WO2011046433A1

WO2011046433A1 - Recyclable carpet and method for manufacturing and recycling thereof

Info

Publication number: WO2011046433A1
Application number: PCT/NL2010/050673
Authority: WO
Inventors: Ludwig Maria Gerardus Irma Cammaert; Wilhelmus Hendricus Maria Stas; Antonius Johannes Maria Timmermans
Original assignee: Desso B.V.
Priority date: 2009-10-12
Filing date: 2010-10-12
Publication date: 2011-04-21
Also published as: NL2003629C2; EP2488072A1

Abstract

The invention relates to a method for manufacturing a carpet which is recyclable (into carpet), comprising of tufting loop-piles onto a tuft substrate, applying a primary coating - to the tuft substrate in order to fix the loop-piles, and applying a secondary coating- to the primary coating, wherein both the primary and the secondary coating comprise a polyolefin. The invention also relates to a thus obtained carpet, a method for recycling thereof and a device for manufacturing or recycling such a carpet.

Description

Recyclable carpet and method for manufacturing and recycling thereof

The present invention relates to a recyclable carpet and to a method and device for manufacturing and recycling thereof. The invention has for its particular object to provide a carpet which can be recycled into carpet, this in its entirety, according to the "cradle to cradle" concept. It is the intention here to reuse the greatest possible part of the materials in order to make the same type of product.

Applying reusable materials in the manufacture of carpet is per se known. Replacing conventional with reusable materials in several or even all components of a carpet has however been found heretofore to be complex, since the per se known reusable materials do not readily allow of being processed together. It is therefore an object of the present invention to realize a carpet which at least to an increased extent meets the "cradle to cradle" objectives.

The invention provides for this purpose a method for manufacturing a carpet which is recyclable (into carpet), comprising the steps of tufting onto a tuft substrate loop-piles which can be finished as loops or as cut pile, applying a primary coating (= backing)- to the tuft substrate in order to fix the loop-piles, applying a secondary coating- to the primary coating, wherein both the primary and the secondary coating comprise a polyoiefin.

A combination of both a primary and a secondary coating with a polyoiefin provides the advantage that both the primary and the secondary coating can be recycled, and more particularly that they do not first need to be separated from each other for this purpose but can be separated and reused together.

Instead of the latex primary coating usual in the prior art, the primary coating according to the present invention can comprise a polyoiefin dispersion. Although a hot-melt application of a polyoiefin can be envisaged, it has been found that applying the polyoiefin by means of a dispersion results in better absorption in the fibres of the tuft thread and substrate, and thereby a better sealing of the tuft thread. A further advantage of using a dispersion is that the method of application can be identical to that of the usual latex, so that this step can fit easily into an existing production process. In addition to fixing the yarn in the tuft substrate, the object of applying a primary coating is generally to provide a fire-retardant action, electrical conduction for preventing static electricity, and to provide form-stability. The secondary coating can for instance comprise a hot-melt (melted) polyolefin which can be applied after optionally at least partial curing of the primary coating.

A (further) advantage of applying the secondary coating in melted form is that this can take place by means of using a doctor blade or roller, so that usual methods for applying conventional bitumen layers can also still be used for this purpose. It has been found that a high filling percentage (CaC0₃ or similar alternatives) can be realized (> 65%) by means of this doctor blade/roller method. This method is therefore highly suitable for enabling processing of the recycled polyolefin fraction. The properties of the carpet (or the carpet tile) are strongly influenced by the process settings during the use of doctor blade or roller. One of the properties which can be influenced is the (undesired) curving of the carpet as a result of stresses introduced into the carpet during the manufacturing process. This is particularly the case with carpet tiles. It has been found that the degree of curving depends on the forced tensile force (more specifically between 7 and 25 kg) with which the cover membrane is laid on the hot polyolefin compound. It has thus also been found that the polyolefin compound temperature preferably lies between 70-85 °C just before application of the cover membrane. The sealing roller can be moistened here in order to prevent polyolefin print-through. It is noted that the described method of application also remains suitable for applications with a bitumen backing.

