DE3618405C1 - Process for the adhesive bonding of two urethane prepolymer compositions, and the use of the process - Google Patents

Abstract

The novel process serves for the treatment of the surface of polyurethane compositions containing free NCO groups during their curing. To this end, said surface is brought into contact with a medium containing either a compound containing, per molecule, at least two hydrogen atoms which are reactive towards isocyanate or containing a compound containing, per molecule, one such reactive hydrogen atom and one alkoxysilane group, in such concentrations that, during the contact, the free NCO groups in the surface layer of the composition are modified in a stable manner. In particular, the surface is brought into contact either with water or compounds containing hydroxyl, sulphhydryl, carboxyl, hydrolysable alkoxysilane and/or primary or secondary amino groups or solutions of these compounds, or with a water/gas mixture, in particular a water vapour/air mixture having a relative humidity of greater than 50%, preferably greater than 70%. The polyurethane compositions are used, inter alia, as substrates for urethane prepolymer compositions containing free NCO groups to be applied to the modified surface layer and to be adhesively bonded thereto. A particularly important use of said compositions is on automobile windows, optionally pretreated with primer, for a ... to be applied to said surface layer for the purpose of installation and sealing of the window into the body and to be adhesively bonded to the surface layer... Original abstract incomplete.

Description

The present invention relates to a method for adhesive connection of two urethane propolymer masses as well Applications of the procedure.

Polyurethanes are used today in various technical fields used; a technically particularly important area is the adhesive and sealing technology. In the relevant literature, e.g. B. in A. Damusis: SEALANTS, Reinhold Publishing Corp, 1967, or also in G. habenicht: KLEBEN, Springer-Verlag, is divided between two-component and one-component A distinction was made between polyurethane adhesive and sealing materials. Because of the simpler application, the One-component materials preferred.

Such materials are usually precursors to high polymers, so-called prepolymers. These connections are e.g. B. from higher molecular weight polyols and an over-stoichiometric amount made on diisocyanate; so they are already partly with Urethane bridges.

Under urethane prepolymer materials, all formable preparations are intended here of prepolymers on the broadest basis with free isocyanate groups can be understood.  

However, free isocyanate groups are present in all such prepolymers are present, the prepolymer z. B. still with humidity react or harden. Such polyurethane prepolymers are u. a. described in U.S. Patent No. 37 07 521 and 37 79 794. A significant field of application of these Urethane prepolymers with free NCO groups is the bond of glass panes in metal frames, especially the modern one Technology of inserting car windows in car bodies.

The technical problems that arise are u. a. in the DE-OS 34 09 960 set out. In particular proposed in that publication for attachment a car window on a mounting flange of a vehicle body first a partial strand of adhesive on the glass pane to be arranged with a calibrated cross-sectional profile, which during installation the glass pane has already hardened. Gluing this Partial strand with the mounting flange is done with the help of a second part of the adhesive, which is to the visible surface of the glass pane through a boundary web of the hardened partial strand is covered. It was recognized early on that it as well as the undisputed advantages of this procedure Disadvantages: In particular, if between the application of the Adhesive partial strand and the assembly of the disc a well-known Time passes (usually a few days to a few weeks) and much longer for washers for repair purposes), is a reliable adhesion of the second part of the adhesive usually not on the first pre-applied strand  given more. However, this leads to unacceptably low strength and sealing values after the installation of such glass panes.

The problem of mutual liability of the first on the disc pre-applied polyurethane layer and the second in the actual Insert the disc to be applied adhesive based on polyurethane are mentioned in the DE-OS only gave two solutions:

• Application of an activator (for example a solvent) immediately before gluing in the pane, and
• - Roughen the surface of the first layer.

Meanwhile, the second proposal in practical execution is hardly ever going to be important, the first thing to note is that thereby the occurrence of the state in which liability between the two polyurethane layers is no longer sufficient Security can be accepted, at most by one short and still indefinite period is extended. In addition, the application of the activator presents immediately the gluing process a highly undesirable additional step represents.

It is the object of the present invention to overcome these drawbacks to avoid and to create a process in which the surface layer  of the first strand applied so modified can be that a secure liability of the second, actual Adhesive and sealing partial strand on the pre-applied, first strand is guaranteed at all times without this chemically immediately before installing the glass pane or to have to be mechanically pretreated, even if between the order of the first strand and the assembly of the Disk has passed a relatively long time.

