All posts tagged hybrid

Hybrid Hotmelt Adhesive with Low Free Isocyanate

Title: POLYURETHANE HOT-MELT ADHESIVE HAVING A LOW CONTENT OF DIISOCYANATE MONOMERS AND GOOD CROSS-LINKING SPEED

Number/Link: WO2015/135833 (German)

Applicant/Assignee: Sika

Publication date: 17-09-2015

“Gist”: Use of mercaptosilane to reduce free monomeric diisocyanate

Why it is interesting: Reduction of the amount of free monomeric diisocyanate in adhesives, coatings, OCF systems etc. remains a hot topic in industrial polyurethane research, mostly because of changing legislation. For example, in the EU the amount of free MDI needs to be below 1% in order to avoid “R-40” (suspect carcinogen) labeling. A number of strategies to reduce free isocyanate have been tried in the past (and mentioned in this blog). Examples are distillation, the use of asymmetric diisocyanates and the use of monols. According to this invention the amount of free monomeric isocyanate in a hotmelt formulation can be reduced by adding a mercaptosilane like e.g. mercaptopropyltrimethoxysilane. The mercaptosilane is said to react preferentially with the monomeric isocyanate. Only a relatively small amount of mercaptosilane is used such that the main curing mechanism is still the isocyanate-water reaction.

Mercaptopropyltrimethoxysilane

PU Sealants using Michael Addition Chemistry

Title: MICHAEL ACCEPTOR-TERMINATED URETHANE-CONTAINING FUEL RESISTANT PREPOLYMERS AND COMPOSITIONS THEREOF

Number/Link: US2015/0252232

Applicant/Assignee: PRC-DeSoto

Publication date: 10-09-2015

“Gist”: A PU prepolymer is capped with Michael accepting groups and then cured with a dithiol

Why it is interesting: This invention is about sulphur containing PU sealants with properties acceptable for the aerospace industry. A bis(vinylsulfonyl)- terminated urethane-polythioether prepolymer is prepared according to the scheme below. The prepolymer can then be cured with a dithiol-ended polyether, catalysed by a tertiary amine. The compositions have an extended pot life and the curing rate can be controlled by using an encapsulated tert-amine as a controlled-release catalyst.

Michael acceptor-terminated prepolymer preparation according to the invention

Urethane-Acrylate Hybrids From Thiol-Ene Chemistry

Title: POLYURETHANE (METH) ACRYLATES USING MODIFIED HYDROXYTHIOLS

Number/Link: US2015/0232422

Applicant/Assignee: Dymax Oligomers and Coatings

Publication date: 20-08-2015

“Gist”: A dihydroxythiol is reacted with an acrylate and then with diisocyanate and hydroxyacrylate

Why it is interesting: This invention relates to radically polymerizable urethane oligomers which are useful as adhesives or coatings. The oligomers are prepared in two stages: first a dihydroxy thiol is reacted with an acrylate resulting in a diol which is then reacted with an excess diisocyanate and then with hydroxyacrylates. For example: thioglycerol is reacted with phenyltioethylacrylate. The resulting diol is then further reacted with TDI and subsequently with polycaprolactonacrylate and hydroxyethylacrylate resulting in the structure below. The urethane oligomers can be used for coatings or adhesives which are said to have improved properties over the existing art, like improved thermal resistance.

A urethane-acrylate oligomer according to the invention

Innovation in Polyurethanes

All posts tagged hybrid

Hybrid Hotmelt Adhesive with Low Free Isocyanate

PU Sealants using Michael Addition Chemistry

Urethane-Acrylate Hybrids From Thiol-Ene Chemistry

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