U.S. patent application number 12/041077 was filed with the patent office on 2008-06-26 for coating formulation and application of organic passivation layer onto iron-based rare earth powders.
This patent application is currently assigned to MAGNEQUENCH, INC.. Invention is credited to PETER CHRISTOPHER GUSCHL.
Application Number | 20080152916 12/041077 |
Document ID | / |
Family ID | 34632914 |
Filed Date | 2008-06-26 |
United States Patent
Application |
20080152916 |
Kind Code |
A1 |
GUSCHL; PETER CHRISTOPHER |
June 26, 2008 |
COATING FORMULATION AND APPLICATION OF ORGANIC PASSIVATION LAYER
ONTO IRON-BASED RARE EARTH POWDERS
Abstract
The present disclosure relates to coating formulations for
neodymium-iron-boron type magnetic powders manufactured from rapid
solidification processes for the purpose, inter alia, of corrosion
and oxidation resistance when exposed to aggressive environments.
The coating formulation preferably contains an epoxy binder, curing
agent, an accelerating agent, and a lubricant. By incorporating
coupling agents and optionally, other specialty additives with the
magnetic powder and the organic epoxy components, additional
oxidation and corrosion prevention, enhanced adhesion and
dispersion between the filler and matrix phases can be achieved.
This disclosure relates to all such rare earth-transition
metal-boron (RE-TM-B) powders produced by rapid solidification and
encompasses both the bonded magnet products that include
combinations of the materials mentioned and the application
processes.
Inventors: |
GUSCHL; PETER CHRISTOPHER;
(Sommerville Grandeur, SG) |
Correspondence
Address: |
JONES DAY
222 EAST 41ST ST
NEW YORK
NY
10017
US
|
Assignee: |
MAGNEQUENCH, INC.
|
Family ID: |
34632914 |
Appl. No.: |
12/041077 |
Filed: |
March 3, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10996348 |
Nov 23, 2004 |
|
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12041077 |
|
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60524633 |
Nov 25, 2003 |
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Current U.S.
Class: |
428/407 ;
427/127 |
Current CPC
Class: |
H01F 1/117 20130101;
Y10T 428/2998 20150115; H01F 1/0576 20130101; B05D 5/12 20130101;
B32B 5/16 20130101; Y10T 428/2991 20150115; B22F 1/0059 20130101;
B05D 7/14 20130101; C22C 2202/02 20130101; Y10T 428/1121 20150115;
H01F 1/0572 20130101 |
Class at
Publication: |
428/407 ;
427/127 |
International
Class: |
B32B 5/16 20060101
B32B005/16; B05D 5/12 20060101 B05D005/12 |
Claims
1-20. (canceled)
21. A process of liquid-coating a rapidly solidified rare
earth-transition metal-boron magnet material, comprising: providing
a homogeneous solution comprising a solvent, an organotitanate or
organozirconate coupling agent, an epoxy resin, a hardener, an
accelerator, and a lubricant, wherein said homogeneous solution is
a homogeneous 8-25% solution; combining a rare earth-transition
metal-boron magnet powder with said homogeneous solution to form a
slurry mixture; stirring said slurry mixture periodically; and
maintaining said slurry mixture at a temperature between
40-60.degree. C., such that said solvent evaporates.
22. The process of claim 21, wherein the solvent is acetone.
23. The process of claim 22, further comprising introducing an
organoclay into the homogeneous 8-25% solution.
24. The process of claim 22, further comprising introducing an
antioxidant agent into to the homogeneous 8-25% solution.
25. The process of claim 22, wherein both an organotitanate and an
organozirconate coupling agent are added to the homogeneous 8-25%
solution.
26. The process of claim 22, wherein said slurry mixture is
maintained at a temperature between 50-60.degree. C.
27. (canceled)
28. The process of claim 21, wherein said solvent is
tetrahydrofuran, and said process further comprises pre-treating
the rare earth-transition metal-boron powder by dissolving a POSS
additive in tetrahydrofuran to form a 50% solution; adding the rare
earth-transition metal-boron powder into the 50% solution; and
evaporating the tetrahydrofuran to produce a pre-treated rare
earth-transition metal-boron powder.
29-48. (canceled)
49. A process of liquid-coating a rapidly solidified rare
earth-transition metal-boron magnet material, comprising: providing
a homogeneous solution consisting essentially of a solvent, an
organotitanate or organozirconate coupling agent, an epoxy resin, a
hardener, an accelerator, and a lubricant, wherein said homogeneous
solution is a homogeneous 8-25% solution; combining a rare
earth-transition metal-boron magnet powder with said homogeneous
solution to form a slurry mixture; stirring said slurry mixture
periodically; and maintaining said slurry mixture at a temperature
between 40-60.degree. C., such that said solvent evaporates.
50. A process of liquid-coating a rapidly solidified rare
earth-transition metal-boron magnet material, comprising: providing
a homogeneous solution comprising a solvent, an organotitanate or
organozirconate coupling agent, an epoxy resin, a hardener, an
accelerator, and a lubricant, wherein said homogeneous solution is
a homogeneous 8-25% solution; and combining a rare earth-transition
metal-boron magnet powder with said homogeneous solution to form a
slurry mixture.
51. The process of claim 50, further comprising stirring said
slurry mixture periodically.
52. The process of claim 50, wherein the solvent is acetone.
53. The process of claim 52, further comprising introducing an
organoclay into the homogeneous 8-25% solution.
54. The process of claim 52, further comprising introducing an
antioxidant agent into to the homogeneous 8-25% solution.
55. The process of claim 52, wherein both an organotitanate and an
organozirconate coupling agent are added to the homogeneous 8-25%
solution.
56. The process of claim 50, wherein said solvent is
tetrahydrofuran, and said process further comprises pre-treating
the rare earth-transition metal-boron powder by dissolving a POSS
additive in tetrahydrofuran to form a 50% solution; adding the rare
earth-transition metal-boron powder into the 50% solution; and
evaporating the tetrahydrofuran to produce a pre-treated rare
earth-transition metal-boron powder.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority of U.S.
Provisional Patent Application No. 60/524,633, filed Nov. 25, 2003,
the disclosure of which is herein incorporated by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to coating formulations for
rare earth-transition metal-boron (RE-TM-B) magnet materials, such
as neodymium-iron-boron type magnetic powders manufactured from
rapid solidification processes for, among other things, the purpose
of corrosion and/or oxidation resistance when exposed to aggressive
environments or for passivation. The present invention also relates
to methods of applying coating formulations to rare
earth-transition metal-boron (RE-TM-B) magnet powders.
BACKGROUND OF THE INVENTION
[0003] Isotropic polymer bonded rare earth permanent magnets have
been used in various advanced motors and electronic devices. With
the miniaturization of motors and electronic devices, it is
necessary to reduce the size of magnets used. To enable effective
miniaturization and efficient energy or signal output, it is
essential for these applications to demand magnets of high flux
densities. Factors determining the flux density of isotropic
polymer bonded magnets can be divided into two parts: the type of
magnet materials used and the volume fraction of the magnet
materials in these polymer bonded magnets.
[0004] The criteria for selecting the type of magnetic materials
are strongly influenced by the operation conditions demanded by the
given applications. The polymer binder used for making polymer
bonded magnets must be able to provide sufficient mechanical
strength to hold magnet powder together and maintain the designed
shape specification up to the intended operation temperature and to
sustain that operation temperature without softening, deforming or
breaking. The magnetic materials must provide sufficient flux to
sustain the desired properties at the operation temperature without
substantial loss of magnetization. The flux aging loss of a magnet
material provides an indication of the magnet material's stability
to heat and protection from corrosive and oxidative environments,
which can affect the magnetic materials' ability to retain magnetic
flux over time durations at certain temperatures. The flux aging
loss of a bonded magnet ultimately determines the magnet's utility
in various applications, and should be minimized if the bonded
magnet is to be used for high temperature applications. The
oxidative or corrosive degradation of the constituent materials and
change in overall magnetic properties should be minimized to
enhance the utility of the bonded magnets.
[0005] The combination and amounts of the organic and magnetic
materials should allow the desired properties previously discussed
to be optimized and attained. The amount of magnet powder in the
polymer-bonded magnets, typically stated as a mass or volume
fraction, is determined by the polymer binder type, molecular
weight of the polymer binder, and the methodology applied in order
to combine said materials effectively. Depending on the molding
method, various polymers are available for making isotropic bonded
magnets. Compression molding, injection molding, extrusion and
calendering are well-known means for producing polymer-bonded
magnets in commercial quantities.
