WO2009070293A1

WO2009070293A1 - One-component, moisture-cure polyurethane adhesive

Info

Publication number: WO2009070293A1
Application number: PCT/US2008/013128
Authority: WO
Inventors: Palitha Abeywardena
Original assignee: Quaker Chemical, Corp.
Priority date: 2007-11-28
Filing date: 2008-11-25
Publication date: 2009-06-04
Also published as: CN101679575B; CN101679575A

Abstract

A one-component, moisture-cure polyurethane adhesive composition includes an isocyanate monomer, at least two polyols, a catalyst, and at least one additive. A method of adhesion includes applying between at least two substrates a one-component, moisture-cure polyurethane adhesive composition, wherein the adhesive composition includes an isocyanate monomer, at least two polyols, a catalyst, and at least one additive.

Description

TITLE OF THE INVENTION

ONE-COMPONENT, MOISTURE-CURE POLYURETHANE ADHESIVE

FIELD OF THE INVENTION

[0001] The present invention relates to a one-component, moisture-cure polyurethane adhesive that may be applied and cures at room temperature and forms permanent bonds by a chemical reaction with moisture from the substrate or environment. More specifically, the polyurethane adhesive is liquid at room temperature and is based on an isocyanate monomer, at least two polyols, a catalyst, and at least one additive.

BACKGROUND OF THE INVENTION

[0002] Two-component polyurethane adhesives are known. U.S. Patent No. 5,723,534, the content of which is hereby incorporated by reference, describes a polyurethane-based adhesive system in which a polyurethane polymer is first applied to one of the substrates to be bonded, an aqueous phase curing agent is then applied to the polyurethane polymer, and the second substrate is finally placed in contact with the polymer.

[0003] Two-component polyurethane adhesives generally offer greater bonding strengths than one-component adhesives, but require physical separation of the two components prior to combination and two steps in the method of bonding using the adhesive in order to prevent chemical instability.

[0004] U.S. Patent No. 7,259,207, the content of which is hereby incorporated by reference, describes a polyurethane adhesive paste that may be expressed from pressurized containers or cartridges. This adhesive allows bonding of substrates in a single step, but requires specialized equipment for its application, includes silica as a thickening agent, and is a paste at room temperature. U.S. Patent No. 5,939,499, the content of which is hereby incorporated by reference, discloses a hot melt polyurethane adhesive composition.

[0005] Clearly, a chemically stable one-component polyurethane adhesive composition that does not require either specialized equipment or elevated temperatures for its application onto a substrate, and displays at least the bonding strengths of commercially available two- component polyurethane adhesives is a desirable goal. SUMMARY OF THE INVENTION

[0006] According to some embodiments, a one-component, moisture-cure polyurethane adhesive composition includes an isocyanate monomer, at least two polyols, a catalyst, and at least one additive.

[0007] According to some embodiments, a method of adhesion includes applying between at least two substrates a one-component, moisture-cure polyurethane adhesive, wherein the adhesive composition includes an isocyanate monomer, at least two polyols, a catalyst, and at least one additive.

DETAILED DESCRIPTION OF THE INVENTION

[0008] As used throughout, ranges are used as shorthand for describing each and every value that is within the range. Any value within the range can be selected as the terminus of the range.

[0009] In some embodiments, a one-component, moisture-cure polyurethane adhesive (IK PU adhesive) composition includes: (A) an isocyanate monomer, (B) at least two polyols, (C) a catalyst, and (D) at least one additive. In some embodiments, a method of adhesion includes applying between at least two substrates a IK PU adhesive composition, wherein the adhesive composition includes an isocyanate monomer, at least two polyols, a catalyst, and at least one additive.

[0010] I. IK PU Adhesive Composition

[0011] The term "about" as used herein shall include the value referenced and all numbers within ± 10 percent of the value referenced. Thus, "about 20" means 20, and 18 to 22 inclusive of 20.

[0012] The term "adhesive" as used herein shall include both adhesive and sealant compositions.

