WO2023107270A1 - Blocked prepolymer compositions with improved storage stability - Google Patents

Abstract

The present invention provides blocked isocyanate prepolymers comprising, in copolymerized form, one or more C8 to C24 hydrocarbyl group-containing phenol blocking agents, such as a cardanol, and one or more monohydric alcohols having a normal boiling point of 110 °C or higher, such as an alkoxypoly(alkylene glycol), for example, a methoxy poly(ethylene glycol). The blocked isocyanate prepolymers exhibit a surprisingly improved storage stability. In addition, the present invention provides methods of making the blocked isocyanate prepolymers comprising reacting a polyol with a molar excess of a polyisocyanate, blocking the resulting prepolymer and then adding the monohydric alcohol under conditions to react the prepolymer and the monohydric alcohol, such as at a temperature of from 60 to 100 °C.

Description

BLOCKED PREPOLYMER COMPOSITIONS WITH IMPROVED STORAGE STABILITY

FIELD

The present invention relates to fluid, long chain hydrocarbyl group-containing phenol blocked isocyanate prepolymer compositions further comprising, in copolymerized form, a monohydric alcohol and having improved storage stability, and to methods for making them. More particularly, it relates to storage stable fluid compositions comprising long chain hydrocarbyl group-containing phenol, such as a CL to C24 alk(en)yl phenol, blocked isocyanate prepolymers and a monohydric alcohol having a boiling point at 1 atmosphere (101.325 KPa) of 110 °C or higher, preferably, a monhydric alcohol containing one or more ether groups, such as a methoxypoly (ethylene glycol).

INTRODUCTION

Blocked isocyanate prepolymer compositions find use in many applications, such as, for example, in adhesives, casting or molding compounds, coatings, or thermal interface materials for use with batteries. One drawback associated with such prepolymers results from their poor storage stability, for example, because of their tendency to gel on storage. Further, materials containing isocyanates can present safe handling issues, such as toxicity to users of resins and compositions containing them. To address these issues and other possible health and safety requirements, such as relevant European Union (EU) regulations, isocyanate containing compositions have been made or modified so that they contain less than 0.1 wt.% of total free isocyanate monomer(s) including, for example, toluene diisocyanate (TDI), or methylene diphenylmethane diisocyanate (MDI) etc.). Blocked isocyanate prepolymers have presented a known way of mitigating the health and safety concerns regarding isocyanate handling. However, it remains desirable to provide blocked isocyanate prepolymers having a reduced tendency to gel over time, such as the time between their manufacture and their use.

More recently, blocked isocyanate prepolymer compositions have been made more storage stable by forming them while distilling the compositions used to make them. However, such distillation methods have a limited utility and may remove reactants and/or create unwanted side reactions such as when dealing with isocyanate containing compositions like aromatic isocyanates that boil at, for example, 100 °C or more at atmospheric pressure.

European patent publication no. EP1114854A1, to Asahi Glass Company Ltd., discloses a reactive hot melt adhesive containing, as the main component, a blocked urethane prepolymer made by reacting a linear urethane prepolymer having isocyanate groups with an aliphatic monoalcohol (A) having a hydroxyl number of from 200 to 560, a blocking agent (B) which is a compound other than (A), and, optionally, a low molecular weight diol having a hydroxyl number of higher than 400. However, the compositions of the Asahi Glass reference have a fluid viscosity only at 110 °C, and do not flow at room temperature. Further, the compositions combine a blocking agent with unblocked prepolymer and with and an aliphatic monoalcohol, which is expected to preferentially extend the prepolymer without effectively forming a blocked isocyanate prepolymer.

The present inventors have endeavored to provide a fluid blocked isocyanate prepolymer composition that demonstrates storage stability by exhibiting an acceptably small change in viscosity upon storage, and to provide methods of making the same.

SUMMARY

In accordance with the present invention a fluid, room temperature reactive composition comprises a Cs to C24 hydrocarbyl group-containing phenol blocked isocyanate prepolymer, the blocked isocyanate prepolymer further comprising, in copolymerized form, a monohydric alcohol having a boiling point at 1 atmosphere (101.325 KPa) of 110 °C or higher or, preferably, 150 °C or higher, and having a hydroxyl number of from 60 to 500. The C« to C24 hydrocarbyl group-containing phenol in the blocked isocyanate prepolymer may comprise an alkyl phenol having a mono-, di-, and/or tri- unsaturated hydrocarbyl group, preferably, a phenol having a mono-, a di-, or a tri- unsaturated pentadecylene group, or a combination of two or more thereof, such as a or a combination of all three thereof, or, more preferably, a phenol having a mixture of a mono-, di-, and tri- unsaturated pentadecylene group, for example, a cardanol. The blocked isocyanate prepolymer comprises a blocked polymer of, in copolymerized form, one or more polyols, preferably, one or more diols, such as one or more polyether polyols having two hydroxyl functional groups, and an excess of one or more polyisocyanates, preferably, one or more aromatic diisocyanates or, more preferably, a toluene diisocyanate (TDI), a mixture of two TDIs, or a mixture of at least one TDI with at least one other aromatic diisocyanate. Preferably, the monohydric alcohol has one or more ether groups, such as, for example, an alkoxypoly(alkylene glycol) or, more preferably, a methoxy poly(ethylene glycol) (MPEG). The amount of the monohydric alcohol in the blocked isocyanate prepolymer composition may range from 0.2 to 10 wt.% or, preferably, from 0.5 to 5 wt.% , from 1 to 3 wt.%, based on the total weight of all reactants used to make the blocked isocyanate prepolymer. The composition may have a cone and plate viscosity at 25 °C and 10 sec ¹ as measured using a rotational rheometer in which the composition was placed between an 80 mm diameter Peltier Plate and a 40 mm, 2 degree cone rotating at a constant angular velocity while the Peltier plate remains at rest, and running a temperature sweep from 25 to 50 °C at a ramp rate of 3 °C/min at a shear rate of 10 sec ¹, ranging from 8 to 50 Pa-s, or, from 10 to 40 Pa-s, or, preferably, from 12 to 33 Pa-s. Further, the compositions exhibit improved storage stability as a change of 20% or less, or, preferably, 10% or less, in their cone and plate viscosity (25 °C and 10 sec ¹) after 14 days storage at 60 °C.

In another aspect of the present invention, a method of making a blocked isocyanate prepolymer having improved storage stability, such as the blocked isocyanate prepolymer of the fluid, room temperature reactive compositionin accordance with the present invention, comprises: reacting one or more polyols, preferably, one or more diols, such as a polyether polyol having two hydroxyl functional groups, or mixtures thereof with a molar excess of one or more polyisocyanates, preferably, one or more aromatic diisocyanates or, more preferably, a toluene diisocyanate (TDI), a mixture of two TDIs, or a mixture of at least one TDI with at least one other aromatic diisocyanate to make an isocyanate functional prepolymer; blocking the isocyanate functional prepolymer with a C« to C24 hydrocarbyl group- containing phenol, such as an alkyl phenol having a mono-, di-, and/or tri- unsaturated hydrocarbyl group, preferably, a phenol having a mono-, di-, and/or tri- unsaturated pentadecylene group, or, more preferably, a phenol having a mixture of a mono-, di-, and triunsaturated pentadecylene group, for example, a cardanol to form a blocked isocyanate prepolymer; and, adding to the blocked isocyanate prepolymer a monohydric alcohol having boiling point of 110 °C or higher, or, preferably, 150 °C or higher and having a hydroxyl number of from 60 to 500, such as a C« to Cis alcohol, like dodecanol, preferably, a monohydric alcohol having one or more ether groups, such as, for example, an alkoxypoly(alkylene glycol) or, more preferably, a methoxy poly(ethylene glycol) (MPEG) under conditions that cause the blocked isocyanate prepolymer and the monohydric alcohol to react with each other, for example, at a temperature of from 60 to 100 °C.

The method of making the blocked isocyanate prepolymer may include one or more or all features of the blocked isocyanate prepolymer of the present invention and as disclosed herein, including each polyol, polyisocyanate, blocking agent, monohydric alcohol, catalyst or solvent or carrier, including any copolymerized forms thereof, any isocyanate prepolymer, any blocked isocyanate prepolymer, and any or all preferred or not preferred forms thereof.

