DE4116800A1 - High-grade fibre-reinforced thermoplastic composite sheet prodn. - by impregnating fibre sheet, esp. silanised glass fibre, with polyamide or polycarbonate etc. for short time under pressure, at specific temps. - Google Patents

Abstract

Prodn. of high-grade composites (I) with a thermoplastic matrix, by impregnating sheets of reinforcing fibre (II) with the thermoplastic (III) in a press for a short time under pressure, with a precisely defined max. residence time for individual vol. elements; the novelty is that the process is carried out at a very high temp. which would normally be expected to result in damage to (III) by itself or to the surface coating on (II) or to produce damage due to the degradation of (III) at the matrix/fibre interface under the action of the surface coating. USE/ADVANTAGE - The method provides a new process for the prodn. of high-grade composite sheet with mechanical strength values considerably higher than the corresp. PU resin/GF composite; high-temp. impregnation enables a considerable increase in prodn. (short residence time) without thermal damage

Description

Process for the production of flat composite structures fabrics made from reinforcing fiber structures and thermoplastics are known. As a batch process is before all described the "film stacking" at the locations of Reinforcing fiber structures with thermoplastic films in be pressed in a static press. A continuous The process is carried out on double belt presses leads. In principle, the thermoplastic in both Ver also open in other ways than in the form of foils be given, for example as a melt, fibers or Powder.

As mentioned for example in DE-OS 37 34 296, who the continuous process on double belt presses Operating temperatures that are usually 20-50 ° C above the melting point of the thermoplastic.

The disadvantage of this method is that Im is relatively long Precise times to achieve a high quality  valuable product are necessary. From this follow comparative wise low manufacturing speeds. this applies especially when using high quality, punch tough, high molecular weight thermoplastics that usually have high melt viscosities. Because of their in Processing is usually a high viscosity amorphous thermoplastics difficult.

A new manufacturing process was surprising high quality flat composite materials with Thermoplastic matrix found by using the reinforcement fiber structures and the thermoplastics of a press leads, in this press, the temperature of the materials increased and the reinforcing fiber structure at short Dwell time with a precisely defined maximum dwell time of individual volume elements using pressure and impregnated at high temperature, except on one usually works at high temperature, otherwise experience has shown damage to the thermoplastic itself or the finishing on the surface of the ver strengthening fibers or by breaking down the thermoplastic in the boundary layer to the fiber under the influence of Finishing leads.

A device is to be understood under a press the one who is capable of both pressure and exert increased temperature on the flat structures. In particular, clocked hydraulic pres with heated plates in one or more floors to understand gene. These presses can either be pure discontinuously or in relation to the product  be operated continuously by using the flat Formed by the clockwise opening and closing de Press pulls or pushes. Also continuous pres sen, for example double belt presses, are included sen.

According to the temperature of the materials in the press can be increased. The exceptionally high Temperature level is only briefly during the Im impregnation process itself. The are preferred solid thermoplastic materials, for example wise as foils, fibers, powders. A before heating the materials to above the melting point of the Thermoplastic is possible. A feed of the Thermoplastics in molten form, for example from the slot die of an extruder is conceivable, however at a lower temperature level than the Im impregnation.

According to the dwell time is high Short temperature level. By applying the high Temperature is reduced significantly. An absolute one However, the value should only be given as an example, because The level, for example, depends on the viscosity of the thermoplastic, of thread thickness and textile binding of the reinforcing fiber structure used and of Filament diameter depends on the reinforcing fibers.

The process has a very narrow residence time distribution at a defined maximum dwell time, d. H. There is none long dwell tails that lead to product damage would lead.  

Preference is given to flat reinforcing fiber structures wise fabrics, knitted fabrics, knitted fabrics of all kinds, braids, Nonwovens, mats and combinations thereof and all Types of unidirectional structures or combinations of unidirectional structures with the mentioned Textiles in question.

Glass fibers should initially be used as reinforcing fibers to be viewed as. It is known that these are in Multi filament shape existing fibers to improve ver various properties in combination with the plastics can be provided with sizes that usually consist of a variety of components exist. This includes u. a. Film formers, adhesion promoters, lubricants, anti statics, plasticizers, emulsifiers.

