JP2008208483A - Surface sheet of sanitary article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material that is useful for a surface sheet of sanitary article, has performance of gradually decomposing in a natural environment and finally disappearing after use, no air pollution in the case of incineration after use and a slight influence to the environment, a soft feeling and an excellent touch. <P>SOLUTION: The surface sheet of sanitary article is constituted of a fabric comprising a core-sheath type conjugate short fiber having a core part composed of a polylactic acid and a sheath part composed of a polymer made of a polyalkylene succinate copolymerized with 1-10 mol% of lactic acid. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface sheet of a sanitary product.

  Plastic materials such as polyethylene and polyvinyl chloride are mainly used in sanitary products such as disposable diapers, sanitary products, and urine pads. These sanitary products are discarded after use for disposal, and the waste is collected and then disposed of by incineration or landfill. However, it is difficult to secure landfill for air pollution and landfill treatment by incineration. There are problems such as. Moreover, since a great deal of labor is required for recovery, it cannot be recovered and left in the natural environment such as in the soil, which may cause various problems such as environmental destruction.

  In order to solve such a problem, for example, Patent Document 1 proposes to use a fiber assembly using a biodegradable polymer such as polylactic acid or polyglycolic acid as a sanitary material.

However, polymers such as polylactic acid and polyglycolic acid are polymers having a high Young's modulus and have a hard texture when fiberized, and are not suitable as materials for sanitary products used in direct contact with the skin because they do not feel well.
Japanese Patent Laid-Open No. 06-264344

  An object of the present invention is to be used for a surface sheet of a sanitary product, and after use, has a performance of gradually decomposing in a natural environment and finally disappearing, and air pollution occurs when incinerated after use. The object is to provide a material that has little impact on the environment, has a practical strength, has a soft texture, and has a good touch.

  As a result of investigations to achieve the above-mentioned problems, the present inventor maintains practical strength by forming short fibers of a specific composite form using polylactic acid having high crystallinity and a specific copolymer. It was a fiber, and when it was made into a fabric using this fiber, it discovered that a soft touch was exhibited and reached | attained this invention.

  That is, the present invention is constituted by a fabric including a core-sheath type composite short fiber in which a core part is composed of polylactic acid and a sheath part is composed of a polymer obtained by copolymerizing lactic acid with 1-10 mol% of polyalkylene succinate. The gist of the surface sheet of a sanitary product is characterized in that.

  Hereinafter, the present invention will be described in more detail.

  The core-sheath type composite short fiber used in the present invention is a core-sheath type composite form in which the core part is composed of polylactic acid, and the sheath part is composed of a polymer obtained by copolymerizing 1 to 10 mol% of lactic acid with polyalkylene succinate. It is the short fiber which has.

  The polylactic acid constituting the core is poly L-lactic acid, poly D-lactic acid, poly DL-lactic acid which is a copolymer of L-lactic acid and D-lactic acid, or a mixture of poly L-lactic acid and poly D-lactic acid. Any of (stereo complex) may be used. When poly DL-lactic acid which is a copolymer of L-lactic acid and D-lactic acid is used, the copolymerization ratio of D-lactic acid and L-lactic acid (D-lactic acid / L-lactic acid) is 100/0 to 95/5. 5/95 to 0/100 is preferable. Copolymers with a copolymerization ratio outside the above range have a low melting point and a high amorphous property, making it difficult to obtain high-strength fibers. In the present invention, the short fiber can maintain a practical strength by arranging polylactic acid having crystallinity in the core of the short fiber.

  The viscosity of polylactic acid is 10 to 80 g / 10 min in melt flow rate (hereinafter abbreviated as MFR) measured at a temperature of 210 ° C. and a load of 20.2 N (2160 gf) according to the method described in ASTM D 1238. It is preferable that it is 20-40 g / 10min. When the MFR is less than 10 g / 10 minutes, not only melt extrusion becomes difficult, but the mechanical strength of the fiber tends to decrease. On the other hand, if the MFR exceeds 80 g / 10 min, it is difficult to obtain a good fiber by melt extrusion.

