Crosslinked polyvinyl alcohol fiber and method for producing the same

Abstract

The present invention relates to crosslinked polyvinyl alcohol raw cord and method for producing the same, and more particularly, to crosslinked polyvinyl alcohol fiber, in which PVA resin having a degree of polymerization of more than 1,000 and a degree of saponification of more than 97.0 mol % is dissolved in dimethyl sulfoxide, the solution is subjected to dry and wet gel spinning using methanol as a coagulation solution, drawn and thermally treated, the resulting polyvinyl alcohol drawn yarn with 500-3,000 deniers is twisted to produce a cabling yarn, the cabling yarn is plied into a 2-ply or 3-ply yarn to produce a raw cord, the raw cord is wound on a bobbin for crosslinking and crosslinked in an aqueous crosslinking solution containing an aromatic aldehyde compound and an acid catalyst. Moreover, the present invention relates to a crosslinker-introducing apparatus, which is used in the above method and can effectively induce the crosslinking reaction of the wound raw cord.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to crosslinked polyvinyl alcohol fiber and method for producing the same, and more particularly, to crosslinked polyvinyl alcohol fiber, in which PVA resin having a degree of polymerization of more than 1,000 and a degree of saponification of more than 97.0 mol % is dissolved in dimethyl sulfoxide (hereinafter, referred to as DMSO), the solution is subjected to dry and wet gel spinning using methanol as a coagulation solution, drawn and thermally treated, the resulting polyvinyl alcohol drawn yarn with 500-3,000 deniers is twisted to produce a cabling yarn, the cabling yarn is plied into a 2-ply or 3-ply yarn to produce a raw cord, the raw cord is wound on a bobbin for crosslinking and crosslinked in an aqueous crosslinking solution containing an aromatic aldehyde compound and an acid catalyst. Moreover, the present invention relates to a crosslinker-introducing apparatus, which is used...

AI Technical Summary

Benefits of technology

[0020] Another object of the present invention is to provide a crosslinker-introducing apparatus, which is used in the above inventive method and allows the polyvinyl alcohol fiber to have excellent hot water resistance and high strength.

[0057] In order to prevent the RFL solution from infiltrating deeply into the inside of the fiber during the RFL dipping process, the raw cord is stretched to a stretch ratio of 0.5-3%, and a dip pick up (DPU) of the RFL is 3.0-9.0 wt %. At a stretch ratio of less than 0.5%, DPU will exceed 9 wt % so that the RFL solution will be infiltrated deeply into the inside of the staple fiber to reduce fatigue resistance. At a stretch ratio of more than 3%, excessive tension will be applied to the raw cord and thus will cause damages to the raw cord. Thermal treatment should be performed at a temperature of 170-230° C., and preferably 200-220° C. where the movement of PVA molecules is the best. By minimizing the tension applied to the fiber to allow for the greatest possible movement of the PVA molecules to maximize a heat treatment effect, the production of a treated high-tenacity PVA cord becomes possible. In a heat treatment process conducted after dipping the raw cord in the RFL solution, it is important that the dipped cord is maintained at a stretch ratio of 0 to −5%. If the stretch ratio in the heat treatment process is above 0%, when the dipped cord is used in a tire cord requiring high fatigue resistance, a cord cutting or separation phenomenon will occur which is due to low fatigue resistance below 60% resulting from the low elongation of the dipped cord. On the other hand, at a stretch ratio below −5%, molecular recrystallization in a vertical direction to the fiber axis will occur due to excessive molecular movement to cause a reduction in tenacity. If the crosslinker is present within the fiber not having been washed in the water-washing process after the crosslinking process, it acts as an impurity in a product where the PVA fiber was used. Thus, heat treatment is performed above 200° C. such that the remaining crosslinker can be reacted or volatilized to further improve crosslinking efficiency.

Problems solved by technology

However, although the PVA fiber produced by this method has excellent mechanical properties, the PVA resin is dissolved in hot water with a high temperature above 100° C. or has reduced mechanical properties, due to the hydrophilicity of PVA resin itself.

Thus, it has many limitations for use in applications, such as tire cords which have the biggest market among the industrial fibers.

Although a very small amount of water is present in the inside of a tire, excess water can flow into the tire when the tire gets damaged.

Also, when the tire temperature is increased to 130° C. as a result of high-speed running of automobile, the water is thermally hydrated to cause damages to the PVA fiber, so that the stability of automobiles is endangered.

Thus, the PVA fiber according to the prior art could not be used as a tire reinforcement material without anxiety.

Also, since the high crystallinity of the PVA fiber results in a reduction in fatigue resistance when it is used for tire cords, this problem needs to be solved.

However, it is difficult to use the PVA fibers as filaments for industrial purpose.

And, when the PVA resin produced by such methods is used in hot water above 130° C., a problem occurs.

In such prior crosslinking methods, when subjected to thermal drawing at a high temperature above 200° C., the crosslinker contained in the PVA undrawn yarn cause crosslinking reaction to reduce drawability, or the crosslinker with low boiling point is volatilized to reduce crosslinking efficiency.

Furthermore, the crosslinking treatment methods as described above have a problem in that, since crosslinking treatment is performed by simply dipping a bobbin wound with a undrawn yarn into the crosslinker, a portion of the undrawn yarn wound inside the bobbin is not impregnated with the crosslinker, and thus, incompletely crosslinked, or the outer side of the undrawn yarn wound on the bobbin is crosslinked at a significantly different level from the inside of the undrawn yarn.

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