Production of heat-cured dispersions for use as chipboard binders

摘要

A process for the production and use of heat-cured binder dispersions (I) based on drying vegetable oils (II), comprising reacting a mixture of (a) vegetable oil (IIA) with a linolenic acid content of more than 50%, alone or in mixtures with vegetable oil(s) (IIB) with a total linoleic/linolenic acid content of more than 50%, and with a total double bond content (DBC) of at least 0.7 mol/100 g solid, (b) a vinyl-containing dicarboxylic acid, anhydride or imide, a vinyl-containing mono- carboxylic acid or amide, or a mixture thereof, and (c) a catalyst, so that (i) the double bond content of (a) as determined by the fatty acid pattern is saturated with (b) to the extent of 80-100 (preferably 90-100, more preferably 90-98) %, (ii) the amount of (c) is 0.5-8 (preferably 1-5, more preferably 1.5-3) wt% based on (a + b), (iii) the reaction is carried out at 180-240 (preferably 200-240, more preferably 215-230) deg C for a period of 0.3-4 (preferably 0.5-3, more preferably 1-2.5) hrs., a nd (iv) the hot resin obtained, optionally after precooling to 160-180 deg C, is diluted/dissolved with 0.1-50 (preferably 1-35, more preferably 3-15) wt% carboxylic acid and cooled to 20-120 (preferably 20-90, more preferably 40-80) deg C, then (x) dispersing 2-12 (preferably 3-8) % resin mixture (iv) in a mixture of (xa) 20-70 (preferably 35-60) % of a 0.5-2% aqueous solution of emulsifier based on cellulose derivatives, (xb) 10-80 (preferably 30-60) % of a 40-65% aqueous paraffin dispersion and (xc) 1-12 (preferably 2-8) % polymeric aromatic isocyanate to give a preconcentrate, (xx) increasing the concentration of component (iv) to 12-42 (preferably 20-42) % by further dispersion after urethanisation of the isocyanate, (xxx) mixing the concentrate obtained with 25-100% optionally capped isocyanate as in (xc) (based on dry resin component in solution iv) and diluting with water to a total dry resin content of 20-50 (preferably 30-40) %, (xxxx) gluing wood chip material with 1-12 (preferably 1-5) wt% of the product (calculated as solid resin) and then (xxxxx) pressing in a hot press at 180-240 deg C and up to 4 MPa to form normal-density chipboard and treating with natural or artificial UV light during or after the cooling process.