Coating processes – Application to opposite sides of sheet – web – or strip
Reexamination Certificate
1999-11-23
2002-08-20
Beck, Shrive P. (Department: 1762)
Coating processes
Application to opposite sides of sheet, web, or strip
C427S348000, C427S422000, C427S424000, C118S314000, C118S320000, C118S322000
Reexamination Certificate
active
06436471
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a plant for coating a multi-sided mineral fibre base layer with a surface coating in the form of a fibrous non-woven fabric formed of a thermoplastic polymer material on at least part of at least two sides of the base layer to form a mineral fibre element, wherein the plant comprises two or more coating devices, means for melting a thermoplastic polymer material, means for supplying the polymer melt obtained to the coating devices, wherein each coating device comprises a number of dispensing units comprising a number of orifices, means for extruding the polymer melt obtained through the orifices and distributing the extruded polymer material on the surface of the mineral fibre base layer, and means for directing one or more high pressure gas streams closely past the orifices in order to elongate the extruded polymer material so as to form thin filaments and/or fibres.
WO 93/16874 discloses a process and an apparatus for applying a coating in the form of a fibrous netting of a thermoplastic polymer material onto the surface of a mineral fibre material. The apparatus used may be a so-called melt blowing die apparatus or a hot melt spray nozzle apparatus.
U.S. Pat. No. 5,501,872 discloses a process and an apparatus for coating a six-sided fibrous batt, the process comprising the steps of passing the batt sequentially through three coating stations, which each comprise two co-operating melt blowing dies disposed so as to coat pairs of opposite batt surface sides. The melt blowing dies are operated discontinuously so as to be shut off while the batt is positioned between coating stations. The melt blowing dies of one coating station are slightly spaced in such a manner that they are in simultaneously operation a part of the time.
The prior art disclosed in U.S. Pat. No. 5,501,872 suffers from the drawback that the two high pressure gas streams ejected from the melt blowing dies of one coating station have opposite directions and hence will interfere with each other creating circumstances of substantial turbulence in a zone surrounding the batt. Such turbulence has a strongly adverse effect on the formation of the surface coating both with respect to the adhesion between the coating and the base layer and with respect to the quality of the coating fabric formed. Thus, the turbulence results in a coating fabric, which has reduced uniformity with respect to fibre/filament diameter and orientation.
The object of the invention is to provide a plant of the type defined in the preamble of claim
1
, with which the above-discussed drawback may be avoided.
SUMMARY OF THE INVENTION
This object is achieved with the plant of the invention, which is characterized in that the coating devices are arranged in separate successive coating sections in such a manner that the coating of individual base layer sides are effected in separate steps.
The invention is based on the recognition that the technical problem of interfering gas streams may be solved by using coating sections designed to coat only one surface side of the base layer, since such a coating section will only generate one high pressure gas stream, and since such coating sections may be spaced in a manner sufficient to avoid any interfering of gas streams of adjacent coating devices.
Also, the plant of the invention presents a number of further advantages. Accordingly, a plant making use of coating sections designed to coat only one base layer side is much more flexible and suitable to be adapted to producing different products than the prior art plant. Thus, the sequence of the coating of the base layer sides to be coated may be selected completely freely and importantly, the plant of the invention has provided the possibility of arranging the horizontally orientated coating devices and the vertically orientated coating devices, respectively, on the same side of the base layer, and such an arrangement involves a number of additional advantages as explained in the following.
Firstly, the arranging of the horizontally orientated coating devices on the same side of the base layer makes control, monitoring and operation of the plant much more easy, since the operators of the plant need not cross the coating production line conveying the base layers in order to gain access to the coating devices, such crossing only being possible at a limited number of points along the production line, where a bridge or a passageway below an elevated section of the production line is provided. Moreover, when two coating production lines are disposed parallel to one another it is possible to provide a common zone between the two lines, from which both lines may be operated.
Secondly, the said arrangement of the coating devices reduces further the interference of the gas streams from adjacent coating devices, since the gas streams will have parallel flow directions.
Finally, providing the coating devices on the same side of the base layer makes it possible to make the plant completely independent of the dimensions of the mineral fibre element to be produced. In order to obtain a uniform coating having an acceptable adhesion to the base layer it is necessary to maintain the distance between the coating device and the base layer surface at a certain level. In the prior art plants, the position of the coating devices have to be adjusted, whenever the production is switched from one type of product to another, such an adjustment requiring a shut-down of the coating plant. This is very undesirable, since the plant for producing the mineral fibre base layer, which is placed up-stream of the coating plant, and which is operated continuously, cannot be shut down temporarily without substantial difficulties and costs.
This technical problem is solved by the present invention. Hence, by providing the horizontally orientated coating devices on the same side of the base layer and by turning the base layer between each coating device while keeping the base layer at one side of the supporting and conveying means, it is possible to make the plant independent of e.g. the width and length of a rectangular base layer. Likewise, by providing the vertically orientated coating devices below the base layer and by turning the base layer between the coating devices, it is possible to make the plant independent of the height of the base layer.
In the following a number of preferred embodiments of the plant of the invention is described.
A first preferred embodiment of the invention is characterized in that it comprises at least one horizontally orientated coating device placed on one side of the base layer and at least one horizontally orientated coating device placed on the opposite side of the base layer.
A second preferred embodiment of the invention is characterized in that it comprises at least two horizontally orientated coating devices placed on the same side of the base layer.
A third preferred embodiment of the invention is characterized in that it comprises four horizontally orientated coating devices and two vertically orientated coating devices. The latter two coating devices may be disposed below the base layer with an upward orientation. Alternatively, one vertically orientated coating device is disposed below the base layer with an upward orientation and the second is disposed above the base layer with a downward orientation.
In general, the coating devices are orientated in a direction perpendicular to the surface of the base layer to be coated.
A fourth preferred embodiment is characterized in that the coating sections are disposed in a straight-line relationship.
A fifth preferred embodiment of the invention is characterized in that the coating sections are disposed in such a manner that the movement direction of the base layer is changed, preferably by 90° one or more times.
A sixth preferred embodiment is characterized in that each coating section comprises means for supporting and conveying the base layer. The supporting and conveying means may have the form of any suitable transport means, such as rotat
Beck Shrive P.
Crockford Kirsten A.
Dickstein Shapiro Morin & Oshinsky LLP.
Rockwool International A/S
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