Patent Application
20180002863
The present invention pertains to a method to manufacture a textile product comprising a first sheet having polyester yarns fastened to this sheet to form a pile thereon, the method comprising providing the sheet, stitching the polyester yarns through the sheet to form the pile on a first surface of the sheet and loops of the yarns at a second surface of the sheet (the second surface being opposite to the first surface), and contacting the second surface of the sheet with a surface of a hot body to at least partly melt the loops of the yarns to fasten the yarns to the sheet. The invention also pertains to a method to use a textile product obtained with the new method and a device for applying the said method.
EP1598476 (Klieverik Heli) describes a method for manufacturing a textile product as indicated supra. In particular, the first sheet serves as a primary backing, which after the yarns have been fastened thereto, can act as an intermediate for making a carpet or other textile product, in which method the backing does not use a latex to anchor the yarns in place. The backing comprises a sheet with piles of thermoplastic yarns (also called fibres) stitched through the thickness of the sheet and protruding from its upper surface. At the lower surface the yarns form loops to provide for an intermediate anchoring of the yarns to the sheet (the yarns can still be removed easily by applying only a light pulling force by hand). The backing is then fed (yarn upwards) along a heated roller surface and its underside is pressed against the roller so the yarns will melt. Klieverik states that after cooling the yarns are firmly anchored to each other and the backing without the need for a latex polymer. One embodiment teaches that a thermoplastic adhesive (such as hot melt adhesive) may be applied additionally as a powder to the underside of the backing so the heated surface melts the yarns and adhesive together to create a good adhesion between the piles, the adhesive and the backing. In another embodiment pressure may be applied after heating (e.g. by a pressure roller) to the backing and piles in a direction perpendicular to the backing surface (i.e. from below) to smear the plasticised yarns together to enhance their mutual adhesion, thus allowing the heated roller to be held at a lower temperature, below that at which the yarns would fuse by heat alone. This method provides the advantage that the intermediate backing can be easily recycled since the yarns and backing sheet can be made from the same polymer. There is no incompatible latex penetrated into the fibre piles. There is also saving in energy and raw material costs compared to prior art methods.
WO 2012/076348 (Niaga) describes a method for manufacturing textile products that even improves the anchor strength of the yarn. In this method when the first yarn bearing sheet is pressed against the heated surface, the relative speed of the sheet and surface are adjusted to provide an additional mechanical force between them in the machine direction (i.e. the direction of transport of the sheet) which spreads the material of the yarn whilst it is still molten resulting in a stronger bond between the first sheet and the yarn. Though in theory in many cases an additional secondary support layer may no longer be necessary, this document does teach that such a support layer may still be useful, especially if it comprises a reactive adhesive relying on thermally reversible reactions between reactive molecules present at the interface between the textile product and the carrier material.
A research disclosure (RD591084) was also published anonymously on 25 Jun. 2013 describing certain methods for manufacturing carpets using a method as described here above in combination with polyester hot melt glues. WO 2014/198731 describes methods corresponding to the methods as known from this Research Disclosure.
WO 00/61853 describes a method for manufacturing a textile product wherein a heated body is brought in contact with the back surface of a primary backing provided with polyester yarns, and thereafter cool down the surface. It is not described that in the heating step, the polyesters yarns are melted. Next to this, the apparatus as described in WO 00/61853 applies a coating layer before the back surface is cooled down.
In many cases, a textile product as known from the art described here above will be glued to either a second sheet (as secondary backing, for example when manufacturing carpet tiles), or glued to a surface to be covered, such as a floor, the interior of a car, the interior of a boat or plane etc. It was found now that when polyester yarns are used, the gluing durability, all things being equal (same glue, same amount of glue per square meter etc.) is less then when for example polyamide yarns are used. Since polyester yarns are generally high in strength, have a high modulus, low shrinkage, great heat set stability, high light fastness and chemical resistance, and are relatively low price, they are used a lot in textile products. Therefore, adequate gluing properties are of the utmost importance.
It is an object of the invention to provide an improved method to manufacture a textile product, which method results in adequate gluing properties when polyester yarns are used.
In order to meet the object of the invention a method to manufacture a textile product as defined in the GENERAL FIELD OF THE INVENTION section has been devised, wherein the second surface is cooled, preferably actively cooled, to force the temperature to be below the glass transition temperature of the polyester yarns (i.e. the glass transition temperature of the polyester material constituting the yarns), preferably within 60 seconds after the contacting of the second surface with the hot body, or even within 59, 58, 57, 56, 55, 54, 53, 52, 51, 50, 49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33, 32, or 31 seconds.
