US2078172A

US2078172A - Coated film

Info

Publication number: US2078172A
Application number: US69729A
Authority: US
Inventors: Abrams Allen; George W Forcey; George J Brabender
Original assignee: Marathon Paper Mills Co
Current assignee: Marathon Paper Mills Co
Priority date: 1936-03-19
Filing date: 1936-03-19
Publication date: 1937-04-20
Anticipated expiration: 1954-04-20

Description

Patented Apr. 20, 1937 UNITED STATES PATENT. OFFICE COATED FILM Application March 19, 1936, Serial No. 69,729

9 Claims.

This invention relates to a coated film mae terial.

One of the objects of this invention is to provide a pressure-scalable flexible film with an adherent flexible non-tacky coating.

Another object of this invention is to coat a flexible film of wax-rubber composition with an adherent coating of lacquer. I A further object of this invention is to provide "a method of coating flexible film materiaiwith a flexible adherent coating composition without impairing the film structure.

Further and other objects of our invention will be apparent from the following specifications and drawing.

On the drawing:

Figure 1 is a sectional view of our film material coated on one side.

Figure 2 is a sectional view of our film material coated on both sides.

Figure 3 is a diagrammatic view of the apparatus for forming and coating a wax rubber film.

Figure 4 is a diagrammatic view of another apparatus for coating the film. I

In Abrams et al. Patents Nos- 2,054,112 and 2,054,115, Sept. 15, 1936 there is disclosed a novel film material and method of making the same. One of the specific"self-sustainingfilms so made consists of a rubber-wax composition containing from at least 6 to 30% rubber. This film may be unvulcanized or vulcanized if desired.

These wax-rubber films have pressure sealing characteristics which are very important for certain uses thereof as for example in forming airtight packages. In some instances however it is not necessary that our film material should have these aforementioned properties particularly when the film is cut into narrow ribbons for use as a tying or ornamental ribbon.

We have discovered a method of eliminating such pressure sealing properties of the type of films produced according to the aforementioned patents by coating such films with a suitable coating composition. At the same time we improve the gloss and appearance of the films. The

self-sustaining characteristics and stiffness of the films are also increased.

Since accordingto our preferred method the coating material ,is applied in a volatile solvent,

it is necessary to select a solvent which will not dissolve orreact with the base film material to be coated. Otherwise there would be a tendency to destroy the structure of the base film and difilculty would be encountered in drivingthe'sol- I vent off after the coating material has been applied, At the same time it .is desirable to utilize a coating material which is fiexible, relatively cheap and which can be applied tothe film without much difiiculty.

The I coating composition which we prefer, using as our base a wax-rubber film, is a lacquer having a substantially high percentage of solids in order to reduce the amount of volatile solvent required and thereby causing the lacquer to flow more smoothly onto the film. This higher percentage of solids must also be accompanied by sufiicient viscosity to permit the formation of a coating film on the outside suriace of the base film which can be smoothed. Obviously the lacquer must wet the film sufilcientlyto cause suitable adhesion.

As an example of a lacquer suitable for coating a wax-rubber film we use a composition consisting of a volatile and non-volatile portion. The non-volatile portion may consist of a composition having:

Percent by weight Acetone soluble resin (e. g.,. General Plastics resin #965) 20 V sec. nitrocellulose '70 Blown castor 011---. 10

This mixture may then be dissolved directly in acetone making up to approximately 25% by weight of the non-volatile matter in .the final lacquer. However, on account of the rapid .evap oration of the acetone, and.the consequent tendency to blush, particularly in moist air, we prefer to add small amountsof solvents which evaporate less readily. Thus, for example, we may use a mixture comprising by weight the following ingredlents:

Percent Acetone 50 Butyl alcohol 10 Anhydrous ethyl 40 Alcohol denatured with say, ethyl acetate keep" the temperature of the sheet at not over I F. I This does not mean however that the air used for drying the film must be kept at that temperature since obviously the evaporation of the solvent requires a considerable amount of heat. The film however does notattain the temperature of 5 the heated air surrounding it unless-it is kept there for a considerable time.

Figure 1 illustrates a sectional view of a waxrubber film i0, coated on one face only with a lacquer composition II. This lacquer may be ap- 10 plied in any known suitable manner such as by means of brushes, rolls or sprays and thereafter drying the coating.

Figure 2 illustrates a sectional view of a waxrubber film coated on both sides with a lacquer 15 composition.

A suitable method of coating the base film ID on both sides consists in leading the film directly from the film forming apparatus into a pan so that the coating composition is applied on both sides of the base film. As illustrated in Figure 3 the wax-rubber composition i1 is sheeted out on a large chilled roll I 5 by means of a heated doctor roll l6 rotating at a slower surface speed than roll i5 and in the same direction as roll IS. The film 25 I 0 is stripped from roll l5 by a stripping roll l8 and is then led over supporting rolls 20, 2| through a suitable lacquer bath, 30, contained in a closed pan 3| having a narrow opening 32 for permitting the withdrawal of film Ill. The

30 coated film passes between two adjustably spaced

bars

33, 34 which remove the excess coating from the base film. The film is then conducted through 'a drying chamber 35 in order to remove all or a major portion of the solvent in the coating com- 5 position. Warm air is supplied to the drying chamber at 36. The solvent fumes are removed through exhaust 31a. The length of the chamber is such that the coating is not tacky by the time it reaches supporting roll 36 and will not stick to 40 the roll. The coated film is then led around roll 31and wound up on roll 38.