DETAILED DESCRIPTION

In accordance with the present invention, compositions of isocyanate prepolymers blocked with long chain hydrocarbon substituted phenols and further comprising, in copolymerized form, a monohydric alcohol in the blocked prepolymer exhibit little gelation on storage. The present inventors have solved the problem of gelation of blocked isocyanate prepolymers having phenolic blocking agents comprising a long chain hydrocarbyl group, such as a mono-, di-, and/or tri- unsaturated pentadecylene group or a Cs to C24 alkyl, alkenyl, alkdienyl or alktrienyl group. Some aromatic blocked isocyanate prepolymer compositions or blocking agents within them solidify or gel on storage. Phenolic blocking agents comprising a long chain hydrocarbyl group do not crystallize in blocked isocyanate prepolymers containing them; however, the inventors have discovered that such blocked isocyanate prepolymers have not been storage stable.

Further, addition of a monohydric alcohol, such as an MPEG, to the blocked isocyanate prepolymer results in more complete elimination of any residual isocyanate regardless of the chemical nature of the addition. By reducing the free isocyanate content in blocked isocyanate prepolymers and including at least one monohydric alcohol, the inventors have discovered blocked isocyanate prepolymer compositions that have reduced viscosity, exhibit excellent storage stability and lower viscosity. Further, prepolymer of the present invention, when used ina two part thermally conductive composition, produce cured parts having lower overall hardness.

The blocked isocyanate prepolymer compositions are readily flowable, having viscosities at 25 °C and 1 sec ¹ of from 10 to 30 Pa-s, wherein the viscosities change little over time at room temperature. In some cases, a reduction in the viscosity of the blocked prepolymer was also observed after adding MPEG to form the inventive blocked isocyanate prepolymer compositions. Accordingly, the present inventors have enabled the provision of relatively low viscosity blocked isocyanate prepolymers in a storage stable composition. Further, the compositions comprise blocked prepolymers that can be crosslinked at room temperature as a two-component composition with a separate component of a primary polyamine. The resulting two-component compositions have a variety of uses and can be used to provide, cured elastomeric polyurethanes suitable for use, for example, as thermal interface materials in batteries or conductive materials in heat intensive applications, such as thermal management of electric vehicle batteries.

Unless otherwise indicated, conditions of temperature and pressure are ambient temperature (21 to 25 °C), a relative humidity of 35 to 50%, and standard pressure (1 atm or 101.325 KPa).

Unless otherwise indicated, any term containing parentheses refers, alternatively, to the whole term as if parentheses were present and the term without them, and combinations of each alternative. Thus, as used herein the term, “(poly)glycol” and like terms is intended to include a glycol, a polyglycol, or mixtures thereof.

All ranges recited are inclusive and combinable. For example, a disclosed cone and plate viscosity at 25° C and 10 sec ¹, measured as defined herein, ranging from 8 to 50 Pa-s, or, from 10 to 40 Pa-s or, preferably, from 12 to 33 Pa-s, includes viscosity ranges of from 8 to 50 Pa-s or, preferably, from 12 to 33 Pa-s, or, from 8 to 10 Pa-s or, from 10 to 12 Pa-s, or, from 10 to 33 Pa-s, or, from 8 to 12 Pa-s, or, from 8 to 50 Pa-s, or, from 12 to 50 Pa-s, or, from 12 to 40 Pa-s, or, from 10 to 40 Pa-s, or, from 8 to 33 Pa-s or, from 33 to 40 Pa-s, or, from 33 to 50 Pa-s, or, from 8 to 40 Pa-s, or from 40 to 50 Pa-s, or, from 10 to 50 Pa-s.

As used herein, the term “ASTM” refers to publications of ASTM International, West Conshohocken, PA.

As used herein, the term “component” refers to a composition containing one or more ingredients which is combined with another component to start a reaction, polymerization, crosslinking or cure. Components are kept separate until combined at the time of use or reaction

As used herein, the term “DIN” refers to publications of the Deutsches Institut fur Normung, the German Institute for Standardization, Berlin, Germany.

As used herein, the term “ISO” refers to the publications of the International Organization for Standardization, Geneva, CH.

As used herein, the term “exotherm” refers to heat generated by a reaction that results in a rising or a least a steady elevated temperature (above room temperature) without the addition of any heat.

As used herein, the term “fluid” refers to a composition that flows in the absence of shear at a pressure of 1 atmosphere and a temperature of from 21 to 25 °C, such as a composition that readily assumes the shape of the container into which it is transferred, or which can readily be poured. As used herein, the term “gel” means a composition that does not flow or which has some yield point, i.e. some applied force was needed to force flow or movement of the gelled material. When visually observed, a gel tends to retain its shape over time. In some cases, a gel could be a completely solidifed material.

As used herein, the term “hydrocarbyl” means a monovalent radical or substituent that contains only carbon and hydrogen atoms, regardless of the presence or absence of rings or unsaturation. A “substituted hydrocarbyl group” may contain other specifically identified atoms, such as oxygen or nitrogen or specifically enumerated functional groups containing atoms other then carbon and hydrogen. For example, a carboxyl group containing hydrocarbyl group is a hydrocarbon radical that contains a carboxyl functional group.

As used herein, the term “hydroxyl number” in mg KOH/g of analyte refers to the amount of KOH needed to neutralize the acetic acid taken up on acetoylation of one gram of the analyte material as determined in accordance with ASTM D4274. The term “average hydroxyl number” refers to the weight average of the hydroxyl number of a mixture of hydroxyl functional compounds. For example, 50/50 w/w blend of a poly(ethylene glycol) having an hydroxyl number of 80 and an all propylene oxide (PO) polyether polyol having an hydroxyl number of 60 would have an average hydroxyl functionality of 0.5(80) + 0.5(60) or (40 + 30) or 70.

As used herein, the term “hydroxyl equivalent weight” or “equivalent weight” or “EW” of a given polyether polyol or polyol refers to calculated value as determined by the equation:

EW = 56,100/hydroxyl number of a given polyol.

As used herein, the term “in condensed form” means the form of a material after polyurethane or isocyanate prepolymer formation are complete, and is not limited to the product of a condensation or addition reaction.

As used herein, unless otherwise indicated, the term “isocyanate index” or simply “index” refers to the ratio of the number of equivalents of isocyanate functional groups to the number of equivalents of hydroxyl groups in a given polyurethane or polyurethane urea forming reaction mixture, multiplied by 100 and expressed as a number. For example, in a reaction mixture wherein the number of equivalents of isocyanate equals the number of equivalents of active hydrogen, the isocyanate index is 100.

As used herein, the term “isocyanate reactive group” refers to an active hydrogen group, such as a hydroxyl group or an amine group that contains an amine hydrogen. As used herein, the term “nominal hydroxyl functionality” refers to the number of hydroxyl groups in an ideal formula of a given diol or polyol, which is not respective of impurities or variability in the formula. The nominal hydroxyl functionality of a poly(oxyalkylene ether) or a poly(ethylene glycol), for example, is two; and the nominal hydroxyl functionality of a glycerol initiated polyol is the same as glycerol, or three (3). Hydroxyl functionality is presumed to equal the functionality of a polyol initiator where the polyol comprises an alkylene oxide adduct of the initiator. The term “nominal hydroxyl functionality” and “formula hydroxyl functionality” can be used interchangeably. The term “average hydroxyl functionality” refers to the weight average of the nominal hydroxyl functionality of a mixture of hydroxyl functional compounds. For example, a 50/50 mole% mixture of ethylene glycol and glycerol has an average hydroxyl functionality of 0.5(2 nominal OH groups in ethylene glycol) + 0.5(3 nominal OH groups in glycerol) or (1 + 1.5) or 2.5.

As used herein, the term “molecular weight” or “MW” of a given polyether polyol or polyol refers to a calculated value as determined by the equation:

MW = (56,100/hydroxyl number) X the nominal hydroxyl functionality of a polyol.

As used herein, the term “number average molecular weight” or “Mn” refers to the total weight of the polymer divided by the number of molecules of polymer. Mn can be determined using well known method, such as by Gel permeation chromatography (GPC) as gainst appropriate standards, to give a distribution of polymer molecular weights. The number of molecules in a sample can be estimated from the GPC data.

