TWO-COMPONENT STRUCTURAL ADHESIVES

Abstract

The present invention relates to a method for bonding substrates of the same or different type using two-component structural adhesives on the basis of aliphatic polyisocyanates and polyaspartic acid esters, and to a two-component structural adhesive, which contains said two components and has a high strength when hardened.

Claims

1. A two-component structural adhesive which has at least the following components, (i) at least one polyisocyanate having free isocyanate groups and having a content of aliphatically bound NCO groups of 16.0 to 24.0 wt. %, which is substantially free of ester and/or ether and/or carbonate groups, (ii) at least one amino-functional polyaspartic acid ester of the general formula ##STR00004## in which n=2, and X represents a divalent organic residue which can be obtained by removing the amino groups from a linear or branched aliphatic diamine, having up to 9 carbon atoms, or preferably by removing the amino groups from 1,4-diaminobutane, 1,6-diaminohexane, 2,2,4-trimethyl-1,6- and/or 2,4,4-trimethyl-1,6-diaminohexane, or particularly preferred by removing the amino groups from 2-methyl-1,5-diaminopentane, wherein R.sup.1 and R.sup.2 are a methyl or an ethyl group, wherein the structural adhesive, in the cured state, has a tensile shear strength of at least 7 MPa, preferably at least 10 MPa, more preferably at least 12 MPa, wherein the tensile shear strength is measured according to standard DIN/EN 1465 (2009-07) between two test bodies made of roughened V2A steel.

2. A method for the structural adhesive bonding together of identical or different substrates with two-component structural adhesives, wherein the method comprises at least the following steps: (1) providing a two-component structural adhesive which contains at least the following components: (i) at least one polyisocyanate having free isocyanate groups and having a content of aliphatically bound NCO groups of 16.0 to 24.0 wt. %, which is substantially free of ester and/or ether and/or carbonate groups, (ii) at least one amino-functional polyaspartic acid ester of the general formula ##STR00005## in which n=2, and X represents a divalent organic residue which can be obtained by removing the amino groups from a linear or branched aliphatic diamine having up to 9 carbon atoms, or preferably by removing the amino groups from 1,4-diaminobutane, 1,6-diaminohexane, 2,2,4-trimethyl-1,6-and/or 2,4,4-trimethyl-1,6-diaminohexane, or particularly preferred by removing the amino groups from 2-methyl-1,5-diaminopentane, and R.sup.1 and R.sup.2 are a methyl or an ethyl group; (2) structurally bonding together at least two identical or different substrates; (3) curing the at least one adhesive bond such that, in the cured state, the same has a tensile shear strength of at least 7 MPa, preferably at least 10 MPa, more preferably at least 12 MPa, wherein the tensile shear strength is measured according to standard DIN/EN 1465 (2009-07), between two test bodies made of roughened V2A steel.

3. Structural adhesive as claimed in claim 1 or a method as claimed in claim 2, wherein X is a residue obtainable by removal of the amino groups from 1,4-diaminobutane, 1,6-diaminohexane, 2,2,4-trimethyl-1,6- and/or 2,4,4-trimethyl-1,6-diaminohexane, preferably by removal of the amino groups from 2-methyl-1,5-diaminopentane.

4. Structural adhesive according to at least one of claim 1 or 3, or method according to claim 2 or 3, wherein i) contains: i) at least one polyisocyanate having free isocyanate groups and based on hexamethylene diisocyanate having a content of aliphatically bound NCO groups of 17.0 to 23.5 wt. %, which is substantially free of ester and/or ether and/or carbonate groups.

5. Structural adhesive according to claim 1 or at least one of claim 3 or 4, or method according to claim 2 or at least one of claim 3 or 4, wherein i) contains i) at least one polyisocyanate mixture comprising alkoxysilane groups.

