NZ229864A - Process and device for producing a sealing and adhesive compound strip - Google Patents

Description

22 9 8 6 Priority Date(s): ..Shl.-SS.- Complete Specification Filed: class: ''J b6'HW19#-' Publication Date: P.O. Journal. r1?: ....

NEW ZEALAND PATENTS ACT, 1953 No.: Date: COMPLETE SPECIFICATION 'E <• i -7 JUL1989 'v! PROCESS FOR THE PRODUCTION OF A SEALING AND ADHESIVE COMPOUND STRIP AND EEVICE FOR IMPLEMENTING THIS PROCESS I/We, Teroson GnbH of Hans-Bunte-Str. 4, 6900 Heidelberg 1, Federal Republic of Germany, a German company hereby declare the invention for whichjdk/ we pray that a patent may be granted to k>k/us, and the method by which it is to be performed, to be particularly described in and by the following statement:- - 1 - (followed by page la) Process for the production of a sealing and adhesive compound strip and device for implementing this process Numerous formulations for single-component sealing and adhesive compounds are already known which contain prepolymers with telechelic isocyanate groups (manufactured from diisocyanates in stoichiometric excess with polyols) and which harden under the 5 influence of moisture. When aromatic isocyanates are used, catalysts - particularly tin compounds - are added to these systems to accelerate the hardening.

These single-component PU-systems are also used inter alia in 10 automobile construction for direct glazing of motor vehicles. Problems can, however, occur when the air moisture is low, particularly when outside temperatures are fairly cold in the period from September to March. The hardening of the sealing compound then occurs so slowly that the window panes have to be 15 held for quite a long time with the aid of suitable holding devices. Further assembly work, e.g. attaching the doors or working with the car body tilted, cannot be carried out as long as the sealing compound has not sufficiently hardened.

It is known from US-PS 37 55 261 that prepolymers with isocyanate end groups can be cross-linked at elevated temperature if a stoichiometric quantity of a complex compound of methylene dianiline and sodium chloride is added to them. At higher temperatures this complex dissociates into free methylene 25 cfianiline and sodium chloride, and the methylene dianiline reacts with the isocyanate groups of the prepolymers to form a cross-linked urea. At room temperature this mixture is storage-stable. In the US patent specification no reference is made to hardening under the effect of moisture. It is also known that 30 these PU-systems can be heated by microwaves to cause them to harden (US-PS 40 81 901). In both processes the complex 22 9 8 6 4 * 22 9 8 6 4 compound, composed of methylene dianiline and sodium chloride, is admixed shortly before the hardening reaction in stoichiometric quantities relative to the reactive isocyanate groups of the polyurethane prepolymers.

Two-component PU-systems are capable of rapid hardening, but handling these is considerably more complicated and requires more sophisticated apparatus.

There is consequently the need for a process using a single-component sealing and adhesive compound on a polyurethane base which can rapidly be hardened sufficiently for an adequate mechanical stability to be achieved. The complete permanent hardening process, e.g. under the influence of moisture, could 15 then take a longer period of time without hindering or impairing the assembly work.

The invention is directed to a process for the production of a sealing and adhesive compound strip, particularly for the 20 direct glazing of motor vehicles, using a moisture-hardening single-component polyurethane composition based on telechelic isocyanate prepolymers obtained from aromatic diisocyanates in stoichiometric excess and polyols, which is characterized in that a compound is used comprising a) a catalyst for the moisture hardening and b) a blocked activatable cross-linking agent and that during the extrusion of the strip a solvent or solvent 30 mixture is continuously injected into the inside of the strip which liberates the cross-linking agent.

Preferably, the blocked activatable cross-linking agent is added in clearly less than stoichiometric quantities.

