A METHOD TO PRODUCE A LAMINATED TEXTILE PRODUCT

Abstract

The present invention pertains to a method to produce a laminated textile product, the product comprising a primary carrier sheet with yarns that form a pile on the front surface thereof, and a secondary carrier sheet adhered to the back surface of the primary carrier sheet, the method comprising providing a lick roller having a mass of molten polymer adhesive at its outer circumference, transporting the primary carrier sheet along the lick roller while its back surface is in contact with the outer circumference of the roller at a contact site, thereby transferring a layer of adhesive to the back surface of the primary carrier sheet, and bringing the secondary sheet in contact with the layer of adhesive to adhere the secondary sheet to the back surface of the primary carrier sheet to produce the laminated textile product, wherein downstream of the contact site between the primary carrier sheet and the lick roller, before the secondary sheet is contacted with the layer of adhesive, cobwebbing of the adhesive between the primary carrier sheet and the lick roller is induced.

Claims

1. A method to produce a laminated textile product, the product comprising a primary carrier sheet with yarns that form a pile on the front surface thereof, and a secondary carrier sheet adhered to the back surface of the primary carrier sheet, the method comprising: providing a lick roller having a mass of molten polymer adhesive at its outer circumference, transporting the primary carrier sheet along the lick roller while its back surface is in contact with the outer circumference of the roller at a contact site, thereby transferring a layer of adhesive to the back surface of the primary carrier sheet, bringing the secondary sheet in contact with the layer of adhesive to adhere the secondary sheet to the back surface of the primary carrier sheet to produce the laminated textile product, wherein downstream of the contact site between the primary carrier sheet and the lick roller, before the secondary sheet is contacted with the layer of adhesive, cobwebbing of the adhesive between the primary carrier sheet and the lick roller is induced.

2. A method according to claim 1, wherein the primary carrier sheet is a fibrous sheet with yarns stitched therein to form the pile on the front surface and loops of yarns at the back surface of the primary carrier sheet.

3. A method according to claim 2, wherein the primary carrier sheet is heat treated to bond the yarns to the sheet by contacting the back surface of the primary carrier sheet with a surface of a hot body to at least partly melt the loops of the yarns to create a mass of molten yarn material at the back surface of the primary carrier sheet before the polymer adhesive is applied to this back surface.

4. A method according to claim 3, wherein the primary carrier sheet is heat treated by providing the surface of the hot body at a relative speed with respect to the back surface of the primary carrier sheet, in particular by providing the surface of the hot body as a stationary object, the primary carrier sheet being transported along the hot body.

5. A method according to claim 1, wherein adhesive is transferred to the back surface of the primary carrier sheet at an amount of between 100 and 600 g/m.sup.2.

6. A method according to claim 1, wherein the primary carrier sheet is provided as a continuous web, guided over a guiding roller directly preceding the lick roller, characterised in that the guiding roller is a bowed roller having its outer surface in contact with the pile.

7. A method according to claim 1, wherein the adhesive has a viscosity of less than 500 Pa.Math.s at 150 C.

8. A method according to claim 7, wherein the adhesive has a viscosity of between 1 and 100 Pa.Math.s at 150 C.

9. A method according to claim 8, wherein the adhesive has a viscosity of between 5 and 55 Pa.Math.s at 150 C.

10. A method according to claim 1, wherein the adhesive is semi-crystalline.

11. A method according to claim 10, wherein the adhesive has a crystallinity between 1 and 50%.

12. A method according to claim 11, wherein the adhesive has a crystallinity between 5 and 35%.

13. A method according to claim 1, wherein the temperature of the polymer adhesive at the contact site is between 120 C. and 160 C.

14. A method according to claim 1, wherein the transport speed of the primary carrier sheet with respect to the lick roller is at least 4 m/min.

15. A polyester adhesive having a crystallinity between 5% and 35% and a viscosity of 5-55 Pa.Math.s at 150 C.

Description

EXAMPLES

[0030] FIG. 1 schematically shows a cross section of a textile product manufactured according to the invention.

[0031] FIG. 2 schematically shows the principle of a coating process using a lick roller.

[0032] FIG. 3 schematically shows the phenomenon of cob-webbing in lick roller coating.

[0033] FIG. 4 schematically shows a laminating process incorporating cob-webbing.

[0034] Example 1 describes how to determine crystallinity of a polymer adhesive.

[0035] Example 2 describes how to determine viscosity of a polymer adhesive.

