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1. (WO2007007091) ADHESIVE FILTER TAPE AND METHOD FOR MAKING THE SAME
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Adhesive filter tape and method for making the same

The present invention relates to a process for making adhesive filter tape and to the tape per se, which is, in particular but not exclusively, for use with open-ended hollow wall or roof materials.

In general, adhesive filter tape is known to be applied along the end of an open ended wall or roof material to prevent dust, pollen, algae, fungal spores and insects etc. from entering whilst providing a breathable barrier to restrict formation of condensation within the wall or roof material. The wall or roof material usually consists of a series of long channels or flutes which are constructed of
polycarbonate forming a multi or single wall sheet.

An example of a prior art adhesive filter tape is shown in EP0920899A. Disclosed therein is a filter tape comprising a length of filter material with longitudinal side portions containing an adhesive material. The adhesive is applied to the tape by squeezing the longitudinal side portions of filter material to thereby force adhesive into the side portions. The tape is supplied in rolls with a releasable silicone treated backing sheet or release paper. The document describes another embodiment wherein double-sided adhesive tape is used.

The present invention provides a method of manufacturing adhesive filter tape comprising a release paper layer and a filter material layer peelable away from the release paper, and a method of manufacturing a roll of said adhesive filter tape, each method comprising the steps of applying adhesive to the release paper and bringing the filter material layer into contact with the release paper whereby the adhesive is situated between the release paper and the filter material. Ideally, the adhesive sticking to the filter material in preference to the release paper.

The method advantageously allows greater control of the adhesive application and less wastage of adhesive by virtue of the fact that the release paper does not absorb adhesive. Where adhesive is applied to the filter material itself, there is a tendency for the adhesive to soak into the material which can weaken it and lead to irregularities in the adhesive coating. Further, because the adhesive does not soak through the release paper, less adhesive is used in the method.

The adhesive is applied in molten form to the release paper, and for this purpose the adhesive may be heated. By applying hot adhesive to the release paper and not the filter material itself, potential damage to the filter material is avoided. Melting of the filter material generally leads to closing of its pores.

A further advantage arises in that once the adhesive has stuck to the filter material it cannot peel away as is the case with double-sided adhesive tape.

The present invention also provides an adhesive filter tape assembly comprising a release paper layer having one or more regions of adhesive thereon and a filter material layer wherein the filter tape comprises at least one adhesive coating transferred thereto from the release paper.

The present invention further provides a method of manufacturing adhesive filter tape comprising a filter material layer having a plurality of pores including the steps of coating at least part of a face of the filter material layer with a release agent without blocking all of the pores, and applying adhesive to the opposite face of the filter material layer.

The present invention also provides an adhesive filter tape assembly comprising a filter material layer having a plurality of pores, wherein the filter material layer has a coating of a release agent on a face and a coating of adhesive on the opposite face.

The invention also provides a method of manufacturing adhesive filter tape having a filter material comprising the step of printing on the filter material.

The invention provides furthermore a method of manufacturing adhesive filter tape comprising a filter material layer having a plurality of pores including the step of applying information on a face of the filter material.

The applying step may comprise printing on to the filter material. Also, print may be applied without blocking pores of the filter material. Furthermore, adhesive may be applied to a face of filter material opposite to the printed face.

Further, the present invention provides a filter tape assembly comprising a filter material layer having a plurality of pores wherein the filter material layer has information printed on a face, and a coating of adhesive on the opposite face.

