AHONEN, Heikki (Nuutalantie 73, Ritvala, FI-37720, FI)
LOUKO, Reijo (Katajaharjunkatu 8, Kuusankoski, FI-45720, FI)
AHONEN, Heikki (Nuutalantie 73, Ritvala, FI-37720, FI)
| Claims: 1. A thermal insulation board made of organic fibres, characterized in that the organic fibres (31) are bound together with polyolefin fibres (32), which are made of waste plastic or recycled plastic. 2. A board according to Claim 1, characterized in that the polyolefin fibres (32) are polyethylene or polypropylene or a mixture thereof. 3. A board according to Claim 1 or 2, characterized in that the quantity of the polyolefin fibers (32) is approximately 1-50 % by weight, especially approximately 2-25 % by weight, of the total weight of the board. 4. A board according to any of Claims 1-3, characterized in that it comprises organic fibres (31) and, possibly, components which protect the polyolefin fibres, such as fire retardants and anti-mould agents or mixtures thereof. 5. A board according to any of Claims 1-4, characterized in that the organic fibres (31) are wood fibres, wood chips, cellulose fibres, lignocellulose fibres or fibres which are sourced from their derivatives or which are made from their recycled products, such as fibres made from recycled paper or recycled cardboard. 6. A method of producing a thermal insulation board from organic fibres (31) which act as basic fibres, according to which method binder is mixed with the fibres, whereafter a board having the desired dimensions is shaped from the fibres, characterized in that the binder used is polyolefin fibres (32), which are made from waste plastic or recycled plastic. 7. The method according to Claim 6, characterized in that the plastic fibres (32) intended to be the binder are prepared at the same time as are the basic fibres (31) but in a different device, and the plastic fibres are blown in between the organic fibres. 8. A method according to Claim 6, characterized in that the basic fibres (31) and the binding fibres (32) are post-heated together in such a way that the binding fibres at least partly melt and adhere to the basic fibres. 9. A method according to any of Claims 6-8, characterized in that the fire retardants are mixed with the binders before the basic fibres and the binding fibres are combined. 10. A method according to any of Claims 6-9, characterized in that a chemical, which in those conditions generates a gas, is mixed with the binder before the binder is defibred in a molten state. 11. A method according to any of Claims 6-9, characterized in that the waste plastic which is melted in order to generate the binding fibres is fed onto a rotating disc (14), from where it is ejected in a fibrous state by the centrifugal force, in which case the rotating disc (14) is heated. |
The present invention relates to a wood fibre insulator according to the preamble of the claim, particularly a wood fibre insulation board.
Typically, an insulator such as this comprises finely ground wood material or material derived from wood, such as wood fibre, wood chip, cellulose fibre or paper fibre or similar.
The present invention also relates to a method according to the preamble of Claim 6 of producing a wood fibre insulator.
Thermal insulators made of wood have long been produced. Initially, sawdust and wood chips produced by a rotating-blade planer, were used. Later, wastepaper was defibred and, later still, wood as such. In this way, a thermal insulator is generated which is easy to blow, and which can be blown either dry or damp into the place that is to be insulated.
For a long time, boric acid and borax have been used as fire retardants in wood-based thermal insulators. At the same time, they also act as effective anti-rot agents. Zinc borate, too, is used for the same purpose. Now, there is a new compound, namely, magnesium sulphate, which is a useful substitute to boron compounds, the use of which compounds it is desirable to limit. Preferably, thermal insulators for houses erected on-site should already be in the form of boards, at least for their use in the floors and walls.
Rock wool, glass wool, polystyrene foam and polyurethane foam are already marketed in the form of boards. Of these, rock wool and glass wool comprise fibrous materials, the fibres of which are bound together with resins, generally with phenol-formalin resin.
When it is necessary to make a wood fibre-based thermal insulator in the form of a board, thus allowing installation as a board, the wood fibres, cellulose fibres or other organic fibres have to be bound together in order to maintain the desired structure and shape. In our earlier patent application FI20095827, a solution is described in which wood fibres and wood chips are bound together with a certain type of organic fibres which comprise polymers that have two different melting points. This solution is very functional per se, but the costs are high and it necessitates the use of special material which has to be sourced from abroad.
It is an aim of the present invention to provide a novel solution for producing wood fibre insulators.
The present invention is based on the principle that material which can be recycled, and which is generated for instance as waste from other activities, is used for binding the fibres. A most advantageous solution for building work in general is that it is possible to use waste material or waste materials. Thus, such wood waste or woodworking waste which can be defibred by dry refining or refining in slightly damp conditions is an advantageous material either together with or separate from waste paper or cardboard used for packing. In the present invention, a thermal insulation panel or board which comprises organic fibres or their derivatives or their recycled products is produced in such a way that the fibres are bound to each other by polyolefin fibres that are made of waste plastic or recycled plastic. According to our invention, a plastic film which is designed to be a binder, or a polymer which melts in similar conditions, for instance polypropylene, is defibred by using heat and kinetic energy to form fibres or/and thin mini films, which are blown in between organic fibres and/or wood chips. More specifically, the product according to the present invention is mainly characterized by what is stated in the preamble of Claim 1.
