Black iron-based composite particles, process for producing the same, paint and rubber or resin composition containing the same

Black iron-based composite particles of the present invention comprise: as a core particle black iron oxide particle or black iron oxide hydroxide particle having an average particle size of 0.08 to 1.0 .mu.m; a coating layer formed on the surface of the black iron oxide particle or black iron oxide hydroxide particle, comprising at least one organosilicon compound selected from the group consisting of: (1) organosilane compounds obtained from alkoxysilane compounds, (2) polysiloxanes, or modified polysiloxanes and (3) fluoroalkyl organosilane compounds obtained from fluoroalkylsilane compounds; and carbon black coat formed on said coating comprising said organosilicon compound, in an amount of 1 to 30 parts by weight based on 100 parts by weight of said black iron oxide particles or black iron oxide hydroxide particles. Such black iron-based composite particles have an excellent dispersibility in a vehicle, or a rubber or resin composition on the basis of a small amount of the carbon black which are desorbed from the surface of the black iron-based composite particles, and a high blackness substantially identical to a blackness of carbon black fine particles used solely, even when carbon black is contained therein only in a small amount.

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What is claimed is:

1. Black iron-based composite particles comprising: black iron oxide particles or black iron oxide hydroxide particles having an average particle size of 0.08 to 1.0 .mu.m; acoating layer formed on the surface of said black iron oxide particle or black iron oxide hydroxide particles, comprising at least one organosilicon compound selected from the group consisting of: (1) organosilane compounds obtained from an alkoxysilanecompounds, (2) polysiloxanes or modified polysiloxanes, and (3) fluoroalkyl organosilane compounds obtained from a fluoroalkylsilane compounds; and a carbon black coat formed on said coating layer comprising said organosilicon compound, in an amount of1 to 30 parts by weight based on 100 parts by weight of said black iron oxide particles or black iron oxide hydroxide particles.

2. Black iron-based composite particles according to claim 1, wherein said black iron oxide particle or black iron oxide hydroxide particle is particle having a coat which is formed on at least a part of the surface of said black iron oxideparticle or black iron oxide hydroxide particle and which comprises at least one compound selected from the group consisting of hydroxides of aluminum, oxides of aluminum, hydroxides of silicon and oxides of silicon.

3. Black iron-based composite particles according to claim 2, wherein the amount of said at least one compound selected from the group consisting of hydroxides of aluminum, oxides of aluminum, hydroxides of silicon and oxides of silicon, is 0.01to 50% by weight, calculated as Al or SiO.sub.2, based on the weight of said black iron oxide particles or black iron oxide hydroxide particles.

4. Black iron-based composite particles according to claim 1, wherein said modified polysiloxanes are ones selected from the group consisting of: (A) polysiloxanes modified with at least one compound selected from the group consisting ofpolyethers, polyesters and epoxy compounds, and (B) polysiloxanes whose molecular terminal is modified with at least one group selected from the group consisting of carboxylic acid groups, alcohol groups and a hydroxyl group.

5. Black iron-based composite particles according to claim 4, wherein said polysiloxanes modified with at least one compound selected from the group consisting of polyethers, polyesters and epoxy compounds are represented by the general formula(III), (IV) or (V): ##STR6##

wherein R.sup.3 is --(--CH.sub.2 --).sub.h --; R.sup.4 is --(--CH.sub.2 --)i--CH.sub.3 ; R.sup.5 is --OH, --COOH, --CH.dbd.CH.sub.2, --C(CH.sub.3).dbd.CH.sub.2 or --(--CH.sub.2 --).sub.j --CH.sub.3 ; R.sup.6 is --(--CH.sub.2 --).sub.k--CH.sub.3 ; g and h are an integer of 1 to 15; i, j and k are an integer of 0 to 15; e is an integer of 1 to 50; and f is an integer of 1 to 300; ##STR7##

wherein R.sup.7, R.sup.8 and R.sup.9 are --(--CH.sub.2 --).sub.q -- and may be the same or different; R.sup.10 is --OH, --COOH, --CH.dbd.CH.sub.2, --C(CH.sub.3).dbd.CH.sub.2 or --(--CH.sub.2 --).sub.r --CH.sub.3 ; R.sup.11 is --(--CH.sub.2--).sub.s --CH.sub.3 ; n and q are an integer of 1 to 15; r and s are an integer of 0 to 15; e' is an integer of 1 to 50; and f' is an integer of 1 to 300; or ##STR8##

wherein R.sup.12 is --(--CH.sub.2 --).sub.v --; v is an integer of 1 to 15; t is an integer of 1 to 50; and u is an integer of 1 to 300.

6. Black iron-based composite particles according to claim 4, wherein said polysiloxanes whose molecular terminal is modified with at least one group selected from the group consisting of carboxylic acid groups, alcohol groups and a hydroxylgroup are represented by the general formula (VI): ##STR9##

wherein R.sup.13 and R.sup.14 are --OH, R.sup.16 OH or R.sup.17 COOH and may be the same or different; R.sup.15 is --CH.sub.3 or --C.sub.6 H.sub.5 ; R.sup.16 and R.sup.17 are --(--CH.sub.2 --).sub.y -- (wherein y is an integer of 1 to 15); wis an integer of 1 to 200; and x is an integer of 0 to 100.

