JPH0348191B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to novel benzimidazoles which are unsubstituted on the benzo ring, a process for their preparation and their use for optical brightening of organic materials. US Pat. No. 3,637,734, No. 4,009,994 and British Patent No. 1,313,332 disclose particularly readily available benzimidazoles which are unsubstituted on the benzo ring of the benzimidazole group. However, these known benzimidazoles have unsatisfactory whitening effects. If it is not quaternized, it is not possible to achieve a high maximum effect. If the benzimidazole group is unsubstituted, quaternized, or non-quaternized in the benzo ring, a high whitening effect cannot be obtained. It is therefore an object of the present invention to provide benzimidazoles unsubstituted in the benzo ring of the benzimidazole group which do not have the above-mentioned disadvantages. According to the present invention, it has therefore been found that a surprisingly high whitening effect can be achieved using some selected benzimidazoles in which the benzo ring of the benzimidazole group is unsubstituted. The novel benzimidazole according to the present invention is represented by the following general formula (1). In the formula, A is

[Formula] or

In the group of formula, R ₁ means cyanomethyl or 1-cyanoethyl, R ₂ is C _1-4 -alkyl or C _3-4 -alkenyl, and R ₄ and R ₅ are each independently hydrogen. Or chlorine. The compounds of formula (1) can also exist as acid adducts and can be used for whitening. Among the compounds of formula (1), preferred are the following formula (2)
This is a compound represented by (2) (In the formula, A′ is

[Formula] or

In the group of formula R ₁ means cyanomethyl or 1-cyanoethyl and R′ ₂ is C _1-4 -alkyl. Preferably R' is methyl. Among the compounds of formulas (1) and (2), the compound of formula (3) below is particularly recommended. (3) In the formula, A″ is

R ₁ means cyanomethyl or 1-cyanoethyl, and R' ₂ is C _1-4 -alkyl. A compound of particular interest from a practical standpoint is a compound represented by the following formula (7). The benzimidazole of formula (1) has the formula benzimidazole of the formula with at least one molar equivalent of an alkylating agent R ₁ X or acrylonitrile in the presence of a base. benzimidazole. In addition, in each of the above formulas, A, R ₁ , R ₃
and X have the meanings given above. Suitable bases include in particular alkali metal or alkaline earth metal salts of weak acids, such as sodium carbonate, potassium carbonate, calcium carbonate, or alkaline earth metal oxides, such as finely divided magnesium oxide. Tertiary amines that are less susceptible to quaternization, such as triisopropanolamine or 2,6-di-t-butylpyridine, can also be used as acid acceptors. In a particularly advantageous embodiment, the benzimidazole of formula (10) which is not yet substituted on the nitrogen is treated with a strong alkali, for example an alkali metal hydroxide such as sodium hydroxide, potassium hydroxide, or an alkali metal hydroxide such as sodium ethylate, potassium ethylate. An alkali metal alcoholate such as is first converted to the corresponding N-alkali metal salt, which is then alkylated. Alkylation is carried out directly in an excess of alkylating agent or in an inert solvent by heating to a temperature of 20 to 150°C, preferably 50 to 140°C, depending on the reactivity of the alkylating agent used. is advantageous. All inert solvents are generally suitable as reaction media. Preferred are inert solvents which dissolve the starting materials and from which the desired product readily precipitates. Examples include: Aromatic hydrocarbons such as benzene, toluene and xylene, halogen hydrocarbons such as trichloroethane, tetrachloroethylene, chlorobenzene or dichlorobenzene; nitro compounds such as nitromethane, nitropropane, nitrobenzene, as well as alkanols and ring-opened or cyclic ethers such as butanol, dichlorobenzene; Butyl ether, ethylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, anisole or dioxane; ketones such as cyclohexanone or methyl ethyl ketone; fatty acid amides such as dimethyl formamide or dimethyl acetamide; sulfoxides and acetate esters or acetic butyl esters such as dimethyl sulfoxide Carboxylic acid esters such as. The benzofuranyl-benzimidazole (wherein R ₁ means cyanomethyl or 1-cyanoethyl and R ₂ means C _1-4 -alkyl or C _3-4 -alkenyl) is produced by the following method. be able to. That is, the expression (wherein R ₂ has the above meaning), a salicylaldehyde of the formula (wherein R ₁ has the above meaning and Ha 1 means fluorine, chlorine or bromine) with a halogen methyl-benzimidazole in the presence or absence of a basic condensing agent. Therefore, it can be manufactured. As basic binders, the following inorganic or organic compounds can be considered. Alkali or alkaline earth metal compounds