DE102020105167A1 - Method for producing a hybrid yarn - Google Patents

Abstract

The invention relates to a method for the production of hybrid yarns, which are intended in particular for parts made of composite material. The process for the production of a hybrid yarn from endless multifilament reinforcing fibers and multifilament thermoplastic fibers is characterized in that the reinforcing fibers are fed with a greater width than the thermoplastic fibers, overlapping in the middle, one above the other, the thermoplastic filament yarns being fed into the needle machine at a higher speed than the reinforcing fibers Run in the needle field of the needling machine and proportions of the thermoplastic filaments through the action of felting needles through the array of parallel, longitudinally oriented endless reinforcing fibers pierced in a loop at an angle of 90 ° cause an intimate adhesion of both components with simultaneous formation of a mixing effect.

Description

The invention relates to a method for the production of hybrid yarns, which are intended in particular for parts made of composite material. Hybrid yarns with a combination of thermoplastic and continuous reinforcing fibers are used to manufacture high-performance composite materials. The endless reinforcing fibers here are mostly glass or carbon fibers. Polypropylene, polyamides, polyester or high-melting special polymers function as thermoplastic components later on as matrices. The advantage of hybrid yarns is their line shape and their high bending flexibility, so that they can be used to manufacture semi-finished products with a high degree of flexibility, high deformability and great three-dimensional design freedom. When pressing such semi-finished products at temperatures above the softening point, the thermoplastic component integrated in the hybrid thread melts and forms a matrix in which the reinforcing fibers are embedded in an oriented manner.

[State of the art]

In the patent literature there are a number of proposed solutions for the production of hybrid yarns. Disadvantages of the prior art are that these methods do not allow the use of high-filament reinforcement rovings such as carbon fibers from 50k, endless reinforcing fibers are impaired in their desired longitudinal orientation, longitudinally oriented reinforcing filaments are constricted with a thermoplastic thread or flexibility is restricted by welding or adhesive binders.

In the patents DE 102011010592 , DE4137406A1 and EP-B 1 56 599 the two types of fibers are spread, mixed with one another by bringing them together via rollers or rods and the mixed yarn is then pulled off in bundles or, if necessary, wrapped with another thermoplastic yarn.

DE19624412A1 describes a method which is characterized in that the thermoplastic component bonds the reinforcing fibers by heating above its melting point.

In the patents EP0207422A2 and EP344650A2 hybrid yarns are produced by means of air turbulence.

US5176868A and JPH01280034A use a mutual twisting of both components for the longitudinal connection of reinforcing fibers and matrix fibers.

WO1999019273A1 describes a method by wrapping the reinforcing filaments with a thermoplastic film.

The patent specification GB-A 21 05 247 describes a method in which a fiber core made of reinforcing fibers is wound with a thermoplastic yarn.

In DE102014019220A1 describes a method for producing a strip-shaped semi-finished product in which reinforcing fibers and matrix material are present in an asymmetrical distribution. Both components are arranged one above the other as a fiber bundle and "... a mixing of matrix fibers and reinforcing fibers is at least largely avoided, with mixing preferably being completely avoided.""An embodiment of the method is preferred which is characterized in that several, preferably identical, fiber bundles are placed next to one another and preferably glued together." The gluing can be done by a size or thermal melting of the thermoplastic component.

[Object of the invention]

The object of the invention is to develop a method for producing a hybrid yarn which allows the use of high-filament reinforcement rovings, such as carbon fibers from 50k, without impairing endless reinforcing fibers in their desired longitudinal orientation and without constricting longitudinally oriented reinforcing filaments by a thermoplastic thread or by welding or adhesive binders limit flexibility. As a new approach, process steps of filament yarn spreading, special thread guidance with textile needling technology and thermal fixation under tension are combined.

The object is achieved in that multifilament filament yarns made of reinforcing fibers and thermoplastic fibers are built up in layers, mixed by needling, then stretched and the stretched hybrid roving is thermally fixed.

Reinforcing fibers within the meaning of the invention include all fibers that are suitable for the production of fiber composite materials. In particular, it includes glass fibers, carbon fibers and aramid fibers.

Thermoplastic fibers in the context of the invention are all fibers made of plastics which are thermoplastically deformable. In particular, it includes fibers made of polyethylene (PE), polypropylene (PP), polyesters such as polyethylene terephthalate (PET), polyetheretherketones (PEEK), polyphenylene sulfide (PPS) and polyamides.

