WO2009095739A1

WO2009095739A1 - Sealant composition based on segmented block co- polymers of mercapto functionalized polymers and isocyanate terminated prepolymers

Info

Publication number: WO2009095739A1
Application number: PCT/IB2008/001316
Authority: WO
Inventors: Volker Burkhardt
Original assignee: Le Joint Francais
Priority date: 2008-01-29
Filing date: 2008-01-29
Publication date: 2009-08-06

Abstract

A composition for extemporaneous mixing, which comprises: - a first composition Cl which comprises at least A one liquid SH- functionalized polymer; - a second composition C2 which comprises at least B one isocyanate- functionalized polyhydroxylated polymer or prepolymer. The use of this composition for preparing sealants.

Description

SEALANT COMPOSITION BASED ON SEGMENTED BLOCK COPOLYMERS OF MERCAPTO FUNCTIONALIZED POLYMERS AND ISOCYANATE TERMINATED PREPOLYMERS

The invention relates to a sealant and adhesive composition and more particularly, to a curable composition of liquid SH-functionalized, notably polysulfide, polymers (PSR) and isocyanate functionalized prepolymers (PUR) which is capable of producing cured thin films, coatings, adhesives and sealants of alternating block copolymers.

Compositions based on liquid polysulfide are being used in a wide range of applications as sealants in the construction industry (insulating glass) and the aerospace industry. These formulas use reinforcing agents like carbon black and active and inactive white fillers like calcium carbonate, silica or titanium dioxide. Liquid polysulfide resins are usually cured with an oxidizing agent such as manganese dioxide, lead dioxide, strontium chromate, sodium perborate or calcium peroxide. The curing mechanism of the liquid polysulfide is based on the oxidation of the SH end groups to S-S-bonds to form a polymer network.

The reaction of liquid polysulfide with a monomeric isocyanate is known in the chemical literature and was described also by Clive Woolward in US 5,212,231 (May 1993). In this patent application, the reaction of a liquid polysulfide with a monomeric isocyanate in the presence of an organometallic or metal salt catalyst, preferably an organotin catalyst like dibutyltin laurate (DBTL) is described. In that prior art application, also the reaction of liquid polysulfide with isocyanate using an amine catalyst is described. But the described method in US-5,212,231 had this strong disadvantage, that, the reaction between water and the isocyanate which was prevalent dominant in that system. The resulting carbon dioxide formed a blown product. As an explanation for that foaming the auto-catalytic effect of the amino group was given.

Thus, there remains the need for a composition based on polysulfide and isocyanate which does not suffer of foaming at the time of curing, which can be cured in the presence of an amine catalyst, which produces films with good weathering resistance, and which requires only small amounts of plasticizers

Surprisingly a method has been found to produce alternating AB block co-polymers based on mercapto functionalized polymers and isocyanate terminated prepolymers which can be used for the production of sealants or adhesives that combine the excellent liquid polysulfide attributes of good resistance to solvents, gasoline, kerosene and diesel and low argon migration, with the polyurethane characteristics of low moisture vapour transmission (MVTR), low water swell, good electrical resistance, and mechanical properties. The segmented polysulfide polyurethane block-copolymer based compositions of the present invention are found to have a greater tensile strength, elastic behaviour and improved adhesion to many types of surface than regular liquid polysulfide based sealants cured with an oxidizing agent. The method can be extended to any SH-functionalized polymer and is not only limited to polysulfides. A first object of the invention is a composition for extemporaneous mixing, which comprises:

- a first composition Cl which comprises at least one liquid SH- functionalized polymer (A);

- a second composition C2 which comprises at least one isocyanate- functional ized polyhydroxylated polymer or pre-polymer (B).

Advantageously, this composition is in two parts. By liquid SH-functionalized polymer is meant a polymer which is liquid at ambient temperature and around, that is to say at a temperature superior or equal to 5⁰C, and up to a temperature of at least 35°C. The liquid SH-functionalized polymer is advantageously selected from the group consisting of SH-terminated polymers, and preferably selected from the group consisting of mercapto-terminated polysulfides, mercapto-terminated polyethers, mercapto-terminated polythioethers and polythiols.

