DE2412180A1 - PROCESS FOR RELEASING CAST FILM FROM THE CARRIER MATERIAL - Google Patents

Description

BA.-3I Aktj.er.gesellschaft

Our reference : OZ pO 446 Ia / IG 6700 Ludwigshafen, 11O-1974

Process for detaching cast films from the carrier material

The invention relates to a method for detaching cast films from carrier materials on which they are produced, by means of a cold buck.

The production of cast films is known. She mostly will made more difficult by the fact that after the solvent has evaporated, the poles often no longer detach from the carrier material. The cause of this difficulty is, on the one hand, the extremely good adhesion of the film to a metallic substrate. On the other hand If the film material is in a plastic state with insufficient tear strength at the temperatures used, so that the force required to overcome adhesion leads to elongation and often tearing. This can get too high Lead production committees.

It is known that this increases the tear strength of the films increase that the carrier material is cooled together with the film (D 15 918 / 39a, P 745 0572). The constant change in temperature, as occurs, for example, with an endless metal belt, leads to high material stress, the consequence of which Tape warps that make it difficult to cast a film that is uniform in thickness. It is also a flawless one Removal of the foil with this method is not guaranteed.

It is also known to coat the carrier material with an anti-caking agent or to reduce the adhesion to add an anti-caking agent to the casting solution (US Pat. No. 3,691,136). In both cases the cast film contains Substances that reduce their areas of application or even make their use impossible.

667/73 - 2 -

509841/0779

- f. - OZ 30 448

The object of the present invention is to overcome the above-described disadvantages of the known methods for producing cast film to overcome and to show a method in which the detachment of the film from the carrier material is possible simple way is done, using uniform foils can be obtained with increased tear strength.

Surprisingly, this succeeds in that the carrier material A cold breaker is added to the film to be detached.

The present invention relates to a process for producing cast films, the substance forming the film being applied in the usual manner in liquid form to a flat, inert carrier material with a smooth surface, any solvent present at least largely being removed, and the film being removed from the carrier material is withdrawn, which is characterized in that the removal of the film takes place from the carrier material by sudden cooling of the film by at least 10 ⁰ C by applying a liquid or gaseous cooling medium to the foil surface "

Preferred embodiments of the method according to the invention consist in that the carrier material does not come into contact with the cooling medium, the film is detached from the carrier material by suddenly cooling the film by at least 50 ^° C., the carrier material is a metal plate or a preferably endless metal belt, the cooling medium Whataa? and the film is not sticky when it is removed from the carrier material.

The construction of the quenching and detachment device can be used for both endless and limited support surfaces applied foils are used. Since the quenched and detached from the carrier material there is no film has adhesive properties, it can be rolled up or processed further.

By means of the process according to the invention, the cast film can be detached from the carrier material without any problems and uniform surfaces are obtained "Films with improved tear resistance.

- 3 -

509841 / (177Q

- 0 - oz ^ O 448

• 3.

The inventive method of film removal by cold shock is explained on the basis of a schematic drawing.

The is on an endless, smooth, inert carrier material (1) the sheet-forming fabric (2) "using, for example a pouring device applied in liquid form. If solvent is also used, this is indicated by corresponding Temperature control, "for example by means of a heated air stream using a suitable suction device largely removed =

In the cooling zone (3), in a width of 5 to 100, preferably 10 to 50 mm produced by applying the cow medium (4) to the surface of the hot foil material (2) is quenched, the film material is quenched and, if necessary at the beginning supported by a release film (5), from the carrier material deducted.

Metal plates are suitable as smooth, inert carrier materials or metal strips, especially polished iron or steel strips (thick, for example <5 mm).

Liquid or gaseous cooling media are suitable for carrying out the cold shock, provided they are not solvents for the Foil material are. For example, water, methanol, acetone, cooling brines, as well as air and similar gases or mixtures are suitable from gaseous and. liquid substances, such as carbon dioxide and organic liquids, provided they are not Are solvents for the film material.

