Method for manufacturing a polypropylene composition with controlled fluidity

Abstract

The method for manufacturing a composition consists in bringing into contact a product containing mostly polypropylene having a controlled fluidity less than 10 g/10 min with highly fluid polypropylene and a polymer grafted with maleic anhydride.

Claims

1. Method for manufacturing a composition, comprising bringing into contact the following three components: a product containing mostly polypropylene having a controlled fluidity according to standard ISO 1133 (230 C., 2.16 kg) less than 10 g/10 min, present in an amount from 82% to 88% inclusive, by total weight of the composition, polypropylene having a controlled fluidity according to standard ISO 1133 (230 C., 2.16 kg) greater than 400 g/10 min, present in an amount from 7% to 13% inclusive, by total weight of the composition, and a polymer grafted with maleic anhydride, present in an amount from 2% to 8% inclusive, by total weight of the composition.

2. Method according to claim 1, said method further comprising two steps, performed in this order: bringing into contact the product containing mostly polypropylene and the polypropylene having a controlled fluidity according to standard ISO 1133 (230 C., 2.16 kg) greater than 400 g/10 min, and adding the polymer grafted with maleic anhydride.

3. Method according to claim 1, wherein the product containing mostly polypropylene and the polypropylene having a controlled fluidity according to standard ISO 1133 (230 C., 2.16 kg) greater than 400 g/10 min are brought into contact so as to obtain a first mixture and the polymer grafted with maleic anhydride is added in a second stage to this first mixture.

4. Method according to claim 1, wherein the polymer grafted with maleic anhydride is Styrene Ethylene Butadiene Styrene (SEBS).

5. Method according to claim 1, wherein the components are brought into contact in an extruder.

6. Method according to claim 1, wherein the components are brought into contact in a plasticating screw.

7. Method according to claim 1, wherein the product containing mostly polypropylene contains between 5% and 10% inclusive of polyethylene, by total weight of said product.

8. Method according to claim 1, wherein the product containing mostly polypropylene is obtained at least partly from recycling.

Description

(1) The invention will be better understood on reading the accompanying figures, which are given solely by way of example and not limiting in any way, in which:

(2) FIG. 1 is a schematic representation of a device according to one embodiment of the invention.

(3) FIG. 2 is a schematic representation of a device according to another embodiment of the invention.

(4) FIG. 3 is a flowchart of a method for manufacturing a part according to one embodiment of the invention.

(5) FIG. 4 is a flowchart of a method for manufacturing a part according to another embodiment of the invention.

(6) FIG. 5 is a perspective view of a part according to the invention manufactured by implementing the methods illustrated on the figures.

(7) We now refer to FIG. 1. FIG. 1 shows an extrusion device according to one embodiment of the invention and designated by the general reference 10.

(8) The device 10 forms an extruder and comprises a stator 12 forming a barrel 14 and a rotor 16 forming a worm screw system (single or twin screw) 18. The screw 18 can rotate freely in the barrel 14. The barrel 14 and the screw 18 define an annular space 19 in which a composition to be extruded is advancing.

(9) The device 10 comprises an upstream inlet 20 adapted for the introduction of compounds, in this case a product containing mostly polypropylene 26 of a controlled fluidity 9 g/10 min, highly fluid polypropylene 28 and SEBS grafted with maleic anhydride 29. The device 10 comprises a hopper 22 to introduce these compounds in the inlet 20. The device 10 also comprises an outlet 31 provided with an extrusion head 24.

(10) FIG. 2 shows a plasticating screw device according to another embodiment of the invention and designated by the general reference 31.

(11) The device 31 forms an injection plasticating screw and comprises a screw 32 surrounded by a barrel 33. The screw 32 can rotate freely in the barrel 33. The barrel and the screw define an annular space 34 in which a composition to be injected is advancing.

(12) The device 31 comprises an upstream inlet 35 adapted for the introduction of compounds, in this case a product containing mostly polypropylene 36 of a controlled fluidity 9 g/10 min, highly fluid polypropylene 37 and SEBS grafted with maleic anhydride 38. The device 31 comprises a hopper 39 to introduce these compounds in the inlet 35. The device 31 also comprises an outlet 40.

