suspension, but also by surface staining, coating or printing. Pulp application can be performed in an aqueous suspension (also referred to as "internal staining") by adding batches to a containment tank or "hydrodisgregator", which generally provides excellent agitation. The addition of batches is done manually by weighing or measuring the dye volumetrically in the container containing the pulp. The dye of the present invention can also be added continuously to a flow of pulp in water by means of a dosing device, such as a gear or piston type pump. The surface dyeing can be carried out, for example, in a paper machine with a roller assembly known as a "sizing press". These rollers form a line of contact, with a sheet of paper traveling between them. A liquid pool for the sizing press is dosed, which generally contains starch and other additives, as well as the dye, on both sides of the sheet. The liquid is absorbed on the surface of the leaf, thus imparting a color to the leaf. Surface coloration is often used in combination with internal staining techniques.

The coloration by coating can be applied by any of several methods in line or offline with a machine to manufacture paper. Coatings suspensions typically contain a pigmented filler (such as clay or titanium dioxide), a latex binder, colorants (such as the dye of the present invention) and other known additives to increase coating performance. The coating mixture is typically applied to the sheet, generally using a roller coated with the coating mixture, and the excess is scraped with a knife. The printing can be carried out using any of several known methods to obtain decorative designs or bulk surface coverage. The dye of the present invention can be, for example, mixed with other additives, such as binders and lubricants, and applied to the surface of a sheet using any of several known printing techniques, such as flexographic printing. Of course, additives and suitable auxiliary agents known in the art can also be added along with said application methods. As used herein, the term "additives" refers to substances that aid the dye of the present invention to bind to various substrates. As used herein, the term "auxiliary agents" refers to substances that are compatible with the dye of the present invention and that aid in the effective production of various grades of paper. Certain substances can, of course, serve as additives and auxiliary agents at the same time. Many additives and auxiliary agents are useful in more than one of the aforementioned application techniques. In practice, however, a narrower group of additives and auxiliary agents is typically used for each application method. For internal staining, for example, suitable additives include rosin sizing, aluminum sulfate, fixing agents (such as products of the amine condensate type), retention aids and inorganic salts (such as sodium chloride). Suitable auxiliary agents for internal staining include alkenyl succinic anhydride, alkyl ketene dimer, fiber retention aids, wet strength resins, biocides and defoamers. For surface coloration (for example, using a size press), suitable additives include starch and surfactants (surfactants). Suitable auxiliary agents for surface coloration include alkenyl succinic anhydride and biocides. For coating coloration, suitable fillers include fillers (such as clay, titanium dioxide, calcium carbonate and the like), latices, lubricants, gloss enhancers and defoamers. For printing, suitable additives include binders, fixing agents, lubricants, humectants and agents for viscosity control. Other suitable additives and auxiliary agents will, of course, be known to those skilled in the art.

The following examples illustrate details for the preparation and use of the compounds of this invention. The invention, set forth in the foregoing description, is not limited in spirit or scope by these examples. Those skilled in the art will readily understand that known variations of the conditions and methods of the following preparative procedures for preparing these compounds can be used. Unless otherwise indicated, all temperatures are degrees Celsius and all percentages are percentages by weight.

EXAMPLES Performance parameters The performance parameters for the dyes of Examples 1-4 were obtained using acidic and alkaline dyes. Acid dyes: Pulp mixtures were prepared by stirring 3 g (dry weight) of kraft pulp of coniferous wood bleached in 100 ml of artificially hardened water at 200 ppm with calcium chloride. A slurry was added to the pulp suspension., 0% (based on the dry weight of the fiber) of an appropriate standard dye or an equivalent amount (determined by the spectral transmission method described below) of a test dye. The colored pulp mixture was stirred for two minutes, after which 4.0 ml of a 0.88% solution of Pexol rosin sizing solution was added. After stirring the suspension for a further five minutes, 10.0 ml of a 1.5% aluminum sulfate solution was added to the suspension. The colored pulp mixture was stirred for twenty minutes, then further diluted with 100 ml of artificially hardened water and poured into a TAPPI sheet mold half full of deionized water. A paper sheet was formed by draining the water from the mold through the forming sieve located at the bottom of the TAPPI mold. The resulting sheet was pressed between blotters, placed on a chromium baking plate and placed in a drying ring to dry in an oven at about 90 ° C. The dry leaves are then compared in terms of color strength and hue difference. Alkaline dyes: Pulp mixtures were prepared by stirring 3 g (dry weight) of kraft pulp of coniferous wood bleached in 100 ml of artificially hardened water at 200 ppm with calcium chloride. A suspension of 3% calcium carbonate (10 ml) was added to the pulp mixture, which was then allowed to mix for five minutes. To this pulp suspension was added 1.0% (based on dry weight of fiber) of an appropriate standard dye or an equivalent amount (determined by the spectral transmission method described below) of a test dye. The pulp suspension stained for fifteen minutes was stirred, after which 2 ml of a 0.3% solution of alkyl ketene dimer sizing agent (available as Hercules 70, from Hercules) was added to the pulp mixture. After stirring the mixture for a further five minutes, the suspension was re-diluted with 100 ml of hardened water, stirred for a further two minutes and poured into a TAPPI sheet mold half full of deionized water. A sheet of paper was formed by draining the water from the mold through the forming screen located at the bottom of the TAPPI mold. The resulting sheet was pressed between blotters, placed on a chromium baking plate and placed in a drying ring to dry in an oven at about 90 ° C. The dried leaves were then compared in terms of color strength and unlike tonality. The performance parameters for the dye of the invention prepared according to Example 1 were determined using the following standards (all from Bayer Corporation): Standard A: Yellow Liquid GXG PONTAMINE® (Yellow Direct Color Index 11). Pattern B: Yellow Liquid for Brilliant Paper PONTAMINE® (Direct Yellow Color Index 4).

