US3135577A - Process for improving the handle of polyethylene terephthalate fabrics with an alkali metal hydroxide and specific quaternary ammonium salts - Google Patents

Description

United States Patent PRGCEQS FUR IMPROVTNG THE HANDLE OF POLYETHYLENE TEREPHTHALATE FABRIQS WTTH AN ALKALI METAL HYDRQXIDE AND SPECEFHC QUATERNARY AMMGNIUM SALTS William Graham Watson, Harrogate, England, assignor to Imperial Chemical Industries Limited, London, England, a corporation of Great Britain No Drawing. Filed Dec. 19, 1960, Ser. No. 76,507 Claims priority, application Great Britain Dec. 22, 1959 7 (Ilaims. (Cl. 8-4155) This invention relates to a process for treating fabrics comprising synthetic polyester filaments or fibres in their drawn condition.

In British Patent No. 652,948 a process is described for producing improved fabrics comprising treating a fabric composed of a fibre forming polyester namely highly polymerised polymethylene terephthalate having 2l0 inclusive carbon atoms in the polymethylene chain with an aqueous solution of caustic soda or caustic potash. The solutions may contain 4-10% by weight of caustic alkali.

Polyethylene terephthalate filament yarn fabrics have intrinsically a good handle and draping properties, but they become harder and stiff during finishing involving heat setting, due to the strains developed during heat setting. Methods used commercially for softening the heat set fabrics are either, winch scouring followed by restentering at 150 C., or a tratment in the presence of a dilute solution of caustic soda as disclosed in the aforementioned British patent specification 652,948, which is carried out using a jig.

By treating the fabrics with caustic alkali, an improved handle is obtained and if the treatment is continued, sheer and thin fabrics may be produced.

I believe that this is brought about by dissolving the polyester from the surface of the filaments and it can be determined by the weight loss of the filaments. The weight loss referred to, is determined by weighing a dried sample of filaments or fabrics before and after the treatment with the alkaline solution.

For commercial practice it is desirable to keep the concentration of the caustic alkali as low as possible while at the same time either maintaining or reducing other treating conditions, e.g. time and temperature. I have found that quite small amounts of specified quaternary ammonium salts, when added to caustic alkali metal hydroxide solutions, bring about an unexpected increase in the loss of weight of the treated fabric. In consequence, the amount of the caustic alkali in the treatment bath can be decreased, either while maintaining the previously established treating conditions or, if desired, by decreasing other treating conditions such as the time and/ or the temperature.

According to my invention, I provide a process for treating fabrics comprising synthetic polyester filaments or fibres in their drawn condition, in which the fabrics, are treated with a solution comprising a caustic alkali metal hydroxide and a quaternary ammonium salt selected from cetyl trimethyl ammonium bromide and lauryl dimethyl benzyl ammonium chloride.

The solutions hereinafter referred to are aqueous solutions, but it should be appreciated that other hydroiiylated liquids, which are soluble and miscible with water, may be used. A suitable caustic alkali hydroxide solution, which is preferred, is sodium hydroxide in water. The amount of sodium hydroxide in the solution may be 0.55%, preferably 13%. Suitable amounts of the specified quaternary ammonium salt are between 0.005 and 0.5%, preferably 0.025 up to 0.1%.

The solutions are preferably applied at elevated temperatures of 110 C. and for treatment e.g. on a jig, between C. and the boiling point of the solution.

The polyesters which may be treated according to my invention have a terephthaloyl group in their molecular repeat unit. They are obtainable by polycondensation from terephthalic acid with glycols having 2-10 carbon atoms in their aliphatic chain, as well as from certain cyclic glycols; minor amounts of other divalent compounds coplymerisable with the terephthaloyl group may be incorporated in amounts up to 15%, such as isophthalic acid and sebacic acid. The polyester, for which this invention is particularly suitable, and which is referred to in the following examples, is polyethylene terephthalate.

I have found that the effect of certain other quaternaries such as cetyl pyridimium bromide, dimethyl phenyl benzyl ammonium chloride and tetramethyl-ammonium bromide is very much less marked. Moreover, some quaternary ammonium compounds crack out from the solution under treating conditions, whereas others leave a dirty deposit on the fabric after treatment.