such as oxides, alcoholates, carbonates, bicarbonates or acetates; ammonium compounds such as ammonium acetate; or tertiary amines such as pyridine. Preference is given to using inorganic compounds of sodium and potassium, especially carbonates. However, mixtures of various weakly basic compounds may also be used. The amount of condensing agent used can vary within wide limits. Although catalytic amounts are sufficient to effect the reaction itself, it is advantageous to use equivalent amounts or several times the equivalent amount. The condensation reaction is advantageously carried out in a solvent that is inert under the reaction conditions. Suitable solvents of this type include nonpolar and dipolar aprotic solvents such as xylene, dichlorobenzene or trichlorobenzene, dimethylformamide, diethylformamide, dimethylacetamide, N-methylpyrrolidone, and mixtures thereof. Preference is given to using anhydrous organic solvents in which the base used is partially or completely soluble. In some cases, the reaction according to the invention can also be carried out in the melt without a solvent, ie in the presence of a weakly basic condensing agent, for example if the starting materials have a low melting point and do not decompose. The reaction temperature can vary within a wide range depending on the method used (with or without a solvent) and the type of compounds to be condensed. If a solvent is used, the reaction temperature is
The temperature is between 50°C and the boiling point of the solvent used, preferably from 50 to 200°C and particularly preferably from 90 to 160°C. If the condensation is carried out without a solvent, the reaction temperature is between the melting point of the mixture of reaction components used and the decomposition temperature of the condensation compound. Preferably temperatures between 100 and 250°C are considered. Compounds of formulas (10), (13), (14) and (15) are known or can be prepared by methods known per se (for example, as described in U.S. Pat.
3637734, British Patent No. 1313332 and German Published Application Nos. 2853765 and 2904829). The above-defined novel compound exhibits remarkable fluorescence in a dissolved or finely dispersed state, although there are some differences depending on the type. The compounds can therefore be used for optical brightening of various synthetic, semi-synthetic or natural organic materials or substances containing such organic materials. Non-limiting examples of the group of organic materials of which fluorescent whitening is contemplated include: Synthetic organic polymeric materials: (a) polymerization products based on organic compounds containing at least one polymerizable carbon-carbon double bond, i.e. their homopolymers, copolymers and post-processed products thereof; products obtained, for example, by crosslinking, grafting or decomposition, polymer blends or modification of reactive groups, e.g. polymers obtained on the basis of α,β-unsaturated carboxylic acids or derivatives of such carboxylic acids; In particular those based on acrylic compounds (e.g. acrylic esters, acrylic acid, acrylonitrile, acrylamide and their derivatives or their methacrylic analogues), olefinic hydrocarbons (e.g. ethylene, propylene, styrene or dienes, as well as so-called ABS- (b) Polymerization products obtained by ring opening, such as polycaprolactam. (c) polycondensation products based on compounds having difunctional or polyfunctional condensable groups; or pre-condensation products, their single and mixed condensation products and products of post-treatment, such as polyesters, especially saturated polyesters (e.g. ethylene glycol/
terephthalic acid polyesters) or unsaturated polyesters (e.g. maleic acid/dialcohol polycondensates and their crosslinked products with copolymerizable vinyl monomers), linear as well as branched polyesters (also based on polyhydric alcohols) (including alkyd resins) polyamides (e.g. hexamethylene diamine adipate), maleic acid resins,
Polyaddition products such as melamine resins, their precondensates and analogues, polycarbonates, silicones, (d) polyurethanes (crosslinked and uncrosslinked). Semi-synthetic organic materials: cellulose esters or cellulose ethers with various degrees of esterification (so-called 2 1/2 acetate, triacetate, etc.), regenerated cellulose (viscose, cuprammonium cellulose) or their post-processed products, casein, plastics, etc. . Natural Organic Materials Natural organic materials of animal or vegetable origin, such as cellulose- or protein-based natural organic materials, such as cotton, wool, flax, silk, natural latker resin, starch, casein, etc. The organic materials subjected to the fluorescent whitening treatment according to the invention can belong to various processing stages (raw materials, semi-finished products or finished products). Furthermore, the organic materials can be in the form of various articles. That is, for example, sheets, profiles, injection molded products,
