The invention discloses a preparation method a
formaldehyde-
free protein-based wood
adhesive. According to the invention, fresh
plant stems and leaves are added into water, and are crushed and press-filtrated, such that a juice is obtained;
soybean meal and separated
animal protein or separated vegetable
protein are sieved by using a
sieve of 60 to 300 meshes; the meshed materials are stirred with water according to a ratio of 0-1:1-0:5-15, until a crude
protein content of the mixture is 7 to 20%; the mixture is placed in a reactor, and is stirred for 30min to 5h under a temperature of 45 to 65 DEG C and a pH value of 8.5 to 13.5, such that the mixture is subject to a reaction; when the temperature is reduced to 35 to 45 DEG C, the fresh
plant stem and leaf juice obtained through the press-
filtration step is added to the mixture of
protein and water while stirring, wherein the juice takes 0.1% to 50% of the weight of the mixture; the content of
adhesive mass crude protein is controlled, that when the
adhesive is used in a plywood, the content is 11 to 13%, and when the adhesive is used in a
fiber board, the content is 5 to 7%; the pH value of the material is regulated to 7.5 to 10.5, and the material is stirred for 15 to 45min; 0.00 to 0.50% of a
preservative is added, and
polyphenol is blended. The adhesive provided by the invention is not polluted by free
formaldehyde,
volatile phenols,
isocyanate or
synthetic resin. A conflict of protein denaturation and
hydrolysis can be regulated by using a
heat denaturation technology. When denaturation is finished, the
reaction temperature and the pH value can be reduced instantly. With the invention, the produced artificial plates satisfy an
international standard of II grade plates. After the plates are boiled for 4 hours by boiled water with a temperature of 100 DEG C, adhesive failure is not occurred.