JPH055261A - Nonwoven fabric consisting of conjugate type filament - Google Patents

Abstract

PURPOSE:To obtain the title nonwoven fabric useful for disposable diaper, etc., and having excellent softness and high density by binding a conjugate type monofilament formed of a specific copolymer and isotactic polypropylene to the above-mentioned copolymer by melt solidification. CONSTITUTION:The objective nonwoven fabric consisting of a conjugate type filament formed of (A) ethylene-propylene random copolymer having 2-5% ethylene content and <=155 deg.C melt peak temperature and (B) isotactic polypropylene and having core-sheath structure each containing the component A as a sheath component and the component B as a core component and obtained by binding the component A to the component B by melt-solidifying the component A with hot air, etc. The nonwoven fabric may have ordinary structure where the component A is bonded to the component B in a state of the components A and B having half-moon cross section.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-woven fabric composed of composite long fibers, which has a particularly high strength and excellent flexibility and can be suitably used as a surface material for sanitary materials such as disposable diapers and sanitary napkins. It relates to a non-woven fabric.

[0002]

2. Description of the Related Art At present, long-fiber nonwoven fabrics represented by spunbonded nonwoven fabrics are used in various fields. The spunbonded nonwoven fabric has advantages that it has high tensile strength and high productivity as compared with a short fiber nonwoven fabric, particularly a card type short fiber nonwoven fabric produced by using a card machine. However, on the other hand, it has the drawback of lacking flexibility. Therefore, the card type short fiber non-woven fabric has been used in a larger amount than the spun bond non-woven fabric for the purpose of directly contacting human skin such as a surface material of a disposable diaper.

However, since the spunbonded non-woven fabric is superior in terms of productivity, the spunbonded non-woven fabric is cost-effective for the disposable use such as the surface material of the disposable diaper. Therefore, various attempts have been made to obtain a flexible spunbonded nonwoven fabric. For example, a non-woven fabric has been proposed in which a composite long fiber composed of a low melting point component and a high melting point component is used to obtain a fibrous web, and then the fibrous web is spot fused at intervals.
In this non-woven fabric, the low melting point component is melted and solidified in the spot fusion zone and the long fibers are bonded to each other. Therefore, the long fibers are not bonded to each other in the area other than the spot fusion-bonding area, and the long fibers are in a state of being easily moved, so that the flexibility is excellent. However, nonetheless, it was not sufficiently flexible.

[0004]

The inventors of the present invention have made various studies in order to obtain a more flexible long-fiber nonwoven fabric, and have found that the following points have not been taken into consideration. That is, no consideration was given to the low melting point component of the composite long fibers used. Since this low melting point component acts as an adhesive in the spot fusion bonding area, it has been conventionally selected on the basis of a low melting point and high adhesive strength. However, in the area other than the spot fusion zone, this low melting point component also forms a part of the long fiber, and therefore affects the flexibility of the long fiber itself.

Therefore, according to the present invention, a relatively flexible material is selected as the low melting point component, and a high melting point component having an affinity with the low melting point component is selected so that the fiber itself has a high flexibility. It is intended to provide a nonwoven fabric having high strength and excellent flexibility by obtaining a long fiber nonwoven fabric by using fibers.

[0006]

Means for Solving the Problems That is, the present invention relates to a first component comprising an ethylene-propylene random copolymer having an ethylene content of 2 to 5% and a melting peak temperature of 155 ° C. or less, and isotactic As a constituent fiber, a composite long fiber formed with a second component made of tic polypropylene,
Further, the present invention relates to a nonwoven fabric characterized in that the composite long fibers are bound to each other by melting and solidifying the first component.

An ethylene-propylene random copolymer is used as the first component, that is, the low melting point component of the composite long fibers which are the constituent fibers of the nonwoven fabric according to the present invention. This ethylene-propylene random copolymer has an ethylene content of 2 to 5%. When the ethylene content is less than 2%, the first component does not exhibit a satisfactory degree of flexibility, which is not preferable. Further, the melting point difference from the second component, isotactic polypropylene, becomes small, and it becomes difficult to use as an adhesive component, which is not preferable. On the other hand, when the ethylene content exceeds 5%, the flexibility cannot be improved any more, and it is difficult to set the spinning conditions, which is not preferable. Ethylene content 2-5
%, Ethylene is assumed to be 100%, and ethylene 2
.About.5% and propylene 98 to 95% are charged and polymerized to produce an ethylene-propylene random copolymer.

The melting peak temperature of this ethylene-propylene random copolymer is 155 ° C. or lower. Here, the melting peak temperature is measured by the following measuring method. That is, the differential scanning calorimeter was used to measure the temperature at which a melting peak was obtained when the ethylene-propylene random copolymer was cooled from the molten state at a cooling rate of 10 ° C./min. If the melting peak temperature exceeds 155 ° C., the melting peak temperature difference from the isotactic polypropylene that is the second component becomes small, and it becomes difficult to use the first component as an adhesive component, which is not preferable.

