DE1569367B1 - USE OF ELECTRICALLY INSULATING COMPONENTS OR SEMI-FINISHED PRODUCTS MADE OF POLYCARBONATE REINFORCED WITH GLASS FIBER FOR ELECTRO-TECHNICAL PURPOSES AND MANUFACTURING PROCESSES - Google Patents

Description

The invention relates to the use of mechanically and thermally stable, electrically insulating components or semi-finished products made up of 10 to 50 percent by weight Glass fiber reinforced polycarbonates or such thermoplastics exist which, like polycarbonates, have a practically linear structure, none in particular Have space-filling side groups and periodically polar in the molecular chain Contain groups, and where the glass fibers consist of hydrolysis-resistant material, have a maximum length of 3 mm, a thickness of 0.5 to 10 g, m and in plastic are evenly distributed and completely wetted by it, for electrotechnical Purposes.

The invention also relates to a method for producing for this use certain components or semi-finished products.

In electrical engineering, insulating materials that are replaced by thermoplastic Deformation processes can be processed into any shaped bodies, such as B. polystyrenes, styrene copolymers, polyolefins, polycarbonates, polymethacrylates, Polyamides, etc., to a considerable extent compared to thermosetting plastics, by pressing processes processable materials and, in particular, new possibilities for the designer opened.

The following reasons were essentially decisive for this: 1. Thermoplastic plastics can be processed more economically; 2. Can out of them particularly complicated and also thin-walled electrical construction parts or Foils or sheet-like semi-finished products are produced for later further processing; 3. the elasticity and the resistance to shock-like mechanical stresses are increased; 4. the electrical and dielectric properties are often essential improved; 5. Under the influence of climatic stresses only lesser ones occur Property changes. These advantages of the thermoplastic over the thermosetting But plastics are also accompanied by some disadvantageous properties; it This concerns the low mechanical stability, the low one Heat resistance and, in some cases, a relatively high susceptibility to cracking.

Attempts have been made to address these adverse properties to enhance.

From the Swiss patent specification 265 203 is a thermoplastic Mixture described in which the glass fibers are evenly distributed. From the for the ratio of length to diameter of the glass fibers given is to infer that the diameter is 0.25 to 12.7 #tm and the maximum length is 0.5 mm. It is a series of thermoplastic, organic compounds enumerated, with polyamides being particularly emphasized. Polycarbonates and these Similar connections are not mentioned, and there is also use for electrotechnical Purposes not addressed.

It is also known the thermal conductivity of pure polystyrene to be improved by adding quartz powder, but at the expense of the mechanical Strength and good processability. It has also been tried at a number of thermoplastics with relatively long glass fibers (> 10 mm) their stability, heat resistance, possibly crack resistance and to increase thermal conductivity.

As far as it can be determined, the incorporation of the glass fibers apparently by overmoulding a continuous strand of glass fiber with the respective one thermoplastic fabric is made on a screw press, and the conveyed The strand is cut into 10 mm long sticks.

Such a method allows the ratio of glass fiber content to vary slightly to the thermoplastic content, z. B. by changing the conveyor speeds the fiberglass strand or the thermoplastic melt, however, occurs as quite essential The disadvantage of such a method is the fact that the glass fibers of the conveyed Strand not evenly due to the thermoplastic melt and inside the strand are practically not wetted at all, what even made of such materials finished products is verifiable.

One is in the further processing, i. H. in the case of thermoplastic Deformation of such materials, e.g. B. by injection molding, forced to use machines use extremely high homogenizing effect, such as screw injection molding machines, halfway homogeneous; To obtain fault-free components with a better than the original one Wetting of the incorporated fibers. Nevertheless it does not succeed in this way Always get components of the same quality.

The influence of the melt viscosity of the respective thermoplastic shows by the fact that there are substances with an extremely low melt viscosity in the processing temperature interval according to the combination method described above for thermoplastics with glass fibers to form reinforced moldings that appear homogeneous still let process; however, in the case of substances with a higher melt viscosity, such as B. in the case of polycarbonates, however, the wetting of the glass fibers is even more incomplete. Defects in the interior of the reinforced moldings and an uneven, rough surface are unavoidable. In addition, the production is flawless, smaller, Complex shaped components that are predominantly used in low-voltage technology find, because of the glass fiber content required for the desired reinforcement Long-fiber reinforced thermoplastics (fiber length> 6 mm) virtually impossible. In the case of electrical insulating parts made of glass fiber reinforced thermoplastics, however In addition to an even, closed surface, complete wetting is also possible The fibers inside the molded parts are a prerequisite for exposure to moisture a decrease in insulation due to the formation of tracking paths along unwetted fibers and thus to avoid the inoperability.