They can be primarily three-dimensional shapes such as various mechanical parts, chips, granules or foams, or primarily two-dimensional shapes such as films, foils, lacquers, coatings, impregnated layers and coverings, and also filaments. They may be primarily one-dimensional in shape, such as fibers, flocks, wires, etc. However, the organic material may be in the form of various homogeneously or heterogeneously dispersed amorphous materials such as powders, solutions, emulsions, dispersions, latexes, pastes or waxes. Fiber materials include, for example, endless filaments (drawn or undrawn), staple fibers, flocks, skeins, textile fibers, yarns,
It may be in the form of thread, non-woven fabric, felt, matte, flocked products, or woven or fiber-bound materials, knitted fabrics, as well as paper, paper pulp, cardboard and the like. The compounds according to the invention are of particular interest for the treatment of organic textile products, especially textile textiles. When the material to be optically whitened according to the invention is a fiber, the fiber may be in the form of a staple fiber or an endless filament, a skein, a woven fabric, a knitted fabric, a non-woven fabric, a flocked product or a bonded material. In any case, the treatment is carried out in an aqueous medium, i.e. in which the compound is present in finely dispersed form (suspension, so-called microdispersion, sometimes solution). It has the advantage of being carried out internally. During the treatment, dispersants, stabilizers, wetting agents and other auxiliary agents can be added if desired. Depending on the type of brightener compound used, it has proven advantageous to carry out the operation in a neutral or alkaline or acidic bath. Processing is typically carried out at a temperature of about 20 to 140°C, such as at or near the boiling point of the processing solution (about 90°C).
℃). In order to finish fibrous substrates such as cloth according to the invention, solutions or emulsions in organic solvents, as used in the so-called dye dyeing in the dyeing industry (pad thermo-dyeing or exhaust dyeing with dyeing machines), are used. can also be used. The novel optical brighteners according to the invention can be added to or incorporated into the material to be treated before or during molding. That is, for example, film,
It can be added to the compression molding or injection molding raw material during the production of sheets (for example, during roll milling of polyvinyl chloride at elevated temperatures) or moldings thereof. If the processing of fully synthetic or semi-synthetic materials is carried out by spinning methods or from spinning solutions/melts, the present optical brighteners can be applied by the following method. Added to starting materials (e.g. monomers) or intermediate products (e.g. precondensates, prepolymers), i.e. before or during polymerization, polycondensation or polyaddition; polymer chips for spinning solutions/melts or Sprinkling on granules; bath dyeing polymer chips or granules for the spinning solution/melt; metered addition to the spinning solution (solution or melt); applying to the spun yarn before drawing. The novel optical brighteners according to the invention can be used, for example, in the following usage forms: (a) in admixture with dyes (for shading) or pigments (colored pigments, in particular white pigments) or in dyeing baths; As an additive to printing paste, discharge printing paste or resist dyeing paste. Furthermore also as a post-processing additive for dyeing, printing or discharge printing. (b) so-called “carriers”, wetting agents, softeners,
Swelling agents, antioxidants, light stabilizers, heat stabilizers,
Chemical bleach (chlorite bleach, bleach bath additives)
Mixed with. (c) in admixture with crosslinking agents, finishing agents (e.g. glues or synthetic finishes) or also in various textile finishing methods, in particular synthetic resin finishing (e.g. "wash-and-wear", "permanent press", " Anti-wrinkle processing (also known as “no-iron”), flame retardant processing, flexible processing,
Combined with antifouling, antistatic, or antifungal treatments. (d) Polymeric carriers (polymerization products, polycondensation products, polyaddition products)
