Classifications

• • 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
  • C08G2170/00—Compositions for adhesives
  • C08G2170/20—Compositions for hot melt adhesives

Definitions

• the present invention relates to mixtures for producing improved reactive hot melt adhesives and to reactive hot melt adhesives obtainable therefrom.
• Reactive hot melt adhesives are solid substances at room temperature. They are melted by heating and applied to a substrate. When cooling, the adhesive solidifies again and thus binds the substrate. In addition, the polymers contained in the adhesive crosslink by reaction with moisture, which results in a final, irreversible curing.
• Adhesives of this type are described, for example, in US Pat. No. 5,021,507.
• the main constituent of these adhesives are compounds with free isocyanate groups, which are usually obtained by the condensation reaction of an excess of polyisocyanate groups with polyol.
• binders consisting of polymers of ethylenically unsaturated monomers were added to these compounds with free isocyanate groups.
• Polyalkyl (meth) acrylates with C 1 to C 2 alkyl groups are typically used as binders. These are polymerized from the corresponding monomers either before addition to the urethanes or in their presence by free, radical polymerization.
• the reactive adhesives obtained in this way are distinguished from US 5,021,507 by an increased elasticity and an improved adhesion to certain metal substrates as well as a longer open time, the time one has to process the adhesive.
• Another disadvantage is that the extractable content in the cured adhesive is quite high. Among other things, this reduces the resistance of the adhesive to solvents.
• Another disadvantage is that the reactive hot melt adhesive often has insufficient viscosity stability in the melt at 130 ° C., which in particular makes it difficult to process.
• Another object of the invention was to improve the viscosity stability of the reactive adhesive at 130 ° C. in the melt in order to improve the processability of the adhesive in the molten state.
• Another object of the invention was to provide a reactive hot melt adhesive which ensures improved elasticity of the adhesive joint and thus improved bonding of the substrates.
• Another object of the invention was to provide a reactive hot melt adhesive which has very good adhesive properties on different materials.
• Another object of the invention was to provide a reactive hot melt adhesive which has a small proportion of extractable components in the cured adhesive and is well resistant to solvents.
• a polymer containing hydroxyl groups and / or amino groups and / or mercapto groups obtainable by polymerizing ethylenically unsaturated monomers, with a polydispersity D of less than 1.8, preferably D less than 1.6, particularly preferably D less than 1.3 , is used as the binder, D being obtained from the quotient of the weight-average molecular weight M w and the number-average molecular weight M n , which can be determined, for example, by gel permeation chromatography, surprisingly succeeds in providing a reactive hot-melt adhesive which has a high initial strength and has no problems with Gelling in the condensation stage.
• the reactive hot-melt adhesive according to the invention can achieve a number of advantages over the prior art which were not readily foreseeable. These include:
• An increased initial strength and a higher elasticity in the cured adhesive joint which is obtained by using a polymer containing hydroxyl groups and / or amino groups and / or mercapto groups as a binder with a higher number average molecular weight at a constant hydroxyl number, with no gelation occurring in the condensation stage.
• An increased initial strength and a higher strength of the cured adhesive joint which is obtained by using a polymer containing hydroxyl groups and / or amino groups and / or mercapto groups as a binder with a higher hydroxyl number and a constant number-average molecular weight.
• An easier processability of the adhesive due to a lower viscosity of the melt of the reactive hot-melt adhesive when using a polymer containing hydroxyl groups and / or amino groups and / or mercapto groups as a binder with the same number average molecular weight and otherwise constant conditions.
• a reactive hot melt adhesive according to the invention is obtainable from a mixture which contains 10 to 80 percent by weight of a compound with free isocyanate groups and 20 to 90 percent by weight of a polymer containing hydroxyl groups and / or amino groups and / or mercapto groups, obtainable by polymerizing ethylenically unsaturated monomers.
• Any compound which has two or more free isocyanate groups per molecule can be selected as the compound according to the invention with free isocyanate groups.