[0013] A. Isocvanate monomer

[0014] Different isocyanate monomers may be used in the preparation of a IK PU adhesive as known to those who are skilled in the art. Suitable isocyanate monomers for use in the present invention should have at least two isocyanate groups per molecule. Various isomers of modified aromatic diisocyanate (MDI), modified aromatic isocyanates, diphenylmethane diisocyanate, blends of such isomers and isocyanates, and combinations thereof may be used in the present invention. However, a modified monomelic MDI is the preferred isocyanate monomer for use in the present invention. In some embodiments, one example of a commercially available modified monomelic MDI suitable for use in the present invention includes Mondur CD produced by Bayer MaterialScience LLC.

[0015] In some embodiments, the IK PU adhesive composition includes an isocyanate monomer. In some embodiments, the IK PU adhesive composition includes a modified aromatic diisocyanate (MDI). In some embodiments, the MDI is modified 4,4- diphenylmethane diisocyanate. In some embodiments, the MDI is liquid at room temperature (~ 25° C). In some embodiments, the IK PU adhesive composition includes an MDI in an amount of about 15 to about 35 percent by weight. In some embodiments, the composition includes an MDI in an amount of about 19 to about 23 percent by weight. In one embodiment, the composition includes an MDI in an amount of about 19 percent by weight. In another embodiment, the composition includes an MDI in an amount of about 19.85 percent by weight. In another embodiment, the composition includes an MDI in an amount of about 22.99 percent by weight. In another embodiment, the composition includes an MDI in an amount of about 21.97 percent by weight.

[0016] B. Polvols

[0017] The term "polyol" as used herein shall include mono functional alcohols, diols and higher functionality hydroxyl compounds.

[0018] In some embodiments, the IK PU adhesive composition includes a mixture of at least two polyols. In some embodiments, the composition includes at least one polyester polyol and at least one polyether polyol.

[0019] i. Polyester Polvols

[0020] Suitable polyols for use in the present invention include polyesters with reactive hydroxyl groups. Reactive hydroxyl groups may be primary, secondary, or tertiary groups. High molecular weight liquid hydroxyl terminated homopolymer resins of butadiene are preferred for their hydroxyl functionality, hydrolytic stability, low temperature flexibility, resistance to aqueous acids and bases, adhesion and electrical insulation properties. In some embodiments, the IK PU adhesive composition includes a polymer of butadiene (polybutadiene) with reactive hydroxyl groups. Preferred commercially available liquid hydroxyl terminated polymers of butadiene for use in the present invention include Poly bd® R-45HTLO resin produced by Sartomer Company, Inc. Poly bd® resins have primary allylic alcohol groups that exhibit high reactivity in condensation polymerization reactions.

[0021] In some embodiments, the IK PU adhesive composition includes at least two polyols, including at least one polyester polyol. In some embodiments, at least one polyester polyol is a liquid hydroxyl terminated homopolymer resin of butadiene. In some embodiments, at least one polyester polyol is a liquid hydroxyl terminated 1,3-butadiene homopolymer. In some embodiments, the IK PU adhesive composition includes a polyester polyol in an amount of about 5 to about 70 percent by weight and more preferably in an amount of about 18 to about 25 percent by weight. In some embodiments, the composition includes a polyester polyol in an amount of about 10 to about 90 percent by weight of the polyol-mixture component of the composition. In one embodiment, the composition includes a polyester polyol in an amount of about 20 percent by weight. In another embodiment, the composition includes a polyester polyol in an amount of about 20.4 percent by weight. In another embodiment, the composition includes a polyester polyol in an amount of about 22.6 percent by weight.

[0022] ii. Polvether Polvols

[0023] Suitable polyols for use in the present invention also include polyethers with reactive hydroxyl groups. The polyether polyol is preferably a hydroxyl terminated polyoxyalkylene polyol. More preferably, the polyether polyol is an ethylene oxide-capped diol that produces urethanes. Preferred commercially available ethylene oxide-capped diols include Poly-G® 55-28 produced by Arch Chemicals, Inc. Poly-G® 55-28 polyol is a stable, practically colorless liquid that is neither volatile nor corrosive, with a low pour point and high flash point. The ethylene oxide cap of Poly-G® 55-28 yields a primary hydroxyl content of approximately 85%, which enhances reactivity, and is suitable in applications requiring high elongation and flexibility, softness, or both.

