WO2009156335A1 - Azo dyes for coloration of polyurethanes - Google Patents

Abstract

The present invention concerns azo dyes of formula (I) where R, X, X¹, R¹, R², R³, n and m are each as defined in claim 1, processes for their preparation and processes for producing colored polyurethane.

Description

DYSTAR TEXTILFARBEN GMBH & CO. DEUTSCHLAND KG 2008/D505/ Dr.My

Azo dyes for coloration of polyurethanes

Polyurethanes are manufactured polymers obtained by polyaddition of building blocks that contain at least two hydroxyl groups and are known as diols with building blocks that contain at least two isocyanate groups and are known as diisocyanates. Polyurethanes are generally produced as foams by generating carbon dioxide through specific inclusion of water during the polycondensation, or by adding gases from the outside.

Colored polyurethanes are generally produced by admixing one of the two components, namely the diol, with a dye containing at least one functional group capable of reacting with the other component, the diisocyanate, to form a covalent bond. The dye is thus incorporated in the polyadduct by means of chemical bonds, and is no longer removable by operations involving washing off.

Aliphatically attached hydroxyl groups have been determined to be particularly useful as reactive groups, and generally two of these groups are incorporated in the molecule. The hydroxyl groups may be situated at the end of long chains obtainable by reaction with ethylene oxide or propylene oxide of dyes containing nucleophilic groups. Such dyes are often liquid at room temperature and can be added in highly concentrated form to the foaming system (see for example US 4,284,729 and EP 0 166 566 A2). The liquid nature of these dyes ensures ease of meterability and promotes good and rapid solubility in the initially charged polyurethane component. The latter is often problematical in the case of pulverulent or pasty dyes. EP 0 837 082 A1 already discloses liquid reactive dyes with which polyurethane foams can be colored in orange shades. However, the strength of the dyes described therein is limited since relatively long polyether chains are needed to obtain room temperature liquid products of sufficiently low viscosity. Surprisingly, it has now been found that the hereinbelow defined dyes of formula I according to the present invention provide relatively low-viscosity liquid products that are useful for coloring polyurethane in orange shades and that are superior in terms of strength to the dyes of EP 0 837 082 A1 at a given consistency.

The present invention accordingly provides azo dyes of formula I

where

R is alkyl-O, aryl-O, alkyl-NH, dialkyl-N, aryl-NH, diaryl-N, where the alkyl and aryl groups can also be substituted; X and X¹ are independently hydrogen, chlorine or bromine; R¹ is hydrogen or methyl;

R² and R³ are independently hydrogen or methyl; and n and m are independently a number from 2 to 100.

Alkyl groups may be straight chain or branched and they have 1 to 8 carbon atoms in particular. Examples are methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl and 2-ethylhexyl, of which methyl and ethyl are particularly preferred.

Substituted alkyl groups are preferably substituted by 1 , 2 or 3 substituents selected from the group consisting of phenoxy, (Ci-C₄)alkoxy-(Ci-C₄)alkoxy, (Ci-C₄)alkoxy and hydroxy.

Aryl groups are in particular phenyl and naphthyl, of which phenyl is particularly preferred.

Substituted alkyl groups are preferably substituted by 1 , 2 or 3 substituents selected from the group consisting of methyl, ethyl, hydroxy and (Ci-C₄)alkoxy.

In formula I, m and n are mean values resulting from the number of equivalents of ethylene oxide (R² and R³ = hydrogen) or propylene oxide (R² and R³ = methyl) used for the preparation. m and n are each preferably 2 to 20.

R² and R³ can be methyl as well as hydrogen within any one molecule. The meanings of hydrogen and methyl can be randomly distributed along the entire side chain, but there can also be regions in which R² and R³ are exclusively hydrogen or exclusively methyl. The azo dyes of formula I according to the present invention are obtainable in a conventional manner.

