JP6870480B2 - Polyethylene spunbonded non-woven fabric - Google Patents

Description

The present invention relates to a polyethylene spunbonded non-woven fabric which is excellent in flexibility, high strength, excellent workability, and can suitably exhibit these effects even when a raw material having a low environmental load is used.

Spun-bonded non-woven fabric made of polyolefin, especially polypropylene spun-bonded non-woven fabric, is widely used mainly for sanitary materials because of its low cost and excellent flexibility.

Many studies have been conducted on techniques for further enhancing the flexibility, which is a characteristic of polyolefin spunbonded non-woven fabrics, and among them, polyethylene, which has a lower elastic modulus than polypropylene, has been studied.

Although polyethylene spunbond has excellent flexibility, it has a problem that the workability of the sheet is inferior. One of the reasons for this is that polyethylene has poor silk-reeling properties and is prone to thread breakage, so there are many sheet defects, and this defect is the starting point for wrapping around rubber nip rollers, etc., and the fiber strength is high. This is because the sheet strength is low because it is low, and tearing or the like is likely to occur during sheet processing. Due to this problem, polyethylene spunbonds that satisfy practical performance have not yet been obtained industrially.

Further, if an attempt is made to reduce the single yarn fineness in order to improve the flexibility and texture, the yarn-forming property of polyethylene tends to be further deteriorated, so that there is a problem that the defects are further increased and the workability is further deteriorated.

Another issue is that polyethylene is generally produced from fossil resources, but petroleum, which is a fossil resource, is an important raw material for the chemical industry, but there is a concern that it will be depleted in the future. In addition, since a large amount of carbon dioxide is emitted when incinerated, it causes a series of problems such as global warming. Under these circumstances, with regard to non-woven fabrics for sanitary materials such as disposable diapers and sanitary napkins, the amount of non-woven fabrics for sanitary materials used in Japan is extremely large, exceeding 200,000 tons per year, and is used. After that, 100% of the waste is disposed of, so much attention is being paid to the use of recycled raw materials and raw materials with low environmental impact.

For non-woven fabrics for sanitary materials, there are demands for improved flexibility and texture, and in order to achieve this, a method of fineness is desired. However, when conventional polyethylene derived from biomass resources is used, At present, the spinning stability is low and a non-woven fabric having a fine fineness cannot be obtained. Further, the non-woven fabric for sanitary materials is required to be low cost because it is a disposable product, but it cannot be produced unless the discharge amount is lowered from the viewpoint of deterioration of spinnability, and the productivity is low and low. Cost reduction has not been achieved. Further, since whiteness as a feeling of cleanliness is required for sanitary material applications, it is not preferable to apply a polymer having low heat resistance and turning yellow due to thermal decomposition. For these reasons, conventional non-woven fabrics using raw materials having a low environmental load cannot be applied to non-woven fabrics for sanitary materials.

Against this background, in order to eliminate the influence of polymerization catalyst residues and the like and to solve the problem of thread breakage during spinning, a metal salt of an aliphatic carboxylic acid having 12 to 22 carbon atoms is added to polyethylene. It has been proposed to contain 800 ppm or less and 200 ppm or more (see Patent Document 1). This technology is a technology that suppresses the thermal decomposition of polyethylene and is considered to be effective in improving the yarn-making property. However, the single yarn fineness is at least 4.8 dtex, and the metal carboxylate when the single yarn fineness is reduced. There is no mention of the effect of adding multiple salts.

In addition, as a countermeasure against yarn breakage during spinning, friction during air soccer towing, and poor fiber opening, in composite fibers (fibers having a core-sheath structure), ethylene-vinyl acetate copolymer and low-density polyethylene are used as sheath components. It has been proposed to use a mixed resin and a mixture of a linear higher fatty acid or a metal salt thereof (see Patent Document 2). This technology is a technology that suppresses fusion between fibers by changing the surface characteristics of the fibers, and is considered to be effective in improving yarn-making property and also in improving sheet workability by lowering the coefficient of friction. However, there is no description about the effect of adding multiple kinds of carboxylic acid metal salts when the single yarn fineness is reduced.

