JP3109629B2 - Polyolefin core-sheath type composite fiber and nonwoven fabric using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001] The present invention relates to a heat-fusible conjugate fiber and a nonwoven fabric using the same. More specifically, the present invention relates to a polyolefin-based heat-fusible conjugate fiber which has a low heat treatment temperature for forming a nonwoven fabric and a heat seal temperature of the nonwoven fabric and which provides a soft nonwoven fabric, and a nonwoven fabric using this fiber.

[0002]

2. Description of the Related Art Nonwoven fabrics using polyolefin-based heat-fusible conjugate fibers are preferred for their soft feel and high strength of nonwoven fabrics, and are used for sanitary purposes such as disposable diapers and cover materials for sanitary products. I have. When a non-woven fabric is formed using a heat-fusible conjugate fiber, the heat treatment is performed by air suction using a suction band dryer or a suction drum dryer.
The method can be roughly classified into a through method and a thermocompression bonding method using a heating roll or the like. In the case of low-weight nonwoven fabrics for use as sanitary materials, it is considered that the thermocompression bonding method is more advantageous than the air-through method in that the production speed during the production of the nonwoven fabric is high and the texture of the nonwoven fabric is soft. In order to increase the production speed by the thermocompression bonding method and obtain a high strength of the non-woven fabric, a relatively high temperature embossing roll or the like is used.

[0003] Polyolefin-based (sheath / core) composite fibers used in the thermocompression bonding method include (HDPE / PP) composite fibers and (HDPE / PET) composite fibers. Also, a fiber in which a core component made of polypropylene is eccentrically composited with a sheath component made of a propylene copolymer (Japanese Patent Publication No.
-26203, JP-A-2-91217, JP-A-2-19
1720) and non-composite fibers in which paraffin and low molecular weight polyethylene are blended with low-density polyethylene (JP-A-63-163).
165511) are also known. In the case of nonwoven fabrics for protection materials, webs with different hydrophilicity and bulkiness should be laminated and thermocompressed with emboss rolls etc. to form a two-layer structure in order to improve various properties such as liquid permeability and bulkiness. There is. In the case of disposable diapers, the upper and lower surfaces of a liquid absorbing layer mainly composed of pulp or the like are covered with nonwoven fabrics having different properties, folded in two, and heat-sealed at the end (waist). It has come to be used.

[0004]

However, the (HDPE / PP) -based composite fibers and (HDPE / PET)
The nonwoven fabric made of the composite conjugate fiber has a drawback that the heat seal strength is low with respect to other polyolefin-based nonwoven fabrics, and the two-layer nonwoven fabric is easily peeled off at the heat seal portion. Also, when the processing speed by hot embossing roll or the like is increased for the purpose of increasing the productivity of the nonwoven fabric, the obtained nonwoven fabric has a low strength. If the processing conditions are high temperature and high pressure, the texture becomes hard even though the strength of the nonwoven fabric increases. There was a disadvantage. The eccentric conjugate fiber has a drawback that the nonwoven fabric is easily wrinkled and has low strength because the web shrinkage during the heat treatment is large. The low-density polyethylene non-composite fiber can be heat-treated at a relatively low temperature and at a high speed, but has a drawback that the texture of the obtained nonwoven fabric is poor because the fiber is melted and deformed into a film at the heat-sealed portion. As described above, in the conventional conjugate fiber, when trying to obtain a nonwoven fabric by low-temperature and high-speed heat treatment, it was not possible to satisfy all of high strength, hand, and heat sealability.

[0005]

SUMMARY OF THE INVENTION The present invention provides a nonwoven fabric having a high strength and a soft texture even by heat treatment at a relatively low temperature and high speed, and a nonwoven fabric having a high heat seal strength with other nonwoven fabrics. It is made for the purpose of the above and has the following configuration. (1): 80-99% by weight of propylene and one or more other
Binary or 3 consisting of 20-1% by weight of seed alpha olefin
99-85% by weight of the starting copolymer and a melting point or softening point of 12
A heat-fusible conjugate fiber having a mixture of 1 to 15% by weight of a saturated hydrocarbon wax at 5 to 60 ° C. as a sheath component and a crystalline polypropylene as a core component. (2) Eccentricity of the core component The composite fiber according to the above (1), which has a degree of 0.1 or less and has a two-dimensional crimp, and (3): the composite fiber according to the above (1) or (2) is used. It is a heat fusion nonwoven fabric.

