Method for producing plastic and elastomeric composites.

p0001The invention relates to a method for the production of components made of plastics and elastomers referred to in the preamble portion of claim 1.

p0002According to such a method, for example, polyurethane components in the RIM or RRIM method are prepared. In the processing of polyurethane in this process, the starting materials polyol and isocyanate have compared to injection molding significantly lower viscosity. Said method is characterized in that as a rule of a component polyol air in quantities of 30 to 70 vol.% Is added and it is highly stretched in dosing to approximately 200 bar. Both components polyol and isocyanate are mixed with about 200 bar, and then to fill the mold cavity of the tool within one second.

p0003By entering the tool enters a sudden release of mixed under high pressure components air, polyol and isocyanate, thereby carried out an expansion of the compressed air. The finely divided air bubbles thereby creating a sort of foam inside out with a dense surface against the mold wall. In the manufacture of components made of polyurethane in the manner described, it is problematic to achieve a very smooth, pore-free surface of the components, the quality satisfies the demands on the paintability. Often arise surface pores, which make a complicated surface treatment required.

p0004The invention has for its object to provide a method of the aforementioned type, which enables the production of components with improved surface finish.

p0005The object is achieved in a method of the type mentioned according to the invention by the features in the characterizing part of claim 1. Advantageous developments may be found in claims 2 to. 6

p0006The invention is based on the finding that the method described the formation of pores depends on flow paths and flow rates in the tool, preferably in places with differences in wall thickness of the manufactured component, ie where a slowing of the flow rate is obtained. The inventive method makes it possible to position-dependent and time-dependent manner to rejuvenate the wall thickness of the manufactured component, for example at the rear during the mold filling process and to normalize towards the end of the mold filling process again and thereby control targeted at each critical component locations, the flow velocity.

p0007Another advantageous solution contains task claim 7 with an advantageous embodiment to claim 8. It is advisable to partial emphasis towards the end of the mold filling / solidification process (chemical crosslinking in thermosets and elastomers - solidification due to cooling of thermoplastics) apply. The partial reprint can make a huge impact far beyond the site of action and the geometry of the emphasis area also. Preferably, the partial reprint is angußfern made because there is the pore problem due to the long distance traveled flow paths and thus the decrease in the flow velocity is greatest. Long distances also require a considerable pressure drop in the tool. The original finely divided gas microbubbles are puffed up, clump together to bubbles and get amplified to the surface where they become a problem for a desired high surface quality. Using a localized reprinting, preferably angußfern. can be counteracted this process. It is very accurate, the time noted at which the partial holding pressure is applied. It is advantageous for this purpose to use those controls that operate reproducibly in short-term range. Due to the applied partial reprinting the surface quality is improved. The pore formation is reduced. Also can be lifted by the local emphasis for example, the density of the component in this region. Thus, the today and mold technology usually significantly different properties on angußfreien component end can be positively influenced. Both homogeneous component properties but deliberately willed locally different properties are achieved over its length or. It is understood that the application of the partial reprinting may be as the only measure to solve the problem already sufficient because already by an improved surface finish is achieved. Instead, the application of the partial reprinting can also be carried in addition to increasing the flow rate as an additional measure by a transverse to the flow direction of narrowing of the mold cross section, whereby all the more a resolution of gas bubbles is effected. Either is within the scope of the invention.

p0008Further advantageous embodiments of the inventive method result from the claims 9 - 12. It is clear that the invention is not only suitable for air-charged polyurethane RIM / RRIM systems, but generally charged for similar low-air-charged, nitrogen-laden or with other gases systems can be used and can be influenced in a simple manner there orientation processes during mold filling. In the same way can be personalized with the inventive method also location-dependent orientation states control the injection molding process. Here is wearing only compared to polyurethane RIM / RRIM process significantly higher pressures bill. The inventive method is also applicable even when extrusion, including glass mat reinforced thermoplastics, or in SMC (sheet molding compound) presses where also location-dependent flow and orientation processes can be controlled in an inventive way. The inventive method can be carried out very easily and without much effort on the tool side. It is advantageous also in that the mechanical properties of the component, in particular the component stiffness and component strength, are in no way impaired.