It has been found that not all combinations of polyolefin can be combined with each other equally well. Determined combinations have been found to delaminate or tear or crack relatively easily after being applied, which is of course undesirable. Good results have been obtained in experiments with a primary coating comprising a dispersion on the basis of polypropylene (with ethene) which, if desired, can comprise an additive from the group of: CaCC>3, ATH (Aluminium trihydrate), an antistatic additive such as potassium (di)formate. The addition of CaCOj, ΑΤΉ can be made in order to achieve a desired weight ratio (a desired stiffness of the final product, fire-retardant action), or to lessen the necessity of adding relatively expensive raw materials. When use is made of recycled polyolefin, the (maximum) amount of additive is preferably determined on the basis of the "foreign" material present in the recycled material.

As stated above, combinations of primary and secondary coatings have been determined which can be used together well. With the polyolefin dispersion as primary coating, a secondary coating comprising a polyolefin can for instance consist of:

A: 71 % filler MS80, 12% VestoPlast VP708, 12% Vestoplast VP508, 5% resin Escorez 1102, or

B: > 65% filler MS80, and ingredients based on DOW Amplify, DOW Infuse, Eastman Regalite, Shell Microwax, Exxon Primol and/or Ciba Irganox. The above stated types A: are based on polybutene and polypropylene, wherein the mixing ratio 12/12 can vary between 0/24 and 24/0 depending on the desired results in terms of processing viscosity, cracking and dimensional stability. Even the molecular chain length can also vary, wherein Vestoplast types VP703 - VP704 can also be applicable.

Additives from the group of: CaC0₃, aliphatic hydrocarbons, acrylate-modified hydrocarbons and/or aluminium (tri)hydrate can be added to the secondary coating. These materials also result in a desired weight being obtained at a given volume, and can above all also be recycled.

The above stated types B: are based on ethylene-octene copolymers and ethylene- hexene copolymers, with the addition of hydroxylated, saturated hydrocarbons, mineral oils and anti-oxidants. In order to obtain a form-retention and prevent wear it is possible to apply respectively a glass scrim or glass fibre and a cover membrane, wherein the latter preferably also comprises a polyolefin. A thus obtained carpet, which can be manufactured in both fitted and carpet tile format, can be collected or returned at the end of its lifespan, after which the yarn, the tuft substrate and the polyolefin layers can be separated so that the separated polyolefin can be melted for reuse and a new carpet can be manufactured according to the above described method. The separated yarn can however be processed to form new yarn, after which carpet can be manufactured with the thus recycled yam, which can for instance be a polyamide 6, polyamide 6.6 or polypropylene.

For the purpose of identifying the substances used and carrying out a pre-selection of recyclable and non-recyclable carpets on the basis of this identification, use can for instance be made of so-called NIR (Near InfraRed) technology. Various methods can be used to separate the different materials, such as cryogenic separation (very low temperatures), chemical separation (solvents) or mechanical separation. The latter method is recommended for environmental and energy reasons.

The present invention also relates to a method and device for processing carpet for the purpose of recycling. The invention relates particularly to a method and device which process the carpet into raw materials, which can in turn be used for the manufacture of carpet.

The recycling of carpet for at least partial reuse thereof is per se known. In order to here separate the yarn from which the piles are manufactured from the material from which the backing is manufactured (usually latex or bitumen), the piles are sheared off just above the backing using a per se known device. If possible, the yarn is used to make new yam and the backing, depending on the material of which it consists, can be used for various purposes, including in determined cases making new backing for carpet

A drawback of this known method is that after shearing of the piles a relatively large amount of yam, and in addition tuft substrate or membrane or other backing materials such as felt, jute and strengthening layers, remains in the backing. This latter is hereby contaminated such that the number of fields of application is limited. These materials left behind are moreover usually downcycled during reuse (i.e. used to produce a product other than that from which they have been recovered) and thereby not utilized effectively as sought after within the cradle to cradle philosophy. It is therefore an object of the present invention to propose a method and device for processing carpet in order to recycle it, which wholly or partially obviates the above stated drawback.