If during the application of the sealing and adhesive compound Mlii. w 22 9 8 6 4 used according to the invention the absolute air moisture is sufficiently high, the composition hardens like conventional single-component adhesive and sealing compounds with the air moisture at room temperature. If, however, the available air 5 moisture is not sufficient for rapid hardening, or if fairly high mechanical strengths are required only a very short time after the application of the adhesive and sealing strip, the blocked cross-linking agent can be activated by injecting the solvent so that partial hardening in the form of a core in the 10 inside of the strip can be achieved in a short time. The further hardening to final strength then takes place by further reaction with air moisture. With a process of this type the user gains the option of deliberately influencing the hardening characteristics of the adhesive strip without having to alter the 15 composition of the adhesive and sealing compound. Using this process the problems described above in the direct glazing of motor vehicles on assembly lines can in particular be solved, but because of the very small amount of equipment needed, the sealing and adhesive composition according to the invention can 20 also be used in motor vehicle work shops in the replacement of windshields.

Although the use in the automobile industry represents a preferred application, the process according to the invention 25 can be used to advantage anywhere where initial strengths are required in a short time which cannot be achieved by conventional moisture-hardening materials alone.

The polyurethane prepolymers are manufactured in a manner known 30 per se from excess aromatic diisocyanate and a polyol. Suitable aromatic diisocyanates are, for example, diphenylmethane diisocyanate (MDI), toluylene diisocyanate (TDI), naphthalene diisocyanate, p-phenylene diisocyanate and 1,3-bis(isocya-natomethyl)benzene and m- or p-tetramethylxylol diisocyanate (m-35 TMXDI or p-TMXDI). 229864 As polyol components polyetherpolyols such as polyethylene oxide, polypropylene oxide, polytetrahydrofuran and their copolymers and polyesterpolyols and hydroxy-functional poly-caprolactone are suitable. The compatible mixtures disclosed in 5 EP-OS 240 698 of polyetherpolyols, polyesterpolyols and hydroxy-functional methacrylate polymers of low molecular weight can also be used.

The preferred catalysts for the moisture-hardening of the 10 aromatic isocyanate prepolymers are tin compounds such as tin (II)-octoate, dibutyltinlaurate and dibutyltinmaleate. In addition, organo-mercury, organo-lead and organo-bismuth compounds, such as for example phenyl-mercury-acetate or lead-naphthenate can be used. Quantities of 0.01 to 1.0 and more 15 particularly 0.02 to 0.5% by weight, are preferably used. Additionally, the aforementioned catalysts can be combined in a known manner with tertiary amines.

As blocked cross-linking agents which can be activated by the 20 addition of solvents, one should mention complexed amines, in particular the complex compound of methylene dianiline (MDA) and NaCl. In this complex the MDA is present in an expanded salt lattice, the stoichiometric composition of this complex is indicated in the literature by (MDA)3.NaCl. This compound can be 25 obtained from the Uniroyal Company under the trade name "CAYTUR". Other complexes of MDA or of 2,3-di(4-amino-phenyl)butane with sodium bromide, sodium iodide, sodium nitrite, lithium chloride, lithium bromide, lithium iodide, lithium nitrite or sodium cyanide are also suitable. Additional-30 ly suitable are the complexes of tris(2-aminoethylamine) with alkaline earth compounds such as, for example, calcium chloride, magnesium chloride or strontium chloride and solid polyamine complexes which are insoluble in the system at temperatures below 60°C and which dissociate sufficiently rapidly under the 35 influence of a solvent. Quantities of 0.25 to 5.0, and more preferably 0.5 to 2.0% by weight of cross-linking agent are 22 98 6 added.

By the addition of suitable solvents these complex compounds dissociate and the liberated polyamine reacts with the isocyan-5 ate groups of the polyurethane prepolymers under formation of urea bonds. The strength required after this pre-crosslinking can be controlled within certain limits; e.g. the number of isocyanate groups reacting can be regulated by the quantity of complex compound added. The selection criteria for this are the 10 temporary mechanical strength required and the time available for the pre-hardening. Due to the addition of the solvent and the liberation of the hardener thereby achieved the pre-hardening takes place in the sealing and adhesive strip from the inside to the outside. A hardened core forms, the diameter 15 of which increases rapidly with time, as can be observed. It is clear that there is no diffusion of the hardener here, instead the reaction is initiated by the freed amine, or water. The complete permanent hardening and the achievement of the final strength is then brought about by the reaction of the remaining 20 isocyanate groups of the prepolymers with the air moisture under the influence of the catalyst.

