FR3111091A1 - Process for recycling a polymer foam, material obtained and uses - Google Patents

Abstract

The invention relates to a process for recycling a polymer foam comprising the following steps: The polymer foam is laminated in the presence of at least one polymer binder, The mixture of the laminated polymer foam and the polymer binder is recovered, in the form of strips, and said strips are divided into fragments of a material usable as raw material, as well as the material obtained and its uses.

Description

Process for recycling a polymer foam, material obtained and uses

The present invention relates to a process for recycling a polymer foam, the material resulting from this process and the uses of this material, in particular as a raw material for the manufacture of a manufactured article.

In the following text, the invention is more specifically described with reference to the recycling of polymer foam mattresses given the volumes concerned, but it extends of course to any polymer foam, such as upholstery foams such as those cushions and padding elements, mat foams and modules used in particular for the practice of gymnastics, wedging or protection elements used in packaging.

The disposal of several million mattresses each year in France is a problem that is attracting more and more attention with the emergence of a wide variety of recycling solutions. Thus, rather than the long practiced burial or incineration, although still relevant, the recovery of mattresses is organized at collection points or by distributors with a view to recycling them. Generally after a hygienization step, the mattresses are broken down into their different components which are respectively valued. But among these, polymer foam remains the most difficult to recycle due to loss of mechanical properties, wear and contamination. After stages of compacting, cutting, gluing and/or expansion, it is essentially recycled in the automobile industry, in particular in the clothing of vehicles for door trim, armrests, in sound and heat insulation, generally after a final forming step in the presence of a binder as well as in the manufacture of new mattresses. It can also be subject to more or less complex chemical treatments to extract certain constituents which are then recovered.

The present invention provides a process for recycling a simple polymer foam making it possible to convert it into a material having a multiplicity of uses and in particular in fields other than those in which foams are generally recycled, said process being in furthermore applicable to any type of polymer.

Thus, by polymer according to the invention is meant any polymer generally used in the manufacture of mattresses, and in particular polyurethanes, polyethylenes, polypropylenes, polystyrenes, natural rubbers (NR) and synthetic rubbers, in particular polyisoprene of (IR), copolymers of styrene butadiene (SBR) and polybutadienes (BR), co- or terpolymers of ethylene propylene and diene (EPM and EPDM), chlorinated or brominated isobutylene isoprene copolymers (IIR, BIIR, CIIR), acrylonitrile butadiene copolymers (NBR), and polychloroprenes (CR), silicone rubbers (VMQ, FVMQ), fluorinated elastomers (FKM), chlorinated and chlorosulfonated polyethylenes (CM, CSM), polyacrylates (ACM), ethylene vinyl acetate (EVM) and ethylene methyl acrylate (AEM) copolymers, hydrogenated nitrile rubbers (HNBR) and epichlorohydrin rubbers (CO, ECO, GECO), kneadable polyurethanes ( AU, EU).

Polymer foam means any foam with open cells or with closed cells, such as those used in bedding. They have a density of the order of 20 to 800 kg/m ³ .

The invention relates to a process for recycling a polymer foam comprising the following steps:

1. The polymer foam is laminated in the presence of a polymer binder,
2. The mixture of the laminated polymer foam and the polymer binder is recovered, in the form of strips or plates, and
3. Said strips are split into fragments of a material that can be used as raw material.

The process of the invention makes use of simple operations which have not been implemented in combination in the recycling of polymer foam, while making it possible to produce in large quantities a base material for the manufacture of articles in many fields of activity. It can thus be used as a raw material in formulations of foam or other materials for construction and in particular for seals and insulation, in the automotive industry.

The first step a) of laminating the polymer foam in the presence of at least one polymer binder, according to the process of the invention, not only allows compaction of the foam, facilitated by the presence of the polymer binder, but, surplus and at the same time to evacuate the air retained in the cells of the foam. This leads to a mixture of the polymer foam and the polymer binder in the form of strips or plates which are recovered according to step b). The mixture resulting from step a) is preferably as coherent as possible, depending on the properties of the raw material thus produced.

The polymer foam can be in the form of chips.

