EP2093318B1 - Flexible composite material, method for its manufacture and application - Google Patents

Description

The present invention relates to a process for producing flexible composite materials, the composites thus obtained and their use. The method of the invention comprises mechanically agitating during drying of binder-impregnated fibrous structures, such as natural fiber felts and natural fiber webs, and / or needling following drying. The composites thus obtained are particularly suitable for further processing of molded parts in compression molding.

Background of the invention

Felt and nonwovens are widely used starting materials, in particular in the production of molded parts in the automotive industry.

In the prior art it is known to treat felts and nonwovens with aqueous solutions. This also includes the impregnation of felts and nonwovens with aqueous binders in order to be able to produce dimensionally stable parts (1). For this purpose, the felts are impregnated with the binder and then dried. In a subsequent thermal treatment, optionally in a hot mold, the binder hardens and there is a stable molding. Such binders generally form solid films after drying, so that, when used in felts or nonwovens, stiffening occurs as a result of the drying process due to the bonding of the fibers, without the binder already curing. This is also disadvantageous to the effect that such "hard", little to inflexible felts and nonwovens can not be wound up.

In order to avoid this, the fibers could already be impregnated and dried before the production of the felt or fleece. In many cases, however, this is technically very complicated to accomplish.

It is also known that correspondingly treated with aqueous binders and dried felts are made reversible again by spraying with water to obtain a flexible product for further processing. The disadvantage here is that an additional step must be performed before processing and interfere with a hot curing of the binder, the existing water.

Alternatively, it is known to stop the drying at a suitable residual moisture (2). A disadvantage, however, proves in this approach, the unstable moisture content, which changes in the storage of unpacked, impregnated felts, as well as the high moisture content, which causes problems especially in the forming and curing in a Heißpreßwerkzeug.

In the case of a natural fiber fleece, which is drenched with Acrodur®-an aqueous acrylate dispersion from BASF AG-and then dried, the manufacturer indicates as the optimum moisture a moisture content of greater than 10%, preferably 20%.

In WO 01/27163 A1 and the corresponding one EP 1 240 205 B1 (BASF) thermally curable polymer dispersions are described as a binder.

In WO 2006/063802 (BASF) describes formaldehyde-free aqueous binders.

It is an object of the present invention to provide a simpler and less expensive process for the production of composites and moldings, which in particular provides flexible composites.

The object is achieved by providing a method for producing flexible composites of sheet-like fibrous structures and binders.

Flat-shaped fiber structure

A starting material of the process according to the invention are sheet-like fiber structures or mats and fabrics, nonwovens or nonwovens or felts.

Under (sheet-like) fiber structures herein textile fabrics such as woven, knitted or nonwoven fabrics are to be understood. They can be made from fibers, shavings, chips or their mixtures exist. An example of such structures are wet or air laid or carded webs. The nonwovens may for example consist of natural or synthetic fibers or of mixtures of natural and synthetic fibers. Examples of natural fibers are fruit fibers, seed fibers and stem fibers such as sisal, jute, hemp, kenaf, flax, cellulose and cotton as well as banana fibers, wool, hair and cork. Examples of synthetic fibers are fibers of polyester, polyacrylonitrile, polyamide, carbon, polyvinyl chloride, polyolefins such as polyethylene and polypropylene, and aramid and inorganic fibers such as mineral fibers and glass fibers.

Preferred sheetlike fibrous structures, starting materials of the process according to the invention, comprise plant fibers and are in particular plant fiber felts or fleeces, which are preferably made of e.g. Jute, sisal, banana, coconut, flax, hemp, kenaf, cotton fibers and mixtures thereof. As starting materials it is also possible to use mixtures of such natural fibers with synthetic fibers, such as polyester fibers, polypropylene fibers or also fibers which are obtained synthetically from renewable raw materials, such as polylactide fibers, or also glass fibers. Nonwovens consisting only of synthetic fibers or of synthetic fibers and glass fibers can also be used as starting materials.

In a preferred embodiment, therefore, the sheet-like fiber structure comprises plant fibers, which are preferably selected from jute, sisal, banana, coconut, flax, hemp, kenaf, cotton fibers and mixtures thereof, and is in particular a corresponding vegetable fiber felt or fleece ,

In the embodiments in which natural or vegetable fibers are used in the sheet-like fibrous structures, their proportion is preferably more than 50% by weight, e.g. 70 to 100 wt .-%.

The sheet-like fiber structure, starting material, preferably has a basis weight of 100 g / m ² to 4000 g / m ² , in particular from 600 g / m ² to 1900 g / m ² .

In a preferred embodiment of the invention, the fiber structure is a mixture of 50% flax fibers and kenaf fibers.

The solidification of the starting material is preferably carried out by mechanical needling. The web may also be consolidated by other felting processes or by thermal bonding with suitable melt fibers or remain unconsolidated as a scrim. (see 1, 3, 4)

binder

Another starting material of the process according to the invention are binders.

The term "binder" as used herein is a binder or binder liquid comprising a polymeric structure dissolved or dispersed in an organic solvent, water or mixtures. A "binder" or a "binding liquid" is also a collective term for the synonyms latex, adhesive, dispersion, plastic dispersion, polymer dispersion, emulsion polymer and polymer solution. (see also section 3.2 Binder fluids in (1)).

• getrocknet, d.h. wasser- und/oder lösemittelfrei,
  und
• chemisch nicht gehärtet und/oder polymerisiert.

Moreover, a "binder" according to this invention does not form a soft elastic film (but a hard film) in the following state:

• dried, ie water and / or solvent-free,
  and
• not chemically cured and / or polymerized.

Binders are known in the art. Preferred suitable binders are described in (1).

The binder is preferably selected from latex, adhesive, dispersion, plastic dispersion, polymer dispersion, emulsion polymer and polymer solution.

Preferably, the binder is present as a solution or dispersion.