For this purpose the invention first provides a method for processing carpet for the purpose of recycling, comprising of grinding at least the backing of the carpet and screening the ground carpet in order to separate the backing from the yarn and tuft substrate. During grinding of the carpet the backing, which may comprise a primary and secondary backing and which, in addition to the yam, may also contain tuft substrate and possible farther components such as cover membranes and possible reinforcements such as jute or glass scrim or glass fibre, is broken up so that it is not only divided into smaller pieces itself, but also loses the attachment to the materials present therein. A mixture of ground backing and yarn and other materials is thus created which are separated from each other in a subsequent step by means of screening. The powder of the backing herein drops through the screen and the yarn remains in the screen and is removed therefrom after sufficient separation has taken place. The method according to the present invention particularly comprises of grinding the carpet in a drum with rotating hammers therein. Such a configuration is suitable because sufficiently great forces can thereby be generated to break up various types of carpet to be recycled. Such a drum also makes continuous operation possible, wherein new carpet for grinding can be added continuously without having to stop the process. Arranged in the drum are yokes between which the hammers strike. As soon as the carpet has been broken up into sufficiently small pieces, it is carried away and discharged to the screening device via a grid.

It has been found that good separating results can be achieved with a cylindrical screen rotating about a substantially horizontal axis. Substantially horizontal is here understood to mean an arrangement with a rotation axis tilted between 0 and 15 degrees, and preferably about 5 degrees relative to the horizontal. The screen preferably extends here between 2 and 8 metres, and particularly about 6 metres, along the rotation axis. During rotation of the screen the ground carpet for screening sinks slowly downward here, wherein the meshes or perforation of the screen can be varied over the length of the screen. A first round of screening does not necessarily result in a sufficiently separated ground carpet because the ground backing can become stuck in the yam. This problem is solved by pulling apart or combing the thus resulting fibre fraction after the screening. Part of the powder already falls out of the yarn here and the rest can then be separated by once again screening the pulled-apart or combed fibre fraction. It has been found that after two rounds of screening a separation has occurred such that the yarn and the backing can be properly processed into new raw materials for manufacturing carpet or for other purposes.

As described above, diverse materials are used to manufacture a carpet backing. A latex backing used mainly for fitted carpet can be separated from the yarn most easily because it is relatively easy to grind and detaches readily. When use is made of a bitumen or polyolefin backing, the bitumen or polyolefin can become sticky during the grinding due to temperature or components of the backing being released. Not only does this make the separation of backing and yam mor difficult, it can also result in the backing (partially) clogging the device used for the grinding.

This problem can be solved by moistening the carpet to be processed before the grinding. The moisture can act here in two ways. Firstly, it lubricates and in this way prevents attachment of the ground backing to the rest of the carpet or the grinder, and in addition it cools or provides heat capacity so that heat created during the grinding does not result directly in adhesion of the backing to the device. In the case of carpet with a bitumen or polyolefin backing this addition will already produce satisfactory results in most cases. If attachment nevertheless occurs, this attachment can be further countered by adding a surface tension reducer such as a soap to the moisture. The carpet for grinding can be sprayed or immersed for this purpose, but if this does not achieve a sufficient degree of penetration of the moisture (which must be present mainly in the vicinity of the backing), the moisture optionally provided with a surface tension reducer can be applied in the carpet by means of a roller. Such a roller can comprise a rotatable sponge and pressing means such as a pressing roller, wherein the sponge is moistened and/or the carpet is moved through a moisture bath. The sponge is placed here on the pile side of the carpet

A further method step in the recycling of carpet with a bitumen or polyolefin backing can comprise of granulating or briquetting the separated backing. It has been found that untreated bitumen or polyolefin powder tends to cake together, so resulting after packaging in large chunks which are relatively difficult to process. Granulating prevents this caking and in addition makes the separated bitumen immediately suitable for use in for instance road construction or in a roof covering application. For these latter purposes relatively large granules can be formed during the granulating with a diameter up to about 1 cm or, in the case of briquetting, briquettes with diameters up to 10 cm. In addition, the granulate of both bitumen powder and polyolefin powder is of course also suitable - also with smaller granules - for the purpose of making new carpet backing therefrom. The option of granulating or briquetting does not detract from the possibility of processing the bitumen or polyolefin powder, in its original forma and whether packaged or not, into a suitable product

This latter applies equally to separated bitumen, polyolefin or latex and yarns, so that a complete cradle to cradle process can be achieved.

The present invention also relates to a device for processing carpet for the purpose of recycling, comprising a grinder, in particular a drum with rotatable hammers therein, and a screen for separating ground carpet into backing and yarn with tuft substrate. The screen is preferably arranged here such that the ground carpet enters the screen directly from a grid in the grinder.

