DE4218434A1 - Continuous fibre-reinforced thermoplastic profile or tape prodn. - by embedding fibre in plastic in extruder to set THF fibre:matrix ratio, then impregnating by heating and moulding to shape - Google Patents

Abstract

A 3-stage process for the prodn. of continuous fibre-reinforced composite profile or tape (I) comprises (1) embedding the fibre string (II) in thermoplastic (III) in the mould of an extruder head and thus setting the fibre/matrix ratio, (2) impregnating the fibre by heating and (3) moulding the composite to the required form. Also claimed are continuous fibre composites (I) contg. unidirectional continuous reinforcing fibres (II) and various thermoplastic matrices (III), and with densities at least 99.8% of the theoretical values. USE/ADVANTAGE - The process enables the prodn. of (I) without the disadvantaes of impregnation with polymer melt (e.g, thermal degradation of the polymer due to prolonged heating, or unsatisfactory end properties due to impregnation with high-viscosity melts); the required fibre/matrix ratio is set in the primary embedding stage, and impregnation is carried out in stage (2) without stripping or otherwise removing excess polymer).

Description

The present invention relates to manufacturing methods for thermoplastics provided with reinforcing fibers. The Her Adjustment methods relate to those composite materials which the reinforcing fibers are arranged in parallel (or predominantly parallel) arrangement in the thermoplastic matrix included.

It is generally known that polymers such. B. thermo plastic polymers, by embedding reinforcement fibers in their mechanical, thermal and others Properties can change: there are also many ver different manufacturing methods for such composites be wrote and are also used in practice. To at for example with continuous fiber reinforced linear profiles to produce a thermoplastic matrix: you can endless Pull reinforcement fibers through an impregnation bath, in which the thermoplastic dissolved in a solvent is. After removing the remaining solvent  the impregnated material remains an endless fiber reinforced Linear profile with thermoplastic matrix in which the ver Strengthening fibers are arranged in parallel. - Also exists the possibility of powder impregnation, in which - after applying thermoplastic powders to the ver strengthening fibers - by melting the thermoplastic the monofilaments of the reinforcing fiber strand in to be impregnated.

Basically, there is the possibility of the endless ver Reinforcing fiber bundle directly through a thermoplastic melt to get such an impregnation hold. But here is the basic one Difficulty that at the melting temperatures which the thermoplastic is not chemically changed or even decomposed, the viscosities of the melted thermoplastics are relatively high, so that Impregnation quality and resulting composite properties often do not satisfy.

EP 0 056 703 (B1) describes a possibility for producing thermoplastic fiber-reinforced linear profiles by means of a melt pultrusion process, which leads to products whose longitudinal bending modulus reaches at least 70% of the theoretically achievable bending modulus. It is characteristic here that in the pultrusion technique the fiber strand is first impregnated and then the fiber / matrix ratio is set. (The latter is done, for example, by stripping excess polymer on a calibration nozzle.) Furthermore, according to this patent specification, such thermoplastic polymers are used which have a melt viscosity of less than 100 Ns / m ² at zero shear rate

It has now been found that continuous fiber-reinforced Li near profiles and tapes with thermoplastic matrices in high Quality can be produced by having the respective Thermoplastics in a multi-stage process with the endless reinforcing fiber strands united. The multi-stage The manufacturing process consists of at least two successive partial steps: a primary Sheathing the fibers with the thermoplastic and a Post-treatment using heat and possibly Print. The primary casing already determines this the final fiber / matrix ratio while the Aftertreatment of the impregnation serves (without that excess thermoplastic stripped or removed becomes).

The invention relates to a method for the manufacture development of a continuous fiber reinforced composite pro files or tape, characterized in that one in a three-stage process works, in which the first step is just a thermoplastic sheath Reinforcing fiber strands in the tool of an extruder head and thus the fiber / matrix ratio nis is set during the second step is impregnated by heat treatment and in one third step a shaping takes place.  