Japanese Unexamined Patent Publication No. 1-221514 Japanese Unexamined Patent Publication No. 10-1687294

An object of the present invention is to provide a polyethylene spunbonded non-woven fabric having excellent flexibility, high strength, and excellent workability.

The above-mentioned problem of the present invention is achieved by the following means.

Consists of polyethylene with a density of 0.915 to 0.965 g / cm ³
A polyethylene spunbonded non-woven fabric having a single yarn fineness of 2.0 dtex or less and having a saturated fatty acid-based additive added to polyethylene so as to satisfy the following conditions A to C.
A. The saturated fatty acid-based additive is a saturated fatty acid or a saturated fatty acid metal salt having 12 to 30 carbon atoms, and comprises two or more kinds of saturated fatty acids or saturated fatty acid metal salts having different carbon atoms.
B. The difference between the maximum and minimum carbon numbers of the saturated fatty acid or the saturated fatty acid metal salt contained in the saturated fatty acid-based additive is 4 or more.
C. The total amount of the saturated fatty acid-based additive added to polyethylene is 0.1 to 10.0 wt%.

According to a preferred embodiment of the non-woven fabric of the present invention, the polyethylene contains 50 wt% or more of plant-based polyethylene.

Further, according to a preferable mode of the nonwoven fabric of the present invention, calcium stearate is contained as a component of the saturated fatty acid-based additive.

The polyethylene spunbonded non-woven fabric of the present invention can further improve the flexibility, the fineness of the single yarn is thin, the tactile sensation is improved, and the strength of the fiber is also increased, so that there is no tearing during sheet processing, and there are further sheet defects. Since the amount is small, the workability can be further improved. In particular, these effects can be suitably exhibited even when a raw material having a low environmental load is used.

Hereinafter, the polyethylene spunbonded nonwoven fabric of the present invention will be described in detail.

The polyethylene (hereinafter, also referred to as PE) spunbonded nonwoven fabric of the present invention is made of polyethylene resin fibers. The polyethylene resin means a polymer having an ethylene unit as a repeating unit. By using a polyethylene resin, a non-woven fabric having excellent flexibility can be obtained.

The PE resin used in the present invention is obtained by dehydrating (1) petroleum-based PE synthesized from ethylene obtained by high-temperature thermal decomposition of naphtha, or (2) vegetable ethanol obtained from sugar cane or the like at a relatively low temperature. Examples thereof include plant-based PE obtained by polymerizing the ethylene produced. Among these, it is preferable to use plant-based PE from the viewpoint of reducing the environmental load.

The density of the PE resin used in the present invention is 0.915 to 0.965 g / cm ³ . When the density is 0.915 g / cm ³ or more, it has appropriate crystallinity, and since it is excellent in yarn-making property and thread strength, it is excellent in sheet strength and processability. Further, when the density is 0.965 g / cm ³ or less, rapid solidification due to crystallization in spinning can be suppressed, and since the yarn-making property is excellent, there are few sheet defects due to thread breakage and the workability is excellent.

The PE resin used in the present invention may be copolymerized with other olefin monomers and styrene monomers as long as the object of the present invention is satisfied. As the copolymerization component, heptene and octene are preferable from the viewpoint of reducing sheet defects and fineness, and octene is more preferable. The copolymerization ratio is preferably 3.0 mol% or less, more preferably 1.0 mol% or less, from the viewpoint of increasing the strength. The plant-based PE contains a large amount of branched monomer components having 4 or less carbon atoms due to impurities in the raw material, and the total amount of these components is preferably 3.0 mol% or less as a copolymerization component.