6. Structural adhesive or method according to at least one of claim 1 to 4 or 5, wherein ii) contains: ii) at least one amino-functional polyaspartic acid ester of the abovementioned formula, in which n=2 and X is a divalent organic residue, which is obtained by removal of the amino groups from 1,6-diaminohexane or by removal of the amino groups from 2-methyl-1,5-diaminopentane, and wherein R.sup.1 and R.sup.2 are an ethyl group.

7. Structural adhesive or method according to at least one of claims 1 to 5 or claim 6, characterized in that the two-component structural adhesive contains at least one further component iii), this further component preferably containing water or being water.

8. Structural adhesive or process according to at least one of claims 1 to 6 or claim 7, characterized in that component iii) contains aliphatic and/or cycloaliphatic diamines, and/or: characterized in that component iii) contains at least one adhesion promoter, preferably at least one functional silane, and/or: characterized in that component iii) contains inorganic and/or organic flame retardants, and/or: characterized in that component iii) contains highly disperse silicic acids and/or: characterized in that component iii) contains polyols.

9. Structural adhesive or method according to at least one of claims 1 to 7 or claim 8, characterized in that the two components i) and ii), where ii) optionally contains component iii), of the structural adhesive are used in a volume ratio of from 60:40 to 40:60 or: characterized in that the two components i) and ii), where ii) optionally contains component iii), are used in a volume ratio of around 50:50.

10. Method according to at least one of claim 2 to 8 or 9, characterized in that the two components in step (2) are applied to the two substrate surfaces with the aid of a 2K cartridge system with static mixer.

11. Substrates, objects or articles, characterized in that they are obtained or obtainable by means of a method and/or by using a structural adhesive according to at least one of claim 1 to 9 or 10 and that are, in particular, adhesively bonded and cured.

Description

EXAMPLE 1

[0109] Production of a Two-Component Structural Adhesive (According to the Invention)

[0110] Component A [Component i)]

[0111] Polyisocyanurate polyisocyanate based on hexamethylene diisocyanate with an NCO content of 23% and a viscosity of 2900 MPas (23° C.), residual monomer content <0.1%, Desmodur Ultra N3300, commercial product from Covestro AG, Leverkusen

TABLE-US-00001 Component B [mixture of components ii) and iii)] 97.5 wt. % polyaspartic acid esters based on 1,6-diaminohexane and maleic acid diethyl ester, [component ii)] 0.5 wt. % demineralized water [component iii)] 2 wt. % 3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane, laromin C260, commercial product from BASF AG, Ludwigshafen [component iii)]

[0112] The two components A and B are filled into a 2K cartridge-Sulzer Mixpac 2K Adhesive A System, from Sulzer Mixpac AG, Haag Switzerland. The application is carried out in a volume ratio of 1:1 using a static Sulzer 2K mixer MAH 06-21 T from Sulzer Mixpac AG.

[0113] This structural adhesive according to the invention hardens reliably even at a temperature of -18° C. within 24 hours.

EXAMPLE 2

[0114] Production of a Two-Component Structural Adhesive (According to the Invention)

[0115] Component A [Component i)]

[0116] Polyisocyanate based on hexamethylene diisocyanate with iminooxadiazine dione structure and an NCO content of 23.5% and a viscosity of 700 MPas (23° C.), residual monomer content <0.3%, Desmodur N3900, commercial product from Covestro AG, Leverkusen

TABLE-US-00002 Component B [mixture of components ii) and iii)] 95 wt. % polyaspartic acid esters based on 2-methyl-1, 5-diaminopentan and maleic acid diethyl ester, Desmophen NH1220, commercial product from Covestro AG, Leverkusen [component ii)]  1 wt. % 3-glycidoxypropyltrimethoxysilane [component iii)]  4 wt. % butane diol-1, 4 [component iii)]

[0117] The two components A and B are filled in a 2K cartridge-Sulzer Mixpac 2K Adhesive A System, supplied by Sulzer Mixpac AG, Haag Switzerland. The application is carried out in a volume ratio of 1:1 by using a static Sulzer 2K mixer MAH 06-21 T from Sulzer Mixpac AG.