Reinforcing fibers and thermoplastic fibers are available as roving or multifilament yarn in bobbin form, the number of bobbins with the selected yarn counts, taking into account the different take-off speeds, determining the subsequent mixing ratio of thermoplastic and reinforcing fibers in the hybrid yarn.

The number of coils for the reinforcing fibers is between 1 and 5, preferably 1 to 2 coils. Different reinforcing fibers or the same fibers with different fineness can be found on the spools. The number of spools of thermoplastic fibers can be significantly higher, since the individual threads are usually very thin. 1 to 20 coils are usual, preferably 4 to 10 coils. These can be different thermoplastic fibers and / or the same fibers of different fineness.

The fineness of the yarn is in the range from 50 dtex to 4000 dtex, preferably in the range from 80 dtex to 3000 dtex. Individual fiber counts are in the range from 1 dtex to 8 dtex.

The take-off speed is between 1 m / min and 30 m / min, preferably between 2 m / min and 10 m / min.

The optimal mixing ratio of reinforcing fibers to thermoplastic fibers is between 30 and 70% by volume or 40 and 80% by weight.

After being withdrawn from a creel, at least one layer of thermoplastic fibers and at least one second layer of reinforcing fibers are formed in a first step. The shifts always alternate. Spreading devices that are preferably connected downstream produce layers of thermoplastic fibers and reinforcing fibers of different widths. The reinforcing fiber layer is spread wider than the thermoplastic fiber layer. The thermoplastic fiber layer is located below the reinforcing fiber layer. But it is also possible to sandwich the reinforcing fibers between two layers of thermoplastic fibers.

The two layers are overlapped in the middle so that the reinforcing fibers are fed to the needle field of a needle machine at a speed V1 and the thermoplastic fibers at a speed V2. V2 is greater than VI by a factor of 1.1 to 1.5, with V1 being identical to the withdrawal speed after the needle field of the needle machine. Immediately in front of the entry into the needle field of a needle machine there are thread guides which are arranged centrally one above the other and which guide the layers of thermoplastic fibers and reinforcing fibers in different inlet widths. This thread guidance ensures that in the immediately following needle process both types of fibers remain arranged one above the other and the narrower thermoplastic fibers entering with excess speed are needled only so wide, according to the choice of guide width, that both components have the same layer width in the hybrid yarn. The loose layering of spread reinforcing fibers and thermoplastic fibers is needled in the needle field of a needle machine with felt needles lying one on top of the other. The reinforcing fibers are transported in parallel lengthways through the needle field under tensile force. The barbs of the felting needles are arranged in such a way that, when the needles are withdrawn, they get caught primarily with the fibers of the thermoplastic fiber layer guided below. This means that the reinforcing fiber layer on top is only minimally damaged by the needles. This maintains the integrity of the reinforcement fiber layer.

The excess thermoplastic fibers are placed in the layering so that when they come in excess, they are drawn as loops vertically between the parallel reinforcing fibers. This leads to a mixing effect between the two components and a mechanical, non-sliding connection of the two mixed textile components. At the exit of the needle loom, the resulting hybrid yarn can be wound up or fed into further processing.

Due to the stress on the thermoplastic component during the needling process, local tensions are built up in the hybrid roving, which lead to undulation of the reinforcing fibers, which are pulled out mechanically by a subsequent stretching process and the 0 ° orientation of the reinforcing fibers that is then formed is thermally fixed by a temperature treatment below the softening temperature of the thermoplastic component can.

The temperature treatment takes place at 20 K to 50 K below the softening temperature of the thermoplastic fiber, preferably at 30 K to 40 K below the softening temperature of the thermoplastic fiber. The hybrid yarn is treated at this temperature for a period of 0.25 to 2 minutes, preferably for a period of 0.5 to 1 minute.

The hybrid yarn has a ribbon structure with a flat cross-section. Layers of thermoplastic fibers and are distributed in the cross-section Layers of reinforcement fibers with pierced thermoplastic fibers.

The choice of the type of felting needle, the stitch density and the penetration depth determine the resulting mixing intensity, the degree of fixation of the two components and the possible needling of individual reinforcing fibers in the overall hybrid thread.