p0009The invention further relates to an apparatus for the production of components made of plastic and Elstomeren referred to in the preamble of claim 13 type. The invention is with respect to this apparatus, the same task, which is indicated at the beginning, is based. This object is achieved according to the invention in such a device by the features in the characterizing portion of claim 13. Advantageous further features of the invention and embodiments to contain the claims 14-43. The thus designed tool is relatively easy and safe to operate. There no great additional effort, so that existing tools can be accordingly without great effort, especially without major cost, upgraded conditionally depending on the case later.

p0010Further details and advantages of the invention will become apparent from the following description.

p0011The full text of the claims above alone is not reproduced to avoid unnecessary repetition, but instead referred only by quoting the claim number on it, but making all these features claim must be regarded as essential to the invention and expressly disclosed at this point. Here are all mentioned in the preceding and following description features as well as the removable only from the drawing features more components of the invention, even if they are not highlighted and especially not mentioned in the claims.

p0012The invention is explained in more detail with reference to embodiments shown in the drawings. Show it:<dl id="dl0001"><dt>Fig. 1</dt><dd>a schematic section of a part of a tool for the manufacture of components made of plastic according to a first embodiment,</dd><dt>FIG. 2 to FIG. 5</dt><dd>are each a schematic section corresponding to that in Fig. 1 of a tool according to a second or third or fourth or fifth embodiment.</dd></dl>

p0013In the first embodiment in Fig. 1, the interest here is part of a tool 10 is shown for the manufacture of components made of plastic. The tool 10 is at least two parts and has an upper tool part 11 and a lower mold part 12, the 13 and 14, with their facing surfaces Formraumwandungen that define a mold cavity 15 therebetween. The Formraumwandungen 13 and 14 are designed so as that, also schematically requires at 16 indicated component made of plastic with regard to its back member 17 and front member 18 produced in the mold space 15 in Fig. 1 in section.

p0014In part 16 of plastic is for example, a component 16 made of polyurethane. The tool 10 is part of a device for the processing of polyurethane in the RIM / RRIM method. This is by air-charged systems.

p0015The processing of polyurethane in the RIM / RRIM process is characterized in that the starting materials polyol and isocyanate are low compared to the plastic injection molding viscosity. In this method, the component polyol will air in quantities of 30 to a maximum of 70 vol.% Mixed and these highly stretched in dosing to approximately 200 bar generally. In the mixing head, the two components polyol and isocyanate are mixed with about 200 bar to fill then within one second the mold cavity 15 of the tool 10th With the entry into the mold cavity 15 of the tool 10 enters a sudden release of mixed under high pressure components air, polyol and isocyanate, thereby carried out an expansion of the compressed air. The finely divided air bubbles thereby creating a sort of foam inside out with a dense surface against Formraumwandungen. 13 and 14 In this production of components made of polyurethane 16 in RIM / RRIM process is a paintable surface finish on the component front panel 18 and possibly also on the component back 17 can be achieved. Air voids, preferably at certain points in the mold cavity 15 of the tool 10 occurring, often lead to the formation of pores on the surfaces of the component 16. In order to meet the demand for paintable surface quality, is then at these sites often wasteful surface treatment necessary. These disadvantages are in the shown air-charged tool 10 eliminated by the measures described below in a simple manner.

