Foremost of concern among the thermal properties of a cured epoxy system is the glass transition temperature, designated as Tg ("T-sub-g"). These polyoxyalkylene polyamines can be prepared by known methods as disclosed in U.S. Pat. Preferred lower alkyl groups include methyl, ethyl, n-propyl and n-butyl.The polyether dicarbamate compounds are formed by the reaction of a hydroxyalkyl carbamate compound with a polyoxyalkylene diamine having a molecular weight value such that the resultant dihydroxyalkyl carbamate containing product has a molecular weight of from about 2000 to about 3000 at temperatures in the range from about 25° C. to about 150° C. in a molar ratio of about mole of hydroxyalkyl carbamate forming compounds for each mole of terminal amine.The diamines that are useful in forming the additives are polyoxyalkylene diamines of the formula: ##STR4## wherein X is a hydrogen, a methyl radical or an ethyl radical; Z is a hydrocarbon alkylene radical having from 2 to 5 carbon atoms; and, n is an average number of from about 15 to about 25. Cycloaliphatic amines and ethyleneamines may also be blended into polyetheramines in applications where a higher Tg is needed to ensure good hardness at somewhat elevated service temperatures. The formulations and properties of the cured resins are shown in Table IV below.This example demonstrates the improved adhesive strength of the epoxy cured with the additive over the epoxy cured with the diethylene glycol bis(propylamine) alone.While the invention has been explained in relation to its preferred embodiment, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification and is intended to cover such modifications as fall within the scope of the appended claims.The adhesion properties of amine-cured epoxy resins are unexpectedly enhanced by addition of certain di-hydroxyalkyl carbamate terminated polyether additives. 3,549,592.Also known to be effective as epoxy curing agents or co-curing agents are various ureas and substituted ureas, such as those disclosed in U.S. Pat. For those formulations that have met the necessary cost and processing requirements, the final performance/suitability of amine-cured epoxy formulations will depend upon their mechanical, thermal and physical properties. For most applications, formulations are best chosen to provide glass transition temperatures that are only slightly higher than the expected service temperature. Some Tg value ranges for several different classes of amines are shown in Table 1. Curing, or crosslinking, is the mechanism in which a functional entity (single molecule or functionality part of an oligomer, pre-polymer or polymer) reacts during the polymerization process with the other elements to be incorporated in the new polymer chains system.
Though other classes of compounds (e.g., anhydrides, phenolic resins and Lewis acids) are used as hardeners for some applications, the breadth of performance imparted by amine hardeners is unmatched. The most preferred polyoxyalkylene polyamine is a polyoxypropylene diamine having a molecular weight of about 230.Another preferred class of polyoxyalkylene polyamines can be depicted by the formula: ##STR2## wherein X, Z, n and r are defined as above and y is 2 or 3.
Nos.
No. Since 1928, the year when the first patent for silanes was granted, Evonik and its predecessors received more than 400 exclusive patents. Generally, those curing agents having at least three reactive amino hydrogens are useful.Exemplary of those amines which can be utilized are alkylene polyamines such as diethylene triamine, triethylene tetramine and the like; oxyalkylene polyamines such as polyoxypropylene, di- and triamine and diamino derivatives of ethylene glycol, such as 1,13-diamino 4,7,10-trioxatridecane.Additionally, aromatic amine curing agents are useful, such as the alkylene-linked polyphenyl amines, phenylene diamines and polycyclic or fused aromatic primary amine compounds. In several applications, such acceleration is beneficial, especially when an epoxy resin is used as an adhesive in flammable environment, thus making elevated temperature cure inconvenient or even hazardous. Generally the number of equivalents of amine groups is from about 0.8 to about 1.2 times the number of epoxide equivalents present in the curable epoxy resin composition, with a stoichiometric amount being preferred.
The resins are characterized by epoxide groups which are cured by reaction with certain catalysts or curing agents to provide cured epoxy resin compositions with certain desirable properties. In this discussion, thermal properties are singled out from other physical properties because of their significant effect on the cured resin mechanical properties.
400 with an amine equivalence of about 70. When choosing between hardeners that have nominally similar processing and performance characteristics, one should not simply go by price alone, but rather, do a calculation, taking into account the cost per pound (or perhaps, unit volume) of the final, cured material.
Adduction of hydrophilic polyetheramines has been used to create reactive surfactants, thus allowing reduction or elimination of un-bound surfactant additives, which may migrate over time and change performance (Figure 3). Nearly all amine hardeners appear to readily absorb atmospheric carbon dioxide. The preferred resins comprise polyglycidyl ethers of a polyhydric phenols cured by incorporating therein a curing amount of a polyoxyalkylenepolyamine of molecular weight from about 200 to 500 and an accelerator combination of piperazine and an alkanolamine, the combination having a combined weight ratio of between about 1:8 to 1:1. A mechanical force moves the media at a rapid speed creating a shear force by collisions and rolling movements.With the increasing regulatory & environmental requirements and the growing expectations of end users, the development of a high-performance water-borne coating system has become a challenge.