The polymer binder is chosen from polymers making it possible to confer cohesion on the compacted polymer foam and mechanical properties depending on the expected material. According to one implementation of step a), the polymer binder is chosen from latex, natural rubber (NR), polyisoprene IR, polyurethanes, styrene butadiene copolymers (SBR) and polybutadienes (BR), ethylene propylene and diene co- or terpolymers (EPM and EPDM), chlorinated or brominated isobutylene isoprene copolymers (IIR, BIIR, CIIR), acrylonitrile butadiene copolymers (NBR), and polychloroprenes (CR) , silicones, chlorinated and chlorosulfonated polyethylenes (CM, CSM), polyacrylates (ACM), ethylene vinyl acetate (EVM) and ethylene methyl acrylate (AEM) copolymers, and hydrogenated nitriles (HNBR)). It can be a polymer identical to or different from the polymer of the foam. Advantageously, it is chosen of the same chemical nature as the polymer foam, in order to promote compatibilization between the foam and the binder and in this way optimize their mixing and obtain a material that is as homogeneous as possible. In a preferred mode, the polymeric binder is a raw rubber or a mixture of raw rubbers. It can be in solid form, for example in the form of shavings, capable of softening during rolling in order to promote its intimate mixing with the polymer foam. It can also be in the form of a more or less viscous paste. So, it can be in the form of mastic. It will be understood that the more the foam/binder mixture is made homogeneous in step a), the better the properties, in particular the mechanical properties, of the material obtained at the end of the process.

By the expression, in the presence of at least one polymer binder, it is understood that the polymer binder can be a mixture of polymers, the combination of which produces a binder, or a mixture of polymer binders, but also that any suitable additive can be added, for example agents promoting the properties of the foam in view of the material to be obtained, dyes, compatibilizing agents, fillers (reinforcing or not), antioxidants, etc.

Rolling step a) can be carried out in any device or rolling mill intended for this operation provided that it is equipped with a feed making it possible to distribute said polymer binder before the compression of the polymer foam, if a prior mixture of polymer foam and polymer binder is not provided. As a preferred example, step a) is carried out in a rolling mill with at least two rolls or in a roll mixer or in an internal mixture. This step can be carried out at room temperature but also at a higher temperature. A person skilled in the art has the skills to determine an appropriate temperature which is chosen in particular according to the polymer binder in order to optimize this step, without risking degrading either the polymer binder or the polymer foam. Depending on the material used, the cylinders have the same or different temperatures. As said above, it(s) is (are) determined to be the most suitable(s) for the polymer foam and the polymer binder chosen. Friction can cause the cylinders to heat up; if necessary, it may be necessary to cool the cylinder or cylinders. This will especially be the case if the binder in the mixture risks degradation or devulcanization, in particular if the binder is a rubber.

According to a variant of the invention mentioned above, it may be provided that, prior to step a), the polymer foam is mixed with the polymer binder, for example in a mixer. At the end of this preliminary mixing, the mixing may not be complete and may be finalized in step a).

The level of polymer binder in the mixture of the polymer foam and the polymer binder depends of course on the nature of the polymer of the foam, the nature of the polymer of the binder, and also on the desired qualities of the material produced. It ranges from about 5 to 40% by weight relative to the weight of the mixture, preferably from 10 to 30%.

In a preferred variant of the invention, the polymer foam is mixed with a binder of raw elastomer type before step a) of rolling until a mixture as homogeneous as possible is obtained, which will be completed by the step a).

According to step b), the mixture of the laminated polymer foam and the polymer binder is recovered, in the form of strips or plates. This cutting step is advantageously carried out in the wake of step a), but not necessarily. In the latter case, the mixture of the laminated polymer foam and the polymer binder can be stored before cutting, for example on a different industrial site. The latter are engaged in step c) in an operation of fractionation into fragments whose size is variable, generally of the order of 4 to 12 mm. Depending on the nature of the polymers used and the destination of the raw material thus manufactured, this size may vary outside this interval.

According to a variant of the invention, it is possible to envisage that the mixture of the laminated polymer foam and of the polymer binder is engaged in step c) without undergoing step b), that is to say that said mixture is split into fragments without having been previously cut into strips or plates.

