ADHESIVE BOND BETWEEN A THERMOPLASTIC MATERIAL AND AN ELASTOMER COMPOSITION

Abstract

An adhesive bond between at least one thermoplastic and an elastomer composition containing at least one polyether having blocked hydroxyl groups as plasticizer. With the adhesive bond, it is possible to bond thermoplastics such as polycarbonate or polystyrene in particular to the elastomer composition essentially without stress cracking and hence reliably and permanently.

Claims

1. An adhesive bond between (i) at least one thermoplastic and (ii) an elastomer composition containing at least one polyether having blocked hydroxyl groups as plasticizer.

2. The adhesive bond as claimed in claim 1, wherein the thermoplastic is a polycarbonate or polystyrene.

3. The adhesive bond as claimed in claim 1, wherein the blocked hydroxyl groups are selected from the group consisting of ester, aceto ester, carbonate and urethane groups.

4. The adhesive bond as claimed in claim 1, wherein 70% to 100% by weight of the repeat units in the polyether consist of 1,2-propyleneoxy groups, and 0% to 30% by weight of the repeat units of 1,2-ethyleneoxy groups.

5. The adhesive bond as claimed in claim 1, wherein the polyether having blocked hydroxyl groups has an average molecular weight M.sub.n in the range from 600 to 12,500 g/mol, determined by means of gel permeation chromatography (GPC) versus polystyrene standard with tetrahydrofuran as mobile phase, refractive index detector and evaluation from 200 g/mol.

6. The adhesive bond as claimed in claim 1, wherein the polyether having blocked hydroxyl groups is derived from at least one hydroxy-functional polyether selected from the group consisting of alcohol-started, polyoxypropylene monools having an OH number in the range from 25 to 90 mg KOH/g, polyoxypropylene diols having an OH number in the range from 9 to 155 mg KOH/g, trimethylolpropane- or glycerol-started, optionally ethylene oxide-terminated polyoxypropylene triols having an average OH functionality in the range from 2.2 to 3 and an OH number in the range from 20 to 230 mg KOH/g, and sugar alcohol-started polyoxypropylene polyols having an average OH functionality in the range from 3 to 6.

7. The adhesive bond as claimed in claim 6, wherein the polyether having blocked hydroxyl groups is derived from an alcohol-started, polyoxypropylene monool having an OH number in the range from 25 to 90 mg KOH/g or a polyoxypropylene diol having an OH number in the range from 45 to 125 mg KOH/g.

8. The adhesive bond as claimed in claim 6, wherein the polyether having blocked hydroxyl groups is derived from a polyoxypropylene diol having an OH number in the range from 14 to 45 mg KOH/g or a trimethylolpropane- or glycerol-started, optionally ethylene oxide-terminated polyoxypropylene triol having an OH number in the range from 20 to 56 mg KOH/g.

9. The adhesive bond as claimed in claim 1, wherein the elastomer composition comprises at least one cured polyurethane polymer or cured silane-modified polymer.

10. The adhesive bond as claimed in claim 1, wherein the elastomer composition contains 5% to 40% by weight of polyethers having blocked hydroxyl groups.

11. The adhesive bond as claimed in claim 1, wherein the elastomer composition has a tensile strength of at least 1 MPa and an elongation at break of at least 50%, determined at 23° C. on dumbbell-shaped test specimens having a thickness of 2 mm, a length of 75 mm, a bar length of 30 mm and a bar width of 4 mm to DIN EN 53504.

12. The adhesive bond as claimed in claim 1, wherein the adhesive bond is part of an article bonded or sealed or coated with the elastomer composition.

13. A process for producing the adhesive bond as claimed in claim 1, comprising the steps of (a) providing at least one thermoplastic substrate, (b) providing a curable composition comprising at least one polyether having blocked hydroxyl groups as plasticizer, (c) applying the curable composition to the plastic substrate, (d) curing the curable composition to give the elastomer composition.

14. The process as claimed in claim 13, wherein the curable composition comprises at least one polymer containing isocyanate and/or silane groups.