As used herein, unless otherwise indicated, the term “average particle size” refers to the median particle size or diameter of a distribution of particles as determined by laser diffraction using a Multisizer 3 Coulter Counter (Beckman Coulter, Inc., Fullerton, CA) according to the procedure recommended by the manufacturer. The term “median particle size” or “D50” is defined as the size at which 50 cumulative % of the particles in the distribution are smaller than the median particle size and 50 cumulative % of the particles in the distribution are larger than the median particle size. The term “D90” refers to the size at which 90 cumulative % of the particles have a size below the stated size. The term “Dio” refers to the size at which 10 cumulative% of the particles have a size below the stated size. Alternatively, an average particle size may be estimated by measuring the surface area of a composition according to 8- 11 ASTM D4315 or by using sieves of various mesh sizes and calculating the average from the cumulative weight of each size fraction. The alternative methods give estimations of the average particle sizes similar to those determined by the laser diffraction method.

As used herein, the term “polyisocyanate” refers to an isocyanate group containing material having two or more isocyanate functional groups, such as a diisocyanate, or a biuret, allophanate, isocyanurate, carbodiimide, dimer, trimer or oligomer thereof made by reaction of an excess of isocyanate with one or more diols.

As used herein, the term “reactants used to make any polymer or prepolymer” include all materials that react into the polymer and any catalysts that remain fugitive in the polymer, such as reactive catalysts.

As used herein, the term “storage stable” means that a composition when left to stand on a shelf at 60 °C and atmospheric pressure for at least 14 days does not form a gel, separate, precipitate out or produce a visible sediment, or gives less than a 20% or, preferably, less than a 10% increase in viscosity over that time period.

As used herein, unless otherwise indicated, the term “viscosity” refers to a cone and plate viscosity at 25 °C and 10 sec ¹ measured using an AR2000 Rotational Rheometer (TA Instruments, New Castle, DE) in which the indicated material was placed between an 80 mm diameter Peltier Plate (with hardened chrome surface, TA instruments) and a 40 mm, 2 degree cone rotating at a constant angular velocity while the Peltier plate remained at rest, and running a temperature sweep from 25 to 50 °C at a ramp rate of 3 °C/min at a shear rate of 10 sec ¹.

As used herein, the phrase “wt. %” stands for weight percent.

The present invention provides fluid, storage stable compositions that comprise a long chain hydrocarbyl group-containing phenol blocked isocyanate prepolymer and, in copolymerized form, one or more monohydric alcohols that will not volatilize during the making or in the use of the composition. The compositions may comprise a blocked isocyanate prepolymer, such as, in copolymerized form, one or more polyols with an excess of any diisocyanate or a polyisocyanate, followed by addition of a blocking agent such as cardanol to form the blocked isocyanate prepolymer, and then followed by addition of the monohydric alcohol, for example, as an endcapping agent. The isocyanate prepolymer to be blocked may be, for example, an isocyanate prepolymer from an excess of an aromatic polyisocyanate and a polyether polyol, a diol or a triol. The blocked isocyanate prepolymer compositions have a cone and plate viscosity at 25 °C and 10 sec ¹ of from 8 to 50 Pa-s, or, from 10 to 40 Pa-s, or, preferably, from 10 to 33 Pa-s, as measured using an AR2000 Rotational Rheometer (TA instruments) in which the indicated material was placed between an 80 mm diameter Peltier Plate (with hardened chrome surface, TA instruments) and a 40 mm, 2 degree cone rotating at a constant angular velocity while the Peltier plate remained at rest, and running a temperature sweep from 25 to 50 °C at a ramp rate of 3 °C/min at a shear rate of 10 sec ¹ with a truncation gap of 54 pm. Once the gap is reached, the analyte sample was trimmed to remove any excess material. In addition, the present invention provides methods of making the storage stable compositions comprising reacting an excess of a polyisocyanate with a diol, glycol or polyether polyol having, for example, two hydroxyl functional groups to form an isocyanate functional prepolymer, blocking the isocyanate functional prepolymer with a long chain hydrocarbyl group- containing phenol, such as a cardanol, and adding a monohydric alcohol thereto under conditions that cause the monohydric alcohol to react with the blocked isocyanate prepolymer, such as blocking reaction conditions.

Suitable isocyanate terminated prepolymers may be any prepolymer(s) prepared by the reaction of one or more polyols with a stoichiometric excess of one or more polyisocyanates. The isocyanate-terminated prepolymer may be prepared by conventional methods known to a person skilled in the art, for example, as disclosed in U.S. Patent Nos. 4,294,951 to Sugita et al., 4,555,562 to Lee et al. and 4,182,825 to Jackie; and International Publication No. WO 2004/074343 to Dow Global Technologies, Inc. The reactive materials may be mixed together and heated to promote reaction of the polyols and the polyisocyanates. The reaction temperature may range from 30 to 150 °C, such as, for example, from 60 to 100 °C. The reaction may be performed in a moisture-free atmosphere. An inert gas such as nitrogen and/or argon may be used to blanket the reaction mixture. Further, an inert solvent can be used during preparation of the isocyanate-terminated prepolymer, although the inert solvent may be excluded. A catalyst to promote the formation of urethane bonds may also be used.

As used herein, the term “Polyisocyanate” refers to any compound that contains two or more isocyanate groups. The polyisocyanate may comprise a diisocyanate; a polymeric isocyanate, such as a dimer or a trimer thereof; an isocyanate prepolymer, such as one formed from an excess of polyisocyanates reacted with one or more polyols, or mixtures thereof. The polyisocyanates may be aromatic, aliphatic, araliphatic or cycloaliphatic polyisocyanates, or mixtures thereof, preferably, aromatic. Suitable polyisocyanates for making the blocked isocyanate prepolymer of the present invention may comprise one or more diisocyanates, preferably an aromatic diisocyanate. Polyisocyanates in the isocyanate composition may have an average isocyanate functionality of 1.9 or more, 2.0 or more, 2.1 or more, 2.2 or more, or even 2.3 or more, and at the same time, 4.0 or less, 3.8 or less, 3.5 or less, 3.2 or less, 3.0 or less, 2.8 or less, or 2.7 or less.

Such polyisocyanates for use in making the prepolymers of the present invention may comprise, for example, an aromatic diisocyanate, an aromatic polyisocyanate, a mixture of these, or a mixture of two or more of these. Examples of useful polyisocyanates in accordance with the present invention may include one or more of toluene diisocyanate, toluene-2,4,6-triisocyanate, m-phenylene diisocyanate or methylene di(phenyl isocyanate), diphenylmethane-4, 4'- diisocyanate, diphenylmethane-2,4'- diisocyanate, hydrogenated diphenylmethane-4, 4'- diisocyanate, hydrogenated diphenylmethane-2,4'-diisocyanate, toluene-2,4-diisocyanate or toluene-2,6-diisocyanate, naphthylene-l,5-diisocyanate, methoxyphenyl- 2,4-diisocyanate; 4,4'- biphenylene diisocyanate, 3,3'-dimethoxy-4,4'- diphenyl diisocyanate, 3,3'-dimethyl-4-4'- biphenyl diisocyanate, 3, 3 '-dimethyldiphenyl methane-4,4'-diisocyanate, 3,3'- dimethyldiphenylpropane-4,4'-diisocyanate, 4,4',4"-triphenyl methane triisocyanate, and 4,4'- dimethyldiphenylmethane-2,2',5,5'-tetraisocyanate, isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), tetramethylene-l,4-diisocyanate, cyclohexane-1,4- diisocyanate, hexahydrotolylene diisocyanate, l-methoxyphenyl-2,4-diisocyanate, isomers thereof, or mixtures thereof. Toluene-2,4-diisocyanate, toluene-2,6-diisocyanate and mixtures thereof are generically referred to as “TDI”. Diphenylmethane-4, 4'- diisocyanate, diphenylmethane-2,4'-diisocyanate and mixtures thereof are generically herein referred to as “MDI”. Particularly useful polyisocyanates may include TDI, or mixtures thereof with MDI or other poly isocyanates.

Preferably, the polyisocyanates are TDI, polymers of TDI, such as a dimer or a trimer thereof, isocyanate prepolymers thereof, or mixtures thereof with other polyisocyanates. Toluene diisocyanate containing prepolymers may result in lower deblocking temperatures along with ease of deblocking and reaction.

The isocyanate terminated prepolymers made in the methods of the present invention may comprise a poly ether backbone and isocyanate terminal groups. The isocyanate-terminated prepolymer may have an isocyanate content (NCO content) of 1 wt.% or more, or, 2 wt.% or more, or, 2.7 wt.% or more, 5 wt.% or more, 6 wt.% or more, 8 wt.% or more, or even 10 wt.% or more, and at the same time, 30 wt.% or less, 25 wt.% or less, 20 wt.% or less, or even 15 wt.% or less, based on the weight of the isocyanate prepolymer. The NCO content herein is measured in accordance with ASTM D5155-19, test method C (2019). The isocyanates used to prepare the isocyanate terminated prepolymers may include any of the above stated diisocyanates, isomers thereof, polymers thereof, prepolymers thereof, or mixtures thereof.

