CA2154243A1 - Reactive hot melt systems containing isocyanate groups - Google Patents
Reactive hot melt systems containing isocyanate groupsInfo
- Publication number
- CA2154243A1 CA2154243A1 CA 2154243 CA2154243A CA2154243A1 CA 2154243 A1 CA2154243 A1 CA 2154243A1 CA 2154243 CA2154243 CA 2154243 CA 2154243 A CA2154243 A CA 2154243A CA 2154243 A1 CA2154243 A1 CA 2154243A1
- Authority
- CA
- Canada
- Prior art keywords
- hot melt
- isocyanate groups
- reactive hot
- hydroxyl
- melt systems
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
- C09J175/00—Adhesives based on polyureas or polyurethanes; Adhesives based on derivatives of such polymers
- C09J175/04—Polyurethanes
- C09J175/06—Polyurethanes from polyesters
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/08—Processes
- C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/08—Processes
- C08G18/16—Catalysts
- C08G18/18—Catalysts containing secondary or tertiary amines or salts thereof
- C08G18/1891—Catalysts containing secondary or tertiary amines or salts thereof in vaporous state
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/40—High-molecular-weight compounds
- C08G18/42—Polycondensates having carboxylic or carbonic ester groups in the main chain
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/70—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the isocyanates or isothiocyanates used
- C08G18/72—Polyisocyanates or polyisothiocyanates
- C08G18/74—Polyisocyanates or polyisothiocyanates cyclic
- C08G18/76—Polyisocyanates or polyisothiocyanates cyclic aromatic
- C08G18/7657—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings
- C08G18/7664—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings containing alkylene polyphenyl groups
- C08G18/7671—Polyisocyanates or polyisothiocyanates cyclic aromatic containing two or more aromatic rings containing alkylene polyphenyl groups containing only one alkylene bisphenyl group
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G2170/00—Compositions for adhesives
- C08G2170/20—Compositions for hot melt adhesives
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Health & Medical Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Medicinal Chemistry (AREA)
- Polymers & Plastics (AREA)
- Adhesives Or Adhesive Processes (AREA)
- Polyurethanes Or Polyureas (AREA)
Abstract
Reactive hot melt systems containing isocyanate groups, based on hydroxypolyols containing ester and/or ether groupings with a hydroxyl number of 15 to 150 and an average functionality of 1.95 to 2.2, and diphenylmethane diisocyanates, with a ratio of isocyanate groups in the diphenylmethane diisocyanates to hydroxyl group in the polyols of 1.4:1 to 2.5:1, which have a content of at least 70 weight % of 2,4'-diphenylmethane diisocyanate, are characterized by a low initial viscosity and enhanced temperature stability and are suitable as solid adhesives for very different areas of use.
Description
~154243 - Reactive hot melt systems containin~ isocyanate ~roups This invention relates to reactive hot melt systems cont:~ining isocyanate groups which have a low initial viscosity and enhanced temperature stability comprising hydroxypolyols having ester and/or ether groupings and special diphenylmethane diisocyanates, and relates to their use as adhesives in very dirr~lent areas of use.
Joining processes employing solvent-free adhesive systems cont~ining 100% solids are currently becoming increasingly important, because the use of solvent-containingsystems necessitates costly solvent recovery inct~ tions and the use of aqueous dispersion or solvent systems necessitates evaporation of the water, which is likewise very cost-intensive. Melt adhesives, which have long been known, provide a technical alternative. Their advantages are that they are applied as hot melts which rapidly solidify on cooling and thereby develop strength. A disadvantage is that the adhesive bonding of substances which are lelllpelalult-sensitive is made difficult due to the high melting lelllpelalules, and since the applied adhesive, unless it is further processed immetli~tçly, transforms due to its rapid solidification into a state in which wetting is no longer taking place and which can only be thermally activated again under extreme conditions of lelllpelatul~;. Moreover the bond has a limited hot strength on account of the thermoplastic character of the hot melt.
One elegant manner of providing the p,ope.ly of melt adhesives, namely of the development of strength on cooling, and at the same time enabling them to be applied at low temperatures whilst obtaining adhesive bonds of good hot strength, is a joining procedure described in principle in DE-OS 2 609 266 which employs reactive hot melt systems based on isocyanate-containing prepolymers of diisocyanates and polyester diols having melting ranges above 40C. Due to their low molecular weights, the products are fluid and workable at temp~,latures a little above the melting range of the polyester. After a chain-lengthening reaction which proceeds on the substrate they attain an adequate molecular weight, which together with the recryst~llic~tion of the crystalline polyester chain segments results in an increased initial strength. The final Le A 30 441 - Foreign Countries Z15g243 strength is reached by the complete reaction of the free isocyanate groups which are still present with atmospheric moisture, for example, with the formation of linear, high molecular weight polyurethane polyureas.
The problem of achieving a balance between the property of the highest possible initial strength and the lowest possible tel,lpelalulc of application or melting of reactive hot melt systems has not yet been solved completely satisfactorily. Systems con~ ng isocyanate groups become increasingly unstable at the elevated tempelalur~;s required for their viscosity on application, even if atmospheric moisture is excluded. This is discernible by a sharp increase in viscosity, and in extreme cases by gelling of the melts. This results in caking in melting vessels and metering devices, which can only be cleaned again at high cost.