15. A method comprising applying a curable composition comprising at least one polymer containing isocyanate and/or silane groups and at least one polyether having blocked hydroxyl groups to at least one thermoplastic substrate and bonding, sealing, or coating the thermoplastic substrate with the composition.

Description

EXAMPLES

[0218] Working examples are adduced hereinafter, which are intended to elucidate the invention described. The invention is of course not limited to these described working examples.

[0219] “Standard climatic conditions” (“SCC”) refer to a temperature of 23±1° C. and a relative air humidity of 50±5%.

[0220] Unless otherwise stated, the chemicals used were from Sigma-Aldrich Chemie GmbH.

[0221] Preparation of Polyethers Having Blocked Hydroxyl Groups:

[0222] Viscosity was measured with a thermostated Rheotec RC30 cone-plate viscometer (cone diameter 25 mm, cone angle 1°, cone tip-plate distance 0.05 mm, shear rate 10 s.sup.−1).

[0223] Infrared spectra (FT-IR) were measured as undiluted films on a Nicolet iS5 FT-IR instrument from Thermo Scientific equipped with a horizontal ATR measurement unit with a diamond crystal. The absorption bands are reported in wavenumbers (cm.sup.−1).

[0224] .sup.1H NMR spectra were measured on a spectrometer of the Bruker Ascend 400 type at 400.14 MHz; the chemical shifts δ are reported in ppm relative to tetramethylsilane (TMS). No distinction was made between true coupling and pseudo-coupling patterns.

[0225] Polyether-1: n-butanol-started acetylated PPG monool with average molecular weight about 800 g/mol

[0226] 120.00 g of n-butanol-started polyoxypropylene monool (Synalox® 100-20B, average molecular weight about 750 g/mol; from DowDuPont Inc.) and 18.74 g of acetic anhydride were initially charged in a round-bottom flask with distillation attachment under a nitrogen atmosphere. Then the reaction mixture was stirred under a gentle nitrogen stream at 130° C., with collection of acetic acid as distillate. Subsequently, the volatile constituents were removed from the reaction mixture at 80° C. and a reduced pressure of 10 mbar. A clear, colorless liquid having a viscosity of 75 mPa.Math.s at 20° C. was obtained.

[0227] FT-IR: 2970, 2931, 2867, 1738, 1454, 1372, 1345, 1296, 1241, 1098, 1014, 959, 925, 866, 827.

[0228] .sup.1H NMR (CDCl.sub.3): 5.02 (hept., 1H, CH.sub.2(CH.sub.3)CH—OAc), 3.75-3.34 (2×m, ca. 39H, OCH.sub.2CH(CH.sub.3)O), 3.33-3.28 (m, 2H, CH.sub.3CH.sub.2CH.sub.2CH.sub.2O), 2.04 (s, 3H, O(CO)CH.sub.3), 1.55 (quint., 2H, CH.sub.3CH.sub.2CH.sub.2CH.sub.2O), 1.36 (sext., 2H, CH.sub.3CH.sub.2CH.sub.2CH.sub.2O), 1.22 (d, 3H, CH.sub.2(CH.sub.3)CH—OAc), 1.17-1.10 (m, ca. 36H, OCH.sub.2CH(CH.sub.3)O), 0.91 (t, 3H, CH.sub.3CH.sub.2CH.sub.2CH.sub.2O).

[0229] Polyether-2: Diacetylated PPG diol with average molecular weight about 1′100 g/mol

[0230] 80.00 g of polyoxypropylene diol (Voranol® P 1010, OH number 110 mg KOH/g; from DowDuPont Inc.) and 18.74 g of acetic anhydride were converted as described for Polyether-1. A clear, colorless liquid having a viscosity of 145 mPa.Math.s at 20° C. was obtained.

[0231] Polyether-3: Diacetylated PPG diol with average molecular weight about 2′100 g/mol

[0232] 160.00 g of polyoxypropylene diol (Voranol® 2000 L, OH number 56 mg KOH/g; from DowDuPont Inc.) and 18.74 g of acetic anhydride were converted as described for Polyether-1. A clear, colorless liquid having a viscosity of 400 mPa.Math.s at 20° C. was obtained.