Surprisingly, it has now been found that this task of the invention thereby solving that the surface of a first Urethane prepolymer composition with free NCO groups after Shaping and in contact with a medium before curing brought, which is either a connection with at least two isocyanate-reactive hydrogen atoms per molecule or a connection with at least one such reactive Hydrogen atom and an alkoxysilane group per molecule in such Contains concentrations that when contacting the free NCO groups in the surface layer of the mass stable be modified, and that on the modified surface layer the first urethane prepolymer mass as a base second urethane prepolymer composition to be adhesively bonded to it is applied with free NCO groups.

When using liquid treatment media, the surface the urethane prepolymer mass with water or compounds with hydroxyl, sulfhydryl, carboxyl, primary amino and / or  secondary amino groups or solutions of these compounds in Be brought in contact, focusing the media in Solutions depending on how they are applied to the surfaces can be up to 50 wt .-%.

When using gaseous media, the surface is advantageously with a water vapor-air mixture with relative Moisture over 70% contacted. Any secondary components or other components of the solutions or the mixtures should be chemically inert to the isocyanate group.

The present invention also relates to the application of the method for gluing glass panes into a frame, in particular for sealing windows in the body of vehicles.

An important area of application is therefore the use such modified polyurethane compositions on optionally with Primer-treated car windows as a base for one the surface layer mentioned for the purpose of installation and sealing the pane to be applied to the body and with the surface layer adhesive sealant to be bonded, also based on urethane prepolymer with free NCO groups.

Even for the specialist is not foreseeable in the context of Process modified a pre-applied polyurethane mass,  that the document is a (within certain, more usual Conditions) practically long enough storage stability as well, with regard to the liability of one subsequently applied polyurethane mass compared with free NCO groups with unmodified or activated documents, shows surprisingly high strength.

The liquids or solutions are preferably based on the sprayed surfaces to be treated; the surfaces mentioned but can also be immersed in or coated with the fluids will. Gas or steam mixtures can be inflated or the coated parts in the corresponding atmospheres be moved or stored.

The concentration of the modification media in the solutions can vary within wide limits. It is mainly of the order type or the order quantity.

Regarding the solvents for the liquid mixtures, it should be noted that these solvents must be chemically inert, especially against NCO groups. Examples of such solvents are ketones, esters, hydrocarbons, ethers and halogenated hydrocarbons.

Modifiers to be used with advantage are in addition to water generally compounds that act as reactive molecular groups Hydroxy, mercapto, amino, alkoxysilane and / or carboxyl groups  contain.

Such a reactive compound can have 2 to 6, preferably 2 to 3, especially 2 reactive molecular groups. Appropriate Substance groups are e.g. B. mercapto alcohols, amino alcohols, Hydroxy, thio or amino carboxylic acids.

Examples of polyalcohols include:

• - ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, 1,3-propanediol, 1,4-butanediol, 2,3-butanediol, glycerol, Pentaerythritol, sorbitol, 1,2-butanetriol, trimethylolpropane.

Examples of mercapto alcohols are:

• - mercaptoethanol, mercaptopropanediol, dimercaptopropanol.

Examples of amino alcohols are:

• - ethanolamine, diethanolamine, diisopropanolamine, triethanolamine, Triisopropanolamine, 2,2′-amino-diethoxyethanol, Aminoethylethanolamine, 2-aminobutanediol-1, 2-aminopropanol-1, 3-aminopropanol-1, N-methylaminopropanediol-2,3, 1-aminopropanediol-2,3, N-methylmethanolamine or hydroxyethylpiperazine.

Examples of amino, hydroxy or thiocarboxylic acids are:

• - glycine, N-methylglycine, alanine, cysteine, serine, lysine, glycolic acid, Lactic acid, malic acid, thioglycolic acid or thiolactic acid.

Examples of alkoxysilanes are:

• Gamma-aminopropyltriethoxysilane,
• Gamma-mercaptopropyltrimethoxysilane,
• N-beta (aminoethyl) gamma-aminopropyltrimethoxysilane,
• - N-N-bis ((trimethoxysilyl) propyl) amine,
• - Gamma-glycidoxypropyltrimethoxysilane.

The method according to the invention is described below with the aid of Embodiments described in more detail. For everyone in the following In the examples described, the same experimental system was used:

On silicate glass sections was first one according to the US PS 37 07 521, Example 2, produced glass adhesive primer applied. Then these primed glass plates with a manufactured according to US-PS 37 79 794, Example 1 Coated polyurethane mass, as usual is used for gluing in car windows. A variant this mass was called polyurethane mass A with a hydrocarbon plasticizer, another than polyurethane mass B with a phthalate plasticizer. The following will be  these coated plates referred to as substrates.

