WO1996000327A1

WO1996000327A1 - Moulded parts for consolidating slopes

Info

Publication number: WO1996000327A1
Application number: PCT/EP1995/002361
Authority: WO
Inventors: Wolfgang Ritter; Stephan Von Tapavicza
Original assignee: Henkel Kommanditgesellschaft Auf Aktien
Priority date: 1994-06-27
Filing date: 1995-06-19
Publication date: 1996-01-04
Also published as: DE4422337A1; EP0767854A1

Abstract

Moulded parts are made of partially or completely biodegradable plastics, in particular thermoplastic starch. They are economic to produce and may be set onto a slope with little effort, but at the same time they remain on the site for a limited period of time, so that the lasting presence of plastic parts on the site is avoided.

Description

"Molded parts for securing embankments"

The invention relates to molded parts made of plastic for securing embankments, in particular the embankments of earth walls.

When creating earth walls and dams, e.g. B. Railway dams and noise barriers along highways, the often very steep embankments are planted so that the plants with their root system secure the top layer of earth against slipping in a visually appealing way. However, before the roots are sufficiently deep, measures to secure the slope must be taken.

As a mechanical stabilization aid, it is known to drive wooden posts into the embankment and to connect them manually to a wicker along the same contour lines. This method has the advantage that the biological material used initially secures the slope very effectively, but then gradually rots after the roots of the new planting have formed. The disadvantage is the high workload and thus the high costs when attaching the fuse.

Another known method for securing embankments is less labor-intensive. Here the top humus layer is secured against slipping down by prefabricated grid-like parts. However, these molded parts cannot be rotten, so that a permanent presence of non-rotten plastics in the field must be accepted, even if the vegetation is sufficient and the stabilization aid is no longer necessary.

The invention is therefore based on the object to develop inexpensive moldings for effectively securing the embankments, on the one hand only require little work to attach to the embankment. On the other hand, a long-term presence of plastic parts in the field should be avoided.

According to the invention, this object is achieved in that the molded parts consist of a partially or completely biodegradable plastic, in particular thermoplastic starch.

Biodegradable plastics are known. Examples include polyhydroxybutyric acid, polyhydroxyvaleric acid, copolymers of these, alkyd resins, cellulose diacetate and so-called thermoplastic starch in various mixtures. The microbiological degradation of alkyd resins based on fatty acid, glycerol and phthalic acid is described in the magazine "färbe + lack", 98th year, 7/1992, pages 505 to 508. In an earth digging test, a weight loss of approximately 3 to 30% was found after 6 weeks of testing and approximately 7 to 35% after 12 weeks of testing. The greater the fatty acid content in the alkyd resin, the greater the mass loss.

Better degradation rates are obtained when using so-called thermoplastic starch. This material is also particularly inexpensive, so that this plastic is suitable for many applications in which the use of other biodegradable plastics is not possible for economic reasons. This applies in particular to the manufacture of the above-mentioned shaped parts for securing embankments.

Thermoplastic starch in a homogeneous mixture with selected synthetic thermoplastic polymer compounds is referred to here and below as thermoplastic starch. For the production, native starch, together with limited amounts of water and, if appropriate, further auxiliaries, is converted in a thermomechanical digestion into a thermoplastic material whose shaping further processing is possible in a conventional manner, "for example by injection molding or calendering. The thermomechanical digestion below The use of elevated temperatures and pressures is particularly important in conventional nell extruders that are upstream of the shaping processing step or that are also used for shaping at the same time.

A partially biodegradable thermoplastic starch can be produced by thermomechanical digestion of the starch with polyethylene or ethylene copolymers. After biodegradation, this material, which can be used in the context of the invention, breaks down into finely divided, very small particles made of polyethylene.

Information on the manufacture, properties and processing of other thermoplastic starches, which are also suitable for use in this invention, can be found, for example, in the patent applications DE 4038 732 AI, DE 41 21 111 AI, DE 42 09 095 AI of the applicant. Reference is expressly made to the content of these publications to supplement the disclosure.

DE 40 38 732 A1 describes the production of thermoplastic starch by coextrusion of starch with aqueous polymer dispersions which contain the synthetic polymer material in a finely dispersed distribution in an aqueous phase. After the starch portion has completely biodegraded, the portion of the synthetic polymer remains in finely divided, powder-like form, provided the synthetic polymer is not also biodegraded. In the latter case, the finely dispersed distribution promotes rapid degradation by microorganisms. DE 4038732 AI mentions polyvinyl acetate and copolymers in particular as an example of the synthetic polymer component. Alternatively, for example, polyurethane made with native fats or a fatty alcohol-acrylate homopolymer and corresponding copolymers can also be used.

DE 41 21 111 AI proposes, as a synthetic thermoplastic polymer for the homogeneous isolation of thermomechanically digested starch, polyesters and / or polyamides which are based at least in part on renewable raw materials, in particular on the basis of native fats and oils. A particularly inexpensive and very readily biodegradable is a thermoplastic starch which has been produced in admixture with alkyd resins. Here too, in order to increase the degradability by soil organisms, it is advantageous if the alkyd resins are built up completely or at least predominantly from raw materials based on renewable raw materials. Such a thermoplastic starch with mixed oxidatively crosslinkable alkyd resins is described in DE 42 09 095 AI. Here is a detailed explanation of the term oxidatively crosslinkable alkyd resins, to which reference is made.