(13) In FIGS. 3 and 4, identical steps are designated by the same reference numbers.

(14) We will now describe one embodiment of the method for manufacturing a part illustrated on FIG. 5 with reference to FIG. 3 schematically illustrating the main steps of this method.

(15) In a step 100, a product containing mostly polypropylene is introduced in an extruder. In this step, a highly fluid polypropylene and a polymer grafted with maleic anhydride are also introduced.

(16) The product containing mostly polypropylene has a controlled fluidity according to standard ISO 1133 (230 C., 2.16 kg) less than 10 g/10 min and is added in an amount from 82% to 88% inclusive, by total weight of the composition. Alternatively, the product contains between 5% and 10% inclusive of polyethylene, by total weight of the product. Optionally, at least some of the product comes from recycling.

(17) The highly fluid polypropylene has a controlled fluidity according to standard ISO 1133 (230 C., 2.16 kg) greater than 400 g/10 min and is added in an amount from 7% to 13% inclusive, by total weight of the composition.

(18) The polymer grafted with maleic anhydride is added in an amount from 2% to 8% inclusive, by total weight of the composition. This polymer is for example SEBS.

(19) In a step 200, the manufactured composition is recovered. Then, in a step 202, the composition is introduced, for example by injection, in a mould and the part 30 is moulded. Lastly, in a step 204, the mould is cooled and the part 30 is extracted. The part 30 may subsequently be surface-treated. In particular, paint may be applied.

(20) Another embodiment of the method for manufacturing a part illustrated on FIG. 5 is described with reference to FIG. 4 schematically illustrating the main steps of this method.

(21) In a step 101, a product containing mostly polypropylene is introduced into a plasticating screw. In this step, a highly fluid polypropylene and a polymer grafted with maleic anhydride are also introduced.

(22) The product containing mostly polypropylene has a controlled fluidity according to standard ISO 1133 (230 C., 2.16 kg) less than 10 g/10 min and is added in an amount from 82% to 88% inclusive, by total weight of the composition. Alternatively, the product contains between 5% and 10% inclusive of polyethylene, by total weight of the product. Optionally, at least some of the product comes from recycling.

(23) The highly fluid polypropylene has a controlled fluidity according to standard ISO 1133 (230 C., 2.16 kg) greater than 400 g/10 min and is added in an amount from 7% to 13% inclusive, by total weight of the composition.

(24) The polymer grafted with maleic anhydride is added in an amount from 2% to 8% inclusive, by total weight of the composition. This polymer is for example SEBS.

(25) In a step 202, the composition is introduced, for example by injection, in a mould and the part 30 is moulded. Lastly, in a step 204, the mould is cooled and the part 30 is extracted. The part 30 may subsequently be surface-treated. In particular, paint may be applied.

(26) Example A of a Sample of a Composition According to the Invention:

(27) A composition was obtained by introducing into an extruder 85% of homopolymer polypropylene of fluidity 9 g/10 min, 10% of highly fluid homopolymer polypropylene and 5% of SEBS grafted with maleic anhydride. The extruded material was then granulated.

(28) A sample of the material so obtained is analysed conventionally by Fourier transform infrared (FTIR) spectroscopy. Briefly, 2 g of pellets of the material to be analysed are pressed at 200 C. to obtain a film about 150 m thick. The film is then studied by FTIR spectroscopy. The presence of maleic acid is associated with a very strong peak between 1700 and 1800 cm.sup.1, which corresponds to detection of the (CO) functions of the maleic acid present in the sample.

(29) Example B of a Sample of a Control Composition:

(30) A control composition was obtained by introducing into an extruder 87.5% of homopolymer polypropylene of fluidity 9 g/10 min and 12.5% of highly fluid homopolymer polypropylene. The extruded material was then granulated. A sample of material was analysed according to the same protocol as above. The FTIR spectroscopy results do not show a strong peak characteristic of the (CO) bonds of maleic acid between 1700 and 1800 cm.sup.1.

