DE2150719A1 - Bonding polyurethane integral foams - without roughening the surface - Google Patents

Abstract

Bonding of foams having integral unfoamed skin is achieved by applying to the surface, prior to bonding, a polyisocyanate e.g. 3,3'-dimethyl-triphenylmethane-4,4',6,6'-tetraisocyanate.

Description

Method of gluing polyurethane foams with a compact surface In many branches of industry, especially in vehicle construction and in the shoe industry, Molded parts made from integral polyurethane foam are increasingly used. These parts starting from polyisocyanates and hydroxyl polyesters and more recently mainly made of hydroxyl polyethers, foamed in molds. You have a cellular one Core and a compact, cell-free edge zone They are soft-elastic to tough-hard-flexible adjustable0 When processing such polyurethane molded parts, the problem often arises the task of connecting them to one another or to other materials, e.g. textiles, rubber, To glue leather or synthetic leather. When trying these molded parts as they arise, Bonding with common adhesives is only completely obvious in practice insufficient strength values. As far as these molded parts are roughened, so the compact skin on its surface is removed, it is possible to use commercially available Adhesives, including those made from polychloroprene or hydroxyl polyurethanes, adhesive bonds produce higher strength.

However, the roughening required for this is very time-consuming and expensive. During this process, the molded parts can easily be damaged. especially of parts with a complicated shape, e.g. of molded soles that only to be glued with part of their surface.

It has now been found that polyurethane foams with more compact Skin, so-called polyurethane integral foam molded parts, preferably not very sticky Qualities made from hydroxyl polyethers and polyisocyanates, without disadvantageous roughening with common adhesives with each other or with other materials with very high strength and durability if their surfaces are previously in suitably treated with a polyisocyanate.

Possible foams of this type are, for example, those according to German patents 851 851, 1 245 102, 1 268 819, the American Patents 3,18,104; 3,178,490; British Patent 1,221,741 and also laid-open specification 1,694,138.

Polyisocyanates are generally used for such treatment, primarily aromatic polyisocyanates, e.g. those produced by the condensation of aniline and formaldehyde be obtained with subsequent phosgenation into consideration. Preferred among the aromatic polyisocyanates are 4,4 ', 4 "triphenylmethane triisocyanate and thiophosphoric acid tris-p-isocyanatophenyl ester, in particular 3,3'-dimethyltriphenylmethane-4,4 ', 6,61-tetraisocyanate. These isocyanates can be diluted with suitable solvents, e.g. methylene chloride or ethyl acetate, come into use.

With regard to the processing, an additive of other substances is e.g. of silica products, of particular advantage. Polyisocyanates according to the invention can be applied with a suitable device, e.g. a brush or by dipping will.

Previously, any trend} present on the surface are medium removed, e.g. by washing with a suitable solvent, e.g. toluene.

A wide variety of adhesives can be used for the subsequent bonding Base, including natural rubber, polychloroprene, nitrile rubber or other synthetic materials Use elastomers. Adhesives made from hydroxyl polyurethanes are preferred, among others them in particular those described in German Offenlegungsschrift 1 930 336 are.

Examples In the examples below, the dimensions were 15 × 3 × 1 cm Polyurethane integral skin foam parts with an average density of 0.5 g / cm3, made from a modified diphenylmethane-4,4'-diisocyanate, a predominantly linear hydroxyl polyalkylene polyether, 1,4-butanediol, water and one Propellant, each coated with one of the following polyisocyanate solutions.

Polyisocyanate solution I: 3,3'-dimethyltriphenylmethane-4,4 ', 6,6'-tetraisocyanate, 2.5% solution in methylene chloride.

Polyisocyanate solution II: triphenylmethane-4,4 ', 4 "-triisocyanate, 3.0 Xig dissolved in methylene chloride.

Polyisocyanate solution III: thiophosphoric acid tris-p-isocyanato-phenyl ester, 5.0 Xig dissolved in methylene chloride.

After a drying time of one hour, the treated in this way was applied Foam parts a chrome-tanned leather strip (15x3 cm) glued, with each one of the following hydroxyl polyurethane adhesives was used.

Adhesive A: 18.4% solution of a hydroxyl polyurethane, prepared from 1.5 moles of diphenylmethane-4,4'-diisocyanate, 1 mole of adipic acid / hexanediol-1,6-hydroxyl polyester (OH number 51) and approx. 0.5 mol 1,4-butanediol in methyl ethyl ketone (Viscosity 21.2 poise at 20dz).

Adhesive B: 18.8% solution of a hydroxyl polyurethane, prepared from 1.4 mol of diphenylmethane-4,4'-diisocyanate, 1 mol of adipic acid / butanediol-1,4-hydroxyl polyester (OH number 49) and 0.4 mol of 1,4-butanediol, dissolved in methyl ethyl ketone (viscosity 22.1 Poise at 2O0C).

Adhesive C: 20.7 solution of a hydroxyl polyurethane, prepared from 1 mol of adipic acid / butanediol-1,4-hydroxyl polyester (OH number 53) and approx. 1 mol Toluylene diisocyanate, in a mixture of ethyl acetate and acetone in a ratio of 4: 1 (Viscosity 19.8 poise at 200C).

Adhesive D: 21.9% solution of a hydroxyl polyurethane, prepared from 1 mol of adipic acid / ethanediol-1,2-hydroxyl polyester (OH number 55) and approx. 1 mol Toluylene diisocyanate, in a mixture of ethyl acetate and acetone in a ratio of 4: 1 (Viscosity 20.2 poise at 200C).

The chrome-tanned leather was before gluing on its grain side, with which it was glued, roughened with a 40 grit sanding belt and with the used adhesive primed.

The strengths of the bonded joints were measured after 1 day in the separation test determined at 200 C according to DIN 53 274. They are in Table 1 given. This table also lists the strength values of bonds that accordingly, but without polyisocyanate treatment of the molded parts.

Table 1 Example of polyisocyanate adhesives Release strength solution (kp / cm) 1 I | A 10.2 2 II A 8.9 3 III A 7.0 Comparison without A 2.2 4 IB 8.2 5 II B 7.9 6 III B 6.8 Comparison without B 1.8 7 IC 8.2 8 II C 7.4 9 III C 5.9 Comparison without C 1.6 10 ID 6.2 11 II D 5.9 12 III D 5.9 Comparison without D 0.8

Claims (1)

Method for gluing polyurethane foams with compact surface, characterized in that a polyisocyanate before gluing is brought to the foam surface.