Cetyl trimethyl ammonium bromide or lauryl dimethyl benzyl ammonium chloride, on the other hand, are very eifective, they are suitable under the treating conditions and are commercially available in bulk at a low cost compared with many other quaternary ammonium compounds.

In the case of low-set fabrics, my treatment may lead to thread slippage in the finished fabric. This may be minimised by embossing the fabric with a fine overall pattern, before the treatment. This not only improves the handle, but imparts greater effective cover to the fabric after treatment. Fabrics in which thread slippage is liable to occur after treatment are taffeta fabrics.

Yet another difficulty has been encountered in that the fabric, even after the caustic treatment, has been found to have a stiff handle. I have discovered that this is associated with inadvertent heat setting of the fabric under tension, which occurs e.g. while the treated fabric is dried which, in commercial practice, is done on a stenter. This second stiffening may be overcome by dryin the fabric at a relatively low temperature, under C., which is insufficient to cause setting, and by keeping the fabric not under tension during drying, or during any operation subsequent to the caustic treatment.

The treatment with the caustic alkali solution is conveniently carried out on available equipment, e.g. using a jig. It is difficult, however, to obtain a uniformly treated fabric, even when the concentration and time of treatment are accurately controlled, because temperature variations, particularly at the ends of the fabric occur (when using a jig), and also because it is difficult or impossible to Watch the progress of the treatment-e.g. by determination of the weight loss in the fabrics, without interrupting the treatment.

Instead of using a jig, in which the fabric is passed through the solution in a trough under a pulley roller, while being unwound from a feed roller and wound up 3 on a takeup roller and back again, a required number of times, an entirely different method may be used for the alkali treatment.

This comprises winding the fabric on a perforated beam and pumping the caustic solution through the beam under pressure to percolate the fabric, and recirculating the percolating solution for a sufiicient time and temperature. Depending on the fabric construction, and the number of layers wound on the beam, the pressure of the solution, which is conveniently read off between the pump and the beam gives a measure of the weight loss of the fabric. Moreover, the time of treatment can be reduced, compared with a treatment on a jig, because of the more efiicient contact between the fabric and the solution under pressure. For instance, a solution containing only 1.5% sodium hydroxide and 0.05% of lauryl dimethyl benzyl ammonium chloride has given a desired weight loss of 5-10% in 2040 minutes at a temperature of only 85 C. This compares most favourably with a treatment on a jig, where the time of treatment required to achieve a comparable weight loss is 1-2 hours, using a 1.5% sodium hydroxide solution and the same amount of quaternary ammonium salt at a commercial boil (about 98100 C.).

A suitable sequence of operation for improving fabrics made from, or containing, a major proportion of synthetic polyester filaments or fibres in their drawn condition comprises the steps of scouring the fabric, heat setting the fabric under controlled tension on a stenter at a temperature of 7030 C. below the melting temperature of the polyester, embossing the fabric with a fine, overall embossing pattern under a pressure of 10-15 tons at a temperature between at least 5 C. below the heat setting temperature and 90 C. above the second order transition temperature, treating the fabric with caustic alkali metal hydroxide solution under pressure, rinsing the fabric, neutralising if necessary, with a dilute solution of acid, e.g. acetic acid, and drying the fabric at a low temperature at least 120 C. below the melting temperature of the polyester, preferably above 90 C., using the smallest possible tension following the treatment with the alkali solution and in all subsequent operations including drying, to avoid stiffening of the fabric and winding the fabric Without creasing on a suitable package, such as a bobbin.

The fabrics usually require to be dyed or printed. Dyeing may be carried out after neutralising and rinsing the fabric following the treatment with the caustic solution and before drying. If the fabric is to be printed, it should be dried before printing. Drying should be carried out at a temperature less than 130 C., in the case of polyethylene terephthalate, and under the smallest possible tension, sufficient only to prevent creasing, so that the fabric does not become stiffened again.

The following examples, in which all parts and percentages are by weight, illustrate, but do not limit, my invention.

Examples 1-5 illustrate the conditions when using cetyl trimethyl ammonium bromide.

Examples 6-8 illustrate the use of lauryl dimethyl benzyl ammonium chloride.

