WO2019109327A1

WO2019109327A1 - Two-part foamable polyurea-polyurethane adhesive composition

Info

Publication number: WO2019109327A1
Application number: PCT/CN2017/115192
Authority: WO
Inventors: Bin Zhao; Bo Li; Xueyu QIU; Xu QI
Original assignee: Henkel Ag & Co. Kgaa; Henkel (China) Co., Ltd.
Priority date: 2017-12-08
Filing date: 2017-12-08
Publication date: 2019-06-13

Abstract

Provided are a two-part foamable polyureapolyurethane adhesive composition and use thereof. In particular, the two-part foamable polyureapolyurethane adhesive composition can be cured at room temperature and form a cured product. The cured product possesses excellent storage stability and is tacky at room temperature so as to foam in-situ at elevated temperature after being applied on substrates.

Description

TWO-PART FOAMABLE POLYUREA-POLYURETHANE ADHESIVE COMPOSITION

Technical field

This invention relates to a two-part foamable polyurea-polyurethane adhesive composition and use thereof. In particular, the invention relates to a two-part foamable polyurea-polyurethane adhesive composition which can be cured at room temperature and forms a cured product. The cured product possesses excellent storage stability and is tacky at room temperature so as to foam in-situ at elevated temperature after being applied on substrates.

Background of the invention

In foamable adhesive applications, normally foams are applied on substrate manually, which takes much labor force and increases cost. To achieve automation in the industrial production, foamable adhesives, which could foam in-situ becomes a good solution. A large part of foam form-in-place technology based on polyurethane is instant foaming, which is often used for foaming inside cavities. (see Becker/Braun, Kunststoff-Handbuch, Volume 7, “polyurethane” , 2nd Edition, Carl Hanser Verlag, Munich, Vienna, 1983, pages 320) . However, expulsion or outflow of the foam mixture in this process is quite annoying. For example, US3280048 describes a heat curable composition for the production of polyurethane foams. The composition is pulverulent mixture, which limits its application as adhesive. In EP0591766, a heat-curable expansible one-component polyurethane composition is described, which uses solid polyhydroxyl compound instead of flowable polyhydroxyl compound to reach good storage stability. When the high temperature is applied, the solid hydroxyl compound melts and reacts with isocyanate groups for cure. Therefore, a good dispersion of solid polyhydroxyl compound is demanded, and high temperature is needed to melt the solid hydroxyl compound. In addition, heat-activated foamable epoxy resins have been described in US5274006, WO2010136086, and WO2004060984. The obtained epoxy based foams are dense and rigid, and are mostly used in automotive, electric appliances, etc. Foamable adhesive compositions, described in US20150322301, also only provides rigid and dense foam.

Thus, there is still a need for a two-part foamable polyurea-polyurethane adhesive composition which can quickly foam in-situ at elevated temperature after being applied onto substrate and cured.

Summary of the invention

The present invention provides a two-part foamable polyurea-polyurethane adhesive composition, comprising

a) a Part A composition, comprising

(a1) an isocyanate group terminated prepolymer,

(a2) a polyisocyanate having on average three or more isocyanate groups per molecule, and

(a3) a foaming agent, and

b) a Part B composition, comprising

(b1) a sterically hindered amine having two or more amine groups,

(b2) a polyol having on average three or more hydroxyl groups per molecule, in which the molar equivalent ratio A) of the sum of the isocyanate groups to the sum of the amine groups and hydroxyl groups is in the range of 0.85 to 2.0, and the molar equivalent ratio B) of the amine groups to the hydroxyl groups is in the range of 0.9 to 5.0.

The present invention also provides a two-part foamable polyurea-polyurethane adhesive kit, comprising the two-part foamable polyurea-polyurethane adhesive composition according to the present invention, and at least two containers assembled separately from one another, in which a first container holds the Part A composition, and a second container holds the Part B composition.

Furthermore, the present invention provides a cured product obtainable by mixing the part A and part B of the adhesive composition or the two-part foamable polyurea-polyurethane adhesive kit according to the present invention at room temperature.

In addition, the present invention concerns a foam obtainable by heating the polyurea-polyurethane adhesive composition according to any one of claims 1 to 11 or the cured product according to any one of claims 17 to 19 at a temperature of 100℃ to 220℃, preferably 140℃ to 200℃ in 3 minutes to 60 minutes, preferably in 5 minutes to 30 minutes.

Detailed description of the invention

In the following passages the present invention is described in more detail. Each aspect so described may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

In the context of the present invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

As used herein, the singular forms “a” , “an” and “the” include both singular and plural referents unless the context clearly dictates otherwise.

The terms “comprising” , “comprises” and “comprised of” as used herein are synonymous with “including” , “includes” or “containing” , “contains” , and are inclusive or open-ended and do not exclude additional, non-recited members, elements or process steps.

The recitation of numerical end points includes all numbers and fractions subsumed within the respective ranges, as well as the recited end points.

All references cited in the present specification are hereby incorporated by reference in their entirety.

Unless otherwise defined, all terms used in the disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of the ordinary skill in the art to which this invention belongs to. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

In one aspect, the present invention provides a two-part foamable polyurea-polyurethane adhesive composition, comprising

a) a Part A composition, comprising

(a1) an isocyanate group (NCO-) terminated prepolymer,

(a3) a foaming agent, and

b) a Part B composition, comprising

(b1) a sterically hindered amine having two or more amine groups,

When the Part A composition and Part B composition in the two-part foamable polyurea-polyurethane adhesive composition of the present invention are mixed at , polyurea reaction occurs first due to the high reactively of amine component with isocyanate groups. The cured product obtained as viscous paste works as adhesive and has an excellent sotrage stability at low temperature. Once heat is applied, the cured product will foam and further cure via polyurethane reaction of polyol and remaning isocyanate groups and foaming agent. Therefore, it was surprising to find that the present two-part foamable polyurea-polyurethane adhesive composition could be applied to manufacture a sandwich structure of substrate-foam-substrate, and foam can be formed in place so as to avoid the foam gluing process in the applications.

The NCO-terminated PU prepolymers of the Part A composition is obtained by reacting a polyol with a stoichiometric excess of polyisocyanate. The polyols used in the preparation of the prepolymer can be any of the polyols conventionally used for the polyurethane synthesis, for example, monomeric polyols, polyester polyols, polyether polyols, polyester-ether polyols, polycarbonate polyols or mixtures of two or more of the above.