[0006] Compression-molded or compacted magnets allow magnets to
reach high, desirable volume fraction (greater than 83%) required
to achieve strong magnetic properties. Typically, thermosetting
polymers, such as, epoxies, phenolics, and other crosslinkable
resins with their respective curing agents are used with the
ideology of producing magnets that will less affected by heat or
chemical attack than the non-coated powders. These materials are
initially low molecular weight substances that can be easily
applied as coatings for the magnetic powders. The components can be
molded and cured to produce magnets that are resistant to high
temperatures (typically, not much greater than 250.degree. C.) and
chemical solvents. The extent of crosslinking or the crosslink
density of the thermosetting binder governs the coating's overall
resistance to oxidation and corrosion as well as the mechanical
strength of the final magnet.
[0007] At high loadings of solid filler the oxidation potential of
the magnetic powders increases and becomes deleterious to the
magnetic properties because of the low degree of organic
protection, where the industry term "loading" refers to the
proportion of magnet powder in the final magnet product. Chemical
additives are introduced into the bonded magnet system in order to
alleviate oxidative effects on the metallic filler particles. U.S.
Pat. No. 5,888,416 to Ikuma et al. discloses the use of various
chelating agents and antioxidants in the rare-earth bonded magnets
of polyphenylene sulfide (PPS), nylon 12 (polyamide), and
polyethemitrile (liquid crystal polymer) thermoplastic binders for
use in extruded magnet compositions. U.S. Pat. No. 5,395,695 to
Shain et al. discloses incorporating successive layers of an
antioxidant, an epoxy novolac resin, and polystyrene onto the
magnet material for improvements in oxidation resistance, with an
emphasis on the sequential layering of the components. Xiao et al.
and Guschl et al. describe the benefits of incorporating an
aminosilane coupling agent onto the powders within a polyphenylene
sulfide binder. See J. Xiao and J. U. Otaigbe, "High Performance,
Lightweight Thermoplatic/Rare Earth Alloy Magnets," Mat. Res. So.
Symp. Proc., 577:75-80 (1999); P. C. Guschl, H. S. Kim, and J. U.
Otaigbe, "Effects of a Nd--Fe--B Magnetic Filler on the
Crystallization of Poly(phenylene sulfide)," J. Appl. Poly. Sci.,
83:1091-1102 (2002). However, the results disclosed in these
references were based solely on magnets with powder loadings on the
order of about 80%, which is lower than those achievable in
compression-molding magnets (on the order of about 90% or more).
U.S. Pat. No. 4,876,305 to Mazany ("Mazany") describes the
application of a combination of aminosilanes and epoxysilane
coupling agents with epoxy resins for oxidation resistance,
comparing oxidation rates to treated and non-treated samples. The
concentrations of magnetic material in the magnets disclosed in
Mazany were fairly low, the magnetic properties of the resultant
magnets, e.g., the flux aging loss, are not considered
relevant.
[0008] U.S. Pat. No. 5,087,302 to Lin et al. discloses a process
where an organotitanate is added to coarse Nd--Fe--B powders during
a milling step to produce sintered magnets with improved magnetic
remnance, coercivity and oxidation resistance. However, since the
milled magnet powder-organotitanate mixture is subjected to a
high-temperature to degassing technique in an inert atmosphere in
order to manufacture the sintered NdFeB magnets, the organotitanate
is removed or "degassed" from the metallic powders.
[0009] Recently published coupling agents that have been utilized
in bonded magnet systems are the organotitanates and
organozirconates. Several Japanese patents describe the use of
these agents and NdFeB powders with mainly nylon 12 resin, epoxy
resins, PPS resin, and other such thermoplastic or thermosetting
binders. See, e.g., JP-03165504 to T. Hitoshi et al.; JP-03222303
to M. Yoshihiko; JP-04011701 to M. Yoshihiko; and JP-04257203 to T.
Hitoshi et al. These disclosures are directed to applications to
injection-molding and extrusion-produced bonded magnets, because
the specification of the material types and compositions disclosed
therein fall well below the magnetic powder loadings disclosed in
the present invention. Chen et al. disclose that a
diaminoethylene-based titanate incorporated into a
NdFeB-epoxy-bonded magnet system improved the bonding of the
components and overall specific density of the magnet. See Q. Chen,
J. Asuncion, J. Landi, and B. M. Ma, "The Effect of the Coupling
Agent on the Packing Density and Corrosion Behavior of NdFeB and
SmCo Bonded Magnets," J. Appl. Phys., 85:8:5684-5686 (1999).
However, no mention is made of the effects of the titanate on the
flux aging loss of the magnet material or of the method in which
the titanate was incorporated into the system. The present
invention provides a more effective technique for protecting rare
earth-transition metal-boron magnetic materials through a
performing liquid coating procedure on the rare earth-transition
metal-boron magnet powders. The present invention is applicable,
for example, to compression-molding magnets.
SUMMARY OF THE INVENTION
[0010] In a first embodiment, the present invention provides a
rapidly solidified rare earth-transition metal-boron magnet
material, comprising a rare earth-transition metal-boron magnet
powder coated with a coating comprising, in an amount by weight of
the magnet powder, of about 0.1 weight percent to about 1 weight
percent of an organotitanate or organozirconate coupling agent,
about 0.18 weight percent to about 4.46 weight percent of an epoxy
resin, about 0.01 weight percent to about 0.27 weight percent of an
amine-based hardener, about 0.004 weight percent to about 0.09
weight percent of an accelerator, and about 0.003 weight percent to
about 0.27 weight percent of a lubricant. The general form of the
coupling agent is:
(RO--).sub.n(Ti or Zr)(--OR'Y).sub.4-n
where R is a neopentyl(diallyl), dioctyl, or
(2,2-diallyloxymethyl)butyl group, Ti or Zr has a coordination
number of 4, R' is a phosphito, pyrophosphato or cyclic
pyrophosphato segment, and Y is a dioctyl or ditridecyl end group,
with 1.ltoreq.n.ltoreq.4. In first aspect according to the first
embodiment, the invention provides a rapidly solidified rare
earth-transition metal-boron magnet material, where the coating
comprises about 0.1 weight percent to about 1 weight percent of the
organotitanate or organozirconate coupling agent, about 0.43 weight
percent to about 3 weight percent of the epoxy resin, about 0.025
weight percent to about 0.18 weight percent of the amine-based
hardener, about 0.009 weight percent to about 0.06 weight percent
of the accelerator, and about 0.009 weight percent to about 0.19
weight percent of the lubricant. In specific embodiment of the
invention, the coating formulations of the first embodiment of the
invention consists essentially of the recited components in the
recited percentage ranges.
[0011] In a second embodiment, the present invention provides a
rapidly solidified rare earth-transition metal-boron magnet
material, comprising a rare earth-transition metal-boron magnet
powder coated with a coating comprising, in an amount by weight of
the magnet powder, of about 0.225 weight percent to about 4.25
weight percent of epichlorohydrin/cresol novolac epoxy resin, about
0.01 weight percent to about 0.26 weight percent of dicyandiamide
hardener, about 0.005 weight percent to about 0.085 weight percent
of an aromatic, tertiary amine accelerator, about 0.004 weight
percent to about 0.27 weight percent of zinc stearate lubricant,
and about 0.35 weight percent to about 0.75 weight percent of an
organotitanate coupling agent of the form
(RO--)Ti(--OR'Y).sub.3
where R is a neopentyl(diallyl), Ti has a coordination number of 4,
R' is a pyrophosphato segment, and Y is a dioctyl end group. In a
first aspect of the second embodiment, the invention provides a
rapidly solidified rare earth-transition metal-boron magnet
material, where the coating comprises about 0.68 weight percent to
about 2.76 weight percent of epichlorohydrin/cresol novolac epoxy
resin, about 0.04 weight percent to about 0.17 weight percent of
dicyandiamide hardener, about 0.01 weight percent to about 0.055
weight percent of the aromatic, tertiary amine accelerator, about
0.01 weight percent to about 0.175 weight percent of the zinc
stearate lubricant. In specific embodiment of the invention, the
coating formulations of the second embodiment of the invention
consists essentially of the recited components in the recited
percentage ranges.