Also prepolymers and solutions or dispersions of these may be suitable binders.

The binder is preferably selected from thermally curable binders. Such thermally curable binders are known in the art and extensively described.

Other binders are known to those skilled in the art, such as UV-curing systems, which cure, for example, only at very high thermal stress without UV light.

It is also possible to use a plurality of binders and mixtures of binders.

Preferred binders are described in: WO 01/27163 A1 respectively. EP 1 240 205 B1 (BASF); WO 2006/063802 (BASF).

A particularly preferred binder is Acrodur® - an aqueous acrylate dispersion (BASF).

Further preferred binders are prepolymers based on furfuryl alcohol (furan resins) or phenolic resins, such as resoles and novolaks.

Depending on the starting material used and the desired further use of the composites according to the invention, the person skilled in the art, with the aid of his specialist knowledge and the teaching of this patent application, can select suitable binders.

The binders may contain other additives, such as water repellents, flame retardants, color pigments, anti-mold agents, wetting agents (surfactants), defoamers.

Preferred water repellents are paraffin dispersions, wax dispersions, organosilicon compounds.

Preferred flame retardants are inorganic flame retardants such as aluminum hydroxide, magnesium hydroxide, ammonium sulfate and phosphate, boron salts, also in combination with organic compounds such as melamine and urea.

Preferred color pigments are organic and inorganic color pigments, such as in EP 1 582 344 A1 described. Further color pigments are known to the person skilled in the art.

Preferred antimold agents are boron oxides, boric acid and salts, and mixtures thereof; 2-mercaptopyridine N-oxide and salts, such as the sodium salt,

The addition of antimold agents is basically possible and common in the art, but not necessary due to the method of the invention (see below).

Inventive method

In step (a) of the process according to the invention, a sheetlike fibrous structure is treated with a binder. This treatment is known in the art and is also referred to as impregnation.

Preference is impregnated with at least one binder. According to the invention, it is also possible to use a plurality of binders and mixtures of binders.

The process step (a) involves known measures for the production of bonded fiber webs.

In this case, at least one binder in an amount of 0.5 to 40 wt .-%, preferably 15 to 30 wt .-%, more preferably about 20 wt .-% (solids content of binder based on the sheet-like fiber structure) is used.

The binder serves to solidify the fiber structures. It can be applied, for example, by spraying, dipping, impregnating or patting or by treating the fiber structure with a foam (3, 4).

Preferred methods for the treatment or impregnation are selected from spraying, rolling or impregnating or impregnating in an impregnating bath.

Particularly preferred is the impregnation in the padder bath, especially if the fiber structure contains natural fibers.

For a description of the preferred soaking method, see (1), p. 375.

In a preferred embodiment, a needled natural fiber mat in roll form is pulled through the padder bath containing the binder (s) with a suitable solids content and optional additives and squeezed between 2 rollers to the desired binder and water content. Thereafter, the impregnated roll is optionally wound and dried via an external dryer (see step (b)).

The winding after the padding takes place in the embodiments in which the dryer used can not be charged directly with the impregnated felt. In a preferred embodiment, after the impregnation, the impregnated mat web is fed directly into the dryer, preferably a perforated drum dryer (see below).

The starting material felt is impregnated in step (a) in a known manner with a binder solution - preferably with an aqueous solution - or a binder dispersion which may contain other additives.

In step (b) of the process according to the invention, the treated sheetlike fibrous structure is dried.

The drying of the fiber structure treated with a binder according to process step (a) is preferably carried out under conditions which do not lead to the curing of the binder.

These conditions are preferably selected depending on the curing temperature of the binder, especially when thermally curable binders are used.

When using other binders or binder systems, other conditions will be selected accordingly.
In the case of UV-curing binders or binder systems which cure in each case with or without UV light or which cure, for example, only at very high thermal stress without UV light.

Thus, the drying of the fibrous structures treated with a binder according to process step (a) is preferably carried out at a temperature which does not exceed the curing temperature of the binder, i. which is below the temperature at which the binder crosslinks. This ensures that the binder does not or at most only partially cured.

The temperature at which the individual binders crosslink or harden depends on the type of binder used. Methods for determining the crosslinking temperature of binders (or also referred to as the curing temperature of the binders) are known in the art.

The water- or solvent-containing felt is dried to the extent that, as far as possible, only the solids content remain in the felt, i. that a water or solvent content of less than 10 wt .-% based on the impregnated felt remains. During drying, preferably, the curing temperature (crosslinking temperature) of the binder is not exceeded in order to avoid premature chemical curing.

The curing temperature of the preferred binder Acrodur® is 130 ° C to 200 ° C or depending on the preparation used at 130 ° C to 160 ° C (see information from the manufacturer).
The drying in step (b) is preferably carried out using this binder in a temperature range of 100 to 130 ° C.

The drying is preferably carried out in a perforated drum dryer.
A preferred screen drum dryer has 4 to 6 drums, as described for example in (1), p 346. Manufacturers of such dryer are z. Fleissner GmbH (Egelsbach, Germany) or Moenus Textilmaschinen GmbH (Gera and Mönchengladbach, Germany).

Step (b) contains two (part) steps (i) and (ii), which are performed either alternatively or in combination.

(Part) Step (i) of step (b) : During drying, the fiber structure is subjected to a mechanical movement according to the invention.

This mechanical movement serves to reduce the stiffness of the fiber structure and preferably to prevent.

This mechanical movement of the fiber structure preferably takes place from a residual moisture content of the fiber structure of less than 20%, more preferably less than 10%.

The "residual moisture" is determined by a standard method by weighing the sample / fiber structure before and after a drying step. Drying takes place in a drying oven until the weight of the sample / fiber structure no longer changes / remains constant (to constant weight), preferably at 110 ° C., and under conditions in which the binder does not cure yet. For resin / binder systems that cure already at 110 ° C, a correspondingly lower temperature is selected. The method for determining the residual moisture differs from the determination of the equilibrium moisture, which is also described herein.

