FOR PRODUCING THE SAME

This invention relates to a layered heat insulating panel having a layer formed by vegetable material and at least one coating layer made of artificial resin covering the layer made of vegetable material, and an apparatus and method for producing said layered heat insulating panel.

Heat insulating materials manufactured nowadays are products made of minerals, mineral wools formed by bonding glass fibers, rock wool, glass wool or plastic foams each molten by high energy consumption, in which mineral or glass fibers having low thermal conductivity and air also with excellent thermal insulation properties trapped between the fibers or in the cells serve as thermal insulation media for construction of buildings.

A common feature of such insulating materials is that a compensation of the amount of C0 ₂ generated during their manufacture by their insulation properties takes place after a relatively long period of time. At the same time, for slowing down climate change is an important demand that no significant increase of greenhouse gases emitted on production of heat insulating products.

A composite, layered panel suitable also for heat insulation disclosed in utility model CN 202556809 attempts to meet this requirement, and it is prepared by using a jute weft knitted biaxial fabric as a surface layer, using straw core materials as a middle layer. During the manufacturing process carrying out hot pressing on the fabric, the core materials and polypropylene short fibers to bond the layers together. Despite its excellent heat insulating properties a disadvantage of the layered product according to this solution is that the fibers forming the core layer of vegetable material must be fixed by hand, e.g. by means of braided strings prior to heat-pressing and the assembly of the laminate, which significantly increases the costs and decreases the productivity of a panel. Another drawback is that the jute fiber layer constituting the surface layer and the polypropylene binder as well as the core layer are easily combustible and therefore its use has significant fire hazard. The insulation of exterior surfaces of buildings by reed boards and constructing thatch roofs are appropriate solutions in view of heat insulation, but the production of reed based insulation materials is also a labor intensive operation, the lifetime of the product is relatively short due to weather effects, and its use requires similar considerations in point of view of fire hazard. Therefore, although the reed plant having a stem with closed cell structure and woody consistency and high compressive strength is available worldwide in large quantities, but its exploitation as an insulating or roofing material takes place nowadays only in a negligible quantity, so that it does not get a significant role in the reduction of the amount of biomass. At the same time, all above applications require careful and manual pre-sorting and grading of the harvested cane, rendering 70-80% of the harvested stems organic waste. Finally, the 60- 70% of this 20-30% amount of reed is usable as an insulator for the production, so the total amount of waste reaches the 79-88% of the harvested cane. A woody stem of a plant having gas-tight chambers does not degrade off over long periods of time, so it does not result inorganic decomposition wastes, and used as insulating material it can significantly reduce or cease the heating energy demand of buildings.

Therefore, the aim of the present invention is to provide a dimensionally stable layered heat insulating panel using Poaceae species, principally reed or cane, which is extremely close to the previously used (mineral wool, Styrol) products by its rated insulation parameters, but having much more favorable environmental impact, durability and dimensional stability due to a substantial amount of renewable components, as compared with products used before.

A further object of the present invention is to provide a method for production of layered heat insulating panel primarily made of renewable materials, especially stems of plants belonging to the family Poaceae, e.g. reed or cane, wherein manual work is basically omitted.

Our further aim is to provide an apparatus for economically achieving the method according to the invention.

The above objects are achieved by a layered heat insulating panel having a layer formed by vegetable material and at least one coating layer made of artificial resin covering the layer made of vegetable material, wherein the layer made of vegetable material is formed by parallelly arranged hollow stems of plants belonging to family Poaceae, each stem are bonded to the coating layer, such that the resin material of the coating layer is partially arranged in the space between the stems forming the vegetable layer and contacting the stems.

The Poaceae plant is advantageously reed. The resin is foamable polyurethane or polyisocyanate resin having two or more components.

At least one surface among its bottom surface and side surfaces is provided with a continuous foam mixture layer.

Paper, plastic film, metal foil, glass fiber, metal mesh, wood or plastic decorative foil is arranged on the layer.

The surface of the layer is ragged.

The object of the invention can also be achieved by a method according to the invention for producing layered heat insulating panel, consisting the steps of : cutting stems of plants belonging to the family of Poaceae into pieces of the same length, and arranging the pieces of stems substantially parallelly to each other in a layer having a desired thickness, and reducing the thickness of the layer of parallelly arranged stems uniformly, while moving it continuously in a feeding direction perpendicular to the stems as long as a predetermined thickness of the layer is achieved, while spraying a multi-component foam forming mixture onto the surface of the layer and forcing at least in part the foam mixture in a liquid state between said stems, so that contacting the foam mixture forced between the stems substantially with all the stems, then further reducing thickness of continuously moving layer impregnated by the foam mixture, while allowing the foam mixture to set, and slicing the foamed layer parallelly to the stems.