It would therefore be desirable if hot melt systems col)~ ing isocyanate groups were available which had an enh~ncecl thermal stability, which could be held in the molten state for a long period at high tempelalul~,s without ill-,~t,~ibly transforming into the gel state or exhibiting a sharp increase in viscosity.
Surprisingly, it has now been found that when certain polyisocyanates are used hot melt systems can be obtained which exhibit a significantly enhanced stability of their viscosity without their other plol)c.lies being impaired.
Accordingly, the present invention relates to reactive hot melt systems cont~ining isocyanate groups having a low initial viscosity and enhanced telllperalule stability, comprising Le A 30 441 - Foreign Countries 215q~43 (i) hydroxypolyols cont~ining ester and/or ether groupings, with a hydroxyl number of 15 to 150 and an average functionality of 1.95 to 2.2, and (ii) diphenylmethane diisocyanates s with a ratio of isocyanate groups in (ii) to hydroxyl groups in (i) of 1.4:1 to 2.5:1, which are characterized in that diphenylmethane diisocyanates are used which have a content of at least 70 weight % of 2,4'-isomers.
The polyols (i) which are used comprise the hydroxyl coll.pounds which are commonly used in polyurethane chemistry, for example such as polyether polyols which are preferably based on bifunctional starters, e.g. propylene glycol or 2,2-bis-4-hydroxyphenylpropane, and propylene oxide which preferably has a hydroxyl numberof 20 to 150. Proportions (5 to 20 weight %, based on (i)) of polyols of higher functionality may also be used conjointly, such as propylene oxide polyether polyols started with trimethylolpropane which have a hydroxyl number from 30 to 500, forexample. When polyols of higher functionality are used conjointly, the hydroxyl number of hydroxypolyols (i) may increase to a value of 180, preferably 160.
The use of crystalline or amorphous hydroxylpolyesters as polyols (i) is plef~ ,d.
Crystalline polyester polyols are be understood as those which exhibit an endothermic m~ximnm above room te",pe,alu,e on differential thermal analysis (DTA). Amorphous polyester polyols are to be understood as those which exhibit no endothermic maximum above room telllpelalulG on dirre.~,.-lial thermal analysis.
Esterification products of adipic acid or dodecane diacid, of ortho-. iso- or terephthalic acid, of carbonic acid or of dimeric fatty acid (polycarboxylic acids obtained by the dimerization of unsaturated fatty acids (e.g. oleic acid)) with glycols, such as ethylene glycol, 1,4-butanediol or 1,6-hexanediol, for example, are preferably used as the Le A 30 441 - Foreign Countries ~15424~
polyester polyols having hydroxyl numbers from 15 to 100, preferably 20 to 75.
Mixtures of acids andtor glycols may also of course be used. The plol)ollional use in conjunction of trimethylolpropane, for example, is also possible. In addition to the above-mentioned dicarboxylic acids, the use of hydroxycaproic acid or caprolactone S is also possible.
The prepa~alion of polyether- and polyester polyols (i) is known and is described, for example, in Ullm~nn~ Encyklopadie der technischen Chemie [Ullmann's Encyclopediaof Tnrlustri~l Chemistry], "Polyesters", Fourth Edition, Verlag Chemie, Weinheim, 1980.
Di-, tri- andlor tetraethylene glycol, 1,4-dimethylolcyclohexane or trimethylolpropane or reaction products of 4,4'-hydroxyphenylpropane with ethylene- and/or propylene oxide should be cited as low molecular weight hydroxyl compounds which are optionally to be used conjointly with coll.ponent (i). Diols cont~ining ions or components which form ionic groups, such as dimethylolpropionic acid, N-methyl diethanolamine andlor reaction products of sodium bisulphite with propoxylated 1,4-butenediol, for example, may also of course be used for special effects. The amount of low molecular weight hydroxyl compounds is preferably 0.01 to 0.5 moles per mole of component (i).
Polyester polyols and polyether polyols (i) preferably have an average functionality of 1.95 to 2.05.
According to the invention, diphenylmethane diisocyanates (ii) are used which have a content of at least 70 weight %, preferably of at least 85 weight ~o, of 2,4'-isomers.
Diphenylmethane diisocyanates (ii) such as these may be prepared by various methods, such as the ~ till~tion of an industrial diphenylmethane diisocyanate mixture, for example.
Le A 30 441 - Foreign Countries 21S~243 The ratio of hydroxyl groups in polyol components (i) to isocyanate groups in diisocyanates (ii) is preferably 1:1.5 to 1:2Ø
The hot melt systems cont~ining isocyanate groups are pl~arcd, for example, by mixing the liquid polyols with an excess of polyisocyanates, whereupon the homogeneous mixture is drawn off or is stirred until a constant NCO value is reached, which is mostly achieved after two hours, and is then drawn off. A temperature of 60 to 150C, preferably 65 to 110C, is selected as the reaction ~ pe,alule. The prep~alion of the reactive hot melt may also of course be carried out continuously in a c~ de of stirred vessels or in suitable mixing units, such as high-speed mixers based on the rotor-stator principle, for example.
It is of course possible to modify the polyester- and/or polyether polyols or part of the same with a deficit of diisocyanates, preferably hexamethylene diisocyanate, and to react the polyols cont~ining urethane groups, after this reaction is complete, with an excess of diisocyanates to form a hot melt co~ ling isocyanate groups.
lt is also possible to conduct the reaction of the polyols with the diisocyanates in the presence of up to 5 weight % of trimers of aliphatic diisocyanates, for example, such as hexamethylene diisocyanate for example, or to add trimers such as these after the completion of prepolymerization.
