DE2461631A1 - DEVICE AND METHOD FOR PROCESSING A CONTINUOUS FIBER HANG AS A REINFORCEMENT MATERIAL - Google Patents

Description

LAWYERS

dr. JUi ?. d;? l. ~ chem. waiter beil 24, Dec. 1974

or! 'jlTr.' Pit-Cli-JiV ,. H.-J. WOLFP
DR. JuR. HAK3 CHR. 3ElL

FRANKFUkTAM MA! N-HIGHEST

AOELONSTRASSE 58

Our no. 19 606 Pr / br

Exxon Research and Engineering Company Linden, N.J.j V.St.A.

Device and method for processing a continuous fiber strand as reinforcement material

The invention relates to a device and a method for the uninterrupted introduction of continuous fiber reinforcement materials in a single screw extruder as opposed to twin (more) screw extruders and in contrast to the introduction of staple fibers and the products resulting therefrom. Molded articles, including Pellets are thereby produced in a continuous and expedient manner with good dispersion of the resulting short reinforcing fibers in the plastic moldings, which are extruded through the shape of the Extruders were obtained.

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It has long been known that various polymers and other materials, e.g. elastomers and plastics, can expediently be mixed, processed and handled in an extruder and finally to pellets, which are suitable for further processing or can be extruded directly into a final molded body.

In recent years there has been the use of fiberglass as a filamentary reinforcement material in thermoplastic (RTP) bodies has become a growing and important practice in the plastics processing industry. These bodies have greatly improved properties over those that contain only the base polymer. The use of glass and other filamentary fibers will increase at quite a rate, since the quality demands on plastics will be considerably higher in the coming years.

The physical properties of thermoplastics can thus be varied by adding glass fibers Way to improve. Staple glass fibers are either separated or premixed with the plastic powder or pellets fed to the feed inlet of an extruder, and that Whole is homogenized after the plastic has melted. When using this system, the The length of the individual glass fibers is often shortened in such a way that their reinforcement function is reduced.

The wear on the extruder is also very great and the Products often contain harmful amounts of material from the screw or barrel.

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When using glass fibers that are too long Lengths are cut (L / D> 250), the separated casts or common feeding, especially in the case of a high proportion of glass fibers, considerable difficulties on.

It is also known that glass fiber reinforced thermoplastics can be formed by extruding materials that are separated entered can be produced. The plastic material comes in powdered or granulated (pelletized) form fed through the feed inlet of the extruder and melted in the kneading zone.

Homogenizing process After the last / _ will be in the first stage Glass fibers of short length are added at the decompression zone and mixed with the melt. To this The length of the fibers is subject to little or no change during the mixing process. The fibers should accordingly be precut to the desired length, for example 0.1 to 1.5 mm. However, it is technically difficult to feed these short fibers evenly.

It is also known to use a continuous glass fiber strand to be introduced into a plastic melt and extruded without breaking the fibers or glass fiber bundles to be applied to the surface of plastic threads after they have been extruded through nozzles.

In both cases, the glass fibers do not advertise homogeneously in the Plastic mass distributed, but lie in bundles parallel to the axis of the pellets. It is not always possible

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lent to process the pellets made in this way. Due to the inhomogeneous distribution of the glass fiber components, thin-walled and complex bodies can be created cannot be produced without difficulty.

Various efforts have been made to overcome these difficulties. One of them will in US Pat. No. 3,520,027, wherein separate streams of fibrous material and powdery Polymer can be layered and poured into an extruder funnel.

Another proposal, which some seem to promise is described in US Patent No. 3,304,282, in which continuous glass fibers are inserted into the vent hole of a twin screw extruder, screw the More, ^ll the mesh, and vent and Knetein * - devices such as kneading discs , Kneading blocks and / or adjustable spaces.

Although the use of a twin screw extruder is a useful technical advance over previous ones Methods means, it has the disadvantage that a twin screw extruder is an extremely expensive piece of equipment is. It would therefore be exceptionally useful and economically important to be in would be able to produce a continuous strand of fibers on a single screw extruder to process and at least the processing economy and product quality as they can be achieved using the much more expensive one

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Twin screw extruder can be achieved.

The invention relates to a new single screw extruder device and a method, wherein a sequence of functionally different screw elements in a certain configuration and sequence, based on a opening for the introduction of a continuous reinforcing fiber strand, are selected and arranged so that excellent dispersion of the resulting staple fibers (formed in situ) while also making excellent fiber reinforced extruded products.

