Cotton-based elasticised yarns to make environment-friendly elasticised fabrics

A method for making an elastic core yarn (50) comprising the steps of:

• prearranging a source (51) of an elastic core (30) comprising an elastic fibre (10) made of a natural rubber containing more than 80% of cis-1,4-polyisoprene, wherein said elastic fibre (10) has a linear mass density set between 200 dtex and 1000 dtex;
• prearranging at least one covering yarn (40) comprising cotton at a weight percentage higher than 50%,
• wherein said covering yarn has a linear mass density set between 6 Nm and 100 Nm,
• said covering yarn (40) twisted with an initial twist direction selected between “Z” and “S”;
• conveying said elastic core (30) and said covering yarn (40) up to a collecting spool (70), at respective predetermined conveying speeds,
• wherein said conveying speed of said elastic core (30) speed ranges
• from an initial speed, at said source (51) of elastic core (30),
• to a final speed at least twice said initial speed, at said collecting spool (70),
• wherein said step of conveying is carried out in such a way that said covering yarn (40) laterally attains a proximity of said elastic core (30) in a wrapping space (35);
• helically wrapping said covering yarn (40) about said elastic core (30) in said wrapping space (35), thus obtaining said elastic core yarn (50);
• wherein said conveying speeds are selected in such a way that, in said step of helically wrapping:
• said covering yarn (40) becomes twisted with a final twist direction opposite to said initial twist direction, i.e. selected between “S” and “Z”, respectively;
• a number T of coils of said covering yarn (40) set between a predetermined minimum value T0 and a predetermined maximum value T1, said minimum and maximum values T0,T1 depending upon said linear mass density Nm, is wrapped about one length unit of said elastic core yarn (50),
• wherein said wrapping space (35) is a protected space enclosed by a container (67).