Adhesion promoter compositions and primer compositions for metal-plastic hybrid components

Abstract

The invention provides an adhesion promoter composition comprising at least one polymer A selected from at least one epoxy resin-phenol resin precondensate, a mixture of at least one epoxy resin-phenol resin precondensate and epoxy resins, a mixture of epoxy resins and phenol resins, polyamide resins and mixtures thereof, and at least one copolyamide-based hotmelt adhesive. Additionally described is a primer composition comprising at least one polymer B selected from saturated polyester resins, epoxy-phenol resin precondensates, mixtures of epoxy resins and phenol resins, and mixtures thereof, at least one crosslinker resin selected from the group consisting of melamine resins, blocked isocyanate resins and mixtures thereof, at least one catalyst, and at least one copolyamide-based hotmelt adhesive.

Claims

1. A primer composition comprising: (a) 8%-23% by weight of at least one polymer B selected from the group consisting of saturated polyester resins, epoxy-phenol resin precondensates, mixtures of epoxy resins and phenol resins, and mixtures thereof; (b) 1.5%-15% by weight of at least one crosslinker resin selected from the group consisting of melamine resins, blocked isocyanate resins and mixtures thereof; (c) 10%-40% by weight of at least one copolyamide-based hotmelt adhesive comprising a copolyamide, at least one block isocyanate, and at least one epoxy component; and (d) 30%-80% by weight of at least one organic solvent, based in each case on the total weight of the primer, where the percentages of all the constituents add up to 100% by weight, wherein the epoxy component of the hotmelt adhesive c) is different from the epoxy resins of the polymer B.

2. A coating comprising at least one layer of the primer composition according to claim 1.

3. A process for producing a hybrid component comprising metal and plastic, the process comprising: applying at least one layer of the primer composition according to claim 1 to the metal; then thermally crosslinking the primer composition; and then applying the plastic to the coated metal and bonding the metal to the plastic.

4. The process according to claim 3, wherein at least one layer of an adhesion promoter composition is applied to the thermally crosslinked primer composition and the adhesion promoter composition is thermally crosslinked before the plastic is applied to the coated metal and the metal is bonded to the plastic.

5. The process according to claim 4, wherein the adhesion promoter composition comprises: at least one polymer A selected from the group consisting of at least one epoxy resin-phenol resin precondensate, a mixture of at least one epoxy resin-phenol resin precondensate and epoxy resins, a mixture of epoxy resins and phenol resins, polyimide resins and mixtures thereof; and at least one copolyamide-based hotmelt adhesive.

6. A metal substrate coated with at least one primer composition according to claim 1.

Description

EXAMPLES

(1) The adhesion of plastic to metal in hybrid components was examined. For this purpose, different metals and plastics were used. Prior to application of primer and adhesion promoter compositions, the metals were cleaned and provided with a chromation V2 as conversion layer V.

(2) A temperature check was made by means of temperature measurement strips which indicate the temperature attained through a colour change (black).

(3) The temperature conditions are: 30 min at 190° C.

(4) To assess the adhesion, tensile shear tests were conducted.

(5) Materials Used:

(6) Primer Compositions

(7) Polymer B, pigments and fillers are adjusted to a mean grain diameter of less than 15 μm; the hotmelt adhesive is then added.

(8) P1: Polyester resin (number-average molecular weight 15 000 g/mol), melamine resin, anticorrosion pigment, filler, colorant, acid catalyst, solvent and copolyamide hotmelt adhesive without epoxy component and blocked polyisocyanate

(9) P2: Epoxy resin-phenol resin precondensate, anticorrosion pigment, fillers, colorant, solvent and copolyamide hotmelt adhesive without epoxy component and blocked polyisocyanate

(10) P3: Polyester (number-average molecular weight 20 000 g/mol), polyisocyanate crosslinker, tin catalyst, solvent and copolyamide hotmelt adhesive without epoxy component and blocked polyisocyanate

(11) P4: Polyester mixture of 2 polyester resins (number-average molecular weights 15 000 and 20 000 g/mol) in combination with blocked isocyanate resin, tin catalysts, solvent and copolyamide hotmelt adhesive without epoxy component and blocked polyisocyanate

(12) P5: Polyester (number-average molecular weight 20 000 g/mol), polyisocyanate crosslinker, tin catalyst, solvent

(13) Adhesion Promoter Compositions

(14) L1: Epoxy resin-phenol resin mixture with copolyamide hotmelt adhesive with epoxy component and blocked polyisocyanate

(15) L2: Epoxy resin-phenol resin precondensate with copolyamide hotmelt adhesive with epoxy component and blocked polyisocyanate

(16) L3: Epoxy resin-phenol resin precondensate with copolyamide hotmelt adhesive without epoxy component and blocked polyisocyanate

(17) L4: Epoxy resin-phenol resin precondensate with copolyamide hotmelt adhesive with epoxy component and blocked polyisocyanate (the copolyamide hotmelt adhesive has a lower molar mass compared to the copolyamide hotmelt adhesive from L2)

