WO2015011066A1

WO2015011066A1 - Method for producing molded products

Info

Publication number: WO2015011066A1
Application number: PCT/EP2014/065566
Authority: WO
Inventors: Vadim Gogichev
Original assignee: Philippe Saint Ger Ag
Priority date: 2013-07-26
Filing date: 2014-07-18
Publication date: 2015-01-29
Also published as: CH708398A1

Abstract

A method for producing a molded article from cellulose fibers containing plant material is provided, comprising the steps of (a) moistening a pre-cut raw material directly originating from cellulose fibers containing plant material by addition of a fluid; (b) feeeding the moistened pre-cut raw material to a disperger equipped with disperger discs having several concentric circles of teeth for defibrating the pre-cut raw material to obtain a pulpy mass comprising individual cellulose or cellulosic fibers or fiber bundles; and (c) forming the molded article from the pulpy mass by a direct shaping method.

Description

Method for producing molded products

TECHN ICAL FI ELD

The invention relates to a method for producing molded products, such as build- ing materials, furniture parts, automotive interiors or packing material, from cellulose fibers containing plant material.

PRIOR ART

Currently there are several materials of organic origin known which are for example suitable for packaging and construction applications. While wood fibers are quite common other natural fibers from crop or grain are used occasionally as fibrous fillers.

US2006043629 proposes to produce a reinforced bio-composite by processing of natural fibers (such as grass, rice straw, wheat straw, industrial hemp, pineapple leaf fibers) with a matrix of soy based bioplastic, by employing a synthetic coupling agent, i.e. a functional monomer modified polymer. Moreover the use of modified soy flour with functional monomers is explained in the context of industrial applications such as reactive extrusion and injection molding.

US20081 8 1 969 addresses discoloration and structural, that is chemical or mechanical, degradation of composite materials comprising cellulosic components such as wood fibers, straw, grasses and other organic material that is cross linked by means of coupling agents to polymer components. The coupling agents, such as grafted-maleic anhydride polymers or copolymers, incorporate functionality capable of forming covalent bonds within or between the polymer and cellulosic components.

Both, US20081 81 969 and US2006043629 describe a composite material comprising fibers originating from organic material and synthetic polymers or synthetic coupling agents for binding the fibers.

CN 1 01 062572 describes a production process for wood plastic composite boards. The process involves defibring wood with a plate refiner to obtain coarse fibers; mixing the fibers with granular waste plastics; and hot pressing the mixture to obtain the composite boards.

WO201 01 497 1 1 describes a method and an apparatus for defibrillating cellulose fibers. The defibrillation is achieved through single and multiple passes of a raw or pre-processed cellulose fiber slurry, with a preferred solid material consistency range of 35 % to 55 %, through twin-screw fiber processing machines.

WO2001 32978 describes a method to produce highly refined cellulose ( HRC) . The method comprises the steps of providing an input material with cellulose- containing raw material, e.g. from agricultural by-products such as corn cubs, husks, and stalks, macerating the input material and shredding the input material with 4% consistency into micro fibers using a plate refiner (also called disk mill). The micro fibers are then passed through a screen filter and diluted to about 1 % solids and dispersed before being homogenized at high pressure to produce HRC gel.

US581 738 1 addresses a method for the production of cellulose-containing mass for forming cellulose-containing composite materials. The method uses fibrous crop by-products (e.g. corn cops and husks) as input material and includes the steps of macerating and homogenizing the input material. The homogenization is done by providing a pressure of at least 300 psi and subsequently removing the pressure within a time interval which will cause the cellulose fibre to break down. The cellulose-containing mass produced by this method is highly refined cellulose ( H RC) .

Also WO2007 1 39563 addresses a similar method as US581 7381 to produce highly refined cellulose ( HRC) to replace the egg content in consumable foods and goods. The homogenization step is carried out using a plate refiner (also called disk mill ) and water is fed into the refiner to assist in keeping the solids flowing without plugging.

