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US-12623998-B2 - Process for preparing a polyisocyanate, polyisocyanate, its use and polyaddition products prepared therefrom

US12623998B2US 12623998 B2US12623998 B2US 12623998B2US-12623998-B2

Abstract

The present invention relates to a process for preparing a polyisocyanate, namely an isocyanate group-terminated polyol polyanthranilic acid ester. The process comprises the step of reacting an anthranilic acid derivative selected from anthranilic acid halide (in particular anthranilic acid chloride), isatoic anhydride or a mixture thereof with a first polyol of a number-average molar mass of at least 200 g/mol and a functionality in the range of 2 to 8, and obtaining, as a result, a polyamine (namely a polyol polyanthranilic acid ester with amine terminal groups) and reacting the polyamine with phosgene and obtaining, as a result, a polyisocyanate (namely an isocyanate group-terminated polyol polyanthranilic acid ester). The invention further relates to the polyisocyanates obtained in this way, their use in polyaddition reactions, and polyaddition products obtainable by these reactions.

Inventors

  • Christos Karafilidis
  • Marina Reithmeier
  • Stefan Wershofen
  • Michael Schedler
  • Michael Baecker

Assignees

  • COVESTRO DEUTSCHLAND AG

Dates

Publication Date
20260512
Application Date
20211209
Priority Date
20201210

Claims (15)