According to the method of the invention, part of the Substrates immediately after applying the coating in the treatments described in the following examples. Subsequently was stored under normal environmental conditions, together with the untreated part of the substrates, until the open time specified in the examples has expired.

Then the substrates with strands of polyurethane mass according to US Pat. No. 3,779,794, Example 1, variant B, coated and for the complete hardening of these strands stored further. In the following, this mass is used as assembly adhesive designated.

Testing the adhesive strength of the assembly adhesive on the substrate was carried out by peeling off, the percentage being the measured value Proportion of cohesively breaking adhesive surface, based on the entire strand area of the applied assembly adhesive, held has been.

Example 1

In this example, the change in liability was one of less than 50% humidity hardened substrate in Dependency from openness to coating with assembly adhesive  examined. The adhesion values obtained are in Table 1 reproduced:

Table 1

Example 2

In this example the same attempt is made as in example 1, repeated on substrates, which after the in the method described in DE-OS 34 09 960 before hanging up assembly adhesive with a solvent activator from a mixture of 90 parts by weight of methyl ethyl ketone and 10 parts by weight N-methylpyrrolidine. table 2 shows the results obtained:

Table 2

Example 3

In Example 3, the substrate surface was invented through 3 days of treatment with water vapor-air mixtures of different relative humidity modified, whereby after 14 Days of open time achieved the following adhesive values with these mixtures were:

Table 3

A blind test for the above example, in which the substrate surface until a water-air mixture is completely hardened exposed to 10% relative humidity was and only afterwards with a 90% relative Treated with moisture resulted in 25% cohesive failure two PU layers.

Example 4

In this example the polyurethane mass A was used as the substrate  used. The modification of the substrate surface according to the invention was carried out by spraying on dilute solutions of the table 4 mentioned chemicals in organic, inert against NCO Solvents such as B. methyl ethyl ketone, toluene or ethyl acetate, immediately after coating. The concentration of solutions was set at 5% in this example. Table 4 summarizes the results obtained after different open times together:

Table 4

The exemplary embodiments therefore show very clearly:

• - Treatment with activators according to the state of the Technology (example 2) results in an extension of the time,  during which the PU surface can be securely glued, but only by about 10 days. Then the percentage drops Cohesive break - d. H. the measure of the bonding capacity the treated surface - to zero.
• - Only the treatment according to the invention according to the examples 3 (90% relative humidity) and 4 brings a technical relevant extension of the good adhesive properties of the modified surfaces.

The examples above clearly show that the values for cohesive break and strength clearly, e.g. T. even around Orders of magnitude better if the method according to the invention is applied. The invention is therefore particularly suitable for the activating modification of the surfaces of if necessary first layers of. applied over primers Polyurethane adhesive sealants on car windows and their uses of the modified polyurethane surface layers as a base for creating an adhesive bond when sealing and gluing glass panes, e.g. B. at the assembly of the same in the car body by means of a Strands of another, freshly applied adhesive sealant.

Claims (5)

1. A process for the adhesive connection of two urethane prepolymer compositions, characterized in that the surface of a first urethane prepolymer composition with free NCO groups after the shaping and before curing is brought into contact with a medium which is either a compound with at least two opposite Contains isocyanate-reactive hydrogen atoms per molecule or a compound with at least one such reactive hydrogen atom and one alkoxysilane group per molecule in such concentrations that when contacted the free NCO groups in the surface layer of the mass are stably modified and that on the modified surface layer of the first urethane Prepolymer mass as a base a second urethane prepolymer mass with free NCO groups to be bonded to it is applied. 2. The method according to claim 1, characterized in that that the surface of the first urethane prepolymer mass with water or compounds with hydroxyl, sulfhydryl, carboxyl, hydrolyzable alkoxysilane and / or primary or secondary Amino groups or with solutions of these compounds in contact brought.   3. The method according to claim 1 or 2, characterized in that the surface of the first urethane prepolymer mass with a water vapor-air mixture with a relative humidity is contacted by more than 70%. 4. Application of the method according to claim 1 for gluing of glass panes in a frame. 5. Application of the method according to claim 1 for sealing Gluing windows in the body of vehicles.