Two-component polyurethane adhesive for adhesively bonding molded fiber parts

Abstract

The invention relates to a two-component polyurethane adhesive containing i) a polyol component including a mixture of three different polyols to ensure crosslinking for a mechanically stable adhesive bonding, and also to achieve hydrophobia to ensure that the crosslinked adhesive layer is impervious to moisture, and glass fibers, and ii) an isocyanate component containing polyisocyanates in an NCO/OH ratio of 0.9:1 to 1.5:1. The polyol component further includes a metal catalyst. The two-component adhesive has a high adhesive strength, a high glass temperature, a low curing time and a sufficiently long processing time, which can adhesively bond also substrates having uneven surfaces. The invention further relates to an article comprising the two-component polyurethane adhesive.

Claims

1. A two-component polyurethane adhesive, comprising i) a polyol component containing at least one catalyst, wherein the catalyst in the two component polyurethane adhesive comprises a metal catalyst and: a. 2 to 30% by weight at least one oleochemical polyol having a number-average molecular weight (Mn) of at least 500 g/mol; b. 5 to 35% by weight at least one polyol that is different from (a) and has 3 to 14 hydroxy groups; c. 5 to 35% by weight at least one polyol that is different from (a) and (b) selected from ethoxylated and/or propoxylated polyphenols; d. 10 to 50% by weight glass fibers or a mixture of different glass fibers; e. 0 to 65% by weight at least one additive or auxiliary that is different from (a) to (d); wherein the mass fractions of the components (a) to (e) are relative to the total weight of the polyol component; and ii) an isocyanate component containing aromatic and/or aliphatic polyisocyanates in an NCO/OH ratio of 0.9:1 to 1.5:1; and wherein the metal catalyst is a tin compound, wherein the catalyst further comprises at least one complexing agent selected from the group consisting of tropolone, maltol, ethylmaltol, 3-hydroxyflavone, salicylhydroxamic acid, N,N-bis(salicylidene) ethylenediamine, kojic acid, 8-hydroxyquinoline, acetylacetone, acetoacetate, gallic acid ethyl ester, dehydroacetic acid, 2,5-dihydroxy-1,4-benzoquinone, dithizone, and tannin; and wherein the crosslinked two-component polyurethane adhesive has a glass transition temperature (Tg) of at least 65 C.

2. The two-component polyurethane adhesive according to claim 1, wherein the glass fibers have a fiber thickness between 5 and 30 m and a fiber length between 50 and 350 m.

3. The two-component polyurethane adhesive according to claim 1, wherein the glass fibers are coated with an aminosilane-based sizing agent, and the sizing agent content of the dried glass fibers is 0.2 to 2.0% by weight relative to the total weight of the coated glass fibers.

4. The two-component polyurethane adhesive according to claim 1, wherein the tin compound does not have a tin-carbon bond.

5. The two-component polyurethane adhesive according to claim 4, wherein the tin compound is a cyclic tin compound of one of formulae I to IV: ##STR00002## wherein: E=N(R.sup.3), O, S, or C(R.sup.3).sub.2; R.sup.1, R.sup.2=H, alkyl, or aryl; R.sup.3=H, alkyl, aryl, or (CH.sub.2).sub.nX, where n=1 to 12, and X=N(R.sup.1).sub.2, OR.sup.1, SR.sup.1, P(R.sup.1).sub.2 or P(O)(R.sup.4).sub.2; R.sup.4=alkyl, aryl, O(C.sub.2H.sub.5), or O-iso(C.sub.3H.sub.7); and Y=halogen, OR.sup.1; OC(O)R.sup.1; SR.sup.1, or OP(O)(R.sup.4).sub.2; wherein the aryl moieties contain 6 to 12 carbon atoms, and the alkyl moieties contain 1 to 12 carbon atoms.

6. The two-component polyurethane adhesive according to claim 1, wherein the polyol component comprises the complexing agent and the metal catalyst in a total amount of 0.01 to about 5% by weight relative to the polyol component.

7. The two-component polyurethane adhesive according to claim 1, wherein the crosslinked adhesive has an E-modulus of at least 4,000 MPa and a tensile strength of at least 40 MPa.

8. The two-component polyurethane adhesive according to claim 1, wherein the oleochemical polyol(s) has/have an OH equivalent weight of 150 to 500 g/eq and an OH functionality of 2.3 to 4.

9. The two-component polyurethane adhesive according to claim 1, wherein component (b) is selected from ethoxylated and/or propoxylated carbohydrates.