[0036] Example 3 describes an experiment assessing laminating strength in relation to induced cobwebbing.

[0037] FIG. 1

[0038] FIG. 1 is a schematic representation of respective layers of an embodiment of a laminated textile product 1 manufactured according to the invention, in this case a carpet tile. The tile comprises a primary carrier sheet 2, the so called primary backing, which is a tufted woven polyester backing. The polyester yarns 5 extend from the first surface 3 of this first sheet and are sealed to the second surface 4 of the sheet using the a yarn melting method as known from WO2014/198731. The weight of this primary sheet is typically about 400-700 g per m.sup.2 (including tufted yarns). In order to provide sufficient mechanical stability for use as an end product such as a carpet tile, the product 1 comprises a primary backing sheet 6, in this case a polyester needle felt backing. The weight of this second sheet is typically about 500-1000 g/m.sup.2. In between the first and second backing is an optional resilient layer 10 (which could for example be a polyester expansion fleece having a weight of 330 g/m.sup.2, obtainable from TWE, Emsdetten, Germany as Abstandsvliesstof). The three layers (first and second backing and intermediate layer) are laminated together using a polymer adhesive, which may be a polyester hot melt glue as obtainable from DSM Coating Resins, Zwolle, the Netherlands, applied as layers 11 and 12 at a weight of about 250 g/m.sup.2.

[0039] FIG. 2

[0040] FIG. 2 schematically shows the principle of a coating process using a lick roller (also referred to as kiss roll in the art) 601. In this embodiment the lick roll comprises a metal coated basic drum that that turns into a fluid polymer adhesive 110, by which a layer of adhesive is formed on the outer circumference of the metal drum. The adhesive is transported towards the substrate 2 to be coated with a thin layer 11 of the adhesive 110. The substrate, in this case the primary backing sheet as depicted in FIG. 1, is supplied via roller 404 and runs along the upper side of the turning roll 601 and contacts the roll at contacting site 401. This site is actually a line that runs along the length of the roll 601 (see FIG. 3). In the art, at the exit of the lick roll (i.e. slightly downstream of the contact site 410) a knife is installed that will scrape off the superfluous coating from the substrate. The speed with which the substrate is introduced, the speed of the lick roll, their mutual contact pressure and surface area, the viscosity of the compounds, and the positioning of the optional squeegee (the knife) determine the final coating weight. Typically this weight varies between 20 and 1200 g/m.sup.2. The roll may have a width up to about 4.20 meters such that common broadloom carpet can be made using this coating method.

[0041] FIG. 3

[0042] FIG. 3 schematically shows the phenomenon of cob-webbing in the lick roller coating process of FIG. 2. This front-side view shows the lick roller 601 in its length direction, in association with substrate 2. The contact site (line) 410 is indicated as well as thin layer 11 of the adhesive on the back of the substrate 2. Immediately downstream of the contact site 410 the phenomenon of cob-webbing is visualised, by schematically showing the row of fine strands 111 of adhesive that extend in a direction perpendicular to the longitudinal direction of the lick roller 601, between the layer 11 and the roll 601. This way, the strands form a row 112 over the length of the roller 601. At site 411 (which is a line that runs parallel to line 410) the strands are at their (average) maximum length and break. Partly they will adhere to the substrate 2 and form a texture of fine strands on the back of that substrate. Using a polymer adhesive as indicated here above in conjunction with FIG. 1, at a process speed of about 10 m/min, the strands typically have a thickness of about 20 m, a length at break of about 10-15 cm (the point of breakage is approximately at the middle of the threads).

[0043] FIG. 4

[0044] FIG. 4 schematically shows a laminating station 400 for use in the present invention. The basic parts of the station consist of laminating rollers 401 and 402. These rollers form a nip wherein two separate layers, both typically conveyed to the nip in the form of a web, are laminated together, in this case using a hot melt adhesive 12 (see FIG. 1). The primary carrier sheet 2 enters the laminating station 400 while being guided with its upper (pile) surface 3 over a bowed roller 303. The transport distance from this roller to the laminating nip, i.e. the length from the bowed roller to the laminating nip measured along the web 2, in this case is about 1.8 meters. Between the bowed roller 303 and the roller laminating 401 is an additional guide roller 405 positioned against the back of sheet 2. Right before entry of the laminating nip, the back side of the sheet 2 passes station 600, at which station the polymer adhesive 110 (in bulk) is metered via lick roller 601, in conjunction with roller 602, as a thin layer 11 to the back of sheet 2 at an amount of about 220 g/m.sup.2. The tension in web 2 is typically between 600 and 3000 N, in this embodiment about 1000 N. Also entering the laminating nip is secondary backing sheet 6 (see FIG. 1) which enters the nip by guidance over roller 406 (which roller is optionally a bowed roller). Both sheets pass the nip while being laminated to each other to form carpet product 1. This product is guided to a further process station (not shown) over bowed roller 303. The tension in web 6 is typically between 200 and 600 N, in this embodiment about 400 N.