In connection with the invention are in particular Film makers and adhesion promoters of interest. The film Formers have the function of fiber over mechanical ones To protect damage, a closed strand to form and, if possible, to train the association properties to participate. They generally exist made of water-dispersible or water-soluble polymers ren, for example from polyvinyl acetates, polyester resins, epoxy resins, polyurethanes, acrylates.

The adhesion promoters have the function, the mechanical ones Properties in the bond between matrix and fiber too improve. As a rule, organofunctional  nelle silanes used, for example amino, epoxy, Vinyl, methacrylic, mercapto or halogen silanes. Further chrome and titanium complex compounds are used.

In the case of glass fibers, this complete size with film formers and adhesion promoters directly during the spinning process applied the fiber. In some cases, for example during further processing of the fibers into glass fabrics or other textiles, however, the glass fiber can Spinning process initially equipped with a size that are not based on the connection to plastics, but on optimal processability in textiles Process is optimized. Such finishes are then removed after finishing textile processing in the Usually by burning. Then the tex Tile structures usually only from aqueous solution the adhesion promoter is applied as a so-called finish.

Film is preferred for thermoplastic matrices formers used, at least partially made of polyure thanen exist. It is known that polyurethane systems have only a very limited thermal stability, i. H. that their decomposition is usually at temperatures starts below 180 ° C. Such systems are therefore for one Generally unsuitable for use at temperatures above 280 ° C net.

Adhesion promoters in particular are made of thermoplastics the group of triethoxysilanes and trimethoxisilanes Vinyl, methacryloxypropyl, aminopropyl and epoxy  group because of their good adhesion properties moves. Γ-Aminopropyltriethoxy are particularly preferred silane, γ-glycidoxy propyltrimethoxysilane or ethoxy silanes, β- (3,4-epoxy-cyclo-hexyl) ethyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane and vinyltriethoxi silane.

These preferred silanes show in the DSC under air in the end clear signs of decomposition at 280-300 ° C, With air access even at 150 ° C. At Epoxisila the decomposition temperatures are usually lower than comparable aminosilanes. In the Combination with film formers are the thermal loading persistence worse.

It would therefore be extremely surprising for the expert if the preferred silanes mentioned at temperatures above 300 ° C in a process that is strictly under air finally works, at least a satisfactory one Adhesion to thermoplastics would result. This applies to Cases where the pure coupling agent in the form of a finish on the fiber, to an even greater extent however, when equipped with the complete size, in which is also the much less thermostable Film maker is included.

Surprisingly, it was found, however, that when in use of fiberglass with finishes that are at least partially made the specified preferred silanes, in particular from the preferred triethoxysilanes and trimethoxisilanes with vinyl, methacryloxypropyl, aminopropyl and  Epoxy groups exist, with the new specified Process composite materials with thermoplastic matrix with receives an excellent level of properties if one at temperatures of more than 300 ° C, preferably more than 320 ° C, particularly preferably more than 340 ° C.

It was also found that when using glass fibers with complete sizes that the specified preferred silanes, especially the preferred tri ethoxisilane and trimethoxisilane with vinyl, methacrylic oxipropyl, aminopropyl and epoxy groups as adhesion medium included with the specified new method Composites with a thermoplastic matrix with one drawn property level, if one at Temperatures of more than 280 ° C, preferably more than 310 ° C, particularly preferably more than 330 ° C works.

In particular, it was found that when using Glass fibers with complete sizes, which the specified preferred silanes, especially the preferred ones Triethoxisilane and trimethoxisilane with vinyl, meth acryloxipropyl, aminopropyl and epoxy groups as Contain adhesion promoters and at the same time film formers, which at least partially consist of polyurethanes, included with the specified new process composite materials with a thermoplastic matrix with an excellent neten property level, if one at Tempera doors of more than 280 ° C, preferably more than 300 ° C, particularly preferably more than 320 ° C.

These findings are all the more astonishing than with the  specified new method at least the partial Access to air is not excluded. The cheap Most conditions exist when the thermoplastic in Foil form is introduced and when the melting Foil the glass surfaces to prevent air ingress Lich seals. Nevertheless, the air in the Inside of the textile structure, for example in that of Warp and weft threads formed by a square, and between the filaments of the reinforcing fibers at least partial degradation even at low Bring about temperatures. Action is even greater Time and air supply when using the polymer in shape of fibers, for example as mixed textiles, or in Form of powder.