The melt flow rate (hereinafter referred to as "MFR") of this ethylene-propylene random copolymer is preferably about 10-60. Where M
FR is measured under JIS K 7210 Table 1, Condition 14. The reason for setting the MFR to this level is to make it similar to the MFR of the second component, isotactic polypropylene, so as to facilitate composite melt spinning.

Isotactic polypropylene is used as the second component forming the composite long fibers, that is, the high melting point component. As the isotactic polypropylene, a conventionally known one is used. The reason for using isotactic polypropylene as the second component is that it has good affinity with the ethylene-propylene random copolymer as the first component. For example, if polyester is used as the second component, the affinity with the ethylene-propylene random copolymer is not sufficient, the adhesive strength with the first component is insufficient, and it becomes difficult to obtain a high-strength nonwoven fabric, Not preferable. The melting point difference between the isotactic polypropylene that is the second component and the ethylene-propylene random copolymer that is the first component is preferably about 20 ° C.

The first component and the second component are combined in an arbitrary structure to form a composite long fiber. In the present invention,
In particular, it is preferable to form a composite long fiber by joining the core-sheath structure or the parallel structure. In the case of the core-sheath structure, the first component is the sheath component and the second component is the core component. The reason why the first component is the sheath component is that the first component is an adhesive component, which is for bonding the long fibers to each other, and therefore needs to be present on the surface of the long fibers. In the case of the parallel structure, the cross section of both the first component and the second component is a half moon shape, and the chord portions are joined to each other, which is a so-called side-by-side composite type. is there. The ratio of the first component and the second component in this composite long fiber is preferably first component: second component = 1 to 9: 9 to 1. If the proportion of the first component is less than this range, the adhesion between the long fibers is not sufficient, and it tends to be difficult to obtain a high-strength nonwoven fabric. Further, if the proportion of the first component is higher than this range, the number of locations where the first component is melted and solidified in the non-woven fabric increases, and the flexibility of the non-woven fabric tends to decrease. Further, the fineness of the composite continuous fiber used in the present invention is preferably about 2 to 5 denier. A composite continuous fiber having a fineness of less than 2 denier is not practical because it is difficult to carry out melt composite spinning. If a fineness of more than 5 denier is used, the rigidity of the long fibers becomes large, and the resulting nonwoven fabric tends to be less flexible.

In the nonwoven fabric according to the present invention, the composite long fibers described above are used as constituent fibers, and the composite long fibers are bonded to each other by melting and solidifying the first component. In order to obtain such a nonwoven fabric, for example, the following method can be adopted. First, the composite long fibers are spun by the composite melt spinning method, and then the composite long fibers are accumulated on a moving wire mesh conveyor to form a fibrous web. Then, the fibrous web is partially heated at intervals or by blowing hot air to the entire fibrous web to heat the first component, and then the first component is solidified to obtain a long length. Connect fibers to each other. At this time, the heating temperature is generally set to a temperature equal to or higher than the melting point of the first component and lower than the melting point of the second component. When the melting point is lower than the melting point of the first component, the first component does not melt, the long fibers cannot be bonded well to each other, and a high-strength nonwoven fabric tends to be difficult to obtain. Also, when heated above the melting point of the second component, the first component and the second component will also melt, the fiber morphology collapses,
A non-woven fabric having good flexibility tends to be difficult to obtain. As described above, the nonwoven fabric according to the present invention is obtained.

When a composite long fiber having a core-sheath structure is used, it is preferable to obtain a nonwoven fabric by partially heating at intervals. Specifically, the fibrous web is introduced between the heated embossing roll and the smooth roll. Then, at the location of the fibrous web corresponding to the convex portion of the embossing roll, the sheath component is melted and solidified, the long fibers are bonded to each other, and a non-woven fabric having spaced point fusion zones is obtained. For example, when a nonwoven fabric is obtained by the following method, the flexibility tends to decrease. That is, the fibrous web is introduced between a heated smooth roll and a smooth roll, or when hot air is blown to the entire fibrous web, all the first components forming the entire surface of the long fibers are melted, There is a tendency for long fibers to bond to each other throughout the nonwoven fabric. Therefore, the long fibers become difficult to move,
This makes it difficult to obtain a non-woven fabric having good flexibility.

