Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2002-11-01
2004-05-11
Thexton, Matthew A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S414000, C523S223000, C501S045000, C428S325000
Reexamination Certificate
active
06734243
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a component which at least partially comprises a material which represents a mixture of glass and plastic. The invention also relates to a process for producing the component.
Components used in electrical engineering and electronics are increasingly being produced from plastic materials, particularly those based on thermoplastics. A filler is added to the plastic material in order to improve the mechanical and thermal properties. In particular, glass is used as the filler. To improve the mechanical stability of the plastic material, the glass is added in the form of glass fibers (glass fiber-reinforced plastics). Furthermore, there are mineral-filled plastic materials in which the glass is present in the form of particles which are typically approximately spherical. With mineral-filled plastics of this type, it is possible to achieve an isotropic shrinkage and distortion behavior for the components produced therefrom.
Mineral-filled plastics of this type are known, for example, from EP 0 365 236 A1 as an alloy in the form of a melt mixture comprising at least one inorganic glass and/or a glass-ceramic and at least one organic thermoplastic or thermoset; the proportion of the glass or glass-ceramic is 30 to 90% by volume. The glass component is a phosphate glass which, for example, has the following composition (mol %): 44 to 58% of P
2
O
5
, 4 to 10% of Al
2
O
3
+B
2
O
3
(with 0 to 7% of Al
2
O
3
and 0 to 10% of B
2
O
3
), 10 to 45% of Li
2
O+Na
2
O (with 0 to 30% of Li
2
O and 10 to 30% of Na
2
O), 0 to 20% of Cu
2
O and 10 to 30% of Li
2
O+CuO
2
. The thermoplastic polymer may be selected from the following group: polyaryl ether ketones, polyphenylene sulfides, polyfluoronated resins, polyetherimides, liquid crystal polyesters, polyether sulfones, polytetrafluorethylenes, polyether ether ketones, polyether ketones, polyethyl terephthalates, polybutyl terephthalates, melamines and polycarbonates. The thermoset may be an epoxy resin, a silicone resin, a polyimide, a phenol formaldehyde resin or a diallyl phthalate.
Glass fiber-reinforced plastics have the drawback that, on account of the preferential direction which is pre-determined by the fibers, the performance of the material has a pronounced anisotropy which above all has adverse effects on the shrinkage and distortion of the component. Plastics provided with a filler in particle form have the drawback above all of being insufficiently rigid and resistant to thermal deformation. Since in known components the vitreous filler is present in the plastic fiber either exclusively in fiber form or exclusively in particle form, it is not possible to optionally avoid one of the abovementioned drawbacks depending on the functional section of the component. For example, a cover cap which is fitted onto a mounting plug for a relay in which the cover region is mechanically stable and at the same time the region which is coupled to the mounting plug and joined thereto in a positively locking manner is resistant to thermal deformation would be desirable. In addition, as the filler content rises, the plastic becomes increasingly difficult to process, since the flow properties of the known glass/plastic mixtures are greatly reduced as the proportion of glass increases. In particular, the production of thin-walled components or of components with a complicated geometry becomes more difficult as a result.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a component which has both regions which are mechanically stable and regions which are dimensionally and thermally stable.
The invention describes a component which at least partially comprises a glass/plastic mixture. This mixture has first regions in which the glass is present substantially in the form of spherical particles. Approximately spherical particles in granule form can also be used as the spherical particles. Furthermore, the mixture has second regions, in which the glass is present in the form of particles in fiber form.
This component according to the invention has the advantage that in the first regions it is subject to extremely little distortion even at elevated temperatures, on account of the isotropy of the spherical particles. Moreover, in the second regions the component has a high mechanical stability, on account of the reinforcement provided by the glass fibers.
Suitable components are in particular also very thin-walled components, for example cover caps. Therefore, it is particularly advantageous to provide a component in which the size of the spherical particles is less than 10 &mgr;m. Accordingly, in principle it is possible to achieve corresponding wall thicknesses of as little as 10 &mgr;m.
Furthermore, a component in which, in the glass/plastic mixture, a low-melting sulfophosphate glass of the following composition: 4 to 10% of Li
2
O, 4 to 10% of Na
2
O, 4 to 8% of K
2
O, 1 to 2% of CaO, 35 to 37% of ZnO, 0 to 3% of La
2
O
3
, 19 to 22% of P
2
O
5
and 19 to 22% of SO
3
is present as the glass and a high-performance thermoplastic is present as the plastic, is particularly advantageous.
A “low-melting” sulfophosphate glass is understood as meaning a glass with a low glass temperature T
2
, in particular a glass with T
2
<300° C. The glass temperature is to be understood as meaning the temperature at which the glass softens and thus becomes able to flow. A “high-performance thermoplastic” is a high-performance polymer and specifically in the present case, a temperature-stable plastic (heat-resistant polymer, high-temperature resistant polymer). The processing temperature T
1
of the plastic is at least 300° C., since only in this way is it possible to ensure that the components produced therefrom are able to withstand soldering baths. The glass temperature T
2
is lower than the processing temperature T
1
, with the result that the glass is in the free-flowing state. As a result, the glass/plastic mixture has very good flow properties for the production of thin-walled components or of components with a complicated geometry.
The glass/plastic mixtures according to the invention have good mechanical and thermal properties and good processing properties, in particular a good ability to flow, even with a high filler content, i.e. a high glass content. Moreover, they are distinguished by an excellent resistance to chemicals, in particular to water, acids and bases, and specifically, surprisingly, without the need for stabilizers to be added. Furthermore, the glass/plastic mixtures have an excellent resistance to abrasion, and the material can be recycled without problems, since there is no shortening of the glass component as occurs in glass fiber-reinforced mixtures.
The glass/plastic mixtures according to the invention preferably include a glass with a glass temperature of 250° C.≦T
2
≦280° C. In the mixtures, it is preferable to use a sulfophosphate glass of the following composition: 4.9% of Li
2
O, 9.4% of Na
2
O, 7.1% of K
2
O, 1.6% of CaO, 36.6% of ZnO, 20.0% of P
2
O
5
and 20.4% of SO
3
. This glass has a glass temperature T
2
of 268° C.
The high-performance thermoplastic used is advantageously a polyether ether ketone (PEEK), a polyetherimide (PEI), a polyphenylene sulfide (PPS), a partially aromatic polyamide, such as polyphthalamide (PPA) or a liquid crystal polymer (LCP). In these polymers, the glass temperature of the glass component is matched to the processing temperature of the thermoplastic material. Further high-performance thermoplastics which can be used are polyaryl ether ketones (PAEK) in general, for example polyether ketones (PEK), and polysulfones (PSU), in particular polyether sulfones (PES) and polyphenylene sulfones (PPSU).
The proportion of the glass component, i.e. of the sulfophosphate glass, in the glass/plastic mixture is preferably 15 to 60% by weight. For certain applications, however, the glass content may be up to 80% by weight. The mixtures may also contain standard additives, such as color pigments and stabi
Greiner Robert
Polese Angelo
Siemens Aktiengesellschaft
Thexton Matthew A.
LandOfFree
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