DE1629324A1 - Process for covering both sides of hydrophilic films - Google Patents

Description

Dr. KABL TÄAETZEE

Patent attorney

6202 Wiesbaden-Blebrlch Eheinganstrasse 176-Rnf 66063

May 2, 1966 Dr Tr-cr

K I668 A

Cellophane Investment Company Limited Alderney CI. ■ '. .

Process for the mutual coating of hydrophilic films

To make hydrophilic substrates, e.g. cellulose films, To make water impermeable, they are known to be coated with 'suitable substances that are in water either are dissolved or dispersed therein. This procedure has the advantage of eliminating the inconvenience which the use of the same substances in volatile Solvents brings with it.

Usually for the purpose indicated above The method used is that you only have one Side of the pad coats and dries, then the the other side is coated with the same coating compound as the first side or with one of them

009887/1638

K 1663__A Dr. Tr- er 2. "5.6 6

different mass. That has the advantage that on jien equalize existing tensions on both sides of the base and to prevent the pad from becoming. rolls afterwards. Then you dry the pad a second time. The amount of substance applied can be can be determined very precisely by means of an air knife, also known as an air brush. The deposits, the maxi are of extremely consistent strength and as thin as you want them to be. Show anyway there are serious difficulties in the process, because the base has a great tendency to stretch along its length to be rolled up immediately after each coating and during the stay in the drying chamber.

If the process is used on an industrial scale, it is essential that the edges of the substrate are not moistened and that an uncoated strip approximately 25 mm wide is left at the edges on each side. As a result of this measure, the pad remains lying sufficiently flat for further treatment, but in the second drying its uncoated edges are fragile and brittle. As a result , cracks easily form, making it difficult to roll up and ^{forcing precautionary measures 1} that limit the running speed. Anyway, the losses are caused by cutting off the uncoated

Margins arise, substantial and costly.

009887MS3

BATH ORIGSMAL

K 1668 A - Dr Tr-cr 2.5.66

By, the invention become: those toanna opportunities and Avoided material losses. Subject of the invention is a variant that consists of it, a hydrophilic one The entire width of the underlay on both sides, one after the other olme Zifisclientrockniiiig with an aqueous mass to coat and thereby the axif one side coated Place a pad between the first and second job

on supports, for example stitz rollers, he ™

traversing the stx-cornering path that is so long that the applied coating solidifies sufficiently can to bexM run over a deflection roller not to be damaged, then the pad too troclining after it is coated on the back and a new one, long enough over supports has traversed an extensive path.

Under the influence of the first coating, the hydro- "

phile pad has the tendency to roll lengthways. This tendency to roll must be counteracted during the time that the water contained in the coating compound needs to penetrate into the hydrophilic base. During this time, the tensions and the tendency of the under-.

situation decreases noticeably. --In the. Vex ~ course of the water inlet

BATH

K 1668 A Dr.Tr-cr Ά. 5.66

the dispersed particles collect in the base on the surface of the pad and dry out and it comes to that the coated surface is strong enough to come into contact with a deflection roller without damage. Then it is possible the back of the pad without preceding

k Drying of the first order to coat. This coating on the back of the film causes the underlay ' ^% to roll lengthways in the opposite direction. This tendency to curl is partially counteracted by the moistening that occurred during the first coating. But it must also be counteracted by long enough support on the other side

the

the document "so that tensions are evened out" After that, the coated substrate can be used in a drying chamber can be introduced, where the two sides are preferably dried evenly it is then rolled up again.

The inventive method consists in that the first drying through a coagulation process is replaced, which takes place on a path extending over supports, for example support rollers, and that this run is on one again "over supports extending path again after the second coating

BATH ORIGINAL

009887/1038

K l6GÖ A ■■ "· ■■. Dr.Tr-cr 2.5.66

is picked up. During the execution of the invention With this method, a well-planar foIdLe is obtained without loss of the edges, which are also covered, and thereby a better quantity result. Another The advantage lies in the simplification and cheaper as a result of the omission of the first drying. Finally, the procedure is permitted because it is only one

Drying there, the - making a better : .g

balanced, coated film. Of the Application is carried out in the usual way for coating performed and the amount of coating applied is regulated by known means, for example with the help of an air knife /

To support the coated film after its first and second coating are used. · free

Moving chromed transport rollers. These rollers ■

only have the purpose of preventing the document rolls on its uncoated side. Man can therefore move the rollers further apart, the further one moves away from the coating station and the tensions in the interior of the base are evened out. The closer they must be, the closer they are to each other The more the pad is moistened, the smaller the The circle of curvature of the path is one of the underlay

009887 / ie38

K 16 68 A Dr .. Tr-er Ii. 5th whether

pass en lälöt. Audi does you good, in places on that Way to use spreader rollers, known type, "including those that are driven, that prevent the formation of longitudinal creases in the substrate and the Loss of width (loss of shrinkage) in the film should decrease after the second tack.