[0024] In some embodiments, the 1 K PU adhesive composition includes at least two polyols, including at least one polyether polyol. In some embodiments, at least one polyether polyol is a hydroxyl terminated polyoxyalkylene. In some embodiments, at least one polyether polyol is an ethylene oxide-capped diol. In some embodiments, the IK PU adhesive composition includes a polyether polyol in an amount of about 5 to about 70 percent by weight and more preferably in an amount of about 45 to about 65 percent by weight. In some embodiments, the composition includes a polyether polyol in an amount of about 10 to about 90 percent by weight of the polyol-mixture component of the composition. In one embodiment, the composition includes a polyether polyol in an amount of about 54 percent by weight. In another embodiment, the composition includes a polyether polyol in an amount of about 54.6 percent by weight. In another embodiment, the composition includes a polyether polyol in an amount of about 46.6 to about 52.8 percent by weight.

[0025] C. Catalysts

[0026] Suitable catalysts for use in the present invention include urethane-forming catalysts such as organometallic carboxylates that result in a moisture-cure adhesive system that develops tack sooner and cures faster than when water alone is used as a curing agent. The organometallic carboxylate catalyst is preferably an organobismuth compound that provides a reduced toxicity alternative to organometallic carboxylates based on lead, mercury or tin without sacrificing performance and produces fast gelling systems. Preferred commercially available organobismuth catalysts include Coscat® 83 produced by Vertellus. Specific benefits of Coscat® 83 include a high selectivity toward the polyol-isocyanate reaction, thus avoiding bubble generation at low levels of moisture; an excellent acute toxicity profile; and improved humid aging performance in urethane systems currently catalyzed with other organometallics or amines.

[0027] Suitable catalysts for use in the present invention also include amine catalysts that provide stable prepolymer systems. In one embodiment, the amine catalyst is 2,2 '- dimorpholinodiethylether (DMDEE). [0028] In some embodiments, the IK PU adhesive composition includes a catalyst in an amount of about 0.005 to about 1 percent by weight. In some embodiments, the IK PU adhesive composition includes a catalyst in an amount of about 0.01 to about 0.5 percent by weight. In one embodiment, the composition includes a catalyst in an amount of about 0.4 percent by weight. In another embodiment, the composition includes a catalyst in an amount of about 0.11 percent by weight. In another embodiment, the composition includes a catalyst in an amount of about 0.13 percent by weight. In some embodiments, the composition includes an organometallic carboxylate catalyst in an amount of about 0.05 to about 1 percent by weight and more preferably in an amount of about 0.10 to about 0.15 percent by weight. In some embodiments, the composition includes an amine catalyst in an amount of about 0.005 to about 0.5 percent by weight and more preferably in an amount of about 0.01 to about 0.1 percent by weight.

[0029] D. Additives

[0030] Suitable additives for use in the present invention may be any compound which will not interfere with the efficacy of the other components in the adhesive composition and which increases adhesion. Suitable additives include, but are not limited to, fillers, plasticizers, and stabilizers. One example of a suitable additive is calcium oxide. Preferred commercially available calcium oxide includes VitaCal™ O Food Grade Calcium Oxide produced by Mississippi Lime Company.

[0031] Other suitable additives for use in the present invention are plasticizers, as known to those skilled in the art, that may be used to enhance the adhesive composition's flow properties and flexibility once the components have cured. Suitable plasticizers may include polymeric resins, elastomers, waxes, oils, and combinations thereof. An example of a preferred commercially available plasticizer suitable for use in the present invention is Polyoil 130, a stereospecific, non-hydrolysable polybutadiene oil produced by Evonik Degussa Corp. Polyoil 130 is an apolar hydrophobic hydrocarbon with low viscosity; water and chemical resistance; electrical insulation properties; solubility in alipathics, aromatics, and ethers; and because of its high content of \,4-cis double bonds, is a highly reactive, oxidatively cross-linking binder.

