DE2719204C2 - Method for producing a multi-ply fibrous web - Google Patents

Description

The invention relates to a statute of limitations for the production of a multi-layer fiber web, preferably paper web, according to the preamble of the claim.

"Unlocking" is to be understood as the bursting and flowing of the starch grains, whereby the starch gelatinized.

The use of starch in the production of paper is basically known from the apr book "Paper chemistry products" by Dr. Longin PI a c zek, 1973, Volume 3. The use of gelatinized or made swellable in cold waster Starch is also known in particular from DE-AS 19 64 531. This type of starch receives its gelatinization and Source properties only through tcr -e pretreatments.

From DE-OS 25 12810 a method is for Production of starch-containing binders, in particular corrugated cardboard glue, is known. To do this, Alluvial starch heated below the gelatinization temperature, if necessary with chemicals treated and diluted with water. A complete swelling is caused by the heat treatment of the glue not achieved. This is unnecessary with corrugated cardboard glue, since the corrugated cardboard gluing under moisture and sufficiently high heating of the webs takes place, so that a gelatinization of the starch in the glue joint is ensured.

Starch gives the fiber web better strength properties. In the case of single-layer fiber webs, their bursting strength and rigidity, in particular, but also their splitting strength are improved. Often the cheaper starch, which is dispersible in cold water but does not gel and does not swell, is sprayed onto the opposite sides of the fiber web layers with the help of spray tubes before they are "squeezed" together, that is, brought into contact with one another be liable. The starch serves to improve this adhesion, which is commonly referred to as splitting strength. After the individual layers have been squeezed together, the fiber web can be passed through the press and dryer sections. In the dryer section, it runs over drying cylinders. Only when heated does this type of starch gelatinize and give the desired binding effect.
The aim of the invention is to achieve the object of improving the splitting strength, bursting strength and rigidity of multilayer fiber webs by using starch.

In the case of multi-ply papers, the innermost plies in particular have poor splitting resistance d. H. only poor adhesion with the neighboring layers. Experiments have shown that the splitting strength can be changed by the influence of heat. This could be due to a change in the heat curve

in the dryer section of the paper machine at least can be partially achieved. However, other disadvantages would have to be accepted. Experiments showed that the used, cold water dispersible starch can only be effective when in The presence of water is heated. The starch grains swell, burst and flow (gelatinize).

These experiments carried out by the inventors led to the finding that the stated object to solve by applying the process steps mentioned in the characterizing part of the claim is.

The invention thus removes the swelling process, for which water and heat are required '25 of the fibrous web carried out before the starch was applied will. The starch is heated up to the gelatinization temperature, but without this fully to achieve. So you only stay a few tenths of a degree Celsius or a few degrees Celsius underneath. This initially led to the objection of experts, especially those who sell the starch Industry that this would result in no advantages, on the contrary, difficulties in Applying the strength would show. The strength could

J5 can no longer be sprayed because the nozzles are sticking would. The test results were all the more surprising. It was shown on the one hand, that the swollen starch can still be sprayed without difficulty. On the other hand, in surprisingly, enormous increases in efficiency, for example, the splice strength of multi-ply paper could be more than tripled.

With the invention, the swelling that can be achieved is no longer due to the limited water and Heat supply of the fiber web is determined by the gelatinization temperature of the known per se Starch grains.

The gelatinization temperature is z. B. with potato starch 65 ° C, with corn starch 75 ° C and at

se wheat starch 80 ° Q

The invention has made it possible to use strength to also produce relatively dry fiber web layers to connect stronger, which neither gels in cold water still swells significantly but is only dispersible in it.

In all applications it is advantageous that the starch be sprayed in a manner known per se can, as this enables a particularly efficient and even application of starch

When using the starch for the production of fiber webs with at least two layers, the starch is to apply to at least one of the opposite sides of these layers before this Layers can be brought into connection with one another. To achieve greater strength properties it is it is often cheaper to apply the starch to the still moist fiber web or fiber web layer before mechanical or thermal drying

is subjected by the press section or dryer section of the paper machine. The penetrates Then starch furthest into the fiber web or the fiber web layer if the thickness is in one area is applied to the fiber web or fiber web layer after the headbox of the paper machine, in which they a drainage d-jirch air pressure difference, Experiences gravity or centrifugal force

A possible application of the invention is described below with reference to the drawing.

Three upper wire sections are arranged above a carrier web 1. The upper wire sections each contain one Upper wire 2a or 26 or 2c, onto which a headbox 3a or 36 or 3c releases the fiber suspension. The first The fiber suspension on the top wire is dewatered by a suction box 4a or 46 or 4c

A spray device 56 is in each case above the second and third upper sieve via the suction box 46 and 4c or 5c for spraying starch slurried according to the invention and heated onto the fiber webs Furthermore, spray devices 6a and 66 are arranged between the upper wires above the carrier web 1 arranged the latter spray the starch via their nozzles on the opposite other side of the fibrous web layers as the spray devices 56 and

5c
Couch rollers 7a or 76 or 7c, around which the

Upper sieves 2a or 26 or 2c run, serve together with counter rollers 8a or 86 or 8c to bunch up the first layer from the upper sieve la onto the carrier web 1 and then to bunch up the subsequent layers.

1 sheet of drawings

Claims (1)

Claim: Process for producing a multi-layer fiber web, preferably paper web, with application of starch, which is dispersed in water and pre-swollen by heating, then up at least one of the fiber web layers is applied and after the fiber web layers have been brought together is digested during the subsequent drying, characterized in that the in Water dispersed starch prior to application to the fibrous web layer as close to the gelatinization temperature is heated so that the starch granules swell substantially completely, however are not yet gelatinized and the application of the so swollen starch to the still wet Fiber web layer takes place by spraying.