[0012] In a third embodiment, the invention provides a rapidly
solidified rare earth-transition metal-boron magnet material,
comprising a rare earth-transition metal-boron magnet powder; and
an organotitanate or organozirconate coupling agent of the general
form
(RO--).sub.n(Ti or Zr)(--OR'Y).sub.4-n
where R is a neopentyl(diallyl), dioctyl, or
(2,2-diallyoxymethyl)butyl group, Ti or Zr has a coordination
number of 4, R' is a phosphito, pyrophosphato or cyclic
pyrophosphato segment, and Y is a dioctyl or ditridecyl end group,
with 1.ltoreq.n.ltoreq.4; where the coupling agent is present in an
amount by weight of the magnet powder of about 0.1 weight percent
to about 1 weight percent. In a first aspect of the third
embodiment, the invention provides a rapidly solidified rare
earth-transition metal-boron magnet material, where the
organotitanate or organozirconate coupling agent is of the
form:
(RO--)(Ti or Zr)(--OR'Y).sub.3
where R is a neopentyl(diallyl) group, Ti has a coordination number
of 4, R is a pyrophosphato segment, and Y is a dioctyl end group,
where the coupling agent is present in is an amount by weight of
the magnet powder of about 0.35 weight percent to about 0.75 weight
percent. In specific embodiment of the invention, the coating
formulations of the third embodiment of the invention consists
essentially of the recited components in the recited percentage
ranges.
[0013] In a fourth embodiment, the invention provides a rapidly
solidified rare earth-transition metal-boron magnet material,
comprising a rare earth-transition metal-boron magnet powder
comprising a pre-coating of an organotitanate or organozirconate
coupling agent of the general form:
(RO--).sub.n(Ti or Zr)(--OR'Y).sub.4-n
[0014] where R is a neopentyl(diallyl), dioctyl, or
(2,2-diallyloxymethyl)butyl group, Ti or Zr has a coordination
number of 4, R' is a phosphito, pyrophosphato or cyclic
pyrophosphato segment, and Y is a dioctyl or ditridecyl end group,
with 1.ltoreq.n.ltoreq.4, present in an amount by weight of the
magnet powder of about 0.1 weight percent to about 1 weight
percent; and a further coating comprising, in an amount by total
weight of the final mixture, of about 0.18 weight percent to about
4.46 weight percent of an epoxy resin, about 0.01 weight percent to
about 0.27 weight percent of an amine-based hardener, about 0.004
weight percent to about 0.09 weight percent of an accelerator, and
about 0.003 weight percent to about 0.27 weight percent of a
lubricant. In a first aspect of the fourth embodiment, the
invention provides a rapidly solidified rare earth-transition
metal-boron magnet material, where the further coating comprises
about 0.43 weight percent to about 3 weight percent of epoxy resin,
about 0.025 weight percent to about 0.18 weight percent of
amine-based hardener, about 0.009 weight percent to about 0.06
weight percent of accelerator, and about 0.009 weight percent to
about 0.19 weight percent of lubricant. In specific embodiment of
the invention, the coating formulations of the fourth embodiment of
the invention consists essentially of the recited components in the
recited percentage ranges.
[0015] In a fifth embodiment, the invention provides a rapidly
solidified rare earth-transition metal-boron magnet material,
comprising a rare earth-transition metal-boron magnet powder
comprising a pre-coating of an organotitanate coupling agent of the
form
(RO--)Ti(--OR'Y).sub.3
[0016] where R is a neopentyl(diallyl) group, Ti has a coordination
number of 4, R is a pyrophosphato segment, and Y is a dioctyl end
group, present in an amount by weight of the magnet powder of about
0.35 weight percent to about 0.75 weight percent; and a further
coating comprising, in an amount by weight of the final mixture, of
about 0.225 weight percent to about 4.25 weight percent of
epichlorohydrin/cresol novolac epoxy resin, about 0.01 weight
percent to about 0.26 weight percent of dicyandiamide hardener,
about 0.005 weight percent to about 0.085 weight percent of an
aromatic, tertiary amine accelerator, and about 0.004 weight
percent to about 0.27 weight percent of zinc stearate lubricant. In
a first aspect of the fifth embodiment of the invention, the
invention provides a rapidly solidified rare earth-transition
metal-boron magnet material comprising the pre-coating of the
organotitanate coupling agent at a concentration range of
0.35-0.75% by weight of the rare earth-transition metal-boron
powder; and the further coating of, by total weight, 0.680%-2.76%
epichlorohydrin/cresol novolac epoxy resin, 0.040-0.170%
dicyandiamide hardener, 0.010-0.055% of the aromatic, tertiary
amine accelerator, 0.010-0.175% zinc stearate lubricant. In
specific embodiment of the invention, the coating formulations of
the fifth embodiment of the invention consists essentially of the
recited components in the recited percentage ranges.
[0017] In a sixth embodiment, the invention provides a rapidly
solidified rare earth-transition metal-boron magnet material,
comprising a rare earth-transition metal-boron magnet powder coated
with a coating comprising, in an amount by weight of the magnet
powder, of about 0.65 weight percent to about 2.5 weight percent of
an epoxy resin, about 0.035 weight percent to about 0.15 weight
percent of an amine-based hardener, about 0.01 weight percent to
about 0.05 weight percent of an accelerator, about 0.04 weight
percent to about 0.16 weight percent of a lubricant, about 0.001
weight percent to about 0.3 weight percent of an organoclay, and
about 0.35 weight percent to about 0.75 weight percent of an
organotitanate or organozirconate coupling agent of the general
form
(RO--).sub.n(Ti or Zr)(--OR'Y).sub.4-n
where R is a neopentyl(diallyl), dioctyl, or
(2,2-diallyoxymethyl)butyl group, Ti or Zr has a coordination
number of 4, R is a phosphito, pyrophosphato or cyclic
pyrophosphato segment, and Y is a dioctyl or ditridecyl end group,
with 1.ltoreq.n.ltoreq.4. In a first aspect of the fifth
embodiment, the invention provides a rapidly solidified rare
earth-transition metal-boron magnet material, wherein the coupling
agent is an organotitanate coupling agent of the form
(RO--)Ti(--OR'Y).sub.3
[0018] where R is a neopentyl(diallyl), Ti has a coordination
number of 4, R is a pyrophosphato segment, and Y is a dioctyl end
group. In a first aspect of the fifth embodiment, the epoxy resin
is epichlorohydrin/cresol novolac epoxy resin, the amine-based
hardener is dicyandiamide hardener, the accelerator is an aromatic,
tertiary amine accelerator, the lubricant is zinc stearate, and the
organoclay comprises bis(hydroxyethyl)methyl tallow alkyl ammonium
salts with bentonite. In a second aspect of the fifth embodiment,
the coating of the rapidly solidified rare earth-transition
metal-boron magnet material comprises about 0.001 weight percent to
about 0.3 weight percent of an organoclay comprising
bis(hydroxyethyl)methyl tallow alkyl ammonium salts with bentonite;
and about 0.35 weight percent to about 0.75 weight percent of an
organotitanate coupling agent of the form
(RO--)Ti(--OR'Y).sub.3
[0019] where R is a neopentyl(diallyl), Ti has a coordination
number of 4, R' is a pyrophosphato segment, and Y is a dioctyl end
group. In specific embodiment of the invention, the coating
formulations of the sixth embodiment of the invention consists
essentially of the recited components in the recited percentage
ranges.
[0020] In a seventh embodiment, the invention provides a rapidly
solidified rare earth-transition metal-boron magnet material,
comprising a rare earth-transition metal-boron magnet powder; which
has been pre-coated with a POSS additive in an amount by weight of
the magnet powder of about 0.1 weight percent to about 5 weight
percent; after which a further coating is applied, which comprises,
in an amount my total weight of the mixture, of about 0.54 weight
percent to about 2.75 weight percent of an epoxy resin, about 0.03
weight percent to about 0.17 weight percent of an amine-based
hardener, about 0.01 weight percent to about 0.06 weight percent of
an accelerator, about 0.035 to about 0.175 weight percent of a
lubricant, about 0.35 weight percent to about 0.75 weight percent
of an organotitanate or organozirconate coupling agent of the
general form
(RO--).sub.n(Ti or Zr)(--OR'Y).sub.4-n
[0021] where R is a neopentyl(diallyl), dioctyl, or
(2,2-diallyloxymethyl)butyl group, Ti or Zr has a coordination
number of 4 or 5, R' is a phosphito, pyrophosphato or cyclic
pyrophosphato segment, and Y is a dioctyl or ditridecyl end group,
with 1.ltoreq.n.ltoreq.4, about 0.003 weight percent to about 0.055
weight percent of an organoclay, and about 0.003 weight percent to
about 0.015 weight percent of an antioxidant agent. In a first
aspect of the seventh embodiment, the invention provides a rapidly
solidified rare earth-transition metal-boron magnet material, where
the coupling agent is an organotitanate coupling agent of the
form
(RO--)Ti(--OR'Y).sub.3
[0022] where R is a neopentyl(diallyl), Ti has a coordination
number of 4, R' is a pyrophosphato segment, and Y is a dioctyl end
group. In specific embodiment of the invention, the coating
formulations of the seventh embodiment of the invention consists
essentially of the recited components in the recited percentage
ranges.
