METHOD FOR WELDING TWO DIFFERENT POLYOLEFIN PLASTICS

Abstract

The invention relates to a method for welding two different polyolefin plastics using a primer, said primer containing at least one maleic anhydride graft polyolefin polymer. The invention also relates to correspondingly welded products.

Claims

1. A method for welding two different polyolefin plastics materials using a primer, wherein the primer contains at least one maleic acid anhydride-grafted polyolefin polymer.

2. The welding method according to claim 1, characterized in that the polyolefin plastics materials polyolefinic polymers can be selected from the group consisting of poly-alpha-olefin homopolymers based on ethene, propene and/or butene, in particular ethene homopolymers or propene homopolymers, and poly-alpha-olefin copolymers based on ethene, propene, 1-butene, 1-hexene and 1-octene, in particular ethylene/alpha-olefin and propylene/alpha-olefin copolymers, preferably copolymers of ethylene or propylene having 1-butene, 1-hexene, 1-octene or a combination thereof.

3. The welding method according to claim 1, characterized in that the first joining part is a polyethylene-plastics material, in particular a HD polyethylene, MD polyethylene, LD polyethylene, UHMW polyethylene or LLD polyethylene plastics material, and the second joining part is a polypropylene plastics material.

4. The welding method according to claim 1, characterized in that the at least one maleic acid anhydride-grafted polyolefin polymer is selected from maleic acid anhydride-grafted polyethylenes or maleic acid anhydride-grafted polypropylenes.

5. The welding method according to claim 1, characterized in that the primer contains a mixture of maleic acid anhydride-grafted polyolefins, in particular a mixture of at least one maleic acid anhydride-grafted polyethylene and at least one maleic acid anhydride-grafted polypropylene.

6. The welding method according to claim 5, characterized in that the at least the ratio of the different maleic acid anhydride-grafted polyolefin polymers, in particular the ratio of maleic acid anhydride-grafted polyethylene to maleic acid anhydride-grafted polypropylene is 0.2:1 to 20:1, in particular 0.5:1 to 10:1, preferably 1:1 to 5:1, particularly preferably 1.5:1 to 3:1.

7. The welding method according to claim 1, characterized in that the at least one maleic acid anhydride-grafted polyolefin or the mixture thereof has a maleic acid anhydride content of from 0.01-15 wt. %, in particular 0.02-10 wt. %, preferably 0.05-8 wt. %, particularly preferably 0.5-5 wt. %, based on the polyolefin polymer or the mixtures thereof.

8. The welding method according to claim 1, characterized in that at least some of the maleic acid anhydride groups of the polyolefin polymer are reacted with amines, in particular aliphatic amines, preferably aliphatic diamines, such as hexamethylenediamine; preferably 5-100 mol %, in particular 10-80 mol %, preferably 20-70 mol % of the maleic acid anhydride groups of the polymer according to the invention or the mixture thereof.

9. The welding method according to claim 1, characterized in that the primer contains, in addition to the maleic acid anhydride-grafted polyolefin polymer, at least one further polymer that is compatible with at least one of the two plastics materials to be welded.

10. An item produced in accordance with a welding method according to claim 1.

Description

EMBODIMENTS

[0085] Materials used and abbreviations: [0086] PP=polypropylene [0087] PE=polyethylene [0088] MAH=maleic acid anhydride [0089] Primer 1=PE-(MD)-(MAH) with MFR (190 C.; 21.6 Kg)=12-22 and PP-MAH with [0090] MFR (230 C.; 2.16 Kg)=7-12 in the ratio of 1:1 w/w compounded [0091] Primer 2=PE-(MD)-(MAH) with MFR (190 C.; 21.6 Kg)=12-22 and PP-MAH with [0092] MFR (230 C.; 2.16 Kg)=7-12 in the ratio of 2:1 w/w compounded [0093] Primer 3=PE-(MD)-(MAH) with MFR (190 C.; 21.6 Kg)=12-22 and PP-MAH with [0094] MFR (230 C.; 2.16 Kg)=7-12 in the ratio of 4:1 w/w compounded [0095] Primer 4=PE-(MD)-(MAH) with MFR (190 C.; 21.6 Kg)=12-22 and Infuse [0096] 9808.15 in the ratio of 2:1 w/w compounded (DOW Chemical Company) [0097] Test fuel composition:

TABLE-US-00001 FAM B vol.-% Methanol 15.00 Water 0.50 Toluene 42.25 Isooctane 25.35 Dilsobutylene 12.68 Ethanol 4.23 Total 100.00
IR: Infrared welding; VIB: Vibration welding;

[0098] Production of the test specimens:

[0099] In order to produce the primer polymers, PE-(MD)-MAH and PP-MAH polymer granulate was premixed in different ratios, melted in the plasticizing unit of an injection molding machine (230 C.) and compounded and processed to form plates of 130 mm70 mm3 mm. The composition of the primers can be found in the following table in Kg.