• Such polyisocyanates are generally known. Low molecular weight polyisocyanates with 2 free isocyanate groups are preferably used.
• These diisocyanates include diisocyanates whose isocyanate groups are linked by an organic radical consisting of branched or unbranched, substituted or unsubstituted, aliphatic alkyl groups. Examples of such compounds are ethylene diisocyanate, ethylidene diisocyanate, propylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate and dichlorohexamethylene diisocyanate.
• the isocyanate groups can be connected by residues which have saturated, cyclic hydrocarbons. These can be unsubstituted or substituted. These include 3-isocyanatomethyl-3,3,5-trimethylcyclohexyl isocyanate, 3-isocyanatomethyl-3,3,5-trimethylcyclohexyl isocyanate cyanurate, cyclopentylene-1,3-diisocyanate, cyclohexylene-1,4-diisocyanate and cyclohexylene-1,2-diisocyanate. Diisocyanates whose organic radical has a substituted or unsubstituted aromatic are particularly preferred.
• These compounds include, for example, toluene diisocyanate, 4,4-diphenylmethane diisocyanate, 2,2-diphenylpropane-4,4-diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate, xylylene diisocyanate, 1,4-naphthylene diisocyanate, 1,5-naphthylene diisocyanate, diphenyl-4 , 4-diisocyanate, azobenzene-4,4-diisocyanate, diphenyl sulfone-4,4-diisocyanate, furfurylidene diisocyanate and 1-chlorobenzene-2,4-diisocyanate.
• Compounds with more than 2 free isocyanate groups that can be used in this invention include, for example, 4,4,4-triisocyanatotriphenylmethane, 1, 3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene and 4,4-dimethyldiphenylmethane -2,2,5,5- tetraisocyanate.
• Further preferred compounds with free isocyanate groups are oligourethanes, so-called urethane prepolymers, which have reactive end groups containing isocyanate.
• Particularly preferred compounds are urethane prepolymers which can be obtained by polycondensation reaction of one or more, low molecular weight compounds with free isocyanate groups and one or more compounds with free hydroxyl groups and / or amino groups and / or mercapto groups.
• Urethane prepolymers which are obtainable by polycondensation of one or more low molecular weight compounds with free isocyanate groups and one or more polyhydroxy compounds are very particularly preferred. Dihydroxy compounds are particularly preferred here.
• OH-terminated polyethers such as polyethylene oxide diol, polypropylene oxide diol, diol copolymers from ethylene oxide and propylene oxide and diols from butylene oxide.
• Polyester polyols such as the OH-terminated condensation product of at least one C 2 -C 8 -dicarboxylic acid and at least one diol from the group of the C 2 -Ct 6 -alkylenediols can also be used.
• low molecular weight diols such as Diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, and tetrapropylene glycol can be used as the diol component.
• more highly functionalized OH components such as, for example, polyethylene oxide triol, polypropylene oxide triol, triol copolymers from ethylene oxide and propylene oxide, triols from butylene oxide can also be used to produce the urethane prepolymer.
• Urethane prepolymers with free isocyanate groups which are obtainable by polycondensation of one or more low molecular weight diisocyanates with one or more low molecular weight diols, are particularly preferred.
• urethane prepolymers obtainable by condensation polymerization of compounds having free isocyanate groups with polyamino- or polymercapto-containing compounds, either alone or together with one or more compounds having free hydroxyl groups, preferably one or more of the compounds listed above can be used with free hydroxyl groups.
• polyamino compounds which can be used in the context of this invention are diaminopolypropylene glycol or diaminopolyethylene glycol, and also low molecular weight compounds such as ethylenediamine, hexaethylenediamine, and the like; for polymer capto compounds polythioether.
• Mixed compounds such as ethanolamine, propanolamine, N-methyldiethanolamine and the like can also be used.
• the molecular weight of the urethane prepolymers is generally in the range from 100 to 50,000 g / mol, preferably between 200 and 30,000 g / mol and particularly preferably between 500 and 20,000 g / mol, without this being intended to limit the molecular weight.
