JPH06184822A - Thermal adhesive conjugate fiber - Google Patents

Abstract

PURPOSE:To provide a PE/PP thermally adhesive conjugate fiber capable of preventing the generation of a perforation phenomenon even when the linear pressure of a heat roller is raised to form nonwoven fabric. CONSTITUTION:The thermally adhesive conjugated fiber is characterized in that the sheath part of the fiber comprises a low melting point polymer containing at least two components of A: polyethylene and B: a random copolymer containing propylene as a main monomer and at least ethylene as a copolymerization component, and in that the core part comprises crystalline polypropylene.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoadhesive conjugate fiber, and more particularly to a thermoadhesive conjugate fiber suitable as a material for obtaining a nonwoven fabric for disposable use by a heat roller method.

[0002]

BACKGROUND OF THE INVENTION Thermoadhesive composite fibers can be made into a non-woven fabric relatively easily by the heat of hot air or a heat roller without using an adhesive, so that they are disposable sanitary materials typified by disposable diapers and sanitary napkins. Widely used in. Various types of heat-adhesive conjugate fibers have been developed, but as a material for the top sheet of a paper diaper that requires a particularly dry feel, a sheath-core type using polyethylene for the sheath portion, Among them, those using polyethylene for the sheath portion and crystalline polypropylene for the core portion (hereinafter sometimes abbreviated as PE / PP fiber) are preferably used.
By the way, in order to provide disposable products at low cost to consumers, it is necessary to manufacture these products with high productivity, and one method is to make the heat-adhesive conjugate fiber into a non-woven fabric by the heat roller method. Is being done.

[0003]

However, since the products for disposable use have low added value, it is currently desired to further improve the productivity in order to reduce the cost. As a method of improving the productivity in the production of a nonwoven fabric by the heat roller method, there are a method of raising the temperature of the heat roller and a method of raising the linear pressure of the heat roller. In that case, the following problems occur.

(1) When the temperature of the heat roller is raised Since the melt viscosity of the resin decreases as the temperature rises,
The spread of the resin at the crimping point between the fibers becomes large.
Along with this, the contact area with the roller increases, and the peeling force from the roller also increases. The strength of the core decreases as the temperature rises. Since the rotation speed of the roller is high, it has to be separated from the roller before it is sufficiently cooled. Due to the above reasons, the non-woven fabric is torn and wrapped around the roller. When the winding around the roller occurs, the temperature of the roller must be once lowered and then the wound non-woven fabric must be removed, but this removing work is very troublesome. For this reason, a method of increasing the linear pressure, which is a method in which wrapping does not occur, is preferable.

(2) When the linear pressure of the heat roller is increased: As the pressure increases, the spread of the resin at the crimping point of the fibers increases. Along with this, the contact area with the roller increases, and the peeling force from the roller also increases. The non-woven fabric becomes locally thin and weak areas are created. Due to the same situation as the above (1), it is not sufficiently cooled. Due to the combination of the above and, the perforation phenomenon occurs.
When the perforation phenomenon occurs, the shape (look) of the nonwoven fabric becomes unsatisfactory, so that the commercial value is reduced or eliminated.

The relationship between the temperature and linear pressure of the heat roller and the properties of the resulting nonwoven fabric generally has the tendency shown in Table 1 below.

[0007]

[Table 1]

The following (a) to (c) can be considered as means for suppressing the occurrence of the perforation phenomenon that occurs when the linear pressure of the heat roller is increased. (A) Use an embossing roller having a small adhesion area (the number of adhesion points per unit area). (B) A release agent is applied to the roller surface. (C) A thermoadhesive conjugate fiber in which the spread of the resin at the crimping point is small is used. However, the above method (a) is not suitable because it leads to a decrease in the strength of the nonwoven fabric. In the method (b), the release agent is transferred to the nonwoven fabric immediately, so that the release agent must be applied frequently, which is very troublesome. further,
Since the effect of the release agent transferred to the non-woven fabric on the human body is unknown, there remains a problem in terms of safety. Therefore, the method of (c) above is considered, but in the existing PE / PP-based fiber, the resin spreads at the pressure-bonding point so that when the linear pressure of the heat roller is increased to make it into a non-woven fabric, a perforation phenomenon occurs. Is very difficult to control.