The fragments recovered in step c) constitute a material which is directly usable as a raw material, it can also be treated before its use as a raw material.

Thus, if the polymer of the treated foam is vulcanized, the fragments recovered in step c) are advantageously devulcanized. According to this variant, the devulcanization process described in patent application WO2013/182830A1 will advantageously be implemented.

The invention also relates to a material comprising a laminated polymer foam and a polymer binder, which can be obtained by a process of the invention as described above.

The invention also relates to any use of such a material and in particular any manufactured article made of at least one material of the invention. Such an article can be made solely of a material of the invention, it can only be made in part with a material of the invention. According to this variant, it advantageously comprises 5 to 20% by weight of a material of the invention and from 95 to 80% of at least one vulcanized rubber.

The invention is illustrated below in the example which follows for the manufacture of a material intended to produce an EPDM foam seal, in support of the appended figures 1-4.

Figure 1 illustrates the pre-mixing of foam and binder.

Figure 2 illustrates the lamination of the foam and binder mixture.

Figure 3 illustrates the cutting of the mixture of laminated foam and binder.

Figure 4 illustrates the grinding of the mixture into fragments.

An EPDM joint-type foam is pre-mixed with an EPDM binder, the content of the binder in the foam/binder mixture being around 25% by weight. The operation is carried out in an internal mixer at a temperature of 90°C for a time necessary to ensure foam/binder mixing.

This operation is illustrated in figure 1. This step is not essential but it allows to optimize the mixing of the foam and the binder.

The mixture is then rolled on a roller mill. No heating is applied but the friction causes a heating which contributes to the homogenization of the homogeneous paste, as illustrated in figure 2.

The rolled mixture is cut into plates with a size of the order of 80 cm x 20 cm, as shown in Figure 3.

The plaques are then crushed into fragments approximately 6-8 mm in size, as shown in Figure 4.

The material thus obtained can be used as a raw material.

Claims (16)

Process for recycling a polymer foam comprising the following steps:

1. The polymer foam is laminated in the presence of at least one polymer binder,
2. The mixture of the laminated polymer foam and the polymer binder is recovered, in the form of strips, and
3. Said strips are split into fragments of a material that can be used as raw material.

Process according to Claim 1, characterized in that the polymer is chosen from polyurethanes, polyethylenes, polypropylenes, polystyrenes, natural rubbers and synthetic rubbers. Process according to Claim 1, characterized in that the polymer binder is identical to or different from the polymer of the foam. Process according to any one of Claims 1 to 3, characterized in that the polymer binder is a raw rubber or a mixture of raw rubbers. Process according to any one of Claims 1 to 4, characterized in that the rolling step a) is carried out in a rolling mill with at least two rolls or in a roll mixer or in an internal mixture. Process according to any one of Claims 1 to 5, characterized in that the polymer foam is in the form of chips. Method according to any one of Claims 1 to 6, characterized in that the polymer binder is in the form of mastic. Process according to any one of Claims 1 to 7, characterized in that, prior to stage a), the polymer foam is mixed with the polymer binder in a mixer. Process according to any one of Claims 1 to 8, characterized in that the content of polymer binder in the mixture of the polymer foam and the polymer binder ranges from 5 to 40% by weight relative to the weight of the mixture, preferably from 10 to 30%. Process according to any one of Claims 1 to 9, characterized in that stage a) is carried out at room temperature or at a higher temperature. Process according to Claim 10, characterized in that the cylinders have identical or different temperatures. Process according to any one of Claims 1 to 11, characterized in that the material recovered in the form of fragments in stage c) can be used directly as raw material or is treated before its use as raw material. Process according to any one of Claims 1 to 12, characterized in that the polymer of the foam is vulcanized, and in that the material recovered in step c) is then devulcanized. Material comprising a laminated polymer foam and a polymer binder, obtainable by a process according to any one of Claims 1 to 13. Manufactured article made of at least one material according to claim 14. Manufactured article according to Claim 15, characterized in that it comprises 5 to 20% by weight of a material according to Claim 14 and from 95 to 80% of at least one vulcanized rubber.