• any polymer obtainable from ethylenically unsaturated monomers, which has a hydroxide functionality and / or amino functionality and / or mercapto functionality of more than 1 together and a polydispersity D less than 1.8, preferably D less than 1.6, particularly preferably D. less than 1, 3, can be used as a binder.
• hydroxyl and / or amino and / or mercapto-containing polymers are obtainable by copolymerizing one or more hydroxy-functionalized and / or amino-functionalized and / or mercapto-functionalized monomers and one or more monomers without such functionality, for example of alkyl esters of acrylic or Methacrylic acid, from vinyl esters, vinyl ethers, fumarates, maleates, styrenes, and acrylonitriles can be used.
• Polymers bearing hydroxyl groups are particularly preferred, which can be obtained by copolymerizing hydroxyl-functionalized (meth) acrylates and (meth) acrylates without a hydroxyl function.
• (meth) acrylates includes methacrylates and acrylates as well
• (Meth) acrylates derived from saturated alcohols such as, for example, methyl (meth) acrylate, ethyl (meth) acrylate,
• Aryl (meth) acrylates such as benzyl (meth) acrylate or
• Phenyl (meth) acrylate where the aryl radicals can in each case be unsubstituted or substituted up to four times;
• Cycloalkyl (meth) acrylates such as 3-vinylcyclohexyl (meth) acrylate, Bornyl (meth) acrylate;
• Trimethyloylpropane tri (meth) acrylate and the respective hydroxy-functionalized and / or amino-functionalized and / or mercapto-functionalized (meth) acrylates on the substituent.
• These include, for example
• compositions to be polymerized can also have further unsaturated monomers which can be copolymerized with the aforementioned (meth) acrylates.
• 1-alkenes such as 1-hexene, 1-heptene
• branched alkenes such as vinylcyclohexane, 3,3-dimethyl-1-propene, 3-methyl-1-diisobutylene, 4-methylpentene-1
• acrylonitrile vinyl esters such as vinyl acetate
• Styrene substituted styrenes with an alkyl substituent in the side chain, such as. B. ⁇ -methylstyrene and ⁇ -ethylstyrene, substituted styrenes with an alkyl substituent on the ring, such as vinyltoluene and p-methylstyrene, halogenated styrenes such as monochlorostyrenes, dichlorostyrenes, tribromostyrenes and tetrabromostyrenes;
• Heterocyclic vinyl compounds such as 2-vinylpyridine, 3-vinylpyridine, 2-methyl-5-vinylpyridine, 3-ethyl-4-vinylpyridine, 2,3-dimethyl-5-vinylpyridine, vinylpyrimidine, 9-vinylcarbazole, 3-vinylcarbazole, 4- Vinyl carbazole, 2-methyl-1-vinyl imidazole vinyl oxolane, vinyl furan, vinyl thiophene, vinyl thiolane, vinyl thiazoles, vinyl oxazoles; Vinyl and isoprenyl ether; Maleic acid derivatives such as maleic anhydride, methyl maleic anhydride, maleimide, methyl maleimide and Dienes, such as divinylbenzene, and the respective hydroxy-functionalized and / or amino-functionalized and / or mercapto-functionalized compounds.
• Maleic acid derivatives such as maleic anhydride, methyl maleic anhydride, maleimide, methyl maleimide and
• these comonomers are used in an amount of 0 to 60% by weight, preferably 0 to 40% by weight and particularly preferably 0 to 20% by weight, based on the weight of the monomers, the compounds being used individually or can be used as a mixture.
• copolymers can also have a hydroxy and / or amino and / or mercapto functionality in the substituent.
• Such monomers include vinylpiperidine, 1-vinylimidazole, N-vinylpyrrolidone, 2-vinylpyrrolidone, N-vinylpyrrolidine, 3-vinylpyrrolidine, N-vinylcaprolactam, N-vinylbutyrolactam, hydrogenated vinylthiazoles and hydrogenated vinyloxazoles.
