Method and Device for Recycling Ropes

Abstract

Method for recycling composite ropes, the method comprising a step of identifying (SO) the type of rope and at least one step of separating components comprising one or the other of the following steps /S1/,/S2/,/S3/,/S4/ as defined below: /S1/—a mechanical separation step, /S2/—a chemical separation step, /S3/—a thermal separation step, /S4/—a biological separation step and machine or installation for recycling composite ropes.

Claims

1. A method for recycling composite strings, the method comprising: —a step of identifying (S0) the type of string, and at least one step of separating components comprising one or the other of the following steps /S1/, /S2/, /S3/, /S4/ as defined below: /S1/—a mechanical separation step, /S2/—a chemical separation step, /S3/—a thermal separation step, /S4/—a biological separation step.

2. The method according to claim 1, wherein the strings to be recycled are sports racket strings (2).

3. The method according to claim 2, wherein the strings to be recycled are tennis racket strings.

4. The method of claim 3, wherein the tennis racket strings comprise an assembly of structural fibers (3) with a coating material (4), wherein the structural fibers comprise aramid fibers and/or polyester and/or polyimide and/or polyolefin and/or polyethylene, and in which the coating material comprises polyurethane and/or an elastomer.

5. The method according to claim 1, wherein, according to the step of mechanical separation (/S1/) of the fibers and the coating, there is provided a peeling step and/or a grinding step of the string strand.

6. The method according to claim 1, wherein the chemical separation step (/S2/) comprises dissolving the coating of the fibers in a solvent.

7. The method according to claim 1, wherein the thermal separation step (/S3/) comprises a vapor-thermolysis step, with heating of the string strand beyond 150°.

8. The method according to claim 1, wherein the step of biological separation (/S4/) comprises the extended contact of the string strands with active biological agents comprising microalgae and/or enzymes, so that certain components of interest in the string strands are degraded by the active biological agents.

9. The method according to claim 1, wherein the step of identifying (S0) for the tennis racket strings consists of making a cross section, taking a photo with magnification, and analyzing the groups of filaments, in order to deduce therefrom a classification among at least the following types: single multifilament, multicore multifilament, multi-core multi-sheath, multi-core single-sheath.

10. The method according to claim 1 further comprising a step of upgrading the products/ components resulting from one of the steps /S1/ to /S4/, the upgrading step comprising the incorporation of the components in new strings, and/or in technical clothing with padding, and/ or in technical protective clothing, and or in flame retardant technical clothing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Other aspects, aims and advantages of the invention will become apparent on reading the following description of an embodiment of the invention, given by way of non-limiting example. The invention will also be better understood in relation to the accompanying drawings in which:

[0032] FIG. 1 shows an illustration of a tennis racket with its string,

[0033] FIG. 2 illustrates several types of strings sections to be recycled,

[0034] FIG. 3 shows a step of mechanical separation by peeling,

[0035] FIG. 4 illustrates a mechanical separation step by grinding,

[0036] FIG. 5 illustrates a chemical separation step,

[0037] FIG. 6 illustrates a thermal separation step,

[0038] FIG. 7 illustrates a biological separation step.

DESCRIPTION OF EMBODIMENTS

[0039] In the various figures, the same references designate identical or similar elements. For reasons of clarity of the presentation, certain elements are not necessarily represented to scale.

[0040] FIG. 1 partially shows a tennis racket with its string. The racket comprises a frame 1 and string 2. The string passes through holes made in the frame. The string forms a sieve. Longitudinal sections intersect cross sections. To complete the operation of installing the string, several knots are created.

[0041] String 2 can break after some wear, or if the stress endured exceeds the threshold that can be tolerated by the type of string in question. Some users or players replace the string preventively as already mentioned.

[0042] To remove the string from the frame, the string threads can be removed through the holes in the frame, after sectioning the string several times.

[0043] We are interested in the very frequent case where the string 2 itself is formed from an assembly of structural fibers with a coating material. When we talk in more detail about the composition of the string, we can also use the term “string strand” to denote a single element of the whole string. The string strand may in some cases include a solid core 32.

[0044] Of particular interest are string strands having an outside diameter of between 0.8 mm and 1.6 mm. According to the example, in particular, string threads having an outer diameter of between 1 mm and 1.5 mm are processed.

[0045] With regard to string strands for tennis rackets, the cross section of the strand has a diameter of between 1.2 mm and 1.4 mm. However, note that smaller to larger diameters are also considered in the method of the present invention.