[0032] Suitable additives for use in the present invention also include stabilizers, as known to those skilled in the art, that provide protection to coatings and light sensitive substrates. Preferred commercially available stabilizers include Tinuvin® 328 and Irganox® 245 produced by Ciba® Specialty Chemicals. Tinuvin® 328 is a UV absorber of the hydroxyphenylbenzotriazole class and Irganox® 245 is a sterically-hindered, phenolic antioxidant.

[0033] In some embodiments, the IK PU adhesive composition includes at least one additive. In some embodiments, the IK PU adhesive composition includes calcium oxide. In some embodiments, the IK PU adhesive composition includes calcium oxide in an amount of about 0 to about 5 percent by weight. In some embodiments, the composition includes a plasticizer. In some embodiments, the plasticizer is an apolar hydrophobic hydrocarbon. In some embodiments, the plasticizer is a stereospecific, non-hydrolysable liquid polybutadiene. In some embodiments, the IK PU adhesive composition includes a plasticizer in an amount of about 0 to about 20 percent by weight and more preferably in an amount of about 7 to about 15 percent by weight. In one embodiment, the composition includes a plasticizer in an amount of about 1 1.3 percent by weight.

[0034] In some embodiments, the 1 K PU adhesive composition includes at least one stablizer. In some embodiments, the 1 K PU adhesive composition includes at least one stabilizer in an amount of about 0 to about 10 percent by weight and more preferably in an amount of about 0.1 to about 1 percent by weight. In some embodiments, the stabilizer provides UV protection. In some embodiments, the stabilizer is a hydroxyphenylbenzotriazole. In some embodiments, the stabilizer provides protection against thermal-oxidative degradation. In some embodiments, the stabilizer is a phenolic anti-oxidant. In one embodiment, the composition includes at least one stabilizer in an about of about 1.5 percent by weight. In another embodiment, the composition includes at least one stabilizer in an amount of about 0.5 percent by weight. In another embodiment, the composition includes at least one stabilizer in an amount of about 0.25 percent by weight.

[0035] II. IK PU Adhesive Properties

[0036] Polyurethane adhesives are generally known for forming very weak initial bonds. Without being bound by any one particular theory, it is hypothesized that the strong mechanical properties and bond strengths of the present invention is due in part to the stoichiometric excess of the isocyanate functional groups (the "NCO" groups). The NCO groups are in excess such that the functional groups of the polyols, the hydroxyl groups, are capped and create cross-linking within the 1 K PU adhesive composition while a number of NCO groups remain available for further reaction. The low initial viscosities of the present invention also allow enhanced penetration into porous filter media when used in filter preparation, and moisture-cure to form polyurethane-based adhesives having good mechanical properties and bond strengths.

[0037] In some embodiments, the IK PU adhesive composition is a liquid or gel at room temperature (~ 25° C). In some embodiments, the density of the IK PU adhesive composition is about 8.5 to about 9 lbs/gallon at 25° C, and more specifically about 8.625 to about 8.815 lbs/gallon at 25° C. In some embodiments, the specific gravity of the IK PU adhesive composition is about 1.02 to about 1.08 at 25° C, and more specifically about 1.03 to about 1.06 at 25° C. In some embodiments, the viscosity of the IK PU adhesive composition is about 5,000 to about 44,000 cps at 25° C, and more specifically about 15,000 to about 44,000 cps at 25° C. In some embodiments, the IK PU adhesive composition theoretically includes free NCO groups in an amount of about 1 to about 15 percent by weight, and more preferably in an amount of about 3 to about 6 percent by weight.

[0038] Water alone is an effective curing agent for the IK PU adhesive composition of the present invention as it is an active source of hydrogen and the NCO groups of the isocyanate react with the water. However, other curatives, as known to those skilled in the art, are also available for use in the present invention. The preferred polyether polyols used in the present invention are hygroscopic and can absorb atmospheric moisture in amounts up to several percent of its weight. In addition, use of an organometallic catalyst in the present invention produces faster set and moisture-cure times.