[Examples]

Embodiment 1

The starting materials are undrawn filament yarns made of polyamide 6 2970 dtex f1080 and a carbon fiber roving CT50-4.4 / 255-T 140 with 50,000 individual filaments. A carbon fiber roving and 7 spools of polyamide yarn are attached to a creel. The thread is drawn off separately for the merged polyamide yarns and the individual carbon fiber roving via a pair of take-off rollers each. The polyamide yarns are drawn off at a speed of 3.5 m / min and the carbon fiber roving at 3 m / min.

After the pair of take-off rollers, there is a three-bar spreader for the carbon fiber roving in front of the entry into the needle loom. Here there is an expansion to a width of 19 - 22 mm. Entry into the needle loom takes place without material jamming. The tensile force required for spreading is created on the one hand by the frictional stress on the spreading rods, on the other hand by the material clamping and pull-off force at the outlet of the needle machine. The spread carbon fiber roving is coming from the take-off roller pair via a 3-bar spreading unit up to the needle field congruently over the converging polyamide threads. At a distance of 2 cm in front of the needle field, both mixture components are narrowed to a defined width using a thread guide. Part of the thread guide is an upper guide slot with a dimension of 3 mm in height and 15 mm in width for the individually spread 50k carbon fiber roving. The 7 polyamide filament yarns (PA6) are guided at a distance of 2 mm in the middle below, with a guide slot with a height of 3 mm and a width of 6 mm. The needling takes place in a needle machine with the stitch direction 1x from above with a stitch density of 13 stitches / cm ² using a Groz Beckert felting needle 15x18x40x3 U222 G 2027, in which the notches move the polyamide fibers from the layer below through the Pull the carbon fiber layer at the top through like a loop.

The hybrid yarn produced by needling is wound up on a disc bobbin at the outlet of the needling machine. The local deviations of the carbon fibers from the preferred 0 ° orientation produced during needling are pulled out after the needling process by stretching under a tensile stress of 20 N and fixed below the softening point of the PA6 by the action of heat.

Under this tension, the drawn hybrid yarn runs into a Thermofix system from Schott & Meissner and is heated at a speed of 3 m / min in a 2 m long heating zone at 180 ° C. with a band gap of 0.2 mm under pressure and then in a 2 m long cooling zone of the Thermofix system. The result is a hybrid yarn tape with 0 ° alignment of the carbon threads with a width of 15-16 mm, a fineness of 6000 tex and a CF content of 60%, which is wound onto a spool at the exit of the Thermofix system.

Embodiment 2

The starting materials are 3 undrawn filament yarns made of Polyamid6 2970 dtex f1080 and a glass fiber filament yarn PPG 1062 Multi-End. A bobbin of the glass fiber filament yarn and 3 bobbins of the polyamide yarn are placed in a creel. The thread take-off is carried out separately for the merged polyamide yarns and the individual glass fiber filament yarn via a pair of take-off rollers each. The polyamide yarns are drawn off at a speed of 3.5 m / min and the glass fiber filament yarn at 3 m / min.

After the pair of take-off rollers, there is a three-bar spreading device for the glass fiber filament yarn before it enters the needle loom. Here there is a spread to a width of 5 to 7 mm. Entry into the needle loom takes place without material jamming. The tensile force required for spreading is created on the one hand by the frictional stress on the spreading rods, on the other hand by the material clamping and pull-off force at the outlet of the needle machine. The spread glass fiber filament yarn, coming from the pair of take-off rollers, is guided congruently over the converging polyamide threads via a 3-bar spreading unit to the needle field. At a distance of 2 cm from the needle field, both mixture components are narrowed to a defined width using a thread guide. Part of the thread guide is an upper guide slot with a dimension of 2 mm in height and 4 mm in width for the individually spread glass fiber filament yarn. The 3 polyamide filament yarns are guided in a guide slot located in the middle below it at a distance of 2 mm and with a dimension of 2 mm in height and 2 mm in width. The needling is done in a needling machine with the stitch direction 1x from above with a Stitch density of 13 stitches / cm ² when using a Groz Beckert 15x18x40x3 U222 G 2027 felting needle, in which the notches pull the polyamide fibers from the layer below through the glass fiber layer above in a loop-like manner when the needle board moves upwards.