The copolymer used for the sheath component in the present invention is composed of 80 to 99% by weight of propylene and ethylene or butene.
One or two other α-olefins, such as 1
1% by weight of a binary or terpolymer, MF
R (230 ° C., 2.16 kg) having a melting point of about 5 to 200 and a melting point of about 120 ° C. to 158 ° C. are used. When the concentration of α-olefin other than propylene in the copolymer is 1% by weight or more, the stereoregularity of the copolymer is moderately disturbed, so that the texture of the nonwoven fabric is softened (the softness is small), which will be described later. , The fusion of the fibers by heat treatment at a relatively low temperature becomes easy, and even if the processing speed to a nonwoven fabric or the heat seal speed is increased, a large nonwoven fabric strength or a large heat seal is obtained. Powerful. However, when the other α-olefin concentration exceeds 20% by weight, it becomes a rubber-like non-woven fabric having a sticky feeling and a bad texture, so that it cannot be used. When the melting point of the copolymer is out of the above range,
This is because any of heat seal speed, heat seal strength, non-woven fabric processing speed, non-woven fabric strength, texture (bending softness) of the non-woven fabric, and the like are deteriorated.

The saturated hydrocarbon wax added to the sheath component preferably has a melting point or softening point of about 60 to 125 ° C., and commercially available petroleum wax or low molecular weight polyethylene can be used. Here, petroleum wax is one that is separated and refined from high-boiling components by rectification and solvent extraction in the process of petroleum refining, and includes paraffin wax, microcrystalline wax,
Petratum is preferred, and among these, microcrystalline wax is preferred in terms of compatibility with the copolymer, reduction of bonding temperature and balance of bonding strength, and those having a molecular weight of about 8,000 or less can be used. The resin may be subjected to a treatment such as carboxylation or sulfonation. If the amount of the saturated hydrocarbon wax added to the sheath component is less than 1% by weight, the effect of lowering the fusion temperature of the fibers is insufficient, and the processing speed into a nonwoven fabric, the heat sealing speed, and the like cannot be increased. Further, the strength of heat sealing with another nonwoven fabric is not improved. If the amount of the saturated hydrocarbon wax added to the sheath component exceeds 15% by weight, the spinnability of the conjugate fiber deteriorates, and the yarn is liable to break during spinning, resulting in large denier spots. Not preferred. By heating during the processing of the nonwoven fabric, the low molecular weight polyethylene of the conjugate fiber becomes a molten film, the air permeability and bulkiness of the nonwoven fabric are deteriorated, and the texture becomes hard and the rubber-like non-woven fabric with a sticky feeling is formed. For this reason, it is not suitable for nonwoven fabrics for sanitary materials.

The crystalline polypropylene used as the core component of the composite fiber in the present invention is a crystalline polymer containing propylene as a main component, and may be a copolymer of propylene with a small amount of other α-olefin. Well, MFR (230 ° C, 2.
16 kg) for a fiber grade having a melting point of about 2-150 and a melting point of about 158 ° C. or more is preferred. Such polymers are obtained by known polymerization methods of propylene (and small amounts of other α-olefins) using Ziegler-Natta catalysts.

[0009] The composite fiber of the present invention is obtained by spinning the above-mentioned sheath component and core component into a sheath-core type by a known composite spinning method, and drawing and drawing.
It can be obtained by crimping. The composite ratio is in the range of sheath / core = 30/70 to 70/30 wt%, and the fineness is about 0.
4 to 10 d / f, and the number of crimps is about 3 to 60 peaks / 25 mm, which are suitable because they have good card passing properties and can obtain a favorable texture and strength of the nonwoven fabric. A composite fiber having a mixture of the above-described copolymer and wax as a sheath component and a crystalline polypropylene as a core component has a large difference in shrinkage between the sheath and core components, so that three-dimensional crimping occurs during heat treatment. It has the potential to easily generate a large shrinkage and to wrinkle easily on the web. When the eccentricity of the core component (indicator of the deviation between the center of the fiber and the center of the core component) increases, the crimp becomes spiral and the shrinkage of the web further increases. Such a latent property (crimpability) can be eliminated by spinning the core component so that the eccentricity is about 0.1 or less.

