JP3109628B2 - Manufacturing method of composite fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a conjugate fiber which is useful for producing a hot roll type nonwoven fabric. The present invention relates to a method for producing an adhesive conjugate fiber.

[0002]

2. Description of the Related Art Polypropylene or polyester is used as a core component of a heat-adhesive fiber, and a sheath component is made of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ethylene-vinyl acetate copolymer, or low-melting polyester. Is known. Such a conventional sheath-core type heat-bondable fiber is usually formed into a web by a carding process or formed into a sheet by a papermaking process, and then heated to a temperature equal to or higher than the melting point of the sheath component to fuse the contact points of the fibers. Nonwoven fabric. As a method of heating and fusing, a hot air bonding method such as a suction band dryer and a suction drum dryer and a hot roll bonding method such as a Yankee dryer and a calender roll are widely used depending on the use of the nonwoven fabric. In recent years, with the increase in demand for nonwoven fabrics, there has been an increasing tendency to employ a hot roll bonding method that is relatively inexpensive and has high productivity not only for wet nonwoven fabrics but also for dry nonwoven fabrics.

[0003]

However, the conventional non-woven fabric obtained by the hot roll bonding method using the heat-bondable fiber as a material has a drawback that the tensile strength is insufficient or the heat-sealing property is poor. In particular, in the case of using a composite fiber of polyethylene (sheath) / polypropylene (core), which is one of the heat-adhesive composite fibers that are often used in recent years because of their characteristics such as low cost, light weight, and soft texture. It has good heat-sealing properties with other non-woven fabrics and films whose surface is formed of the same material as the sheath component of this fiber. There is a problem that the sealing property is extremely low. Therefore, there has been a strong demand for the appearance of a polypropylene-based heat-adhesive conjugate fiber which is suitable for a hot roll bonding method and has high tensile strength and is useful as a material for a nonwoven fabric having excellent heat sealability.

[0004]

Means for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, propylene
96% by weight (hereinafter simply abbreviated as%), ethylene 2
A composite weight ratio (sheath component) is defined by using a crystalline copolymer composed of 10% and butene-12 to 10% (hereinafter sometimes simply referred to as a terpolymer) as a sheath component and crystalline polypropylene as a core component. (Core component) = 20/80 to 60/40. It was found that the intended purpose was achieved by drawing the composite undrawn yarn obtained by spinning at a draw ratio of less than 3.0.
The present invention has been completed. Hereinafter, the present invention will be described in more detail.

In the present invention, the terpolymer used for the sheath component of the conjugate fiber is a copolymer obtained by polymerizing propylene, ethylene and butene-1 with the known Ziegler-Natta catalyst to the above-mentioned respective component amounts. It is essentially a random copolymer. If the content of each of the comonomers (ethylene and butene-1) in the copolymer is less than 2%, the resulting fiber will have insufficient heat adhesion. As the content of the comonomer increases, the melting point of the copolymer decreases and the thermal adhesiveness also increases.However, since the surface friction coefficient of the obtained fiber increases and the processability in the card process and the like deteriorates, Those having a content higher than the above upper limit of 10% are not suitable for industrial production. In the present invention, the polypropylene used for the core component of the conjugate fiber is a crystalline polypropylene generally used for fibers.

[0006] The conjugate fiber of the present invention can be produced from the above terpolymer and crystalline polypropylene using a known sheath-core type composite yarn apparatus and drawing apparatus. In order to smoothly carry out this production, the terpolymer has a melt flow rate (A
According to STM D-1238 (L), the MFR may be 3-50, and the crystalline polypropylene preferably has an MFR of 3-50. Further, in the case of a production method in which stretching is not performed such as a spun bond method or a melt blow method, the MFR may be more than this range. The reason why the composite weight ratio of the sheath component and the core component (sheath component / core component) is limited to 20/80 to 60/40 is that if the sheath component is less than 20%, the thermal adhesiveness of the obtained fiber is reduced. Non-woven fabrics made of styrene cannot obtain sufficient tensile strength and heat sealability, and if the sheath component exceeds 60%, the thermal adhesiveness is sufficient but the thermal shrinkage of the fiber increases, and the dimensional stability is increased. Is reduced. still,
The relationship between the sheath component and the core component may be either concentric or eccentric, but the concentric type is preferred because the web shrinks little during heat treatment.