(31) Example C of a Sample of a Composition According to the Invention:

(32) A composition was obtained by introducing in the input silo of an injection press 85% of homopolymer polypropylene of fluidity 9 g/10 min, 10% of highly fluid homopolymer polypropylene and 5% of SEBS grafted with maleic anhydride. After injecting the mixture in a mould, a sample of the shaped material is then analysed according to the same protocol as above. The FTIR spectroscopy results show a strong peak between 1700 and 1800 cm.sup.1.

(33) Example D of a Sample of a Control Composition:

(34) A composition was obtained by introducing in the input silo of an injection press 87.5% of homopolymer polypropylene of fluidity 9 g/10 min and 12.5% of highly fluid homopolymer polypropylene. After injecting the mixture in a mould, a sample of the shaped material is analysed according to the same protocol as above. The FTIR spectroscopy results do not show a strong peak characteristic of the (CO) bonds of maleic acid between 1700 and 1800 cm.sup.1.

(35) Example E of a Sample of a Composition According to the Invention:

(36) A composition was obtained by introducing in an extruder 85% of a product containing mostly homopolymer polypropylene and 8% of polyethylene, the product having a fluidity of 9 g/10 min. 10% of highly fluid homopolymer polypropylene were added, as well as 5% of SEBS grafted with maleic anhydride. The extruded material was then granulated. A sample of the material obtained was analysed according to the same protocol as in the preceding examples. The FTIR spectroscopy results show a strong peak between 1700 and 1800 cm.sup.1.

(37) Example F of a Sample of a Control Composition:

(38) A composition was obtained by introducing in an extruder 87.5% of a product containing mostly homopolymer polypropylene and 8% of polyethylene, the product having a fluidity of 9 g/10 min. 12.5% of highly fluid homopolymer polypropylene was added. The extruded material was then granulated. A sample of the material obtained was analysed according to the same protocol as above. The FTIR spectroscopy results do not show a strong peak characteristic of the (CO) bonds of maleic acid between 1700 and 1800 cm.sup.1.

(39) Example G of a Sample of a Composition According to the Invention:

(40) A composition was obtained by introducing in the input silo of an injection press 85% of a product containing mostly homopolymer polypropylene and 8% of polyethylene, the product having a fluidity of 9 g/10 min. 10% of highly fluid homopolymer polypropylene and 5% of SEBS grafted with maleic anhydride were added. After injecting the mixture in a mould, a sample of the shaped material is analysed according to the same protocol as above. The FTIR spectroscopy results show a strong peak between 1700 and 1800 cm.sup.1.

(41) Example H of a Sample of a Control Composition:

(42) A composition was obtained by introducing in the input silo of an injection press 87.5% of a product containing mostly homopolymer polypropylene and 8% of polyethylene, the product having a fluidity of 9 g/10 min. 12.5% of highly fluid homopolymer polypropylene was added. After injecting the mixture in a mould, a sample of the shaped material is analysed conventionally according to the same protocol as above. The FTIR spectroscopy results do not show a strong peak characteristic of the (CO) bonds of maleic acid between 1700 and 1800 cm.sup.1.

(43) FIG. 5 shows the part 30. The part 30 forms an outer skin of a body part for motor vehicle, in this case a bonnet. The thickness of the part 30 is less than 3 mm. The compositions of examples A and C can be used to manufacture such a part. The same applies for compositions E and G. The parts manufactured using the latter compositions comply with the specifications imposed for parts of virgin material. However, with the compositions of examples B, D, F and H, it was not possible to manufacture parts complying with these specifications.

(44) The invention is not limited to the embodiments described and other embodiments will be clearly apparent to those skilled in the art.

(45) Thus, the composition can be manufactured using a device other than an extrusion device or a plasticating screw or with the components incorporated in a different order.

(46) When the method is carried out in two separate steps, the two steps can be performed in a different mixer.

(47) Parts other than body parts for motor vehicle and even parts for sectors other than the automotive industry can also be manufactured.

(48) The product containing mostly polypropylene may contain a polymer other than polyethylene.

(49) The polymer grafted with maleic anhydride is not limited to SEBS but may be another polymer such as polypropylene.