  1. 1 . A process for preparing a polyisocyanate comprising: (A) reacting an anthranilic acid derivative comprising anthranoyl halide, isatoic anhydride or a mixture thereof with a first polyol of functionality b and the general formula X—(OH) b , where b has a value of 2 to 8 and X is a radical that derives from the first polyol by removal of all alcohol groups, and where the first polyol has a number-average molar mass of at least 200 g/mol, to obtain a polyamine of the formula in which a=b−1; and (B) reacting the polyamine with phosgene to obtain a polyisocyanate of the formula
  2. 2 . The process as claimed in claim 1 , in which the first polyol comprises a polyether polyol, a polyester polyol, a polyetherester polyol, a polycarbonate polyol, a polyether polycarbonate polyol, a polythioether polyol or a mixture of two or more thereof.
  3. 3 . The process as claimed in claim 1 , in which the reaction of the anthranilic acid derivative with the first polyol is conducted in the presence of a basic catalyst.
  4. 4 . The process as claimed in claim 1 , in which the reacting of the anthranilic acid derivative with the first polyol is conducted at a temperature of 0° C. to 120° C.
  5. 5 . The process as claimed in claim 1 , in which a gas formed in step (A) is removed in gaseous form, chemically bound or physically bound during the reaction of the anthranilic acid derivative with the first polyol.
  6. 6 . The process as claimed in claim 1 , in which the polyamine obtained in step (A) is isolated by a method comprising filtration, distillation, sublimation, crystallization, precipitation or a combination of two or more thereof.
  7. 7 . The process as claimed in claim 1 , in which the reacting of the polyamine with phosgene in step (B) is conducted at a temperature of 0° C. to 200° C.
  8. 8 . The process as claimed in claim 1 , in which phosgene is used in step (B) in a stoichiometric excess based on the amino groups of the polyamine.
  9. 9 . The process as claimed in claim 1 , in which step (B) is followed by: (C)(i) reacting the polyisocyanate obtained in step (B) with an organic compound comprising 2 or more acidic hydrogen atoms to obtain a polyaddition product.
  10. 10 . The process as claimed in claim 9 , in which the organic compound comprising 2 or more acidic hydrogen atoms comprises a third polyol and/or a polyamine, and the polyaddition product obtained is an elastomer, a thermoplastic, a foam, an adhesive or a sealant.
  11. 11 . The process as claimed in claim 1 , in which step (B) is followed by: (C)(ii) reacting the polyisocyanate obtained in step (B) with water to obtain a foam, an adhesive, or a sealant.
  12. 12 . A polyisocyanate of the formula in which X is a radical which derives from a first polyol having a number-average molar mass of at least 200 g/mol, having functionality b, and being of the general formula X—(OH) b , where b has a value of 2 to 8, by removal of all alcohol groups, and in which a=b−1.
  13. 13 . A method of producing a polyaddition product, comprising reacting the polyisocyanate as claimed in claim 12 with a compound comprising 2 or more acidic hydrogen atoms.
  14. 14 . The method as claimed in claim 13 , in which the compound comprising 2 or more acidic hydrogen atoms comprises a third polyol, a polyamine and/or water.
  15. 15 . A polyaddition product formed from a polyisocyanate as claimed in claim 12 and a compound comprising 2 or more acidic hydrogen atoms.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a national stage application under 35 U.S.C. § 371 of PCT/EP2021/084975, filed Dec. 9, 2021, which claims the benefit of European Application No. 20213043.1, filed Dec. 10, 2020 and European Patent Application No. 21194917.7, filed Sep. 3, 2021, each of which is incorporated herein by reference. FIELD The present invention relates to a process for preparing a polyisocyanate, namely a polyol-polyanthranilic ester terminated by isocyanate groups. The process comprises the reaction of an anthranilic acid derivative selected from anthranoyl halide (especially anthranoyl chloride), isatoic anhydride or a mixture thereof with a first polyol of a number-average molar mass of at least 200 g/mol and functionality in the range from 2 to 8 to obtain a polyamine (namely a polyol-polyanthranilic ester having aminic end groups) and reacting the polyamine with phosgene to obtain a polyisocyanate (namely a polyol-polyanthranilic ester terminated by isocyanate groups). The invention further relates to the polyisocyanates thus obtainable, to the use thereof in polyaddition reactions, and to polyaddition products thus obtainable. BACKGROUND Polyurethane prepolymers containing isocyanate groups (=polyurethane structures having reactive NCO end groups) have long been known in the prior art. They are obtained by reacting a stoichiometric excess of a polyisocyanate component (for example methylene diphenylene diisocyanate, optionally in a mixture with higher homologs thereof, the polyphenylene polymethylene polyisocyanates) with a polyol component (for example a polyester polyol, a polyesterether polyol or a mixture of different polyol types), and are used, for example, in the production of elastomers, coatings, bonding agents and the like. In general, the aim is to keep the residual content of unconverted polyisocyanate component as low as possible in order not to impair later use and to prevent volatilization of volatile polyisocyanates during use. There has been no lack of attempts to improve the preparation of polyurethane prepolymers in such a way that such problems do not occur or are at least minimized. For this purpose, it is common practice, for example, to free the crude products from the prepolymer synthesis of residual constituents of polyisocyanate component used by thin-film distillation, which is energy-intensive and costly. For example, EP-A 0 590 398 describes the use of low-monomer isocyanate-terminated polyurethane prepolymers that have been obtained by removing the monomeric polyisocyanates by distillation. However, the fundamental procedure for preparation of prepolymers with NCO end groups has been retained. By contrast, the present invention takes an alternative route that likewise leads to NCO-terminated prepolymers, but does so not by the customary route of urethanization of low molecular weight polyisocyanates with a deficiency of polyols, but rather proceeding from reactive derivatives of anthranilic acid. It is known that anthranilic acid can be converted to polyanthranilic esters, and such polyanthranilic esters can be used in polyaddition reactions, for instance as crosslinkers, as chain extenders or as reactant in the preparation of polyureas. For instance, the following publications describe the following: the article “Estergruppen enthaltende Polyamine als Baukomponenten für die Polyurethanchemie”[Polyamines Containing Ester Groups as Structural Components for Polyurethane Chemistry] in Angew. Makromol. Chem. 1972, 26, 29-45: the use of such esters as structural components for polyurethane elastomers, US patent application US 2003/0212291 A1: the use thereof as crosslinkers, German patent specification DE 20 40 644: the use thereof as chain extenders, and US patent specification U.S. Pat. No. 3,808,250: the use thereof as amine component in the preparation of polyureas by reaction with isocyanates. WO 89/00589 A1 (also published as U.S. Pat. No. 4,829,099 and DE 38 51 428 T2) relates to adhesives produced from metabolically compatible polyisocyanate or polyisothiocyanate monomers. More particularly, this document relates to surgical adhesive polymers derived from these polyisocyanate monomers, which are not metabolized to give toxic products. One example of a possible route to such products which is described is the reaction of a polyhydric alcohol with an aromatic nitro acid chloride (for instance 2—and especially 4-nitrobenzoyl chloride), followed by catalytic hydrogenation of the nitro group to an amine group and phosgenation thereof to give an isocyanate group. (It is not possible to perform the catalytic hydrogenation before the reaction with the polyhydric alcohol because the acid chloride group in that case would be reduced to an aldehyde or even an alcohol group.) This synthesis route is complex and associated with not inconsiderable yield losses. The amines obtained as intermediates after the hydrogenation are comparatively high-m