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EP-4741433-A1 - TWO-COMPONENT POLYURETHANE COMPOSITION WITH IMPROVED ADHESION AND ADJUSTABLE POT LIFE

EP4741433A1EP 4741433 A1EP4741433 A1EP 4741433A1EP-4741433-A1

Abstract

The present invention relates to a polyurethane composition comprising a first component and a second component, wherein the first component comprises at least one polyol, at least one diol, at least one compound having at least one thiol group, and the second component optionally comprises at least one polyol and at least one polyisocyanate, wherein one of the two components additionally contains at least one metal catalyst for the reaction of hydroxyl groups and isocyanate groups, which can form thio complexes, and wherein the polyurethane composition additionally contains at least 10 wt%, based on the total polyurethane composition, of a flame retardant. Such a composition allows the open time of the polyurethane composition to be adjusted as desired within certain limits, making it possible to achieve long open times with subsequent very rapid curing of the composition, and also has the advantages of a flame-retardant composition and exhibits particularly good adhesion to aluminium substrates. Further aspects of the invention include the use of the polyurethane composition and a method for bonding substrates, as well as articles resulting from the method for bonding, which is the subject of this invention. The composition according to the invention is particularly suitable as a structural adhesive for bonding two substrates, especially in the automotive sector, or as a sealant or potting compound.

Inventors

  • CHATPHAKAWAN, Phanarin

Assignees

  • Sika Technology AG

Dates

Publication Date
20260513
Application Date
20241111

Claims (15)

  1. Polyurethane composition consisting of a first component A and a second component B, wherein - the first component A - at least one polyol P; - at least one diol O with an average molecular weight of less than 250 g/mol; - includes at least one compound T which has at least one thiol group; and - The second component B - optionally a polyol P; - includes at least one polyisocyanate I; wherein one of the two components A and B additionally contains at least one metal catalyst K for the reaction of hydroxyl groups and isocyanate groups, which can form thio complexes, and wherein the polyurethane composition additionally contains at least 10 wt%, based on the total polyurethane composition, of a flame retardant F.
  2. The polyurethane composition according to claim 1, characterized in that the polyol P comprises a medium OH functionality in the range of 2 to 4 and/or a medium molecular weight in the range of 250 to 10,000 g/mol and/or an OH number in the range of 250 to 600 mg KOH/g.
  3. The polyurethane composition according to one of claims 1 to 2, characterized in that the polyol P comprises polybutadiene polyols, polycarbonate polyols, polyester polyols, polyether polyols, poly(meth)acrylate polyols or a mixture of these polyols.
  4. Polyurethane composition according to one of claims 1 to 3, characterized in that the diol O is a linear aliphatic diol with two primary hydroxyl groups linked via a C2 to C9 carbon chain, in particular selected from the group consisting of 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol and 1,9-nonanediol.
  5. Polyurethane composition according to one of claims 1 to 4, characterized in that the polyisocyanate I is a liquid form at room temperature of 4,4'-, 2,4'- or 2,2'-diphenylmethane diisocyanate and any mixtures of these isomers (MDI) in the form of polymeric MDI or MDI with proportions of oligomers or derivatives, in particular carbodiimides.
  6. Polyurethane composition according to one of claims 1 to 5, characterized in that the metal catalyst K comprises a tin(IV) compound and/or a bismuth(III) compound.
  7. Polyurethane composition according to one of claims 1 to 6, characterized in that the metal catalyst K is contained in the first component A.
  8. Polyurethane composition according to one of claims 1 to 7, characterized in that the flame retardant F is solid under standard conditions.
  9. Polyurethane composition according to one of claims 1 to 8, characterized in that the flame retardant F comprises an organophosphorus compound, in particular phosphoramidates and/or phosphates, and/or metal hydroxides, in particular aluminium hydroxides.
  10. Polyurethane composition according to one of claims 1 to 9, characterized in that the flame retardant F comprises a combination of aliphatic phosphoramidate, preferably in a range of 5 to 20 wt.%, fine-grained ammonium polyphosphate, preferably in a range of 10 to 30 wt.%, and precipitated Aluminium hydroxide, preferably in a range of 20 to 60 wt.%, all based on the first component A, is included.
  11. Polyurethane composition according to one of claims 1 to 10, characterized in that the first component A is in each case related to the total composition of component A - 10 to 40 wt% polyol P; - 1 to 5 wt% Diol O; - 0.1 to 5 wt.% compound T; - 0.01 to 2.5 wt.% metal catalyst K; - 15 to 80 wt.% flame retardant F; - 0 to 8 wt% solvent LM; - 0 to 10 wt% plasticizer WM; - 0 to 40 wt.% filler FS; And that the second component B refers to the entire composition of component B. - 25 to 75 wt% polyol P; - 15 to 70 wt% polyisocyanate I; - 0 to 6 wt.% adhesion promoter HV; - Contains 0 to 40 wt% filler FS , and may contain other components.
  12. Methods for bonding a first substrate to a second substrate include the following steps: i) Mixing the first and second components of a polyurethane composition according to any one of claims 1 to 11; ii) Applying the mixed polyurethane composition to at least one of the substrate surfaces to be bonded; iii) Joining the substrates to be bonded within the potting time; iv) Curing of the polyurethane composition.
  13. The method according to claim 12, characterized in that the substrate is a metal and/or a metal alloy, in particular aluminium.
  14. An article produced by the bonding method according to one of claims 12 to 13.
  15. Use of a polyurethane composition according to any one of claims 1 to 11 as a structural adhesive for bonding two substrates, particularly in automotive applications, or as a sealant or potting compound.

