Microfibre

The microfibres are textile fibers whose Titer is lower than one decitex (1g/10km). What corresponds to a diameter lower than 9 micrometers. They can be artificial or synthetic (Polyester, Polyamide, Acrylique, etc). They appeared in the Années 1980, whereas the polyester had passed from mode.

There exist also super-microfibres whose title is lower than 0,4 decitexes and also ultra-microfibres whose title is lower than 0,1 decitexes.

Fabrics

The choice of the microfibres is done on a search for particular characteristics which are, for example, the Perméabilité to the steam with a low permeability to the air, the sealing with water, a specific touch, the filter effect, etc

These fabrics initially intended for the sport clothing and of mountain which require good solidities light and wet, with the outerwears standard Parka for which one needs a good solidity light, with hospital clothing which requires, inter alia, a high solidity with washing, from now on are used in all the sectors of the Vêtement until the Lingerie.

But, if they bring particular characteristics, the wire microphone have on the other hand a price more raised (double) that traditional wire. This explains why the weaver, to save on the price of the matter, often uses mixtures with traditional wire in the same texture (the mixture more generalized being simply the chain out of traditional wire and woven out of microphone). In addition, to obtain effects, the weaver can use brilliant wire jointly containing 0,05% of matifiant semi-chechmate or chechmate 1,5% of matifiant titanium. This use of the wire shining for returned fabric increases the quantity of dyeing necessary to dye micro wire, this factor is to be taken into account not only with respect to the composition of fabric but also of its final cost because of a more expensive dyeing.

Dyeing of the microfibres

The microfibres require a technique of particular dyeing which had with their caractéristiques.
This part indicates under micro name, microfilament or microfibre, only of mesh and chain and screen carried out in multifilaments micro traditional Polyester without taking account of the use of the microfilaments obtained by bursting of wire.

Dyeing preparation

For the chain and weaves, the chains are generally pasted with a product containing soluble resin polyester, acrylic gluing being more exceptional. The name of the product used is generally communicated to the dyer who knows that these gluings are sensitive to earthy waters, heavy metals, the electrolytes with high concentration and that the pH of the bath of treatment of désencollage must obligatorily be lower than 9. But let us not forget that with the spinning, in texture, with knitting, warping, the filaments were oiled. If the composition of these oilings remains confidential and the rate of application acknowledged at each very approximate stage of the die, the total on fabric or knitting can be evaluated very exactly. One notes whereas, on conventional wire fabrics, this rate varies from 1,5 to 3% in chain and screen, and from 2 to 4% in mesh, but that out of microphone, it reaches 3 to 5% in chain and screen and 3 to 8% in mesh. Indeed, producers and texturateurs noted, well before the dyers, that the microfibres absorb more irregularly than the traditional filaments from where need for supersaturating them. An oiling contains mainly lubricating bases to improve the coefficient of friction, anti-static, additives.
The lubricating bases can be:

Insoluble in the water of origin: vegetable with, in corollary, of the problems of oxidation; mineral, in general paraffinic, the naphtaléïques ones being excluded because of their incompatibility with the élasthanne S, increasingly used; esters organic, expensive but increasingly employed; waxes paraffinic.
Water soluble. They are Polyglycol S, esters of polyglycols or modified silicones esterified. The anti-static ones can be: nonionic, as the esters of polyglycol which bring hydrophilite (while exploiting the length of the absorbent chains, one obtains more anti-static products or more lubricants); anion, as the phosphoric esters which bring electric conductibility; cation ammonium ternary reserved for the dyeing in the mass.

The additives include/understand emulgator S (always present) and optionnellement of the Fongicide S, sequestering, of silica colloidal.

Désencollage and Désensimage

The mesh is not pasted and the thermal pretreatment is not essential. In this case, it is logical of désensimer then to dye, even désensimer in the bath of dyeing. The oil of oiling being emulsible car, one will make a first aqueous 70°C treatment (water alone). In the case of fabrics traditional continuous polyester chain weaves micro polyester with a pasted chain polyester, one would be tempted to dye directly in the bath of désencollage like one does it for fabrics entirely out of traditional wire. This is to be proscribed because, on the one hand, of the rate of high oiling and, on the other hand, of the need for preforming fabric between the désencollage and the dyeing to avoid thermomigrations at the time of a post forming, when one can avoid it, which is not always the cas.
Nevertheless, one notes on certain dark colors, the Rouge S in particular, of the Tache S of dyes. It would seem that the coloring one goes up on the part Lipophile of not dispersed oil, which leads quickly to an aggregate. Moreover, some dispersing contained in the dye could be at the origin of the problem.

