WO2005011951A1

WO2005011951A1 - Process and apparatus for manufacturing insulating panels, with sprayed expansible resins

Info

Publication number: WO2005011951A1
Application number: PCT/IT2003/000491
Authority: WO
Inventors: Maurizio Morandi
Original assignee: Metecno S.P.A.
Priority date: 2003-08-01
Filing date: 2003-08-01
Publication date: 2005-02-10
Also published as: EP1651416A2; AU2003274717A8; WO2005011950A3; AU2003253303A1; AU2003274717A1; WO2005011950A2; CN1839025A

Abstract

A novel method for the production of insulating panels (20) is described, wherein, a quick-reaction, expandable polyurethane resin (13) is sprayed onto a strip (4), after the sprayed resin (13) has expanded, further resin (17) is applied normally in the liquid condition, thus forming the insulating core of the panels. The invention also relates to the apparatus with which the method is implemented.

Description

Title "Method and apparatus for the production of insulating panels with spray application of expandable resins" Description

The invention relates in general to the production of composite insulating panels. As is .known, these panels, which are also commonly known as "sandwich" panels, are widely used in the civil and industrial construction field to form walls, roofs, coverings, slabs, sectional doors, etc.; they are also used to construct cold-storage rooms, or containers intended for low temperatures.

The panels considered herein comprise basically two opposed faces between which there is a core of insulating foam constituted by expanded resin, also commonly known as foam; the foam is generally polyurethane foam but may also be phenolic foam or foam of another type.

The continuous production of these panels is performed starting with two sheet- metal strips which are advanced through the apparatus one above the other. After an initial step of profiling of the strips, the resin is applied to the lower strip and then expands whilst the strips pass through a continuos double-strip press which keeps them apart by a distance equal to the thickness of the finished panel. This continuous production method has been known for some time and, for further information on the subject, reference should be made to existing publications and to the many patents of which the applicant of the present application is the proprietor.

However, it should be pointed out that, in order to produce quality panels, it is important that the expansion of the polymer resin should take place evenly; for this purpose, one of the conditions to be complied with is that there should be no bubbles of air or other gases in the vicinity of their outer faces because these may cause problems.

One of these problems is delamination of the panels, that is, detachment of their faces.

In fact, as the temperature conditions vary between day and night or between summer and winter, the gas contained in the bubbles expands cyclically, leading to progressive fatigue of the foam and the propagation of the void regions inside it; in the long term, this situation leads to detachment of the face of the panel. For this reason, a method for the continuous production of panels in which the liquid resin poured from a nozzle bar is spread uniformly on the surface of the strip by air jets is known from German patent application No. 197 41 523. The effect of these air jets is to eliminate the gas bubbles from the mass of liquid resin, thus producing the desired result.

However, this method of application of the resin does not seem to be easy to implement because the impact of the air on the resin camiot be uniform over the entire width of the strip; the device described in the German patent application in fact has suitable devices for limiting the edge effects, that is to say, the accumulations of resin which form along the edges of the strip because of the non- uniformity of the effect of the air in this region.

Moreover, this known application method appears to depend significantly on the viscosity of the resin since the effect of the air thereon will clearly be different according to how liquid the resin is.

In other words, the known method may be difficult to implement according to the type of panels to be produced; thus, for example, it is not stated that it is effective in the same manner both for the production of panels with polyurethane resins and for the production of panels with phenolic resins.

The same applies if the speed of advance of the sheet-metal strip to which the resin is applied is increased in order to increase panel production or if the quantity of resin applied is increased because it is desired to make thicker panels. In the light of these remarks, the problem underlying the present invention is therefore that of providing a method for the continuous production of insulating panels in which the polymer resin is applied uniformly to at least one of the strips in a manner such as to prevent the formation of bubbles in the vicinity of the strips, also achieving improved adhesion between the foam and the surface of the strip. The concept for the solution of this problem consists in the spray application of a first layer of resin onto the surface of the strip; the surface is in fact thus covered uniformly without lack of homogeneity which might give rise to bubbles. Once the spray-applied layer has expanded, a second layer of liquid resin can be poured thereon, thus producing an insulating core of the desired thiclαiess and density.

