| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | August 28, 2001 |
| PATENT TITLE |
Package of polyurethane elastic yarn for heat bonding |
| PATENT ABSTRACT | A package of polyurethane elastic yarn for heat bonding which weighs more than 1 kg and measures such that the diameter-to-width ratio is greater than 0.5 and which is obtained from polyurethane elastic yarn by giving it 3.0-10.0 wt % of a finishing agent and then winding it up, said finishing agent is polypropylene glycol-based polyol used alone or composed of component (A) which is a polypropylene glycol-based polyol and component (B) which is a reaction product of a polypropylene glycol-based polyol and an organic diisocyanate compound. The finishing agent contains component (B) in an amount less than 30 wt % and have an apparent viscosity of 50-250 mPa.multidot.s at 30.degree. C. and a surface tension of 30-45 dyn/cm |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | August 18, 1999 |
| PATENT FOREIGN APPLICATION PRIORITY DATA | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A package of polyurethane elastic yarn for heat bonding which is obtained from polyurethane elastic yarn by treating it with 3.0-10.0 wt % of a finishing agent and then winding it, said finishing agent being a polypropylene diol and/or triol having a weight-average molecular weight of 200-1500, which is obtained by the polymerization of propylene oxide alone or by the polymerization of propylene oxide and ethylene oxide. 2. A package of polyurethane elastic yarn for heat bonding as defined in claim 1, wherein the finishing agent is one which has an apparent viscosity of 50-250 mPa.multidot.s at 30.degree. C. and a surface tension of 30-45 dyn/cm. 3. A package of polyurethane elastic yarn for heat bonding as defined in claim 2, which weighs more than 1 kg and measures such that the ratio of winding thickness to winding width is greater than 0.5. 4. A package of polyurethane elastic yarn for heat bonding as defined in claim 1, which weighs more than 1 kg and measures such that the ratio of winding thickness to winding width is greater than 0.5. 5. A package of polyurethane elastic yarn for heat bonding which is obtained from polyurethane elastic yarn by treating it with 3.0-10.0 wt % of a finishing agent and then winding it, said finishing agent being composed of component (A), which is a polypropylene diol and/or triol having a weight-average molecular weight of 200-1500 obtained by the polymerization of propylene oxide alone or by the polymerization of propylene oxide and ethylene oxide and component (B) which is a reaction product of the component (A) and an organic diisocyanate compound. 6. A package of polyurethane elastic yarn for heat bonding as defined in claim. 5, wherein the finishing agent contains component (B) in an amount less than 30 wt % thereof. 7. A package of polyurethane elastic yarn for heat bonding as defined in claim 6, wherein the finishing agent is one which has an apparent viscosity of 50-250 mpa.multidot.s at 30.degree. and a surface tension of 30-45 dyn/cm. 8. A package of polyurethane elastic yarn for heat bonding as defined in claim 6, which weighs more than 1 kg and measures such that the ratio of winding thickness to winding width is greater than 0.5. 9. A package of polyurethane elastic yarn for heat bonding as defined in claim 5, wherein the finishing agent is one which has an apparent viscosity of 50-250 mPa.multidot.s at 30.degree. and a surface tension of 30-45 dyn/cm. 10. A package of polyurethane elastic yarn for heat bonding as defined in claim 5, which weighs more than 1 kg and measures such that the ratio of winding thickness to winding width is greater than 0.5. |
| PATENT DESCRIPTION |
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a package of polyurethane elastic yarn to be used for heat bonding. More particularly, the present invention relates to a package of polyurethane elastic yarn to be used to form the waist and leg parts of disposable diaper which need elastic properties. The polyurethane elastic yarn exhibits good bonding properties when disposable diapers undergo bonding such as hot-melt bonding, fusion bonding, and ultrasonic bonding during their production. The package keeps its good appearance in shape without slipping down of yarn layer and also permits good unwinding without mutual sticking of the polyurethane elastic yarn. 2. Description of the Prior Art Owing to its good elastic properties, polyurethane elastic yarn is used in various fields where extensibility and fittability are required. Polyurethane elastic yarn is usually supplied in the form of package and hence it is given a finishing agent so that it does not stick mutually in the package and it is unwound without unnecessary resistance. In addition, in the case where polyurethane elastic yarn is used continuously it is necessary to replace packages frequently. The less the amount of yarn in the package, the greater the frequency of replacement. In order to reduce the frequency of package replacement, it has become common practice to make packages larger. In the case of large packages, application of finishing agent is indispensable to prevent yarn sticking which occur particularly in the core layer of the package. Unfortunately, a polyurethane elastic fiber treated with a finishing agent has the disadvantage of