DE1719118B2 - Adhesives based on hydroxyl polyurethanes - Google Patents

Description

It is known solutions of uncrosslinked, linear hydroxyl-polyurethanes from diisocyanates and hy- so Use droxyl polyester as adhesives.

Such adhesives, e.g. B. Solutions of polyurethanes based on adipic acid / ethanediol polyester and Tolylene diisocyanate are used in many fields, e.g. B. in the shoe industry for sole bonding or used in the packaging industry for duplicating plastic foils. The executed Under normal stress, bonds have a satisfactory strength and durability.

A major disadvantage, however, is that of relative proportions poor resistance of these bonds under the simultaneous influence of moisture and Heat, e.g. B. in tropical areas. Under these conditions, they quickly lose their high strength one and eventually dissolve.

French patent specification 12 44 108 discloses high molecular weight polycarbonate copolymers which have both diphenol and glycol units in their molecule. Owing to their high molecular weight, the polycarbonate copolymers practically no longer have any terminal hydroxyl functions, but can nevertheless be vulcanized by crosslinking with a polyisocyanate, ie converted into the infusible and insoluble state. Already in the absence of the polyisocyanate, the polycarbonate copolymers have French Patent 12 44 108 150 ^u C lying softening points. An explanation for the chemical reaction that takes place during polyisocyanate vulcanization is not given in French patent specification 12 44 108. Due to the high softening point even of the pure polycarbonate copolymers, it must be assumed that they cannot be adhesives which can be "activated", for example, by heating to 80 ° C. The polycarbonate copolymers of French patent specification 12 44 108, which are reacted with polyisocyanates, are of course far less suitable for such heat activation.

It has now been found that with reaction products of linear hydroxyl-carbonic acid polyestera and diisocyanates can be used to produce adhesives whose bond is considerably more resistant exhibit in a humid and warm environment. The resistance of these polyurethanes before they are processed to glue during storage and transport is also increased and the finished adhesives turn out even with the usual use of solvents technical purity than considerably more stable. In addition, the polyurethanes have the Preference is given to "activated" in a solvent-free state by heating to around 80 ° C, i. H. again to be able to be made adhesive.

The present invention thus relates to an adhesive consisting of a solution of reaction products of polycarbonates with polyisocyanates and, where appropriate, customary additives in organic solvents, characterized in that the reaction products of polycarbonates with polyisocyanates hydroxyl polyurethanes based on diisocyanates and hydroxyl polycarbonates des Hexanediols (1.6) of the molecular weight range 600 to 2500 can be used.

The required as starting material for the production of the polyurethanes used according to the invention Polycarbonates containing hydroxyl groups are made from hexanediol (1,6) and carbonic acid derivatives accessible by processes known per se.

Any aliphatic, z. B. hexamethylene diisocyanate (l, o), l-methyl-cyclohexane-2,4- and 2,6-diisocyanate and Ger iels of these isomers, araliphatic such as 1,4-xylylene diisocyanate as well as aromatic diisocyanates, among these in particular 1,5-naphthylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4- and 2,6-tolylene diisocyanate and mixtures of these Isomers and m- and p-phenylene diisocyanate.

The polyurethanes to be used in the adhesive according to the invention are generally produced by reacting the components at a higher temperature, e.g. B. in the range from 100 to 160 ⁰ C, in an approximate molar ratio of 1: 1 of hydroxyl polycarbonate to diisocyanate, but a very small excess of hydroxyl polycarbonate should be present. The hydroxyl polycarbonate used should expediently be anhydrous in order to avoid disruptive branching reactions. It can therefore, for. B. before the reaction by known methods, such as by azeotropic distillation with benzene, carefully dehydrated.

The polyurethanes obtained in this way are initially relatively soft products, which under the influence of their crystallization at room temperature form products of high Shore hardness solidify. Even under abnormal conditions (humidity, heat) they can be stored excellently and can be used in numerous common solvents, e.g. B. Chlorinated hydrocarbons such as Methylene chloride or trichlorethylene, esters such as ethyl acetate or ketones such as acetone or methyl ethyl ketone, to solve. Even when using solvents of technical purity, these solutions the z. B. in small amounts of water or alcohols, an excellent stability and are suitable excellent as adhesives in the most diverse areas for gluing the most diverse Materials, preferably rubber, leather, textile or plastic.