EXAMPLE 1 Samples of polyethylene terephthalate plain weave fabrics from 50 denier Terylene (registered trademark) filament yarn were immersed in a glass beaker containing boiling aqueous caustic soda solution. The solution contained 1%, 2% or 3% by weight, of caustic soda and 0.05% cetyltrimethylammonium bromide. The samples were treated for a period of 15 minutes, rinsed, and the loss in weight of the dried fabric samples, before and after the treatment, determined by weighing. Table 1 summarizes the results of the treatment, which are compared with the results obtained without the addition of the quaternary ammonium salt.

Table 1 Percent Percent Cetyl Percent loss Caustic Trimethyl in weight No.

Soda Ammonium of fabric Bromide EXAMPLE 2 Samples of fabric as used in Example 1 were treated for 15 minutes in a beaker at the boil, and Table 2 illustrates the effect of small amounts of up to 0.2% of cetyl trimethyl ammonium bromide, when added to the caustic soda solution. It will be seen that the eifect is most marked when the first 0.05 are added; quantities up to 0.2% do not seem to cause a corresponding further increase in the loss in weight of the fabric, when the solution contains caustic soda of 1%, 2% and 3% by weight and when the treating time is only 15 minutes.

Table 2 Percent Cetyl Trimethyl Ammonium Bromide 1% NaOH 2% NaOH 3% NaOI-I Weight loss of fabric (percent) Table 3 illustrates the very marked effect of temperature, using 3% sodium hydroxide and 0.05% cetyltrimethyl ammonium bromide for 15 minutes. The samples are the same as described in Example 1.

Table 3 EFFECT OF TEMPERATURE OF TREATMENT BATH ON WEIGHT LOSS USING 3% NaOH +0.05 CETYL TRIMETHYL AMMONIUM BRO- MIDE IN A BEAKER FOR 15 MINUTES Temperature, C 60 70 100 Percent weight loss of fabric (percent)- 0.8 2. 3 5. 5 12. 9 26.0

EXAMPLE 4 Table 4 illustrates the effect of small amounts up to 0.05% of the quaternary salt cetyl trimethyl ammonium bromide as used in Example 1 and also the effect upon the time of the treatment for 15 minutes, compared with 30 minutes, both at C., and using 3% by Weight of aqueous caustic soda solution.

It will be seen that even quite small amounts up to 0.05% have a considerable eifect on the weight loss, which increases with increasing amounts of the quaternary ammonium salt, but which does not rise consistently with the amounts added, during a relatively short treating time of fifteen minutes. As the treating time is increased to 30 minutes, the loss in weight is at least doubled for the Table 4 EFFECT OF QUANTITIES OF UP TO 005% OF CETYL TRI- METHYL AMMONIUM BROMIDE WHEN ADDED TO 3% CAUSTIC SODA SOLUTIONS-TREATED 15 MINS. AND 30 MINS. AT 95 C.

7 Percent Cetyl Trimethyl Ammonium 15 mins. at Bromide 95 EXAMPLE 5 Table 5 EFFECT OF TIME OF TREATMENT USING 3% NaOH+ 0.05% CETYL TRIMETHYL AMMONIUM BROMIDE FABRIC TREATED AT 98 C. ON LABORATORY WINCH Mlinutes on winch Percent weight loss 10 6.3 12.3 19.0 26.4 '30 27.6 40 31.1

EXAMPLE 6 Samples of polyethylene terephthalate taffeta, denier 24 filament, filament yarn fabric are treated in a laboratory alkali resisting beaker with an aqueous solution containing 3% sodium hydroxide and 0.05 lauryl dimethyl benzyl ammonium chloride at 90 C., using a Water bath for heating, for 30 minutes. The weight loss of the fabric is 32.2%. The treated fabric has a sheer appearance and a silky soft handle.

By comparison, samples of fabric treated under the same conditions without the addition of the quaternary ammonium salt show a weight loss of only 3.5%. The following table illustrates the effect of other quaternaries under the same conditions as described in Example 6. It will be seen that there is no appreciable improvement, except in the case of cetyl trimethyl ammonium bromide.

Table 6 3% SODIUM HYDROXIDE AQUEOUS SOLUTION Weight Loss after 30 mins. at 90 C.

