FI94325C - Process and apparatus for producing a fiber product - Google Patents

Abstract

In a method for making a fibrous product from vegetable-based cellulosic fibers, an air flow (A) is used for forming a mat on an advancing forming platform (1). The mat is bonded by means of thermally bondable binder fibers, such as thermoplastic fibers intertwined with the cellulosic fibers such that, upon being brought to a binding state through the action of heat, said binder fibers bond the cellulosic fibers to each other in the mat. The thermally bondable binder fibers intertwined with cellulosic fibers are subjected to the action of heat already in air flow (A) carrying the fibers onto forming platform (1) by setting temperature of the air flow sufficiently high.

Description

94325

Method and apparatus for making a fiber product

The invention relates to a method for producing a fibrous product according to the preamble of appended claim 1 and to an apparatus for producing a fibrous product according to the preamble of appended claim 9.

WO 82/03359 discloses a method in which a moldable mat is made from wood fibers by having thermoplastic bonding fibers among the wood fibers which, when melted and solidified, bind the fibers together. The carpet is formed by the so-called by a dry method on a moving belt by means of a stream of air which conveys the fibers to the belt and passes through the mat. The carpet is then bonded by passing the carpet thus formed through a furnace having a sufficiently high temperature to soften the bonding fibers and thus enter the adhesive space connecting the wood fibers.

In addition to making carpets using binders that do not pose a risk to occupational safety and the environment, the above method can easily be used to produce products that can be subsequently • molded into the desired shape by heat, as the thermoplastic properties of the bonding fibers can soften them again. wherein, due to the deformation caused to the mat and the subsequent cooling, they are caused to bind the mat to a new shape.

The use of wood fibers and other vegetable cellulosic fibers 35 in the manufacture of fiber products is attractive in the sense that they are renewable natural raw materials that are abundantly available, pleasant to handle as material and do not pose health risks. The fiber mat made of these 94325 2 fibers is also a good thermal insulator. However, it is precisely this feature that causes a problem in the manufacture of the product if it is desired to manufacture it by the above-mentioned method. Namely, when handling 5 products in an oven, the oven has to be made quite long so that heat can also penetrate into the interior of the mat-like product to bind the fibers. If thick products were to be made, the ovens would have to be made disproportionately long so that the mat 10 would also be properly bonded from its center as it came out of the oven. Another option would be to drastically raise the temperature, which would, however, lead to damage to the surface structure of the product, as the thermoplastic fibers therein would then completely melt away into spherical droplets incapable of bonding the fibers together, breaking the mat. It is clear that the above methods are not economically viable either.

The object of the invention is to eliminate the above-mentioned drawbacks and to provide a method and an apparatus by means of which it is possible to produce very thick nonwovens with excellent thermal insulation properties from wood fibers. To achieve this object, the method according to the invention is mainly • characterized by what is set forth in the characterizing part of the appended claim 1. When the thermoplastic binder fibers among the vegetable cellulosic fibers are made to soften already in the air stream conveying the fibers to the forming substrate by arranging the air flow temperature high enough, the thermal insulation properties of the fibers are not impaired. Thermoplastic binder fibers bind wood fibers together already in the carpet formation stage. In practice, this makes it possible to form a very thick carpet, since new fibers which bind to the carpet can be piled on the carpet previously formed at the carpet-forming point, in principle in any large quantities.

94325 3

Other preferred embodiments of the method according to the invention are set out in the appended dependent claims 2-8. For example, the mat can be compressed to the desired extent by means of an air flow while it is still in a mouldable state after formation. In the post-treatment of the carpet, it is preferably used to form the insulation of the building element, whereby the health-safe properties of the product can be utilized.

The apparatus according to the invention, in turn, is characterized by what is set forth in the characterizing part of the appended claim 9. An air duct is led from the heater to the air chamber in which the mat is formed on the transport base, whereby the bonding fibers can be heated to a binding space already in the air chamber. The equipment does not require a long oven to heat-bond the product. Other preferred embodiments of the apparatus according to the invention are set out in the appended dependent claims.

The invention will now be described in more detail with reference to the accompanying drawings, in which Figure 1 shows a side view of a carpet forming part of an apparatus according to the invention, Figure 2 shows a part of Figure 1 cut from above, Figure 3 shows one example of a finished product, Figure 4 shows a detail of Figure 1 '35 on a larger scale, and Figure 5 shows diagrammatically the principle of operation of the whole apparatus.

