Wood adhesives for producing particle boards
A composition based on phenolic resin comprising at least one phenolic resin, a vegetable protein hydrolysate, preferentially a wheat gluten hydrolysate, and an agent for accelerating curing, and also to the process for the production thereof.
1. A composition based on phenolic resin, characterized in that it comprises at least one phenolic resin, a wheat gluten hydrolysate, and an agent for accelerating curing selected from triacetin, butyrolactone, caprolactone and propylene carbonate; wherein the phenolic resin is a product of resinous reaction of a phenol with an aldehyde and wherein the phenol:aldehyde mole ratio is from 1:1.5 to 1:1.7.
2. The composition as claimed in claim 1 , characterized in that the phenol and the wheat gluten hydrolysate are mixed in a phenol:wheat gluten hydrolysate ratio of 3.2:1 to 7.2:1 by weight.
3. The composition as claimed in claim 1 , characterized in that the content of agent for accelerating curing is between 4% and 10% by weight of the resin solids.
4. The composition as claimed in claim 1 , characterized in that the wheat gluten hydrolysate is obtained by acid or enzymatic hydrolysis.
5. The composition as claimed in claim 1 , characterized in that the wheat gluten hydrolysate is obtained by enzymatic hydrolysis and has an average molecular weight of between 3 and 20 kDa.
6. The composition as claimed in claim 1 , characterized in that the wheat gluten hydrolysate is also deamidated.
7. A process for the formation of a composition based on phenolic resin, said phenolic resin being a product of resinous reaction of a phenol with an aldehyde, characterized in that the process comprises the following steps:
mixing phenol and a wheat gluten hydrolysate, in the presence of a base solution and of a molar excess of 10% of formaldehyde in a mixer;
heating the mixture obtained to a temperature of between 90 and 98° C. and maintaining it at this temperature for approximately 15 minutes up to one hour;
adding an additional amount of formaldehyde so as to achieve a phenol:formaldehyde ratio of 1:1.5 to 1:1.7;
continuing the reaction until a resin with a viscosity of between 0.5 and 0.8 Pa·s at 25° C. is obtained;
mixing the resin obtained with an agent for accelerating curing selected from triacetin, butyrolactone, caprolactone and propylene carbonate.
8. A rigid phenolic foam board comprising a composition as claimed in claim 1 .
9. A particle or fiber board comprising a composition as claimed in claim 1 .
10. The composition as claimed in claim 3 , characterized in that the content of agent for accelerating curing is between 6% and 8% by weight of the resin solids.
11. The composition as claimed in claim 5 , characterized in that the wheat gluten hydrolysate is obtained by enzymatic hydrolysis and has an average molecular weight of between 4 and 15 kDa.