The hot melt systems have an almost unlimited storage life when they are stored at room temperatures up to 40C with the exclusion of moisture. They can be modified in the usual manner with inorganic or organic fillers, colorants, resins and/or extender oils and constitute excellent adhesives.
They are applied at an elevated temperature, wherein the hot melt systems are melted continuously or batch-wise at temperatures of 80 to 160C and the melts are brought Le A 30 441 - Foreign Countries 215g~43 into contact with the substrates to be adhesively bonded. Bonding is firstly effected physically due to the increase in viscosity or by recryst~lli7~tion of the polyester segm~-nt~, and is effected later by chemical reaction of the isocyanate groups with moisture or other Zerewitinoff-active groups, e.g. with glycols.
s The substrate and atmospheric moisture are normally sufficient for bonding, but the reaction may of course be accelerated by providing an additional misting with media cont~ining water, glycols or catalysts, such as water vapour containing triethylamine.
Co",paled with systems based on conventional diphenylmethane diisocyanates of co~ ble molar compositions, hot melt systems of the type claimed are distinguished by a lower viscosity and, particularly when crystalline polyester polyols are used, by their more rapid cryst~lli7~tion and thus by their more rapid initial solidification or shorter "open time", as described in DE 3 931 845 for example. In particular, however, the thPrm~l stability of the systems is significantly improved and thusconstitutes a technical advance which makes the class comprising these hot melt systems even more attractive. Moreover it is now possible to produce hot melts cont~inin~ isocyanate groups based on very viscous polyester polyols, which can be used, despite the requisite high proces~ing te"lp~,~lules, without the very disadvantageous sharp increase in viscosity which occurred hitherto during proces.~ing In particular, considerably improved reactive hot melt adhesives are thus accessible for the adhesive bonding of valve bags. They solve the problem which existed hitherto, which consists of the combination of properties which are actually m~ lly exclusive which is required for trouble-free production, namely a very high viscosity or abrasion-resistance of the applied adhesive film for compounds which provide very good stability of viscosity of the adhesive which is present at very high lelllpel~lul~s in the melt application vessel and in the applicator unit.
Le A 30 441 - Foreign Countries 215~243 In the same manner, the production of technically improved reactive hot melt adhesives for composite film manufacture is also possible.
The hot melt systems according to the invention can be used as adhesives for a S diversity of applications, for example as a mounting adhesive for the preliminary fixing of components, as a bookbinding adhesive, or as adhesives for the manufacture ofvalve bags, composite films or l~rnin~te.
Le A 30 441 - Foreign Countries 21542~3 Examples Polyester polyols A-l A crystalline hydroxyl polyester of adipic acid and 1,6-hexanediol: hydroxylS number 28.0, acid number 0.6, average functionality 2.0 A-2 An amorphous hydroxyl polyester of neopentyl glycol and a mixture of adipic acid and isophthalic acid in a 6:4 molar ratio:
hydroxyl number 56.2, acid number 0.7, average functionality 2.0 0 A-3 An amorphous hydroxyl polyester, Dynacoll 7210 manufactured by Huls AG, with a hydroxyl number of 33 and an average functionality of 2.0 A-4 An amorphous hydroxyl polyester, Dynacoll 7110 manufactured by Huls AG, with a hydroxyl number of 52 and an average functionality of 2.0 Diisocyanates C-l A diisocyanatodiphenylmethane mixture conlainillg 87.1 % 2,4'-, 11.2 %
4,4'- and 1.7 % 2,2'-isomers C-lA A diisocy~n~todiphenylmethane ~ lule containing 77.0 % 2,4'-, 22 % 4,4'- and 1 % 2,2'-isomers C-2 4,4'-diisocyanatodiphenylmethane (100 %).
Preparation of prepolymers The molten polyols were dehydrated for 60 minutes at 100C and at about 20 mbar with stirring.
The diisocyanate was added at about 80 to 90C and stirred under nitrogen until a constant isocyanate content was obtained.
~e A 30 441 - Foreign Countries ~1542g3 The prepolymer was introduced into cartridges.
Investi~tinn of the hot melt systems After storage for two weeks at room telllpel~lule the cartridges were melted at 130 to 140C for 60 minutes in an oven.
The isocyanate content of the liquid prepolymer was determined by titration withdibutylamine.
The liquid hot melt was applied to beechwood test pieces and its curing characteristics were determined using a "CUREM" (see DE 3 931 845), divided into a wetting phaseA (seconds) and a cryst~lli7~tion phase B (seconds). For this purpose the adhesive in the joint gap of the m~teri~l~ to be adhesively bonded was subjected to sinusoidally lS alternating shear loading, and the shear forces thus arising were continuously measured. The measured shear forces were displayed as a function of time (in seconds). The shear was produced via a frequency-controlled thrust motor and a fine threaded spindle. The displacement was 20011m, and the loading frequency was 1 Hz.
The joint gap measured 0.2 mm and the telllpeldluie of the test piece clamping jaws was set at 20+2C. McasulGlllents were recorded for 10 minutes.
The cohesion strength was determined on the beechwood test pieces (after 24 hours and after 7 days) [see Table 2].
