JP3132202B2 - Method for producing heat-fusible conjugate fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the production of heat-fusible conjugate fibers .
About the method .

[0002]

^2. Description of the Related Art A low-weight nonwoven fabric having a basis weight of about 10 to 45 g / m ² is used for surface materials such as disposable diapers and sanitary articles. Further, with the diversification of uses of the nonwoven fabric, the performance required for the nonwoven fabric has been advanced, and the nonwoven fabric has been required to maintain high strength of the nonwoven fabric with a minimum weight of the nonwoven fabric, and to be bulky and soft in texture. In order to satisfy such demands, it is necessary that the nonwoven fabric is composed of heat-fusible conjugate fibers of fine size and that the low melting point component that contributes to heat-sealing of the heat-fusible conjugate fibers is flexible. It is a condition. JP 63
JP-A-92722 discloses a heat-fusible conjugate fiber of fine fineness using polyester as the first component and low-rigidity linear low-density polyethylene as the second component, and a heat-fusible nonwoven fabric comprising the conjugate fiber. However, the strength of the nonwoven fabric is low and the above requirements are not satisfied. JP-A-63-135549 discloses a method for producing a heat-fusible nonwoven fabric comprising heat-fusible conjugate fibers using a specific high-crystalline polypropylene as the first component and polyethylene as the second component. According to this method,
It is stated that a nonwoven fabric having a high bulkiness and a good bulkiness maintenance rate, which is not possible with a nonwoven fabric using a conventional polyolefin-based heat-fusible conjugate fiber, is obtained. However, the nonwoven fabric obtained by this method has the disadvantages of low nonwoven fabric strength and hard texture.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing a heat-fusible conjugate fiber which is large in strength and bulkiness of a nonwoven fabric and which is optimal for producing a nonwoven fabric having a soft texture. To provide.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have reached the invention described below. That is, the density is 0.905 or more, and the isotactic pentad fraction of the boiling n-heptane insoluble portion is 0.9%.
A first component made of polypropylene having a pentad fraction of 0.002 or less and having two or more different configurations, and a density of 0.940 or more and a 0.1% or less.
955 or less and a melt flow rate (MFR; 1)
(90 ° C.) a high-density polyethylene having a ratio of 8 to 25, and a weight ratio of the first component to the second component in the range of 45:55 to 35:65. Is obtained by compound spinning into a parallel type or a sheath-core type so that at least a part of the yarn is continuously present in the longitudinal direction to obtain an undrawn yarn. 13
It is stretched at a temperature of 90 ° C. or more and 130 ° C. or less by stretching at a temperature of 0 ° C. or less and 0.85 times or more of the maximum stretching ratio, and then having a tensile resistance of 40 g / g.
This is a method for producing a heat-fusible composite fiber having a heat shrinkage of not less than d and not more than 5%.

[0005]

Here, the isotactic pentad fraction of polypropylene refers to A.I. Macromolecules 6 , 925 (197) by Zambelli et al.
It is an isotactic fraction in pentad units in a polypropylene molecular chain measured using a method published in 3), that is, ¹³ C-NMR. Therefore, the isotactic pentad fraction is the fraction of propylene monomer units in which five consecutive propylene monomer units are isotactically bonded. A pentad fraction with two heterogeneous configurations is such that three out of the five monomer unit configurations in the molecular chain have a common configuration and the other two have the opposite configuration. Pentad fraction.

The polypropylene used as the first component of the conjugate fiber in the present invention has a density of 0.905 or more, an isotactic pentad fraction (P ₀ ) of boiling n-heptane-insoluble portion of 0.950 or more, and 2 Pentad fraction (P ₂ ) having a number of different configurations is 0.0
02 or less. In the case of a heat-fusible conjugate fiber using polypropylene whose P ₀ is less than 0.950 as the first component, the web shrinks during heat treatment for forming a nonwoven fabric, and a bulky nonwoven fabric cannot be formed. Further, P ₂ can not be obtain similar bulky woven or non-hot-melt adhesive conjugate fibers with the polypropylene in excess of 0.002 in the first component. The polypropylene used in the present invention has a density of 0.905 or more, preferably 0.910 or more, without being subjected to the extraction treatment. A heat-fusible conjugate fiber using a polypropylene having a density of less than 0.905 as the first component cannot provide a bulky nonwoven fabric as described above. Although there is no particular limitation on the melt flow rate (MFR; 230 ° C.) of this polypropylene, a polypropylene having a melt flow rate of about 5 to 45 is preferably used from the viewpoint of easy spinning. The polypropylene used as the first component in the present invention is obtained by polymerizing propylene in the presence of a specific catalyst as described in Japanese Patent Publication No. 1-48922, and has a greater rigidity than ordinary polypropylene. It is coalesced, and the boiling n-heptane insoluble portion accounts for 95% or more of the whole polymer.

