US 2904840 A
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United States Patent "ice WREQEIBERS B:Y. .SWELLING; THE :EIBERSLAN D 'QXYGEN N 151 U.
FRichard "Hochreuter, Rorschach, .Switz erland, assignor to Feldmuhle A.-G., Rorschach, Switzerland .N -Drawing. ApplicationAugustll, 1955 Serial ,No. 527,889-
fllaims priority, application Switzerland December- 27, 1954 2 GI mS- (.Cl- :18.48)
The present invention relates to the production of aerated synthetic fibres,-, panticnlarly such fibres of the ,n lyamide, .polyes e an p lx o itr yp 'Itjis generally known, that fibers consisting ofregenstated, cellulosehave a substantially higher thermal con- .ductivity incomparison with native cellulose fibers, and @1181 the heat insulating capacity of garments, which are made offregenerated cellulose "fibers, is accordingly only In order to overcome thisdrawback, it has already .been, proposed to provide heat-insulating voids within the regenerated cellulose fibers, and such methods have been reportedin the--literature in several instances. According to one, offthosemethodsa spinning composition having finely divided gasbubbles suspended therein is produced by either-adding gas evolving substancesgto the spinning solution or by directly aerating saidsolution-with air or another gas, and then coagulating the formed dispersionduring the spinning operation. Generally the gas'is only -liberated from the gas evolving;substance'after the spinning composition emerges from the spin-neret. According toanother method, some suitable solid or liquid-substance-is added to-.:tl'1e sp-inningsolution, which substance is subsequently dissolvedout -of the filaments, whereby fine hollow spaces are formed withinthe *fibers.
' A similar ---result canbe obtained, if the cellulose fiber is swelled in an aqueous medium, which contains unstable compounds, the latter beingsubsequentlydecomposed under evolution of gas. However, those above-mentioned procedures have-heretofore only-been applied to regenerated cellulose fibers.
It is therefore an object-of the present invention to provide ,means. facilitating the manufacture; of aerated fully-synthetic; fibers, such .as ,polyarnide polyester 01' polyaci'ylonitrile fibers which. will; have, improved heat in ulating properties,
,A, further object, of the;.inv,ention isto provide ,means enabling ,.manufacture..of. aerated, fully synthetic fibers,
. .whichwill haueimproved optical ch ract ristic Still. another object. of the. invention. is, to, provide 7 means ,contribnting-totthe manufacture. of; aerated. fully synthetic or-chemical fibres, Whidtaemtfid fiberswill have unbroken surfaces.
The. ully, ynthe iafibers whi h may h reated by the .nra e io h iin ention. include. polyamid fibres vof. th .pnlyhe amethxl neadiaminecadipic acid typ ch as. 1 .6 nylon, and. h poly-fimiuocaproic acid ype,.,,s.uch a nylon? polyester. fibre hs cha ,polyethy cn terep th lat .(Teryl ne), ndpnlyac ylo it ile fibr ssu h. a
A r at varie y of oth. inorganic. n san csubstances, can be .use d as swelling agent; Examples. of suitable compounds, are, chl'oroacetic acid, acetic acid, formic acid, mineral acids, saturated salt solutions, chlorarhydrate solution, phenols,. g lycols etc. Itis understood, that. the particular chosen swelling agent will depend'on the type of synthetic fibers used. Thus for polyamide fibers chloroacetic acid, acetic acid, formic acid and mixtures thereofhave been found particularlysuit- Patented Sept. 22, 1959 able. For polyester fibers hydrpxlyic compounds such as phenol; canjbe conveniently used; Forjfi bers ofjthe polyacrylonitrile type, e. g an ethanolic solution of calcium thiocyanate was foundjto be suitable.
Among the h n-co pound hi h w l. vo ve the gas or oxygen respectively within the fibrillae of the treated chemical'fibers, hydrogenperoxide has been found most suitable; however, sodium peroxide and similar peroxy compoundsare also satisfactory for the rnethod of the invention.
The employed catalyst serves to accelerate the rate of decomposition of the peroxides within the fibres. Suitable catalysts include heavy metals, such as silver, gold, platinum, palladium, rhodium, iridium, osmium, mercury, manganese, cobalt, iron and-copper, either. in metallic form. or in the form=of theii -salbcompounds. Aqueous solutionsof potassiumpermanganate, of manganous salts,
such as manganous chloride and: manganous sulphate,
and of cobaltous. salts, such as cobaltous sulphateare particularly satisfactory'forrthe purpose of the invention.