The adhesives according to the invention can be used as customary additives for modifying their adhesive technology Properties and to adapt to the requirements of the respective intended use others high molecular weight compounds (e.g. nitro or acetyl cellulose, chlorinated polyolefins, vinyl chloride / vinyl acetate copolymers), Resins (e.g.

Rosin derivatives, phenol, ketone, phthalate resins), Fillers (e.g. silicates) or other substances are used.

It can also be of technical advantage to use ilen adhesives to increase adhesion or for increasing the heat resistance of your bonds Crosslinking agents such as polyisocyanates, e.g. B. 4,4 ', 4 "-Triphenylme & antriisocyanat or thiophosphoric acid (-p-isocyanatophenyl) -triester, to add.

To carry out gluing, the adhesives according to the invention are applied to the optionally roughened or otherwise pretreated material surfaces to be joined in solution, e.g. B. in the solvents already mentioned, brought. This can be done with a roller, brush, spatula, spray gun or another device. The adhesive spreads are, if necessary, before combining until the solvents evaporate to a large extent, stored in the open. Already solvent-free, Solidified but still uncrosslinked adhesive layers can be removed by heating (e.g. by infrared radiation to about 80 ° C) "activated", d. H. can be made adhesive again. It is also possible to on any solidified adhesive layers one of the materials to be joined in liquid Shape, e.g. B. to apply a heated to 150 to 180 ° C polymer that solidifies on the adhesive layer.

The adhesive bonds obtained are particularly notable for their particularly high resistance in warm and humid climate.

example 1

400 g of dehydrated hexanediol (1,6) polycarbonate with OH number 54 are melted and at 130 mixed with 40 g of 1,5-naphthylene diisocyanate up to 140 ° C. The mixture is heated to 140 ° C. for 8 hours for complete conversion.

From this reaction product an adhesive solution with a viscosity of 50 poise is made with methyl ethyl ketone, measured at 20 ° C. in a Brookfield viscometer.

To produce test specimens, a linen fabric weighing 250 g / cm ^{2 is} impregnated twice with this adhesive solution. A third spread, also applied with a brush, is used for the actual gluing. Before applying the next one, the previous one must be completely dry. The third coating is left to dry as an adhesive spread for only 20 minutes and the adhesive is then carried out by folding the coated areas together under the pressure of a 2 kg metal roller.

ίο After the bond has set for 5 days At 20 ° C., test specimens 15 × 3 cm in size are cut from them and their separation strength is determined. It results a separation strength of 5.2 kg / cm.

The other test specimens are now placed in a saturated steam atmosphere at 70 ° C. After two weeks, two test specimens are taken, their separation strength after storage of 5 days at 20 ° C is determined.

With the polyurethane adhesive according to the example

^ao , a practically unchanged separation strength of 5 kg / cm was determined for test specimens removed after two months.

In a comparative test carried out under the same conditions, in which a

Solution of a known polyurethane made from adipic acid / ethanediol polyester the OH number 56 and toluylene diibocyanate was used at almost same initial strength of the bonds of 5.4 kg / cm already after two weeks a drop in

Separation strength observed to 1.1 kg / cm. After a The adhesive bond was completely destroyed after a month.

Example 2

400 g of hexanediol (1,6) polycarbonate with an OH number of 54 are, as described in Example 1, with 47.6 g 4,4-Diphenylmethane diisocyanate converted to a hydroxyl polyurethane.

From this, as described in Example 1, an adhesive is produced, which is tested in the same way Way done.

The bonds produced in this way were saturated with water vapor Atmosphere at 70 ° C after two months compared to its initial strength of 5.1 kg / cm practically undiminished separation strength of 4.9 kg / cm.

Claims (1)

Claim: Adhesive consisting of a solution of reaction products of polycarbonates with Polyisocyanates and optionally customary additives in organic solvents, characterized in that the reaction products of polycarbonates with polyisocyanates Hydroxyl polyurethanes based on diisocyanates and hydroxyl polycarbonates des Hexanediols (1.6) of the molecular weight range 600 to 2500 can be used.