These and further characteristics of the invention are set out in the appended claims; they will become clearer from the following description of a non-limiting embodiment of the invention which is illustrated in the appended drawings, in which:

Figure 1 shows schematically apparatus for the continuous production of panels according to the invention,

Figure 2 -shows a detail of the apparatus of Figure 1, Figure 3 is a section taken on the line IH-IH of Figure 1,

Figure 4 is a perspective view of a panel formed in accordance with the invention, and

Figures 5 and 6 show a variant of the above-mentioned apparatus in views similar to those of Figures 2 and 3, respectively.

The first of these drawings shows apparatus, generally indicated 1, which produces panels according to the invention continuously, starting with two spools 2, 3 of metal strips 4 and 5.

In the apparatus 1, after the strips have been unrolled, they are processed by respective forming machines 6 and 7 to form therein the usual edges, ribs, profiling, etc., in known manner.

Downstream of the forming machines, the strips 4 and 5 advance close together as far as the zone for the application of expandable resin; this operation is performed in two steps.

In particular, the first step is constituted by the spray application of a quick- reaction resin by a head 9; for this purpose, the head 9 moves to and fro (as indicated by the arrows in Figure 3) along a cross-member 10 arranged above the strip 4 and is provided with a spray nozzle of a type known per se and not shown in the drawings. The speed of advance of the lower strip 4 is established in a manner such that the resin sprayed thereon expands (at least partially), forming a layer 13 which covers the strip 4 uniformly, before reaching a position below a second cross-member 11.

A pouring nozzle 12 of known type (which may be a single nozzle or a comb nozzle such as that of German application No. 197 41 523) is movable to and fro along the second cross-member 11 and performs the second resin-application step by pouring onto the expanded layer 13 a resin of the same type as that sprayed previously but in the liquid condition (the vertical broken line in Figure 3 indicates the pouring line).

The liquid resin then expands, filling the space between the strips 4 and 5 whilst they pass through a continuous press 14 which is also known per se.

Downstream of the continuous press, a semi-finished product 16 formed by the two strips 4 and 5 with the expanded sprayed layer 13 and an insulating core 17 of foam of the second resin is thus obtained; the semi-finished product is then cut by a cutter 18, thus forming finished panels 20 such as that of Figure 4.

The production process described above solves the problem underlying the invention.

In fact, the spray application distributes the resin uniformly over the entire surface of the strip 4 so that the resulting layer 13 is free of internal voids or bubbles.

This is due to the atomization of the resin supplied by the spray system, which enables the surface of the strip 4 to be covered with a thin film of small droplets which is similar to that of paints applied by the same method and in which gas bubbles cannot therefore form on to the strip.

In order to achieve good spray application of the resin it will suffice to select the speed of movement of the head 9 along the cross-member 10 appropriately in dependence on various parameters such as, for example, the width of the strip, its speed of advance, the type of spray nozzle mounted on the head 9, the supply pressure of the nozzle, its distance from the strip, the type of resin applied, etc.

Moreover, since the resin is of the quick-reaction type, it produces a film 13 of foam on which the liquid resin can subsequently be applied in known manner; the interface between the two resins advantageously reduces the presence and/or the size of any voids in the mass of the second resin when it expands.

In contrast with the prior art referred to above, this production method is reliable and easy to implement and does not require complex adaptive modifications each time the resin, the speed of the strip 4, or other production parameters are changed.

In fact, practically all polymer resins (polyurethane resins or the like), that is, both one-part and two-part resins, can be applied by the spray technique; this technique is well known and has been used for some time in the panel-production field and changes in the type of resin do not therefore alter the efficacy of the production process of the invention.

Similarly, if the speed of advance of the strip is changed (for example, to increase panel production) it will suffice to move the spray head 9 with the cross-member

10 upstream slightly so as to allow the quick-reaction resin to expand before it reaches the second nozzle bar 11.