The following drawings serve for further explanation the invention.

Figure 1 is a schematic side view of a cross section of the working portion of a preferred embodiment the extruder device according to the invention;

Figure 2 illustrates a preferred mixing device;

Figure 3 illustrates another mixing device that includes an interrupted thread;

Figure H shows a full cross-sectional view of a preferred extruder device, with the individual screw elements shown in their preferred position.

It is important to note that the theoretical Reinforcement ability of fiber reinforcements in large

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Dimensions of the length / diameter (L / D) ratio of the fibers (Aspect ratio) depends. This ratio must be quite high, e.g., about 300 to 1, preferably 200 to 1 and more preferably 100 to 1. If the pasers are too short, the desired reinforcing effect will be minimal or nonexistent.

One of the advantages of the invention is that not only continuous fiber reinforcement strands in economical and expediently can be used, but that the pasers produced by the automatic shearing action arise inside the extruder, have the correct length / diameter (L / D) ratio.

Another advantage of the invention is that there is little or no polymer material to be treated The opportunity is given to stack up or to collect small balls or lumps separate from the reinforcement material *.

The device according to the invention can expediently be used for any polymeric material which can be handled by an extruder and which can be improved by the incorporation of relatively short-thread or fibrous reinforcing material. The main use for the device according to the invention is in the processing of thermoplastics, such as polyolefins, polyvinyl chloride, styrene homopolymers and copolymers, polyesters, polyamides, nylons, polycarbonates, engineering plastics and acrylates.

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It is also possible to use the method of processing material that is normally considered to be thermosetting Plastic is said to be applied at a point before the crosslinking reaction has finished and wherever the material is still in a state in which it can be heat-softened internally and processed.

Processable materials also include all types of elastomers including butyl rubber, Polyisobutylene, ethylene-propylene elastomers, ethylene-propylene-diene terpolymer elastomers and their mixtures with themselves and with other materials such as plastics.

Blends of all different types of polymers including elastomers, thermosets and Thermoplastics can also be processed with the aid of the method according to the invention. It is also possible in the polymer to be processed in each case graft reactions perform, so that a simultaneous grafting and incorporation of thread-like materials takes place. There are several simple and practical ones Grafting process. For example, the GB-PS ' 679,562, U.S. Patent 3,177,269, and U.S. Patent 3,177,270, all of them Method of grafting in an extruder.

The extruder may conveniently be arranged in a sequence wherein the grafting reaction occurs at one point takes place before the introduction of the continuous fiber or thread strand. It is also possible to use the information in the U.S. S.N. 240 494 to carry out the grafting reaction described.

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This patent describes various monomers and other issues relevant to this grafting reaction.

The extruder device and the method for the continuous introduction of continuous filament materials can appropriately attached to known extruder reactions and become part of it.

The polymer material to be treated in the extruder can in any convenient form including granules, chips or pellets.

Generally speaking, one application of the invention is to produce glass-containing pellets that are in a precompounded form are to be sold to the end former. Except, the deformer uses such precompounded Pellets, it is generally desirable to mix powder with glass and not pellets because better dispersion of the glass fibers in the final molded body is achieved. Where the appearance of the surface importantly, the pre-compounded pellets reduce the appearance of fiber clumps on the surface of the Shaped bodies that would appear if ordinary pellets were mixed with glass. This can be a be a definite advantage where aesthetic considerations play a role, especially large ones Moldings.

Continuous fiber strands, in particular glass fiber strands, the from several (sometimes up to 100) fiber bundles with a very large number (sometimes more than 10,000) individual, threads are particularly suitable. Single threads

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have a mean diameter of about 10 to ΙΟ "cm. The pastes can be made with conventional sizing agents, such as plastics, starch, various silanes or complex chromium compounds. In general, it has been found that the silane sizes improve the adhesion to thermoplastics. It is also known that the graft polymers adhere well to fibers, which have been treated with a suitable functional silane such as an amino, epoxy or chlorosilane. However, graft polymers adhere exceptionally well to glass fibers that are completely free of any sizing agents are.

Another advantage of the invention is that pellets or moldings with very high glass concentrations are readily available.

In general, the glass content of molded bodies which have been extruded from the extruder is from about 5 to 90 », preferably 10 to 60 and particularly preferably 15 to 50 wt -.% Filamentous fibers, in particular glass fibers.

Although glass fibers are preferred, it is possible to use other fibers that have reinforcing properties own. These include natural fibers, such as asbestos, and synthetic fibers, such as DuPont's polymer B, polyimide fibers, Fibers made from polyparabanic acids and polyhydantoins.