The mechanical movement is preferably achieved by rolling or the deflection over several rollers. Preferably, a meandering reversal of the mat web is carried out over small radii.

In one embodiment, the drying is carried out by the repeated passage through a perforated drum dryer with downstream deflection rollers.
Preferably, however, the drying is carried out in a perforated drum dryer with 4 to 6 drums (corresponding to (1), page 346) and downstream pulleys. The number of drums depends on the throughput speed (= production speed) and the basis weight of the felt.

In order to prevent the felt or nonwoven web from becoming stiff, according to the invention the still warm, almost dry felt at a residual moisture content of less than 20%, preferably less than 10%, is deflected over several rolls in order to introduce a mechanical movement into the system. This results in contrast to a conventional (known in the art) leading out of the nonwoven web from the dryers used a flexible, movable felt.

It is also possible to omit the first softening step by deflection over different rolls and to pass the web or blanks directly through a needle machine (see step (ii) of (b)).

The (part) steps (i) (mechanical movement during drying) and (ii) (needling subsequent to drying) of step (b) are performed either alternatively or in combination.

(Part) Step (ii) of Step (b): Following drying, the dried, optionally mechanically moved, sheet-like fibrous structure treated in the preceding steps may be mechanically needled.

The sheet-like fiber structure is preferably used in almost completely dried or almost dry state, ie with residual moisture <10%, preferably a moisture content between 0 and 8 wt .-%.

This step of needling is directly connected to the drying process or is performed separately.

The needling is preferably carried out in a conventional in the art needle machine, preferably with double-sided needling.

In this subsequent step, which is directly connected to the first drying process, but can also be carried out separately, in this step of the invention (step (ii) of (b)), the almost dry felt web (residual moisture <10%) by a commercially available needle machine guided.

Subsequently, in step (c), the composite according to the invention, which is characterized in more detail below, is obtained.

1. (a) Behandlung eines flächenförmigen Fasergebildes mit Bindemittel,
2. (b) Trocknen des behandelten flächenförmigen Fasergebildes bei Bedingungen, die nicht zur Härtung des Bindemittels führen,
   1. (i) wobei während des Trocknens, bevorzugt ab einer Restfeuchte von weniger als 20%, mechanische Bewegung erfolgt wobei die mechanische Bewegung das Steifwerden des Fasergebildes verringert und bevorzugt verhindert und/oder
   2. (ii) wobei das behandelte und auf eine Restfeuchte von weniger als 10% getrocknete flächenförmigen Fasergebilde anschließend an die Trocknung mechanisch vernadelt wird,
3. (c) Erhalten des flexiblen Verbundwerkstoffs.

The process according to the invention accordingly preferably comprises the following steps:

1. (a) treatment of a sheetlike fibrous structure with binder,
2. (b) drying the treated sheet-like fibrous structure under conditions which do not cure the binder,
   1. (i) during the drying, preferably from a residual moisture content of less than 20%, mechanical movement takes place whereby the mechanical movement reduces the stiffness of the fiber structure and preferably prevents and / or
   2. (ii) wherein the treated and dried to a residual moisture of less than 10% sheet-like fiber structure is then needled mechanically after drying,
3. (c) obtaining the flexible composite.

The steps (i) (mechanical movement during drying) and (ii) (needling subsequent to drying) of step (b) are carried out either alternatively or in combination.

1. (a) Behandlung eines flächenförmigen Fasergebildes mit Bindemittel,
2. (b) Trocknen des behandelten flächenförmigen Fasergebildes bei Bedingungen, die nicht zur Härtung des Bindemittels führen,
   1. (i) wobei während des Trocknens, bevorzugt ab einer Restfeuchte von weniger als 20%, mechanische Bewegung erfolgt, wobei die mechanische Bewegung das Steifwerden des Fasergebildes verringert und bevorzugt verhindert
3. (c) Erhalten des Verbundwerkstoffs.

In one embodiment (with alternative execution), the method according to the invention comprises the following steps:

1. (a) treatment of a sheetlike fibrous structure with binder,
2. (b) drying the treated sheet-like fibrous structure under conditions which do not cure the binder,
   1. (i) during the drying, preferably from a residual moisture of less than 20%, mechanical movement takes place, wherein the mechanical movement reduces the stiffness of the fiber structure and preferably prevents
3. (c) obtaining the composite.

1. (a) Behandlung eines flächenförmigen Fasergebildes mit Bindemittel,
2. (b) Trocknen des behandelten flächenförmigen Fasergebildes bei Bedingungen, die nicht zur Härtung des Bindemittels führen,
   1. (ii) wobei das behandelte und auf eine Restfeuchte von weniger als 10% getrocknete flächenförmigen Fasergebilde anschließend an die Trocknung mechanisch vernadelt wird,
3. (c) Erhalten des flexiblen Verbundwerkstoffs.

In a further embodiment (with alternative execution), the method according to the invention comprises the following steps:

1. (a) treatment of a sheetlike fibrous structure with binder,
2. (b) drying the treated sheet-like fibrous structure under conditions which do not cure the binder,
   1. (ii) wherein the treated and dried to a residual moisture of less than 10% sheet-like fiber structure is then needled mechanically after drying,
3. (c) obtaining the flexible composite.

1. (a) Behandlung eines flächenförmigen Fasergebildes mit Bindemittel,
2. (b) Trocknen des behandelten flächenförmigen Fasergebildes bei Bedingungen, die nicht zur Härtung des Bindemittels führen,
   1. (i) wobei während des Trocknens, bevorzugt ab einer Restfeuchte von weniger als 20%, mechanische Bewegung erfolgt, wobei die mechanische Bewegung das Steifwerden des Fasergebildes verringert und bevorzugt verhindert
      und
   2. (ii) wobei das behandelte und auf eine Restfeuchte von weniger als 10% getrocknete flächenförmigen Fasergebilde anschließend an die Trocknung mechanisch vernadelt wird,
3. (c) Erhalten des Verbundwerkstoffs.