Such a grid can be arranged in a discharge on the underside of the grinder and be provided with specific dimensions for the processing of carpet Experiments have shown that a good operation (blocking pieces which are too large as against becoming clogged due to meshes which are too small) is achieved with a grid with openings of 20 to 25 mm. A grid can still more particularly be applied which has a number of partitions, varying between 3 and 6, extending only in radial direction of the rotation of the device. In a further embodiment the device comprises a feed, such as a conveyor belt optionally provided with sections, for dosed feeding of carpet pieces, in particular carpet tiles, to the grinder. The possible sections can be arranged by means of partitions co-displacing with the conveyor belt and placed at a distance such that carpet tiles of a usual size can be laid therebetween, for instance at 30, 40, 50 or 60 cm, depending on what is usual at a determined geographical location.

When the device is used to recycle fitted carpet, this carpet can for this purpose first be cut to size or made smaller in other manner to a size enabling feed into the grinder.

In an embodiment the device according to the present invention comprises a cylindrical screen substantially rotatable about a horizontal axis. This is understood to mean a screen with a rotation axis tilted at an angle between 0 and 15 degrees, and preferably about 5 degrees, relative to the horizontal.

The invention will now be elucidated with reference to the following figures. Herein:

Figure 1 shows the structure of a carpet according to the present invention; Figure 2 shows the production process for manufacturing such carpet;

Figure 3 shows a device for pulverizing carpet to be recycled;

- Figure 4 shows a schematic representation of the separation of the carpet of figure 1;

Figure 5 shows a schematic representation of a device for performing the method according to the present invention;

Figure 6 shows a perspective interior view of a drum and hammers of a grinder; - Figure 7 shows a view of a first type of grid for use in the grinder;

Figure 8 shows a view of a second type of grid for use in the grinder; and Figure 9 shows a perspective view of a drum screen for use in the present invention. Figure 1 shows a carpet 1 manufactured according to the present invention. Carpet 1 comprises a tuft substrate 2 provided with yarn 3 tufted therein. In the shown embodiment a side with long (cut) loop-piles of yarn 3 is situated on the upper side of carpet 1. A so-called "upside down" carpet can however be manufactured, in which a short pile is situated on the upper side of carpet 1 , or both sides can be short. The loops need not necessarily be cut. The yarn is fixed to a tuft substrate 2 by means of a polyolefin applied by means of hot-melt or dispersion. Applied hereto by means of a hot-melt is a polyolefin layer 4 which can be provided with several additives and on which is arranged an optional glass scrim or glass fibre 5, or a recyclable or degradable variant thereof. An optional polyolefin cover membrane 6 is also present. The carpet can be embodied as fitted carpet or as carpet tile in diverse dimensions.

Figure 2 shows a diagram 7 of a manufactiiring process of a carpet according to the present invention. The process comprises of feeding in 8 a tuft substrate, which can be a conventional tuft substrate, with yarn,- to which a primary coating is applied in step 9. The primary coating comprises a polyolefin dispersion or hot-melt, wherein the coated tuft substrate is then dried in two steps 10, 11 and then fed through 12 to a device 13 for applying a secondary coating. A polyolefin hot-melt is applied for this purpose by means of doctor blade 14- to the carpet already provided with a tuft substrate. The secondary hot-melt for spreading with the doctor blade is prepared by heating 19 the polyolefin and subsequently mixing 16, 17 the polyolefin with additives such as a filler 18. The thus obtained carpet is then dried and cut 15, and is ready for use.

Figure 3 shows a grinding device 20 for recycling carpet according to the present invention. The grinding takes place by feeding 21 and moistening 22 the carpet, which is then pulverized 23 and from which remains polyolefin 24 separated after rotating screening which can be reused in the process of Figure 2. Also obtained from the fibres is PES or Polyamide which can be processed into new yarn. Figure 4 shows carpet 1 of figure 1 which after manufacture serves firstly for use 25 and at the end of a lifespan is collected 26 and then separated, for instance according to the process 27 elucidated in figure 3. The raw materials are then recycled 30, wherein a new backing 31 and new yam 32 result. Figure 5 shows a schematic representation of a device 51 for performing the method according to the present invention. Device 51 comprises a grinder 52 provided with a feed device 53 for feeding carpet to grinder 52. In the shown case the feed device is formed by a conveyor belt provided with sections for dosed feed of carpet pieces, in particular carpet tiles, to grinder 52. A discharge of grinder 52 is connected to a screen 54 for separating ground carpet into backing and yarn with tuft substrate. In the shown embodiment screen 54 is embodied as a cylindrical screen rotating about a substantially horizontal axis. Substantially horizontal is here understood to mean at an angle V of 0- 15, and in particular about 5 degrees to the horizontal.