According to a first variant, the SH-functionalized polymer is selected from the group consisting of mercapto-terminated polysulfides. Advantageously, the SH-functionalized polymer has a SH functionality comprised between 2 and 2.5 -SH reactive groups per polymer chain, preferably between 2 and 2.1 -SH reactive groups per polymer chain. Preferably, component A has an average molecular weight between 1000 and 8000 Daltons, preferably between 1000 and 5000 Daltons, and a low degree of branching.

The preferred liquid polysulfide polymer A for use in the compositions of the present invention is a mercapto terminated liquid polysulfide, advantageously with a structure of polysulfide bonds Sx (with 1 < x < 10, and advantageously 1 < x < 5) in a polymer, which means that the number of consecutive - S- atoms in the polymer chain is comprised between 1 and 10, and advantageously it is comprised between 1 and 5.

According to a favourite variant, component A is a mercapto terminated liquid polysulfide of average molecular weight comprised between 1000 and 8000 Daltons, preferably between 1000 and 5000 Daltons. Preferred liquid polysulfide polymers for use in the compositions of the present invention have a degree of branching comprised between 0 and 4, advantageously between 0 and 3, more preferably between 0 and 2.5, and even more preferably between 0.5 and 2.0 expressed as mole percent of branch parts with regards to backbone.

According to another favourite variant component A has an average structure responding to the formula HS-[R^SS]₃-CH₂-CHR²CH₂-[SS-R¹Jb -SH, with R¹= C₂H₄-O-CH₂-O-C₂H₄ and R²^SS-R¹J_c-SH with a, b, c, integers and a+b+c=n wherein n is in the range from 5 to 60, most preferably between 10 and 40.

Polysulfide polymers have two or more sulfur-sulfur linkages. Suitable polysulfides are commercially available from Akzo Nobel under the name THIOPLAST (S) and from Toray under the name of THIOKOL ®. THIOPLAST ® and THIOKOL ® products are available in a wide range of molecular weights, for example, from less than 1100 to over 8000 Dalton. The crosslink density of these products also varies, depending on the amount of crosslinking agent used. The "SH" content, i.e. the mercaptan content, of these products can also vary. The mercaptan content and molecular weight of the polysulfide can affect the cure speed of the blend, with cure speed increasing with molecular weight. In some embodiments, it is desired to use a combination of polysulfides to achieve the desired molecular weight and/or crosslink density in the polymer blend. Different molecular weights and/or crosslink densities can contribute different characteristics to the blend and compositions incorporating the blend. For example, blends wherein the polysulfide component comprises more than one polysulfide polymer and one of the polysulfide polymers has a molecular weight of approximately 1000 have desirable non-crystallization properties. The commercial polymers Thioplast Gl 12 ® or Thiokol LP32 ® and Thioplast Gl 31 ® or Thiokol LP 31 ® are particularly suitable for producing compositions to be used as highly viscous, low modulus sealants for construction, aerospace, automotive and insulating glass application. Compositions of low viscosity, and for high modulus applications use preferably Thioplast G21® or Thiokol LP23®. They can also be used in blends with Thioplast G4 ® and/or Thioplast G44 ® or Thiokol LP3 ® and/or Thiokol LP33 ®. Other commercial references with equivalent properties may be used.

In the compositions of the present invention the SH-functionalized polymer can also be selected from mercapto-terminated polyethers and polythioethers having a polyether or polythioether moiety in the main chain, like for example the products commercialized as Permapol ® P2, P3 and P5.