4,94325

Figure 1 shows a mat-forming section with a fiber feeder 11. As the feeder, either a vertical device 11a known per se, in which the fibers are introduced by means of an air flow, or a horizontal conveyor 11b with fiber pretreatment devices known per se can be used. At the lower end of the feeder 11 there is a feed roller 2, the surface of which has spikes with a dense division. Towards the surface 10 of the feed roll 2, a horizontal narrow nozzle gap at the end of the first air duct 3 is directed. Below the nozzle gap there is an orifice of the second air duct 4, a constriction point is created between the lower wall and the surface of the feed roll 2. This throttling point is followed by an obliquely downwardly expanding air chamber 6, the lower end of which is closed by an air-permeable forming base 1. On the opposite side of the forming base 1 there is a collecting chamber 10.

The forming base 1 consists of an endless belt passed through rollers, which is arranged to move across the chamber 6. In the direction of movement of the forming base, it passes after the chamber 6 across the second air chamber 8, forming its lower surface.

At the beginning of the first air duct 3 there are fans 12 arranged in parallel, which provide a uniform air flow over the entire width of the duct 6. These fans 12 are shown in broken lines in Fig. 30. The tube forming the beginning of the second air duct 4 also has a fan 13 arranged to blow air heated to the second air duct 4 by the heater 7. The heater 7 can be, for example, an ordinary gas burner.

The mat formation takes place in the apparatus in such a way that the mixture of cellulosic fibers and thermoplastic binder fibers is fed by a feed device towards the feed roll 2. Fig. 4 94425 5 sa 4 shows the mat formation in more detail below. The spikes 2a of the rotating feed roll 2, marked in the figure on the outermost layer of the feed roll, take the fibers with them. In the direction of rotation 5 of the feed roll, they next fall into the area of action of the horizontal nozzle gap 3a extending across the width of the first air duct 3. The high velocity air flow A1 from the nozzle slot detaches the fibers from the feed roll 2 as it wipes the surface of the roll and conveys them over the mouth 4a of the second air duct 4 to the constriction point 2b between the lower wall of said mouth 4a and the feed roll 2 surface. After the throttling point, the fibers are completely detached from the feed roll 2 and enter the air chamber 6, which has a constant width and corresponds to the width of the mat to be formed, in an expanding cross-sectional area in the direction of transport of the fibers. The expansion of the chamber is effected in such a way that the front and rear walls extending in the axial direction of the feed roll 2, i.e. in the width direction of the resulting mat, diverge from each other.

20

Air is led through the second air duct 4 as an air flow A2 to the mouth opening 4a. This second air flow A2 has a higher temperature than the first air flow A1 introduced through the first air duct 3. This air flow A2 coincides with the air flow A1 due to the ejector effect of the throttling point 2b and mixes with it into the air flow A conveying the fibers to the end of the air chamber 6. The feed rate of this higher temperature air flow A2 is arranged so that the temperature causes the surface of the thermoplastic binder fibers among the cellulosic fibers to soften to a state where they are able to bind the fibers into a mat. These fibers can be well affected by the air because they are exposed in the air stream. The end of the air chamber 6 is closed by a forming base 1 running across the chamber, which may be a woven wire or an air permeable planar material 6 94325. At the inlet of the conveyor, i.e. after the front wall of the air chamber, the fibers that strike at the outermost form immediately form a bonded mat, and on top of this 5 a continuously increasing thickness, similarly bound mat, begins to accumulate. Since the resulting mat is porous, the air flow A enters the collection chamber 10 on the opposite side through the mat and the forming substrate 1 below it.

10

Figure 1 shows the subsequent treatment of the carpet. In the direction of travel of the forming base 1 downstream of the chamber 6, there is a sealing roller 14, the distance of which from the forming base 1 is adjustable. The sealing roller prevents air 15 from passing in the direction of travel of the forming base 1 away from the air chamber above the mat. After the sealing roll, the forming base 1 conveys the mat to a second air chamber 8, which is located above the forming base 1. An air duct 9 is introduced into the upper end of the air chamber 8. The second air chamber 8 is widening in the flow direction of the air flow introduced from the air duct 9 towards the forming base 1, i.e. the chamber walls on the inlet side and the outlet side of the forming base move away from each other. By means of the pressure of the air flow B introduced into the chamber, for example, the mat can still be pressed to the desired size v to bring its density to the desired value.

In this case, the air flow is passed through a porous mat and a forming base 1 supporting it to a second collecting chamber 15 on the opposite side. The air flow B introduced into the second air chamber 8 is then in such a heat state that the binder fibers remain soft. them, i.e. the mat can be shaped to the desired density so that the deformation is permanent. After the second chamber 8, the mat is transferred from the forming substrate 1 to a conveyor 16, which takes the bound mat product forward for further processing.