[0046] The coating material, marked 4, comprises polyurethane and/or an elastomer. Note that to designate “coating”, we also speak of “sheathing”. The tensile strength mechanical pstringrty of the coating material string is less than that of structural fibers; but the coating material does contribute to the cohesion of the string strand.

[0047] As illustrated in FIG. 2, the structure of the string strand can be of several types: single multifilament, multicore multifilament, multicore multi sheath, multi core single sheath.

[0048] FIG. 2, example A: solid core, 1 sheathing

[0049] FIG. 2, example B: solid core, multi-sheath

[0050] FIG. 2, example C: multifilament, coreless

[0051] FIG. 2, example D: solid multi-core, 1 sheath

[0052] FIG. 2, example E: solid multi-core, 1 sheath

[0053] FIG. 2, example F: multi-core, multi-duct

[0054] FIG. 2, example G: multi-core, multi-duct

[0055] The structural fibers, generally denoted 3 in the figures, comprise aramid and/or polyester and/or polyamide and/or polyolefin and/or polyethylene fibers.

[0056] The structural fibers used for tennis strings or for other types of strings (see list above) include in particular: [0057] Aramid: Zylon (PBO); Kevlar (PPD-T); Kevlar 49; Black Technora, [0058] Polyester: Pen or Pentex (PEN); Polyester (PES), Polyamide: Nylon; Polyamide, [0059] Polyolefins: Spectra or Dyneema; HDPE polyethylene, [0060] Titanium: Titanium (Ti), [0061] Carbon: Carbon fibers, [0062] Elastomer: Polybutylene; elastomers (rubbers).

[0063] Aramids

[0064] Aramid fibers are recognized for their excellent impact resistance, and are widely used in the manufacture of personal protective equipment (helmets, cut resistant gloves, bulletproof vests, etc.). In boating, Kevlar® or Technora® products are appreciated for their very good strength and low elongation at break (around 3.5%), as well as their remarkable stability under static load (no creep). In other words, these fibers are very strong (five times more so than stainless steel), very weakly elastic and do not stretch over time.

[0065] Aramid fibers are also used as reinforcements in composite materials, in order to provide good temperature stability to the end products (up to 200° C. depending on the matrix). However, we can note some less positive points: limited resistance to UV and significant cost.

[0066] Polyesters

[0067] Polyester fibers are consumer fibers known for their longevity, UV resistance and excellent mechanical and chemical resistance.

[0068] Polyester fiber can be recycled mechanically or chemically, each method having certain advantages and disadvantages. The mechanical method involves collecting plastic bottles and industrial waste, while the chemical process reuses textile products made from polyester to reduce them to monomers and then transform them back into textiles.

[0069] The polyester recycling method allows materials to be recreated almost indefinitely: items or fabrics can be recycled many times without losing quality. In addition, chemically produced recycled polyester does not contain heavy metals, unlike its counterpart made with freshly extracted petroleum.

[0070] Polyamides

[0071] Polyamide or nylon fiber is a so-called “technical” synthetic fiber. It is used in textile and plastic industrial applications, and finds application in a wide range of products requiring high strength materials. Polyamide is widely used for gears, fittings and bearings, in the automotive industry for underlying parts, and as a material for power tool housings. It is also used in the manufacture of a wide variety of strands, strings, filaments, netting and tire cords, as well as hosiery and knitted garments.

[0072] There are a wide variety and many grades of types of polyamides available industrially, known by the acronyms ‘PAx.x’.

[0073] The main strengths of polyamide are its very good mechanical properties (traction, fatigue, impact, abrasion resistance), as well as good resistance to fuels and oils. On the other hand, it is sensitive to humidity in the ambient air, and has fairly limited UV resistance. Despite everything, polyamides exhibit an excellent cost/performance balance.

[0074] Polyamides are currently very infrequently recycled, for reasons related to the chemistry of the polymers (nylon is more difficult to recycle than polyester).

[0075] Polyolefins

[0076] Polyethylenes, from the polyolefin family, are part of the so-called “mass market” plastics, with very high consumption. They are one of the plastics that lend themselves to recycling, although they are often destined for low value-added applications. They are subdivided into many sub-categories, each with specific characteristics (PEHD, PEBD, PEBDL, UWMWPE . . . ).

