WO2016179256A1 - Adhesive formulation - Google Patents

Adhesive formulation Download PDF

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Publication number
WO2016179256A1
WO2016179256A1 PCT/US2016/030733 US2016030733W WO2016179256A1 WO 2016179256 A1 WO2016179256 A1 WO 2016179256A1 US 2016030733 W US2016030733 W US 2016030733W WO 2016179256 A1 WO2016179256 A1 WO 2016179256A1
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WO
WIPO (PCT)
Prior art keywords
formulation
polyester polyol
curable
another embodiment
present
Prior art date
Application number
PCT/US2016/030733
Other languages
French (fr)
Inventor
Sergio Grunder
Daniel Schneider
Stefan Schmatloch
Andreas Lutz
Francois M. Casati
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Dow Global Technologies Llc
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Publication of WO2016179256A1 publication Critical patent/WO2016179256A1/en

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    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/0838—Manufacture of polymers in the presence of non-reactive compounds
    • C08G18/0842—Manufacture of polymers in the presence of non-reactive compounds in the presence of liquid diluents
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
    • C08G18/12—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step using two or more compounds having active hydrogen in the first polymerisation step
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/16—Catalysts
    • C08G18/22—Catalysts containing metal compounds
    • C08G18/24—Catalysts containing metal compounds of tin
    • C08G18/244—Catalysts containing metal compounds of tin tin salts of carboxylic acids
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/16—Catalysts
    • C08G18/22—Catalysts containing metal compounds
    • C08G18/24—Catalysts containing metal compounds of tin
    • C08G18/244—Catalysts containing metal compounds of tin tin salts of carboxylic acids
    • C08G18/246—Catalysts containing metal compounds of tin tin salts of carboxylic acids containing also tin-carbon bonds
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/30—Low-molecular-weight compounds
    • C08G18/302—Water
    • C08G18/307—Atmospheric humidity
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/4009—Two or more macromolecular compounds not provided for in one single group of groups C08G18/42 - C08G18/64
    • C08G18/4018—Mixtures of compounds of group C08G18/42 with compounds of group C08G18/48
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/48—Polyethers
    • C08G18/4804—Two or more polyethers of different physical or chemical nature
    • C08G18/4812—Mixtures of polyetherdiols with polyetherpolyols having at least three hydroxy groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/48—Polyethers
    • C08G18/4825—Polyethers containing two hydroxy groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/48—Polyethers
    • C08G18/4833—Polyethers containing oxyethylene units
    • C08G18/4837—Polyethers containing oxyethylene units and other oxyalkylene units
    • C08G18/4841—Polyethers containing oxyethylene units and other oxyalkylene units containing oxyethylene end groups
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
    • C08G18/72—Polyisocyanates or polyisothiocyanates
    • C08G18/74—Polyisocyanates or polyisothiocyanates cyclic
    • C08G18/76—Polyisocyanates or polyisothiocyanates cyclic aromatic
    • C08G18/7657—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings
    • C08G18/7664—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings containing alkylene polyphenyl groups
    • C08G18/7671—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings containing alkylene polyphenyl groups containing only one alkylene bisphenyl group
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
    • C09J175/00—Adhesives based on polyureas or polyurethanes; Adhesives based on derivatives of such polymers
    • C09J175/04—Polyurethanes

Definitions

  • the present invention is related to an adhesive formulation; and more specifically, to an adhesive formulation employing a solid polyester polyol and to a formulation that can be dual cured.
  • the modern fabrication of vehicles involves several applications of elastic and structural adhesives to bond parts, body structures, and building blocks increasing the performance of the vehicles and facilitating the assembly, respectively.
  • Several parts are commonly bonded outside the body shop in the trim shop using mainly two component (“2K”) polyurethane (PU) adhesives.
  • 2K polyurethane
  • One component (“IK”) PU adhesives have been well established in the automotive industry and are commonly cured by moisture.
  • the IK PU adhesives comprise PU prepolymers bearing terminal isocyanate (NCO) groups.
  • the NCO groups react with water molecules (e.g., humidity) when placed in an ambient environment (relative humidity [r.h.] > 0 percent [%], preferably 20 % to 80 %) forming carbon dioxide and an amine; the amine reacts again with NCO groups causing crosslinking and curing of the polymer.
  • the parts are commonly fully cured (all NCO groups consumed) after 7 days at an ambient environment.
  • IK PU adhesives includes encapsulated NCOs and such known IK PU adhesives can be cured by heat. Heat curing of the IK PU adhesives accelerates the curing of the system.
  • the known systems are not able to cure with humidity due to the lack of non-encapsulated isocyanate groups, and therefore, the whole assembly needs to be heated. Heating the whole assembly is disadvantageous because it impedes, in many cases, the manufacturing process particularly for large assemblies which need to go through a heating cycle (i.e. in an oven or the like).
  • whole assemblies usually contain parts which further contain heat sensitive parts and heating the whole assemblies can potentially damage the heat sensitive parts of the assemblies.
  • EP2024457B1 discloses an adhesive/sealant composition which is suitable for curing by two curing mechanisms: (1) heat and (2) moisture.
  • the heat- and moisture-curing composition described in EP2024457B 1 includes at least one isocyanate-functional prepolymer having substantially terminal isocyanate groups and at least one polyamine having at least 2 primary or secondary amino groups per molecule and a melting point above 55 °C.
  • the composition may be at least partly thermally cured, and alternatively may cure completely with ambient atmospheric moisture.
  • EP2024457B 1 describes the use of solid polyamines, particularly
  • EP2024457B1 1,12-dodecanediamine, in an isocyanate functional prepolymer-bearing adhesive formulation.
  • the dual cure heat- and moisture-curing adhesive formulation of EP2024457B1 relies on solid insoluble amines.
  • the amines disclosed in EP2024457B 1 are not encapsulated.
  • EP2024457B 1 does not disclose the use of a solid polyester polyol in an adhesive formulation wherein the solid polyester polyol melts when heated and which liberates entangled hydroxyl groups, which in turn, may react with isocyanate groups in the formulation. Instead, EP2024457B 1 uses solid amines.
  • WO88/06165 describes sealants and adhesives and their use.
  • WO88/06165 discloses a heat- and moisture-curing one-component polyurethane sealant and an adhesive based on telechelate isocyanate prepolymers made from aromatic diisocyanates in stoichiometric excess and polyalcohols.
  • the sealant/adhesive formulation of WO88/06165 also contains (a) a catalyst for the moisture-curing, in particular a tin compound, and (b) a blocked, heat activated crosslinking agent, in particular a methylene dianiline/sodium chloride complex compound or a polyamino- or hydroxyfunctional compound in microencapsulated form.
  • WO88/06165 describes a dual cure (heat and moisture) adhesive formulation based on isocyanate functional prepolymers and latent diamine salts.
  • the salts disclosed which are formed, e.g. of methylene diamine(MDA) with sodium chloride, are reported to be inert at room temperature but act as a hardener when heated above 115 °C.
  • WO88/06165 does not disclose solid polyester polyols which melt when heated and then, in turn, react with isocyanates to crosslink the system. Instead, the process of W088/06165 is to deactivate a certain amine as its sodium chloride salt.
  • the composition of WO88/06165 contains blocked amines, not solid polyesters.
  • WOO 1/88005 A2 discloses polyurethanes containing dispersed crystalline polyesters.
  • WOO 1/88005 A2 describes a polyurethane foam formulation which includes toluene diisocyanate (TDI) and water.
  • TDI toluene diisocyanate
  • WO01/88005A2 does not disclose a one-part polyurethane adhesive formulation, but instead discloses a foam.
  • WO01/88005A2 discloses a process for producing resilient polyurethane foams by foaming an organic polyisocyanate, an isocyanate-reactive compound and a fusible polymer.
  • WO01/88005A2 further discloses that an improvement in the hardness of the foams is achieved without adversely affecting the other properties of the foams, such as tensile strength and elongation.
  • WO01/88005A2 discloses that the polyester is only used in a foam producing process described in
  • WO 2008/076146A1 describes compositions useful as an adhesive for installing vehicle windows.
  • WO 2008/076146A1 discloses, in one embodiment, a composition comprising: (a) one or more isocyanate functional poly ether polyurethane prepolymers; and (b) one or more prepolymers of one or more polyisocyanates and one or more polyesters wherein the terminal groups on the polyester polyol polyurethane prepolymer are the residue of a monofunctional polyalkylene glycol (hereinafter capped polyester polyurethane prepolymer) or one or more polyester polyols which are capped with the residue of one or more monofunctional isocyanates (hereinafter isocyanate capped polyesters); wherein the composition is a low viscous paste at a temperature of from about 40 °C to about 80 °C and is a high viscous paste at a temperature of from about 400 °C or less.
  • a monofunctional polyalkylene glycol hereinafter capped polyester polyure
  • the composition further includes (c) one or more catalysts for the reaction of isocyanate moieties with hydroxyl groups.
  • WO 2008/076146A1 discloses, in another embodiment, a method of bonding two or more substrates together by contacting two or more substrates together with the above composition, in the form of a low viscous paste, disposed along at least a portion of the area wherein the substrates are in contact with each other.
  • a preferred embodiment disclosed in WO 2008/076146A1 includes the above composition being heated to about 40 °C to about 80 °C and converting the composition into a low viscous paste prior to contacting the composition with one or more substrates.
  • WO 2008/076146A1 describes the use of temperature dependent viscosity modifiers based on polyester polyols which are converted to isocyanate functional prepolymers. Those prepolymers with a polyester backbone have a melting point above room temperature, but below the application temperature of the adhesive. After the adhesive is applied, the adhesive cools down which causes the polyester comprising prepolymers to crystallize causing the viscosity of the adhesive to increase. The viscosity increase is based on a physical phenomenon rather than a chemical crosslinking.
  • the low viscous paste producing process described in WO 2008/076146A1 suffers from the disadvantage(s) of not having a dual cure mechanism; the reported adhesives can only be cured by moisture without being able to be activated by heat.
  • WO2008/076146A1 describes IK PU adhesives which can only be cured by moisture, not by heat and not by a dual cure mechanism.
  • WO2008/076146A1 is used only as a rheology modifier and comprises a polyester polymer which is further reacted with isocyanates to offer a polyester-based prepolymer.
  • IK PU adhesive having a dual cure mechanism including a dual cure adhesive formulation based on insoluble solid polyester polyols which can be cured by (1) heat and/or (2) moisture; and wherein the IK PU adhesive does not suffer from the disadvantages of the known prior art curing mechanisms.
  • the present invention addresses the problems encountered by using prior art adhesive formulations by providing a fundamentally different approach from the approaches described in prior art.
  • the present invention utilizes solid insoluble polyester polyols to form a dispersion that can be added to an isocyanate functional adhesive formulation.
  • the solid polyester polyols are used as active heat activated curing agents (active crosslinkers) to render a one-component isocyanate functional formulation which is moisture curable, heat curable, or both, i.e., dual curable.
  • active crosslinkers active crosslinkers
  • the dispersion of the polyester polyols is stable in the reactive adhesive formulation.
  • the above adhesive formulation of the present invention includes a IK PU formulation which is capable of being cured by dual cure mechanisms such as by (1) heat and/or (2) moisture.