p0016In the tool 10, an insert 19 is at least included which has at least has a movable surface portion 20th In the illustrated embodiment of the insert 19 preferably in the upper tool part 11 is, with its 13 Formraumwandung the component backside is shaped 17th The insert 19 is accommodated there in a specially shaped recess 21st The picture is taken here by the undercut, so by positive engagement. The recess 21 has for this purpose in direction to the wedge-shaped Formraumwandung 13 tapered walls 22 to 25 and within the walls 24 and 25 also have recesses 26 and 27 respectively. 19 is also the use according to this particular shape of the recess 21 formed. The insert 19 can be flexible and, if necessary, inflatable with advantage at least in the region of its location-variable surface portion 20th the introduced into the recess 21 insert 19 can thus be adjusted by deforming the contour and dimensions of the recess 21 by flexible training. The insert 19 is zBaus an elastomer, eg hard rubber part, formed. So that it can be inflated, it has at least one hollow chamber 28 which has been introduced by specific manufacturing technique in the manufacture of the insert 19th The hollow chamber 28 is arranged with preference so that the insert 19, especially the spatially variable surface portion 20 can be inflated, so that it has in FIG. 1 with dashed lines indicated, bulging contour in this state. Here, the hollow chamber 28 may be aligned approximately parallel to Formraumwandung 13 of the tool part 11 in the deflated state of the insert 19 and formed as a relatively narrow rectangular chamber beidseitg left and right cross-section larger chamber portions. The insert 19 contains internally a debouching via an indicated nozzle 29 into the hollow chamber 28 channel 30. The tool part 11 contains a in communication with the channel 30 channel 31 via the channels 30, 31 is the hollow chamber 28 to a not further shown connected gas pressure source and the pressure can be controlled.

p0017In the upper tool part 11 form-fit held insert 19 forms, with the at least has a movable surface portion 20 a part of the Formraumwandung 13 of this tool part 11. The source of gas pressure and from there via the channels 31, 30 fed into the hollow chamber 28 pressure medium forms a this insert 19, especially its variable site-surface part 20, associated with drive means, which operates in this area part of the twentieth By means of this drive means of the surface portion 20 is required, with a reduction of the cross section of the mold cavity 15 at this point in the in FIG. 1 indicated by dashed lines form adjustable or in opposite directions, see normalization of mold cavity cross section at this point in the initial position shown in FIG. 1 by solid lines adjustable. In this normal state, thus the face member 20 extends within the usual shaping contour of the Formraumwandung 13. In contrast, the surface portion is in the inflated state of the insert 19 and indicated by dashed lines state This shaping contour of the Formraumwandung 13 via under reduction of the cross section of the mold space 15 in this area.

p0018In this way, it is possible that in this gas-loaded tool 10 at predetermined, critical points of the manufactured component 16 corresponding sites of the tool 10, where one placed corresponding inserts 19 described type, the flow velocity of the entering into the mold cavity 15 mix during the mold filling process varies and controls. Thus, one can the flow rate at the beginning of the mold filling process, first by enabling the insert 19 and inflation of the face member 20 to increase in the dotted in Fig. 1 position, and then normalize the end of the mold filling process again by the surface part 20 again, the solid in FIG. 1 occupies position lines shown. It is thus possible, at desired locations of the tool 10 to reduce the cross section of the mold space 15 to the beginning of the mold filling process and normalize the end of the mold filling process again. This can be by means of the connected in the described manner to the insert 19 by gas pressure source of gas pressure and / or pressure fluid, eg. B. Pressure oil accomplish. So you can control the gas pressure with the internal pressure in the mold cavity 15 of the tool 10th This can, for. B. carried out preferably by means of a high-speed control device. Particularly advantageously, it may be, when the internal pressure in the hollow chamber 28 of the insert 19 is chosen at the beginning of mold filling is greater than the internal pressure in the mold space 15 and towards the end of mold filling process is less than the internal pressure in the mold space 15, thereby the at least one inflatable and vorwölbbare surface portion 20 of the insert 19 is bulged to the beginning of the mold filling process and thereby the mold cavity cross-section is reduced and runs back into its normal state within the rest of the shaping contour of the Formraumwandung 13 towards the end of mold filling.

