Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2001-08-28
2003-08-12
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S297400, C428S320200, C525S480000, C525S481000, C528S163000
Reexamination Certificate
active
06605354
ABSTRACT:
This invention relates to a high nitrogen containing triazine-phenol-aldehyde (T-P-A) condensate which has a low melt viscosity.
The high nitrogen, e.g., 15%-23%, condensate of this invention is an effective curing agent and also provides fire-retardant properties to epoxy compositions. The low melt viscosity of the condensate affords reduced viscosity solutions with better wetting of re-enforcement materials such as glass cloth and fiber, thereby providing composites, e.g., laminates, for printed wire boards with superior properties. The condensate of this invention is also suitable in the manufacture of molded products as well as for other uses enjoyed by phenolic novolac resins.
BACKGROUND AND PRIOR ART
As flame-retardants for epoxy as well as other resins, addition-type flame retardants such as low molecular weight halides, antimony trioxide and phosphorus compounds are often used. However, such addition type flame-retardants not only adversely influence the properties of the resins to which the flame retardants are added but can cause problems due to their toxicity. More recently halogenated polyhydroxystyrene as well as certain triazine-phenol-aldehyde (T-P-A) condensates have been described as flame retardant additives for epoxy resins. However, the halogenated polymers give off hydrogen halides during a fire whereas the T-P-A condensates have a number of shortcomings.
A major shortcoming of the prior art T-P-A condensates is their high melt viscosity and low nitrogen content. Illustratively, T-P-A condensates used as flame retardants with epoxy resins in both U.S. Pat. Nos. 5,955,184 and EP 0877040 B1 have melt viscosities which are significantly higher than those of the instant invention and nitrogen contents which are below those of the instant invention.
SUMMARY OF THE INVENTION
In one aspect, this invention is directed to the preparation of a triazine-phenol-aldehyde (T-P-A) condensate which has a melt viscosity of less than about 2,000 cps at 175° C. and contains at least 15% by weight of nitrogen. Such a novel condensate can be prepared by any one of the following four methods.
(1) A first method referred to herein as the high basicity amine catalyst method which comprises the following:
(a) Charging to a reaction vessel, a triazine, about 6 to 12 moles of a phenol for each mole of triazine, from about 0.1% to 2% of a secondary or tertiary amine having a pK basicity of at least 10, and about 2.2 to 3.5 moles of formaldehyde for each mole of triazine to form a reaction mixture. The quantity of the amine is based on the weight of phenol charged to the reaction mixture.
(b) Heating the reaction mixture at a temperature of about 40° C. to about 120° C. until the reaction mixture is substantially free of formaldehyde wherein the triazine is a member selected from the group consisting of melamine, a mixture of melamine with benzoguanamine wherein the quantity of benzoguanamine is not more than about 50% by weight of the mixture, a mixture of melamine and acetoguanamine wherein the quantity of acetoguanamine is not more than about 50% by weight of the mixture, and a mixture of melamine, benzoguanamine, and acetoguanamine wherein the quantity of benzoguanamine is not greater than about 35% by weight of the mixture, the acetoguanamine is not greater than about 35% by weight of the mixture and the melamine is at least 50% by weight of the mixture, wherein said phenol is a member selected from the group consisting of phenol itself, an alkyl phenol wherein the alkyl has from 1 to 4 carbon atoms substituted in the meta-position of the phenol, a meta-substituted alkoxy phenol having from 1 to 4 carbon atoms in the alkoxy group, and a mixture of phenol itself, the meta-substituted alkyl phenol and the meta-substituted alkoxy phenol; and
(c) after reaction of substantially all of the formaldehyde, heating the reaction mixture at a temperature of at least about 100° and reacting phenol in the reaction mixture until reaction of the phenol is substantially completed.
(2) A second method is referred to herein as the low basicity amine catalyst method.
(a) This method charges to a reactor the same quantities of triazine, phenol, formaldehyde and amine as in method (1) above to form a reaction mixture but the amine catalyst has a pK basicity value of less than 10 and the reaction mixture is heated at a temperature of about 40° C. to 80° C. to react the formaldehyde.
(b) After the reaction mixture is substantially free of formaldehyde an acid having a pK acidity value of about 0.5 to 3.8 in an amount of about 2% to 4% by weight of the reaction mixture is added to the mixture in those instances wherein the reaction mixture does not contain at least 1.5% by weight of the triazine reactant of benzoguanamine and/or acetoguanamine. When the triazine charge contains such quantity of benzoguanamine and/or acetoguanamine such acid addition is not needed. The reaction mixture is then heated at a temperature of at least about 100° C. until reaction of the phenol is substantially completed.
(3) A method referred to herein as the low temperature acid catalyst method.
(a) This method uses the same quantities of triazine, phenol and formaldehyde as in methods (1) and (2). Instead of an amine catalyst, the catalyst is that of an acid in a quantity of about 0.05% to about 0.3%, based on the weight of phenol, wherein the acid has a pK acidity value of about 0.5 to 3.8.
(b) The aldehyde content in the reaction mixture is reacted at a temperature of not higher than about 80° C., e.g., from about room temperature when the catalyst is formic acid or the phenol is liquified with water or formalin. Preferably the reaction mixture is heated at a temperature of not higher than about 80° C. such as that of about 40° C. to about 70° C. until the mixture is substantially free of aldehyde. After the reaction mixture is substantially free of aldehyde, about 2.0% to 4.0% by weight of the reaction mixture of an acid having a pK acidity of abut 0.5 to 3.8 is added to the reaction mixture, at a temperature of the reaction mixture of not higher than about 80° C. such as that of about 50° C. to 80° C. and preferably at a temperature of about 50° C. to about 70° C.
(d) The temperature of the reaction mixture is then raised to at least about 100° C. until reaction of the phenol is substantially complete.
(4) A fourth method is referred to herein as the high temperature acid catalyst method.
(a) The same quantities of triazine and phenol as in the previous three methods are charged to a reactor to form the reaction mixture. However, about 0.2% to 2% of an acid catalyst having a pK acidity of about 0.5 to about 3.8 is charged to the reaction mixture as well as only about one half of the total amount of the total quantity of 2.2 to 3.5 moles of formaldehyde for each mole of triazine.
(b) The reaction mixture is heated at a temperature of about 70° C. to 110° C. until the mixture is substantially free of formaldehyde.
(c) After the reaction mixture is substantially free of formaldehyde, the reaction mixture is heated to a temperature of about 120° to 160° C. for about 0.5 to 2.5 hours.
(d) The reaction mixture is then cooled to a temperature which does not exceed about 110° C. such as that of about 80° C. to 110° and the remainder of the formaldehyde is added;
(e) The reaction mixture is then heated to a temperature of above about 120° C. until reaction of the phenol is substantially complete.
In place of the aldehyde being substantially all formaldehyde, the above methods also comprise the substitution of up to about 20 mole percent of the formaldehyde with an equal molar quantity of another aldehyde.
In another aspect, this invention is directed to the condensate prepared by the above described methods.
In still another aspect, this invention provides a composition comprising a high (at least 15%) nitrogen containing triazine-phenol-aldehyde (T-P-A) condensate with melt viscosity up to about 2,000 cps at 175° C. and a solubility at about 25° C. of at least 80% by weight by the 90:10 methanol:water solvent method.
In yet ano
Borden Chemical, Inc.
Dawson Robert
Feely Michael J
Maskas George P.
Van Wyck Kenneth P.
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