[0233] Polyether-4: Diacetylated PPG diol with average molecular weight about 4′100 g/mol

[0234] 600.0 g of polyoxypropylene diol (Acclaim® 4200, OH number 28 mg KOH/g; from Covestro AG) and 33.7 g of acetic anhydride were converted as described for Polyether-1. A clear, colorless liquid having a viscosity of 1′150 mPa.Math.s at 20° C. was obtained.

[0235] Polyether-5: Diacetylated PPG diol with average molecular weight about 8′100 g/mol

[0236] 600.0 g of polyoxypropylene diol (Acclaim® 8200, OH number 14 mg KOH/g; from Covestro AG) and 16.8 g of acetic anhydride were converted as described for Polyether-1. A clear, colorless liquid having a viscosity of 3′800 mPa.Math.s at 20° C. was obtained.

[0237] Polyether-6: PPG diol having two p-toluenesulfonylurethane end groups and average molecular weight about 12′400 g/mol 600.0 g of polyoxypropylene diol (Acclaim® 12200, from Covestro AG; average molecular weight about 12′000 g/mol) and 13.5 g of p-toluenesulfonyl isocyanate were initially charged in a round-bottom flask with distillation attachment under a nitrogen atmosphere. Then the reaction mixture was stirred at 130° C. under a gentle nitrogen stream for 3 hours. Subsequently, the volatile constituents were removed from the reaction mixture at 80° C. and a reduced pressure of 10 mbar. A clear, colorless liquid having a viscosity of 12′700 mPa.Math.s at 20° C. was obtained.

[0238] Commercial substances used: [0239] DINP: diisononyl phthalate (Palatinol® N, from BASF SE) [0240] DIDP: diisodecyl phthalate (Palatinol® 10-P, from BASF SE) [0241] DINCH: diisononyl cyclohexane-1,2-dicarboxylate (Hexamoll® DINCH, from BASF SE) [0242] DOA: di(2-ethylhexyl) adipate (Adimoll® DO, from Lanxess AG) [0243] ATBC: acetyl tributyl citrate [0244] FAE: aliphatic fatty acid ester (Sovermol® 1058, from BASF SE) [0245] Chalk: Omyacarb® 5-GU (from Omya AG) [0246] Carbon Monarch® 570 (from Cabot Corp.) black: [0247] Fumed silica: Aerosil® R 972 (from Evonik Industries AG) [0248] DMDEE 2,2′-dimorpholinodiethyl ether [0249] pTSI p-toluenesulfonyl isocyanate

[0250] Preparation of Polymers Containing Isocyanate Groups:

[0251] Polymer P1:

[0252] 727.0 g of polyoxypropylene diol (Acclaim® 4200, from Covestro AG; OH number 28.5 mg KOH/g) and 273.0 g of diphenylmethane 4,4′-diisocyanate (Desmodur® 44 MC L, from Covestro AG) were converted by a known method at 80° C. to a polymer having an isocyanate group content of 7.6% by weight, a viscosity of 5.2 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of about 18% by weight. Subsequently, the volatile constituents, especially a majority of the monomeric diphenylmethane 4,4′-diisocyanate, were removed by distillation in a short-path evaporator (jacket temperature 180° C., pressure 0.1 to 0.005 mbar, condensation temperature 47° C.). The polymer thus obtained had an isocyanate group content of 1.8% by weight, a viscosity of 15.2 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of 0.08% by weight.