• These monomers are preferably used such that the polymer obtained therefrom has a glass transition temperature in the range from -48 ° C. to 105 ° C., in a preferred embodiment from 15 to 85 ° C.
• the polymer containing hydroxyl groups and / or amino groups and / or mercapto groups preferably has a number average molecular weight greater than or equal to 5,000 g / mol and less than or equal to 100,000 g / mol, particularly preferably greater than or equal to 7,000 g / mol and less than or equal to 80,000 g / mol and very particularly preferably greater than or equal to 10,000 g / mol and less than or equal to 60,000 g / mol.
• the polymer containing hydroxyl groups and / or amino groups and / or mercapto groups has a hydroxyl number greater than or equal to 4 and less than or equal to 80, particularly preferably greater than 6 and less than 60 and very particularly preferably greater than 8 and less than 40, without this being intended to impose a restriction.
• the hydroxyl number indicates how many milligrams of potassium hydroxide are equivalent to the amount of acetic acid that is bound by 1000 mg of substance during acetylation. Since acetylation involves the introduction of an acetyl group into organic compounds which contain OH, SH and NH 2 groups, SH and NH 2 groups are also detected by the hydroxyl number.
• the polymer containing hydroxyl groups and / or amino groups and / or mercapto groups can have a hydroxyl number of preferably less than or equal to 40,000 for a number-average molecular weight greater than or equal to 25,000 g / mol, and for a number-average molecular weight greater than 25,000 g / mol Mol and less than or equal to 60,000 g / mol have a hydroxyl number of preferably less than or equal to 20 and, with a number average molecular weight greater than 60,000 g / mol and less than or equal to 100,000 g / mol, a hydroxyl number of preferably less than or equal to 10, without being restricted thereby should be done.
• the required polydispersity D of the polymer containing hydroxyl groups and / or amino groups and / or mercapto groups of less than 1.8, preferably D less than 1.6, particularly preferably D less than 1.3, can be obtained in different ways.
• the polymer containing hydroxyl groups and / or amino groups and / or mercapto groups obtained, in the event that it has a polydispersity D greater than, for example, 1.6 can be fractionated such that individual fractions with a polydispersity D less than 1, 6 can be obtained.
• This fractionation according to the molecular weight takes place with the aid of physical separation methods and is described, for example, in GB 1, 000.185 and DE 3242130.
• the theoretical foundations for this separation process are, for example, Hans Georg Elias, Macromolecules, Volume 2, 6th edition, Weinheim 2001, page 311-319.
• a reactive hot-melt adhesive is particularly preferred, characterized in that the polymer which contains hydroxyl groups and / or amino groups and / or mercapto groups is produced by a polymerization mechanism which enables a polydispersity D of less than 1.8.
• Particularly preferred polymerization methods here are ionic polymerization, RAFT polymerization or ATRP.
• Catalytic polymerization methods using organometallic complexes can also be used according to the invention.
• the mechanism of ionic polymerization is generally known in the literature (see Hans Georg Elias, Macromolecules, Volume 1, 6th Edition, Weinheim 1999, pages 214-261) and will not be explained further here.
• the mechanism of ionic polymerization enables the molecular weight and the molecular weight distribution to be controlled in a polymerization.
• ATRP Atom Transfer Radical Polymerization
• a transition metal compound is reacted with a compound that has a transferable atomic group.
• the transferable atomic group is transferred to the transition metal compound, whereby the metal is oxidized.
• This reaction forms a radical that adds to ethylenic groups.
• the transfer of the atomic group to the transition metal compound is reversible.
• a controlled polymerization system is formed, whereby the structure of the polymer, the molecular weight and the molecular weight distribution can be controlled.
• Theoretical foundations of this polymerization mechanism are explained in: Hans Georg Elias, Macromolecules, Volume 1, 6th Edition, Weinheim 1999, page 344. Application examples are disclosed in WO 98/40415, WO 00/47634 and WO 00/34345, to which express reference is made for purposes of disclosure.