Preferably supporting the layer on both sides continuously.

Reed as a plant of family Poaceae is advantageously used, and

A foamable polyurethane or polyisocyanate resin having two or more components is used as a foam forming mixture.

Providing at least one of surfaces by a continuous foam mixture layer.

The object of the invention is further achieved by providing an apparatus for producing layered heat insulating panel, and it contains a hopper for receiving parallel stems of plants; and a clustering board connected to the hopper and consisting of lower guide elements and upper guide elements converging in the direction of a gap; and a foaming board connected to the gap of the clustering board and consisting of lower guide elements and upper guide elements; and a nozzle suitable for spraying foamable resin mixture onto the foaming board; and an inlet opening of a pair of conveyor belts to be moved in a synchronized manner is arranged at the end of the foaming board opposite said gap; and flexible arms fixed to at least one rotating translation shaft are arranged between said guide elements of the boards. An angle at the inlet opening formed by the pair of conveyor belts is between 5-15°.

The hopper preferably is provided with a vibrator.

The apparatus can be provided with lateral guide elements as well.

The method and apparatus according to the invention allows the use of previously non utilized organic materials with a wide range of changes of mechanical, fire-retardant and geometric properties, depending on the further processing. As a heat insulating material, its life expectancy exceeds 70 years, if isolated in respect of weather conditions (sunshine and rain).

The invention will now be described in further details with reference to the accompanying drawings. In the drawings:

Fig. 1 is a longitudinal section view of the heat insulating panel according to the invention, and

Fig. 2 shows a preferred embodiment of an apparatus for producing heat insulating panel according to the invention.

Figure 1 is a longitudinal section view of a section of a heat insulating panel 1 according to the invention. In the illustrated embodiment, the insulating panel 1 has two layers 2,3, between which there is no explicit interface region, that is during production a material forming an outer layer 3 of the insulating panel 1 penetrates partially into space 7 between stems 5 forming a core layer 2 of the panel 1 thereof, and reaches a bottom surface 9 of the panel 1, thus fixing the stems 5 to each other. The stems 5 arranged in the core layer 2 are preferably sections of vegetable stems 5 of plants belonging to the family of Poaceae. The Poaceae plants have hollow straw-stem or lignescent reed stem divided by stem-nodes (Nodus). This structure is a load bearing one as compared with the diameter thereof, but it is yet flexible. The straw-stem is usually unbranched, therefore, and by reason of the foregoing reasons, it is especially suitable for the objectives of the present invention. Producing the insulating panel 1 according to the present invention, the worldwide spread reed (Phragmites australis) belonging to the family of Poaceae was primarily used, but hollow stems 5 having a diameter of 2-15 mm of several Poaceae plants, such as bamboo (Bambuseae), common reed (Phragmites communis) native in North America, or cereal species also belonging to the family of Poaceae (wheat, rye, rice, barley, oats), and even for example the meadow foxtail (Alopecurus pratensis) are suitable for the objectives of the invention. In the layer 2 of the insulating panel 1 stems 5 having about the same cross-sectional area are preferably arranged substantially parallelly and closely adjacent to each other. Air trapped in cavity 6 of stems 5 gives an excellent thermal insulation property to the panel 1. In a preferred embodiment, an outer surface 8 of the layer 3 of the insulating panel 1 is a planar surface, while a surface 9, which is a lower one in view of the representation, is formed by material discontinuously arranged between the layer 3 and the surface of the stems 5. In a further preferred embodiment of the insulating panel 1, surfaces 9,10,11 of the panel may be provided with a layer of foam mixture, if it is required by the end-user.