As a suitable example of PE resin, in petroleum-based PE, (1) medium-density polyethylene, high-density polyethylene, and (2) ethylene main chain have branching components different from ethylene, such as butene or hexene, 4-. A copolymer of methylpentene, heptene, octene, etc. is preferable because the thread strength can be increased.

In plant-based PE, (1) poly (ethylene-RAN-butylene) mono-OL, (2) ethylene / 1-hexenkopolymer, (3) butene-ethylene-hexene-polymer, or (4) Any of polyethylene is preferable from the viewpoint that the thread strength can be increased.

The PE fiber constituting the spunbonded non-woven fabric is preferably a PE single component fiber. In the fiberization of PE, it is possible to combine it with other polymers (core sheath, sea island, side-by-side), but in the present invention, the characteristics of PE are fully expressed and fineness that is difficult to reach by composite spinning is achieved. Therefore, a single PE component is preferable.

In order to obtain a PE single component yarn, it is preferable to perform melt spinning using the above-mentioned PE resin as a raw material, but it is also possible to blend a plurality of types of PE resins as a raw material. In that case, in order to achieve the low environmental load, which is one of the objects of the present invention, it is preferable that the plant-based PE is contained in an amount of 50 wt% or more.

The PE resin may be blended with a small amount of other component polymers. Examples of the other component polymer include polyolefin-based polymers such as polypropylene and poly4-methylpentene having a melting point close to PE, as well as low-melting point polyester and low-melting point polyamide. However, in order to fully express the characteristics of polyethylene, the weight ratio of the blend is preferably 5 wt% or less, more preferably 2 wt% or less. Further, a pigment for coloring, an antioxidant, a lubricant such as polyethylene wax, a heat-resistant stabilizer and the like may be added to the PE resin.

In the present invention, a saturated fatty acid-based additive is added to PE so as to satisfy the following conditions A to C.
A. The saturated fatty acid-based additive is a saturated fatty acid or a saturated fatty acid metal salt having 12 to 30 carbon atoms, and comprises two or more kinds of saturated fatty acids or saturated fatty acid metal salts having different carbon atoms.
B. The difference between the maximum and minimum carbon numbers of the saturated fatty acid or the saturated fatty acid metal salt contained in the saturated fatty acid-based additive is 4 or more.
C. The total amount of the saturated fatty acid-based additive added to polyethylene is 0.1 to 10.0 wt%.

Saturated fatty acids having 12 to 30 carbon atoms refer to C12 dodecanoic acid to C30 melissic acid. As for the metal salt, the metal species are preferably an alkali metal selected from Li, Na and K, an alkaline earth metal element selected from Be, Mg, Ca and Ba, and Al and Zn. Since two or more kinds of saturated fatty acids or saturated fatty acid metal salts are used in the present invention, the mixed state can be made appropriate by interaction. Therefore, as the metal species, Be, Mg, Ca, Ba, Al, Zn having a divalent value or more can be used. More preferably, Ca is most preferable from the viewpoint of availability. In the present invention, it is important that two or more kinds of saturated fatty acids or saturated fatty acid metal salts have an interaction with each other. Therefore, it is preferable to use a saturated fatty acid metal salt having a valence of two or more, and Ca stearate is particularly used. It is most preferable to add it from the viewpoint of availability.

In the present invention, two or more kinds of saturated fatty acids or saturated fatty acid metal salts having 12 to 30 carbon atoms having different carbon atoms are used, and the difference in carbon number between the one having the maximum carbon number and the one having the minimum carbon number is 4 That is all. When the difference in carbon number is 4 or more, an appropriate interaction is exhibited, the yarn-making property is excellent, there are few sheet defects, and the sheet processability is also excellent. If the difference in carbon number is excessively large, the interaction will decrease, so it is preferably 15 or less.

In the present invention, the object is achieved by using two or more kinds of saturated fatty acid-based additives having a difference in carbon number of 4 or more in combination, and the effects thereof are described below.