[0039] III. Preparation of IK PU Adhesive

[0040] The IK PU adhesive composition of the present invention is a reaction mixture of polyols and isocyanates in which the latter is in stoichiometric excess. A mixture of at least one polyester polyol and at least one polyether polyol is reacted with an isocyanate in the presence of an organometallic catalyst and an additive. This polyol-isocyanate reaction may be carried out at room temperature to produce a liquid or gel polyurethane adhesive with about 1 to about 15 percent free NCO groups by weight.

[0041] IV. Method of Use

[0042] The method of adhesion using the 1 K PU adhesive composition of the present invention essentially comprises applying the adhesive to one of the substrates that is to be bonded and placing the second substrate in contact with the adhesive. In some embodiments, the IK PU adhesive composition of the present invention may be used as a filter adhesive. In some embodiments, the IK PU adhesive composition may be applied at room temperature or at a higher temperature.

EXAMPLES

[0043] The following examples further describe and demonstrate some embodiments within the scope of the present invention. These examples are given solely for the purpose of illustration and are not to be construed as limitations of the present invention as many variations thereof are possible without departing from the scope and spirit of the present invention.

Example 1: IK PU Adhesive Composition (with calcium oxide)

Example 2: IK PU Adhesive Composition (with polybutadiene oil)

Example 3: IK PU Adhesive Composition (with DMDEE)

[0044] A. Adhesion Data

[0045] The following procedure was followed for Example 1 and Example 2 IK PU adhesive compositions using four different commercial membrane/tricot systems and then repeated using commercially available 2K PU adhesives. The IK PU adhesive composition of the present invention was applied on a first membrane layer and the tricot was put on the adhesive. The IK PU adhesive composition of the present invention was then applied on the tricot for a total adhesive thickness of 20 mils. The second membrane layer was laminated to the adhesive composition. The test specimen was kept under pressure at ambient conditions, typically at 25° C and 50 percent relative humidity, and cured for 24 hours.

[0046] B. Testing

[0047] Each laminate specimen was cut into one-inch strips and T-peeled at ambient room temperature conditions after a 24 hour cure. The T- values were obtained using a Mark- 10 (model MG50) instrument. Averages of the maximum T-peel values are reported in the Table 1 below.

Table 1: T-peel adhesion values of IK PU adhesive (present invention) compared to commercial 2K PU adhesives

[0048] C. Adhesion Results

[0049] i. Example 1 : IK PU adhesive (with calcium oxide)

[0050] Membrane 1 : The IK PU adhesive composition of the present invention is better than all average maximum values of both competitor 2K PU adhesives.

[0051] Membrane 2: The 1 K PU adhesive composition of the present invention is comparable to both competitor 2K PU adhesives. [0052] Membrane 3: The IK PU adhesive composition has higher average values than both competitor 2K PU adhesives.

[0053] ii. Example 2: IK PU adhesive (with polvbutadiene oil plasticizer)

[0054] Membrane 1 : The IK PU adhesive composition of the present invention has higher initial value averages than both competitor 2K PU adhesives.

[0055] Membrane 2: The IK PU adhesive composition of the present invention is comparable to both competitor 2K PU adhesives.

[0056] Membrane 3: The IK PU adhesive composition of the present invention has higher average values than both competitor 2K PU adhesives.

[0057] Membrane 4: The IK PU adhesive composition of the present invention is better than all average maximum values of both competitor 2K PU adhesives.

[0058] Although the foregoing description is directed to the preferred embodiments of the invention, it is noted that other variations and modifications in the details, materials, steps and arrangement of parts, which have been herein described and illustrated in order to explain the nature of the preferred embodiments of the invention, will be apparent to those skilled in the art, and may be made without departing from the spirit or scope of the invention.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. A one-component, moisture-cure, polyurethane adhesive composition comprising:

(a) an isocyanate monomer;

(b) at least two polyols;

(c) a catalyst; and

(d) at least one additive.