Natural product-based alkyd resins of the type which are particularly preferred according to the invention are based on glycerol as a 3-functional polyol component and fatty acids of natural origin as an onofunctional carboxylic acid component. The onofunctional reactants are used on average in such amounts that the desired reaction with dicarboxylic acids - for example phthalic acid or phthalic anhydride - becomes possible. At least predominantly natural product-based modified alkyd resins of this type are characterized, for example, in that more than 50% by weight and preferably between 60 and 70% by weight of the alkyd resin is formed from these natural product-based components, in particular glycerol and mono-functional fatty acids, while at the same time The rest of the dicarboxylic acids and optionally additional diol components are present in the polymer molecule.

In summary, it is therefore proposed in a preferred embodiment of the invention that the molded parts consist of thermoplastic starch which is present in the blend with decomposable polymers, in particular polyvinyl acetate, alkyd resins, polyesters and / or polyamides. The complete decomposability of the polymers and thus of the entire material is ensured in particular if they are at least partially constructed from raw materials based on renewable raw materials. At the same time, the synthetic polymers sufficiently ensure the mechanical stability of the molded parts according to the invention.

A targeted selection of the admixed excipients, especially the synthetic thermoplastic polymer compounds enables the desired material properties to be set, for example the chronological course of the decrease in mechanical strength. An extension of the usage properties is also possible by using modified or hydrophobized starch. Another possibility for extending the use properties over time is to coat the finished molded parts with a waterproof, but nonetheless biodegradable layer. In particular, a coating with polyhydroxybutyric acid, with oxidatively crosslinking alkyd resins, with substances which are degradable by climatic influences or biodegradable and which cure under the action of ultraviolet radiation is proposed here. The coating can also consist of a composition of the named and possibly other substances.

Irrespective of the choice of the type of starch, the mixed-in synthetic polymer compound and the coating, the mechanical stability of the molded parts can also be adjusted by means of introduced fibers, with biodegradable fibers also being preferred here. Examples of such fillers are coconut and wood fibers as well as wool and hair waste.

The molded parts according to the invention for securing embankments can have a different geometry in accordance with the respective type of use. Thus, band-shaped plastic parts are possible which, as in the known method, can be braided around wooden posts driven into the slope. It is therefore proposed that the shaped parts have the geometric shape of tapes with dimensions such that they can be braided around wooden posts driven into the slope.

In another advantageous variant, the molded parts are gratings made of the biodegradable plastic with strip-shaped strip surfaces lying perpendicular to the plane of the grating.

The above grating can be manufactured in different ways. In an advantageous embodiment of the invention, the grating is composed of strips and secured with a rotten one Construction adhesive. Examples of such an adhesive are described in DE 32 04 504 AI. These are special (meth) acrylic lat compounds. Reference is expressly made to this publication in order to disclose the details.

Another manufacturing variant is, however, particularly preferred. Here, a grating with the desired length and width is continuously extruded as a block with honeycomb-shaped channels, which is cut by a cross cutter according to the desired thickness of the grating after it leaves the extruder head. For this purpose, a number of displacement torpedoes corresponding to the number of honeycomb-shaped channels are provided in the outlet channel of the extruder head and are attached to webs within the head. This type of extrusion system is known in principle from the manufacture of plastic tubes, although only a displacement torpedo is provided there.

In an alternative embodiment of the invention, a flat slope guard with straps made of the biodegradable plastic is produced by braiding the straps into mats, which are placed on the slope.

In the manufacture of the above-mentioned strips and gratings, the thermoplastic starch can first be produced as granules and then extruded into the molded parts. However, the molded parts are preferably molded in one work step simultaneously with the production of the thermoplastic starch, for example in an extruder. It is therefore proposed that the thermomechanical digestion of the starch be carried out in an extruder and the product extruded into the molded parts using the same extruder. Production can take place at a fixed production site or, in a preferred embodiment, with a mobile extruder directly on site. The production directly at the place of use is particularly advantageous in the case of gratings, because the transport of the large empty volume that is unavoidable with the finished gratings is avoided. Only the mobile extruder and the granulate made of thermoplastic starch or a premix are transported to the place of use. In the extrusion, the strips and gratings are in particular produced directly with the desired dimensions, so that post-processing is not necessary.

Several exemplary embodiments of the invention are described in more detail below with reference to drawings. Show it

FIG. 1 shows a perspective view of an embankment with the straps according to the invention for securing in a first embodiment of the invention,

FIG. 2 shows a perspective view of a grating according to the invention in a second embodiment of the invention,

Figure 3 is a schematic representation of a manufacturing step in the manufacture of the gratings and

Figure 4 is a mat braided from the tapes of the invention.