The isocyanate (NCO) -terminated PU prepolymers of the resin component are obtained by reacting a polyol or a polyol mixture with a stoichiometric excess of polyisocyanate. The polyols used in the preparation of the prepolymer may be any and all polyols commonly used for polyurethane synthesis, e.g., polyols, polyester polyols, polyether polyols, polyester ether polyols, polycarbonate polyols, or mixtures of two or more of the foregoing.

Polyether polyols can be produced from a large number of alcohols which contain one or more primary or secondary alcohol groups. As initiators for the production of the tertiary amino group-free polyethers, the following compounds, for example, or mixtures of these compounds, may be used: water, ethylene glycol, propylene glycol, glycerol, butanediol, butanetriol, trimethylolethane, pentaerythritol, hexanediol, 3-hydroxyphenol, hexanetriol, trimethylolpropane, octanediol, neopentyl glycol, 1, 4-hydroxymethylcyclohexane, bis (4-hydroxyphenyl) dimethylmethane, and sorbitol. Ethylene glycol, propylene glycol, glycerol, and trimethylolpropane are preferably used, particularly preferably ethylene glycol and propylene glycol, and in a particularly preferred exemplary embodiment, propylene glycol is used.

Suitable as cyclic ethers for the production of the polyethers described above are alkylene oxides, such as ethylene oxide, propylene oxide, butylene oxide, epichlorohydrin, styrene oxide, or tetrahydrofuran, or mixtures of these alkylene oxides. The use of propylene oxide, ethylene oxide or tetrahydrofuran or mixtures of these is preferred. Propylene oxide or ethylene oxide or mixtures thereof are particularly preferably used. Propylene oxide is most particularly preferably used.

Polyester polyols may be produced, for example, by reacting low molecular weight alcohols, in particular ethylene glycol, diethylene glycol, neopentyl glycol, hexanediol, butanediol, propylene glycol, glycerol, or trimethylolpropane with caprolactone. Also suitable as polyfunctional alcohols for producing polyester polyols are 1, 4-hydroxymethylcyclohexane, 2-methyl-1, 3-propanediol, 1, 2, 4-butanetriol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol, and polybutylene glycol.

Other suitable polyester polyols can be produced by polycondensation. For instance, difunctional and/or trifunctional alcohols can be condensed with a substoichiometric quantity of dicarboxylic acids or tricarboxylic acids, mixtures of dicarboxylic acids or tricarboxylic acids, or reactive derivatives thereof, to form polyester polyols. Suitable dicarboxylic acids are, for example, adipic acid or succinic acid and higher homologues thereof with up to 16 C atoms, and also unsaturated dicarboxylic acids, such as maleic acid or fumaric acid, as well as aromatic dicarboxylic acids, in particular the isomeric phthalic acids, such as phthalic acid, isophthalic acid or terephthalic acid. Examples of suitable tricarboxylic acids include citric acid or trimellitic acid. The aforementioned acids can be used individually or as mixtures of two or more thereof. Particularly suitable alcohols are hexanediol, butanediol, ethylene glycol, diethylene glycol, neopentyl glycol, 3-hydroxy-2, 2-dimethylpropyl 3-hydroxy-2, 2-dimethylpropanoate, or trimethylolpropane, or mixtures of two or more thereof. Particularly suitable acids are phthalic acid, isophthalic acid, terephthalic acid, adipic acid, or dodecanedioic acid or mixtures thereof. Polyester polyols with high molecular weight include, for example, the reaction products of polyfunctional, preferably difunctional, alcohols (optionally together with small quantities of trifunctional alcohols) and polyfunctional, preferably difunctional, carboxylic acids. Instead of free polycarboxylic acids, (if possible) the corresponding polycarboxylic anhydrides or corresponding polycarboxylic acid esters with alcohols having preferably 1 to 3 C atoms can also be used. The polycarboxylic acids may be aliphatic, cycloaliphatic, aromatic, or heterocyclic, or both. They may optionally be substituted, for example by alkyl groups, alkenyl groups, ether groups, or halogens. Examples of suitable polycarboxylic acids include succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, dodecanedioic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylene tetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimer fatty acid, or trimer fatty acid, or mixtures of two or more thereof.

Polyesters obtainable from lactones, for example based on ε-caprolactone, also known as “polycaprolactones, ” or hydroxycarboxylic acids, for example ω-hydroxycaproic acid, can also be used.

It is, however, also possible to use polyester polyols of oleochemical origin. Such polyester polyols may, for example, be produced by complete ring opening of epoxidized triglycerides of a fat mixture containing at least in part an olefinically unsaturated fatty acid with one or more alcohols having 1 to 12 C atoms and subsequent partial transesterification of the triglyceride derivatives to yield alkyl ester polyols having 1 to 12 C atoms in the alkyl residue.

Polycarbonate polyols may, for example, be obtained by the reaction of diols, such as propylene glycol, 1, 4-butanediol or 1, 6-hexanediol, diethylene glycol, triethylene glycol or tetraethylene glycol or mixtures of two or more of these diols with diaryl carbonates, for example diphenyl carbonates, or phosgene.

The molecular weight of the polyols used to synthesize the prepolymer is preferably in the range of 100 to 20000 g/mol, in particular, 330 to 4500 g/mol. The mean functionality may be in the range of 2 to 4.5. The PU prepolymer preferably has a polyether/polyester backbone.

The stoichiometric excess of polyisocyanate is -in relation to the molar ratio of NCO groups to OH groups -in particular, 1: 1 to 1.8: 1, preferably 1: 1 to 1.6: 1, and especially preferably 1.05: 1 to 1.5: 1.

