JP2008174896A - Safety net - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a safety net excellent in weather resistance and having biodegradability by solving problems of a conventional safety net. <P>SOLUTION: The net is composed of a polylactic acid mainly containing 0.1-1.5% of a difunctional phosphorus compound and having a melting point above 130°C, wherein the net preferably has a of fiber breaking strength of more than 4.5 cN/dtex and a breaking elongation of more than 15%, and preferably the fiber is a dope-dyed fiber. The safety net is excellent in weather resistance in use, maintaining its performance for a long period and having biodegradability due to the structure, the net is outstandingly useful because easy disposal without affecting the global environment by being buried in the ground. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a safety net, and more particularly to a safety net that has sufficient mechanical properties and excellent weather resistance when used as a building material, and has biodegradability when discarded after use. It is.

  In recent years, the safety of work has been emphasized even in construction work sites, and safety nets have been widely used. Properties required for the safety net include knitting strength and impact resistance, and further excellent weather resistance and flame resistance are desired.

Conventionally, as described in Patent Document 1, polyethylene terephthalate fibers have been frequently used for safety nets. A safety net made of polyethylene terephthalate is excellent in mechanical properties, but it has a problem that the weather resistance is not sufficient and the strength is greatly reduced by long-term use outdoors. In addition, since products obtained from polyethylene terephthalate are not biodegradable in disposal after use, there is no choice but to dispose of them only by incineration or landfilling. In addition, there were problems such as causing environmental destruction when illegally disposed of.
Japanese Patent Publication No. 61-2145

  The purpose of the present invention is to have excellent mechanical properties and weather resistance during use, and since it gradually decomposes and disappears in the natural environment after use, there is no concern about air pollution due to incineration. It is to provide a safety net that does not cause destruction.

  In order to solve the above problems, the safety net of the present invention mainly has the following configuration. That is, the safety net is composed of fibers mainly composed of an aliphatic polyester having a melting point of 130 ° C. or higher.

  The safety net of the present invention has excellent weather resistance during use, and not only maintains its performance over a long period of time, but also has biodegradability. It is extremely useful because it can be easily disposed of without affecting the quality.

  The aliphatic polyester that can be used in the present invention is not particularly limited as long as it has a melting point of 130 ° C. or higher. Polylactic acid, poly-3-hydroxypropionate, poly-3-hydroxybutyrate, poly-3- Hydroxybutyrate valerate and blends, modified products and the like thereof can be used. In the present invention, the melting point refers to the temperature of the melting peak obtained by DSC measurement. When the melting point is lower than 130 ° C., the fusion between the single fibers becomes remarkable at the time of spinning, especially at the time of spinning, and further, the quality of the product is remarkably impaired such as poor stretchability. Preferably, the melting point is 150 ° C. or higher, more preferably the melting point is 170 ° C. or higher.

  Excellent weather resistance can be obtained by using these aliphatic polyesters as the material of the fibers constituting the safety net. In addition, these aliphatic polyesters are highly biodegradable or hydrolyzable and have the advantage that they are easily degraded in the natural environment after use. Furthermore, the degradability can be controlled by changing the design of the safety net according to the fineness and fiber structure of the fibers used, or the knitting structure and coating.

  Among the aliphatic polyesters, polylactic acid is particularly preferable. The method for producing polylactic acid is a two-step lactide in which L-lactic acid, D-lactic acid, and LD-lactic acid (racemic lactic acid) are used as raw materials to once generate lactide, which is a cyclic dimer, and then perform ring-opening polymerization. And a one-step direct polymerization method in which the raw material is directly subjected to dehydration condensation in a solvent are known. The polylactic acid preferably used in the present invention may be obtained by any production method. In the case of a polymer obtained by the lactide method, the cyclic dimer contained in the polymer is vaporized at the time of melt spinning to cause yarn unevenness. Therefore, the cyclic dimer contained in the polymer at a stage before melt spinning. The content of is desirably 0.1 wt% or less.

  The average molecular weight of polylactic acid is preferably as high as possible, and is usually at least 50,000, preferably at least 100,000, and preferably 100,000 to 300,000. When the average molecular weight is at least 50,000, the strength properties of the fiber can be improved, which is preferable.

  The polylactic acid preferably used in the present invention may be a copolymerized polylactic acid obtained by copolymerizing other components having ester forming ability in addition to lactic acid. The copolymerizable component includes glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, hydroxycarboxylic acids such as 6-hydroxycaproic acid, ethylene glycol, propylene glycol, butanediol, neo Compounds containing a plurality of hydroxyl groups in the molecule such as pentyl glycol, polyethylene glycol, glycerin, pentaerythritol or derivatives thereof, succinic acid, adipic acid, sebacic acid, fumaric acid, terephthalic acid, isophthalic acid, 2,6- Examples thereof include compounds containing a plurality of carboxylic acid groups in the molecule, such as naphthalenedicarboxylic acid, 5-sodium sulfoisophthalic acid, and 5-tetrabutylphosphonium isophthalic acid, or derivatives thereof.