One of the problems with the workability of PE spunbond is that (1) yarn breakage occurs during spinning due to inferior yarn-making performance, and roll winding occurs due to fluff starting from the yarn end. It was found that (2) due to the poor releasability of the PE fiber with respect to the roll, fluffing occurs even in the portion where the yarn is not broken, and wrapping occurs. There is also a method of applying an oil agent or the like to improve the releasability with the roller, but it is not a preferable method because of the poor tactile sensation caused by the oil agent and the adverse effect on heat fusion in the processing process. Therefore, by adding a saturated fatty acid-based additive having a relatively low carbon number (C12 to C16) to the PE resin, we have found a means for improving the releasability, that is, the sheet processability, which is the problem of (2). However, the low-carbon (C12 to C16) saturated fatty acid-based additives have the disadvantages that they tend to bleed on the fiber surface, resulting in poor tactile sensation (stickiness) and the effect of improving releasability.

Therefore, it was conceived to further add a saturated fatty acid-based additive having a relatively high carbon number (C18 to C30). High-carbon saturated fatty acid-based additives are difficult to bleed and stay inside the fiber, and high-carbon saturated fatty acid-based additives interact with low-carbon saturated fatty acid-based additives, resulting in low carbon number. The bleeding of the saturated fatty acid-based additives (C12 to C16) can be set in an appropriate range.

In addition, the combined use of high-carbon and low-carbon saturated fatty acid-based additives also produced a new synergistic effect. That is, it was found that the yarn breakage at the time of spinning, which is the problem of the above-mentioned (1), can be reduced probably because of the plasticizing effect of the saturated fatty acid-based additive. It is considered that this effect is also due to the fact that the plasticization effect is enhanced and the fluidity is enhanced by the combined use of high carbon number and low carbon number.

The low-carbon saturated fatty acid-based additive present on the yarn surface not only reduces the friction of the fiber, improves the releasability and improves the workability, but also improves the balance of moisture permeability / moisture retention. It was also found that it has an effect of diffusing water, spreads water, and can be uniformly absorbed by a water-absorbent polymer when used as a sanitary material. Therefore, it is possible to always give a smooth and comfortable touch until the water absorption limit is reached.

In the present invention, the total amount of the saturated fatty acid-based additive added to PE is 0.1 to 10.0 wt%. When the addition amount is 0.1 wt% or more, the above-mentioned effect is exhibited, the silk-reeling property is excellent, the sheet defects are few, and the sheet processability is also excellent. Since this effect increases as the amount added increases, 0.3 wt% or more is preferable, and 0.6 wt% or more is more preferable. Further, when the content is 10.0 wt% or less, bleeding of a saturated fatty acid-based additive having a low carbon number on the fiber surface can be suppressed, and deterioration of tactile sensation (stickiness) and deterioration of heat-sealing property can be suppressed. From this viewpoint, the addition amount is preferably 2.0 wt% or less, more preferably 1.0 wt% or less.

Regarding the balance between the high carbon number saturated fatty acid type additive and the low carbon number saturated fatty acid type additive, the weight ratio of (low carbon number) :( high carbon number) = (1-55) :( 99-45) Is desirable. When the high carbon number saturated fatty acid type additive is 45 wt% or more of the total amount of the additive, it stays firmly in the fiber, and the bleeding of the low carbon number saturated fatty acid type additive can be suppressed. Since a low-carbon saturated fatty acid-based additive acts on the surface properties, the effect can be exhibited if the ratio is 1 wt% or more of the total additive.

The basis weight of the polyethylene spunbonded non-woven fabric of the present invention is preferably 5 to ^{50 g / m 2.} When the basis weight is within the above range, the flexibility of the non-woven fabric can be suitably exhibited. From this point of view, the basis weight is more preferably 10 to ^{30 g / m 2.}

The cross-sectional shape of the fibers constituting the polyethylene spunbonded nonwoven fabric of the present invention is preferably round. In a flat or irregular cross section, the geometrical moment of inertia is larger than that of a round cross section having the same cross-sectional area depending on the bending direction, so that the fibers may become hard and the flexibility of polyethylene may be impaired. Therefore, a round cross section is preferable.