  For the purpose of improving the durability of the core-sheath-type composite short fiber used in the present invention, a terminal blocking agent such as an aliphatic alcohol, a carbodiimide compound, an oxazoline compound, an oxazine compound, or an epoxy compound may be added to polylactic acid. . In addition, polylactic acid includes cyclic lactones such as ε-caprolactone, α-hydroxybutyric acid, α-hydroxyisobutyric acid, α-hydroxyacids such as α-hydroxyvaleric acid, ethylene, and the like as long as the object of the present invention is not impaired. Glycols such as glycol and 1,4-butanediol, and dicarboxylic acids such as succinic acid and sebacic acid may be contained.

  In the core-sheath type composite short fiber used in the present invention, the sheath part is composed of a polymer obtained by copolymerizing 1 to 10 mol% of lactic acid with polyalkylene succinate. In addition, when making the polymer of a sheath part function as a thermoadhesive component, it is preferable to set the melting | fusing point of the polymer of a sheath part 30 degreeC or more lower than melting | fusing point of the polylactic acid of a core part.

  The polyalkylene succinate in the sheath polymer is a copolymer of succinic acid and an alkylene diol such as ethylene glycol or butane diol, such as ethylene succinate, butylene succinate or propylene succinate. Further, in the range not impairing the object of the present invention, the above repeating units include cyclic lactones such as ε-caprolactone, α-hydroxy acids such as α-hydroxybutyric acid, α-hydroxyisobutyric acid, α-hydroxyvaleric acid, Although glycols such as ethylene glycol and 1,4-butanediol and dicarboxylic acids such as succinic acid, adipic acid, sebacic acid and malic acid may be copolymerized, the copolymerization amount thereof is in the range of 30 mol% or less. It is preferable that

  The polymer of the sheath part is obtained by copolymerizing 1 to 10 mol% of lactic acid with polyalkylene succinate. When the polymer of the sheath is formed by copolymerization of lactic acid, the compatibility between the polymer constituting the sheath and the polylactic acid constituting the core is dramatically improved. When the compatibility of the core and sheath polymers is low, it is difficult to increase the strength of the fiber itself. Further, when the sheath polymer functions as a thermal adhesive component, that is, when the core-sheath composite short fiber used in the present invention is used as the thermal adhesive fiber, the melted sheath polymer is an interface with the core. Behaves so as to decrease, and the phenomenon of flowing and agglomerating into islands occurs, so that the adhesive strength is lowered. The core-sheath-type composite short fiber used in the present invention is obtained by containing lactic acid in the polymer of the sheath part, that is, by containing a common component with the polylactic acid constituting the core part. The compatibility with polylactic acid is improved, the above-mentioned phenomenon is hardly caused, and a high-strength fiber is obtained, and the strength of the fabric itself using this fiber can be improved.

  When the amount of lactic acid to be copolymerized in the sheath is less than 1 mol%, the compatibility between the polymer in the sheath and the polylactic acid in the core is not sufficiently improved, and the above effects are hardly obtained. On the other hand, if the copolymerized lactic acid exceeds 10 mol%, the compatibility with polylactic acid is better, but the inherent flexibility of polyalkylene succinate is impaired, and the resulting fiber is hard and lacks flexibility. Then, since the fabric containing this fiber is inferior to the touch, the object of the present invention is not achieved. In the present invention, it is preferable to use a polymer in which lactic acid is copolymerized with polyalkylene succinate in an amount of 1 to 5 mol% for the sheath.

  The lactic acid copolymerized with the polyalkylene succinate may be L-lactic acid or D-lactic acid. Moreover, although lactic acid is based on what is copolymerized by a monomer unit, a part of oligomer unit (about 2-10 pieces) may be included in the range which does not impair the effect of this invention. .