[0118] This structural adhesive according to the invention hardens reliably even at a temperature of −18° C. within 24 hours.

EXAMPLE 3

[0119] Production of a Two-Component Structural Adhesive (According to the Invention)

[0120] Component A [Component i)]

[0121] Commercially available polyisocyanate based on hexamethylene diisocyanate with biuret structure and an NCO content of 22% and a viscosity of 8000 MPas (23° C.), Desmodur N100, residual monomer content <0.3%, commercial product from Covestro AG, Leverkusen

TABLE-US-00003 Component B [mixture of components ii) and iii)] 92.5 wt. % polyaspartic acid esters based on 2-methyl-1, 5-diaminopentan and maleic acid diethyl ester, Desmophen NH1220, commercial product from Covestro AG, Leverkusen [component ii) ] 5 wt. % highly disperse silica (HDK H18 from Wacker Chemie AG, Burghausen [component iii)] 2 wt. % 1-amino-3,3,5-trimethyl-5-aminomethylcyclohexane (Vestamine IPD from Evonik AG Essen), [component iii)] 0.5 wt. % demineralized water [component iii)]

[0122] The two components A and B are filled into a 2K cartridge-Sulzer Mixpac 2K Adhesive A System, from Sulzer Mixpac AG, Haag Switzerland. The application is carried out in a volume ratio of 1:1 using a static Sulzer 2K mixer MAH 06-21 T from Sulzer Mixpac AG.

[0123] This structural adhesive according to the invention hardens reliably even at a temperature of -18° C. within 24 hours.

EXAMPLE 4

[0124] Production of a Two-Component Structural Adhesive (According to the Invention)

TABLE-US-00004 Component A [component i), mixture of two polyisocyanates] 60 wt. % polyisocyanurate polyisocyanate based on hexamethylene diisocyanate with an NCO content of 23% and a viscosity of 900 MPas (23° C.), Desmodur N3600, commercial product from Covestro AG, Leverkusen are mixed with 40 wt. % polyester-modified polyisocyanurate polyisocyanate the invention relates to a base of hexamethylene diisocyanate having an NCO content of 11%, a viscosity of 6000 MPas (23° C.) and a polyester content of 45 wt. %, Desmodur N3800, commercial product from Covestro AG, Leverkusen Component B [mixture of components ii) and iii) ] 80 wt. % polyaspartic acid esters based on 2-methyl-, 5-diaminopentan and Maleic acid diethyl ester, Desmophen NH1220, commercial product from Covestro AG, Leverkusen [component ii)] 20 wt. % Martinal OL 104 LEO (precipitated aluminium hydroxide from Huber, Martineswerk GmbH, Bergheim [component iii)]

[0125] The two components A and B are filled into a 2K cartridge-Sulzer Mixpac 2K Adhesive A System, from Sulzer Mixpac AG, Haag Switzerland. The application is carried out in a volume ratio of 1:1, using a static Sulzer 2K mixer MAH 06-21 T from Sulzer Mixpac AG.

[0126] This structural adhesive according to the invention also cures at a temperature of −18° C. within 24 hours.

[0127] Comparison of the Adhesive Properties

[0128] The two-component adhesives were applied to roughened V2A steel test bodies having a length of 100 mm and a width of 25 mm on one side in order to determine the tensile shear strengths in accordance with the DIN/EN 1465 (2009-07), and then adhesively bonded to the respectively applied gap dimension over an overlap length of 12 mm. The correction time was determined as the time in which the two bonded test bodies can still be displaced manually without expenditure of force. The assembly stability was determined as the time after which the bonded test bodies can be loaded with a mass of 1 kg at one end with horizontal fixing.

[0129] The tensile shear strength was determined with the aid of a tensile testing machine (Shimadzu, AGS-X HC 20 KN) after a time interval of 48 hours (22° C., 40% rel.

