CS242019B1 - A method of making a cross-linking preparation - Google Patents

Abstract

Method for producing a preparation with a crosslinking effect, which is suitable as an additive to polyurethane and polychloroprene adhesives. By adding this preparation to* 1 adhesives, the initial and final strength of the adhesively bonded joints and the resistance of the joints to elevated temperatures are significantly increased. The stated purpose is achieved by dissolving 0.01 to 0.5 parts by weight of hexamethylenetetramine in 100 parts by weight of dichloromethane and, after dissolution, adding 0.1 to 0.5 parts by weight of dibutyltin dilaurate or 10 to 20 parts by weight of 6-caprolactam and only then adding 50 to 130 parts by weight of diphenylmethane diisocyanate raw material with a minimum content of the 4,4'-diphenylmethane diisocyanate isomer of 95% by weight to this solution.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for the production of crosslinking agents based on a solution of 4,4'-diphenylmethane diisocyanate, hexamethylene tetramine and activators based on organometallic tin or amine salts in dichloromethane for hydroxylpolyurethane adhesives and chloroprene adhesives. base materials.

In the footwear industry, isocyanates are used as crosslinking agents for polyurethane and polychloroprene adhesives. The use of these products in polyurethane adhesives for bonding natural or synthetic leather with soles based on polyvinyl chloride, integral polyurethane foam or a thermoplastic elastomer is justified by the crosslinking reaction of the NCO groups of the isocyanate composition. The most common isocyanates are triphenylmethane triisocyanate, thiophosphoric triisocyanatophenyl ester, polyphenylene polymethylene isocyanate and addition products of trimethylolpropane and hexanetriol with toluene diisocyanate. These products are mostly used as solutions in organic solvents. These substances are manufactured by complex technological processes, which results in high prices of these products. The addition of isocyanates to polychloroprene adhesives is due to the fact that the NCO cross-linking of the isocyanate groups to form urethane bonds occurs on the hydroxyl groups of the polymer, which are formed by the hydrolysis of chlorine atoms by air humidity.

The isocyanates used, which have at least three functional isocyanate groups, ensure from the beginning of the addition reactions a considerable initial strength of the glued joints due to the resulting spatial network. Theoretically, two-functional isocyanates can also be used for the cross-linking reactions, since the cross-linking reaction takes place in hydroxyl-terminated hydroxyl groups on the hydroxylpolyurethanes as well as the cross-linking of the internal groups with active hydrogen (Domorow: Polyurethanes, Prague 1961, 21, 22) Despite these assumptions, however, the use of 4,4-diphenylmethane diisocyanate solutions as cross-linking agents in adhesives does not give good results.When compared to the triisocyanates used, there is a marked decrease in the initial strength of the glued joints. The low density of the spatial network results in poor mechanical properties of the resulting polymer gel.

Higher reaction rates and hence higher initial strengths are achieved by the use of some compounds which activate the -NCO groups. These are usually organometallic salts of tin and cobalt, tertiary amines or as described in the description of the invention to U.S. Pat. Certificate No. 176 732, water in an organic solvent of the ketone type. However, these activators can only be used as an additive to the adhesive, to which a diphenylmethane diisocyanate solution is then added until shortly before the materials are bonded. However, the concentration of activator in the adhesive must be large in order to ensure sufficient diphenylmethane diisocyanate activity, but there is a risk that exceeding it will cause a sharp drop in initial strength.

These drawbacks are overcome by the crosslinking agent composition of polyurethane and chloroprene adhesives containing 4,4 lep-diphenylmethane diisocyanate, hexamethylenetetramine, dibutyltin dilaurate or 6-caprolactam in solution in dichloromethane. The cross-linking preparation is prepared by the process according to the invention, which consists in that it is initially in 100 wt. parts of dichloromethane dissolve 0.01 to 0.5 wt. 0.1 to 0.5 wt.% of hexamethylenetetramine and in this solution are further dissolved with stirring. parts by weight of dibutyltin dilaurate or 10 to 20 wt. 50 to 130 wt.% of 6-caprolactam are added and only into this solution. % of 4,4‘-diphenylmethane diisocyanate with a content of 4,4‘-isomer of at least 97% by weight;

The technical effect of the process according to the invention is that it makes it possible to prepare a cheap polyisocyanate-based crosslinking agent for polyurethane and polychloroprene adhesives. In this formulation, the formed polyisocyanate in solution in the activated state is an activator which provides the required rate of spatial mesh formation, initial bond strength, and solution stability. The method of manufacturing the cross-linking agent is simple and easy to control.

The production of the crosslinking agent according to the invention consists in pouring a weighed amount of dichloromethane into a plastic container in which the weighed amount of hexamethylenetetramine is dissolved with stirring. After dissolution, the weighed amount of dibutyltin dilaurate or 6-caprolactam is dissolved in the solution with stirring. Only a weighed amount of 4,4‘-diphenylmethane diisocyanate was introduced into this solution and dissolved with stirring. After mixing, the solution is allowed to stand for 24 hours in a well sealed plastic container to settle the debris at the bottom of the container.

