JPS607746B2 - heat shrinkable string - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat-shrinkable string, and more specifically, by covering high-heat-shrinkable fibers with low-heat-shrinkable fibers, the shrinkage force and shrinkage rate of the high-heat-shrinkable fibers are effectively utilized. The present invention relates to a heat-shrinkable string that can exhibit flexibility and maintain its flexibility even after shrinkage.

Generally, heat-shrinkable cords are mainly known in the form of films or threads, and the heat-shrinking force generated by winding the cord and heating it is utilized. However, film-like heat-shrinkable materials have limitations in thickness and thermal stress, and when high shrinkage force is required, extra labor is required such as increasing the number of wraps, and the resulting tightening force is still unsatisfactory. ing. On the other hand, with twisted thread-like cords, the cord hardens significantly after shrinking when heated, which poses the risk of damaging or distorting the object to be tightened, and also because heat setting is impossible due to the nature of the fibers that make up the cord. It has drawbacks such as difficulty in untwisting, cumbersome handling due to the occurrence of fraying and untwisting, and insufficient heat shrinkage due to binding of the cords to each other.

The present inventors conducted extensive research to develop a heat-shrinkable cord free of the above-mentioned drawbacks, and as a result, they arrived at the heat-shrinkable cord of the present invention.

That is, the present invention has a dry heat shrinkage rate of at least 10% at 150 qo, a melting point of 180° C. or higher, and 100 qo.
An inner core material containing a multifilament with a thermal stress of 0.3 u/d or more at qo and a low heat shrinkage or spontaneous heat shrinkage rate of 5% or less at 150°C and a melting point of 200°C or more. It is a heat-shrinkable string composed of an outer covering layer made of braided or knitted fiber threads having extensibility. The heat-shrinkable string according to the present invention can effectively utilize the heat-shrinkability of the highly shrinkable multifilament of the inner core material, so it has excellent tensile strength and maintains flexibility even after heat-shrinking. Because of this, it has the characteristics of not damaging the object to be tightened.

The inner core material used in the present invention has a dry heat shrinkage rate (JISL-1073) of at least 10% at 15 mm.
Preferably 15% or more and a melting point of 180qC or more,
and thermal stress at 10,000 mm (thread length: 5 t, initial load: 0.0
5 qo/d, and the stress applied to the yarn when the temperature is increased at a rate of 24 qo/min) is at least 0.3 qo/d or more, preferably 0.4 qo/d or more, particularly preferably 0.5 qo/d or more. It is usually a filament east or tow containing more than 'd filament.

Particularly preferred is a filament east or tow consisting of 100% of the filament. The filament can be obtained by selecting the composition and molecular weight of the polymer, the draw ratio of the spun filament, setting conditions, etc.
Nylon, aramid, etc. are preferred. Particularly preferred are mono- or copolymerized polyesters containing ethylene terephthalate repeating units as a main component. A high draw ratio, for example 3.0, is usually obtained from a polyester having a high molecular weight, for example, an intrinsic viscosity of 0.6 or more, measured at 3000 in phenol/tetrachloroethane (6/4 weight ratio). Peep or higher, preferably 3.5
It is particularly preferable that the number of filaments is unset or insufficiently set. The filaments are preferably used in a merely gathered state, but if necessary, they may be used after being lightly twisted, heated, or braided to the extent that shrinkage is not inhibited. In order to fully exhibit the heat shrinkability of the filament, the slipperiness can be improved by treatment with waxes, organopolysiloxane, perfluoro compounds, etc.

In addition, the fiber material constituting the outer covering layer of the string in the present invention is a fiber yarn having low heat shrinkage or spontaneous heat extensibility, preferably having a dry heat shrinkage rate of 5 at 150°C.
% or less and has a melting point of 200% or more.

Generally, filament yarns are preferred, and examples include drawn and set polyester fiber yarns, polyamide fiber yarns, crosslinked phenol formaldehyde fiber yarns, and rayon fiber yarns. In addition to drawn yarns, highly oriented drawn fiber yarns can also be used. In the present invention, a string is manufactured using the above-mentioned inner core material and the fiber material constituting the outer skin covering layer, but it is preferable to use fibers for forming the outer skin covering layer on the inner core material in view of the tightening force, appearance, etc. Manufactured by braiding threads.