There now follows by way of example a detailed description of an embodiment of the invention with reference to the accompanying schematic drawings in which:

Fig. 1 is a perspective view of a first filter tape according to the present invention;

Fig. 2 is a cross-sectional view (not to scale) of a prior art filter tape;
Fig. 3 is a perspective view of a portion of a hollow wall or roof sheet/tile with the filter tape of Fig. 1 applied thereto;
Fig. 4 is a plan view of a second filter tape according to the present invention;

Fig. 5 is a perspective view of a hollow roof sheet/tile;
Fig. 6 is a perspective view of a roll of release paper for use in the manufacture of the tapes of Figs. 1 and 4;
Fig. 7 is a plan view of a portion of release paper for use in the manufacture of the tapes of Figs. 1 and 4;
Fig. 8 is a schematic view of a production line for making filter tape according to the present invention;
Fig. 9 is a plan view of a third filter tape according to the present invention;
Fig. 10 is a schematic view of a second production line for making filter tape
according to the present invention; and
Fig. 11 is a cross-sectional view of a fourth filter tape according to the present invention.

- A -

Fig. 1 shows a filter tape assembly comprising a filter tape 2 and a release paper 3 shown partially peeled away from the filter tape material 2. The filter tape 2 is of a filter material 4 and comprises a line of adhesive 1 provided along each side edge of the filter material 4 which has been transferred to the filter material from the release paper 3. The adhesive 1 (e.g. a contact adhesive) can be applied as longitudinal strip as shown or, alternatively, in a non-continuous or continuous pattern along the edges of the filter material. The filter material comprises non-woven spun bonded polypropylene. However, it will be understood that other types of filter material may be used. The release paper 3 has a differential release coating. This means that at least one side of the release paper has a lower coefficient of friction than the filter material so that the adhesive tends to adhere to the filter material in preference to the said one side of the release paper. A low coefficient of friction may be achieved by means of a coating (e.g. a wax or silicon coating) provided on the release paper.

Fig. 2 shows a prior art filter tape 2' where the adhesive 1 ' has soaked through the entire thickness of the filter material 4'. A release paper 3' is provided, but only after the adhesive has been applied to the filter material.

Fig. 3 shows in perspective a hollow sheet for a wall or roof (or roof tile) comprising multi-walled polycarbonate sheeting with a filter tape 2 applied over an open end 7 thereof. The filter tape prevents entry of dust, pollen, algae, fungal spores, insects and the like from entering flutes 9 which extend inside the sheet or tile. It can be seen that the adhesive coated parts 1 fold over on to opposite sides of the sheet or tile, and hold a central portion 6 of the filter tape 2 (which central portion 6 is free of adhesive so as to be capable of performing a filtering function) over the end 7 of the sheet/tile. A sheet/tile is shown with its open end 7 uncovered in Fig. 5.
Fig. 4 shows a filter tape 2, wherein on the top side (i.e. the side opposite that to which the adhesive is applied) text and/or symbols such as arrows are printed to advise the user of any desired information. In particular, this is useful for pointing out a side of the tile which has been treated with a UV protection agent. Fig. 9 shows a specific example of this. When the sheets or tiles are used in
conservatory roofing for example, it is important that the sheets/tiles are orientated correctly, or deletorious effects due to UV rays of the sun such as tile
discolouration will occur. The tiles usually come with a removable protective liner which indicates the face of the tile which is coated with UV protection agent. However, once this liner has been removed it is easy to forget which side of the tile has been treated. The tape according to the present invention overcomes this problem whilst ensuring the pores do not get blocked. Other information may be printed on the tape, such as its year of manufacture, batch number, or trade marks for example.

Fig. 6 shows a roll of release paper 3 including lines of adhesive 9, 10, 11 on one side. The lines of adhesive 10, 11 along the edges of the paper 3 have a width equal to that of the adhesive strips 1 in the final filter tape 2 product and half of that of the central lines of adhesive 9.

One side of the release paper 3 has a lower coefficient of friction than the other. The adhesive is nevertheless releasable from both sides of the paper 3. This may be achieved through use of appropriate coatings on each side of the paper as will be apparent to a reader skilled in the art. By virtue of the differential release coatings, the adhesive preferentially sticks to one side of the release paper 3, so that when the release paper is rolled up on itself prior to application to the filter material, it can be unwound without the adhesive transferring to the opposite side of the release paper. The adhesive is provided on the paper 3 as an unsupported glue line rather than in the form of a double-sided adhesive tape. Subsequently, a sheet of filter material 2 is laminated onto the release paper 3. The glue lines preferentially stick to the filter material which is more readily gripped by the adhesive than either surface of the differentially coated release paper liner. The glue lines do not soak into the filter material, but attach to its surface.