It must be taken into account that, in particular, when Apply the bonding agent in the form of a finish only thin surface films are formed. The total share of the adhesion promoter is usually of the order of magnitude 0.1%.

It was also found that the new process over surprisingly also in relation to the used Thermoplastics at unusually high processing temperatures can be carried out, the otherwise normal lead to damage to the thermoplastic, esp especially under the influence of the sizes in the Interface between the matrix and the fiber. Also there composite materials of good quality are obtained.

The following are examples of reinforcing fibers  wise inorganic fibers from silicate and nothing all kinds of likatic glasses, carbon, Boron, silicon carbite, metals, metal alloys, Metal oxides, metal nitrides, metal carbides and silica be understood.

The well-known thermopla plastic materials can be understood, for example also those used as copolymers, block polymers, graft polymers, copolymers and polymeric mixtures Gen. Polyamides are preferred, particularly preferred Polyamide 6, polyamide 66 and polyamide 12, polycarbonate and polyphenylene sulfide.

In particular, polyamide 6 can be used at temperatures of more than 300 ° C, preferably more than 320 ° C, particularly preferably of more than 340 ° C with the specified fiber systems to composite materials of high quality work.

In particular, polyamide 66 can be used at temperatures of more than 320 ° C, preferably more than 330 ° C, particularly preferably of more than 340 ° C with the specified fiber systems to composite materials of high quality ver work.

In particular, polycarbonate can be used at temperatures of more than 320 ° C, preferably more than 330 ° C, particularly preferably of more than 340 ° C with the specified fiber systems to composite materials of high quality ver work.  

In particular, polyphenylene sulfide can be used at tempera doors of more than 365 ° C, preferably more than 380 ° C, particularly preferred of more than 390 ° C with the specified fiber systems for composite materials of high quality process.

A comparison with usual processing temperatures, for example in injection molding and extrusion NEN that these processing temperatures found are exceptionally high. For example, B. Carlowitz in plastic tables (Carl Hanser-Verlag, Munich, Vienna, 1986) for polyamide 6 processing systems temperatures of 230-280 ° C in injection molding and 240-300 ° C in extrusion, for polycarbonate from 270-310 ° C in Injection molding and 240-280 ° C in extrusion, for polyphene ylene sulfide at 315-360 ° C by injection molding.

The information in this book can also be used by others Thermoplastics for assessing the poss high processing temperatures the. As a rule, the possible processing lies temperatures by at least 10 ° C, preferably 30 ° C, esp ders preferably 40 ° C above the highest for injection molding or Extrusion specified processing temperature.

This is all the more astonishing since the process, as in described individually, not under strict air exclusion It is known that many thermoplastics are against air sensitive to high temperatures. At for example, polyamide 6 leaves clear oxides in air Recognize symptoms that also with a reduction  mechanical characteristics.

It is also surprising that this high processing temperatures even in the presence of certain sizes are possible on the fiber surfaces. So you can at for example the highly stress-sensitive Polycar bonat in the presence of aminopropyltriethoxisilane Temperatures up to 360 ° C with composite materials good mechanical properties.

One advantage of these high processing temperatures is a significant reduction in the necessary impregnation times to achieve a high quality Product are necessary. This results in a clear one Increase production speeds on a front existing plant. This is especially true when used of high-quality, impact-resistant, high-molecular thermo which usually have high melt viscosities point. Because of their generally high viscosities is also the processing of amorphous thermoplastics, at example of polycarbonate or polyetherimide rig.

The term good quality mentioned in the invention the composite materials can only be based on model texti lien be defined because the individual ampl Kung fiber textiles depending on the textile binding at mecha behave very differently.

Since this is an evaluation of the process conditions is only one type of glass fabric  be determined. The quality level should then with the Level in the known impregnation with unsaturated Polyester (UP) resins are compared.

This standard fabric is intended to be plain weave and a basis weight of 345 g / m ² with 6 threads / cm EC 9-68 · 5 t0 in the warp direction and 5.3 threads / cm EC 9-272 Z in the weft direction (from Interglas, Ulm, quality 92 150).

For this fabric, the term "good quality" means that the tensile strength values in the warp direction according to the information from Interglas for the UP- Resin matrix to 90%, preferably 100%, the bending structure 95%, preferably 105%. The tensile strength specified by Interglas is 340 MPa, the bending strengths 430 MPa, each at 43 vol% glass (List No. 79, January 1985).

