Reactive binding agent with an extended pot life

Details Reactive binding agent with an extended pot life Reactive binding agent with an extended pot life

2001-03-02

2003-04-15

Gorr, Rachel (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From reactant having at least one -n=c=x group as well as...

C528S056000, C528S058000, C528S065000, C528S079000

Reexamination Certificate

active

06548615

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to reactive compositions (reactive binders) based on isocyanate-containing compounds and polyols with an extended pot life at room temperature and high reactivity at elevated temperature and to the use of these compositions for coating substrates of any type at all, primarily flexible substrates such as textiles and leather or for use in a reaction injection moulding (RIM) process.
Low solvent or solvent-free reactive compositions based on NCO prepolymers with long pot lives have been known for some time, such as, for instance, the combination of blocked NCO prepolymers and cycloaliphatic diamines. In this case, a ketoxime-blocked NCO prepolymer based on aromatic polyisocyanates is mixed with a diamine as a chain extender and then cured by heating with elimination of the ketoxime and optionally evaporation of the solvent. Reactive compositions of this type for the coating of flexible substrates are described, for example, in DE-A 29 02 090.
Reactive compositions based on ketoxime-blocked prepolymers of aliphatic polyisocyanates are also known (EP-A 65 688). However, these require much higher curing temperatures than systems based on aromatic polyisocyanates, which is the reason why reactive systems based on aliphatic polyisocyanates have not hitherto been widely used in industry.
Thus, elimination of the ketoxime takes place during curing of the described systems, which in itself means that the vent gas has to be treated, even when the systems do not contain solvents. In addition, the blocking of free NCO groups leads to additional urethane groups and thus to increased viscosity of the prepolymers, which in most cases has to be compensated for by the addition of solvents.
In contrast, reactive binders which do not eliminate constituents are described in EP-A 825 209. These are excellent for the coating of textiles and other two-dimensional substrates due to their favourable reaction kinetics and very good mechanical film properties.
These are isocyanate prepolymers which are crosslinked with certain diols as chain extenders. These coating agents have pot lives of 6 to 16 hours when catalyst systems consisting of organic tin compounds and thiol group-containing compounds such as are described in U.S. Pat. No. 4,788,083 are used.
Now, the object was to extend the pot lives to 24 hours while retaining the same curing conditions in order to ensure that the reactive binder can be worked with on two consecutive days.
Surprisingly, it has now been found that the pot life of reactive binders consisting of isocyanate-containing compounds and polyols, catalysed by a combination of tin compounds and thiol group-containing compounds, can be considerably extended by adding small amounts of hydrolysable halogen compounds.
SUMMARY OF THE INVENTION
Thus, the invention provides reactive compositions consisting of isocyanate-containing compounds A and polyols B, characterised in that they also contain a catalyst combination consisting of
C) an organic tin or bismuth compound,
D) a thiol group-containing compound or a polyphenol which is able to react with an isocyanate group in the presence of a tertiary amine as activator and with adjacent hydroxyl groups or mixtures,
E) a hydrolysable halogen compound,
wherein the molar ratio SH and/or OH:metal is 2 to 500 and the molar ratio halogen/metal is 0.05 to 10.
DETAILED DESCRIPTION OF THE INVENTION
The molar ratio SH/metal is preferably between 2 and 5, which means that the molar ratio halogen/metal preferably takes on a value between 0.2 and 4.
The compositions may be cured either by the effect of heat or by activators (amines), as described in U.S. Pat. No. 4,788,033. Thermal curing at temperatures of 60 to 190° C., however, is preferred.