  The melting point of the polymer in the sheath is preferably 90 ° C. or higher. When the melting point is less than 90 ° C., adhesion tends to occur at the time of spinning or stretching, and the operability tends to be inferior. The upper limit of the polymer in the sheath is not particularly limited, but when this polymer functions as a thermal adhesive component, it is preferably 140 ° C. or lower. When the melting point exceeds 140 ° C, the difference in melting point between the polylactic acid constituting the core portion and the polylactic acid with good crystallinity and high versatility (melting point of about 170 ° C) is reduced. If this is the case, the set temperature range will be reduced, and it will be difficult to raise the set temperature sufficiently so that the core will not be affected by heat. This is because it tends to be.

  The viscosity of the polymer in the sheath is preferably 10 to 80 g / 10 min, MFR measured at a temperature of 190 ° C. and a load of 20.2 N (2160 gf), in accordance with the method described in ASTM D 1238. More preferably, it is / 10 minutes. When the MFR is less than 10 g / 10 minutes, not only melt extrusion becomes difficult, but the mechanical strength of the fiber tends to decrease. On the other hand, even if the MFR exceeds 80 g / 10 min, it is difficult to obtain a good fiber by melt extrusion.

  The fineness of the core-sheath type composite short fiber used in the present invention is preferably about 1 to 10 dtex, more preferably 1 to 5 dtex in consideration of productivity, operational stability, flexibility, and the like.

  In the core-sheath-type composite short fiber used in the present invention, the core part, the sheath part, and the core-sheath ratio are not particularly limited, but the core / sheath volume ratio is preferably 30/70 to 70/30.

  In addition, the shape of the core-sheath type composite short fiber used in the present invention is not limited to a circular cross section, and may be any shape as long as the polymer of the core part covers the polylactic acid of the core part. It may be a square shape, a multileaf shape, a gourd shape, an alphabet shape, or other various non-circular shapes (an irregular shape).

  Furthermore, the core-sheath type composite short fiber used in the present invention includes various pigments, dyes, water repellents, water absorbents, flame retardants, stabilizers, antioxidants, ultraviolet absorbers, metal particles, crystal nucleating agents, lubricants, plastics. Agents, antibacterial agents, fragrances and other additives may be mixed and added according to the purpose.

  The core-sheath type composite short fiber used in the present invention is obtained by the following method. That is, a polyester in which 1 to 10 mol% of lactic acid is copolymerized with polylactic acid and polyalkylene succinate is melt-spun using an ordinary composite spinning device (concentric core-sheath type composite spinning device), and cooling and oiling agent are used. After the application, it is wound up without stretching. The undrawn yarn is focused on a tow of several hundred thousand to two million dtex, drawn at a draw ratio of 2 to 5 times, a draw temperature of 40 to 80 ° C, and subjected to heat treatment at 80 to 130 ° C. Subsequently, after applying mechanical crimping with a push-in crimper, applying a finishing oil, drying with a dryer, and cutting to the desired length (fiber length of about 5 to 150 mm) with a cutter such as an EC cutter. Use short fibers.

  The obtained short fibers are made into spun yarn and then made into a fabric by knitting or weaving, or made into a non-woven fabric (fabric) by creating a web using short fibers and then integrating them by thermal bonding or entanglement.

  The surface sheet of the sanitary article of the present invention is a fabric containing the above-described core-sheath type composite fiber. The fabric constituting the surface sheet can exhibit excellent flexibility by using the core-sheath composite short fiber as a constituent fiber. From the viewpoint of flexibility, the fabric preferably contains 30% by mass or more of the core-sheath type composite short fiber, and more preferably, all the fibers constituting the fabric are the core-sheath type composite short fiber. Other fibers may be mixed. Examples of the fabric obtained by mixing other fibers include a fabric using a yarn obtained by blending, cross-twisting, fine spinning and cross-twisting the core-sheath type composite short fiber and another fiber, and the core-sheath type composite short fiber. Examples thereof include a fabric in which a spun yarn containing fibers and other yarns are woven and knitted, and a mixed nonwoven fabric in which the core-sheath composite short fiber and other fibers are mixed. As other fibers to be mixed, for the purposes of the present invention, fibers that decompose in nature are used, biodegradable synthetic fibers such as polylactic acid fibers, rayon fibers such as viscose, cupra, polynosic, lyocell, etc. And solvent-spun cellulose fibers, and natural fibers such as silk, cotton and hemp.

