JPS6328147B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a strand formed from a plurality of filamentous fibers of a thermoplastic polymer.
To explain in more detail, it is formed from a large number of filamentous fibers that have irregular and periodic changes in cross-sectional area size along the length, and have a moderate initial elastic modulus and a high elastic recovery rate. Regarding string-like objects.

Conventionally, string-like materials such as straw, hemp, metal, etc., and string-like materials of thermoplastic polymers, such as polypropylene and nylon, have been used as packing materials, particularly as binding materials. Particularly recently, with the development and development of automatic packaging machines, polypropylene string-like materials have been used in large quantities as binding materials for cardboard boxes and the like. However, this string-like material has a low elongation and a low elastic recovery rate, requires a great deal of force when tightening, and has the disadvantage that it tends to loosen after tightening.

Therefore, the present inventors conducted extensive research in order to provide a packaging binding material that can be sufficiently tightened with an appropriate force and does not loosen, and as a result, the present invention was achieved.

That is, the present invention provides a string-like article formed from a large number of filament-like fibers made of a thermoplastic polymer, which includes: (2) The filamentous fibers have irregular and periodic changes in cross-sectional area along their length, and The coefficient of variation of the cross-sectional area in the longitudinal direction [CV(F)] is in the range of 0.05 to 1.0, and (3) the filamentous fiber has an initial elastic modulus of at least 5 g/de and an elastic recovery rate of
% elongation) of at least 70%.

In the present invention, the string-like object includes not only thick threads, thin cloth-like strings, and ropes made by twisting fibers, but also rope-like objects, belt-like objects, and tape-like objects. The cross-sectional shape of the string-like material may be approximately circular or flat, or may have other shapes.

In the present invention, the filament internal cross-sectional area variation coefficient [CV(F)] indicates the variation in fineness in the longitudinal direction (axial direction) of the filament, and it refers to the variation in the fineness of the filament in the longitudinal direction (axial direction). , select 3cm at any one point and convert it to 1mm
The size of the cross-sectional area for each interval is measured by microscopic observation, and the average value () of the 30 cross-sectional areas and the standard deviation (σA) of the 30 cross-sectional areas are calculated using the following formula (1).
It can be calculated from

More specifically, this new elastic filament fiber (filament) has a non-circular cross-section and has irregular and periodic changes in cross-sectional area along the length of the filament. In addition, it also has a change in cross-sectional shape and has the above-mentioned characteristics.

In the filament-like fiber bundle forming the string-like article of the present invention, each filament-like fiber has the above-mentioned characteristics, and the fiber (filament)
The filament is characterized in that the size of the cross-sectional area of each filament when the bundle is cut in a direction perpendicular to the axis is substantially randomly different.

The thermoplastic polymer forming the filamentous fibers may be any thermoplastic crystalline polymer such as polyolefins such as polypropylene and polyethylene; polyamides such as nylon-6 and nylon-66; and polyester. Isotactic polypropylene (which may also contain small amounts of isotactic polypropylene) is especially suitable. Furthermore, a small amount of a rubbery material such as a polyester elastomer or a polyurethane elastomer may be blended.

Furthermore, these thermoplastic polymers may contain a plasticizer, a viscosity increaser, etc. in order to increase their plasticity and melt viscosity. Furthermore, a nucleating agent that increases crystallinity may be added. The polymer also contains light stabilizers, pigments, and pigments that are commonly used as additives for fibers.
Heat stabilizers, flame retardants, lubricants, matting agents, etc. may be added.

The method for producing the filamentous fibers forming the string-like material of the present invention is disclosed in the specifications of Japanese Patent Application No. 126105/1987, which the present inventors previously proposed, and an example thereof is shown below.

When extruding a thermoplastic synthetic polymer melt through a spinneret having a large number of slits to produce a filamentary fiber bundle, discontinuities occur in adjacent slits on the melt discharge side of the spinneret. Convex part (mountain)
is provided, and the melt extruded from one slit through the slits or concave areas (valleys) existing between the protrusions (mountains) is extruded from other slits adjacent thereto. The melt is extruded from a spinneret that can communicate with the melt, and at this time, the melt is extruded through the slits while being cooled by supplying a cooling fluid to the melt discharge surface of the spinneret and its vicinity. A filamentary fiber bundle can be produced by withdrawing the liquid and converting the melt into a number of separate fibrous streamlets, which are solidified. Furthermore, the filamentary fibers may be drawn 1.5 to 4 times.

