Process For The Optical Brightening Of Fibrous Materials Of Synthetic Polyamides Or Cellulose Esters

Abstract

Fibrous materials of synthetic polyamides or cellulose esters are capable optical brightening according to the so-called thermosol process (padding at ambient temperature with subsequent fixation by a heat treatment) when fixing in the presence of an auxiliary consisting of a polyalkylene glycol and a fatty alcohol oxethylate. Optionally foam-depressing phosphoric acid alkyl esters and branched carboxylic acid esters are used additionally.

Description

The present invention relates to a process for the optical brightening of fibrous materials consisting of synthetic polyamides or cellulose esters by impregnating the material with a liquor containing an optical brightener with subsequent fixation by a heat treatment which comprises fixing the brightener in the presence of an auxiliary consisting of a polyalkylene glycol of the formula

HO--(C.sub.n H.sub.2n O) .sub.x --H

in which n is 2 or 3 and x is a number of 2 to 22, and a fatty alcohol oxethylate of the formula

RO(C.sub.2 H.sub.4 0).sub.z --H

in which R is alkyl or alkenyl of eight to 24 carbon atoms and z is a number of 3 to 16.

A further object of this invention is a composition of matter, useful as an auxiliary in said process, consisting of a polyalkylene glycol of the formula

HO--(C.sub.n H.sub.2n 0).sub.x --H

in which n is 2 or 3 and x is a number of 2 to 22 and a fatty alcohol oxethylate of the formula

RO(C.sub.2 H.sub.4 O).sub.z --H

in which R is alkyl or alkenyl of eight to 24 carbon atoms and z is a number of 3 to 16.

It is known to optically brighten synthetic fibrous materials of linear polyesters according to the so-called thermosol process with a satisfactory effect. Said method comprises padding the material at ambient temperatures with solutions or suspensions of an appropriate water-insoluble brightener and submitting it to a subsequent heat treatment. The heat treatment aimed at the fixation of the brightener is preferably effected at temperatures allowing simultaneous thermostabilization of the fibrous material. With polyester fibers these temperatures generally range from about 170.degree. to 220.degree. C.

It has been attempted to apply the thermosol method also to the treatment of fibrous materials of synthetic polyamides, however, in that case the effects produced with the optical brighteners are essentially worse than achieved with usual exhaustive methods. Owing to this fact the thermosoling of optical brighteners on polyamide fibers has not attained yet any importance.

In optically brightening fibrous materials of cellulose esters, especially cellulose triacetate according to the thermosil process, substantially the same drawbacks are met with.

Now, it has been found that said difficulties can be overcome and fibrous materials on the basis of synthetic polyamides or cellulose esters can be brightened by the thermosoling method with a good effect using as auxiliary a mixture of a polyalkylene glycol and an oxethylated fatty alcohol.

The object of the invention hence is a process for the optical brightening of fibrous materials of synthetic polyamides or cellulose esters by impregnating the material with a liquor containing an optical brightener and fixing the brightener, subsequently, by a heat treatment in the presence of an auxiliary consisting of a polyethylene glycol of about 2 to 22 --(C.sub.n H.sub.2n O)-- units in which n is 2 or 3 and an oxethylated fatty alcohol, the aliphatic radical of which contains at least eight to 24 carbon atoms comprising 3 to 16 ethylene glycol ether units.

To the composition of matter to be used according to the invention a foam-depressing compound is advantageously added, for example an aliphatic carboxylic acid ester corresponding to the general formula

wherein R.sub.1 and R.sub.2 represent saturated or unsaturated aliphatic groups which may be identical or different, having from four to 18 carbon atoms, one or both of said groups containing at least one side chain of one to four carbon atoms which chains preferably are in the .alpha.-position in the acid radical while in the .alpha. or .beta.-position in the alcohol radical. As appropriate esters of the indicated type the following may be cited by way of example: 2-ethyl-capric acid-2-ethylhexyl ester, 2-ethyl-capric acid-2-ethyl-butyl-ester, 2,2,3-trimethyl-butyric acid-2-ethylhexyl ester, 2-ethyl-capric acid isooctyl ester, 2-ethyl capric acid isobutyl ester, the ester of 2-ethyl capric acid and 2,6,8-trimethylnonanol-(4) as well as the 2-ethyl capric acid ester of 2,6-dimethyl-heptanol-(4).