7. Black iron-based composite particles according to claim 1, wherein said alkoxysilane compound is represented by the general formula (I):

wherein R.sup.1 is C.sub.6 H.sub.5 --, (CH.sub.3).sub.2 CHCH.sub.2 -- or n-C.sub.b H.sub.2b+1 -- (wherein b is an integer of 1 to 18); X is CH.sub.3 O-- or C.sub.2 H.sub.5 O--; and a is an integer of 0 to 3.

8. Black iron-based composite particles according to claim 7, wherein said alkoxysilane compound is methyl triethoxysilane, dimethyl diethoxysilane, phenyl triethoxysilane, diphenyl diethoxysilane, methyl trimethoxysilane, dimethyldimethoxysilane, phenyl trimethoxysilane, diphenyl dimethoxysilane, isobutyl trimethoxysilane or decyl trimethoxysilane.

9. Black iron-based composite particles according to claim 1, wherein said polysiloxanes are represented by the general formula (II): ##STR10##

wherein R2 is H-- or CH3--, and d is an integer of 15 to 450.

10. Black iron-based composite particles according to claim 9, wherein said polysiloxanes are ones having methyl hydrogen siloxane units.

11. Black iron-based composite particles according to claim 1, wherein said fluoroalkylsilane compounds are represented by the general formula (VII):

wherein R.sup.18 is CH.sub.3 --, C.sub.2 H.sub.5 --, CH.sub.3 O-- or C.sub.2 H.sub.5 O--; X is CH.sub.3 O-- or C.sub.2 H.sub.5 --; and z is an integer of 0 to 15; and a' is an integer of 0 to 3.

12. Black iron-based composite particles according to claim 1, which further comprise a blackness (L* value) of 15 to 18.

13. Black iron-based composite particles according to claim 1, which further comprise a particle size of 0.082 to 1.05 .mu.m.

14. Black iron-based composite particles according to claim 1, which further comprise a BET specific surface area value of 1 to 200 m.sup.2 /g.

15. Black iron-based composite particles according to claim 1, which further comprise a geometrical standard deviation of particle sizes of 1.01 to 1.8.

16. Black iron-based composite particles according to claim 1, wherein said black iron oxide particles are magnetite particles or manganese-containing hematite particles.

17. Black iron-based composite particles according to claim 1, wherein said black iron oxide hydroxide particles are manganese-containing goethite particles.

18. Black iron-based composite particles according to claim 1, wherein the amount of said coating organosilicon compounds is 0.02 to 5.0% by weight, calculated as Si, based on the total weight of the organosilicon compounds and said black ironoxide particles or black iron oxide hydroxide particles.

19. Black iron-based composite particles according to claim 1, wherein said carbon black coat is obtained by mixing carbon black fine particles having a particle size of 0.005 to 0.05 .mu.m with the black iron oxide particles or black iron oxidehydroxide particles coated with at least one organosilicon compound while applying a shear force.

20. Black iron-based composite particles according to claim 1, wherein the thickness of said carbon black coat is not more than 0.04 .mu.m.

21. A process for producing black iron-based composite particles defined in claim 1, which process comprises: mixing as core particles black iron oxide particles or black iron oxide hydroxide particles having an average particle size of 0.08 to1.0 .mu.m together with at least one compound selected from the group consisting of: (1) alkoxysilane compounds, (2) polysiloxanes or modified polysiloxanes, and (3) fluoroalkylsilane compounds

by using an apparatus capable of applying a shear force to the core particles, thereby coating the surface of said black iron oxide particle or black iron oxide hydroxide particle with the said compounds; mixing the obtained black iron oxideparticles or black iron oxide hydroxide particles coated with the said compounds and carbon black fine particles having an average particle size of 0.005 to 0.05 .mu.m in an amount of 1 to 30 parts by weight based on 100 parts by weight of the coreparticles by using an apparatus capable of applying a shear force to the core particles, thereby forming carbon black coat on the surface of a coating layer comprising the organosilicon compounds.

22. A process for producing black iron-based composite particles according to claim 21, wherein said black iron oxide particles or black iron oxide hydroxide particles as core particles are coated with at least one compound selected from thegroup consisting of hydroxides of aluminum, oxides of aluminum, hydroxides of silicon and oxides of silicon.

23. A paint comprising: said black iron-based composite particles defined in claim 1; and a paint base material.

24. A paint according to claim 23, wherein the amount of said black iron-based composite particles is 1.0 to 100 parts by weight based on 100 parts by weight of said paint base material.

25. A rubber or resin composition comprising: said black iron-based composite particles defined in claim 1; and a base material for rubber or resin composition.

26. A rubber or resin composition according to claim 25, wherein the amount of said black iron-based composite particles is 0.5 to 200 parts by weight based on 100 parts by weight of said base material for rubber or resin composition.