The present invention has been made in view of the above-mentioned present situation of manufacturing nonwoven fabrics, and an object of the present invention is to suppress the occurrence of the perforation phenomenon even when the linear pressure of the heat roller is increased to make the nonwoven fabric. It is to provide a PE / PP-based heat-bondable composite fiber that can be used.

[0010]

The present invention has been made to achieve the above object, and the heat-adhesive conjugate fiber of the present invention has a sheath portion, High density polyethylene, and B. The present invention is characterized in that the main component of the monomer is propylene and it is made of a low melting point polymer containing at least two components as a copolymerization component and a random copolymer containing at least ethylene, and the core part is made of crystalline polypropylene.

The present invention will be described in detail below. The sheath portion of the heat-adhesive conjugate fiber of the present invention is composed of a low melting point polymer containing at least two components of the high density polyethylene (A) and the random copolymer (B). Here, as the high-density polyethylene of A, various high-density polyethylene conventionally used as a material for the heat-bondable composite fiber can be used.

The random copolymer of B must also contain at least ethylene as a copolymerization component in addition to propylene as the main component as described above. The reason is that the random copolymer of B and the high-density polyethylene of A are melt-spun in a mixed state, but if both components are not uniformly mixed at this time, spinning cannot be performed. As such a random copolymer, in addition to ethylene-propylene random copolymer, ethylene-propylene-butene-1 random copolymer containing ethylene-propylene and α-olefin as the third copolymerization component is preferable. Used for.

The sheath portion in the heat-adhesive conjugate fiber of the present invention may be a low melting point polymer consisting of only two components of the high density polyethylene of A and the random copolymer of B, or these two components. Besides, it may be a three-component low melting point polymer containing a linear low-density polyethylene as the third component. By incorporating linear low-density polyethylene as the third component, spinnability can be improved.

When the sheath is made of a low-melting polymer consisting of only two components, the high-density polyethylene A and the random copolymer B, the proportion of the random copolymer in the low-melting polymer is 15 wt% or less. Preferably. As the proportion of random copolymer increases, the degree of perforation in the nonwoven decreases, but
When it exceeds wt%, the peculiar meeting of polyethylene is lost.
On the other hand, if it is less than 5% by weight, the effect due to the addition of the random copolymer is insufficient. From the viewpoint of cost, it is preferable to set the upper limit of the proportion of the random copolymer to 10 wt%. A particularly desirable ratio of the random copolymer is 5 to 10% by weight.

When the sheath is formed of a three-component low-melting polymer containing a linear low-density polyethylene as the third component, the proportion of the linear low-density polyethylene in the low-melting polymer has a spinnability. A small amount that is improved is sufficient. When the content of the linear low-density polyethylene is increased, stable spinning can be achieved even if the random copolymer of B is contained in a large amount. It's not a good idea because it only spoils the peculiarities of polyethylene and polyethylene.

By forming a sheath portion from such a low melting point polymer, the melting point of the sheath portion can be increased without impairing the dry feel peculiar to polypropylene, and the spread of the resin during pressure bonding can be suppressed. it can. Then, by increasing the melting point of the sheath and suppressing the spread of the resin at the time of pressure bonding, it becomes possible to suppress the occurrence of the perforation phenomenon even when the linear pressure of the heat roller is increased.

On the other hand, the type of crystalline polypropylene forming the core in the thermoadhesive conjugate fiber of the present invention is not particularly limited, and various crystals conventionally used as materials for the thermoadhesive conjugate fiber. Polyethylene can be used.

The heat-adhesive conjugate fiber of the present invention is not particularly limited except that the above polymer is used as the polymer of the sheath portion and the core portion, and is formed in the same manner as the conventional PE / PP fiber. It The thermoadhesive conjugate fiber of the present invention may be concentric or eccentric, but the concentric type is particularly preferable. The heat-adhesive conjugate fiber of the present invention is spun and stretched based on a usual method for producing a sheath-core type conjugate fiber, and further subjected to mechanical crimping or natural crimping of about 8 to 20 pieces / inch by a conventional method. Therefore, it can be easily obtained. The draw ratio at this time is preferably 3 to 5 times. From the viewpoint of suppressing the occurrence of the perforation phenomenon, it is preferable that the stretching ratio is high.

In obtaining a nonwoven fabric by the heat roller method using the heat-adhesive conjugate fiber of the present invention as a material, the heat-adhesive conjugate fiber of the present invention may be used alone or may be mixed with rayon, polyester fiber or the like to obtain a conventional method. A web is produced by the above method, and the web is fused at a roller temperature of about 130 to 145 ° C.
The linear pressure of the heat roller at this time can be made higher than before.