For instance, a compound of formula Il

where R, X and X¹ are each as defined above, is diazotized and coupled onto a compound of formula III

where R¹, R², R³, m and n are each as defined above. After the reaction has taken place, the azo dyes of formula I can be removed from the reaction medium with organic water-immiscible solvents. Free-flowing orange dye oils are obtained after drying and evaporation of the solvent.

Compounds of formula Il in which at least one of X and X¹ is not hydrogen are obtainable by halogenation of compounds of formula IV

where R is as defined above.

When X and/or X¹ represent bromine, the bromination can be effected with elemental bromine or bromine sources (for example sodium bromide/hydrogen peroxide) in organic solvents (for example acetic acid), in mineral acids or else without solvent in a conventional manner.

When one of X and X¹ represents chlorine, the monochlorinated compounds are advantageously obtainable with N-chlorosuccinimide by following T. E. Nickson et al., Synthesis 1985, 669-670.

In general, the halogenation reactions mentioned give mixtures of the nonhalogenated, monohalogenated and bishalogenated 4-aminobenzoic acid derivatives of formula IV. These can be used in that form in the further synthesis, so that mixtures of azo dyes of formula I are obtained in this case. It is advantageous here that the hue desired for the resulting dye mixture can be fine tuned via the ratio of the individual components of formula II.

The compounds of formula III are likewise obtainable by following methods known from the literature, see for example US 3,157,633. To this end, compounds of formula V

where R¹ is as defined above, are reacted with ethylene oxide and/or propylene oxide under base catalysis. The reaction is preferably carried out first with propylene oxide and then with ethylene oxide, but the reverse procedure is also possible. Ethylene oxide and propylene oxide can also be used concurrently, in which case they are incorporated in the polyether chains in a random manner. The materials obtained through these reactions represent mixtures of compounds of various chain lengths and chain constitutions, in which the distribution of the molar masses approximately conforms to a Gaussian distribution.

The formulae described in this patent application thus describe a mean value which results from the number of equivalents of ethylene oxide and propylene oxide used. This mean value also roughly corresponds to the molar mass which results from the number average determined in gel permeation chromatography. The average number of equivalents of ethylene oxide and propylene oxide incorporated can also be determined from the integrals of ¹H NMR spectra.

The azo dyes of formula I are incorporable in the polyurethane polymer, with covalent bonds, by reaction of their terminal hydroxyl groups with isocyanate groups of the polyurethane-building blocks. They are therefore very useful for coloration of polyurethane, particularly polyurethane foams, in that they are notable for very high fastnesses to migration. High color strength is a further advantage of azo dyes of formula I, so that only small amounts are needed for coloration. In addition, the polyurethane system becomes only minimally adulterated with foreign substances, which minimizes the risk of foam disruptions.

The present invention accordingly also provides a process for producing colored polyurethane by polyaddition of a diol component with a diisocyanate component in the presence of a dye, wherein said dye is an azo dye of formula I

where

R is alkyl-O, aryl-O, alkyl-NH, dialkyl-N, aryl-NH, diaryl-N, where the alkyl and aryl groups can also be substituted; X and X¹ are independently hydrogen, chlorine or bromine; R¹ is hydrogen or methyl;

R² and R³ are independently hydrogen or methyl; and n and m are independently a number from 2 to 100.

The polyaddition of the diol component with the diisocyanate component is carried out according to methods which have been previously described and which are known to one skilled in the art (see for example EP 0 166 566 A2 and the references cited therein). In the course of the polyaddition, the azo dye of formula I becomes incorporated in the polyurethane structure via covalent bonding through its hydroxyl groups.

The azo dye of formula I may be added to the reaction mixture of diol component and diisocyanate component before or during the polyaddition reaction. Preferably, however, the dye is added to the diol component before the diol component comes into contact with the diisocyanate component. In a preferred version, the azo dye of formula I is admixed to a polyether polyol or a polyester polyol and this preparation can then be used for the polyaddition with a diisocyanate. The polyether polyols and polyester polyols contain at least two and preferably at least three hydroxyl groups. Polyester polyols are obtainable for example by reaction of phthalic acid or adipic acid with polyalcohols, examples being glycol, diethylene glycol, thethylene glycol, 1 ,4-butanediol, glycerol or thmethylolpropane.