p0019The tool according to the invention thus makes it possible, dependent on location, the wall thickness of the product to the component 16 through the insert 19 at the component back 17 to rejuvenate during the mold filling process and normalize the end of the mold filling process again and thereby make a flow rate control at critical points of the manufactured component 16 , In this manner, to influence the flow paths and flow rates in the mold space 15 of the tool 10 during mold filling such that the formation of pores on the surface of the molded portion 16 is avoided. This may be a function of location and time pending perform during mold filling. In this way, the formation of pores and thus an unsatisfactory surface quality is prevented without this example, has an adverse effect on the mechanical properties of the thus prepared component 16, in particular the component stiffness and strength of the component.

p0020Although above the invention based air laden polyurethane RIM / RRIM systems has been described, it can generally be used for similar low-laden air, nitrogen-laden or laden with other gases systems. So there is much less viscous melts in the injection molding process. Inventive tools are also used to influence orientation processes during mold filling. When used in injection molding can be location-dependent control orientation states by means of inventive tools. On the tool side, in particular with regard to the insert 19, while the considerably higher in injection molding compared to polyurethane RIM / RRIM process pressures in the mold space is to wear 15 bill. In addition, the inventive concept can also during extrusion, are used in particular glass mat reinforced thermoplastics, application, because here position-dependent flow and thus orientation processes play an important role in the later part properties, so that the latter can be favorably influenced by site-dependent control of orientation states here.

p0021It is advantageous when varying the flow rate, in particular the transverse to the flow constriction to increase the flow rate and resolution of gas bubbles makes, as long as the molding material is still flowable, wherein the constriction is then withdrawn in order to avoid a weakening of the component ,

p0022Not particularly is pointed out in FIG. 1, the tool 10 in the region of the insert 19, may be provided with a heater to preferred sites, in particular. Thereby, it is possible to vary the flow velocity thereby to increase for example, first and then to return to normal, that heated prescribed positions of the tool 10th This heating can preferably control time-dependent. The heater can serve specifically the heating of the insert. The heater may be formed of at least a hot runner or formed as an electric heater and preferably be time-dependent controllable.

p0023The possibility of heating of the insert 19 is separate to the rest of the tool 10 further essential. In particular with viscous thermoplastic and Duroplastschmelzen - but also in polyurethane systems - a considerable flow resistance is built up by the wall thickness taper, which requires a higher injection pressure. Possibly could impede the complete mold filling the transverse to the flow constriction. All these disadvantages can be eliminated by heating the insert 19th Heating can, for example, by an induction coil in the insert 19 or by a hot runner. The heating can reduce locally or repealed otherwise the solidification or thickening due to cooling of the melt in the mold wall. For liquids, such as PUR, can be through the local heating due to emerging local additional viscosity decrease an additional change in the flow rate, and that an additional increase of reach. Although this increases the chemical reaction speed. However, it involves high-speed operations so that the influence of the viscosity will predominate. Such heating is not only possible with inserts 19 according to the first embodiment, but also in metal and plastic inserts. In metal and ceramic inserts can be additionally provided that an electric heater is provided, even time-dependent control the heating to save energy, for example, or special flow effects, ie viscosity reductions, to achieve time-dependent.

p0024The apparatus shown in Fig. 1 also makes it possible, especially towards the end of mold filling process at predetermined, critical points of the manufactured component 16 corresponding locations of the tool 10 has a partial bearing on the component to be molded exercise. It is appropriate in most cases to make the variation of the flow rate or the application of the partial reprinting of angußfernen points of the tool 10th The partial reprint is applied towards the end of the mold filling / solidification process (chemical crosslinking in thermosets and elastomers or solidification due to cooling of thermoplastics), where it affects the geometry of the emphasis area also. This is based on the following consideration. Preferably the insert is located 19 angußfern because there the pores problem due to the long distance traveled flow paths and thus the decrease in the flow rate will be greatest. Long distances also require a considerable pressure drop in the tool 10. The finely divided gas microbubbles inflate to clump together to bubbles and get amplified to the surface where they become a problem for one worth striving for high surface quality. Using a localized reprinting, preferably applied angußfern, this process can be counteracted. It is precisely at the time when the acts of emphasis. For this purpose, suitable controls that operate reproducibly in the range of thousandths of a second recommended. Furthermore, can be set via a local reprinting eg raise the density of the component region angußfernen 16th This allows the current in tool technology usually significantly different properties on angußfreien component end positively influence so that homogeneous component characteristics over its length or different desired local properties can be achieved selectively.