Examples example 1

The above-mentioned standard glass fabric with plain weave and with a basis weight of 345 g / m ^{2 is used} with 6 threads / cm EC 9-68 · 5 t0 in the warp direction and 5.3 threads / Icm EC 9-272 Z in the weft direction (Interglas, Ulm, quality 92 150).

The fabric is with a finish consisting of γ-amino propyltriethoxisilane (A 1100 from Union Carbide) equipped.

5 layers of this fabric are on a double belt press with 4 layers of foil, each approx. 0.2 mm thick made of polyamide 6 (Durethan B 31 F from Bayer) Composite plate pressed. There is one 1.45 mm thick board with a fiber content of approx. 46 vol.%.

There is one in the high temperature zone of the press Belt temperature of 360 ° C and a pressure of 30 bar. At the The stack is pre-entered into the high temperature zone warms, a thermocouple in the core shows 110 ° C. The Gross residence time (including heating) in the Be range of high band temperature is 2.1 min. The Thermocouple in the core of the plate indicates that the Temperature of 360 ° C also reached inside the plate becomes.  

The plate produced has a tensile strength in the warp direction 415 MPa and a flexural strength of 635 MPa. If you take into account the comparative sample from lnterglas UP resin matrix to a glass content of 46 vol .-% um, this results in values of 360 and 480 MPa for tensile and Flexural strength. The color of the plate is bright, despite the high temperature and the limited air access is not a brown discoloration to be feared with polyamide occurred. The composite panel produced has thus despite the very high processing temperature very good quality.

Example 2

The experiment is carried out with identical starting materials and identical press configuration repeated. Changed are temperature and pressure in the high temperature zone.

At 330 ° C and 20 bar there is a dwell time of 4.2 min strengths of 434 MPa or 609 for tension and bend.

At 350 ° C and 40 bar there is a dwell time of 2.1 min strengths of 454 MPa or 644 for tension and bend.

At 370 ° C and 40 bar there is a dwell time of 2.1 min strengths of 449 MPa or 608 for tension and bend.  

At 370 ° C and 40 bar there is a dwell time of 0.9 min strength of 453 MPa or 631 for tension and bend.

The deviations in the quality data for the individual set conditions are within the statistical scatter. At 370 ° C you can therefore with one Seventh of the gross residence time in the heating zone is the same achieve the same quality as at 330 ° C.

Example 3

5 layers of the same fabric with the same equipment as in Example 1 on a double belt press 4 layers of foil, each approx. 0.2 mm thick, consisting of Polyphenylene sulfide (Tedur KU 1-9500-80 from Bayer) a composite plate pressed. There is one 1.45 mm thick board with a fiber content of approx. 46 vol%.

The pressing is carried out at a belt temperature of 390 ° C, a pressure of 30 bar and a residence time of 0.9 min carried out.

The plate has a tensile strength of 410 MPa and a Flexural strength of 570 MPa. If you calculate the comparison Interglas sample with UP resin matrix on one Glass content of 46 vol .-% um, values of 360 or 480 MPa for tensile or bending strength. Which he witnessed composite panel has therefore despite the very high processing temperature a very good quality.  

Example 4

The same experiment as in Examples 1 to 3 is carried out Polycarbonate film (Makrofol DE 1-4 from Bayer) leads. The polycarbonate used at 300 ° C a shear rate of 20 / s a viscosity of 1500 Pa · s, is therefore considered to be a very high viscosity To designate melt.

At a belt temperature of 360 ° C, a pressure of 40 bar and a residence time of 2.1 min Processing to a high quality composite material. The Tensile strength is 405 MPa, the bending strength is 610 MPa.

Example 5

A carbon fiber fabric in an Atlas weave with a basis weight of 365 g / m ² with 4.5 threads / cm of 400 tex each is used in the warp and weft directions. Torayca T 300 is used as fiber.

2 layers of this fabric are on a double belt press with 2 layers of 0.2 mm thick film and one layer 0.125 mm thick film consisting of polycarbonate (Makrofol DE 1-4), ver to a composite plate presses. A plate with a thickness of 0.9 mm is created a fiber content of approx. 45% by volume.