10. The two-component polyurethane adhesive according to claim 1, wherein component (c) is selected from the group consisting of propoxylated Bisphenol A, propoxylated Bisphenol B, propoxylated Bisphenol F, or mixtures thereof.

11. The two-component polyurethane adhesive according to claim 1, wherein component (c) is selected from the group consisting of propoxylated Bisphenol A, propoxylated Bisphenol B, propoxylated Bisphenol F, or mixtures thereof, with a degree of propoxylation of 2.

12. A two-component polyurethane adhesive according to claim 1, wherein the aromatic polyisocyanate is 2,4-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, a mixture of 2,4-diphenylmethane diisocyanate and 4,4-diphenylmethane diisocyanate, a polymeric isocyanate based on 2,4- and/or 4,4-diphenylmethane diisocyanate having an NCO functionality of 2.0 to 3.2, or a mixture of two or more of the aforementioned aromatic polyisocyanates.

13. The two-component polyurethane adhesive according to claim 1, wherein the aliphatic polyisocyanate is a trimerized hexamethylene diisocyanate.

14. The two-component polyurethane adhesive according to claim 1, wherein the polyol component comprises 20 to 40% by weight glass fibers or mixture of different glass fibers.

15. The two-component polyurethane adhesive according to claim 1, wherein the at least one complexing agent is selected from the group consisting of tropolone, maltol, ethylmaltol, 3-hydroxyflavone, salicylhydroxamic acid, N,N-bis(salicylidene) ethylenediamine, kojic acid, acetylacetone, acetoacetate, gallic acid ethyl ester, dehydroacetic acid, 2,5-dihydroxy-1,4-benzoquinone, dithizone and tannin.

16. An article comprising the two-component polyurethane adhesive according to claim 1 adhesively bonded to a substrate comprising metal, plastic, foam, fiber composite, a fiber-containing shaped body, a fiber composite or a fiber-containing shaped body comprising glass fibers, carbon fibers, natural fibers, or synthetic fibers embedded in a plastic matrix.

17. An article comprising two substrates bonded together by cured reaction products of the two-component polyurethane adhesive according to claim 1.

18. The article of claim 17 where each substrate independently comprises metal, plastic, foam, a fiber composite, a fiber-containing shaped body, a fiber composite and a fiber-containing shaped body, wherein fiber is selected from glass fibers, carbon fibers, natural fibers, or synthetic fibers.

Description

EXAMPLES

Example 1 (not According to the Present Invention)

(1) Polyol component (OH component):

(2) TABLE-US-00001 Sugar-based polyol.sup.1) 22.5 Sovermol 805 .sup.2) 5.0 Sovermol 819 .sup.3) 10.0 Propoxylated Bisphenol A .sup.4) 10.5 Molecular sieve 8.0 Calcium carbonate, coated 44.0

(3) Isocyanate component (NCO component):

(4) TABLE-US-00002 Lupranat MIS .sup.5) 58.5 Desmodur N 3300 .sup.6) 30.0 Molecular sieve 5.5 Pyrogenic silicic acid 6.0
1) OH functionality between 4 and 5
2) fatty acid esters, Fa. BASF, OH equivalent weight 330 g/eq, OH functionality 3.5
3) fatty acid esters, Fa. BASF, OH equivalent weight 234 g/eq, OH functionality 2.6
4) OH equivalent weight 174 g/eq, degree of propoxylation: ca. 2
5) MDI mixture made of 50% by weight 4,4-MDI and 50% by weight 2.4-MDI, Fa. BASF, NCO content 33.5% by weight
6) trimerized hexamethylene diisocyanate, Fa. Bayer Material Science, NCO content 21.8%, NCO equivalent weight 193 g/eq

(5) Mixing ratio: 100 parts by weight of the polyol component to 60 parts by weight of the isocyanate component

(6) TABLE-US-00003 Pot time (at room temperature) 165 min Glass transition temperature 75 C. Tensile strength (24 hr., 80 C.) 46.1 MPa Tensile strength (7 hr., 70 C.) 27.9 MPa E-module 3880 MPa t/min 0 40 50 60 70 Compressibility (open time) .sup.0) + + + + (+) Tensile shear strength/MPa 16.0 16.0 14.7 12.9 9.6 .sup.0) + ~ good, (+) ~ still good, ~ insufficient

Example 2 (not According to the Present Invention)

(7) Polyol component (OH component):