The polythioether is a polymer comprising at least one polythioether linkage, i.e., -[- CH₂-CH₂-S-CH₂-CH₂-]-. Typical polythioethers have from 8 to 200 of these linkages. Suitable polythioethers typically have a number average molecular weight of 1000 to 10,000, such as 2,000 to 5,000 or 3,000 to 4,000. For a polythioether component that contains reactive functional groups, the average functionality typically ranges from 2.05 to 3.0, such as from 2.1 to 2.6. A specific average functionality can be achieved by suitable selection of reactive ingredients. Examples of suitable polythioethers are available from PRC-Desoto International, Inc., under the trademark PERMAPOL ®, such as PERMAPOL ® P-2, PERMAPOL ® P-3. Ie or PERMAPOL ® P-3. As with the polysulfide component, combinations of polythioethers can be used to prepare the polythioether component according to the present invention. The polymer blends of the present invention can be prepared according to any standard means known in the art, such as by mixing the polysulfide component and polythioether component and blending in a standard mixer such as a planetary mixer. The ratio of polysulfide component to polythioether component in the blend can range from 10:90 to 90:10. A 50:50 ratio is particularly suitable for some embodiments. The molecular weight of the present polymer blend is typically from 1000 to 8000, such as 3500 to 4500 Dalton. It may be desirable to further mix the polymer blend of the present invention with other polymers or additives to control various physical performance parameters of the blend. An also suited polymer in this embodiment is the reaction product of a polysulfide, DMDS, and an amine. Such a product is commercially available from PRC-DeSoto International, Inc. as PERMAPOL ® P-5.

Monomeric polythiols or low molecular weight polythiols like pentaerythritol tetra (3-mercaptopropionate), trimethylpropane-tri (3- mercaptopropionate), glycol-di (3-mercaptopropionate) or propyleneglycol (3- mercaptopropionate) are also suited and can be used in the compositions of the invention as SH-functionalized polymer. Such molecules are particularly appropriate, alone or in mixture with other SH-terminated polymers, to control the hard/soft degree in the SH-terminated polymer based part of the alternating AB-block co-polymer. The composition Cl can also comprise a catalyst. The presence of a catalyst in Cl reduces the time of reaction between components A and B. It is used when appropriate according to the type of application concerned.

The catalysts used in this invention are preferably amine catalysts. Advantageously, they are selected from the group consisting of tertiary amines, such as trietyl amine, N,N,N',N'-tetrametylguanidine, benzyl dimethyl amine, bis-(2- dimetylaminoethyl)ether, benzyldimethylamine, N,N,-dimethylcyclohexylamine, pentamethyldiethylenetriamine, N-ethylmorpholine, N-methylmorpholine, 2,2'- dimorpholinodiethylether, 1 ,3 ,5-tris(3-(dimethylamino)propyl)hexahydro-triazine, 1 ,4- diazabicyclo[2.2.2]octane, l,3,5-tris(3-dimethylamino)propyl)-hexahydro-alpha- triazine, and polymers thereof. Two or more catalysts may also be used in combination. Morpholino derivatives (molecules comprising a morpholine cycle in their structure) are a group of favourite catalysts. The preferred amount of amine, preferably tertiary amine, for use in the compositions of the present invention is between 0.001 — 0.3 weight percent with regards to the total weight of the SH-functionalized polymer. The amount of catalyst depends on the desired curing speed and on the choice of a specific amine. Heavy metal catalyst, commonly used to cure urethane polymers, like for example stannous acetate, stannous octanate, dibutyl tin dilaurate, dibutyl tin maleate, mercury-based catalysts, although they can be used in the compositions of the invention, are not specifically requested in these compositions.

Heavy metal peroxides, like manganese peroxide, lead peroxide or calcium peroxide, commonly used in liquid polysulfide-based sealants are also not necessary, although they may be employed in the compositions of the invention.

One advantage of the invention is that the polymerization reaction can be performed in the absence of heavy metal compounds, and without the disadvantages of prior art amine-catalyzed polymerizations. All formulations presented in this application are preferably heavy metal and solvent free.

The composition Cl, in addition to the SH-terminated polymer A and the catalyst can also comprise one or more of the following compounds:

-Plasticizers - Adhesion promoters

- Fillers

- Water-absorbing compounds.

