US2017144A - Photographic dry mounting tissue - Google Patents

Description

Patented mo par M Arthur W. M. Dickins and Neil S. Kocher, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New York No Drawing. Application September 18, 1933, Serial No. 689,876

2 Claims.

I'his invention relates to dry mounting tissue, such as is used in mounting photographic prints on cardboard or on the leaves of albums, etc., by means of heat and pressure. One' object of our 5 invention is to provide a dry mounting tissue which will be satisfactory for use even after prolonged storage. Another object is to provide a dry mounting tissue which can be used at a moderate temperature and over a fairly wide range of temperature. Other objects will hereinafter appear.

The use of dry mounting tissue for mounting photographic prints is well known in the art. The dry mounting tissue in common use consists of thin tissue paper impregnated with shellac. The tissue is placed between the back of the photographic print and the cardboard or paper surface on which it is desired to mount the print, and the whole assemblage is subjected to heat and pressure, for instance by means of a warm flat-iron. This has the eifect of softening the shellac and causing the mounting tissue to adhere to both the print and the mount, thus mounting the print without the warping which is liable to occur when paste or glue is used. However, the shellac-impregnated paper deteriorates during storage and becomes useless, and it is, therefore, highly desirable that a dry mounting tissue be found which will be useful after having been kept for long periods of time. It is also desirable to find a mounting tissue which is operative at relatively low temperatures, to avoid possible scorching of the prints by the use of a very hot iron, and which is operative over a relatively wide range of temperature, so that the temperature of the iron need not be so closely controlled in mounting the prints.

We have discovered that a dry-mounting tissue having all of these desirable characteristics can be prepared by coating paper with a composition of nitrocellulose, tricresyl phosphate and shellac or other suitable resin.

We prefer to use nitrocellulose of half-second viscosity, because compositions containing it soften at a lower temperature than compositions containing nitrocelluloses of higher viscosity. Nitrocellulose of higher viscosity may be used when it is possible or desirable to employ higher temperatures for the mounting.

The solvent mixture employed inpreparing and coating the adhesive composition must contain a solvent for the shellac or other resin, as well as being a solvent for the nitrocellules and tricresyl phosphate. The solvent mixture which we prefer to use is a mixture of acetone and ethyl alcohol, in the proportions of 20 to 50% of acetone less.

and to 50% of ethyl alcohol. The ethyl alcohol may, of course, be denatured. Other solvent combinations may be used, such as mixtures of ethyl acetate and ethyl alcohol or mixtures of ethyl acetate, butyl acetate and methyl, ethyl and 5 butyl alcohols, the particular combination depending on the time of drying desired. The proportions of the active components of the adhesive composition which we prefer to use are as follows: nitrocellulose parts, tricresyl phosphate 10 to parts, shellac or other resin 10 to 200 parts. Even a smaller ratio of shellac or other resin may be employed although some is desirable. The concentration of the solution depends upon the method by which it is to be coated upon the 1 paper in making the mounting tissue. If the paper is to be dipped into the solution, the concentration of nitrocellulose should be about 6 to 7% when half-second nitrocellulose is used, with the tricresyl phosphate and shellac in the abovestated proportions to the nitrocellulose. If the solution is to be spread on the paper, the nitrocellulose concentration should be about 16%.

Both sides of the paper are ordinarily coated with the solution. Suitable forms of apparatus for coating paper by dipping and by spreading are well known in the art. The solvents may be recovered if desired.

Dry mounting tissue made according to our invention has a working range, in mounting, of 0 about 200 to 240 F., whereas dry mounting tissue made by merely impregnatingpaper with shellac has a working range of about 240 to 255 F. It will, therefore, be seen that the working. range of our product is both lower and wider than that of the dry mounting tissue now in common use. The temperature at which our tissue is operative can be varied by varying the proportions of the active components of the adhesive composition. The keeping qualities of our novel dry mounting tissue are far better than those of the tissue prepared by impregnating paper with shellac. At ordinary room temperatures it remains smooth, dry and flexible over long periods. of time. When subjected to accelerated testing. by being maintained at an elevated temperature, our novel dry mounting tissue was still in good condition after flve times the period required to render the old type-of dry mounting tissue use- 50 Other resins which we' may use in place of shellac are ester gum, gum mastic, and dammar and the like. Dry mounting tissues prepared with these resins according to our invention have beenfound to have working ranges of from 210 to 55 300 F, By suitably varying the proportions of nitrocellulose, tricresyl phosphate and resin, the temperature at which adhesion can be effected may be varied as desired.

While we have referred to paper as the support, it will be understood that we may use any type of paper, such, for instance, as tissue paper, yoshino paper, etc.,' and that we may also use cloth or other thin material as the support. we may also make a mounting tissue without any support, by coating our composition on a plate, wheel, or other fiat coating surface and stripping it therefrom although we' prefer, of course, to employ one of the supports above named. 1

what we claim as our invention and desire to be secured by Letters Patent of the United States is:

l; A photographic dry mounting tissue consisting of paper coated on both sides with a composition consisting essentially oi parts of low- 5 viscosity nitrocellulose, from to parts 0! tricresyl phosphate, and from 10 to 200 parts of shellac.

2. A photographic dry mounting tissue consisting of paper coated on both sides with a com- 10