The nonwoven fabric of the present invention is formed into a web by using the above-mentioned conjugate fiber of the present invention by a card method or the like, and then subjected to heat treatment by a thermocompression bonding method or an air-through method to a temperature higher than the fusion temperature of the sheath component of the conjugate fiber. Can be produced by heat-sealing the intersections of the fibers. In particular, a non-woven fabric formed by a thermocompression bonding method using an embossing roll or the like is preferably used for applications such as a non-woven fabric for safety materials because of its high strength. The nonwoven fabric of the present invention can also be produced by mixing other types of fibers with the above-mentioned conjugate fibers. Other types of fibers that can be used in combination may be fibers that do not deteriorate or melt during heat treatment, and examples thereof include polypropylene fibers, polyester fibers, polyamide fibers, rayon, and cotton. When used in combination with other types of fibers, the amount of the composite fiber of the present invention must be about 20% by weight or more in order to maintain sufficient nonwoven fabric strength and heat seal strength. .

[0011]

The present invention will be described more specifically with reference to examples and comparative examples. The evaluation methods for the physical properties and the like used in each example are shown below. Fiber elongation: Measured according to JIS-L-1015. Fiber eccentricity: The cross section of the fiber was photographed under a microscope and calculated by the following equation. Eccentricity (h) = r / dr r: radius of the entire fiber d: distance from the center point of the entire fiber to the center point of the core component Web shrinkage: 100 g / m ² carded web 2
The sheet was cut into a 5 cm square, and the area shrinkage (%) after the heat treatment for 5 minutes in a dryer at 145 ° C. was measured.

Nonwoven fabric strength: A carded web is heat-treated using a thermocompression bonding device composed of embossing rolls having a projected area of 24% heated to a predetermined temperature and flat metal rolls, and has a basis weight of 25 g / m2. The nonwoven fabric of No. ² was used. A sample piece having a width of 15 cm is taken with the machine direction of the nonwoven fabric as the length direction (MD) and the direction perpendicular to the machine direction of the nonwoven fabric (CD) as the width direction, and a 5 cm wide sample is cut. The tensile strength in the length direction was measured at a pulling speed of 10 cm / min (g / 5 cm). Bending resistance of nonwoven fabric: According to JIS L 1096 (45 ° cantilever method). Heat seal strength of nonwoven fabric: width (CD) 2.5c
m, the end of two specimens of 10 cm length (MD) is 1c in length
m and heat-seal using a heat-sealing machine heated to a predetermined temperature (heat-seal area 2.5 cm).
² ), with a tensile tester, gripping distance 10cm, pulling speed 1
Heat seal strength was measured at 0 cm / min (g /
2.5 cm).

Examples 1 to 4 and Comparative Examples 1 to 4 In each of these examples, the composition of a mixture of a binary or tertiary copolymer containing propylene as a main component and a saturated hydrocarbon wax used as a sheath component, The polypropylene used as a component is shown in Table 1. The composite ratio (weight ratio) of the sheath component and the core component is 50/50, and the spinning temperature (sheath / core = 270/270).
° C) and stretched 2.4 times to 14 peaks / 25m
m mechanical crimp, and a single yarn fineness of 2.2 dtex / f,
A core-sheath type composite fiber staple having a fiber length of 50 mm was obtained. These composite fibers are passed through a carding machine and weighed about 25 g / m ^2.
And a web having a convex area of 24% heated to a predetermined temperature and a flat roll made of embossing roll, and a linear pressure of 25 kg / cm and a speed of 5 m.
/ Min thermocompression bonding conditions, and a basis weight of about 25 g / m ²
Was obtained. Table 1 also shows the physical properties of the respective raw materials used, and the physical properties of the obtained fibers and nonwoven fabric.
Table 1 shows that the composite fiber of the present invention has a C
It can be seen that the strength of the nonwoven fabric in the direction D is high, and that the nonwoven fabric is soft (low in softness. Even if low molecular weight polyethylene is mixed, the softness is not so high). On the other hand, in the case of a conjugate fiber having a saturated hydrocarbon wax content less than the specification of the present invention, the nonwoven fabric strength in the CD direction is low when the thermocompression bonding temperature is low, and when the thermocompression bonding temperature exceeds the specification of the present invention, the nonwoven fabric is hard (hard and soft). The degree is large).