Polyether alcohols are obtained for example by ethehfying the aforementioned alcohols.

The diisocyanates may be aliphatic and aromatic in nature and may also contain more than two isocyanate groups. Tolylene diisocyanate (TDI) and diphenylmethane diisocyanate (MDI) are the most common.

The ratio of polyol to diisocyanate depends on the molar masses, and it is normal to use a small excess of the diisocyanate. The molar ratio of polyol to diisocyanate can be for example between 1 :0.85 to 1 :1.25. To produce more rigid foams, it is generally customary to use diisocyanate excesses of 100-300%.

The addition polymerization customarily utilizes stabilizers and activators or catalysts.

Preferred stabilizers are for example silicones, which may comprise between 0.1 % and 2% and preferably between 0.5% and 1.6% of the entire foam-forming mixture.

Possible activators are amines, preferably tertiary amines. They may comprise 0.05% to 1 % and preferably 0.07% to 0.6% of the mixture.

Polyurethane foam is produced according to the same principle, the foam being produced by the addition of blowing gas or by the addition of water to the diol/polyol component, leading to the formation of carbon dioxide blowing gas. The production of colored polyurethane foams is described in detail in US 2004/0254335 for example.

By using the azo dyes of formula 1 it is thus possible to produce colored polyurethane foams having no disruptions in foam structure and good fastnesses, that likewise form part of the subject matter of the present invention.

The examples which follow illustrate the invention. Parts are by weight. Example 1 a) An initial charge is prepared of 30.5 parts of methyl 4-aminobenzoate and 18.2 parts of sodium acetate (anhydrous) in 315 parts of acetic acid. The mixture is heated to 40⁰C, maintained at 40⁰C for 30 min and then cooled down to room temperature. A solution of 8 parts of bromine in 10.5 parts of acetic acid is added dropwise at 20-25°C during 30 min. The mixture is subsequently stirred at 20-25⁰C for 45 min and then admixed, at this temperature, with a solution of 4 parts of bromine in 5.2 parts of acetic acid added dropwise during 15 min. This is followed by stirring at room temperature for 16 h. This is followed by a further five additions of, in each case, 4 parts of bromine dissolved in 5.2 parts of acetic acid added dropwise at 20-25°C during 15 min. Each addition is followed by 3 h of stirring at 20-25°C. After the last addition, the mixture is stirred at 20-25⁰C for 16 h, and then 200 parts of ice are added. This is followed by 16.2 parts of 40% sodium hydrogensulfite solution being added and the mixture is subsequently stirred at 20-25°C for 30 min. The reaction mixture is then poured onto 2500 parts of an ice-water mixture followed by stirring for 2 h. Filtration with suction, washing with water and drying leaves 47.15 parts of a white solid. It consists of a mixture of about 80% of the compound of formula Ma

and about 20% of the compound of formula Mb

which are partly in the form of their hydrobromide.

b) 9.2 parts of the mixture obtained as per a) are introduced into 29.4 parts of 18% hydrochloric acid, followed by cooling to 0°C. 7.68 parts of 40% sodium nitrite solution are added dropwise over 1.5 h at 0-4⁰C. The mixture is subsequently stirred at 0°C for 3 h. This is followed by filtration and removal of excess nitrite with a little sulfamic acid. 55.2 parts of a coupler prepared from N,N-bis(hydroxyethyl)-m-toluidine and 20 equivalents of propylene oxide (PO) and 7 equivalents of ethylene oxide (EO) as described in US 3,157,633 are initially charged in 280 parts of ice-water and admixed with the above diazotization mixture at below 0⁰C. The mixture is subsequently stirred at 0⁰C for 2 h and then adjusted to pH 7 with about 44 parts of 30% aqueous sodium hydroxide solution. This is followed by multiple extractions with methylene chloride, the combined organic phases are washed with water and dried over sodium sulfate, and the solvent is removed in a rotary evaporator to leave 61 parts of the azo dye of formula Ia in the form of an orange oil (λ_max (DMF) = 478 nm)