The invention is therefore based on the object for the electrotechnical Application of certain, highly insulating components, such as B. plug, pin or Solder lugs, bobbins, holding bodies for electrical components, such as. B. Ferrites, or semi-finished products such. B. panels and profiles, made of thermoplastics indicate that compared to such workpieces from currently known thermoplastic Plastics both mechanically and thermally stable and in a simple way can always be produced with the same quality.

The object is achieved by the use specified at the beginning.

A length of glass fiber is particularly advantageous in this use from 1 to 2 mm and a fiberglass thickness from 1 to 4 #tm. The fiberglass content is, based on the total weight, preferably 20 to 30 percent by weight.

The process of manufacturing components designed for this use or semi-finished products is characterized according to the development of the invention, that the glass fibers used for reinforcement with finely divided, preferably granulated thermoplastic material premixed, then under reduced pressure in a Screw press incorporated into the melted plastic under the influence of heat and the material thus obtained using appropriately trained Nozzles and known extraction or shredding devices either into semi-finished products or is processed into granulated strands, both of which are then made from the granules Finished components as well as semi-finished products can be produced by methods known per se.

The incorporation of the glass fibers is preferably carried out under reduced pressure Pressures of 300 torr and less, preferably 1 to 10 torr, in the fill zone a screw press.

The surface of the glass fibers can be desized, or it can be it is advantageous to use glass fibers with a coating (so-called finish), z. B. are provided with a silane or volane coating. This coating preferably exists from the plastic to be reinforced with glass fibers, namely from polycarbonate or such a thermoplastic that is practically linear like polycarbonate Has structure, has no particularly space-filling side groups and in the Molecular chain periodically contains polar groups.

Have a plastic material reinforced with glass fibers in this way the components or semi-finished products technically favorably utilizable stability and Heat resistance, including the thermal conductivity and possibly the Crack resistance as well as the impact strength and the insulation capacity the known are considerably improved. In addition, the workability of the material on piston or screw injection molding machines.

In principle, for the production of the components or semi-finished products or the plastic materials for the products also use known processes; However, it has been found that for the production of such components or Semi-finished products, the properties of which are very demanding, see above specified method is advantageous.

Fine-particle plastic in the specified sense includes both powdery, spherical or granular material produced by cutting or grinding to understand. Among them is granulated material with the size of the granulate grain 2 to 4 mm in diameter and 2 to 4 mm in length are preferred.

As a mixing unit, it is expedient to use one over the plasticizing zone and the press head used a heated screw press in different zones. she should also be designed so that the material to be mixed under reduced pressure, if possible can be added in a continuous manner. The mix, consisting of the to be reinforced, optionally pre-dried thermoplastic insulating material in granulate or powder form and well-dried glass fibers as described further above Kind in proportions of 10 to 50, preferably 20 to 30 percent by weight, based on the total mixture, e.g. B. for discontinuous work in a suitable Mixing machine premixed and as a coarse mixture in the feed hopper of the screw press given, which is expediently provided with a device that has a uniform Material replenishment in the screw zone guaranteed. The screw press itself must be constructed in such a way that in the closed hopper with the plasticizing zone filled and, of course, pressure from a suitable suction pump under working conditions of about 300 torr, preferably 10 to 1 torr, can be maintained.

You can work in the glass fibers with complete wetting and avoid air inclusions, proceed in such a way that after loading the hopper the plasticizing zone and / or the press head are heated so high that the respective the substance to be reinforced is sufficiently melted, d. H. about 180 to 300 ° C. The extrusion process is then started, with a first one after the exit The delivery rate through the press head nozzle in the feed hopper is that specified above Pressure is generated. The initially further promoted, with numerous air pockets interspersed and milky in appearance strand is discarded until the promoted Mixture free of noticeable air inclusions, d. H. is well translucent. Of the Strand or, if a multi-hole nozzle is used, the conveyed strands can be fed into known way by a suitable; downstream device in granules cut from 2 to 4 mm in length and put on a piston or screw injection molding machine under practically the same processing conditions as for the unreinforced Fabric apply to be processed. You get even with a very complicated design flawless moldings.