(18) Metal variants M1: DX56D Z140 MBO in 1.0 mm

(19) M2: DX53D Z140 MBO in 0.6 mm

(20) M4: AW-5754 AlMg3 H22 DIN EN 485-2

(21) M5: CuZn37 to DIN EN 17670 T1

(22) M6: Titanium-zinc to EN 988

(23) Plastic Variants

(24) K1: PA6GF30 Durethan BKV30 H2.0 from LANXESS Deutschland GmbH

(25) K2. PA6.6 Durethan A30 S from LANXESS Deutschland GmbH

(26) K3: PA1010 VESTAMID Terra DS18 from Evonik Industries AG

(27) K4: PA1010GF65 VESTAMID Terra BS1429 from Evonik Industries AG

(28) K5: PA1010CF30 VESTAMID HTplus TGP3561 from Evonik Industries AG

(29) K6: PA6T VESTAMID HTplus M1000 from Evonik Industries AG

(30) K7: PA6TGF50 VESTAMID HTplus M1035 from Evonik Industries AG

(31) K8: PBTGF30 VESTODUR GF30 from Evonik Industries AG

(32) K9: PC Makrolon 2205 from Bayer AG

(33) K10: PA12CF Composite from Evonik. Fibre composite material sheets of thickness 1.0 mm, composed of VESTAMID L1600 (nylon-12) and of carbon fibre fabric having continuous fibres, were used. The fabric has a weight of about 285 g/m.sup.2 with an orientation of 0°/90°. The fibre composite material sheets were produced in a pressing process.

(34) A) Laboratory Studies by Means of Coating Bar Application

(35) For this purpose, in the laboratory, variants of the primer were applied by means of spiral coating bars to sheets of DX56D Z140 MBO steel, thickness 1 mm (M1) in DIN A4 format with a conversion layer (phosphation) and then subjected to thermal crosslinking in a circulation dryer for 55 s. The peak metal temperature (PMT) was defined as being in the region of 216° C. or 232° C. The primer-coated DIN A4 sheets were cooled at room temperature.

(36) TABLE-US-00001 Oven temperature PMT in DLT in Coating Primer in ° C. ° C. μm bar no. P2 345 216 11-13 22 P1 345 216 15-17 20 P3 355 232 12-16 22 P4 355 232 12-16 24 P5 355 232 14-16 24 P5 355 232 14-16 24 DLT: dry layer thickness

(37) Thereafter, the sheets were endowed with an adhesion promoter composition by means of spiral coating bar no. 42 and subjected to thermal crosslinking in a circulation dryer for 70 s (PMT=216° C.). The samples were subsequently cooled at room temperature. The dry layer thickness was 35 μm in each case.

(38) The sheet specimens of thickness 1 mm which had been coated in this way were cut to a size of 50 mm×36 mm and coated with the plastic (thickness 2 mm) on one side in an injection mould with an Arburg 370 S injection moulding machine at a mould temperature of 110° C. and a melt temperature of 280° C. The total length of the specimens was 60 mm. The region of overlap between plastic and metal sheet is 18 mm×50 mm. The tensile shear samples were then tested on a universal tensile tester, based on ISO 527, with a test speed of 10 mm/min at 23° C. and 50% relatively air humidity, and the breaking stress of the samples was determined. For this purpose, the samples, after the in-mould coating, were either subjected to heat conditioning or were not, and the tensile shear strengths (bond strengths) of conditioned and unconditioned samples were compared.

(39) TABLE-US-00002 Bond strength Bond strength Adhesion in MPa; in MPa; Remarks Primer promoter unconditioned conditioned (conditioned) P2 L2 3.3 11.1 plastic fractures P1 L2 3.8 11.5 plastic fractures P3 L2 4.8 5.9 P4 L2 3.6 11.1 plastic fractures P5 L2 2.4 9.5 plastic fractures P5 L3 5.5 10.8 plastic fractures

(40) In the laboratory tests by means of a coating bar laboratory test, the coated and in-mould-coated hybrid composite samples with a conditioning step had increased bonding forces (breaking stresses) compared to the unconditioned samples.

(41) In addition, adhesion to various metal alloys was examined analogously to the above experiments, except that the metal sheets were cut to size of about 25 mm×60 mm.

(42) TABLE-US-00003 Mould Bond strength Adhesion temperature in MPa Metal Primer promoter in ° C. unconditioned M5 none none 80° C. n.a. M5 P1 L4 80° C. 0.7 M6 none none 80° C. n.a. M6 P1 L4 80° C. 1.0 M7 none none 80° C. n.a. M7 P1 L4 80° C. 1.7 M8 none none 80° C. n.a. M8 P1 L4 80° C. 2.3 M9 none none 80° C. n.a. M9 P1 L4 80° C. 3.4 n.a.: no adhesion

(43) B) Plant Experiment

(44) The compositions were applied by means of roll application in a coil coating process in a corresponding coating plant and subsequent thermal crosslinking (thermal curing) of the coating layer applied in a flow oven. Before the actual application of coating material or primer, the metal surface was subjected to pretreatment (cleaning, production of a conversion layer V1—phosphation or V2—chromation). The metal used was a galvanized steel strip DX53D Z140 MBO (steel S2) of layer thickness 0.6 mm and a width of 390 mm. The dry layer thicknesses of the primer compositions were 9 to 13 μm, and those of the adhesion promoter compositions 18 to 28 μm. The peak metal temperature (PMT) was defined as a range of 216° C. to 224° C.