The single yarn fineness of the fibers constituting the polyethylene spunbonded non-woven fabric of the present invention is 2.0 dtex or less. The single yarn fineness referred to in the present invention refers to a value measured by the method described in Examples. By setting the single yarn fineness to 2.0 dtex or less, in addition to the flexibility of polyethylene, the decrease in the moment of inertia of area due to the small single yarn fineness is also exhibited, further improving the flexibility and improving the tactile sensation. To do. From this viewpoint, the single yarn fineness is preferably 1.8 dtex or less, more preferably 1.5 dtex or less. The lower limit of the single yarn fineness is about 0.5 dtex.

For the same reason, the fiber diameter of the fibers constituting the polyethylene spunbonded non-woven fabric is preferably 17.0 μm or less, more preferably 16.0 μm or less, still more preferably 15.0 μm or less. The fiber diameter referred to in the present invention refers to a value measured by the method described in Examples. The lower limit of the fiber diameter is about 8.0 μm.

The birefringence (Δn) of the single yarn constituting the polyethylene spunbonded nonwoven fabric of the present invention is preferably 0.035 or more. Δn in the present invention refers to a value measured by the method described in Examples. When Δn is 0.035 or more, the molecular orientation can be increased and the strength of the fiber can be increased. From this viewpoint, Δn is more preferably 0.037 or more.

The single yarn strength constituting the polyethylene spunbonded nonwoven fabric of the present invention is preferably 120 MPa. The single yarn strength referred to in the present invention refers to a value measured by the method described in Examples. When the single yarn strength is 120 MPa or more, yarn breakage during processing can be suppressed and the workability is excellent. From this viewpoint, the single yarn strength is more preferably 130 MPa or more.

The melting point of the polyethylene spunbonded non-woven fabric of the present invention is preferably 120 ° C to 131 ° C. The melting point referred to in the present invention refers to a value measured by the method described in Examples. The melting point of the PE resin is generally about 130 to 135 ° C., and the crystallinity is lowered by branching and copolymerization of other kinds of monomers, and the melting point is also lowered. When the melting point is 120 ° C. to 131 ° C., the crystallinity is appropriate and the fiber strength is improved.

The heat of crystal melting of the polyethylene spunbonded nonwoven fabric of the present invention is preferably 100 to 175 J / g, more preferably 150 to 175 J / g. The amount of heat of crystal melting referred to in the present invention refers to a value measured by the method described in Examples. Similar to the melting point, the amount of heat of crystal melting also decreases due to branching and copolymerization of other types of monomers, and the amount of heat of crystal melting also decreases. When the amount of heat for melting the crystal is 100 to 175 J / g, the crystallinity is appropriate and the fiber strength is improved.

The polyethylene spunbonded non-woven fabric of the present invention can be widely used for medical hygiene materials, daily life materials, industrial materials, etc., but it has excellent flexibility, good tactile sensation, high strength, and few product defects, so that it has good workability. Moreover, since the environmental load can be reduced, it can be particularly preferably used as a sanitary material. Specifically, they are disposable diapers, sanitary napkins, base cloths for poultices, and the like.

Next, a specific example of the method for producing the polyethylene spunbonded nonwoven fabric of the present invention will be described.

The raw material used is PE resin, and its density, saturated fatty acid-based additives, other copolymers, etc. are as described above.

The melting point of the PE resin is also substantially the same as the melting point of the non-woven fabric, preferably 125 ° C to 131 ° C. The PE resin preferably has a melt index (MI) of 10 to 200 g / 10 minutes, and more preferably 20 to 100 g / 10 minutes. The melt index referred to here refers to a value measured at 190 ° C. and a load of 2.16 kg in accordance with ASTM D1238. By using PE resin in such a range, even if it is towed at high speed, it has excellent spinnability, so there are few sheet defects and fineness can be achieved. Can be enhanced.