The plasticizers for use in the compositions of this invention are characterized by having low volatility, low water absorption properties and excellent compatibility with the mercapto-terminated polysulfides, and/or mercapto-terminated polyethers, and/or mercapto-terminated polythioethers and/or mercapto-functionalized compounds, according to the choice of the SH-functionalized polymer. Plasticizers used in this invention are preferably selected from the chemical group of phtalic acid esters, chlorinated hydrocarbons and glycol benzoates. In the compositions of the invention, plasticizers based on phtalic acid esters, like butylbenzyl phtalate, octyl benzyl phtalate or dioctyl phtalate are prefered. Also suited are plasticizers from the group of glycol dibenzoates like dipropylene glycol dibenzoate, diethylene glycol dibenzoate or monopropylene glycol dibenzoate and mixtures thereof. From the family of chlorinated hydrocarbons, one can name C 14-Cl 7 chlorinated paraffins. Those with a chlorination degree between 40-63% (by weight of chlorine atoms with regards to the total weight of the chlorinated paraffin) are preferred. Plasticizers may be used alone or in combination. Adhesion promoters can be selected from: organosilanes and titanates, like for example a mercaptosilane or a glycidoxysilane or an organo-titanate, commercially available from DEGUSSA, WACKER, OSI or KEN-REACT.

Light stabilizers can be selected from: bis (2,2,6,6,-tetramethyl-4- piperidyl) sebacate (Tinuvin 765 ® or Eversorb 93 ®) and bis (l-octyloxy-2,2,6,- tetramethyl-4- piperidyl)-sebacate (Tinuvin 123 ®).

The use of bis (2,2,6,6,-tetramethyl-4-piperidyl) sebacate and/or bis

(l-octyloxy-2,2,6,-tetramethyl-4- piperidyl)-sebacate produces a good combination of the catalytic effect of tertiary amines and the UV-stabilisation effect of an HALS (Hindered Amine Light Stabilizer). Such compounds may also be used in combination with tertiary amines.

Fillers can be selected from: calcium carbonate, silica, carbon black, titanium dioxide, pigments.

Preferably, fillers are selected from the group consisting of calcium carbonate and silica, most preferably a precipitated calcium carbonate and/or natural calcium carbonate and/or coated precipitated calcium carbonate and/or coated natural calcium carbonate and/or hydrophobic silica.

Preferably, the filler can also be selected from the group consisting of carbon black and color pigments, most preferably hydrophobic carbon black and hydrophobic pigments.

The water-absorbing compound can be for example a molecular sieve, a calcium oxide.

The composition Cl is prepared by mixing of the components at ambient temperature. The composition C2 comprises at least one NCO-functionalized polyhydroxylated polymer B.

NCO-functionalized, preferably NCO-terminated, polyhydroxylated polymers and/or prepolymers are based on organic polyisocyanates which can be selected from the group consisting of aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates, for example ethylene diisocyanate, 1 ,4-tetramethylene diisocyanate, 1,6- hexamethylene diisocyanate, 1,12-dodecane diisocyanate, cyclobutane 1,3 -diisocyanate, cyclohexane 1,3- diisocyanate and cyclohexane -1,4- diisocyanate and also any desired mixtures of these isomers, 1- isocyanato-3,3,5- trimethyl-5-isocyanatomethylcyclohexane, 2,4- hexahydrotolylene diisocyanate and 2,6-hexahydrotolylene diisocyanate and also any desired mixtures of these isomers, hexahydro-1,3- phenyl ene diisocyanate and/or -1,4- phenylene diisocyanate, perhydro- 2,4'- diphenylmethanediisocyanate and/or perhydro -4,4'-diphenylmethanediisocyanate, 1.3- phenylene diisocyanate and 1,4-phenylene diisocyanate, isophorone diisocyanate,

2.4- tolylene diisocyanate and 2,6-tolylene diisocyanate, and also any desired mixtures of these isomers, diphenylmethane 2,4'- diisocyanate and/or diphenylmethane -4,4'- diisocyanate, naphthylene 1,5 -diisocyanate, 4,4'-diphenyl methane diisocyanate, triphenylmethane 4,4',4"-triisocyanate, 1,5 -naphthalene diisocyanate, xylene diisocyanate, furfuryliden diisocyanate, triphenyl methane-triisocyanate, 3,3'- dimethoxy-4,4'-diphenylene diisocyanate, polyphenyl-polymethylene polyisocyanates as are obtained by anilineformaldehyde condensation followed by phosgenization, m- and p-isocyanatophenylsulfonyl isocyanates, perchlorinated aryl polyisocyanates, polyisocyanates-containing carbodiimide groups, polyisocyanates-containing allophanate groups, polyisocyanates-containing isocyanurate groups, polyisocyanates- containing urethane groups, polyisocyanates-containing acylated urea groups, polyisocyanates-containing biuret groups, polyisocyanates-containing ester groups, reaction products of the above-mentioned isocyanates with acetals, polyisocyanates containing polymeric fatty acid radicals and polymers thereof.