The carboxylic acid esters are preferably applied in admixture with a phosphoric acid ester of an aliphatic alcohol having four to eight carbon atoms, such as tri-n-butyl-phosphate, tri-n-octylphosphate, especially triisobutyl phosphate.

The foam-depressing agents are generally added to the composition of matter of the invention each in an amount in the range of from 0.5 to 5 percent, referred to the weight of the composition.

The instant process may be carried out by applying to the material to be brightened a solution, dispersion or emulsion containing the optical brightener, the polyalkene glycol, the oxethylated fatty alcohol and, optionally, further adjuvants, predying said material, subjecting it to a heat treatment in a thermosoling device and finishing it thereafter, in usual manner. The optical brightening agents can be applied from an organic or, preferably, aqueous bath. It is likewise possible to apply the brightener and the auxiliary of the invention with, optionally, the foam-depressing agents to the fibrous material separately in any sequence, prior to the heat treatment. The heat treatment for the fixation of the optical brightener is generally conducted at temperatures between about 170.degree. and 220.degree. C., preferably 180.degree. and 210.degree. C. It lasts, approximately, 5 to 60, preferably 5 to 40 seconds and proceeds either in the form of dry heating or, if desired, in using a small amount of steam.

As polyalkylene glycols to be used according to the invention compounds of the general formula

HO--(C.sub.n H.sub.2n 0).sub.x H,

are suitable wherein n is 2 and 3 and x represents a number from about 2 to 22. Preferred are polyethylene glycols of a medium molecular weight in the range of from 200 to 600. However, polypropylene glycols or polyethylene-propylene glycols or mixtures of both are likewise appropriate.

As oxethylated fatty alcohols may serve compounds of the formula

RO--(CH.sub.2 --CH.sub.2 --0).sub.z H

wherein z represents a number from about 3 to 16, preferably 5 to 10, and R is a saturated or unsaturated aliphatic radical of eight to 24, preferably 12 to 18 carbon atoms.

The mixing ratio of the polyalkylene glycols and oxethylated fatty alcohols may vary within wide limits. Generally, about 0.01 to 1 part by weight, preferably 0.05 to 0.5 part, of oxethylated fatty alcohol is used per each part by weight of the polyalkylene glycol. The composition of matter of the invention should advantageously be applied in an amount from about 0.05 to 2.5 percent, preferably, 0.2 to 1.5 percent, calculated on the weight of the fibrous material.

The process of the invention may be carried out with the aid of optical brightening agents suitable for fibrous materials of polyamide or cellulose acetate. Preferred are optical brighteners of the pyrazoline series corresponding to the general formula ##SPC1## in which R' stands for an aryl radical, which may be substituted and X for the vinyl group or the radical --CH.sub.2 --CH.sub.2 --Y in which Y is a hydroxy group, a primary or secondary amino group, an acylamino group or an alcoxy radical which may be substituted, a --OSO.sub.3 Me--or --SO.sub.3 Me--group wherein Me represents hydrogen or a metal cation. Such optical brighteners have, for example, been disclosed in Belgian Pats. Nos. 631,367, 661 139, 670 161 and 701 986. For use on fibrous materials of synthetic polyamides predominantly water-soluble brighteners of the indicated type are employed.

The brightening agents are applied in usual concentrations, generally, in an amount in the range of from about 0.01 to 2 percent, preferred to the weight of the fibrous material.