Le A 30 441 - Foreign Countries ._ Testin~ the stora~e stability (Table 3) The hot melt systems were melted at 120C in aluminium cartridges and stored for 24 hours or 72 hours. Viscosities were determined at 120C at a shear rate of D = 50 Vs using an MC-10 cone/plate viscometer (manufactured by Physika).
Table 1 (moles) Pol-A moles TMP* (moles) diiso. C NCO/OH % NCO
1 1.0 A-1 / 1.9 C-1 1.9 1.69 1 A 1.0 A-1 / 1.9 C-2 1.9 1.59 2 1.0 A-1 0.25 2.61 C-1 1.9 1.99 2 A 1.0 A-1 0.25 2.61 C-2 1.9 2.00 3 1.0 A-1 0.1 2.12 C-1 1.85 1.53 3 A 1.0 A-1 0.1 2.12 C-2 1.85 1.51 4 1.0 A-2 / 2.0 C-1 2.0 3.59 4 A 1.0 A-2 / 2.0 C-2 2.0 3.54 1.0 A-1 0.1 2.19 C-1 1.9 1.74 5 A 1.0 A-1 0.1 2.19 C-2 1.9 1.69 6 1.0 A-1 0.25 2.47 C-1 1.8 1.72 6 A 1.0 A-1 0.25 2.47 C-2 1.8 1.62 7 1.0 A-3 / 2.0 C-l A 2.0 2.06 7 A 1.0 A-3 / 2.0 C-2 2.0 2.19 8 1.0 A-4 / 2.0 C-1 A 2.0 3.24 8 A 1.0 A-4 / 2.0 C-2 2.0 3.29 *TMP = trimethylolpropane Le A 30 441 - Foreign Countries 215~ 24 3 Table 2 Wetting Crysr~ion Strength in N/mm' (sec.) (sec.)after 24 hours 7 days 5.0 12.6 lA 65 120 8.1 15.0 2 60 85 6.0 14.6 - 2 A 100 150 8.3 15.1 1 1 5.0 13.0 5 A / / 8.9 14.8 7 1 1 0.2 3.4 7 A I 1 1.8 3.8 8 1 1 2.0 3.1 8 A I 1 1.8 8.2 The tests denoted by A were each comparative tests. The more rapid initial 20 solidificationofthehotmeltsystems based on crystalline polyesters (1-3) according to the invention can clearly be seen.
Le A 30 441 21~4293 Table 3 Adhesive Viscosity (Pas) at 120C after s~orage for 0 hours24 hours 72 hours 1 9.0 I A 22.0 2 S.0 - 16.0 28.0 2 A 15.0 145.0 596.0 3 13.0 3 A 35.0 4 2.8 6.1 13.4 4 A 4.4 13.3 67.9 6.0 12.0 20.0 5 A 19.0 80.0 242.0 6 6.8 17.5 72.0 6 A 24.0 240.0 crocclinl~Pd 7 5.0 7.6 12.0 7 A 7.8 18.0 58.0 8 6.7 17.0 64.0 ~0 8 A 8.5 16.0 crosslin~d The lower initial viscosity and the reduced increase in viscosity at elevated temperature after the period of storage can clearly be seen for the hot melt systems according to the 25 invention.
Le A 30 4~1
Joining processes employing solvent-free adhesive systems cont~ining 100% solids are currently becoming increasingly important, because the use of solvent-containingsystems necessitates costly solvent recovery inct~ tions and the use of aqueous dispersion or solvent systems necessitates evaporation of the water, which is likewise very cost-intensive. Melt adhesives, which have long been known, provide a technical alternative. Their advantages are that they are applied as hot melts which rapidly solidify on cooling and thereby develop strength. A disadvantage is that the adhesive bonding of substances which are lelllpelalult-sensitive is made difficult due to the high melting lelllpelalules, and since the applied adhesive, unless it is further processed immetli~tçly, transforms due to its rapid solidification into a state in which wetting is no longer taking place and which can only be thermally activated again under extreme conditions of lelllpelatul~;. Moreover the bond has a limited hot strength on account of the thermoplastic character of the hot melt.
One elegant manner of providing the p,ope.ly of melt adhesives, namely of the development of strength on cooling, and at the same time enabling them to be applied at low temperatures whilst obtaining adhesive bonds of good hot strength, is a joining procedure described in principle in DE-OS 2 609 266 which employs reactive hot melt systems based on isocyanate-containing prepolymers of diisocyanates and polyester diols having melting ranges above 40C. Due to their low molecular weights, the products are fluid and workable at temp~,latures a little above the melting range of the polyester. After a chain-lengthening reaction which proceeds on the substrate they attain an adequate molecular weight, which together with the recryst~llic~tion of the crystalline polyester chain segments results in an increased initial strength. The final Le A 30 441 - Foreign Countries Z15g243 strength is reached by the complete reaction of the free isocyanate groups which are still present with atmospheric moisture, for example, with the formation of linear, high molecular weight polyurethane polyureas.
The problem of achieving a balance between the property of the highest possible initial strength and the lowest possible tel,lpelalulc of application or melting of reactive hot melt systems has not yet been solved completely satisfactorily. Systems con~ ng isocyanate groups become increasingly unstable at the elevated tempelalur~;s required for their viscosity on application, even if atmospheric moisture is excluded. This is discernible by a sharp increase in viscosity, and in extreme cases by gelling of the melts. This results in caking in melting vessels and metering devices, which can only be cleaned again at high cost.
