Glass/plastic compounds

Details Glass/plastic compounds Glass/plastic compounds

2002-10-15

2004-10-26

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...

C524S103000, C524S261000, C524S403000, C524S405000, C524S415000, C523S223000

Reexamination Certificate

active

06809134

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to glass/plastic compounds based on thermoplastic, and to a process for producing them.
BACKGROUND OF THE INVENTION
Reinforced plastics materials, mainly based on thermoplastics, are used in electrical engineering and electronics to produce appliances and components. The reinforced thermoplastics used are usually thermoplastic compounds which contain glass fibers.
It is known that, on account of external contamination of the insulation caused by deposits of dust and chemicals or other contamination, a current, known as a tracking current, can flow on insulating-material surfaces when a voltage is applied. In the case of plastic insulating materials, this leads to the formation of a conductive tracking path on the plastic surface, which is attributable to thermal degradation products formed from the polymer matrix. However, the insulating action of the plastic is thus lost. The voltage level at which a conductive tracking path is formed is dependent on the material. This phenomenon, i.e. the occurrence of tracking currents and the formation of tracking paths, limits the possible uses of the various groups of polymer materials as electrical insulants to a certain extent, since in many cases a high tracking resistance is also demanded for use in electrical engineering as well as a high electrical strength.
Particularly in the case of electrical and electronic parts and components, high demands are imposed on the tracking resistance, i.e. the CTI value (CTI=Comparative Tracking Index). For example, in the case of relay components for actuators and caps, CTI values of at least ≧125 V, and generally even ≧175 V, are required. For relay base bodies in what are known as “white goods”, this requirement is generally ≧175 V, and for use in the automotive sector this value is at least ≧225 V. For other applications in electrical engineering or electronics, for example in housings, the requirements may even be significantly higher still.
It is known that high-temperature thermoplastics, i.e. high-performance thermoplastics, apart from partially aromatic polyamides, have only a noticeably low tracking resistance of approx. 100 to 175 V. This low tracking resistance may even be reduced further when reinforcing materials, such as glass fibers, are added. As a result, many possible applications for the high-temperature thermoplastics remain out of reach.
SUMMARY OF THE INVENTION
It is an object of the invention to provide glass/plastic compounds based on thermoplastics which have a high tracking resistance.
According to the invention, this is achieved by glass/plastic compounds which contain the following components:
a low-melting sulfophosphate glass of the following composition (in mol %): 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
,
a high-performance thermoplastic, and
an organic additive and/or a mineral filler, and if appropriate also
carbon black and/or a sterically hindered phosphite or phenol.
A “low-melting” sulfophosphate glass is understood as meaning a glass with a low glass transition temperature T
g
, in particular a glass with T
g
<approx. 500° C. A “high-performance thermoplastic” is a high-performance polymer, and specifically, in the present case, a heat-resistant polymer (“high-temperature resistant polymer”). This is important because both the temperature during production of the compounds and the working temperature (of the compounds) is >300° C.
The glass/plastic or glass/polymer compounds according to the invention have a high tracking resistance: the CTI value may be up to 250 V and above. This opens a wide range of applications for the novel high-performance compounds in electrical and electronic parts and components, i.e. a wider range of uses. It is also important that the high tracking resistance is achieved with even relatively small amounts of additives, which has a highly positive effect on the free-flowing properties and the mechanical properties.
The German Patent Application bearing the reference number 199 60 548.3 (application date: Dec. 15, 1999) describes glass/plastic compounds based on thermoplastic which contain the following components:
a low-melting sulfophosphate glass of the following composition (in mol %): 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
, and
a high-performance thermoplastic.
Compared to these compounds, the glass/plastic compounds according to the invention, which contain an organic additive and/or a mineral filler, have a CTI value which is increased by 50 to 100 V. If these compounds additionally contain carbon black and/or a sterically hindered phosphite or phenol, the tracking resistance is increased further, specifically to CTI values of ≧250 V.
In addition to the improved tracking resistance, the glass/plastic compounds according to the invention also 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 chemicals resistance, in particular to water, acids and bases, and specifically, which is surprising, without the addition of stabilizers. Furthermore, these glass/plastic compounds have an excellent resistance to abrasion and the materials can be recycled without problems, since there is no shortening of the glass component as is the case in compounds reinforced with glass fibers.
The sulfophosphate glasses which are present in the glass/plastic compounds according to the invention have a glass transition temperature of 250° C.<T
g
<280° C. It is preferable for a sulfophosphate glass of the following composition (in mol %) to be used in the compounds: 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
. A glass of this type has a glass transition temperature of 268° C. By way of example, another glass has the following composition (in mol %): 9% of Li
2
O, 5% of Na
2
O, 7% of K
2
O, 1.6% of CaO, 37% of ZnO, 20.4% of P
2
O
5
and 20% of SO
3
(T
g
=280° C.). By way of example, a further glass has the following composition (in mol %): 4.8% of Li
2
O, 9.2% of Na
2
O, 6.9% of K
2
O, 1.6% of CaO, 35.9% of ZnO, 2.0% of La
2
O
3
, 19.6% of P
2
O
5
and 20.0% of SO
3
(T
g
=275° 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 transition temperature of the glass component is matched to the working 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 polyethersulfones (PES) and polyphenylene sulfones (PPSU).
The level of the glass component, i.e. of the sulfophosphate glass, in the glass/plastic compounds is preferably 15 to 60% by weight, based on the level of sulfophosphate glass and high-performance thermo-plastic. For certain applications, however, the glass contents may be up to 80% by weight. The compounds may also contain standard additives, such as coloring pigments and stabilizers. There are possible applications in, for example, sensors, actuators, plug connectors and relays.
The organic additive is preferably melamine cyanurate, a polysiloxane or a halogenated flame retardant, such as poly(haloaryl (meth)acrylate) and halogenated polystyrene. Further additives which can be used are elastomers, for example olefinic elastomers, rubbers, polyamides, fluoropolymers and organosilanes, such as 3-mercaptopropyl-trimethoxysilane.
The mineral filler is preferably mica, calcium sulfate (CaSO
4
) or a zi

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