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Polyisocyanate mixtures, a process for their preparation and their use in coating compositions

a technology of polyisocyanate and mixture, which is applied in the field of modified polyisocyanate mixture, can solve the problems of merely moderate acid resistance, scratch resistance and the general inadequate reflow of such coating composition, and achieves the effects of reducing the number of reflows, and improving the reflow ra

Inactive Publication Date: 2006-05-25
COVESTRO DEUTSCHLAND AG
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention is about polyacrylate-modified polyisocyanates which are prepared from aromatic, araliphatic, cycloaliphatic and / or aliphatic polyisocyanates. These polyisocyanates have certain structural units that make them suitable for use in binder compositions. The invention also includes a process for preparing these polyisocyanates by reacting a portion of the isocyanate groups of a starting polyisocyanate with a monoalcohol containing acrylate and / or methacrylate groups, and optionally other unsaturated monomers. The resulting polyacrylate-modified polyisocyanates have improved properties such as increased flexibility and resistance to yellowing. The invention also includes binder compositions containing these polyacrylate-modified polyisocyanates, which can be used in various applications such as water-dilutable or aqueous binder compositions.

Problems solved by technology

Disadvantages of such coating compositions include the somewhat slow drying at room temperature and slightly elevated temperature, and also the merely moderate acid resistance.
The scratch resistance and the reflow of such coating compositions, however, are generally inadequate.
A disadvantageous consequence with these mixed trimers is that, due to the fraction of IPDI, which is necessary for the requisite hardness and rapid physical drying, the amount of isocyanate groups (relative to the molecular weight) is lower than in the case of pure HDI trimers, with attendant economic drawbacks.
With regard to the use of the polyisocyanate, this necessitates an economically undesirably high amount of polyisocyanate curative and an increased volume of solvent for adjusting the application viscosity of the coating composition.
This patent does not disclose anything regarding the possibility of using polyisocyanates of such high viscosity, in combination with suitable polyols, to prepare polyurethane coating compositions having improved chemical resistance.
This circumstance harbours economic drawbacks.

Method used

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  • Polyisocyanate mixtures, a process for their preparation and their use in coating compositions
  • Polyisocyanate mixtures, a process for their preparation and their use in coating compositions
  • Polyisocyanate mixtures, a process for their preparation and their use in coating compositions

Examples

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examples

[0065] Abbreviations and ingredients used:

[0066] HEA: Hydroxyethyl acrylate

[0067] HEMA: Hydroxyethyl methacrylate

[0068] HPMA: Hydroxypropyl methacrylate

[0069] Desmodur® HL BA: Aromatic-aliphatic polyisocyanate based on toluene diisocyanate / hexamethylene diisocyanate (HDI), 60% in butyl acetate, NCO content 10.5%, available from Bayer MaterialScience AG, Leverkusen DE.

[0070] Desmodur® IL BA: Aromatic polyisocyanate based on toluene diisocyanate, 51% in butyl acetate, NCO content 8.0%, available from Bayer MaterialScience AG, Leverkusen DE.

[0071] Desmoduro® 3200: Aliphatic, biuret group-containing polyisocyanate based on HDI, solvent-free, NCO content 23.0%, available from Bayer MaterialScience AG, Leverkusen DE.

[0072] Desmodur® N 3300: Isocyanurate group-containing polyisocyanate based on HDI, solvent-free, NCO content 21.8%, available from Bayer MaterialScience AG, Leverkusen DE.

[0073] Desmoduro® N 3600: Low viscosity, isocyanurate group-containing polyisocyanate based on HD...

use examples

[0105] These examples describe the preparation of ready-to-use coating compositions based on the polyisocyanates PIC in comparison with the corresponding non-polyacrylate-modified starting polyisocyanates, the application of these coating compositions, and the testing of the resulting coating films.

[0106] The general coating properties were assessed by preparing transparent varnishes. For that purpose the polyisocyanates were each combined with a polyol at an NCO / OH equivalent ratio of 1:1. The polyol used was Desmophen® A 870, a polyacrylate polyol available from Bayer MaterialScience AG, Leverkusen, DE, which has a solids content of 70% by weight in butyl acetate, a viscosity of 3500 mPa·s at 23° C., an acid number of 7.5 mg KOH / g (based on as-supplied form) and an OH content of 2.95% by weight (based on as-supplied form). Based on resin solids (sum of the solid fractions of polyol and polyisocyanate) the following amounts of additives were used.

% by weight,Constituentssolids o...

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Abstract

The present invention relates to polyacrylate-modified polyisocyanates which are i) prepared from aromatic, araliphatic, cycloaliphatic and / or aliphatic polyisocyanates having an NCO content of 5% to 25% by weight, an NCO functionality ≧2, a viscosity measured as solvent free resin of 150 to 200,000 mPa·s at 23° C., and ii) contain at least one structural unit of the formula (I) wherein R is hydrogen or a methyl group, R1 is an optionally heteroatom-containing hydrocarbon radical and R2 is a hydrocarbon radical having at least one isocyanate group and optionally urethane, allophanate, biuret, uretdione, isocyanurate and / or iminooxadiazinedione groups and n ist a number ≧1. The present invention also relates to a process for preparing these polyisocyanates and to binder compositions containing these polyisocyanates, which may be hydrophilically modified, and a compound having NCO-reactive groups.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to modified polyisocyanate mixtures based on polyisocyanates and polyacrylate units, to a process for preparing them and to their use as a curing component in polyurethane coating compositions. [0003] 2. Description of Related Art [0004] With polyurethane coating compositions, particularly if they are to be used in the vehicle, industrial or furniture sectors, especially great value is generally placed on the resistance of such coating compositions to different environmental influences. The criteria are frequently hardness, chemical resistance and solvent resistance, scratch resistance, including what is called “reflow”, light stability and weather resistance. [0005] By “reflow” is meant the ability of a cured coating (film) to compensate for minor film damage (in the Jim range), caused by scratching or impact on the film, by cold flow of the coating composition into the damaged site. [...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C08G18/00
CPCC08G18/6229C08G18/6254C08G18/672C08G18/8116Y10T428/31551C08G18/70C08F220/06C09D133/04C09D175/04
Inventor WAMPRECHT, CHRISTIANMELCHIORS, MARTINSCHMITZ, JORG
Owner COVESTRO DEUTSCHLAND AG
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