It is also possible to employ the isocyanate group-containing distillation residues as they are or dissolved in one or more of the above-mentioned polyisocyanates, which are obtained in the course of the industrial preparation of isocyanates. Particular preference is given in general to the polyisocyanates which are readily obtainable industrially, for example aromatic isocyanates such as 2,4- tolylene diisocyanate and 2,6-tolylene diisocyanate and any desired mixtures of these isomers ("TDI"), polyphenyl-polymethylene-polyisocyanates as prepared by aniline- formaldehyde condensation followed by phosgenization ("crude MDI"), and polyisocyanates containing carbodiimide, urethane, allophanate, isocyanurate, urea or biuret groups ("modified polyisocyanates").

Most preferred are aromatic organic isocyanates like diphenyl methylene 4,4 '-diisocyanate and diphenyl methylene 2,2 '-diisocyanate and aliphatic organic isocyanates, most preferably isophorone diisocyanate. Advantageously, component B is an isocyanate functionalized, preferably NCO-terminated, polymer and/or prepolymer with a molecular weight between 1000-20000 Dalton, more preferably between 1000-10000 Dalton.

Polyhydroxy-polymers used in isocyanate-functionalized, preferably NCO-terminated, polyhydroxy polymers and/or prepolymers can be selected from the group of polyether polyols, aromatic or aliphatic polyester polyols, OH-terminated polybutadiene (HTPB), C₁₂-C₂₄ aliphatic (fatty chemical) polyalcohols etc. They also may be used in combination. The polyol polymer used in the invention may be converted into readyily curable isocyanate terminated polymer and/or prepolymer by the reaction of a polyisocyanate with said polyol using NCO:OH ratio between 1.7 to 2.2, preferably about 1.9-2.1. Polyethers and polyesters having terminal hydroxyl groups are known and are prepared, for example, by polymerizing epoxides such as ethylene oxide, propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin with themselves, for example in the presence of BF₃, or by addition reaction of these epoxides, alone or as a mixture or in succession, with starting components containing reactive hydrogen atoms, such as alcohols, ammonia or amines, for example ethylene glycol, propylene 1,3- and 1,2-glycol, trimethylolpropane, 4,4'- dihydroxydiphenylpropane, aniline, ethanolamine or ethylenediamine. Sucrose polyethers are also suitable in accordance with the invention. In many cases preference is given to those polyethers which predominantly (up to 90 % by weight, based on all the OH groups present in the polyether) contain primary OH groups. Furthermore, polyethers modified by vinyl polymers, as are formed, for example, by polymerizing styrene and acrylonitrile in the presence of polyethers, are suitable, as are polybutadienes containing OH groups. Especially compounds containing from two to eight hydroxyl groups, especially those of molecular weight from 800 to 10 000, preferably from 1000 to 6000, for example polyethers containing at least 2, generally 2 to 8, but preferably 2 to 4, hydroxyl groups. The isocyanate-terminated polyhydroxylated polymers may be used alone or in combination.

The isocyanate-terminated polyhydroxylated polymers are prepared by mixing of the isocyanate compound with the polyhydroxylated polymer in appropriate quantity.Preferably this reaction is performed at a temperature superior or equal to 50°C, more preferably above 60°C, advantageously in dry conditions.

The functionality of NCO-terminated polyhydroxylated polymers and/or prepolymers B is advantageously superior or equal to 2 NCO groups per polymer chain. Preferably it is about 2.

The NCO/OH molar ratio in the isocyanate-terminated polyhydroxylated polymer is advantageously selected between 1.7 and 2.2, preferably about 1.9 to 2.1. This parameter is controlled by the OH- value of the polyhydroxylated polymer and the ratio and NCO-content of the NCO-functionalized reaction partner.