Finally, as a further advantageous result achieved by the invention, it should be pointed out that it prevents the poor or inadequate adhesion of the foam to the face of the panel which sometimes occurs when liquid resin is deposited on the strip.

Naturally, variants of the above-described embodiment of the invention are possible.

In the first place, it should be pointed out that the type and shape of the panels may differ from that shown in Figure 4; thus, there may be panels that are profiled on one or both faces, or even curved panels produced by continuous dies and methods developed by the applicant of the present application.

Moreover, the production process may include heating steps implemented by ovens or lamps disposed along the path of the strips 4 and 5, as is already known for^'the production of panels; for example, an oven or lamps may be arranged upstream of the resin-application zone, that is, upstream of the spray head 9 on the cross-member 10, in order to accelerate the expansion of the resin sprayed onto the lower strip 4. With regard to the spraying of the resin, in addition to the nozzles described above, it should be pointed out that there may be various solutions in relation to the type and shape of the nozzles; the nozzles will be those that are most suitable for the operative conditions existing at the time in question, such as the size and shape of the panel (profiled, corrugated, flat, curved, etc.) the type of apparatus

(continuous, discontinuous) by which it is produced, the resins used as insulation, etc.

A possible alternative to the spray head 9 movable along the cross-member 10 of the previous embodiment is shown in Figures 5 and 6 in which, for simplicity, the same numbering has been retained for similar elements.

As can be seen, in this embodiment, instead of the head 9, there is a fixed nozzle bar 30 in which a plurality of nozzles spray the resin onto the strip 4 with jets which cover its surface uniformly.

Similarly, with regard to the application of the liquid resin, instead of the pouring nozzle 12 movable along the cross-member 11, in this variant, a fixed bar 31 of pouring nozzles has been used (the vertical broken lines indicate the pouring lines).

Finally, it should be pointed out that the spraying of the resin may also be performed on the upper strip, as an alternative to or in combination with the spraying of the lower strip; there may consequently be methods and apparatus for the production of panels in accordance with the invention in which the spraying is performed on only one of the strips (that is, only the upper strip or the lower strip) or on both strips.

These and other equivalent variants nevertheless fall within the scope of the appended claims.

Claims

1. Method for the continuous production of insulating panels, comprising the steps of:

- advancing an upper strip (5) and a lower strip (4) longitudinally in a substantially supferimposed condition,

- applying a substantially liquid expandable polymer resin to one of the strips (4, 5), and causing the resin to expand whilst the strips (4, 5) are kept apart by a predetermined distance substantially equal to the thickness of the panels to be produced, characterized in that it comprises a step of spraying of a quick-reaction, expandable polymer resin onto at least one of the strips (4, 5).

2. Method according to Claim 1, in which the substantially liquid resin is applied to a layer (13) formed by the sprayed and at least partially expanded quick- reaction resin.

3. Method according to Claims 1 and 2 in which the strip onto which the quick- reaction, expandable resin is sprayed is the lower strip (4).

4. Method according to the preceding claims in which the strips (4, 5) are made of metal.

5. Method according to the preceding claims in which the resins applied are one- part or two-part polyurethane resins.

6. Apparatus for the production of panels according to the method of the preceding claims, characterized in that it comprises means (9, 10; 30) for spraying a first expandable polymer resin and means (11, 12; 31) for applying a second, substantially liquid, expandable polymer resin onto at least one of the strips (4).

7. Apparatus according to Claim 6 in which the means (9, 10; 30) for spraying the first resin are arranged upstream of the means (11, 12; 31) for applying the second, substantially liquid resin.

8. Apparatus according to Claims 6 and 7, in which the means for spraying the first resin comprise a spray head (9) movable to and fro transversely relative to the direction of advance of the strip (4) onto Which the resin is sprayed.

9. An insulating panel produced by the method of Claims 1 to 5, characterized in that it comprises two opposed faces (4, 5), a layer (13) of expanded polymer resin applied to one of the faces by spraying, and an insulating core (17) of expanded polymer resin disposed between the layer (13) and the other face of the panel.