WO20020592 1 2 addresses a method for preparing natural fiber-based composite materials containing a powdery protein (e.g. gluten or zein) as the sole binder component. The natural fibers are mixed with the binder material, water is added to adjust the moisture content and subsequently the mixture is submitted to a heat pressure treatment to form the composite material. The production of the fibers is not discussed. WO201 0064069 from the same inventor describes a method for producing cellulose-containing mass by subjecting an mixture of water, cellulose-containing organic material and ferromagnetic particles to a electromagnetic field to disintegrate the organic material to a particle size of not less than 1 micrometer. The cel- lulose-containing mass obtained this way may be further processed to molded articles.

WO201 1 0391 2 1 and WO201 2 1 30957 from the same inventor also describe methods for producing cellulose-containing mass without the use of synthetic polymer binders or coupling agents. In WO201 1 0391 2 1 an input material com- prising water and cellulose-containing organic material is subjected to a wet- milling process at elevated temperatures with high-speed cutting mills. The process leads to fine grinding of the cellulose-containing input material. In WO201 2 1 30957 the input material is subjected to homogenization using a refiner, such as a conical refiner, a homogenizer or a high-speed wet-milling ma- chine. During homogenization the cellulose-containing raw material is reduced to an average particle size of 1 - 2 mm. The large amounts of water needed for processing the input material is removed in a subsequent step before forming the composite materials.

The methods of WO201 0064069, WO20 1 1 0391 2 1 and WO201 2 1 30957 al- low to produce composite materials without requiring the use of exogenous polymeric components, i.e. polymeric component originating not from the organic raw material being processed, for bonding the organic materials, for example the plant particles to each other. EXPLANATION OF THE I NVENTION

It is an objective of the invention to provide an improved and cost-efficient method to produce molded articles from cellulose fibers containing plant material. It is another objective to produce these molded articles without requiring the use of exogenous polymeric components, i.e. polymeric component originating not from the cellulose fibers containing plant material. It is another objective to improve the boding capabilities of the defibrated plant material for forming high strength molded articles.

The objectives of the present invention are achieved by a method according to claim 1 . Thus according to the invention, the method for producing a molded article from cellulose fibers containing plant material comprises the following steps: (a) moistening a pre-cut raw material directly originating from cellulose fibers containing plant material by addition of a fluid; ( b) feeding the moistened pre-cut raw material to a disperger equipped with disperger discs having several concentric circles of teeth for defibrating the pre-cut raw material to obtain a pulpy mass comprising individual cellulose or cellulosic fibers or fiber bundles; and (c) forming the molded article from the pulpy mass by a direct shaping method.

The raw material directly originates from cellulose fibers containing plant material. Thus, ideally it has not been processed before in a way that the chemical structures of the cellulose fibers are altered.

The idea of the method lies in the fact that during manufacturing natural forms of plant material are defibrated, i.e. pre-cut material is disintegrated into small cellu- lose or cellulosic fibers or bundles of a few fibers, as their organic linkages of intracellular and intercellular structures are broken, until a pulpy mass is produced . Such a pulpy mass is used further as molding sand: it is reshaped with new geometrical form, and structural linkages between the small cellulose or cellulosic fibers of fiber bundles are recovered while this pulpy mass is curing.

The invention allows to produce molded articles without requiring the use of exogenous polymeric components for bonding the raw materials, for example the plant particles or fibers to each other. In the context of the present invention, the term exogenous polymeric components denotes polymeric component not originating from cellulose fibers containing plant material, e.g. synthetic polymers.

It was discovered that the known methods produce a slurry with small particles of the starting raw material, however, the methods are unable to sufficiently defi- brate the fibers of the raw material and also to activate the cellulose forming the main part of the fibers. Using a disperger the pre-cut raw material can be processed to obtain fibers with a optimized diameter to length ratio as compared to the methods of the prior art, where the fibers are simply cut to fine particles of less than 2 mm. Thus, with the method of the invention the fibers or bundles of fibers can more efficiently be freed from each other and still maintain an optimal length. Instead of simply cutting the pre-cut material to even smaller pieces the kneading effect of a disperger leads to defibrated longer particles with a smaller average diameter. In addition, the disperger causes damage the outer shell layer of each individual fiber or fiber bundle, without disturbing the internal structure in order to maintain maximum fiber strength, thereby activating the cellulose for later rebonding. Thus, the molded article from cellulose fibers containing plant material may be produced without the use of exogenous polymeric components, e.g. synthetic polymers or binders, or natural binder proteins, e.g. gluten or zein.

