WO2012107055A1

WO2012107055A1 - Low binder content shaped body made of bulrush leaf fibres

Info

Publication number: WO2012107055A1
Application number: PCT/EP2011/000565
Authority: WO
Inventors: Robert Schwemmer
Original assignee: Naporo Klima Dämmstoff Gmbh
Priority date: 2011-02-07
Filing date: 2011-02-07
Publication date: 2012-08-16
Also published as: DE112011104852A5

Abstract

The invention relates to a low binder content shaped body based on 90 to 100 per cent by weight of bulrush leaf fibres having high surface smoothness and excellent mechanical properties and also to a method for producing this shaped body.

Description

Binder-poor shaped bodies of cattail leaf fibers

The invention relates to a low-binder molding based on 90 to 100 weight percent cattail leaf fibers with high surface smoothness and excellent mechanical properties and to a process for the preparation of this molding.

Especially for the production of plates from vegetable raw materials, the vegetable raw materials are crushed, wets the bed with an adhesive and pressed again into a compact body. Most widely used are wood-based boards, such as chipboard, so-called MDF (Oriented Strand Board) boards (medium-density fiberboard). For example, but also plates of cork, straw, hemp fibers and from the leaves of cattail (Latin name "Typha") are formed in this way.

A material property of such formed plates is their swelling behavior when exposed to water. Especially for boards made of wood-based materials, there is a wealth of publications on how the thickness swelling by selection and / or design and / or treatment of the binder can be kept small.

As an example, the DE 37 33 630 AI and US 3,892,586 AI called. Achieving a good (ie low) QuellVerhaltens is thus associated with the use of relatively expensive and biologically often rather undesirable binders. In US 3,892,586 AI, for example, a thermal insulation board is described, which consists of 40 percent by weight of crushed straw with a particle size of 1 mm to 5 mm and 60 percent by weight of binders, mainly bitumen but also slaked lime and resin.

In order for panels to be suitable for use as parts of structures in terms of swelling behavior, they must not swell under the influence of moisture than OSB panels. In a conventional, standardized test (24 hours in water lying) whose thickness swelling is a maximum of 20%. In the case of plates based on shredded, wetted with adhesive and compressed cattail could so far with economic and construction no such low thickness swelling be realized siologisch meaningful means.

Uncultivated cattail leaf mass is very light with about 60 kg / m ³ . This is mainly due to the fact that the plant consists of about 85 percent by volume of a light sponge fabric. This sponge fabric can absorb up to five times its weight in water. In the production of board materials, the material is first crushed. The density of the shredded material is between 20 and 60 kg / m ³ , among other things also depending on the comminution technology. This material is compacted to form a compact body of typically 50-300 kg / m ³ when the body is to be used for thermal insulation. If the product is to be used for other purposes, it can also be compressed to 700 kg / m ³ and more. When the finished product comes into contact with moisture again, moisture is absorbed and the body swells up.

In DE 197 57 418 AI an insulating plate of compressed cattail granulate is proposed, wherein the individual Granulatteile before pressing are mainly greater than 1 cm. The granules are mixed with 35% by weight latex adhesive and pressed into plates. Although the panels produced in this way have a high thermal insulation capacity which can be used for building purposes, they are often not usable despite the high proportion of adhesive due to the high swelling under wet conditions.

The Granulatteile of cattail granules are - like most plant stems and leaves with respect to their swelling behavior anisotropic. By orderly aligning particles for pressing, the swelling behavior in a preferred direction can be kept deliberately small. The manufacturing process is so consuming and expensive.

In addition, common moldings of natural fibers such as hemp, flax or sisal and plastic fibers such as polypropylene (often in a mixing ratio of about 50% to 50%) generally have rough surfaces. To meet high design requirements, they must therefore be reworked with complex procedures.

Based on this prior art, the inventor has set itself the task of providing a molded article based on 90 to 100 percent by weight of cattail leaf fibers, wherein the thickness swelling of the correspondingly produced shaped body should be low due to the influence of water. Compared with known production processes for this purpose, only small amounts of adhesives, glues or binders should be present in the molding. In addition, the molded body should have a high surface smoothness, so that eliminates a costly reworking as by grinding or polishing.