The instant process is applicable to fibrous materials on the basis of polyamides, for example those prepared from adipic acid and hexa-methylene diamine (polyamide 66) or adipic acid, hexamethylene-diamine and caprolactam (polyamide 66/6), caprolactam (polyamide 6) or .omega.-aminoundecylic acid (polyamide 11) and also to fibrous materials of cellulose esters, especially cellulose triacetate. Said process provides goods of a uniform, high degree of whiteness.

The following examples are to illustrate the invention but they are not intended to limit it thereto. The parts and percentages being by weight unless otherwise stated.

EXAMPLE 1

A knit fabric made of polycaprolactam (polyamide 6) was impregnated with a liquor containing per liter 15 g. of an auxiliary consisting of 85 parts of polyethylene glycol of a molecular weight of 400, 10 parts of an addition product of 5 mols of ethylene oxide to 1 mol of a fatty alcohol having on an average 13 carbon atoms, 2.5 parts of triisobutyl phosphate and 2.5 parts of 2 ethylcapric acid-2-ethyl-butyl ester, 15 g./l. of an optical brightening agent corresponding to the formula ##SPC2##

and 0.3 g./l. of citric acid.

The fibrous material was squeezed off between cylinders until its moisture content represented 70 percent of its dry weight and, subjected, subsequently, for 20 seconds to a treatment by hot air of 190.degree. C.

The knit fabric thus treated displayed an outstanding degree of whiteness substantially higher than that produced, under equal conditions, without the use of the auxiliaries.

EXAMPLE 2

A laundered and dried fabric of polyamide 6.6 was treated with a liquor containing per liter 25 g. of an auxiliary consisting of 75 parts of polypropyleneglycol of a molecular weight of 250, 15 parts of an addition product of 8 mols of ethylene oxide to 1 mol of a branched fatty alcohol having on an average 13 carbon atoms, 5 parts of triisobutylphosphate and 5 parts of 2 ethyl-capric acid-2-ethyl-butyl ester, 25 g./l. of an optical brightening agent having the composition specified in example 1 and 0.5 g./l. of citric acid. To the liquor moreover, 30 mg./l. of dyestuff C.I. No. 51 319 (cf. Color Index, 2nd edition (1956))were added in order to improve the shade of the brightener.

The fibrous material was squeezed off in usual manner between cylinders to a moisture content representing 55 percent of its dry weight, dried subsequently, during 30 seconds at 130.degree. C. and subjected, thereafter, for 20 seconds to a treatment in hot air at 200.degree. C.

The fabric thus treated showed an excellent degree of whiteness essentially superior to that produced, under equal conditions, without the auxiliaries.

EXAMPLE 3

A knit fabric made from polyamide 6 was treated with a liquor containing per liter 25 g. of an auxiliary consisting of 85 parts of polyethylene glycol of a molecular weight of 200, 10 parts of an addition product of 5 mols of ethylene oxide to 1 mol of stearyl alcohol, 2.5 parts of triisobutyl phosphate and 2.5 parts of 2-ethyl capric acid-2-ethylbutyl ester, 5.7 g./l. of an optical brightening agent corresponding to the formula ##SPC3## (disclosed in French Pat. No. 1,300,489) The fibrous material was squeezed off between cylinders to a moisture content of 30 percent of its dry weight and subjected, subsequently, during 20 seconds to treatment in hot air of 190.degree. C.

The knit fabric thus handled displayed a high degree of whiteness.

EXAMPLE 4

A fabric of triacetate fibers was impregnated with a liquor containing per liter 20 g. of the auxiliary specified in example 1, 2.25 g./l. of an optical brightening agent of the formula ##SPC4## and 5 g./l. of an addition product of 8 mols of ethylene oxides to 1 mol of nonylphenol. The fibrous material was squeezed off between cylinders to a moisture content of 60 percent of its dry weight and exposed during 20 seconds to a temperature of 190.degree. C. The fabric exhibited an excellent degree of whiteness.

