JP2908454B2 - Thermally bonded nonwoven fabric with excellent bulkiness, easy compressibility, and easy recovery from compression - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a heat-bonded nonwoven fabric excellent in bulkiness, easy compressibility, and easy recovery from compression.

[PRIOR ART] Heat-bondable fibers for heat-bonding nonwoven fabrics are described in, for example, JP-A-57-6617, JP-A-57-210015, JP-A-57-95311, and JP-A-5-95311.
7-95312, 58-23917, 58-41912, 58-2031
No. 17, 61-201015, 62-69822, 62-156310
And No. 62-184119. The structure of the heat-adhesive fiber disclosed therein has a sheath-core conjugate structure or a side-by-side conjugate structure, and since both are solid, they are inferior in bulkiness and easy to use. It also lacked compressibility and recoverability from compression.

On the other hand, hollow composite fibers having excellent bulkiness, easy compressibility, and easy recovery from compression are disclosed in JP-B-45-30048, JP-B-45-20208, and JP-B-47-17.
No. 089, Japanese Patent Application Laid-Open No. Sho 61-152824, etc., and improvement studies on these techniques are continuously conducted, but they are still sufficiently excellent in bulkiness, easy compressibility, and easy recovery from compression. At present there is no such thing. Also, since these fibers were not originally developed as heat-adhesive fibers for heat-bonded non-woven fabrics, they lacked consideration for heat-bonded non-woven fabrics. Naturally, heat-bonded non-woven fabrics obtained from the above fibers were bulky and easily compressible. However, the non-woven fabric was not sufficiently excellent in compressibility / recoverability, and lacked dimensional stability when a nonwoven fabric was manufactured.

[Problems to be Solved by the Invention] Therefore, in the present invention, it has been studied to provide a nonwoven fabric which is excellent in dimensional stability in addition to bulkiness, easy compressibility, easy recovery from compression.

[Means for Solving the Problems] The heat-bonded nonwoven fabric having excellent bulkiness, easy compressibility, and easy recovery from compression according to the present invention, which can solve the above problems,
A heat-bonded nonwoven fabric obtained by using a side-by-side type heat-bondable conjugate fiber composed of two polymers having compatibility and a melting point or a softening point different from each other by 39 ° C. or more, wherein the fiber straddles the two polymers. A continuous hollow in the longitudinal direction, and the hollow ratio of the hollow in the cross section of the fiber is 10% or more. Here, a polymer composed of two polymers having different melting points or softening points by 39 ° C. or more is a preferred embodiment of the present invention. Furthermore, a heat-bonded nonwoven fabric obtained using the above-mentioned conjugate fiber is also included in the scope of the present invention.

[Operation] The hollow conjugate fiber used in the present invention has a cross-sectional shape of, for example, a side-by-side type in which two polymers A and B are joined as shown in FIG. 1 (a) or (b). It has a composite structure, and the hollow 1 is formed continuously over the two polymers in the longitudinal direction of the fiber.

The two polymers constituting the conjugate fiber are compatible with each other, and have different melting points or softening points by 20 ° C. or more. Since the hollow conjugate fiber used in the present invention is of the side-by-side type as described above, if the two polymers are not compatible, the separation of the two polymers occurs. Therefore, the compatibility of the two polymers is particularly important.

By the way, as for the hollow conjugate fiber, for example, two kinds of polymers are separately melted by two extruders, merged by a block, and both polymers are side-by-side from a C-type nozzle as shown in FIG.
It can be obtained by compound spinning into a side mold, and its cross-sectional shape is as described above. At this time, the C-type nozzle is divided into left and right A 'and B' at the center line, and the component discharged from the A 'side is polymer A.
When the component discharged from the B 'side is a polymer B, the polymer A discharged from the A' side flows and adheres to form a hollow fiber as shown in FIG. (Hereinafter, the polymer A is referred to as an adhesive component A. On the other hand, the component composed of the polymer B is a component which exhibits a resilience to compression from a direction perpendicular to the axis of the hollow conjugate fiber because it is curved in a semicircular shape. Component B).

At this time, if the melting point or softening point of the adhesive component A is lower than that of the skeletal component B by 20 ° C. or more, the adhesive component A cannot sufficiently flow and adhere. The hollow ratio is 10% or more, preferably 20%
% Or less, a hollow straddling the adhesive component A and the skeleton component B is not formed, and the skeleton component is insufficiently curved, and the ability to recover the fiber from compression (easy to recover from compression) is reduced. descend.