94325 7

If a product with a particularly low density is desired, the post-treatment by means of a second air chamber 8 can be omitted. The density of the product can also be adjusted already at the carpet formation stage by the speed of the air flow A in the air chamber 6 5, on which the force with which the fibers strike the carpet depends.

Figure 5 schematically shows one possibility of arranging air flows in the invention. The airflows 10 are circulated so that the airflow A entering the collecting chamber 10 forming the mat is led through the fan 12 to the first air duct 3. During this time the airflow has time to cool to such an extent that the first airflow A1 from the nozzle opening 3a is below its temperature , which softens the connective fibers. In this case, this air flow A1 only acts to separate the fibers from the feed roller 2. However, this can provide preheating, in which case the air flow A2 from the air duct 4 does not have to be arranged at a considerably high temperature. Said air flow A2 is led to the second air duct 4 from the heater 7 by means of a fan 13. The air duct 4 branches into an air duct 9 connected to the second air chamber 8, whereby part of the heated air flow A1 blown by the fan is taken as the air flow B performing the after-treatment of the carpet.

This also ensures that in the after-treatment the air flow B has a sufficiently high temperature and since it originates from the air duct 4, through which only 30 heated air passes, its temperature is in fact higher than the temperature of the air chamber 6. However, this air does not: melt the binder fibers because they are surrounded by cellulose fibers acting as thermal insulators and, on the other hand, the air flow rate per surface area remains small due to the size of the chamber 8.

The air flow B entering the second collecting chamber 15 on the other side of the forming base 1 is recirculated back to the heater 7 through the air duct 18. Air also enters the chamber 8 with the mat from the chamber 6. This air enters the circulating air going to the heater 7 through the collecting chamber 15. In order to maintain the air balance, a part of the air passing through the first air duct 3 is led out along the duct 17. To replace this, in addition to the recirculated air, replacement air is taken from the outside into the heater 7. Air can also be recirculated from the duct 17 to the heater 7, but this degree of recirculation 10 is determined by the impurities accumulated in the air during the formation of the mat.

Figure 5 further shows normal measuring and control devices for adjusting the air flow temperatures to the desired ones.

Figure 3 shows a preferred fibrous product in the manufacture of which a flexible mat with a density of about 18-25 kg / m3 20 has been used. This is a planar rigid building element 5, in which the mat is placed as a layer 5c forming a thermal insulation between the outer cladding 5a and the inner cladding 5e of the building element. The layer 5c can also be formed from several superimposed mats so that the thickness of the layer becomes 10-20 cm. In the example of Fig. 3, on the outer cladding side, a wind shield 5b of nonwoven fabric is attached to the surface of the insulating layer 5c, whereby a ventilation gap is left between the outer cladding and the wind shield. Correspondingly, a vapor barrier film 5d is attached to the inner cladding side 30, which may comprise a laminated plastic film on the surface of the insulating layer 5c. An inner cladding 5e made of gypsum board is attached to the steam barrier 5d.

Other final product forms can also be considered for the mat made according to the invention. Thus, when using denser mats than thermal insulation mats, they can be used like chipboard.

I: 94325 9

All vegetable cellulosic fibers, in particular fibers from woody plants, such as mechanically produced pulp, are suitable as raw material for the carpet. In this case, the density of the mat can be influenced by the choice of the degree of grinding of the fibers. In addition, the fibers can be from any wood species, but in particular the fibers obtained from willow and wound are advantageous due to their length, since they can then be well bonded together. Cotton or jute can also be thought of as a raw material, either alone or as a mixture with wood fibers. As the thermoplastic bonding fiber, any thermoplastic polymer, i.e. a thermoplastic, such as polypropylene or polyester, can be used.

It is also possible to use bicomponent fibers in which the part is a lower temperature softening polymer. The temperature of the air flow A through the air chamber 6 can be adjusted according to the softening point 20 of the binder fiber material, and this point at which the surface of the fibers softens into the adhesive space is between 100 ° ... 200 ° C with the most commonly used thermoplastic polymeric materials. The structure of the mat can also be influenced by the choice of the ratios of the thermoplastic binder fiber and the cellulose fiber, but as forming the structure of the product. the basic raw material is vegetable cellulose fiber, which is always the bulk of the carpet mass.