[0023] In a second aspect of the seventh embodiment, the POSS
additive is trisilanolphenyl or epoxycyclohexyl POSS. In a third
aspect of the seventh embodiment, the antioxidant agent is a
butylated reaction product of p-cresol and dicyclopentadiene
antioxidant. In a fourth aspect of the seventh embodiment, the
epoxy resin is epichlorohydrin/cresol novolac epoxy resin, the
amine-based hardener is dicyandiamide hardener, the accelerator is
an aromatic, tertiary amine accelerator, the lubricant is zinc
stearate lubricant; and the organo clay additive is
bis(hydroxyethyl)methyl tallow alkyl ammonium salts with
bentonite.
[0024] In a fifth aspect of the seventh embodiment, the pre-coating
is a trisilanolphenyl or epoxycyclohexyl POSS in an amount of about
0.1 weight percent to about 1 weight percent, by weight of the
magnet powder; and the further coating comprises, by total weight
of the mixture, of about 0.54 weight percent to about 2.75 weight
percent of epichlorohydrin/cresol novolac epoxy resin, about 0.03
weight percent to about 0.17 weight percent of dicyandiamide
hardener, about 0.01 weight percent to about 0.06 weight percent of
an aromatic, tertiary amine accelerator, about 0.035 weight percent
to about 0.175 weight percent of zinc stearate lubricant,
[0025] about 0.35 weight percent to about 0.75 weight percent of an
organotitanate coupling agent of the form
(RO--)Ti(--OR'Y).sub.3
[0026] where R is a neopentyl(diallyl), Ti has a coordination
number of 4, R' is a pyrophosphato segment, and Y is a dioctyl end
group, about 0.003 weight percent to about 0.07 weight percent of
an organoclay comprising bis(hydroxyethyl)methyl tallow alkyl
ammonium salts with bentonite, and about 0.003 weight percent to
about 0.015 weight percent of a butylated reaction product of
p-cresol and dicyclopentadiene antioxidant.
[0027] The present invention also provides a process of
liquid-coating a rapidly solidified rare earth-transition
metal-boron magnet material, comprising the steps of providing a
solution comprising a solvent, an organotitanate or organozirconate
coupling agent, an epoxy resin, hardener, an accelerator, and a
lubricant, wherein said homogeneous solution is a homogeneous 8-25%
solution; combining a rare earth-transition metal-boron magnet
material with the homogeneous solution to form a slurry mixture;
stirring the slurry mixture periodically; and maintaining said
slurry mixture at a temperature between 40-60.degree. C., such that
said solvent evaporates. In different embodiments, the solvent is
acetone or tetrahydrofuran. Various other components can be
introduced into to the homogeneous 8-25% solution, including an
organoclay, an antioxidant agent, an organotitanate or
organozirconate coupling agent, or both types f coupling agents. In
a specific embodiment, the mixture is maintained at a temperature
between 50-60.degree. C. In an alternate embodiment, the rare
earth-transition metal-boron material is pre-treated by dissolving
an organotitanate or an organozirconate coupling agent in acetone
to form a 50% solution; adding the rare earth-transition
metal-boron powder into the solution; and evaporating the acetone
solvent to produce the pre-treated rare earth-transition
metal-boron powder. In a specific embodiment, the solvent is
tetrahydrofuran, and the process further comprises pre-treating the
rare earth-transition metal-boron powder by dissolving a POSS
additive in tetrahydrofuran to form a 50% solution; adding the rare
earth-transition metal-boron powder into the solution; and
evaporating the tetrahydrofuran to produce said pre-treated rare
earth-transition metal-boron powder. In specific embodiment of the
process of liquid-coating a rapidly solidified rare
earth-transition metal-boron magnet material, the coating consists
essentially of the recited components in the recited percentage
ranges.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] FIG. 1: Flux aging loss at 180.degree. C. after 100 hours of
cured PC-2 magnets with and without a coupling agent.
[0029] FIG. 2: A comparison of the flux aging loss for cured PC-2
magnets of each embodiment aged at 180.degree. C. for 100
hours.
[0030] FIG. 3: A comparison of the flux aging loss for cured PC-2
magnets of first and fourth embodiments aged at 180.degree. C. for
100 hours.
[0031] FIG. 4: A comparison of the flux aging loss for cured PC-2
magnets of first, third and fifth embodiments aged at 200.degree.
C. for 100 hours.
[0032] FIG. 5. Flux aging loss of MQP 14-12.TM. bonded magnets with
and without LICA 38 coupling agent after 100 hours at 180, 200, and
225.degree. C.
[0033] FIG. 6. Flux aging loss of non-silanated and silanated
MQP-B.TM. liquid-coated magnets at 180.degree. C. after 78
hours.
DETAILED DESCRIPTION OF THE INVENTION
[0034] The present invention provides coating formulations for
rapidly solidified rare earth-transition metal-boron (RE-TM-B)-type
bonded magnetic materials, and methods of applying such
formulations to the magnet materials, with emphasis on their
protection against oxidation. Specifically, the flux aging loss of
any bonded magnet must be minimized in order for high temperature
applications to be considered. While not being bound by any
specific theory, it is believed that the incorporation of organic
materials, such as polymers with the inorganic metallic powders
provides a means to passivate and prevent oxidative tendencies by
reducing the reactivity of the filler surfaces or by decreasing the
permeation of energetic oxygen molecules to the filler surfaces.
Additionally, the coated powders allow a higher degree of
flexibility and moldability for producing bonded magnets.
[0035] The coating formulations and processes of the present
invention provide for bonded magnets with higher powder loadings,
i.e., higher proportions of magnet materials contained in the final
magnet, than achievable from other methods. Prior art references
disclose magnets with powder loadings lower than those achievable
in the present invention, which is on the order of about 95% to
about 99% or more by weight of the magnet. For example, magnets
made using, e.g., polyphenylene sulfide (PPS) or nylon 12
(polyamide), such as injection-molded bonded magnets, usually
contain only about 85% to about 93% by weight or less of magnet
powder, corresponding to about 50-70% by volume.
[0036] The prior art for bonded magnets, using polymeric binders,
has focused on dry blending techniques. These methods physically
mix organic powders, such as thermosetting resins, with the
magnetic powders in the absence of solvents. Compaction and/or
compression molding are used in order to form the solid magnets by
initially fusing the organic powder between the inorganic
particles. These resultant magnets contain weakly bound
particulates with nonuniformities and, as a result, a degree of
porosity, which can be detrimental in terms of oxidation, flux
aging loss, and overall magnetic and physical properties.
[0037] Liquid coating techniques assuage these problems associated
with dry blending by providing a uniform organic layer on the
powders. This resulting uniformity provides more effective
oxidation protection following the cure reaction of the
thermosetting binder. Both liquid and solid, dissolvable resins and
other additives are permissible for the application process.
[0038] The polymer-coated powders of the present invention have
improved thermal stability in comparison to the magnetic powders
alone. Further, more effective protection can be achieved through
the addition of particular specialty chemical additives. While
certain antioxidants can be effective for protective purposes to
some extent, the presence of the antioxidants only mildly deters
oxygen molecules from reaching the filler surfaces. Because the
antioxidant molecules are freely suspended within the binder matrix
and deposited on the filler particles (such as in a physisorption
process), they have limited ability in oxidation protection. In
other words, little to no interaction between thermoplastic
binders, filler particles and these additives may occur (such as in
a chemisorption). Possible side reactions of binders with reactive
epoxide functional groups of epoxy resins may happen if the
antioxidant agent contains active amine groups. However, although
complete protection from oxidation may not be possible for systems
that contain solely antioxidants, their use does aid in oxidation
prevention. Accordingly, the inventive formulations may optionally
contain antioxidant agents to provide further flux aging loss
resistance. Non-limiting examples of antioxidant agents include a
butylated reaction product of p-cresol and dicyclopentadiene
antioxidant, and
tetrakis-[methylene-(3,5-di-tert.-butyl-4-hydroxy-cinnamate)]methane
antioxidants.
[0039] As used herein, the term "epoxy resins" refer to synthetic
uncured or unreacted resins containing epoxide functional groups
with an aromatic backbone. Non-limiting examples of epoxy resins
include epichlorohydrin/cresol novolac epoxy resin and
epichlorohydrin/bisphenol A epoxy resin types. The epoxy-based
coated powders with the specialty additives (e.g., coupling agents,
antioxidants, etc.) are in the uncured state prior to the
manufacture of the final cured magnets.
[0040] It has been discovered that coupling agents allow protection
by way of altering the powders surface through beneficial chemical
or weaker physical (hydrogen) bonding. It is believed that the
coupling agents form protective layers on the powder that are
compatible and potentially reactive, if appropriately selected,
with the surrounding organic passivation coating, permitting
additional interaction between the components of the magnet. The
preferred coupling agents for application in the invention provide
thermal stability to the magnet and limit oxidation.
