MANUFACTURING METHOD OF ISOLATED TUBES WITH IMPROVED PROPERTIES Russian patent published in 2017 - IPC B29C44/12 B29C44/38 C08G18/18 F16L59/147 

FIELD: technological processes.

SUBSTANCE: method includes a polyurethane system introducing into the annular gap formed between the inner and outer tubes, foaming and allowing the polyurethane system to cure. The polyurethane system comprises at least one isocyanate component (a), at least one polyol mixture (b) comprising a crosslinking agent (b3) constituting glycerin and at least one catalyst. The start time of the polyurethane system is less or equal to the filling time. In this case, the noted catalyst is an amine corresponding to the general formula (I) R¹R²N(CR³R⁴)_n-X, where R¹, R², R³, R⁴, n and X have the following values: R¹, R² independently of one another represent an alkyl residual with 1-8 carbon atoms, R³, R⁴ independently of each other represent hydrogen atoms, alkyl residuals with 1-8 carbon atoms, n is an integer from 1 to 6, and X is OR⁵ or NR⁶R⁷, where R^{5 is} an alkyl radical with 1-8 carbon atoms or a heteroalkyl residual with 1-8 carbon atoms, R6 independently of the other hydrogen atoms, an alkyl residual with 1-8 carbon atoms, R7 an alkyl residual with 1-8 carbon atoms or a heteroalkyl residual with 1-8 carbon atoms.

EFFECT: process of the invention makes it possible to obtain tubes having a reduced total bulk density and low thermal conductivity having thicker insulating layers and to simplify the production of longer pipe sections.

11 cl, 2 tbl