Feeder and shapeable composition for production thereof

1. Feeder for use in the foundry industry, comprising

(a) rice husk ash containing, based on the total amount of the constituents detectable in the rice husk ash by quantitative phase analysis by means of x-ray diffractometry

(i) crystalline modifications of silicon dioxide,

(ii) monoclinic feldspar and

(iii) amorphous silicon dioxide,

a total content of at least 70 wt. % of

(i) crystalline modifications of silicon dioxide and

(ii) monoclinic feldspar,

(b) cured binder

(c) optionally fibre material,

(d) optionally one or more further fillers,

(e) optionally an oxidizable metal and an oxidizing agent for the oxidizable metal.

2. Feeder according to claim 1 , characterized in that the content of the silicon dioxide contained in the rice husk ash which is present in the form of crystalline modifications contains proportions of one or more crystalline modifications of silicon dioxide from the group consisting of cristobalite, tridymite and quartz.

3. Feeder according to claim 1 , characterized in that

the carbon content of the rice husk ash (a) is less than 1 wt. %, and/or

the grain size of the rice husk ash (a) is 0.2 to 2 mm, and/or

the bulk density of the rice husk ash (a) is 200 to 400 g/liter, and/or

the thermal conductivity of the rice husk ash (a) is 0.12 to 0.13 W/mK at 100° C. and 0.39 to 0.4 W/mK at 1,000° C.

4. Feeder according to claim 1 , characterized in that the cured binder (b) is the curing product of a two-component system which comprises a phenolic resin containing free hydroxyl groups and a polyisocyanate as a reaction partner.

5. Feeder according to claim 1 , characterized in that it contains hollow spheres as a further filler (d),

wherein, based on the total weight of the shapeable composition of the feeder, the total amount of

(a) rice husk ash containing, based on the total amount of the constituents detectable in the rice husk ash by quantitative phase analysis by means of x-ray diffractometry (i) crystalline modifications of silicon dioxide, (ii) monoclinic feldspar and (iii) amorphous silicon dioxide, a total content of at least 70 wt. % of (i) crystalline modifications of silicon dioxide and (ii) monoclinic feldspar,

and

(d) hollow spheres

is in the range of from 5 to 90 wt. %, and the weight ratio of the rice husk ash (a) to hollow spheres (d) is at least 0.1.

6. Feeder according to claim 1 , characterized in that it contains as a further filler (d) rice husk ash which contains, based on the total amount of the constituents detectable in the rice husk ash by quantitative phase analysis by means of x-ray diffractometry (i) crystalline modifications of silicon dioxide, (ii) monoclinic feldspar and (iii) amorphous silicon dioxide, a total content of less than 70 wt. % of (i) crystalline modifications of silicon dioxide and (ii) monoclinic feldspar, and, based on the total weight of the shapeable composition of the feeder, the amount of such rice husk ash (d) is at most 10 wt. %.

7. Shapeable composition for the production of feeders for the foundry industry, comprising

(a) rice husk ash containing, based on the total amount of the constituents detectable in the rice husk ash by quantitative phase analysis by means of x-ray diffractometry

(i) crystalline modifications of silicon dioxide,

(ii) monoclinic feldspar and

(iii) amorphous silicon dioxide, a total content of at least 70 wt. % of

(i) crystalline modifications of silicon dioxide and

(ii) (ii) monoclinic feldspar,

(b) binder,

(c) optionally fibre material,

(d) optionally one or more further fillers,

(e) optionally at least one oxidizable metal and an oxidizing agent for the oxidizable metal.

8. Shapeable composition according to claim 7 , characterized in that the binder (b) is a two-component system which comprises a phenolic resin containing free hydroxyl groups (OH groups) and a polyisocyanate as a reaction partner.

9. Shapeable composition according to claim 7 , characterized in that

it contains hollow spheres as a further filler (d),

wherein, based on the total weight of the shapeable composition, the total amount of

(a) rice husk ash containing, based on the total amount of the constituents detectable in the rice husk ash by quantitative phase analysis by means of x-ray diffractometry (i) crystalline modifications of silicon dioxide, (ii) monoclinic feldspar and (iii) amorphous silicon dioxide, a total content of at least 70 wt. % of (i) crystalline modifications of silicon dioxide and (ii) monoclinic feldspar,

and

(d) hollow spheres

is in the range of from 5 to 90 wt. %, and the weight ratio of the rice husk ash (a) to hollow spheres (d) is at least 0.1.

10. Shapeable composition according to claim 7 , characterized in that it contains as a further filler (d) rice husk ash which contains, based on the total amount of the constituents detectable in the rice husk ash by quantitative phase analysis by means of x-ray diffractometry (i) crystalline modifications of silicon dioxide, (ii) monoclinic feldspar and (iii) amorphous silicon dioxide, a total content of less than 70 wt. % of (i) crystalline modifications of silicon dioxide and (ii) monoclinic feldspar,

and, based on the total weight of the shapeable composition, the amount of such rice husk ash (d) in which a content of less than 70% of the contained silicon dioxide is present in the form of crystalline modifications, is at most 10 wt. %.

11. Process for the preparation of a shapeable composition for the production of feeders for the foundry industry, comprising the steps

provision of a rice husk ash (a) containing, based on the total amount of the constituents detectable in the rice husk ash by quantitative phase analysis by means of x-ray diffractometry (i) crystalline modifications of silicon dioxide, (ii) monoclinic feldspar and (iii) amorphous silicon dioxide, a total content of at least 70 wt. % of (i) crystalline modifications of silicon dioxide and (ii) monoclinic feldspar,

mixing of the rice husk ash (a) provided with

(b) binder,

(c) optionally fibre material and

(d) optionally one or more further fillers

(e) optionally an oxidizable metal and an oxidizing agent for the oxidizable metal, so that, based on the total weight of the shapeable composition, the amount of rice husk ash (a) which contains, based on the total amount of the constituents detectable in the rice husk ash by quantitative phase analysis by means of x-ray diffractometry (i) crystalline modifications of silicon dioxide, (ii) monoclinic feldspar and (iii) amorphous silicon dioxide, a total content of at least 70 wt. % of (i) crystalline modifications of silicon dioxide and (ii) monoclinic feldspar, in the shapeable composition is in the range of from 5 to 50 wt.

12. Process according to claim 11 , characterized in that rice husk ash which contains, based on the total amount of the constituents detectable in the rice husk ash by quantitative phase analysis by means of x-ray diffractometry (i) crystalline modifications of silicon dioxide, (ii) monoclinic feldspar and (iii) amorphous silicon dioxide, a total content of less than 70 wt. % of (i) crystalline modifications of silicon dioxide and (ii) monoclinic feldspar, is heat-treated at a temperature of at least 1,300° C. until, based on the total amount of the constituents detectable in the rice husk ash by quantitative phase analysis by means of x-ray diffractometry (i) crystalline modifications of silicon dioxide, (ii) monoclinic feldspar and (iii) amorphous silicon dioxide, the total content of (i) crystalline modifications of silicon dioxide and (ii) monoclinic feldspar has risen to at least 70 wt. %.

13. Process according to claim 11 , characterized in that the heat treatment is carried out at a temperature of between 1,400 and 1,500° C.

14. Process according to claim 11 , characterized in that the rice husk ash is heat-treated at least until it has assumed a pink colour shade.