At the same time also small particles of cellulose and pectin are produced, which will continue to play an important role in the forming of molded articles, in addition to the direct contact between the individual fibers. The small particle fill in voids between the individual fibers, thus contributing to the formation of additional bonds. Optionally, additional cellulose may be added to fill in these voids.

A further advantage of the method is, that it uses considerably less water or fluid, because the material fed to the disperger has optimally a considerably higher consistency compared to the known methods that use slurries with a low consistency. Thus, the method is also more cost-efficient.

Advantageously, the cellulose fibers containing plant material origins from higher plants, preferably from the group of true grasses of the family Gramineae ( Poaceae) such as cereal crop, or from cotton, hemp or flax or a mixture thereof. The cellulose fibers containing plant material can be derived from farm waste of cereals (e.g. maize, rye, wheat, oats, barley, sorghum, rape, rice etc. and combinations thereof) , staple fibers (e.g. cotton, flax, hemp, etc. ) , what makes such molded articles economically compatible due to low price of the starting material. The cellulose fibers containing plant material is preferably made of stalk parts of higher plants, cell envelopes or membrane that contain sufficient quantity of cellulose, i.e. a high-molecular polysaccharide or glucan composed of 1 ,4-linked D- glucose. Preferred plant materials are cereal straw or rice straw. Good results were achieved by using wheat straw as cellulose fibers containing plant material.

Advantageously, the cellulose fibers containing plant material is cut or shredded to obtain a pre-cut raw material with a predetermined average particle size. For easy handling of the pre-cut raw material the average particle size may be approximately 20 mm to 50 mm.

In a further preferred variant of the process according to the invention the length of the pre-cut raw material, preferably straw , is up to 30 cm.

Before feeding the pre-cut raw material to the disperger it is moistened by addition of a fluid. In its simplest embodiment, the fluid may be water or steam. However, organic solvents may be used depending on the demands on the manufac- turability and on the characteristics of plant material. In this case it may be necessary after disperging to extract the solvent from the pulp. Also a liquid having a pH-value of about 8 or above, more preferably about 8.4 or above may be used for moistening the pre-cut raw material, which is especially suitable in the case that the organic material is straw, e.g. rice or wheat or rye straw. The fluid for moistening can be e.g. 0. 1 N H₂S0₄ or 1 N NaOH . Depending on the moisture content of the pre-cut raw material the amount of fluid, e.g. water, added is 40 to 1 00 percent by dry weight of the pre-cut raw material, such that the consistency of the material subjected to the disperger is about 50 to 70 percent, preferably 60 to 70 percent, more preferably about 60 percent. In a further preferred variant the fluid is added to the pre-cut raw material for moistening at an amount of 35 to 500 percent by dry weight of the pre-cut raw material.

The temperature of the fluid, mainly when using water, may be in the range of 80°C to 95°C, to more rapidly soften the pre-cut raw material. When using steam or water vapor the temperature may be higher, e.g. up to 1 20°C.

However, it is also advantageous to use cold water for moistening the pre-cut raw material. An example for cold water is tap water. It has been observed, that it is not necessary to bring the water to a certain temperature before moistening the pre-cut raw material. In the following process steps the moistened pre-cut raw material is exposed to high mechanical forces, such as friction and/or shearing forces. Said forces lead to heating, so an additional supply of further thermal energy to the water is not required.

Ideally the pre-cut raw material is moistened immediately before feeding the raw material to the disperger. Optionally, the moistened pre-cut raw material may be macerated or cooked for several hours. During maceration or cooking the mois- tened pre-cut raw material becomes softened mainly as a result of being wetted or steeped. Partial hydrolysis of the cellulose may occur.

The defibrating of the pre-cut raw material forms the crucial step of the method. Therefore, the moistened pre-cut raw material is fed to a disperger for defibrating the pre-cut raw material to obtain a pulpy mass comprising cellulose or cellulosic fibers or fiber bundles with an average length in the range of 1 to 1 0 mm, preferably 3 to 1 0 mm, and/or an average diameter in the range of 0.03 to 1 mm.

