THERMOPLASTIC ELASTOMER COMPOSITIONS ADHERING TO METAL SURFACES

Abstract

Thermoplastic elastomer compositions which have excellent adhesion to metals and are extremely stable vis--vis the influence of acids and lyes. Further, a method for producing the thermoplastic elastomer compositions and a composite material as well as the use of the latter in various composite materials.

Claims

1. A thermoplastic composition comprising (A) a polar-functionalized thermoplastic elastomer containing a styrene-containing block copolymer having a weight average molecular weight (M.sub.w) of from 50,000 to 500,000 g/mol, wherein the polar-functionalized thermoplastic elastomer has polar groups selected from the group consisting of carboxylic acid, carboxylic acid anhydride, epoxy, hydroxy, amine, and amide groups, (B) an adhesion-supporting resin, comprising aliphatic or aromatic synthetic resins or mixtures thereof, and (C) a process oil.

2. The composition according to claim 1, wherein the thermoplastic elastomer has a Shore A hardness of from 30 to 90 ShA.

3. The composition according to claim 1, wherein the styrene-containing copolymer is an A-B-A triblock copolymer.

4. The composition according to claim 3, wherein the A block of the triblock copolymer is polystyrene and the B block of the triblock copolymer comprises polybutadiene, polyisoprene and/or polyisobutene.

5. The composition according to claim 4 wherein, in the A block the styrene monomers can be partially or completely replaced with derivatives of styrene, preferably -methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 4-tert-butylstyrene, 4-cyclohexylstyrene or vinylnaphthalines, preferably 1-vinylnaphthaline, or 2-vinylnaphthaline.

6. The composition according to claim 4, wherein the B block comprises a mixture of dienes.

7. The composition according to claim 4, wherein the B blocks are partially or completely hydrogenated.

8. The composition according to claim 1, wherein the thermoplastic elastomer has a grafting level of the polar groups of from 0.5 to 5.0%, relative to the polar-functionalized thermoplastic elastomer.

9. A composite material comprising a metal, glass, ceramic, thermoplastic, or any mixture thereof and the composition of claim 1.

10. The composite material according to claim 9, wherein the metal comprises aluminium, copper, titanium, steel, stainless steel, or any alloy thereof.

11. A method for the production of a thermoplastic elastomer composition according to claim 1 comprising using an extruder, internal mixer, or kneader.

12. A method for producing a composite material using a thermoplastic elastomer composition according to claim 1 and a further substance comprising a metal, glass, ceramic, thermoplastics and mixtures thereof, wherein the composite material is produced using injection moulding, injection moulding-insertion methods, extrusion, compression moulding methods, any combination thereof.

13. The method of claim 11, wherein the extruder is a twin screw extender.

14. The method of claim 13, wherein the composite material is produced using injection moulding, injection moulding-insertion methods, extension, or any combination thereof.

15. The method of claim 14, where the compsite materal is produced by injection moulding-insertion methods.

Description

EMBODMENT EXAMPLES

[0081] 1. Production of the TPE Compounds

[0082] All of the TPE compounds developed and tested according to the invention were produced on a twin screw extruder with co-rotating screws and a melting pump. The screw diameter is 27 mm, the L/D ratio is 46. The extruder has eight temperature-adjustable extruder zones. The rotational speed of the screw lies between 100 and 800 rpm. Granulation then takes place under water.

[0083] 2. Raw materials Used

[0084] Polar-functionalized TPS (A):

[0085] KRATON FG 1901GT, KRATON MD 66845 GS

[0086] Adhesion-supporting resins (B):

[0087] ENDEX 155, NORSOLENE W140, EASTOTAC H-130R

[0088] Process oils (C):

[0089] Shell Ondina 941

[0090] Optionally MAH-grafted thermoplastic (PE):

[0091] SCONA TSPE 2102GAHDS

[0092] Further raw materials were used for the comparison examples.

[0093] Non-functionalized TPS:

[0094] Kraton G 1651 ES, SEPTON 4033

[0095] Thermoplastics (PP):

[0096] Moplen HP 501 L

[0097] TPU:

[0098] DESMOPAN 487

[0099] Filler:

[0100] OMYACARB 5 GU

[0101] As described, all the examples were produced using twin screw extruders. The following Table 1 shows the corresponding proportions by weight of the components used.

TABLE-US-00001 TABLE 1 Composition of the compounds Reference Reference Reference Exam- Exam- Exam- Exam- example I example II example III ple IV ple V ple VI ple VII MAH-g-SEBS (HMW*) wt. % 0 0 0 0 60 0 0 MAH-g-SEEPS (LMW*) wt. % 0 0 0 60 0 52 52 aromatic resin wt. % 0 0 0 20 20 17 0 aliphatic resin wt. % 0 0 0 0 0 0 17 process oil wt. % 39.5 38 0 19.0 19.0 24.5 25 TPS (SEBS, HMW*) wt. % 22 0 0 0 0 0 0 TPS (SEEPS, LMW*) wt. % 0 45 0 0 0 0 0 TPU wt. % 0 0 99.5 0 0 0 0 PP wt. % 15 16 0 0 0 0 0 MAH-g-PE wt. % 0 0 0 0 0 5.5 5.5 filler wt. % 22 0 0 0 0 0 0 pigment wt. % 0.5 0 0 0.5 0.5 0.5 0 stabilizers wt. % 1.0 1.0 0.5 0.5 0.5 0.5 0.5 *LMW = low molecular weight; HMW = high molecular weight

[0102] 3. Production of the Metal/TPE Compound Bond

[0103] Metal plates of aluminium which was pre-treated by means of the NMT method, were not further treated, but used directly.