The apparatus according to the invention has been used to make various mats from wood fibers and polyester fibers derived from spruce. Air flow rate:. the throttling point before the air chamber has then been 42 m / s, and the surface speed of the feed roller 2 has then been about 10 m / s slower. The poly-35 ester fibers used as binder fibers have accounted for 15-20% of the total amount of fibers fed. The basis weights of the mats obtained have varied between 100 g / m 2 and 3000 g / m 2 and their densities have ranged from 18 kg / m 3 to 400 kg / m 3, 94325 10 whereby the former product corresponds mainly to glass or rock wool used as thermal insulation and the latter to particle board.

5 The obtained products have excellent thermal insulation properties due to the low heat transfer coefficient of vegetable cellulosic fibers and the formation of a fluffy mat suitable for insulating purposes.

10

In addition, the resulting mats can be post-treated to improve some of the properties. For example, carpets can be subjected to fire and mold treatment. The fibers fed to the mat can also be treated in this way.

• 1

Claims (13)

94325 Claims; A method of manufacturing a fibrous product, wherein a mat of the plant cellulosic fibers is formed into a forward moving forming substrate (1) by an air stream (A), and the mat is bonded by thermoplastic binder fibers among the cellulosic fibers so that they soften the cellulose fibers , that the thermoplastic bonding fibers among the cellulosic fibers are made to soften already in the air stream (A) conveying the fibers to the forming substrate (1) by arranging the temperature of the air stream sufficiently high. A method according to claim 1, wherein the fibers are fed to the air flow (A) by means of a feed roll (2) or the like, characterized in that the fibers are separated from the feed roll (2) or the like by air flow (AI), to which a second air flow (A) is then introduced. A2), as a result of which the temperature of the combined air flow (A) formed by the air flows (A1, A2) rises so that the bonding fibers soften. A method according to claim 1 or 2,! characterized in that after the mat is formed by the air flow (A) on the forming substrate (1), it is post-treated by passing the air flow (B) through the mat, the mat being supported on the opposite side to the inflow direction of the air flow. :. A method according to claim 3, characterized in that in the post-treatment the density of the mat is increased by means of the pressure caused by the air flow (B) against the mat 35. Method according to one of Claims 2, 3 or 4, characterized in that the fibrous air flow (A1) and the second air flow (A2) with a higher temperature are introduced into their own air ducts (3, 4) and the air flows are recirculated so that a part of the air flow (A) passing through the forming base (1) causing the carpet formation 5 is led to the air duct (3) of the separating air flow (A1) for preheating the air flow. Method according to one of Claims 3, 4 or 5, characterized in that part of the higher-temperature air flow (A2) passing through the air duct is led to the finishing of the mat, whereby it forms at least part of the air flow (B) through the mat. 15 Method according to one of the preceding claims, characterized in that the resulting mat is placed as thermal insulation (5c) in the building element (5) between its outer cladding (5a) and its inner cladding 20 (5e). Method according to Claim 7, characterized in that a gypsum board is placed as the inner cladding (5e). 25 . ' Apparatus for manufacturing a fibrous product having an air chamber (6) at the beginning of which an air channel (3, 4) enters and the end of which is closed by a movable forming base (1), the apparatus further comprising means (11, 2) for plant cellulose fibers and feeding the thermoplastic binder fibers to the air chamber (6) to form a mat by the air flow (A) introduced from the air duct (3, 4) onto the forming substrate (1) and means for heating the thermoplastic binder fibers 35 so that they bind to each other in the mat , characterized in that the apparatus comprises an air heater (7) from which an air duct (4) 94325 is led to the air chamber (6) for heating the binder fibers to a binding space already in the air chamber (6). Apparatus according to claim 9, comprising a feed roller (2) or the like at the beginning of the air chamber (6), characterized in that a first air duct (3) is directed to the beginning of the air chamber (6) towards the feed roller (2) or the like. to detach it, wherein the second air duct 10 consisting of the above-mentioned air duct (4) connected to the air heater is led to the air chamber (6) in the air flow direction to the point following the inlet (3a) of the first air duct (3). 15 Apparatus according to claim 9 or 10, characterized in that the air chamber (6) is followed in the direction of movement of the forming base (1) by a second air chamber (8) with a base supporting the mat, preferably formed by the same forming base (1) from 20 air chambers, and an air duct (9) is connected to the second air chamber (8) for conducting an air flow (B) through the mat. Apparatus according to claim 10 or 11. . to, characterized in that the first air duct (3) communicates in the air supply direction with the collecting chamber (10) on the opposite side of the forming base (1) from the air chamber (6). 30 Apparatus according to Claim 11 or 12, characterized in that the air duct (4) between the air heater (7) and the air chamber (6) branches into an air duct (9) connected to the second air chamber (8). 35 14 94325