Method for producing structural components made of recycled thermoplastic material

Abstract

The invention relates to a method for producing structural components formed of a thermoplastic material matrix that is filled with fibers, said method making provision for: formulating a matrix comprising at least 30% by weight of a recycled resin obtained from a recycle stream of said thermoplastic material and less than 70% by weight of a reference resin obtained from another stream of said thermoplastic material, said formulation being carried out such 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.

Description

[0001] DESCRIPTION

[0002] Title: Manufacturing process for structural components made from recycled thermoplastic material

[0003] The invention relates to a method for manufacturing structural components formed from a thermoplastic material matrix which is loaded with fibers, as well as to a structural component manufactured by such a method for integration into a guide bearing.

[0004] The use of thermoplastic materials is very widespread in the manufacture of rolling components or guide bearings, particularly for their physicochemical properties but also for reasons of cost and weight.

[0005] To meet the requirements of the specifications of the industries concerned, particularly the automotive industry, the thermoplastic materials used are generally virgin products, i.e. new, directly from a production line based on petroleum derivatives.

[0006] These materials have the disadvantage of being rarely, if at all, recycled at the end of their life, which has a significant impact on the environment.

[0007] The invention aims to improve the prior art by proposing a method for manufacturing structural components from a thermoplastic material which uses a resin derived 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.

[0008] To this end, according to a first aspect, the invention proposes a method for manufacturing structural components formed from a matrix of thermoplastic material which is loaded with fibers, said method providing for: - formulating a matrix comprising at least 30% by weight of a recycled resin from a recycling channel of said thermoplastic material and less than 70% by weight of a reference resin from another channel 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;

[0009] - adding fibers to the matrix to obtain a composite of loaded thermoplastic material;

[0010] - injection molding said composite to obtain the structural components.

[0011] According to a second aspect, the invention provides a structural component manufactured by such a method, said component being integrated into a guide bearing.

[0012] Other objects and advantages of the invention will appear in the following description, which develops different particular embodiments.

[0013] A method of manufacturing structural components formed from a thermoplastic material matrix filled with fibers is described below, as well as a structural component manufactured by such a method for integration into a guide bearing.

[0014] The structural component may in particular form a cover or support for a suspension stop, a covering part for a clutch stop, a bearing cage, or even a part of a self-aligning bearing.

[0015] The method provides for formulating a matrix comprising:

[0016] - at least 30% by weight of a recycled resin from a thermoplastic material recycling channel; and

[0017] - less than 70% by weight of a reference resin from another sector of said thermoplastic material. The reference resin comes from a sector of production 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.

[0018] 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 significantly.

[0019] According to one embodiment, the recycled resin comes, in particular exclusively, from production waste, i.e. from post-industrial recycling channels (PIR, for “Post Industrial Recycled resin”).

[0020] Indeed, plastic materials from end-of-life or post-use recycling (PCR, for "Post Consumer Recycled resin") channels most often appear unsuitable for the requirements of the specifications of the targeted industries, particularly the automotive industry, due to a great variability of material sources, as well as a lack of control over the stresses, particularly mechanical, chemical and / or thermal, undergone by these materials in application. Thus, thermoplastic materials from these recycling channels generally have reduced technical characteristics and robustness, as well as insufficient performance.

[0021] Advantageously, the recycled resin comes from a textile fiber recycling chain based on thermoplastic material, in particular textile fibers from production scraps, excluding production outside tolerances. Indeed, this solution makes it possible to reduce the quantity of waste produced by this industry, and thus contribute to reducing its impact on the environment.

[0022] According to one embodiment, the recycled resin is, in particular, exclusively derived from a mechanical recycling process, in particular by grinding textile production waste, because chemical recycling processes, in particular by depolymerization and repolymerization, appear in most cases to be counterproductive for the desired ecological objective.

[0023] 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 being able to be based on glass.

[0024] To ensure a compromise between the recycling of the thermoplastic material and meeting the specifications requirements 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. In particular, the viscosity index of the matrix is ​​thus defined as a percentage value of the viscosity index of the reference resin conventionally used in the application.

[0025] This definition is relevant insofar as the viscosity index of a thermoplastic material is correlated with the average length of the macromolecular chain of the polymer constituting it, the latter largely determining the mechanical resistance of said material.

[0026] According to one embodiment, the viscosity index of the matrix is ​​measured according to standard NF EN ISO 307, relating to the determination of the viscosity index of polyamides, this standard providing for measuring the viscosity index of a polyamide diluted in a suitable solvent, in particular based on sulfuric acid (H2SO4).