EXAMPLE 5

A knit fabric of polyamide 6 was treated with a liquor containing per liter 25 g. of an auxiliary consisting of 85 parts of polyethylene glycol of a molecular weight of 200, 10 parts of an addition product of 5 mols of ethylene oxide to 1 mol of olealcohol, 2.5 parts of triisobutyl phosphate and 2.5 parts of 2-ethyl capric acid 2-ethyl-butyl ester, 5.7 g./l. of an optical brightening agent of the formula specified in example 1 and 0.5 g./l. of citric acid. The fibrous material thus wetted was squeezed off between cylinders until having a moisture content of 50 percent of its dry weight and subjected, thereafter, for 20 seconds to a hot air treatment at 190.degree. C.

The knit fabric thus treated displays an excellent degree of whiteness.

Claims

We claim:

1. A process for the optical brightening of a fibrous material of a synthetic polyamide or cellulose ester which comprises impregnating the fibrous material with a liquor containing an optical brightener, and subsequently fixing the optical brightener by a heat treatment in the presence of an auxiliary consisting essentially of

a. a polyalkylene glycol of the formula

HO--(C.sub.n H.sub.2n O).sub.x --H

wherein n represents 2 or 3 and x represents a number from 2 to 22, and b. a fatty alcohol oxethylate of the formula

R--O--(C.sub.2 H.sub.4 O).sub.z --H

wherein R represents an alkyl or alkenyl group containing eight to 24 carbon atoms and z represents a number from 3 to 16,

the ratio of the components being about 0.01 to 1 part by weight of oxethylate per one part by weight of glycol.

2. The process of claim 1, wherein there is added to the auxiliary,

a. from 0.5 to 5 percent by weight, calculated on the weight of the auxiliary, of a carboxylic acid ester of the formula

wherein R.sub.1 and R.sub.2 are alkyl or alkenyl of four to 18 carbon atoms, at least one of R.sub.1 and R.sub.2 being branched, and

b. from 0.5 to 5 percent by weight, calculated on the weight of the auxiliary, of a phosphoric acid alkyl ester, the alkyl radicals of which contain four to eight carbon atoms.

3. The process according to claim 1, which comprises adding the auxiliary together with the optical brightener to the fibrous material.

4. An auxiliary composition consisting essentially of

a. a polyalkylene glycol of the formula

HO--(C.sub.n H.sub.2n O).sub.x --H

wherein n represents 2 or 3 and x represents a number from 2 to 22, and

b. a fatty alcohol oxethylate of the formula

R--O--(C.sub.2 H.sub.4 O).sub.z --H

wherein R represents an alkyl or alkenyl group containing eight to 24 carbon atoms and z represents a number from 3 to 16,

the ratio of the components being about 0.01 to 1 part by weight of oxethylate per one part by weight of glycol.

5. The composition defined in claim 4 wherein the ratio of components is 0.05 to 0.5 parts by weight oxethylate to one part by weight glycol.

6. The composition defined in claim 4 which additionally contains from 0.5 to 5 percent by weight of an aliphatic carboxylic acid ester of the formula

wherein R.sub.1 and R.sub.2 are alkyl or alkenyl of four to 18 carbon atoms, at least one of R.sub.1 and R.sub.2 being branched.

7. The composition defined in claim 4 which additionally contains from 0.5 to 5 percent by weight of a phosphoric acid alkyl ester, the alkyl radicals of which contain four to eight carbon atoms.

8. The composition defined in claim 4 which additionally contains

a. from 0.5 to 5 percent by weight of an aliphatic carboxylic acid ester of the formula

wherein R.sub.1 and R.sub.2 are alkyl or alkenyl of four to 18 carbon atoms, at least one of R.sub.1 and R.sub.2 being branched, and

b. from 0.5 to 5 percent by weight of a phosphoric acid alkyl ester, the alkyl radicals of which contain four to eight carbon atoms.