Suitable polyols for preparing the isocyanate terminated prepolymer may be any polyol known in the art, including, for example, ethylene glycol, 1 ,2-propanediol, 1,3 -propanediol, 1,3- butanediol, 1,4-butenediol, 1 ,4-butynediol, 1,5-pentanediol, neopentyl-glycol, bis (hydroxymethyl) cyclohexanes, such as l,4-bis(hydroxymethyl)cyclohexane, 2- methylpropane-l,3-diol, methylpentanediols, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol, poly butylene glycols, polyoxyethylene glycols, polyoxypropylene glycols, polyoxypropylene- polyoxyethylene glycols, glycerol, polyoxypropylene triols, polyoxypropylene-polyoxyethylene triols or mixtures thereof. The functionality of a suitable polyol may range from 1.9 to 3.1; and the polyol may have a number average molecular weight of from 500 to 10,000 or a hydroxyl number from 10 to 500 mg KOH/g , for example, from 20 to 200 mg KOH/g.

Polyether polyols may be prepared by adding an alkylene oxide, such as ethylene oxide (EO), propylene oxide (PO), butylene oxide (BO), or a combination thereof, to an initiator having from 2 to 8 active hydrogen atoms (e.g., such that the initiator includes hydroxyl groups and excludes amines). For example, exemplary poly ether polyols for prepolymer formation may include those having a number average molecular weight in Dalton (Da) of from 100 to 10000 g/mol (Da) , for example, 1000 Da or more, or, 2000 Da or more, or, 3,000 Da or more, or 3500 Da or more, or, up to to 8000 Da, or, up to 6000 Da, or, up to 5000 Da, or, up to 4500 Da. The poly ether polyols may have a functionality from 2 to 8, or, of at least 2, or, at least 3, or, up to 8, or, up to 6 active hydrogen atoms per molecule.

The one or more poly ether polyols may include a polyoxypropylene containing polyol such as an ethylene oxide capped polyoxypropylene diol or triol and/or poly oxypropylene diol or triol. Exemplary polyether polyols are those available under the trade name VORANOL™ polyols (Dow Incorporated, Midland, MI (Dow)).

The production of polyols by alkoxylation of an initiator may be done by procedures known in the art. For example, a polyol may be made by the addition of an alkylene oxide (EO, PO, or BO), or a combination of alkylene oxides to the initiator by anionic or cationic reaction or use of double metal cyanide (DMC) catalyst. For some applications only one alkylene oxide monomer may be used; for some other applications a blend of monomers may be used, and in some cases a sequential addition of monomers, such as PO followed by an EO feed or EO followed by PO, may be used. If a copolymer, a polyether polyol may be a block and/or random copolymer as well as a capped copolymer.

Other suitable polyols include polyester polyols, hydroxyl-terminated poly(butadiene) polyols, polyacrylate polyols and amine-initiated polyols. Exemplary polyols having an amine initiator may be self-catalytically active and are available under the trade name VORANOL™ and VORACTIV™ polyols (Dow).

Preferred polyols may be polyether polyols having two hydroxyl functional groups, such as those with a hydroxyl functionality of 1.9 to 2.2 and a number average molecular weight ranging from 1000 Da to 3000 Da.

Catalysts may be used in small amounts, for example, from 0.0015 to 5 wt.% of the total weight all of the reactants used to form the blocked isocyanate prepolymer. The amount depends on the catalyst or mixture of catalysts and the reactivity of the polyols and isocyanate as well as other factors familiar to those skilled in the art. A known catalyst may be used. For example, catalysts that may catalyze isocyanate prepolymer reactions include tertiary amine catalysts and tin or metal catalysts, such as carboxylates. Examples of commercially available tertiary amine catalysts include: trimethylamine, triethylamine, N-methylmorpholine, N-ethylmorpholine, N,N- dimethylbenzylamine, N,N-dimethylethanolamine, N,N- dimethylaminoethyl, N,N,N',N'- tetramethyl-l,4-butanediamine, N,N- dimethylpiperazine, l,4-diazobicyclo-2,2,2-octane, bis(dimethylaminoethyl)ether, triethylenediamine, and dimethylalkylamines where the alkyl group contains from 4 to 18 carbon atoms. Mixtures of tertiary amine catalysts may be used.

The blocked isocyanate prepolymer may be the reaction product of an isocyanate terminated prepolymer, including any residual monomeric diisocyanate, and a blocking agent. For producing blocked isocyanate prepolymers, the blocking agent may be added after the formation of the isocyanate prepolymer, or during the formation of the isocyanate prepolymer, preferably, the blocking agent is added after the formation of the isocyanate prepolymer, The blocked isocyanate prepolymer may be formed by mixing and reacting one or more of the isocyanates with one or more blocking agents. Suitable isocyanate blocking agents for the isocyanate terminated prepolymer are C« to C24 aliphatic organic group substituted monophenolics, such as hydrocarbyl group-containing monophenolics. For example, the isocyanate blocking groups for the isocyanate terminated prepolymer are monophenolics with at least one hydrocarbyl substituent on one or more aromatic ring(s). One blocking group for the isocyanate terminated prepolymer is nonylphenol.

Preferably, the blocked isocyanate prepolymer is made from TDI using an all PO polyol having a number average equivalent weight of from 500 to 3000 and hydroxyl functionality 1.9 to 3.1, with an NCO content of from 2 to 15 wt.% , based on the total weight of the blocked isocyanate prepolymer before blocking.

Preferably, the blocking agent for the isocyanate terminated prepolymer comprises a cardanol. Cardanol is a plant-derived product derived from cashew nut shells. The cardanol containing blocking agent may be a cashew nut shell liquid (CNSL) that is a by-product of cashew nut processing, such as that may be extracted from a layer between a nut and a shell of a cashew nut. The CNSL may have a cardanol content of at least 85 wt.%, based on a total weight of the CNSL, and may additionally include less preferred cardols or methylcardols, each of which have two hydroxyl groups, and/or anacardic acid as secondary ingredients. The CNSL may be subjected to a heating process at the time of extraction from the cashew nut, a decarboxylation process, and/or a distillation process. The CNSL may include from 85 to 100 wt.%, or , from 90 to 99 wt.% of cardanol, based on a total weight of the CNSL. The CNSL may include less than 8.5 wt.%, for example, from 0 to 8 wt.%, from 0 to 5 wt.% of cardol or methylcardol, with a remainder being anacardic acid. Decarboxylated CNSL, not including anacardic acid, may be exposed to at least one distillation process.

Suitable amounts of the blocking agent, as expressed in equivalents of the hydroxyl groups of the blocking agent to the moles of isocyanate groups to be blocked, may range from 85 mole% or more, or, 95 mole % or more or, preferably, at least 100 mole %. A small excess of blocking agent is preferred, for example, an excess of up to 20 mole %, or, up to 15 mole %, for example, from 5 to 15 mole %, or, more preferably, up to 10 mole %, based on the total moles of free isocyanate groups, i.e. that are available to block. For example, the amount of blocking agent groups used for blocking may be from 95 mole % to 110 mole %, based on the moles of the free isocyanate groups on the prepolymer.

Suitable amounts of the blocking agent may range from 1 wt.% or more, or, 3 wt.% or more, or, 5 wt.% or more, or, 7 wt.% or more, or, 9 wt.% or more, or, 10 wt.%, or more, based on the total weight of the reactants used to make the blocked isocyanate prepolymer. The amount of the blocking agent may comprise 10 wt.% or less, or, 20 wt.% or less, or, 40 wt.% or less, or, 60 wt.% or less, or, 80 wt.% or less, based on the total weight of the reactants used to make the blocked isocyanate prepolymer. Thus, the total amount of the blocking agent may comprise from 1 to 60 wt.% or, preferably, from 3 to 40 wt% or, preferably, from 5 % to 40 wt.% , based on the total weight of the reactants used to make the blocked isocyanate prepolymer.