It would therefore be desirable if hot melt systems col)~ ing isocyanate groups were available which had an enh~ncecl thermal stability, which could be held in the molten state for a long period at high tempelalul~,s without ill-,~t,~ibly transforming into the gel state or exhibiting a sharp increase in viscosity.
Surprisingly, it has now been found that when certain polyisocyanates are used hot melt systems can be obtained which exhibit a significantly enhanced stability of their viscosity without their other plol)c.lies being impaired.
Accordingly, the present invention relates to reactive hot melt systems cont~ining isocyanate groups having a low initial viscosity and enhanced telllperalule stability, comprising Le A 30 441 - Foreign Countries 215q~43 (i) hydroxypolyols cont~ining ester and/or ether groupings, with a hydroxyl number of 15 to 150 and an average functionality of 1.95 to 2.2, and (ii) diphenylmethane diisocyanates s with a ratio of isocyanate groups in (ii) to hydroxyl groups in (i) of 1.4:1 to 2.5:1, which are characterized in that diphenylmethane diisocyanates are used which have a content of at least 70 weight % of 2,4'-isomers.
The polyols (i) which are used comprise the hydroxyl coll.pounds which are commonly used in polyurethane chemistry, for example such as polyether polyols which are preferably based on bifunctional starters, e.g. propylene glycol or 2,2-bis-4-hydroxyphenylpropane, and propylene oxide which preferably has a hydroxyl numberof 20 to 150. Proportions (5 to 20 weight %, based on (i)) of polyols of higher functionality may also be used conjointly, such as propylene oxide polyether polyols started with trimethylolpropane which have a hydroxyl number from 30 to 500, forexample. When polyols of higher functionality are used conjointly, the hydroxyl number of hydroxypolyols (i) may increase to a value of 180, preferably 160.
The use of crystalline or amorphous hydroxylpolyesters as polyols (i) is plef~ ,d.
Crystalline polyester polyols are be understood as those which exhibit an endothermic m~ximnm above room te",pe,alu,e on differential thermal analysis (DTA). Amorphous polyester polyols are to be understood as those which exhibit no endothermic maximum above room telllpelalulG on dirre.~,.-lial thermal analysis.
Esterification products of adipic acid or dodecane diacid, of ortho-. iso- or terephthalic acid, of carbonic acid or of dimeric fatty acid (polycarboxylic acids obtained by the dimerization of unsaturated fatty acids (e.g. oleic acid)) with glycols, such as ethylene glycol, 1,4-butanediol or 1,6-hexanediol, for example, are preferably used as the Le A 30 441 - Foreign Countries ~15424~
polyester polyols having hydroxyl numbers from 15 to 100, preferably 20 to 75.
Mixtures of acids andtor glycols may also of course be used. The plol)ollional use in conjunction of trimethylolpropane, for example, is also possible. In addition to the above-mentioned dicarboxylic acids, the use of hydroxycaproic acid or caprolactone S is also possible.
The prepa~alion of polyether- and polyester polyols (i) is known and is described, for example, in Ullm~nn~ Encyklopadie der technischen Chemie [Ullmann's Encyclopediaof Tnrlustri~l Chemistry], "Polyesters", Fourth Edition, Verlag Chemie, Weinheim, 1980.
Di-, tri- andlor tetraethylene glycol, 1,4-dimethylolcyclohexane or trimethylolpropane or reaction products of 4,4'-hydroxyphenylpropane with ethylene- and/or propylene oxide should be cited as low molecular weight hydroxyl compounds which are optionally to be used conjointly with coll.ponent (i). Diols cont~ining ions or components which form ionic groups, such as dimethylolpropionic acid, N-methyl diethanolamine andlor reaction products of sodium bisulphite with propoxylated 1,4-butenediol, for example, may also of course be used for special effects. The amount of low molecular weight hydroxyl compounds is preferably 0.01 to 0.5 moles per mole of component (i).
Polyester polyols and polyether polyols (i) preferably have an average functionality of 1.95 to 2.05.
According to the invention, diphenylmethane diisocyanates (ii) are used which have a content of at least 70 weight %, preferably of at least 85 weight ~o, of 2,4'-isomers.
Diphenylmethane diisocyanates (ii) such as these may be prepared by various methods, such as the ~ till~tion of an industrial diphenylmethane diisocyanate mixture, for example.
Le A 30 441 - Foreign Countries 21S~243 The ratio of hydroxyl groups in polyol components (i) to isocyanate groups in diisocyanates (ii) is preferably 1:1.5 to 1:2Ø
The hot melt systems cont~ining isocyanate groups are pl~arcd, for example, by mixing the liquid polyols with an excess of polyisocyanates, whereupon the homogeneous mixture is drawn off or is stirred until a constant NCO value is reached, which is mostly achieved after two hours, and is then drawn off. A temperature of 60 to 150C, preferably 65 to 110C, is selected as the reaction ~ pe,alule. The prep~alion of the reactive hot melt may also of course be carried out continuously in a c~ de of stirred vessels or in suitable mixing units, such as high-speed mixers based on the rotor-stator principle, for example.
It is of course possible to modify the polyester- and/or polyether polyols or part of the same with a deficit of diisocyanates, preferably hexamethylene diisocyanate, and to react the polyols cont~ining urethane groups, after this reaction is complete, with an excess of diisocyanates to form a hot melt co~ ling isocyanate groups.
lt is also possible to conduct the reaction of the polyols with the diisocyanates in the presence of up to 5 weight % of trimers of aliphatic diisocyanates, for example, such as hexamethylene diisocyanate for example, or to add trimers such as these after the completion of prepolymerization.
