Compositions – Magnetic – With wax – bitumen – resin – or gum
Patent
1997-04-07
1999-08-03
Bonner, Melissa
Compositions
Magnetic
With wax, bitumen, resin, or gum
252 6255, 148104, 524413, 264429, 2641761, H01F 108, H01F 126, H01F 1113, H01F 137
Patent
active
059321342
DESCRIPTION:
BRIEF SUMMARY
The invention is directed to a polymer-based composition for producing magnetic and magnetizable molded articles.
The composition consists of a permanent-magnetic and/or ferromagnetic metal-containing compound and a polymer. Furthermore, the invention is directed to a process for producing said composition, the use of said composition, molded articles made of said composition, and a process for producing said molded articles, as well as to magnetic molded articles and a process for producing same.
According to prior art, anisotropic permanent magnets made of metal powders may be produced in various ways. The most widely used process for producing sintered, anisotropic permanent magnets made of powders is the pressing in a magnetic field and subsequent sintering of the pressed parts. Thus, permanent magnets of various types are produced, wherein the magnetic orientation is preferably arranged in the pressing direction or across the pressing direction. However, such a process for pressing metal powders for permanent magnets having a radial preferred orientation can be applied only within limits for magnets having a low height-diameter ratio, and magnets thus prepared possess only weak magnetic properties. Using this process, pole-oriented ring magnets are produced as well. Here, however, the process is disadvantageous due to loading problems, the weak orientation, and the occurrence of cracks in the sintered parts.
Another familiar process for producing the sintered, anisotropic magnets is the continuous drawing process. This process produces a radial anisotropy wherein the resulting energy density is, however, only slightly higher than in isotropic magnets.
In addition to these processes based on the use of metal powders, other processes are known wherein the metal powders are bound to polymers by means of binders. Thus, for the production of anisotropic permanent magnets from metal powder, a bonding between the powder and a polymer is generated initially, and the mass thus prepared is further processed by pressing, injecting, calendering or extruding, and establishing the preferred orientation using mechanical or magnetic methods.
As a rule, these anisotropic, plastic-bound permanent magnets exhibit better properties than the isotropic permanent magnets made of the same magnetic material and, in addition, may have various preferred orientations, such as axial, diametrical, radial, and multipole. However, due the embedding in polymers, the energy density is limited, and the high values of the appropriately sintered permanent magnets cannot be achieved.
Various compositions are known from prior art, which contain a polymer in addition to a permanent-magnetic and/or ferromagnetic, metal-containing compound. In particular, these compositions are used in the production of plastic-bound permanent magnets or induction magnets.
DE-A-2,952,820 describes matrix-bound permanent magnets having highly oriented magnetic particles, as well as the production of same. A hot-melt polyamide resin is used as non-magnetic binder. The granulated mixture of ferrite and polyamide is placed in an injection molding machine and exposed to a magnetic field during injection.
The drawback in this process is that the magnets thus produced have a relatively high shrinkage and poor dimensional stability which results from the absorption of water by the polyamide. In most cases, complicated tools for producing injection moldings can be produced from this material only by expensive subsequent processing.
DE-A-2,736,642 likewise reports plastic-bound permanent magnets and a process for their production. Here, polystyrene is used as the plastic, with benzene being used as a solvent. The powdered, permanent-magnetic metal and polystyrene which has been dissolved in benzene, are mixed and premagnetized in a magnetic field. After evaporation of the solvent and grinding, an injectable granulate is obtained which is subjected to final magnetization after injection molding. This process suffers from the drawback that the polymer matrix is dissolved
REFERENCES:
patent: 4000229 (1976-12-01), Wainer
patent: 4148846 (1979-04-01), Owens et al.
patent: 4327346 (1982-04-01), Tada et al.
patent: 5563001 (1996-10-01), Gay
patent: 5578670 (1996-11-01), Nakazawa et al.
Christ Hubert
Meyerhoff Hans-Peter
A. Schulman GmbH
Bonner Melissa
LandOfFree
Polymer-based composition for producting magnetic and magnetizab does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Polymer-based composition for producting magnetic and magnetizab, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Polymer-based composition for producting magnetic and magnetizab will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-846894