However, the present invention is not limited thereto, and it may also be manufactured by winding a tape woven from fiber yarns forming an outer covering layer around the inner core material. Even in the case of braiding, which is a preferred embodiment of the present invention, a twill braided structure is preferable to a flat braided structure. In other words, by making the braided structure as shown in Fig. 1 twill and reducing the number of coarse stitches as much as possible, the contact area between the outer skin yarns can be reduced and the frictional resistance can be reduced. It can demonstrate excellent cotton-tightening power. FIG. 2 is an explanatory cross-sectional view showing an example of the heat-shrinkable string of the present invention, where 1 is an inner core material and 2 is an outer covering layer. Such a heat-shrinkable string is formed by repeatedly intersecting the fiber threads of the outer skin covering layer at a certain angle. When the outer covering layer-forming fiber yarn shrinks due to heat, it acts to tighten the inner core material and acts to inhibit the shrinkability of the inner core material. Therefore, it is preferable that the fiber yarn forming the outer covering layer is in a state as close to parallel to the axial direction of the string as possible, and it is also preferable that it has low shrinkage and spontaneous heat extensibility. In addition, the ratio a/b of the total cross-sectional area of the filaments of the inner core material (a) to the total cross-sectional area of the fiber yarns forming the outer covering layer (b) is at least 1/3 to exhibit shrinkage characteristics, particularly a high shrinkage rate. It is preferable because it means The heat-shrinkable string thus obtained exhibits excellent tightening force and shrinkage rate through heat treatment, and also maintains its flexibility even after shrinkage, so that it does not damage the object to be fastened.

After shrinkage occurs, the diameter of the string increases (usually by around 10%), which makes the string-like arrangement denser, preventing internal resin leakage, etc., and making it possible to obtain uniform tightening force over the entire surface of the tightened object. can. It also has the advantage that when used as a binding string, the knot is difficult to unravel after heat shrinkage occurs. Hereinafter, the heat-shrinkable string of the present invention will be explained with reference to Examples.

Example inner core material: 150qo, dry heat shrinkage rate: approximately 19%, melting point: 2
55oo, 100oo polyethylene terephthalate filament yarn with a thermal stress of 0.65 min/d was redrawn straight, and a polyethylene terephthalate filament yarn with a dry heat shrinkage rate of 2.5% at 150°C and a melting point of 257°C was added to this as an outer covering layer forming fiber yarn. Using 16 filaments, the heat-shrinkable cord (total cross-sectional area of the filaments of the inner core material/outer skin covering layer forming fiber yarn) is braided with a twill braided structure in which every two fiber threads intersect. Total cross-sectional area: 1/2.3) was manufactured.

Note that the number of stitches was reduced to the minimum number that would allow the outer covering layer-forming fiber yarn to restrain the inner core material. This silk string is 100-200q
It is possible to exert a thermal stress of 65% or more of the total thermal stress of the monofilament at the corresponding temperature in the temperature range of
It exhibited a high shrinkage rate of 6 powders at 50°C. This shrinkage rate was about 95% higher than that of monofilament. The fine diameter is 150℃60 compared to before heat treatment.
The degree of flexibility increased by about 11% after the heat treatment for 1 minute, but the flexibility was comparable to that before the heat treatment.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a twilled braided structure which is an example of the outer covering layer of the heat-shrinkable string of the present invention, and FIG. 2 is an explanatory diagram showing an example of the heat-shrinkable string of the present invention. It is a diagram. 1: Inner core material, 2: Outer covering layer. Figure 1 Figure 2

Claims (1)

[Claims] 1. The dry heat shrinkage rate at 150°C is at least 10% or more, the melting point is 180°C or more, and the thermal stress at 100°C is 0.
．． Inner core material containing multifilament of 3 g/d or more, dry heat shrinkage rate at 150°C of 5% or less, and melting point of 20
A heat-shrinkable string composed of an outer covering layer formed by braiding or weaving fiber threads having low heat-shrinkability or spontaneous heat-stretchability at 0° C. or higher. 2. The heat-shrinkable string according to claim 1, wherein the outer skin covering layer is braided in a twill pattern. 3. The heat-shrinkable string according to claim 1, wherein the outer skin covering layer is braided with as few twills as possible.