According to the present invention, polyisocyanates having two or more isocyanate groups may be used to prepare the prepolymer. In one embodiment, the polyisocyanate is a monomeric diisocyanate. Suitable polyisocyanates are for example 1, 5-naphthylene diisocyanate (NDI) , 2, 4-or 4, 4′-diphenylmethane diisocyanate (MDI) , hydrogenated MDI (H12MDI) , xylylene diisocyanate (XDI) , tetramethylxylylene diisocyanate (TMXDI) , di-and tetraalkylene diphenylmethane diisocyanate, 4, 4′-dibenzyl diisocyanate, 1, 3-or 1, 4-phenylene diisocyanate, tolylene diisocyanate (TDI) , 1-methyl-2, 4-diisocyanatocyclohexane, 1, 6-diisocyanato-2, 2, 4-trimethylhexane, 1, 6-diisocyanato-2, 4, 4-trimethylhexane, 1-isocyanatomethyl-3-isocyanato-1, 5, 5-trimethylcyclohexane (IPDI) , tetramethoxybutane 1, 4-diisocyanate, butane 1, 4-diisocyanate, hexane 1, 6-diisocyanate (HDI) , dicyclohexylmethane diisocyanate, cyclohexane 1, 4-diisocyanate, ethylene diisocyanate, methylene triphenyl triisocyanate (MIT) , phthalic acid bis-isocyanatoethyl ester, trimethylhexamethylene diisocyanate, 1, 4-diisocyanatobutane, 1, 12-diisocyanatododecane, and dimer fatty acid diisocyanate.

Suitable examples of polyisocyanates having on average three or more isocyanate groups per molecule used for the preparation of the prepolymer (a1) or the polyisocyanate (a2) according to the present invention are polyisocyanates obtained by trimerization or oligomerization of diisocyanates or by reaction of diisocyanates with low molecular weight polyfunctional compounds containing hydroxyl or amino groups. Commercially obtainable examples are trimerization products of the isocyanates HDI, MDI or IPDI or adducts of diisocyanates and low molecular weight triols, such as trimethylolpropane or glycerol. Further examples include isocyanurates of HDI, isocyanurates of IPDI, HDI based biurets, MDI oligomers, TDI isocyanurates, TDI-trimethylolpropane.

Commercially available products of polyisocyanates having on average three or more isocyanate groups per molecule include Wannate HT-100, Wannate HB-100 from Wanhua Co. Ltd., Tolonate HDT, HDT-LV, HDT-LV2 from Vencorex Chemicals, Desmodur N-100, N-3200, N-3300, N-3600, N-3800, XP2410, HL, BUEJ 471 from Covestro.

Aliphatic, cycloaliphatic, or aromatic isocyanates may in principle be used, but aromatic diisocyanates are particularly suitable. Examples of suitable diisocyanates include methylene diphenyl diisocyanates (MDIs) such as 4, 4-methylene diphenyl diisocyanate, 2, 4-methylene diphenyl diisocyanate, or 2, 2-methylene diphenyl diisocyanate.

PU prepolymers may be produced in a known manner from the above-mentioned polyols and polyisocyanates. A prepolymer containing NCO groups may here be produced from the polyols and isocyanates. Examples thereof are described in EP-A 951493, EP-A 1341832, EP-A 150444, EP-A 1456265, and WO 2005/097861.

The at least two NCO-terminated PU prepolymer is preferably an aromatic isocyanate-terminated, and more preferably, MDI-terminated-polyurethane prepolymer made of a polyether/polyester polyol mixture and an aromatic diisocyanate such as MDI.

The corresponding prepolymers typically have an NCO content of 5-20 wt %(determined according to Spiegelberger, DIN EN ISO 1 1909: 2007-05) , and have a mean NCO functionality of 2 to 3.

Due to the excess isocyanate used, the NCO-terminated PU prepolymers usually have certain amounts of isocyanate monomers, i.e., in particular, aromatic polyisocyanate monomers, such as, for example, MDI, typically in amounts of 0.1 to 25 wt %in relation to the total weight of prepolymers and monomers.

The molecular weight (MN) of the prepolymer is usually within the range from 500 g /mol to 100000 g /mol, preferably from 600 g /mol to 25,000 g /mol more preferably from 700 g /mol to 6000 g /mol. The preparation of the NCO-terminated prepolymers is well-known to the skilled worker and carried out for example such that the liquid at reaction temperatures polyols are mixed with an excess of the polyisocyanates and the resulting mixture is stirred until a constant NCO-value. As the reaction temperature are temperatures ranging from 40 ℃ to 180 ℃, preferably selected 50 ℃ to 140 ℃. In one embodiment, the prepolymer used in the present invention is in liquid or paste form at room temperature (about 20 ℃ to about 30 ℃, e.g. 25 ℃) .

The isocyanate group terminated prepolymer is present in an amount of 20%to 90%, preferably 30%to 80%by weight of all components of the adhesive composition.

As mentioned above, suitable examples of polyisocyanates having on average three or more isocyanate groups per molecule used as the polyisocyanate (a2) according to the present invention are trimers or higher oligomers of monomeric diisocyanate, obtained by trimerization or oligomerization of monomeric diisocyanates or by reaction of monomeric diisocyanates with low molecular weight polyfunctional compounds containing hydroxyl or amino groups. Commercially obtainable examples are trimerization products of the isocyanates HDI, MDI or IPDI or adducts of diisocyanates and low molecular weight triols, such as trimethylolpropane or glycerol. Further examples include isocyanurates of HDI, isocyanurates of IPDI, HDI based biurets, MDI oligomers, TDI isocyanurates, TDI-trimethylolpropane.

The amount of the component (a2) is present in an amount of 1%to 30%, preferably 5%to 25%by weight of all components of the adhesive composition.

According to the present invention, the foaming agents that may be used include an organic foaming agent and an inorganic foaming agent.

The organic foaming agents that may be used include, for example, azo foaming agents such as azodicarbonamide (ADCA) , barium azodicarboxylate, azobisisobutyronitrile (AIBN) , 2, 2'-azobisisobutyric acid dimethyl ester (AIBME) , azocyclohexylnitrile, and azodiaminobenzene; N-nitroso foaming agents such as N, N′-dinitrosopentamethylenetetramine (DTP) , N, N′-dimethyl-N, N′-dinitroso terephthalamide, and trinitrosotrimethyltriamine; hydrazide foaming agents such as 4, 4′-oxybis (benzenesulphonyl hydrazide) (OBSH) , paratoluene sulfonylhydrazide, diphenyl sulfone-3, 3′-disulfonylhydrazide, 2, 4-toluene disulfonylhydrazide (TSH) , p, p-bis (benzenesulfonyl hydrazide) ether, benzene-1, 3-disulfonylhydrazide, and allylbis (sulfonylhydrazide) ; semicarbazide foaming agents such as p-toluoylenesulfonyl semicarbazide and 4, 4′-oxybis (benzenesulfonyl semicarbazide) ; polyamine carbamates such as Z-methylpiperazine carbamate, ethylenediamine carbamate, and hexamethylenediamine carbamate (HMDC) , fluoroalkane foaming agents such as trichloromonofluoromethane and dichloromonofluoromethane; triazole foaming agents such as 5-morphoryl-1, 2, 3, 4-thiatriazole; and other known organic foaming agents. The organic foaming agents that may be used also include thermally expansible microparticles containing microcapsules in which thermally expansive material is encapsulated. Commercially available products, such as Expancel DU series from AkzoNobel, Microsphere F and FN series from Matsumoto Yu-shi-Seiyaku Co., Ltd. may be used as the thermally expansible microparticles. These foaming agents may be used alone or in combination of two or more kinds.