The following table shows the changes in properties, the organic plastic used being a polycarbonate with a K value of 50 (7, measured on 0.5% solutions in chloroform) and the polycarbonate being used by transesterification of diphenyl carbonate 4,4'-Dioxydiphenylpropane-2,2 was prepared. Reinforced with fiberglass in the specified manner, fiberglass content Property unreinforced in percent by weight 10 I 20 I 30 45 Density ') [g / cm3] ................... 1.18 1.25 1.31 1.38 1.52 Shrinkage [° / o] ') ................. 0.55 0.29 0.23 Post-shrinkage [° / o] ') ....... ..... . 0.1 0.02 0.02 Flexural strength ') [kp / cm2] ........... 10004) 12504) 15104) 1750 1710 Impact strength ') [cmkp / cm2] ....... without breakage 87 52 38 26 Notched impact strength ') [cmkp / cm2] ... 25 5.6 5.0 4.5 4.0 Ball indentation hardness HK 252) [kp; cm2] ... 680 1145 1300 1410, 1620 Footnotes at the end of the table Continuation of the table Reinforced with fiberglass in the specified manner, fiberglass content Property unreinforced in percent by weight 10 20 I 30 45 Linear thermal expansion coefficient [° C-]. . . . . . . . . . . . . . . . 7.8-10-5 3.8-10-5 3.2-10-5 Heat resistance l) according to Martens [° C]. . . . . . . . . . . 110 117 126 132 137 Water absorption3) after 1 month [° / o] 0.36 0.30 0.28 0.28 0.25 Dielectric constant3) at 103 Hz and 25 ° C. . . . ..... ......... . ... 3.3 3.3 3.4 3.8 3.9 Dielectric loss factor3) at 103 Hz and 25'C. . . . . . . . . . . . 1.5.10-3 1.5-10-- 2.0-10-3 2.5.10-3 3.0-10-3 Specific volume resistance3) [S2 cm] ........................> 101 '>101',> 101 '>101'> 101 ' 1) Measured on standard small bars (4 - 6 - 50). 2) Measured on flat bars (4 - 10 - 50). 3) Measured on circular disks with a thickness of 1 mm. q) limit bending stress. The table first shows that the visual curl and post-shrinkage of the materials reinforced with glass fibers according to the invention are reduced to about half and one fifth, respectively. As a result, the components or semi-finished products according to the invention can be manufactured with high dimensional accuracy, an advantage; which is particularly important with today's requirements (miniature technology). As can also be seen from the table, the flexural strength, the ball indentation hardness, the linear thermal expansion coefficient, the dimensional stability under heat, the water absorption and the dielectric constant are sometimes considerably improved. The specific volume resistance is unchanged compared to the unreinforced material, which can be described as a very good result. The change in the dielectric loss factor takes place within limits which can be described as entirely acceptable for the stated purposes. Reinforcing with glass fibers also improves the thermal conductivity here.

Only the impact strength becomes noticeable through the reinforcement lowered. However, this effect is in the reinforcement of thermoplastics with short To describe glass fibers as a general phenomenon. So one observes that with thermoplastic insulating materials reinforced with short glass fibers that are non-polar or only have a weakly polar structure, this by incorporating short glass fibers The generally observed drop in impact strength is only an insignificant technical one uninteresting improvement in stability and heat resistance. Significant increases in properties in terms of stability and heat resistance is observed in thermoplastics with a polar structure, e.g. B. from copolymers Styrene and acrylonitrile in an approximate molar ratio of 1: 1 and a K value of 65. Even so, these improvements do not outweigh the drop in impact strength.

One that is surprisingly cheap for use in electrical engineering In contrast, according to the invention, a balanced change in properties is found in the case of very impact-resistant thermoplastic insulating materials, which have a practically linear structure, none have particularly space-filling side groups and periodically in the molecular chain Contain polar groups, as is particularly the case with polycarbonates, the are reinforced with fiberglass of the specified size and quantity.