  • the dual cure IK PU formulation of the present invention can be applied to a substrate; and then by applying heat (e.g., induction, infrared, hot air, and the like) to the formulation, the formulation can be cured, pre-cured, or spot cured at critical positions on the substrate sufficient to give the bonded part handling strength. In a second step, if needed, the formulation can be further cured at ambient conditions by moisture. This adds advantages in performance of the adhesive and facilitates the assembly.
  • the advantages of a dual cure IK formulation include, but not limited to, for example, lower investment costs for application equipment and increased application process stability.
  • the dual cure IK PU formulations or systems of the present invention can potentially be used as a substitute for currently known 2K PU systems.
  • the dual curing adhesive composition and process provides improvements in productivity and quality of bonding.
  • Productivity can be achieved through heat curing (e.g., the reaction of the isocyanate with the polyester polyol) which allows for a fast curing process.
  • Quality of bonding can be obtained through moisture curing (e.g., the reaction of isocyanate with water and subsequent crosslinking).
  • the dual cure IK PU formulations of the present invention over IK PU heat cure adhesives include, but not limited to, for example, the possibility to adjust the de-blocking temperature by selecting a specific polyester polyol with a given melting point (different molecular weight polyester polyols). Another advantage can be the non-toxicity of polyester polyols of the present invention, particularly in comparison to highly toxic amines known in the art. Still another advantage of the present invention is the dual cure IK PU adhesive formulations of the present invention have the capability of providing a strong bonding, due to the presence of ester moieties, through hydrogen bonding.
  • the adhesive formulations of the present invention have the capability of being cured by moisture which makes the system more tolerable to curing conditions.
  • the formulation of the present invention can be cured by moisture, and the formulation can optionally be cured by heat, i.e. heat is advantageous but is not required for curing.
  • partial heat curing of the present invention formulation can be carried out without the need for a large oven.
  • spot curing i.e., partial heat curing
  • IR infrared
  • curing can be accelerated by heat using a IK PU system and spot curing.
  • a predetermined number of infrared heat stations can be used along the assembly line to cure the adhesives within 1 - 10 minutes at selected spots on automotive parts.
  • the material is cured at strategic places on the parts to offer handling strength.
  • the dual cure IK PU formulations of the present invention exhibits fast handling strength (e.g., handling strengths below 15 minutes), and fast curing (e.g., curing below 15 minutes).
  • One embodiment of the present invention is directed to a dispersion of the polyester polyol suitable to be introduced in a curable adhesive formulation.
  • the dispersion includes, for example, (a) at least one solid polyester polyol having a melting point of from about 50 °C to about 150 °C; and (b) and at least one plasticizer compound.
  • Another embodiment of the present invention is directed to a process for preparing the above dispersion of the polyester polyol suitable to be introduced into a curable adhesive formulation.
  • Still another embodiment of the present invention is directed to a curable formulation useful as an adhesive formulation including (i) at least one polymer resin,
  • the above dispersion of polyester polyol and (iii) optionally, at least one filler; wherein the curable formulation advantageously exhibits the dual cure property/mechanism of being curable by moisture, and/or curable by heat.
  • Yet another embodiment of the present invention is directed to a process for preparing the above curable adhesive composition.
  • Even still another embodiment of the present invention is directed to a cured product prepared by curing the adhesive material on a substrate.
  • Even yet another embodiment of the present invention is directed to a process for producing the above cured product.
  • the present invention realizes the benefit of enabling a IK PU adhesive formulation to be cured by both heat and/or moisture.
  • Thermal cure means that crosslinking of the formulation is being initiated by a heat trigger.
  • Moisture cure means that crosslinking of the formulation is being initiated by moisture.
  • Water reacts with isocyanate groups to form carbamic acid which after C0 2 loss is turned into an amine, which in turn, reacts with isocyanates.
  • Double cure means a curing system that includes at least the following two curing mechanisms: (1) thermal cure and (2) moisture cure crosslinking mechanism.
  • Structural stability herein, with reference to a composition, means the handling strength of assembled parts, as measured in terms of lap shear strength. A lap shear strength higher than 0.8 megapascal (MPa) is considered to offer assembled parts an adequate handling strength.
  • the dispersion of a polyester polyol includes a mixture of: (a) at least one solid polyester polyol having a melting point of from about 40 °C to about 150 °C in one embodiment, from about 50 °C to about 120 °C in another embodiment, and from about 60 °C to about 110 °C in still another embodiment; and (b) and at least one plasticizer compound.
  • the polyester polyol, component (a), useful in preparing the dispersion of the polyester polyol of the present invention can include for example a polyester polyol with an average molecular weight of from about 1,000 g/mol to about 6,000 g/mol in one embodiment, from about 2,000 g/mol to about 4,000 g/mol in another embodiment, and from about 2,500 g/mol to about 3,500 g/mol in still another embodiment.
  • the polyester polyol may be selected from one or more of the following products: reaction products of an excess polyol with an aliphatic or aromatic diacids or anhydride; linear co-polyesters with primary hydroxyl functionality and medium molecular weight; and mixtures thereof.
  • suitable polyester polyols, component (a), useful for preparing the dispersion of the present invention may include one or more of the polyesters described in WO2009/140001A1, which is incorporated herein in its entirety, and particularly from page 3, line 7 to page 5, line 5, which describes useful crystalline or liquid linear co-polyesters having primary hydroxyl functionality.
  • the polyester polyols, useful in the present invention can also include the polyester polyols described in WO 2001/088005, which is incorporated herein in its entirety, and particularly from page 11 to page 13.
  • the linear co-polyesters useful in the present invention may be described as having, in certain non- limiting embodiments, a Tg (measured according to German Institute of Standardization - "DIN” - 53765) ranging from about -20 °C to about 60 °C.
  • the crystalline linear co-polyesters may be alternatively defined, in non-limiting embodiments, as having a melt viscosity, as measured at 80 °C using the parallel plate method according to German Institute of Standardization's DIN EN ISO 3219:1993, ranging from about 0.5 Pascal-seconds (Pa-s) to about 15 Pa-s; or as measured at 130 °C using the above same method ranging from about 0.3 Pa-s to about 4 Pa-s.
  • the liquid linear co-polyesters generally have a melt viscosity ranging from about 2 Pa-s to about 11 Pa-s, as measured at 80 °C using the parallel plate method according to German Institute of Standardization' s DIN EN ISO 3219:1993.
  • Crystalline linear co-polyesters may alternatively be characterized by their melting temperature (Tm) as measured according to DIN 53765.
  • Tm melting temperature
  • the Tm of the co-polyesters may range from about 30 °C and about 150 °C in one embodiment; from about 40 °C to about 120 °C in another embodiment; and from about 50 °C to about 100 °C in still another embodiment.
  • the linear co-polyesters may have hydroxyl numbers (mg KOH/g as measured according to DIN 53240-2) from about 15 to about 50. In another embodiment, the hydroxyl number of the co-polyester may be from about 18 to about 40.
  • the primary hydroxyl functionality of the linear co-polyester may range from 2 to about 8 in one embodiment, from 2 to about 4 in another embodiment, and 2 in still another embodiment.
  • Suitable processes for producing the linear co-polyesters useful in the invention may be described in, for example, G. Oertel, Polyurethane Handbook, 2nd ed., Hanser, publisher.
  • the processes for producing the co-polyesters may include, in non-limiting embodiments, for example (1) linear polycondensation of linear dicarboxylic acids and linear dihydroxyl compounds; (2) the reaction of linear dicarboxylic acid chlorides and linear dihydroxyl compounds; and (3) transesterification using linear dihydroxyl compounds and esters of the linear dicarboxylic acids.
  • polycondensation of linear dicarboxylic acids and linear dihydroxyl compounds may be particularly convenient.
  • suitable linear dicarboxylic acids may be used and include, in non-limiting embodiments, linear aliphatic dicarboxylic acids having 2 carbon atoms to about 20 carbon atoms in one embodiment, and from about 6 carbon atoms to about 15 carbon atoms in another embodiment, in the alkylene radical.
  • These linear diacids react with linear dihydroxyl compounds, for example linear diols, having from 2 carbon atoms to about 20 carbon atoms in one embodiment, and diols having from about 6 carbon atoms to about 15 carbon atoms in another embodiment.
  • the diacid is substantially free of any ethylenically unsaturated groups (i.e., carbon-carbon double bonds).
  • These acids include, for example, aliphatic dicarboxylic acids such as glutaric acid, succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid,
  • aromatic dicarboxylic acids are not suitable for use in the present invention because their melting points are too high (e.g., greater than about 180 °C) for those having an equivalent weight of at least about 1,000.
  • di- and multi- functional alcohols useful in the present invention may include ethylene glycol; diethylene glycol; triethylene glycol; propylene glycol; dipropylene glycol; 1,3-propanediol; 1,2-butanediol; 1,4-butanediol;
  • the polyesters prepared by polycondensation of linear dicarboxylic acids and linear dihydroxyl compounds are made from a diacid and a diol such that the repeating unit of the acid plus the alcohol has, in total, at least about 9 carbons atoms; and in another embodiment, a total of from about 10 carbon atoms to about 30 carbon atoms.
  • One preparation method for making the diacid/diol linear co-polyesters is known in the art.
  • An example of such co-polyesters available commercially is a linear co-polyester having a molecular weight of about 3,500 and a Tm of about 65 °C, sold by
  • Evonik Industries under the tradename DYNACOLLTM 7381.
  • Other related products useful in the present invention may include the products described in a technical leaflet entitled "DYNACOLL 7000, The Building Block System for Moisture Curable Hot Melt Adhesives and Sealants.”
  • Preferred embodiments of products useful in the present invention may include products described under the tradename DYNACOLL 7200 series and
  • the suitable polyester polyol useful in the formulation of the present invention includes, for example DYNACOLL 7000 series commercially available from Evonik Industries. Similar compounds from other suppliers may also be useful in the present invention.
  • the polyester polyol, component (a), useful in preparing the dispersion of the polyester polyol of the present invention can include other optional compounds such as, for example, stabilizers, especially stabilizer products which prevent or slow down hydrolysis.
  • stabilizer products can include, for example, STABAXOL® additives which are commercially available from Rhein Chemie Rheinau GMBH.
  • the preparation method involving the transesterification of a polyester with an alcohol may be suitably carried out using an alcohol having at least 2 hydroxyl groups.
  • Preferred embodiments of the alcohols are alcohols having 2 to 4 hydroxyl groups.
  • the process for producing such polymers is known in the art such as described in G. Oertel, Polyurethane Handbook, 2nd ed., Hanser, publishers, incorporated herein by reference.
  • the melting point of the polyester polyol is the melting point of the polyester polyol.
  • the solid polyester polyol of the present invention exhibits a melting point of from about 40 °C to about 150 °C in one embodiment, from about 50 °C to about 120 °C in another embodiment, from about 60 °C to about 110 °C in still another embodiment, and from about 70 °C to about 90 °C in yet another embodiment.
  • polyester polyol Another key property of the polyester polyol is the functionality of the polyester polyol which can be for example from 2 to 4 in one embodiment, 2 to 3 in another embodiment, and 2 in still another embodiment.
  • Still another key property of the polyester polyol is the hydroxyl number of the polyester polyol which can be for example from about 10 mg KOH/g to about 100 mg KOH/g in one embodiment, from about 20 mg KOH/g to about 80 mg KOH/g in another embodiment, and from about 30 mg KOH/g to about 60 mg KOH/g in still another embodiment.