The disperger is specialized machinery, which is equipped with two disperger discs facing each other and rotation relative to each other usually by rotating one of the two discs. The discs are provide with several, e.g. 4 to 7, preferably 5 , concentric circles teeth. Typically the teeth are tapered. The teeth may be provided with grooves along their tapered sides. The circles of teeth on the rotating disc may intermesh with the circles of teeth on the static disc. The teeth of the two disc do not touch each other. For optimal defibration the discs may be arranged such that a minimal gap between the teeth of the two discs of 1 .2 mm to 2.5 mm, preferably 1 .5 to 2.0 mm, is formed.

Such arrangement of the disperger discs provide for a strong kneading effect, thus defibrating the pre-cut raw material to obtain a pulpy mass comprising individual cellulose or cellulosic fibers or fiber bundles with optimal length to diameter ratio and activated cellulose to promote the formation of hydrogen bonds as well as increase the total surface area of fiber available for bonding when forming the molded articles. Thus, the kneading effect does not simply cut the raw material to even smaller pieces but the fibers or bundles of fibers are loosened from each other more efficiently.

The pulpy mass forms the base material for a vast range of molded articles with a wide range of shapes, forms and designs. The molded articles may be building materials, furniture parts, automotive interiors, packaging, etc.. Said molded articles may be produced by direct shaping methods like casting, injection molding, pressing or extruding or by subsequently machining the aforementioned.

The term molded articles encompasses end-products, such as for example panels, as well as semi-products, e.g. a core material of a laminated construction such as a sandwich construction, for example. In case of the latter, certain properties of the product may be improved for example in that at least one liner is adhesively bonded to said semi-product. An advantage of such sandwich constructions is that different properties such as structural strength, light-weight construction, fire resistance or a combination thereof are conferrable to a product. Depending on the embodiment of the product, one or several layers or liners may be made of metal, glass or carbon fibers or meshing. Such non-organic fibers may be even added to and mixed with the pulpy mass before forming the molded articles.

Alternatively and/or in addition thereto, the molded articles may be subject to suitable surface treatment that is discussed later on in this description.

The process of forming the molded articles typically involves drying and/or curing of the pulpy mass, which denotes an extracting of excessive liquid. Processes of structural linkage recovery appear while the pulpy mass is shaped, for example by curing in casts or molds. Such processes are actually an integration of remains of beta-glucose n-molecules into molecular compound with a common polymer formula [C₅H₇0₂(OH )₃]_n. The presence of glucose molecules with three hydroxyl groups [(OH) groups] in each rest allow that linkage between said rests is facilitated through lateral hydroxyl groups by abstraction of water molecules from them. Therefore, structural linkage recovery of the organic material in the mass takes place as soon as excessive liquid of the mass is extracted, for example by desiccation or drying in case of water, resulting in a curing process.

In case of water being used as the fluid the dehydration process is carried out under a predetermined temperature by any of a range of known suitable techniques. Such techniques are comprising and/or combining compression, extrusion and filtration as well as absorption, vacuum drying, blow-drying, heating, radiation, patting, vaporization under blower and other methods of desiccation, including natural air drying for example. Selection of a specific method of dehydration depends upon the specific requirements on the process and/or the article to be molded. As an example the product is dried at a temperature between 80 to 90°C, until the final product has less than 20% humidity, preferably less than 1 4% . The drying can last 1 6 to 24 hours.

Depending on the characteristics of the pulpy mass and/or the requirements on the molded article to be produced, the post-processing of the mass is performed by at least one of molding, compression molding, injection molding. However, other shaping techniques for producing the product may be suitable. In case of compression molding it is conceivable that a mixing container or a part thereof form a half of the mold at the same time. As general molding techniques are known to the person skilled in the art there a detailed description thereof is omitted. Moulding under pressure can be performed at 1 20 - 220°C.

Depending on the demands and the manufacturability, the molding and curing operation are carried out together or in sequence.