Surprisingly, it was found that forced cooling of the second surface, such that its temperature is forced to drop below the glass transition temperature of the polyester yarns (i.e. below the glass transition of the polyester material used for constituting the yarns), a gluing property can be obtained which is the same as when using polyamide yarns. The reason for this is not 100% clear, but without being bound to theory, it is believed that the molten polyester, as long as this is above its glass transition temperature can rearrange to a structure that is less favourable for gluing the ultimate layer to a further sheet or other surface (for example from a relatively flat homogenous state, which is very advantageous for gluing, to a more discontinuous and/or bumpy state which is less advantageous for gluing). By cooling the second surface below the glass transition temperature of the polyester yarns, the state wherein the molten yarns are forced, i.a. due to the contact with the hot body, can be durably fixated. This way, it appears that gluing properties can be obtained comparable with those of a textile product wherein polyamide yarns are used. Without active cooling, the temperature of the second surface may not cool fast enough to prevent rearrangement of the molten polyester, and therefore active cooling is preferred Typically, when relying only on non-active cooling (thus, no cooling medium is forced to be contacted with the object to be cooled and one relies solely on radiation), depending on the circumstances, it may take more than 15 minutes before the temperature of the second surface drops below the glass transition temperature of the polyester. With active cooling, this temperature drop can be arrived at faster, for example within 5 minutes, 4 minutes, 3 minutes, 2 minutes or even, as indicated here above, within 60 seconds.
The invention also pertains to the use of a textile product obtainable in line with the above described method to cover a surface of a building or any other artificial or natural construction.
The invention also pertains to a device for use in manufacturing a textile product comprising a first sheet having polyester yarns fastened to this sheet to form a pile thereon, the yarns being stitched through the sheet to form the pile on a first surface of the sheet and loops of the yarns at a second surface of the sheet, the device comprising a hot body that can be heated to above a melting temperature of the polyester yarns, means for contacting the second surface of the sheet with the hot body, transport means for transporting the sheet along the hot body while the second surface is in contact therewith, and cooling means, preferably active cooling means, for cooling the second surface to a temperature below the glass transition temperature of the polyester yarns within 60 seconds after the second surface is in contact with the hot body (which typically equals a distance of at maximum 10 meters between the, preferably active, cooling means and the position where the hot body contacts the second surface, assuming a typical process speed of 10 m/min), and downstream of the cooling means, a means for applying a layer of adhesive to the second surface.
A textile product is a product that comprises textile (i.e. material made mainly of natural or artificial fibres, often referred to as thread or yarn), optionally with other components such as backing layers, carrier layers and/or adhesives. Laminated textile products typically comprise an upper layer of pile attached to a backing (where the raised pile fibres are also denoted as the “nap” of the product), but may also be flat weave. Such products can be of various different constructions such as woven, needle felt, knotted, tufted and/or embroidered, though tufted products are the most common type. The pile may be cut (as in a plush carpet) or form loops (as in a Berber carpet).
A polyester yarn is a yarn in which the yarn forming substance is any long chain synthetic polymer composed at least 85% by weight of an ester of a dihydric alcohol (HOROH) and a di-acid, for example terephthalic acid. The most widely used polyester yarn is made from the linear polymer polyethylene terephtalate, and this polyester class is generally referred to simply as PET. Typically, the polyesters used for yarns have a melting point (Tm) of about 250 to 280° C. and a glass transition temperature (Tg) of about 150 to about 180° C.
A loop of a yarn is a length of this yarn that is curved away from the basic part of the yarn (not excluding that the loop is longer than the main part itself). For a textile product, the basic part of the yarn is the part that forms the upper, visible part of the product. For example, for a carpet this is the part of the yarns that forms the pile. For clothing, this is the part of the yarn that forms part of the outer surface of the clothing.
The glass transition temperature is the temperature at which an amorphous solid becomes soft upon heating or brittle upon cooling. The Tg is the temperature region where the polymer (when heated) transitions from a hard, glassy material to a soft, rubbery material. The glass transition temperature is always lower than the melting temperature (Tm) of the crystalline state of the material. The Tg can be established by using Differential Scanning calorimetry (DSC) at speed of 20K/min as commonly known in the art, typically by defining the midpoint of the said temperature region as Tg.