[0104] Untreated metal plates of aluminium, steel and copper were successively pre-treated as follows:

[0105] a) Grinding of the surface to remove dirt and oxide layer using Scotch-Brite WR-RL abrasive web roll, red, Art. No. 61152.

[0106] b) Degreasing with acetone

[0107] All the metal plates had the dimensions 115 mm60 mm1 mm. These plates were placed in the injection moulding tool using injection moulding-insertion methods and flooded with TPE melt. A centrally positioned TPE strip with a width of 20 mmm and a thickness of 1 mm was hereby produced as bond to the metal (see FIG. 1).

[0108] The thus-produced material bonds served as test pieces and were firstly subjected to the following tests for a minimum conditioning period of 24 hours under standard climate conditions. At least two samples of test pieces of the same bond were always produced.

[0109] 4. Testing of the Adhesion

[0110] All the adhesion measurements were carried out on the test pieces produced following conditioning (see FIG. 1), on the basis of VDI 2019.

[0111] The pulling-off of the TPE strip took place at 90 to the metal plate test piece (see FIGS. 2 and 3 and VDI 2019). Adhesion measurements were additionally carried out on samples which have undergone chemical testing (see below under 6.).

[0112] 5. Testing of the Further Parameters

[0113] For the testing of the further parameters, test plates of pure TPE compounds of Table 1 with the dimensions 125 mm125 mm2 mm were produced. Hardness, density, tensile strength and elongation at break were measured according to Table 2. The determination of hardness and density was carried out on these test plates or parts thereof. For the determination of tensile strength and elongation at break, S2 test pieces with a density of 20.05 mm which had been punched out of the pure TPE test plates were used in each case.

TABLE-US-00002 TABLE 2 Method Standard Determination of hardness ISO 7619-1 Determination of density DIN EN ISO 1183-1 Determination of tensile DIN 53504 strength and elongation at break

[0114] 6. Testing of Chemical Resistance

[0115] On the basis of DIN ISO 1817, respective test pieces (test pieces of FIG. 1 for adhesion testing, S2 test pieces for tensile strength and elongation at break, test plates or parts of the test plates named under 5. for hardness and density) were exposed to the following chemicals in succession: [0116] 85% phosphoric acid at 80 C. for 3 minutes [0117] 30% nitric acid at 23 C. for 3 minutes [0118] 70% sulphuric acid at 23 C. for 60 minutes [0119] ammonium hydroxide pH 10 at 23 C. for 3 minutes

[0120] After each step the respective test pieces were thoroughly rinsed with distilled water. Following the action of all the chemicals, the samples were examined with respect to their parameters. If there were shown to be slight changes in the parameters in the case of hardness (5 ShA), elongation at break (20%), tensile strength (30%) and swelling behaviour (2%) the material was considered resistant. Resistance in the named test is hereafter to be equated with chemical resistance. Table 3 shows the starting values of the TPE compounds of Table 1. Table 4 shows the changes in the parameters after examination of the chemical resistance. In addition to the named parameter determinations, test pieces were assessed visually according to the grey scale (DIN EN 20105-A02/ISO 150-A02). Resistance is assumed if the test pieces are assessed not worse than grey scale level 4/5.

TABLE-US-00003 TABLE 3 Starting data of the TPE compounds before testing for chemical resistance Reference Reference Reference Exam- Exam- Exam- Exam- example I example II example III ple IV ple V ple VI ple VII density g/cm.sup.3 1.025 0.89 1.196 0.94 0.942 0.93 0.918 hardness ShA 60 60 86 75 73 71 50 tensile strength MPa 4.8 8.7 41.8 14.8 10.3 8.7 7.1 elongation at % 700 710 540 490 650 510 630 break adhesion to N/mm none none 4 4.8 none 4.4 2.3 aluminium in the NMT adhesion to N/mm none none none 3.7 none 3.5 1.7 aluminium adhesion to steel N/mm none none none none 4.6 2.7 adhesion to N/mm none none none none 4.4 copper

TABLE-US-00004 TABLE 4 Data of the TPE compounds following the action of the chemicals Reference Reference Reference Exam- Exam- Exam- Exam- example I example II example III ple IV ple V ple VI ple VII volume % 0 0 3.6 0 0 0 hardness ShA 0 2 8 1 1 3 tensile strength % 10.9 24.8 13.9 25.4 26.4 15.3 elongation at % 6.8 2.5 19.6 2.8 0.2 1.6 break grey scale level 5 5 <1* 5 5 5 *no longer assessable with grey scale, colour impression completely changed

[0121] 7. Discussion

[0122] Examples I, II and III represent references. Although the compound of Example I is resistant to the above-named chemicals, it does not adhere to metals. Also, exchanging the non-functionalized TPS used for lower molecular weights does not change the behaviour. The reference compound III, a TPU, adheres well to aluminium pre-treated according to the NMT method, poorly to less pre-treated metals, but is not resistant to chemicals. Furthermore, pure TPUs are at the upper limit of the desired Shore A hardness. All the other examples IV to VII according to the invention achieve the objects of the present invention.