Lower cost reusable polymer binder
View Patent ↗Exemplary embodiments provide compositions for erasable media and methods of forming polymers for erasable media. The method can include providing a first monomer, the first monomer including one or more alkoxylated bisphenols and adding at least one second monomer and a catalyst to the first monomer to form a mixture at a first temperature, the second monomer selected from the group consisting of an organic diacid, a dialkyl ester of the organic diacid, and combinations thereof. The method can also include melt condensing the mixture by increasing the temperature from the first temperature to a second temperature over a first amount of time to form one or more polymers, wherein the one or more polymers has an acid value in the range of about 0.1 mg-KOH to about 12 mg-KOH.
1. An erasable medium comprising:
a substrate, wherein the substrate is selected from the group consisting of paper, glass, ceramic, wood, plastic, fabric, textile, metal, plain paper, coated paper, no tear paper, and mixtures thereof; and
a photochromic layer disposed over the substrate, the photochromic layer comprising one or more photochromic polymers dispersed in at least one polymer binder, at least one of the one or more photochromic polymers having the following general formula:
wherein x ranges from about 1 to about 10, n ranges from about 1 to about 1000, and m ranges from 1 to about 1000, and
the at least one polymer binder having one of the following general formulas:
wherein x ranges from about 1 to about 10, n ranges from about 1 to about 1000, and m ranges from 1 to about 1000, and
wherein each of the photochromic polymer and the polymer binder has a glass transition temperature in the range of about 30° C. to about 150° C.
2. The erasable medium of claim 1 , wherein the polymer binder has an acid value in the range of about 0.1 mg-KOH to about 12 mg-KOH.
3. The erasable medium of claim 1 , wherein a portion of the photochromic layer changes from a colorless state to a colored state upon exposure to a temperature in the range of about 30° C. to about 150° C. and a radiant energy.
4. The erasable medium of claim 3 , wherein a portion of the photochromic layer comprises an image having an image lifetime of at least about 3 days.
5. The erasable medium of claim 4 , wherein the image has an initial optical density difference with a surrounding background area of about 0.75 or greater.
6. The erasable medium of claim 5 , wherein after 3 days from the exposure, the image has an optical density difference with a surrounding background area of at least about 40% of the initial optical density difference.
7. The erasable medium of claim 3 , wherein the portion of the photochromic layer changes from the colored state to the colorless state upon exposure to a temperature in the range of about 50° C. to about 200° C.
8. The erasable medium of claim 1 further comprising a second photochromic layer disposed over the substrate on a side opposite to the photochromic layer, the second photochromic layer comprising one or more photochromic polymers dispersed in at least one polymer binder, at least one of the one or more photochromic polymers having the following general formula:
wherein x ranges from about 1 to about 10, n ranges from about 1 to about 1000, and m ranges from 1 to about 1000; and
the at least one polymer binder having one of the following general formulas:
wherein x ranges from about 1 to about 10 and
wherein each of the photochromic polymer and the polymer binder has a glass transition temperature in the range of about 30° C. to about 150° C.