A sheet is a substantially two dimensional mass or material, i.e. a broad and thin, typically, but not necessarily, rectangular in form, and inherently has two opposite surfaces.
Stitching is a method of mechanically making a yarn part of an object by stitches or as if with stitches, such as by tufting, knitting, sewing, weaving etc.
Active cooling is forced cooling by using forced convection of a cooling medium, or forced conduction of heat to such a cooling medium, which medium can be a gas, liquid or solid. Simple cooling down in essentially stationary air, thus relying solely on heat radiation, is not a form of active cooling. For active cooling, cooling air, cooling liquid or another cooling medium is forced to contact the object to be cooled, for example by blowing cooling air along the object or contacting the object with a cooling element.
A laminate is a structure comprising multiple stacked layers mechanically connected to each other.
Resilient means to be able to deform and automatically return to the original configuration.
A hot melt adhesive is a thermoplastic adhesive that is designed to be melted, i.e. heated to transform from a solid state into a liquid state to adhere materials after solidification. Hot melt adhesives are typically non-reactive, crystalline and comprise low or no amount of solvents so curing and drying are typically not necessary in order to provide adequate adhesion.
Fibrous means consisting basically out of fibres. “Basically” means that the basic mechanical constitution is arranged out of fibres: the fibres may however be impregnated or otherwise treated or combined with a non-fibrous material such that the end material also comprises other constituents than fibres. Typical fibrous sheets are woven and non-woven textile products, or combinations thereof.
In a first embodiment of the invention the second surface is cooled, preferably actively cooled, to force the temperature to be below the glass transition temperature of the polyester yarns within 30 seconds after the contacting of the second surface with the hot body, or even within 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6,5, 4, 3 or 2 seconds or even within 1 second.
In another embodiment the surface is actively cooled by contacting the second surface with a cold body, i.e. a body having a temperature below the glass transition temperature of the polyester yarns. It appears that by actually contacting the second surface with a cold body, a surface can be obtained which is very smooth, most probably due to an extra mechanical pressing of the molten fraction of the yarns to become a more flat and/or more homogenous layer. This further improves gluing properties of the second surface, such as for example the amount of glue needed to obtain a strong and durable bond (which is typically less for a smooth surface when compared to a rough surface).
In a further embodiment the cold body is a stationary beam having a contacting surface that runs in essence parallel to the second surface. A stationary body appears to give a good cooling and smearing result and is relatively easy to maintain. In still a further embodiment the cold body is maintained at a temperature below the glass transition temperature of the polyester yarns by actively cooling the body using convection and/or conduction. In particular at high process speeds, the cold body needs active cooling to remain at a temperature below the glass transition temperature of the polyester yarns. Such cooling can be provided for example by using a cooling liquid that is forced to flow through the cold body, or by using cooling fins through which cold air is blown etc.
In another embodiment the surface of the hot body has a relative speed (and thus moves at a relative speed greater than 0 m/s) with respect to the second surface of the first sheet. As such, the use of a hot body that has a relative speed with respect to the second surface during the melting process of the yarns is known from WO 2012/076348. It now appears that this feature is ideally suitable for use in a method wherein the yarns are polyesters yarns, and the molten fraction is actively cooled in accordance with the present invention. This combination of features leads to a durable textile product having excellent gluing properties. In a further embodiment the surface of the hot body is stationary, whereas the first sheet is transported along the hot body.
In an embodiment wherein the textile product is a laminate of the first sheet and a second sheet, after the second surface of the first sheet has been processed according to any of the embodiments as described supra, an adhesive is applied to this second surface to which adhesive the second sheet is adhered. In a further embodiment the adhesive is a hot melt adhesive, for example a hot melt adhesive that comprises at least 50% by weight of a polymer chosen from the group consisting of polyurethane, polycarbonate, polyester, polyamide, poly(ester-amide), polyolefine, mixtures thereof and/or copolymers thereof.