In a preferred embodiment (with combined implementation), the method according to the invention comprises the following steps:

1. (a) treatment of a sheetlike fibrous structure with binder,
2. (b) drying the treated sheet-like fibrous structure under conditions which do not cure the binder,
   1. (i) during the drying, preferably from a residual moisture of less than 20%, mechanical movement takes place, wherein the mechanical movement reduces the stiffness of the fiber structure and preferably prevents
      and
   2. (ii) wherein the treated and dried to a residual moisture of less than 10% sheet-like fiber structure is then needled mechanically after drying,
3. (c) obtaining the composite.

Inventive flexible composite

The product of the process of the invention is a composite of the fibrous structure and binder which has advantageous properties over conventional composites.

The composite according to the invention is a flexible composite because it is a flexible, deformable and "soft" composite (felt) with sufficient binder content, preferably in the range of 15 to 30 wt .-% (solids content of binder based on the sheet-like fiber structure)). Moreover, the composite material according to the invention has only a low residual moisture content and can therefore be stored open for months without appreciable change in humidity. In one embodiment, the weight loss of the treated treated felt upon open storage and 16 to 22% resin / binder content is 6 to 9% by weight; for weight loss see below.

The composite according to the invention is deformable in the same way as untreated felts and can be cured in a Heißpreßwerkzeug to form a dimensionally stable part.

Conventional composites, however, lead to hard composites when completely dry after binder impregnation. Hard composite or hard mat means that the composite / mat can not be wound up on the surface using commercially available cores (diameter approx. 15 to 25 cm) without noticeable cracks.

Such a binder-containing felt (composite according to the invention) can therefore be prepared in known manner, e.g. used for the production of automotive parts.

A preferred embodiment of the composite of the invention, such as a resinated felt mat, has a preferred basis weight in the range of 800 to 2,200 g / m ² . The respective preferred basis weights depend on the further use. use preferred basis weights Interior door panels 1,600 - 2,000 g / m ² hat racks 1,800 - 2,200 g / m ² headliners 800 - 1,100 g / m ² Backrest shells for seats 1,700 - 2,200 g / m ²

Other parameters of the composite of the invention are component related, i. they are determined by the further use of the composite. Other parameters are blank formats, variations in the needling density of the starting mat (which influences warpage behavior), other fiber combinations (e.g., hemp instead of flax).

The composite of the invention is distinguishable from conventional composites, e.g. by microscopic observation or by observation through a magnifying glass, z. B. 2- to 4-fold linear magnification with a magnifying glass - as in the accompanying figures. The attached figures are in original scale and in 2x magnification (see also drawn scale).

The soft, impregnated and dried composite / felt obtained in accordance with the invention can be stored open, wherein a moisture dependent on the fibers used, the binder used and the room humidity is established as equilibrium moisture content from the environment.

The "equilibrium moisture content" is determined by the weight loss during hot pressing, resulting in curing of the binder. The weight loss in this determination method additionally includes possible cleavage products from the curing reaction (in the binder Acrodur® reaction water from the Polykondensationsreaktion) and at higher temperature vaporizable substances from natural fibers, such as waxes and oils.
The method for determining the equilibrium moisture differs from the determination of the residual moisture, which is also described herein.

The equilibrium moisture content is preferred by the weight loss when pressing the impregnated composite / felt at 210 ° C / 60 sec. Thus, it also contains and evaporates constituents from the fibers, such as the natural fibers, and possibly constituents exiting from the binder as reaction water.

For the experimental determination of the "equilibrium moisture content", the impregnated mat / composite is weighed prior to insertion into the hot pressing tool and then after pressing at 210 ° C., 60 seconds. weighed back while still warm. From the difference, the weight loss, referred to as moisture, in percent, based on the dry pressed part obtained, calculated.

• Ausgangsstoff Fasergebilde:    Mischung von jeweils 50 % Flachsfasern und Kenaffasern
• Ausgangsstoff Bindemittel:    Acrodur®, BASF
• Festkörper-Bindemittelanteil:    20 bis 30 Gew.-%, insbesondere 25 Gew.-%
• Raumfeuchte:    40 % r.F. (relative Luftfeuchtigkeit)
• resultierende Gleichgewichtsfeuchte    ungefähr 7 Gew.-%.

In a preferred embodiment

• Starting material fiber structure: mixture of 50% flax fibers and kenaf fibers
• Starting material Binder: Acrodur®, BASF
• Solid binder content: 20 to 30% by weight, in particular 25% by weight
• Room humidity: 40% rh (relative humidity)
• resulting equilibrium moisture about 7 wt .-%.

Due to the low moisture content of the composites of the invention, e.g. the use of anti-mold agents, especially when using natural fibers, not necessary.

The result is a "soft", pliable and deformable felt, a flexible composite that is capable of forming even more deformed parts without pretreatment or preforming processes by forming in a hot stamping tool without cracking or breakage.

The skilled person would expect straight with the use of natural fibers such as flax, hemp, kenaf, jute, sisal, but also other plant fibers that the needle process, a substantial destruction of the fibers occurs, so that the mechanical properties of the subsequently compressed felt compared to a non-treated mat drop significantly.

However, the inventors' experiments show that, on the contrary and completely unexpectedly, no deterioration of the mechanical properties occurs. In the 3-point bending test z. For example, according to DIN EN ISO 178, the values for the modulus of elasticity and the flexural strength remain unchanged regardless of the treatment within the scope of the usual scattering. In the case of the impact strength according to Charpy, DIN EN ISO 179, the treatment shows a slight tendency to subsidence, with the areas of the compacts / molded parts consisting of untreated and the composites treated according to the invention clearly overlapping within the standard deviation (± 1 s). See example.
Other properties such as the water absorption after 24 hours of water storage, measured according to DIN 52 351, obtained from the composites of the invention obtained compacts / moldings, rather, have an improvement in that the water absorption and the thickness swelling is reduced. See also example.

