Glass/plastic compounds

Details Glass/plastic compounds Glass/plastic compounds

2002-10-21

2004-07-13

Thexton, Matthew A. (Department: 1714)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Processes of preparing a desired or intentional composition...

C524S403000, C524S414000

Reexamination Certificate

active

06762219

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to glass/plastic compounds based on thermoplastics, and also to a process for their preparation.
In electrical engineering and electronics, reinforced plastics materials, especially based on thermoplastics, are used for producing devices or components. The reinforced thermoplastics usually used here are thermoplastic compounds comprising glass fiber. However,—in particular at high filler levels—these materials have disadvantageous processing performance due to poor flowability and high tooling wear. The mechanical properties are moreover frequently anisotropic—due to orientation of the glass fibers during processing. In the case of moving parts produced from materials of this type, operation results in significant formation of crumb, and this impairs function particularly in the case of devices used in electrical engineering. In addition, if the material of glass-fiber-reinforced thermoplastics is recycled, the glass fibers degrade. The consequence of this is significant impairment of mechanical properties of compounds prepared using these glass fibers.
EP 0 365 236 A1 discloses an alloy in the form of a melt mixture made from at least one inorganic glass and/or one glass ceramic, and from at least one organic thermoplastic or thermoset polymer. The glass or glass ceramic content here is from 30 to 90% by volume. The glass component is a phosphate glass, for example one with the following composition (in mol %): from 44 to 58% of P
2
O
5
, from 4 to 10% of Al
2
O
3
+B
2
O
3
(with from 0 to 7% of Al
2
O
3
and from 0 to 10% of B
2
O
3
), from 10 to 45% of Li
2
O+Na
2
O (with from 0 to 30% of Li
2
O and from 10 to 30% of Na
2
O), from 0 to 20% of Cu
2
O and from 10 to 30% of Li
2
O+Cu
2
O. The thermoplastic polymer is one selected from the following group: polyaryl ether ketones, polyphenylene sulfides, polyfluorinated resins, polyetherimides, liquid-crystalline polyesters, polyether sulfones, polytetrafluoroethylenes, polyether ether ketones, polyether ketones, polyethyl terephthalates, polybutyl terephthalates, melamines and polycarbonates. The thermoset polymer may be an epoxy resin, a silicone resin, a polyimide, a phenolformaldehyde resin, or a diallyl phthalate.
To improve the moisture resistance of alloys of the abovementioned type—and corresponding composites—it is known that, besides the matrix material made from thermoplastic or thermoset polymer and the phosphate glass, use may be made of a water-soluble stabilizer component which is a source of metal cations of valency 2+ or higher (see EP 0 587 082 A1 and EP 0 587 083 A1). Metal cations of this type are Ba
2+
, Mg
2+
, Ca
2+
, Al
3+
, Zn
2+
, Sr
2+
, and Fe
3+
. However, the stabilizer component, which is a metal oxide or another metal compound, markedly impairs processing performance at high filler content, i.e. high glass content, by causing a considerable rise in viscosity.
Other known glasses for glass/plastic blends are those with low glass transition temperature, based on alkali metal zinc pyrophosphates and on alkali metal zinc sulfophosphates (see: G. H. Beall in “Proceedings of XVII International Congress on Glass”, Peking, China, Oct. 9-14, 1995, pages 174-183). Examples of the composition of the glasses are as follows (in mol %):
pyrophosphate glasses: from 30-40% of P
2
O
5
, from 20 to 55% of ZnO, from 0-4% of Al
2
O
3
and from 10-30% of R
2
O, i.e. from 3-12% of Li
2
O, from 4-18% of Na
2
O
3
, from 0-12% of K
2
O, and from 0-17% of Cu
2
O;
sulfophosphate glasses: from 21-33% of P
2
O
5
, from 9-17% of SO
3
, from 35-51% of ZnO, and from 10-20% of R
2
O, where R
2
O is mixed alkali.
These glasses are used together with the following thermoplastic polymers: polyether ketones, aromatic liquid-crystalline polyesters, polyaryl sulfones, perfluoroalkoxy resins, and polyetherimides.
Glass/plastic compounds, in particular those based on thermoplastics and used to produce glass-reinforced plastics parts or glass-reinforced plastics structures, are intended to have a specific property profile. The following applies to the properties of the material or the properties of the plastics parts:
homogeneous filler distribution
dimensional stability
solder bath resistance (SMD capability)
miniaturizability of the glass structures extending to the &mgr; range
good chemicals resistance, i.e. resistance to water, acids and bases
intrinsic flame retardancy
good tracking resistance
high capability for recycling or reprocessing.
The following processing requirements have to be complied with:
minimum processing temperature (however, processing temperature is inevitably above 260° C. due to the requirement for solder bath resistance)
viscosity of the components plastic, i.e. thermoplastic, and glass, selected to be appropriate to one another (under processing conditions)
good flowability at high filler levels
possibility of controlling the glass structures (isotropic or anisotropic)
low tooling wear (due to advantageous abrasive properties).
Another criterion is a low level of crumb formation during operation, i.e. low abrasion, in particular in the case of moving parts. In addition, to permit recycling of material, a demand is that recycling does not damage the reinforcing material, i.e. the glass component. Furthermore, it is intended that the glass/plastic compounds be capable of production with maximum cost-effectiveness and minimum cost.
When glasses are used in electrical engineering or electronics, good moisture resistance is of decisive importance. However, known glasses with low glass transition temperature, i.e. from about 220 to 230° C. are susceptible to hydrolysis and in certain instances water-soluble. Although addition of copper oxide (Cu
2
O) is claimed in principle to permit production of glasses with greater hydrolysis resistance and a glass transition temperature of from about 230 to 250° C., glasses of this type are still markedly more susceptible to hydrolysis than glasses with high glass transition temperature (see: G. H. Beall, loc. cit.); in addition, industrial production is excessively complicated and excessively expensive. On the other hand, glasses with glass transition temperature T
g
>300° C. cannot be used for the stated purpose. The reason is that the glasses are insufficiently flowable until the temperature is above the glass transition temperature by from 70 to 80° C., and therefore processing with a thermoplastic becomes possible only at temperatures above 370-380° C.
SUMMARY OF THE INVENTION
It is an object of the invention to provide glass/plastic compounds based on thermoplastics, which to a very substantial extent meet the requirements placed on the properties of compounds of this type, and also the demands with regard to processing, operation, and recycling of material. The glass here is in particular intended to have relatively high flowability and hydrolysis resistance, and it is also intended that fine distribution of the glass (<10 &mgr;m) be possible at any desired concentration.
According to the invention, this is achieved by way of glass/plastic compounds which comprise the following components:
a sulfophosphate glass with a low melting point and having the following composition: from 4 to 10% of Li
2
O, from 4 to 10% of Na
2
O, from 4 to 8% of K
2
O, from 1 to 2% of CaO, from 35 to 37% of ZnO, from 0 to 3% of La
2
O
3
, from 19 to 22% of P
2
O
5
, and from 19 to 22% of SO
3
, and
a high-performance thermoplastic.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A “low-melting” sulfophosphate glass is a glass with low glass transition temperature T
g
, in particular a glass with T
g
<about 500° C. A “high-performance thermoplastic” is a high-performance polymer, and specifically in the present case a heat-resistant polymer or high-temperature-resistant polymer. This is important because the temperature during preparation of the compounds is >300° C., as is the processing temperature (for the compounds).
The glass/plastic compounds of the invention or glass/polymer compou

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