In a further embodiment of the laminated textile product, an intermediate layer is provided between the first sheet and the second sheet wherein the intermediate layer is resilient to allow local deformation of this layer along the second surface of the first sheet or along the surface of the second sheet adjacent to the intermediate layer. This embodiment appears to be suitable to prevent or at least mitigate a common problem of laminated textile products: internal strain in the laminate, in particular due to the influence of moist, temperature or other environmental variables. Internal strain on its turn may lead to various problems. With carpet tiles for example, internal strain may lead to the problem of curl: the edges or corners of the tiles tend to curl up. Curling of edges or corners is a problem since the edges in general to not coincide with an edge of the surface to be covered, and thus, the curled up edges or corners may lead to irregularities in center areas of the covered surface. With broadloom carpet, internal strain may lead to deformation such that interstices are formed at the joint of two sections of carpet. Also, for any laminated textile product, internal strain may lead to bulges and local excessive wear. An important reason for the occurrence of internal strain is that the laminate inherently comprises different layers (note: the term “layer” or “sheet” does not exclude that the layer or sheet is actually constituted out different sub-layers) that need to provide very different properties to the textile product (from now on also called “carpet”, not excluding other types of textile products such as upholstery, clothing and wall coverings): the first sheet, also called primary backing, needs to stably bear the pile yarns. The second sheet, also called secondary backing, in general provides dimensional stability to the textile product. For this reason, the structure of the different layers is inherently different. And thus, even when for example the first and second sheet are made of the same material, the occurrence of internal strain due to different deformations by the action of moist and temperature, is inherently present. The problem is even increased when different materials are being used for constituting the sheets, in particular when these materials per se expand and contract differently due to moist and or temperature. For example, typical polymers used for making carpet are polyamide, polyester and polyalkylene. These polymers have totally different deformation characteristics due to moist and temperature. It has now been surprisingly found that this problem can be solved or at least mitigated when using a resilient layer as described here above in between the first and second sheet. Without being bound to theory, it is believed that due to the resilient properties as defined here above, it is provided that each of the sheets may expand or contract (“deform”) in the horizontal direction independently of an expansion or contraction of the other sheet, and thus, that no (or only low) internal strain (which may lead to curl or other deformation) may arise. This can be understood as follows: due to the resiliency of the intermediate layer which allows local deformation of the material in this layer along the surface of at least one sheet, the horizontal deformation of (one of) the sheet(s) may now be locally absorbed by the intermediate layer, without mechanical forces being transferred directly from the first sheet to the second sheet or vice versa.
In a further embodiment the intermediate layer is a knitted layer. A knitted layer, although the fibres are in essence endless, appears to be perfectly suitable to allow only local deformation. Like a tubular knitted sock that fits every curve of a foot, a knitted layer can easily deform locally without transferring forces to neighboring areas. A knitted layer for use in the present invention is for example Caliweb®, obtainable from TWE, Emsdetten, Germany.
In another embodiment each of the first sheet, the second sheet, the adhesive and, if present, the resilient layer, are made of polyester. This embodiment has the advantage that the textile product is a mono-material product which makes recycling much easier.
The invention will now be further explained based on the following figures and examples.
Example 1 provides process parameters for a method according to the invention
Example 2 is an example of a specific laminated textile product according to the invention
The (intermediate) textile product to be processed with the above described configuration (the product itself is not shown in
Downstream of the heating blocks, at both sides of the transport path 200 of the intermediate textile product to be processed, is an active cooling means 300. In this embodiment, the means 300 comprise inverted domes 301 and 302. Through these domes, cold cooling air can be blown towards the textile product, in order to actively cool the heated surface of the textile product. Although depending on the glass transition temperature of the polyester one dome may be sufficient, in this embodiment, in order to cool the heated surface fast enough, preferably within 60 seconds after the textile product has been fully heated with heating body 505, two domes are used.
The hot melt adhesive may be optionally provided as a layer having a thickness of less than 1 mm, usefully less than 0.5 mm, more usefully from 0.2 to 0.4 mm. Whereas in the prior art carpets on the market, the hot melt layer typically has a thickness well above 1 mm, applicant found that when reducing the thickness of this layer to 1 mm or below an adequate adhesion can still be obtained. Therefore the adhesive layer present in textile products of the present invention may have preferred mean thickness of from 50 microns to 1 mm, more preferably from 0.1 mm to 0.8 mm, most preferably from 0.2 mm to 0.4 mm. The amount of HMA used to form the adhesive layer in textile products of the present invention may be from 0.01 to 1000 g/m2 of HMA per area of the adhesive layer. In another embodiment the HMA may be applied in an amount of from 0.05 to 800 g/m2. In a still yet other embodiment HMA may be applied in an amount from 0.1 to 600 g/m2.
Example 1 provides process parameters for a method according to the invention. In this example, the process parameters for a set up as depicted in
Example 2 is an example of a specific laminated textile product according to the invention. Reference numbers refer to parts corresponding to the textile product as shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 15150689.6 | Jan 2015 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/050224 | 1/7/2016 | WO | 00 |