• the ATRP can be used as follows:
• the initiators for ATRP can be described by the formula Y- (X) m , where Y is the core molecule that comprises the polymer. The rest of Y is believed to form radicals.
• the radical X represents a transferable atom or a transferable atom group and m represents an integer in the range from 1 to 10, depending on the functionality of the group Y. If m> 1, the different transferable atom groups X can have a different meaning. If the functionality of the initiator is> 2, star-shaped polymers are obtained.
• Preferred transferable atoms or atom groups are halogens, such as Cl, Br and / or J.
• group Y is believed to form radicals that serve as starting molecules, which radical attaches to the ethylenically unsaturated monomers.
• the group Y therefore preferably has substituents or groups which can stabilize radicals. These substituents include - CN, -COR and -C0 2 R, where R each represents an alkyl or aryl radical, aryl and / or heteroaryl groups.
• Alkyl radicals are saturated or unsaturated, branched or linear hydrocarbon radicals with 1 to 40 carbon atoms, such as, for example, methyl, ethyl, propyl, butyl, pentyl, 2-methylbutyl, pentenyl, cyclohexyl, heptyl, 2-methylheptenyl, 3-methylheptyl, octyl, nonyl, 3-ethylnonyl, decyl, undecyl, 4-propenylundecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, cetyleicosyl, docosyl and / or eicosyltetratriacontyl.
• Aryl radicals are cyclic, aromatic radicals which have 6 to 14 carbon atoms in the aromatic ring. These radicals can be substituted. Substituents are, for example, linear and branched alkyl groups with 1 to 6 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, 2-methylbutyl or hexyl; Cycloalkyl groups such as cyclopentyl and cyclohexyl; aromatic groups such as phenyl or naphthyl; Ether groups, ester groups and halides. In order to obtain a hydroxyl number according to the invention, copolymerization is carried out with functionalized monomers. Part of the monomers contributes to hydroxy-functionalized and / or amino-functionalized and / or mercapto-functionalized side groups.
• aromatic radicals include, for example, phenyl, xylyl, toluyl, naphthyl or biphenyl.
• heteroaryl denotes a heteroaromatic ring system in which at least one CH group is replaced by N or two adjacent CH groups by S or O, such as a residue of thiophene, furan, pyrrole, thiazole, oxazole, pyridine, pyrimidine and benzo [a] furan, which may also have the aforementioned substituents.
• the initiator is generally used in a concentration in the range from 10 " mol / L to 3 mol / L, preferably in the range from 10 " 3 mol / L to 10 "1 mol / L and particularly preferably in the range from 5 * 10 " 2 mol / L to 5 * 10 "1 mol / L without being restricted thereby.
• the ratio of initiator to monomer gives the molecular weight of the polymer if the entire monomer is reacted.
• This ratio is preferably in the range of 10 "3 to 1 to 0.5 to 1, particularly preferably in the range from 5 * 10 " 3 to 1 to 5 * 10 "2 to 1.
• catalysts which comprise at least one transition metal.
• the transferable atomic group and the catalyst reversibly form a compound, the oxidation state of the transition metal being increased or decreased. It is assumed that radicals are released or captured, so that the radical concentration remains very low.
• the addition of the transition metal compound to the transferable atomic group enables or facilitates the insertion of ethylenically unsaturated monomers into the YX or Y (M) Z -X bond, where Y and X have the abovementioned meaning and M denotes the monomers, while z represents the degree of polymerization.
• Preferred transition metals here are Cu, Fe, Cr, Ni, Co, Nd, Sm, Mn, Mo, Pd, Pt, Re, Rh, Ir and / or Ru, which are used in suitable oxidation states. These metals can be used individually or as a mixture. It is believed that these metals catalyze the redox cycles of the polymerization, for example the redox couple Cu + / Cu 2+ or Fe 2+ / Fe 3+ is effective. Accordingly, the metal compounds as halides, such as for example chloride or bromide, as alkoxide, hydroxide, oxide, sulfate, phosphate, or hexafluorophosphate, trifluoromethanesulfate added to the reaction mixture.