Mix this optical brightener with. (e) As an additive to so-called “master batches”. (f) As an additive to various industrial products to improve their market value (e.g. to improve the appearance of soaps, detergents, pigments). (g) In combination with other substances with fluorescent whitening action. (h) Add when preparing the spinning bath. That is, it is used as an additive to a spinning bath or to certain baths prior to drawing, such as those used to improve lubricity for subsequent processing operations of synthetic fibers. (i) For various purposes in photographic technology, for example as scintillators for electrophotographic reproduction or supersensitization. (j) As a laser dye depending on the type of substituent. When the whitening process according to the invention is combined with a fiber treatment or finishing process, it is recommended that it be carried out using a stable formulation containing the present brightener at a concentration such that the desired whitening effect is obtained. Advantageous in many cases. In some cases, the present brighteners achieve their full effect by post-treatment. Such post-treatment can be a chemical treatment (eg, acid treatment), a thermal treatment (eg, heating), or a combination of both. For example, when a large number of fiber substrates, such as polyester fiber products, are fluorescently whitened using the brightener of the present invention, the following operation is preferably performed. That is, the fibers to be treated are impregnated with an aqueous dispersion (or solution as the case may be) of the present brightener at a temperature below 75°C, for example at room temperature. Then
Dry heat treatment is performed at a temperature of 100℃ or higher. On this occasion,
It is generally desirable to pre-dry the fibers at a mildly elevated temperature, such as at least 60°C and up to about 130°C. The dry heat treatment is preferably carried out at a temperature of 120 to 225°C. This heat treatment is carried out, for example, by heating in a drying chamber, by ironing in a defined temperature range, or alternatively by treatment with dry superheated steam. Predrying and subsequent heat treatment in the dry state can be carried out one after the other or can be combined into a single working step. The amount of the novel optical brightener used according to the invention, based on the material to be treated, can vary within a wide range. For example, small amounts as low as 0.0001% by weight may already give a noticeable and long-lasting effect, while doses as high as about 0.8% by weight may be used, and if desired up to about 2% by weight. The amount used is also possible. However, for most practical purposes, a useful and preferred amount range is 0.0005 to 0.5 weight percent. For various reasons, it is often advantageous to use the present brighteners not as such, ie, alone, but in admixture with various auxiliary and bulking agents, such as sodium formate, sodium acetate or lactate. The novel optical brighteners in which n is the number 1 in formula (1) and its dependent formulas have the particular advantage that they are stable to chlorous acid. Examples of the present invention are described below. Parts and percentages in the examples are always by weight unless stated otherwise. Further, unless otherwise specified, melting points and boiling points are uncorrected. Example 1 2-Benzimidazolyl-2'yl-6-methoxybenzofuran (see British Patent No. 1313332)
A mixture of 27.3 g, 100 ml of chloroacetonitrile and 14.7 g of ground anhydrous potassium carbonate is stirred at reflux temperature for 6 hours. At this time, the starting material becomes a solution, and then the reaction product precipitates out. After cooling to room temperature, it is filtered with suction and the residue is washed repeatedly with isopropanol and water. Thus, 19.3 g of a compound represented by the following formula (100) was obtained. The product is recrystallized from perchlorethylene and xylene (pale yellow crystals, melting point 188-191°C). Compounds of the following formulas (101) and (102) were obtained in the same manner as above. Example 2 The procedure of Example 1 was repeated using 60 ml of 2-bromopropionitrile in place of the chloroacetonitrile in Example 1 above, and adding an additional 8.9 g of potassium carbonate in portions during the course of the reaction. . As a result, a compound of the following formula (200) was obtained. Purification of the product was carried out first by chromatography on neutral activity 1 aluminum oxide using ethylene chloride and then by recrystallization from isopropanol (melting point 72° C.). Example 3 (Reference example) 2-Benzimidazolyl in 450 ml of methanol
27.3 g of 2'-yl-6-methoxy-benzofuran are dissolved and 19.8 g of a 30% solution of sodium methylate are added dropwise to this hot solution with stirring. The methanol is evaporated and finally completely removed in vacuo. Bromoacetic acid ethyl ester to its solid residue
50 ml are added and the suspension is stirred for 1 hour at 50°C. After cooling to room temperature, add 250 ml of methylene chloride.
dilute by adding and separate the insoluble material. The resulting solution is evaporated in vacuo and the residue is taken up in 450 ml of hot ethylene chloride. When cooled to 0°C, the product precipitates, which is filtered with suction, washed with ethylene chloride, and dried under vacuum at 70°C.
