Method of making silver-containing dispersions with nitrogenous bases

Abstract

A method is used to prepare silver nanoparticle cellulosic polymer composites. A cellulosic polymer, reducible silver ions in an amount of a weight ratio to the cellulosic polymer of 5:1 to 50:1, and an organic solvent are mixed. Each organic solvent has a boiling point at atmospheric pressure of 100° C. to 500° C. The Hansen parameter (δTPolymer) of the cellulosic polymer is less than or equal to the Hansen parameter (δTSolvent) of the organic solvent. The resulting premix solution is heated to at least 75° C., and a (d) nitrogenous base is added to provide a concentration of the nitrogenous base in an equimolar amount or in molar excess in relation to the amount of reducible silver ions, thereby forming a silver nanoparticle cellulosic polymer composite. After cooling, the silver nanoparticle cellulosic polymer composite is isolated and re-dispersed in an organic solvent to provide a non-aqueous silver-containing dispersion.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]Reference is made to the following commonly assigned and copending patent application, the disclosures of all of which are incorporated herein by reference:[0002]U.S. Ser. No. 15 / 456,686, filed Mar. 13, 2017 by Shukla and Donovan;[0003]U.S. Ser. No. 15 / 456,827, filed Mar. 13, 2017 by Shukla, Donovan, and Gillmor;[0004]U.S. Ser. No. 15 / 456,868, filed Mar. 13, 2017 by Shukla and Donovan;[0005]U.S. Ser. No. 15 / ______ (filed on even date herewith by Shukla and Donovan) and entitled “Silver-containing Non-Aqueous Compositions Containing Cellulosic Polymers” (Attorney Docket K002183 / JLT);[0006]U.S. Ser. No. 15 / ______ (filed on even date herewith by Shukla, Donovan, and Klubek) and entitled “Method of Making Silver-containing Dispersion” (Attorney Docket K002190 / JLT); and[0007]U.S. Ser. No. 15 / ______ (filed on even date herewith by Shukla and Donovan) and entitled “Non-Aqueous Silver-containing Dispersions” (Attorney Docket K002192 / JLT).FIELD OF...

AI Technical Summary

Benefits of technology

The present invention provides a simple, safe, and inexpensive way to generate a non-aqueous dispersion of silver nanoparticles. This is achieved by using a nitrogenous base to facilitate faster silver ion reduction in the presence of a cellulosic polymer and organic solvents. The resulting silver nanoparticles are stabilized by the cellulosic polymers and organic solvents, which provide physical stability using inexpensive and environmentally safe dispersing agents. The inventive compositions and methods can be used to provide compositions or dispersions of silver nanoparticles that can be used in various ways, for example, as applied to a substrate in a pattern for further processing.

Problems solved by technology

While silver as an electrical conductor has a wide range of potential uses in the field of printed electronics, the microfabrication of electrically-conductive tracks (grids, wires, or patterns) by photolithographic and electroless techniques is time consuming and expensive, and there is an industrial need for direct digital printing to simplify the processes and to reduce manufacturing costs.

Unfortunately, even these temperatures render the ink incompatible with many polymeric and paper substrates used in flexible electronic and biomedical devices.

However, these methods require that high quantities of purchased silver particles be uniformly dispersed within the photocurable compositions so that coatings or printed patterns have a sufficiently high concentration of catalytic sites.

Scaling such curing procedures to high volume use can be difficult and hard to reproduce on a consistent scale, especially to produce fine line electrically-conductive meshes or grids where the uniformity and size of fine lines are subjected to highly rigorous standards.

However, the conventional technologies have difficulties in the control of particle sizes and large-scale production of particles.

However, the phosphene amino acid reactant is an expensive material.

However, hydrazine is a toxic material and it would not be desirable to include it in a manufacturing process.

An inherent problem that faces users of cellulosic polymers is their general insolubility in most common solvents.

It is usually difficult to predict if cellulose will gel in a given organic solvent, and in most cellulose acetate / solvent systems, gelation occurs after the solution is heated to a specific temperature and subsequently cooled.

Although, as described above, a number of methods to make silver nanoparticles and compositions containing them are known, a number of challenges remain which need to be addressed before such compositions can be used in printed electronic applications.

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