The method according to the present invention is, in turn, characterized by what is stated in the preamble of Claim 6.
Considerable advantages are achieved with the present invention. Thus, it is possible to use inexpensive waste or recycled polymer material, and prepare it in situ. In addition, by performing local defibring, it is easier to manage the quantity of material used if and when it is desired to adjust the strength properties and the density of the insulation panel to be produced.
The binding fibres are blown, either hot or warm, in between the basic fibres, in which case it is not necessary to introduce much, if any, heat while the finished panel is being worked on. Furthermore, it is possible to avoid separate breaking open of binding fibre packages and scattering of the binding fibre.
Another important consideration is that it is possible to use all kinds of polyolefin waste plastic, such as shopping bags and other plastic bags, wrappings and sacks. It is well known that in Finland waste plastic, such as shopping bags, are nowadays sorted at almost all chain stores by the customers. Thus, relatively clean waste polyethylene films are available, the general reuse of which films is otherwise very limited because of the printing on them.
According to our invention, when polymer material is brought into a wood fibre structure in order to bind the organic fibres together, the fire retardants used also prevent these polymers from burning. In the following, the present invention will be examined more closely with the aid of a detailed description and the accompanying drawings.
Figure 1 shows a basic diagram of a simplified structure of the defibring apparatus used in the present invention;
figure 2 shows a belt which is used for shaping the fibre insulation panels, and
figure 3 shows an aggregate of organic fibres and plastic.
As described above, according to the present invention, recycled plastic and waste paper or/and waste wood are used for producing thermal insulation panels, and particularly as a binder for binding together organic fibres. The basic fibres used for insulation panels, i.e. insulation boards, are organic fibres, typically wood fibres, wood chips, cellulose fibres, lignocelluloses fibres, or fibres which are sourced from their derivatives or which are composed of them, or fibres which are made from recycled products of organic materials, such as fibres made from recycled paper or recycled cardboard. The basic fibres and the binder fibres are mixed together and shaped as desired, for instance into a board. The quantity of binding fibre used is generally approximately 1-50 %, especially approximately 1-25 %, most suitably approximately 2-20 %, of the weight of the base material fibres. The dimensions of the plastic fibres are in the range that corresponds to the dimensions of the organic fibres, i.e. approximately 0.1-100 mm, typically approximately 0.5-50 mm, especially approximately 0.7-25 mm.
In order to ensure the bonding between the polymer fibre and the organic fibre, it is advantageous (but not necessary) to heat the panel blank, which is made for instance by blowing and shaping onto a moving belt, and then to cool it before longitudinal cutting.
According to a preferred embodiment of the present invention, the binder of the fibre insulator comprises totally recycled material. Naturally, it is possible to use, besides recycled or waste material, also traditional binders or for instance special fibres, which were mentioned above. Generally, the percentage of recycled plastic in the binder of the insulating material is approximately 20-100 % by weight, especially approximately 50-100 % by weight. Naturally, it is possible to blow the binding fibres in a molten state in between the basic fibres, in which case only cooling is needed before transverse cutting. It should be noted that the basic fibres, too, are warmed by the dry refining.
According to one embodiment, when the binder fibres are heated, the temperature should be occasionally over 120 °C.
It is possible to mix fire retardants, such as boric acid, borax and boron salts or magnesium sulphate and similar salts, with the binders before the basic fibres and the fire retardants are combined. This solution can be carried out in such a way that the necessary fire retardants or part of them are added during the stage in which the polymer material is melted, in which case the crystal water released from the retardants blows fine bubbles into the polymer fibres, which bubbles, in turn, increase the insulating capacity of the insulator. Antimony oxide is a well-known effective fire retardant for protecting polymers. This, too, can be added during the melting stage.
Generally, the quantities of fire retardants and anti-mould agents added are approximately 0.01-20 % by weight of the binder quantity, especially approximately 0.05-10 % by weight.
In order to generate microfoam in the fibres, it is possible to add also other gas-generating chemicals into the polymer. Examples of such chemicals are ammonium bicarbonate, water and many nitrogen-releasing chemicals, such as azodi carbon amide and sulphohydrazine.
According to a preferred embodiment, the binding plastic fibres are prepared at the same time as are the basic fibres (i.e. organic fibres) but in a separate device, and are then blown together in a molten and adhesive state.
According to another preferred embodiment, the basic fibres and the binding fibres together are post-heated in such a way that the binding fibres at least partly are adhered to the basic fibres by melting. In order to defibre plastic, the molten waste plastic is fed onto a rotating disc, from where it is ejected in a fibrous state by the centrifugal force. The rotating disc can be heated.