It will now be returned to the figures in detail, the scheme of Figure 1 is suitable for understand the overall device concept. The feed section 11 of the extruder 10 is "a common one."

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The decompression section 12, which follows section 11, is equipped with an opening 13.

The key to the decompression section is using a section with a relatively small one Core cross-section so that the pressure within the decompression section 12 is reduced and fiberglass strands or other thread-like strands can be fed to the opening 13 without them Immediately confuse how that at this point in a snail core with a relatively large cross-section of the Would be case.

It is likely that the strand would entangle itself on a large snail core. aside from that a core with a relatively large cross section would pump the polymer out of the opening through the the strand is to be fed continuously.

A particularly preferred embodiment is to have a multiple-thread worm in the decompression section 12, such as a double-thread worm, albeit a common single-thread worm is satisfactory.

The decompression section 12 in the extruder 10 is immediately followed by the homogenization zone Ik , which has the function of conveying the mixture of polymer and fibers away from the opening 13 (vent hole). It also develops the pressure that is required to move the resulting polymer-fiber mixture through the next

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Step, namely the mixing section 15, where there is good mixing of the glass with the polymer melt .

It is also usually required to go into the decompression stop 12 to incorporate a trap (not shown) to prevent the polymer from entering the opening 13 (vent hole) rises and thus the prevents filamentary material, e.g., fiberglass strand, from entering the extruder device.

Homogenization zone 16 is used to provide a Stage for developing the pressure required to pass through the resulting well mixed Paser polymer mixture poking the holes at the end of the extruder 10.

All screw elements used can be standard designs be. The novelty and practicality of the device consists in the combination of the special Arrangement and cylinder configuration and position of the opening in relation to these various screw elements to achieve the particular unique purpose set forth here. The novelty of the Process consists in the sequence of process steps, which consist of continuous processing of fiber strands allows to obtain a polymer / short fiber composition.

The elements of the mixing section 15 can be Egan mixers. These particular facilities are shown in Figun-2 Figure 3 illustrates wherein the core has a series of channels cut into the periphery of the device are. This has a number of dead spiral channels

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on the periphery of the core. When the polymer and glass mixture is subjected to pressure, it becomes out of the Inlet channels pushed out and over the outer surface to the outer channels. This results in a thin layer mixing of glass and polymer melt under very high shear rates.

In a preferred embodiment of the invention, two such Egan mixers are back-to-back in Mixing section 15 used.

Another type of mixing device that is in the mixing section 15 can be suitably used is a helical shape, the discontinuous helical shape Has threads on the core.

FIG. 3 illustrates an embodiment of a screw element with a discontinuous thread.

Figure 4 illustrates an actual cross-sectional view of a preferred single screw extruder incorporating the specific elements of the invention set forth herein. It is essentially a more detailed implementation of the scheme of FIG. 1 and is used to expressly show preferred embodiments. The same numbering system ₍ as already described) is used therein.

The extruder apparatus and the method of using the same can be illustrated in connection with that illustrated in FIG Embodiment will be explained.

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In actual operation using the configuration of Figure 4, a 5 cm extruder was used with a Length η / diameter (L / D) ratio of 36: 1 used, wherein the extruder was divided into 36 units of the same length. Each of these units is shown below referred to as a 0 unit. The polymer was fed into hopper 17 at the initial unit of the extruder 10 and introduced into the loading zone 11, in the there is a feed screw 17, which is one of several individual screw elements, as in individual is described here represents.

The loading section as shown in FIG contains, towards its end, eirfliomogenization zone-like Section followed by a decompression section 12, which is located at 15 0. Of the The fiberglass strand was inserted into the opening .13, and ran through the 50 long decompression section 12, the 5 0 long homogenization zone 14, the 4 0 long mixing section 15 (double 2 0 Egan mixer) and the 8 0 long final homogenization zone 16.

Polypropylene powder, which was introduced into the hopper 17, was used as the plastic. The fiberglass strand was a multi-thread strand * The resulting glass fiber-containing polypropylene pellets had a good looks with no frayed edges. When molded into a large test panel, they had a good one Appearance, and the plate performed well when tested for physical properties.