The PE resin is subjected to melt spinning without being particularly dried. For melt spinning, a known melt spinning method using an extruder such as a single-screw or twin-screw extruder can be applied. The extruded polymer is weighed by a known weighing device such as a gear pump via a pipe, passed through a foreign matter removing filter, and then guided to a mouthpiece. At this time, the temperature from the polymer pipe to the base (spinning temperature) is set to about 160 to 250 ° C. in order to improve the fluidity.

The mouthpiece used for discharge preferably has a hole diameter D of the mouthpiece hole of 0.10 mm or more and 0.60 mm or less, and has a land length L of the mouthpiece hole (the length of a straight pipe portion same as the hole diameter of the mouthpiece hole). The L / D defined by the quotient divided by the pore size is preferably 1.0 or more and 10.0 or less.

The yarn discharged from the mouthpiece hole is cooled and solidified by air. The temperature of the cooling air may be determined in balance with the cooling air speed from the viewpoint of cooling efficiency, but is preferably 50 ° C. or less from the viewpoint of fineness uniformity. In addition, the cooling gas cools the yarn by flowing it in a direction substantially perpendicular to the yarn. At that time, the speed of the cooling air is preferably 5 m / min or more from the viewpoint of cooling efficiency and fineness uniformity, and preferably 100 m / min or less from the viewpoint of silk reeling stability. Further, it is preferable to start cooling within 20 mm or more and 500 mm or less from the base to cool and solidify. If cooling is started at a distance of less than 20 mm, the surface temperature of the base may drop and the discharge may become unstable. If cooling is not started within 500 mm, the stability of the thinning behavior cannot be maintained and it becomes stable. You may not be able to spin.

The yarn discharged from the mouthpiece hole is towed by an accelerated air flow at a position of 400 mm or more and 7,000 mm or less from the mouthpiece. The accelerating air flow may be made to seal the region where the cooling air is blown, and the air flow velocity may be accelerated by gradually reducing the cross-sectional area of the sealed region toward the downstream of the spinning line, but the air flow velocity may be higher. It is preferable to use an ejector in order to obtain. The yarn is accelerated by this air flow velocity, and the spinning speed, which is the running speed of the fiber, reaches a speed close to the air flow velocity. The spinning speed refers to the value calculated by the following formula.

Spinning speed (km / min) = Q ・ 10 / D
Q: Single hole discharge amount (g / min), D: Single yarn fineness (dtex)
The spinning speed is preferably 3.0 km / min or more for fineness and high strength, and more preferably 4.0 km / min. Similarly, the air flow velocity is preferably 3.0 km / min or more. The upper limit of the spinning speed is about 10.0 km / min.

The air-towed yarn is opened by passing through an opening portion that reduces the flow velocity of the surrounding air, and then lands on a net conveyor that is air-sucked from the back surface and is collected. The collected web is conveyed on a conveyor at 10 to 1200 m / min, and then embossed and calendered to obtain a spunbonded non-woven fabric.

The important point in terms of the process of the PE spunbonded non-woven fabric of the present invention is high-speed spinning at a spinning speed of 3 km / min or more. Although spunbonding is a high-speed spinning process, it does not stretch the fibers after solidification, so the strength of the fibers is dominated by the fiber structure formed before solidification. Therefore, in order to increase the strength, it is important to apply high stress to the fibers from the completion of thinning to the solidification and to fix the molecular chains in a highly oriented state. High-speed spinning is effective in spunbonding as a means of applying high stress to the yarn, but depending on the polymer type, thinning tends to proceed upstream of the spinning line (a place near the base), and in some cases, yarn breakage occurs. .. In the present invention, PE having a specific range of densities is used, and by adding a specific saturated fatty acid-based additive, fluidity is improved, thinning is slowed down, yarn breakage is prevented upstream of the spinning line, and crystallization occurs. It is presumed that the structure can be fixed by applying sufficient stress until solidification due to the above, aligning the molecular chains, and sufficiently crystallizing, so that the strength can be increased.

