Low formaldehyde emission urea-formaldehyde resins containing a melamine additive
AssigneeBorden, Inc.
InventorsDavid W. Shiau, Eric Smith
Life of this patent
Estimating the term…
Abstract
A melamine-urea-formaldehyde resin characterized by a low rate of formaldehyde emission when cured. Made by a process where the initial reaction mixture has an F/U molar ratio of from about 3:1 to about 1:1, and undergoes a methylolation reaction at an alkaline pH. Preferably at least some of the melamine is present in the initial reaction mixture. The subsequent condensation is at a substantially neutral pH. Has a final F/U molar ratio of 1.3:1 to 0.9:1, a final F/Ueq molar ratio of 1.3:1 to 0.7:1, and a melamine content of from 0.15% to 40% by weight, dry solids basis. Useful for adhesive purposes, particularly as a particleboard binder characterized by low emission rate.
Claims36
A process for adhesively securing a first item to a second using a curable melamine-urea-formaldehyde base resin, comprising
- disposing between a first item and a second item a binding amount upon curing of a curable melamine-urea-formaldehyde base resin comprising a melamine-urea-formaldehyde condensate that has a final molar ratio of formaldehyde to urea of 1.3:1 to 0.9:1, a final molar ratio of a formaldehyde to urea-equivalent of 1.3:1 to 0.7:1, and a melamine content of from 0.15% to 40% by weight of said condensate, dry solids basis, the melamine being incorporated in the resin, wherein said condensate is formed from an initial reaction mixture comprising urea and formaldehyde and having a molar ratio of formaldehyde to urea of from 3:1 to 1:1, that has undergone a methylolation reaction at an alkaline pH, been adjusted in pH to 6.0 to 8.3, had any remaining amount of urea and melamine added, then been condensed,
- then curing said resin, said cured resin being characterized by a formaldehyde emission, as determined by the two hour desiccator procedure of the National Particleboard Association, not in excess of about 0.4 micrograms per ml.
A process for making particleboard by applying to a furnish a curable melamine-urea-formaldehyde resin binder formulation in an aqueous vehicle having a pH above 7.0, said resin comprising a melamine-urea-formaldehyde condensate that has a final molar ratio of formaldehyde to urea of 1.3:1 to 0.9:1, a final molar ratio of formaldehyde to urea-equivalent of 1.3:1 to 0.7:1, and a melamine content of from 3% to 6% by weight of said condensate, based on liquid resin weight at 65% solids, the melamine being incorporated in the resin, wherein said condensate is formed from an initial reaction mixture comprising urea and formaldehyde and including at least some of the melamine and having a molar ratio of formaldehyde to urea of from 2.2:1 to 2.0:1, that has undergone a methylolation reaction at an alkaline pH, been adjusted in pH to 6.0 to 8.3, had any remaining amount of urea and melamine added, then been condensed, said formulation having a solids content of from about 45% to about 70%, an a viscosity in the range 60-800 cps, at 25.degree. C.,
- then bonding said furnish and applied binder formulation under heat and pressure and curing said resin binder,
- said finished particleboard being characterized by a formaldehyde emission, as determined by the two hour desiccator procedure of the National Particleboard Association, not in excess of about 0.4 micrograms per ml.
An improved pressed composite of lignocellulosic material bound together by a cured resin binder, which composite is characterized by reduced emission of formaldehyde, wherein said binder as applied to said lignocellulosic material comprises a curable melamine-urea-formaldehyde base resin that is formed from the methylolation reaction at an alkaline pH of an initial reaction mixture comprising urea and formaldehyde and having a formaldehyde to urea initial molar ratio of 2.2:1 to 2.0:1, that has undergone a methylolation reaction at an alkaline pH, been adjusted in pH to 6.0 to 8.3, had any remaining amount of urea and melamine added, then undergone a condensation reaction to produce a condensate that has a final molar ratio of formaldehyde to urea of 1.3:1 to 0.9:1, a final molar ratio of formaldehyde to urea-equivalent of 1.3:1 to 0.7:1, and a melamine content of from about 0.15% to about 40% by weight of said condensate, dry solids basis, the melamine being incorporated in the resin.
A melamine-urea-formaldehyde resin composition that is characterized by a pH above 7.0 and by a low rate of formaldehyde emission when fully cured, comprising, a melamine-urea-formaldehyde condensate that has a final molar ratio of formaldehyde to urea of 1.3:1 to 0.9:1, a final molar ratio of formaldehyde to urea-equivalent of 1.3:1 to 0.7:1, and a melamine content of from 0.15% to 40% by weight of said condensate, dry solids basis, the melamine being incorporated in the resin, wherein said condensate is formed from an initial reaction mixture comprising urea and formaldehyde and having a molar ratio of formaldehyde to urea of from 3:1 to 1:1, which initial reaction mixture has undergone a methylolation reaction at an alkaline pH, been adjusted in pH to 6.0 to 8.3, had any remaining amount of urea and melamine added, then been condensed.
A process for making a curable resin characterized by a reduced emission level of formaldehyde from the cured resin, comprising:
- reacting urea and formaldehyde at an initial molar F/U ratio in the range from 3:1 to 1:1, under conditions that cause methylolation to occur at an alkaline pH,
- adjusting the pH to from about 6.0 to about 8.3,
- adding any remaining amount of urea to a final F/U molar ratio of from 1.3:1 to 0.9:1, and condensing, and
- in said process, prior to condensing the reaction mixture, adding melamine in an amount of from about 0.15% to about 40% by weight of the condensate, dry solids basis, the melamine being incorporated in the resin, to attain a final F/U equivalent ratio of from 1.3:1 to 0.7:1.
Dependencies are inferred from the claim text.