Next, the filamentary fibers and filamentary fiber bundle are heat-treated to obtain the filamentary fibers and bundle thereof that form the string-like article of the present invention.

In this case, heat treatment methods include various methods such as a hot air circulation method, a radiant heating method using an infrared heater or a sheath heater, a heating drum contact method, and a heating method using hot water or steam. One of these methods may be used or a combination thereof may be used.

The heat treatment temperature may be within the range of "melting point -5° C." to "glass transition point +20° C." of the polymer forming the filamentous fibers. "Melting point -5
If the processing temperature exceeds 20°C, blocking occurs between the fibers, while at a treatment temperature lower than 20°C above the glass transition point, the filamentary fibers obtained do not exhibit excellent elastic recovery. For example, in the case of filamentary fibers made of crystalline polypropylene,
A heat treatment temperature of 155°C to 120°C is preferred.

Stretching may also be performed prior to the heat treatment described above, which is generally preferred.

The heat treatment time depends on the heat treatment temperature, but may be about 10 seconds to 60 minutes. The filamentary fibers during heat treatment may be in a tensioned state or may be in a non-tensioned state. Preferably, elastic filamentous fibers having better elastic recovery properties can be obtained in the same processing time if the fibers are kept under some tension.

Furthermore, cold stretching can be performed after the above heat treatment.

When the bundle of filamentous fibers forming the string-like object of the present invention is cut at an arbitrary position in a direction perpendicular to the filament axis, the cross-sectional area of each filament varies. It is expressed as a coefficient [CV(A)] and ranges from 0.05 to 1.5.

This CV(A) is calculated by randomly extracting 100 partial focusing bodies from the above focusing body, measuring the size of each cross section by observing the cross section at an arbitrary position under a microscope, and calculating the average value () Then, find the standard deviation (σB) of the 100 cross-sectional areas and use the following formula (2). It can be calculated from

The filamentous fibers forming the string-like article of the present invention have a non-circular cross section, and have irregular periodic changes in cross-sectional area along the length direction of the filament. Moreover, the cross-sectional shape also changes accordingly.
Moreover, the degree of non-circularity of the cross section is the circumference of the cross section 2
The irregularity coefficient (D/
d) is preferably at least 1.1;
Furthermore, it is more preferable that the deformation coefficient changes along the length direction.

The bundle of filamentous fibers forming the string-like object of the present invention is arranged approximately parallel to the length of the string-like object and bundled, and at any position of the bundle, the direction perpendicular to the filament axis is The cross-section of each filament when the bundle is cut at will be substantially different in size and shape at random, and furthermore, the cross section of each filament will be substantially different in size and shape when the bundle is cut in a direction perpendicular to the filament axis at any position of the bundle. The cross-sections of each filament when cut are substantially randomly different in size, and the shape of each cross-section is non-circular, and the degree of non-circularity is such that the cross-section is randomly different. When 10 pieces are extracted, the irregularity coefficient (D/d) expressed as the ratio of the maximum interval (D) between the two circumscribing parallel lines of the cross section to the minimum interval (d) between the two circumscribing parallel lines is on average at least 1.10 is substantially satisfied.

The average fineness within the bundle of filaments forming the filament fiber bundle in the present invention is 0.01
A range of denier to 200 denier is preferred and the filament may be an undrawn filament.

As mentioned above, the filamentous fibers and bundle thereof forming the string-like material of the present invention have [CV(F)]
Range of 0.05 to 1.0, [CV(A)] range of 0.05 to 1.5,
It is preferable that the irregularity coefficient is 1.1 or more. [CV
(F)] is less than 0.05, slippage between fibers tends to occur and it is difficult to integrate them into a string-like material. Moreover, if it exceeds 1.0, defective areas that cause stress concentration will appear.

When [CV(A)] is less than 0.05, [CV(F)] is also small and slippage between fibers tends to occur; on the other hand, [CV(A)]
If it exceeds 1.5, it means that there is a large variation in the fineness between the fibers, the strength balance of each fiber is likely to be lost, stress concentration is likely to occur, and the overall strength of the string-like material is weakened.

