POLYFUNCTIONAL ALCOHOLS AS CROSS-LINKERS IN PMI FOAMS

Abstract

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.

Claims

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? C.

2. The method according to claim 1, wherein an amount of the polyol in the mixture is selected such that hydroxyl number 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.

4. The method according to claim 3, wherein the diol 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 hydroxyl number 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 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.

Description

EXAMPLES

[0062] 49 parts by weight of methacrylic acid, 50 parts by weight of methacrylonitrile, 7 parts by weight of tert-butanol, 2 parts by weight of tert-butyl methacrylate, 0.22 part by weight of MgO, 0.04 part by weight of tert-butyl perpivalate, 0.036 part by weight of tert-butyl per-2-ethylhexanoate, 0.1 part by weight of tert-butyl perbenzoate, 0.103 part by weight of cumyl perneodecanoate, 50 ppm of 1,4-benzoquinone and 0.3 part by weight of Moldwiz INT20E (release agent; manufacturer: Axel Plastics), and also the amounts of polyols specified in Table 1, were mixed and the mixture was stirred until a homogeneous solution was obtained. The solution was polymerized at 41? C. for hours between two glass plates, sealed by a surrounding sealing bead, to form 2 polymer slabs 3 mm thick. After cooling and removal from the glass plates, the polymer slabs were conditioned at 115? C. for 3 hours and then foamed in a forced-air oven at 215? C. for 2 hours. The densities obtained are shown in Table 1.

TABLE-US-00001 TABLE 1 Amounts of polyol Density Example Polyol used (parts by weight) [kg/m.sup.3] comparative 0 61 example 1 example 1 ethylene glycol 0.2 70 example 2 ethylene glycol 0.8 97 example 3 ethylene glycol 1.5 109 example 4 1,10-decanediol 0.8 80 example 5 1,10-decanediol 1.5 91 example 6 glycerol 0.8 97 example 7 polyTHF2000 2 63 example 8 polyTHF2000 5 71

[0063] The formulations of the examples differ only in the nature and amount of the polyols used. It is evident that the nature and amount of the polyol used has a significant effect on the density of the PMI foam (for identical foaming temperature and foaming time [2 h]). The density of the end-product foam can therefore be adjusted merely by varying the amount and/or nature of the crosslinker.