p0025In the second embodiment shown in FIG. 2 are for the parts corresponding to the first embodiment, used by 100 large numerals, thereby to avoid repetition of the description of the first embodiment by reference.

p0026In this second embodiment in FIG. 2, the insert 119 a plate 140 to which the spatially variable surface part forms here 120th The plate 140 covers the rear side thereof a pressure chamber included in the upper tool part 111 141, which is connected via the passage 131 to a gas pressure source, not shown. Under the pressure of the pressure medium in the pressure chamber 141, the plate 140 is ortsverändebar. The plate 140 is vorwölbbar due to the pressure of the pressure medium into the dashed lines in Fig. 2 indicated form, can be thereby the cross section of the mold cavity 15 at this point, if necessary, reduced or normalized by opposite snapback movement of the plate 140 to the initial position again. In the simplest case, the plate 140, for example from a spring, in particular of a metallic leaf spring and this example of a bistable elastic spring, which can be resiliently defer drop in pressure in the pressure chamber 141 by itself in the position shown, the pressure chamber 141 towards convex starting position , The plate 140 is fixed for example on both sides by at least one fastener 142 on the tool part. This is only an example of a vorwölbbare under the pressure in the pressure chamber plate 141 140th

p0027In the third embodiment shown in FIG. 3 of the application 219 is dimensionally stiff. He has a piston 250 on which in the drawn with dotted lines position is pushed out slidably with a guide member 249 within a rear thereof arranged pressure chamber 241 in the upper tool part 211, and under the pressure of the pressure medium in the pressure chamber 241st The pressure chamber 241 simultaneously forms the cylinder in which the piston 250 is guided with its guide part 249th

p0028The pressure chamber 241 is connected via the passage 231 in the tool part 211 to the gas pressure source, not shown. Upon extension under the pressure of the pressure medium, the piston 250 is secured against complete extension through the larger-diameter guide portion 249, which then abuts against a shoulder 251 in the tool part 211th In another, not shown embodiment, the piston 250 is designed as a hollow piston which contains the back pressure chamber in its hollow interior so that it an additional pressure chamber similar to the pressure chamber 241 in the upper tool part 211 is not required, but only the cylinder bore for receiving and guiding the piston. This can be saved in the axial direction of the piston space.

p0029The operation of the tool 110 in FIG. 2 or 210 in FIG. 3 generally corresponds to that which is initially explained in detail with reference to the first embodiment shown in FIG. 1.

p0030The stroke of the piston 250, with the above is in accordance with this gesrichelter for narrowing the mold cavity cross-section line, for example, can be limited by means of exchangeable shims. These liners can be eg between the guide member 249 and the shoulder 251 attach. As can be seen, the end forming the piston 250 on the mold cavity cross section above the surface part 220, this is aerodynamically shaped to its passing into the mold cavity 215 top, and is indeed curved convex here. Not further shown but it when the piston 250, and that at least the stationary variable-surface part 220, at least on the the mold cavity 215 side facing a not particularly exposed wear protection layer 252, for example, from plastic, ceramic od.dgl.besteht is advantageous. This provides protection against all kinds of abrasive materials is created and increases the service ability of the piston 250th Such abrasive materials are, for example in the polyol short fiber contained further but also quartz, talc or the like.

p0031Not further shown is a plunger 250 associated with heating, by means of the latter can be heated. The heater is designed for example as electric heating and time-dependent controllable. For this purpose, the same applies as mentioned for the first embodiment in Fig. Was executed. 1 may be applied also by means of the piston 250, if necessary, a partial reprint. In this respect the same applies, as mentioned for the first embodiment in FIG. 1 is carried out, is incorporated herein referenced to avoid unnecessary repetition.