[0041] Organosilane coupling agents have been used extensively for
organic-inorganic systems within aqueous and/or alcohol-rich
solutions, due to their reactivity with surface hydroxyl chemical
groups present on filler particles such as glass fibers, metal
hydroxides, silica and silicates. A monolayer of reacted
organosilane is formed on the filler surface through condensation,
following the hydrolysis reaction in water.
[0042] The amine-based silanes, or aminosilanes, are among the most
commonly used silanes, due to the high reactivity between the lone
pair electrons that reside on a nitrogen atom of primary, secondary
and tertiary amines and the epoxide functional group of epoxy
resins. The aforementioned reaction of the silane with the
inorganic filler particle couples those two entities together, and
the epoxy-amine reaction establishes a bond between the silane and
epoxy resin. Ultimately, this creates a crosslinked structure
involving every reactable component of the system.
[0043] Due to their greater coupling effect and ease of reaction
with filler particles in the absence of a solvent, organotitanate
and organozirconates (which have similar reaction mechanisms) have
received more attention than organosilanes in some respects. The
organosilanes offer typically a single coupling site on the
molecule with a single hydroxyl group on the filler particle,
depending upon the extent of the hydrolysis and condensation
reactions during pretreatment. The organotitanates or
organozirconates allow at best three coupling sites, giving rise to
more complete coverage of a monolayer. In addition to this
information, organotitanates can also react with surface protons of
inorganic filler particulates that may be devoid of hydroxyl
groups. The organotitanate or organozirconate is also found to aid
in the curing process to create the bonded magnet, possibly by
aiding in the cross-linking process. These agents can be applied to
filler surfaces via solvent-blending or direct melt-blending
processes with the polymer binder and inorganic filler within a
compounder or injection molder, which require no pretreatment. This
invention focuses on the solvent-blending or liquid coating method
of application.
[0044] Because of the efficiency of these organic coupling agents,
concentrations that range between 0.1 and 1.0% (by weight) are
sufficient for optimal properties (e.g. enhanced processing,
mechanical strength, adhesion, and chemical resistance). This
statement is particularly important for the manufacture of
polymer-bonded magnets. The more coupling agents added to the
system, then the lower the potential magnetic strength of the
magnet will be, since the magnetic flux is directly related to the
amount of magnetic material present. The use of small amounts of
the coupling agents allows appropriate coupling with minimal
reduction of magnetic properties. Typical thicknesses of coupling
agents are on the order of one micron at these concentrations
mentioned.
[0045] New materials are being added to polymeric systems called
"nanofillers" or "nanoadditives" and are showing remarkable
improvements in a system's thermal stability, mechanical strengths,
oxygen permeability and processability. These additives are
primarily inorganic and consist of a silica-based structure with
organic functionalities. At least one of the spatial dimensions of
said nanofillers is of the nanometer range (0.001 to 0.1 microns).
With this minute dimension the aspect ratios tend to be on the
order of 100 to 1000, which give rise to the mentioned improvements
in overall properties. Typical concentrations of these nanofillers
can vary within 0.1 to 10.0% by weight relative to the polymer
binder. Examples of a currently used nanofiller material are clay
fillers (typically bentonite or montmorillonite). This material is
modified, for example, with alkyl ammonium salts in order to
guarantee proper compatibility with the matrix material. These
"organoclays" are a popular new addition to the growing field of
polymer nanocomposites for both thermosetting and thermoplastic
systems. Specifically for thermosets, organoclays have been
effectively incorporated either through high-shear melt or solvent
blending. Effective dispersion of the organoclays' silicate layers
throughout the polymer phase yields favorable property
enhancement.
[0046] Another family of the nanofillers distinction that has
lately received much attention has the general name of polyhedral
oligomeric silsesquioxanes or POSS. Polyhedral oligomeric
silsesquioxanes or POSS are referred to herein as "POSS additives."
These compounds are comprised of nano-sized silica-based cages with
a vast number of organic functionalities. Proper selection of the
most appropriate functionality, whether reactive or inert, can
allow many polymeric systems to become hybridized into unique
polymer nanocomposites.
[0047] Through liquid coating with the organotitanates and/or
organozirconates, nanofillers (e.g., organoclays, POSS additives)
and antioxidants in the presence of an epoxy resin, dicyandiamide
hardener, tertiary amine accelerator, and zinc stearate lubricant,
the present invention provides a high-volume fraction bonded magnet
by way of compression or compaction molding. The methods of the
present invention retain the organotitanate coupling agent in the
mixture during and after the steps of mixing the coating
compositions with the magnet powder, as it is found that such
intimate mixing between organotitanate and various components aids
in yielding epoxy-bonded magnets with enhanced performance, such as
improved flux aging loss. In specific embodiments of the present
invention, the organotitanate or organozirconate coupling agent are
admixed with the other constituents of the coating formulation. In
other embodiment of the invention, the organotitanate or
organozirconate coupling agent can be added to the magnet powder in
a pre-coating step before introduction of the other constituents of
the coating formulation.
[0048] The addition of accelerator in the coating formulations of
the present invention reduces the curing temperature for creating
the bonded magnet from a temperature on the order of around
200.degree. C. or more to a temperature of around 170.degree. C.
The lower curing temperature reduces the possibility of oxidation
of the magnet material during the formation of the bonded magnet.
This is beneficial for providing a bonded magnet with a lower flux
aging loss, and better performance.
[0049] The addition of the lubricant results in lower ejection
pressures for removing the bonded magnet from the die press, which
helps prolong the life of the die press.
[0050] The present invention also provides a coating formulation
applicable to rare earth-transition metal-boron (RE-TM-B) magnet
powders, such as neodymium-iron-boron type magnetic powders
manufactured from rapid solidification processes for, among other
things, the purpose of corrosion and oxidation resistance when
exposed to aggressive environments. The coating formulation
preferably contains an epoxy binder, curing agent, an accelerating
agent, and a lubricant. By incorporating coupling agents and
optionally, other specialty additives with the magnetic powder and
the organic epoxy components additional oxidation and corrosion
prevention, enhanced adhesion and dispersion between the filler and
matrix phases can he achieved. This invention is applicable to all
such rare earth-transition metal-boron (RE-TM-B) magnet powders
produced by rapid solidification and encompasses both the bonded
magnet products that consist of combinations of the materials
mentioned and the application processes. Experimental testing of
the magnets of the present invention revealed the exceptional
properties derived from the coating formulations of the
invention.
[0051] Solvent or liquid coating is an effective manner in which
each organic component can be blended with solid filler particles.
It has been discovered that applying a low-viscosity, volatile
carrier fluid containing dissolved low-molecular weight binder
components and additives effectively allows the deposition of a
protective, organic layer on the magnetic powders under ambient or
moderate-temperature conditions. This procedure ensures a fast and
simple production of compression moldable, liquid-coated, RE-TM-B
powders for high-temperature applications.
[0052] In another aspect, the present invention provides rapidly
solidified rare earth-transition metal-boron (RE-TM-B) type
magnetic materials with a protective passivation coating for high
temperature and aggressive environment exposure. The bonded magnets
are formed from the coated magnetic powders that have been
compacted and subsequently cured. The resulting bonded magnets,
that arise from the liquid coating process, including
organotitanate coupling agents in the epoxy system, show
significant improvement in flux loss aging as compared to magnets
made without coupling agent at temperatures or exceeding
180.degree. C. FIG. 1 shows the stark contrast in flux aging loss
at 180.degree. C. after 100 hours between magnets (operating at a
load line PC=2) formulated in the absence of coupling agents (No
CA) or that have been liquid-coated with an organotitanate or
organozirconate agent (LICA 38, KZ OPPR, KR 55). The presence of
the organic coupling agent reduces the degree of oxidation of these
powders, making them suitable for numerous high
temperature/corrosive environment applications. Five embodiments of
the present invention are disclosed, including one non-coupled
magnetic powder system and four coupled magnetic powder systems for
passivation. The exemplary coupled systems include a coupling
agent-coated powder, a coupling agent-epoxy-coated powder and two
coupling agent-nanoadditive-coated powders.
[0053] In many embodiments, the present invention provides a
magnetic material that has been rapidly solidified then thermally
annealed, preferably within the temperature range of 300.degree. C.
to 800.degree. C. for about 0.5 to about 120 minutes. The magnetic
material has the composition, in atomic percentage, of
R.sub.uFe.sub.100-u-v-w-x-yCo.sub.vM.sub.wB.sub.x, wherein R is any
rare earth element including yttrium; M is one or more of Zr, Nb,
Ti, Cr, V, Mo, W, Hf, Al, Mn, Cu, and Si. Further, the values for
u, v, w and x are as follows: 7.ltoreq.u.ltoreq.13,
0.ltoreq.v.ltoreq.20, 0.ltoreq.w.ltoreq.7 and 4.ltoreq.x.ltoreq.10.