In the present invention, the polyethylene used as the second component of the heat-fusible conjugate fiber has a density of 0.940 or more and 0.9 or more.
It needs to be 55 or less. A heat-fusible conjugate fiber using a polyethylene having a density of less than 0.940 as the second component cannot obtain high nonwoven fabric strength. or,
In the case of a heat-fusible conjugate fiber using a polyethylene having a density exceeding 0.955, the hand of the nonwoven fabric becomes hard, and such a polyethylene cannot be used. Further, this polyethylene needs to have a melt flow rate (MFR; 190 ° C.) of 8 to 25. In the heat-fusible conjugate fiber using polyethylene having an MFR of less than 8, the feel of the nonwoven fabric becomes hard, and in the heat-fusible conjugate fiber using polyethylene exceeding 25, the nonwoven fabric strength becomes low. Neither can be used.

The weight ratio of the first component and the second component is 3
The ratio is in the range of 5:65 to 45:55, and the second component is arranged in a parallel type or a sheath-core type so that at least a part of the fiber surface is continuously present in the length direction, and the tensile resistance is 40 g /
The heat shrinkage is 5% or less at d or more. When the weight ratio of the first component is less than 35% or the tensile resistance is less than 40 g / d, the nonwoven fabric using such a heat-fusible conjugate fiber has poor bulkiness and deteriorates feeling and strength. Also decrease. If the weight ratio of the first component exceeds 45%, the bulkiness of the nonwoven fabric is improved, but high strength of the nonwoven fabric cannot be obtained. Further, even when the weight ratio of the first component and the second component is within the above range, the heat shrinkage ratio is 5%.
%, The shrinkage of the web at the time of heat treatment at the time of forming the nonwoven fabric becomes large, and a uniform thin nonwoven fabric without wrinkles cannot be obtained. Here, the tensile resistance is a factor of the rigidity of the fiber calculated under the measurement conditions described later.
It is a shrinkage ratio when treated at 0 ° C. for 3 minutes.

The heat-fusible conjugate fiber of the present invention, which has a tensile resistance, a heat shrinkage, etc. within the above-mentioned ranges, is an undrawn yarn obtained by conjugate spinning the above two components by a known melt spinning method. , Stretching zone
The temperature of the entire assembly is 90 ° C to 130 ° C, preferably 9 ° C.
After stretching at a temperature of 2 to 125 ° C. and 0.85 times or more of the maximum stretching ratio, preferably 0.87 times or more, and more preferably 0.95 times or more, and optionally crimping,
It is obtained by annealing at a temperature of 90 ° C. or more and 130 ° C. or less. Here, the temperature of the whole drawing zone means a temperature of a portion which substantially contributes to drawing. That is, when using a stretching apparatus having a stretching roll at the entrance and the exit of the stretching chamber, it means not only the stretching roll but also the temperature of the stretching chamber. Specifically, in the case of using a multi-stage stretching apparatus including the A roll group, the B roll group, and the C roll group,
This also means that a cover or the like is provided in the stretching zone between the roll groups to form a stretching chamber, and the temperature of the chamber is also heated to 90 ° C. or more. Furthermore, if the A-roll group consists of seven rolls, this does not mean that a small space between the seven rolls is heated.

When the stretching temperature is lower than 90 ° C., a fiber having a high tensile resistance cannot be obtained.
It is not preferable because the fusion of the fibers by polyethylene occurs remarkably. When the stretching ratio is 0.85 times or less of the maximum stretching ratio, it is impossible to obtain a film having a high tensile resistance.
The maximum stretching ratio refers to a stretching ratio at which fluff starts to be generated in the tow when the stretching ratio is gradually increased. After stretching, annealing is performed at a temperature of 90 ° C. or more and 130 ° C. or less for about 0.5 to 30 minutes to obtain a material having a low heat shrinkage. If the annealing temperature is less than 90 ° C., an annealing time of 30 minutes or more is required, and a material having a low heat shrinkage rate cannot be obtained. The heat-fusible conjugate fiber of the present invention is often cut into a predetermined length and used as a staple for ease of processing into a nonwoven fabric.

