NO138218B - NON-FLAMMABLE THREADS AND FIBERS ON POLYAMIDE-IMID BASE, AND PROCEDURES FOR THE MANUFACTURE OF THESE - Google Patents

Description

The present invention relates to industrial innovation

product non-combustible threads based on polyamide-imide to which a large amount of activated carbon has been added.

By "non-combustible threads" is meant threads that include

favorable result is submitted to the test published in the "American Association of Textile Chemists and Colourists"

no..34 - 1966.

The present invention also relates to a method for producing these threads.

It is already known from the French patent no.

1,188,128 and its Supplement No. 88,023 to prepare mixtures of finely divided carbon black and polymer based on acrylonitrile whose apparent density is less than 0.400 and to spin mixtures containing a large proportion of carbon black to obtain black fibers, but these fibers has only a small, specific surface area.

It is also known to produce fibers or

threads based on copolymers of acrylonitrile and vinylidene

chloride or sodium alginate containing 10 - 30? graphite and thus few fibers which are intended to be made non-combustible by the addition of carbon or graphite.

It is well known to use soot for pigmentation

masses of different types of polymers, but the amount of pigment that is incorporated is preferably of size

order of 1% and does not exceed 3% of the total quantity of the material, if one wishes to draw or spin under good conditions and to obtain threads of sufficient quality for use as they are and not carbonized or graphitized.

It has likewise been proposed in French patent no. 1,540,997 to produce porous acrylic fibers, but the specific surface areas for these fibers do not exceed 55 to 60 m<2>/g.

Until now, however, the attempts to incorporate activated carbon into other textile materials such as polypropylene and polyamides have not resulted in the production of textile articles which are homogeneous while maintaining a satisfactory activity.

The present invention aims to achieve the above-mentioned goals and thus relates to non-combustible threads and fibers based on polyamide-imide which comprise polymers with the chain unit amide-imide with the formula:

and optionally a chain of amides with the formula: -NH-Ar-j^-NH-CO-R-0- where Ar-^ indicates a divalent aromatic residue, Ar2 indicates a trivalent aromatic residue and R indicates a divalent aromatic residue, and these threads and fibers are characterized by the fact that they contain 8 to 35% active carbon, calculated on the amount of dry matter, and have an iodine value of 100-500 and a specific surface of 90-300 m<2>/g.

The present invention further relates to a method for producing the above-mentioned fibres, and this method is characterized by the preparation of a solution of polyamide-imide with amide-imide chain units with the formula:

and optionally chain units of amides with the formula: -NH-Ar^-NH-CO-R-0- where Ar^ denotes a divalent aromatic residue, Ar2 denotes a trivalent aromatic residue and R denotes a divalent aromatic residue , i: a polar organic solvent containing 8-35% activated carbon in relation to the weight of carbon and polymer and that this solution is wet-spun in a coagulation bath which essentially consists of water and solvent for the polymer,

after which the threads are drawn, washed and dried in a known manner.

The polyamide-imides with the above formula are obtained by reaction in a polar organic solvent in essentially stoichiometric quantities of at least one aromatic diisocyanate and a reactive acid comprising at least one aromatic, aliphatic or cycloaliphatic acid anhydride and optionally a dibasic acid.

Among the diisocyanates which can be used for the production of these polymers, mention can be made of monocyclic diisocyanates such as toluylene diisocyanates and the bicyclic diisocyanates which are preferably symmetrical such as diisocyanate-diphenylmethane, diisocyanate-diphenyl-propane and diisocyanate-diphenyl

-ether.

The acid anhydride used is preferably trimellitic acid anhydride. Among the dibasic acids, terephthalic acid is preferably used. isophthalic acid, the amount of dibasic acid in the reactive acid generally being between 5 and 95% in moles, preferably 20 - 80% in relation to the mixture of anhydride and dibasic acid.

The activated carbon used according to the present invention is a form of carbon with a particularly large surface area

f

very small grain size which is of the order of a few * jm and which has active centers which. contains other substances such as oxygen..

