DE2048443A1 - Stiffening felts - by impregnating with binder emulsion or dispersion and passing through coagulant- contg bath - Google Patents

Abstract

Fibre felt for prodn. of leathery stiffeners for clothing is (i) impregnated with a heat-sensitised binder dispersion or emulsion at temps. below the coagulating temp. and (ii) impregnating felt is treated with a bath above coagulating temp. and coontg. a coagulating agent, e.g. CaCl2, ZnCl2, which induces binder coagulation at room temp.

Description

Method for uniformly impregnating fibrous sheets with binders As is well known, a fleece is used in the production of non-woven fabrics impregnated with a binder such as latex.

This is followed by drying at a higher temperature.

The excess water is removed by evaporation and the binder cured or vulcanized.

The end product can be used for a wide variety of purposes will. The best known are the stiffening inserts known under the name VLIESELINE for clothing.

These stiffening inserts are usually only 0.1 mm thick, so that the Impregnation does not present any particular difficulty.

Problems only arise here when you manufacture thicker products, which are e.g. 1 mm and more thick, and which are e.g.

find use as a leather substitute. In the manufacture of these leather substrates In principle, the same procedure is used as for the production of the thinner VLIESELINE stiffening inserts.

Only the thickness of the starting fiber fleece is important in leather production greater.

Now, of course, the impregnation becomes more difficult as the thickness increases. Today, however, we have already succeeded in initially creating leather fiber fleeces several cm thick uniformly impregnated with a latex or a binder dispersion.

Difficulties then arise with the subsequent drying.

The binder, which is initially evenly distributed in the fleece, has namely the tendency to migrate to the surface of the web as it dries. He follows drying by irradiation with infrared lamps, the binder will turn itself focus on the side that is hotter. In the present case it is the that is, the side that is directly exposed to the radiation.

If you let a wet, impregnated fleece run into a hot air chamber, then it should be noted that the temperature inside the fleece is of course essential is lower (as long as the fleece is wet, the temperature must logically always below 100 0C) than the temperature on the two surfaces of the fleece, For example, they are directly exposed to air at 140 ° C. In this Fall, the binder migrates from the inside to the two surfaces, whereby in the borderline case, the middle of the fleece is completely depleted of binder. This in turn has the consequence that such products delaminate all the more easily, ever thicker they are.

In order to avoid these delamination phenomena, it has already been proposed that to impregnate a fleece with a so-called coagulable latex. After impregnation the latex is then coagulated. The binder falls out of the latex, like like cheese made from sour milk. The precipitated solid particles can now be found during do not change their position during the subsequent drying process, so that during drying only a very small amount of binder migration occurs.

Coagulation can be brought about in a number of ways. The so-called heat-sensitized latices coagulate as soon as a certain one Temperature has been reached.

If, for example, a butadiene-styrene copolymer is used in small amounts of an ammonium salt, there is initially no change in the at room temperature Enter latex.

You can therefore impregnate the fleece in the usual way. However, if the temperature of one with such a butadiene-styrene dispersion is increased impregnated fleece to over 50 ° C, coagulation occurs more or less spontaneously instead, as can be seen from DAS 1.103.883, for example.

It is also known to achieve coagulation e.g. by that a fleece, which is mixed with a conventional binder dispersion, such as latex, has impregnated, leads through a 10 goat Ca Cl2 solution. When the binder comes into contact With the Ca C12, coagulation takes place here even at room temperature. In both In some cases, however, the coagulation does not occur suddenly, so there are certain disadvantages still have to be accepted.

For example, if you leave something impregnated with natural or synthetic rubber or latex Run the fleece through an aqueous Ca Cl2 solution, then considerable parts of the Latex washed out of the fleece. In this way a lot of binding agent is lost. In addition, the binder does not precipitate in the form of solid beads, but rather often in the form of a goo.

When working with heat-sensitized latices, coagulation occurs also not suddenly, but within a larger temperature range. The first parts drop out at e.g. 50 ° C, while the last parts of the Do not coagulate latex until 0 at 70 C or even higher temperatures.

Since the coagulation thus extends over a longer period of time, The undesired binding agent migration can also occur here.

The aim of the invention is now to achieve a sudden precipitation of the entire binder.

According to the invention, this is achieved by using a fleece impregnated with a commonly known heat-sensitized latex. The coagulation according to the invention, however, it does not take place by impregnating it in this way Only exposes the fleece to the action of a higher temperature.

So far, this has been done by either placing the fleece in a hot air chamber or let it run into hot water.

According to the invention, it is rather that with a heat-sensitized Binder-impregnated fleece is exposed to a hot, aqueous solution, which in turn contains a substance that is capable of a Cause coagulation. These are especially alkaline earth salts, in particular CaC12, ZnC12 In this way coagulation is about lomal faster than when working according to well-known procedures. The result is a complete, uniform one Distribution of the binder in the end product. It is also found that these products feel softer and more leather-like than if you had a fleece of a given composition with the same binder in the same concentration in a known manner for coagulation brings.

According to the invention, practically all heat-sensitized persons on the market can be used Find latices and binder dispersions use. If that to be impregnated If nonwoven fabric contains polyamide fibers, then it is not advisable to use a concentrated one ZnCl2 solution to work, as this is known to attack 2 polyamide fibers too strongly. In this case you would work with a less concentrated CaC12 solution. You can choose the cheapest coagulation additives in the hot coagulation bath can simply be determined empirically in preliminary tests.

Example: You prepare in the usual way with the help of several cards and cross layers a fleece, consisting of 30% polyester fibers (Trevira) 60% polyamide fibers (Nylon 66) 10 viscose fibers This fleece is then needled and then the Exposed to the action of hot water vapor.

There is an area shrinkage of 20%. After shrinking the weight is 680 g / m2.

Then it is impregnated with a 45; own butadiene-acrylic-nitrile dispersion such that a wet pick-up of 350; he follows. This so impregnated fleece is then in tape form at a speed of 10 m / min. by a 20 ßige CaCl2 solution, whose temperature is 80 ° C, passed through.

An immediate and complete coagulation occurs.

After coagulation, the excess water becomes the now is practically free of binders, removed by squeezing with rollers. After squeezing, the water content is only around 40%. During the subsequent Drying at 170 ° C. also removes this residual water.

The final product then weighs 136o g / m2 when dry. It will then then split and sanded one or more times.

Claims (1)

Claim Method for uniformly impregnating fibrous sheets with binders, characterized in that a non-woven fabric with a heat-sensitized Binder dispersion or emulsion at temperatures below the coagulation temperature impregnated and then the so impregnated fleece exposed to the action of a bath exposes whose temperature is above the coagulation temperature and which also contains a coagulant that already coagulates at room temperature of the binder initiates.