  • the polyester polyol is used in a sub-stoichiometric amount in relation to the isocyanate groups of the prepolymer.
  • concentration of the polyester polyol compound used to form the dispersion of a polyester polyol of the present invention may range generally from about 1 weight percent (wt %) to about 20 wt % in one embodiment, from about 2 wt % to about 10 wt % in another embodiment, from about 3 wt % to about 7 wt % in still another embodiment, and from about 4 wt % to about 6 wt % in yet another embodiment, based on the total weight of the components in the dispersion of the polyester polyol.
  • the plasticizer, component (b), useful in preparing the dispersion of the polyester polyol can include, for example, phthalates, glycol ethers, liquid polycarbamates, liquid polyurea, solvents inert to isocyanates, and mixtures thereof.
  • the plasticizer, component (b), useful for preparing the dispersion of the present invention may include for example diisononyl phthalate (DINP) such as Vestinol 9 which is a diisononyl phthalate compound
  • the polyester polyol is soluble in the plasticizer at elevated temperatures, such as for example when the plasticizer is heated to > about 60 °C; but is not soluble at temperatures between about 10 °C to about 50 °C, because at these lower temperatures, stable fine polyester polyol particles are formed and precipitated.
  • the fine polyester polyol particles stay in suspension in the plasticizer when stirring of the dispersion is stopped. This dispersion can be stable for up to several months.
  • a polyether polyol being used as the carrier, instead of the plasticizer.
  • the plasticizer used to form the dispersion of a polyester polyol of the present invention may be used in a concentration of for example, in the range of from about 3 wt % to about 67 wt % in one embodiment, from about 7 wt % to about 33 wt % in another embodiment, from about 10 wt % to about 23 wt % in still another embodiment, and from about 13 wt % to about 20 wt % in yet another embodiment, based on the total weight of the components in the dispersion of the polyester polyol. If the plasticizer concentration is below 3 wt %, the polyester polyol may not be soluble in the plasticizer at elevated temperatures; and if the plasticizer concentration is more than 67 wt %, the final adhesive formulation may exhibit reduced mechanical properties.
  • the present invention dispersion formulation may include various optional compounds.
  • an optional stabilizer compound, component (c) can be used in preparing the dispersion of the polyester polyol.
  • the optional stabilizer compound, component (c), useful for preparing the dispersion of the present invention may include for example benzoyl chloride; other stabilizers; and mixtures thereof.
  • Other stabilizers useful in the present invention may include for example hydrogen chloride, hydrogen fluoride, hydrogen bromide, phosphoric acid, nitrous acid, nitric acid, sulfurous acid, sulfuric acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, thionyl chloride, and mixtures thereof.
  • the storage stability of the dispersion is greater than about 1 month in one embodiment, greater than about 3 months in another embodiment, greater than about 6 months in still another embodiment, and greater than about 9 months in yet another embodiment.
  • the storage stability can be from about 1 month to about 12 months in one embodiment, from about 2 months to about 11 months in another embodiment, from about 3 months to about 10 months in yet another embodiment, and from about 6 months to about 9 months in even still another embodiment.
  • the optional stabilizer compound when added to the dispersion of a polyester polyol of the present invention, generally, may be used in a concentration of for example, in the range of from about 0.0001 wt % to about 1.0 wt % in one embodiment, from about 0.001 wt % to about 0.1 wt % in another embodiment, from about 0.03 wt % to about 0.07 wt % in still another embodiment, and from about 0.04 wt % to about 0.06 wt % in yet another embodiment, based on the total weight of the components in the dispersion of the polyester polyol.
  • the dispersion composition of the present invention is produced by first admixing, blending, or mixing: (a) a polyester polyol; (b) at least one plasticizer; and (c) any other optional compound as desired and as described above; and then heating the mixture at a temperature sufficient to mix the components and produce a dispersion composition.
  • the preparation of the dispersion composition of the present invention may be achieved by blending, in known mixing equipment, (a) a polyester polyol; (b) at least one plasticizer; and (c) optionally, any other desirable additives. Any of the above-mentioned optional additives may be added to the dispersion composition during the mixing or prior to the mixing to form the dispersion composition.
  • All the compounds of the dispersion composition are typically mixed and dispersed at a temperature enabling the preparation of an effective dispersion composition having the desired balance of properties for a particular application.
  • the temperature during the mixing of all dispersion components may be generally from about 60 °C to about 150 °C in one embodiment, and from about 70 °C to about 100 °C in another embodiment. Lower the mixing temperatures helps to minimize pre-reacting the components in the dispersion composition and to maximize the pot life or stability of the dispersion composition.
  • the preparation of the dispersion composition of the present invention, and/or any of the steps thereof, may be a batch or a continuous process.
  • the mixing equipment used in the process may be any vessel and ancillary equipment well known to those skilled in the art.
  • the dispersion exhibits various advantageous properties.
  • the polyester polyol precipitates leading to a milky dispersion of the polyester polyol in the plasticizer.
  • the polyester polyol be dispersed as fine particles in the plasticizer.
  • the average particle size of the polyester polyol particles can be of a size below about 500 micrometers in one embodiment, below about 300 micrometers in another embodiment, below about 100 micrometers in still another embodiment, and below about 50 micrometers in yet another embodiment.
  • the particles size of the polyester polyol may be from about 1 micrometer to about 500 micrometers.
  • the polyester polyol dispersed as fine particles allows faster melting of the polyester polyol and a better distribution of the isocyanate reacted polyester polyol in the final formed polyurethane polymer.
  • the curable formulation useful as an adhesive formulation typically contains (i) at least one polymer resin which generally includes a thermosetting or a thermoplastic polymer resin such as an isocyanate functional prepolymer; (ii) the dispersion composition of polyester polyol described above; and (iii) optionally, any other additive such as an organic or inorganic filler.
  • the curable formulation is first prepared, then applied to a substrate, and then the curable formulation is dual cured to form a cured adhesive material, particularly for adhering at least two substrates together.
  • the polymer resin compound, component (i), useful in preparing the present invention curable formulation can be selected from one or more of the following thermosetting resins such as polyurethane resins, epoxy resins, and isocyanate functional prepolymers; and mixtures thereof.
  • Isocyanate functional prepolymers include the reaction product of a diisocyanate and a polyol. These prepolymers can optionally contain a plasticizer, for example, diisononyl phthalate.
  • the diisocyanate used to prepare the prepolymer can be, for example, methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), and mixtures thereof. In one preferred embodiment, MDI is used.
  • the polyol used to prepare the prepolymer can be, for example, a polyether polyol.
  • the polyether polyol can be, for example, 2 to 3 functional.
  • the polyether polyol can have, a molecular weight of, for example, from about 1,000 to about 4,500. Mixtures of ethylene-oxide propylene-oxide polyether polyols may also be used.
  • the isocyanate functional prepolymer may contain, for example, from about 0.1 % NCO to about 10 % NCO in one embodiment, from about 0.4 % NCO to about 5 % NCO in another embodiment, and from about 0.6 % NCO to about 3 % NCO in still another embodiment.
  • the polymer resin compound, component (i), useful for preparing the curable formulation of the present invention may include for example the isocyanate functional prepolymers described above.
  • any polymer resin compound used in the present invention contains at least one or more isocyanate groups.
  • the isocyanate groups can cure with water or with a polyol such as a polyester polyol.
  • such prepolymer is liquid at room temperature.
  • the concentration of the polymer resin compound used in the curable formulation of the present invention may range generally from about 1 wt % to about 99 wt % in one embodiment, from about 10 wt % to about 80 wt % in another embodiment, from about 30 wt % to about 70 wt % in still another embodiment, and from about 40 wt % to about 60 wt % in yet another embodiment, based on the total weight of the components in the curable formulation.
  • the prepolymer is an essential component to provide the capability to cure the adhesive. Also, the viscosity of the formulation may be controlled based on the amount of prepolymer used.
  • component (ii) useful in preparing the present invention curable formulation has been described in detail above and includes such dispersion described above as component (ii).
  • the concentration of the dispersion composition used in the curable formulation of the present invention may range generally from about 1 wt % to about 80 wt % in one embodiment, from about 5 wt % to about 60 wt % in another embodiment, from about 7.5 wt % to about 40 wt % in still another embodiment, and from about 10 wt % to about 30 wt % in yet another embodiment, based on the total weight of the components in the curable formulation.
  • concentrations of the dispersion composition used in the curable formulation of the present invention may range generally from about 1 wt % to about 80 wt % in one embodiment, from about 5 wt % to about 60 wt % in another embodiment, from about 7.5 wt % to about 40 wt % in still another embodiment, and from about 10 wt % to about 30 wt % in yet another embodiment, based on the total weight of the components in the curable formulation.
  • composition outside the ranges described above does not lead to crosslinking of the formulation.
  • optional compounds can be added to the formulation.
  • the optional compounds that may be added to the formulation of the present invention may include compounds that are normally used in curable resin formulations known to those skilled in the art.
  • the optional components used in the formulation are used, for example, in a concentration sufficient to prepare the formulation with minimal impact to the thermal and mechanical properties of the formulation or to the final product made from the formulation.
  • Optional compounds that can be added to the formulation may include, for example, compounds that can be added to the formulation to enhance application properties (e.g. surface tension modifiers or flow aids), reliability properties (e.g. adhesion promoters) the reaction rate, the selectivity of the reaction, and/or the catalyst lifetime.
  • application properties e.g. surface tension modifiers or flow aids
  • reliability properties e.g. adhesion promoters
  • optional compounds that may be added to the formulation may include, curing agents (also referred to as a hardeners or a crosslinking agents); catalysts; solvents; fillers; pigments; toughening agents; flexibilizing agents, processing aides; flow modifiers; adhesion promoters; diluents; stabilizers; plasticizers; curing catalysts; catalyst de- activators; flame retardants; aromatic hydrocarbon resins, coal tar pitch; petroleum pitch; carbon nanotubes; graphene; carbon black; carbon fibers, or mixtures thereof.
  • curing agents also referred to as a hardeners or a crosslinking agents
  • catalysts solvents
  • fillers include, pigments; toughening agents; flexibilizing agents, processing aides; flow modifiers; adhesion promoters; diluents; stabilizers; plasticizers; curing catalysts; catalyst de- activators; flame retardants; aromatic hydrocarbon resins, coal tar pitch; petroleum pitch; carbon nanotubes; graphene; carbon black;
  • the amount of the optional compounds, when used in the formulation of the present invention may be for example, from 0.001 wt % to about 90 wt % in one embodiment, from about 0.01 wt % to about 70 wt % in another embodiment; from about 10 wt % to about 60 wt % in still another embodiment; and from about 20 wt % to about 50 wt % in yet another embodiment.
  • the formulation of the present invention is produced by first admixing, blending or mixing: (i) at least one polymer resin; and (ii) the dispersion described above; and then heating the mixture at a temperature sufficient to mix the components and produce a curable formulation, which can subsequently be fully cured by a dual cure mechanism such as heating and moisture.
  • the formulation may include any one or more of the optional compounds as desired and as described above.
  • the preparation of the formulation of the present invention may be achieved by blending, in known mixing equipment, (i) at least one polymer resin; (ii) the dispersion described above; and optionally (iii) any other desirable additives. Any of the above-mentioned optional additives may be added to the formulation during the mixing or prior to the mixing to form the curable formulation.