Outer layer 3 of the insulation panel 1 is made of dimensionally stable synthetic resin foam having swelling properties, such as a known foaming mixture of two or multi- component polyurethane and polyisocyanate, which serves for holding the stems 5 together in the core layer 2 and forming the contour of the panel 1 as well. The preferably used polyisocyanate foam is a resin having thermal conductivity coefficient λ = 0.025-0.041 W / mK and an apparent density of 16-150 kg / m ³ and restricted combustibility, having also a special feature that the process of expansion starts within 10-30 seconds and stops 25-90 seconds after mixing its components. However, it is deformable between the start and stop of the expansion process, so that the foam can be pressed among the vegetable stems 5 as well as to the boundary surfaces 8,9 due to the increasing pressure, but the surface 9 will not be covered by the foam as a continuous layer, ensuring the dimensional stability and bond strength of the product. Due to its properties mentioned above the insulating panel 1 can be used advantageously as a thermal insulating element in vertical and horizontal surfaces of buildings, but it is also suitable for a load-bearing masonry block or even for forming earthquake-resistant building structures, for building or insulating walls of buildings to be built by rapid house-building technology, or for cavity filling. EaGh application can use the same base product, that is the form of the end product, such as heat insulating panel 1, self- bearing insulating panel 1 laminated with metal, wood or other type of coating, self bearing insulating masonry panel 1, can be chosen on the base of properties rated (e.g. according to diameter) at the start of the production. The common reed allows, for example, a wall structure having dimensions 0,2 xO, 2x0, 5m and a compressive strength of 0.7 MPa and a low heat transfer capacity of U = 0.2 m ² W°K to be built by using of its lower 1 m stem section (that is equivalent to a wall structure having a thickness of 0.6 m made of Ytong blocks). It is essential to keep a continuous quality control covering all panels 1. In this case, there is no need traditional concrete or metal structures except a ceiling support crowning. Insulating panel 1 according to the invention is continuously prepared by a method according to the invention, in such a way that assorting plant stems 5 collected in the nature or cultivation by its diameter only, if it is needed. Since stems 5 having approximately the same cross section, but belonging not necessarily to the same species are preferably used in the heat insulating panel 1 , stems 5 having a diameter between 0-30% of average deviation are assorted in the same group . Stems 5 assorted in the same group are cut into pieces of same length, preferably 0.5-1.5 meters, e.g 1 m, but of course, the length may vary in either direction to suit the needs. The prepared stems 5 are arranged parallel to each other in arbitrary, e.g. 70 mm thickness, which is initially greater than the thickness of the finished layer 2. The thickness of layer 2 consisting of substantially parallel vegetable stems 5 is uniformly reduced, while moving it continuously in a feeding direction E being perpendicular to the stems 5 as long as a predetermined thickness of the layer 2 is achieved, while spraying a multi-component foam forming mixture onto the surface of the layer 2, which flows, yet in a liquid state, partially between and beneath the stems 5. Then further reducing the thickness of the continuously moving layer 2 impregnated by the foam mixture, so that supporting a pressing in a plane the solidifying surface 8 of upper layer 3 from above and supporting the surface 9 from underneath by their whole surface 8,9 area, as long as a final thickness of the layer 2 is achieved. The supporting force is then held until the foam mixture solidifies during moving. Subsequently, the layer 2 fixed between the layer 3 and the bottom surface 9 by the hardened foam mixture, as well as the layer 3 are sliced parallelly to the stems 5 up to panels 1 having desired lengths, and sides 10, 11 being perpendicular to the cut can be edged off, if necessary.

In a preferred embodiment of the method according to the invention, layers 2,3 are continuously supported also by both their lateral sides, that is in planes perpendicular to the stems 5, in order to prevent the foam mixture from partial escaping laterally from layers 2,3 before having solidified. In this case, the edging off of lateral sides 10,11 is not required.

The method for producing insulating element 1 according to the invention can be achieved by the apparatus 12 according to the present invention seen in Figure 2. The apparatus 12 contains a storing and feeding hopper 13 serving to receive vegetable stems 5 cut to a desired size, which is provided preferably by a vibrator unit 14. The stems 5 move along to an inclined clustering board 16 sloping in a feed direction E through a adjustable lower slot 15 of the hopper 13, which board 16 is formed by lower guide elements 16b and upper guide elements 16c confining parallel gaps 16a. The lower guide elements 16b converge to the upper guide elements 16c in the feed direction E, that is the cross section of the clustering board 16 decreases in the direction E. Flexible arms 18 mounted in at least one translation shaft 17 extend into the gaps 16a of the clustering board 16 and while rotating, push the plant stems 5, which arrive to a horizontal foaming board 20 positioned in continuation of the inclined clustering board 16 through a gap 19 properly adjusted according to the planned thickness of the panel 1. The design of the foaming board 20 is similar to that of the clustering board 16, that is it is formed by lower guide elements 20b and upper guide elements 20c confining parallel gaps 20a, but a cross section of the space between lower guide elements 20b and upper guide elements 20c is constant in the feed direction E, so that lower guide elements 20b and upper guide elements 20c are parallel. Due to flexible arms 22 also mounted in at least one translation shaft 21 the stems 5 move along in a thickness according to the size of the gap 19 in the horizontal foaming board 20, while the multi-component foam mixture is sprayed onto the surface of the stems 5 through a nozzle 23 set in appropriate height, and flows partly between the stems 5 yet in a liquid state. The foam mixture is continuously transferred to the nozzle 23 by means of a pump unit driven by a hydraulic cylinder provided by two cylinder cases having equal power providing controlled flow of material and being suitable for transferring several components.