• halides such as for example chloride or bromide
• the preferred metallic compounds include Cu 2 0, CuBr, CuCI, Cul, CuN 3 , CuSCN, CuCN, CuN0 2 , CuN0 3 , CuBF 4 , Cu (CH 3 COO) Cu (CF 3 COO), FeBr 2 , RuBr 2 , CrCI 2 and NiBr 2 .
• the transition metals can be used as metal in the zero oxidation state, in particular in a mixture with the aforementioned compounds for catalysis, as is shown, for example, in WO 98/40415.
• the reaction rate of the reaction can be increased. It is believed that this increases the concentration of catalytically active transition metal compound by proportioning transition metals with metallic transition metal in a high oxidation state.
• the molar ratio of transition metal to initiator is generally in the range from 0.0001: 1 to 10: 1, preferably in the range from 0.001: 1 to 5: 1 and particularly preferably in the range from 0.01: 1 to 2: 1, without that this should result in a restriction.
• the polymerization takes place in the presence of ligands which can form a coordination compound with the metallic catalyst or catalysts. Among other things, these ligands serve to increase the solubility of the transition metal compound. Another important function of the ligands is that the formation of stable organometallic compounds is avoided. This is particularly important since these stable compounds would not polymerize under the chosen reaction conditions. Furthermore, it is believed that the ligands facilitate the abstraction of the transferable group of atoms.
• ligands are known per se and are described, for example, in WO 97/18247, WO 98/40415. These compounds generally have one or more nitrogen, oxygen, phosphorus and / or sulfur atoms via which the metal atom can be bonded. Many of these ligands can generally be represented by the formula R 16 -Z- (R 18 -Z) mR 17 , in which R 16 and R 17 independently denote H, C- to C 20 alkyl, aryl, heterocyclyl, which may can be substituted. These substituents include alkoxy radicals and the alkylamino radicals. R 16 and R 17 can optionally form a saturated, unsaturated or heterocyclic ring.
• Z means O, S, NH, NR 19 or PR 19 , where R 19 has the same meaning as R 16 .
• R 18 independently denotes a divalent group with 1 to 40 C atoms, preferably 2 to 4 C atoms, which can be linear, branched or cyclic, such as a methylene, ethylene, propylene or butylene group. The importance of alkyl and aryl has been explained previously.
• Heterocyclyl radicals are cyclic radicals with 4 to 12 carbon atoms, in which one or more of the CH 2 groups of the ring are replaced by hetero atom groups, such as O, S, NH, and / or NR, where the radical R, which has the same meaning, like R 16 has.
• Another group of suitable ligands can be represented by the formula
• R 1 , R 2 , R 3 and R 4 independently denote H, Ci to C 2 o alkyl, aryl, heterocyclyl and / or heteroaryl radical, the radicals R 1 and R 2 or R 3 and R 4 together can form a saturated or unsaturated ring.
• Preferred ligands here are chelate ligands which contain N atoms.
• the preferred ligands include triphenylphosphine, 2,2-bipyridine, alkyl-2,2-bipyridine, such as 4,4-di- (5-nonyl) -2,2-bipyridine, 4,4-di- (5 -heptyl) -2,2 bipyridine, tris (2-aminoethyl) amine (TREN), N > N, N ', N ", N" -pentamethyldiethylenetriamine, 1, 1, 4,7,10,10-hexamethyltriethlyentetramine and / or tetramethylethylenediamine.
• TREN (2-aminoethyl) amine
• N > N, N ', N ", N" -pentamethyldiethylenetriamine 1, 1, 4,7,10,10-hexamethyltriethlyentetramine and / or tetramethylethylenediamine.
• Further preferred ligands are described, for example, in WO 97/476
• ligands can form coordination compounds in situ with the metal compounds or they can first be prepared as coordination compounds and then added to the reaction mixture.
• the ratio of ligand to transition metal depends on the denticity of the ligand and the coordination number of the transition metal. In general, the molar ratio is in the range 100: 1 to 0.1: 1, preferably 6: 1 to 0.1: 1 and particularly preferably 3: 1 to 0.5: 1, without any intention that this should impose a restriction.