As further activatable cross-linking agents polyamino- or polyhydroxyfunctional compounds are to be considered which are 25 microencapsulated and therefore are not available for a reaction with the isocyanate prepolymers during storage at room temperature. The functionality and molecular weight of the polyamino-or polyhydroxy-functional compounds in this case follow the desired mechanical properties of the hardened adhesive and 30 sealing material. Preferably, in this case these are difunct-ional amines of low molecular weight or alcohols, because these owing to their low molecular weight are only added in very low percentages. For the encapsulation the cross-linking agent is dispersed in sufficiently fine particles and then a shell of a 35 suitable monomer is polymerized on to the nucleus of the cross-linking agent. Examples of suitable polymers are polymethyl- 22 0864 methacrylate, produced by the additoin of liquid or dissolved polyisocyanates, which then react with the surface of the cross-linking agent to form a strong shell, and polycyanoacrylates, produced by the additon of cyanoacrylate monomers, which react 5 with the cross-linking agent in an anionic polymerization on the surface. Further possibilities for the production of the inert shell around the cross-linking agent are the known coazervation techniques, by which gelatine shells are produced on the surface of the cross-linking agent. In addition to the processes listed 10 here for the production of a sealed polymer shell around the cross-linking agent many other polymers and copolymers are suitable to produce this shell. The following selection criteria are to be observed: the monomer for the shell should have as little solubility as possible in the cross-linking agent and be 15 completely polymerizable at relatively low temperatures. The shell polymer thus produced must have a softening point of above 6 0°C and should not swell with the remaining constituents of the adhesive and sealing compound below 60°C, or be soluble in them.

The encapsulated cross-linking agent preferably has a melting or softening point between 60 and 90°C, so that it can be placed in an inert solvent during the encapsulation process as a very •> finely divided dispersion. Examples of such cross-linking agents are diamines such as ethylene dianiline, 2,3-di(4-amino-25 phenyl)butane, hexamethylene diamine and dodecamethylene diamine. Examples of suitable diols are neopentylglycol, hexandiol, decandiol, hydroxypivalic acid neopentylglycolester and other polyesterdiols with a melting or softening point between 60 and 120°C. Such encapsulated cross-linking agents 30 have an advantage over the salt complexes of diamines in that they contain no salts such as sodium chloride.

The single-component polyurethane system used according to the invention distinguishes itself in that the cross-linking agents 35 described have only to be added in a very low percentage to the single-component, moisture-hardening adhesive and sealing 11 »•> < \ • < f» A /C. JOU'l materials. By this means the desirable properties of these will not be affected, e.g. excellent adhesion is achieved to painted metal and pre-treated glass which is absolutely necessary for the direct glazing of automobiles. The system thus has an 5 extremely good stability and can therefore be extruded in the desired profile form onto the glass pane or the flange parts.

To activate the blocked or micro-encapsulated cross-linking agent, polar aprotic solvents can be used according to the 10.invention. Suitable, for example, are acetaldehyde and its derivatives, benzonitrile, n-butylacetate, -y-butyrolactone, chlorobenzene, alkylsubstituted chlorobenzenes, chloroform, 2-caprolactone, cyclopentane carboxaldehyde, dichlormethane, diethoxysulphide, diethyleneglycoldiester, 2,2'-(dimethylamino)-15 diethylester, dimethylformamide, dimethylsulphoxide, 2,6-dimethyl-4-pyrone, dioxan, ethylacetate, formaldehyde, dimethyl-acetal, hexamethylphosphoric acid triamide, isobutylmethyl-ketone, methylethylketone, N-methylpyrrolidone, methoxybenzene, 2-methyl-4-pentanone, 2-methylpyrazine, nitroaliphates, nitrobenzene, 2,4-pentadione, phosphoric acid tributylester, pyridine, tetrahydrofuran, tetrahydronaphthaline, trichloro-ethylene, valeraldehyde, N-vinylimidazol and N-vinylpyrrolidone. Particularly preferred are r-butyrolactone, tetrahydrofuran, N-vinylpyrrolidone and N-methylpyrrolidone. Mixtures of several 25 solvents can also be used. Moreover, water can be added to the aprotic solvents, provided that it does not hinder the activation of the blocked or microencapsulated cross-linking agent, which can easily be tested in each individual case. Preferably, i the water content does not, however, amount to more than around 30% by weight in relation to the solvent as a whole. The water can on the one hand react with isocyanate groups, on the other hand it may activate the cross-linking agent, by e.g. dissolving the salt from the MDA-complex or by dissolving the shell polymer in the case of encapsulated compounds.