The temperatures of the cooling media are generally between +150 and -20 ⁰ C. The extension of the cooling zone and the withdrawal speed of the film depends on the thickness of the film and is generally from 5 to 100, preferably 10 to ram 50 and 0.05 to 50 m / minute, preferably 0.1 to 10 m / minute.

509841/0779

- #> - O.Z. 50 448

Suitable as the film-forming substances are the melts or solutions of polymeric substances usually used for cast films, in particular those which are obtained from boiling solvents because of their thermal resistance, such as polyimides, polyamide-imides, polybydantoins, polyester-imides, polyester-terepbtbalates and polyester attachments Such poles can be completely dried out before they are peeled from the substrate, but it is advantageous if they contain 1 to 40%, preferably 5 to 30%, release solvent and are then in a plastic state on the substrate.

As a solvent for the polymeric substances forming the films In general, polar solvents such as IT-Metbylpyrrolidon, Dimetbylacetamid, Dimetbylf orraamid, Dimethyl sulfoxide, aromatic and aliphatic chlorine compounds, Nitro compounds and the like.

According to the method according to the invention, films are obtained which do not show any damage, side tears or tears during detachment Have experienced stretching. Such films can be rolled up immediately and stored indefinitely. It's not necessary, to additionally protect the surface of the film against sticking.

The parts and percentages mentioned in the following examples are parts by weight or percentages by weight

example 1

A 22 percent strength polyamide-imide solution, prepared from trimellitic anhydride, 4,4'-diaminoaipbenylmethane and 4,4'-diphenylmethane diisocyanate in N-methylpyrrolidone was poured onto a polished steel belt at 120 ⁰ G at a strength of 400 / rev. The circulation time of the belt was 10 minutes, the solvent being evaporated at temperatures of up to 170 ^° C. down to 10 percent by weight. Shortly before the film was to be peeled off the tape, the surface of the film (170 ^° C.) was quenched over its entire width with a strong water jet. The film was sprinkled in such a way that

- 5 509841/0779

OZ J> 0

that the temperature of the film fell below 50 ⁰ C, preferably below 30 ⁰ G, while the temperature of the tape did not change or changed insignificantly. A film with high strength (tear strength over 600 kgf · cm ") and without mechanical damage with a smooth, hard surface was obtained. The film also contained 10 percent by weight of N-methylpyrrolidone,

Example 2

A 16prozentige polyimide solution prepared from pyromellitic dianhydride and 4,4'-Diarainodiphenylather in dimethylacetamide was infused at 130 ⁰ G on a polished steel strip in a thickness of 600 / U. The temperature of the air (counter-current) was allowed to 2 minutes at 120 ⁰ C, after which the temperature rose to 17O ⁰ C within 3 minutes. The film was held at this temperature for 20 minutes. At the separation point, the film was sprayed with ice-water, so that the temperature of the film up to 15 ⁰ C fell while the temperature of the band at 170 ⁰ C remained. A perfect film with a residual solvent of 3 ⁰ Jo was obtained. The tear strength of the film was over 1,100 kgf · cm "" ² .

- 6 509841/0779

Claims (6)

- 6 - ο.ζ. 50,448 claims 1.) Process for the production of cast films, where in the usual ¥ ice the substance of the film is applied in liquid form to a flat, inert carrier material with a smooth surface, any solvent present is at least largely removed, and the film is peeled off from the carrier material, characterized in that that the film is detached from the carrier material by sudden cooling of the film by at least 10 ⁰ G by applying a liquid or gaseous cooling medium to the film surface. 2. The method according to claim 1, characterized in that «that the carrier material does not come into contact with the Züh! Medium. 3. The method of claim 1 or 2, characterized in that the detachment of the film takes place from the carrier material by sudden cooling of the film by at least 50 ⁰ C. 4. The method according to claim 1, 2 or 3, characterized in that the carrier material is a metal plate or a preferably endless metal belt. 5. The method according to claim 1, 2, 3 or 4, characterized in that the cooling medium is water. 6. The method according to any one of the preceding claims, characterized in that the film is not sticky when detached. BASF Aktiengesellschaft _; Sign. 509841/0779