The inorganic foaming agents that may be used include, for example, hydrogencarbonates such as sodium hydrogencarbonate and ammonium hydrogencarbonate; carbonates such as sodium carbonate and ammonium carbonate; nitrites such as sodium nitrite and ammonium nitrite; boron hydride salts such as sodium borohydride; azides; and other known inorganic foaming agents. These foaming agents may be used alone or in combination of two or more kinds.

Foams are produced by decomposition of the foaming agents at a given elevated temperature. Decomposition of the foaming agents release N₂, CO, NH₃, H₂O and/or CO₂ gases/vapors that forms the foam matrix cells. Based on the decomposition temperature of the foaming agent, subjecting the foamable adhesive, i.e. the cured product with respect to polyurea reaction to a temperature to or above the decomposition temperature of the foaming agent releases gas in the adhesive and foam is created. The foams are in a closed-cell structure. The foaming agents may be present in an amount of 1%to 15%, preferably 2%to 10%by weight of all components of the adhesive composition.

According to the present invention, suitable sterically hindered amines having two or more amine groups, preferably two amine groups are aspartic ester amines or aromatic diamines. Examples of aromatic diamines are those sterically hindered to reduce reactivity when combined with polymeric isocyanate of the Part A composition component. Such aromatic amines include, but are not limited to toluene diamine, 1-methyl-3, 5-diethyl-2, 4-diaminobenzene, 1-methyl-3, 5-diethyl-2, 6-diaminobenzene (also known as DETDA or diethyl toluene diamine) , di (methylthio) toluene diamine, 1, 3, 5-triethyl-2, 6-diaminobenzene, toluene diamine derivatives containing halogen groups, cyano groups, alkoxy, alkylthio, alkenyl or carbonylic moieties, m-phenylene diamine, p-phenylene diamine, 4', 4'-methylenedianiline, 4, 4'-diaminodiphenyl sulfone, 2, 6-diamino-pyridine, 4, 4'-methylene-bis- (3-chloroaniline) , 4, 4'-methylene-bis- (3-chloro-2, 6-diethylaniline) , 4, 4-methylene-bis- (3-chlor-2.5-diethylaniline, 3, 3'-di-isopropyl-4, 4'-diaminodiphenylmethane, 3, 5, 3', 5'-tetraethyl-4, 4'-diaminodiphenylmethane, propylene-di-4-aminobenzoate, isobutyl 4-chloro-3, 5-diaminobenzoate, bis- (2-aminophenyl) disulfide, bis- (4-aminophenyl) disulfide, 3, 3'- carbomethoxy-4, 4'-diamino diphenylmethane, 1, 2-bis (2-aminophenylthio) ethane, dimethylthiotoluenediamine (DMTDA) , 0, 1, 8-diamino-p-menthane, α, α, α', α'-tetramethyl xylene diamine, N, N'-ditertiary-butylethylene diamine, and mixtures thereof.

Sterically hindered amines having two or more amine groups can include an aspartic ester amine. The aspartic ester amine can include a compound of formula:

wherein R¹ is a divalent organic group having from 1 to 40 carbon atoms and R² is independently an organic group having from 1 to 40 carbon atoms or from 1 to 8 carbon atoms or from 1 to 4 carbon atoms. In some embodiments, the aspartic ester amine includes a cycloaliphatic aspartic ester diamine of formula:

In other embodiments, the aspartic ester amine includes an aliphatic aspartic ester diamine of formula:

Preferably, the aspartic ester amines are selected from selected from N, N’-diethyl maleate-2-methylpentamethylenediamine, N, N’-diethyl maleateaminodicyclohexylmethane, and N, N’-diethyl maleate-aminodimethyldicyclohexylmethane, and mixture thereof.

Commercial obtainable aspartic ester amines are Desmophen NH1220, NH1420, NH1520 from Covestro, and F220, F420, F520 from Feiyang Chemicals.

In the present invention, the sterically hindered amine having two or more amine groups is present in an amount of 1%to 25%, preferably 5%to 20%by weight of all components of the adhesive composition.

Also contained in Part B composition is a polyol having three or more hydroxyl groups. The polyol having high functionalities ensures that after reacting with isocyanate group in Part B compositions to obtain a cured product of adhesive having good storage stability, the cured product still possess sufficient hydroxy groups to react with excess isocyanate group at elevated temperature, and foam in the presence of foaming agent. Preferably, the polyol used as component (b2) has three or more, preferably 3-6 hydroxyl groups. If polyols having less than three hydroxyl groups (i.e., diol) are used, the rigidness of the foam will be poor and the storage stability of the cured adhesive product is not satisfactory.

As examples of the component (b2) , polyether polyols include, but not limited to glycerol or its derivatives, pentaerythritol or its derivatives, sugar alcohols or their derivatives, ethylene oxide or propene oxide capped amines, and mixture thereof. These polyether polyols obtained by modifying polyhydric alcohols having more than three hydroxyl groups such as trimethylolpropane, glycerol, pentaerythritol, sorbitol, sucrose, and quadrol with cyclic ether compounds such as ethylene oxide (EO) , propylene oxide (PO) , butylene oxide, and tetrahydrofuran can be given. Specific examples include EO-modified trimethylolpropane, PO-modified trimethylolpropane, tetrahydrofuran-modified trimethylolpropane, EO-modified glycerol, PO-modified glycerol, tetrahydrofuran-modified glycerol, EO-modified pentaerythritol, PO-modified pentaerythritol, tetrahydrofuran-modified pentaerythritol, EO-modified sorbitol, PO-modified sorbitol, EO-modified sucrose, PO-modified sucrose, EO-modified sucrose, EO-modified guadrol and the like. Of these, EO-modified trimethylolpropane, PO-modified trimethylolpropane, PO-modified glycerol, PO-modified sorbitol are preferable as the component (b2) .