In another aspect, the present invention provides methods of making the blocked isocyanate prepolymer composition comprising reacting one or more polyols with an excess of a polyisocyanate to form an isocyanate functional prepolymer, then blocking the isocyanate functional prepolymer with a long chain hydrocarbyl group-containing phenol blocking agent to form a blocked isocyanate prepolymer, and then adding a monohydric alcohol to the composition under conditions that cause reaction of the blocked isocyanate prepolymer and the monohydric alcohol, such as at a temperature of from 60 to 100 °C. More particularly, the methods comprise: reacting one or more polyols, preferably, one or more diols or triols, such as a polyether polyol having two or three hydroxyl functional groups, or mixtures thereof with a molar excess of one or more polyisocyanates, preferably, one or more aromatic diisocyanates or, more preferably, a toluene diisocyanate (TDI), a mixture of two or more TDIs, or a mixture of at least one TDI with at least one polyisocyanate, such as an aromatic diisocyanate, to make an isocyanate functional prepolymer; blocking the isocyanate functional prepolymer with a C« to C24 hydrocarbyl phenol group, such as an alkyl phenol having a mono-, di-, and/or tri- unsaturated hydrocarbyl group, preferably, a phenol having a mono-, di-, and/or tri- unsaturated pentadecylene group, or, more preferably, a phenol having a mixture of a mono-, di-, and tri- unsaturated pentadecylene group, for example, a cardanol to form a blocked isocyanate prepolymer; and, adding to the blocked isocyanate prepolymer a monohydric alcohol having boiling point of 110 °C or higher, or, preferably, 150 °C or higher and having a hydroxyl number of from 60 to 500, preferably, a monohydric alcohol having one or more ether groups, such as, for example, an alkoxypoly(alkylene glycol) or, more preferably, a methoxy poly(ethylene glycol) (MPEG).

Each of the formation of the isocyanate prepolymer, blocking it to form the blocked isocyanate prepolymer and adding the monohydric alcohol to the blocked isocyanate prepolymer comprises combining the indicated materials to form a reaction mixture at from 60 to 100 °C, or, preferably, from 70 to 97 °C for a reaction period, such as from 2 to 24 hours, for example, from less than 12 to 18 hours. Each of the formation of the isocyanate prepolymer, the blocking thereof and the addition of the monohydric alcohol may comprise reacting at from 60 to 100 °C, or, preferably, from 70 to 97 °C for a reaction period, such as from 1 to 8 hours, for example, from less than 1.5 hours to 4.5 hours. The adding of the monohydric alcohol may take place from 60 to 100 °C or, preferably, from 70 to 97 °C for a reaction period of from 1 to 6 hours, for example, from less than 1.5 hours to 4 hours. In each of the forming the prepolymer and the blocking, a catalyst, such as, a tertiary amine, a metal containing catalyst, such as a tin catalyst, a carboxylate salt, for example, a mixed metal carboxylate catalyst, such as a zinc and zirconium carboxylate may be added in conventional amounts.

The blocked isocyanate prepolymers of the present invention can be used to make thermally conductive two-component compositions. Additionally, the prepolymers of this invention could be utilized in other applications utilizing blocked isocyanate prepolymers such as coatings, elastomers, adhesives, and epoxy composites.

A particular example of a composition that comprises the blocked isocyanate prepolymer of the present invention may comprise a paste of one or more blocked isocyanate prepolymers, and one or more thermally conductive fillers, such as aluminum trihydrate (ATH). Although the filler increases the viscosity of the paste composition, the viscosity of the paste must be low enough to allow mixing with an amine as a curing component in a curable two-component composition, of which the isocyanate component is one component. The two components cure at from 10 to 50 °C when combined. Suitable amines may include, primary polyether amines having a molecular weight, as determined by the hydroxyl number of the polyether used to make the polyether amine, in the range of 300 Da to 5000 Da and a hydroxyl functionality of the polyether used to make the poly ether amine of from 2.5 to 3.5. Particularly preferred are the primary aliphatic JEFF AMINE™ series of polyether amines (Huntsman Chemicals, Salt Lake City, UT); including, JEFFAMINE™ T-3000 and JEFFAMINE™ T-5000; JEFFAMINE™ T-403 or available from BASF including Baxxodur™ EC 3003, Baxxodur™ EC 311, Baxxodur™ EC 310. A combination of triamines, diamines and monoamines could be used to adjust the cure profile and mechanical properties such as hardness of the final product.

The cured product of the two-component composition has a relatively low cure hardness as measured in accordance with ASTM D2240 using a Shore OO durometer of from 40 to 90 Shore OO, or from 50 to 85 Shore OO, or from 60 to 80 Shore OO. Such two-component compositions may find use as thermal interface materials in applications requiring removal of heat from a heat source such as an electric vehicle battery. The two components of the curable composition are reactive with one another and when contacted or mixed upon application, undergo a curing reaction wherein the reaction product of the two components is a cured product which can provide thermally conductive interface between two surfaces. The mixture of the blocked isocyanate prepolymer composition and the amine composition may be cured at a temperature ranging from 0 to 60 °C; or, the mixture of the blocked isocyanate prepolymer composition and the amine composition may be cured at a temperature ranging from 10 to 50 °C. For example, the mixture of the blocked isocyanate prepolymer composition and the amine composition may be cured at a temperature from 15 to 45 °C. Preferably, the mixture of the blocked isocyanate prepolymer composition and the amine composition are cured at room temperature (e.g. RT) from 18 to 40 °C.

Curing is indicated by increase in the viscosity after mixing the two components, with the eventual formation of a cured solid having a measurable hardness. The cured composition may have a range of cure hardness. Preferably the cure hardness as measured in accordance with ASTM D2240 using a Shore OO durometer is from 40 to 95 Shore OO, or 50-90 Shore OO, or 60 to 85 Shore OO.

The composition may cure in less than 14 days, or less than 10 days, or, preferably, in less than 7 days, greater than 30 minutes. Cured compositions may have a thermal conductivity > 0.5 Watts/meter. Kelvin (W/m-K), or > 1 W/m-K, or most preferably > 1.5, W/m-K, or < 50 W/m-K. Cured composition may have a density of from 1 gm/cc to 4 gm /cc, or from 1.5 to 3.5 gm/cc or preferably, from 1.9 to 3.1 gm/cc.

The high thermal conductivity and low hardness described above makes the curable composition particularly suitable for use as a gap fillers for electric vehicle applications such as in assemblies of energy storage devices. Curable composition could be used to move the heat away from a heat source to a heat sink. Additionally, pre-cured thermal interface gap pads can also be prepared from this composition. Thermal gap pads having a desired thickness are cured, cut to a desired shape and compressed to fix in place.

Blocked isocyanate prepolymers of the present invention result in lower hardness of the cured articles, which is advantaged for gap fillers as products with lower hardness can provide better thermal contact between a heat source and heat sink.

In the two-component compositions for use as thermal interface materials, the blocked isocyanate prepolymer component or the amine component containing one or more amines may further comprise one or more additives. Either of the blocked isocyanate prepolymer composition or the amine composition may also contain one or more moisture scavengers, plasticizers, adhesion promoters, thixotropic agents, color agents, antioxidants, wetting agents, filler treatment agents, surface treatment additives or a combination thereof.

The amine component comprises one or more catalysts, which may or may not be fugitive. Suitable catalysts may be a carboxylate salt, a tertiary amine, an amidine, a guanidine, a diazabicyclo compound or a combination thereof. Fugitive catalysts comprise a reactive group, such as an active hydrogen.

A plasticizer, may be mixed into either or the blocked isocyanate component or the amine component in an amount of from 0 to 20 wt.%, or from 2 to 12 wt.% or from 4 to 10 wt.%, based on the total weight of the two-component composition. Suitable plasticizers may be any common plasticizers useful in polyurethane and well known to those skilled in the art. The plasticizer may be present in an amount sufficient to disperse the prepolymer/amine or to reduce the viscosity of the composition. One example of a suitable plasticizer may be a methyl ester derivative of soybean oil. Other plasticizers such as phthalates, trimethyl pentanyl diisobutyrate (TXIB); or, terephthalates may also be used. Yet other useful plasticizers may include glycol ether esters, partially hydrogenated terpenes commercially available as "HB-40" (Eastman, Kingsport, TN), chloroparaffins, alkyl naphthalenes, and the like.