In the present invention, the composite undrawn yarn obtained by composite spinning into a sheath-core type is drawn at a draw ratio of less than 3.0, preferably at most 2.5, more preferably at most 2.0. I do. When the draw ratio is 3.0 or more, the molecular orientation of the composite fiber increases, the softening point and the melting point increase, and the thermal adhesiveness decreases. Can not. Further, since the heat shrinkage of the fiber is significantly increased, problems such as a decrease in the dimensional stability of the nonwoven fabric and the occurrence of spots occur. On the other hand, the heat-adhesive conjugate fiber drawn at a low draw ratio of less than 3.0 has a low single yarn strength, but has excellent heat-adhesiveness because the orientation is kept low, and a heat shrinkage. Is low.

[0008]

In general, the tensile strength of a nonwoven fabric obtained by the hot roll bonding method greatly depends on the strength of the single yarn of the heat-bondable fiber when the bonding points of the fibers are sufficiently strong.
On the other hand, when the bonding point is weak, the breaking of the nonwoven fabric is caused by the breaking of the bonding point, so that the tensile strength of the nonwoven fabric is hardly affected by the strength of the single yarn, and its value is very small. Since the conjugate fiber of the present invention suppresses the molecular orientation and improves the thermal adhesiveness, the strength of the single yarn is reduced by lowering the draw ratio, but the bonding point is strong. It can be secured.
Note that the stretching ratio of 1.0 means that stretching is not substantially performed, but this applies to the above-described spun bond method, melt blow method, or a case where only crimping is performed in a normal stretching step. . The heat-adhesive conjugate fiber of the present invention is a ternary copolymer in which the sheath component is mainly composed of propylene and contains an appropriate amount of a comonomer. Therefore, the affinity between the sheath component and the core component is extremely large. Since the peeling at the boundary surface of the sheath and core does not easily occur, not only a high strength, high heat sealing nonwoven fabric can be easily obtained by the hot roll method, but also thermal adhesion to other materials such as rayon and pulp. For example, these are cut into staples having an appropriate fiber length, mixed and formed into a web, and then heat-bonded to obtain a nonwoven fabric having a sufficient tensile strength.

[0009]

EXAMPLES The present invention will be described in detail with reference to Examples and Comparative Examples.
explain. The conjugate fiber and non-woven fabric obtained in each example
The physical properties of the cloth were evaluated by the following methods. Table 1 shows the results.
It was shown to. Non-woven fabric tensile strength: Use a miniature card machine for sample short fibers
About 20g / m ^TwoAt 130 ° C
Heated metal roll with a diameter of 165 mm (upper: convex area ratio is 2
Line between 5% embossing roll, bottom: flat roll)
Pressure of 20 kg / cm and a speed of 6 m / min.
Woven. From the obtained nonwoven fabric, the machine flow direction (hereinafter M
D) and a direction perpendicular to it (hereinafter referred to as D).
5cm each for CD)
Create a specimen of width and use a tensile tester to
Measure tensile strength at 10cm, tensile speed 10cm / min
Set. Heat sealability: Not used for measuring the tensile strength of the nonwoven fabric
Cut out a 5 cm wide sample from the woven fabric and use a high-density polyethylene
Len (sheath) / polypropylene (core) (50/50) composite
Approximately 20 g / m2 of fiber (2 d / f)^TwoNon-woven
Fabric (A) or polypropylene fiber (2d / f)
Weight 20g / m^TwoWidth cut from non-woven fabric (B)
A 5cm test piece and a tip are overlapped by 1cm in length,
3kg / cm^TwoThermocompression bonding at 150 ° C. for 3 seconds under pressure
Using a tensile tester as a composite material, gripping distance 10c
m, peel strength is measured at a pulling speed of 10 cm / min.
You. Web heat shrinkage: Short fiber sample was measured using a miniature card machine.
Is about 200g / m^TwoHot air circulating dry
Web after heat treatment at 145 ° C for 5 minutes in a dryer
Is measured in the MD direction.