[0253] Polymer P2:

[0254] 725.0 g of ethylene oxide-terminated polyoxypropylene triol (Desmophen® 5031 BT, from Covestro AG; OH number 28 mg KOH/g) and 275 g of diphenylmethane 4,4′-diisocyanate (Desmodur® 44 MC L, from Covestro AG) were converted by a known method at 80° C. to a polymer having an isocyanate group content of 7.6% by weight, a viscosity of 6.5 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of about 20% by weight. Subsequently, the volatile constituents, especially a majority of the monomeric diphenylmethane 4,4′-diisocyanate, were removed by distillation in a short-path evaporator (jacket temperature 180° C., pressure 0.1 to 0.005 mbar, condensation temperature 47° C.). The polymer thus obtained had an isocyanate group content of 1.7% by weight, a viscosity of 19 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of 0.04% by weight.

[0255] Polymer P3:

[0256] 724.0 g of polyoxypropylene triol (Acclaim® 6300, from Covestro AG; OH number 28 mg KOH/g) and 276.0 g of diphenylmethane 4,4′-diisocyanate (Desmodur® 44 MC L, from Covestro AG) were converted by a known method at 80° C. to a polymer having an isocyanate group content of 7.5% by weight, a viscosity of 9.9 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of about 20% by weight. Subsequently, the volatile constituents, especially a majority of the monomeric diphenylmethane 4,4′-diisocyanate, were removed by distillation in a short-path evaporator (jacket temperature 180° C., pressure 0.1 to 0.005 mbar, condensation temperature 47° C.). The polymer thus obtained had an isocyanate group content of 1.7% by weight, a viscosity of 34.7 Pas at 20° C. and a monomeric diphenylmethane 4,4′-diisocyanate content of 0.06% by weight.

[0257] Production of Curable Compositions and Adhesive Bonds to Polycarbonate:

[0258] Compositions Z1 to Z12 (Two-Component)

[0259] For each example, the first component (“component 1”) used was the commercial A component specified in tables 1 and 2 (SikaForce®-7777 L05, structural two-component PU adhesive with A component based on polyol, filled, gray; or SikaForce®-7584, flexible two-component PU adhesive with A component based on polyol, filled, black, both from Sika Schweiz AG). The second component (“component 2”) used was mixtures of 80 parts by weight of Adiprene® LFM E730 (MDI-terminated, difunctional, polyether-based polyurethane polymer with NCO content 7.35% by weight and a low content of monomeric MDI, from Lanxess AG) and 20 parts by weight of the respective plasticizer specified in tables 1 and 2; the mixtures were produced by means of a centrifugal mixer (SpeedMixer™ DAC 150, FlackTek Inc.) with exclusion of moisture and stored.

[0260] The two components were processed with exclusion of moisture in the mixing ratio specified in tables 1 and 2 by means of the centrifugal mixer to give a homogeneous paste, and this was immediately used or tested as follows: Each composition was used to produce multiple adhesive bonds to polycarbonate. For this purpose, the paste was applied in each case to an isopropanol-degreased plaque of polycarbonate PC1 (=Makrolon® GP Clear 099, from Covestro AG) of size 150×30×2 mm in the middle over an area of 30×30 mm in a layer thickness of 2 mm, and stored/cured under standard climatic conditions for 7 days. Several adhesive bonds of this kind were then clamped across a round piece of timber having a diameter of 35 mm that had been mounted on a board and secured at the ends such that each adhesive bond was fixed in a curved position. This arrangement was stored in an air circulation oven at 80° C. for 24 h or 7 days and then, after conditioning under standard climatic conditions for 24 h, assessed visually as to the extent to which the plaque persisted in the curved state and whether stress cracks were visible in the polycarbonate. The results are reported in tables 1 and 2 as “Bending of PC1” and “Crazing of PC1”.

[0261] For the crazing, the numbers mean:

[0262] 0: no cracks

[0263] 1: few short superficial cracks at the edges of the composition

[0264] 2: some short superficial cracks at the edges of the composition

[0265] 3: some deeper cracks over the entire width of the plaque

[0266] 4: many deeper cracks over the entire width of the plaque

[0267] 5: very many deeper cracks over the entire width of the plaque

[0268] Compositions labeled “(Ref.)” are comparative examples.