Hereinafter, the present invention will be described in more detail with reference to Examples. Each characteristic value in the examples was obtained by the following method.

A. Fiber diameter and single yarn fineness The fiber diameter was determined from the microscopic observation of the side surface of the fiber, measured 10 times per level, and the average value was taken as the fiber diameter. Next, the fiber was treated as a round cross section, and the single yarn fineness was determined from the fiber diameter using the following formula.

Single yarn fineness ^{(dtex) = π · ρ ·} d 2/400
ρ: Resin density (g / cm ³ ), d: Fiber diameter (μm)
B. Birefringence of single yarn (Δn)
Using a single yarn extracted from the non-woven fabric, measurement was performed three times per sample level by the compensator method using a polarizing microscope (BH-2 manufactured by OLYMPUS), and the average value was obtained.

C. Thermal characteristics Differential scanning calorimetry (DSCQ1000 manufactured by TA Instruments) is used to measure differential scanning calorimetry under nitrogen and at a heating rate of 16 ° C./min. Was ΔHm (J / g).

D. Single yarn strength A web before calendar processing is collected, a single yarn is pulled out from this by about 50 mm, and according to the method described in JIS L1013: 2010, the sample length is 20 mm and the tensile speed is 20 mm / min. Tencilon UCT-100 manufactured by Orientec Co., Ltd. was used to measure 10 times per level, and the average value was set to strong (cN). In addition, A. The fiber cross-section was obtained by assuming that the fiber diameter obtained in (1) was a round cross section, and the strength was divided by the fiber cross-section to obtain the single yarn strength (MPa).

E. Sheet defects A 10 cm square area at the center of the spunbonded non-woven fabric in the width (CD) direction is visually observed with a loupe, and the fiber diameter is three times or more larger than the average fiber diameter due to thread breakage. Those with rounded pieces of fibers that appeared to be three times or more thicker than the average fiber diameter were treated as defects, and the number was counted. This observation was repeated 5 times in the longitudinal direction (MD) of the non-woven fabric, and the total number was taken as the number of sheet defects.

F. Sheet flexibility A sensory evaluation of the sheet tactile sensation was performed, and a score was given by absolute evaluation, with 5 points being excellent in flexibility and 1 point being inferior. This was done by 10 people and the average score was defined as flexibility (points).

G. Sheet workability The sheet was run at 20 m / min for 5 minutes using a rubber nip roller. The state of the roll deposits and the sheet at this time was observed, and points were given according to the following criteria to determine workability (points).

5 points: No fiber deposits on the roll, no fluffing or tearing of the sheet.

4 points: There are fiber deposits on the roll, but no fluff or tear of the sheet is seen.

3 points: There are fiber deposits on the roll and there is fluff on the sheet, but no tearing is seen.

2 points: There are fiber deposits on the roll, there is fluff on the sheet, and there is tearing.

1 point: The sheet wraps around the roll due to the tearing of the sheet.