[0020]

When the thermoadhesive conjugate fiber of the present invention is used,
Even if the linear pressure of the heat roller is increased, the viscosity of the resin at the time of pressure bonding is high, so the resin does not spread much at the pressure bonding point. Therefore, the peeling from the roller is relatively smooth, and the phenomenon of winding around the roller or punching does not occur. As a result, conventional PE /
Since the linear pressure of the heat roller can be increased as compared with the case of manufacturing a nonwoven fabric by the heat roller method using PP fibers,
It becomes possible to manufacture a nonwoven fabric at a high production rate.

[0021]

EXAMPLES Examples of the present invention will be described below.
The invention is not limited to these examples. Example 1 (1) Production of heat-adhesive conjugate fiber UBE Polypro ZS1276 [product name, melt flow rate (MFR) = 30] manufactured by Ube Industries, Ltd. was used as the crystalline polypropylene of the core part, and the sheath part was made low. As the melting point copolymer, 90 parts by weight of high-density polyethylene [Suntech J310 (product name) manufactured by Asahi Kasei Co., Ltd., MFR = 20] and ethylene-propylene random copolymer [Idemitsu Polypro Y2035G manufactured by Idemitsu Petrochemical Co., Ltd. (product Name), M
FR = 20, ethylene content = 4 wt%] Using a mixture of 10 parts by weight, two single-screw extruders and a hole diameter of 0.6
A non-stretched concentric sheath core in which the cross-sectional area ratio of the sheath portion to the core portion is 4/6 and the single yarn danyl is 6.0 de by a concentric sheath-core type composite fiber spinning equipment equipped with a circular nozzle for composite fiber of mm. A type composite fiber was obtained. Then, this concentric sheath-core type composite fiber was added to 3.7
It was drawn twice and mechanically crimped to obtain a heat-adhesive conjugate fiber of the present invention composed of staple fibers having a fiber length of 51 mm, a single yarn denier of 2.0 de, and a crimping number of 14 pieces / inch.

(2) Manufacture of Nonwoven Fabric First, the obtained staple fiber was passed through a card machine to prepare a uniform web having a basis weight of 20 g / m ² . Then, using an embossing roller having a roller diameter of 150 mmφ and an adhesion area ratio of 17%, a non-woven fabric was produced under the conditions of an embossing roller temperature of 136 ° C., a flat roller temperature of 141 ° C., a linear pressure of 100 kg / cm, and a roller speed of 21 m / min. Table 2 shows the physical properties of the obtained nonwoven fabric.

Comparative Example 1 First, a staple fiber was obtained in the same manner as in Example 1 except that ethylene-propylene random copolymer was not used as a raw material for the sheath. Using this staple fiber and the same embossing roller as in Example 1, a total of three types of nonwoven fabrics were produced under the conditions shown in Table 2. Table 2 shows the physical properties of the obtained non-woven fabrics.

[0024]

[Table 2]

As is clear from Table 2, when the fiber of the comparative example is used, the perforation phenomenon becomes conspicuous when the linear pressure is increased and the roller speed is increased. On the other hand, when the fiber of the example is used, even if the linear pressure is increased and the roller speed is increased, the perforation phenomenon does not occur, and high-speed production is possible. Moreover, the strength of the non-woven fabric and the dry feel unique to polyethylene are not impaired.

[0026]

As described above, by using the heat-adhesive conjugate fiber of the present invention, a high-strength nonwoven fabric can be produced at high speed by the heat roller method without impairing the dry feel peculiar to polyethylene. Will be possible.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yutaro Kasai 2-1-1 Yabuda Nishi, Gifu City, Gifu Ube Nitto Kasei Co., Ltd.

Claims (2)

[Claims] 1. The sheath comprises: High density polyethylene, and B. A sheath-core type thermal adhesive characterized in that the main component of the monomer is propylene and a low-melting polymer containing at least two components of a random copolymer containing at least ethylene as a copolymerization component, and the core part is made of crystalline polypropylene. Composite fiber. 2. The low melting point polymer is A. High density polyethylene, and B. The heat according to claim 1, wherein the main component of the monomer is propylene and a random copolymer containing at least ethylene as a copolymerization component, and the proportion of the random copolymer in the low melting point polymer is 15 wt% or less. Adhesive composite fiber.