  In order to reduce the melt viscosity, aliphatic polyester polymers such as polycaprolactone, polybutylene succinate, and polyethylene succinate can be used as an internal plasticizer or as an external plasticizer.

  The breaking strength of the fiber used in the safety net of the present invention is preferably 4.5 cN / dtex or more, more preferably 5.0 cN / dtex or more. By setting it as such a range, the fabric weight of the safety net for achieving desired knitting strength does not become too large.

  Further, the breaking elongation of the fiber used in the safety net of the present invention is preferably 15% or more, and more preferably 18% or more. By setting it within this range, the safety net is sufficiently stretched to receive an impact, the stress is not concentrated on a specific part and is not easily broken, and the deceleration (G value) when the safety net receives a human body is reduced. And damage to the human body can be reduced.

  A coloring pigment, a flame retardant, an ultraviolet stabilizer, a matting agent, a deodorant, a yarn friction reducing agent, an antioxidant and the like can be added to the aliphatic polyester of the present invention as necessary.

  In addition to inorganic pigments, cyanine, styrene, phthalocyanine, anthraquinone, perinone, isoindolinone, quinophthalone, quinocridone, thioindigo, and the like can be used as the color pigment. . The coloring of the fibers is preferable not only from the viewpoint of design properties but also from the viewpoint of improving the weather resistance of the fibers.

  In order to impart flame retardancy to the safety net of the present invention, the fiber preferably contains 0.1 to 1.5% of a bifunctional phosphorus compound as a flame retardant. Specifically, the bifunctional phosphorus compound as a flame retardant preferably has a structure represented by the following chemical formulas (I) to (III).

(In the formulas (I) to (III), R 1 and R 5 are the same or different groups and represent hydrocarbon groups having 1 to 18 carbon atoms, and R 2 and R 3 are the same or different groups, respectively. A hydrocarbon group having 1 to 18 carbon atoms or a hydrogen atom, A1 represents a divalent organic group, A3 represents a trivalent organic residue, R4 represents a carboxyl group or an ester thereof, and R6 represents a carboxyl group or a group thereof. Represents a divalent ester-forming functional group that forms a ring with A2 via an ester or a group represented by (IV) below.)

  Preferable specific examples of the phosphorus compound in the above formula (I) include dimethyl phenylphosphonate, diphenyl phenylphosphonate and the like.

  Preferable specific examples of the phosphorus compound in the formula (II) include (2-carboxyethyl) methylsulfinic acid, (2-carboxyethyl) phenylphosphinic acid, (2-methoxycarboxyethyl) phenylphosphinic acid methyl, (4 -Methoxycarbonylphenyl) phenylphosphinic acid methyl, (2- (β-hydroxyethoxycarbonyl) ethyl) methylphosphinic acid ethylene glycol ester, and the like.

  Preferable specific examples of the phosphorus compound in the above formula (III) include (1,2-dicarboxyethylphosphine oxide (2,3-dicarboxypropyl) dimethylphosphine oxide, (2,3-dimethoxycarbonylethyl) dimethylphosphine. Oxide, (1,2-di (β-hydroxyethoxycarbonyl) dimethylphosphine oxide, and the like.

  Among the compounds represented by the above formulas (I) to (III), the phosphorus compound of the formula (II) is particularly preferably used because it has good copolymerizability with the polyester and less scattering during the polycondensation reaction.

  The addition amount of the bifunctional phosphorus compound is preferably 0.1 to 1.5%. By making the addition amount within such a range, the effect of improving the flame retardancy is sufficient, while the mechanical properties and weather resistance of the fiber can be made excellent.

  Further, benzophenone-based, benzotriazole-based, and hindered amine-based compounds can be preferably used as the ultraviolet stabilizer. The blending amount at this time is preferably 0.005 to 1.0 wt% with respect to the fiber weight.

  The fiber used in the present invention may be obtained by ordinary melt spinning. That is, after the dried polymer is melted by, for example, an extruder or a pressure melter, it is measured by a metering pump, filtered in a spinning pack or the like, and then discharged from a die. The discharged yarn is cooled and solidified by cooling air or the like, then applied with an oil agent, taken up, and then drawn. The diameter of the discharge hole of the die is preferably about 0.2 to 1.0 mm in the case of a round cross section. In the cooling region, a gas heated or cooled to about 40 to 70 ° C. at normal temperature may be sprayed at a linear velocity of 15 to 50 m / min. The conditions for this cooling region may be selected according to setting conditions such as the melt viscosity, the single fiber fineness, the draft rate, and the number of single fibers of the polymer to be spun.