Quaternary Ammonium Salt 0.05%

1 Fabric badly stained.

EXAMPLE 7 A 1000 yard length of a polyethylene terephthalate filament yarn fabric, as used in Example 6, is scoured, heat set on a stenter at 210 C. under controlled tension, allowing 3% relaxation in the warp and weft, the heat set fabric is embossed with a crepe design between two bowls. One of the bowls consists of annular paper washers compressed between solid metal discs, so that the peripheries of the paper washers form the surface of one of the bowls. The other bowl is of metal with the crepe design engraved on it and this bowl is maintained at 210 C. During embossing a slight deformation of the filaments occurs, under a pressure of 10-15 tons, as measured on hydraulic rams carrying the paper surface bowl. The embossed fabric is then treated on a jig comprising a feed roller, a trough with the solution and a trolley roller in the trough for immersing the fabric in the solution and a wind-up roller. The trough with the solution is heated by steam injection and maintained at -98 C. The fabric is processed by running it through the solution six times which takes one hour. The solution is an aqueous solution consisting of 3% sodium hydroxide and 0.05%. lauryl dimethyl benzyl ammonium chloride in water. The Weight loss in the fabric is 6%. The fabric is rinsed still on the jig in running water, while passing from the feed roll to the take-up roll and back to the feed roll. It is then neutralised by running it through a dilute solution of acetic acid, rinsed again with water, scoured again with water containing 1 gram per litre of a commercially available detergent consisting of a polyethylene oxide condensate, at 9598 C., and dried. Drying of the fabric is carried out on a pin stenter with no tension. For this purpose, the stenter setting as previously used for heat setting is slightly decreased weft- Wise, by resetting the weft pins, and the fabric is overfed on the stenter chain. The fabric is only sufiiciently tensioned at the cold part of the stenter to allow threading up and spreading of the fabric without creasing between selvedges. It is then passed through driven nip rolls which slightly over-feed the fabric as it is placed on the travelling pin chains by a brush roll, so that the fabric is gripped between the chains at the selvedge, allowing for any Width contraction up to 1.5%. The over-feed of the nip rolls is 5%, but the actual over-feed of the fabric as placed on the stenter chains is somewhat less, about 3% because of the previous tensioning on the cold part of the stenter on the entry rollers, up to the nip rolls. The fabric passes through a heated dryingzone in which circulating air is maintained at 120 C., whereby the fabric becomes dry and is taken off the pin chains by means of a stripping bar and a second set of driven nip rolls, at the other end of the stenter, where the fabric is wound up on a suitable package by a surface drive from the nip rolls. The nip rolls and chains are driven at the same surface speed. A soft uncreased and crease resisting fabric with a very desirable soft silky handle is obtained.

Unless the above precautions during drying are taken the fabric becomes stiffened.

EXAMPLE 8 This example illustrates the use of a caustic solution with lauryl dimethyl benzyl ammonium chloride under pressure. 500 yards of a taffeta satin fabric is scoured and heat set, as described in Example 7. The fabric is a 50 denier, 24 filament, polyethylene terephthalate filament yarn, 36" wide fabric weighing 2.43 oz. per square yard. The heat set fabric, instead of being treated on a jig, is now wound on a 3 inch diameter perforated beam on which the perforations at each end have been blanked off, so that the perforations extend symetrically about 1 inch less than the width of the fabric, i.e. about 34 inches. During winding a transverse motion is used corresponding to the width of one selvedge of the fabric, thus avoiding a build-up of material, but ensuring that when liquid is pumped through the perforated beam under pressure, it will percolate the whole width of the fabric and will not excessively escape sideways between fabric layers and on the ends of the beam. The beam is mounted in a closed cylinder communicating with the atmosphere through an expansion tank for pumping a caustic solution through the beam and the fabric under pressure, so that the fabric becomes immersed in the solution in the cylinder and the solution is circulated by the pump under pressure. The caustic solution is an aqueous solution of 0.5% sodium hydroxide and 0.05% lauryl dimethyl benzyl ammonium chloride which is pumped to percolate the fabric on the beam and continuously recycled for 30 minutes at 85 C.

The fabric is rinsed with water, acidified with dilute acetic acid scoured and rinsed again, whilst still on the beam by replacing the caustic solution and pumping the appropriate liquids through the beam and the fabric.