The hot melt systems have an almost unlimited storage life when they are stored at room temperatures up to 40C with the exclusion of moisture. They can be modified in the usual manner with inorganic or organic fillers, colorants, resins and/or extender oils and constitute excellent adhesives.
They are applied at an elevated temperature, wherein the hot melt systems are melted continuously or batch-wise at temperatures of 80 to 160C and the melts are brought Le A 30 441 - Foreign Countries 215g~43 into contact with the substrates to be adhesively bonded. Bonding is firstly effected physically due to the increase in viscosity or by recryst~lli7~tion of the polyester segm~-nt~, and is effected later by chemical reaction of the isocyanate groups with moisture or other Zerewitinoff-active groups, e.g. with glycols.
s The substrate and atmospheric moisture are normally sufficient for bonding, but the reaction may of course be accelerated by providing an additional misting with media cont~ining water, glycols or catalysts, such as water vapour containing triethylamine.
Co",paled with systems based on conventional diphenylmethane diisocyanates of co~ ble molar compositions, hot melt systems of the type claimed are distinguished by a lower viscosity and, particularly when crystalline polyester polyols are used, by their more rapid cryst~lli7~tion and thus by their more rapid initial solidification or shorter "open time", as described in DE 3 931 845 for example. In particular, however, the thPrm~l stability of the systems is significantly improved and thusconstitutes a technical advance which makes the class comprising these hot melt systems even more attractive. Moreover it is now possible to produce hot melts cont~inin~ isocyanate groups based on very viscous polyester polyols, which can be used, despite the requisite high proces~ing te"lp~,~lules, without the very disadvantageous sharp increase in viscosity which occurred hitherto during proces.~ing In particular, considerably improved reactive hot melt adhesives are thus accessible for the adhesive bonding of valve bags. They solve the problem which existed hitherto, which consists of the combination of properties which are actually m~ lly exclusive which is required for trouble-free production, namely a very high viscosity or abrasion-resistance of the applied adhesive film for compounds which provide very good stability of viscosity of the adhesive which is present at very high lelllpel~lul~s in the melt application vessel and in the applicator unit.
Le A 30 441 - Foreign Countries 215~243 In the same manner, the production of technically improved reactive hot melt adhesives for composite film manufacture is also possible.
The hot melt systems according to the invention can be used as adhesives for a S diversity of applications, for example as a mounting adhesive for the preliminary fixing of components, as a bookbinding adhesive, or as adhesives for the manufacture ofvalve bags, composite films or l~rnin~te.
Le A 30 441 - Foreign Countries 21542~3 Examples Polyester polyols A-l A crystalline hydroxyl polyester of adipic acid and 1,6-hexanediol: hydroxylS number 28.0, acid number 0.6, average functionality 2.0 A-2 An amorphous hydroxyl polyester of neopentyl glycol and a mixture of adipic acid and isophthalic acid in a 6:4 molar ratio:
hydroxyl number 56.2, acid number 0.7, average functionality 2.0 0 A-3 An amorphous hydroxyl polyester, Dynacoll 7210 manufactured by Huls AG, with a hydroxyl number of 33 and an average functionality of 2.0 A-4 An amorphous hydroxyl polyester, Dynacoll 7110 manufactured by Huls AG, with a hydroxyl number of 52 and an average functionality of 2.0 Diisocyanates C-l A diisocyanatodiphenylmethane mixture conlainillg 87.1 % 2,4'-, 11.2 %
4,4'- and 1.7 % 2,2'-isomers C-lA A diisocy~n~todiphenylmethane ~ lule containing 77.0 % 2,4'-, 22 % 4,4'- and 1 % 2,2'-isomers C-2 4,4'-diisocyanatodiphenylmethane (100 %).
Preparation of prepolymers The molten polyols were dehydrated for 60 minutes at 100C and at about 20 mbar with stirring.
The diisocyanate was added at about 80 to 90C and stirred under nitrogen until a constant isocyanate content was obtained.
~e A 30 441 - Foreign Countries ~1542g3 The prepolymer was introduced into cartridges.
Investi~tinn of the hot melt systems After storage for two weeks at room telllpel~lule the cartridges were melted at 130 to 140C for 60 minutes in an oven.
The isocyanate content of the liquid prepolymer was determined by titration withdibutylamine.
The liquid hot melt was applied to beechwood test pieces and its curing characteristics were determined using a "CUREM" (see DE 3 931 845), divided into a wetting phaseA (seconds) and a cryst~lli7~tion phase B (seconds). For this purpose the adhesive in the joint gap of the m~teri~l~ to be adhesively bonded was subjected to sinusoidally lS alternating shear loading, and the shear forces thus arising were continuously measured. The measured shear forces were displayed as a function of time (in seconds). The shear was produced via a frequency-controlled thrust motor and a fine threaded spindle. The displacement was 20011m, and the loading frequency was 1 Hz.
The joint gap measured 0.2 mm and the telllpeldluie of the test piece clamping jaws was set at 20+2C. McasulGlllents were recorded for 10 minutes.
The cohesion strength was determined on the beechwood test pieces (after 24 hours and after 7 days) [see Table 2].