  • All the compounds of the formulation are typically mixed and dispersed at a temperature enabling the preparation of an effective curable formulation having the desired balance of properties for a particular application.
  • the temperature during the mixing of all components may be generally from about -10 °C to about 50 °C in one embodiment, and from about 10 °C to about 40 °C in another embodiment.
  • the preparation of formulation of the present invention, and/or any of the steps thereof, may be a batch or a continuous process.
  • the mixing equipment used in the process may be any vessel and ancillary equipment well known to those skilled in the art.
  • the reaction process for producing the cured material of the present invention includes carrying out the curing reaction at process conditions to enable the preparation of an effective cured material having the desired balance of properties for a particular application, particularly for forming an adhesive product.
  • the curing mechanism of the present invention i.e. the process of curing the curable formulation described above, includes for example at least the following alternative curing routes for curing the curable formulation: (1) a moisture cure only; (2) a heat cure only, or (3) a dual cure mechanism wherein the dual cure mechanism (3) includes (A) a heat pre-cure followed by (B) a moisture cure.
  • the heat pre-cure (A) can be carried out, for example, by partial cure of the whole bond line, or partial or full cure of parts of the adhesives (i.e., spot cure).
  • the present invention curing mechanism is an improvement over other curing mechanisms of the prior art.
  • the present invention includes curing the curable formulation discussed above to form a cured composite article (a thermoset, a thermoplastic, or both) via a dual cure of heat cure followed by moisture cure.
  • the curable formulation may be cured using the curing mechanism of moisture only at a predetermined temperature (for example below 60 °C or below a temperature at which heat curing is initiated for a particular formulation), for a predetermined period of time, and at a predetermined relative humidity sufficient to cure the formulation to form a cured material.
  • a predetermined temperature for example below 60 °C or below a temperature at which heat curing is initiated for a particular formulation
  • the moisture cure is generally carried out at a relative humidity of from about 1 % to about 100 % in one embodiment, from about 10 % to about 80 % in another embodiment, and from about 20 % to about 70 % in still another embodiment.
  • the formulation is cured at a relative humidity of 50 %.
  • the moisture cure can be carried out at a temperature of from about 0 °C to about 60 °C, from about 10 °C to about 40 °C in another embodiment, and from about 15 °C to about 35 °C in still another embodiment.
  • the humidity moisture curing mechanism above may be carried out a predetermined time of generally from about 12 hours to about 14 days at room temperature (about 23 °C) in one embodiment, from about 1 day to about 10 days in another embodiment, and from 3 days to about 7 days in still another embodiment.
  • the curable formulation may be cured using a dual cure mechanism of (A) a pre-cure heat curing mechanism and (B) a moisture curing mechanism to complete the curing.
  • the curing mechanism of the curable formulation may be carried out by first pre-curing the formulation at a predetermined temperature of generally from about 60 °C to about 180 °C in one embodiment, from about 70 °C to about 150 °C in another embodiment, and from about 80 °C to about 120 °C in still another embodiment.
  • the heating time to carry out the curing process for preparing the cured material using the pre-cure heating step of the dual cure mechanism may be generally from about 30 seconds (s) to about 60 minutes (min) in one embodiment, from about 1 min to about 30 min in another embodiment, and from 5 min to about 15 min in still another embodiment.
  • the curable formulation may be carried out by moisture.
  • the formulation is moisture cured at a predetermined relative humidity (to provide the necessary moisture), at a predetermined temperature, for a predetermined period of time, sufficient to completely cure the formulation to form a fully cured material.
  • the heat pre-cured composition described above can be cured by moisture at a relative humidity of from about 1 % to about 100 % in one embodiment, from about 10 % to about 80 % in another embodiment, and from about 20 % to about 70 % in still another embodiment. In one preferred embodiment, the formulation is cured at a relative humidity of 30 %.
  • the moisture cure can be carried out at a temperature of from about 0 °C to about 60 °C, from about 10 °C to about 40 °C in another embodiment, and from about 15 °C to about 35 °C in still another embodiment.
  • the humidity moisture curing mechanism above may be carried out a predetermined time of generally from about 12 hours to about 14 days at room temperature (about 23 °C) in one embodiment, from about 1 day to about 10 days in another
  • the preparation of the cured material of the present invention, and/or any of the steps thereof, may be a batch or a continuous process.
  • the equipment employed to carry out the reaction includes equipment known to those skilled in the art.
  • the cured material (i.e. the cross-linked product made from the curable formulation) of the present invention does not exhibit a glass transition temperature (Tg) at a particular temperature range sufficient to process the cured material.
  • the temperature at which the cured material does not exhibit a Tg (no Tg property) for the cured material can be generally at a temperature of from about -20 °C to about 80 °C in one embodiment, from about -20 °C to about 70 °C in another embodiment, and between about -10 °C and 60 °C in still another embodiment.
  • the Tg of the cured precursor composite material can be measured by the method described in ASTM D7426 (or by the method according to German Institute of Standardization - "DIN" - 53765).
  • Some non-limiting examples of enduse applications wherein the cured product of present invention may be used include, for example, adhesive formulation.
  • the adhesive formulation can then be used in automobile enduse applications.
  • the adhesive formulation may be used to bond parts in the automobile assembly.
  • the bonded parts can include, for example, composite to composite parts, composite to metal parts, glass to glass, glass to metal, glass to plastic, plastic to plastic; and the like.
  • the application of the adhesives to the parts can include for example, composite bonding, direct glazing, add-on bonding, and the like.
  • a 500 milliliter (mL) glass reactor was charged with DYNACOLL 7330 (30.0 g) and diisononyl phthalate (100 g).
  • the resultant mixture in the reactor was heated to 120 °C to form a homogeneous solution.
  • the solution was stirred under vacuum for one hour (hr). After 1 hr of stirring, the solution was allowed to cool to room temperature (23 °C, RT) while continuing to stir.
  • a precipitate of the polyester polyol in diisononyl phthalate formed in the reactor.
  • benzoyl chloride 60 mg was added to the mixture, and then the mixture was stirred for another 30 minutes (min).
  • a stable polyester polyol dispersion was produced by the above procedure.
  • the following compounds were added into a lab reactor (500 mL glass reactor): 22.8 % Voranol 2000L (liquid at RT), 33.5 % Voranol CP 4610 (liquid at RT) and 34.2 % Vestinol.
  • the resulting mixture was heated up to 120 °C under vacuum and then the mixture was mixed for 60 min. Then the mixture was cooled down to 50 °C and 9.5 % Isonate M125 was added to the mixture. The resultant mixture was mixed for an additional 2 min and then 0.01 % Metatin S-26 was added to the mixture. The mixture was allowed to react for 30 min under nitrogen. Then the resulting mixture was mixed for 20 min under vacuum.
  • the NCO content of the reaction product produced after the above mixture was allowed to react was 1.4 %.
  • a planetary mixture is charged with the prepolymer T-715 (Comparative Example A) (150 g), Fomrez UL-28 (160 mg), and diisononyl phthalate (48.5 g).
  • Calcinated clay (Polestar 200R, 59.54 g) and carbon black (Printex 30, 60 g) are then added to the mixture; and the resultant mixture is mixed under vacuum until a dispersion is obtained.
  • Lap shear strengths of Inventive Example 1 and Comparative Example A were measured according to DIN EN 1465 on e-coated steel substrates.
  • the bonding area of the substrates was 10 mm x 25 mm bonding area, and a 2 mm bonding height.
  • Humidity cured samples were cured by atmospheric water for seven days at an environment of 23 °C and 50 % relative humidity (RH). Heat cured samples were cured in an oven at 140 °C for 15 min. Lap shear strengths measurements of samples, cured and conditioned, were taken as follows:
  • Humidity cured seven days at room temperature (RT).
  • Table II summarizes the results of lap shear strength measurements obtained from samples prepared in Inventive Example 1 and Comparative Example A.
  • Inventive Example 1 and Comparative Example A are lK polyurethane adhesives which can be cured by atmospheric water. When the samples were cured for seven days at 23 °C with 50 % relative humidity, Comparative Example A reaches a lap shear strength of 4.13 MPa whereas Inventive Example 1 shows a lap shear strength of 3.88 MPa. The cure of Comparative Example A cannot be accelerated by heat. When a lap shear sample of
  • Comparative Example A is heated for 15 min at 140 °C and conditioned for 30 min, no lap shear experiments can be performed on the sample because the sample is still wet and pasteous. If Comparative Example A is heated for 15 min at 140 °C and then conditioned for seven days at RT, a lap shear strength of 4.13 MPa is observed, indicating that heat is not harming the sample since the sample reaches almost the same lap shear strength as the Comparative Example A which is only cured at seven days RT.

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Abstract

A polyester polyol dispersion composition including a mixture of: (a) at least one solid polyester polyol; (b) at least one plasticizer compound; and a curable adhesive formulation including (i) at least one isocyanate functional prepolymer polymer resin; and (ii) the above polyester polyol dispersion composition; and a cured adhesive material made by curing the above curable formulation.

Description

ADHESIVE FORMULATION
FIELD
The present invention is related to an adhesive formulation; and more specifically, to an adhesive formulation employing a solid polyester polyol and to a formulation that can be dual cured.
BACKGROUND
The modern fabrication of vehicles involves several applications of elastic and structural adhesives to bond parts, body structures, and building blocks increasing the performance of the vehicles and facilitating the assembly, respectively. Several parts are commonly bonded outside the body shop in the trim shop using mainly two component ("2K") polyurethane (PU) adhesives. One component ("IK") PU adhesives have been well established in the automotive industry and are commonly cured by moisture. The IK PU adhesives comprise PU prepolymers bearing terminal isocyanate (NCO) groups. After the IK PU adhesive has been applied to the parts, the NCO groups react with water molecules (e.g., humidity) when placed in an ambient environment (relative humidity [r.h.] > 0 percent [%], preferably 20 % to 80 %) forming carbon dioxide and an amine; the amine reacts again with NCO groups causing crosslinking and curing of the polymer. The parts are commonly fully cured (all NCO groups consumed) after 7 days at an ambient environment.
Other known IK PU adhesives includes encapsulated NCOs and such known IK PU adhesives can be cured by heat. Heat curing of the IK PU adhesives accelerates the curing of the system. However, the known systems are not able to cure with humidity due to the lack of non-encapsulated isocyanate groups, and therefore, the whole assembly needs to be heated. Heating the whole assembly is disadvantageous because it impedes, in many cases, the manufacturing process particularly for large assemblies which need to go through a heating cycle (i.e. in an oven or the like). In addition, whole assemblies usually contain parts which further contain heat sensitive parts and heating the whole assemblies can potentially damage the heat sensitive parts of the assemblies.
Some adhesive formulations that can be cured by dual cure mechanisms, for example by (1) heat and (2) moisture, are known in the art. For example, EP2024457B1 discloses an adhesive/sealant composition which is suitable for curing by two curing mechanisms: (1) heat and (2) moisture. The heat- and moisture-curing composition described in EP2024457B 1 includes at least one isocyanate-functional prepolymer having substantially terminal isocyanate groups and at least one polyamine having at least 2 primary or secondary amino groups per molecule and a melting point above 55 °C. The composition may be at least partly thermally cured, and alternatively may cure completely with ambient atmospheric moisture.