The heat-fusible composite obtained by the production method of the present invention
Fiber (hereinafter, simply referred to as the heat-fusible conjugate fiber of the present invention)
The nonwoven fabric used was a fiber aggregate consisting of only the heat-fusible conjugate fiber of the present invention or a heat-fusible conjugate fiber of the present invention in 2 fibers.
A mixed fiber aggregate with other fibers containing 0% by weight or more is formed into a web by a known carding method, an air-lay method, a dry pulp method, a wet papermaking method, a tow opening method, or the like. By heat-sealing the contacts of the heat-fusible composite fiber. As the heat treatment method, any of a method using a dryer such as a hot air dryer, a suction band dryer, a yankee dryer, and a method using a pressurized roll such as a flat calender roll and an emboss roll are used. Can also be used. The heat treatment temperature is a temperature equal to or higher than the melting point of the second component of the conjugate fiber and equal to or lower than the melting point of the first component, and is in a range of about 120 to 155 ° C. The processing time is about 5 seconds or more when using the dryer or the like,
When using the above-mentioned pressure roll, the time is generally 5 seconds or less. Other fibers that can be used as a mixture with the heat-fusible conjugate fiber of the present invention can be freely used as long as they do not deteriorate by the above-mentioned heat treatment and do not inhibit the object of the present invention. Polyester, polyamide, polypropylene , Polyethylene, other synthetic fibers, natural fibers such as cotton and wool, and fibers such as rayon. The heat sealability of the present invention
In a non-woven fabric using fibers , the heat-fusible fibers act as a binder.

[0013]

The present invention will be described below in detail with reference to examples. The measurement methods and definitions of the physical property values shown in the examples are collectively shown. Density: A sample piece was prepared by a press method of JIS K-6758, and measured by a density gradient tube method of JIS K-7112. Boiling n-heptane insoluble part of polypropylene: 5 g of polypropylene was completely dissolved in 500 ml of boiling xylene, and this was poured into 5 liter of methanol, and the precipitated polymer was dried and then heated with boiling n-heptane for 6 hours. It is an extraction residue obtained by soxhlet extraction. An isotactic pentad fraction (P ₀ ) and a pentad fraction with two heterogeneous configurations (P
₂ ): Regarding the boiling n-heptane insoluble portion of polypropylene, Macromolecules 6 , 925 (197)
It was measured by the method described in 3). The method for determining the assignment of peaks in NMR measurement is described in the above-mentioned Journal, 8 , 687 (19).
75). FT-N
Using a 270 MHz MR apparatus, the signal detection limit was improved to 0.001 in isotactic pentad fraction by 27,000 integrated measurements. Melt flow rate (MFR; 230 ° C): ASTM
According to condition (L) of D1238. Melt flow rate (MFR; 190 ° C): ASTM
According to condition (E) of D1238.

Nonwoven fabric strength: The breaking strength of a 5 cm wide test piece cut in the fiber direction (MD) and the direction perpendicular thereto (CD) according to JIS L1085 (test method for nonwoven fabric interlining)
The measurement was performed at a grip interval of 10 cm and a tensile speed of 30 ± 2 cm. The unit is kg / 5cm. Bulkiness: A load of 10 g / cm ² was applied to the sample, and immediately after that, the thickness A (mm) was measured, and the ratio to the weight per unit area B (g / m ² ) (A / B) × C. Volume (cm ³ / g), where C is unit correction and C = 1000. Non-woven fabric feel: A sensory test was conducted by five panelists, and all were determined to be soft without any rough feeling due to wrinkles, etc. (good), and good when three or more were determined (good). In the case where three or more persons judged that they had a rough feeling due to wrinkles or the like or lacked a soft feeling, they were evaluated as unacceptable (x). Tensile resistance: A tensile strength test of the conjugate fiber was performed according to the method of JIS-L-1015, and a stress A (g) at 5% elongation was obtained.
And the stress B (g) at the time of 10% elongation, and the fineness C of the sample
It was calculated from (d) by the following equation. Tensile resistance = [(BA) / ｛(10% -5%) / 10
0%｝] / C Thermal shrinkage: The shrinkage of the composite fiber after heating at 125 ° C. for 3 minutes under no load using a dryer was determined, and the average value of 20 samples was shown.