Surprisingly, the object can be achieved according to the invention by the above-ground leaf mass of cattail on the one hand is comminuted unusually fine, on the other hand, the dust content is removed from the bed obtained. Specifically, the weight fractions of individual size classes of fibers are within the following limits:

Less than 15% by weight of the fibers have a dimension in at least two dimensions which is less than 0.2 mm.

Less than 40% by weight of the fibers have a dimension greater than 10 mm in at least two dimensions.

For more than 30% by weight of the fibers, the smallest dimension in at least two dimensions is in the range of 0.2 mm to 5 mm.

The solution according to the invention is based on the surprising finding that, when using tubular bulbs as the starting material, the swelling behavior of a shaped body formed therefrom is significantly more dependent on the degree of comminution of the raw material than when using, for example, wood or straw as the starting material.

In order to make possible the low binder content of the shaped bodies according to the invention, the natural self-binding forces of the cattail leaf fibers are exploited, which are activated according to the invention. In the cattail waxes and oils are present, which protect the plant from natural moisture. These waxes and oils are similar to carnauba wax (the hardest known plant wax). They can be melted by heating (melting point about 90 ° C). As a result, these substances can act as hot-melt adhesives and bind the cattail leaf fibers into a compact shaped body. The main fraction in the hexane extract (nonpolar portions) consists predominantly of fatty acids, hydroxy fatty acids and sterols. Palmitic acid and sitosterol are present in higher concentrations. However, it was also possible to find some semipolar compounds whose main fraction consists of ferulic acid (3-methoxy-4-hydroxycinnamic acid). The main fractions in the acetone / water extract (polar fractions) are, in addition to traces of aromatic compounds, sugars and sugar colloids. The moldings according to the invention can be coated more easily and post-treated because of their very smooth surface. For example, a shaped body according to the invention has an average roughness in the range of 3 to 10 m or a roughness depth in the range of 70 to 130 m.

The above-ground leaf mass of cattail consists essentially of sponge tissue and leaf tissue. The sponge tissue is essentially isotropic. The leaf tissue, which is also referred to as "stem outer skin", holds the sponge fabric as a thin layer in intact cattail leaf and, like wood, has a unique fiber direction. The leaf tissue is therefore strongly anisotropic with respect to many material properties such as thermal conductivity.

In an advantageous embodiment, the highest possible proportion of the cattail leaf fibers used is elongated, contains leaf tissue, and the direction of the longer dimension of the fibers coincides with the fiber direction of the leaf tissue contained in the fibers.

The invention thus relates to a shaped body containing 90 to 100 weight percent fibers of the above-ground leaf mass of cattail (the remainder may be any fibers, eg other biodegradable fibers, scaffold fibers or binding fibers or conventional sprayable or dispersible binders), characterized in that the weight fractions of individual size classes of cattail leaf fibers are within the following limits:

less than 15% by weight of the fibers have a dimension in at least two dimensions which is less than 0.2 mm,

less than 40% by weight of the fibers have a dimension greater than 10 mm in at least two dimensions, and

at more than 30% by weight of the fibers, the smallest dimension in at least two dimensions is in the range of 0.2 mm to 5 mm, the shaped body having a highly smooth surface and a density in the range of 120-1200 kg / m ³ .

Advantageously, the molded article according to the invention may contain 93, 95 or 98 percent by weight of cattail leaf fibers.

According to one embodiment of the invention, the molding has a density in the range of 200-700 kg / m ³ .

According to a further embodiment of the invention, the weight fraction of cattail leaf fibers having a dimension in at least two dimensions that is less than 0.2 mm, less than 10 percent.

According to another embodiment of the invention, more than 70 weight percent of the cattail leaf fibers are of elongate shape such that the larger dimension is at least 50 percent longer than the next smaller, transverse dimension and the larger dimension is substantially parallel to the fiber direction of cattail leaf tissue.

