Production of aluminium hydroxide coated glass microspheres

Details Production of aluminium hydroxide coated glass microspheres Production of aluminium hydroxide coated glass microspheres

1999-07-22

2001-01-09

Beck, Shrive (Department: 1762)

Coating processes

Particles, flakes, or granules coated or encapsulated

Inorganic base

C427S212000, C427S226000, C427S376100, C427S397700

Reexamination Certificate

active

06171651

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention provides a method for the coating of glass microspheres with an aluminium hydroxide.
2. Background Art
Applications for aluminium hydroxide coated glass microspheres are for example in the production of light weight glass-reinforced plastic composite materials for use in mass transportation.
Aluminium hydroxide is well-established in the plastics industry as a halogen-free filler which is used to impart fire retardant and smoke suppressing properties to synthetic thermosetting resin systems. Moreover, the trend towards stricter requirements on the burning behavior of plastics means an increasing demand for aluminium hydroxides which can be incorporated in plastics at ever higher filling levels. In glass-reinforced unsaturated polyester composites for example it is not uncommon for the aluminium hydroxide content of the composite material to be >50 wt. %.
In mass transportation for instance, it is possible to achieve the strict fire requirements on composite materials by using aluminium hydroxide alone as fire retardant filler. At the same time, however, the long term trend in composite materials is towards lighter weight composites which reduce energy costs. In the railways, for example, less weight means an increased pay-load for high speed trains and less wear and tear on the tracks.
Aluminium hydroxide (Al(OH)
3
) has a density of 2.42 g/cm
3
which is considerably higher than the ca 1.1 g/cm
3
of a synthetic resin. The use of aluminium hydroxide by itself therefore raises the density and hence overall weight of the end-composite. In addition, the glass fibres used for structural composites contribute further to increased weight due to the even higher density of ca 2.6 g/cm
3
.
Well-established in the art is the incorporation of hollow microspheres of aluminium silicate or borosilicate glass to decrease the overall weight of plastic composite materials and enhance their thermal insulation characteristics. Such microspheres are available in particle sizes which are similar to those of aluminium hydroxide but they have densities in the range of 0.1-1.0 g/cm
3
, so that their incorporation in even relatively small amounts can provide a significant reduction in weight of the end composite. The problem when using hollow glass microspheres however is the need to maintain acceptable mechanical properties of the end composite. This is particularly important for structural plastic composite materials. However, the well-rounded, smooth surfaces of the hollow glass microspheres militate against an effective “bond” between the inorganic filler and the organic resin so that the use of hollow of glass microspheres is generally accompanied by a deterioration in physical properties of the composite material.
BROAD DESCRIPTION OF THE INVENTION
An objective of the present invention therefore is to avoid the problems associated with the methods known in the art and to develop a method for applying an aluminum hydroxide directly onto the surface of hollow glass microspheres.
The objective of the invention is achieved with the process according to the invention, comprising the steps of
a) adding an organic complexing agent to an aqueous solution of an acidic aluminium salt
b) raising the pH of the solution to a value of ≦9,
c) adding a predetermined amount of said glass microspheres to said solution to form a suspension
d) hydrothermally treating said suspension in an oxidizing atmosphere at about 150° C. to 350° C. and
e) separating the aluminium hydroxide coated glass microspheres from the suspension.
It has been surprisingly discovered that a glass microsphere coated following the process of the invention provides uniform aluminium hydroxide coating which remains firmly attached to the underlying glass microsphere surface during further processing thereby allowing the incorporation into synthetic resin of aluminium hydroxide coated glass microspheres with their associated fire retardant properties and providing a substrate for using conventional additives which increase compatibility and strengthen the “bond” between the inorganic and organic phases.


REFERENCES:
patent: 4624798 (1986-11-01), Gindrup et al.
patent: 4632951 (1986-12-01), Fuhr et al.
patent: 5182318 (1993-01-01), Savin
patent: 5196267 (1993-03-01), Barder et al.
patent: 5232775 (1993-08-01), Chamberlain et al.
patent: 5501871 (1996-03-01), Henderson
patent: 5614255 (1997-03-01), Kimura et al.
patent: 5667726 (1997-09-01), Miyazaki et al.
patent: 5670209 (1997-09-01), Wyckoff
patent: 5674624 (1997-10-01), Miyazaki et al.
patent: 41 34 839 (1992-04-01), None
patent: 0 482 821 (1992-04-01), None
patent: 0 573 706 (1993-12-01), None

Affiliated with

Also associated with

Rating

Production of aluminium hydroxide coated glass microspheres does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Production of aluminium hydroxide coated glass microspheres, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Production of aluminium hydroxide coated glass microspheres will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2462181