The invention provides a method for the production of Thermoplastic bonded with parallel endless endless Reinforcing fibers ready, which are multi-stage Manufacturing processes, which consists of at least two successive steps exist, where in first step the reinforcement fiber bundle with the Ther moplastics covered in the final weight ratio ratio combined and in one or more on it following step the coated fiber bundle, without Ver Change the fiber / matrix ratio, using heat and optionally impregnated with pressure and in the form is brought.

The production methods according to the invention are in conflict set for the pultrusion described in EP-A 00 56 703, in which is first impregnated and then dosed.

It is now known that many thermoplastic polymers at low shear rates (from zero shear rate to 10 ² s ^-1 ) and the respective processing temperature of the melt have viscosity values which are well above 100 Ns / m ² . On the other hand, with the same polymer type, molecular branching and / or broad molecular weight distributions lead to melt viscosities that are never higher at shear rates and lower at high shear rates than with unbranched polymer. - So there are many types of polymer with which it should be difficult or impossible to obtain composite profiles or strips by melt impregnation according to the prior art (e.g. EP-A 56 703).

Surprisingly, it has now further been found that the thermoplastic matrices which have melt viscosities of 100 Ns / m and more at low shear rates (from zero shear rate to 10 ² s ^-1 ) and the respective processing temperature can also be used with the production processes according to the invention, if these at high shear rates (about 10 ³ -10 ⁵ s ^-1 ) and the respective processing temperature of the melt have viscosity values below 100 Ns / m ² .

Thus, it is also an object of the present invention that such thermoplastics are used for the production of continuous fiber-reinforced linear profiles and tapes which have melt viscosities of 100 Ns / m and more and at high shear rates at low shear rates (from zero shear rate to 10 ² s ^-1 ) (about 10 ³ -10 ⁵ s ^-1 ) have viscosity values below 100 Ns / m ² .

In general, the thermoplastic matrix fiction, ge moderate composite materials from a wide range of thermo plastic materials exist. It is essential that the thermoplastic has a low softening interval or has a lower melting point than the material, of which the reinforcing fibers are made. Come into question for example thermoplastics in the broadest sense, d. H. Substances that are reversible or intermediate thermo behave plastically, e.g. B. thermoplastics and thermoplastic phases of thermosets.

Examples of thermoplastics are polyolefins, vinyl poly merisates such as polyvinyl halides, polyvinyl esters, poly  vinyl ethers, polyacrylates, polymethacrylates, and or ganic cellulose esters, polyamides, polyurethanes, poly ureas, polyimides, polyesters, polyethers, polysty role, polyhydantoins, polyphenylene oxides, polyphenylene sulfides, polysulfones, polycarbonates, phenolic resin precursors fer, furan resin precursors, melamine resin precursors, epoxy resin precursors, compounds with polymerizations and / or double bonds capable of polyaddition, poly imide precursors, polyether ketones, polyether sulfones, Po lyetherimide, polyamideimide, polyfluoroalkene, polyester carbonates and liquid crystal polymers: also non-polar thermoplastic polymers (e.g. polyolefins), which polar groups were grafted on.

Preferred thermoplastics are the species mentioned above, but with the special property that their molecular polymer chains have branches and / or have broader molecular weight distributions (M _w / M _n 5).

For example, polyphenylene is particularly preferred sulfide, polybutylene terephthalate, PBTB (Pocan B 7375® the Bayer), ABS (Novodur® from Bayer), bisphenol A- Polycarbonate (Makrolon 6385® from Bayer), poly carbonate-ABS blend (Bayblend® from Bayer, polyamide 6 (Durethan B 30 S® from Bayer), polyamide 66® (e.g. Durethan A 30S® from Bayer). Their viscosities (in or in the vicinity of their processing area) playfully listed in Table 1:

The reinforcing fibers are arranged in parallel it is endless reinforcing fibers, the z. B. as Single fibers (monofilament), rovings, skeins, yarns, threads or ropes. Preferably, the individual filaments diameter in the range of 0.5 to 50 µm. Under endless reinforcement fibers or Filaments are understood to mean those in general have a length which is approximately the length of the linear profile or the band.