In addition, the magnetic material exhibits a remanence (Br) value
from about 6 to about 12 kG and an intrinsic coercivity (H.sub.ci)
value from about 5.0 to about 15 kOe.
[0054] Any number of thermosetting polymer binders may be selected,
such as, urea formaldehyde (amino resins), phenolics, thermosetting
polyurethane resins, alkyd resins, or epoxy resins. Curing agents
or hardeners contain functional groups that react with functional
groups of the resin and are required to cause the crosslinking or
cure reaction. Examples of curing agents are aliphatic (linear),
cycloaliphatic, tertiary, and aromatic amines; amine adducts;
amidoamines; polyamides; or anhydrides. Typically, these agents are
added to the resin at about 1 to 6 phr (per hundred parts resin),
depending on the desired extent of cure of the final crosslinked
product. The accelerator, which increases the reactivity of the
curing agent, can be a tertiary amine, e.g. imidazole, amine
adduct, or amine-based complex, e.g. BF.sub.3 mono-ethylamine
complex. Accelerator concentrations fall within the range of 1 to 4
phr. For ease of processing, a lubricant such as fatty acids, metal
(e.g., zinc or calcium) stearates, fluoropolymer resins, polyolefin
or polyester resins, etc. is used. Typically lubricants are
measured relative to the amount of solid filler present. The
concentration range of lubricant may be 0.01 to 0.5 phf (per
hundred parts filler) and is dependent on the desired final
properties of the resulting bonded magnet. Antioxidant
concentrations tend to exist within the range of 0.5 to 1.5 phr
(per hundred parts resin), and are useful for oxygen radical
consumption in a system.
[0055] The appropriate amounts of coupling agent and nanofiller
(e.g., organoclay and POSS additive) for a specific system are
determined empirically for optimization of its final desired magnet
properties. Preferably the concentration ranges of coupling agent,
organoclays and POSS additive added to the entire system should
fall within 0.1 to 1.0% by weight (based on amount of binder and
filler), 1.0 to 10.0% by weight (based on amount of resin), and 0.1
to 1.0% by weight (based on amount of binder and filler),
respectively.
[0056] In a specific embodiments, a multifunctional
epichlorohydrin/cresol novolac epoxy resin, with a dicyandiamide
curing agent, a tertiary amine accelerator and zinc stearate
lubricating agent in the polymer binder system are used for
compression-molding purposes both including and excluding coupling
agent. Any of the following coupling agents are applicable to this
invention: organosilanes, organotitanates, organozirconates, and
organozircoaluminates. For these embodiments the recommended
coupling agents for the epoxy-bonded RE-TM-B magnets are the
organotitanates and organozirconates, which are of the general
form
(RO--).sub.nTi(--OXR'Y).sub.4-n
and
(RO--).sub.nZr(--OXR'Y).sub.4-n
[0057] The RO is the hydrolyzable group that reacts with surface
protons or hydroxyl groups, where R may be short or long chained
alkyls (monoalkoxy) or unsaturated allyls (neoalkoxy). Ti and Zr
are typically tetravalent titanium and zirconium atoms,
respectively, where both may have higher or lower valence as well.
X is the binder functional groups, such as phosphate, phosphito,
pyrophosphato, sulfonyl, carboxyl, etc. R' is the thermoplastic
functional group such as: aliphatic and non-polar isopropyl, butyl,
octyl, isostearoyl groups; napthenic and mildly polar dodecylbenzyl
groups; or aromatic benzyl, cumyl phenyl groups. Y is the
thermosetting functional group that typically is reactive, e.g.
amino or vinyl groups. n represents the functionality of the
molecule. A functionality of n=2 implies that there exist two
reactive hydrolyzable groups and two organofunctional groups for
compatibility with the polymer binder. Examples of the various
functionalities of these coupling agents are displayed in Table 1.
The liquid coupling agent organotitanates and organozirconates with
pyrophosphato and phosphito binder functional groups were found to
be most effective for oxidation resistance, due to their reactive
nature with surface protons and hydroxyls present on the magnetic
powders surfaces.
TABLE-US-00001 TABLE 1 Functional groups of organotitanate and
organozirconate coupling agents Titanate Symbol Chemical Group
Chemical Name Type n R (CH.sub.3).sub.2--H -- isopropyl monoalkoxy
.sup. 1-4.sup..dagger. H.sub.3 -- methyl monoalkoxy 1
C.sub.7H.sub.15--H.sub.2C-- octyl alkoxy 1-4
CH.sub.3CH.sub.2C(CH.sub.2OCH.sub.2CH.dbd.CH.sub.2)--H.sub.2 --
2,2-diallyloxymethyl allyloxy 4 CH.sub.2.dbd.CHCH.sub.2OCH.sub.2
CH.sub.3CH.sub.2C--H.sub.2 -- neopentyl(diallyl)oxy neoalkoxy 1
CH.sub.2.dbd.CHCH.sub.2OCH.sub.2 R, X, Y --(
.dbd.O)C.sub.17H.sub.35 isostearoyl monoalkoxy 3 --( .dbd.O)
(CH.sub.3).dbd.CH.sub.2 methacryl monoalkoxy 2-3 --(O.dbd.
.dbd.O)-AR--C.sub.12H.sub.25 dodecylbenzenesulfonyl monoalkoxy 3
--(HO-- .dbd.O)--O--( .dbd.O)--(C.sub.8H.sub.17).sub.2
pyrophosphato neoalkoxy 3 .sup..dagger.The titanium and zirconium
atoms may have coordination numbers greater than 4. AR is an
aromatic benzene unit. The italicized, bold-type atom is the
primary connecting atom of the functional segment. Information
taken from Ken React Reference Manual.
[0058] The liquid coating process requires an appropriate solvent
for proper dissolution of the organic resin, hardener, accelerator,
lubricant and coupling agent. Polar protic solvents, such as,
alkanols or alkoxy-based alcohols and aprotic solvents, such as,
ketones, aromatics, and glycol-based ethers are useful for epoxy
resin dissolution. Protic solvents may not always be advisable, due
to the possible side reaction of a proton-donating solvent molecule
with the epoxide group of the resin monomer. Since most amine-based
curing agents and accelerators are polar molecules, the
aforementioned solvents could be appropriate for these components.
Stearates or fatty acids are also polar since they contain the
carboxylate ion. Many of the organotitanates and organozirconates
can vary in solubility with particular solvents. The
pyrophosphato-, phosphate-, and phosphito-functional
titanates/zirconates, due to their aprotic polarity, have very good
solubility in the following solvents: isopropanol, xylene, toluene,
dioctyl phthalate and ketones. Other coupling agents of different
functionality may have limited solubility in most conventional
solvents. When using the recommended components in this invention,
acetone has proven to be a very acceptable carrier fluid, for both
coupled and non-coupled systems, because of its ability to dissolve
the ingredients well and high vapor pressure at ambient
temperature.
[0059] Various embodiments of the invention contain and/or require
a proper mixing procedure in order to obtain optimal
characteristics. In the first embodiment of the present invention,
the RE-TM-B magnet powders are coated with a homogeneous solution
of the epichlorohydrin/cresol novolac epoxy resin, a dicyandiamide
curing agent, a tertiary amine accelerator and zinc stearate
lubricating agent in acetone. Once added to the organics solution,
mixing of the RE-TM-B magnet powders continues while the mixture is
heated above room temperature for solvent removal.
[0060] In the second embodiment of the present invention, a
coupling agent is incorporated with the RE-TM-B magnet powders
through a precoating process. An organotitanate-acetone solution is
added to the magnetic powders and stirred followed by the
subsequent evaporation of acetone. The pretreated RE-TM-B powders
are then subjected to the mixing procedure as in the first
embodiment that includes the epoxy system organic components.
[0061] In the third embodiment of the present invention, the
organotitanate coupling agent is incorporated with the RE-TM-B
magnet powders and the epoxy system organic components through an
admixing process. The RE-TM-B magnet powders are blended with a
homogeneous acetone solution of the epichlorohydrin/cresol novolac
epoxy resin, a dicyandiamide curing agent, a tertiary amine
accelerator, zinc stearate lubricating agent, and the coupling
agent. The relative amounts of the resin, curing agent, accelerator
and lubricant are reduced accordingly in order to maintain an
RE-TM-B powder mass percent of 98.3% when incorporating the
coupling agent. FIG. 2 shows a plot of the flux aging loss results
for cured magnets according to the first, second and third
embodiments of the present invention.