The pressure measured between the pump and the beam is 18 lb. per square inch at the beginning of the treatment with the caustic solution and this drops to 15 lb. per square inch after 30 minutes, thus indicating the thinning of the fabric. The fabric is unwound from the beam and dried on the stenter, as described in Example 7. The treated fabric weight 2.3 oz. per square yard. The fabric has a softer handle and does not crease as before the treatment.

The differences in weight loss on four commercial runs using a beam for percolating the liquid through the fabric under pressure showed that the largest difference between any two pieces of fabric was less than Fabrics treated on a jig in eight runs, on the other hand, varied by as much as 50% in average weight loss. Moreover, the ends of the fabric treated on the jig showed a smaller weight loss than the remaining fabric, the treatment was therefore less uniform and the ends of the fabric had a stiffer handle than the centre portion.

If it is desired to print the fabric, this is conveniently carried out after drying, care being taken, particularly during roller printing, that no tension is applied, or only sufiicient tension to prevent creasing of the fabric.

The preceding description relates to polyethylene terephthalate filament yarn fabrics for which our process is particularly suitable, but it is also applicable to fabrics comprising filaments or fibres melt spun from other synthetic polyesters or copolyesters, which contain up to of a second component and to fabrics which may contain a minor proportion of other fibres, e.g. cellulosic fibres, particularly flax or even cotton, but in the latter case the treatment should be limited to prevent excessive degradation of the other fibres.

What I claim is:

1. A process for improving the handle of fabrics of polyethylene terephthalate filaments and fibers in their drawn condition which comprises contacting said fabrics with an aqueous solution containing 0.55% of a caustic alkali metal hydroxide and 0.005-0.5% of a member of the group consisting of lauryl dimethyl benzyl ammonium chloride and cetyl trimethyl ammonium bromide until a portion of the surface of the filaments has been dissolved.

2. A process for treating fabrics according to claim 1 in which the solution comprises 13% sodium hydroxide and 0.0250.1% of the lauryl dimethyl benzyl ammonium chloride.

3. A process for treating fabrics according to claim 1 in which the solution is applied at a temperature of 4. A process for treating fabrics according to claim 3 in which the solution is applied at a temperature between C. and the boiling point of the aqueous solution.

5. A process for treating fabrics as set forth in claim 1 in which the fabrics are treated under pressure and said solution is pumped under pressure through a plurality of layers of the fabric to percolate the fabric.

6. A process for treating fabrics according to claim 5 wherein the time of treatment is controlled according to the drop in pressure required to pump the solution through the fabric 7. A process according to claim 5 in which the fabric is wound together in a helix and the said solution is pumped under pressure from the inside of the helix to the outside.

References Cited in the file of this patent UNITED STATES PATENTS 2,461,603 Hunter et al. Feb. 15, 1949 2,590,402 Hall et al. Mar. 25, 1952 2,618,954 Dourdeville Nov. 25, 1952 2,670,622 Dourdeville Mar. 2, 1954 2,828,528 Gajjar Apr. 1, 1958 2,852,833 Mueller Sept. 23, 1958 2,998,296 Hennemann Aug. 29, 1961 OTHER REFERENCES American Dyestuff Reporter, Nov. 28, 1949, page 862. Du Pont Bulletin D 76, March 1956, 8-Teryl. McCutcheon, Soap and Chemical Specialties, December 1957, page 65

Claims (1)

1. A PROCESS FOR IMPROVING THE HANDLE OF FABRICS OF POLYETHYLENE TEREPHTHALATE FILAMENTS AND FIBERS IN THEIR DRAWN CONDITION WHICH COMPRISES CONTACTING SAID FABRICS WITH AN AQUEOUS SOLUTION CONTAINING 0.5%5% OF A CAUSTIC ALKALI METAL HYDROXIDE AND 0.005-0.5% OF A MEMBER OF THE GROUP CONSISTING OF LAURYL DIMETHYL BENZYL AMMONIUM CHLORIDE AND CETYL TRIMETHYL AMMONIUM BROMIDE UNTIL A PORTION OF THE SURFACE OF THE FILAMENTS HAS BEEN DISSOLVED.