Under some circumstances it may be advantageous to add to the ; iw 0;- '\ ■ 3 ."3 0 NOV 1990''7 22 98 64 Vw solvent or solvent mixture an additive which prevents the formation of a hollow channel inside of the sealing strip since such channel may impair the mechanical strength of the strip. Suitable additives of this type are especially the isocyanate 5 prepolymers forming also the base of the sealing and adhesive composition, but without the catalyst and the cross-linking agent. Generally the content of such additives, especially of isocyanate prepolymer, in the injection mixture is up to 10% by weight, preferably about 2 to 8% by weight.

When applying the sealing and adhesive compound strip to a substrate, e.g. a glass pane for a motor vehicle, the solvent injection is best started with only a slight delay compared with the extrusion of the strip, and ended shortly before the 15 completion of the extrusion to avoid premature hardening of the two ends of the strip and to make it possible to join them without a weld. In addition, this prevents the solvent or solvent mixture from running out of the strip, because the ends of the strip remain closed. Due to the partial permanent 20 hardening in the remaining areas of the glass/metal bond the window can be fixed with sufficinet firmness within a very short time after insertion in the vehicle body, thus avoiding slipping. The partial hardening of the adhesive and sealing compound makes any additional mechanical fixing of the glass 25 pane unnecessary. The complete permanent hardening of the adhesive and sealing material occurs by reaction with the air moisture present at room temperature.

A device suitable for carrying out the process according to the 30 invention in the form of an extrusion nozzle is shown schematically in cross-section in Figures la and lb. The adhesive and sealing compound is supplied to the extrusion nozzle from above at 2. It exits laterally below from the triangular die opening 3 and is applied to the appropriate 35 substrate (e. g. the glass pane) in the form of a strip which is triangular in cross-section. An injection needle 4 for the solvent or solvent mixture is attached to the extrusion nozzle from the side, and the solvent enters the needle at 5. The exit opening 6 of the injection needle points in the extrusion f direction and is located in the region of the centre axis of the die opening 3 which forms the strip, so that the solvent can be injected in longitudinal direction into the interior, and preferably into the centre of the profiled strip. The solvent or solvent mixture can be added in doses with the aid of a plunger burette or a similar dosing device. A specific stoichiometric 10 ratio need not be maintained here.

Figure 2 shows in cross-section a profiled strip manufactured according to the invention. The profiled strip 11 contains the injected solvent 12 approximately in the centre (Figure 2a). 15 After a short time a hardened core 13 of a considerably greater diameter has already formed concentrically from the solvent (Figure 2b) and soon afterwards the permanently hardened area 14 reaches the outer boundary surfaces of the profile (Figure 2c) . In Figure 3 the state in Figure 2b is shown once again in 20 section in perspective.

C c m 229864 The following examples are intended to provide a more detailed explanation of the invention without, however, limiting it.

Example 1 An adhesive and sealing material is manufactured in a vacuum planetary mixer from the following components: 52.44% PU-prepolymers of a polyetherol and MDI with 10 reactive isocyanate end groups (isocyanate equivalent weight 3400) 31.35% of a mixture of carbon black and finely divided calcium carbonate in the weight ratio of 2:1 14.97% C-7-Cix-alcohol phthalate as a plasticiser 0.20% nickel dibutyl dithiocarbamate 0.04% dibutyl tin maleate as a catalyst 1.00% complex compound (MDA)3NaCl as a blocked cross-linking agent.