The performance parameters for the dye of Example 1 of the invention were also compared with the comparative dyes of Examples 2 and 3. The relative color strengths of the dyes of the examples and the standard dyes were used when comparing their color properties . The transmission spectra were obtained for known dilutions of each test dye and the pattern in a range of approximately 300 to 700 nm. Since the molar concentrations of the dyes of Examples 1-3 were not determined, their molar extinction coefficients (ie, absolute absorbances) are not known. However, a comparison of the relative absorbances at the maximum absorption (? Ma) of each dye and the standard was used to determine the relative amounts of each dye and the corresponding pattern that would have to be applied to the paper samples to obtain samples dyed that had similar reflectance forces. Specifically, the relative absorbances at the maximum absorption (? Max) of each dye and the pattern were compared to determine the relative amounts of each dye and the corresponding pattern that would have to be applied to the paper samples to obtain samples dyed with strengths of similar reflectance. Bleached kraft paper sample sheets were prepared as described above, using 1% solutions of appropriate dye patterns and the indicated amounts of the dyes of Examples 1-3. (for which the quantities were adjusted as described above to account for the difference in the relative light absorbances of the dye solutions). The stained paper sheets were compared to determine the reflectance color strengths (by visual evaluation and instrumental measurements), the tone (by visual evaluation and instrumental measurements), the stability against light (by visual evaluation) and the whitening (by visual evaluation) using methods described below. In addition, the characteristic of the two faces was determined by the visual evaluation method described below.