Le A 30 441 - Foreign Countries ._ Testin~ the stora~e stability (Table 3) The hot melt systems were melted at 120C in aluminium cartridges and stored for 24 hours or 72 hours. Viscosities were determined at 120C at a shear rate of D = 50 Vs using an MC-10 cone/plate viscometer (manufactured by Physika).
Table 1 (moles) Pol-A moles TMP* (moles) diiso. C NCO/OH % NCO
1 1.0 A-1 / 1.9 C-1 1.9 1.69 1 A 1.0 A-1 / 1.9 C-2 1.9 1.59 2 1.0 A-1 0.25 2.61 C-1 1.9 1.99 2 A 1.0 A-1 0.25 2.61 C-2 1.9 2.00 3 1.0 A-1 0.1 2.12 C-1 1.85 1.53 3 A 1.0 A-1 0.1 2.12 C-2 1.85 1.51 4 1.0 A-2 / 2.0 C-1 2.0 3.59 4 A 1.0 A-2 / 2.0 C-2 2.0 3.54 1.0 A-1 0.1 2.19 C-1 1.9 1.74 5 A 1.0 A-1 0.1 2.19 C-2 1.9 1.69 6 1.0 A-1 0.25 2.47 C-1 1.8 1.72 6 A 1.0 A-1 0.25 2.47 C-2 1.8 1.62 7 1.0 A-3 / 2.0 C-l A 2.0 2.06 7 A 1.0 A-3 / 2.0 C-2 2.0 2.19 8 1.0 A-4 / 2.0 C-1 A 2.0 3.24 8 A 1.0 A-4 / 2.0 C-2 2.0 3.29 *TMP = trimethylolpropane Le A 30 441 - Foreign Countries 215~ 24 3 Table 2 Wetting Crysr~ion Strength in N/mm' (sec.) (sec.)after 24 hours 7 days 5.0 12.6 lA 65 120 8.1 15.0 2 60 85 6.0 14.6 - 2 A 100 150 8.3 15.1 1 1 5.0 13.0 5 A / / 8.9 14.8 7 1 1 0.2 3.4 7 A I 1 1.8 3.8 8 1 1 2.0 3.1 8 A I 1 1.8 8.2 The tests denoted by A were each comparative tests. The more rapid initial 20 solidificationofthehotmeltsystems based on crystalline polyesters (1-3) according to the invention can clearly be seen.
Le A 30 441 21~4293 Table 3 Adhesive Viscosity (Pas) at 120C after s~orage for 0 hours24 hours 72 hours 1 9.0 I A 22.0 2 S.0 - 16.0 28.0 2 A 15.0 145.0 596.0 3 13.0 3 A 35.0 4 2.8 6.1 13.4 4 A 4.4 13.3 67.9 6.0 12.0 20.0 5 A 19.0 80.0 242.0 6 6.8 17.5 72.0 6 A 24.0 240.0 crocclinl~Pd 7 5.0 7.6 12.0 7 A 7.8 18.0 58.0 8 6.7 17.0 64.0 ~0 8 A 8.5 16.0 crosslin~d The lower initial viscosity and the reduced increase in viscosity at elevated temperature after the period of storage can clearly be seen for the hot melt systems according to the 25 invention.
Le A 30 4~1
Claims (4)
1. A reactive hot melt containing isocyanate groups and having a low initial viscosity and enhanced temperature stability, comprising (i) a hydroxypolyol containing ester or ether groups, with a hydroxyl number of 15 to 150 and an average functionality of 1.95 to 2.2, and (ii) a diphenylmethane diisocyanate with a ratio of isocyanate groups in (ii) to hydroxyl groups in (i) of 1.4:1 to 2.5:1, characterized in that the diphenyl-methane diisocyanate has a content of at least 70 weight % of
2,4'-isomers.
2. A reactive hot melt according to claim 1, character-ized in that component (i) is a crystalline hydroxypolyester polyol.
2. A reactive hot melt according to claim 1, character-ized in that component (i) is a crystalline hydroxypolyester polyol.
3. A reactive hot melt according to claim 1, character-ized in that component (i) is an amorphous hydroxypolyester polyol.