Another method of coating films is illustrated in Figure 4. The'film [0, is passed between rolls 40 and 4| which apply the coating composition 45 to opposite sides of the film. A nozzle 42 supplies the coating composition to the surface of roll 40 at a point before it comes into contact with the film l0. Roll 4| is partially immersed in the coating composition 43 contained in vessel 44 and ap- 50 plies the composition to the lower surface of the film Hi. The surface coating is smoothed by rolls 45 and 46 rotating at a surface speed of about 5% of the film travel. Roll 45 rotates in clockwise direction and roll 46 in counterclockwise di- 55 rection in relation to the film travel, in order to smooth the surface coating. The coated film then passes through adrier 4'! where the solvent in the coating'composition is removed. The film is then wound up on roll 49.

60 We may incorporate pigments or other coloring materials in the lacquer or coating composition used. By using the same color in the coating composition as that of the base film we enhance the depth and lustre of the color in the 5 finished product. We may also start with an uncolored base film and produce a colored product by employing a colored coating composition.

The coated film produced by our process has many useful and valuable properties. When us- 7 ing a wax-rubber composition for the base film containing say about 25% rubber and lacquering V the same an unusually strong, glossyfllm is produced which is adaptable fortying purposes, for general use where ornamental ribbons are now 75 used as in floral wreaths and decorations, Our

coated film is waterproof, moistureproof, greaseproof, and is therefore not soiled or stained by water or oily substances as is the case with ribbons made of silk or other fibrous materials. Our coated film retains a fresh appearance after much 5 handling and exposure to air.

Another characteristic of the lacquered waxrubber film is that the coating does not crack or peel upon bending, creasing or slight stretching thereof and adheres to the base film under all normal conditions.

The comparatively thin flexible non-tacky coating layer on the tacky film serves to eliminate the tackiness of the film. However when the coated film of our preferred example is stretched sufiiciently the coating layer being less flexible than the base film is broken thereby exposing the pressure sealing surface of the base film. It is therefore possible to form a pressure sealed bond with our coated film by stretching the film and then applying pressure thereto, thereby bringing pressure-scalable portions of the base film into contact.

It is obvious that many modifications may be made in our coated film. For example, we may coat only one surface of the film thereby producing a sheet having pressure-sealable and non pressure-scalable surface. We may also coat the base film in spots, stripes or other configurations on one or both sides thereby leaving pressure-sealable areas in the finished sheet. We may also coat the base film in such manner so as to produce alternate coated and uncoated areas instead of coating the entire surface of the base film.

We claim:

1. A flexible stretchable base film comprising a wax and a rubber and having an adherent flexible non-tacky coating, said coating being less flexible than the said base film whereby upon stretching the coating is broken to expose the surface of the base film.

2. A flexible stretchable wax-rubber film base having a non-tacky adherent lacquer composition coating thereon, said coating being less flexible than the said base film whereby upon stretching the coating is broken to expose the surface of the base film.

3. A flexible stretchable wax-rubber base film comprising from at least 6 to 30% rubber having thereon a non-tacky adherent lacquer composi- 50 tion coating, said coating being less flexible than the said base film whereby upon stretching the coating is broken to expose the surface of the base film.

4. A flexible stretchable wax-rubber base film comprising about 25% rubber provided with a non-tacky adherent lacquer coating, said coating being less flexible than the said base film whereby upon stretching the coating is broken to expose the surface of the base film.

5. A flexible stretchable wax-rubber base film comprising from at least 6 to 30% of rubber and having at least one surface thereof provided with a flexible non-tacky adherent coating, said coating being less flexible than the said base film whereby upon stretching the coating is broken to expose the surface of the base film.

6. A flexible stretchable base film comprising a vulcanized wax-rubber composition, said base film being provided with an adherent flexible non-tacky coating, said coating being less flexible than the said base film whereby upon stretching the coating is broken to expose the surface of the base film.

7. A flexible stretchable base film made of a vulcanized wax-rubber composition, comprising from at least, 6 to 30% rubber, said base fllm being provided with an adherent flexible nontacky waterproof coating, said coating being less 5 flexible than the said base film whereby upon stretching the coating is broken to expose the surface of the base film.

8. The method of coating 9. flexible stretchable wax-rubber base film which comprises the steps 10 of applying thereto a coating composition containing a volatile solvent which will not destroy said base film, smoothing said coating composition and evaporating the solvent to produce a flexible dry non-tacky adherent coating on said 15 base film, said coating being less flexible than the