Once the filter material and release paper have been pressed, touched or contacted together, with the adhesive located therebetween, the laminated sheets of filter material and release paper are cut into strips. As shown by Fig. 8, the sheet is cut along lines 8 which run along the middle of the adhesive lines 9. At the location of the two outer lines 10, 11 the sheet is not slitted because the lines 10, 11 are already of the correct width. Hence, no wastage of edge portions of the sheet occurs. After slitting, each resulting strip of tape is wound onto a roll to achieve the finished product.

Fig. 8 illustrates an additional process whereby the filter material itself is treated with a release coating/agent such as silicone on its top surface thus obviating the need for the release paper in the finished product. A master roll of filter material is located at (a). This is unwound and corona treated at (b) so as to enable an anchor for silicone which is then applied to the filter material by means of a cylindrical roller and doctor blade shown at (c). The material is then cured using UV light at (d) and rewound back into roll form at (e).

It is important that the silicone does not affect the filter material adversely e.g. by closing pores in the material. The filter material is formed with a pocked surface such that it has raised face parts 15 and recessed face parts 16 as shown in the schematic cross-sectional view (not to scale) of the filter material 4 in Fig. 11. The silicone 17 is applied to the filter material so that it only touches the raised face parts 15, allowing the recessed parts or pores 16 to filter in the normal manner. A similar arrangement is used with reference to Fig. 4, i.e. when ink is printed onto the filter material it is only applied to the raised face parts 15 to avoid clogging the pores 16.

Adhesive can then be applied to the filter material (on the side opposite to that provided with the release coating/agent) using the earlier described method. Thus, the filter material is laminated onto release paper which has been coated with adhesive as explained with reference to Fig. 6. The release paper is then removed either before or after the slitting process, and the final product without release paper is wound onto slit rolls. The adhesive may also be applied directly to the filter material without using release paper.

Advantageously, the lack of release paper makes the filter tape considerably easier to use. With traditional filter tape, the user not only has to align the filter material with the open end of the roof or wall sheet/tile, but then has to remove the release paper or liner whilst applying the filter material to the tile. This can be a very awkward and time consuming process. Alternatively, a whole length of filter tape could be removed from the roll and the release paper be peeled away in its entirety before applying the filter material to the tile. This method can also be difficult and may lead to misalignment of the filter material relative to the sheet/tile if the user is not very careful. Without the release paper layer, the user can simply roll the filter material directly from the roll onto the sheet/tile without having to peel away any release paper. A further advantage is that less waste is produced on site during use of the filter tape. Also, release paper is a low-friction product which has been known to cause accidents due to slipping if left on the floor. Further, if the release paper is not used during manufacture of the filter tape, to apply the adhesive to the filter material, less material waste occurs during the manufacturing process.

Fig. 10 shows schematically a production line for making filter tape which does include the release paper in the finished product. A master roll of release paper 18 and a master roll of filter tape 19 dispense their respective products which are laminated together at a laminating roll 20. The laminated sheets 21 are then slit by slitting means 22 (such as blades) into strips of the finished product, which are wound onto rolls 23 of generally the same width as the strips.

AIl of the embodiments described herein are combinable with one another. For example, it is possible to make a filter tape assembly which has a release agent coating on its top face and adhesive on its bottom face, wherein the adhesive is applied to the filter material using a release liner and information is printed on the top face of the filter material.

The present invention is not limited to the specific embodiments described above. Alternative arrangements and suitable materials will be apparent to a reader skilled in the art.