The molecular weight of the polyether polyol (b2) is preferably from 100 to 2,000, and more preferably from 160 to 1,000.

As examples of commercially available products of polyether polyols used as the component (b2) , Sunnix TP-400, GP-600, GP-1000, SP-750, GP-250, GP-400, GP-600 (manufactured by Sanyo Chemical Industries, Ltd. ) , TMP-3 Glycol, PNT-4 Glycol, EDA-P-4, EDA-P-8 (manufactured by Nippon Nyukazai Co., Ltd. ) , G-300, G-400, G-700, T-400, EDP-450, SP-600, SC-800 (manufactured by Asahi Denka Kogyo Co., Ltd. ) , PN-400, ST-481 (manufactured by Kukdo Chemical (Kunshan) Co., Ltd. ) and the like can be given.

These polyether polyols can be used either individually or in combinations of two or more as the component (b2) .

In the present invention, the polyol is present in an amount of 0.5%to 50%, preferably 1%to 40%by weight of all components of the adhesive composition.

Additives inert to the components comprised in the two-part foamable polyurea-polyurethane adhesive composition according to the present invention and conventionally used in the art of adhesives to satisfy different properties and meet specific application requirements can optionally be included from 0%by weight to about 20%by weight in the adhesive composition. Such additives include, for example, surfactant, thermoplastic polymers, plasticizers, fillers, pigments, curing catalysts, dissociation catalysts, anti-oxidants, flow modifiers, dyestuffs, flame retardants, inhibitors, UV absorbers, adhesion agents, stabilizers, tackifiers and waxes which may be incorporated in minor or larger amounts into the adhesive formulation, singly or in combination, depending on the purpose.

Optionally, catalysts may be contained in Part A composition to facilitate the reaction between active hydrogen containing compounds and isocyanates. Suitable tertiary amine catalysts include N, N', N"-dimethylaminopropylhexahydrotriazine (Polycat 41) and 1, 4-diazabicycloctane, and suitable metallic catalysts include dibutyltin dilaurate, dibutyltin diacetate, ferric acetyl acetonate, nickel acetylacetonate, dibutyltin dialkyl acid, stannous octoate, dibutyltin diisooctyl mercapto acetate, dibutyl tin diisooctyl maleate, and mixtures of these catalysts. The preferred organo metallic catalyst is the dibutyltin dialkyl acid catalyst known as DABCO 125 catalyst available from Air Products, Allentown, Pa. The preferred tertiary amine catalyst is N, N', N"-dimethylaminopropyl-hexahydrotriazine. Conventional catalytic amounts of either organotin catalyst or tertiary amine catalyst or combinations thereof are optionally used in the curative of this invention. From about 0.1 part by weight to 1.0 part by weight organotin catalyst and from about 0.3 part by weight to about 3.0 parts by weight amine catalyst are optionally used in 100 parts adhesive. In one embodiment, the two-part foamable polyurea-polyurethane adhesive composition contains essentially no, and preferably no catalyst in Part A composition and/or Part B composition.

The Part A composition may also contains a silicone surfactant. The silicone surfactant is used to form a foam from the mixture, as well as to control the size of the bubbles of the foam so that a foam of a desired cell structure is obtained. Preferably, a foam with small bubbles or cells therein of uniform size is desired since it has the most desirable physical properties such as compressive strength and thermal conductivity. Also, it is critical to have a foam with stable cells which do not collapse prior to forming or during foam rise.

Silicone surfactants optionally used in the preparation of polyurethane or polyisocyanurate foams in the present invention are available under a number of trade names known to those skilled in this art. Such materials have been found to be applicable over a wide range of formulations allowing uniform cell formation and maximum gas entrapment to achieve very low density foam structures. The preferred silicone surfactant comprises a polysiloxane polyoxyalkylene block co-polymer. Some representative silicone surfactants useful for this invention are Momentive's L-5130, L-5180, L-5340, L-5440, L-6100, L-6900, L-6980 and L-6988; Air Products DABCO series; and B-8404, B-8407, B-8409 and B-8462 from Evonik Industries AG of Essen, Germany. Others are disclosed in U.S. Pat. Nos. 2,834,748; 2,917,480; 2,846,458 and 4,147,847. The silicone surfactant component is usually present in the foamable adhesive composition in an amount of from about 0.5 wt. %to about 5.0 wt. %, preferably from about 1.0 wt. %to about 4.0 wt. %, and more preferably from about 1.5 wt. %to about 3.0 wt. %, by weight of the foamable adhesive composition.

The foamable adhesive composition may optionally contain a non-silicone surfactant, such as a non-silicone, non-ionic surfactant. Such surfactant may include oxyethylated alkylphenols, oxyethylated fatty alcohols, paraffin oils, castor oil esters, ricinoleic acid esters, turkey red oil, groundnut oil, paraffins, and fatty alcohols. A preferred non-silicone non-ionic surfactant is LK-443 which is commercially available from Air Products Corporation. When a non-silicone, non-ionic surfactant used, it is usually present in the foamable adhesive composition in an amount of from about 0.25 wt. %to about 3.0 wt. %, preferably from about 0.5 wt. %to about 2.5 wt. %, and more preferably from about 0.75 wt. %to about 2.0 wt. %, by weight of the foamable adhesive composition.

The two-part foamable polyurea-polyurethane adhesive composition of the present invention optionally contains from 0 to about 50%by weight, preferably 5 to about 35%by weight a thermoplastic polymer which cooperates with the other adhesive composition components to provide the desired properties of the cured adhesive products according to the present invention. Preferably, the thermoplastic polymer is selected to be of similar polarity and compatible with first polyol, isocyanate, (meth) acrylate polymer, diluent and other optional components like tackifier or plasticizer. The preferred optional thermoplastic polymers include polyurethanes, homopolymers or random copolymers of olefinic monomers including but not limited to, (meth) acrylic acid, vinyl esters (vinyl acetate and vinyl propionate) , vinyl ethers, styrene, acrylamides, methacrylamides, fumarates, maleates, acrylonitrile, ethylene, propylene and derivatives thereof. Most preferred are homopolymers or random copolymers of ethylene, propylene, vinyl esters and derivatives thereof. Suitable commercially available thermoplastic polymers include but not limited to Pearlbond TPU series from Lubricant and Evatane series from Arkema.

