US1790615A - op vienna - Google Patents

Description

Patented Jan. 27, 1931 ,UNITED STATES PATENT OFFICE FRITZ- NEUZBER AND- RUDOLF NOWAK, OF VIENNA, AUSTRIA, ASSIGNORS TO OSKAR TREIBI'I'SCH, OF VIENNA, AUSTRIA y PROCESS FOR THE MANUFACTURE OF METALLIZED FIBBOUS MATERIALS METALLIZED WITH A NOBLE METAL Ho Drawing. Application filed February 23, 1928, Serial No. 256,479, and in Austria February 26, 1927.

This invention relates to a process of metallizing fibrous materials, such as for instance fabrics of alltkinds, laces or like materials, especially where the metal used is one of the noble metals.

' It is already known to coat'a fibrous material with metal such as the noble metals, gold, silver, etc., in order to impart the samewith the appearance of a fabric consisting of metal-threads. However up to now a simple process which can be carried out at little expense has not been discovered by which a uniform firmly adhering coating of metallic appearance is produced and which yields an article in which the character of fabric and the softness of the fabric base is maintained.

The known galvanic process of metallizing call for rendering conducting the non-conducting surface of the fabric by means of graphite or like means. Already this intermediate layer impairs the final product. However in spite thereof a fabric metallized in the galvanic manner is provided with a considerable number of drawbacks. The strength of adhesion of'the galvanic coating precipitated on the fabric fibres is too small compared with the strain to which a fabric is subjected during use. Further as in the case of the present bases the galvanic coating has to be of considerable thickness, the greatest part of the,softness of the base is lost. This thick metal coating renders the galvanic process very expensive, because in most cases coatings of precious metal are called for. Thereby the strength of adhesion is not increased no matter how thick may be the galvanic metal coating. The difficulties are well known which are met with if it is consequence of the character of the galvanically precipitated metal, are increased in the event of the fine-threaded bases in question.

Many experiments have been made already to improve the galvanic process for the present object. For instance it has been proposed to precipitate a very thin galvanic metallic coating'on the fabrics rendered conducting by means of graphite and to compress the said coating in mechanical manner and to apply on the compressed coating a second metallic coating also by a galvanic process. The first thin metallic coating, which is precipitated on the fabrics coated with graphite and compressed in mechanical manner, is quite useless and again has to be sufiiciently treated in the galvanic bath. An essential improvement of the product is not attained by this process. Of course also in this case the conducting intermediate layer of graphite is troublesome, the thickness of the metallic coating is not reduced butstill increased and the repeated galvanic treatment and the'mechanical treatment render the carrying out of the process very complicated and expensive.

Another proposal aimed at improving the conductiveness of the fabric-base for example U. S. Patent No. 675,413. This process consists in that the fabric is introduced into a metallic salt solution in which the metal is precipitated on the fabric in a powdery and porous condition by means of suitable reducing agents. Colloidal substances such as gelatine, collodion, glue and the like were added to the reducing metallic salt solution, in order to improve the strength of adhesion of the said conductive coating.

The fabric metallized in this way is useless, because the metallic coating possesses a gray and poor appearance; and a powdery" and porous structure, but like a layer of graphite is adapted as conductive base for the subsequent galvanization. The galvanic coating applied. to a base of this kmd possesses, of course, the same drawbacks as all the other galvanic metal' coatings. As, all known processes of metallizati'on are based on the galvanic methods for producing the metal coating, the difficulties connected therewith usually arise, so that heretofore it has not been possible to produce in asimpleand inexpensive manner perfect metallized fabrics in large pieces, whereby the character I and softness of the fabrics are not altered reduction from a meta lie salt solution. As

already mentioned the metal, precipitated on ,the fabric by reduction from a metallic salt solution and possessing a finely powdery structure, has a poor non-metallic, appearance and small adhesive properties only, and the fabrics metallized in this simple and inex ensive manner: may just be suited for a su sequent galvanization, but they cannot be 'used ortermed a final product.

Applicant has discovered the surprising fact that metallized fibrous material made in lmown fashion by means of noble metal salt solutions may be converted in an extremely sim 1e manner into valuable end products. Even ifthe adhesive property of the metallic powder precipitated by reduction in known manner is. very small, this process possesses the advantage, that the in-] dividual small metal-parts not only are precipitated on the surface of the fabric but also in the pores and spaces between. the individual fibres of the fabrics. Now according to the present inventiona fabric metallized in this way is subjected to amechanical treatment by pressure, beating, friction and the like and thereby the metallic powder precipitated on the fibres of the fabrics is compressed to a uniform, highly glossy metallic coating, which very firmly adheres to the fabrics, because it is directly anchored in the latter. I