EP2024457B 1 describes the use of solid polyamines, particularly
1,12-dodecanediamine, in an isocyanate functional prepolymer-bearing adhesive formulation. Upon heating the mixture above the melting point of the polyamine, the system can be heat cured. The dual cure heat- and moisture-curing adhesive formulation of EP2024457B1 relies on solid insoluble amines. The amines disclosed in EP2024457B 1 are not encapsulated. Moreover, EP2024457B 1 does not disclose the use of a solid polyester polyol in an adhesive formulation wherein the solid polyester polyol melts when heated and which liberates entangled hydroxyl groups, which in turn, may react with isocyanate groups in the formulation. Instead, EP2024457B 1 uses solid amines.
Aside for the currently high cost of 1,12-dodecanediamine, another disadvantage of using 1,12-dodecanediamine as disclosed in EP2024457B 1, is the toxicity of 1,12-dodecanediamine which is described in Valentine et al., Inhalation Toxicology of Fumed Dodecanediamine, Inhalation Toxicology, (2004), 16 (10), pp. 721-9. The article above discloses that dodecanediamine (DDDA) has dermal irritative properties and skin contact with DDDA is to be avoided. Exposure via inhalation of DDDA is also to be avoided because, although DDDA is stable under ambient conditions, DDDA processed at elevated temperatures may fume, forming a carbamate after reaction with atmospheric carbon dioxide.
WO88/06165 describes sealants and adhesives and their use. WO88/06165 discloses a heat- and moisture-curing one-component polyurethane sealant and an adhesive based on telechelate isocyanate prepolymers made from aromatic diisocyanates in stoichiometric excess and polyalcohols. The sealant/adhesive formulation of WO88/06165 also contains (a) a catalyst for the moisture-curing, in particular a tin compound, and (b) a blocked, heat activated crosslinking agent, in particular a methylene dianiline/sodium chloride complex compound or a polyamino- or hydroxyfunctional compound in microencapsulated form. WO88/06165 describes a dual cure (heat and moisture) adhesive formulation based on isocyanate functional prepolymers and latent diamine salts. The salts disclosed, which are formed, e.g. of methylene diamine(MDA) with sodium chloride, are reported to be inert at room temperature but act as a hardener when heated above 115 °C.
WO88/06165 does not disclose solid polyester polyols which melt when heated and then, in turn, react with isocyanates to crosslink the system. Instead, the process of W088/06165 is to deactivate a certain amine as its sodium chloride salt. The composition of WO88/06165 contains blocked amines, not solid polyesters.
WOO 1/88005 A2 discloses polyurethanes containing dispersed crystalline polyesters. WOO 1/88005 A2 describes a polyurethane foam formulation which includes toluene diisocyanate (TDI) and water. WO01/88005A2 does not disclose a one-part polyurethane adhesive formulation, but instead discloses a foam. WO01/88005A2 discloses a process for producing resilient polyurethane foams by foaming an organic polyisocyanate, an isocyanate-reactive compound and a fusible polymer. WO01/88005A2 further discloses that an improvement in the hardness of the foams is achieved without adversely affecting the other properties of the foams, such as tensile strength and elongation. WO01/88005A2 discloses that the polyester is only used in a foam producing process described in
WO88/06165 to yield a stiff foam product, not as a dual cure mechanism.
WO 2008/076146A1 describes compositions useful as an adhesive for installing vehicle windows. WO 2008/076146A1 discloses, in one embodiment, a composition comprising: (a) one or more isocyanate functional poly ether polyurethane prepolymers; and (b) one or more prepolymers of one or more polyisocyanates and one or more polyesters wherein the terminal groups on the polyester polyol polyurethane prepolymer are the residue of a monofunctional polyalkylene glycol (hereinafter capped polyester polyurethane prepolymer) or one or more polyester polyols which are capped with the residue of one or more monofunctional isocyanates (hereinafter isocyanate capped polyesters); wherein the composition is a low viscous paste at a temperature of from about 40 °C to about 80 °C and is a high viscous paste at a temperature of from about 400 °C or less.
In a preferred embodiment of the composition disclosed in
WO 2008/076146A1, the composition further includes (c) one or more catalysts for the reaction of isocyanate moieties with hydroxyl groups. WO 2008/076146A1 discloses, in another embodiment, a method of bonding two or more substrates together by contacting two or more substrates together with the above composition, in the form of a low viscous paste, disposed along at least a portion of the area wherein the substrates are in contact with each other. A preferred embodiment disclosed in WO 2008/076146A1 includes the above composition being heated to about 40 °C to about 80 °C and converting the composition into a low viscous paste prior to contacting the composition with one or more substrates.
WO 2008/076146A1 describes the use of temperature dependent viscosity modifiers based on polyester polyols which are converted to isocyanate functional prepolymers. Those prepolymers with a polyester backbone have a melting point above room temperature, but below the application temperature of the adhesive. After the adhesive is applied, the adhesive cools down which causes the polyester comprising prepolymers to crystallize causing the viscosity of the adhesive to increase. The viscosity increase is based on a physical phenomenon rather than a chemical crosslinking.
The low viscous paste producing process described in WO 2008/076146A1 suffers from the disadvantage(s) of not having a dual cure mechanism; the reported adhesives can only be cured by moisture without being able to be activated by heat.
WO2008/076146A1 describes IK PU adhesives which can only be cured by moisture, not by heat and not by a dual cure mechanism. The polyester-prepolymer disclosed in
WO2008/076146A1 is used only as a rheology modifier and comprises a polyester polymer which is further reacted with isocyanates to offer a polyester-based prepolymer.
There is a need in the industry for a IK PU adhesive having a dual cure mechanism including a dual cure adhesive formulation based on insoluble solid polyester polyols which can be cured by (1) heat and/or (2) moisture; and wherein the IK PU adhesive does not suffer from the disadvantages of the known prior art curing mechanisms.
SUMMARY
The present invention addresses the problems encountered by using prior art adhesive formulations by providing a fundamentally different approach from the approaches described in prior art. For example, the present invention utilizes solid insoluble polyester polyols to form a dispersion that can be added to an isocyanate functional adhesive formulation. In the present invention, the solid polyester polyols are used as active heat activated curing agents (active crosslinkers) to render a one-component isocyanate functional formulation which is moisture curable, heat curable, or both, i.e., dual curable. At room temperature (23 °C), the dispersion of the polyester polyols is stable in the reactive adhesive formulation. However, by heating the mixture of components in the reactive adhesive formulation to a temperature above the melting point of the polyester polyol, the terminal hydroxyl groups of the polyester polyol derivative are liberated; and then the hydroxyl groups of the polyester polyols are able to react with the isocyanate functional groups present in the isocyanate functional adhesive formulation causing curing or partial curing of the polymer present in the isocyanate functional adhesive formulation. Hence, chemical crosslinking is observed in the formulation of the present invention. Therefore, the above adhesive formulation of the present invention includes a IK PU formulation which is capable of being cured by dual cure mechanisms such as by (1) heat and/or (2) moisture.
The dual cure IK PU formulation of the present invention can be applied to a substrate; and then by applying heat (e.g., induction, infrared, hot air, and the like) to the formulation, the formulation can be cured, pre-cured, or spot cured at critical positions on the substrate sufficient to give the bonded part handling strength. In a second step, if needed, the formulation can be further cured at ambient conditions by moisture. This adds advantages in performance of the adhesive and facilitates the assembly. The advantages of a dual cure IK formulation include, but not limited to, for example, lower investment costs for application equipment and increased application process stability. The dual cure IK PU formulations or systems of the present invention can potentially be used as a substitute for currently known 2K PU systems. In general, the dual curing adhesive composition and process provides improvements in productivity and quality of bonding. Productivity can be achieved through heat curing (e.g., the reaction of the isocyanate with the polyester polyol) which allows for a fast curing process. Quality of bonding can be obtained through moisture curing (e.g., the reaction of isocyanate with water and subsequent crosslinking).
Some of the other advantages of the dual cure IK PU formulations of the present invention over known 2K formulations include, but not limited to, for example,
(1) no mixing of the formulation is required, and therefore, no or minimal mixing errors can be encountered when using the present invention; and (2) there is a lower investment cost for pump equipment. One of the advantages of the dual cure IK PU formulations of the present invention over IK PU heat cure adhesives include, but not limited to, for example, the possibility to adjust the de-blocking temperature by selecting a specific polyester polyol with a given melting point (different molecular weight polyester polyols). Another advantage can be the non-toxicity of polyester polyols of the present invention, particularly in comparison to highly toxic amines known in the art. Still another advantage of the present invention is the dual cure IK PU adhesive formulations of the present invention have the capability of providing a strong bonding, due to the presence of ester moieties, through hydrogen bonding.
There are several advantages of the dual cure IK PU adhesive formulations of the present invention over single heat cure IK PU adhesives. For example, the adhesive formulations of the present invention have the capability of being cured by moisture which makes the system more tolerable to curing conditions. In another embodiment, the formulation of the present invention can be cured by moisture, and the formulation can optionally be cured by heat, i.e. heat is advantageous but is not required for curing. In addition, partial heat curing of the present invention formulation can be carried out without the need for a large oven. In another embodiment, spot curing (i.e., partial heat curing) can be carried out such as for example with infrared (IR) lamps.
As an illustration of using a IK PU system of the present invention in the automotive industry, for example, curing can be accelerated by heat using a IK PU system and spot curing. For example, in an automobile assembly line, a predetermined number of infrared heat stations can be used along the assembly line to cure the adhesives within 1 - 10 minutes at selected spots on automotive parts. As a result, the material is cured at strategic places on the parts to offer handling strength.
Some of the advantages of the dual cure IK PU formulations of the present invention over single humidity cure IK PU include, but not limited to, for example, the dual cure formulation of the present invention exhibits fast handling strength (e.g., handling strengths below 15 minutes), and fast curing (e.g., curing below 15 minutes).
One embodiment of the present invention is directed to a dispersion of the polyester polyol suitable to be introduced in a curable adhesive formulation. The dispersion includes, for example, (a) at least one solid polyester polyol having a melting point of from about 50 °C to about 150 °C; and (b) and at least one plasticizer compound. Another embodiment of the present invention is directed to a process for preparing the above dispersion of the polyester polyol suitable to be introduced into a curable adhesive formulation.
Still another embodiment of the present invention is directed to a curable formulation useful as an adhesive formulation including (i) at least one polymer resin,
(ii) the above dispersion of polyester polyol, and (iii) optionally, at least one filler; wherein the curable formulation advantageously exhibits the dual cure property/mechanism of being curable by moisture, and/or curable by heat.
Yet another embodiment of the present invention is directed to a process for preparing the above curable adhesive composition.
Even still another embodiment of the present invention is directed to a cured product prepared by curing the adhesive material on a substrate.
Even yet another embodiment of the present invention is directed to a process for producing the above cured product.
The present invention realizes the benefit of enabling a IK PU adhesive formulation to be cured by both heat and/or moisture.
DETAILED DESCRIPTION
"Thermal cure", "thermal curing" and "thermal curable" herein, with reference to a curing mechanism of a formulation, means that crosslinking of the formulation is being initiated by a heat trigger.
"Moisture cure", "moisture curing" and "moisture curable" herein, with reference to a curing mechanism of a formulation, means that crosslinking of the formulation is being initiated by moisture. Water reacts with isocyanate groups to form carbamic acid which after C02 loss is turned into an amine, which in turn, reacts with isocyanates.