In one particular embodiment of the present invention, the two-part foamable polyurea-polyurethane adhesive composition of present invention comprises a two-part foamable polyurea-polyurethane adhesive composition, comprising:

a) a Part A composition, comprising

(a1) 20%to 90%, preferably 30%to 80%by weight of an isocyanate group terminated prepolymer,

(a2) 1%to 30%, preferably 5%to 25%by weight of a polyisocyanate having on average three or more isocyanate groups per molecule, and

(a3) 1%to 15%, preferably 2%to 10%by weight of a foaming agent, and

b) a Part B composition, comprising

(b1) 1%to 25%, preferably 5%to 20%by weight of a sterically hindered amine having two or more amine groups,

(b2) 0.5%to 50%, preferably 1%to 40%by weight of a polyol having on average three or more hydroxyl groups per molecule,

in which the molar equivalent ratio A) of the sum of the isocyanate groups to the sum of the amine groups and hydroxyl groups is in the range of 0.85 to 2.0, preferably 0.9 to 1.8, and more preferably 1.0 to 1.6, and the molar equivalent ratio B) of the amine groups to the hydroxyl groups is in the range of 0.9 to 5.0, preferably 0.9 to 4.5, and more preferably 1.0 to 4.0, and the weight percentages are based on the total weight of all components of the composition.

As used herein, the term molar equivalent ratio refers to the number of hydroxyl, amine or isocyanate groups in the reactants/components. Thus, for example, 10 moles of a polyethylene glycol has two hydroxyl groups per mole, and 1 mole of a triisocyanate has three isocyanate groups per mole; the molar equivalent ratio of glycol hydroxyl groups to triisocyanate groups is (10*2) / (1*3) = 6.67. According to the present invention, the molar equivalent ratio A) of the sum of the isocyanate groups to the sum of the amine groups and hydroxyl groups is in the range of 0.85 to 2.0, preferably 0.9 to 1.8, and more preferably 1.0 to 1.6. The molar equivalent ratio B) of the amine groups to the hydroxyl groups is in the range of 0.9 to 5.0, preferably 0.9 to 4.5, and more preferably 1.0 to 4.0. If the molar equivalent ratio A) is higher than 2.0 or lower than 0.85, the foam structure will not be obtainable. If the molar equivalent ratio A) is lower than 0.7, the storage stability will be poor. If the molar equivalent ratio B) is higher than 5.0, the mixture will not be foamable, and the storage stability will be poor. If the molar equivalent ratio B) is lower than 0.9, the foams have no sufficient resilience.

The two-part adhesive comprises various weight and volume ratios of the Part A composition and Part B composition. For example, the weight ratio of the Part A : Part B compositions may be from about 1: 1 to about 8: 1 and the volume ratio of the Part A: Part B compositions may be from about 1: 1 to about 3: 1, it being understood that various other volume and weight ratios are within the scope of the invention, as one skilled in the art will appreciate, after reading this disclosure, that all ranges and values within these explicitly stated ranges are contemplated.

The two parts of the two-part adhesive composition may be separately mixed and stored until the user is ready to prepare the curable composition. For example, the first part may be mixed and stored in a first package, and the second part may be mixed and stored in a second package. The two packages may be housed together, so that the combination of the first and second parts can take place at the user's convenience. It is particularly useful that first part be maintained physically separated from the second part until curing is desired, so as to avoid unintentional mixing and thus premature curing of the final composition. In another aspect, the present invention concerns a kit for two-part foamable polyurea-polyurethane adhesive composition comprising the two-part foamable polyurea-polyurethane adhesive composition according to the present invention, and at least two containers assembled separately from one another, in which a first container holds the Part A composition, and a second container holds the Part B composition.

The two-part polyurea-polyurethane adhesive composition may be applied in a process for adhering substrates, such as metal and composite materials. The process generally comprises providing the adhesive composition described herein and applying the Part A composition and Part B composition to one or more surfaces of at least a first substrate and then placing at least one surface of a second substrate in contact with the polyurea-urethane adhesive composition, allowing the adhesive composition to cure at room temperature, then heating the cured product at an elevated temperature from 100℃ to 220℃, preferably 140℃ to 200℃ in 3 minutes to 60 minutes, preferably in 5 minutes to 30 minutes to further cure and form foam in-situ. Substrates include composite materials comprising unsaturated polyester resin materials, vinyl ester resin materials, epoxy resin materials; metals, plastic films and other plastic materials. In embodiments, the process is used to adhere composite materials together or to adhere metal to composite materials. The process can further comprise surface treatment of one or more of the surfaces that come into contact with the polyurea-urethane adhesive composition, but in embodiments no surface treatment is applied to the substrates.

The invention further encompasses parts comprising two or more pieces where the pieces are adhered together, such as a part for an automobile or other transportation vehicle, like a motorcycle, bicycle, train, boat, airplane or space vehicle. The parts comprise at least two substrates and one or more layers of the polyurea-polyurethane adhesive composition, which adheres the substrates to each other.

According to the present invention, the cured adhesive product is tacky at room temperature and no tacky at 4℃.

According to the present invention, the cured adhesive product is stable at 4℃ for at least one day.

According to the present invention, the cured adhesive product is formable at temperature of 100℃ to 220℃, preferably 140℃ to 200℃ in 3 minutes to 60 minutes, preferably in 5 minutes to 30 minutes.

According to the present invention, the formed foam has a density of from 50 kg/m³ to 400 kg/m³, and preferably 60 kg/m³ to 300 kg/m³.

According to the present invention, the formed foam has an expansion ratio from 2.5 to 20, and preferably from 3 to 15.

According to the present invention, the formed foam has a tensile strength from 0.01 MPa to 0.3 MPa, and preferably from 0.03 MPa to 0.25 MPa.

According to the present invention, the formed foam has an elongation at break from 60%to 200%, and preferably from 70%to 180%.