TABLE-US-00002 Primer no. PE-(MD)-MAH PP-MAH Ratio PE-MAH:PP-MAH w/w 1 5 5 1:1 2 10 5 2:1 3 8 2 4:1

[0100] The plates were milled down to 130 mm68 mm3 mm and the 130 mm3 mm surface was welded, until impact and by means of IR and vibration welding, to PE and PP in each case having the same surface area. 24 hours after welding, 8 mm was milled off from both ends of the plate, the rest of the plate was halved (cut perpendicular to the joining plane) and was tested by means of a tensile test at room temperature and at a testing speed of 50 mm/s. The following table gives the results for each combination of primer, plastics material and welding method used, together with the tensile strength (in MPa) which was achieved for the welded test specimens:

TABLE-US-00003 Tensile Welding strength Polymer 1 Polymer 2 Primer no. method MPa PE Lupolen GX5038BG25 PP Sabic VIB 11.12 4935 PE Lupolen GX5038BG25 PP Sabic IR 10.30 4935 PE Lupolen GX5038BG25 2 VIB 17.28 PE Lupolen GX5038BG25 2 IR 18.81 PP Sabic 4935 2 VIB 18.05 PP Sabic 4935 2 IR 20.59 PE Lupolen GX5038BG25 3 VIB 16.60 PP Sabic 4935 3 VIB 14.94

[0101] The results show that the samples welded using Primer no. 2 exhibit outstanding tensile strength. In this case the (Primer no. 2) PE and (Primer no. 2) PP composite approximately achieves the basic PE strength of 19.13 MPa. Thus, using the primer, particularly rigid welding of the plastics materials PE and PP can be achieved.

[0102] The plates that were IR welded in the same way were stored for 14 days at 25 C. in the test fuel FAM-B in order to test the media resistance of the welded connection. The tensile strengths of the welded and milled plates at room temperature at a testing speed of 50 mm/s are shown in the following table.

TABLE-US-00004 Tensile strength Polymer 1 Polymer 2 Primer no. Aging MPa PE Lupolen PP Sabic 14 days at 25 C. in 0.51 GX50386G25 4935 FAM-B PE Lupolen 2 14 days at 25 C. in 12.86 GX5038BG25 FAM-B PP Sabic 2 14 days at 25 C. in 11.51 4935 FAM-B

[0103] The results show outstanding aging resistance of the welded samples with respect to the test fuel FAM-B.

[0104] In order to test the PE/primer-polymer/PP composite having a separate primer layer, plates of 130 mm3 mm of Primer 2 were IR welded to PP Sabic 4935. The primer plates were then milled down such that 0.5 mm of the primer layer remained on the PP plate, and the primer layer was welded to PE Lupolen GX5038BG25 plates also of 130 mm3 mm. A structure of PE/(Primer 2)/PP was thus achieved.

[0105] After 24 hours, the IR welded polymers were tested in the tensile test as described above at room temperature at 50 mm/s.

[0106] The samples exhibited outstanding tensile strength of 15.14 MPa. Outstanding strength of Primer 2 could thus be obtained when welding PE and PP.

Reaction of PE-MAH and PP-MAH with Hexamethylenediamine:

[0107] PE-MAH and PP-MAH were reacted in a solution with hexamethylenediamine. The amounts of reactant and solvent used are listed in the following table.

TABLE-US-00005 Primer no. PE-MAH PP-MAH Hexamethylenediamine Xylene 5 17.5 g 17.5 g 1.0 g 315 ml 6 10.0 g 10.0 g 0.5 g 180 ml 7 10.0 g 10.0 g 0.8 g 180 ml

[0108] PE-MAH and PP-MAH were dissolved in xylene at 130 C. in a 500-ml two-necked flask, and the amine, dissolved in 20 ml xylene, was then slowly introduced, drop-by-drop, by means of a dropping funnel. After 2.5 hours under reflux, the reaction mixture was poured into 500 ml water, filtered by means of a Bchner funnel and washed a number of times with small amounts of acetone. Colorless solids were obtained after drying in a vacuum.

[0109] The primer polymers obtained were melted down on PE Lupolen GX5038BG25 and on PP Sabic 4935 by means of warm gas, and the adherence was tested for quality after cooling. Primers 5, 6 and 7 exhibited outstanding adherence with respect to PE and to PP.