In this way, 33.5 g of a compound represented by the following formula (300) is obtained. After recrystallization from isopropanol, the product appears in the form of almost colorless crystals, with a melting point of 178-180
°C (decomposition). Example 4 (Reference example) 2-Benzimidazolyl in 100 ml of ethanol
27.3 g of 2'-yl-6-methoxy-benzofuran was suspended and added to this suspension with stirring at 70°C.
Add 11 ml of 10N aqueous potassium hydroxide solution. The resulting solution is thoroughly concentrated in vacuo. 50 ml of chloroacetic acid ethyl ester are added to the solid residue, the suspension is stirred at 130° C. for 30 minutes and, after cooling, diluted with 100 ml of methylene chloride. Insoluble material is filtered off and the solution is evaporated in vacuo. The residue is taken up in 100 ml of hot acetone and cooled to 0°C.
During this cooling, the product gradually precipitates. After filtration, the product is washed with acetone and evaporated to dryness in vacuo at room temperature. Thus, 10.2 g of a compound of the following formula (400) was obtained. The product can be recrystallized from acetone: melting point 153-158°C (decomposed). Example 5 27.3 g 2-benzimidazolyl-2'-yl-6-methoxy-benzofuran, 80 ml chloroacetic acid methyl ester and powdered anhydrous potassium carbonate
A mixture consisting of 15.2 g is stirred at 90° C. for 4 hours.
Remove insoluble matter by heating. Concentrate the liquid thoroughly in vacuo and into 80 ml of warm methanol.
After cooling to 0°C, 50 ml of water is added to the solution while stirring. At this time, the reaction product gradually precipitates. The precipitate is filtered off with suction, washed repeatedly with a 1:1 mixture of methanol and water and dried over calcium chloride in vacuo. Recrystallization from carbon tetrachloride yields 23.0 g of a compound of the following formula (500). Melting point 111-113 °C (from isopropanol). Add 8.4 g of this product to 20 ml of chloroacetonitrile.
Stir at 120°C for 2 hours. The solution is thoroughly concentrated on a rotary evaporator in vacuo. The residue is taken up in 70 ml of chloroform and the precipitated product is filtered off with suction. Wash three times with 20 ml each of chloroform and vacuum dry. Thus, 7.7 g of a compound of the following formula (501) was obtained. Melting point: 150℃ (decomposition). This compound can be recrystallized from ethanol. Example 6 (Reference Example) 4.2 g of 6-methoxy-coumaryl chloride and 4.3 g of the compound of the following formula (600) are suspended in 20 ml of pyridine. This suspension is stirred for 30 minutes at 100°C. When this solution is cooled to 5°C, the reaction product will precipitate. The precipitate is filtered by suction, washed repeatedly with acetone and toluene, and dried under vacuum at 100°C.
Thus, 5.9 g of a compound of the following formula (601) was obtained. The product is in the form of pale yellow crystals and has a melting point of 215-216°C (decomposed). Example 7 39.6 g of 2-benzimidazolyl-2'-yl-6-methoxy-benzofuran was added to acrylonitrile.
Add 180 ml and 18.5 g of triethylamine and stir at reflux temperature for 44 hours. After removing triethylamine and excess acrylonitrile, the residue is dissolved in toluene. Strain when hot and allow to cool. The precipitated product is filtered off with suction, washed with toluene and dried under vacuum at 100°C. Thus, 43.2 g of a compound of the following formula (700) was obtained. Melting point 131-133°C (after recrystallization from toluene). Add 6.4 g of this product to 20 ml of chloroacetonitrile.
and heated to reflux temperature for 3 hours. In this solution
Add 80 ml of methyl ethyl ketone and allow to cool. The crystallized product is filtered off with suction, washed repeatedly with methyl ethyl ketone and dried under vacuum at 100°C. Thus, 5.7 g of a compound of the following formula (701) was obtained. Melting point 195-201℃. This product can be recrystallized from isopropanol. Example 8 20ml of methanol and 11ml of 10N caustic soda solution
was heated and 29.5 g of 2-benzimidazolyl-2'-yl-5-(p-chlorophenyl)-furan was dissolved therein. Concentrate the solution completely in vacuo.
100 ml of chloroacetonitrile are added and the suspension is stirred at 70° C. for 4 hours. After cooling to room temperature, dilute with 100 ml of methanol and 10 ml of water, filter, and wash the residue repeatedly with methanol and water. This was vacuum dried at 100℃ (28.0
g) and recrystallized from n-butanol.
