Method for welding polyamide and poly(meth)acrylate plastics

Abstract

The invention relates to a method for welding a polyamide plastic and a poly(meth)acrylateparticularly a polymethyl methacrylateplastic using a primer, said primer containing at least one copolymer synthesised from at least one styrene or styrene derivative and at least one maleic anhydride or maleic anhydride derivative. The invention also relates to correspondingly welded products.

Claims

1. A method for welding polyamide plastics and poly(meth)acrylate plastics, comprising: providing a polyamide plastic substrate having a surface defining a joining zone on a portion of that surface, providing a poly(meth)acrylate plastic substrate having a surface defining a joining zone on a portion of that surface, applying a primer onto the joining zone surface of at least one of the polyamide plastic substrate and the poly(meth)acrylate plastic substrate, positioning the polyamide plastic substrate joining zone adjacent the poly(meth)acrylate substrate joining zone so that the primer is disposed between the joining zones, and welding the polyamide plastic substrate joining zone to the poly(meth)acrylate substrate joining zone, wherein the primer contains at least one copolymer synthesized from at least one styrene or styrene derivative and at least one maleic anhydride or maleic anhydride derivative.

2. The welding method according to claim 1, wherein the polyamide plastic is 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 and mixtures based on said polyamides.

3. The welding method according to claim 1, wherein the poly(meth)acrylate plastic is made up of 50 to 100 wt. % methyl methacrylate, the poly(meth)acrylate plastic has molar mass (weight average Mw) of more than 50000 g/mol, and/or the poly(meth)acrylate plastic is a poly(methylmethacrylate) plastic.

4. The welding method according to claim 1, wherein the at least one copolymer has a molar ratio of styrene to maleic anhydride of from 1:0.01 to 1:2.

5. The welding method according to claim 1, wherein the at least one copolymer comprises a monomer selected from the group consisting of acrylates and methacrylates.

6. The welding method according to claim 1, wherein the at least one copolymer has a maleic anhydride content of 0.1-50 wt. %, based on the copolymer.

7. The welding method according to claim 1, wherein the at least one copolymer of the primer has a glass transition temperature Tg of more than 30 C.

8. The welding method according to claim 1, wherein the at least one copolymer has a weight-average molecular weight Mw in the range of from 5000-2000000 g/mol.

9. The welding method according to claim 1, wherein the primer contains, in addition to the at least one copolymer, at least one further polymer that is compatible with at least one of the polyamide plastic or the poly(meth)acrylate plastic to be welded.

10. The welding method according to claim 1, wherein the primer contains 10-90 wt. % of organic solvent, based on the total weight of the primer.

11. The welding method according to claim 10, wherein the organic solvent has a vapor pressure at 20 C. of from 1 to 600 hPa, and the organic solvent is selected from the group consisting of tetrahydrofuran, methyl isobutyl ketone (MIBK), cyclohexanone and mixtures thereof.

12. An object produced according to the welding method according to claim 1.

13. The welding method according to claim 1, wherein the step of welding comprises hot gas welding, hot plate welding, ultrasonic welding, high frequency welding, friction welding, laser welding, infrared welding, thermal contact welding, thermal pulse welding, microwave welding, induction welding or a combination thereof.

14. The welding method according to claim 1, wherein the step of welding comprises ultrasonic welding, friction welding, infrared welding or a combination thereof.

15. The welding method according to claim 1, wherein the welded polyamide plastic substrate joining zone and the poly(meth)acrylate substrate joining zone form a weld seam.

16. The welding method according to claim 1, wherein the polyamide plastic substrate is welded to the poly(meth)acrylate substrate only in their respective joining zones.

17. The welding method according to claim 1, wherein the step of welding comprises heating the polyamide plastic substrate and the poly(meth)acrylate plastic substrate only in their respective joining zones.

18. The welding method according to claim 1, wherein the primer is an aqueous dispersion or emulsion.

Description

EMBODIMENTS

(1) Materials used and abbreviations:

(2) PA=polyamide

(3) PA 6=polycaprolactam, Durethan BKV30

(4) PA 6.6=poly-(N,N-hexamethylene adipamide); Ultramid A3K

(5) PMMA=poly(methylmethacrylate)

(6) PMMA 1=Polycasa G87E

(7) PMMA 2=Plexiglas 8N

(8) MAH=maleic anhydride

(9) Peroxide=Luperox A75 (75 wt. % benzoyl peroxide, 25 wt. % water)

(10) THF=Tetrahydorfuran

(11) MIBK=methyl isobutyl ketone

(12) CH=cyclohexanone

(13) Copolymer SM1=styrene-maleic anhydride copolymer having 15 wt. % MAH and Mw 170000 g/mol

(14) Copolymer SM2=styrene-maleic anhydride copolymer having 8 wt. % MAH and Mw 250000 g/mol

(15) Copolymer SM3=styrene-maleic anhydride copolymer having 26 wt. % MAH and Mw 180000 g/mol

(16) Copolymer SM4=styrene-maleic anhydride copolymer; Mw 180000 g/mol and partially esterified with isobutyl/methyl

(17) IR: infrared welding; IR-FR: infrared/friction welding; US: ultrasonic welding

(18) Preparation of the Styrene-Maleic Anhydride-Methyl Methacrylate Copolymers SMA 5 and 6

