Synthesis of and uses of alkaline earth metal stannates

Abstract

The present invention provides a particularly advantageous form of alkaline earth metal hydroxystannate and alkaline earth metal stannate exhibiting a BET specific surface area of from 20 to 200 m2/g. A method of producing such particulate material and evidence of its benefits in use such as in at a reduction in a polymer sample at elevated temperature is also disclosed.

Claims

1. An alkaline earth metal stannate or an alkaline earth metal hydroxystannate, where an alkaline earth metal is; having a surface area using the B.E.T. method of from 20 to 200 m.sup.2/g, and the alkaline earth metal stannate or the alkaline earth metal hydroxystannate is in a form of particles and a surface weighted mean D(3,2) particle size as determined by light scattering is 1 to 4 microns.

2. The alkaline earth metal stannate or the alkaline earth metal hydroxystannate of claim 1 in which the surface area is from 50 to 90 m.sup.2/g.

3. The metal stannate or hydroxystannate of claim 1 in which the surface weighted mean D(3,2) particle size as determined by light scattering is 1.5 to 3.0 microns.

4. A polymer comprising a component that evolves acid at elevated temperature in combination with the alkaline earth metal stannate or the alkaline earth metal hydroxystannate of claim 1.

5. The polymer of claim 4 in which the polymer is polyvinyl chloride.

6. A masterbatch comprising 20% by weight or more of the alkaline earth metal stannate or the alkaline earth metal hydroxystannate of claim 1.

7. The masterbatch of claim 6 in which the masterbatch comprises one of polyvinyl chloride, a polyolefin or a polyamide.

Description

(1) The present invention is illustrated by the figures in which:

(2) FIG. 1 shows a two thousand times magnification of Calcium Hydroxystannate produced by the present invention;

(3) FIG. 2 shows a two thousand times magnification of calcium stannate produced by the present invention;

(4) FIG. 3 shows a four thousand times magnification of Calcium Hydroxystannate produced by the present invention;

(5) FIG. 4 shows a four thousand times magnification of calcium stannate produced by the present invention;

(6) FIG. 5 shows a two thousand times magnification of stannate produced by a comparative method;

(7) FIG. 6 shows a two thousand times magnification of stannate produced by a comparative method;

(8) the comparative method and micrographs are as disclosed in T. Ivetić1, M. V. Nikolić, P. M. Nikolić, V. Blagojević, S. Ðudić, T. Srećković and M. M. Ristić, Science of Sintering, 39 (2007) 153-160, Investigation of Zinc Stannate Synthesis Using Photoacoustic Spectroscopy. This article is particularly relevant as its objective is to provide a high surface area stannate. The figures clearly show the contrast between the very high surface area of the present method which comprises a combination of large cubic crystals which cement together a matrix of finer particulate material having high porosity.

(9) It has also been found that when polymer, such as PVC, polyethylene, polypropylene and PTFE is extruded under pressure and temperature in an injection moulding apparatus that the backpressure can increase over time. However, a composition in which a zinc stannate is replaced by a calcium stannate (composition as tables 1 and 2) show that backpressure increase over time is reduced. This is attributed to a lubricating effect from the calcium stannate. This is particularly marked for PVC where HCl gas evolution may also contribute to backpressure. A preliminary comparison of

(10) Temperatures herein are 20° C. unless specified otherwise, pressure is atmospheric pressure. Test methods are those methods current at the date of application.