Example 1
Table 1 shows the polyethylene (PE) species used in the study. Table 2 shows the types of saturated fatty acid-based additives. The saturated fatty acid-based additives listed in Table 2 are added to the PE resin having the values of PE type and MI shown in Table 1, melt-extruded with a uniaxial extruder, and spun cap while measuring with a gear pump. The resin was supplied to. The spinning temperature (base temperature) is 230 ° C., and the single hole discharge rate is 0.6 g / min from a mouthpiece having 600 mouthpiece holes with a hole diameter D of 0.30 mm and a land length L of 0.70 mm in the CD direction. The polymer was discharged under the conditions. The introduction hole located directly above the mouthpiece hole was a straight hole, and the connection portion between the introduction hole and the mouthpiece hole was tapered. The discharged polymer was passed through a heat insulating region of 50 mm, and then cooled and solidified from the outside of the yarn by an air flow at 25 ° C. and 40 m / min. After that, it was towed by an accelerated air flow with an ejector installed at a position 550 mm from the base. The threads that passed through the ejector were collected on a net conveyor and transported at a speed of 20 m / min. Then, calendering was performed to obtain a polyethylene spunbonded non-woven fabric of ^{18 g / m 2.}

Table 3 shows the spinning speed calculated from the single yarn fineness and the single hole discharge amount. The spinning speed was 4.0 km / min, but during the test for about 10 minutes, no noticeable yarn breakage was observed and the spinnability was good.

The obtained sheet characteristics are shown in Table 3. As can be seen from Table 3, there are few sheet defects, and since the single yarn fineness is as thin as 2.0 dtex or less, it is excellent in flexibility and workability.

Examples 2, 3 and Comparative Example 1
As shown in Table 3, the test was carried out under the same conditions as in Example 1 except that the PE type was changed and the traction speed at the ejector was changed to change the spinning speed to obtain a polyethylene spunbonded non-woven fabric.

Table 3 shows the spinning speed calculated from the single yarn fineness and the single hole discharge amount. In Example 2, the spinning speed was 5.0 km / min, but during the 10-minute test, no noticeable yarn breakage was observed and the spinnability was good. Further, Comparative Example 1 was inferior in spinnability, and the calculated spinning speed was 2 km / min.

The obtained sheet characteristics are shown in Table 3. In Comparative Example 1, since the single yarn fineness is 4.0 dtex, the flexibility is inferior, and since Δn is small, the single yarn strength is low and the workability is also inferior. It can be seen that in Examples 2 and 3, since the single yarn fineness is small, the flexibility is excellent, the sheet defects are few, and the workability is also excellent.

Examples 4 to 7, Comparative Example 2
Tested under the same conditions as in Example 1 except that the PE species were changed, the saturated fatty acid additive species and amount were changed, the traction speed at the ejector was changed, and the spinning speed was changed as shown in Table 3. Was carried out to obtain a polyethylene spunbonded non-woven fabric.

Table 3 shows the spinning speed calculated from the single yarn fineness and the single hole discharge amount. Table 3 shows the obtained sheet characteristics. In Comparative Example 2, the saturated fatty acid-based additive species had a small number of carbon atoms and therefore bleeded on the surface, resulting in a sticky texture, sheet defects, and inferior flexibility. It can be seen that Examples 4 to 7 have excellent flexibility, few sheet defects, and excellent workability.

Claims (3)

It is composed of polyethylene having a density of 0.915 to 0.965 g / cm ³ , a single yarn fineness of 2.0 dtex or less, and a saturated fatty acid-based additive is added to polyethylene so as to satisfy the following conditions A to C. Polyethylene spunbonded non-woven fabric characterized by being made of
A. The saturated fatty acid-based additive is a saturated fatty acid or a saturated fatty acid metal salt having 12 to 30 carbon atoms, and comprises two or more kinds of saturated fatty acids or saturated fatty acid metal salts having different carbon atoms.
B. The difference between the maximum and minimum carbon numbers of the saturated fatty acid or the saturated fatty acid metal salt contained in the saturated fatty acid-based additive is 4 or more.
C. The total amount of the saturated fatty acid-based additive added to polyethylene is 0.1 to 10.0 wt%. The polyethylene spunbonded non-woven fabric according to claim 1, wherein the polyethylene contains 50 wt% or more of plant-based polyethylene. The polyethylene spunbonded non-woven fabric according to claim 1 or 2, which contains calcium stearate as a component of a saturated fatty acid-based additive.