Kodak patent for liquid ascorbic acid developer

[psvensson]

Happened upon U.S. patent no. 6,686,135 in the U.S. PTO database while looking for something else. It describes a single-solution developer that uses a miscible organic solvent to improve the stability of ascorbic acid in water. The approach sounds similar to Gainer's methods, but this solution has water and sulfite too!


Ascorbic acid developing agent 0.1 to 0.5 mol/l

Auxiliary Co-developing agent 0.0005 to 0.01 mol/l

Preservative (e.g.sulfite ions) 0.001 to 0.2 mol/l

Buffer 0.01 to 0.2 mol/l

Organic solvent to water weight ratio 0.1:1 to 1:1

pH 9 to 11

 

[psvensson]

Here are some specific formulas they tested for longevity:

TABLE III
COMPONENT Control Example 1 Example 2
Water 1000 g 600 g 700 g
Diethylene glycol 0 400 g 300 g
Sodium erythorbate 100 g 50 g 50 g
HMMP** 3 g 1.5 g 1.5 g
Versenex 80 37.5 g 18.75 g 18.75 g
(40% solution)*
pH 10 10 10
*Versenex 80 contains pentasodium diethylenetriaminepentaacetic acid
**4-hydroxymethyl-4-methyl-1-phenyl-3-pyrazolidone

HMMP sounds like something close to phenidone. Versenex appears to be a sequestering agent.

Here's a two-part formula that was even more stable:

COMPONENT Part A Part B
Water 600 g .about.250 g
Diethylene glycol 400 g 0
Ascorbic acid 81 g 0
HMMP 3 g 0
Versenex 80 (40% solution) 37.5 g 0
Sodium sulfite 2 g 0
Potassium sulfite (45%) 0 900 g
Borax (5 mol) 0 30 g
pH 45 10.23

 

[psvensson]

In another patent, from last year, they demonstrate that sugars can be mildly effective stabilizing compounds for ascorbic acid. Patent number 6,673,528.

 

[psvensson]

Patent 6,489,090 covers the use of sodium pyruvate and oxalacetic acid as preservatives. Neither seems as good as using an organic solvent.

 

[Gerald Koch]

HMMP is Kodak's Dimezone S developing agent.

 

[Tom Hoskinson]

Sounds like a business plan. Add water, the developing reagents will oxidize/degrade and you will sell more developer.

 

[titrisol]

Look into Sep/Oct 1999 PhotoTecniques.... The genesis of Xtol