where X = 84% H, 16% Br

Examples 2 to 9

The bromination mixtures Mc to Ne are obtained similarly to Example 1 a

The bromination mixtures Mc to Me can be used in the procedure indicated in Example 1 b) to obtain the following azo dyes.

The compound of formula III was in each case the compound obtained according to US 3,157,633 by reaction of N,N-bis(hydroxyethyl)-m-toluidine (R¹ = Me) or N,N-bis(hydroxyethyl)aniline (R¹ = H) with the stated equivalents of propylene oxide (PO) and ethylene oxide (EO).

All dyes of Examples 2 to 9 constitute free-flowing orange oils. Example 10

100 parts of a polyether polyol (obtained by etherification of butane-1 ,4-diol), containing about 1 % by weight of N,N,N',N'-tetramethyl-2,2'-oxybis(ethylamine) as catalyst, are initially charged. 1 part of the dye of Example 1 b) is added to the initial charge. The mixture is intensively stirred by means of a dissolver disk for 20-30 sec. Then, 60 parts of diphenylmethane 4,4'-diisocyanate are speedily added before intensive mixing together for 7 sec by means of the dissolver disk. The contents are then poured into a vessel to form the foam, for which cups made of paper or paperboard are suitable. After about 5 min, the components will have reacted off and after a further 10 min the foam will have cured. It is allowed to cool down to room temperature. 20 min after cooling down, the foam can be sawn open to assess its hue. The foam obtained has a bright orange color, no foam disruptions and has very good washfastnesses.

Repeating the foaming described with the dyes of Examples 2 to 9 likewise gives orange foams without foam disruptions and with very good washfastnesses.

Repeating the foaming described with the dyes of Examples 2 to 9 likewise gives orange foams without foam disruptions and with very good washfastnesses.

Claims

What is claimed is:

1. An azo dye of formula I

where

R is alkyl-O, aryl-O, alkyl-NH, dialkyl-N, aryl-NH, diaryl-N, where the alkyl and aryl groups can also be substituted;

X and X¹ are independently hydrogen, chlorine or bromine; R¹ is hydrogen or methyl; R² and R³ are independently hydrogen or methyl; and n and m are independently a number from 2 to 100.

2. A process for preparing an azo dye of formula I as claimed in claim 1 , which comprises a compound of formula Il

where R, X and X¹ are each as defined in claim 1 , being diazotized and coupled onto a compound of formula III

where R¹, R², R³, m and n are each as defined in claim 1.

3. A process for producing colored polyurethane by polyaddition of a diol component with a diisocyanate component in the presence of a dye, wherein said dye is an azo dye of formula I

where

R is alkyl-O, aryl-O, alkyl-NH, dialkyl-N, aryl-NH, diaryl-N, where the alkyl and aryl groups can also be substituted;

X and X¹ are independently hydrogen, chlorine or bromine;

R¹ is hydrogen or methyl;

R² and R³ are independently hydrogen or methyl; and n and m are independently a number from 2 to 100.

4. The process as claimed in claim 3, wherein the polyurethane is produced in the form of a foam.

5. A colored polyurethane, colored with an azo dye of formula I

where

R is alkyl-O, aryl-O, alkyl-NH, dialkyl-N, aryl-NH, diaryl-N, where the alkyl and aryl groups can also be substituted;

X and X¹ are independently hydrogen, chlorine or bromine;

R¹ is hydrogen or methyl;

R² and R³ are independently hydrogen or methyl; and n and m are independently a number from 2 to 100.