The hybrid yarn produced by needling is wound up on a disc bobbin at the outlet of the needling machine. The local deviations of the glass fibers from the preferred 0 ° orientation produced during needling are pulled out after the needling process by stretching under a tensile stress of 6 to 8 N and thermally fixed below the softening point of the PA6.

Under this tension, the drawn hybrid yarn runs into a Thermofix system from Schott & Meissner and is heated at a speed of 3 m / min in a 2 m long heating zone at 180 ° C. with a band gap of 0.2 mm under pressure and then in a 2 m long cooling zone of the Thermofix system. The result is a hybrid yarn tape with a width of 5 to 7 mm with a fineness of 3225 tex and a GF content of 65%, which is wound onto a spool at the exit of the Thermofix system.

List of reference symbols

1

Creel

2

Reinforcement fiber roving

3

Thermoplastic filament yarns

4th

Take-off device for the reinforcement fiber roving

5

Take-off device for the thermoplastic filament yarns

6th

Spreader for the reinforcement fiber roving

7th

Thread guide for the reinforcement fiber roving and thermoplastic filament yarns

8th

Needle board of the needle machine

9

Downholder of the needle machine

10

Needle machine needle plate

11

Hybrid yarn

12th

Intermediate winding

13th

Braked hybrid yarn payoff

14th

Streckfeld

15th

Double belt press, fixing zone

16

End winding of the hybrid yarn

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102011010592 [0003]
• DE 4137406 A1 [0003]
• EP 156599 B [0003]
• DE 19624412 A1 [0004]
• EP 0207422 A2 [0005]
• EP 344650 A2 [0005]
• US 5176868 A [0006]
• WO 1999019273 A1 [0007]
• GB 2105247 A [0008]
• DE 102014019220 A1 [0009]

Claims (11)

Process for the production of a hybrid yarn from endless multifilament reinforcing fibers and multifilament thermoplastic fibers, characterized in that the reinforcing fibers are fed with a greater width than the thermoplastic fibers, overlapping in the middle, one above the other, the thermoplastic filament yarns into the needle field at a higher speed than the reinforcing fibers the needling machine and proportions of the thermoplastic filaments through the action of felting needles through the flock of parallel, longitudinally oriented continuous reinforcing fibers pierced in a loop at an angle of 90 ° cause an intimate adhesion of both components with simultaneous formation of a mixing effect. Procedure according to Claim 1 , characterized in that the reinforcing fibers are glass fibers, carbon fibers or aramid fibers, preferably glass fiber or carbon fiber rovings with a fineness> 2 ktex. Procedure according to Claim 1 , characterized in that the thermoplastic fibers are thermoplastically deformable polymers, preferably made of polyethylene (PE), polypropylene (PP), polyesters such as polyethylene terephthalate (PET), polyetheretherketones (PEEK), polyphenylene sulfide (PPS) and polyamides (P) . Procedure according to Claim 1 , characterized in that the excess speed of the thermoplastic component is preferably 1.1 to 1.5 times, but not greater than twice. Procedure according to Claim 1 until 4th , characterized in that the thermoplastic component runs into the needle field of a needle machine in a smaller strand width than the reinforcing fiber strand and the distance between this guide is less than 20 cm, preferably less than 5 cm, in front of the entry into the needle field. Procedure according to Claim 1 until 5 , characterized in that the reinforcing fibers are guided longitudinally through a needle loom under a tensile force of 3 to 30 N. Procedure according to Claim 1 , characterized in that several layers of reinforcing fibers and thermoplastic fibers can be fed to the needle loom, preferably 2 to 5 layers, the bottom layer always being a thermoplastic fiber layer. Procedure according to Claim 1 until 7th , characterized in that the intermixing needling takes place on both sides or on one side. Procedure according to Claim 1 until 8th , characterized in that the reinforcing fibers are spread and fed to a needle loom. Procedure according to Claim 1 until 9 , characterized in that the hybrid threads are stretched after needling with a tensile stress of 1 to 7 mN / tex, preferably 2 to 4 mN / tex and thermally at temperatures below the softening point of the thermoplastic component under pressure to form a ribbon. Procedure according to Claim 1 until 10 , characterized in that after needling, the hybrid yarn is tempered at a temperature of 10 K to 50 K below the softening temperature of the thermoplastic fiber for a period of at least 5 s, preferably 30 s to 60 s.

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