Due to their outstanding material properties, such as, for example, low swelling due to the influence of water and very good thermal insulation, the molded articles according to the invention can be used for thermal insulation (against heat or cold), soundproofing or impact sound insulation or as semi-finished products for construction, furniture and industrial products (also in the electronics industry) become. In the automotive industry, for example, they can be used for the production of interior trim. Furthermore, they are used as a ground cover.

The method used according to the invention for the production of the molding according to the invention is characterized in that

a) Cattail leaves are first cut transversely to their longitudinal direction into pieces of 0.5 to 25 cm in length, preferably 1 to 8 cm in length, b) then, for example, in a mill or in a Zerspaner (the crushing device used is negligible) further crushed and optionally the resulting cattail leaf fibers are freed, for example, by sieving or blowing out dust, the weight fractions of individual size classes of the cattail leaf fibers lying within the following limits:

less than 40% by weight of the fibers have a dimension greater than 10 mm in at least two dimensions,

if more than 30% by weight of the fibers, the smallest dimension is in at least two dimensions in the range of 0.2 mm to 5 mm,

optionally up to 10% by weight of any other fibers added (eg other biodegradable fibers, scaffold fibers or tie or support fibers),

c) the cattail leaf fibers obtained after steps a) to b) are laid to form a nonwoven, and

d) the nonwoven obtained after step c) 2 to 60 min at 130 to 200 ° C. is pressed to a molding at a pressure of 1 - 400 bar.

According to one embodiment of the method according to the invention, the nonwoven is pressed for 2 to 60 minutes at 130 to 200 ° C at a pressure of 5 - 100 bar to form a shaped body.

According to a further embodiment of the method according to the invention, the crushing of the cut cattail leaves takes place in a hammer mill, the lateral surface of which comprises the drum has longitudinal slots 3 to 5 mm wide and 1 to 9 centimeters in length, the longitudinal direction of the slots being in the circumferential direction of the hammer mill. But it can also be used other crushing devices.

According to a further embodiment of the method according to the invention, the nonwoven laying takes place by the air-lay method (preferred) or on a carding machine. Both methods are well known to the person skilled in the art, so that no further explanation is required. For the nonwoven, the industry also offers various other methods, such. As direct web formation or simple spreading, which are also suitable for the present task. The basis weight of the obtained fiber mat is 0.5 to 50 kg / m ² , preferably 1 to 20 kg / m ² .

According to a further embodiment of the method according to the invention is carried out before pressing a nonwoven consolidation by needling or by the thermobonding method (preferred). Both methods are well known to the person skilled in the art, so that no further explanation is required.

The needling can be done on one side and two sides. Can be needled, for example, with 2 to 400 punctures / cm ² , preferably 4 to 50 punctures / cm ² . The stroke frequency can be, for example, 60 to 3,000 strokes / min, preferably 150 to 1,500 strokes / min.

When thermobonding the fleece and setting the desired plate thickness or density. The plate density or thickness is adjusted with an overflowing band, which compresses the nonwoven fabric to a thickness of about 3 mm to 350 mm, thereby giving it a uniform surface. The heating of the web takes place with a supply air temperature of 110 to 200 ° C, preferably from 140 to 170 ° C. The Thermobondierofen is also suitable for removing the residual moisture in the nonwoven fabric.

The results in Table 1 on page 10 show that the mechanical Properties of the shaped body thus produced (transverse tensile strength and Young's modulus) are surprisingly better than in other renewable raw materials with 15% of binder.

Example:

A leaf bundle of dry cattails is cut transversely to the fiber direction of the leaf tissue to just under 1 cm long pieces and then further comminuted in a hammer mill. The hammer mill has a revolving in a drum anchor, which is provided at the periphery with projections - which are referred to as hammers. The lateral surface of the drum is provided with longitudinal slots of 4 times 80 mm in cross-sectional area, with the larger dimension in the circumferential direction. For crushing the pipe piston pieces they are entered into the chamber. In the chamber they are smashed by the hammers and the resulting fibers fall out of said longitudinal slots. Due to the crushing behavior of cattail pieces, most of the resulting fibers are elongate, the longitudinal direction being parallel to the fiber direction of the leaf tissue contained in the fibers. By this crushing process is achieved that a high proportion of the sponge fabric of the bed formed occurs in the fibers in which it adheres in parallel as in its original position on the stem outer skin.

