Manufacturing process for structural components made from recycled thermoplastic material

Abstract

The invention relates to a method for manufacturing structural components formed from a thermoplastic material matrix that is loaded with fibers, said method comprising: formulating a matrix comprising at least 30% by weight of a recycled resin from a recycling stream of said thermoplastic material and less than 70% by weight of a reference resin from another stream of said thermoplastic material, said formulation being carried out so that the viscosity index of the matrix is ​​not less than 75% of the viscosity index of the reference resin; adding fibers to the matrix to obtain a composite of loaded thermoplastic material; injection molding said composite to obtain the structural components.

Description

Title of the invention: Method for manufacturing structural components from recycled thermoplastic material

[0001] The invention relates to a method for manufacturing structural components formed from a thermoplastic material matrix which is loaded with fibers, as well as a structural component manufactured by such a method for integration into a guide bearing.

[0002] The use of thermoplastic materials is very widespread in the manufacture of bearing components or guide bearings, in particular for their physico-chemical properties but also for reasons of cost and weight.

[0003] To meet the requirements of the specifications of the industries concerned, in particular the automotive industry, the thermoplastic materials used are generally virgin products, i.e. new, directly from a production chain from petroleum derivatives.

[0004] These materials have the disadvantage of being little or not recycled at the end of their life, which leads to a significant impact on the environment.

[0005] The invention aims to improve the prior art by proposing a process for manufacturing structural components from a thermoplastic material which uses a resin from the recycling of said material in order to limit the environmental impact of said manufacturing, while guaranteeing the mechanical performance required by the use of said structural components.

[0006] To this end, according to a first aspect, the invention proposes a method for manufacturing structural components formed from a thermoplastic matrix that is filled with fibers, said method comprising: - formulate a matrix comprising at least 30% by weight of a recycled resin from a recycling stream of said thermoplastic material and less than 70% by weight of a reference resin from another stream of said thermoplastic material, said formulation being carried out so that the viscosity index of the matrix is ​​not less than 75% of the viscosity index of the reference resin; - adding fibers to the matrix to obtain a composite of filled thermoplastic material; - to injection mold said composite to obtain the structural components.

[0007] According to a second aspect, the invention provides a structural component manufactured by such a process, said component being integrated into a guide bearing.

[0008] Other objects and advantages of the invention will appear in the following description, which develops different specific modes of implementation.

[0009] A method for manufacturing structural components formed from a thermoplastic material matrix loaded with fibers is described below, as well as a structural component manufactured by such a method for integration into a guide bearing.

[0010] The structural component can in particular form a cover or support for a suspension stop, a cover piece for a clutch stop, a cage for a bearing, or a part of a self-aligning bearing.

[0011] The process involves formulating a matrix comprising: - at least 30% by weight of recycled resin from a thermoplastic material recycling stream; and - less than 70% by weight of a reference resin from another sector of said thermoplastic material.

[0012] The reference resin is from a production line of the thermoplastic material, said virgin resin being chosen in particular to meet the mechanical requirements of the specifications of the structural component to be manufactured.

[0013] Advantageously, the matrix comprises at least 50% by weight of recycled resin, which makes it possible to reduce its environmental impact, and therefore the overall environmental impact of manufacturing the structural component in a significant way.

[0014] According to one embodiment, the recycled resin comes, in particular exclusively, from production scraps, i.e. from post-industrial recycling channels (PIR, for the English "Post Industrial Recycled resin").

[0015] Indeed, plastic materials from end-of-life or post-consumer recycled (PCR) channels often appear unsuitable for the specifications of the target industries, particularly the automotive industry, due to the wide variability of material sources and a lack of control over the mechanical, chemical, and / or thermal stresses these materials undergo in application. Thus, thermoplastic materials from these recycling channels generally exhibit reduced technical characteristics and robustness, as well as insufficient performance.

[0016] Advantageously, the recycled resin comes from a textile fiber recycling stream based on the thermoplastic material, in particular from textile fibers originating from production scraps, excluding out-of-tolerance production. Indeed, this solution makes it possible to reduce the amount of waste produced by this industry, and thus contribute to reducing its environmental impact.

[0017] According to one embodiment, the recycled resin is, in particular, exclusively obtained from a mechanical recycling process, notably by grinding production scraps textiles, because chemical recycling processes, particularly depolymerization and repolymerization, appear in most cases to be counterproductive to the ecological objective pursued.

[0018] The thermoplastic material constituting the matrix may in particular be based on polyamide, in particular chosen from polyamide 6 and / or polyamide 6.6, the fibers may be glass-based.

[0019] To ensure a compromise between the recycling of the thermoplastic material and the satisfaction of the requirements of the specifications of the industries concerned for structural components, the formulation of the thermoplastic matrix is ​​carried out so that the viscosity index of the matrix is ​​not less than 75% of the viscosity index of the reference resin.

[0020] Indeed, the viscosity index of a thermoplastic material is correlated with the average macromolecular chain length of the polymer constituting it, the latter largely determining the mechanical resistance of said material.

[0021] According to one embodiment, the viscosity index of the matrix is ​​measured according to the standard NF EN ISO 307, relating to the determination of the viscosity index of polyamides, this standard providing for the measurement of the viscosity index of a polyamide diluted in a suitable solvent, in particular based on sulfuric acid (H2SO4).

[0022] Alternatively, the viscosity index can be measured using other methods, in particular in the molten state of the thermoplastic material.

[0023] The process then involves, after formulation of the thermoplastic matrix: - to add fibers to the matrix to obtain a composite of filled thermoplastic material; - to injection mold said composite to obtain the structural components.