A number of conventional tin catalysts may be used as organic tin compounds C). Conventional tin catalysts include, for example, tin(II) octoate, dibutyltin dicarboxylates such as dibutyltin dioctoate, tin mercaptides such, as dibutyltin dilauryl mercaptide or dialkyltin bis-(2-ethylhexyl)-mercaptoacetate, tin(II) acetate, tin(IV) oxide, tin(II) citrate, tin(II) oxalate, tetraphenyltin, tetrabutyltin, tri-n-butyltin acetate, di-n-butyltin dilaurate, and mixtures thereof.
A number of conventional bismuth catalysts may be used as organic bismuth compounds C). Conventional bismuth catalysts include, for example, bismuth tricarboxylates, e.g. acetates and oleates, bismuth nitrate, bismuth sulfide, basic bismuth dicarboxylates, e.g. bismuthyl neodecanoate, bismuth subsalicylate and bismuth subgallate, and mixtures thereof.
A number of monofunctional and polyfunctional mercaptans are successfully used as compounds which contain thiol groups (SH compounds, mercaptans) D), according to the invention. Examples of suitable mercaptans are:
trimethylolpropane tri-(3-mercaptopropionate), pentaerythrityl tetra-(3-mercaptopropionate), glycol di-(3-mercaptopropionate), glycol dimercaptoacetate, trimethylolpropane trithioglycolate, mercaptodiethyl ether, ethanedithiol, thiolactic acid, mercaptopropionic acid and esters thereof, thiophenol, thioacetic acid, 2-mercaptoethanol, 1,4-butanedithiol, 2,3-dimercaptopropanol, toluene-3,4-dithiol, &agr;,&agr;′-dimercapto-p-xylene, thiosalicylic acid, mercaptoacetic acid and esters, 2-ethylhexyl mercaptoacetate, dodecanedithiol, didodecanedithiol, dithiophenol, di-p-chlorothiophenol, dimercaptobenzothiazole, 3,4-dimercaptotoluene, allyl mercaptan, benzyl mercaptan, 1,6-hexanedithiol, 1-octanethiol, p-thiocresol, 2,3,5,6-tetrafluorothiophenol, cyclolhexyl mercaptan, methyl thioglycolate, various mercaptopyridines, dithioerythritol, 6-ethoxy-2-mercaptobenzothiazole and d-limonene dimercaptan and mixtures thereof.
In addition to the monofunctional or polyfunctional mercaptan monomers or oligomers D), a number of polymeric compounds may be synthesised or modified in such a way that they contain thiol groups. Specific examples of mercaptans which may be used to prepare polymeric compounds with functional mercaptan groups for use in the formulations for reaction mixtures according to the invention are 1,4-butanedithiol, 2,3-dimercaptopropanol, toluene-3,4-dithiol and &agr;,&agr;′-dimercapto-p-xylene. Examples of other suitable mercaptan compounds are thiosalicylic acid, mercaptoacetic acid, 2-mercaptoethanol, dodecanedithiol, didodecanedithiol, dithiolphenol, di-p-chlorothiophenol, dimercaptobenzothiazole, 3,4-dimercaptotoluene, allyl mercaptan, 1,6-hexanedithiol, mercaptopropionic acid, p-thiocresol, d-limonene dimercaptan, cyclohexyl mercaptan, methyl thioglycolate, mercaptopyridines, dithioerythritol and 6-ethoxy-2-mercaptobenzothiazole.
Substantially any oligomeric or polymeric compounds may be modified in such a way that they contain thiol groups. Specific examples of mercaptan group-containing polymeric compounds may be derived from epoxy resins and epoxy-modified diglycidyl ethers of bisphenol A compounds, mercapto-functional urethanes, various aliphatic polyethylene or polypropylene glycol (diglycidyl ether) adducts and glycidyl ethers of phenol resins. Other suitable polymers with mercaptan groups are polyamide resins, e.g. condensation products of dimerised fatty acids which are reacted with a difunctional amine such as ethylene diamine followed by reaction with 3-mercaptopropionic acid. A number of acrylic resins and vinyl resins are also suitable for modification in accordance with the present invention.
Another group of compounds which has proven useful in the context of the invention is a certain class of polyphenols with adjacent hydroxyl groups which are characterised in that they react with an isocyanate group in the presence of a tertiary amine activator. In the absence of the tertiary amine catalyst, however, these polyphenols do not react with isocyanate groups over a relatively long period of time. The polyphenols which react with functional isocyanate groups in the presence of a tertiary amine activator behave like mercapto groups in the presence of tertiary amine activators. Also, heat promotes the release of an

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