When carrying out the above-mentioned process, the fibers which may have been previously dried are treated either in filament form or inf'orm of fabric or tissues successively with-a suitabl swelling agent, 'with, a catalyst for promotingthe decomposition of peroxides. and a] peroxy-compound, preferably hydrogen peroxide; The individualsteps of the process can be carried out at room temperature or alternatively, at elevated: temperature. In some cas sthe, fiber-s arficonveniently. immersed in diluted aceticacid after. the peroxide treatment for a short period of. time.' By the-process Qf thfi) inventionthe gas or oxygen bubbles evolve, and voids are generatedwithin the fibrillae of the fibers.v The inflation of the fibers can be controlled as to different degrees by forming smaller or largerbubbles, by ernploying predetermined concentrationsofthereagents -or-by change .ofithe pH value of the treatment baths. Despite the inflation of the full synthetic fiberstructurebymeans of smaller or larger bubbles, the structureitself'and-the Wallsanclsurfacesthereof will not bedestroyed or broken.
The chemical fibers treated in thismannerpossess a multiplicity, of uniformly distributedfihollow spaces. The volume of the fibers isthereby substantially increased, resulting in improved heat insulating properties, a lower specific gravity and a higher covering power of said fibers. The numerous internal curved interfaces of the fibrillae further result in; increased difiusion of the, refiected; light, whereby a subdued, lustre is conferred upon the fibers. In: comparison-.withrnassive fibers both; the dry and wet tenacity ofthe described hollow fibers is but slightly reduced and is still higher than the-corresponding tenacity of viscose rayon Example 1' A mpl of yl ifibe s sswellcd fo m nutes in o r e a ti a i 1 s. exc ss. cetic acidi tion is completed. The fibers;are-thoroughly rinseduwith water and dried. The thustreated fibersshow a considerable increased. water absorption, the latter amounting to approximately 46% as compared with"13'% inzthe untreated material.
Example A sample of "6 nylon fibers undelustered) is swelled for 1 minute in 70% aqueous chloroacetic acid,
rinsed with water and subsequently dipped into a 10% aqueous solution of manganous sulphate. The sample is washed for a short time with water and pulled through a 2% solution of caustic soda. The fibers are then treated for minutes with hydrogen peroxide of 40% strength, the 6 nylon, which is soaked with the solution of the catalyst, being strongly puffed up by the decomposing hydrogen peroxide during this operation. After removal from the peroxide bath the sample is washed several times with water and dried. The fibers have now a delustered appearance, and when they are examined under the microscope, they show a multiplicity of elongated bubbles or voids, particularly along the fiber axis.
Example 3 A sample of "6 nylon fibers is swelled for 1 minute in 70% aqueous chloroacetic acid, washed with water and subsequently treated for 2 minutes with a 2% aqueous solution of potassium permanganate. After washing out the excess catalyst, the sample is immersed for 5 minutes in a aqueous sodium hydroxide solution, rinsed and dipped into a bath of hydrogen peroxide of 40% strength. After 8 minutes it is removed therefrom, washed and dried.
Example 4 A sample of 6 nylon fibers is swelled for 20 minutes in a mixture of 85 parts of acetic acid and parts of formic acid. The fibers are then dipped into a 10% solution of manganous chloride in hydrochloric acid and left therein for 3 minutes. The sample is then treated with a solution of sodium peroxide in hydrochloric acid. After 3 minutes the fibers are washed with cold water, centrifuged and dried. The fibers show big spherical bubbles or voids.
Example 5 A sample of 66 nylon fibers is swelled for 1 minute in a mixture of 35 parts of formic acid and 65 parts of acetic acid. After removal of the excess swelling agent, the fibers are treated for 2 minutes with a 1% aqueous solution of potassium permanganate.
The sample is then shortly washed with water, treated for 3 minutes with a 10% aqueous sodium hydroxide solution, washed again with water and finally dipped for 5 minutes into a bath containing hydrogen peroxide of 40% strength. It is then rinsed and dried.
Example 6 A 2 gm. sample of 66 nylon is swelled for 1 minute in a mixture of 35 parts of formic acid and 65 parts of acetic acid. After removal of the excess swelling agent, the fibers are treated for 2 minutes with a 10% aqueous solution of manganous sulphate. After the fibers have been washed for a short time with water, they are immersed for 3 minutes into a 10% solution of caustic soda, washed again with water and finally dipped for 5 minutes into hydrogen peroxide of 30% strength. The excess hydrogen peroxide is thoroughly washed out with water, and the sample is dried at 60 C. The fibers show a grained appearance and are greatly interspersed with fusiform voids.