The polymer which can be used as the adhesive component and the skeletal component may be one having compatibility and different in melting point or softening point by 20 ° C. or more. For example, in the case of polyester, the acid component is terephthalic acid / isophthalic acid 95 / 5-30 / 7
The modified polyester which is 0 or a mixture of the modified polyester and polybutylene terephthalate is used as the adhesive component A, and the polyethylene terephthalate is used as the skeleton component B. For polyolefins, a combination of polyethylene (adhesive component A) and polypropylene (skeleton component B), or a combination of modified polyethylene or modified polypropylene (adhesive component A) with unmodified polyethylene or polypropylene (skeleton component B), etc. Is exemplified. Further, polyvinyl alcohol may be added to impart water absorption in relation to the use, or a third component having good compatibility may be added.

Known spinning nozzles for producing hollow conjugate fibers can be used, but selection of the nozzle is important because the cross-sectional shape of the fiber is mainly determined by the nozzle shape. Also, the discharge amount and the viscosity of the two molten polymers from the nozzle have a great influence on the shape of the hollow portion. Therefore, it is necessary to consider the viscosity of the polymer during spinning and the distribution of the orifice flow. For example, FIG. 1 (a) shows a fiber cross-sectional shape when the adhesive component has a low viscosity, FIG. 1 (b) shows a case where the adhesive component has a high viscosity, and FIG. In (b), the degree of curvature of the skeleton component is small.

The spinning temperature is suitably 275 to 290 ° C for the polyester type and 180 to 290 ° C for the polyolefin type. Since the spinning temperature depends on the melt viscosity of the polymer and affects the fiber cross-sectional shape, it is important to select a suitable spinning temperature.

Spinning speed is 500-6000m / min, preferably 1500-5000m /
Minutes. If the speed exceeds 6000m / min, problems such as thread breakage may occur.
If it is less than 00 m / min, productivity is poor.

After spinning and drawing as described above, it is stretched in one or two steps by a draw frame method, a direct draw method, or the like. The stretching temperature is a temperature at which the polymer on the low melting point side or the polymer at the low softening point does not adhere, for example, 50 to 120 ° C. for a polyester type and 40 to 100 ° C. for a polyolefin type. The stretching ratio is preferably 0.6 times or more of the breaking stretching ratio so as not to cause unstretched residue, and 0.85 times or less so as not to cause breakage and peeling of a single yarn. In addition, three-dimensional crimps may appear on the fiber during spinning, but if the three-dimensional crimps are of a degree that does not cause a problem in card passability, they can be used as a nonwoven fabric. It can be spun at such a high speed that it does not occur and can be directly wound up in an undrawn state. Even with such a method, a hollow composite fiber oriented and crystallized can be produced. The fiber diameter is adjusted according to the application, but is preferably 3 denier or less to make the fiber softer.

As described above, it is possible to obtain a bonded conjugate fiber composed of two polymers, straddling the two polymers, and having a hollow continuous in the fiber length direction. Since the fibers are oriented and are composed of two components having different heat shrinkage differences, they have a three-dimensional helical crimping ability for heat treatment. In this case, the reciprocal (1 / ρ) of the radius of curvature of the three-dimensional helical crimp developed when heat-treated without tension at a temperature about 10 ° C. lower than the bonding temperature of the fiber is 0.5 to 5 mm ⁻¹ . Preferably
It is necessary to combine the two polymers so that such a value results in a shrinkage difference. In addition, since the skeleton component is curved, the torsional moment can be reduced, which is a preferable characteristic for easy compression.

Further, the hollow conjugate fiber is mechanically crimped by a usual method, for example, a press crimper or the like, to be a crimped fiber, and cut into a length according to the application to form a staple. The number of crimps is preferably 8 or more / inch, and the crimp ratio is preferably 5% or more. The reason for this is that if these values are not reached, the spreading entanglement during card web formation cannot be maintained, and the buckling point at the time of mechanical crimping becomes the nucleus of the three-dimensional helical crimp during heat treatment. This is because shrinkage is controlled.