• the monomers, the transition metal catalysts, the ligands and the initiators are selected depending on the desired polymer solution.
• a high rate constant of the reaction between the transition metal-ligand complex and the transferable atomic group is believed to be essential for a narrow molecular weight distribution. If the rate constant of this reaction is too low, the concentration of radicals becomes too high, so that the typical termination reactions occur, which are responsible for a broad molecular weight distribution.
• the exchange rate depends, for example, on the transferable atom group, the transition metal, the ligands and the anion of the transition metal compound. Those skilled in the art will find valuable information on the selection of these components, for example, in WO 98/40415.
• the polymerization can be carried out under normal pressure, negative pressure or positive pressure.
• the polymerization temperature is also not critical. In general, however, it is in the range from -20 ° to 200 ° C, preferably 0 ° to 130 ° C and particularly preferably 60 ° to 120 ° C.
• the polymerization can be carried out with or without a solvent.
• solvent is to be understood broadly here.
• Reversible addition fragmentation chain transfer (RAFT) polymerization is also based on a radical mechanism with transfer reactions and, like the ATRP, is an important polymerization technique for producing polymers with a narrow molecular weight distribution and a controlled structure. This mechanism is described in WO 98/01478 and EP 0 910 587, to which express reference is made for purposes of disclosure is taken. Further application examples are disclosed in EP 1 205492.
• both the urethane prepolymers and a product obtainable from mixing the compound having free isocyanate groups with the polymer containing hydroxyl groups and / or amino groups and / or mercapto groups have a ratio of isocyanate equivalents to hydroxyl and / or amino and / or mercapto equivalents, also known as the Isocyanafmdex, of greater than 1 and preferably not greater than 3.
• An isocyanate index greater than 3 results in a high content of free isocyanate in the finished adhesive, which leads to the appearance of toxic vapors when the adhesive is heated to the processing temperature.
• the isocyanate index can be set, for example, in the polycondensation of compounds with free isocyanate group and polyhydroxy, polyamino or polymer capto compounds by a person skilled in the art by reacting these compounds with one another in a specific ratio.
• the mixture can be used directly to make a reactive hot melt adhesive as described above, the Adhesive formulations, if desired, additives such as plasticizers, compatible tackifiers, catalysts, fillers, antioxidants, pigments, stabilizers and adhesion promoters based on thiol / silane can be added.
• additives such as plasticizers, compatible tackifiers, catalysts, fillers, antioxidants, pigments, stabilizers and adhesion promoters based on thiol / silane can be added.
• the reactive hot-melt adhesives obtained in this way are preferably processed at temperatures of approximately 120 ° C., without this being intended to restrict the temperature range during processing.
• These reactive hotmelt adhesives preferably have viscosities at a temperature of 120 ° C., measured according to Brookfield, in the range from 3 to 50 Pa.s, preferably from 3 to 20 Pa.s.
• the reactive hot melt adhesives show excellent properties. This includes in particular that the adhesives have excellent shear strength after final curing. After 7 days of curing at room temperature under normal atmospheric humidity, the shear strength is preferably greater than 10 MPa.
• These reactive hot melt adhesives also have excellent viscosity stability at 130 ° C. After 16 hours at 130 ° C., they preferably only show a viscosity increase of less than 50%.
• the extractable proportion of an adhesive was determined after curing. For this purpose, they were subjected to Soxlet extraction with methylene chloride over a period of 6 hours. The samples thus treated were then dried at 75 ° C. and the weight loss compared to the starting adhesive was determined by weighing.
• the extractable fraction determined in this way is preferably less than 10 for adhesive compositions according to the invention Percentage by weight, based on the initially used, hardened adhesive.
• these reactive hot melt adhesives can have an open time in which the adhesive can be processed of greater than 400 seconds.

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• Organic Chemistry (AREA)
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• Polyurethanes Or Polyureas (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

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