[0014]

[Table 1]

Heat seal test 1 Among the above nonwoven fabrics, a nonwoven fabric obtained by thermocompression bonding at a temperature of 132 ° C. is used, at a temperature of 120 to 130 ° C. and a pressure of 3 kg / cm.
^{2. The} same type of nonwoven fabric was heat-sealed with each other for 3 seconds. Table 2 shows the heat seal strength. From this table, it can be seen that the nonwoven fabric of the present invention has a high heat seal strength even at a low temperature (120 ° C.).

[0016]

[Table 2]

Heat seal test 2 Composite fiber of high density polyethylene sheath component and polypropylene core component (single yarn denier 1.5 d / f, fiber length 51 m)
m, 16 crimps / 25 mm of mechanical crimp) is formed into a web by the carding method, and is heat-treated with a dryer at a temperature of 145 ° C. to obtain a nonwoven fabric having a basis weight of 23 g / m ² (hereinafter, may be referred to as an ESC nonwoven fabric). I got A heat seal test was performed on the ESC nonwoven fabric and the nonwoven fabric obtained by thermocompression bonding at 132 ° C. in the above Examples and Comparative Examples. Heat seal conditions are:
The temperature was 120 to 140 ° C., the pressure was 3 kg / cm ² , and the time was 3 seconds. The heat seal strength is shown in Table 2. From this table, it can be seen that the nonwoven fabric of the present invention has a high heat seal strength at a low temperature even with other types of polyolefin-based nonwoven fabric.

Heat seal test 3 The nonwoven fabric (132) obtained in Examples 2 and 4 and Comparative Examples 1 and 4
C), and the nonwoven fabric obtained in Comparative Examples 1 and 2 and Examples 1 and 2 (thermo-compression bonded at 132 ° C.)
And an ESC nonwoven fabric were subjected to a heat seal test. The heat seal conditions were as follows: temperature 128 ° C., pressure 8.5 kg / cm ² ,
Performed for a time of 0.5-2.5 seconds. The heat seal strength is shown in Table 3. From this table, it can be seen that the nonwoven fabric of the present invention
It can be seen that the heat seal strength is large even if the run time is short.

[0019]

[Table 3]

Examples 5 to 7 and Comparative Examples 5 to 7 A composite fiber produced under the same conditions as in Example 4 except that the spinning was performed while changing the eccentricity, and After heat treatment at 145 ° C. for 5 minutes, the web shrinkage was measured. In addition, these composite fibers were used in Examples 1 to 3.
Thermocompression bonding at a temperature of 132 ° C as in the case of No. 4 and a basis weight of 25 g / m
A hot-pressed nonwoven fabric of No. ² was obtained. 40 g of these nonwoven fabrics and basis weight
/ M ² heat seal test with polypropylene non-woven fabric by spun bond method (temperature 128 ° C, pressure 10kg / c)
m ² , time 4 seconds). For comparison, a heat seal test was also performed on the ESC nonwoven fabric used in the heat seal test 2 and the spunbond polypropylene nonwoven fabric (Comparative Example 7). Table 4 shows the test results. From this table, it can be seen that the composite fiber having an eccentricity of 0.1 or less has a low web shrinkage. Further, it can be seen that the heat seal strength is large.

[0021]

[Table 4]

[0022]

According to the present invention, the nonwoven fabric can be produced by heat treatment at a low temperature and in a short time, and the nonwoven fabric has a high strength, a low softness and a soft feel. Further, the nonwoven fabric using this composite fiber has a heat seal which is shorter than that of the polyolefin nonwoven fabric in a short time, and has a high heat seal strength. Such a nonwoven fabric is used for covering a disposable diaper.
It can be used in materials, disposable clothing, bandages, etc.

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Claims (3)

(57) [Claims] 1. A polyolefin-based sheath-core type heat-fusible conjugate fiber comprising a low-melting-point sheath component and a high-melting-point core component, wherein the sheath component is 80 to 99% by weight of propylene and one or more other components. 99 to 85% by weight of a binary or terpolymer consisting of 20 to 1% by weight of a kind of α-olefin, and 1 to 15% by weight of a saturated hydrocarbon wax having a melting point or a softening point of 125 to 60 ° C. A composite fiber characterized by the above. 2. The eccentricity of a core component is 0.1 or less and 2
The conjugate fiber according to claim 1, wherein a dimensional crimp is provided. 3. A nonwoven fabric containing the composite fiber according to claim 1 or 2 in an amount of 30% by weight or more, and the intersection of the fibers is fixed by fusion of the composite fiber.