  Examples of the form of the fabric that is the surface sheet of the sanitary product include woven fabric, knitted fabric, and non-woven fabric, but the polymer of the sheath portion of the core-sheath-type composite short fiber is heated or melted or softened as a thermal adhesive component. It is good also as a fabric which is made to function, and the constituent fibers are bonded to each other to have good shape retention and excellent strength. In this case, since the polymer of the sheath portion is excellent in softness, the fused portion in the polymer of the sheath portion that is melted or softened does not become too hard, and the fabric has a soft feel without a feeling of roughness. In order to further improve the flexibility and further improve the touch, the nonwoven fabric is preferably a nonwoven fabric in which the constituent fibers are integrated by hydroentanglement to maintain the nonwoven fabric form. In this case, the polymer of the sheath portion of the core-sheath-type composite short fiber exhibits a form of a composite short fiber without functioning as a thermal adhesive component (not fused by melting or softening). There should be. In the present invention, if importance is attached to the softness and the touch feeling, all the fibers constituting the fabric are made into the core-sheath type composite short fibers, and the constituent fibers are integrated by hydroentanglement so that the nonwoven fabric is integrated. It is a preferred embodiment that a surface sheet of a sanitary product is formed by a nonwoven fabric that retains its form.

  The sanitary products in the present invention are sanitary products such as sanitary napkins, panty shields, adult diapers, baby diapers, incontinence pads, nursing sheets, disposable underwear and the like. In these, they are used as a surface sheet that is a material that directly touches the skin or a material that covers the outer surface.

  The present invention relates to a sanitary article comprising a fabric including a core-sheath-type composite short fiber having a core part made of polylactic acid and a sheath part made of a polymer obtained by copolymerizing a specific amount of lactic acid with polyalkylene succinate. Since it is a surface sheet, it is a material that has no air pollution and little environmental impact when incinerated after use. In addition, it is possible to provide a sanitary article surface sheet having a soft texture and a good touch while having practical strength.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples. In addition, the measuring methods, such as a characteristic value in an Example, are as follows. Moreover, the measuring method of MFR is as having mentioned above.
(1) Melting point (° C)
Using a differential scanning calorimeter DSC-2 manufactured by Perkin Elma Co., Ltd., measurement was performed under the condition of a heating rate of 20 ° C./min, and the temperature giving an extreme value in the obtained melting endotherm curve was defined as the melting point.
(2) Single yarn fineness (dtex)
It measured by the method of JIS L-1015 7-5-1A.
(3) Tensile strength of nonwoven fabric (cN / 25mm width)
The nonwoven fabric was cut into strips having a width of 25 mm and a length of 150 mm to prepare a sample. This sample was stretched and cut using a UTM-4 type Tensilon manufactured by Orientec Corp. under the conditions of a grip interval of 100 mm and a tensile speed of 100 mm / min, and the maximum strength was read. In the present invention, a tensile strength of 1000 cN or more is assumed to have a practical strength.
(4) Bending softness of non-woven fabric (cm)
Based on the 45 degree cantilever method described in JIS L-1096, the moving distance (cm) until the tip of the nonwoven fabric contacted the 45 degree slope was measured. In the present invention, flexibility was good when the bending resistance (movement distance) was less than 10 cm.
(5) Texture of non-woven fabric The softness of the texture was sensorially evaluated by a hand test with 10 panelists. When 9 or more out of 10 people evaluated that the texture was soft, ◯, when 5 to 8 people evaluated that the texture was soft, Δ, and when it was 4 or less, ×.