For carrying out the present invention, it is generally advantageous to use an activated carbon of good iodine value and with a specific surface that is generally above 1000 m/g in order to achieve a maximum effect.

According to the present invention, it has surprisingly <q>g unexpectedly been found that with the help of the present method it is possible to incorporate up to 35% activated carbon in relation to the total weight of activated carbon and polymer without causing disturbances during spinning and further that in the thus obtained threads or fibres, the active centers in the coal retain most of their activity in the final articles.

Fabrics produced by proceeding from the aforementioned threads are widely used as protective fabrics against toxic gases and also have the advantage of being non-flammable.

only thanks to the properties of the polyamide-imides.

Thanks to their great adsorbing capacity, the threads according to the present invention can also be used in the production of cigarette filters or anti-pollution filters.

The adsorption capacity of threads which. contains activated carbon is determined by the iodine number, which represents the number of mg of iodine that is bound per grams of dry matter.

The specific surface area for the threads is measured according to the BET method (Brunauer-Emmett-Teller) and is described in numerous publications.

To produce threads and fibers as described above, a solution of polyamide-imide is extruded through a spinning nozzle in a polar organic solvent which, in addition to the polymer, contains 8 - 35? activated carbon in relation to the total weight of polymer and activated carbon. Beyond 35?' activated carbon, spinning becomes impossible.

The polymer used must have an intrinsic viscosity of between 0.8 and 1.6 (preferably between 0.9 and 1.4).

The viscosity is measured at 25°C based on a solution of 0.5 wt. polymer per volume of polar organic solvent. N-methyl-pyrrolidone is preferably used as an organic solvent.

For the preparation of the solution to be spun, it is generally preferred to first prepare a main mixture containing the solvent, the polymer and one large amount of activated carbon.

The main mixture is ground so that a good homogeneity is obtained for the polymers and the carbon to avoid agglomeration of carbon grains and thus ultimately to achieve easier spinning.

A certain amount of polymer solution in N-methyl-pyrrolidone is then added to this main mixture. Spinning solution produced in this way is crushed immediately before spinning and then filtered.

The spinning is carried out as wet spinning in a coagulation bath which essentially consists of water and solvent for the polymer in an amount which can vary between 30 and 65% at ambient temperature.

The filaments are drawn in the usual way by means of any device known in this field, e.g. in air at ambient temperature at an amount .which is generally between 1.2 X and 2.5-X. The drawing helps to give the threads good physical and mechanical characteristics without reducing them

number of active sites in the carbon that preserves its adsorbing ability. The threads are then washed continuously in water and at ambient temperature, e.g. by passing through and past one or more vessels or on rollers to remove solvents

light which is then re-applied.

The drying can be carried out as usual, e.g. on rollers.

In general, it is preferred to dry at a temperature that does not exceed 150°C in order to preserve the activity of the threads.

In order to achieve an almost total removal of solvent, the threads can be subjected to a thermal treatment at a temperature which can vary from 200 - 220°C in a drying oven or preferably a final washing in a known manner, e.g.

with a volatile organic compound such as acetone.

In the following examples, the percentages are by weight

center.

Example 1.

Mån prepares a solution A of polyamide-imide at . reaction of trimellitic anhydride, diisocyanate-4,4'-diphenyl-

methane and terephthalic acid in N-methyl-pyrrolidone. The obtained poly-

more has a viscosity of 1.11 and the resulting solution has a concentration of 21 percent by weight of polymer.

On the other hand, a mixture B is prepared which contains 70 g of polymer obtained in the preceding with 780 g of N-methyl-pyrrolidone and 150 g of activated carbon. a grain size of

3 and a specific surface of 1270 m /g and iodine number of 1100

and which is pre-painted. The mixture B which is prepared on

in this way is ground and an equal amount of solution A as prepared in the preceding is added to it.

After filtering using a filter that is con-

composed of a woven fabric (longotte), cotton and a pre-fabric (finette).

with diameter 9.20 mm, into a coagulation bath containing

• }\ 0% water pg 60% N-methyl-pyrrolidone, and kept at a tempera-

trip at 22°C.