Examples 1-2, Comparative Examples 1-4 Core-sheath type die having a core component of polypropylene shown in Table 1 and a sheath component of various polyethylenes shown in Table 1, having a pore diameter of 0.6 mm and a number of holes of 350. Was spun into a core-sheath composite fiber having a single yarn denier of 8 d / f. 90% of the undrawn yarn
Using a stretching device equipped with a stretching roll and a chamber heated to a predetermined temperature of １００100 ° C., the film is stretched to a predetermined ratio of 0.91 times or more of the maximum stretching ratio, and crimped by a crimper. After annealing for one minute, the resultant was cut with a cutter to obtain a heat-fusible conjugate staple having a single yarn denier of 2 d / f and a fiber length of 51 mm. Table 1 shows the properties and spinning conditions of the raw material polymer. The obtained heat-fusible conjugate fiber staple was made into a web having a basis weight of 20 g / m ² by a card machine, and the web was heat-treated at a predetermined temperature of 135 to 140 ° C. for 5 seconds by using a drier to obtain a heat-fusible fiber. A nonwoven fabric was obtained in which the intersections were heat-sealed. Table 2 shows nonwoven fabric forming conditions and nonwoven fabric characteristics.
It was shown to. From the results in Tables 1 and 2, it can be seen that the conjugate fiber according to the present invention has a high tensile resistance of 40 g / d or more and a low heat shrinkage of 5% or less. The nonwoven fabric obtained by using this composite fiber has high strength of the nonwoven fabric in both the vertical (MD) and horizontal (CD) directions, has a good bulkiness, has no wrinkles, and has a good texture. However, it can be seen that the nonwoven fabric obtained by using a conjugate fiber other than the present invention is poor in any of nonwoven fabric transverse strength (CD), bulkiness, and texture.

Example 3, Comparative Examples 5 to 7 Using the polypropylene and polyethylene shown in the respective examples in Table 1, the same core-sheath type die as in Example 1 was used to form a polypropylene core and a polyethylene single-sheath denier 14d /
The core-sheath composite fiber of f was spun. This undrawn yarn was drawn using the same drawing apparatus as in Example 1, the drawing roll and the chamber were all set to 90 ° C., and drawn at 0.85 times or more of the maximum drawing ratio. Annealing and cutting for 5 minutes, single yarn denier 3d / f fiber length 51
mm of the heat-fusible conjugate fiber staple was obtained. The obtained composite fiber was formed into a web using a card machine in the same manner as in Example 1,
Next, heat treatment was performed at 140 ° C. for 5 seconds, and the basis weight was 20 g / m ^2.
Was obtained. Table 1 shows the spinning conditions of the conjugate fiber and Table 2
Shows the characteristics of the nonwoven fabric. From the results in each table, it is understood that the conjugate fiber of the present invention has a high tensile resistance of 40 g / d or more and a low heat shrinkage of 5% or less. The heat-sealed non-woven fabric obtained using this composite fiber has strong non-woven fabric and good bulkiness,
There are no wrinkles and the texture is good. However, the non-woven fabric obtained by using a conjugate fiber other than the present invention has a non-woven fabric with a lateral strength (C
It can be seen that D), bulkiness and texture are bad.

Examples 4 to 5 and Comparative Examples 8 to 10 Using polypropylene and polyethylene shown in Table 1, parallel type composite fibers having a single yarn denier of 12 d / f were spun by a parallel type die. This undrawn yarn was drawn using the same drawing device as in Example 1, and the entire drawing roll and chamber were turned into 110
And stretched at 0.83 times or more of the maximum stretch ratio.
In the same manner as described above, crimping, annealing and cutting at 100 ° C. for 5 minutes were performed to obtain a parallel type heat-fusible conjugate fiber staple having a single yarn denier of 4 d / f and a fiber length of 64 mm. The obtained composite fiber staple (15 to 25% by weight) and single yarn denier 6
d / f Polyethylene terephthalate fiber staple having a fiber length of 51 mm (85 to 75% by weight) was mixed with a carding machine to form a web in the same manner as in Example 1.
To obtain a nonwoven basis weight 20 g / ^{m 2} and s between heat treatment.
Table 1 shows the spinning conditions and the like of the conjugate fiber, and Table 2 shows the characteristics and the like of the nonwoven fabric. In Comparative Example 8, the same composite fiber as in Example 4 is used. From the results in each table, it is understood that the conjugate fiber of the present invention has a high tensile resistance of 40 g / d or more and a low heat shrinkage of 5% or less. The heat-sealed nonwoven fabric containing the composite fiber in an amount of 20% by weight or more has good nonwoven fabric strength, bulkiness, no wrinkles, and good texture. However, it can be seen that the nonwoven fabric obtained by using a conjugate fiber other than the present invention has a low nonwoven fabric transverse strength (CD).