Description

Technical field The invention relates to the field of two-component polyurethane compositions and their use, in particular as adhesives. State of the art Two-component polyurethane compounds based on polyols and polyisocyanates have been used for a long time. Compared to one-component compounds, two-component polyurethanes have the advantage of curing quickly after mixing, allowing them to absorb and transmit higher forces in a short time. For use as structural adhesives, such compounds must meet high demands regarding strength and adhesion, as they are components of load-bearing structures. In particular, these compounds require good mechanical properties in their cured state, such as high tensile and tensile shear strengths, while simultaneously exhibiting a certain degree of elasticity. Furthermore, in industrial manufacturing, for example, it is desirable for such compounds to cure as quickly as possible, even when used as sealants or potting compounds, thus reducing cycle times. To achieve the desired mechanical properties and, above all, particularly rapid curing, high proportions of isocyanates are advantageous in such compositions. These isocyanates are present in one of the two components as free or polymer-bound polyisocyanates and cure upon mixing with the other component, which contains polyols, forming a polymeric network. However, a high isocyanate content leads to problems. Especially when using crosslinking catalysts, which are essential for selective, optimal crosslinking and curing, such isocyanates become problematic. Two-component systems react almost uncontrollably fast, and the pot lives are far too short for an application as described above. For the application of two-component polyurethane compounds, it is generally desirable to combine a sufficiently long pot life with subsequent very rapid curing and exceptionally fast strength development. However, this is hardly achievable with current two-component compounds. Either the pot life is very short for compounds that cure and build strength quickly, or the curing and strength development are slow when compounds with a long pot life are used. Therefore, two-component polyurethane compositions were developed that exhibit a long pot life, adjustable within certain limits, enabling the processing of even larger structural or manufactured parts. These compositions also cure very quickly after application, exhibiting strength and elasticity sufficient for structural bonding within an extremely short time, e.g., hours to a few days. Such a two-component polyurethane composition is available in EP3645594B1 This publication discloses special catalyst systems comprising a metal catalyst and thiol-containing compounds, which allow for an adjustable, long pot life and subsequent very rapid curing of the composition. Furthermore, it describes EP4127008A1 Two-component polyurethane composition with high hydrophobicity and adjustable pot life. With the increasing use of batteries and electronic devices, the demand for suitable structural adhesives for contact with these electronic components or devices has risen considerably. In the assembly of electric vehicles, the large and heavy batteries and numerous electronic parts are often installed in a battery box, which is bonded with a structural adhesive. The battery box is often made of aluminum. It was manufactured because this material allows for a reduction in the weight of the heavy components. However, aluminum is very difficult to bond with the adhesive compositions known from the prior art. A key requirement for these adhesives is high fire resistance, as batteries and electronics generate significant amounts of heat during operation and, in the event of a malfunction, such as a short circuit, can lead to a battery fire. It would therefore be desirable to obtain a two-component polyurethane composition that incorporates a catalyst system offering a long, adjustable pot life and subsequent extremely rapid curing, while also possessing the advantages of a flame-retardant composition, particularly for bonding such battery boxes. Furthermore, such a composition must be able to establish sufficiently strong adhesion to the metal surface to be bonded, especially aluminum. Adhesion to aluminum, in particular, often poses a significant challenge for conventional two-component polyurethane adhesives. Even adhesives with adjustable pot lives, such as those described in [reference to relevant product information], exhibit this limitation. EP3645594B1 revealed insufficient adhesion to aluminium substrates. Description of the invention The object of the present invention is therefore to provide a two-component polyurethane composition with adjustable pot life that meets the requirements of an application as an adhesive in the automotive sector, in particular good adhesion to aluminium should be achieved. Surprisingly, this problem is solved with the polyurethane composition according to claim 1. The comp