Apart from the NCO-terminated polyhydroxylated polymer, the composition C2 can also comprise: -Plasticizers

- Adhesion promoters

- Fillers - Water-absorbing compounds

The plasticizer, the adhesion promoters, the water-absorbing compound, the antioxidants, and/or light stabilizers and the filler may be selected from the same group of compounds as above-disclosed for Cl. The amount of B in the two parts compositions of the invention is calculated with regards to the SH-content of the SH-functionalized polymer.

The NCO/SH molar ratio, between the NCO functions of B and the SH functions of A, is advantageously selected between 1.0 and 1.2. Preferably an NCO/SH ratio of about 1.0-1.1 is preferred. The composition is prepared by mixing of all the components at an appropriate temperature.

Another object of the invention is a method for the preparation of a

SH-functionalized polymer and an NCO-terminated polymer based alternating AB block co-polymer, said method comprising the step of mixing a composition Cl and a composition C2 as above-disclosed. Said mixing produces the curing of the SH- functionalized polymer A by the NCO-terminated polymer B.

A mixing ratio from 100:100 to 100:1 (by weight) of liquid SH- terminated polymer (for example polysulfide) and NCO-terminated polyhydroxylated polymer, most preferable 100:10 is preferably used.

Preferably, the ratio of viscosity between Cl and C2 is between 0.01 to 100, more preferably between 0.1 and 10 and most preferably close to 1.

Thanks to the method used in the invention, no statistical polymer blends are obtained, but strictly alternating block co-polymers.

The advantages of this method, among others, comprise:

Allophanate reaction, normally observed when NCO compounds are reacted with polysulfides, is avoided. Reaction of isocyanate with moisture to form CO₂ and urea is also avoided.

As heavy metals are not necessary, and not recommended, in the method of the invention, catalyst poisoning by sulphur from the mercapto- functionalized polymer is avoided. The most noticeable advantages of the compositions of the invention are the speedy hardening and absence of foaming. This was reached without having to use any heavy metal catalyst or any heavy metal peroxide to cure the liquid polysulfide based Cl -Part. Foaming was reduced by using raw materials without any active hydrogen and using a molecular sieve to dry the formulation from water. Another object of the invention is a sealant comprising at least one alternating AB block co-polymer wherein A is an HS-functionalized polymer; and B is a polyhydroxylated polymer or prepolymer as above disclosed. The compositions according to the invention can be advantageously used for various purposes and for the preparation of various shaped articles. Examples are:

1. Adhesives, Coatings, sealants 1.1 Elastomer.

1.2. Electrical and electronic industry : Bushes, cable connections, components for electrical control and adjustment, electromagnetic switches, hard and elastomeric encapsulants, gear shift cable castings for motor vehicle electrics, insulants, printed circuits, potting, semiconductors, switches, switch gears, medium and high voltage transformers.

1.3. Automotive: Bonding of textile onto foam, direct glazing of vehicle windscreens, glazing replacement, fastening of various car components, vacuum lamination of foil to fiberboard. Automotive applications, in particular as instrument clusters, sound insulation, carpeting, seating, decorative trim, exterior applications such as weather stripping, exterior trim, light lens units, and windshield assemblies, recreational vehicle side walls.

1.4. Building and civil engineering

Bonding of sandwich insulation panels, flooring, roofs, sealing of car parks, concrete pavements, industrial floors, one component sealant for vertical joints (precast concrete panels, expansion joints), pourable joint sealants for vertical surfaces (floor-to-wall joints).

1.5. General industry

Electronics industry, household goods, loudspeaker acoustic panels, office furniture, metal window frames, air conditioning systems, buses, containers, lorries, metal/sheet metal constructions, railway carriages, sewerage works, silos and ventilation systems.

1.6. Insulated glazing

1.7. Sandwich construction

Binding of similar substrates together or to other materials such as metals, plastics and rigid foam; used in a variety of laminated panels, such as panels for buildings, caravans, partition walls, refrigerated trucks, containers and cold storages. 1.8-Hotmelts

EXPERIMENTAL PART In the example "parts" refers to "parts by weight". In the examples, the properties of the tested samples were evaluated as follows, unless otherwise indicated: Work life and cure time were evaluated by using the time to 10 and 90% of cure respectively, as measured by a BOHLIN Gemini 150 rheometer at 25 ⁰C.