Further post-processing may be performed, e.g. for improving the resistance of the molded article made of the pulpy mass against moisture or water, or to enhance its durability against chemically aggressive environments, the microbiological resistance, to confer the molded articles with required characteristics in view of a special type of resistance, a specific color, a particular smell or a combination thereof. For this purpose, specific modifiers and/or additives may be added into the pre-cut raw material and/or the pulpy mass prior to the extraction of any excessive liquid content.

Additional synthetic polymers may be used for coating or surface treating of the molded article components depending on their further use.

Depending on the requirements, said specific modifiers and/or additives may be employed for achieving a particular homogeneity of the pulpy mass and/or the molded article.

Special attention shall be paid to the fact, that several types of plant cells are encrusted by or containing compounds like inorganic minerals, for example silicates, or organic minerals like oxalates. The directed selection of cellulose fibers containing plant materials containing certain amounts of said compounds like for example minerals can be used to provide pulpy masses and molded articles providing certain properties demanded by end-users. For instance, by selecting raw materials with employing the ability that the mentioned materials can acquire or significantly improve such characteristics and properties as conductance, transcalency (i.e. the thermal conductivity) , soundproofness, resistance against moisture deformation, chemical and microbiological exposure and so on. In addition exogenous modifiers may be added if the pulpy mass does not satisfy the requirements on the composite material.

Production of materials with predetermined properties ( resistance, hydropathy, durability against chemically aggressive milieu, microbiological resistance, additional and/or special type of resistance, color, smell etc. ) including those required by consumer's priorities is achieved by adding specific modifiers into homogeneous mass before dehydration and/or using special supplemental techniques while preparing homogeneous mass for curing.

Additionally, stones or other solid non-organic material can be removed from the cellulose fibers containing plant material or the pre-cut raw material in a separate optional step. This step is ideally performed before the moistening step and has the advantage the machines for further processing are not damaged or quickly worn off by e.g. stones. To even increase the mechanical strength of the molded article additional cellulose may be added after the defibrating step to the pulpy mass before forming the articles. Examples for additional cellulose aremethyl cellulose and/or carboxy methyl cellulose, preferably in the form of a sodium salt, and/or microcrystalline cellulose. The carboxy methyl cellulose (CMC) can be e.g. from Fischer Chemicals Chemicals AG, Riesbachstrasse 57, CH-8034 Zurich, Switzerland with the CAS Number 9004-32-4. If additional cellulose and what kind of additional cellulose is added depends on the product for which the pulpy mass will be used. The addition of additional cellulose leads to stronger molded articles.

Microcrystalline cellulose ( MCC) is a highly crystalline particulate cellulose consisting primarily of crystallite aggregates obtained by removing amorphous (fibrous cellulose) regions of a purified cellulose source material by hydrolytic degradation. As an example, 5 to 1 0 weight percent, preferably 7 weight percent of MCC, preferably with a mean size range of about 1 5 to 40 microns, may be added to the pulpy mass.

Optionally, the pulpy mass may be mixed, e.g. with a ribbon mixer, to obtain a homogenous paste-like mass, especially when adding additional ingredients (e.g. additional cellulose), before forming the molded articles.

It has been observed that it is advantageous to operate the mixer, preferably a ribbon mixer, with a high rotation speed ( RPM ) . During the movement of the pulpy mass in the mixer, e.g. supported by screws, the pulpy mass is pressed against the walls of the mixer. Thus, the higher the rotational speed the greater the pressure exerted to the pulpy mass.

BRI EF EXPLANATION OF THE FIGU RES

The invention is described in greater detail below with reference to embodiments that are illustrated in the figures. The figures show:

Fig. 1 a flow chart of the method according to the invention; and

Fig. 2 a test setup for processing pre-cut raw material.

EM BODI M ENTS OF TH E INVENTION

Fig. 1 shows a flow chart of an embodiment according to the invention. The starting material, i.e. the cellulose fibers containing plant material, is preferably rice straw or wheat straw, as it is readily available as a by product from farming. However, other cellulose fibers containing plant materials as described above may be used. The used plant material should comprise large amounts of cellulose fibers in order to produce high-strength molded articles. The cellulose fibers containing plant material is cut to an average particle size in the range of 20 mm to 50 mm. This can be done in house or already pre-cut material 1 may be obtained. The loose pre-cut material 1 can be easily transported and further processed.