Dyeing

There is well a certain correlation between the developed surface of the filament and the absorptive quantity of dye, but this correlation is too weak to transpose a formula for traditional polyester on micro polyester.

Dyes

Kinetics of rise of the dye: the microfibres absorb more dye and more quickly at the beginning of the cycle of dyeing (phase of absorption) from where plain risk of evil.

Coloristic intensity

In the case of a mixed fabric polyester, i.e. traditional chain continuous wire, micro screen (figures C and D), one notes that with 2% of dye Bleu 56 (small molecules) beyond 110°C, the conventional chain continues to absorb dye whereas the micro screen is already in a phase of migration and rejects dye. The variation of nuance will be growing if the dyeing is prolonged. If a dye with large molecules were used, the phenomenon would start with 130°C instead of 110°C. With 6% of Blue 56 (Ci) (small molecules), the things occur in the same way, but the variation coloristic is less. If a dye with large molecules were used, the two curves would be closer.

Three-color process

The Trichromie usually used on traditional polyester (Orange 30, Red 167/1, Blue 79) is not adapted to the microfibres. One could possibly use the yellow three-color process 211, Rouge 82 (or Red 73) and Blue 84, but, with this formula, solidities light and wet prove often insufficient. Quickly entered, but quickly left, the small molecules are to be drawn aside, even in clear colors. This explains why the majority of the dye manufacturers worked out ranges specific for microfibres polyester not referred to the dye index (by commercial prudence) with well adapted three-color processes. As example, at Dystar, Orange Resolin K3GLS 150%, Red Resolin K3GLS 200%, Blue Resolin KFBL 200%, at BASF, Brown Yellow Dispersol XF, Ruby Dispersol F, Navy blue Dispersol XF, at CIBA, Yellow Terasil W5SL, Red Terasil W4BS, Blue Terasil WRB or WGS.
It is, for the two last three-color processes, of the molecules whose chromophoric grouping is destroyed at the time of alkaline stripping intended to eliminate the dye nonrelated to fiber. Certain chemists consider that it is necessary to prefer to them dyes at anthraquinonic bases with those at azo bases. The latter have, in addition, a solidity light which decreases considerably with the concentration.

The process

The dyeing on beam is very difficult, even impossible out of autoclave, because of the strong density of the texture with the presence of oligomers. On jet, a fast speed is necessary, which gives interest standard air jet cigar (Thies, Isaka, Alliance, etc) With regard to the process, we can make some suggestions based on the practice of this dyeing:

to start the dyeing 15°C low than for the traditional fabrics polyester, is 40 with 50°C;
to slow down the curve of rise in temperature at least until 110°C;
to carry out at the end of the dyeing an examination: (reducing cleaning);
to add an agent of migration (those of the antibarrure type which go up on fiber before the dye are still the best);
to optimize the stage and boarding times (to gain one hour, it is 20% of productivity in more);
the anticassures are generally not necessary because of the micro flexibility of fabrics.

Solidity of the dyeings

The end user expects that solidities dyeing of the articles in microfibres are as good as out of traditional wire. Out of polyamide, there are no differences, out of polyester, that of déconvenues.
In solidity light, the fall is from 1 to 1,5 point on microphone in clear and average colors. One explains it by a rise in the temperature of dyed surface causing a faster degradation of the dye, from where a fall of solidity light even more important in dark colors. For corser still this problem, one notes that certain blue azo fall on microphone to a solidity from 3 in three-color process compared to 6 on traditional polyester. In wet solidity, it is normal that the results are lower on microphone since the fiber contains twice more dyes and that it has a larger contestable surface. This is why a reducing soaping is recommended, even for the clear colors.

Fortunately, the use of certain additives polysiloxane type slow down the deterioration of wet solidities of the azo dyes. In addition, the fabrics microphone can with difficulty be adopted for applications in car because of limited wet solidities.

Thermal solidities

For the same reasons as in the case of wet solidities, solidities with the thermo-migration are worse in the case of micro than in the case of traditional polyester. The good sense would be to heat less, to be satisfied with a preforming and not postformer. As for drying, of course, not sursécher.

Source

Conference pronounced with congress ACIT 1997 in Epinal.

See too

textile Fiber

Category: Textile fiber Category: Polymer

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