In this way, 20.9 g of a compound of the following formula (800) is obtained. The product is a pale yellow crystal with a melting point of 223~
226° (from xylene). 6.7 g of this product was added to bromoacetic acid ethyl ester.
Pour into 20ml and stir at 100℃ for 2 hours. After the starting materials have dissolved, the desired product precipitates out in bulk. This is diluted with 50 ml of methyl ethyl ketone, filtered with suction at about 40° C. and the residue is washed with methyl ethyl ketone. After drying, 7.3 g of a compound of the following formula (801) is obtained. After recrystallization from water, the product is obtained as pale yellow crystals with a melting point of 170°C (indistinct). Example 9 (Reference example) 2-benzimidazolyl-2'-yl-5-(p
-chlorophenyl) - 5.9 g of furan and 3.3 g of powdered anhydrous potassium carbonate were added to chloroacetonitrile.
Add to 30 ml and stir at reflux temperature for 18 hours. The excess chloroacetonitrile is evaporated off in vacuo, the residue is boiled first with 80 ml and then 20 ml of water and the aqueous phase is decanted at 100°C. The combined aqueous phase is clarified while hot after addition of activated carbon. After concentrating to some extent and cooling, the product crystallizes. The product is filtered off with suction, washed with water and dried under vacuum at 100°C. However, the following formula (900)
1.8 g of the compound is obtained. The product is in the form of pale yellow crystals, which still contain 1/2 mole of water of crystallization. melting point 205
~207℃ (3:7 alcohol and acetonitrile)
after recrystallization from the mixture). Using an equivalent amount of 2-benzimidazolyl-2'-yl-5-phenylfuran in place of the furan derivative used in this example, and carrying out the same procedure as above, a compound of the following formula (901) was prepared. was gotten. Similarly, a compound of the following formula (902) was obtained. Example 10 (Reference Example) 2-Benzimidazolyl-2'-yl-5 was used instead of the starting material 2-benzimidazolyl-2'-yl-6-methoxy-benzofuran in Example 3.
The procedure described in Example 3 was carried out using -(p-chlorophenyl)-furan to obtain a compound of formula (1000) below. Example 11 (Reference Example) 7.0 g of 2-[1'-cyanoethyl-benzimidazol-2'-yl]-5-(p-chlorophenyl)-furan (US Pat. No. 3,637,734) was added to about 30 ml of chloroacetonilyl. Stir for 8 hours at reflux temperature.
Excess chloroacetonyl is removed in vacuo, the residue is boiled three times with 40 ml of water each time and the aqueous phase is decanted each time at 100°C. Activated carbon is added to the combined aqueous solution and clarified while hot. After cooling, the product crystallizes. The crystals are filtered off with suction, washed with water and dried under vacuum at 100°C. Therefore, compound 5.2 of the following formula (1100)
get g. Melting point 225°C (after recrystallization from n-propanol). Example 12 Polyacrylonitrile fiber fabric [Orlon 75
(Orlon 75)] was treated in an aqueous bath with a bath ratio of 1:20 in a dyeing machine. The aqueous bath used was 0.1% based on the weight of the treated fabric (100), (200),
(300), (601), (701), (801), (900) or (1100) optical brightener and adduct 1 of 35 moles of ethylene oxide added to 1 mole of stearyl alcohol
g/ and 1.5 ml/85% formic acid. The treatment was carried out according to the following temperature program: 40-97°C/30 min, 97°C/30 min, 97-40°C/15
Minutes. The polyacrylonitrile fabric was then rinsed with running softened water for 30 seconds and placed in a drying chamber to dry at 70°C. Fabrics treated in this way showed a high whitening effect. Example 13 A modified polyacrylonitrile fabric (Courtelle) was treated in an aqueous bath with a bath ratio of 1:20 in a dyeing machine. The aqueous bath used was 0.1% based on the weight of the treated fabric (300), (601),
(701), (900) or (1100) optical brightener,
Oxalic acid 1g/, polyphosphate as complexing agent 0.25g/ and sodium bisulfite 0.125
g/. The treatment was carried out according to the following temperature program: 40-97°C/30 min, 97°C/30 min.
min, 97−40°C/15 min. Thereafter, the polyacrylonitrile fabric was rinsed in running softened water for 30 seconds and dried in a drying chamber at a temperature of 70°C. The fabric treated in this way showed an excellent whitening effect. Example 14 A freshly spun and drawn undried polyacrylonitrile tow (equivalent to 3.0 g dry weight) was spun while still wet at a temperature of 45° C. for 4 seconds.
