DE2029296A1 - (meth)acrylic foams - polymerised and foamed in one operation by heating the monomer in presence of urotropine - Google Patents

Abstract

Foams with fine pores and low densities (0.11-0.54 g/cm3) suitable for decorative, insulating or adsorption purposes, also as additives to modify various fillers e.g. mortars, plastics, etc. and also in granular form when hydrophilically modified as soil improvers produced by polymerising and foaming in one operation monomers pref. of (meth)acrylic acid (opt. together with 50% of other olefinic unsat. cpds). in presence of up to equal amts of urotropine (opt. with up to equal amts of other foaming agents, pref. urea) and opt. also of initiators (peroxides, redox systems, pref. N contg. radical donors) at 0.5-5% by heating the monomers with the mentioned additives (opt. also fillers, flame retardants etc) to 30-250 degrees C in moulds or by extruding the mixture through heated jets.

Description

Process for the production of foams Object of the present invention Invention is a process for the production of foams from at least 50 % By weight of (meth) acrylic acid through polymerization and simultaneous foaming 0 Die The object is achieved in that (meth) acrylic acid and optionally other monomers be polymerized in the presence of urotropine.

The invention thus provides a method for producing Foams, characterized in that (meth) acrylic acid, optionally in a mixture with up to 50% by weight of other olefinically unsaturated compounds thermally or in the presence of substances which form free radicals - in the presence of urotropine is polymerized at temperatures of 30 to 200 ° C, with simultaneous foaming The (meth) acrylic acid used can be anhydrous or

contain up to 25% by weight, preferably up to 15% by weight, of water, The (meth) acrylic acid can be up to 50% by weight by one or more monomers of the following Groups to be replaced: 1.) Esters of α, ß unsaturated carboxylic acids with 3 - 5 carbon atoms in the carboxylic acid residue and 1 - 18 carbon atoms in the alcohol component; preferably Esters of (meth) acrylic acid with 1 - 8 carbon atoms in the alcohol component.

2.) Amides and nitriles of α, ß unsaturated carboxylic acids with 3 - 5 carbon atoms, preferably (meth) acrylamide and (meth) acrylonitrile.

3.) Vinyl aromatics with 6 - 10 carbon atoms in the aromatic core, preferably core and side-chain-substituted styrenes such as styrene, α-methylstyrene, p-methylstyrene, p-ChlorstyrolO 4.) Unsaturated polyesters based on maleic and / or fumaric acid esters.

5.) Cross-linking substances such as divinylbenzene, glycol di (meth) acrylate, methylene-bis- (meth) -acrylamide, in amounts up to 10% by weight, based on on total monomers.

Acrylic acid and / or methacrylic acid without the addition of any other are preferred Monomers used.

The polymerization and simultaneous foaming of the monomers takes place at temperatures from 30 to 2500C, preferably at temperatures from 50 to 2000C.

The polymerization can be thermal or by adding free radicals forming substances are triggered. Radical generators are peroxides such as tert-butyl pivalate, tert-butyl octoate, lauroyl peroxide, benzoyl peroxide, cumene hydroperoxide, di-tert-butyl peroxide, tert-butyl hydroperoxide or nitrogen-containing radical formers such as azodiisobutyronitrile and called derivatives. Redox systems can also be used. To be favoured nitrogen-containing radical formers such as azodiisobutyronitrile are used.

The free radical formers are preferred in amounts of 0.05 to 15% by weight used in amounts of 0.5 to 5% by weight, based on polymerizable compounds0 as Foaming agent added to the foaming mixture prior to polymerization urotropine (hexamethylenetetramine) is used. The weight ratio of Monomers to foaming agent is between 1: 9 and 9: 1, preferably between 1: 3 and 3: 1.

The polymerization and simultaneous foaming can be continuous or be carried out discontinuously.

In addition to urotropine as a foaming agent, urea, Alkyl ureas such as methyl urea, alkylol urea such as methylol ureas, cyanamide, Dicyandiamide, dicyandiamidine, guanidine in the form of its salts, urethanes such as methyl urethane, Ammonium salts of inorganic or preferably organic acids such as ammonium nitrate, Ammonium carbonate, ammonium formate, ammonium oxalate, ammonium carbamate, ammonium malemate, Ammonium maleate and salts of organic and inorganic acids of primary amines to be present. Preferably, urea can be present in addition to urotropin.

The amounts of the aforementioned additives can be up to 100% by weight, based on on urotropine.

It is also possible to use other additives such as volatile solvents, Fillers and dyes, pore regulators, flame retardant, fertilizing or biologically active To use auxiliary materials and the like.

In detail, the process can be carried out in such a way that one monomers and optionally radical formers and other additives, optionally under Cooling intimately mixed to form a solution or a slurry.

The foaming mixture can be introduced into a mold and the polymerization can be triggered by brief heating. During the exthermen Polymerization takes place at the same time as the foam is formed.

Sometimes freshly made mixtures of the components especially when using larger amounts of radical formers to spontaneous self-heating with good foaming.

The polymerization and simultaneous foaming can also be carried out in one Press or during the extrusion of the mixture through accordingly trained, optionally heated nozzles take place.

The foams obtained by the process of the invention are slightly yellowish in color, with a fine-pored structure and generally have bulk weights below 0.5g / cm30 The foams obtained can be torn into flakes or in some cases granulate into small particles, in what form they are used as soil improvers can be used.

The foams obtained according to the invention are used for decorative insulating or adsorption purposes and, in addition to other uses, in particular for purposes of Can be used for soil improvement, as they can be made hydrophilic very easily. They are also used as additives to other plastics, plastic precursors, Paints, mortars, casting compounds, concrete, clay, plaster, etc. are suitable for their property profile to vary.

The parts given in the examples relate to the weight, unless otherwise noted Examples 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Methacrylic acid part 1 0.5 0.5 Acrylic acid part 1 1 0.5 1 4 2 3 4 0.5 1 1 1 2 0.9 Azodiisobutyronitrile Tle 0.05 0.05 0.03 0.02 0.03 0.02 0.03 0.03 0.00 0.05 0.05 0.05 0.05 0.03 Lauroyl peroxide Tle 0.02 Urotropin Tle 1 1 2 1 1.5 1.1 1 1 1 1 1 1 1 2 0.5 urea part 1 1 1 1 0.5 0.5 dicyandiamide part 0.5 1 1 ammonium formate Part 0.5 1 ammonium acrylate part 1 methyl acrylate part 1 glycol dimethacrylate part 0.1 Density of the foam g / cm³ 0.52 0.3 0.15 0.5 0.45 0.2 0.18 0.11 0.25 0.54 0.33 0.32 0.21 0.35 0.45 The experiment according to example no. 10 is carried out by heating the mixture carried out until foaming without the use of a radical generator, with a thermally initiated polymerization reaction is triggered. Mixing the reactants in the examples it is pressed through a nozzle heated to about 75 ° C, polymerisation and foaming (formation of a foam strand) taking place. The process is extremely thermal and temperatures of up to around 250 ° C can occur.

Acrylic acid used in Example 3 contained 9.5% by weight of water.

Claims (1)

Patent claim: 1. Process for the production of foams, d a d u r c h marked, that (meth) acrylic acid, optionally in a mixture with up to 50% by weight of other olefinic acids unsaturated compounds, thermally or in the presence of free radicals Substances polymerized in the presence of Urotropin at temperatures of 300-2500C is, at the same time foaming takes place.