(45) Steel sheet strips (about 25 mm×60 mm) were cut out of the sheets for the in-mould coating experiments. The coated steel sheet strips, after being inserted into an injection mould, were subjected to in-mould coating with plastics K1-K9, and these were used to produce tensile shear samples for adhesion tests.

(46) The single-sided processing of the plastic was effected in an Arburg Allrounder 420 C injection moulding machine at a melt temperature of 280° C., a mould temperature of 80° C. and 120° C., and an injection rate of about 30 ccm/sec. It was important here to provide an injection delay of about 15 s, so that the metal sheet strip inserted could be preheated to mould temperature, giving a favourable effect on adhesion. The region of overlap between plastic and metal was 25 mm×25 mm. The thickness of the overmoulded plastic was 4 mm. After demoulding, the individual tensile shear test samples were separated from the sprue.

(47) The test samples thus produced were stored at 50% relative humidity for at least 24 h at 23° C. in order to ensure a uniform state of conditioning. The test samples are then clamped into a standard Zwick/Roell Z-020 tensile tester and tested with a velocity of 5 mm/min at 23° C. with a distance between the clamps and the overlap region of about 25 mm/side.

(48) The tensile shear strength measured (in MPa) is reported in table which follows for the coating composed of primer composition and adhesion promoter composition.

(49) TABLE-US-00004 Mould Bond strength Bond strength Adhesion temperature in MPa in MPa Metal V Primer promoter Plastic in ° C. unconditioned conditioned M1 V1 none L1 K1 80 1.9 7.2 M1 V1 none L1 K1 120 6.2 7.4 M2 V2 P1 L2 K1 80 6.5 7.7 M2 V2 P1 L2 K1 120 7.7 7.6 M4 V2 P1 L2 K1 80 5.3 5.7 M4 V2 P1 L2 K1 120 6.2 6.2 M2 V2 none none K1 80 n.a. n.a. M2 V2 none none K1 120 n.a. n.a. M2 V2 P1 L4 K1 80 6.6 5.8 M2 V2 P1 L4 K1 120 7.8 6.8 M2 V2 none none K2 80 n.a. n.r. M2 V2 P1 L4 K2 80 4.2 n.r. M2 V2 none none K3 80 n.a. n.r. M2 V2 P1 L4 K3 80 0.7 n.r. M2 V2 none none K4 80 n.a. n.r. M2 V2 P1 L4 K4 80 6.0 n.r. M2 V2 none none K5 80 n.a. n.r. M2 V2 P1 L4 K5 80 6.5 n.r. M2 V2 none none K6 120 n.a. n.r. M2 V2 P1 L4 K6 120 material n.r. fractures M2 V2 none none K7 120 n.a. n.r. M2 V2 P1 L4 K7 120 6.0 n.r. M2 V2 none none K8 80 n.a. n.r. M2 V2 P1 L4 K8 80 2.6 n.r. M2 V2 none none K9 80 n.a. n.r. M2 V2 P1 L4 K9 80 1.5 n.r. n.a.: no adhesion; n.r.: no result

(50) The coating composed of primer composition and adhesion promoter composition, in an advantageous manner, already achieves high values for adhesion here, especially with a high mould temperature (120° C.) without a subsequent heat conditioning operation on the samples after in-mould coating.

(51) The subsequent conditioning increases the adhesion, especially in the case of the lower mould temperature of 80° C.

(52) C) Pressing Experiment

(53) The bond between plastic and coated metal was obtained by a pressing operation in a hydraulic hot press (manufacturer: Paul Weber, name: TEMPRESS). This is done by inserting the coated metal sheet having dimensions of about 60×25×0.6 mm into a template in one half of the hot press. An injection-moulded plastic sheet having dimensions of 60×25×4 mm is positioned thereon. The half of the press on the metal sheet side is heated to about 200° C.-230° C. Thereafter, the plastics component and the coated metal sheet are pressed at a pressure of about 32 bar with a hold time of about 5 min to give a composite body (tensile shear bar specimen) (overlap area 25 mm×25 mm).

(54) The application of the adhesion promoter compositions and testing of bond strength were conducted analogously to the plant experiments.

(55) TABLE-US-00005 Bond strength in Adhesion Mould MPa Metal V Primer promoter Plastic temperature in ° C. unconditioned M2 V2 none none K1 200° C. n.a. M2 V2 P1 L4 K1 200° C. 2.8 M2 V2 none none K7 230° C. n.a. M2 V2 P1 L4 K7 230° C. 3.6 M2 V2 none none K10 230° C. n.a. M2 V2 P1 L4 K10 230° C. 6.0 n.a.: no adhesion