[0077] High tenacity polyethylene fibers (commonly called “Ultra-High Molecular Weight Polyethylene”, or UHMWPE) have the advantages of lightness (density of 0.95 compared to that of aramid of 1.44) and with a high capacity for converting kinetic energy into thermal energy. They are increasingly used in bulletproof vests and other ballistic applications, in competition with Kevlar, to reduce weight.

[0078] The polyethylene fibers of the Dyneema™ range (from the manufacturer DSM) and Spectra™ (from the manufacturer Honeywell) are characterized by their very high resistance, and this for a minimum weight. Indeed, for equal weight, such a fiber is up to 15 times stronger than high-grade steel and 40% stronger than an aramid fiber. In addition, these fibers are lighter than water, extremely durable and resistant to mold, UV rays and chemicals.

[0079] As for the drawbacks, it should be noted a poor resistance to temperature (creep from 90° C.; aramid only degrades at 400° C.), as well as poor adhesion pstringrties which make composite applications delicate (surface treatment required).

[0080] Titanium

[0081] Titanium is a light and resistant metal, considered “noble”. It exhibits interesting industrial properties such as its resistance to corrosion, erosion and fire. It is ductile and biocompatible and also exhibits mechanical properties which allow the shaping of thin and light parts.

[0082] Because of its many qualities, it is used in many areas with high added value: medical, aeronautics, petrochemicals and new mechanical and leisure sports, where weight reduction becomes a gauge of performance. Titanium is a metal which combines very interesting mechanical qualities and excellent resistance in corrosive environments, which makes surface treatments unnecessary and makes titanium “ecological”. In addition, its density is 2 times lower than that of steels.

[0083] Titanium is mainly used in the form of alloys in aeronautics and for many industrial applications (energy, chemicals, etc.). Given the large part of production waste, the recycling of chips is well organized to recover as much material as possible. It is not uncommon to see that machining chips can represent up to 90% of titanium consumption in the production of a part. These chips are used as by-products, as in the case of the structural fibers of strings.

[0084] Carbon

[0085] Carbon fibers come from petroleum and exhibit extremely interesting properties: unfailing rigidity and mechanical stability, ultra-light weight and insensitivity to UV rays. Provided it is not exposed to impact, the life of carbon fiber is virtually unlimited.

[0086] Carbon fibers are now found in many advanced technical applications, where mechanical resistance, combined with a very low density are good assets: sports equipment, automobiles, aeronautics, robotics, military equipment, helicopter propellers, wind turbines, drones.

[0087] One of the most suitable technologies for recycling carbon fibers is pyrolysis. The material is subjected to a high temperature (between 400° C. and 700° C.), in order to lead to a degradation of the resin and a separation of the constituents. Solid or gaseous residues are thus obtained, depending on the conditions, which can be used as fuels (energy recovery, see below). The fibers can be recovered at the end of the process to be reintroduced into plastics or composites. The main advantage of this technique is the preservation of the mechanical properties of the recycled carbon fibers.

[0088] Method

[0089] After collection, the recycling process begins with an identification step (denoted SO) of strings. For tennis racket strings in particular, the identification step consists in making a transverse cut (by chisel, cutter or other sharp tool) after which a photo is taken with magnification, for example using a smartphone or digital camera.

[0090] The step of identification by section and plate can comprise an analysis of the groups of filaments, to deduce a classification among at least the following types: single multifilament, multicore multifilament, multicore multicore sheath, single-sheath multi-core. You can then consult a web-page reference base of sections and determine the section which most closely resembles the plate obtained just before. This process can advantageously be supported by a smartphone application.

[0091] Alternatively, the identification step is to take a reference written on the cord itself. The product identification sheet is then consulted on a web page and the type of filamentous structure and coating is found there.

[0092] Alternatively, the identification step is to identify a mark representative of the manufacturer of the string strand.

[0093] According to yet another embodiment, the color or colors present on the outer sheath of the string strand can be used to determine the type of string, which forms another method for identification step S0.

[0094] According to yet another embodiment, both a mark representative of the manufacturer and a color representative of the type of string strand are recorded to conclude an identification of the type of string strands to be recycled (step S0).

[0095] After identification, the process involves selecting one or more steps below in order to separate the string strand into components or small individual pieces.

[0096] Preferably, the step of collecting used strings will support the use of recovery bins, in particular selective bins, each designed to receive a particular type of string.

