|Title of Invention||
"METHOD FOR MANUFACTURING NON-EXPANDED POLYURETHANE"
|Abstract||Method for manufacturing rigid polyurethane characterized in that said method comprises reacting the NCO groups of a polyisocyanate with the phenolic OH groups of cashew nut shell liquid (CNSL) wherein the said CNSL is pre-heated in the present of a small quantity of sulphuric acid at a temperature of 130°C to 180°C to avoid the expansion.|
|Full Text||The present invention relates to a method for manufacturing rigid polyurethane.
The present invention is a divisional out of Indian Patent Application No. IP2188/DEL/96.
Cashewnut shell oil (CNSO) is a by-product of the cashew nut preparation food industry.
This liquid, which is found in the shell of the nut and is released when the shell is opened, is a 9:1 mixture of a fatty acid (anacardic acid, which has one phenyl radical at the benzenoid ring) and a biphenol (cardol), both with side chains with 15 carbon and 27 hydrogen atoms and one with three double bonds.
The current uses of this product are mainly in the field of phenoplastics, where, by neglecting the double bonds of the chains:
the fatty acid is decarboxylated with a small quantity of sulphuric
the phenyl radicals are reacted with aldehyds. The results are products
characterised by their great resistance to heat and abrasion.
Japanese patent n° 33-27 905 of Showa of 1st October 1958 contains a new application for this product by reacting it with di- and or polyisocyanates. This method of manufacturing polyurethane, owing to a reaction between the CNSO and a polyisocyanate, demonstrates the possibility of dimerising the CNSO in the presence of a polymerisation catalyst at temperatures of up to 140°C. The results of this method are products with high viscosity, which have to be washed and dried before they are used practically with isocyanates.
German patent n° 2152 606 of 22nd October 1971, belonging to Bayer AG, shows in the context of a process for the internal plastification of an epoxy resin, that phenyl radicals can be used to temporarily block the NCO radicals from the excess polyisocyanates of the prepolymers. After a subsequent reaction, when tertiary amines take the place of the phenyls, these remain free in the final product.
Contents of the invention
The present invention demonstrates a simpler way of manufacturing polymers made of CNSO and a cleaner way of manufacturing products with blocked NCO radicals, by linking up the free phenyl radicals to an available aldehyde. Thanks to the processes invented, it is possible to manufacture products as varied as rigid foam,) elastomers, thermoplastic rubber or single-component resins without solvents.
DESCRIPTION OF THE INVENTION
According to the present invention there is provided a method for manufacturing rigid polyurethane wherein the NCO groups of a polyisocyanate react with the phenolic OH groups of cashew nut shell liquid (CNSL), the expansion is avoided by previous heating of the CNSL and the additional of a small quantity of sulphuric acid.
CNSO can, together with the polyisocyanates, react on three different levels:
1. The COOH of the fatty acid, following the Wurtz reation:
RCOOH+OCN = RCO-NHR+CO2
2. The double bonds of the side chains, and
3. The phenyl radicals of the rings.
The first level is always interesting when a product is intended to be expanded. Thus, with the simultaneous attack of a polyisocyanate on the three levels, a rigid foam of excellent quality can be obtained. Different components which can be polymerized can be obtained either by simply heating the CNSO or by the following method: add a small quantity of diluted sulphuric acid to the CNSO and heat. At around 130°C, the CO2 of the carboxyl is released. By heating further, concentration and dimerisation increase. By additing a polyisocyanate, more or less reticulated products are obtained.
In relation to the above-mentioned Bayer patent and the possibility of temporarily blocking the NCO radicals of an isocynate, the following method is used: CNSO is heated up to 180°C with a small quantity of diluted sulphuric acid. It is left to cool down to 120°C and then an equivalent quantity of toluene di-isocyanate (TDI) is added. This mixture is kept at 80°C until there is no more free isocyanate.
Starting with such a product and adding a second one, it is easy to manufacture a single -component glue.
This second component would be, for example, a mixture of CNSO and Furfural, which had been heated beforehand with a small quantity of triethylamine and then cooled down to room temperature. (It has been discovered that such a mixture remains stable at this temperature.)
If the quantity of Furfural in the second mixture corresponds to the total quantity of decarboxylated CNSO and the mixture of the first preparation is heated up with the mixture of the second preparation to a temperature higher than 150°C, then the initially blocked NCO radicals will be released and react with the COOH of the second preparation. The phenyl radicals react with the Furfural and give a very brilliant, hard but nevertheless flexible product.
As in the Bayer patent, the preparation with the blocked isocyanate can be used to flexibilize epoxy resins or, by heating it up, to make elastic products.
As explained in the example below, an equivalent mixture of CNSO and Furfural can be used as a component for the manufacture of a rigid foam, provided that a polyisocyanate can react beforehand with the OH of the CNSO carboxyls.
A mixture of lOOg of CNSO and 28g of Furfural is heated up to 150°C. This is quickly mixed with either 32g of toluene di-isocyanate (TDI) or 49g of methylene bisphenyl isocyanate (MDI), resulting in expansion, reticulation and hardening. The resulting rigid form acquires its final characterized after a few days.
Here follows the quantification of the manufacture of the above-mentioned single-component glue.
A first mixture of 34g of CNSO and 19g of Furfural is heated up to 150°C, while stirring.
A second mixture containing 34g of CNSO and 0.68g of sulphuric acid (50%) is heated up to 170°C, cooled down to 110°C and completed with 7g of TDI. It is stirred slowly for 4 hours under nitrogen at a temperature of 70°C and then cooled down.
By mixing the first preparation with the second one, a stable liquid is obtained, which has a temperature higher than 140°C, when the NCO radicals are released from the phenyl radicals and can react with the COOH of the CNSO from the first mixture. The free phenyl radicals react with the rest of the Furfural from the first mixture.
In order to produce rigid foam, l00g of CNSO are mixed with 90g of MDI. The exothermic reaction and expansion are almost immediate. Hardening occurs about an hour later, depending on the temperature.
l00g of CNSO are heated up to 300°C then cooled down to room temperature. 40g of MDI are added and the preparation is mixed. After the exothermic reaction, a duromer of good mechanical and chemical resistance is obtained.
1. Method for manufacturing rigid polyurethane characterized in that said method comprises reacting the NCO groups of a polyisocyanate with the phenolic OH groups of cashew nut shell liquid (CNSL) wherein the said CNSL is pre-heated in the present of a small quantity of sulphuric acid at a temperature of 130°C to 180°C to avoid the expansion.
2. Method for manufacturing non-expanded polyurethane using CNSL as a polyol substantially as hereinbefore described with reference to the foregoing examples.
|Indian Patent Application Number||1227/DEL/2000|
|PG Journal Number||19/2011|
|Date of Filing||02-Aug-2000|
|Name of Patentee||MARTIN ERNST STIELAU|
|Applicant Address||MELIDES, CAVEIRA, P-7570 GRANDOLA, PORTUGAL|
|PCT International Classification Number||C08G 18/00|
|PCT International Application Number||N/A|
|PCT International Filing date|