[0062] As can be seen in FIG. 2, the magnetic material according to
the second embodiment (Precoated CA) exhibits improved properties
over the magnetic material of the first embodiment (No CA) due to
the incorporation of the coupling agent (CA) through precoating the
magnet powders. Furthermore, an enhancement of the flux aging loss
of the RE-TM-B powders is attained when the organotitanate is
admixed with the epoxy system components, as seen in FIG. 2 for the
third embodiment (Admixed CA).
[0063] The magnetic material according to the fourth embodiment of
the present invention has a similar formulation to the magnetic
material of the third embodiment, but differs due to the addition
of bentonite clay powder that has been chemically treated to
contain bis(hydroxyethyl)methyl tallow alkyl ammonium salts within
the admixing acetone solution. The relative amounts of the resin,
curing agent, accelerator and lubricant are reduced accordingly in
order to maintain a magnetic powder weight percent of 97.6% when
incorporating the organoclays. FIG. 3 shows a plot of the flux
aging loss results for cured magnets according to the first and
fourth embodiments of the invention. The incorporation of the
additive of the treated bentonite clay powder within the admixing
acetone solution results in a significant improvement in the flux
loss of the magnetic material according to the fourth embodiment as
compared to the first embodiment.
[0064] The magnetic material according to the fifth embodiment of
the present invention has a similar formulation to the magnetic
material of the fourth embodiment, but differs due to the initial
precoating of a silanol-POSS with phenyl group functionality on the
magnetic powders. A POSS-tetrahydrofuran (THF) solution is added
and then stirred with the magnetic powders, followed by the
evaporation of the THF solvent. The pretreated powders are then
subjected to the mixing procedure in the fourth embodiment with
admixing the organics-acetone solution. The relative amounts of the
resin, curing agent, accelerator and lubricant are reduced
accordingly in order to maintain a magnetic powder weight percent
of 97.6% when incorporating the organoclays. FIG. 4 shows the
improved flux aging loss results for cured magnets according to the
fifth embodiment as compared to the cured magnets of the first and
third embodiments.
EXAMPLES
Example 1
[0065] Commercially available MQP.TM.-B powder is liquid-coated
with an epichlorohydrin/cresol novolac epoxy resin EPON 164.TM.
(Shell Chemical Company), dicyandiamide curing agent (SKW
Trostberg), a tertiary amine accelerator, Fenuron.TM., (SKW
Trostberg), and zinc stearate in a 8% acetone solution. The resin,
curing agent, accelerator, and zinc stearate are added together
with the acetone in a glass 500 mL beaker. The mixture is stirred
periodically in order to produce a homogeneous solution of the
organic components. The MQP.TM.-B powder is subsequently added to
the solution, allowing the addition of more acetone to sufficiently
immerse the powders in the solution (roughly 1 mL of acetone per 5
grams of MQP powder). The overall proportions and compositions of
the components are shown in Table 1a. The beaker containing the
mixture is then placed on a hot plate and heated at 50.degree. C.
The contents are periodically stirred while the acetone evaporates.
For complete drying the powders are removed from the beaker and
spread evenly on a flat surface within a fume hood.
TABLE-US-00002 TABLE 1a Component Mass (g) Weight Percent (%)
Example 1 MQP .TM.-B 100.0 98.272 EPON 164 Resin 1.600 1.572
Dicyandiamide 0.096 0.094 Accelerator 0.032 0.031 Zinc Stearate
0.030 0.029
Example 2
[0066] Commercially available MQP.TM.-B powder is liquid-coated
with 0.6% LICA 38.TM. (Kenrich Petrochemicals, Inc.) (see Table 2).
The coupling agent is added to acetone in a glass 500 mL beaker
creating a 50% solution. The MQP.TM.-B powder is added to the
solution, allowing the addition of more acetone to sufficiently
immerse the powders in the solution. The compositions of the
components are shown in Table 3. The beaker containing the mixture
is then placed on a hot plate and is heated at 50.degree. C. The
contents are periodically stirred while the acetone evaporates. For
complete drying the powders are removed from the beaker and spread
evenly on a flat surface within a fume hood.
TABLE-US-00003 TABLE 2 Organotitanate/Organozirconate Coupling
agent Nomenclature Coupling Agent Chemical Name LICA 38 .TM.
neopentyl(diallyl)oxy-tri(dioctyl) pyrophophato titanate KR 55 .TM.
tetra(2,2-diallyoxymethyl)butyl- di(ditridecyl)phosphito titanate
KR 238M .TM. methacrylate functional amine adduct of
di(dioctyl)pyrophosphate ethylene titanate KZ OPPR .TM. cyclo
(dioctyl) pyrophosphato dioctyl zirconate SIA0610 .TM.
.gamma.-aminopropyltriethoxysilane
TABLE-US-00004 TABLE 3 Composition of Example 2 Component Mass (g)
Weight Percent (%) Example 2 MQP .TM.-B 100.0 99.393 LICA 38 .TM.
0.611 0.607
Example 3
[0067] Commercially available MQP.TM.-B powder is pre-coated with
LICA 38.TM. (Kenrich Petrochemicals, Inc.) before further
liquid-coating with an epichlorohydrin/cresol novolac epoxy resin
EPON 164.TM. (Shell Chemical Company), dicyandiamide curing agent
(SKW Trostberg), a tertiary amine accelerator, Fenuron.TM., (SKW
Trostberg), and zinc stearate in a 8% acetone solution. The
coupling agent is added together with the acetone in a glass 500 mL
beaker in a 50/50 solution. The mixture is stirred periodically in
order to produce a homogeneous solution of the organic components.
The MQP.TM.-B powder is subsequently added to the solution,
allowing the addition of more acetone to sufficiently immerse the
powders in the solution. The overall proportions and compositions
of the powder and coupling agent are shown in Table 3. The beaker
containing the mixture is then placed on a hot plate and is heated
at 50.degree. C. The contents are periodically stirred while the
acetone evaporates. For complete drying the powders are removed
from the beaker and spread evenly on a flat surface within a fume
hood. Following the drying step, the precoated powders are added to
the 8% acetone solution with epoxy resin, curing agent,
accelerator, and zinc stearate. The acetone is then allowed to
evaporate while the powder-organics-acetone mixture is periodically
stirred. Table 4 shows the respective amounts of each
component.
TABLE-US-00005 TABLE 4 Compositions of Example 3 and 4 Component
Mass (g) Weight Percent (%) Examples 3 and 4 MQP .TM.-B 100.0
98.272 EPON 164 Resin 1.044 1.026 Dicyandiamide 0.063 0.062
Accelerator 0.021 0.021 Zinc Stearate 0.020 0.019 LICA 38 .TM.
0.611 0.600
Example 4
[0068] Commercially available MQP.TM.-B powder is admixed with LICA
38.TM. (Kenrich Petrochemicals, Inc.), an epichlorohydrin/cresol
novolac epoxy resin EPON 164.TM. (Shell Chemical Company),
dicyandiamide curing agent (SKW Trostberg), a tertiary amine
accelerator, Fenuron.TM., (SKW Trostberg), and zinc stearate in a
8% acetone solution. The resin, curing agent, accelerator, zinc
stearate and titanate are added together with acetone in a glass
500 mL beaker, creating a 8% organics solution. The mixture is
stirred periodically in order to produce a homogeneous solution of
the organic components. The MQP.TM.-B powder is subsequently added
to the solution, allowing the addition of more acetone to
sufficiently immerse the powders in the solution (see Table 4 for
compositions). The beaker containing the mixture is then placed on
a hot plate and is heated at 50.degree. C. The contents are
periodically stirred while the acetone evaporates. For complete
drying the powders are removed from the beaker and spread evenly on
a flat surface within a fume hood. FIG. 1 shows the flux aging loss
results of magnets following this recipe compared to other
organotitanates or organozirconates or no coupling agent at all.
FIG. 2 shows a comparison of the products of the liquid-coating
methods in the absence of a coupling agent (Example 1), precoated
MQP.TM.-B with coupling agent (Example 3), and admixed MQP.TM.-B
with coupling agent, as described in the first and second
embodiments of the invention.
[0069] This method is also performed under the same conditions by
using MQP.TM.-14-12 powders. FIG. 5 displays the flux aging results
at various temperatures for MQP.TM.-14-12 magnets in the absence of
comprised of LICA 38.TM. (No LICA), and including 0.6% LICA
38.TM..