Tensile strength was measured using H-block glass-glass samples as demonstrated in DIN EN 1279-Part 4, pulled at 10 mm per minute at 23⁰C / 50% r.H. using an INSTRON 4505 tensile testing machine.

Elongation was measured using H-block glass-glass samples as demonstrated in DIN EN 1279-Part 4, pulled at 10 mm per minute at 23°C / 50% r.H. using an INSTRON 4505 tensile testing machine.

Hardness was measured using a ZWICK automatic Shore A gauche.

Viscosity was measured by a BOHLIN Gemini 150 rheometer at 25 °C.

All tests were carried out with the most favorable isocyanate index for the composition. A minimum 10% excess of the stoichiometric molar ratio of NCO groups to SH-groups was evaluated and was used in all examples.

As liquid polysulfides we have used the following commercial references: Thioplast G21 ®, Thiokol LP23 ®, Thioplast Gl 31 ®, Thiokol LP31 ®, Thioplast G4 ®, Thiokol LP3 ®, Thioplast Gl 12 ® and Thiokol LP 32 ®.

Table 1 shows the calculated SH-contents of the liquid polysulfides based on their viscosity and crosslinking used in this invention. Table 1:

(*)TCP= tri chloro propane / present in the commercial references As isocyanates in the following samples aliphatic and aromatic polyisocyanates and monoisocyanates based on diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and toluene diisocyanate were used.

Formulation examples for sealants containing a segmented liquid polysulfide / polyurethane AB-block co-polymer - Formulation examples for the liquid polysulfide based A-Part (Base) The liquid polysulfide (Thioplast, available from AKZO or Thiokol, available from TORAY), a plasticizer (phthalic acid ester, available from FERRO or a benzoate, available from VELSICOL), an adhesion promoter (Mercaptosilane or glycidoxysilane or organo-titanate, available from DEGUSSA, WACKER, OSI or

KEN-REACT), a catalyst (tertiary amine, available from Huntsman), a hindered amine light stabilizer (available from CIBA or EVERLIGHT Chemicals), a precipitated calcium carbonate (available from SOLVAY or SPECIALTY MINERALS), a natural calcium carbonate (available from OMYA or REVERTE) and a molecular sieve (available from W.R. Grace)

The components were introduced in the following quantities as shown in Table 2 in weight percent with regards to the total weight of the reaction mixture:

The liquid polysulfide, the plasticizer, the silane based adhesion promoter, the tertiary amine and the light absorber were added to a dispenser disc mixing device and mixed under temperature control (not higher than 30 °C) for 30 min under vacuum (pressure: - 1 bar).

The precipitated calcium carbonate, the natural calcium carbonate and the molecular sieve were added in steps to a mixing device and mixed thoroughly under temperature control (not higher than 70 °C) for 30 min minimum under vacuum (pressure: - 1 bar).

- Formulation examples for the 4,4'-diphenyl methane diisocyanate (MDI) / polyol based prepolvmer (curative Part)

A polyether based polyol (available from BAYER or DOW), a plasticizer (phthalic acid ester, available from FERRO or a benzoate, available from VELSICOL), a carbon black (available from DEGUSSA or CABOT), a precipitated Silica (available from DEGUSSA or WACKER), a natural calcium carbonate (available from OMYA or REVERTE), a 4,4'- diphenyl methane diisocyanate (MDI) (available from BASF or DOW)

The polyether polyol and the plasticizer were added to a dispenser disc mixing device and mixed under temperature control (not higher than 30 °C) for 15 min minimum under vacuum (pressure: - 1 bar). The carbon black was added in 4 steps. The batch was thoroughly mixed under temperature control (not higher than 50 °C) for 30 min under vacuum (pressure: - 1 bar). The precipitated silica was added in 2 steps. The batch was thoroughly mixed and sheared under temperature control (not higher than 60 ⁰C) for 30 min under vacuum (pressure: - 1 bar). The diisocyanate was added under strong and thorough mixing in one step to the mixing device. The blend reacts under smoothly mixing and under temperature control (at 80 °C) for 45 min under vacuum (-1 bar).