Despite the observed drop, the impact strength and notched impact strength are in line still in an area that takes advantage of the substantially increased Stability and heat resistance. It is also surprising that that according to the procedure according to the invention, a similarly high gain in stability is achieved can be as with the incorporation of much longer glass fibers under incomplete Wetting. The invention offers a significant further advantage in the the glass fiber reinforcement significantly reduced the susceptibility to cracking of those susceptible to stress cracking 4,4'-Dioxydiphenylpropane-2,2 polycarbonates. That has been very problematic so far permanent encapsulation of metal parts with these substances prepared according to the invention Reinforcement no difficulties.

The substances reinforced according to the invention are suitable as above already briefly mentioned, not only for the production of moldings by injection molding, but also for the production of z. B. rod, tube or plate-shaped semi-finished products according to methods known for processing thermoplastics, e.g. B. by extrusion. The processing of such semi-finished products, e.g. B. to thin plates or panels that Find very diverse uses in the electrical industry, z. B. immediately can be combined with the mixing process by placing the screw press on which the next Mixing process described above is carried out with a slot nozzle and a downstream take-off unit. A separate implementation the mixing and processing process is of course also possible.

Such tabular semi-drawings show compared to the known composite materials based on paper phenolic resin, paper melamine resin, paper epoxy resin or Glass fabric epoxy resin and others various advantages: You have much better ones electrical and dielectric properties (see table) are always included Room temperature can be punched without cracks and creepage (the punching quality of a Polycarbonate semifinished products with 20 and 30 percent by weight short glass fiber content shows. after DIN 53488 grade 2) and can, if necessary, thermoplastic deformation, z. B. be subjected to a largely arbitrary profiling.

The method described allows various variants. The short glass fibers to be incorporated can be of the same fabric are impregnated before being mixed with the thermoplastic to be reinforced insulating material with a solution of low body content, so that the fibers are provided after removal of the solvent with a thin adherent over- train. The mixing process itself can, as already indicated, be carried out semi- or fully continuously by z. B. used a storage vessel directly connected to the hopper of the extruder, in which glass fibers and thermoplastic material to be reinforced are simultaneously premixed by a suitable device, or by removing glass fibers and the thermoplastic material to be reinforced from separate containers connected to the hopper of the screw press in the each desired quantity ratio in the hopper, mixed there and conveyed into the screw zone.

Although, as described, the components or semi-finished products according to the invention are preferably used in electrical engineering, according to the invention Reinforced thermoplastics can be used wherever there are improved properties of the kind described.

Claims (9)

Claims: 1. Use of mechanically and thermally stable, electrically insulating components or semi-finished products made up of 10 to 50 percent by weight Glass fiber reinforced polycarbonates or such thermoplastics exist which, like polycarbonates, have a practically linear structure, none in particular Have space-filling side groups and periodically polar in the molecular chain Contain groups, and where the glass fibers consist of hydrolysis-resistant material, a maximum length of 3 mm, a thickness of 0.5 to 10 #tm and in plastic are evenly distributed and completely wetted by it, for electrotechnical Purposes. 2. Use according to claim 1, characterized in that the glass fibers have a length of 1 to 2 mm. 3. Use according to claim 1 or 2, characterized characterized in that the glass fibers have a thickness of 1 to 4 μm. 4. Use according to claim 1, 2 or 3, characterized in that the glass fiber portion, based on the total weight, 20 to 30 percent by weight. 5. Method of manufacture of components intended for use according to one of claims 1 to 4 or Semi-finished products, characterized in that the glass fibers used for reinforcement premixed with finely divided, preferably granulated thermoplastic material, then under reduced pressure in a screw press under the influence of heat be incorporated into the melted plastic and the material thus obtained using appropriately designed nozzles and known extraction or shredding devices is processed either into semi-finished products or into granulated strands, in which case both finished components and semi-finished products according to known per se from the granulate Process are generated. 6. The method according to claim 5, characterized in that that incorporation under reduced pressure of 300 torr and less, preferably at 1 to 10 Torr, in the feed zone of the screw press. 7. Procedure according to claim 5 or 6, characterized by the use of glass fibers which have a desized surface. B. Method according to claim 5 or 6, characterized through the use of glass fibers with a coating (so-called finish) are provided. 9. The method according to claim 8, characterized in that glass fibers are used, the coating of which consists of the plastic to be reinforced.