TABLE-US-00001 TABLE 1 Composition (in parts by weight) of Z1 to Z6 and properties of the adhesive bonds therewith. “v. severe” stands for “very severe” Z2 Z3 Z4 Z5 Z6 Composition Z1 (Ref.) (Ref.) (Ref.) (Ref.) (Ref.) Component 1: 100.0 100.0 100.0 100.0 100.0 100.0 SikaForce ®-7584, A component Component 2: 80.0 80.0 80.0 80.0 80.0 80.0 Adiprene ®  LFM E730 Plasticizer Polyether-1 DINP DINCH DOA ATBC FAE 20.0 20.0 20.0 20.0 20.0 20.0 Mixing ratio.sup.1 100/126 100/126 100/126 100/126 100/126 100/126 Bending 1d 80° C. slight moderate moderate severe moderate severe of PC1 7d 80° C. slight moderate moderate v. severe moderate v. severe Crazing 1d 80° C. 1 4 4 4 4 4 of PC1 7d 80° C. 1 4 5 5 4 5 .sup.1in parts by weight of component 1/component 2

TABLE-US-00002 TABLE 2 Composition (in parts by weight) of Z7 to Z12 and properties of the adhesive bonds therewith. Z8 Z9 Z10 Z11 Z12 Composition Z7 (Ref.) (Ref.) (Ref.) (Ref.) (Ref.) Component 1: 100.0 100.0 100.0 100.0 100.0 100.0 SikaForce ®-7777 L05, A comp. Component 2: 80.0 80.0 80.0 80.0 80.0 80.0 Adiprene ® LFM E730 Plasticizer Polyether-1 DINP DINCH DOA ATBC FAE 20.0 20.0 20.0 20.0 20.0 20.0 Mixing ratio.sup.1 100/72 100/72 100/72 100/72 100/72 100/72 Bending 1d 80° C. slight moderate moderate moderate moderate moderate of PC1 7d 80° C. slight severe severe severe severe severe Crazing 1d 80° C. 1 4 4 4 4 4 of PC1 7d 80° C. 3 5 5 5 5 5 .sup.1in parts by weight of component 1/component 2

[0269] Compositions Z13 to Z16 (One-Component)

[0270] For each composition, the ingredients specified in table 3 were mixed in the amounts specified (in parts by weight) by means of a centrifugal mixer (SpeedMixer™ DAC 150, FlackTek Inc.) with exclusion of moisture at 3000 rpm for one minute.

[0271] An adhesive bond of each composition to polycarbonate was produced. For this purpose, the composition was applied to a plaque of polycarbonate PC1 (=Makrolon® GP Clear 099, from Covestro AG) of size 150×30×2 mm in the middle in the form of a bead over an area of 10×30 mm in a layer thickness of about 2 mm, and stored/cured under standard climatic conditions for 7 days. The adhesive bond was then clamped across a round piece of timber having a diameter of 35 mm that had been mounted on a board and secured at the ends such that the adhesive bond was fixed in a curved position. This arrangement was stored in an air circulation oven at 80° C. for 24 h and then, after conditioning under standard climatic conditions for 24 h, assessed visually on the scale specified for composition Z1 as to whether stress cracks were visible in the polycarbonate. The result is reported as “Crazing of PC1”.

[0272] To determine the mechanical properties, each composition was applied to a PTFE-coated film to give a film of thickness 2 mm, the film was stored under standard climatic conditions for 14 days, and a few dumbbells having a length of 75 mm with a bar length of 30 mm and a bar width of 4 mm were punched out of the film and these were tested in accordance with DIN EN 53504 at a strain rate of 200 mm/min for Tensile strength (breaking force), Elongation at break, Modulus of elasticity 5% (at 0.5%-5% elongation) and Modulus of elasticity 50% (at 0.5%-50% elongation).

[0273] To determine the strength of a bond, lap shear strength (LSS) was determined on glass. For this purpose, composite specimens were produced by bonding two glass plates that had been degreased with isopropanol and pretreated with Sika® Primer 207 (from Sika Schweiz AG) in such a way that the overlapping adhesive bond had dimensions of 12×25 mm and a thickness of 4 mm and the glass plates protruded at the top ends. After the composite specimens had been stored under standard climatic conditions for 7 d, lap shear strength was tested to DIN EN 1465 at a strain rate of 20 mm/min.