p0032In the fourth embodiment shown in Fig. 4, the insert 319 as in the first embodiment in Fig. 1 flexible. He has a membrane 354, which on the mold cavity 315 facing side carries the surface portion 320 and may also be provided on this page with a wear-resistant coating, not shown further. The membrane 354 covers a back pressure chamber 341 disposed thereon, which is connected via the passage 331 in the tool member 311 to the gas pressure source, not shown. The membrane 354 is fixed to the tool part 211 by fasteners 342nd It is under the pressure of the pressure medium in the pressure chamber 341 auswölbbar elastically into the position shown with dashed lines position. If this pressure from the pressure chamber 341, the membrane 354 is under the pressure prevailing in the mold cavity 315 backpressure opposite directions in this direction deferrable in the illustrated starting position. Since the membrane 354 under the pressure in the pressure chamber 341 in the dashed position vorwölbbar concerns attending a favorable flow profile. In another, not shown embodiment 4 is provided as a rolling diaphragm or the like as a disc-shaped diaphragm 354 of FIG.. The membrane 354 is elastic at least in limits. It consists, for example, or the like from an elastomer plastic. With regard to further features, in particular the anti-wear layer and the heating device, referenced in the foregoing description, where these additional features in the fourth embodiment shown in FIG. 4 may also be given.

p0033All embodiments have been explained in FIG. 1 - 4 in common with regard to the operation of the insert that the operation is based on the back side mounted pressure into the mold cavity cross-sectional narrowing position result in a movement, which is indicated by dashed lines, while the provision as takes place solely under the back pressure in the mold cavity or the latter is the trigger for the provision, which applies as for the embodiment in FIG. 2.

p0034In the fifth embodiment shown in FIG. 5 one at the use 419 special drive device 460 is provided instead. This comprises a hydraulic cylinder 461, which is controlled by a servo valve indicated rapid 462nd

p0035Incidentally, the fifth embodiment is similar to FIG. 5 to the third embodiment in Fig. 3. There is the following difference, however. While in the third embodiment in Fig. 3 of the local piston 250 to surface portion 220 forms at its end 5 of the piston is in the fifth embodiment in FIG. 450 guided in a bore 463 of the tool part 411 displaced, the piston 450 at its end 464, which is also curved convexly outward, presses against a firmly clamped membrane 465, and this bulge to the narrowing of the cross section of the mold space 415, as shown in FIG. 5, the left of the center line shows. In the retracted state of the piston 450, the center line 5 of the shown in Fig. Right, the membrane 465 closes around the mold cavity 415 with the facing surface of the tool part 411 from. In the fifth embodiment shown in FIG. 5 thus has the diaphragm 465 to spatially variable surface portion 420.

p0036The membrane 465 is supported by a frame 466, which is held replaceably on the tool part 411, the edge non-positively and / or positively held. The membrane 465 is designed for example in the unloaded state at least approximately cup-shaped, the edge portion 467 is under attacked from the frame 466 from below and pressed against the inside of a bearing surface in the tool part 411th In the area of ​​the edge portion 467, the membrane has 465 a projecting toward the mold cavity 415 bead 468 which is received in a corresponding seat 469 of the frame 466th In this way, a positive support is given. It is understood that the ratios can also be kinematically reversed. The diaphragm 465 is, for. Example, from an elastomer. It may preferably be provided on the mold cavity 415 facing side with a wear-resistant coating. The frame 466 is removably received in a recess 421 of the tool part 411 and fixed there by means of screws 470th In this way, the frame 466 with the membrane 465 is easily replaceable. The stroke of the piston 450 is adjustable and limitable. serve to stroke limiter as replaceable liners 471, which can be placed back between the tool part 411 and a larger-diameter end shoulder 472 of the piston 450 and are interchangeable there.

p0037also apply to this fifth embodiment in FIG. 5 otherwise the other features which are already explained. The operation of the tool 410 also corresponds to that of the preceding embodiments.