Color strength of reflectance a. Visual. The stained sheets were visualized under a standard light source (MacBeth light cabinet equipped with a D65 light source). The observed strength of each test dye is given in relation to a pattern (shown in each table as parts). b. Instrument. The stained sheets were analyzed using a color measuring device (Data Color Systems, ACS model CS-5). The instrument measures the absorbance to the -ma for each sheet and (using the Kubelka-Munk K / S equation) automatically calculates the difference in color strength between the sheets dyed with a test dye and those dyed with a pattern . The results are given in each table as parts. Tone a. Visual. Visually stained sheets were examined under the same conditions as those described above for visual color strength. Any difference in tone is given using standard coloristic difference terms used to describe tone and brightness / lack of brightness. The terms of the difference are based on the Gray AATCC Scale and are described as follows: Yellow tints Ro or trace Trace green Light red Light green Unmistakable red Unequivocal green Considerable red Considerable green Very ro Very green Dark red Dark green b. Instrument. The color measurement device described above for the reflectance color strength provided color readings in the CIELAB measuring system and in the CIÉ CMC system (2: 1) for sheets of colored paper. In the CIELAB system, the term L * refers to clarity, for which a higher value is a lighter color and a lower value is a darker color; the term a * corresponds to red (positive values) or green (negative values); the term b * corresponds to yellow (positive values) or blue (negative values), the term C * refers to chromaticity, 'an indication of color saturation, and is calculated as the square root of the sum of the squares of a * and b * and the term h refers to hue. The results are given in terms of the difference (ie delta values) between the corresponding values L *, a *, b *, C * and h of sheets stained with the test dyes and the corresponding values of the patterns. In the CIÉ CMC system (2: 1), the term L * refers to clarity, for which a higher value is a lighter color and a lower value is a darker color; the term C * refers to chromaticity, an indication of color saturation, and H * refers to hue. The results are given in terms of the difference (ie, delta values) between the corresponding values L *, C * and H * of sheets stained with the test dyes and the corresponding values of the standards. The differences between the delta values for acidic dyes and the corresponding alkaline dyes are given as "values ?" , for which values close to zero indicate tone stability at pH changes. Stability against light Stability against light was determined using the general method of AATCC Test Method 16E-1993. Strips covered with sheets of dyed paper were placed in an apparatus for measuring the solidity of the light and a portion of each strip was exposed to the light source for a period of several hours, during which time the strips were examined periodically. Exposure to light was continued until the exposed portion of the strips exhibited an observable color paling that approximated an "Inequivocal" rating on the Gray AATCC Scale. The exposure time (in hours) necessary to produce this degree of paleness is shown in the tables. The results of stability against light are also described in terms of shade changes. A "break within tone" indicates a pale condition that is of the same hue, or hue, as the original non-pale dye. An "out of tune break" indicates a pale condition that is of a different shade from the original non-pale dye. B1acheability Bleaching tests were used to determine the amount of color removed from the stained paper using sodium hypochlorite. For each test, sample leaves were again reduced to sample by mixing vigorously in water. The paste was collected in a sieve and suspended in a vessel using sufficient water to form a 4% suspension of paste. Samples were separately treated at 60 ° C for 30 minutes with 4% sodium hypochlo- phate (or the equivalent required to obtain 2% available chlorine) at about pH 10. The bleached pulp samples were then poured into a mold for TAPPI leaves half full of deionized water. The sheet of paper formed was pressed by draining the water from the mold through the forming screen located at the bottom of the sheet mold between blotters and dried at about 93 ° C in a drum-type electric dryer. The resulting dyed paper sheets were compared with sheets of unbleached paper in terms of color strength. Samples in which less color remains are considered more bleachable. The results are given in the tables either as the percentage of color that remains in relation to the unbleached stained samples, or as visual descriptions according to the following scale: Valuation Color remaining Non-whitening 81% to 100% Partly bleachable 21% to 80 % Practically bleachable 6% to 20% Bleachable 0% to 5% Feature of both sides Shorter paper fibers and fillers (such as clay or titanium dioxide) tend to concentrate more intensely on one side (top side) of a sheet of paper. Consequently, the two sides can exhibit different properties. For example, the two sides of a sheet of paper are generally referred to as the top side (or side of the felt) and the bottom side (or side of the wire). The characteristic of the two faces is the property of certain dyes to color more intensely the longer fibers or the shorter fibers of paper and / or fillers. The following method was used to determine the characteristic of the two sides for the dyes of Examples 1-3. 5 grams of pulp mixtures containing dyes were diluted to one liter and divided into equal portions. A portion was diluted to one liter and passed under vacuum through a round mold equipped with a 100/120 mesh screen. This sheet was removed from the mold and marked as the wire side. The second portion was also diluted to one liter and passed under vacuum through a round mold. The filtrate obtained from both filtrations was then carefully poured through the second sheet so as not to form a hole in the sheet. The second sheet was removed from the mold and marked as the felt side. The two sheets were then dried at about 93 C in an electric drum dryer and compared in terms of relative color strength. A dye was considered to be on the side of the wire or the bottom if the first sheet was more intensely colored and on the side of the felt or on top if the second sheet was more intensely colored (see tables). The characteristic of the top side is generally considered a desirable property for alkaline staining, which is the prevalent method now used in US paper mills.

Preparation of the diazonium precursor A mixture of 74.1 g (0.20 mol) of flavonic acid in 330 ml of water was stirred until a smooth suspension was obtained, which was solubilized by the addition of 31.9 g of aqueous sodium hydroxide. at 50%, which gave a pH of 6.8-7.2. The free flavonic acid was again precipitated from the alkaline solution by slow addition of hydrochloric acid and cooled to 20 C by the addition of ice. To the cooled flavonic acid 56 ml of 40% aqueous sodium nitrite was added over a period of one hour. The resulting mixture was then stirred for two hours at a temperature of not more than 35 C. The excess nitrite was decomposed by addition of 0.4 g of sulfamic acid and the resulting bisdiazonium salt was isolated from the flavonic acid by filtration and washed until the Congo Red essay paper is neutral. The filter cake of the diazomo salt was used for the examples without further purification.