The process is therefore suitable, unlike the prior art, to produce soft, binder precoated and dry felts, from which e.g. More deformed automotive parts, such as supports for door panels, can be produced.

Uses of the composite according to the invention

According to the invention, the flexible composite materials according to the invention are used as molded parts and shaped bodies, preferably in the automobile industry.

Typical applications of moldings and moldings for the automotive industry are: door panels, hat racks, instrument panels, headliners, etc.

• Kofferschalen;
• Maschinenabdeckungen;
• Einsätze für Schränke, Schubladen, Möbelrückwände;
• Schalen und Rückenlehnen für Stühle, Bürostühle, Sessel;
• Gartenmöbel (Gartentische, Stühle, Liegen);
• als Trägerwerkstoff für Dekorpapier, Dekorstoffe und Holzfurniere.

Other uses include, for example

• Case shells;
• Machine covers;
• Inserts for cabinets, drawers, furniture backs;
• Bowls and backrests for chairs, office chairs, armchairs;
• Garden furniture (garden tables, chairs, loungers);
• as carrier material for decorative paper, decorative fabrics and wood veneers.

• die Verwendung eines erfindungsgemäßen Verbundstoffs
• und die Erwärmung der Verbundstoffs auf eine Temperatur, die größer oder gleich der Härtungstemperatur des Bindemittels ist.

The invention further provides methods of compression molding. Such a method comprises:

• the use of a composite according to the invention
• and heating the composite to a temperature greater than or equal to the curing temperature of the binder.

Definition of terms:

The terms "pulp", "nonwoven", "nonwoven", "felt" and "composite" or "composite" used herein are terms commonly used in the art.

At this point, common definitions are taken from the literature, such as e.g. (5) and (1), especially p. 1-3.

A "pulp" is a textile raw material from vegetable, animal, mineral or synthetically produced fibers, eg. Eg silk, artificial silk.

"Nonwoven" (also short "fleece") is a textile fabric made of individual fibers. In contrast, fabrics, knits and knits are made from yarns and membranes are made from films. A "fleece" consists of loosely connected fibers, which are not yet connected to each other. The strength of a fleece is based only on the fiber's own liability, but can be influenced by Avivagen. To be able to process and use the fleece, it must be solidified, for which various methods can be used. Only a solidified nonwoven is to be called a nonwoven fabric. In colloquial language, this difference is not made.

A "felt" is a fabric of pressed, entangled, non-woven, mostly animal fibers. A "felt" is a nonwoven fabric made of wool and / or other textile fibers. The cleaned, combed and processed to fleece and possibly colored raw wool or fibers are brought by a mostly mechanical processing (felting and walking) in a solid material. The individual fibers are intertwined with each other. For dry felting, the dry wool is shaped using special needles. This method is the precursor of needling with a needle bar. Needle felt is made mechanically with numerous barbed needles. In this case, the barbs are arranged in reverse as in a harpoon, so that the fibers are pressed into the felt and the needle easily goes out again. Repeated grooving entangles the fibers with each other and may subsequently be aftertreated chemically or with steam. Such needled nonwovens can be produced not only from wool but also from virtually all other fibers. Needle felt is today's industrially produced felt. In addition, the entanglement with a pulsed water jet or with a binder is still possible. Here also fibers without scale structure can be used (eg: polyamide, polyester).

A "composite" is a material of two or more bonded materials. The composite material has different material properties than its individual components. Material properties and geometry of the components are important for the properties of the composites. In particular, size effects often play a role. The connection is made by fabric or form-fitting or a combination of both.

The present invention will be further clarified in the following figures and examples without, however, being limited thereto. The cited references are hereby fully incorporated by reference. The example shown clearly shows that the method according to the invention leads to a flexible, flexible resin mat without losing the mechanical properties required for further processing.

characters

• Figur 1 zeigt die Oberfläche eines unbehandelten Nadelfilzes aus Flachs- und Kenaffasern (Ausgangsstoff Fasergebilde), wie er beispielsweise für die Herstellung eines erfindungsgemäßen weichen, harzgetränkten Filzes verwendet werden kann. Die Einstiche der zur Verfestigung benutzten Nadeln sind als dunkle Löcher deutlich sichtbar. Der Nadelfilz ist weich und biegsam.
• Figur 2 zeigt die entsprechende Oberfläche eines mit einem Acrylharz (Acrodur®) durch Foulardieren getränkten Nadelfilzes gemäß Figur 1, der anschließend in einem Trockenschrank vollständig getrocknet wurde und durch offene Lagerung bei Raumbedingungen seine Gleichgewichtsfeuchte wieder aufgenommen hat. Der beharzte Filz zeigt keine erkennbaren Nadeleinstiche mehr auf. Das Produkt ist hart und nicht flexibel. Nur durch Erhöhung der Feuchtigkeit durch Einwirkung von Wasser auf einen Feuchtigkeitsgehalt > 15 % stellt sich reversibel eine Flexibilität ein. Das feuchte Produkt entspricht dem aktuellen Stand der Technik.
• Figur 3 zeigt die Oberfläche eines mit Bindemittel getränkten Filzes, wie bei Figur 2 beschrieben, bei dem gegen Ende der Trocknung durch mechanische Bewegung, die durch Umlenkung über Radien erzeugt wird, eine vollständige Versteifung des trockenen Filzes verhindert wurde (Bewegung während des Trocknens in Schritt (b)). Der Filz wurde vollständig getrocknet und dann unter Raumbedingungen wieder auf Gleichgewichtsfeuchte äquilibriert. Im Gegensatz zum Filz nach Figur 2 ist das Produkt biegsam und flexibel. In der Oberflächenstruktur sind keine charakteristischen Änderungen gegenüber dem Produkt aus Figur 2 erkennbar.
• Figur 4 zeigt einen getränkten Filz entsprechend Figur 3, der in einem weiteren erfindungsgemäßen Verfahrensschritt durch eine Nadelmaschine geführt wurde (Schritt (c)), wie sie z.B. auch zum Verfestigen von Vliesen gemäß Figur 1 (Ausgangsstoffen) verwendet wird. Im Gegensatz zu Figur 2 und 3 sind die Einstiche der Nadeln deutlich als dunkle Punkte erkennbar. Das gezeigte Produkt wurde unter Technikumsbedingungen foulardiert und anschließend mit mehrmaligem Durchlauf durch einen Siebtrommeltrockner mit nachgeschalteten Umlenkrollen vollständig getrocknet (entspricht dem Zustand von Figur 3). Die trockene aufgerollte Filzbahn wurde unter Raumbedingungen gelagert und in einem letzten Schritt durch eine handelsübliche Nadelmaschine mit beidseitiger Vernadelung geführt. Nach der Behandlung ist der trockene Filz deutlich biegsamer und flexibler als ein behandelter Filz gemäß Figur 3. Der Filz fühlt sich weich und geschmeidig an und unterscheidet sich dadurch in den Eigenschaften sehr deutlich von einem Filz gemäß Figur 2. Gegenüber dem Stand der Technik ist der Filz aber nicht feucht und fühlt sich auch nicht feucht an.