Under certain circumstances, the fibers thus obtained can already fulfill the conditions mentioned above for the fiber size distribution. It is recommended to remove the dust content (fibers with a size of less than 0.2 mm in at least two dimensions), for example to blow it out or expel it.

Depending on the nature of the raw material, it may be necessary to dry the fibers until the remaining bed has a density of 20 - having 30 kg / m ^3.

Of course, other ways of shredding can be chosen.

For example, can also be machined by means of a so-called Messerwellenenzerspaners. In this case, an inner armature and an outer, provided with knives drum rotate coaxially in the opposite direction of rotation. The cattail leaf material to be cut is removed by blades of the outer drum in the gap between the two rotating bodies. The clippings fall through gaps in the outer drum to the outside. Good results are achieved with a knife shaft achieved in which the blades protrude inward a millimeter from the circumference of the outer drum surface and wherein the gap width for the passage of the cut material is 2.4 mm. Again, it is advisable to remove the dust from the resulting clippings.

The molded body thus formed has a thickness swelling of seven to fifteen percent when placed in water for twenty-four hours. This swelling is so low that the molding may be used, for example, according to the common building standards as a plate-shaped material.

The molding according to the invention can be used well in plate form for thermal insulation or thermal insulation. The thermal conductivity of the individual fibers is greater than normal in the fiber direction. If one wishes to use the shaped body according to the invention in plate form for heat insulation, it is therefore useful to ensure that the individual fibers are oriented so that their fiber direction is as possible transverse to the direction in which the heat flow is to be prevented. Using the example of thermal insulation boards, the orientation or orientation of the individual fibers should therefore be as close as possible to the plane of the board. In addition, the shaped body according to the invention in plate form is also suitable for sound insulation and impact sound insulation. Also building boards or housings for electronic devices can be molded. Further application possibilities can be found in furniture construction and in the automotive industry.

A first measure with which an alignment or orientation can be achieved is to perform as many fibers in their fiber direction as possible longer than in the two normal directions and the fibers already at the fleece laying so that their longitudinal direction as possible transverse to that direction lies, in which later good thermal insulation effect is to be achieved. The direction in which good thermal insulation is achieved is the vertical. The fibers can be made in a simple manner, that they are longer in the direction of their fibers predominantly than in the other two dimensions, by first cutting the cattail leaves in a defined length transversely to the fiber direction and then disintegrating them randomly in a mill, for example a hammer mill. The fibers preferably break along their longitudinal direction.

The outstandingly smooth surfaces and mechanical properties (modulus of elasticity, transverse tensile strength) of the shaped bodies according to the invention in comparison to shaped bodies. pern from other natural fiber composites are shown in Table 1.

Table 1: Property comparison of compression (density = 1 g / cm ³ ) of different

Table 2: Property comparison of grouting (density = 1 g / cm ³ ) of various natural fiber composites with glue-free cattail fibers

Fibrous binder Resin content Mean roughness depth R, bending E transverse tensile strength / flexural strength a Modulus / Flexural strength

NOT A WORD

[%] [pm] [pm] [MPa] [MPa]

Kenaf PF 15 25.27 ± 2.18 289.04 ± 35.73 932.5 ± 1190 22.5 ± 14.0

(100%) PF 30 24.00 ± 4.88 300.23 ± 74.51 4343 ± 1064.5 53.8 ± 12.1

Flax PF 15 12.89 ± 1.18 136.45 ± 11.07 574 ± 230 17.4 ± 3.2

(100%) PF 30 13.37 ± 0.36 159.49 ± 12.00 4839 ± 886.5 47.5 ± 13.5

Hemp PF 15 20,90 ± 2,19 259,77 ± 50,24 2276,5 ± 230 37,9 ± 9,0

(100%) PF 30 20.72 ± 1.63 260.20 ± 39.80 6186.5 ± 500 73.3 ± 4.5

Coco (coconut) PF 15 32.57 ± 2.87 351, 82 ± 41, 85 n.d. n.d.