Example 1 The bis-diazonium salt of flavonic acid prepared from 0.20 mol of flavonic acid, as described above, was suspended in 240 ml of water and then added uniformly over a period of thirty minutes to a mixture of 102.2 g (0.82 mol) of 45% potassium hydroxide, 50.4 g (0.42 mol) of 90% p-cresol and 240 g of ice, during which time the temperature was allowed to rise at approximately 18 ° C. An additional 23 g (0.18 mol) of 45% potassium hydroxide was added and the mixture was stirred for a further two hours. The mixture was clarified by passing it through a glass fiber filter. The clarified solution contained 860 g of the dye. The spectroscopic analysis of the dye solution indicated a? Max of about 435 nm, with weak shoulders at about 380 nm and about 455 nm. The bleached kraft paper dyed by the methods described above exhibited a dull yellow color. The performance data for the dye of Example 1 of the invention and Patterns A and B are shown in Table 1. (Due to severe color changes in the alkali, Pattern B is unsuitable for use in alkaline stain and was not studied) . The performance data for the dye of Example 1 of the invention and Comparative Examples 2 and 3 are shown in Table 2. l Table 1 Comparison of the dye of Example 1 of the invention with Patterns A and B Acid dyes Alkaline dyes fifteen Example 2 (comparative The method of Example 1 was repeated, except for the use of 99% -cresol instead of p-cresol and only the first addition of potassium hydroxide. Spectroscopic analysis of the resulting dye solution indicated an acute? Max at approximately 413 nm. The bleached kraft paper dyed by the methods described above exhibited a yellow color of a bright shade and greener than the paper dyed with the dye of Example 1 of the invention. The performance data are shown in Table 2. Example 3 (comparative) The method of Example 1 was repeated, except for the use of 99% o-cresol instead of p-cresol and only the first addition of potassium hydroxide. The spectroscopic analysis of the resulting dye solution indicated an acute? Max at approximately 411 nm. The bleached kraft paper dyed by the methods described above exhibited a yellow color distinctly greener than the paper dyed with the dye of Example 1 of the invention. The performance data are shown in Table 2. { 1) The CIELAB values in the alkaline dyes columns include the differences ("values?") Between the values of the acid dyes and the corresponding values of the alkaline dyes. fifteen The data of Table 2, particularly the values? A * and? H, show that the dye of the invention prepared as described in Example 1 exhibited much more stability of tone at pH changes than comparative dyes prepared according to Examples 2 and 3 and what is, therefore, more suitable for coloring paper in alkaline papermaking conditions. Table 2 also shows that the dye of Example 1 of the invention exhibited a desirable top-side characteristic in the alkali dyes, while the comparative dye of Example 2 had uniform sides and the comparative dye of Example 3 had a side-on characteristic. down in the same staining conditions. Although the dye of Example 1 of the invention exhibited a relatively lower light stability compared to the comparative dyes of Examples 2 and 3, its stability to light was slightly higher than that of Direct Yellow 11 (i.e. Pattern A; see Table 1) and should be acceptable for the manufacture of kraft brown paper shades. Example 4 (comparative) The method of Example 1 was repeated, except for the use of 46.25 g of catechol (ie, o-dihydroxybenzene) in place of p-cresol and only the first addition of potassium hydroxide . A suspension was obtained in place of a solution and the almost insoluble component could not be completely dissolved for the test. This dye exhibited a very poor affinity for the bleached pa-pei kraft and imparted only a very pale yellow color, which was much weaker in strength than that produced by the dyes of Examples 1-3.

Claims (6)

R e i v i n d i c a c i o n s

1. A dye that has the formula where each M is a hydrogen ion, an alkali metal ion or RaRbRcRdN + where Ra, Rb, Rc and Rd are independently hydrogen, C?-C6 alkyl or d-C6 hydroxyalkyl.

2. A dye according to Claim 1, wherein each M is a potassium ion.

3. A method for imparting color to a substrate, comprising applying a dye according to Claim 1 to said substrate.

4. A method for imparting color to paper, paperboard or cardboard, consisting of applying a dye according to Claim 1 by an internal or surface dyeing technique to said paper, card or cardboard.

5. A colored substrate prepared by the method of Claim 3.

6. A paper, cardboard or colored cardboard prepared by the method of Claim 4. Summary This invention relates to a dye having the formula (I) where each M is a hydrogen ion, an alkali metal ion or RaRbRRdN + (wherein Ra, Rb, Rc and Rd are independently hydrogen, C?-C6 alkyl or C hidro-C hidro hydroxyalkyl) This invention also relates to the use of the dye.