Example 5
[0070] Commercially available MQP.TM.-B powder is admixed with KR
55.TM. (Kenrich Petrochemicals, Inc.), an epichlorohydrin/cresol
novolac epoxy resin EPON 164.TM. (Shell Chemical Company),
dicyandiamide curing agent (SKW Trostberg), a tertiary amine
accelerator, Fenuron.TM., (SKW Trostberg), and zinc stearate in a
8% acetone solution. The resin, curing agent, accelerator, zinc
stearate and titanate are added together with acetone in a glass
500 mL beaker, creating a 8% organics solution. The mixture is
stirred periodically in order to produce a homogeneous solution of
the organic components. The MQP.TM.-B powder is subsequently added
to the solution, allowing the addition of more acetone to
sufficiently immerse the powders in the solution (see Table 5 for
compositions). The beaker containing the mixture is then placed on
a hot plate and is heated at 50.degree. C. The contents are
periodically stirred while the acetone evaporates. For complete
drying the powders are removed from the beaker and spread evenly on
a flat surface within a fume hood. FIG. 1 shows the flux aging loss
results of magnets following this recipe compared to other
organotitanates or organozirconates or no coupling agent at
all.
TABLE-US-00006 TABLE 5 Compositions of Example 5 Component Mass (g)
Weight Percent (%) Example 5 MQP .TM.-B 100.0 98.272 EPON 164 Resin
1.137 1.117 Dicyandiamide 0.068 0.067 Accelerator 0.023 0.022 Zinc
Stearate 0.021 0.021 KR 55 .TM. 0.509 0.500
Example 6
[0071] Commercially available MQP.TM.-B powder is admixed with KZ
OPPR.TM. (Kenrich Petrochemicals, Inc.), an epichlorohydrin/cresol
novolac epoxy resin EPON 164.TM. (Shell Chemical Company),
dicyandiamide curing agent (SKW Trostberg), a tertiary amine
accelerator, Fenuron.TM., (SKW Trostberg), and zinc stearate in a
8% acetone solution. The resin, curing agent, accelerator, zinc
stearate and titanate are added together with acetone in a glass
500 mL beaker, creating a 8% organics solution. The mixture is
stirred periodically in order to produce a homogeneous solution of
the organic components. The MQP.TM.-B powder is subsequently added
to the solution, allowing the addition of more acetone to
sufficiently immerse the powders in the solution (see Table 6 for
compositions). The beaker containing the mixture is then placed on
a hot plate and heated at 50.degree. C. The contents are
periodically stirred while the acetone evaporates. For complete
drying the powders are removed from the beaker and spread evenly on
a flat surface within a fume hood. FIG. 1 shows the flux aging loss
results of magnets following this recipe compared to other
organotitanates or organozirconates or no coupling agent at
all.
TABLE-US-00007 TABLE 6 Compositions of Example 6 Component Mass (g)
Weight Percent (%) Example 6 MQP .TM.-B 100.0 98.272 EPON 164 Resin
1.137 1.117 Dicyandiamide 0.068 0.067 Accelerator 0.023 0.022 Zinc
Stearate 0.021 0.021 KZ OPPR .TM. 0.509 0.500
Example 7
[0072] Commercially available MQP.TM.-B powder is pretreated in a
0.5% aqueous solution of the aminosilane SIA0610.TM. (Gelest). The
powders are stirred for 10 minutes, and then they are placed in an
oven at 110.degree. C. for 30 minutes followed by drying under a
fume hood for 24 hours. An 8% solution of an epichlorohydrin/cresol
novolac epoxy resin EPON 164.TM. (Shell Chemical Company),
dicyandiamide curing agent (SKW Trostberg), a tertiary amine
accelerator, Fenuron.TM., (SKW Trostberg), and zinc stearate in a
acetone is prepared in a glass 500 mL beaker. Stirring of the
mixture is performed periodically in order to produce a homogeneous
solution of the organic components. The dry silane-coated powders
are subsequently added to the acetone solution, allowing the
addition of more acetone to sufficiently immerse the powders in the
solution. The overall proportions and compositions of the
components are shown in Table 7. The beaker containing the mixture
is then placed on a hot plate and heated at 50.degree. C. The
contents are periodically stirred while the acetone evaporates. For
complete drying the powders are removed from the beaker and spread
evenly on a flat surface within a fume hood. FIG. 6 shows a
comparison the flux aging loss of untreated (uncoupled) MQP.TM.-B
and SIA0610-coated MQP.TM.-B that have been subjected to the
liquid-coating process.
TABLE-US-00008 TABLE 7 Compositions of Example 7 Component Mass (g)
Weight Percent (%) Example 7 MQP .TM.-B 100.0 98.272 EPON 164 Resin
1.137 1.550 Dicyandiamide 0.068 0.094 Accelerator 0.023 0.031 Zinc
Stearate 0.021 0.029 SIA0610 .TM. 0.031 0.030
Example 8
[0073] Commercially available MQP.TM.-B powder is admixed with
organotitanate LICA 38.TM. (Kenrich Petrochemicals, Inc.), an
epichlorohydrin/cresol novolac epoxy resin EPON 164.TM. (Shell
Chemical Company), dicyandiamide curing agent (SKW Trostberg), a
tertiary amine accelerator, Fenuron.TM., (SKW Trostberg), zinc
stearate, and organoclay Cloisite 30B.TM. (Southern Clay Products)
in a 8% acetone solution. The resin, curing agent, accelerator,
zinc stearate, organotitanate, and organoclay are added together
with acetone in a glass 500 mL beaker. The mixture is stirred
periodically in order to produce a homogeneous solution of the
organic components. The MQP.TM.-B powder is subsequently added to
the solution, allowing the addition of more acetone to sufficiently
immerse the powders in the solution (see Table 8 for compositions).
The beaker containing the mixture is then placed on a hot plate and
heated at 50.degree. C. The contents are periodically stirred while
the acetone evaporates. For complete drying the powders are removed
from the beaker and spread evenly on a flat surface within a fume
hood.
TABLE-US-00009 TABLE 8 Composition of Example 8 Component Mass (g)
Weight Percent (%) Example 8 MQP .TM.-B 100 97.605 EPON 164 Resin
1.457 1.422 Dicyandiamide 0.087 0.085 Accelerator 0.029 0.028 Zinc
Stearate 0.091 0.089 LICA 38 .TM. 0.615 0.600 Cloisite 30B .TM.
0.175 0.171
Example 9
[0074] Commercially available MQP.TM.-B powder is precoated with a
trisilanolphenyl POSS.TM. additive (Hybrid Plastics) before further
liquid-coating with an epichlorohydrin/cresol novolac epoxy resin
EPON 164.TM. (Shell Chemical Company), dicyandiamide curing agent
(SKW Trostberg), a tertiary amine accelerator, Fenuron.TM., (SKW
Trostberg), zinc stearate, an organotitanate LICA 38.TM. (Kenrich
Petrochemicals, Inc.) an organoclay Cloisite 30B.TM. (Southern Clay
Products), and an antioxidant Ralox LC.TM. (Degussa, butylated
reaction product of p-cresol and dicyclopentadiene) in a 8% acetone
solution. The resin, curing agent, accelerator, zinc stearate,
organotitanate, organoclay and antioxidant are added together with
acetone in a glass 500 mL beaker. The mixture is stirred
periodically in order to produce a homogeneous solution of the
organic components. The MQP.TM.-B powder is subsequently added to
the solution, allowing the addition of more acetone to sufficiently
immerse the powders in the solution (see Table 9 for compositions).
The beaker containing the mixture is then placed on a hot plate and
heated at 50.degree. C. The contents are periodically stirred while
the acetone evaporates. For complete drying the powders are removed
from the beaker and spread evenly on a flat surface within a fume
hood.
TABLE-US-00010 TABLE 9 Composition of Example 9 Component Mass (g)
Weight Percent (%) Example 9 MQP .TM.-B 100.0 97.605 EPON 164 Resin
1.050 1.025 Dicyandiamide 0.063 0.061 Accelerator 0.021 0.020 Zinc
Stearate 0.066 0.064 LICA 38 .TM. 0.130 0.490 Cloisite 30B .TM.
0.615 0.600 Trisilanolphenyl POSS .TM. 0.500 0.123 Ralox LC .TM.
0.011 0.011
Miscellaneous
[0075] Many modifications and variations of this invention can be
made without departing from its spirit and scope, as will be
apparent to those skilled in the art. The specific embodiments
described herein are offered by way of example only, and the
invention is to be limited only by the terms of the appended
claims, along with the full scope of equivalents to which such
claims are entitled.
References Cited
[0076] All references cited herein are incorporated herein by
reference in their entirety and for all purposes to the same extent
as if each individual publication or patent or patent application
was specifically and individually indicated to be incorporated by
reference in its entirety for all purposes.
* * * * *