1. A method for producing a magnetic powder comprising:
a first step of producing a R\u2014Fe\u2014B-based rare earth isotropic magnetic powder using a scrap rare earth magnet through a hydrogenation, disproportionation, hydrogen desorption, recombination (HDDR) process; and
a second step of mixing the R\u2014Fe\u2014B-based rare earth isotropic magnetic powder with an anisotropic magnetic powder.
2. The method for producing magnetic powder according to claim 1, wherein the scrap rare earth magnet is recovered from process scraps produced from a process for producing a rare earth sintered magnet, defective goods, discarded goods and combinations thereof.
3. The method for producing magnetic powder according to claim 1, wherein in the first step, the HDDR process is conducted using the rare earth scrap magnet ground to an average particle size of about 0.1\u02dc1000 \u03bcm.
4. The method for producing magnetic powder according to claim 1, wherein a hydrogenation process in the HDDR process comprises charging the scrap rare earth magnet, applying vacuum to about 2*10-2 torr or less and then supplying hydrogen to provide a pressure of about 0.3\u02dc1.0 atm.
5. The method for producing magnetic powder according to claim 1, wherein a disproportionation process in the HDDR process comprises maintaining a temperature at about 780\u02dc830\xb0 C. for about 10 min to about 1 hour.
6. The method for producing magnetic powder according to claim 1, wherein a desorption process in the HDDR process comprises releasing hydrogen to provide a pressure of about 200 torr and maintaining the pressure for about 5\u02dc20 min.
7. The method for producing magnetic powder according to claim 1, wherein the first step further comprises coating the produced isotropic magnetic powder with an amide-based lubricant.
8. The method for producing magnetic powder according to claim 1, wherein the anisotropic magnetic powder is selected from common anisotropic SmFeN powder and common anisotropic NdFeB powder, and wherein the anisotropic magnetic powder is mixed with the isotropic magnetic powder produced in the first step at a ratio of about 5\u02dc95 wt % based on the total weight of the isotropic magnetic powder plus the anisotropic magnetic powder.
9. The method for producing magnetic powder according to claim 1, wherein the anisotropic magnetic powder is a combination of common anisotropic SmFeN powder and common anisotropic NdFeB powder, wherein the common anisotropic SmFeN powder is mixed at the ratio of about 15\u02dc25 wt % based on the total weight of the isotropic magnetic powder plus the anisotropic magnetic powder.
10. The method for producing magnetic powder according to claim 8, wherein the isotropic magnetic powder produced in the first step is ground to an average particle size of about 100\u02dc225 \u03bcm, the common anisotropic SmFeN powder is ground to an average particle size of about 3\u02dc5 \u03bcm, and the common anisotropic NdFeB powder is ground to an average particle size of about 130\u02dc170 \u03bcm before mixing thereof.
11. The method for producing magnetic powder according to claim 9, wherein the isotropic magnetic powder produced in the first step is ground to an average particle size of about 100\u02dc225 \u03bcm, the common anisotropic SmFeN powder is ground to an average particle size of about 3\u02dc5 \u03bcm, and the common anisotropic NdFeB powder is ground to an average particle size of about 130\u02dc170 \u03bcm before mixing thereof.
12. A method for producing a magnet comprising:
a first step of producing a R\u2014Fe\u2014B-based rare earth isotropic magnetic powder using a scrap rare earth magnet through a hydrogenation, disproportionation, hydrogen desorption, recombination (HDDR) process;
a second step of mixing the R\u2014Fe\u2014B-based rare earth isotropic magnetic powder with an anisotropic magnetic powder;
a third step of kneading a thermosetting or thermoplastic synthetic resin in with the mixture from the second step; and
a fourth step of forming a magnetic field using a magnetic field forming machine.
13. The method for producing magnet according to claim 12, wherein the third step comprises kneading the synthetic resin at a ratio of about 1\u02dc10 wt % synthetic resin based on the total weight of the synthetic resin plus the mixture from the second step.
14. The method for producing magnet according to claim 12, wherein the third step comprises kneading the synthetic resin followed by drying at about 60\xb0 C. or less under a vacuum condition for about 30 min\u02dc2 hours.
15. The method for producing magnet according to claim 12, wherein the fourth step comprises molding a magnetic field compression-molded body having a density of about 5.5 gcc or more at a pressure of about 6\u02dc14 toncm2 or less.
16. The method for producing magnet according to claim 15, wherein the fourth step comprises heat-treating at about 130\u02dc170\xb0 C. for about 30 min\u02dc2 hours after molding the magnetic field compression-molded body.
17. The method for producing magnet according to claim 12, which further comprises a fifth step of heating at about 80\u02dc120\xb0 C. for about 20\u02dc40 min.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A rubber-modified styrene type polymer comprising from 1 to 15 parts by weight of a dispersed phase made of a rubber-like elastic material and from 99 to 85 parts by weight of a continuous phase made of a polymer comprising from 35 to 75 wt % of styrene type monomer units and from 65 to 25 wt % of (meth)acrylate type monomer units, wherein the rubber-like elastic material is a styrene-butadiene block copolymer comprising from 30 to 50 wt % of styrene monomer units and from 70 to 50 wt % of butadiene monomer units, the weight average molecular weight (Mw) of the polystyrene portions of the styrene-butadiene block copolymer is from 45,000 to 75,000, and the ratio (MwMn) of the weight average molecular weight to the number-average molecular weight (Mn) is from 1.20 to 1.80.