Urea mixtures and methods for making and using same
View Patent ↗Urea mixtures and methods for making and using same are provided. In at least one specific embodiment, the urea mixture can include urea, a urea-aldehyde resin, a liquid medium, and a sugar. The urea mixture can have an aldehyde to urea molar ratio of about 0.2:1 to about 0.7:1. The urea mixture can have a sugar concentration of about 2 wt % to about 8 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar.
1. A urea mixture, comprising:
urea, a urea-aldehyde resin, a liquid medium, and a sugar, wherein the urea mixture has an aldehyde to a total urea molar ratio of about 0.2:1 to about 0.4:1, a freezing point of −12° C. to 20° C., and a sugar concentration of about 2 wt % to about 8 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar.
2. The urea mixture of claim 1 , wherein the aldehyde to the total urea molar ratio is about 0.3:1 to about 0.4:1.
3. The urea mixture of claim 1 , wherein the urea mixture has a urea concentration of about 30 wt % to about 65 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar.
4. The urea mixture of claim 1 , wherein the urea mixture has a sugar concentration of about 5 wt % to about 7 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar.
5. The urea mixture of claim 1 , wherein the urea mixture has a non-volatile solids content of about 40 wt % to about 70 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar.
6. The urea mixture of claim 1 , wherein the urea mixture does not contain melamine.
7. The urea mixture of claim 1 , wherein:
the sugar comprises a disaccharide,
the urea mixture comprises at least 40 wt % to about 70 wt % of the urea, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar, and
the urea mixture has a non-volatile solids content of at least 60 wt % to about 70 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar.
8. The urea mixture of claim 1 , wherein:
the urea-aldehyde resin comprises a urea-formaldehyde resin,
the urea-formaldehyde resin has a weight average molecular weight of about 700 to about 5,000,
the urea mixture has a urea concentration of about 30 wt % to about 65 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar,
the urea mixture has a sugar concentration of about 4 wt % to about 7 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar,
the urea mixture has a non-volatile solids content of at least 40 wt % to about 70 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar, and
the sugar comprises a disaccharide.
9. The urea mixture of claim 1 , wherein:
the urea-aldehyde resin comprises a urea-formaldehyde resin,
the urea-formaldehyde resin has a weight average molecular weight of about 700 to about 5,000,
the urea mixture has a urea concentration of about 35 wt % to about 65 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar,
the urea mixture has a sugar concentration of about 4 wt % to about 7 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar,
the sugar comprises sucrose,
the urea mixture has a viscosity of 700 cP to 2,200 cP at a temperature of about 25° C., and
the urea mixture has a non-volatile solids content of at least 60 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar.
10. The urea mixture of claim 1 , wherein the urea mixture has a viscosity of 700 cP to 2,200 cP at a temperature of about 25° C.
11. The urea mixture of claim 1 , wherein:
the urea mixture has a non-volatile solids content of at least 50 wt % to about 80 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar, and
the urea-aldehyde resin comprises a urea-formaldehyde resin.
12. The method of claim 1 , wherein:
the urea mixture has a non-volatile solids content of at least 55 wt % to about 80 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar,
the urea mixture comprises at least 40 wt % to about 70 wt % of the urea, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar, and
the urea-aldehyde resin comprises a urea-formaldehyde resin.
13. A method for making a urea mixture, comprising:
reacting an aldehyde and urea at a molar ratio of about 1.6:1 to about 2.4:1 in the presence of a liquid medium to produce a urea-aldehyde resin;
adding urea to the urea-aldehyde resin to provide an intermediate mixture comprising urea, the urea-aldehyde resin, and the liquid medium; and
adding a sugar to the intermediate mixture to produce a urea mixture comprising the urea, the urea-aldehyde resin, the liquid medium, and about 2 wt % to about 8 wt % of the sugar, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar, wherein the urea mixture has an aldehyde to a total urea molar ratio of about 0.2:1 to about 0.4:1, and a freezing point of −12° C. to 20° C.
14. The method of claim 13 , wherein the aldehyde to the total urea molar ratio of the intermediate mixture is about 0.3:1 to about 0.4:1.
15. The method of claim 13 , wherein the urea mixture has a urea concentration of about 30 wt % to about 65 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar.
16. The method of claim 13 , wherein the urea mixture has a liquid medium concentration of about 10 wt % to about 60 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar.
17. The method of claim 13 , wherein the urea mixture does not contain melamine.
18. The method of claim 13 , wherein the sugar is a monosaccharide.
19. The method of claim 13 , wherein:
the urea-formaldehyde resin is synthesized under acidic reaction conditions, and
the urea mixture has a non-volatile solids content of at least 60 wt % to about 80 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar.
20. A method for making a composite product, comprising:
contacting a plurality of lignocellulosic substrates with a resin composition, wherein the resin composition comprises an aldehyde-based resin and a urea mixture, wherein the urea mixture comprises urea, a urea-aldehyde resin, a liquid medium, and a sugar, wherein the urea mixture has an aldehyde to a total urea molar ratio of about 0.2:1 to about 0.4:1 and a freezing point of −12° C. to 20° C., and wherein the urea mixture has a sugar concentration of about 2 wt % to about 8 wt %, based on the combined weight of the urea, the urea-aldehyde resin, the liquid medium, and the sugar; and
at least partially curing the resin composition to produce a composite product.