4. A reactive hot melt according to any one of claims 1 to 3, characterized in that component (ii) comprises a diphenylmethane diisocyante having a 2,4'-isomer content of more than 85 weight %.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4426130.6 | 1994-07-22 | ||
| DE19944426130 DE4426130A1 (en) | 1994-07-22 | 1994-07-22 | Reactive hot melt systems containing isocyanate groups |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2154243A1 true CA2154243A1 (en) | 1996-01-23 |
Family
ID=6523964
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2154243 Abandoned CA2154243A1 (en) | 1994-07-22 | 1995-07-19 | Reactive hot melt systems containing isocyanate groups |
Country Status (4)
| Country | Link |
|---|---|
| EP (1) | EP0693511A1 (en) |
| JP (1) | JPH0860129A (en) |
| CA (1) | CA2154243A1 (en) |
| DE (1) | DE4426130A1 (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7101950B2 (en) | 2003-08-22 | 2006-09-05 | Dow Global Technologies Inc. | Composition useful as an adhesive for installing vehicle windows |
| US7199207B2 (en) | 2002-02-08 | 2007-04-03 | Henkel Kommanditgesellschaft Auf Aktien | Neutral-coloured 1K polyurethane adhesive |
| US8097675B2 (en) | 2008-03-28 | 2012-01-17 | Bayer Materialscience Ag | 2,2′-MDI-based isocyanate mixtures, polyisocyanate polyaddition products prepared therefrom, processes for making the same and methods for their use |
| US8242229B2 (en) * | 2007-01-29 | 2012-08-14 | Bayer Materialscience Ag | Polyurethanes cured with amines and their preparation |
| US20130025784A1 (en) * | 2010-04-01 | 2013-01-31 | Henkel Corporation | Methods for making aqueous polyurethane dispersions of aromatic polyisocyanate mixtures and compositions |
| US8399595B2 (en) | 2007-07-23 | 2013-03-19 | Dow Global Technologies Llc | Two part polyurethane curable composition having substantially consistent G-modulus across the range of use temperatures |
| US8668804B2 (en) | 2008-08-22 | 2014-03-11 | Dow Global Technologies Llc | Adhesive composition adapted for bonding large mass parts to structures |
| US9637667B2 (en) | 2001-10-13 | 2017-05-02 | Henkel Ag & Co. Kgaa | Reactive polyurethane compositions with a low residual monomer content |
Families Citing this family (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5939488A (en) * | 1997-10-15 | 1999-08-17 | National Starch And Chemical Investment Holding Corporation | Fast setting polyurethane hot melt adhesive composition comprising low hydroxyl number/high molecular weight polyester diols |
| DE60100395T2 (en) * | 2000-05-10 | 2004-04-22 | Rohm And Haas Co. | Hotmelt adhesive |
| JP4817278B2 (en) * | 2001-08-31 | 2011-11-16 | コニシ株式会社 | Method for producing moisture-curing urethane resin composition |
| DE10343750A1 (en) * | 2003-09-22 | 2005-04-28 | Henkel Kgaa | Polyurethane hot melt adhesives with long reactivity |
| DE102012200018A1 (en) | 2012-01-02 | 2013-07-04 | Bayer Materialscience Ag | Reactive polyurethane preparations |
| JP6391916B2 (en) * | 2013-06-21 | 2018-09-19 | 日東電工株式会社 | Optical pressure-sensitive adhesive layer, optical film with pressure-sensitive adhesive layer, and image display device |
| CN104152100A (en) * | 2014-08-20 | 2014-11-19 | 刘骏 | Manufacturing method of polyurethane hot-melt sealant |
| WO2020264159A1 (en) * | 2019-06-25 | 2020-12-30 | H.B. Fuller Company | Moisture curable polyurethane hot melt adhesive composition having low levels of diisocyanate monomer |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1077352A (en) | 1975-03-06 | 1980-05-13 | Usm Corporation | Coating and bonding method particularly for sole attaching |
| DE3524333A1 (en) * | 1985-07-08 | 1987-01-08 | Basf Ag | POLYURETHANE ADHESIVE BLENDS |
| US4808255A (en) * | 1987-05-07 | 1989-02-28 | H. B. Fuller Company | Thermally stable reactive hot melt urethane adhesive composition having a thermoplastic polymer, a compatible, curing urethane polyester polyol prepolymer and a tackifying agent |
| EP0448825A3 (en) * | 1990-03-23 | 1992-04-29 | Bayer Ag | Melt adhesive process |
| DE4136490C2 (en) * | 1991-11-06 | 2003-04-30 | Bayer Ag | Solvent-free coating systems |
-
1994
- 1994-07-22 DE DE19944426130 patent/DE4426130A1/en not_active Withdrawn
-
1995
- 1995-07-10 EP EP95110708A patent/EP0693511A1/en not_active Withdrawn
- 1995-07-14 JP JP7200241A patent/JPH0860129A/en active Pending
- 1995-07-19 CA CA 2154243 patent/CA2154243A1/en not_active Abandoned
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9637667B2 (en) | 2001-10-13 | 2017-05-02 | Henkel Ag & Co. Kgaa | Reactive polyurethane compositions with a low residual monomer content |
| US7199207B2 (en) | 2002-02-08 | 2007-04-03 | Henkel Kommanditgesellschaft Auf Aktien | Neutral-coloured 1K polyurethane adhesive |
| US7101950B2 (en) | 2003-08-22 | 2006-09-05 | Dow Global Technologies Inc. | Composition useful as an adhesive for installing vehicle windows |
| US8242229B2 (en) * | 2007-01-29 | 2012-08-14 | Bayer Materialscience Ag | Polyurethanes cured with amines and their preparation |
| US8399595B2 (en) | 2007-07-23 | 2013-03-19 | Dow Global Technologies Llc | Two part polyurethane curable composition having substantially consistent G-modulus across the range of use temperatures |
| US8097675B2 (en) | 2008-03-28 | 2012-01-17 | Bayer Materialscience Ag | 2,2′-MDI-based isocyanate mixtures, polyisocyanate polyaddition products prepared therefrom, processes for making the same and methods for their use |
| US8668804B2 (en) | 2008-08-22 | 2014-03-11 | Dow Global Technologies Llc | Adhesive composition adapted for bonding large mass parts to structures |
| US20130025784A1 (en) * | 2010-04-01 | 2013-01-31 | Henkel Corporation | Methods for making aqueous polyurethane dispersions of aromatic polyisocyanate mixtures and compositions |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0693511A1 (en) | 1996-01-24 |
| DE4426130A1 (en) | 1996-01-25 |
| JPH0860129A (en) | 1996-03-05 |
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