[0024] The composite may in particular comprise at least 20% by weight of fibers, and more particularly of the order of 25% by weight of glass fibers. Examples

[0025] During a first series of laboratory tests, three samples of thermoplastic resins intended for use in manufacturing suspension bump stop covers for motor vehicles were analyzed, including: - a 100% virgin “control 1” resin, exclusively from a thermoplastic material production line, based on polyamide 6.6 loaded with 35% glass fibers (PA66 GF35); - a first resin "test 1.1" and a second resin "test 1.2", containing respectively: • for the “test 1.1” resin: polyamide 6 reinforced with 40% glass fibers (PA6 GF40), the thermoplastic resin being composed of 30%

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[0030] by weight of recycled resin and 70% by weight of reference resin; • for the “test 1.2” resin: polyamide 6 loaded with 35% glass fibers (PA6 GF35), the thermoplastic resin being made up of 50% by weight of a recycled resin and 50% by weight of a reference resin. These three samples were prepared according to the NF EN 307 standard to measure the viscosity index of a polyamide. Thus, after determining the ash content by calcination for 90 minutes in a furnace at 650°C (according to ISO 3451-4), a vacuum conditioning process was carried out for 5 hours at 70°C, and each of these resins was dissolved in 96% sulfuric acid to prepare a solution with a concentration of 0.005 g / mL, which was then placed under stirring at room temperature for at least one hour. Filtration using a sintered glass filter funnel on the said solution then made it possible to remove the glass fibers contained in the resins, in order not to distort the viscosity index measurements. The following equipment was used to carry out these tests: - a HERAEUS vacuum oven; - a METTLER AE 200 precision balance; - a volumetric flask; - a sintered glass filter funnel; - a Ubbelohde 4-station PROLINE PV24 LAUDA viscometer with an internal capillary diameter of 1.03 mm; - a DLK25 LAUDA refrigeration generator. For each of the samples thus prepared, the flow times were determined in a bath thermostated at 25°C and the viscosity indices were calculated according to the standardized formula. The corresponding results are listed in the following table: Sample Average viscosity index (cmVg) Standard deviation (cmVg) Control 1 151.8 0.1 Test 1.1 130.8 0.7 Test 1.2 145 1.8 Following these tests, it was found that the viscosity indices of the test resins were no less than 75% of that of the "control 1" resin, with a loss of -14% for the "test 1.1" resin and a loss of only -4.5% for the "test" resin. 1.2.

[0031] These three resins were used to manufacture suspension bump stop covers, which were then assembled with serial parts to form complete suspension bump stops. These bump stops were tested on endurance, sealing, torque, and release test benches, and the results confirm that test resins 1.1 and 1.2, like control resin 1, meet all the technical requirements of the application.

[0032] Following the same protocol and with the same equipment, two samples of thermoplastic resins intended for use in manufacturing rolling body retention cages for motor vehicle bearings were then analyzed, including: - a 100% virgin “control 2” resin, exclusively from a thermoplastic material production chain, based on polyamide 6.6 loaded with 25% glass fibers (PA66 GF25); - a "test 2" resin containing 5% by weight of a reference resin and 95% by weight of a recycled resin, based on polyamide 6.6 loaded with 30% glass fibers (PA66 GF30).

[0033] For each of these samples, the calculated viscosity indices are listed in the following table: Sample Average viscosity index (cmVg) Standard deviation (cmVg) Control 2 145 0.4 Test 2 151.3 0.0

[0034] Following these tests, it was found that the viscosity index of the resin "Test 2" was superior to that of the "control 2" resin, with a gain of 4.3%.

[0035] Thus, these two series of tests have made it possible to demonstrate the possibility of replacing part of the thermoplastic resin of the matrix with an equivalent recycled resin, in suitable proportions, while retaining sufficient mechanical resistance properties to obtain structural components that meet the requirements of the specifications of the industries concerned.

Claims

Demands

1. A method for manufacturing structural components formed from a thermoplastic material matrix that is filled with fibers, said method comprising: - formulating a matrix comprising at least 30% by weight of a recycled resin from a recycling stream of said thermoplastic material and less than 70% by weight of a reference resin from another stream of said thermoplastic material, said formulation being carried out so that the viscosity index of the matrix is ​​not less than 75% of the viscosity index of the reference resin; - adding fibers to the matrix to obtain a filled thermoplastic material composite; - injection molding said composite to obtain the structural components.

2. A manufacturing process according to claim 1, characterized in that the recycled resin comes from production scraps.

3. A manufacturing process according to any one of claims 1 or 2, characterized in that the recycled resin is derived from a textile fiber recycling stream based on the thermoplastic material.

4. A manufacturing process according to any one of claims 1 to 3, characterized in that the reference resin is obtained from a production line of the thermoplastic material.

5. A manufacturing process according to any one of claims 1 to 4, characterized in that the recycled resin is obtained from a mechanical recycling process.

6. A manufacturing process according to any one of claims 1 to 5, characterized in that the matrix comprises at least 50% by weight of recycled resin.

7. A manufacturing method according to any one of claims 1 to 6, characterized in that the composite comprises at least 20% by weight of fibers.

8. A manufacturing method according to any one of claims 1 to 7, characterized in that the thermoplastic material is polyamide-based.

9. A manufacturing method according to any one of claims 1 to 8, characterized in that the fibers are glass-based.

10. Structural component manufactured by a process according to any one of claims 1 to 9, said component being integrated into a guide bearing.

11. Structural component according to claim 10, characterized in that it forms a cover or support for a suspension stop, a cover piece for a clutch stop, a cage for a bearing, a part of a self-aligning bearing.