Terpene ether developing solvent for photopolymerizable printing plates

Abstract

Flexographic printing plates are produced by exposing the photopolymer plates to a light source and washing out (developing) the masked out, non-exposed areas with a solvent. The invention provides terpene ether solvents suitable for use in the development of photopolymer printing plates. The solvents, which include terpene ethers alone or mixed with co-solvents and / or non-solvents, are effective in developing a large number of different photopolymer printing plates and can produce images superior to those obtained with commercially available solvents currently used in such applications.

Description

FIELD OF THE INVENTION [0001] The present invention relates to an improved solvent and process for the production of flexographic printing plates crosslinked by photopolymerization. More specifically, the invention relates to a solvent system using terpene ethers, alone or in combination with co-solvents and / or non-solvents, as washout solvents for the unpolymerized material in the printing plates to develop a relief image and a method for developing printing plates. BACKGROUND OF THE INVENTION [0002] Washout processes for the development of photopolymerizable flexographic printing plates are well known and is described in detail in U.S. Pat. No. 5,240,815 which is incorporated herein by reference. Ordinarily, exposed plates are washed (developed) in a developing solvent that can remove the unpolymerized material while leaving the polymerized (cured) material intact. The solvent typically used in such processes include: (a) chlorohydrocarbons, such as trichloroethylene, perchloroeth...

AI Technical Summary

Benefits of technology

[0011] The present invention comprises solvents for use in the processing of a wide variety of photopolymeric materials used to form photopolymer printing plates. These solvents, which comprise terpene ethers either alone or in the presence of other organic materials (co-solvents and non-solvents), can be used with a variety of polymeric systems, including, but is not limited to SBS and SIS polymer systems, as well as a large number of nitrile rubber and other copolymer systems. The terpene ethers are natural products with low toxicity and are relatively safe to use compared with other solvent systems. Terpene ethers, it has been discovered, provide a unique combination of reduced cost, improved plate quality, low volatility, improved regulatory compliance, low toxicity, reduced washout time, and biodegradability.

[0012] It is, therefore, an object of the present invention to provide a solvent system and a process for the preparation of relief plates crosslinked by photopolymerization, in which the washout time and the drying time are substantially shorter compared with the conventional process solvents, and wherein the relief plates suffer neither excessive surface swelling nor under-washing and are characterized by improved relief depths and sidewall structure.

[0013] Another object of the present invention is to provide a process for the preparation of relief plates crosslinked by photopolymerization which is capable of operation without expensive explosion protection.

[0015] It is another object of the present invention is to provide solvent systems which minimizes workplace hazards and requires minimal regulatory reporting.

Problems solved by technology

One important disadvantage of the known solvents and the procedures for their use is that the solvents being used as developers may act too slowly, cause swelling of the plates and / or cause damage to the fine detail in the plate by undercutting and / or pinholing.

Moreover, when non-chlorinated solvents are used in the washout process, long drying times may be necessary.

Furthermore, many of these solvents have flashpoints of less than 100° F., so that the process can only be operated in special, explosion-protected plants.

When chlorohydrocarbons and other toxic chemicals are used, their toxicity also gives rise to disposal problems and worker safety issues.

The need for different solvent systems is particularly inconvenient, especially if different photopolymer systems are being processed at the same facility.

Furthermore, many of the solvents used to develop the plates are toxic or suspected carcinogens.

However, they have proven to be hazards in the workplace because of their tendency to spontaneously combust thereby causing fires.

However, terpene esters tends to breakdown through repeated distillation which limits the recyclability of the solvent.