The obtained staples are opened by carding to form a web, and the webs are laminated in a single layer or alternately in the opening direction, and the melting point or softening point of the adhesive component is increased by about 1 to 30 at about + 20 ° C.
Heat-bonded non-woven fabric for 10 minutes. At this time, fibers other than the hollow composite fibers obtained as described above may be used in combination, but it is necessary to select a fiber having adhesiveness. In addition, the expansion strain at the time of opening the card causes the three-dimensional spiral crimping in addition to the above-mentioned three-dimensional spiral crimping ability. At the time of this dry heat treatment, the three-dimensional spiral crimp of the composite fiber itself appears, and the three-dimensional spiral crimp is added to the mechanical crimp, resulting in a more bulky property. Also, when fibers are bonded together, only the low melting point or low softening point components are bonded together, so the degree of freedom of movement of each fiber under compression deformation increases,
This is also taken into account the bulkiness, easy compressibility, easy compressibility and recoverability of the hollow composite fiber itself, and bulkiness due to crimping, easy compressibility, and easy compressibility and recovery. It becomes excellent in recoverability. Further, the nonwoven fabric thus obtained has excellent dimensional stability due to entanglement due to fiber crimping (mechanical crimping + three-dimensional crimping) and thermal bonding.

When the nonwoven fabric obtained as described above is applied to batting, sanitary materials, disposable articles, and the like, the nonwoven fabric becomes bulky, has excellent compressibility and recoverability easily, and has excellent dimensional stability.

[Example] An example of the present invention will be described below. The characteristic evaluation method in the present invention is as follows.

(1) Compatibility Two films composed of different polymers are laminated and heat-treated at a pressure of 5 kg / cm ² for 30 minutes or more at a melting point or higher, and then a width 2c.
The peel strength of both components in a m, 5 cm long film is 500 or more (g): compatible 200 to less than 500 (g): slightly compatible △ 200 or less (g): not compatible did.

(2) Melting point difference Two polymer samples (2 mg) were measured with a differential thermal analyzer (DSC).
After holding at 30 ° C. for 30 minutes, when the temperature was lowered at 5 ° C./min, the first endothermic peak temperature was Tm ₁ and the second endothermic peak temperature was Tm ₂ , and Tm ₁ −
Tm ₂ was taken as the difference between the two melting points.

(3) Hollow ratio Wrapped hollow composite fiber with acrylic resin
After curing at 40 ° C or less, cut out into 5-20μm slices
The cross-sectional area So of the entire fiber and the cross-sectional area Si of the hollow portion in the fiber cross-sectional micrograph of 200 × 10 times were obtained and calculated by the following equation.

(4) Three-dimensional helical crimping ability After the hollow conjugate fiber is subjected to dry heat treatment at a low melting point or a softening point of a low melting point component or a softening point of −10 ° C. in a non-tension state, a projection view as shown in FIG. 3 is obtained. , Dimensions D and L were determined, and the reciprocal 1 / ρ of the radius of curvature was determined by the following equation.

(5) Bulkiness Open the staple fiber with a card, and weigh 50 g /
Create a web such that m ^2, melting point also softening point + 20 ° C.
After drying and heat treatment for 10 minutes at room temperature, the fibers are alternately superposed in the fiber opening direction, and the density under a load of 0.6 g / m ² (cm ³ /
g). At this time more than 120 (cm ³ / g): lower than ◎ 100 to 120 as bulky good (cm ³ / g): less than ○ 70～100C as bulkiness somewhat better (m ³ / g): was slightly inferior bulkiness △ Less than 70 (cm ³ / g): Poor bulkiness was evaluated as x.

(6) Bulk density was determined by the the bulk density of the web created was measured under 25 g / cm ² load (cm ³ / g) (5) with the easily compressible said (5) (cm ³
/ g) is 50 or more (cm ³ / g): good as softness ◎ 25 to less than 50 (cm ³ / g): slightly good as soft ○ 15 to less than 25 (cm ³ / g): soft Less than △ 15 (cm ³ / g) as slightly poor: poor in softness and evaluated with × (7) Three-dimensional helical crimping state The fiber of the web after the dry heat treatment obtained in (5) above was taken under a stereoscopic microscope at 50 × magnification. Observed and ranked as follows:

Good steric spiral crimping: ◎ Medium steric spiral crimping: ○ Little steric spiral crimping: △ No steric spiral crimping: × (8) Easy recovery from compression Toyo Baldwin After applying a load of 0 to 100 g / cm ² 50 times repeatedly to the web prepared in the above (5) using Type II Tensilon, the thickness in the no-load state is ti, and the thickness in the no-load state immediately after the web preparation is t _0. And (t ₀ −t _i ) / t
₀ was obtained and 0.9 or more at this time: good recoverability ◎ 0.7 to less than 0.9: slightly good recoverability ○ 0.5 to less than 0.7: slightly poor recoverability Δ less than 0.5: poor recoverability was evaluated as x. (Where n = 5) Experiment Nos. 1 to 7 Copolymerized polyester (melting point: 133 ° C., intrinsic viscosity: 0.610) having an acid component of terephthalic acid / isophthalic acid = 70/30 as an adhesive component, polyethylene terephthalate (Melting point: 265 ° C, intrinsic viscosity: 0.620) As a skeleton component, change the nozzle hollow ratio so that the composite ratio becomes 40/60, and change the block position to discharge from the C-type nozzle at a spinning temperature of 285 ° C and take off speed of 1300m / Min after pick-up at 70 ° C in a wet bath
The hollow composite fiber was drawn by a factor of 2.0 to 2.6 to obtain a staple by subjecting the fiber to mechanical crimping and cutting to 61 mm. Further, the staple was opened to prepare a web having a basis weight of 50 g / m ² , and the web was subjected to dry heat treatment at 130 to 160 ° C. for 10 minutes. The heat-treated nonwoven fabric was obtained by alternately stacking the webs subjected to the dry heat treatment in the fiber opening direction. Table 1 shows the properties of the hollow conjugate fiber and the heat-bonded nonwoven fabric obtained in the above step.

Experiment No. 8-11 High-density polyethylene (MI20, manufactured by Toyo Soda Co., Ltd.) with a melting point of 121 ° C was used as an adhesive component, and polypropylene with a melting point of 160 ° C (MI3
0, Mitsui Toatsu Co., Ltd.) as a skeletal component, spinning at a spinning temperature of 220 ° C., and stretching in a 50 ° C. wet bath.
To obtain a composite fiber. Table 1 shows the characteristics.

Experiment No.12 High-density polyethylene (MI16, manufactured by Toyo Soda) using low-density polyethylene (MI22, manufactured by Toyo Soda) as an adhesive component
Was treated in the same manner as in Experiments Nos. 8 to 11 except that was used as a skeleton component. Table 1 shows each characteristic value. In Table 1, those within the limits regulated by the present invention were regarded as Examples, and those outside the limitations were regarded as Comparative Examples.

As is evident from Table 1, when a heat-bonded non-woven fabric is produced from the hollow conjugate fiber of the present invention, a non-woven fabric excellent in various properties can be obtained.

[Effect of the Invention] Since the present invention is configured as described above, the use of the hollow conjugate fiber of the present invention makes it possible to obtain a heat-bonded nonwoven fabric which is more excellent in bulkiness, easy compressibility, and easy recovery from compression. Can,
The heat-bonded non-woven fabric has excellent dimensional stability.

[Brief description of the drawings]

1 (a) and 1 (b) are cross-sectional views of the hollow conjugate fiber used in the present invention, FIG. 2 is a plan view of a nozzle for obtaining the hollow conjugate fiber used in the present invention, and FIG. 3 is the present invention. FIG. 4 is a projection view after heat treatment of the hollow conjugate fiber used in the step (1) without tension, and FIG. 4 is a view showing a fiber cross-sectional shape in Table 1. 1 ... hollow, 2 ... bonded part

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinjiro Yamazaki 2-2-2 Dojimahama, Kita-ku, Osaka-shi, Osaka Inside Toyobo Co., Ltd. (56) References JP-A-61-19815 (JP, A) JP-A-48-36418 (JP, A) JP-A-61-245327 (JP, A) JP-B-43-1776 (JP, B1)

Claims (1)

(57) [Claims] 1. A heat-bonded nonwoven fabric obtained by using a side-by-side type heat-bondable conjugate fiber composed of two polymers having compatibility and different melting points or softening points by 39 ° C. or more, wherein the fibers are composed of the two fibers. Having a continuous hollow spanning the polymer in the length direction, wherein the hollow ratio of the hollow in the fiber cross section is 10% or more. Excellent heat bonded nonwoven.