(19) TABLE-US-00001 Mixing ratio styrene/methyl methacrylate/maleic Methyl Maleic anhydride Styrene methacrylate anhydride Peroxide Copolymer [mol/mol/mol] in g in g in g in wt. % SMA 5 1/1/1 6.25 6.01 5.93 0.1 SMA 6 1/1/0.2 8.33 7.98 1.54 0.1

(20) Copolymers were synthesized from styrene, methyl methacrylate and maleic anhydride, according to the above table, by means of bulk radical polymerization. All the starting materials and the initiator were weighed into a 1 liter 2-neck flask and heated very slowly in an oil bath and while being stirred vigorously by a magnetic stirrer, to an oil bath temperature of 95 C. After a solid compound had formed, said compound was heated to 140 C. for 4 hours. The reaction product was dissolved in 100 ml THF and, after being cooled to 20 C., was precipitated in 300 ml methanol. After filtration using a Buchner funnel, the resulting copolymers were freed of residual solvent under vacuum. Colorless solids were obtained.

(21) Preparation of Primers 1-10:

(22) In order to prepare the primers, the polymer components were dissolved in solvent, by mechanical stirring, and degassed at 25 C. The composition of the primers in g can be found in the following table.

(23) TABLE-US-00002 Primer 1 2 3 4 5 6 7 8 9 10 SM1 50 105.27 105.27 SM2 105.27 SM3 105.27 SM4 17.5 17.5 SMA5 10 SMA6 10 PMMA 1 50 90.04 PMMA 2 90.04 90.04 90.04 15 15 THF 67.5 40 40 MIBK 93.36 93.36 364.69 364.69 364.69 364.69 CH 35.84 35.84 140 140 140 140 67.5
Preparation of Primers 11 to 13:

(24) Copolymers were synthesized from styrene, methyl methacrylate and maleic anhydride, according to the above table, by means of emulsion polymerization in water. The respective ratios of the monomers to one another can be found in the following table.

(25) TABLE-US-00003 Mixing ratio styrene/methyl methacrylate/maleic Styrene Methyl Maleic Primer anhydride [mol/mol/mol] in g methacrylate in g anhydride in g 11 1/2/1 24.5 47.0 23.0 12 1/1/0.2 42.9 42.9 8.6 13 1/1/0.1 14.6 14.0 1.4

(26) Primers 11 and 12 were prepared in such a way as to result in an emulsion having a water content of 52 wt. % and 0.5 wt. % of the surfactant Disponil SDS G. For primer 13, the water was removed and the resulting copolymer was dissolved in 75 wt. % THF.

(27) It was possible to prepare dispersions of the copolymers and/or primers that, at room temperature, did not exhibit any sedimentation for several weeks.

(28) General Test Execution:

(29) The primers were applied, at room temperature, to the surface (130 mm3 mm) of the lower half of the PA plastics material to be welded (deviations therefrom are marked accordingly in the following table). 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. The pre-dried plastics components having a geometry of 130 mm68 mm3 mm were subsequently welded end-to-end to the 130 mm3 mm surface. The tensile strength was determined at room temperature and at a traction speed of 5 mm/s. The following tables in each case show the tensile strength (in MPa) that was able to be achieved for the welded test specimens, for the combination of the primer with the plastics materials and welding method used:

(30) IR and IR-FR Welding:

(31) TABLE-US-00004 Polymer combination (welding method) PA6 + PMMA1 PA6 + PMMA1 PA6 + PMMA2 PA6 + PMMA2 Primer (IR) (IR-FR) (IR) (IR-FR) No 0 0 0 0 primer 1 0 1.87 0 1.58 (comparison) 2 6.01 5.77 3 10.56 10.67 10.94 12.01 7 Application on PMMA; 13.57 9 6.33 10 12.43 11.73 12 Application on both parts to be joined; 5.69 13 Application on both parts to be joined; 15.51

(32) Ultrasonic Welding:

(33) TABLE-US-00005 Polymer combination (welding method) Primer PA6 + PMMA2 (US) No primer 1.15 4 8.4 5 9.5 6 9.7 7 Application on PA; 6.11 8 PA12 + PMMA2 7.59 10 5.34 11 6.46 12 4.06 13 8.44

(34) The results show that the samples welded using a primer exhibit excellent tensile strength. It can also be seen that the primers comprising a mixture of cyclohexanone and methyl isobutyl ketone as the solvent do not have any bubbles after the solvent has evaporated. However, the time required for the solvent to evaporate increases with cyclohexanone.

(35) Ageing Test of Welded Samples:

(36) For the ageing test, the PA plastics substrate was coated with primer 7, as carried out above. Subsequently, the plastics materials PA 6.6 and PMMA 2 were connected by means of manual hot plate welding at a temperature of approximately 280 C. and a heating time of 15 seconds for the PMMA and 45 seconds for the PA 6.6. For the ageing test, the samples were then stored at a temperature for a specified time and subsequently, following further storage at room temperature for 24 hours, the tensile strength test was carried out at room temperature. The results are as follows:

(37) TABLE-US-00006 Storage condition 8 days 24 50 C. and hours 24 hours 24 hours 8 days 80% atmospheric 20 C. 50 C. 70 C. 50 C. humidity Tensile 17.08 13.47 11.33 12.92 12.41 strength in MPa

(38) The results show excellent ageing stability of the welded samples.