[0130] atmospheric humidity, test speed 2 mm/minute). The values for the tensile strengths given in the table below were determined as the mean value, measured on three test bodies in each case.

TABLE-US-00005 TABLE 1 Comparison of adhesive data Example 1 Example 2 Example 3 Example 4 Correction time 35 sec 180 sec 30 sec 220 sec (23° C.) Assembly stability 150 sec 540 sec 140 sec 500 sec (23′° C.) Tensile shear strength 7.6 MPa 9.2 MPa 7.9 MPa 7.0 MPa (Beech wood) 8.4 MPa 11.0 MPa 8.6 MPa 7.4 MPa (no/1 mm gap) (no/1 mm gap) (no/1 mm gap) (no/1 mm gap) Tensile shear strength 12.2 MPa 16.4 MPa 12.5 MPa 10.0 MPa (Roughened V2A-steel) 13.5 MPa 16.4 MPa 13.2 MPa 10.4 MPa (no/1 mm gap) (no/1 mm gap) (no/1 mm gap) (no/1 mm gap) Tensile shear strength 11.6 MPa 14.2 MPa 11.6 MPa 10.2 MPa (Roughened aluminum) 11.8 MPa 14.8 MPa 12.2 MPa 11.0 MPa (no/1 mm gap) (no/1 mm gap) (no/1 mm gap) (no/1 mm gap) Tensile shear strength 7.2 MPa 10.2 MPa 9.4 MPa 7.0 MPa (ABS, precleaned with 8.0 MPa 10.5 MPa 10.0 MPa 7.5 MPa isopropanol) (no/1 mm gap) (no/1 mm gap) (no/1 mm gap) (no/1 mm gap) Tensile shear strength 7.6 MPa 9.8 MPa 7.4 MPa 7.5 MPa (Polycarbonate, 7.8 MPa 10.0 MPa 7.2 MPa 7.9 MPa precleaned with (no/1 mm gap) (no/1 mm gap) (no/1 mm gap) (no/1 mm gap) isopropanol) Tensile shear strength 8.4 MPa 11.2 MPa 9.2 MPa 7.8 MPa (PVC (hard), precleaned 8.8 MPa 11.0 MPa 9.5 MPa 8.6 MPa with isopropanol) (no/1 mm gap) (no/1 mm gap) (no/1 mm gap) (no/1 mm gap)

EXAMPLE 5

COMPARATIVE EXAMPLE

[0131] V2A test specimens were bonded according to the statements made above using a commercially available two-component polyurethane adhesive Easy-Mix PU-90, polyurethane adhesive from Weicon GmbH, Munster. This adhesive has a correction time of 70 sec at 23° C. and an assembly strength of 9 minutes. The ratio of the correction time to the assembly strength is thus considerably less favorable.

[0132] In the case of an adhesive test at a temperature of 0° C. this adhesive no longer cured.

EXAMPLE 6

COMPARATIVE EXAMPLE (ANALOGOUS TO WO 2009-07/003596)

[0133] 166 g of the prepolymer from Example Al of WO 2009-07/003596 was intimately mixed with 23.4 g of the polyaspartic acid ester based on 2-methyl-1,5-diamopentane and maleic acid diethyl ester, Desmophen NH1220, commercial product from Covestro AG, Leverkusen [component ii)] in a plastic beaker. The mixture was processed for 5 minutes at 23° C. Using the fresh mixture, V2A test specimens were bonded in accordance with the procedure described above without a gap (“no gap”) and with a gap width of 1 mm. This adhesive ws allowed a correction time of 300 sec at 23° C. and an assembly strength of 50 minutes. The tensile shear strength was determined with the aid of a tensile testing machine after a time of 48 hours. The tensile strengths were determined as the mean value, measured on in each case three test bodies, using: [0134] 2,9 MPa (without gap) [0135] 2,7 MPa (1 mm gap width)

[0136] This flexible adhesive is thus unsuitable for producing structural adhesives