(100%) PF 30 34.2 ± 1.94 444.64 ± 11.98 2049.5 ± 696.5 44.4 ± 9.1

Kenaf / Flax PF 15 22.08 ± 2.02 294.70 ± 39.15 1488.5 ± 792.5 29.3 ± 5.3

(50/50) PF 30 22.85 ± 2.30 256.44 ± 45.71 5877.5 ± 884.5 50.3 ± 13.1

Hemp / Flax PF 15 15.93 ± 0.98 175.98 ± 8.37 1420 ± 518.5 20.4 ± 7.4

(50/50) PF 30 12.83 ± 1.81 174.99 ± 14.25 5524 ± 601 67.1 ± 7.3

Wood (wood) / PF 15 17.86 ± 2.27 237.80 ± 54.57 n.d. n.d.

Flax

PF 30 17.14 ± 1.61 219.25 ± 24.95 1202 ± 149 15.1 ± 0.9

(75/25)

Cattail 0 4,96 ± 0,51 100,98 ± 10,00 3100 ± 92 21 ± 2

The following standards were used for the roughness measurements:

1) DIN EN ISO 3274: Nominal properties of stylus instruments

2) DIN EN ISO 4287: Designations, definitions and characteristics of the surface finish

3) DIN EN ISO 4288: Rules and procedures for assessing the surface quality

Claims

claims

1. molded body containing 90 to 100 weight percent fibers of the above-ground leaf mass of cattail, characterized in that the weight fractions of individual size classes of cattail leaf fibers are within the following limits:

2. Shaped body according to claim 1, characterized in that the shaped body has a density in the range of 200 - 700 kg / m ³ .

3. Shaped body according to claims 1 or 2, characterized in that the weight fraction of cattail leaf fibers, which have a dimension in at least two dimensions, which is smaller than 0.2 mm, less than 10 percent.

Shaped body according to one of the preceding claims, characterized in that more than 70% by weight of the cattail leaf fibers are of elongated shape such that the larger dimension is at least 50% longer than the next smaller transverse dimension and the larger one Dimension substantially parallel to the fiber direction of the cattail leaf tissue.

5. Use of a shaped article according to any one of the preceding claims for Wäm mediation, sound insulation or impact sound insulation or as a semi-finished product for construction, furniture and industrial products.

6. A process for producing a shaped article according to one of the preceding claims, characterized in that

a) Cattail leaves are first cut transversely to their longitudinal direction into pieces of 0.5 to 25 cm in length,

b) are then further comminuted, wherein the weight fractions of individual size classes of cattail leaf fibers are within the following limits: less than 15% by weight of the fibers have a dimension in at least two dimensions which is less than 0.2 mm,

at more than 30% by weight of the fibers, the smallest dimension is in at least two dimensions in the range of 0.2 mm to 5 mm, c) the cattail leaf fibers obtained after steps a) to b) are laid to a nonwoven, and

d) the nonwoven fabric obtained after step c) is compressed for 2 to 60 minutes at 130 to 200 ° C at a pressure of 1 to 400 bar to give a shaped article.

7. The method according to claim 6, characterized in that the nonwoven 2 to 60 min at 130 to 200 ° C at a pressure of 5 - 100 bar is compressed to form a shaped body.

8. The method according to claims 6 or 7, characterized in that the crushing of the cut cattail leaves takes place in a hammer mill, the drum comprising the circumferential surface has longitudinal slots 3 to 5 mm wide and 1 - 9 centimeters in length, wherein the longitudinal direction of the slots lies in the circumferential direction of the hammer mill.

9. The method according to any one of claims 6 to 8, characterized in that the nonwoven laying takes place by the air-lay method or on a carding machine.

10. The method according to any one of claims 6 to 9, characterized in that prior to pressing by needling or by the Thermobonding- method takes place a nonwoven.