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Claims (16)

Patent claims: /1./ Process for the continuous introduction of a thread-like reinforcing material in a single-screw extruder, characterized in that one A. A heat softenable polymeric material into one Introduces an extruder, which has a single movable displacement screw with different core cross-sections to demarcate several specific zones arranged in the order given namely: loading zone, decompression zone, first homogenizing zone, mixing zone, second homogenizing zone / has; B. introducing this heat-softenable polymeric material directly into the loading zone, so become soft lets that it is conveyed by the screw of the loading zone into a decompression zone, regulates the polymer volume so that it is smaller in the decompression zone than in the charging zone and thereby creating a reduced pressure in the decompression zone; C. a continuous filament reinforcing material into that which has been heat softened Introduces polymer containing decompression zone through an opening therein D; with the aid of the pumping action of the first homogenizing zone, the heat-softened polymer and the thread-like polymer Reinforcing material in the mixing zone ■ promotes the heat-softened polymer and the thread 509828/08 6 3 Shaped material is subject to mixing forces that are sufficient about the formation and dispersion of small individual staple fibers from the thread-like material to effect these fibers in the polymer, and E. then the well-mixed mixture of staple fibers and heat-softened polymer through a Extrusion opening using the second homogenizing zone as a pressure generator for the transport promotes. 2. The method according to claim 1, characterized in that there is used as the thread-like material glass fiber strand. 3. The method according to claim 1 or 2, characterized in that the mixing forces by Egan mixer applied thin film high shear forces. l ». Method according to one of Claims 1 to 3, characterized characterized in that the heat-softenable polymer with one or more reactive compounds either before mixing with the filamentary material or simultaneously with mixing with the thread-like material grafts. 5 .. The method according to claim Ί, characterized in that one of the reactive compounds is acrylic acid, glycidyl acrylate or himic anhydride (Himic anhydride) used. 509828/0863 6. The method according to any one of claims 1-5, characterized in that the polymer is a Cp bis Cg olefin polymer used. 7. The method according to claim 6, characterized in that the polymer is either a high or low pressure polyethylene used. 8. The method according to claim 6, characterized in that the polymer used is polypropylene. 9. The method according to claim 6, characterized in that an elastomer is used as the polymer. 10. The method according to claim 9, characterized in that the elastomer is an ethylene-propylene copolymer or an ethylene-propylene-diene terpolymer is used. 11. Extruder device, characterized by A. a hollow extruder cylinder with outer, inner, beginning, middle and end parts, B. a single screw extruder, composed of individual screw core elements with different cross-sections and different punctures that are operable in the cylinder are built-in to convey material through the cylinder and to consist of filaments To process material as it is introduced into the cylinder, 509828/0863 C. Loading devices at the beginning of the Cylinder for the introduction of heat-softenable polymers and for the initiation of the promotion of heat-softenable polymer through the rest of the extruder barrel, D. Decompression devices so designed and designed to operate under reduced pressure stand than the preceding extruder section, with openings in the extruder barrel through which Continuous thread material can be continuously introduced into the decompression devices and screw assemblies with core portions of relatively small cross-section so constructed and are designed to prematurely break and entangle the continuous filament material with the core to prevent E. Means for conveying the resulting mixture of heat-softened polymer and filamentary Material to the mixing devices in the cylinder, which are so designed and intended are to shearly grasp the heat-softenable material and the filamentary material, j breaking the latter and the resulting; broken fibers carefully with the heat-softened To mix material F. Means for removing the so-mixed heat-softened material and the broken fibers from the extruder barrel. 509828/08 63 12. Extruder device according to claim 11, characterized in that the mixing device is a high shear thin film forming device, which contains a cylindrical or conical screw segment, with an outlet end built into the cylinder longitudinally and an inlet end for flowing material shearly between the cylinder and the To take cylindrical or conical screw segment containing (1) inlet lobes on the surface of the screw segment assembly, which end in dead turns before the outlet end and (2) outlet grooves on the surface of the screw segment assembly at the outlet end, which end before reaching the inlet end. 13. Apparatus according to claim 11 or 12, characterized in that the threads on the screws there are double threads in the decompression zone. Ik. Device according to Claims 11 to 13, characterized in that the opening in the decompression zone is equipped with discharge devices in order to prevent the penetration of heat-softened polymer into this opening. 15. Apparatus according to claim 12 to 14, characterized in that that the mixer includes two back-to-back Egan mixers. 509828/0863 16. The apparatus of claim 11, 13 and 14, characterized characterized in that the mixing device is a screw with interrupted threads. For: Exxon Research and Engineering Company .ΗΛΙ.1 Dr H. "ff.Wolff lawyer 509828/0863 Blank page