The method according to the invention is applicable to everyone

hydrophilic pad that the water quickly enough to able to absorb. It is suitable, for example, for coating films made of regenerated cellulose, Hydroxyethyl cellulose, carboxymethyl cellulose, cellulose ethers and others. It is also suitable for coating paper.

When working according to the invention, a hydrophilic Backing any = dispersible or soluble in water "Substance are applied, namely the film-forming Resins tirid especially those based on waterproofing of copolymers made from high proportions of vinylidene chloride in addition to other monomers are produced, for example Acrylic esters, methacrylic esters, "unsaturated acids, vinyl esters or acrylonitrile.

009817/1638

K 1668 A Dr Tr-cr 2 * 5.66

The method is particularly suitable for making films made of regenerated cellulose with the help of substances of this kind that are leak-proof and heat-sealable. Such coatings can be applied in the form of solutions in volatile solvents, but with the inconvenience inherent in such operation. Once the way, in the copolymers of vinylidene chloride is higher »ä than 85%, such coatings can ntir from aqueous, dispersion are formed of optionally-soluble auxiliaries are added and the erfirtdungsgemäße method proves to check then particularly suitable.

• In this case, dispersions with about 1/3 & Ά solids are used. This means that up to 20 to 25 g of coating mass can be applied to one square meter ••• on each side without difficulty, which corresponds to 7 to 8 g of solid material per square meter and side. These quantities can be reduced to "5 to 5 g of coating mass per square meter on each side, corresponding to approximately 1.5 g of solid".

to The amount of applied coating mass should not

βο to be reduced too much, because you hit the coating roller Press the squeegee down hard and the

(^ The air pressure of the squeegee would have to increase considerably. It is also

advisable the proportion of solids in the enamel not to decrease too much because the proportion is too high

BATH

ιai

IC 1668 A Dr Tr-cr 2.5.66

Water Shrinkage of the substrate in the drying chamber xind increase in weight per square meter while remaining the same Amount of coating would bring with it.

In the case of the second coating, the coating composition analogous to the first «coating applied and thus properties identical on both sides of the film r, "Awarded. In the case of one -the one from dex- used in the other coating different coating compounds are applied and their • The sole purpose may be to make the treated film permanent to be installed flat.

The film can be dried in any suitable dryer. Advantageously and preferably, one uses a dryer in which the moving air acts symmetrically on both sides of the film F, for example, a dryer of the type of jet dryer. In this way, balanced drying is obtained and the coated film lies very flat.

In, the accompanying drawing schematically shows a Device for carrying out the invention Procedure shown, but not to this

K 1666 A Dr Tr-cr £ .5.66

Device is bound, but can also be exercised with other devices ». The transport organs and spreader rolls, which are known and are not necessary for an understanding of the invention, are not shown.

According to the drawing, a hydrophilic film 1 is from the Roll 2 unrolled and, after some leadership, walzen} has paused at the time of passing the Coating station 4 with an aqueous dispersion coated, the strength of which is regulated by the air knife 5 will. The film then runs on a number of guide rollers 6 in the direction of a path forward,

which is long enough to allow the water contained in the coating composition to penetrate into the interior of the film. In the meantime, the desired degree of coagulation occurs in the applied surface layer . "■ _""■". - "_ ■""""-'■■"' -.

Then the back of the film is aitl the coating '"-" ■ -' station 7 coated with the same coating compound, whose strength is regulated by the air knife: & while the alö erüTfce * coated side of the film the deflection roller-9 Foil then runs on a number

uote87 / teat

K 1668 A Dr Tr-cr p. 5.66

Guide rollers 10 forward on a path the length of which allows the water in the second dispersion to penetrate
into the interior of the pad.

The coated film then enters the drying chamber one, Tvo them vertically from the bottom up, then around one Guide roller runs around from top to bottom. On this one ^ Each of its sides is exposed to a warm breeze.

sets, which is shown schematically by the arrows I3 is. After leaving the dryer, the coated film runs over the cooled rollers 14 before it opens the roller 15 is wound up.

'■ BAD ORIGINAL

009 887/163 *

Claims (1)

/ Ϊ629324 K € 68 V P1 a te nt a u s ρ ar1 Uc h _e; 1 _.; Process for double-sided coating of running hydrophilic foils by coating with substances dissolved or dispersed in water and drying of the coated foils, characterized in that »? reacting a HYDX ~ ophile, T ^{e ort} ii ^xer role lcomraende Folienbahii on einci "side over its entire width, the Tnit wäjiarigen solution or dispersion coated filmbildendei- substances film untei- support its uncoated side .up to the occurred! Koagulation.- "-the ΓUmbildenden Subststaiz mid until the absorption of the applied amount of water through the film, the still co-coated film side is coated in an analogous manner, if necessary using another film-forming substance, with subsequent coagulation or absorption of the constituents of the τί-aqueous coating mass And the Film coated on both sides dries. \ 2. * Method according to claim 1, characterized in that a copolymerization of vinylidene chloride in which the vinylidene chloride component predominates is used as the film-forming substance in the aqueous coating compound, for CELLOPHANEINVESTMENT COMPANY LIMITED < (The patent attorney) 0096817163 «