Wood adhesive formulation

Abstract

The invention relates to a formulation comprising: —a first component which is formed from at least one isocyanate and at least one amino resin, wherein said amino resin is the condensation product of an aldehyde with a compound selected from the group comprising urea, melamine, benzoguanamine, glycoluril, acetoguanamine and mixtures thereof; and —a second component comprising at least one polyether, wherein said polyether comprises at least one ethylene oxide moiety and at least one isocyanate reactive group selected from the group comprising hydroxyl, amino, epoxy, and thiol, preferably hydroxyl.

Claims

1. A lignocellulosic body consisting of: (i) a plurality of lignocellulosic materials, (ii) a two component adhesive formulation applied onto the lignocellulosic materials for bonding the lignocellulosic materials, the two component adhesive formulation consisting of: (a) a first adhesive component which is formed from at least one isocyanate selected from hexamethylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, polymeric MDI, chlorophenylene-2,4-diisocyanate, naphthylene-1,5-diisocyanate, diphenylene-4,4′-diisocyanate, 4,4′-diisocyanate-3,3′-dimethyl-diphenyl, 3-methyl-diphenylmethane-4,4′-diisocyanate, diphenyl ether diisocyanate, cyclohexane-2,4-diisocyanate, cyclohexane-2,3-diisocyanate, 1-methylcyclohexyl-2,4-diisocyanate, 1-methylcyclohexyl-2,6-diisocyanate, bis-(isocyana-tocyclohexyl)methane, 2,4,6-triisocyanatotoluene, 2,4,4-triisocyanatodiphenylether, isophorone diisocyanate, butylene diisocyanate, trimethylhexamethylene diisocyanate, isocyanatomethyl-1,8-octane diisocyanate, tetramethylxylene diisocyanate, 1,4-cyclohexanediisocyanate, tolidine diisocyanate, and a mixture thereof and 64% by weight to 95% by weight, based on 100% by weight of the formulation of at least one amino resin, wherein said amino resin is the condensation product of an aldehyde with a compound selected from the group comprising urea, melamine, benzoguanamine, glycoluril, acetoguanamine and mixtures thereof; and (b) a second adhesive component comprising at least one polyether compound, acting as a compatibilizing agent, having an average molecular weight of from 3500 to 40000 and an average nominal functionality of 2 to 6, wherein said polyether compound comprises at least 15% by weight ethylene oxide groups based on 100% by weight of the at least one polyether compound and at least one ethylene oxide moiety and at least two isocyanate reactive groups selected from the group consisting of hydroxyl, amino, epoxy, and thiol, and wherein the polyether compound is a reaction product of ethylene oxide and a polyfunctional initiator and, optionally, at least one other cyclic oxide; and wherein the ethylene oxide content to isocyanate is of at least 10% by weight based on the combined weight of the at least one isocyanate and the at least one polyether; and (iii) optionally, an additive selected from the group comprising a hardener, a surfactant, a release agent, a wax, or a pigment.

2. The lignocellulosic body according to claim 1, wherein said amino resin is the condensation product of a compound as defined in claim 1 with an aldehyde selected from the group comprising formaldehyde, acetaldehyde, crotonaldehyde, acrolein, benzaldehyde, and furfural.

3. The lignocellulosic body according to claim 1, wherein the polyfunctional initiator is selected from the group consisting of ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, cyclohexane dimethanol, resorcinol, bisphenol A, glycerol, trimethylolopropane, 1,2,6-hexantriol, pentaerythritol and mixtures thereof.

4. The lignocellulosic body according to claim 3, wherein the at least one other cyclic oxide is propylene oxide.

5. The lignocellulosic body according to claim 1, wherein the at least one isocyanate is present in an amount of at least 0.5% by weight based on 100% by weight of the total adhesive formulation.

6. The lignocellulosic body according to claim 1, wherein the at least one polyether is present in an amount of at least 0.01% by weight based on 100% by weight of the total adhesive formulation.

7. The lignocellulosic body according to claim 1, wherein the adhesive formulation has an ethylene oxide content greater than 30% by weight based on the combined weight of the at least one isocyanate and the at least one polyether.

8. The lignocellulosic body according to claim 1, wherein the additive is present in an amount of at least 0.01% by weight based on the total adhesive formulation.

9. The lignocellulosic body according to claim 1, where the additive is an ammonium salt.

Description

Comparative Example 1

(1) 2.10 g of polymeric methylene diphenyl isocyanate pMDI (Suprasec 5025) was mixed with 7.90 g of UF and 0.2 g of ammonium sulfate (hardener) at 25° C.

(2) There was no polyether additive, and the EO content to MDI was 0.0%. Gel time was 1 min 40 sec and the gelation exotherm was 100.0° C.

Comparative Example 2

(3) 1.80 g of polymeric methylene diphenyl isocyanate pMDI (Suprasec 5025) was mixed with 8.00 g of UF and 0.2 g of ammonium sulfate (hardener) at 25° C. Thereafter, 0.20g of dimethoxy polyethylene oxide M.sub.w 500 (DME 500) was added to this mixture and stirred at 25° C.

(4) The added polyether did not comprise isocyanate-reactive functional groups, and the EO content to MDI was 10.0%. Gel time was 1 min 55 sec and the gelation exotherm was 100.0° C.

Example 3

(5) 1.80 g of polymeric methylene diphenyl isocyanate pMDI (Suprasec 5025) was mixed with 8.00 g of UF and 0.2 g of ammonium sulfate (hardener) at 25° C. Thereafter, 0.20 g of polyethylene glycol monomethyl ether M.sub.w 500 (MoPEG 500) was added to this mixture and stirred at 25° C.

(6) The added polyether was a mono-reactive polyether with EO content to MDI of 10.0%. Gel time was 1 min 40 sec and gelation exotherm was 90.0° C.

Example 4

(7) 1.90 g of polymeric methylene diphenyl isocyanate pMDI (Suprasec 5025) was mixed with 6.50 g of UF and 0.2 g of ammonium sulfate (hardener) at 25° C. Thereafter 0.80 g of a poly(oxyethyl/oxypropyl)polyether M.sub.w 3500 (Daltocel F442) was added to this mixture and stirred at 25° C.

(8) The added polyether was a di-reactive polyether with EO content to MDI of 22.0%. Gel time was 1 min 26 sec and gelation exotherm was 79.0° C.

Example 5

(9) 1.90 g of polymeric methylene diphenyl isocyanate pMDI (Suprasec 5025) was mixed with 6.50 g of UF and 0.2g of ammonium sulfate (hardener) at 25° C. Thereafter, 1.60 g of a poly(oxyethyl/oxypropyl)polyether M.sub.w 3500 (Daltocel F442) was added to this mixture and stirred at 25° C.

(10) The added polyether was a di-reactive polyether with EO content to MDI of 33.0%. Gel time was 1 min 26 sec and gelation exotherm was 60.0° C.

(11) Compared to the comparative examples 1 and 2, the results obtained in the examples according to embodiments of the invention showed that the combination of UF and MDI with a polyether improved miscibility of the mixture. In addition, the ethylene oxide content in the polyether or in the final mixture significantly reduced the gel time and/or the temperature needed to start the cure reactions. In this way, glue (adhesive) properties can be controlled through choice of the polyether in the composition as claimed.

(12) It is to be understood that although preferred embodiments and/or materials have been discussed for providing embodiments according to the present invention, various modifications or changes may be made without departing from the scope and spirit of this invention.