FIG. 1 shows an earth wall 1 with a steep slope as noise protection along a road. To protect against slipping of earth masses, wooden posts 3 have been driven into the slope 2 and strips 4 made of thermoplastic starch have been braided. The strips 4 with a cross section of approximately 3 × 100 m were produced simultaneously with the production of the thermoplastic starch by means of extrusion through a slot die.

After a certain period of time, when the vegetation not shown in FIG. 1 has formed sufficient roots to secure the slope 2, not only the wooden posts 3 but also the strips 4 rot.

Figure 2 shows an alternative molded part for securing the slope, namely a grating 5 made of thermoplastic starch. The grating has the dimensions 120 x 80 x 10 cm with a honeycomb spacing of 10 cm and a material thickness of about 3 mm. For the production of the grating 5, on the one hand, strips with the dimensions 120 x 10 x 0.3 cm or 80 x 10 0.3 cm can be assumed. These tapes are milled, joined and glued at the joints. Suitable two-component adhesives based on methyl methacrylate are suitable as adhesives, for example the adhesive with the trade name "Stabilit Express" (product from Henkel KGaA) or epoxy adhesives, for example "Stabilit Ultra" from the same manufacturer. A high-strength, but rotable structural adhesive is preferably used, as described for example in DE 3204504 AI, in order to ensure the rotting of the entire system in the ground.

An alternative procedure is used to economically manufacture the grating 5 in large numbers. FIG. 3 shows a schematic representation of an extruder head 7 in which the displaceable torpedoes (not visible) for producing the honeycomb-shaped channels 6 are fastened in block 8.

For the sake of clarity, only nine channels 6 are drawn. The number of honeycombs is in fact of the order of 100. Transversely to the exit direction, segments 10 approximately 10 cm wide are cut off with the cross cutter. The sectional plane is indicated by a dashed line 10. The separated segment represents the finished grating, which can be used immediately to secure embankments.

As an alternative to the grating, the grid-like mat mesh shown in FIG. 4 can be used. The tapes 4 here also consist of thermoplastic starch.

The distance between adjacent, parallel bands 4 is selected depending on the slope angle and the type and nature of the ground in order to achieve optimum slope protection. If necessary, the tapes can also have protrusions projecting upwards, which additionally prevent the soil from slipping off. Reference list

Earth wall

embankment

Wooden pole

tape

Grating

Channels, honeycombs

Extruder head

block

Cross cutter

Cutting plane

Claims

Patent claims

1. Molded parts made of plastic for securing embankments, in particular the embankments (2) of earth walls (1), so that they are partially or completely biodegradable from one

Plastic, especially thermoplastic starch.

2. Molded parts according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the molded parts consist of thermoplastic starch, which are present in the blend with decomposable polymers, especially polyvinyl acetate, alkyd resins, polyesters and / or polyamides.

3. Molded parts according to claim 1 or 2, so that the molded parts consist of thermoplastic starch, in the manufacture of which modified or hydrophobized starch has been used.

4. Molded parts according to one of the preceding claims, that the molded parts have a coating of a water-resistant but nonetheless biodegradable material.

5. Shaped parts according to claim 4, d a d u r c h g e k e n n z e i c h n e t that the coating consists of polyhydroxybutyric acid, oxidatively cross-linking alkyd resins, a by climate influences or biodegradable, under the action of ultraviolet radiation substance or a composition thereof and optionally other substances.

5. Molded parts according to one of the preceding claims. characterized in that the molded parts made of fibers, in particular rotten

Contain fillers.

7. Shaped parts according to one of the preceding claims, characterized in that the shaped parts have the geometric shape of the strips (4) with such dimensions that they are driven into the embankment (2) by wooden posts (3) and / or to the Embankment (2) can be braided mats.

8. Shaped parts according to one of claims 1 to 6, d a d u r c h g e k e n n z e i c h n e t that they are made of the biodegradable plastic grid gratings (5) with strip-shaped, perpendicular to the plane of the grating (5) lying strip surfaces.

9. A method for producing the molded parts according to one of the preceding claims, characterized in that modified or hydrophobized starch is converted together with limited amounts of water and optionally other auxiliaries in a thermomechanical digestion into a thermoplastic material and thereafter or simultaneously with the thermomechanical see brings into the desired shape.

10. A method for producing the molded parts according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the molded parts are coated after the shaping with a waterproof, but nonetheless biodegradable substance.

11. The method according to claim 10, characterized in that the molded parts after molding with polyhydroxybutyric acid, oxidatively crosslinking alkyd resins, a material which is cured by climatic influences or biodegradable, cures under the action of ultraviolet radiation or a composition thereof and, if appropriate, other substances.

12. A method for producing the molded parts according to claim 8, d a d u r c h g e k e n n z e i c h n e t that the grid (5) is composed of strips (8) and secured with a rotten construction adhesive.

13. A method for producing the molded parts according to claim 8, d a d u r c h g e k e n n z e i c h n e t that one extrudes a block with honeycomb channels and then divided transversely.

14. A method for producing the molded parts according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the thermomechanical digestion of the starch in an extruder

(7) and extrudes the product to the molded parts with the same extruder.

15. A method for producing the molded parts according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the molded parts are produced at the place of use with a mobile extruder.