For the length of the pre-cut material, preferably the straw, up to 30 cm is rec- ommended. In a moistening step 3 the pre-cut raw material 1 is moistened with a fluid 2, preferably with water at a temperature of 80°C to 90°C to obtain a moistened pre-cut raw material with a high consistency in the range of 50 to 70 % , preferably about 60% . Thus, the amount of fluid added is in the range of 40 to 1 00% by dry weight of the pre-cut raw material. Other fluids may be used as described above. Optionally, the moistened raw material may be allowed to macerate during a maceration step 4 for a predetermined time in order to soften it before feeding the raw material to a disperger.

The effect of softening the pre-cut raw material may also be enhanced by using a speedheater for a more uniform heating and humidification of the raw material, preferably but not necessarily using steam.

In a further preferred variant of the method according to the invention cold water is used for moistening the pre-cut raw material. An example for cold water is tap water. Depending on the starting material a cleaning step (not shown) to remove stones and other solid non-organic material from the starting plant material or the pre-cut raw material may be desired. The cleaning step may be performed before or directly after cutting the starting material or even after the moistening step 3. The removal of stones may be important to prevent damaging the disperger and to reduce its wearing down.

The moistened raw material is then submitted to a disperger to perform the defi- brating step 5 until a pulpy mass comprising individual cellulose or cellulosic fibers or fiber bundles with an average length in the range of 1 to 1 0 mm, preferably 3 to 1 0 mm, and/or an average diameter in the range of 0.03 to 1 mm.

The disperger 5 is equipped with two disperger discs facing each other and rotation relative to each other usually by rotating one of the two discs. The discs are provide with concentric circles teeth. Preferably, the teeth are tapered. The teeth may be provided with grooves along their tapered sides. The circles of teeth on the rotating disc intermesh with the circles of teeth on the static disc. The teeth of the two disc do not touch each other. For optimal defibration the discs may be arranged such that a minimal gap between the teeth of the two discs of 1 .2 mm to 2.5 mm, preferably 1 .5 to 2.0 mm, is formed. Depending on the starting material the gap may be even lager. The disperger 5 processes the moistened pre-cut raw material by a strong kneading and shearing effect, thereby defibrating the pre-cut raw material with less reduction of the fiber length as compared to the prior art methods. The kneading and shearing effect activated the cellulose of the fibers by cracking the cell envelopes to promote the formation of hydrogen bonds as well as increase the total surface area of fibers available for bonding when later forming the molded articles. The defibrating step may be performed with a disperger such as the Disperger HTD.ED or DX.CI from Voith GmbH, Germany.

The pulpy mass obtained from the defibrating step 5 may be directly subjected to a shaping step 8 for forming the molded article 9.

Optionally, excess liquid of the pulpy mass may be removed in a liquid removing step (not shown) e.g. by sedimentation, filtration, extrusion or pressing out. However, the consistency of the raw material used in the disperger for defibrating may already be optimal for forming the molded articles.

To obtain a homogenous paste-like mass for forming the molded articles 9, the pulpy mass obtain from the disperger 5 may be subjected to a mixing step 6, e.g. by a ribbon mixer. With the mixing step further ingredients 7 as described above may be added. It has been observed that it is advantageous to operate the ribbon mixer with a high rotation speed.

The pulpy mass from the disperger or the homogenous paste-like mass after mixing is then used for forming the molded articles 9 by a direct shaping method 8, such as casting, injection molding, pressing or extruding.

An advantage of the method is to form molded articles using cellulose fibers containing plant material without the need of additional synthetic polymer resins for re-bonding the fibers together. Additional synthetic polymers may be used for coating or surface treating of the molded article components depending on their further use.