Example 7 A hank (11 g.) of 66 nylon is swelled for 2 minutes in 200 cc. of glacial acetic acid. The excess swelling agent is then squeezed out and the hank is dipped into 300 cc. of a 0.1% aqueous potassium permanganate solution. After seconds it is removed therefrom, rinsed for a short time with water and immersed for 3 minutes into a bath containing 250 cc. of a 5% sodium hydroxide solution. The hank is subsequently thoroughly washed, squeezed out and treated with 300 cc. of hydrogen peroxide of 40% strength. After 10 minutes the hank is thoroughly washed with water and dried. After the treatment the individual fibers are greatly interspersed Example 8 A sample of 6 nylon fibers (undelustered) is swelled for Z'min'utes in glacial acetic acid. -The excess swelling agent is then squeezed out and the fibers are immersed for 10 minutes in a 10% aqueous solution of cobaltous sulphate. The fibers are then placed for 3 minutes in a 2% solution of caustic soda, washed with water and treated with hydrogen peroxide 'of 35% strength. The vigorous reaction, which sets in immediately, subsides after 3 minutes, whereupon the sample is removed from the bath, rinsed several times with water, freed from adhering water in the centrifuge and dried. The individual fibers have a delustered appearance which is due to the many very fine bubbles or voids.
Example 9 A 6 nylon fabric is swelled for 5 minutes in a mixture of 15 parts of concentrated formic acid and parts of glacial acetic acid. It is then freed from excess swelling agent and immersed for 2 minutes in a 1% aqueous solution of potassium permanganate. After shortly washing the piece of fabric with water, it is dipped for 5 minutes in to a 10% aqueous solution of sodium hydroxide, washed, centrifuged and finally treated with hydrogen peroxide of 40% strength. After 3 minutes the fabric is removed from the hydrogen peroxide bath, is placed for 2 minutes in acetic acid of 10% strength, whereby it assumes a pure white appearance. It is then rinsed with water and dried.
Example 10 A sample of Terylene fibers is swelled in phenol for a few minutes at a temperature of about 50 C. The excess swelling agent is then washed out with acetone and the fibers are dipped for 5 minutes into a 1% aqueous solution of potassium permanganate. The sample is centrifuged, placed for 2 minutes in a 2% solution of caustic soda and subsequently in hydrogen peroxide of 35% strength. When the reaction has subsided, the fibers are washed several times with water and dried. The voids within the fibers, which are generated by the above treatment, can be easily observed under the microscope.
Example 11 A sample of Orlon fibers is swelled for 3 minutes in a saturated ethanolic solution of calcium thiocyanate and then shortly Washed with water.
The fibers are subsequently placed into a 4% ho aqueous solution of potassium permanganate, rinsed again with water and pulled through a 5% solution of caustic soda. The sample is again washed with Water and then treated with hydrogen peroxide of 40% strength, which has been warmed to 70 C. The treatment is continued for 10 minutes, whereupon the fibers are rinsed and dried.
Various changes and modifications may be made without departing from the spirit and scope of the present invention and it is intended that such obvious changes and modifications be embraced by the annexed claims.
Having thus described the invention, What is claimed as new and desired to be secured by Letters Patent, is:
1. A method of manufacture of aerated synthetic hydrophobic polyamide fibres of polyhexamethyleneadipamide and poly 5 aminocaproic acid, comprising the steps of treating said fibres for between 1 minute to about 20 minutes with an aqueous solution containing a swelling agent, said swelling agent consisting of at least one member of the group consisting of acetic acid, chloroacetic acid and formic acid, washing said fibres to remove any excess swelling agent therefrom, treating said fibres with an oxygen generating catalyst consisting of approximately a 1% aqueous solution of potassium permanganate for about 1 minute until said fibres show an intense violet color, washing said fibres with water until the fibres are a pale rose color, immersing the fibres in a solution of about 40% hydrogen peroxide for about 5 minutes until said hydrogen peroxide is decomposed under the influence of said catalyst evolving gas bubbles inflating said fibres without breaking the walls and surfaces of said fibres and thus creating voids in said fibres.
2. A method of manufacture of aerated synthetic hydrophobic polyamide fibres of polyhexamethyleneadipamide and poly 5 aminocaproic acid, comprising the steps of treating said fibres for between 1 minute to about 20 minutes with an aqueous solution containing a swelling agent, said swelling agent consisting of at least one member of the group consisting of acetic acid, chloroacetic acid and formic acid, washing said fibres to remove any excess swelling agent therefrom, treating said fibres for between 1 minute to about minutes in a solution containing about 0.1 to 10% of an oxygen generating catalyst selected from the group consisting of permanganates, manganous salts and cobaltous salts, and immersing said fibres for up to about 3 to 10 minutes in a solution of about to concentration of a peroxide compound selected from the group consisting of sodium peroxide and hydrogen peroxide, until said peroxide compound is decomposed under the influence of said catalyst evolving gas bubbles inflating said fibres without breaking the walls and surfaces of said fibres and thus creating voids in said fibres.
References Cited in the file of this patent UNITED STATES PATENTS 2,218,385 Schulze Oct. 15, 1940 FOREIGN PATENTS 244,446 Great Britain Mar. 24, 1927 299,710 Great Britain Jan. 27, 1930 1,032,715 France Apr. 1, 1953 1,071,702 France Mar. 10, 1954 OTHER REFERENCES Rayon and Synthetic Textiles, May 1950, page 91.