Animal litter and process for the production thereof

The invention relates to animal litter or bedding made from or in conjunction with a porous material, as well as to a process for the production thereof, the pH value of porous materials being adjusted to between approximately 5.0 to approximately 9.0 in the end product by treatment with liquid or gaseous acid substances in order to obtain an optimum smell reducing action.

The invention relates to animal litter or bedding material, produced from 
or in conjunction with a porous material, together with a process for the 
production thereof. 
In the case of known materials for the production of animal litter, they 
are mainly natural products having a mineral or organic origin, such as 
pumice, clay material such as e.g. alumina, fire clay and the like, wood 
flour, peat and kieselguhr which, as a result of their porous structure, 
are able to absorb liquids in the said pores. 
For example, DAS No. 2,902,079 discloses such an animal litter, in whose 
production porous material with a porous structure is used. The porous 
matrial used therein is a calcium silicate granular material having a pH 
value of generally 8.7 to 10. 
The known animal litter made from calcium silicate granular material with a 
pore radius of less than 500 nm is stable as regards shape and consistency 
and has a bactericidal action. 
However, during prolonged use of such materials an unpleasant smell is 
given off, so that it is frequently necessary to change the litter, 
although the absorption characteristics thereof are not really exhausted. 
The problem of the invention is therefore to improve known animal litter 
materials in such a way that it is possible to prevent undesired smells 
which occur even when such materials have been used for a short time, and 
as a result permit a longer use of the litter. 
According to the invention, this problem is solved by a porous material, 
whose pH value is between approximately 5.0 and approximately 9.0, 
preferably between approximately 5.8 to 6.2. 
The invention also relates to a process for producing such a material in 
which the porous material is treated with a gaseous or liquid acid 
substance. 
As a result of this novel treatment of per se known materials using 
substances whose pH value drops to a weak acid range, it has surprisingly 
proved possible to bring about an unexpected reduction of the smell. 
Particularly in view of the fact that e.g. cat's urine, which is weakly 
acid, is not prevented from giving off a smell after prolonged use by 
neutral to weak basic adsorbents, it was very surprising that such a 
reduction of the smell resulted from lowering the pH value to a weak acid 
range. 
It has proved particularly advantageous to use the calcium silicate 
granular material with a uniform pore size distribution described in DAS 
No. 2,902,079 as the porous material, which is set to the desired pH value 
by exposing to an atmosphere containing gaseous acid substances or by 
spraying with acid solutions and subsequent drying. 
Other porous materials, such as e.g. clays and the like can also be used. 
It is also possible to add to the animal litter according to the invention 
further deodorants, perfume oils and the like. 
It is also possible to add to the animal litter according to the invention 
colour indicator systems, which indicate the decline in effectiveness of 
the material. 
Further features and advantages of the invention can be gathered from the 
following description in which specific embodiments are described.

EXAMPLE 1 
The animal litter according to the invention was produced by using as the 
starting material commercial alumina with a particle size between 2 to 5 
mm, conveyed by a conveyor belt in uniform quantity to an oblique 
proportioning screw. A solution of phosphoric acid was sprayed onto the 
surface of the alumina particles at the transition point from the conveyor 
belt to the proportioning screw using a spray nozzle system during the 
free fall of the product. 
A uniform wetting of the carrier material surface resulted from the rotary 
movement of the proportioning screw. The quantity to be sprayed on it is 
adjusted by continuous control of the pH value in the finished product, so 
that the pH value is in the range between approximately 5 and 
approximately 7. 
The product is then dried in a rotary drier to a residual moisture content 
of less than 10%, whilst setting a drying temperature of approximately 
210.degree. C. 
A non-tacky, dry, odourless product is obtained having good absorption 
characteristics, particularly for cat's urine. 
EXAMPLE 2 
Production of calcium silicate granular material suitable as cat's litter 
50.4 to 57.0% by weight of quartz powder with a particle size below 100 mm, 
29.0 to 42.0% by weight of quicklime and 7.6 to 16.5% by weight of calcium 
hydroxide were processed to granulated calcium silicate in the manner 
described in DAS No. 2,902,079. The finished product has an alkaline pH 
value in the range 8.7 to 10. 
Treatment of the calcium silicate granular material for reducing the pH 
value 
The thus produced calcium silicate granular material is crushed to a 
particle size between approximately 2 and 5 mm, screened and dedusted. The 
thus produced calcium silicate particles are conveyed by means of a 
conveyor belt in uniform manner to an oblique proportioning screw 
(obliquity approximately 40%). 
An acid solution is sprayed onto the surface of the calcium silicate 
particles by means of a spray nozzle at the transition point from the 
conveyor belt to the proportioning screw. 
The spraying solution consists of 31% by weight of a 95% phosphoric acid 
solution mixed with 69% by weight of an aluminum sulphate solution having 
a density of 1.30 to 1.34 and a pH value between 2 and 3.5. 
The quantity of liquid to be sprayed on is regulated by continuous control 
of the end product, so that the latter has a pH value between 5.8 and 6.2. 
After passing through the proportioning screw, in which the surface of the 
calcium silicate particles is uniformly wetted, the treated granular 
material is transferred into a rotary drier. At a drying temperature of 
approximately 210.degree. C., drying takes place to an end product 
residual moisture content of less than 10%. 
The thus produced, treated calcium silicate granular material has superior 
properties, particularly with respect to cat's urine compared with known 
animal litter materials. 
Apart from those specifically described in examples 1 and 2 in connection 
with the production of the animal litter according to the invention, it is 
also possible to use other salts or acids for obtaining an acid pH value. 
It is also possible to acidify such substances by treating with acid gases, 
e.g. sulphur trioxide, hydrochloric acid gas or other acids in gaseous 
form, which can optionally be carried out particularly inexpensively when 
such acid gases are available from other chemical processes. 
The inventive features disclosed in the description and claims may be 
essential to the realisation of the different embodiments of the invention 
either individually or in random combination.