Laminated inhibited films

In addition, process schemes for manufacturing laminated inhibited films by co-extrusion are presented in Fig. 2.11. Working volumes of extruders 1 for processing polymer materials (A, B, C) are connected with extrusion head body 2. The head is fitted with several annular slots that form, on blowing, a multilayered hose 3. Two-ply films can be formed from the same [7] or two different (Fig. 2.11a) polymers. Three-layered films can, correspondingly, incorporate two (Fig. 2.11b) or three different (Fig. 2.11c) polymer materials. 

Fig. 2.11. Process schemes for inhibited laminated hose films (a) two-layered and (b) three-layered films of two polymer materials A and B, (c) three-ply film of three materials A, B and C. (1) extruder, (2) extrusion head, (3) hose, (4) pumping unit...

Slot extrusion is used to form flat inhibited films and laminated films. To this end, flat co-extrusion, extrusion pasting and lamination methods are used [7,14,18,28,34,40,82]. Commonly, preliminary granulated mixtures of film-forming pol3miers and Cl participate in extrusion. To avert foaming of the melt by VCI vapors, adsorbents like silica gel [7] are introduced into the polymer composition. 

A special setup is used for manufacture of a three-layered inhibited film whose middle layer is embossed and the cells are filled with a non-drying inhibiting composition (Fig. 2.14). The setup consists of extruders 1 with slot heads 3, vacuum-forming drum 4 and Cl batcher 2 [4,83]. The film blank is directed by guide rollers 5 and 6 to the assembly unit of the laminated material equipped with a heat chamber 7. 

Calendering is used for manufacture of laminated and combined inhibited films by pasting, i.e. by bonding film blanks using glues or pol3mier melts [34]. 

A modification of the laminated anticorrosion film coat used on trunk Pipelines is shown in Fig. 2.58 [4,165]. The film consists of two barrier PE-based layers, 1 and 2. The first of these has strip substrates 1 bonded by glue 4 to a cellular layer 3 containing a mixture of heat-resistant mineral oil and Cl (sodium benzoate) 5. The second layer 2 is a separating layer and is weakly adhered to layer 3. Prior to application of the coating, layer 2 is removed and the film material is pasted over the metal pipeline, with inhibited layer 3 facing the surface being protected. Laminated materials of this t q)e are usually based on very strong cross-linked or oriented films to make the insulation more reliable and reduce its penetrability to ambient matter [4]. 

Plastic scrims are related to the same category of inhibited plastics. In a non-woven form, the inhibited film is first extruded. The polymer webbing (usually melt-blown inhibited polymer fibers) is then laminated to the film. Zerust ferrous plastic scrim is used in the manufacture of airtight packages inside which a protective atmosphere is created by VCI vapors. The fibrous scrim layer also protects packed goods from impact damage. 

Inhibited laminate and combined films contain, as a rule, layers whose main function is to support mechanical load, to be a barrier to dust, corrosion-... 

The structure of inhibiting laminated films (Fig. 2.12) is distinguished by the solid state of their outer (barrier) layers. They are commonly produced from polymers that are incompatible with Cl (Fig. 2.12, layer A). Polymer layers facing the protected metal surface posses a restricted compatibility with Cl and contain structural areas incorporating the Cl in one of the states (Fig. 2.12, layers B and C). 

A scheme of appl3dng an inhibited coating in a polymer melt onto the film base by extrusion lamination [34] is illustrated in Fig. 2.13. A similar procedure is employed at Cortec and Northern Instruments Co. for paper production with a laminated layer of inhibited PE. 

Fig. 2.13. Extrusion-lamination scheme for production of two-layered inhibited polymer film materials (1) unwinding machine (2) film base, (3) extruder with a slot head, (4) inhibited polymer composition, (5) pinch roller, (6) cooling shaft, (7) coiler...

Fig. 2.58. Rust-inhibiting of pipelines using a laminated film incorporating Cl in its adhesive layer (1) barrier PE layer (2) separating PE layer (3) inhibited cellular layer (4) adhesive layer (5) cells containing Cl...

Therefore, many countries in the world have banned the application of highly toxic Cl in inhibited polymer materials, including coatings, films, paper-film laminates, etc. For instance, sodium nitrite has been forbidden for... 

Unoriented Films. Unoriented multilayer films can be obtained by coextrusion of layers of 3GN and PET. Alternatively, multilayer films can be formed in a continuous lamination process using heat or optionally adhesive layers to bond the separate layers. Press lamination can also be used to form multilayer films by pressing layers of individual films at elevated temperature and pressure. Prior to film formation, the pol5miers are generally dried by heating to a temperature of 5°C below the crystallization temperature of the polymer under vacuum or inert atmosphere. The films can be rapidly cooled after extrusion to inhibit crystallization. ... 

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