Melt composition for the production of man-made vitreous fibres

1. A melt composition for the production of man-made vitreous fibers comprising the following oxides, by weight of composition:

SiO 2

39-43 weight %

Al 2 O 3

20-23 weight %

TiO 2

up to 1.5 weight %

Fe 2 O 3

5-9 weight %,

CaO

8-18 weight %

MgO

5-7 weight %

Na 2 O

up to 10 weight %,

K 2 O

up to 10 weight %,

P 2 O 5

up to 2%

MnO

up to 2%

R 2 O

up to 10 weight %

wherein the proportion of Fe(2+) is greater than 80% based on total Fe;

wherein the reading for Fe(0) content in the melt, measured using a magnetic analyser, is less than 900 ppm.

2. A melt composition according to claim 1 , wherein the reading for Fe(0) content in the melt, measured using a magnetic analyser, is less than 500 ppm.

3. A method of forming man-made vitreous fibers comprising fiberising a melt composition according to claim 1 by a spinning cup method to form fibers and collecting the formed fibers.

4. A method of forming a melt composition as defined in claim 1 , comprising heating and melting mineral material in a furnace to produce a mineral melt and, if necessary, adjusting the oxidation state of the melt such that the proportion of Fe(2+) based on total Fe is greater than 80%.

5. A melt composition according to claim 1 , wherein the proportion of Fe(2+) is greater than at least 90% based on total Fe.

6. A melt composition according to claim 1 , wherein the proportion of Fe(2+) is greater than at least 95% based on total Fe.

7. A melt composition according to claim 1 , wherein the proportion of Fe(2+) is greater than at least 97% based on total Fe.

8. Man-made vitreous fibers having a composition comprising the following oxides, by weight of composition:

SiO 2

39-43 weight %

Al 2 O 3

20-23 weight %

TiO 2

up to 1.5 weight %

Fe 2 O 3

5-9 weight %,

CaO

8-18 weight %

MgO

5-7 weight %

Na 2 O

up to 10 weight %,

K 2 O

up to 10 weight %,

P 2 O 5

up to 2%

MnO

up to 2%

R 2 O

up to 10 weight %

wherein the proportion of Fe(2+) based on total Fe is greater than 80%;

wherein the reading for Fe(0) content in the man-made vitreous fibers, measured using a magnetic analyser, is less than 900 ppm.

9. Man-made vitreous fibers according to claim 8 , wherein the dielectric loss factor ∈″ of the fibers is less than 0.02.

10. Man-made vitreous fibers according to claim 8 , wherein the reading for Fe(0) content in the man-made vitreous fibers, measured using a magnetic analyser, is less than 500 ppm.

11. Man-made vitreous fibers according to claim 8 , wherein the ratio of K 2 O to Na 2 O calculated by weight of oxides is from 1:2 to 4:1.

12. Man-made vitreous fibers according to claim 8 , wherein the fibers are formed by a spinning cup method.

13. A man-made vitreous fibre product comprising man-made vitreous fibers according to claim 8 and binder.

14. A man-made vitreous fibre product according to claim 13 , wherein the product comprises less than 4% shot.

15. A melt composition according to claim 8 , wherein the proportion of Fe(2+) is greater than at least 90% based on total Fe.

16. A melt composition according to claim 8 , wherein the proportion of Fe(2+) is greater than at least 95% based on total Fe.

17. A melt composition according to claim 8 , wherein the proportion of Fe(2+) is greater than at least 97% based on total Fe.

18. A method of forming a melt composition, the method comprising the steps of:

heating and melting mineral material in a furnace to produce a mineral melt; and

adjusting, if necessary, the oxidation state of the melt such that the proportion of Fe(2+) based on total Fe is greater than 80%;

wherein the melt composition comprises the following oxides, by weight of composition:

SiO 2

39-43 weight %

Al 2 O 3

20-23 weight %

TiO 2

up to 1.5 weight %

Fe 2 O 3

5-9 weight %

CaO

8-18 weight %

MgO

5-7 weight %

Na 2 O

up to 10 weight %

K 2 O

up to 10 weight %

P 2 O 5

up to 2%

MnO

up to 2%

R 2 O

up to 10 weight %

wherein the reading for Fe(0) content in the man-made vitreous fibers, measured using a magnetic analyser, is less than 900 ppm;

wherein the oxidation state of the melt is adjusted by subjecting the melt to an electrical potential.

19. A method according to claim 18 , wherein the oxidation state of the melt is adjusted by subjecting the melt to an electrical potential using graphite electrodes.

20. A method of forming a melt composition, the method comprising the steps of:

heating and melting mineral material in a furnace to produce a mineral melt; and

adjusting, if necessary, the oxidation state of the melt such that the proportion of Fe(2+) based on total Fe is greater than 80%;

wherein the melt composition comprises the following oxides, by weight of composition:

SiO 2

39-43 weight %

Al 2 O 3

20-23 weight %

TiO 2

up to 1.5 weight %

Fe 2 O 3

5-9 weight %

CaO

8-18 weight %

MgO

5-7 weight %

Na 2 O

up to 10 weight %

K 2 O

up to 10 weight %

P 2 O 5

up to 2%

MnO

up to 2%

R 2 O

up to 10 weight %

wherein the reading for Fe(0) content in the man-made vitreous fibers, measured using a magnetic analyser, is less than 900 ppm;

wherein the furnace is a submerged arc furnace.

21. A method according to claim 20 , wherein the furnace is a submerged arc furnace using graphite electrodes.

22. A method of forming a melt composition, the method comprising the steps of:

heating and melting mineral material in a furnace to produce a mineral melt; and

adjusting, if necessary, the oxidation state of the melt such that the proportion of Fe(2+) based on total Fe is greater than 80%;

wherein the melt composition comprises the following oxides, by weight of composition:

SiO 2

39-43 weight %

Al 2 O 3

20-23 weight %

TiO 2

up to 1.5 weight %

Fe 2 O 3

5-9 weight %

CaO

8-18 weight %

MgO

5-7 weight %

Na 2 O

up to 10 weight %

K 2 O

up to 10 weight %

P 2 O 5

up to 2%

MnO

up to 2%

R 2 O

up to 10 weight %

wherein the reading for Fe(0) content in the man-made vitreous fibers, measured using a magnetic analyser, is less than 900 ppm;

wherein the step of heating and melting of mineral material in a furnace comprises:

suspending powdered carbonaceous fuel in preheated combustion air and combusting the suspended carbonaceous fuel to form a flame,

suspending particulate mineral material, which has been preheated in the flame, and melting the mineral material in a circulating combustion chamber and thereby forming the melt composition.

23. A method according to claim 22 , wherein the particulate material has been preheated to at least 500° C.

24. A method according to claim 22 , wherein the particulate material has been preheated to at least 700° C.