(8) TABLE-US-00004 Sugar-based polyol.sup.1) 22.5 Sovermol 805 .sup.2) 5.0 Sovermol 819 .sup.3) 10.0 Propoxylated Bisphenol A .sup.4) 10.5 Molecular sieve 8.0 Calcium carbonate, coated 8.0 Glass fibers .sup.7) 36.0

(9) Isocyanate component (NCO component):

(10) TABLE-US-00005 Lupranat MIS .sup.5) 58.5 Desmodur N 3300 .sup.6) 30.0 Molecular sieve 5.5 Pyrogenic silicic acid 6.0
7) short fibers with aminosilane sizing agent, fiber thickness between 5 and 30 m, fiber length between 50 and 350 m, sizing agent content of the dried glass fibers 0.2 to 2.0% by weight

(11) Mixing ratio: 100 parts by weight of the polyol component to 60 parts by weight of the isocyanate component

(12) TABLE-US-00006 Pot time (at room temperature) 165 min Glass transition temperature 75 C. Tensile strength (24 hr., 80 C.) 56.0 MPa Tensile strength (7 hr., 70 C.) 36.4 MPa E-modulus 4,800 MPa t/min 0 40 50 60 70 Compressibility (open time) .sup.0) + + + + (+) Tensile shear strength/MPa 17.3 17.0 14.9 13.5 10.5

Example 3 (According to the Present Invention)

(13) Polyol component (OH component):

(14) TABLE-US-00007 Sugar-based polyol.sup.1) 22.500 Sovermol 805 .sup.2) 5.000 Sovermol 819 .sup.3) 10.000 Propoxylated Bisphenol A .sup.4) 10.500 Molecular sieve 8.000 Calcium carbonate, coated 7.665 Glass fibers .sup.7) 36.000 Dibutyltin dilaurate 0.035 8-Hydroxyquinoline 0.300

(15) Isocyanate component (NCO component):

(16) TABLE-US-00008 Lupranat MIS .sup.5) 58.5 Desmodur N 3300 .sup.6) 30.0 Molecular sieve 5.5 Pyrogenic silicic acid 6.0

(17) Mixing ratio: 100 parts by weight of the polyol component to 60 parts by weight of the isocyanate component

(18) TABLE-US-00009 Pot time (at room temperature) 65 min Glass transition temperature 75 C. Tensile strength (24 hr., 80 C.) 56.3 MPa Tensile strength (7 hr., 70 C.) 51.1 MPa E-module 4880 MPa t/min 0 40 50 60 70 Compressibility (open time) .sup.0) + + + (+) Tensile shear strength/MPa 17.0 17.3 14.0 10.1 1.0

(19) The example 3 according to the present invention has a sufficiently long open time, but has a desired shorter curing time than the comparison examples.

Example 4

(20) The composition of the OH component corresponds to the examples 2 and 3, but the amounts of coated calcium carbonate and glass fibers were varied according to the following tables. The isocyanate component is unaltered.

(21) Compositions according to example 2 (without catalyst) with varying amounts of coated calcium carbonate and glass fibers:

(22) TABLE-US-00010 Coated calcium carbonate 44.0 34.0 24.0 14.0 8.0 Glass fibers .sup.7) 0.0 10.0 20.0 30.0 36.0 Tensile strength/MPa (7 hr., 70 C.) 27.9 28.8 31.0 35.0 36.4 Tensile strength/MPa (24 hr., 80 C.) 46.1 47.0 48.6 54.1 56.0

(23) Compositions according to example 3 (with catalyst) with varying amounts of coated calcium carbonate and glass fibers:

(24) TABLE-US-00011 Coated calcium carbonate 43.66 33.66 23.66 13.66 7.66 Glass fibers .sup.7) 0 10.0 20.0 30.0 36.0 Tensile strength/MPa (7 hr., 70 C.) 34.0 34.8 36.5 47.5 51.1 Tensile strength/MPa (24 hr., 80 C.) 46.1 46.8 48.9 53.9 56.3

(25) The results show that in the catalyst-free system, the difference in tensile strength between curing in 7 hr. at 70 C. and 24 hr. at 80 C. is greater than in the catalyst-containing system, and that the difference in tensile strength in the catalyst-containing system is reduced as the glass fiber concentration increases.

(26) In the catalyst-containing system, the higher the content of glass fibers, the closer the tensile strength after 7 hr. of curing at 70 C. is to the tensile strength after 24 hr. of curing at 80 C. Thus, the glass fibers intensify the catalyst action in the catalyst-containing adhesives.