Hybrid adhesive and the use thereof in engineered wood boards

1. A hybrid adhesive, for use in the production of wood-based materials, comprising

at least one polycondensation adhesive being a polyamide, a polyester, and/or a formaldehyde condensate adhesive,

at least one polyaddition adhesive being polycyanurate, and/or polyurethane adhesive, and

at least one oxidic, hydroxidic or oxihydroxidic nanoparticle with a size between 2 and 100 nm,

wherein the at least one nanoparticle is a SiO 2 -based nanoparticle, which is used in the hybrid adhesive in an amount between 1 and 15 wt %;

wherein the at least one nanoparticle is modified with at least one compound of the general Formula (I)

R a SiX (4-a)   (I),

or the general Formula (II)

O b X c (OH) d R e SiO (4-b-c-d-e)/2   (II),

wherein X is H, OH or a hydrolyzable radical selected from the group consisting of halogen, alkoxy, carboxy, amino, monoalkylamino or dialkylamino, aryloxy, acyloxy, and alkylcarbonyl,

wherein R is a non-hydrolyzable organic radical R selected from the group consisting of substituted and non-substituted alkyl, substituted and non-substituted aryl, substituted and non-substituted alkenyl, substituted and non-substituted alkynyl, substituted and non-substituted cycloalkyl, and combination thereof, which can be interrupted by —O—,

wherein R includes at least one functional group Q which is selected from the group consisting of epoxy, hydroxy, ether, carboxy, alkynyl, acrylic, acryloxy, methacrylic, methacryloxy, mercapto, cyano, alkoxy, isocyanato, aldehyde, alkylcarbonyl, acid anhydride and phosphoric acid group, and

wherein the substituent(s) for the substituted alkyl R are selected from the group consisting of epoxy, hydroxy, ether, carboxy, alkynyl, acrylic, acryloxy, methacrylic, methacryloxy, mercapto, cyano, alkoxy, isocyanato, aldehyde, alkylcarbonyl, acid anhydride, phosphoric acid group, and combinations thereof,

R and X each can be the same or different from each other, and

a=1, 2, 3,

b, c, d=0 or 1, and

e=1, 2, 3.

2. The adhesive according to claim 1 , wherein X is selected from the group consisting of fluorine, chlorine, bromine, iodine, C 1-6 alkoxy, methoxy, ethoxy, n-propoxy, butoxy, C 6-10 aryloxy, phenoxy, C 2-7 acyloxy, acetoxy, propionoxy, C 2-7 alkylcarbonyl, and acetyl.

3. The adhesive according to claim 1 , wherein R is selected from the group consisting of substituted and non-substituted C 1 -C 30 alkyl, substituted and non-substituted C 5 -C 25 alkyl, substituted and non-substituted C 2 -C 6 alkenyl, substituted and non-substituted C 2 -C 6 alkynyl, and substituted and non-substituted C 6 -C 10 aryl.

4. The adhesive according to claim 1 , wherein R is selected from the group consisting of methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, t-butyl, pentyl, hexyl, cyclohexyl, vinyl, 1-propenyl, 2-propenyl, butenyl, acetylenyl, propargyl, phenyl and naphthyl.

5. The adhesive according to claim 1 , wherein the functional group Q is an epoxide, a glycidyl, a glycidyloxy or an isocyanato group.

6. The adhesive according to claim 1 , wherein the at least one polycondensation adhesive is a phenol-formaldehyde-resin adhesive (PF), a cresol/resorcinol-formaldehyde-resin adhesive, urea-formaldehyde-resin adhesive (UF) and/or melamine-formaldehyde-resin adhesive (MF).

7. The adhesive according to claim 1 , wherein the at least one polyaddition adhesive is a polyurethane adhesive on the basis of polydiphenylmethane diisocyanate (PMDI).

8. The adhesive according to claim 1 , wherein the at least one nanoparticle has a size between 2 and 50 nm.

9. A method for the production of an adhesive according to claim 1 , comprising the following steps:

a) incorporating at least one nanoparticle into a dispersion or suspension of at least one polyaddition adhesive,

b) addition of at least one first compound of the general Formula (I) and/or (II) and possibly a polymerization starter,

c) addition of at least one second compound different from the first compound of the general Formula (I) and/or (II),

d) optionally addition of at least one catalyst, in particular an acid, and

e) mixing the dispersion prepared in step c) or d) with at least one polycondensation adhesive.

10. A method for the production of an adhesive according to claim 1 , comprising the following steps:

a) mixing at least two different compounds of the general Formulae (I) and (II),

b) addition of at least one nanoparticle to the mixture prepared in step a) and optionally addition at least one catalyst, in particular an acid,

c) addition of at least one polycondensation adhesive, and

d) final addition of at least one polyaddition adhesive.

11. An engineered wood board, in particular a wood particle board and/or wood fiber board, comprising at least one adhesive according to claim 1 .

12. A method for the production of an engineered wood board according to claim 11 , comprising the following steps:

a) producing wood chips from suitable timber,

b) chipping the wood chips to wood particles or wood fibers,

c) temporary storage of the wood particles or wood fibers, in particular in silos or bunkers,

d) drying the wood particles or wood fibers,

e) sorting or classifying the wood particles or wood fibers corresponding to the size of the wood particles or wood fibers,

f) possibly further comminution of the wood particles or wood fibers,

g) applying the wood particles or wood fibers onto a transport belt by means of pneumatic and/or spreader classification,

h) compressing the wood particles or wood fibers arranged on the transport belt,

wherein at least one adhesive according to claim 1 can be added before, during and/or after any of the steps b) to h).

13. The method according to claim 12 , wherein the adhesive is sprayed onto the wood particles or wood fibers.

14. A method of adhering wood based materials comprising applying the adhesive of claim 1 to a wood based material.

15. A method according to claim 14 , wherein the adhesive is applied to the wood based material to prepare an engineered wood board.