For comparison an adhesive and sealing material was manufactured as shown above but the complex compound was replaced with the same proportions of filler and plasticiser.

For the subsequent hardening experiments adhesive bonds were 30 made from glass panes (dimensions 100 x 25 x 5 mm); the surfaces to be adhered to were pretreated with isopropanol and a suitable primer. The dimensions of the adhering joint were 25 x 8 x 5 mm. The respective tensile strength was measured in N/cm2 for each of the hardening conditions given in the subsequent tables.

With the materials used according to prior art the rate of hardening is very much dependent on the moisture available. Table 1 shows the tensile strengths measured on pretreated O <"»' > Q '.I A .-(CJOUM glass-glass bonds at 25% and 50% air moisture using the mixture without the complex compound.

Table 1 25% r.h. 50% r.h.

Time N/cm2 N/cm2 1 day 3 days 10 7 days 68 ± 4 175 ± 44 255 ± 60 110 ± 25 338 + 40 442 ± 21 (Break generally cohesive) The above sealing and adhesive composition was hardened by the 15 injection of a solvent mixture at 25% and 50% air moisture and a temperature of 23°C. Table 2 shows the tensile strengths (N/cm=) measured on the glass-glass bond using various solvent mixtures: A 70% by weight Y-butyrolactone + 30% by weight water B 70% by weight tetrahydrofuran + 30% by weight water C 70% by weight N-vinylpyrrolidone + 30% by weight water >> i <<* /; ■ ■''V ; C3 0 NOV 2990/ Table 2 A B Time % r.h. 50% r.h. % r.h. 50% r.' 1 day 3 days 7 days 142+42 346±41 354+22 195+70 318±87 357±29 103+19 211+ 2 268+47 88 + 27 236±92 358+64 o C % r.h. 50% r.i 80 + 30 120±53 180+104 194±104 321+64 320+11 N) 1 ro ro cx> cx> 4S O O ' \ ' > ' • A - c.«; o n -i Example 2 f0**.

To determine the rate of through-hardening with moisture 5 excluded, various solvents were injected in triangular extrusions into the material of Example 1. Directly after the application of the extrusions the material was packed in aluminium foil to exclude moisture. The rate of through-hardening was determined using the diameter of core formation; at 10 mm diameter complete through-hardening is achieved. Without the injection of solvent no hardening occurred at all under these conditions.

Table 3 Time (h) NVP:HaO 70:30 Core (mm) BL 100 Core (mm) BL/H=0 70/30 Core (mm) 0.5 1 2 4 6 3.0 3.6 5.0 7.0 10.0 NVP = N-vinylpyrrolidone BL = Y-butyrolactone Example 3 2.5 3 6 9 3.1 3.8 .2 7.0 .0 C>'\ ^ .

O, 0 WOV/99Q •' Dodecamethylene diamine was ground in a mortar mill to a grain fineness < 100 (im. In an apparatus consisting of a three neck flask, a rotary pump and a photo reactor equipped with a 250 W mercury vapor lamp, 6 0 g of the amine was processed in the 35 three neck flask to an aqueous dispersion containing 20% solid material. In a nitrogen atmosphere 100 g of methylmethacrylate, in which was dissolved 0.1% of a photoinitiator of the benzoin ether type, was dripped into this dispersion with constant stirring. The dispersion was in addition continually pumped from <pk r) o a a. o -I the photoreactor into the three neck flask and continually pumped from the photoreactor into the three neck flask and back. After three hours the additon of monomer ended, for complete polymerisation the dispersion was pumped for an additional 2 5 hours through the photoreactor. The thus encapsulated amine was then filtered off and dried in a high vacuum.

A 3% dispersion of this amine in a prepolymer plasticizer mixture, as used for the manufacture of the adhesive/sealing 10 material in Example 1, exhibits a fully satisfactory storage stability. If this mixture is mixed with a solvent as in example 1, it is permanently hardened after a short time, i.e. the encapsulated amine is suitable for the process according to the invention. Particularly preferred solvents are in addition to 15 those already mentioned above (Y-butyrolactone etc.) butyl-acetate, chloroform and diethylene glycoldiester.

