Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Patent
1995-10-16
2000-04-25
Sergent, Rabon
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
222129, 2521822, 25218222, 521130, 521131, 521137, 521140, 521159, B65D 8314, C08J 914, C08J 912, C08K 501
Patent
active
060544996
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
This invention relates to a prepolymer composition for producing polyurethane insulating foams from pressure tanks which consists of a prepolymer component with at least one PU prepolymer with a content of NCO groups of 4 to 20 wt % and usual additives as well as a propellant component. The invention furthermore relates to the use of polybutadiene as an additive to prepolymer compositions for producing one component (1C) and two component (2C) polyurethane insulating foams for controlling cell opening and dimensional stability, as well as to pressure cans with such a prepolymer composition and optionally a separate polyol component for producing 1C and 2C polyurethane insulating foams.
The inventive prepolymer composition is used for producing polyurethane insulating foams which are used particularly for insulating purposes by foaming in cavities. The main areas of application are the construction industry, but also technical products in which cavities must be filled to avoid condensation nests. When one-component polyurethane foams are spoken of, these are applied by discharging the prepolymer composition from pressure tanks, for example aerosol cans, on the spot with the help of propellants with a bulk density of 10 to 50 g/l, and processed. 1C foams are moisture-hardening, i.e. they can be cured solely with the help of the moisture contained in the air and substrate moisture.
Two-component polyurethane foams require a second hydroxy component for curing the prepolymer composition, generally a polyol which must be added directly before foam formation. Curing can be accelerated by catalysts. Bulk densities in 2C foams are characteristically 10 to 100 g/l.
Transitional forms between 1C and 2C foams are possible. In this case a quantity of a hydroxyl component insufficient for reacting the isocyanate groups is added to the prepolymer before discharge. The invention also covers such "1.5C foams", as well as foams which are produced with more than one separately added component.
Conventional prepolymer compositions for 1C and 2C polyurethane insulating foams contain a prepolymer component having a minimum content of reactive NCO groups. The prepolymer itself is a polymer of suitable viscosity with terminal NCO groups. The composition contains a certain quantity of monomeric isocyanate. Suitable isocyanates are for example isophorone diisocyanate, referred to as IPDI, tolylene diisocyanate, also referred to as TDI, diisocyanatotoluene, 1,5diisocyanatonaphthalene, referred to as NDI, triisocyanatotrimethylmethane, 1,6-diisocyanatohexane, referred to as HDI, or 4,4-diisocyanatodiphenylmethane in a raw and pure form or as a mixture. An especially common one is 4,4-diisocyanatodiphenylmethane, also referred to as MDI, which is used both in a raw form (raw MDI) and in the form of pure 2,4- and 4,4-isomers or mixtures thereof. One can likewise use the two common TDI isomers alone or in a mixture. For producing the prepolymer component one reacts such isocyanates with hydroxy polyethers, polyesters or polyvalent alcohols, making sure the prepolymer acquires a viscosity suitable for the composition.
As mentioned above, PU prepolymers suitable for producing polyurethane insulating foams from pressure tanks contain a residual content of unreacted monomeric isocyanate which can be up to 40%. This residual content is usually due to manufacturing, but is also desirable since it has turned out that this residual content has a positive effect on the serviceability, in particular the inherent and dimensional stability, of the produced foams. On the other hand monomeric isocyanates are deemed dangerous substances subject to identification because of their toxicity, despite their generally rather low volatility. MDI, the preferred initial isocyanate for 1C foams, is subject to a maximum working place concentration of 500 ppm. Because of the toxicity of the contained substances packings having residues of these prepolymers are subject to cost-intensive restrictions on disposal.
Although it is possible to produce low
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Pauls Mathias
Schumacher Rene
Rathor AG
Sergent Rabon
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