METHOD FOR WELDING TWO POLYAMIDE PLASTICS

Abstract

The present invention relates to a method for welding two polyamide plastics using a primer, the primer containing at least one polymer synthesized from at least one maleic anhydride or maleic anhydride derivative. The invention also relates to correspondingly welded products.

Claims

1. A method for welding two polyamide plastics using a primer, the primer containing at least one polymer synthesized from at least one maleic anhydride or maleic anhydride derivative.

2. The welding method according to claim 1, characterized in that the polyamide plastics are selected from the group consisting of polyamide 6, polyamide 6.6, polyamide 6.10, polyamide 6.12, polyamide 10.10, polyamide 11, polyamide 12, polyamide 10.12, polyphthalamides, optically transparent polyamides or mixtures based on said polyamides, in particular the first join partner is selected from the polyamide plastics from the group consisting of polyamide 6, polyamide 6.6, polyamide 6.10, polyamide 6.12 and/or the second join partner is selected from the polyamide plastics from the group consisting of polyamide 10.10, polyamide 11, polyamide 12.

3. The welding method according to claim 1, characterized in that the polymer is a copolymer consisting of at least one styrene or styrene derivative and at least one maleic anhydride or maleic anhydride derivative.

4. The welding method according to claim 3, characterized in that the at least one copolymer has a molar ratio of styrene to maleic anhydride of from 1:0.01 to 1:2, preferably 1:0.05 to 1:1, particularly preferably 1:0.1 to 1:0.3.

5. The welding method according to claim 1, characterized in that the at least one polymer has a maleic anhydride content of 0.1-50 wt. %, in particular 0.5-40 wt. %, preferably 4-30 wt. %, particularly preferably 8-26 wt. %, based on the polymer.

6. The welding method according to claim 1, characterized in that the at least one polymer of the primer has a glass transition temperature Tg of more than 30 C., in particular more than 80 C., particularly preferably more than 100 C.

7. The welding method according to claim 1, characterized in that the at least one polymer has a weight-average molecular weight Mw in the range of from 5000-2000000 g/mol, in particular from 50000-1000000 g/mol, preferably from 100000-500000 g/mol.

8. The welding method according to claim 1, characterized in that the primer contains, in addition to the first polymer, at least one further polymer that is compatible with at least one of the two plastics materials to be welded, preferably at least one polyamide polymer.

9. The welding method according to claim 1, characterized in that the primer contains at least one solvent, in particular at least one organic solvent, the primer preferably having a solvent content of 10-90 wt. %, in particular 50-85 wt. %, particularly preferably 60-80 wt. %, based in each case on the total weight of the primer.

10. The welding method according to claim 9, characterized in that the at least one solvent has a vapor pressure at 20 C. of from 1 to 600 hPa, in particular 2 to 200 hPa, particularly preferably 5 to 20 hPa, preferably the solvent is selected from the group of tetrahydrofuran, methyl isobutyl ketone (MIBK), cyclohexanone and mixtures thereof.

11. An object produced according to a welding method according to claim 1.

Description

Embodiments

[0086] PA=polyamide [0087] PA 6=Polycaprolactam [0088] PA12=Polylauryl lactam [0089] MAH=maleic anhydride [0090] MIBK=methyl isobutyl ketone [0091] CH=cyclohexanone [0092] PS=polystyrene having Mw=192000 g/mol [0093] Copolymer SM1=styrene-maleic anhydride copolymer having 15 wt. % MAH and Mw=170000 g/mol [0094] Copolymer SM2=styrene-maleic anhydride copolymer having 8 wt. % MAH and Mw=250000 g/mol [0095] Copolymer SM3=poly(styrene-co-maleic acid) partially isobutyl/methyl esterified having [0096] Mw=180000 g/mol [0097] US=Ultrasonic welding

[0098] Preparation of primer 1-4:

In order to prepare the primers, the polymer components were dissolved in solvent at 90 C., by mechanical stirring, and left to cool to 20 C. The composition of the primers in g can be found in the following table.

TABLE-US-00001 Primer 1 2 3 4 PS 30 SM1 30 SM2 30 SM3 32.5 MIBK 50 50 50 CH 20 20 20 67.5

[0099] General test execution:

An AWS (American Welding Society) test specimen without an energy director. The lower half of the test specimen consists of a base plate of 50 mm12.4 mm2.8 mm having a centrally arranged, perpendicular web 9.4 mm high and 2.5 mm wide (T-shape). The upper half of the test specimen consists of a base plate of 50 mm12.4 mm2.8 mm having a centrally arranged, perpendicular web 3 mm high and 2.5 mm wide (T-shape). A double T-shape is achieved by welding the surfaces of the central webs.

[0100] The primers were applied, at room temperature, to the surface (50 mm2.5 mm) of the lower half of the test specimen of an AWS (American Welding Society) test specimen, without an energy director, of the PA12 plastics material to be welded. Subsequently, the primer was dried of solvent for 24 hours at room temperature. After drying, the thickness of the primer was approximately 0.2 mm. Subsequently, the upper half of the test specimen, having a geometry of 50 mm2.5 mm, was welded edge-to-edge to the 50 mm2.5 mm surface of the lower half of the test specimen. The tensile strength was determined after 24 hours and at a traction speed of 5 mm/s. The following table in each case shows the tensile strength (in MPa) that was able to be achieved, at room temperature, for the welded test specimens, for the combination of the primer with the plastics materials used:

[0101] Ultrasonic weldina:

TABLE-US-00002 Tensile strength Primer Polymer 1 Polymer 2 MPa (US) No primer PA12 Grilamid PA6 Grilamid 4.06 TRS 90 TR30LS 1 PA12 Grilamid PA6 Grilamid 3.91 TRS 90 TR30LS 2 PA12 Grilamid PAG Grilamid 6.43 TRS 90 TR30LS 3 PA12 Grilamid PA6 Grilamid 7.73 TRS 90 TR30LS 4 PA12 Grilamid PA6 Grilamid 15.26 TRS 90 TR30LS

[0102] The results show that the samples welded using a primer containing MAH exhibit excellent tensile strength. The tests with no primer or with a polystyrene as the primer do not have sufficient strength. It can also be seen that the primer layer comprising cyclohexanone as the solvent does not have any bubbles after the solvent has evaporated. However, the time required for the solvent to evaporate increases as the cyclohexanone content in the formulation increases.