The rotating cylindrical screen 54 is connected to an installation for combing, pulling apart and opening the fibre fraction (fibre opener 55). Fibre opener 55 is connected to a second cylindrical rotating screen 54a, wherein the perforation of screen 54a can possibly, but not necessarily, differ from the perforation of screen 54.

After passing through screen 56 the fibre fraction can be pressed into bales for discharge and reuse.

Figure 6 shows the interior of grinder 52 of figure 5, in which is shown a drum 57 with rotatable hammers 56 therein, which hammers strike the carpet against an anvil 58 and therein grind the supplied carpet. The carpet is carried along by the hammers as soon as it has been broken into sufficiently small pieces. As soon as this has taken place, it falls to the bottom part of the grinder, a discharge for ground carpet, where it comes to lie on a grid, which in the shown embodiment is a removable grid for the purpose of enabling modification of the size of the openings thereof to the type of carpet used.

Figure 7 shows a first embodiment 58 of the grid, which is provided with openings of 20 to 25 mm. Such a grid has been found particularly suitable for grinding cut-pile carpet.

Figure 8 shows a second embodiment 59 of a grid for the discharge of carpet from the grinder. This grid only has partitions 60 extending in radial direction of the rotation of the device at interspacing of 120 to 180 mm, and has been found particularly suitable for loop-pile carpet.

Figure 9 shows a perspective view of the interior 61 of drum screen 54 and 56 of figure 5. It can be seen that the drum screen is constructed from different sections A, B, C, D, E and F, which are provided with perforations with a diameter of 2 mm to 8 mm increasing/decreasing in the throughfeed direction. Also arranged are longitudinally extending ribs G, H and I which ensure that the ground carpet is moved reciprocally during the screening.

Claims

Method for processing carpet for the purpose of recycling, comprising of:

grinding at least the backing of the carpet;

screening the carpet with the at least ground backing in order to separate the backing from the tuft substrate with yarn.

2. Method as claimed in claim 1 , comprising of:

- performing step A in a drum with rotating hammers therein.

3. Method as claimed in claim 1 or 2, comprising of:

- performing step B in a cylindrical screen rotating about a substantially horizontal axis.

4. Method as claimed in any of the claims 1 -3, comprising of:

C. pulling apart or combing the thus resulting fibre fraction after the screening.

5. Method as claimed in claim 4, comprising of:

D. once again screening the pulled-apart or combed fibre fraction after step C.

6. Method as claimed in any of the foregoing claims, comprising of:

E. moistening the carpet to be processed before performing step A.

7. Method as claimed in claim 6, comprising of:

- adding a surface tension reducer such as a soap to the moisture during step E.

8. Method as claimed in claim 6 or 7, comprising of:

- applying the moisture in the carpet during step E by means of rolling.

9. Method as claimed in any of the foregoing claims, comprising of:

F. granulating, briquetting or packaging the separated powdered backing.

10. Method as claimed in any of the foregoing claims, comprising of:

- processing the separated backing and/or the separated yarn in the manufacture of a new carpet.

Device for processing carpet for the purpose of recycling, comprising:

a grinder, in particular a drum with rotatable hammers therein;

a screen for separating ground carpet into backing and yarn with tuft substrate.

Device as claimed in claim 11, comprising:

a discharge for discharging ground carpet from the grinder, comprising a grid with openings of a minimum of 16.1 x 2.1 cm.

Device as claimed in claim 11, comprising:

a discharge for discharging ground carpet from the grinder, comprising a grid having a number of partitions, varying between 3 and 6, extending only in radial direction of the rotation of the device.

Device as claimed in claim 11, comprising:

a feed, such as a conveyor belt provided with sections, for dosed feeding of carpet pieces, in particular carpet tiles, to the grinder.

15. Device as claimed in any of the claims 11-14, wherein the screen is a cylindrical screen rotating about a substantially horizontal axis.