Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Finishing or perfecting composition or product
Reexamination Certificate
2000-03-27
2001-09-18
Le, Hoa Van (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Finishing or perfecting composition or product
Reexamination Certificate
active
06291141
ABSTRACT:
The invention relates to a washing solvent for layers of photopolymer which are cured (crosslinked) by exposure to light.
The said photopolymers are used to print various plates, preferably using the flexographic printing technique. They are basically elastomers which contain polymerisation photoinitiators.
In order to produce these printing plates, in particular those used for flexographic printing, the photopolymers are exposed to actinic light. The part of the photopolymer required to be in relief is polymerised by passing it under actinic light. The unpolymerised part of the photopolymer can then be washed out with a washing solvent which dissolves and removes it, thus leaving the part of the photopolymer which has been polymerised and hardened by the light in relief.
The washing solvent should dissolve the unpolymerised layer of photopolymer as rapidly as possible. The solvent should then evaporate from the body of the photopolymer so that it is thoroughly dry.
It is fairly easy to obtain this performance with highly volatile solvents such as methyl ethyl ketone, benzene, toluene, trichloroethane, trichloroethylene, tetrachloroethane, etc.
The unacceptable disadvantage involved in the use of these solvents is that they are hazardous, and their use and disposal consequently creates serious problems of health, safety and environmental protection.
These solvents also have a very strong, unpleasant, pungent odour, which remains incorporated in the printing plates.
The object of this invention is to produce a washing solvent of the kind described above which possesses the following characteristics: not toxic or hazardous; a high flash point; a very faint odour; a fast washing speed and a fast drying speed in the oven; no disposal problems, recoverable and recyclable.
In order to achieve these objectives, and the other advantages which will be described below, this invention offers a washing solvent designed to remove the unpolymerised part of a photopolymer exposed to light, in particular in flexographic printing processes, characterised in that the said solvent comprises 25 to 70% in weight of an alicyclic hydrocarbon, 15 to 50% in weight of an aromatic hydrocarbon and 10 to 30% in weight of an aliphatic alcohol.
In accordance with the invention, the said alicyclic hydrocarbon is preferably chosen from among the terpenes with the formula C10 H16, of both dextro- and laevo-isomeric forms, and in the racemic form dipentene.
The said aromatic hydrocarbon is preferably a mixture of aromatic hydrocarbons with the formula C10.1 H14.3.
The said aliphatic alcohol is chosen from among the high-boiling aliphatic alcohols with the formula C7 H16.0, C8 H18.0.
REFERENCES:
patent: 5061606 (1991-10-01), Telser et al.
Balducci Pier Angelo
Bovati Walter
Chimeko S.r.l. Trade Chimico Ecologico
Hedman & Costigan ,P.C.
Le Hoa Van
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