Table 2:

Claims

1) A composition for extemporaneous mixing, which comprises:

- a first composition Cl which comprises at least one liquid SH- fiinctionalized polymer (A); - a second composition C2 which comprises at least one isocyanate- functionalized polyhydroxylated polymer or prepolymer (B).

2) A composition according to claim 1, wherein the liquid SH- functionalized polymer A is selected from the group consisting of: mercapto-terminated polysulfϊdes, mercapto-terminated polyethers, mercapto-terminated polythioethers and polythiols.

3) A composition according to anyone of claim 1 or claim 2, wherein component A is a mercapto terminated liquid polysulfide which has an average molecular weight between 1000 and 8000 Dalton, more preferably between 1000 and 5000 Dalton and a SH functionality comprised between 2 and 2.5 -SH reactive groups per polymer chain, preferably between 2 and 2.1 -SH reactive groups per polymer chain

4) A composition according to Claim 3, wherein component A is a mercapto terminated liquid polysulfide with a structure of polysulfide bonds Sx with 1 < x < 10, and advantageously 1 < x < 5.

5) A composition according to anyone of claim 1 to claim 3, wherein component A has an average structure of the formula HS-tR'-SSl_a-C^-CHR^^-tSS-

R¹J_b -SH, with R¹= C₂H₄-O-CH₂-O-C₂H₄ and R^[SS-R¹J_c-SH with a, b, c, integers and a+b+c=n, wherein n is in the range from 5 to 60, most preferably between 10 and 40.

6) A composition according to anyone of claim 1 or claim 2, wherein component A is a mercapto terminated polyether or polythioether. 7) A composition according to anyone of claim 1 to 6, wherein the

NCO- functionalized polyhydroxylated polymer and/or prepolymer is NCO-terminated and based on aromatic organic isocyanates like diphenyl methylene 4,4'-diisocyanate and diphenyl methylene 2,2 '-diisocyanate and aliphatic organic isocyanates, most preferably isophorone diisocyanate. 8) A composition according to anyone of claim 1 to 7, wherein component B is an isocyanate terminated polymer and/or prepolymer with a molecular weight between 1000-20000 Dalton, more preferable between 1000-10000 Dalton.

9) A composition according to anyone of claim 1 to 8, wherein component B is an isocyanate terminated polymer and/or prepolymer derivated from a polyol selected from the group consisting of: a polyether polyol; an aromatic or aliphatic polyester polyol; Ci₂-C₂₄ aliphatic polyalcohols; hydroxy-terminated polybutadiene (HTPB). 10) A composition according to anyone of claim 1 to 9, wherein the NCO/OH molar ratio in the isocyanate-terminated polyhydroxylated polymer B is selected between 1.7 and 2.2, preferably 1.9 to 2.1

1 1) A composition according to anyone of claim 1 to 10, wherein Cl further comprises a catalyst preferably selected from the group consisting of tertiary amines.

12) A composition according to Claim 11, wherein the catalyst is a morpholino derivative, preferably 2,2 ^'-dimorpholinodiethylether.

13) A composition according to anyone of claim 1 to 12, wherein the weight ratio of component A to component B is 100: 1 to 1 :100.

14) A composition according to anyone of claim 1 to 13, wherein NCO/SH molar ratio, between the NCO functions of B and the SH functions of A, is selected between 1.0 and 1.2, preferably 1.0 and 1.1

15) A composition according to anyone of claim 1 to 14, wherein it further comprises at least one component selected from the group consisting of: a. Plasticizers b. Adhesion promoters c. Fillers d. Water-absorbing compounds 16) A composition according to Claim 15, wherein it comprises at least one molecular sieve.

17) A composition according to anyone of claim 1 to 16, wherein the ratio of viscosity between Cl and C2 is between 0.01 and 100, more preferably between

0.1 and 10 and most preferably close to 1. 18) A method for the preparation of a SH-functionalized polymer and an NCO-terminated polymer based alternating AB block co-polymer, said method comprising the step of mixing a composition Cl and a composition C2 according to anyone of claim 1 to 17.

19) A sealant comprising at least one alternating AB block co-polymer wherein A is an HS-functionalized polymer; and B is a polyhydroxylated polymer or prepolymer according to anyone of claim 1 to 10.