Example 6, Comparative Examples 11 to 13 and Comparative Example 1
4-15 The undrawn yarn obtained in Example 3 was drawn using the same drawing apparatus as in Example 1, the draw roll temperature was kept constant at 90 ° C., and the draw ratio was 0.69 to 0.89 times the highest draw ratio. Stretched, crimped, etc., and subjected to annealing (Comparative Examples 14 and 15), and annealing (120 ° C. ×
5 minutes) composite fiber (Example 6, Comparative Example 11-1)
3) was obtained. The obtained composite fiber staple was formed into a web using a carding machine in the same manner as in Example 1, and then heat-treated at 140 ° C. for 5 seconds to obtain a nonwoven fabric having a basis weight of 20 g / m ² . Table 3 shows the spinning conditions and the like of the conjugate fiber, and Table 4 shows the nonwoven fabric characteristics and the like. From each table, it can be seen that the composite fiber obtained by drawing at 0.85 times or more of the maximum drawing ratio and annealing treatment has a high tensile resistance of 40 g / d or more and a low heat shrinkage of 5% or less. (Example 6). However, those having a draw ratio of less than 0.86 times the maximum draw ratio (Comparative Examples 11 to 13) have a low tensile resistance of less than 40 g / d, and the non-annealed conjugate fibers (Comparative Examples 14 to 15) are heat-resistant. It can be seen that the shrinkage ratio is as high as 5% or more. The heat-sealed nonwoven fabric (Example 6) obtained by using the conjugate fiber of the present invention has good nonwoven fabric strength, good bulkiness, no wrinkles, and good texture. However, it can be seen that the nonwoven fabric obtained by using a conjugate fiber other than the present invention has either low nonwoven fabric transverse strength (CD), low bulk, wrinkles, or poor texture.

Example 7, Comparative Examples 16-18 and Comparative Example 1
9-20 The undrawn yarn obtained in Example 1 was drawn by using the same drawing apparatus as in Example 1, changing the drawing roll temperature and the temperature of the drawing chamber, and keeping the drawing ratio constant at 0.93 times the maximum drawing ratio. Then, a crimped composite fiber without annealing (Comparative Examples 19 and 20) and a composite fiber with annealing (105 ° C. × 5 minutes) (Example 7, Comparative Examples 16 to 18) were obtained. The resulting composite fibers and the same manner as in Example 1 web using a carding machine, then to obtain a 140 ° C. for 5 seconds between heat treated having a basis weight of 20 g / m ² non-woven fabric. Table 3 shows the spinning conditions and the like of the conjugate fiber, and Table 4 shows the drawing conditions and nonwoven fabric characteristics. From each table, it can be seen that the composite fiber obtained by drawing and annealing at all temperatures in the drawing zone at 90 ° C. or more has a high tensile resistance of 40 g / d or more and a low heat shrinkage of 5% or less. (Example 7). However, the one stretched without heating the chamber (Comparative Examples 16 to 18) had a tensile resistance of 4
It is as low as less than 0 g / d. The composite fiber without annealing treatment (Comparative Examples 19 to 20) had a tensile resistance of 40 g / d.
It can be seen that the heat shrinkage ratio is low, or lower, or the heat shrinkage ratio is as high as 5% or more. The heat-sealed nonwoven fabric obtained by using the conjugate fiber of the present invention has good nonwoven fabric lateral strength and bulkiness, no wrinkles, and good texture. However, it can be seen that the nonwoven fabric obtained by using a conjugate fiber other than the present invention has either low lateral strength, low bulk, wrinkles or poor texture.

[0020]

As is clear from the examples, the heat-fusible conjugate fiber of the present invention has a high tensile resistance and a low heat shrinkage. In addition, by processing the heat-fusible conjugate fiber obtained in the present invention into a nonwoven fabric, it was possible to achieve both high strength and high bulkiness, which were not possible before. Furthermore, the improved bulkiness has made it possible to obtain a nonwoven fabric having a very soft feel compared to conventional nonwoven fabrics.

[Table 1]

[Table 2]

[Table 3]

[Table 4]

Claims (1)

(57) [Claims] (1) a density of 0.905 or more, and an isotactic pentad fraction of a boiling n-heptane insoluble portion is 0.950;
A first component made of polypropylene having two or more different configurations and having a pentad fraction of 0.002 or less, and a density of 0.940 or more and 0.95 or more;
5 or less and a melt flow rate (MFR; 190
C) is at least 8 and at most 25, and the second component is a high-density polyethylene having a weight ratio of the first component to the second component in the range of 45:55 to 35:65. An undrawn yarn is obtained by compound spinning into a parallel type or a sheath-core type so that a part thereof is continuously present in the length direction, and the temperature of the undrawn yarn is set to 90 ° C. or more and 130 ° C. Or less, and stretched at a draw ratio of 0.85 times or more of the highest draw ratio to obtain a drawn yarn.
A method for producing a heat-fusible conjugate fiber having a tensile resistance of 40 g / d or more and a heat shrinkage of 5% or less, characterized by annealing at a temperature of not more than ℃.