In some cases,'particularly in thecase of a somewhat thicker metal coating, the surface of this metal coating shows the characteristic of a more or less coherent foil after havin been treated in the mechanical manner. owever this partly surface-character disa pears already in case of a very small mechanical influence to which the fabrics are subjected, for instance on rolling up or off the finished goods. Thereby the original soft character of the fabrics is re-established terial in known manner by the reduction of a metal salt solution therein and thereupon, andhereafter treating the fibrous material by mechanical treatment such as by pressure, impact, friction, etc., in order to produce a strongly adherent metallic covering having a ure metallic sheen. 1

n carrying out the present-invention, the metallic salt solution (for instance silver nitrate) together with collodial members,

such as glutin, gelatine andthe like, aieaplied to the fibrous material, preferably 1n a ot condition, and subsequently the same is reduced in known manner by any convenient reducing-agent, for instance formaldehyde, hydroxylamin, hydrazin. After the reducing action has been carried out the fibrous material is washed by means of a convenient solvent and subsequentlydried.- Now the fibrous material is treated in a frictional calenderingmachine, lustring-de- 1 treatment. For this object the fibrous ma terial is subjected, after the com ression of the metal coating, to a mechanica treatment, suchas stretching, extension or the like, in cracking machines, calender, mangle or like machines, whereby the more or less coherent metal-layer is torn up and the soft character of the fabric base -is reestablished.

According to the present process the metal coating does not fly off even in case of a very thick metal coating. However on treating in a cracking machine, calender, mangle or the like a fibrous material metallized in a galvanic way accordin to the known processes, particularly in t e case of thick metal coatin s, the galvanic coating will crack and fly o and the result is a quite useless product.

By the process accordin to the present invention a very durable fa ric possessingall the features of a fabric consisting of metal threads, is produced ina most simple and inex ensive manner and at very little expen iture of metal. By employing suitable machines for compressing the metal'coating, of course not only highly glossy but also dead metal'surfaces of all desired shades may be\ produced, or the highly glossy compressedmetal coating can be deadened subsequently.-

Further it has been found, that it is possible to improve the qualit and particularly the metallic a pearance o the finished article by a suita le treatment of the powdery metal, precipitated from the metallic salt solution on the fibrous material. It has been found, that the reducing action does not proceed entirely quantitatlvelf up to the metal; In art intermediate products are produced, which separate with the powdery metal on the fibrous material and cannot be simply removed from the latter by washing with water. These parts which are not reduced are the cause for the various difiiculties durin the subsequent mechanical treatment of the fibrous material. Particularly the colour and the metallic appearance of the finished article are considerably impaired by the residues which are not washed out.

According to the present invention. these drawbacksv are removed in that, after the precipitation of the powdery metal by the reducing action, the fibrous material is treated with solvents, which dissolve or remove the combination not reduced up to the metal.

Various solvents, such as for example ammonia, potassium cyanide, organic ammonbases, aminoand amido-bases, sodium-thiosulphate and so forth, can be employed for dissolving the combinations which are not entirel reduced, the choice of the solvent depen ing on the kind of metal and fibrous material as employed.

An essential improvement of the metallic lustre of the finished article is attained by treating the fibrous material with an acidsolvent after the precipitation of the reduced metals, the acidity of the said solvent being such, that the acid does not damage the al ready reduced metal or the fibres of the material; For instance formic acid, diluted sulphuric acid and the like may be employed as acid-solvent.

These after-treatments are performed in that, after reducing the metallic salt solution in usual manner in an alkaline way, the metallized fibrous material is at first washed in water, subsequently treated with one of" the solvents above stated and hereafter again washed in water.

In. case of a subsequent treatment with acidous solvents it is of advantage to treat way as a consequence of the'particular modeof manufacture. In most cases the strength and possibility of treating is increased or promoted, so that the process according to the present invention is adapted also for fibrous materials of inferior quality.

We claim:

A process for the manufacture of metal- I lized fibrous material which comprises precipitating a noble metal in powder form in and upon said fibrous material in known manner by the reduction of a noble metal salt solution, treating said fibrous material thus.

coated with noble metal in powdery form with-solvents which will dissolve out matter which has not been completely reduced to metallic form, the said solvent containing a;

protective colloid such as gelatine, glue and the like, and thereafter compressing by mechanical treatment (pressure, impact, friction) to produce a strongly adherent covering of pure metallic appearance on said 1 fibrous material.

In testimony whereofwe aflix our signathe fibrous material, after washing with a diluted soda-solution in order to remove even the last traces of the acid which is detriwhich is fully equivalent to the lustre of thepure' metal.

The fabrics made according to the present invention have a very nice appearance and are very soft. Neither the strength nor the working up of the fabric is impaired in any