Immersed in a 100ml aqueous treatment bath. The aqueous treatment bath contained 0.0005% of a brightener of formula (300), (601), (900) or (1100) and was adjusted to a pH of 4 with concentrated oxalic acid solution. After this, the wet tow was rinsed briefly with water and dried at 90-100°C. In this way, polyacrylonitrile fibers with good whitening were obtained.
Dyeing with brighteners can also be carried out, for example, at pH 6 (adjusted by addition of sodium acetate). The dyeing speed can be increased by increasing the temperature of the dyeing bath to, for example, 40°C. By increasing the concentration of the optical brightener, for example up to 0.005%, the whitening effect can be further improved. Example 15 Based on the weight of the material to be whitened, 0.3
An aqueous solution containing % of an optical brightener of formula (300), (801) or (900) was prepared. This solution was heated at 30°C.
It was heated to 2 to 5 mol% isophthalic acid-
Dacron, a modified polyester fabric prepared by co-condensation with 5-sulfonic acid sodium salt (
Dacron) 64 was added to the above solution. At this time, the bath ratio was maintained at 1:25. Raise the bath temperature to 100°C in 10 minutes, hold at this temperature for 20 minutes, and
It was cooled to 50°C in minutes. The fabric was then rinsed under cold running water and ironed to dry at 180°C. Fabrics treated in this way showed a high whitening effect.

Claims (1)

[Claims] 1 formula (wherein A is a group of [formula] or [formula], R ₁ means cyanomethyl or 1-cyanoethyl, R ₂ is C _1-4 -alkyl or C _3-4 -alkenyl, and R ₄ and R ₅ independently of each other mean hydrogen or chlorine). 2 formulas (wherein A' is [formula] or a group of [formula], R ₁ means cyanomethyl or 1-cyanoethyl, and R' ₂ is C _1-4 -alkyl) Claim 1 Benzimidazole as described in. 3 formulas (wherein A″ means a group of [formula], R ₁ means cyanomethyl or 1-cyanoethyl, and R′ ₂ is C _1-4 -alkyl) Benzimidazole according to the formula 4. The benzimidazole according to claim 3. 5 formula (wherein A is a group of [formula] or [formula], R ₁ means cyanomethyl or 1-cyanoethyl, R ₂ is C _1-4 -alkyl or C _3-4 -alkenyl, R ₄ and R ₅ independently means hydrogen or chlorine) In the method for producing benzimidazole of the formula using at least one molar equivalent of the alkylating agent R ₁ X or acrylonitrile in the presence of a base, (In each of the above formulas, A and R ₁ have the meanings given above, and X means an organic or inorganic colorless acid group). 6. Process according to claim 5, characterized in that the alkylation reaction is carried out in an excess of alkylating agent or in an inert organic solvent at a temperature of 20 to 150°C. 7 formula (wherein, R ₁ means cyanomethyl or 1-cyanoethyl, R ₂ means C _1-4 -alkyl or C _3-4 -alkenyl), a method for producing benzofuranyl-benzimidazole of the formula (wherein R ₂ has the above meaning), a salicylaldehyde of the formula (wherein R ₁ has the above meaning and Ha 1 means fluorine, chlorine or bromine) with a halogen methyl-benzimidazole in the presence or absence of a basic condensing agent. How to characterize it. 8 In a method for fluorescent whitening of organic materials, the material to be brightened is (wherein A is a group of [formula] or [formula], R ₁ means cyanomethyl or 1-cyanoethyl, R ₂ is C _1-4 -alkyl or C _3-4 -alkenyl, R ₄ and A process characterized in that a benzimidazole (R ₅ independently of one another means hydrogen or chlorine) is incorporated or applied. 9. The method according to claim 8, characterized in that polyacrylonitrile is used as the organic material. 10 Based on the weight of the material to be brightened
9. Process according to claim 8, characterized in that from 0.0001 to 2% of brightener is used.