EXAMPLE 1 As a sheath component, a terpolymer having an MFR of 15 consisting of (ethylene: 3%, butene-1: 5% and propylene: 82%) was used, and an MFR of 10 was used as a core component. And a composite ratio of 40/60 (sheath component / core component) at a spinning temperature of 300 ° C. by using a composite spinning apparatus equipped with a nozzle having a diameter of 0.6 mm.
The yarn was spun at a take-up speed of 1000 m / min to obtain a concentric sheath-core composite undrawn yarn having a single yarn fineness of 4.0 d / f. next,
This composite undrawn yarn is drawn 2.4 times at a drawing temperature of 95 ° C.
After applying mechanical crimping and drying at 80 ° C., the fiber was cut into 38 mm to obtain a conjugate fiber staple. Example 2 A composite fiber staple was obtained under the same conditions as in Example 1 except that the composite ratio of the sheath component and the core component was 60/40.

Comparative Examples 1-2 Composite fiber staples were obtained under the same conditions as in Example 1 except that the composite ratio of the sheath component and the core component was changed to 70/30 and 10/90. Example 3 Using the same raw material resin as in Example 1, a composite ratio of 50/50 was used.
Spinning was performed at a spinning temperature of 300 ° C. and a take-up speed of 1000 m / min to obtain a concentric sheath-core composite undrawn yarn having a single yarn fineness of 2.4 d / f. Next, the composite undrawn yarn was drawn at a draw ratio of 1.2.
The film was stretched under the conditions of a draw temperature of 95 ° C., mechanical crimped, dried at 80 ° C., and then cut to 38 mm to obtain a composite fiber staple. Examples 4 to 6 The single yarn fineness and the draw ratio of the composite undrawn yarn were set to (3.5 d / f:
(1.8 times), (4.0 d / f: 2.4 times) and (5.0 times)
(d / f: 2.8 times), composite fiber staples were obtained under the same conditions as in Example 3. Comparative Examples 3 and 4 The single yarn fineness and the draw ratio of the composite undrawn yarn were set to (5.5 d / f:
A composite fiber staple was obtained under the same conditions as in Example 3 except that (3.2 times) and (6.0 d / f: 3.6 times) were used.

Example 7 3 comprising a sheath component (ethylene: 7%, butene-1: 3% and propylene: 90%) having an MFR of 10
Using a base copolymer, crystalline polypropylene having an MFR of 10 as a core component, a composite ratio of 50/50, a spinning temperature of 300 ° C., and a take-off speed by a composite spinning apparatus equipped with a nozzle having a diameter of 0.6 mm. Spinning was performed at 1000 m / min to obtain a concentric sheath-core composite undrawn yarn having a single yarn fineness of 3.5 d / f. Next, this composite undrawn yarn is drawn under the conditions of a draw ratio of 1.8 times and a drawing temperature of 95 ° C., and mechanical crimping is performed.
After drying at 80 ° C., it was cut to 38 mm to obtain a conjugate fiber staple. Example 8 A composite was prepared under the same conditions as in Example 7, except that a terpolymer having an MFR of 10 and comprising a sheath component (ethylene: 2%, butene-1: 7% and propylene: 91%) was used. Fiber staples were obtained.

Comparative Example 5 The same conditions as in Example 7 were used except that a ternary copolymer containing 1% each of ethylene and butene-1 and 98% propylene and having an MFR of 15 was used as a sheath component. A composite fiber staple was obtained.

[0014]

[Table 1]

[0015]

The conjugate fiber of the present invention has a good feel (feel), high strength, and heat sealability when it is formed into a web having a desired basis weight using a card machine and then subjected to point bonding with a hot roll. This nonwoven fabric can be used as a surface material of sanitary materials such as sanitary napkins and disposable diapers, or as a medical material such as surgical gowns. Further, the nonwoven fabric obtained by the wet method using the conjugate fiber of the present invention also has high strength and high heat sealability, and thus is widely used not only in the general paper field but also as a tea bag and other packaging materials.

Claims (1)

(57) [Claims] 1. 88 to 96% by weight of propylene (hereinafter simply referred to as%), 2 to 10% of ethylene, and butene-1
Unstretched composite obtained by spinning a crystalline copolymer consisting of 2 to 10% as a sheath component and a crystalline polypropylene as a core component at a composite ratio (sheath component / core component) of 20/80 to 60/40. A method for producing a conjugate fiber, comprising drawing a yarn at a draw ratio of less than 3.0.