The attached figures are in the original scale (left picture) and in 2x magnification (right picture), see the drawn scale.

• FIG. 1 shows the surface of an untreated needle felt of flax and kenaf fibers (starting material fiber structure), as it can be used for example for the production of a soft, resin-impregnated felt according to the invention. The punctures of the needles used for consolidation are clearly visible as dark holes. The needle felt is soft and flexible.
• FIG. 2 shows the corresponding surface of an impregnated with an acrylic resin (Acrodur®) by padding needle felt according to FIG. 1 , which was then completely dried in a drying oven and resumed its equilibrium moisture content by open storage under ambient conditions. The felted felt no longer shows noticeable needle punctures. The product is hard and not flexible. Only by increasing the humidity by the action of water to a moisture content> 15% reversibly sets a flexibility. The moist product corresponds to the current state of the art.
• FIG. 3 shows the surface of a binder-soaked felt as in FIG. 2 described in which towards the end of the drying by mechanical movement, which is generated by deflection over radii, a complete stiffening of the dry felt was prevented (movement during drying in step (b)). The felt was completely dried and then re-equilibrated to equilibrium moisture under room conditions. Unlike the felt after FIG. 2 the product is flexible and flexible. In the Surface texture are not characteristic changes compared to the product FIG. 2 recognizable.
• FIG. 4 shows a soaked felt accordingly FIG. 3 , which was guided in a further method step according to the invention by a needle machine (step (c)), as for example, also for solidifying nonwovens according to FIG. 1 (Starting materials) is used. In contrast to FIG. 2 and 3 the punctures of the needles are clearly recognizable as dark spots. The product shown was padded under pilot plant conditions and then completely dried with repeated passes through a sieve drum dryer with downstream deflection rollers (corresponds to the state of FIG. 3 ). The dry rolled felt web was stored under room conditions and passed in a final step through a commercially available needling machine with double-needle needling. After treatment, the dry felt is significantly more flexible and flexible than a treated felt according to FIG. 3 , The felt feels soft and supple and thus differs very clearly in its properties from a felt FIG. 2 , Compared to the state of the art, the felt is not damp and does not feel damp.

example

Several blanks of 300 x 300 mm from a natural fiber mat were soaked in a resin solution (binder) under the same conditions, and the excess resin portion was then pressed between two rollers using a laboratory tuft. The impregnated mats thus obtained were dried in a laboratory drying oven and then brought to equilibrium moisture content by open storage in the laboratory.

Row A: [prior art; without steps (b) (i) and / or (ii) according to the invention

The first part was completely dried after padding and then left open for 48 hours to reach equilibrium moisture under room conditions.

Row C: [Inventive step (b) (ii)]

A part of row A was passed through a needle machine after complete drying and subsequent adaptation to room conditions in a further step.

Row B: [Inventive step (b) (i)]

Another part of the impregnated blanks was mechanically deflected several times at the end of drying via a roller with a diameter of 11 cm, dried and again deflected.

Row D: [inventive steps (b) (i) and (ii)]

A part of row B was passed through a needle machine after adaptation to room conditions in a further step.

After a final open storage, the resinated blanks treated as described above were pressed in a hot plate die and the properties determined. Table 1 shows the individual values of the blanks of the rows A-D during fouling and pressing.

Natural fiber mat used (starting material):

• 50% by weight flax and 50% by weight kenaf, mechanically needled
• (Starting) basis weight: 1476 g / m ²
• (Outlet) humidity: 9.9%

Resin solution (binder) used:

2.5 kg Acrodur®, BASF AG (delivery state with 50% solids content) 2.5 kg water

The resin application (treatment with binder) corresponds to a resin solids content of 25.9 wt .-% based on the natural fiber mat.

The wet blanks were dried in a laboratory drying oven at 110 ° C. in a simple position next to each other.

To carry out the needling, an untreated natural fiber mat was provided with sufficient punched holes, into which the prepared samples of rows C and D were then sewn. The untreated natural fiber mat served exclusively as a transport aid through the needle machine.

Needle parameters:

• Double needle machine, 1 x from above, 1 x bottom needles (Manufacturer: Fehrer)
• Penetration depth: 1.0 mm
• Puncture density: 40 U / cm ²

Press parameters:

• Electrically heated plate tool, temperature top / bottom 190-200 ° C
• Press time: 3 sec.
• Ventilation cycle: 60 sec.
• Pressing distance: 2.0 mm

• Presse schließen, bis Pressdruck aufgebaut ist
• 3 sek. pressen
• kurz entlüften (Pressdruck auf "0" zurücknehmen = Lüftungstakt")
• Pressdruck erneut aufbauen und 60 sek. weiterpressen
• Presse öffnen
• Bauteil/Presskörper entnehmen.