According to the present invention, the formed foam has a compression set from 1.5%to 15%, and preferably from 2%to 10%.

Examples

The following examples are intended to assist one skilled in the art to better understand and practice the present invention. The scope of the invention is not limited by the examples but is defined in the appended claims. All parts and percentages are based on weight unless otherwise stated.

The following tests were used to determine complex viscosity, density, tensile strength, elongation at break, recovery and stability.

Testing and evaluation methods

The viscosity the prepolymer compositions was measured by a Rheometer MCR301 using a PP25 parallel-plate PP25, at 25 ℃, gap 1 mm, oscillation (γ=0.5%, ω=10 rad/s) .

The tensile strength, resilience, expansion ratio, elongation at break and compression set were measured according to ASTM D3574-2008 (Standard Test Methods for Flexible Cellular Materials-Slab, Bonded, and Molded Urethane Foams) . The compression set or the constant deflection compression set is expressed as a percentage of the original thickness.

Materials

Isocyanate group terminated prepolymer is a TDI-terminated poly (tetramethylene glycol) prepolymer commercially available under the trade name of H1225 from Huatian Rubber Co., Ltd.

Polyisocyanate 1 is a low viscosity HDI trimer, commercially available under the trade name of HDT LV2 from Vencorex Chemicals.

Polyisocyanate 2 is a HDI trimer, commercially available under the trade name of HT-100 from Wanhua Co. Ltd.

Polyisocyanate 3 is a solid TDI dimer, commercially available under the trade name of Addolink TT from Rhein Chemie.

Foaming agent 1 is NaHCO₃, commercially available under the trade name of sodium bicarbonate from Sinopharm Chemical Reagent Co., Ltd.

Foaming agent 2 is a hexamethylene diamine carbamate (HMDC) commercially available from Zigong Tianlong Chemical Co., Ltd.

Foaming agent 3 is an azobisisobutyric acid dimethyl ester (AIBME) commercially available under the trade name of V601 from Huaxing Chemical Co., Ltd.

Sterically hindered amine 1 is an aspartic ester diamine, commercially available under the trade name of F220 from Feiyang Chemicals.

Sterically hindered amine 2 is an aspartic ester diamine, commercially available under the trade name of F420 from Feiyang Chemicals.

Polyol 1 is a PO-modified pentaerythritol, commercially available under the trade name of POLYDO PN400 from Kukdo Chemical Co., Ltd.

Polyol 2 is glycerol, commercially available from Sinopharm Chemical Reagent Co., Ltd.

Polyol 3 is a trifunctional polyether polyol, commercially available under the trade name of CP6055 from the DOW Chemical Company.

Polyol 4 is diethanol amine (DEA) commercially available from Sinopharm Chemical Reagent Co., Ltd.

Polyol 5 (BIZ-16-0525-1) is a polyol having a ratio NCO/NH₂ of 1, a functionality of 4, and equivalent weight of 860, which was prepared before using by the following procedure: 2.1 g DEA and 50 ml ethyl acetate were added into a 250 ML flask, then H1225-ethyl acetate solution (32.3 g H1225 dissolved in 50 ml ethyl acetate) was added dropwise to the flask. After addition, the mixture was stirred for another 1 hour. After removal of the solvent, the prepared prepolymer with 4 functionality was obtained.

Polyol 6 is trimethylolpropane (TMP) commercially available Sinopharm Chemical Reagent Co., Ltd.

Polyol 7 is a polyethylene glycol having a functionality of 2, an average molecule weight of 2000 g/mol commercially available under the trade name of PEG-2000 from Sinopharm Chemical Reagent Co., Ltd.

Polyol 8 is a polyethylene glycol having a functionality of 2, an average molecule weight of 1000 g/mol commercially available under the trade name of PEG-1000 from Sinopharm Chemical Reagent Co., Ltd.

Preparation

According to the amount listed in Table 1, an isocyanate group terminated prepolymer, a polyisocyanate having on average three or more isocyanate groups per molecule, a foaming agent and additives (if present) were mixed at room temperature. The mixture was stored as Part A composition. A polyol having on average three or more hydroxyl groups per molecule, a sterically hindered amine having two or more amine groups and additives (if present) were mixed. The obtained clear solution was stored as Part B composition.

After mixing Part A compositions and Part B compositions, the mixtures had a dramatic viscosity increase in the first 20 minutes, and then the viscosity increase went slowly. The mixtures could be directly laminated on a piece of Spandex. Then another piece of Spandex was placed as a cover. The textile samples were put in an oven at 180℃ for foaming. After 5 minutes, the samples were taken out from the oven for cooling. Assemblies having sandwich structure of textile-foam-textile were thus obtained.

In addition, the composition mixtures were laminated on a silicon coated PET releasing film to make foamable adhesive films. the tackiness of the films were tested if the adhesive films stored at 4℃ in a refrigerator turned to non-tacky and could be tailored easily. The storage stability of the films was test by storing the films at 4℃ for several days, and “Good” means the films returned to a tacky state at room temperature and exhibited a sufficient foaming performance, after storing for one day. “Poor” means that the films could not return to a tacky state at room temperature and/or could not foam sufficiently, after storing for one day.

The testing results of inventive and comparative examples were shown in Tables 1 and 2, respectively.

As shown in Table 1, all inventive examples exhibited an excellent adhesion to the substrate after being cured at room temperature. The cured adhesive products possessed a good storage stability at 4℃. Examples 1, 2, 3, 6 and 8 possessed more than one week storage stability at 4℃. After being heated in-situ, the cured adhesives according to the present invention quickly formed between the substrates a flexible foam which had excellent properties such as density, expansion ratio and tensile strength.

Compared to the excellent performance profile of foams and cured products achieved by inventive examples, as shown in Table 2, All comparative examples exhibited inferior storage stability that could not be stable after being stored for one day. In addition, the obtained foams in CEs. 1, 6 and 8 were tacky due to the low molar equivalent ratio A. CE 2 possessed good foam properties, but had poor storage stability and should foam immediately after the parts were mixed. Moreover, the obtained foam of CE 2 was in yellow colour due to the usage of TDI dimer. CE 5 was foamable, but could not hold cellular structure after foaming. As CEs 3 and 4 contained bifunctional polyol, the obtained foams possessed lower expansion ratio and higher compression set. CE 7 exhibited a higher compression set and poor resilience due to the lower molar equivalent ratio B.