The chemical structure of the reinforcing fibers can vary be of all kinds. It is only essential that the reinforcing fibers have a higher softening or Have melting point than the present Thermoplastic matrix. Examples of fiber materials are inorganic materials such as silicate and non-silica all kinds of cat glasses, carbon, Boron, silicon carbide, metals, metal alloys, metal oxides, metal nitrides, metal carbides and silicates, as well organic materials such as natural and synthetic Polymers, for example polyacrylonitrile, polyester, ultra-stretched polyolefin fibers, polyamides, poly imides, aramids, liquid crystal polymers, polyphenylene sulfides, polyether ketones, polyether ether ketones, poly etherimide, cotton and cellulose. Are preferred high-melting materials, such as glasses. Carbon, aramids, liquid crystal polymers, poly phenylene sulfides, polyether ketones, polyether ether ketones and polyetherimides.  

The manufacturer to be used in the context of this invention techniques are multi-stage processes, whereby in the first Step (or in the first steps) the thermoplastic without substantial fiber impregnation the reinforcing fiber structure is brought. This can happen at speeds up to 300 m / min. The In principle, thermoplastic can be used as a powder Melt or deposited from a solution applied will.

In a preferred embodiment, the to be reinforcing fiber strand laying an extruder head fed centrally, with ring-shaped polymer emerging the fiber strand sheathed like a tube (principle of Cable sheathing in technical practice). Here becomes a definite and final matrix / fiber Ver ratio set.

Other wrapping techniques are also conceivable. So can the reinforcing fibers in a pressure room with the Polymer strand can be combined, the fiber speed and the speed of the polymer stranges are about the same size. With a subsequent one It will then pass through a fine heated duct - without stripping polymer - stripped the sheathing closed.  

Then the coated product is individually or Assembled subjected to heat treatment. This can happen, for example, that the preheated tubular continuous fiber material over five to ten hot and linearly arranged steel pins meandering guided and thereby (at speeds of e.g. B. 50 m / min) is impregnated. Then fixie tion and shaping, for example through cooled pres send rollers (speeds: e.g. 50 m / min).

Other impregnation methods are also conceivable. So can the incoming jacketed continuous fiber strands warmed and fed to calender rolls. Is too it is possible to be the coated fiber material in a heated and pressurized double belt press to let go.

Claims (5)

1. A process for producing an endless fiber reinforced composite profile or strip, characterized in that one works in a three-stage process, in which in the first step only a thermoplastic sheathing of the reinforcing fiber strands is carried out in the tool of an extruder head and the fiber / matrix ratio is thereby set, while in the second work step is impregnated by heat treatment and in a third step shaping takes place. 2. Endless fiber composites with unidirectional endless reinforcing fibers and various Thermoplastic matrices, obtainable according to claim 1, the densities of these fiber composites at least 98.8% of the theoretical value pass. 3. The method according to claim 1, characterized in that thermoplastics are used which at low shear rates (from zero shear rate to 10 ² s ^-1 ) melt viscosities of 100 Ns / m and more and at high shear rates (about 10 ³ -10 ⁵ s ^-1 ) have viscosity values below 100 Ns / m ² . 4. Fiber composite materials, produced according to claim 1, consisting of glass and / or carbon fibers and a polyphenylene sulfide matrix, whose viscosity at a shear rate below 50 s ^{-1 is} between 200 and 400 Ns / m ² and at a shear rate above 10 ⁴ s ^{- 1 is} between 15 and 50 Ns / m ² . 5. Fiber composite materials, produced according to claim 1, consisting of glass and / or carbon fibers and a polyamide matrix, the viscosity of which at a shear rate below 50 s ^{-1 is} between 100 and 200 Ns / m ² and at a speed of minion over 10 ⁴ s ^{- 1 is} between 10 and 50 Ns / m ² .