Tabelle 1 Eigenschaften der Zuschnitte beim Foulardieren und Pressen: Gewicht des Zuschnitts
(300x300 mm) Harzauftrag Pressen Nr. Reihe vorher [g] nach Foulardieren [g] (Festkörper) ¹⁾ [g] Gewichtsverlust ²⁾ [%] 1 A 133 266 33,3 7,4 2 C 132 262 32,5 7,6 3 C 138 275 34,3 7,2 4 A 136 273 34,3 7,3 5 A 132 263 32,8 8,8 6 A 134 269 33,8 6,6 7 C 136 278 35,5 7,3 8 A 136 274 34,5 9,3 9 C 131 268 34,3 7,5 10 D 127 260 33,3 8,4 11³⁾ --- 130 266 34,0 12 D 134 271 34,3 10,0 13 B 130 277 36,8 6,8 14 B 126 256 32,5 6,4 15 D 140 291 37,8 10,1 16 D 134 274 35,0 11,3 17 B 134 274 35,0 6,6 18 B 130 267 34,3 6,1 19 D 133 274 35,3 11,4 20 B 130 267 34,3 6,0 Mittelwert⁴⁾ 133 270 34,4 8,0 ¹⁾ Der Festkörpergehalt der eingesetzten Harzlösung beträgt 25 Gew.-%. Aus der aufgetragenen Harzmenge ([Gewicht nach Foulardieren] - [Gewicht vorher]) bei 25% Festkörpergehalt wird der aufgetragene Festkörper in [g] berechnet.
²⁾ Der Gewichtsverlust beim Pressen wurde durch Wiegen der Zuschnitte vor Einlegen in die Presse und unmittelbar nach Entnehmen der gepressten Zuschnitte bestimmt. Der Gewichtsverlust beinhaltet die in dem eingelegten Zuschnitt vorhandene Restfeuchte sowie das bei der Härtungsreaktion des Harzes entstandene Reaktionswasser, sowie eventuell weitere flüchtige Substanzen aus den Naturfasern.
³⁾ Zuschnitt Nr. 11 wurde aufgrund eines Bearbeitungsfehlers nicht mehr weiter verfolgt.
⁴⁾ Alle Zuschnitte wurden in der Reihenfolge 1 bis 20 getränkt und später auch in dieser Reihenfolge abgepresst. Das Gewicht des Zuschnitts vorher und nach Foulardieren - einschließlich des daraus berechneten Harzauftrags - sind unabhängig von der erst nachher erfolgten Behandlung und zeigen die Schwankung innerhalb des Versuchs. Ebenso zeigt der Gewichtsverlust beim Pressen die Schwankungsbreite an. Der Mittelwert dient ausschließlich als Orientierungshilfe. The press time runs as follows:

• Close press until pressing pressure is built up
• 3 sec. press
• vent briefly (press down to "0" = ventilation cycle ")
• Build pressure again and 60 sec. more pressing
• Open press
• Remove component / compact.

<b> Table 1 </ b> Characteristics of blanks for padding and pressing: Weight of the blank
(300x300 mm) resin application Press No. line before [g] after padding [g] (Solids) ¹⁾ [g] Weight loss ²⁾ [%] 1 A 133 266 33.3 7.4 2 C 132 262 32.5 7.6 3 C 138 275 34.3 7.2 4 A 136 273 34.3 7.3 5 A 132 263 32.8 8.8 6 A 134 269 33.8 6.6 7 C 136 278 35.5 7.3 8th A 136 274 34.5 9.3 9 C 131 268 34.3 7.5 10 D 127 260 33.3 8.4 11 ³⁾ --- 130 266 34.0 12 D 134 271 34.3 10.0 13 B 130 277 36.8 6.8 14 B 126 256 32.5 6.4 15 D 140 291 37.8 10.1 16 D 134 274 35.0 11.3 17 B 134 274 35.0 6.6 18 B 130 267 34.3 6.1 19 D 133 274 35.3 11.4 20 B 130 267 34.3 6.0 Mean ⁴⁾ 133 270 34.4 8.0 ¹⁾ The solids content of the resin solution used is 25 wt .-%. From the applied resin quantity ([weight after padding] - [weight before]) at 25% solids content, the applied solids are calculated in [g].
²⁾ The weight loss during pressing was determined by weighing the blanks before loading in the press and immediately after removing the pressed blanks. The weight loss includes the residual moisture present in the inserted blank as well as the water of reaction formed during the curing reaction of the resin, as well as possibly further volatile substances from the natural fibers.
³⁾ Blank No. 11 was discontinued because of a processing error.
⁴⁾ All blanks were soaked in the order 1 to 20 and later also pressed in this order. The weight of the blank before and after padding - including the calculated resin application - are independent of the subsequent treatment and show the variation within the experiment. Similarly, the weight loss during pressing indicates the fluctuation range. The mean value serves only as a guide.

Results: 1. Evaluation of the feel and softness after drying and treatment (before pressing)

Row A: Hard, stiff, "like a board". Row B: Blanks pliable, clearly noticeable resistance, goes back to starting position. Row C: Blanks flexible, slightly stiffer than row B. Row D: Blanks easy to bend, character like a non-resinous, strong
needled NF mat, does not go back to starting position.