[0274] Shore A hardness was determined according to DIN 53505 on test specimens cured under standard climatic conditions for 7 d.

[0275] The results are reported in table 3.

[0276] Compositions labeled “(Ref.)” are comparative examples.

TABLE-US-00003 TABLE 3 Composition (in parts by weight) and properties of Z13 to Z16. Z13 Composition (Ref.) Z14 Z15 Z16 Polymer P1 17.5 17.5 17.5 17.5 Polymer P2 17.5 17.5 17.5 17.5 Plasticizer DINP Polyether-1 Polyether-2 Polyether-4 20.4 20.4 20.4 20.4 Carbon black 10.0 10.0 10.0 10.0 Chalk 32.0 32.0 32.0 32.0 Fumed silica 2.0 2.0 2.0 2.0 DMDEE 0.2 0.2 0.2 0.2 pTSI 0.4 0.4 0.4 0.4 Crazing of PC1 4 1 1 0 Tensile strength [MPa] 3.8 5.2 5.5 5.8 Elongation at break 772 831 856 816 [%] Modulus of elasticity 1.57 1.59 1.56 1.74 5% [MPa] Modulus of elasticity 0.83 0.90 0.86 1.01 50% [MPa] LSS (glass) [MPa] 2.41 2.71 2.13 2.74 Shore A 38 39 38 39

[0277] Compositions Z17 to Z20 (one-component)

[0278] For each composition, the ingredients specified in table 4 were mixed in the amounts specified (in parts by weight) by means of a centrifugal mixer (SpeedMixer™ DAC 150, FlackTek Inc.) with exclusion of moisture at 3000 rpm for one minute.

[0279] An adhesive bond of each composition to polycarbonate was produced. For this purpose, the composition was applied to a plaque of polycarbonate PC2 (=Makrolon® AL2447, from Covestro AG) of size 150×70×5 mm in the middle in the form of a bead over an area of 10×100 mm in a layer thickness of about 2 mm, and stored/cured under standard climatic conditions for 7 days. The adhesive bond was then clamped across a round piece of timber having a diameter of 35 mm that had been mounted on a board and secured at the ends such that the adhesive bond was fixed in a curved position. This arrangement was stored in an air circulation oven at 80° C. for 24 h and then, after conditioning under standard climatic conditions for 24 h, assessed visually as to the extent to which the plaque persisted in the curved state and whether stress cracks were visible in the polycarbonate. The results are reported as “Bending of PC2” and “Crazing of PC2”. For the crazing, the scale specified for composition Z1 was used.

[0280] The mechanical properties of tensile strength, elongation at break, modulus of elasticity 5% and modulus of elasticity 50% were tested as described for composition Z13.

[0281] The results are reported in table 4.

TABLE-US-00004 TABLE 4 Composition (in parts by weight) and properties of Z17 to Z20. Composition Z17 Z18 Z19 Z20 Polymer P1 30.0 30.0 30.0 30.0 Polymer P3 5.0 5.0 5.0 5.0 Plasticizer Polyether-3 Polyether-4 Polyether-5 Polyether-6 20.4 20.4 20.4 20.4 Carbon black 10.0 10.0 10.0 10.0 Chalk 32.0 32.0 32.0 32.0 Fumed silica 2.0 2.0 2.0 2.0 DMDEE 0.2 0.2 0.2 0.2 pTSI 0.4 0.4 0.4 0.4 Bending of PC2 slight slight slight slight Crazing of PC2 2 1 0 0 Tensile strength 6.4 6.7 n.d. 6.9 [MPa] Elongation at 960 970 n.d. 950 break [%] Modulus of 1.76 1.76 n.d. 1.76 elasticity 5% [MPa] Modulus of 0.89 0.91 n.d. 0.84 elasticity 50% [MPa] “n.d.” stands for “not determined”