[0097] S1—Mechanical Separation Step

[0098] FIG. 3 illustrates a peeling step and/or a step of grinding the string strand. When the length of the string strand to be processed allows it, the string strand can be passed through a machine similar to an extruder 36 shown in FIG. 3.

[0099] In this machine 36, rasps mounted on rollers 37 are sandwiched together and, using the rotary movement of the rollers, the rasps peel the coating material from at least the outer edge of the section of the string strand. The heart 21 of the string is under tension and comes out of the machine without the outer edge coating 22, which is collected in a container at the outlet of the peeling machine 36. The arrangement is horizontal in the example illustrated. There can be several rasps in series (several passes of peeling).

[0100] As for the grinding step, the latter allows the string strand to be cut into small pieces which can then be treated by a chemical, thermal or biological separation step. For this, as illustrated in FIG. 4, a crusher 44 comprises a hopper 46 into which pieces of string strand are poured. Two (or more) counter-rotating rollers 47, by virtue of a plurality of surface teeth, shred the string strand. At the low side exit, small unit elements 48 collect in a container.

[0101] S2—Chemical Separation Step

[0102] In this case, a solvent is used to completely and reliably separate the technical fibers from the coating material. You can use trichlorethylene, trichloroethane, dichloromethane, tetrachloroethane, acetone, etc . . . .

[0103] FIG. 5 illustrates dissolution equipment comprising a tank 53 filled with a solution with the aforementioned solvent 54. String strands 55 are immersed therein, without any particular constraint on their length (short strands, long strands).

[0104] After a predetermined time, the action of the solvent solution is considered sufficient and the resulting solution is sieved, the fibers are retained by the sieve and the coating material dissolved in the solvent solution passes through.

[0105] S3—Thermal Separation Step

[0106] FIG. 6 illustrates a piece of equipment with a vapo-thermolysis step, with heating of the string strand above 150°. Here, stationary equipment has been shown, but an embodiment with progressive displacement is also provided.

[0107] Depending on the melting points of the different components, the constituents are gradually separated by increasing the temperature. The components that have the lowest melting point are recovered first and the components that have the highest melting point, last.

[0108] In the example shown, the string strand 65 is placed, without any particular constraint on its length (short strands, long strands), in an oven 63 and then heated to a first predetermined temperature T1, for example 160° C., in order to melt one of the constituents of the cord. Heating 66 can be done by different means, a burner, infra-red lamp rails, an induction furnace, etc . . .

[0109] The molten part is then extracted and the remainder is separated.

[0110] Of course, it is possible to repeat the operation described above with a second predetermined temperature T2, for example 220° C. in order to melt another component of the cord which is then separated as a melted part.

[0111] According to an example, in the logic of increasing temperatures, we can first separate the polyolefins, then the polyesters, then the polyurethanes, then the polyamides, etc. Carbon and titanium fibers are the last remaining components.

[0112] S4—Biological Separation Step

[0113] The biological separation step involves extended contact of the string strands with active biological agents including microalgae and/or enzymes.

[0114] Thus, certain components of interest in rope strands are degraded by said active biological agents. It is noted that, even if the time required is longer, this solution is the most economical in energy in achieving the separation of the components.

[0115] Furthermore, such a biological separation step is also used to process natural gut strings for recycling. Active biological agents comprising microalgae and/or enzymes degrade natural gut strings into elementary chemical components which then no longer have any negative impact on the environment.

[0116] FIG. 7 illustrates dissolution equipment comprising a tank 73 filled with a solution with greedy enzymes 74 and/or microalgae. String threads 75 are immersed therein, without any particular constraint on their length (short strands, long strands).

[0117] After a predetermined time, the action of the greedy enzymes and/or microalgae is considered sufficient and the resulting solution is sieved, the fibers are retained by the sieve and the coating material dissolved in solution passes through.

[0118] Recovery of Separated Constituents

[0119] In addition, there is a step for upgrading the products/components from one of the steps /S1/ to /S4/.

[0120] The recovery step includes, for example, the incorporation of the components into new strings, and/or into technical clothing with padding, and/or into technical protective clothing, and/or into flame retardant technical clothing.

[0121] The recovery step can include energy recovery, whereby one or more residues from the aforementioned separation step are burned.

[0122] Other Considerations

[0123] It should be noted that the different steps and solutions for the identification, separation and recovery steps are applicable, mutatis mutandis, to types of strings other than tennis strings, in particular the technical strings used for sailing, rock climbing, mountaineering or other sports, as well as the strings of stringed musical instruments.