One or, preferably, both the blocked isocyanate component and the amine component may comprise at least one filler. The amount of the filler may range from 40 to 98 wt.%, or, from 60 to 95 wt.%, or, from 75 to 93 wt.%, or, from 80 to 92 wt.%, all wt.%s, based on the weight of the two-component composition. Different filler sizes or fillers may be blended to obtain the desired filler loading and viscosity of a formulation. Preferably, the filler is aluminum trihydrate (ATH). Thus, in accordance with the present invention, a thermally conductive two- component composition may comprise the blocked isocyanate prepolymer composition as disclosed herein in its various forms and preferreds thereof, and, further comprise, as a separate component, an amine composition, wherein at least one of the blocked isocyanate prepolymer composition or the amine composition comprises from 60 to 98 wt.% of a thermally conductive filler as measured by the total weight, respectively, of the blocked isocyanate prepolymer composition or the amine composition.

EXAMPLES

The following examples illustrate the present invention. Unless otherwise indicated, all temperatures are ambient temperatures (21-25 °C), all pressures are 1 atmosphere and relative humidity (RH) is 35 to 50 %. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value inherently contains certain errors necessarily resulting from the standard variation found in their respective testing measurements.

The materials used in the Examples and not otherwise defined, below, are set forth in Table 1, below. Abbreviations used in the examples include: Da: Daltons; EO: Ethylene oxide; OHn: Hydroxyl Number; NCO: Isocyanate; PO: propylene oxide; TXIB: (2,2,4-trimethyl-l,3- pentanediol diisobutyrate). TABLE 1: Materials

Test Methods: In the Examples that follow, the following test methods were used. Where applicable, standard deviations in all data were within acceptable limits. All applicable test results are shown in Tables 2, 3, and 4, below.

Viscosity: was a cone and plate viscosity at 25 °C and 10 sec ¹ measured using an AR2000 Rotational Rheometer (TA instruments) in which the indicated material was placed between a Peltier Plate (80 mm diameter with hardened chrome surface, TA instruments) and a 40 mm, 2 degree cone with a truncation gap of 54 microns rotating at a constant angular velocity while the Peltier plate remained at rest, and running a temperature sweep from 25 to 50 °C at a ramp rate of 3 °C/min at a shear rate of 10 sec ¹. Once the gap is reached, the analyte sample was trimmed to remove any excess material.

Fourier Transform Infrared (FT-IR) spectra were measured in accordance with attenuated total reflectance (ATR) using a Nicolet iS50 FT-IR (Thermo Fisher Scientific, Pittsburgh, PA) IR spectrometer. Approximately 15 mg of the indicated sample was transferred to the ATR and the infrared spectrum was collected from 4000 to 650 cm'¹ using a resolution of 4 cm'¹ and 16 scans.

The isocyanate content (NCO content) of a given composition was determined in accordance with ASTM D5155-19, test method C (2019) using a Mettler DE55 (Mettler Toledo, Columbus, OH) autotitrator equipped with two titration stands, a rinse pump, a dose pump and an autosampler carousel. The sample was added to a solution of trichlorobenzene, delivered using the rinse pump, and 2N dibutylamine (in toluene) dispensed by the autotitrator using a 20- mE burette. The resulting solution was stirred for 20 minutes. Then the reaction mixture was diluted with methanol, dispensed via the dose pump, and back titrated with IN hydrochloric acid (aqueous) using a 20-mL burette.

Storage Stability: The indicated compositions were aged at 60 °C for two weeks (14 days) in an oven to observe their storage stability. Thermal conductivity was determined in accordance with ISO 22007-2 using the Hot Disk Thermal Constants Analyzer (TPS 2500S, Thermtest Instruments, Fredericton, NB, Canada). All measurements were completed with a Kapton encased thermal probe using a double-sided measurement with two-6 mm cups, at 150 mW heating power and 5 second measurement time.

Hardness was measured using a Shore 00 durometer in accordance with ASTM D2240.

Squeeze force was measured using a TA instruments TA-XT plus texture analyzer equipped with a 50 kg load cell. After dispensing the paste onto a flat heavy-duty aluminum substrate, an acrylic probe with a diameter of 40 mm was lowered to sandwich the test material against the flat substrate to achieve a standard 5.0 mm gap thickness. Any excess overflow material was trimmed away with a flat-edge spatula. After trimming, the test started and the probe was moved to a final thickness of 0.3 mm, at a rate of 1.0 mm/sec while the force was recorded. The specific force value recorded at the gap of 0.5 mm is reported as the “squeeze force”. A lower squeeze force is a better result.

Specific Gravity was measured in accordance with ASTM D 792-00 by measuring sample weight in air and in water.

Synthesis Examples: The blocked isocyanate prepolymer materials and compositions comprising them tested in the following examples were made, as follows:

In Comparative Example (CE) CE1 to CE3, all are prepolymers prepared from toluene diisocyanate (TDI) and Polyether diol with varying NCO contents, catalysts or process conditions. NCO% for each prepolymer is recorded in the table.

CE1: 35.05 g of TDI was weighed in a speed mixer cup, which was charged with 115.01 g of Polyether diol and 0.0155 g Tin catalyst, and mixed at 2350 RPM for 1 minute and placed in oven at 70° C, to digest the reaction for -2 hours and form an NCO prepolymer. 110 g of the NCO prepolymer was weighed in the speed mixer cup and charged with 0.03 gm T-9 catalyst and 53.92 g cardanol, then mixed at 2350 RPM for 2 to 3 minutes and then transferred into a dry glass jar and placed in oven at 80 to 85 °C. The temperature was maintained at ~85 °C in an oven for 4.5 hours.

CE2: 28.35g of TDI was weighed in dry 500ml dry reactor equipped with an overhead stirrer, N2 in and N2 out, a thermocouple and a heating mantle. 172 g Polyether diol (water content of 72 ppm) was charged and 0.0275 grams tin catalyst (-129 ppm). The mixture was stirred at from 300 to 500 RPM and slowly heated to 70 to 75 °C, where the reaction was digested for ~2.0 hours to form an isocyanate prepolymer and its NCO content was measured. To 171 g of the isocyanate prepolymer in a reactor, Tin catalyst (0.115 g, 500 ppm) was charged and the mixture was heated to 95 °C with stirring. 41.6 grams Cardanol was charged dropwise over ~15 minutes using an addition funnel. The temperature was maintained at ~95 °C for 2 hours, and then for additional 2 hours after adding (0.115 g, 500 ppm) additional tin catalyst.

Example 2: To 207.61 g of the NCO prepolymer of CE2, 2.21 g MPEG (~1 wt.%) was charged and the temperature was held at 95 °C for 2 hours.

CE3: To 28.06 grams TDI weighed in dry 500ml dry reactor equipped with an overhead stirrer, N2 in and N2 out, a thermocouple and a heating mantle, 172.2 g of Polyether diol (water = 103 ppm) was charged, 0.0439 g 50 wt.% Mixed carboxylate with Zinc and Zirconium 2 in TXIB was charged. The resulting mixture was stirred at 300 to 500 RPM and slowly heated to 75 to 80 °C, where the reaction was digested for ~2.0 hours. The reaction was stopped and cooled down to 25 °C and the NCO content of the blocked isocyanate prepolymer was measured.

175 g the prepolymer in the reactor was slowly heated to 95 °C with stirring, and 0.2330 g of Mixed carboxylate with Zinc and Zirconium 2 catalyst was charged. Then 42.5 g of Cardanol was charged using an addition funnel, with dropwise addition completed in ~25 minutes. Temperature remained at 95 °C until the reaction which continued for 2 hours was completed. Blocking was continued for an additional 2 hours thereafter with 0.2288 gm additional catalyst and reaction was run for additional 2 hours. FT-IR was run both before and after blocking. An area count of the isocyanate peak in FTIR can be seen in Table 3, below.

Example 3: To 212.5 g of the prepolymer of CE3, 1 wt. % MPEG was charged, and reaction was run at 95 °C for 1.5 hours.

Example 4: 47 g TDI was weighed in dry 500ml dry reactor equipped with an overhead stirrer, N2 in and N2 out, a thermocouple and a heating mantle. To this, 153 g Poly ether diol was charged, then 0.0439 grams 50 wt.% Mixed carboxylate with Zinc and Zirconium 2 in TXIB was charged in the reactor. The mixture was stirred at 300 to 500 RPM and slowly heated to 75-80 °C. The heated mixture was digested the reaction for ~2.0 hours, and then the reaction was stopped and cooled down to 25 °C to form an NCO prepolymer. NCO content was measured.

