Polyfunctional alcohols as cross-linkers in PMI foams
The invention relates to the production of PMI foams, more particularly to their formulating ingredients, which lead to particular facility in adjusting the density at given foaming temperature.
1. A method for producing a foam of poly(meth)acrylimide, the method comprising:
polymerizing a mixture comprising (meth)acrylonitrile, (meth)acrylic acid, a polyol having between 2 and 10 hydroxyl groups, at least one initiator and at least one blowing agent to form a slab or a powder,
optionally temperature-conditioning the mixture, and
then foaming the mixture at a temperature between 120 and 300° CU,
wherein crosslinking does not occur until during foaming.
2. The method according to claim 1 , wherein an amount of the polyol in the mixture is selected such that a hydroxyl number of the mixture is between 0.0008 and 0.2 mol of OH groups/100 g of polymer.
3. The method according to claim 1 , wherein the polyol is a diol or a higher polyol.
4. The method according to claim 3 , wherein the diol or the high polyol is ethylene glycol, 1,10-decanediol, beta-hydroxyalkylamides, OH-telechelic polytetrahydrofuran having an average molar mass between 500 and 8000 g/mol, or comprises an OH-telechelic polyolefin, a polycarbonate, a polyoxymethylene, a polyethylene glycol, a polypropylene glycol, a polyglycerol or a polyester each having a molar mass between 200 and 10 000 g/mol.
5. The method according to claim 1 , wherein the polyol comprises glycerol, pentaerythritol, xylitol, alditols or another sugar alcohol.
6. The method according to claim 1 , wherein
an amount of the polyol in the mixture is selected such that a hydroxyl number of the mixture is between 0.001 and 0.1 mol of OH groups/100 g of polymer.
7. The method according to claim 1 , wherein the mixture consists of
20 to 60 wt % of (meth)acrylonitrile,
40 wt % to 78 wt % of (meth)acrylic acid,
0 to 20 wt % of further monofunctional, vinylically unsaturated monomers,
one or more polyols in an amount such that a hydroxyl number of the mixture is between 0.0008 and 0.2 mol of OH groups/100 g of polymer,
1 wt % to 15 wt % of a blowing agent, of a copolymerizable blowing agent or of a blowing agent mixture,
optionally 0 to 5 wt % of further crosslinkers,
an initiator system, and
customary additional substances.
8. A space, air, water, rail or land vehicle, a wind turbine or sports equipment, comprising: a foam of poly(meth)acrylamide obtained from the method according to claim 1 .
9. A bead foam, sandwich material, or pultrudate, comprising: a foam of poly(meth)acrylamide obtained from the method according to claim 1 .
10. A space, air, water, rail or land vehicle, a wind turbine or sports equipment, comprising: the bead foam, sandwich material, or pultrudate according to claim 9 .