2. The adhesive composition of claim 1, wherein the isocyanate monomer is a modified aromatic diisocyanate (MDI).

3. The adhesive composition of claim 2, wherein the isocyanate monomer is a modified 4,4-diphenylmethane diisocyanate.

4. The adhesive composition of claim 2, wherein the isocyanate monomer is liquid at room temperature.

5. The adhesive composition of claim 1, wherein at least one polyol is a polyester polyol.

6. The adhesive composition of claim 5, wherein the polyester polyol is a hydroxyl terminated homopolymer resin of butadiene.

7. The adhesive composition of claim 5, wherein the polyester polyol is a liquid hydroxyl terminated 1,3 -butadiene homopolymer.

8. The adhesive composition of claim 1, wherein at least one polyol is a polyether polyol.

9. The adhesive composition of claim 8, wherein the polyether polyol is a hydroxyl terminated polyoxyalkylene.

10. The adhesive composition of claim 8, wherein the polyether polyol is an ethylene oxide-capped diol.

11. The adhesive composition of claim 1, wherein the catalyst is an organometallic carboxylate catalyst.

12. The adhesive composition of claim 11, wherein the catalyst is an organobismuth compound.

13. The adhesive composition of claim 1, wherein at least one additive is a filler.

14. The adhesive composition of claim 13, wherein the filler is calcium oxide.

15. The adhesive composition of claim 1, wherein at least one additive is a plasticizer.

16. The adhesive composition of claim 15, wherein the plasticizer is a polybutadiene oil.

17. The adhesive composition of claim 1, wherein at least one additive is a stabilizer.

18. The adhesive composition of claim 17, wherein the stabilizer provides UV protection.

19. The adhesive composition of claim 18, wherein the stabilizer is a hydroxyphenylbenzotriazole.

20. The adhesive composition of claim 17, wherein the stabilizer provides protection against thermo-oxidative degradation.

21. The adhesive composition of claim 20, wherein the stabilizer is a phenolic antioxidant.

22. A method of adhesion, comprising: applying a one-component, moisture-cure polyurethane adhesive between at least two substrates, wherein the adhesive composition includes:

(a) an isocyanate monomer;

(b) at least two polyols; (c) a catalyst; and

(d) at least one additive.

23. The method of claim 22, wherein the isocyanate monomer is a modified aromatic diisocyanate (MDI).

24. The method of claim 23, wherein the isocyanate monomer is a modified 4,4- diphenylmethane diisocyanate.

25. The method of claim 23, wherein the isocyanate monomer is liquid at room temperature.

26. The method of claim 22, wherein at least one polyol is a polyester polyol.

27. The method of claim 26, wherein the polyester polyol is a hydroxyl terminated homopolymer resin of butadiene.

28. The method of claim 26, wherein the polyester polyol is a liquid hydroxyl terminated 1,3 -butadiene homopolymer.

29. The method of claim 22, wherein at least one polyol is a polyether polyol.

30. The method of claim 29, wherein the polyether polyol is a hydroxyl terminated po lyoxyalkylene .

31. The method of claim 29, wherein the polyether polyol is an ethylene oxide-capped diol.

32. The method of claim 22, wherein the catalyst is an organometallic carboxylate catalyst.

33. The method of claim 32, wherein the catalyst is an organobismuth compound.

34. The method of claim 22, wherein at least one additive is a filler.

35. The method of claim 34, wherein the filler is calcium oxide.

36. The method of claim 22, wherein at least one additive is a plasticizer.

37. The method of claim 36, wherein the plasticizer is a polybutadiene oil.

38. The method of claim 22, wherein at least one additive is a stabilizer.

39. The method of claim 38, wherein the stabilizer provides UV protection.

40. The method of claim 39, wherein the stabilizer is a hydroxyphenylbenzotriazole.

41. The method of claim 38, wherein the stabilizer provides protection against thermo-oxidative degradation.

42. The method of claim 41, wherein the stabilizer is a phenolic anti-oxidant.