Claims

A two-part foamable polyurea-polyurethane adhesive composition, comprising

a) a Part A composition, comprising

(a1) an isocyanate group terminated prepolymer,

(a2) a polyisocyanate having on average three or more isocyanate groups per molecule, and

(a3) a foaming agent, and

b) a Part B composition, comprising

(b1) a sterically hindered amine having two or more amine groups,

(b2) a polyol having on average three or more hydroxyl groups per molecule, in which the molar equivalent ratio A) of the sum of the isocyanate groups to the sum of the amine groups and hydroxyl groups is in the range of 0.85 to 2.0, and the molar equivalent ratio B) of the amine groups to the hydroxyl groups is in the range of 0.9 to 5.0.
The two-part foamable polyurea-polyurethane adhesive composition according to claim 1, wherein component a1) is a reaction product of a polyol with a stoichiometric excess of polyisocyanate.
The two-part foamable polyurea-polyurethane adhesive composition according to claim 2, wherein the polyol is selected from the group consisting of monomeric polyols, polyester polyols, polyether polyols, polyester-ether polyols, polycarbonate polyols, and mixture thereof.
The two-part foamable polyurea-polyurethane adhesive composition according to claim 2 or 3, wherein the polyisocyanate is a monomeric diisocyanate.
The two-part foamable polyurea-polyurethane adhesive composition according to any one of claims 1 to 4, wherein component a1) is present in an amount of 20%to 90%, preferably 30%to 80%by weight of all components of the adhesive composition.
The two-part foamable polyurea-polyurethane adhesive composition according to any one of claims 1 to 5, wherein component a2) is a trimer or higher oligomer of monomeric diisocyanate.
The two-part foamable polyurea-polyurethane adhesive composition according to any one of claims 1 to 6, wherein component a2) is present in an amount of 1%to 30%, preferably 5%to 25%by weight of all components of the adhesive composition.
The two-part foamable polyurea-polyurethane adhesive composition according to any one of claims 1 to 7, wherein the foaming agent is selected from azo foaming agent, N-nitroso foaming agent, hydrazide foaming agent, semicarbazide foaming agent, polyamine carbamate, fluoroalkane foaming agent, triazole foaming agent, thermally expansible microparticle, hydrogencarbonate, carbonate, nitrite, boron hydride salt, azide, and combinations thereof.
The two-part foamable polyurea-polyurethane adhesive composition according to any one of claims 1 to 8, wherein component a3) is present in an amount of 1%to 15%, preferably 2%to 10%by weight of all components of the adhesive composition.
The two-part foamable polyurea-polyurethane adhesive composition according to any one of claims 1 to 9, wherein the component b1) is selected from an aspartic ester amine, an aromatic diamine, and combination thereof.
The two-part foamable polyurea-polyurethane adhesive composition according to any one of claims 1 to 10, wherein component b1) is an aspartic ester amine selected from N, N’ -diethyl maleate-2-methylpentamethylenediamine, N, N’ -diethyl maleateaminodicyclohexylmethane, N, N’ -diethyl maleate-aminodimethyldicyclohexylmethane, and mixture thereof.
The two-part foamable polyurea-polyurethane adhesive composition according to any one of claims 1 to 11, wherein component b1) is present in an amount of 1%to 25%, preferably 5%to 20%by weight of all components of the adhesive composition.
The two-part foamable polyurea-polyurethane adhesive composition according to any one of claims 1 to 12, wherein component b2) is selected from glycerol or its derivatives, pentaerythritol or its derivatives, sugar alcohols or their derivatives, ethylene oxide or propene oxide capped amines, and mixture thereof.
The two-part foamable polyurea-polyurethane adhesive composition according to any one of claims 1 to 13, wherein component b2) is present in an amount of 0.5%to 50%, preferably 1%to 40%by weight of all components of the adhesive composition.
The two-part foamable polyurea-polyurethane adhesive composition according to any one of claims 1 to 14, wherein the molar equivalent ratio A) is in the range of 0.9 to 1.8, and preferably in the range of 1.0 to 1.6.
The two-part foamable polyurea-polyurethane adhesive composition according to any one of claims 1 to 15, wherein the molar equivalent ratio B) is in the range of 0.9 to 4.5, and preferably in the range of 1.0 to 4.0.
A kit for two-part foamable polyurea-polyurethane adhesive composition, comprising the two-part foamable polyurea-polyurethane adhesive composition according to any of claims 1 to 16, and at least two containers assembled separately from one another, in which a first container holds the Part A composition, and a second container holds the Part B composition.
A cured product obtainable by mixing the part A and part B of the adhesive composition according to any one of claims 1 to 16 or the two-part foamable polyurea-polyurethane adhesive kit according to claim 17 at room temperature.
The cured product according to claim 18, which is tacky at room temperature and no tacky at 4℃.
The cured product according to claim 18 or 19, which is formable at temperature of 100℃ to 220℃, preferably 140℃ to 200℃ in 3 minutes to 60 minutes, preferably in 5 minutes to 30 minutes.
A foam obtainable by heating the polyurea-polyurethane adhesive composition according to any one of claims 1 to 16 or the cured product according to any one of claims 17 to 20 at a temperature of 100℃ to 220℃, preferably 140℃ to 200℃ in 3 minutes to 60 minutes, preferably in 5 minutes to 30 minutes.
A method of bonding materials together which comprises providing polyurea-polyurethane adhesive composition according to any one of claims 1 to 16 and applying the Part A composition and Part B composition to one or more surfaces of at least a first substrate, placing at least one surface of a second substrate in contact with the polyurea-urethane adhesive composition, allowing the adhesive composition to cure at room temperature, and heating the cured product at an elevated temperature from 100℃ to 220℃, preferably 140℃ to 200℃ in 3 minutes to 60 minutes, preferably in 5 minutes to 30 minutes to further cure and form foam in-situ.
The use of the polyurea-polyurethane adhesive composition according to any one of claims 1 to 16 or the cured product according to any one of claims 17 to 20 in bonding articles having substrates made of composite materials selected from unsaturated polyester resin materials, vinyl ester resin materials, epoxy resin materials, metals, plastic materials, and mixture thereof.