From the foaming board 20 the stems 5 treated by foaming mixture come into an inlet opening 26 of a pair of conveyor belts 24,25 having synchronized motion and exerting pressing force to the layers 2,3. The conveyor belts 24,25 are converged toward each other in the region of the opening 26 and include an angle of 5-10° along a length of preferably 0.3- 0.4 m at the intake side. Stems 5 treated by foam mixture and brought in between the conveyor belts 24,25 due to the initial decrease of the distance between the conveyor belts 24,25 are compacted in a desired range, e.g. their bulk weight become 70-80% of that can be measured on the foaming board 20, and the thickness of the layer, e.g. 50 mm set in the gap 1 decreases preferably to 30-40 mm.

Stems 5 treated with foaming mixture will arrive between the conveyors 24,25 from the foaming board 20, when the froth of the foaming mixture just begins and its volume starts to increase. Conveyor belts 24,25 move in a synchronized variable speed manner and have a coating treated by release agent. In a preferred embodiment of the apparatus 12 according to the present invention Teflon coated lateral guides 27,28 are used, and the cross-sectional size of the insulating element 1 according to the invention is defined by the size of a closed, preferably rectangular cross-section formed by the lateral guides 27,28 and by conveyors 24,25.

The length of conveyors 24,25 is set so that the swelling process of the foaming mixture is already completed between the conveyor belts 24,25, that is the foaming rate is controlled by the change of the proportion of components to be fitted to the longitudinal size of the conveyors 24,25.

The layered 2,3 product consisting of 5 stems and solidified foam mixture leaving the conveyors 24,25 comes into a cutting unit not shown but known per se in the art. An area of 60-80% of the upper surface 8 and 5-25% of the lower surface 9 of the finished panel 1 cut up to its final length are covered by foaming mixture, and it can be used immediately.

Example

Reed stems 5 rated by diameter were used as plant stems, which moved to the sloping clustering board 16 from a hopper 13 through a slot 15 opened to 5 cm, due to the vibration of a pneumatic vibrator 14 fixed to the hopper 13. The distance between lower and upper guide elements 16b, 1 c of the sloping clustering board 16 gradually reduced to 35 mm at the gap 19, while flexible arms 18 made of spring steel pushed the stems 5 toward the horizontal foaming board 20. Two nozzles 23 set at 20-40 cm above the upper stems 5 sprayed foaming mixture at a rate of 0.4 liter/minute over the surface of the stems 5 with such a force that the mixture penetrated partly between the stems 5 up to the surface 9. Upper and lower conveyor belts 24,25 having Teflon covering and set apart by 30 mm forwarded the stems 5 and provided a closed cross-section for forming the swelling foam. Leaving the conveyors 24,25 having synchronized motion the product is moved continuously through an air-powered, fast- moving cutter framework, that sliced a panel 1 from the product of a desired size. The cut off, finished panel 1 was pushed from the cutter framework by the product behind it, which was fallen in a storing site. The heat insulating panels 1 thus produced can be glued together using additional spraying operations and adjusting the distance of the conveyor belts 24,25 to increase thickness or surfaces 9,10,11 can be provided with a layer of foam mixture also by further spraying and by using conveyors 24,25 with adjustable distance, if it is desired by the final use. Moreover, paper, plastic film, metal foil, glass fiber, metal mesh, wood or plastic decorative foil can be glued onto the layer 3 afterwards or during the ongoing production, disposing any above material between the conveyor belt 25 and the layer 3. The panel 1 can also be made with surface 8 suitable for plastering or by various surface 8 roughness, if the surface of conveyor belt 25 is roughened accordingly.

A key advantage of the panel 1 according to the invention as compared with products used before is that it is a dimensionally stable layered heat insulating product, which is extremely close to the previously used (mineral wool, Styrol) products by its rated insulation parameters, but having much more favorable environmental impact, durability and dimensional stability due to a substantial amount of renewable components, as compared with products used before. The method and apparatus for production of layered heat insulating panel 1 according to the invention enable to produce a heat insulating panel 1 primarily made of renewable materials, especially stems of reed or cane, wherein manual work is basically omitted, and the exploitation of the natural base material is far better than that of the prior art methods, rendering the production of the heat insulating product made of renewable material more economical.