Fig. 2 shows a test setup for producing pulpy mass for the manufacture of a molded article from cellulose fibers containing plant material. Pre-cut straw material 1 0 with an average particle size of about 20 mm was obtained from wheat stalks. The pre-cut material 1 0 with a consistency of 1 00% was fed to a heating screw 1 1 . Steam 1 2 was added to increase the temperature and the moisture content of the raw material to obtain a consistency of 60 - 70 % . The moistened pre-cut raw material was then fed to a disperger 1 3 to defibrate the pre-cut raw material in order to obtain a pulpy mass 1 4 comprising individual cellulose or cel- lulosic fibers or fiber bundles. The discs had five concentric circles of teeth. Various gap width between the teeth of the disperger discs in the range of 1 .7 to 4. 1 mm were used. Various temperature setting were used for the heating the moistened pre-cut raw material in the range of 50°C to 90°C (degree Celsius) . Several samples with different parameter settings of the disperger (e.g. gap, temperature, power input, speed, etc. ) . The samples were also compared to samples using a conventional refiner with refiner discs having several clusters of parallel bar-like blades and grooves.

All samples from the disperger were superior to the samples from the refiner. Best results were achieved with a gap width between 1 .7 and 2. 1 mm and a temperature of 85°C to 90°C.

LIST OF REFERENCE N UM BERS

1 pre-cut raw material

2 fluid / water

3 moistening

4 maceration (optional)

5 defibrating / disperger

6 mixing step

7 further ingredients

8 shaping step

9 molded article

1 0 pre-cut straw material

1 1 heating screw

1 2 steam

1 3 disperger

1 4 pulpy mass

Claims

1. Method for producing a molded article from cellulose fibers containing plant material comprising the following steps: a. moistening a pre-cut raw material directly originating from cellulose fibers containing plant material by addition of a fluid; b. feeding the moistened pre-cut raw material to a disperger equipped with disperger discs having several concentric circles of teeth for de- fibrating the pre-cut raw material to obtain a pulpy mass comprising individual cellulose or cellulosic fibers or fiber bundles; and c. forming the molded article from the pulpy mass by a direct shaping method.

2. Method according to claim 1 , wherein the cellulose fibers containing plant material is a higher plant selected from the group of true grasses of the family Gramineae ( Poaceae) , cotton, hemp, flax or mixtures thereof.

3. Method according to claim 1 , wherein the cellulose fibers containing plant material is straw from wheat, rice or rye.

4. Method according to one of the preceding claims, wherein a fluid is added to the pre-cut raw material for moistening at an amount of 35 to 500 percent by dry weight of the pre-cut raw material.

5. Method according claim 4, wherein the fluid is added to the pre-cut raw material at an amount of 40 to 1 00 percent by dry weight of the pre-cut raw material.

6. Method according to one of the preceding claims, wherein before defibrat- ing the moistened pre-cut material has a consistency of 50% to 70%, preferably about 60% .

7. Method according to one of the preceding claims, wherein before defibrat- ing the moistened pre-cut raw material is heated to a temperature in the range of 80°C to 95°C.

8. Method according to one of the preceding claims, wherein the moistening is performed with steam or water, preferably cold water.

9. Method according to one of the preceding claims, wherein the moistened pre-cut raw material is defibrated to a pulpy mass comprising cellulose or cellulosic fibers or fiber bundles with an average length in the range of 1 to 1 0 mm, preferably 3 to 1 0 mm, and/or an average diameter in the range of 0.03 to 1 mm.

10. Method according to one of the preceding claims, wherein the disperger is equipped with two disc provided with several concentric circles of teeth, wherein the circles of teeth of one disc intermeshes with the circles of teeth of the other disc.

1 1. Method according to one of the preceding claims, wherein the discs are arranged such that a minimal gap between the teeth of discs of 1 .2 mm to 2.5 mm, preferably 1 .5 to 2.0 mm, is formed.

12. Method according to one of the preceding claims, wherein the direct shaping method is selected from the group of casting, injection molding, pressing and extruding.

1 3. Method according to one of the preceding claims, wherein the molded article from cellulose fibers containing plant material are produced without the use of exogenous polymeric components, e.g. synthetic polymers or binders, or natural binder proteins, e.g. gluten or zein.

14. Molded article from cellulose fibers containing plant material produced with the method according to on to the preceding claims.