When the composite long fibers having a parallel structure are used, it is also preferable to partially heat them at intervals to obtain a non-woven fabric, and hot air is blown over the entire fibrous web. It is also preferable to obtain a non-woven fabric.
This is because in the case of the composite continuous fiber having the parallel structure, the entire surface of the fiber is not formed with the first component. That is, in the case of the composite type continuous fibers having the parallel structure, the contact points between the continuous fibers in the fibrous web are the first components (this is referred to as A part) and the second components (this is B part). And the first component and the second component (this is referred to as C part). Therefore, even if the entire fibrous web is heated, in the portion B, the long fibers do not melt and solidify, and the long fibers easily move in this part. Therefore, the flexibility of the obtained non-woven fabric is not lower than that of the one having a core-sheath structure. Further, when hot air is blown to obtain a non-woven fabric, the fibrous web is not compressed in the thickness direction as compared with the case where the fibrous web is introduced between smooth rolls, so that there is also an advantage that a bulky non-woven fabric can be obtained. ..

The basis weight of the nonwoven fabric according to the present invention can be arbitrarily determined, but is generally 10 g / m ^{2 to} 30 g / m ^2.
It is preferably about the same. If the basis weight is less than 10 g / m ² , the nonwoven fabric is too thin and difficult to handle,
Alternatively, it is unsuitable for use as a surface material for disposable diapers. On the other hand, when the basis weight exceeds 30 g / m ² , the nonwoven fabric tends to be thick and the flexibility tends to decrease. As described above, the non-woven fabric according to the present invention can be suitably used mainly as a surface material of sanitary materials such as disposable diapers and sanitary napkins, and can also be used as a base material for wiping cloths and a material for clothing.

[0016]

The non-woven fabric according to the present invention comprises a first component comprising the above-mentioned specific ethylene-propylene random copolymer,
A composite long fiber formed with a second component made of isotactic polypropylene is used as a constituent fiber.
The ethylene-propylene random copolymer serves as an adhesive component for bonding the composite long fibers to each other and imparts flexibility to the composite long fibers. The reason why the ethylene-propylene random copolymer imparts flexibility to the composite long fibers is as follows. That is, the ethylene component imparts irregularity to the copolymer, which reduces the crystallinity of the copolymer. When the crystallinity decreases,
This is because the density of the copolymer is reduced and therefore the rigidity of the copolymer is reduced. On the other hand, isotactic polypropylene is a skeleton component of the composite long fiber and imparts high strength to the composite long fiber. Therefore, the non-woven fabric including the composite long fiber as a constituent fiber also has high strength.

[0017]

[Examples] Tensile strength, texture, and
The apparent density and bulkiness are measured and calculated by the following methods. [Tensile strength] The tensile strength in the longitudinal and transverse directions was measured by the Tensilon tensile test according to JIS L 1096, and the average value of both was calculated. [Hand feeling] With the handle odometer method of JIS L 1096 E method,
The vertical and horizontal textures were measured, and the average value of both was calculated. The size of the sample was 20 cm × 20 cm, and the slot width was 6.35 mm. [Apparent Density and Bulkiness] Using a compression tester KES-FB3 manufactured by Kato Tech Co., Ltd., the thickness under a load of 0.5 g / cm ² is measured with a measurement area of 2 cm ² , and this is defined as A (mm). Also 50g
/ Cm ² Measure the thickness under load and call this B (mm). When the basis weight of the measured sample is M (g / m ² ), X = M / (A × 1000) is calculated and X is taken as the apparent density (g / cm ³ ). Also, Y = [(A−B) / A] × 1
00 is calculated and Y is taken as the bulkiness (%).

Example 1a An ethylene-propylene random copolymer (MFR30, ethylene content 4.5%, melting peak temperature 139.9 ° C) was used as the first component (sheath component), and isotactic polypropylene (MFR30, melting peak temperature 161.6 ° C). Was used as a second component (core component) and several core-sheath type composite spinnerets with 120 holes were used for composite melt spinning. The spinning conditions at this time were such that the spinning temperature was 230 ° C., the single hole discharge rate was 1 g / min, and the composite ratio of the sheath component and the core component was 1: 1. Immediately after spinning, it was stretched by air sucker to obtain a composite long fiber having a fineness of 2 denier. This composite type long fiber was opened and accumulated by a fiber opening device and a web forming device provided below the air sucker to obtain a fiber web having a basis weight of 23 g / m ² .
This fibrous web was introduced between a pair of rolls consisting of a hot embossing roll in the upper stage and a smooth roll in the lower stage, and was partially fusion-bonded to obtain a nonwoven fabric in which the total area of the fusion-bonded region was 5%. .. The hot embossing roll at this time was provided with a large number of convex portions, and the tips of the convex portions were round and had a diameter of 0.6 mm. The temperature of the hot embossing roll was 130 ° C.

Example 1b A nonwoven fabric was obtained in the same manner as in Example 1a except that the temperature of the hot embossing roll was 140 ° C.