A particularly affordable apparatus, in which it is possible to defibre plastic efficiently, has been developed for the implementation of the present invention. The apparatus is shown in the accompanying drawings and it is described more closely below. For the sake of thoroughness, it should be noted here that although examples of defibring equipment occur in the patent literature, they have not been used for the purpose mentioned above, nor are their structures suitable for that purpose. US Patent No. 4,119,421 describes how it is possible to generate fibres from molten material (rock) by using two rotating cylinders, onto which cylinders molten material is spilled and from which cylinders the material is blown away by an air current, in which case it is defibred. According to another US Patent No. 4,001,357, fibres are generated from thermoplastic molten material by pouring the material through a Laval nozzle by applying air pressure in such a way that the air pressure generates supersonic speed. According to US Patent No. 4,251,320, molten rock is defibred with the help of a rotating cylinder, in a gas flow channel, which flow defibres and cools the material.
US Published Patent Application No. 20090068430 describes how a thermal insulator is produced from organic fibres by using polyvinyl alcohol fibres as binder, and polyolefin fibres that become soft when heated. The insulator comprises salts of K and P, in which case it is possible to use the insulator (to supplement boron compounds) as fertilizer, too. The product is said to be biologically decomposable.
According to US Published Patent Application No. 20060148364, insulation boards are afforded high compressive strength by using waste plastic granules 22-37 % of the board weight to bind the fibres. In addition, approximately 13 % of thermoplastic binding fibres are used in the application.
The production engineering is similar to that used for producing cardboard on a paper machine, where material is imported layer by layer until the desired thickness is reached.
However, when polymer material is defibred, there is a major difference compared to previously described processes of producing mineral fibres. Molten polymers adhere to almost any material, which is not the case with molten rock. Consequently, the defibring method must be such that the tools remain essentially clean, and continuously generate a product of uniform quality, without clogging.
Furthermore, the defibrator for defibring the polymer material must be such that it is suitable for waste and recycled polymers, including impurities.
Therefore, in the present invention it is not important how the polymer material is defibred. Rather, in principle, it is possible to use any methods as long as the fibres and the molten polymer do not adhere to the defibring device. A novel apparatus has been developed for this purpose.
According the present preferred embodiment, transportation of heat into the polymer mass takes place in such a way that a feed screw compresses plastic into a cylinder, the walls of which are heated and which thus melt the polymer. The defibring of the polymer takes place by means of one or several simultaneous mechanisms.
Kinetic energy can be brought into the molten polymer mass either by a jet of air or by expanding the air which has remained inside the mass, or, alternatively, by means of a rotating disc. With the help of a rotating drum or a similar device, a thermal insulator called rock wool, for instance, is produced from molten rock material.
When the defibred polymer and the defibred organic material are blown together and shaped into a desired board shape and cooled, the objective is achieved, i.e. an insulation panel that maintains its shape. The required thickness of the board is easily achieved by adjusting the speed of the conveyor belt/mould belt. The properties of the product are, in turn, modified by changing the ratio between the basic fibres and the binding fibres.
In the following, the structure of the apparatus according to a preferred embodiment is examined:
Figure 1 shows a feed funnel 10 for waste plastic, a feed screw 13 which is driven by a motor 11, a heat jacket 12 which can be oil-heated or electrically heated, and a disc for disintegrating 14, and an air nozzle 15.
Figure 2 shows a conveyor belt 21 and a smoothing device 22 and the recycle 23, 24 to the feed.
Figure 3 shows the structure of a finished product. The shaded fibres 32 are polymers, which bind together for instance wood fibres 31.
The operation of a defibrator is based on the simple idea of having only a rapidly rotating disc 14, onto which a screw 13 feeds a molten polymer mass, and from which the exiting mass meets a jet of disintegrative air or inert gas which is generated by a blower and a nozzle 15.
After that, the polymer fibres 18 are conducted with the help of an air flow into a flow of organic fibres, preferably immediately after they have exited from the defibrator through the outlet pipe 16.
This combined flow is led into a mould or onto a conveyor belt having edges, which belt acts as a mould. This principle is shown in figure 2.
The conveyor belt 21 is equipped with edges and a planing blade 22 which removes excess mass and returns that mass to the feed via the blower and the feeding line 24.
It is obvious that it is possible to change the size of the fibres by regulating the speed of the rotating heated disc 14 and, also, by changing the temperature of the molten polymer. The speed of the air exiting from the air nozzle 15 is always constant, if the pressure ratio is above 1.89, the air reaches the speed of sound.
At higher pressures, the speed remains the same, but the air undergoes greater cooling and it cools the disintegrated fibres faster. Preferably, the breaking disc is electrically heated, in order to prevent the molten polymer from solidifying onto its surface.
Naturally, it is possible to strengthen a finished thermal insulation panel by increasing the quantity of polymeric binding fibres, and/or, by increasing the density of the insulation panel by means of compression. It is possible to regulate the basic density of thermal insulation panels by modifying the degree to which the organic fibres are refined. The finer the degree of defibring or fibrillating, the lower the density achieved. Typically, the densities are within the range of 30-70 kg/m . However, care should be taken to ensure that there are enough fire retardants, i.e. boric acid and sodium tetraborate, to smother a smouldering thermal insulation panel. Generally, a total quantity of approximately 5.5 % of these boron compounds is enough for fire retardant purposes; also, a suitable quantity of MgS0 4 is used, in order to ensure that the material aggregate fulfils the anti-smouldering requirements.
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