The yarns drawn in air to 1.51 X are washed on rollers at a speed of 11.7 m/min before being dried in a known manner and treated in a dryer for 2 hours 30 minutes at 240°C under a pressure of 5 mm Hg.

The threads thus treated are non-combustible and

contains 35? activated carbon and has the following characteristic features:

As a comparison, a polypropylene containing 10? sweet. Spinning is very difficult due to clogging of the nozzle openings. The yarn obtained has a specific surface area of less than 10 m<2>/g.

Likewise, as a comparison, a thread is produced according to example 1 in the French patent no. 88,023/1,188,128 and the thread had 29% soot and a specific surface of 34 m/g.

Example 2

In the same way as in example 1, a solution A of polyamide-imide in N-methyl-pyrrolidone is prepared with a polymer concentration of 21% by weight.

A mixture is prepared which contains 136 g of polymer obtained in the preceding with 796 g of N-methyl-pyrrolidone and 68 g of activated carbon, with a specific surface of 1270 m 2 /g, an iodine number of 1100 and which was previously ground. This mixture C is added after grinding to an equivalent amount of solution A to produce a spinning solution containing 79.3? N-methyl-pyrrolidone, 17.3? polymer and 3.4? activated carbon.

The spinning of the solution is carried out in a coagulation bath which consists of 40? water and 60? N-methyl-pyrrolidone at approx. 22°C, at a speed of 8 m/min through a spinning nozzle having 90 apertures of diameter 0.12 mm and provided with a filter composed of longotte, cotton and finette. The air-drawn threads with a draw of 2 X are washed on rollers at a speed of 16 m/min and then dried in the usual way at approx. 90°C and thermally treated under the same conditions as in example 1.

The characteristic features of the non-combustible wire are the following:

Example 3

A solution A is prepared of a polyamide-imide which is identical to that used in example 1 and with the same concentration in N-methyl-pyrrolidone.

Separate solutions D are prepared which contain - - 70 g of the polymer obtained in the above and respectively 780 g, 877.6 and 905.6 g of N-methyl-pyrrolidone, but add respectively 150 g,;53.4 g and 24.4 g of activated carbon and 780 g of N-meth.yl.l-pyrrolidone and adding varying amounts of activated carbon with a specific surface area of 1495 m 2 /g, iodine value of 1660, the carbon having been previously ground.

Each of the solutions D is mixed with "solution A

in equal parts.

After filtration, the spinning solutions thus obtained are extruded. in a coagulation bath composed of 40? water and 60% N-methyl-pyrrolidone kept at room temperature, and through a spinning nozzle having 32 openings with a diameter of 0.2 mm.

The air-drawn threads have 2X elongation and are washed in water at room temperature and are then dried at a temperature of 96°C and washed for 30 minutes in acetone.

You get non-combustible threads whose characteristics are listed in the following table:

Claims (3)

1.. Non-combustible threads and fibers based on polyamide- imide comprising polymers with the chain unit amide-imide med the formula: and optionally a chain of amides with the formula: -NH-Ar-^-NH-CO- R-0- where Ar^ denotes an aromatic divalent residue, Ar^ denotes a trivalent aromatic residue and R denotes a divalent aromatic residue, characterized by the threads and fibres contains 8-35% active carbon, calculated on the amount of dry matter and has an iodine value of 100-500 and a specific surface area of 90-300 m<2>/g. 2. Process for the production of non-combustible threads as specified in claim.1, characterized by that a solution of polyamide-imide with chain is prepared amide-imide units with the formula: and optionally chain units of amides with the formula: -NH-Ar^- NH-CO-R-0- where Ar-^ indicates an aromatic divalent residue, Ar2 an gives a trivalent aromatic residue" and R" indicates a divalent aroma tic residue, in a polar organic solvent which contained where 8-35% activated carbon in relation to the weight of carbon and polymer, and that this solution is wet spun in a coagulation bath which essentially consists of water and solvent for it polymers, after which the threads are drawn, washed and dried in a known manner. 3. Method as set forth in claim 2, characterized in that the polar organic solvent used in the spinning solution and the coagulation bath is N-methylpyrrolidone.