Surprisingly, the production of the crosslinking agent according to the invention substantially alters the crosslinking properties of 4,4‘-diphenylmethane diisocyanate after the preparation of hexamethylenetetramine in solution in dichloromethane. The resulting product in solution forms with the hydroxylpolyurethane adhesives a perfect spatial network and in closed solutions highly ductile insoluble gels. Since only the trilzoocyanate exhibits this cross-linking reaction, the formation of the product from 4,4 dif-diphenylmethane diisocyanate and hexamethylenetetramine can be explained by reaction on the activated methylene groups of hexamethylenetetramine according to the following schematic procedures. The activation of methylene groups is enhanced by the polarization of the N-C bond due to the strong polar solvent dichloromethane (Beyer, Organic Chemistry, Prague 1358, p. 39).

H, C 94 ^{C. H} 'ί & A A Í A ^ ^

CH,!> ^N

CH, f (*) 9

-N ~ CH + -O = C = N ~ RNC = QI ¹ fe © _ • -> - C "~ C" N "R ~ 'N — C ~ O Γ l U ·'

O η

-nccnRnco ^{1 1} OH _ V _ _

-N-C-C-N-R-N = C = O-li-t

In the preparation of the cross-linking agent according to the invention, 50 to 130 wt. parts of the diphenylmethane diisocyanate feedstock used 0.01 to 0.5 wt. 0.1 parts by weight of hexamethylenetetramine; parts by weight of dibutyltin dilaurate or 10 to 20 wt. parts of 6-caprolactam previously dissolved in 100 wt. parts of dichloromethane. Outside these ranges of substances, a favorable technical effect and stability of the formulation solution are not achieved. The diphenylmethane diisocyanate raw material used has the following physical properties: density 1190 kg / m ⁵ , melting point 38 degrees Celsius, 4,4'-isomer content in the raw material 97% by weight.

The embodiments of the process according to the invention characterize its essence.

Example 1

A cross-linking composition consisting of 100 wt. parts by weight of dichloromethane, 0.25 wt. 0.25 parts by weight of hexamethylenetetramine; parts of dibutyltin dilaurate and 100 parts by weight of 4,4'-diphenylmethane diisocyanate were prepared by dissolving 0.25 kg of hexamethylenetetramine in 100 kg of dichloromethane and after complete dissolution 0.25 kg of dibutyltin dilaurate was added and after complete dissolution 100 kg of melt of 4,4'-diphenylmethane diisocyanate. The whole solution was thoroughly mixed and allowed to stand for 24 hours.

Example 2

A cross-linking composition consisting of 100 parts by weight of dichloromethane, 0.25 parts by weight of hexamethylenetetramine, 15 parts by weight. Of 6-caprolactam and 100 pbw of 4,4'-diphenylmotanedisocyanate was prepared by dissolving 0.25 kg of hexamethylenetetramine in 100 kg of dichloromethane and after complete dissolution 15 kg of 6-caprolactam was added and after complete dissolution 100 kg of melt were added. Of 4'-diphenylmethane diisocyanate. The whole solution was thoroughly mixed and allowed to stand for 24 hours.

Example 3

A cross-linking composition was prepared in accordance with Example 1, containing 100 wt. parts by weight of dichloromethane, 0.15 wt. 0.15 parts by weight of hexamethylenetetramine; parts by weight of dibutyltin dilaurate and 60 wt. parts of 4,4‘-diphenylmethane diisocyanate.

42 7

The crosslinking agents produced by the process of the invention are applied to the chloroprene adhesives at a concentration of 5% by weight. they provide the required level of initial and final strengths of glued joints for a combination of leather and rubber materials. When applied at 8% by weight to polyurethane adhesives, they provide the required strength level for combinations of leather or synthetic top materials and polyvinyl chloride, leather or synthetic top materials and integral polyurethane foam, leather or synthetic top materials and thermoplastic elastomer.

Claims (1)

Subject A process for the preparation of a cross-linking product based on a product prepared from 4,4‘-diphenylmethane diisocyanate, hexamethylene tetramine and dibutyltin dilaurate or 6-caprolactam for polyurethane and chloroprene adhesives, characterized in that it is first initially in 100 wt. parts by weight of dichloromethane dissolve 0.01 to 0.5 wt. 0.1 parts by weight of hexamethylene-allyz tetramine; parts by weight of dibutyltin dilaurate or 10 to 20 wt. parts of 6-caprolactam and only 50 to 130 wt. % by weight of diphenylmethane diisocyanate raw material with a minimum isomer content of 4,4‘-diphenylmethane diisocyanate of 95% by weight;