Furthermore, if the deformation coefficient is less than 1.1, the cross-sectional shape becomes close to a perfect circle, which tends to cause slippage between the fibers and makes it difficult to integrate them into a string-like object. Furthermore, the filamentous fibers forming the string of the invention may be partially joined to each other. The joining method may be by hot pressing or by using a binder.

The filamentary fibers of the present invention preferably have an initial elastic modulus of at least 5 g/de, more preferably 10 g/de or more. Also, its elastic recovery rate (50% elongation) is preferably at least 70%, more preferably 80%. Initial elastic modulus is 5g/
If it is less than de, the tightening force is too small, the binding force is weak, it is difficult to maintain the binding state, and it is easy to loosen. Furthermore, if the elastic recovery rate is less than 70%, it will be difficult to recover even if it is stretched, so it will likely become loose when tied.

The method for measuring the initial elastic modulus and elastic recovery rate is shown below.

The initial elastic modulus of the filament fiber is 4 cm.
10% of the load elongation curve is determined by tensileon at a head speed of 100%/min.
The intersection of the tangent at the extension point and the tangent at the 2% extension point was found, and the displacement at the intersection was a%, the stress was bg, and the denier was Cde.

Initial elastic modulus = b/a/100×C (g/de)...(3) Furthermore, the elastic recovery rate is determined using Tensilon, and the sample length is 4.
cm, stretch it to 50% at a head speed of 100%/min, then immediately release the stress and return to the original state at the same speed, repeat this 4 times, and at the 5th tension, the tension between the knobs starts to increase from zero. The elastic recovery rate (R ₅₀ ) was determined according to the following formula (4), where the distance is a cm.

Elastic recovery rate (R ₅₀ ) = (1-a-4/4) x 100% ... (4) The present invention will be described in detail with reference to Examples below, but the present invention is not limited in any way by these Examples. It's not a thing.

Example 1 Chips of polypropylene (fiber grade S-115M manufactured by Ube Industries, Ltd.) were fed in a fixed amount from a hopper to an extruder with an inner diameter of 20 mm, melted and kneaded in a temperature range of 200 to 280°C, and the chips were attached to the tip of the extruder. A gear pump fed the molten polymer at a rate of 15 g per minute to the spinning head, and the molten polymer was discharged from a rectangular nozzle having a forming area of 5 cm ² to obtain a filamentous fiber bundle. The base is a 50-mesh plain-woven wire mesh (stainless steel) (manufactured by Nippon Filcon).
was used. Furthermore, the filamentous fiber bundle is
Tension (fixed length) heat treatment was performed for 1 minute using a heat treatment device using an infrared heater having an ambient temperature of 150°C. The obtained filamentary fiber had an initial elastic modulus of 11 g/de, an elastic recovery rate (50% elongation) of 92%,
[CV(F)] was 0.29, [CV(A)] of the bundle of filamentary fibers was 0.40, and the shape coefficient was 1.5. Further, the filamentous fiber bundles were twisted together to obtain a string-like material having a diameter of about 1 mm.

When cardboard boxes measuring 50 cm vertically, 30 cm horizontally, and 40 cm deep were stacked in two rows and three tiers and bound using the string-like material, they were tightened with appropriate force and did not loosen even when subjected to vibration. .

Example 2 The filamentous fiber bundles obtained in Example 1 were arranged in parallel without twisting and heated at 155°C under a linear pressure.
By performing hot pressing at 10 kg/cm, a tape-like string-like product having a thickness of 0.2 mm and a width of 5 cm in which each filament was partially bonded to each other was obtained. The string-like material was tied in the same manner as in Example 1, and the results were very favorable.

Claims (1)

[Scope of Claims] 1. A string-like article formed from a large number of filament-like fibers made of a thermoplastic polymer, wherein: (1) the string-like article is such that each filament-like fiber extends in the longitudinal direction of the string-like article; (2) These filamentous fibers have irregular and periodic changes in cross-sectional area along their length. (3) The filament fiber has an initial elastic modulus of at least 5 g/de and a coefficient of elastic recovery (50
% elongation) of at least 70%. 2 When the string-like material is cut at right angles to its length, the cross-sectional area of each filament varies within the range of 0.05 to 1.5, expressed as the coefficient of variation of the cross-sectional area within the bundle [CV(A)]. A string-like object according to item 1. 3. The string-like article according to item 1 or 2, wherein the thermoplastic polymer is crystalline polypropylene.