Example 1
Polybutylene having polylactic acid (MFR 21 g / 10 min, copolymerization ratio of D-lactic acid / L lactic acid = 1.3 / 98.7, melting point 170 ° C.) and 3.0 mol% L-lactic acid copolymerized Succinate (MFR 32 g / 10 min, melting point 109 ° C.) is used as the sheath, 560 holes, circular cross-section core-sheath composite spinneret is used, and the core-sheath ratio is core: sheath = 50: 50 as the melt volume ratio. And melt-spun at a spinning temperature of 230 ° C. and a spinning speed of 800 m / min to obtain an undrawn yarn of polylactic acid-based composite fiber. Next, the obtained undrawn yarn was drawn at a drawing temperature of 60 ° C. and a draw ratio of 3.50 times, and then crimped by a push-type crimper, and after applying a finishing oil agent, at 70 ° C. It was dried and cut to a fiber length of 51 mm to obtain a core-sheath type composite short fiber having a fineness of 2.2 dtex.

Using a polylactic acid regular fiber (melting point 170 ° C.) having a fineness of 1.7 dtex and a fiber length of 51 mm as a main fiber, the obtained core-sheath type composite fiber 30% by mass and 70% by mass of the main fiber are put on a card machine, A web having a basis weight of 50 g / m ² was prepared. The web was passed through a continuous heat treatment machine and heat treated at 130 ° C. for 1 minute to produce a nonwoven fabric.

  Table 1 shows the results of evaluating the tensile strength, stiffness and texture of this nonwoven fabric.

Examples 2-3 and Comparative Example 1
Table 1 shows the results obtained in the same manner as in Example 1 except that the amount of lactic acid copolymerized with polybutylene succinate as shown in Table 1 was used as the sheath polymer of the core-sheath composite fiber. It is shown in 1.

Example 4
A polylactic acid-based composite fiber and a polylactic acid-based composite fiber were used in the same manner as in Example 1 except that polyethylene succinate (MFR 29 g / 10 min, melting point 101 ° C.) obtained by copolymerizing 3.0 mol% of L-lactic acid was used as the sheath polymer. A nonwoven fabric was obtained. The results are shown in Table 1.

Comparative Example 2
The polymer in the same manner as in Example 1 except that a copolymer ratio of L-lactic acid / D-lactic acid of 8.8 / 91.2 (MFR = 24/10 minutes, melting point 130 ° C.) was used as the sheath polymer. A lactic acid-based composite fiber and a nonwoven fabric were obtained. The results are shown in Table 1.

Example 5
A core-sheath type composite short fiber having a fineness of 2.2 dtex obtained in Example 1 was applied to a card machine, a web having a basis weight of 50 g / m ² was prepared with a random web, and this web was supported on a 100-mesh wire mesh. from the web side, subjected to high-pressure water jet pressure 100 kg / cm ^2, then turned over the web on the wire mesh, was further subjected to high-pressure water jet pressure 100 kg / cm ^2. Thereafter, the web was squeezed with a mangle roll, dried through a drier to remove water in the web, and a nonwoven fabric having a basis weight of 50 g / m ² was obtained. The results are shown in Table 1.

As is apparent from Table 1, Examples 1 to 5 satisfying the requirements of the present invention were sufficiently strong in nonwoven fabric and very soft in texture. Moreover, Example 5 which employ | adopted only the core-sheath-type composite short fiber as a constituent fiber, and employ | adopted the hydroentanglement method as a nonwoven fabric means was very excellent in a softness | flexibility (texture) of the softness and the touch. .

  On the other hand, in Comparative Example 1, the amount of lactic acid in the sheath polymer was small and the compatibility with the polylactic acid in the core was not sufficient, resulting in poor adhesion and poor nonwoven fabric strength. .

Further, in Comparative Example 2 using polylactic acid having a low melting point for the sheath, the strength of the nonwoven fabric was high, but the nonwoven fabric had high rigidity and lacked softness.

Claims (2)

The core portion is composed of polylactic acid, and the sheath portion is composed of a fabric including a core-sheath type composite short fiber composed of a polymer obtained by copolymerizing 1 to 10 mol% of lactic acid with polyalkylene succinate. Sanitary article surface sheet. The sanitary article surface sheet, wherein the fabric according to claim 1 is a non-woven fabric, and the constituent fibers of the non-woven fabric are integrated by hydroentanglement to maintain the non-woven fabric form.