Use of a polymer material on the basis of modified hydrocolloids

Details Use of a polymer material on the basis of modified hydrocolloids Use of a polymer material on the basis of modified hydrocolloids

1995-10-05

1997-11-25

Nutter, Nathan M.

Plastic and nonmetallic article shaping or treating: processes

Encapsulating normally liquid material

Liquid encapsulation utilizing an emulsion or dispersion to...

264 43, 264 46, B01J 1308, B01J 1314

Patent

active

056908695

DESCRIPTION:

BRIEF SUMMARY
The object of the invention is the use of a polymer material, based on modified hydrocolloids, as coating material.
The business economy, industry and handicraft as well as cottage industries have long been especially seeking and asking for packaging systems to be used with critical working materials, with which these materials can be temporarily and/or latently rendered inert for storage, handling and like purposes. By critical working materials there are meant inter alia dangerous, combustible, volatile, auto-oxidizable reactive, thermo-sensitive, polymerizable, and/or toxic compounds which, for example, react prematurely with one another, contaminate the environment and/or can harm man and beast. For dealing with critical working substances, there are a number of legal regulations, insofar as they fall, inter alia under the regulations concerning hazardous substances, hazardous material transports, the environment and work hygiene.
For temporarily rendering inert critical working materials, microencapsulation technology offers itself as an ideal packaging system. By microencapsulation there is meant the encapsulation of finely dispersed liquid and/or solid phases by coating them with film-forming polymers which are deposited on the material to be covered after emulsification and coacervation or a border surface polymerization. The resulting microcapsules have protective envelopes and can be dried into a powder. In this manner a number of working materials can be transformed into a "dry mass". The microcapsule content can then be released again as needed, thermal, mechanical, chemical or enzymatic action, insofar as the content substances are still present. Practical experiences however, especially those from uses in technical fields, show that the microcapsule wall materials known to this date are diffusion-tight--and therefore sufficiently stable in storage--only for a few specific capsule content substances. This is also one of the reasons why the microencapsulation techniques have prevailed only with a few product areas, such as, for example, use with or without release properties or vitamins as
While in the product areas a) to c) no diffusion-proof microcapsule walls are required, this is a basic precondition in the case of screw-thread safeguarding agents.
In order to be able to achieve diffusion tightness for storage times of up to 3 months only, the microcapsule walls had to be equipped in separate, expensive and time-consuming additional process steps with secondary or tertiary walls. Such measures often led to unsatisfactory results.
The causes leading to protective covering walls that are not tight with respect to the content substances are often of complicated nature. They depend not only on the number of wall layers, on their thickness and properties; to the essential causal parameters known to this date there belong, inter alia: which leads to contractions covering wall water and in polar, possibly water-containing, organic solvents so-called "verhikel" bridges, especially in liquid media another.
Accordingly, for use in the technical field, there are described in the patent literature a number of microencapsulated products, but most of which have not been able to find acceptance in industrial practice, inter alia because of deficient diffusion tightness and therewith deficient storage stability. Thus, in DE-OS 20 27 737 there is described a hardenable multi-component adhesive or casting-composition system in which, by complicated cross-over combinations of unsaturated polyester resins and polyepoxy resins and their hardening agents, there can be produced mixtures that can practically be handled by microencapsulation technology. Here, 4 reactants at least are necessary, so that the protective coating walls are characterized by inhomogeneous untightness. In consequence of excessively thick microcapsule walls, furthermore, no high capsule destruction quota is assured under application conditions. This system, accordingly, could not become widespread in industrial practice.
In DE-OS 17 69 353

REFERENCES:
patent: 5051304 (1991-09-01), David et al.

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