Example 1

[0045] Example 1 describes how to determine the crystallinity of a polymer adhesive. The determination is based on ASTM standard D3418 (Standard Test Method for Transition Temperatures and Enthalpies of Fusion and Crystallization of Polymers by Differential Scanning calorimetry) using a Mettler STARe differential scanning calorimeter. For the actual measurement an adhesive sample of 10 mg is placed in a sample cup. This sample is kept in an oven for 15 minutes at 150 C. After this, the sample is cooled to 50 C. and then heated to 250 C. at a speed of 5 C./min. The sample is kept at 250 C. for 1 minute and thereafter directly cooled to 25 C. at a speed of 5 C./min. From the obtained DSC data the percentage of crystallinity in the sample polymer is calculated using the Mettler STARe SW 9.2 software.

[0046] For two polyester adhesives obtained via DSM Coating Resins, Zwolle, The Netherlands, which adhesives have excellent properties in order to obtain cobwebbing in the sense of the present invention, the crystallinity was determined this way. For the first polyester adhesive (denoted A), being a low molecular weight PET (Mw=18,704 g/mol) based on diethyleneglycol, butanediol, adipic acid and terephthalic acid, the crystallinity was 11%. For the other adhesive (denoted B), also a low molecular weight adhesive (Mw=25,541 g/mol), but being based on hexanediol and butanediol, next to adipic acid and terephthalic acid, the crystallinity was 15%.

[0047] In an alternative embodiment of the adhesive A, sebasic acid was used instead of adipic acid. This adhesive had a crystallinity of 14%. In another embodiment wherein as the alcohol component a mixture of ethanediol and hexanediol was reacted with terephthallic acid, the crystallinity arrived at was 26%. By varying the starting components and or relative amounts used, adequate adhesive could be obtained having a crystallinity between 5-35%, all having a low melt viscosity of about 5-55 Pa.Math.s at 150 C. (established using a method as described under example 2).

Example 2

[0048] The viscosity of a polymer adhesive is measured by using a cone and plate viscometer (Brookfield CAP 2000+, available from Brookfield Ametek, Middleboro, Mass., USA) with a 24 mm diameter spindle and a cone angle of 1.8 degrees (Brookfield Cap 2000+spindle #4). Samples are heated to 150 C. At 150 C. the spindle is lowered on the sample. The sample is measured at 21 rpm for 30 seconds. The viscosity is determined automatically by the viscometer's default algorithm. For the two adhesives (A and B) indicated here above under Example 1, the viscosities are 6.3 Pa.Math.s and 27.1 Pa.Math.s at 150 C. respectively. For the alternative adhesives mentioned in Example 1, viz. the adhesives having a crystallinity of 26% and 14%, the viscosity established this way was 28.2 Pa.Math.s and 24 Pa.Math.s respectively. These adhesives have an effective practical operating window for inducing cob-webbing.

Example 3

[0049] In this example an experiment assessing laminating strength in relation to induced cobwebbing is described. To assess the effect of cob-webbing on the lamination strength an experiment was conducted with one particular adhesive, but wherein the temperature of the adhesive at the lick roll was varied between 130 C., 140 C. and 150 C. and the process speed varied between 2 and 8 m/min. It was expected that in the experiments with the higher process speed, cob-webbing would be induced more easily. Indeed, at a process speed of 8 m/min, at each temperature cob-webbing was introduced. The lamination strength was tested manually and scored on a scale from 1 to 5. It was good at each temperature (4 or higher). There was clear cob-webbing in each case. At a process speed of 2 m/min, cob-webbing could not be noticed at a temperature of 150 C. (threads shorter than 1 cm). The laminating strength was scored with a 1, far too low for practical purposes. At a temperature of 140 C. cob-webbing was induced, and the laminating strength increased to 3. This is a reasonable score. At a temperature of 130 C. the cob-webbing phenomenon further increased showing as longer and thicker threads. The laminating strength however was still scored at 3.