"Dual cure", "dual curing" and "dual curable" herein, with reference to a composition, means a curing system that includes at least the following two curing mechanisms: (1) thermal cure and (2) moisture cure crosslinking mechanism.
"Structural stability" herein, with reference to a composition, means the handling strength of assembled parts, as measured in terms of lap shear strength. A lap shear strength higher than 0.8 megapascal (MPa) is considered to offer assembled parts an adequate handling strength.
One embodiment of the present invention is directed to a dispersion of a polyester polyol suitable to be introduced into a curable adhesive formulation. In accordance with a preferred broad embodiment of the present invention, the dispersion of a polyester polyol includes a mixture of: (a) at least one solid polyester polyol having a melting point of from about 40 °C to about 150 °C in one embodiment, from about 50 °C to about 120 °C in another embodiment, and from about 60 °C to about 110 °C in still another embodiment; and (b) and at least one plasticizer compound. The polyester polyol, component (a), useful in preparing the dispersion of the polyester polyol of the present invention can include for example a polyester polyol with an average molecular weight of from about 1,000 g/mol to about 6,000 g/mol in one embodiment, from about 2,000 g/mol to about 4,000 g/mol in another embodiment, and from about 2,500 g/mol to about 3,500 g/mol in still another embodiment. For example, the polyester polyol may be selected from one or more of the following products: reaction products of an excess polyol with an aliphatic or aromatic diacids or anhydride; linear co-polyesters with primary hydroxyl functionality and medium molecular weight; and mixtures thereof.
In one preferred embodiment, suitable polyester polyols, component (a), useful for preparing the dispersion of the present invention may include one or more of the polyesters described in WO2009/140001A1, which is incorporated herein in its entirety, and particularly from page 3, line 7 to page 5, line 5, which describes useful crystalline or liquid linear co-polyesters having primary hydroxyl functionality. In addition, the polyester polyols, useful in the present invention can also include the polyester polyols described in WO 2001/088005, which is incorporated herein in its entirety, and particularly from page 11 to page 13.
The linear co-polyesters useful in the present invention may be described as having, in certain non- limiting embodiments, a Tg (measured according to German Institute of Standardization - "DIN" - 53765) ranging from about -20 °C to about 60 °C. The crystalline linear co-polyesters may be alternatively defined, in non-limiting embodiments, as having a melt viscosity, as measured at 80 °C using the parallel plate method according to German Institute of Standardization's DIN EN ISO 3219:1993, ranging from about 0.5 Pascal-seconds (Pa-s) to about 15 Pa-s; or as measured at 130 °C using the above same method ranging from about 0.3 Pa-s to about 4 Pa-s. The liquid linear co-polyesters generally have a melt viscosity ranging from about 2 Pa-s to about 11 Pa-s, as measured at 80 °C using the parallel plate method according to German Institute of Standardization' s DIN EN ISO 3219:1993. Crystalline linear co-polyesters may alternatively be characterized by their melting temperature (Tm) as measured according to DIN 53765. For example, the Tm of the co-polyesters may range from about 30 °C and about 150 °C in one embodiment; from about 40 °C to about 120 °C in another embodiment; and from about 50 °C to about 100 °C in still another embodiment.
In some non-limiting embodiments, the linear co-polyesters may have hydroxyl numbers (mg KOH/g as measured according to DIN 53240-2) from about 15 to about 50. In another embodiment, the hydroxyl number of the co-polyester may be from about 18 to about 40. The primary hydroxyl functionality of the linear co-polyester may range from 2 to about 8 in one embodiment, from 2 to about 4 in another embodiment, and 2 in still another embodiment.
Suitable processes for producing the linear co-polyesters useful in the invention may be described in, for example, G. Oertel, Polyurethane Handbook, 2nd ed., Hanser, publisher. The processes for producing the co-polyesters may include, in non-limiting embodiments, for example (1) linear polycondensation of linear dicarboxylic acids and linear dihydroxyl compounds; (2) the reaction of linear dicarboxylic acid chlorides and linear dihydroxyl compounds; and (3) transesterification using linear dihydroxyl compounds and esters of the linear dicarboxylic acids. Of the above preparation methods, polycondensation of linear dicarboxylic acids and linear dihydroxyl compounds may be particularly convenient.
For example, suitable linear dicarboxylic acids may be used and include, in non-limiting embodiments, linear aliphatic dicarboxylic acids having 2 carbon atoms to about 20 carbon atoms in one embodiment, and from about 6 carbon atoms to about 15 carbon atoms in another embodiment, in the alkylene radical. These linear diacids react with linear dihydroxyl compounds, for example linear diols, having from 2 carbon atoms to about 20 carbon atoms in one embodiment, and diols having from about 6 carbon atoms to about 15 carbon atoms in another embodiment. In one preferred embodiment, the diacid is substantially free of any ethylenically unsaturated groups (i.e., carbon-carbon double bonds). These acids include, for example, aliphatic dicarboxylic acids such as glutaric acid, succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid,
undecanedioic acid and dodecanedioic acid; and cyclo-aliphatic dicarboxylic acids such as 1,3- and 1 ,4-cyclohexane dicarboxylic acid; and combinations thereof. In general, aromatic dicarboxylic acids are not suitable for use in the present invention because their melting points are too high (e.g., greater than about 180 °C) for those having an equivalent weight of at least about 1,000. Examples of di- and multi- functional alcohols useful in the present invention may include ethylene glycol; diethylene glycol; triethylene glycol; propylene glycol; dipropylene glycol; 1,3-propanediol; 1,2-butanediol; 1,4-butanediol;
1,6-hexanediol; 1,9-nonanediol; 1,10-decanediol; 1,12-dodecanediol; neopentyl glycol; and mixtures thereof.
In one preferred embodiment, the polyesters prepared by polycondensation of linear dicarboxylic acids and linear dihydroxyl compounds, are made from a diacid and a diol such that the repeating unit of the acid plus the alcohol has, in total, at least about 9 carbons atoms; and in another embodiment, a total of from about 10 carbon atoms to about 30 carbon atoms.
One preparation method for making the diacid/diol linear co-polyesters is known in the art. An example of such co-polyesters available commercially is a linear co-polyester having a molecular weight of about 3,500 and a Tm of about 65 °C, sold by
Evonik Industries under the tradename DYNACOLL™ 7381. Other related products useful in the present invention may include the products described in a technical leaflet entitled "DYNACOLL 7000, The Building Block System for Moisture Curable Hot Melt Adhesives and Sealants." Preferred embodiments of products useful in the present invention may include products described under the tradename DYNACOLL 7200 series and
DYNACOLL 7300 series. In one preferred embodiment, the suitable polyester polyol useful in the formulation of the present invention includes, for example DYNACOLL 7000 series commercially available from Evonik Industries. Similar compounds from other suppliers may also be useful in the present invention.
In another embodiment, the polyester polyol, component (a), useful in preparing the dispersion of the polyester polyol of the present invention can include other optional compounds such as, for example, stabilizers, especially stabilizer products which prevent or slow down hydrolysis. Such stabilizer products can include, for example, STABAXOL® additives which are commercially available from Rhein Chemie Rheinau GMBH.
The preparation method involving the transesterification of a polyester with an alcohol may be suitably carried out using an alcohol having at least 2 hydroxyl groups. Preferred embodiments of the alcohols are alcohols having 2 to 4 hydroxyl groups. The process for producing such polymers is known in the art such as described in G. Oertel, Polyurethane Handbook, 2nd ed., Hanser, publishers, incorporated herein by reference.
One of the key properties of the polyester polyol is the melting point of the polyester polyol. In general, the solid polyester polyol of the present invention exhibits a melting point of from about 40 °C to about 150 °C in one embodiment, from about 50 °C to about 120 °C in another embodiment, from about 60 °C to about 110 °C in still another embodiment, and from about 70 °C to about 90 °C in yet another embodiment.
Another key property of the polyester polyol is the functionality of the polyester polyol which can be for example from 2 to 4 in one embodiment, 2 to 3 in another embodiment, and 2 in still another embodiment.
Still another key property of the polyester polyol is the hydroxyl number of the polyester polyol which can be for example from about 10 mg KOH/g to about 100 mg KOH/g in one embodiment, from about 20 mg KOH/g to about 80 mg KOH/g in another embodiment, and from about 30 mg KOH/g to about 60 mg KOH/g in still another embodiment.
In general, the polyester polyol is used in a sub-stoichiometric amount in relation to the isocyanate groups of the prepolymer. For example, the concentration of the polyester polyol compound used to form the dispersion of a polyester polyol of the present invention may range generally from about 1 weight percent (wt %) to about 20 wt % in one embodiment, from about 2 wt % to about 10 wt % in another embodiment, from about 3 wt % to about 7 wt % in still another embodiment, and from about 4 wt % to about 6 wt % in yet another embodiment, based on the total weight of the components in the dispersion of the polyester polyol. If the polyester polyol is added to the formulation at a concentration below 1 wt % or above 20 wt %, the crosslinking is not sufficient to give any handling strength (i.e., low lap shear strengths are obtained). The plasticizer, component (b), useful in preparing the dispersion of the polyester polyol can include, for example, phthalates, glycol ethers, liquid polycarbamates, liquid polyurea, solvents inert to isocyanates, and mixtures thereof.
In one preferred embodiment, the plasticizer, component (b), useful for preparing the dispersion of the present invention may include for example diisononyl phthalate (DINP) such as Vestinol 9 which is a diisononyl phthalate compound
commercially available from Evonik Industries.
One of the key properties of the polyester polyol is the solubility of the polyester polyol. In one preferred embodiment, the polyester polyol is soluble in the plasticizer at elevated temperatures, such as for example when the plasticizer is heated to > about 60 °C; but is not soluble at temperatures between about 10 °C to about 50 °C, because at these lower temperatures, stable fine polyester polyol particles are formed and precipitated. The fine polyester polyol particles stay in suspension in the plasticizer when stirring of the dispersion is stopped. This dispersion can be stable for up to several months. Although not a preferred embodiment, alternatively the same procedure above could be applied with a polyether polyol being used as the carrier, instead of the plasticizer.
The plasticizer used to form the dispersion of a polyester polyol of the present invention, generally, may be used in a concentration of for example, in the range of from about 3 wt % to about 67 wt % in one embodiment, from about 7 wt % to about 33 wt % in another embodiment, from about 10 wt % to about 23 wt % in still another embodiment, and from about 13 wt % to about 20 wt % in yet another embodiment, based on the total weight of the components in the dispersion of the polyester polyol. If the plasticizer concentration is below 3 wt %, the polyester polyol may not be soluble in the plasticizer at elevated temperatures; and if the plasticizer concentration is more than 67 wt %, the final adhesive formulation may exhibit reduced mechanical properties.
The present invention dispersion formulation may include various optional compounds. For example an optional stabilizer compound, component (c), can be used in preparing the dispersion of the polyester polyol. In a preferred embodiment, the optional stabilizer compound, component (c), useful for preparing the dispersion of the present invention may include for example benzoyl chloride; other stabilizers; and mixtures thereof. Other stabilizers useful in the present invention may include for example hydrogen chloride, hydrogen fluoride, hydrogen bromide, phosphoric acid, nitrous acid, nitric acid, sulfurous acid, sulfuric acid, hypochlorous acid, chlorous acid, chloric acid, perchloric acid, thionyl chloride, and mixtures thereof.