The pressing is carried out at a belt temperature of 360 ° C, a pressure of 40 bar and a residence time of 2.1 min  carried out. You get a high quality composite fabric with a tensile strength of 535 MPa and a flex strength of 440 MPa, each in the warp direction.

Example 6

It becomes a right / right mixed knit made of glass and Made of polyamide fibers and on a double belt press pressed into a compact composite material. The The glass fiber used is a 320 tex roving R 25 BX 3G from Owens-Corning fiberglass, with a full size is equipped with a silane coupling agent. The polyamide 6 yarn of type Enkalon 540 T from Akzo has 272 tex.

The pressing is carried out at a belt temperature of 350 ° C, a pressure of 20 bar and a residence time of 2.1 min carried out. You get a high quality composite fabric that becomes rigid after an expansion process Body of 5 mm thickness leads, the impregnation excellent and has good stiffness characteristics points. The color is light with no discernible browning.

Example 7

A glass fiber textile is used by a multiaxial warp knitting machine with fiber direction ± 45 ° C on the basis of the thread EC 9-68 tex with the same amount of fibers in both directions and a weight per unit area of 395 g / m ² . The fibers are equipped with the fully sized Silenka 1383, which contains an adhesion promoter containing silane.

This biaxial textile is combined with a layer of Ge knit from Example 5 and two layers of polyamide film B 31 F 0.1 and 0.2 mm thick on a double belt press pressed into a compact composite material.

The pressing is carried out at a belt temperature of 350 ° C, a pressure of 22 bar and a residence time of 2.1 min carried out. You get a high quality composite fabric after an expansion process of the knitted layer leads to a rigid body of 6 mm thickness, which extends is impregnated and has good characteristics for the Has rigidity. In particular, the multi axial textile well impregnated and practically undyed.

Claims (10)

1. Process for the production of high-quality composites with a thermoplastic matrix, characterized in that the reinforcing fiber structures and the thermoplastics are fed to a press, the temperature of the materials is increased in this press and the reinforcing fiber structure with a short dwell time with exactly defi nated maximum residence time of the individual volume elements impregnated using pressure and high temperature, whereby one works at an exceptionally high temperature level, which experience has shown otherwise to damage the thermoplastic itself or the size on the surface of the reinforcing fibers or by degrading the thermoplastic in the boundary layer to the fiber leads under the influence of the sizes. 2. The method according to claim 1, characterized in that that you use glass fiber structures that with Fini shes are equipped that at least partially the specified preferred silanes, in particular from the preferred triethoxisilane and trimethoxi silanes with vinyl, methacryloxypropyl, amino propyl and epoxy groups exist, and that one Temperatures of more than 300 ° C works. 3. The method according to claim 1, characterized in that you use glass fiber structures that with com  complete finishing are equipped, at least some of the preferred silanes indicated, especially the preferred triethoxysilanes and Trimethoxysilanes with vinyl, methacryloxypropyl, Aminopropyl and epoxy groups as adhesion promoters included, and that one at temperatures of more works as 280 ° C. 4. The method according to claim 1, characterized in that you use glass fiber structures that with com complete finishing are equipped, at least partially the specified preferred silanes, ins especially the preferred triethoxysilanes and Trimethoxysilanes with vinyl, methacryloxypropyl, Aminopropyl and epoxy groups as adhesion promoters included and at the same time a film maker who consists at least partially of polyurethane, and that you work at temperatures of more than 280 ° C. tet. 5. The method according to claim 1, characterized in that the thermoplastics used at unusual high temperatures to composite materials be at least 10 ° C above that of Carlowitz specified for injection molding or extrusion highest processing temperatures. 6. The method according to claim 1, characterized in that the thermoplastic used is polyamide 6 and at temperatures of more than 300 ° C with the specified given fiber systems to composite materials is being processed.   7. The method according to claim 1, characterized in that the thermoplastic used is polyamide 66 and at temperatures of more than 320 ° C with the specified given fiber systems to composite materials is being processed. 8. The method according to claim 1, characterized in that the thermoplastic used is polycarbonate and at temperatures of more than 320 ° C with the specified fiber systems into composite materials is tested. 9. The method according to claim 1, characterized in that the thermoplastic used polyphenylene sulfide and with temperatures of more than 365 ° C specified fiber systems for composite materials is processed. 10. The method according to claim 1, characterized in that the specified press is a static clock press or is a double belt press.