being very poor in bonding properties due to the finishing agent present on it. This is true in the case where the gather of a disposable diaper is formed by adhesion or heat bonding with another material. One way to solve this problem is disclosed in Japanese Patent Publication No. 50429/1993. According to this disclosure, a polyurethane elastic yarn is given a finishing agent composed mainly of silicone oil in an amount less than 2 wt % and then wound up such that its apparent elongation in the package is within a certain range for the amount of the finishing agent applied. Such polyurethane elastic yarn exhibits good adhesion properties with adhesive in the production of disposable diapers. The advantage of this method is that the polyurethane elastic fiber is not so poor in adhesion properties because of the smaller amount less than 2 wt % of the finishing agent used. On the other hand, this method has the disadvantage that the package of the polyurethane elastic yarn gives a poor appearance in shape because it is wound up with a lower tension than usual so as to prevent mutual sticking of yarn. This is true in the case where the apparent elongation is low even though it is within the certain range for the amount of the finishing agent used. Conversely, with a great apparent elongation, the polyurethane elastic yarn is not unwound smoothly due to mutual sticking of the yarn in the package. Thus, it is substantially difficult to obtain the package of polyurethane elastic yarn which appearance has a good in shape and is unwound smoothly by simply reducing the amount of finishing agent and defining the apparent elongation. Japanese Patent Laid-open No. 152264/1998 discloses a package of elastic yarn which is given 2-5 wt % of a finishing agent, for example silicone oil, having a surface tension of 25-30 dyn/cm. It is claimed that this package is unwound smoothly and keeps its adhesion properties when used to make a disposable diaper. However, it has been found that the finishing agent having a surface tension of 25-30 dyn/cm as specified above does not provide satisfactory adhesion properties even when it is used in an amount of 2-5 wt %. BRIEF SUMMARY OF THE INVENTION The present invention was completed in order to overcome the above-mentioned disadvantages. Thus, it is an object of the present invention to provide a package of polyurethane elastic yarn for heat bonding, said package keeping its good appearance in shape and being capable of unwinding adequately without mutual sticking of yarn. This object is achieved by giving polyurethane elastic yarn a finishing agent which exhibits excellent heat bonding properties and permits smooth unwinding while preventing mutual sticking of yarn in the package. The present invention covers a package of polyurethane elastic yarn for heat bonding which is obtained from polyurethane elastic yarn by giving it 3.0-10.0 wt % of a finishing agent and then winding it, said finishing agent being composed of component (A) which is a polypropylene glycol-based polyol and component (B) which is a reaction product of a polypropylene glycol-based polyol and an organic diisocyanate compound. According to the present invention, the finishing agent should preferably contain component (B) in an amount less than 30 wt % or it may contain component (A) alone. According to the present invention, the finishing agent should have an apparent viscosity of 50-250 mPa.multidot.s at 30.degree. C. and a surface tension of 30-45 dyn/cm. According to the present invention, the package of polyurethane elastic yarn for heat bonding weighs more than 1 kg and measures such that the ratio of winding thickness to winding width is greater than 0.5. DETAILED DESCRIPTION OF THE INVENTION The polyurethane elastic yarn in the present invention is not specifically restricted. It may be either one which is obtained by wet spinning or dry spinning or by melt spinning. The polyurethane elastic yarn may be incorporated with a light stabilizer, a UV light absorbent, an agent to prevent discoloration by gas, a dye, an activating agent, a delustering agent, etc. Component (A) which is used as a finishing agent in the present invention is a polypropylene glycol-based polyol, which is a diol and/or triol obtained by polymerization of propylene oxide alone or with ethylene oxide and has a weight-average molecular weight of 200-1500. With the molecular weight lower than 200, it unfavorably contains a low-molecular weight fraction which hinders heat bonding. With the molecular weight higher than 1500, it has such a high viscosity as to cause mutual sticking of yarn, preventing smooth unwinding. Incidentally, the polyol may have its hydroxyl groups partly esterified or acylated. Component (B) is a reaction product of a polypropylene glycol-based polyol and an organic diisocyanate compound. The polyol is a diol and/or triol obtained by polymerization of propylene oxide alone or with ethylene oxide. The organic diisocyanate compound is one or more members selected from 4,4'-diphenylmethane diisocyanate, 3,3'-dichloro-4,4'-diphenylmethane diisocyanate, m-xylylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, etc. The polypropylene glycol-based polyol should preferably have a weight-average molecular weight of 200-2000. With a molecular weight lower than 200, it would cause obtained component (B) to