The isocyanate prepolymer was heated to 95 °C with stirring, and 0.2874 grams mixed carboxylate with Zinc and Zirconium 2 catalyst in TXIB was charged. To this, 113 g of Cardanol was charged using an addition funnel, with dropwise addition completed in ~25 minutes. The temperature reached 95 °C upon completion in 2 hours. Reaction was continued blocking for an additional 2 hours with more of the same catalyst (-500 ppm) to form a blocked isocyanate prepolymer.

To 284 g of the prepolymer, 11.9 g of MPEG was added (-4.2 wt.%) and digested at 95 °C for 1 hour.

Example 5: 35.5 g TDI was weighed into a dry 250ml dry reactor set up with an overhead stirrer, N2 in and N2 out, a thermocouple and a heating mantle. 115.5 g of Polyether diol (water = 204 ppm) and ~0.0202grams Tin catalyst (-134 ppm) was charged to the reactor and the mixture was stirred at 300 to 500 RPM while slowly heating at 70 to 75 °C. The reaction was digested for -2.25 hours. The reaction was stopped and cooled down to 25 °C under N2. The NCO content of the isocyanate prepolymer was measured.

To 113 g of the isocyanate prepolymer in a reactor, 500 ppm Tin catalyst (0.0976 g) was added and the mixture was heated to 95 °C with stirring. 67.2 gm Cardanol was added using an addition funnel and dropwise addition was completed in -10 minutes. Temperature was maintained at -95 °C for 7 hours, after which was charged 1.78 grams MPEG (-1 wt.%) and temperature was held for 1 hour. After the 1 hour, 0.02 g tin catalyst was added and the reaction held for 1 hour.

Example 6: 62.55 gm TDI was weighed in a dry 500ml dry reactor equipped with an overhead stirrer, N2 in and N2 out, a thermocouple and a heating mantle. 137.75 g Polyether diol (water = 68 ppm) and 0.02 grams Tin catalyst was charged to the rector. The mixture was stirred at 300 to 500 RPM, slowly heated applied to 70 to 75 °C, and was digested for - 2.25 hours to form an isocyanate prepolymer. NCO content was measured.

To 180 g of the NCO prepolymer in the reactor, 500 ppm Tin catalyst (0.1845 g) was charged, and heated to 95 °C with stirring. After heating, Cardanol (170.5 g) was added using an addition funnel, and dropwise addition was completed in -30 minutes. The temperature was maintained at 95 °C for 2 hours after adding 500 ppm Tin catalyst to form a blocked isocyanate prepolymer. To the blocked isocyanate prepolymer was charged 3.4 g MPEG and the temperature was held at 95 °C for 1.5 hours.

Example 7 : 70.4 g TDI was weighed in dry 500ml dry reactor equipped with an overhead stirrer, N2 in and N2 out, a thermocouple and a heating mantle. 80.25 gm Polyether diol (Water = 68 ppm) and 0.018 g Tin catalyst (-120 ppm) was charged to the reactor. The mixture was stirred at 300 to 500 RPM and slowly heated to 70 to 75 °C. The reaction was digested for ~ 2.25 hours to form an isocyanate prepolymer. NCO content was then measured.

To 130.2 gm of isocyanate prepolymer in the reactor, 1000 ppm Tin catalyst (0.404 g) was charged and the resulting mixture was heated to 95 °C with stirring. Cardanol (209 g) was added using an addition funnel and dropwise addition was completed in ~30 minutes. Temperature was maintained at ~ 95 °C for 6 hours to form a blocked isocyanate prepolymer. To the blocked isocyanate prepolymer was charged 3.45 g MPEG (~1 wt.%) and the temperature was held for 1 Vi hours.

TABLE 2: Storage Stability by Viscosity

*- Denotes Comparative Example; 1. Not determined

As shown in Table 2, above, the compositions of Inventive Examples 2, 3, 4, 5, 6 and 7 all exhibited a viscosity increase of 20% or less, or a viscosity decrease upon heat aging at 60 °C after two weeks. In contrast, the compositions of Comparative Examples 1, 2 and 3 (CE1, CE2 and CE3) which did not contain a monohydric alcohol, all exhibited at least a 150% viscosity increase under the same aging conditions. Thus, in all of the comparative examples, the viscosity increased significantly, even an order of magnitude, after heat aging, indicating poor storage stability. The results clearly demonstrate a dramatic improvement in the storage stability of blocked prepolymers when a treated or capped monohydric alcohol, such as MPEG, after blocking to form a blocked isocyanate prepolymer.

Table 3, below shows the area count for an NCO FT-IR peak (2270 cm ¹) for the isocyanate prepolymer, any cardanol blocked prepolymer, and after addition of the MPEG. As shown in Table 3, below, no peak or a very small isocyanate signal was detected by FT-IR after adding the MPEG. After the MPEG addition, all of the inventive prepolymers had a tiny or non detectable NCO peak in FTIR at 2270 cm ¹. Isocyanate content was estimated from a internally generated calibration curve using TDI as a benchmark. Accordingly, the FT-IR spectra confirmed a reduction in NCO peak at a wavelength of 2269 to 2272 cm'¹ by cardanol blocking and further reduction when the blocked prepolymer is treated with MPEG.

TABLE 3: Isocyanate Content via FT-IR

*- Denotes Comparative Example, which is an intermediate product of the inventive example having the same number. 1. From calibration curve.

Two-component curable composition with high thermal conductivity:

Examples 8 A and 8B, below, provide a curable composition with high thermal conductivity formed using the blocked isocyanate prepolymers of the present invention. The Examples show the utility of the blocked isocyanate prepolymer of inventive Example 4 in forming a curable two-component thermally conductive composition for use as a gap filler for EV batteries. The ingredients shown in Table 4, below, for Examples 8A (blocked isocyanate composition) and 8B (amine composition) were mixed separately using a high speed mixer to obtain the two individual thermally conductive pastes. As shown in the table below, both components individually have a high thermal conductivity and a low squeeze force. To measure the mix properties, the two components were combined in a 1:1 wt ratio and mixed using a high speed mixer. As shown below, the resulting composition cured at room temperature to form a solid part with a 70 to 75 shore 00 hardness and a high thermal conductivity (~ 3W/m-K) and low specific gravity (-2.03 gm/cc). Such properties make this composition useful as a thermally conductive gap filler.

TABLE 4: Thermally Conductive End Use Composition

CE9: 64 grams (734.8 mEq.) of Toluene diisocyanate (T-80 Type I) was weighed in 500 ml oven dry reactor and set up with overhead stirrer, N2 in and N2 out tube, thermocouple, and heating mantle. 336 grams Polyether diol (341.54 mEq.) and 100 ppm of Tin catalyst catalyst (0.04 grams) were charged. Mixture was stirred at 300-500 RPM and slow heat applied to get

75-80° C. Mixture was digested for ~2.0 hours and desired NCO was achieved. % NCO measured = 4.16.

150 grams of 4.16 % TDI Prepolymer was charged in 500 ml dry reactor and set up with overhead stirrer, N2 in and N2 out tube, thermocouple and heating mantle Heat applied to get 75-80° C with stirring. -1000 ppm of Dabco 33LV catalyst and 47.0 grams of Cardanol charged.

Temperature reached to 80° C in - 10 minutes. Continued reaction for 2 hours and isocyanate concentration was analyzed using FT-IR. 0.41 % NCO concentration was found using in-house calibration curve method. Second aliquots of -1000 ppm of Dabco 33LV catalyst was added and continued the blocking for 3 more hours. No significant reduction on the isocyanate peak observed. Calculated NCO found to be 0.38% -10 grams of the product were discharged for analysis.

Example 9: 190 grams of the blocked prepolymer for CE-9 was charged in dry 500 ml reactor and set up with overhead stirring, N2 in and out tube, thermocouple, and heating mantle. 1.0 wt. % MPEG (1.9 grams) was charged with stirring and digested at 75-80° C for 1 hour. Isocyanate concentration was found to be 0.26% by FT-IR. Blocking deem to completion. 0.5 grams of Benzoyl Chloride was charged. Product was discharged in jar.

CE10: 94 grams of Toluene diisocyanate (T-80 Type I) was charged in 500 ml oven dry reactor and set up with overhead stirrer, N2 in and N2 out tube, thermocouple, and heating mantle. 306 grams Polyether diol and 0.04 grams of Tin catalyst were charged. Mixture was stirred at 300-500 RPM and slow heat applied to get 75-80° C. Mixture was digested for ~2.0 hours and desired NCO was achieved. % NCO measured = 8.3

150 grams of 8.33 % TDI Prepolymer was charged in 500 ml dry reactor and set up with overhead stirrer, N2 in and N2 out tube, thermocouple and heating mantle Heat applied to get 75-80° C with stirring. -1000 ppm of Dabco 33LV catalyst and 94.0 grams of Cardanol charged. Temperature reached to 80° C in - 10 minutes. Continued reaction for 2 hours Second aliquots of -1000 ppm of Dabco 33LV catalyst was added and continued the blocking for 3 more hours.