One of the key properties of the optional stabilizer such as benzoyl chloride compound is its capability of providing storage stability to the dual cure adhesive composition containing the polyester polyol dispersion of the present invention. Generally, the storage stability of the dispersion is greater than about 1 month in one embodiment, greater than about 3 months in another embodiment, greater than about 6 months in still another embodiment, and greater than about 9 months in yet another embodiment. In other embodiments, the storage stability can be from about 1 month to about 12 months in one embodiment, from about 2 months to about 11 months in another embodiment, from about 3 months to about 10 months in yet another embodiment, and from about 6 months to about 9 months in even still another embodiment.
The optional stabilizer compound, when added to the dispersion of a polyester polyol of the present invention, generally, may be used in a concentration of for example, in the range of from about 0.0001 wt % to about 1.0 wt % in one embodiment, from about 0.001 wt % to about 0.1 wt % in another embodiment, from about 0.03 wt % to about 0.07 wt % in still another embodiment, and from about 0.04 wt % to about 0.06 wt % in yet another embodiment, based on the total weight of the components in the dispersion of the polyester polyol.
Generally, the dispersion composition of the present invention is produced by first admixing, blending, or mixing: (a) a polyester polyol; (b) at least one plasticizer; and (c) any other optional compound as desired and as described above; and then heating the mixture at a temperature sufficient to mix the components and produce a dispersion composition. For example, the preparation of the dispersion composition of the present invention may be achieved by blending, in known mixing equipment, (a) a polyester polyol; (b) at least one plasticizer; and (c) optionally, any other desirable additives. Any of the above-mentioned optional additives may be added to the dispersion composition during the mixing or prior to the mixing to form the dispersion composition.
All the compounds of the dispersion composition are typically mixed and dispersed at a temperature enabling the preparation of an effective dispersion composition having the desired balance of properties for a particular application. For example, the temperature during the mixing of all dispersion components may be generally from about 60 °C to about 150 °C in one embodiment, and from about 70 °C to about 100 °C in another embodiment. Lower the mixing temperatures helps to minimize pre-reacting the components in the dispersion composition and to maximize the pot life or stability of the dispersion composition.
The preparation of the dispersion composition of the present invention, and/or any of the steps thereof, may be a batch or a continuous process. The mixing equipment used in the process may be any vessel and ancillary equipment well known to those skilled in the art.
The dispersion, once prepared, exhibits various advantageous properties. For example, when the solution is cooled to ambient temperatures (or below 60 °C), the polyester polyol precipitates leading to a milky dispersion of the polyester polyol in the plasticizer. It is important that the polyester polyol be dispersed as fine particles in the plasticizer. For example, the average particle size of the polyester polyol particles can be of a size below about 500 micrometers in one embodiment, below about 300 micrometers in another embodiment, below about 100 micrometers in still another embodiment, and below about 50 micrometers in yet another embodiment. In one preferred embodiment, the particles size of the polyester polyol may be from about 1 micrometer to about 500 micrometers. The polyester polyol dispersed as fine particles allows faster melting of the polyester polyol and a better distribution of the isocyanate reacted polyester polyol in the final formed polyurethane polymer.
Another broad embodiment of the present invention is directed to a curable adhesive composition or formulation which is useful for adhering substrates or parts, particularly parts used in the automobile manufacturing industry. The curable formulation useful as an adhesive formulation typically contains (i) at least one polymer resin which generally includes a thermosetting or a thermoplastic polymer resin such as an isocyanate functional prepolymer; (ii) the dispersion composition of polyester polyol described above; and (iii) optionally, any other additive such as an organic or inorganic filler. In a preferred embodiment of the present invention, the curable formulation is first prepared, then applied to a substrate, and then the curable formulation is dual cured to form a cured adhesive material, particularly for adhering at least two substrates together.
The polymer resin compound, component (i), useful in preparing the present invention curable formulation can be selected from one or more of the following thermosetting resins such as polyurethane resins, epoxy resins, and isocyanate functional prepolymers; and mixtures thereof.
Isocyanate functional prepolymers include the reaction product of a diisocyanate and a polyol. These prepolymers can optionally contain a plasticizer, for example, diisononyl phthalate. The diisocyanate used to prepare the prepolymer can be, for example, methylene diphenyl diisocyanate (MDI), hexamethylene diisocyanate (HDI), toluene diisocyanate (TDI), and mixtures thereof. In one preferred embodiment, MDI is used. The polyol used to prepare the prepolymer can be, for example, a polyether polyol. The polyether polyol can be, for example, 2 to 3 functional. In addition, the polyether polyol can have, a molecular weight of, for example, from about 1,000 to about 4,500. Mixtures of ethylene-oxide propylene-oxide polyether polyols may also be used. The isocyanate functional prepolymer may contain, for example, from about 0.1 % NCO to about 10 % NCO in one embodiment, from about 0.4 % NCO to about 5 % NCO in another embodiment, and from about 0.6 % NCO to about 3 % NCO in still another embodiment.
In a preferred embodiment, the polymer resin compound, component (i), useful for preparing the curable formulation of the present invention may include for example the isocyanate functional prepolymers described above. In general, any polymer resin compound used in the present invention contains at least one or more isocyanate groups. The isocyanate groups can cure with water or with a polyol such as a polyester polyol. Advantageously, such prepolymer is liquid at room temperature.
In general, the concentration of the polymer resin compound used in the curable formulation of the present invention may range generally from about 1 wt % to about 99 wt % in one embodiment, from about 10 wt % to about 80 wt % in another embodiment, from about 30 wt % to about 70 wt % in still another embodiment, and from about 40 wt % to about 60 wt % in yet another embodiment, based on the total weight of the components in the curable formulation. The prepolymer is an essential component to provide the capability to cure the adhesive. Also, the viscosity of the formulation may be controlled based on the amount of prepolymer used.
The dispersion, component (ii), useful in preparing the present invention curable formulation has been described in detail above and includes such dispersion described above as component (ii).
In general, the concentration of the dispersion composition used in the curable formulation of the present invention may range generally from about 1 wt % to about 80 wt % in one embodiment, from about 5 wt % to about 60 wt % in another embodiment, from about 7.5 wt % to about 40 wt % in still another embodiment, and from about 10 wt % to about 30 wt % in yet another embodiment, based on the total weight of the components in the curable formulation. Use of concentrations of the dispersion
composition outside the ranges described above does not lead to crosslinking of the formulation.
In preparing the curable formulation of the present invention, optional compounds can be added to the formulation. The optional compounds that may be added to the formulation of the present invention may include compounds that are normally used in curable resin formulations known to those skilled in the art. The optional components used in the formulation are used, for example, in a concentration sufficient to prepare the formulation with minimal impact to the thermal and mechanical properties of the formulation or to the final product made from the formulation.
Optional compounds that can be added to the formulation may include, for example, compounds that can be added to the formulation to enhance application properties (e.g. surface tension modifiers or flow aids), reliability properties (e.g. adhesion promoters) the reaction rate, the selectivity of the reaction, and/or the catalyst lifetime.
For example, optional compounds that may be added to the formulation may include, curing agents (also referred to as a hardeners or a crosslinking agents); catalysts; solvents; fillers; pigments; toughening agents; flexibilizing agents, processing aides; flow modifiers; adhesion promoters; diluents; stabilizers; plasticizers; curing catalysts; catalyst de- activators; flame retardants; aromatic hydrocarbon resins, coal tar pitch; petroleum pitch; carbon nanotubes; graphene; carbon black; carbon fibers, or mixtures thereof. Generally, the amount of the optional compounds, when used in the formulation of the present invention, may be for example, from 0.001 wt % to about 90 wt % in one embodiment, from about 0.01 wt % to about 70 wt % in another embodiment; from about 10 wt % to about 60 wt % in still another embodiment; and from about 20 wt % to about 50 wt % in yet another embodiment.
Generally, the formulation of the present invention is produced by first admixing, blending or mixing: (i) at least one polymer resin; and (ii) the dispersion described above; and then heating the mixture at a temperature sufficient to mix the components and produce a curable formulation, which can subsequently be fully cured by a dual cure mechanism such as heating and moisture. Optionally, the formulation may include any one or more of the optional compounds as desired and as described above.
For example, the preparation of the formulation of the present invention may be achieved by blending, in known mixing equipment, (i) at least one polymer resin; (ii) the dispersion described above; and optionally (iii) any other desirable additives. Any of the above-mentioned optional additives may be added to the formulation during the mixing or prior to the mixing to form the curable formulation.
All the compounds of the formulation are typically mixed and dispersed at a temperature enabling the preparation of an effective curable formulation having the desired balance of properties for a particular application. For example, the temperature during the mixing of all components may be generally from about -10 °C to about 50 °C in one embodiment, and from about 10 °C to about 40 °C in another embodiment.
The preparation of formulation of the present invention, and/or any of the steps thereof, may be a batch or a continuous process. The mixing equipment used in the process may be any vessel and ancillary equipment well known to those skilled in the art.
One important advantage of using the present invention is the chemical and mechanical properties of the uncured formulation and of the cured formulation are preserved, i.e., the dual cure mechanism of the present invention does not adversely affect the properties of the uncured formulation or of the cured formulation including properties such as viscosity, Tg, chemical resistance, and the like. In one embodiment, the curable formulation exhibits a viscosity sufficient to allow the curable formulation to be processable and handleable in conventional formulation equipment. In general, the reaction process for producing the cured material of the present invention includes carrying out the curing reaction at process conditions to enable the preparation of an effective cured material having the desired balance of properties for a particular application, particularly for forming an adhesive product.
The curing mechanism of the present invention, i.e. the process of curing the curable formulation described above, includes for example at least the following alternative curing routes for curing the curable formulation: (1) a moisture cure only; (2) a heat cure only, or (3) a dual cure mechanism wherein the dual cure mechanism (3) includes (A) a heat pre-cure followed by (B) a moisture cure. The heat pre-cure (A) can be carried out, for example, by partial cure of the whole bond line, or partial or full cure of parts of the adhesives (i.e., spot cure). The present invention curing mechanism is an improvement over other curing mechanisms of the prior art. In a preferred embodiment, the present invention includes curing the curable formulation discussed above to form a cured composite article (a thermoset, a thermoplastic, or both) via a dual cure of heat cure followed by moisture cure.
For example, in one embodiment, the curable formulation may be cured using the curing mechanism of moisture only at a predetermined temperature (for example below 60 °C or below a temperature at which heat curing is initiated for a particular formulation), for a predetermined period of time, and at a predetermined relative humidity sufficient to cure the formulation to form a cured material. In this embodiment, the moisture cure is generally carried out at a relative humidity of from about 1 % to about 100 % in one embodiment, from about 10 % to about 80 % in another embodiment, and from about 20 % to about 70 % in still another embodiment. In one preferred embodiment, the formulation is cured at a relative humidity of 50 %. The moisture cure can be carried out at a temperature of from about 0 °C to about 60 °C, from about 10 °C to about 40 °C in another embodiment, and from about 15 °C to about 35 °C in still another embodiment. The humidity moisture curing mechanism above may be carried out a predetermined time of generally from about 12 hours to about 14 days at room temperature (about 23 °C) in one embodiment, from about 1 day to about 10 days in another embodiment, and from 3 days to about 7 days in still another embodiment.