increase a content of hard segments which gives rise to undesirable gel. With the molecular weight higher than 2000, it would cause obtained component (B) to have a high apparent viscosity which results in mutual sticking of yarn and makes unwinding difficult. The reaction to produce the component (B) should be carried out in such a way that the amount of isocyanate groups in an organic diisocyanate compound or the total amount of isocyanate groups in two or more organic diisocyanate compounds is 50-90 eq %, preferably 50-70 eq %, of the amount of hydroxyl groups in the polyol used. If the ratio of isocyanate groups is higher than this, obtained component (B) has such a high degree of polymerization that it is poor in compatibility with component (A) and hence the resulting finishing agent has an adverse effect on unwinding. Moreover, if the ratio of isocyanate groups is more higher, obtained component (B) contains residual isocyanate groups which react with component (A) and the resulting finishing agent has a viscosity outside the range specified in the present invention. Conversely, if the ratio of isocyanate groups is lower than specified above, the polyol partly remains unreacted, producing an adverse effect on heat bonding properties. The reaction condition is not specifically restricted so long as it permits complete reaction between the polyol and the organic diisocyanate. The finishing agent of the present invention is a polypropylene glycol-based polyol alone or a mixture of component (A), which is a polypropylene glycol-based polyol, and component (B), which is a reaction product of a polypropylene glycol-based polyol and an organic diisocyanate compound. The finishing agent contains component (B) in an amount less than 30 wt %. According to the present invention, the finishing agent should have an apparent viscosity of 50-250 mPa.multidot.s at 30.degree. C. and a surface tension of 30-45 dyn/cm. If the ratio of component (B) is higher than 30 wt %, the finishing agent has an adverse effect of unwinding. If the apparent viscosity is lower than 50 mPa.multidot.s, the finishing agent has an adverse effect on heat bonding properties. If the apparent viscosity is higher than 250 mPa.multidot.s, the finishing agent results in mutual sticking of yarn and poor unwinding due to uneven application of the finishing agent. If the surface tension is lower than 30 dyn/cm, the finishing agent has an adverse effect on heat bonding. If the surface tension is higher than 45 dyn/cm, the finishing agent results in mutual sticking of yarn and poor unwinding. As mentioned above, component (B) used in the present invention is a urethane-based compound with a low degree of polymerization. Therefore, the finishing agent containing it produces the effect of preventing mutual sticking of yarn and promoting heat bonding when applied to polyurethane elastic yarn. According to the present invention, the finishing agent may be composed of component (A) alone without component (B). Such a single-component finishing agent permits the elastic yarn to exhibit good heat bonding properties and produces the effect of preventing mutual sticking of yarn and promoting unwinding. However, for better heat bonding properties, it is desirable that the finishing agent contain component (B) in an amount less than 30 wt %, preferably 5-30 wt %. According to the present invention, the finishing agent is applied to polyurethane elastic yarn such that the loading is 3.0-10.0 wt %. Application may be accomplished by bringing the polyurethane elastic yarn into contact with a roller carrying the finishing agent while polyurethane elastic yarn travels from the spinneret to a paper tube or from one package to another for rewinding. With a loading less than 3.0 wt % of the finishing agent mutual sticking of yarn is caused, adversely affecting unwinding, and also heat bonding properties are deteriorated. With the loading in excess of 10.0 wt % of the finishing agent adversely affects the shape of package. As mentioned above, the package of the present invention keeps its good appearance in shape and the polyurethane elastic yarn wound on the package of the present invention exhibits good heat bonding properties, does not stick mutually, and is unwound adequately. As mentioned above, the present invention provides a package of polyurethane elastic yarn. This yarn has good bonding properties and does not stick mutually in the package, and the package permits the yarn to be unwinded smoothly while keeping its good appearance in shape. These effects are produced when polyurethane elastic yarn is given a finishing agent in an amount of 3.0-10.0 wt %. The finishing agent is polypropylene glycol-based polyol used alone or a mixture of component (A) which is polypropylene glycol-based polyol and component (B) which is a reaction product of polypropylene glycol-based polyol and an organic diisocyanate compound. The finishing agent has an apparent viscosity of 50-250 mPa.multidot.s at 30.degree. C. and a surface tension of 30-45 dyn/cm. The package of polyurethane elastic yarn can be made larger easily and the polyurethane elastic yarn will be used in various fields where heat bonding is required. |
| PATENT EXAMPLES | available on request |
| PATENT PHOTOCOPY | available on request |
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