Example 10: 234 grams of the blocked prepolymer of CE-10 was charged in dry 500ml reactor and set up with overhead stirring, N2 in and out tube, thermocouple, and heating mantle. 1.0 wt. % MPEG (2.30 grams) was charged with stirring and digested at 75-80° C for 1 hour. 0.5 grams of Benzoyl Chloride was charged. Product was discharged in jar.

CE11: 124 grams of Toluene diisocyanate (T-80 Type I) was charged in 500 ml oven dry reactor and set up with overhead stirrer, N2 in and N2 out tube, thermocouple, and heating mantle. 276 grams of polyether diol and 0.04 grams of tin catalyst were charged. Mixture was stirred at 300-500 RPM and slow heat applied to get 75-80° C. Mixture was digested for -2.0 hours and desired NCO was achieved. % NCO measured = 12.23.

150 grams of 12.23 % TDI Prepolymer was charged in 500 ml dry reactor and set up with overhead stirrer, N2 in and N2 out tube, thermocouple and heating mantle Heat applied to get 75-80 C with stirring. -1000 ppm of Dabco 33LV catalyst and 139 grams of Cardanol charged. Temperature reached to 80° C in - 10 minutes. Continued reaction for 2 hours. Second aliquots of -1000 ppm of Dabco 33LV catalyst was added and continued the blocking for 3 more hours.

Example 11: 278 grams of the blocked prepolymer of CE11 was charged in dry 500ml reactor and set up with overhead stirring, N2 in and out tube, thermocouple, and heating mantle. 1.0 wt. % MPEG (2.80 grams) was charged with stirring and digested at 75-80° C for 1 hour. 0.7 grams of Benzoyl Chloride was charged. Product was discharged in jar.

TABLE 5: Viscosity Reduction for Prepolymer

CE12: 434.2 grams TDI (T-80 Type (I) was weighed in dry 3L dry reactor set up with overhead stirrer, N2 in and N2 out, thermocouple and heating mantle. 966.3 grams V2000LM polyol was charged and stirred for 10 minutes. Then 0.28 grams 50 wt.% KKAT XK604 catalyst in TXIB was charged in the reactor. Mixture was stirred at 300-500 RPM and slow heat applied to get 75-80° C. Mixture was digested for ~2.0 hours and desired NCO was achieved.

1229 grams of TDI Prepolymer was charged in 3L dry reactor and set up with overhead stirrer, N2 in and N2 out, thermocouple and heating mantle Heat applied to get 95° C with stirring. 0.2874 grams 50 % Mixed carboxylate of Zinc and Zirconium 2 in TXIB was charged. 1169 grams of Cardanol (1.05 eq.) charged using addition funnel drop wise addition and completed in -25-30 minutes. Temperature reached to 95° C upon completion. Continued reaction for 2 hours and isocyanate concentration was analyzed using FT-IR. 2.33 % NCO concentration was found with in-house calibration curve. 500 ppm additional Mixed carboxylate of Zinc and Zirconium 2catalyst was charged and digested for 2 more hours and analyzed for isocyanate concentration using FT- IR technique. 0.57% NCO was found.

Example 12: 534 grams of the blocked prepolymer of CE 12 was charged in dry IL reactor and set up with overhead stirring, N2 in and out, thermocouple and heating mantle. 2.4 wt. % MPEG (12.9 grams) and 100 ppm 50 wt. % KKAT XK-604 catalyst (0.1068 grams) was charged with stirring and digested at 95° C for 2 hours. Isocyanate concentration was found to be 0.30 % by FT-IR. Product was discharged in jar.

Two-component curable composition with high thermal conductivity:

Example 13 and CE13: Examples 13 and CE13, below, provide a curable composition with high thermal conductivity formed using the blocked isocyanate prepolymers of the present invention. The ingredients shown in table below, for Examples 13 and comparative example 13 were mixed separately using a high speed mixer to obtain individual thermally conductive pastes for A&B side. Individual pastes have high tmeral conductivity and low squeeze force.

Squeeze force of individual A-side and B-side compositions for inventive example 13 show minimal (<20%) change after aging at 60°C for 1 week, showing that thermally conductive compositions prepared from prepolymers of present invention have good shelf stability.

To measure hardness, the two components were combined in a 1:1 wt ratio and mixed using a high speed mixer and allowed to cure at room temperature for 14 days

Examples below show that use of MPEG terminated prepolymer in Example 13 results in lower hardness of the cured part, compared to the prepolymer without MPEG in comparative example 13. Lower hardness is preferred for the gap fillers, as products with lower hardness can provide a better contact between heat source and heat sink, showing the advantage of prepolymers of this invention.

TABLE 6: Thermal Conductivity for Two-component Curable Composition

Claims

1. A fluid composition comprising: a CL to C24 hydrocarbyl group-containing phenol blocked isocyanate prepolymer, the blocked isocyanate prepolymer further comprising, in copolymerized form, a monohydric alcohol having a boiling point at 1 atmosphere (101.325 KPa) of 110 °C or higher and having a hydroxyl number of from 60 to 500.

2. The fluid composition of claim 1 , wherein the CL to C24 hydrocarbyl group-containing phenol in the blocked isocyanate prepolymer comprises an alkyl phenol having a mono-, a di-, or a triunsaturated hydrocarbyl group, or a combination of two or more thereof.

3. The fluid composition of claim 2, wherein the CL to C24 hydrocarbyl group-containing phenol in the blocked isocyanate prepolymer is a cardanol.

4. The fluid composition of claim 1, wherein the blocked isocyanate prepolymer comprises, in copolymerized form, one or more polyols and a toluene diisocyanate (TDI), a mixture of two TDIs, or a mixture of at least one TDI with at least one other aromatic diisocyanate.

5. The fluid composition of claim 1, wherein the monohydric alcohol has a boiling point at 1 atmosphere (101.325 KPa) of 150 °C or higher.

6. The fluid composition of claim 5, wherein the monohydric alcohol is an alkoxypoly (alkylene glycol).

7. The fluid composition of claim 6, wherein the monohydric alcohol is methoxy poly(ethylene glycol).

8. The fluid composition of, wherein the amount of the monohydric alcohol in the blocked isocyanate prepolymer composition ranges from 0.2 to 10 wt.%, based on the total weight of all reactants used to make the blocked isocyanate prepolymer.

9. The fluid composition of claim 1 having a cone and plate viscosity at 25 °C and 10 sec ¹ as measured using a rotational rheometer in which the composition was placed between an 80 mm diameter Peltier Plate and a 40 mm, 2 degree cone rotating at a constant angular velocity while the Peltier plate remains at rest, and running a temperature sweep from 25 to 50 °C at a ramp rate of 3 °C /min at a shear rate of 10 sec ¹, ranging from 8 to 50 Pa-s; and, further wherein, the compositions exhibit improved storage stability as a change of 20% or less in their cone and plate viscosity (25° C and 10 sec ¹) after 14 days storage at 60 °C.

10. A thermally conductive composition prepared from the fluid composition of claim 1.

11. A thermally conductive composition comprising: a Cs to C24 hydrocarbyl group-containing phenol blocked isocyanate prepolymer, the blocked isocyanate prepolymer further comprising, in copolymerized form, a monohydric alcohol having a boiling point at 1 atmosphere (101.325 KPa) of 110 °C or higher and having a hydroxyl number of from 60 to 500; wherein the thermally conductive composition has a thermal conductivity > 0.5, W/m-K.

12. A method of making a blocked isocyanate prepolymer having improved storage stability as claimed in claim 1 comprising: reacting one or more polyols with a molar excess of one or more polyisocyanates to make an isocyanate functional prepolymer; blocking the isocyanate functional prepolymer with a C« to C24 hydrocarbyl group- containing phenol; and, adding to the blocked isocyanate prepolymer a monohydric alcohol having boiling point of 110 ° C or higher and having a hydroxyl number of from 60 to 500 under conditions that cause the blocked isocyanate prepolymer and the monohydric alcohol to react with each other.