Example 4 Methylene dianiline was ground in a mortar mill to a grain fineness < 100 |im. 40g of the amine was dispersed in dry petrol ether to form a 20% dispersion in a three neck flask with moisture excluded. Under rapid agitation 28g of a liquid diphenylmethane diisocyanate (MDI, isocyanate equivalent weight 143) was dripped into this dispersion over four hours. After a further 3 hours agitation no isocyanate could be detected in the dispersion using the infrared spectrum. The finely divided solid was filtered off and dried under vacuum.

A 3% dispersion of this amine encapsulated with polyurea in a prepolymer/plasticizer mixture also shows a fully satisfactory storage stability and rapid permanent hardening when solvent is added, i.e. the encapsulated amine is suitable for the process according to the invention. The solvents already mentioned above 35 (x-butyrolactone etc.) are particularly preferred. • .. » i- ' <* J •V C' - ■'"J 't-'\ v"30 NOV 1990$ '• ,o.-/ n IS 229864 i* t

Claims (18)

WHAT WE CLAIM IS:

1. A method of producing a sealing and adhesive compound strip using a moisture-hardening single-component polyurethane composition based on telechelic isocyanate prepolymers of aromatic diisocyanates in stoichiometric excess and polyols, characterized in that a composition comprising a) a catalyst for the moisture hardening and b) a blocked activatable cross-linking agent is used and during the extrusion of the strip a solvent or solvent mixture is continuously injected into the inside of the strip which liberates the cross-linking agent.

2. The method of claim 1, characterized in that the composition comprises a tin compound as catalyst.

3. The method of claim 1, characterized in that the composition comprises as blocked cross-linking agent a methylene dianiline/sodium chloride complex compound.

4. The method of claim 1, characterized in that the composition comprises as blocked cross-linking agent a polyamino- or hydroxyfunctional compound in microencapsulated form.

5. The method of claim 4, characterized in that the polyamino-or hydroxyfunctional compound is solid at room temperature but liquid at temperatures above 60°C.

6. The method of one of the claims 4 or 5, characterized in that the shell of the microcapsules consists of a poly(meth)acry- late.

7. The method of claim 6 wherein said microcapsules consists 0f polymethylmethacrulate.

8. The method of claim 1, characterized in that a pe-Lajr ^aprotic solvent is used as solvent. f* -It - 229864 O

9. The method of claim 8, characterized in that the solvent is selected from the group comprising y~butyrolactone, tetrahy-drofuran, N-vinylpyrrolidone, N-methylpyrrolidone or mixtures of these.

10. The method of claim 8, characterized in that up to 30% by weight of water is added to the solvent or solvent mixture.

11- The method of claim 1, characterized in that an isocyanate prepolymer is added to the solvent or solvent mixture.

12. The method of claim 11, characterized in that the isocyanate prepolymer is present in the injection mixture in an amount of up to 10% by weight.

13. The method according to claim 1, characterized in that in the production of the sealing and adhesive strip the solvent injection is started with a slight time delay compared with the extrusion of the strip and is ended shortly before the completion of the extrusion.

14. The method of any one of • claims 1 to 13 for the direct w glazing of motor vehicles.

15. A method is claimed in any one of claims 1 to 14 substantially as hereinbefore described with reference to any example thereof and/or any of the accompanying drawings. C

16. Device for implementing the method of any one of claims 1 to 15, characterized by an extrusion nozzle for the sealing and adhesive strip with an injection needle for the solvent, which opens into the nozzle, the exit opening of which needle points in the extrusion direction and is located in the region of the centre axis of the extrusion die forming the strip. 22 9864 -n-

17.. a device as claimed in claim 16 substantially as hereinbefore described with reference to any of the accompanying drawings.

18- A sealing and adhesive compound strip prepared by a method as claimed in anyone of claims 1 to 13 and 15. DATED THIS ^ DAY OF ") -j 19 A. J. PARK & SON PER //'* 1 __ J AGENTS FOR THE APPLICANTS