In another embodiment, the curable formulation may be cured using a dual cure mechanism of (A) a pre-cure heat curing mechanism and (B) a moisture curing mechanism to complete the curing. For example, the curing mechanism of the curable formulation may be carried out by first pre-curing the formulation at a predetermined temperature of generally from about 60 °C to about 180 °C in one embodiment, from about 70 °C to about 150 °C in another embodiment, and from about 80 °C to about 120 °C in still another embodiment. For example, the heating time to carry out the curing process for preparing the cured material using the pre-cure heating step of the dual cure mechanism may be generally from about 30 seconds (s) to about 60 minutes (min) in one embodiment, from about 1 min to about 30 min in another embodiment, and from 5 min to about 15 min in still another embodiment.
After the pre-curing heating step above, a second curing mechanism
(i.e., moisture cure) of the curable formulation may be carried out by moisture. The formulation is moisture cured at a predetermined relative humidity (to provide the necessary moisture), at a predetermined temperature, for a predetermined period of time, sufficient to completely cure the formulation to form a fully cured material. For example, the heat pre-cured composition described above can be cured by moisture at a relative humidity of from about 1 % to about 100 % in one embodiment, from about 10 % to about 80 % in another embodiment, and from about 20 % to about 70 % in still another embodiment. In one preferred embodiment, the formulation is cured at a relative humidity of 30 %.
The moisture cure can be carried out at a temperature of from about 0 °C to about 60 °C, from about 10 °C to about 40 °C in another embodiment, and from about 15 °C to about 35 °C in still another embodiment.
The humidity moisture curing mechanism above may be carried out a predetermined time of generally from about 12 hours to about 14 days at room temperature (about 23 °C) in one embodiment, from about 1 day to about 10 days in another
embodiment, and from 3 days to about 7 days in still another embodiment.
The preparation of the cured material of the present invention, and/or any of the steps thereof, may be a batch or a continuous process. The equipment employed to carry out the reaction includes equipment known to those skilled in the art.
One important advantage of using the present invention is the chemical and mechanical properties of the cured formulation are preserved i.e., the present invention does not adversely affect the properties of the cured material. The cured material (i.e. the cross-linked product made from the curable formulation) of the present invention, more particularly for use in the automotive industry, for example does not exhibit a glass transition temperature (Tg) at a particular temperature range sufficient to process the cured material. For example, the temperature at which the cured material does not exhibit a Tg (no Tg property) for the cured material can be generally at a temperature of from about -20 °C to about 80 °C in one embodiment, from about -20 °C to about 70 °C in another embodiment, and between about -10 °C and 60 °C in still another embodiment. The Tg of the cured precursor composite material can be measured by the method described in ASTM D7426 (or by the method according to German Institute of Standardization - "DIN" - 53765).
Some non-limiting examples of enduse applications wherein the cured product of present invention may be used include, for example, adhesive formulation. The adhesive formulation can then be used in automobile enduse applications. For example, the adhesive formulation may be used to bond parts in the automobile assembly. The bonded parts can include, for example, composite to composite parts, composite to metal parts, glass to glass, glass to metal, glass to plastic, plastic to plastic; and the like.
The application of the adhesives to the parts can include for example, composite bonding, direct glazing, add-on bonding, and the like.
EXAMPLES
The following examples and comparative examples further illustrate the present invention in detail but are not to be construed to limit the scope thereof.
In the following Examples, various materials, terms and designations are used such as for example the raw materials listed in Table I as follows:
Table I - Raw Materials
Figure imgf000022_0001
Inventive Synthesis Example 1 - Preparation of Polyester Polyol Dispersion
A 500 milliliter (mL) glass reactor was charged with DYNACOLL 7330 (30.0 g) and diisononyl phthalate (100 g). The resultant mixture in the reactor was heated to 120 °C to form a homogeneous solution. The solution was stirred under vacuum for one hour (hr). After 1 hr of stirring, the solution was allowed to cool to room temperature (23 °C, RT) while continuing to stir. A precipitate of the polyester polyol in diisononyl phthalate formed in the reactor. When the resultant mixture in the reactor reached RT, benzoyl chloride (60 mg) was added to the mixture, and then the mixture was stirred for another 30 minutes (min). A stable polyester polyol dispersion was produced by the above procedure.
Comparative Synthesis Example A - Prepolymer T-715 Preparation
The following compounds were added into a lab reactor (500 mL glass reactor): 22.8 % Voranol 2000L (liquid at RT), 33.5 % Voranol CP 4610 (liquid at RT) and 34.2 % Vestinol. The resulting mixture was heated up to 120 °C under vacuum and then the mixture was mixed for 60 min. Then the mixture was cooled down to 50 °C and 9.5 % Isonate M125 was added to the mixture. The resultant mixture was mixed for an additional 2 min and then 0.01 % Metatin S-26 was added to the mixture. The mixture was allowed to react for 30 min under nitrogen. Then the resulting mixture was mixed for 20 min under vacuum. The NCO content of the reaction product produced after the above mixture was allowed to react was 1.4 %.
Inventive Example 1
A planetary mixture was charged with 150 g of T-715 (Comparative Synthesis Example A), and 63 g of the above described polyester polyol dispersion
(Inventive Synthesis Example A) prepared in Inventive Example 1. The resultant mixture was mixed (8.8 Hz) at room temperature for 30 min under vacuum. Fomrez UL-28 (160 mg) was added to the mixture and stirred into the mixture with a wooden spatula. Polestar 200R (45 g) and Printex 30 (60 g) was added to the above mixture and the mixture was mixed for 5 min under a nitrogen atmosphere. Then, the mixture was mixed for 1 hr under vacuum (23 °C, 8.8 Hz). Aluminum cartridges (150 mL) were then filled with the resultant mixed material.
Comparative Example A - Preparation of Adhesive Formulation
A planetary mixture is charged with the prepolymer T-715 (Comparative Example A) (150 g), Fomrez UL-28 (160 mg), and diisononyl phthalate (48.5 g).
Calcinated clay (Polestar 200R, 59.54 g) and carbon black (Printex 30, 60 g) are then added to the mixture; and the resultant mixture is mixed under vacuum until a dispersion is obtained.
Mechanical Testing:
Lap shear strengths of Inventive Example 1 and Comparative Example A were measured according to DIN EN 1465 on e-coated steel substrates. The bonding area of the substrates was 10 mm x 25 mm bonding area, and a 2 mm bonding height.
Humidity cured samples were cured by atmospheric water for seven days at an environment of 23 °C and 50 % relative humidity (RH). Heat cured samples were cured in an oven at 140 °C for 15 min. Lap shear strengths measurements of samples, cured and conditioned, were taken as follows:
15 min at 140 °C, conditioned for 30 min at room temperature; 15 min at 140 °C, conditioned for seven days at room temperature;
Humidity cured seven days at room temperature (RT).
The results of lap shear measurements are described in Table II.
Table II - Lap Shear Measurements of Inventive Example 1 and Comparative Example A
Figure imgf000024_0001
Table II summarizes the results of lap shear strength measurements obtained from samples prepared in Inventive Example 1 and Comparative Example A. Both
Inventive Example 1 and Comparative Example A are lK polyurethane adhesives which can be cured by atmospheric water. When the samples were cured for seven days at 23 °C with 50 % relative humidity, Comparative Example A reaches a lap shear strength of 4.13 MPa whereas Inventive Example 1 shows a lap shear strength of 3.88 MPa. The cure of Comparative Example A cannot be accelerated by heat. When a lap shear sample of
Comparative Example A is heated for 15 min at 140 °C and conditioned for 30 min, no lap shear experiments can be performed on the sample because the sample is still wet and pasteous. If Comparative Example A is heated for 15 min at 140 °C and then conditioned for seven days at RT, a lap shear strength of 4.13 MPa is observed, indicating that heat is not harming the sample since the sample reaches almost the same lap shear strength as the Comparative Example A which is only cured at seven days RT.
On the other hand, when the sample of Inventive Example 1 is heated for 15 min at 140 °C and conditioned for 30 min at room temperature, a lap shear strength of 1.23 MPa is obtained. This indicates that the addition of the solid polyester polyol to the adhesive formulation is rendering the adhesive heat curable. When a sample of Inventive Example 1 is heated for 15 min at 140 °C and further conditioned for seven days at RT, a lap shear strength of 3.88 M Pa is obtained for Inventive Example 1. This lap shear strength value of 3.88 M Pa is very close to the lap shear strength value of the same sample when cured seven days at RT (3.64 MPa). This indicates the dual cure nature of the Inventive Example 1 of the present invention; i.e., Inventive Example 1 can be cured by heat or by moisture or both.

Claims

CLAIMS:
1. A polyester polyol dispersion composition comprising a mixture of: (a) at least one solid polyester polyol having a melting point of from about 60 °C to about 140 °C; and (b) at least one plasticizer compound.
2. The dispersion composition of claim 1 , wherein the at least one solid polyester polyol is selected from the group consisting of crystalline solid polyester polyol, semi-crystalline solid polyester polyol, and mixtures thereof.
3. The dispersion composition of claim 1, wherein the at least one plasticizer compound is diisononyl phthalate.
4. The dispersion composition of claim 1 , wherein the concentration of the at least one solid polyester polyol is from about 5 weight percent to about 30 weight percent; wherein the concentration of the at least one plasticizer compound is from about 10 weight percent to about 30 weight percent.
5. The dispersion composition of claim 1, wherein the average particle size of the at least one solid polyester polyol is from about 1 micron to about 500 microns.
6. The dispersion composition of claim 1, including further a benzoyl chloride; wherein the concentration of benzoyl chloride is from about 0.01 weight percent to about 0.1 weight percent.
7. A process for preparing a polyester polyol dispersion composition comprising admixing: (a) at least one solid polyester polyol having a melting point of from about 60 °C to about 140 °C; and (b) at least one plasticizer compound.
8. A curable adhesive formulation comprising
(i) at least one polymer resin, and
(ii) the dispersion composition of claim 1 ;
wherein the curable composition can be crosslinked by humidity at a relative humidity of 1 percent to 99 percent and/or by heat above a temperature of about 70 °C.
9. The curable formulation of claim 8, wherein at least one polymer resin is selected from the group of polyurethane resins, epoxy resins, isocyanate functional prepolymers, and mixtures thereof.
10. The curable formulation of claim 8, wherein at least one polymer resin is an isocyanate functional prepolymer, said prepolymer comprising a reaction product of methylene diphenyl diisocyanate and a polyetherpolyol.
11. The curable formulation of claim 8, wherein the concentration of at least one polymer resin is from about 30 weight percent to about 70 weight percent.
12. A process for preparing curable formulation useful as an adhesive formulation comprising admixing:
(i) at least one polymer resin, and
(ii) the dispersion composition of claim 1 ;
such that a curable formulation is formed; and wherein the curable composition can be crosslinked by humidity at a relative humidity of 1 percent to 99 percent and/or by heat above a temperature of about 70 °C.
13. The process of claim 12, wherein at least one polymer resin is an isocyanate functional prepolymer, said prepolymer comprising a reaction product of methylene diphenyl diisocyanate and a polyetherpolyol.
14. A cured adhesive material comprising a reaction product prepared by curing the curable composition of claim 8.
15. The cured adhesive material of claim 14, wherein at least one polymer resin is an isocyanate functional prepolymer, said prepolymer comprising a reaction product of methylene diphenyl diisocyanate and a polyetherpolyol.
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