2. Physical properties

(after pressing)
using test specimen series from the impregnated, optionally treated and pressed blanks (test plates) <b> Table 2 </ b> line Density ¹⁾
[g / cm ³ ] s Modulus of elasticity ²⁾
[N / mm ² ] s Bending strength ²⁾
[N / mm ² ] s A 0.75 0.05 3785 891 35 8.3 B 0.80 0.04 3968 751 38 8.1 C 0.86 0.05 4487 667 43 7.5 D 0.89 0.04 4886 908 49 9.9 ¹⁾ DIN 52 355
²⁾ 3-point bending test according to DIN EN ISO 178, 40 mm span (modulus of elasticity = modulus of elasticity)
s standard deviation line density
[g / cm ³ ] s Impact resistance ³⁾
[kJ / m ² ] s A 0.93 0.06 13 2.4 B 1.01 0.08 11 2.1 C 1.05 0.09 13 2.5 D 0.95 0.05 10 2.2 ³⁾ Impact strength according to Charpy, DIN EN ISO 179
s standard deviation line density
[g / cm ³ ] s Water absorption 5)
[%] s Thickness swelling 5)
[%] s A 0.83 0.03 70 10 27 2.1 B 0.79 0.04 66 10 26 2.6 C 0.83 0.04 54 11 25 2.2 D 0.87 0.05 53 9 20 1.4 ⁵⁾ measured according to DIN 52 351
s standard deviation

references

1. (1) W. Albrecht, H. Fuchs, W. Kittelmann: Nonwovens. WILEY-VCH Verlag, 2000, (ISBN 3-527-29535-6 )
2. (2) B. Reck, J. Turk; BASF AG, Ludwigshafen, Germany Thermally curable, aqueous acrylic resins - a new class of thermosetting binders for wood and natural fibers, 2nd International Wood and Natural Fiber Composites Symposium June 28-29, 1999 in Kassel / Germany. (www.uni-kassel.de/fb15/ifw/wpc/zu_downloaden/Tagung_1999_PDF/25%20Reck.pdf )
3. (3) Wuzella G .: A new composite material based on natural fibers and a thermoset - technology, applications and properties. High Performance Structures and Materials. Ostend, Belgium, 3.-5. May 2006, lecture
4. (4) Wuzella, G .: A new composite material based on natural fibers and a thermoset: technology, applications and properties. High Performance Structures and Materials III, WIT Press, UK Ed .: CA Brebbia; ISBN 1-84564-162-0, 2006, 53-62, printed ,
5. (5) Gehard Wahrig, Hildegard Kramer, Harald Zimmermann: Brockhaus Wahrig German Dictionary in 6 volumes, FA Brockhaus Wiesbaden, 1981, (ISBN 3-7653-0312-7 ).

Claims (20)

1. A method for producing a flexible composite from laminar fiber structures and binding agents, comprising the steps of

   (a) treating a laminar fiber structure with binding agent,

   (b) drying the treated laminar fiber structure at conditions that do not result in curing of the binding agent,

   (i) wherein during drying, preferably at a residual moisture content of the fiber structure of less than 20%, mechanical moving is carried out,
   wherein the mechanical moving reduces and preferably eliminates the stiffening of the fibre structure,
   and/or

   (ii) wherein the treated laminar fiber structure, which is dried to a residual moisture content of less than 10%, is mechanically needled subsequent to the drying,

   (c) obtaining the flexible composite.
2. The method of claim 1, wherein the laminar fiber structure comprises plant fibers and is in particular a plant fiber felt or plant fiber nonwoven fabric.
3. The method of claim 1 or 2, wherein the plant fibers are selected from jute fibers, sisal fibers, banana fibers, coconut fibers, flax fibers, hemp fibers, kenaf fibers, cotton fibers and mixtures thereof.
4. The method of any one of claims 1 to 3, wherein the laminar fiber structure has a grammage from 100 g/m² to 4000 g/m², in particular from 600 g/m² to 1900 g/m²,.
5. The method of any one of claims 1 to 4, wherein the binding agent is selected from thermal curable binding agents.
6. The method of any one of claims 1 to 5, wherein the binding agent is a solution or dispersion.
7. The method of any one of claims 1 to 6, wherein the treatment with binding agent in step (a) is carried out using an impregnation method.
8. The method of any one of claims 1 to 7, wherein the drying is carried out at a temperature which does not exceed the curing temperature of the binding agent.
9. The method of any one of claims 1 to 8, wherein the drying is carried out until a residual moisture content of less than 20%, in particular less than 10%, is reached
10. The method of any one of claims 1 to 9, wherein the drying is carried out until a residual moisture content of less than 20%, in particular less than 10%, is reached and then the mechanical moving is carried out.
11. The method of claim 10, wherein the mechanical moving is carried out using rolls, in particular via direction change across several rolls.
12. The method of any one of claims 1 to 11, wherein the drying is carried out until a residual moisture content of < 10% is reached, preferably a moisture content between 0 and 8% by weight.
13. The method of one claim 12, wherein the treated laminar fiber structure, which is dried to a residual moisture content of < 10% and which preferably has a moisture content between 0 und 8% by weight, is mechanically needled subsequent to the drying.
14. A flexible composite, obtained by a method of any one of claims 1 to 13, wherein the composite has an equilibrium moisture content of <10%.
15. The composite of claim 14, obtained from a mixture of each of 50 % flax fibers and kenaf fibers and an aqueous acrylate dispersion as binding agent, preferably with a solid-binding agent content between 15 to 30% by weight.
16. The composite of claim 14 or 15 having an equilibrium moisture content of about 7%.
17. The composite of any one of claims 14 to 16, having a grammage from 800 g/m² to 2200 g/m².
18. Use of a composite of any one of claims 14 to 17 as molded part, preferably in the automobile industry.
19. The use of claim 18 for producing of suitcase shells; machine covers; inserts for cabinets, drawers and furniture back walls; shells and backrests for chairs, office chairs, armchairs; garden furniture; as substrate for decor paper, furnishing fabrics and wood inlays.
20. A method for compression molding, comprising
    the use of a composite of any one of claims 14 to 17
    and heating the composite to a temperature which is higher or equal to the curing temperature of the binding agent.

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