[0027] Alternatively, the viscosity index can be measured from other methods, including in the molten state of the thermoplastic material.

[0028] The process then provides, after formulation of the thermoplastic matrix: - adding fibers to the matrix to obtain a composite of loaded thermoplastic material;

[0029] - to injection mold said composite to obtain the structural components.

[0030] The composite may in particular comprise at least 20% by weight of fibers, and more particularly around 25% by weight of glass fibers.

[0031] Examples

[0032] In a first series of laboratory tests, three samples of thermoplastic resins intended for use in the manufacture of suspension bump stops for motor vehicles were analyzed, including:

[0033] - 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);

[0034] - a first resin “test 1.1” and a second resin “test 1.2”, containing respectively: o for the resin “test 1.1”: polyamide 6 filled with 40% glass fibers (PA6 GF40), the thermoplastic resin being made up of 30% by weight of a recycled resin and 70% by weight of a reference resin; o for the resin “test 1.2”: polyamide 6 filled 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.

[0035] 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 the ISO 3451-4 standard), a vacuum conditioning of 5 hours at 70°C was carried out and each of these resins was dissolved in 96% sulfuric acid so as to prepare a solution with a concentration of 0.005 g / mL, which was then stirred at room temperature for at least one hour.

[0036] Filtration carried out using a sintered glass filter funnel on the said solution then made it possible to eliminate the glass fibres contained in the resins, so as not to distort the viscosity index measurements.

[0037] To carry out these tests, the following equipment was used:

[0038] - a HERAEUS vacuum oven;

[0039] - an AE 200 precision scale from METTLER;

[0040] - a measuring flask;

[0041] - a sintered glass filter funnel;

[0042] - a LAUDA PROLINE PV24 4-station Ubbelohde viscometer with an internal capillary diameter of 1.03 mm;

[0043] - a LAUDA DLK25 refrigeration generator.

[0044] For each of the samples thus prepared, the flow times were determined in a thermostatically controlled bath at 25°C and the viscosity indices calculated according to the standard formula. The corresponding results are listed in the following table:

[0045] At the end of these tests, it was found that the viscosity indices of the test resins are not 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 1.2” resin. Thus, these tests make it possible to determine that the selected recycled resins can be used to implement a manufacturing process according to the invention. In particular, the recycled resins used were finely selected from the wide variety of available sources, in particular on the basis of their viscosity index, so as to guarantee a sufficient polymer chain length to satisfy the level of mechanical strength required in the application.

[0046] 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 unclipping 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.

[0047] Following the same protocol and with the same equipment, two samples of thermoplastic resins intended to be used to manufacture rolling body retention cages for motor vehicle bearings were then analyzed, including:

[0048] - a 100% virgin “control 2” resin, exclusively from a thermoplastic material production line, based on polyamide 6.6 loaded with 25% glass fibers (PA66 GF25);

[0049] - 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).

[0050] For each of these samples, the calculated viscosity indices are listed in the following table: Following these tests, it was found that the viscosity index of the “test 2” resin was higher than that of the “control 2” resin, with a gain of 4.3%.

[0051] Thus, these two series of tests made it possible to demonstrate the possibility of replacing part of the thermoplastic resin in the matrix with an equivalent recycled resin, in suitable proportions, while retaining sufficient mechanical resistance properties to obtain structural components meeting the requirements of the specifications of the industries concerned.

Claims

CLAIMS 1. A method of manufacturing structural components formed from a matrix of thermoplastic material which is loaded with fibers, said method providing for: - formulating a matrix comprising at least 30% by weight of a recycled resin from a recycling channel of said thermoplastic material and less than 70% by weight of a reference resin from another channel 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.

2. Manufacturing method according to claim 1, characterized in that the recycled resin comes from production scraps.

3. Manufacturing method according to one of claims 1 or 2, characterized in that the recycled resin comes from a textile fiber recycling channel based on the thermoplastic material.

4. Manufacturing method according to any one of claims 1 to 3, characterized in that the reference resin comes from a thermoplastic material production line.

5. Manufacturing method according to any one of claims 1 to 4, characterized in that the recycled resin comes from a mechanical recycling process.

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

7. 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. Manufacturing method according to any one of claims 1 to 7, characterized in that the thermoplastic material is based on polyamide.

9. 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 method according to any one of claims 1 to 9, said component being integrated in a guide bearing.

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

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