  For stretching, either a two-step method of winding once before stretching or a direct spinning stretching method in which stretching is performed without winding after spinning may be used. The take-up speed is preferably 4000 m / min or less from the viewpoint of fiber strength and 300 m / min or more from the viewpoint of productivity. The draw ratio varies depending on the take-up speed and may be adjusted so that the elongation of the obtained fiber is in the above range. Further, it is preferable that a heating zone is provided immediately under spinning and before cooling and solidification to heat the yarn to a temperature equal to or higher than the melting point of the polymer to increase the strength of the fiber. Stretching may be one-stage stretching or multi-stage stretching of two or more stages, but from the viewpoint of obtaining strength, 2 to 4 stage stretching is preferable, and before winding, heat treatment is performed at a temperature about 20 to 80 ° C. lower than the melting point of the polymer. It is preferable that a relaxation treatment of 1 to 20% is performed from the viewpoint of dimensional stability. The fineness and the number of filaments of the multifilament obtained by spinning are preferably 250 to 4000 dtex and 20 to 500, respectively.

  First, 2-6 yarns of the obtained polyester fiber are put together in the net, and then twisted, 2-8 yarns of the twisted yarn are combined, and the twisted yarn is twisted in the opposite direction to the twisted yarn. obtain. Next, a net is obtained by knitting the obtained twisted yarn with a Russell knitting machine or the like. The obtained net may be further subjected to heat treatment at 100 to 160 ° C. for about 30 to 300 seconds as necessary.

  In the case where the heating zone is installed immediately before spinning and before cooling and solidification, the temperature of the heating zone is preferably 120 to 350 ° C. and the length is preferably 5 to 300 cm. The heating zone conditions may also be selected according to setting conditions such as the melt viscosity, the single fiber fineness, the draft rate, and the number of single fibers of the polymer to be spun. As a method for applying heat necessary for drawing the yarn, a known method such as a heating roll, steam, a contact hot plate, a heat pin, or a dry heat non-contact heater may be used.

  The features of the present invention will be specifically described below with reference to examples.

The measurement method employed in this example is shown below.
(A) The strength and elongation of the fiber were measured at a yarn length of 25 cm and a tensile speed of 30 cm / min using a Tensilon tensile tester in a temperature-controlled room at an air temperature of 20 ° C. and a humidity of 65%.
(B) Flame resistance was measured according to JIS L 1091 (Method D).
(C) Weather resistance The weather resistance of the safety net was determined by measuring the tensile strength after the treatment for 100 hours according to the weather resistance A method of JIS L 1096, and determining the retention rate relative to the tensile strength before the treatment.
(D) A biodegradable safety net was buried in the soil for 6 months, the strength of the fiber after removal was measured, and the strength retention was calculated.

[Examples 1 and 2]
The amount of [2- (β-hydroxyethoxycarbonyl) ethyl] methylphosphinic acid in the table as phosphorus content, styrene yellow, cyanine blue and carbon in a 1: 1.5: 0.1 weight ratio. A poly L-lactic acid having a weight average molecular weight of 200,000 containing 0.3% by weight of a colorant adjusted in proportion was spun at 240 ° C. and heated and stretched 7 times to obtain polylactic acid fibers of 1110 dtex and 144 filaments. The obtained fiber was knitted with a front of 7000 dtex and a back of 4700 dtex using a Russell knitting machine, and a safety net with a basis weight of 410 g / m ² was obtained. The properties of the obtained fiber and safety net are shown in Table 1.

[Example 3]
A polylactic acid fiber similar to Example 1 was obtained except that no colorant was contained, and a safety net was obtained in the same manner as Example 1. The properties of the obtained fiber and safety net are shown together in Table 1.

[Comparative Example 1]
A polylactic acid fiber similar to that in Example 1 was obtained except that no phosphorus compound was contained, and a safety net was obtained in the same manner as in Example 1. The properties of the obtained fiber and safety net are shown together in Table 1.

[Comparative Example 2]
A polylactic acid fiber was obtained in the same manner as in Example 1 except that it did not contain a colorant and a phosphorus compound, and a safety net was obtained in the same manner as in Example 1. The properties of the obtained fiber and safety net are shown together in Table 1.

[Comparative Example 3]
Using 1110 dtex, 144 filament polyethylene terephthalate fiber (indicated as PET in Table 1), a safety net was obtained in the same manner as in Example 1. The properties of the fiber and safety net are shown together in Table 1.

[Comparative Example 4]
Using 1110 dtex, 144 filament polycaprolactone fiber (indicated as PCL in Table 1), a safety net was obtained in the same manner as in Example 1. The properties of the fiber and safety net are shown together in Table 1.

Claims (3)

  A safety net comprising a fiber mainly composed of polylactic acid containing 0.1 to 1.5% of a bifunctional phosphorus compound and having a melting point of 130 ° C or higher.   The safety net according to claim 1, wherein the fiber has a breaking strength of 4.5 cN / dtex or more and a breaking elongation of 15% or more.   The safety net according to claim 1 or 2, wherein the fiber is an original yarn.