Example 2a An ethylene-propylene random copolymer (MFR30, ethylene content 4.5%, melting peak temperature 139.9 ° C) was used as the first component, and isotactic polypropylene (MFR30,
The composite melt spinning was performed by using several parallel type composite spinnerets with 120 holes as the second component having a melting peak temperature of 161.6 ° C).
The spinning conditions at this time were such that the spinning temperature was 230 ° C., the single hole discharge rate was 1 g / min, and the composite ratio of the first component and the second component was 1: 1. Immediately after spinning, it was stretched with air sucker to obtain a composite continuous fiber having a parallel structure with a fineness of 2 denier, in which the chord portions of the first component and the second component having a semi-lunar cross section were joined. This composite type long fiber, by the fiber opening device provided below the air sucker, the web forming device,
The fibers were opened and collected to obtain a fiber web having a basis weight of 23 g / m ² . This fibrous web was introduced between a pair of rolls consisting of a hot embossing roll in the upper stage and a smooth roll in the lower stage, and was partially fusion-bonded to obtain a nonwoven fabric in which the total area of the fusion-bonded area was 5%. .. At this time, the hot embossing roll is provided with a large number of protrusions, and the tips of these protrusions are round and have a diameter of 0.6 m.
It was m. The temperature of the hot embossing roll was 130 ° C.

Example 2b A nonwoven fabric was obtained in the same manner as in Example 2a except that the temperature of the hot embossing roll was 140 ° C.

Example 3a The fibrous web obtained in Example 2a was introduced into a hot air circulation type rotary dryer, and hot air having a temperature of 160 ° C. was blown onto the fibrous web. The hot air melted or softened the first component of the composite long fibers to bond the composite long fibers to each other to obtain a nonwoven fabric.

Example 3b A nonwoven fabric was obtained in the same manner as in Example 3a except that the temperature of hot air was 170 ° C.

Comparative Example 1 Using only the first component (core component), isotactic polypropylene, used in Example 1a, spinning temperature 230
Melt spinning was performed at 0 ° C. to obtain a non-composite type long fiber having a fineness of 2 denier. This non-composite type long fiber was treated in the same manner as in Example 1a to obtain a fiber web having a basis weight of 23 g / m ² . Then, this fibrous web was introduced between the pair of rolls used in Example 1a to obtain a non-woven fabric in which the total area of the spot fusion bonded area was 5%. In addition,
At this time, the temperature of the hot embossing roll was 150 ° C.

COMPARATIVE EXAMPLE 2 The fibrous web obtained in Comparative Example 1 was used and introduced into the hot air circulation type rotary dryer used in Example 3a to obtain a nonwoven fabric. At this time, the temperature of the hot air was 185 ° C.

Table 1 shows the tensile strength, feel, apparent density and bulkiness of the nonwoven fabrics obtained in Examples 1a to 3b and Comparative Examples 1 and 2.

[Table 1] As is clear from the place shown in Table 1, Examples 1a to 2
In the non-woven fabric obtained in b, only the ethylene-propylene random copolymer, which is the first component, is melted and solidified in the spot fusion-bonded area to bond the composite long fibers to each other, and the composite long fibers in the other areas are combined. The fiber contains the ethylene-propylene random copolymer in its original form. Therefore, it can be seen that the nonwoven fabric has high tensile strength, excellent texture, and has both strength and flexibility. Example 3
In the non-woven fabrics obtained in a and 3b, the first component is in contact with the composite long fibers, and the ethylene-propylene random copolymer as the first component is melted and solidified to form a space between the composite long fibers. Are connected. The ethylene-propylene random copolymer, which is the first component, remains in the original form in the portion where the first component is not in contact with the composite long fibers. Therefore, it can be seen that the nonwoven fabric has high tensile strength, excellent texture, and has both strength and flexibility. The non-woven fabrics obtained in Comparative Examples 1 and 2 have non-composite filaments composed of only an isotactic polypropylene component as constituent fibers, and thus the constituent fibers themselves have poor flexibility, and thus are obtained in Examples. It is inferior to non-woven fabric in terms of texture.

[0027]

As described above, the nonwoven fabric according to the present invention is a composite formed of the first component made of a specific ethylene-propylene random copolymer and the second component made of isotactic polypropylene. The long fibers are used as constituent fibers. Therefore, the ethylene-propylene random copolymer exerts the effect of imparting flexibility to the composite long fibers and thereby imparting flexibility to the nonwoven fabric. In addition, since the composite long fibers are bonded to each other by using the ethylene-propylene random copolymer as an adhesive component, there is an effect that a nonwoven fabric excellent in strength can be obtained.

[Procedure amendment]

[Submission date] July 15, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

[0004]

The inventors of the present invention have made various studies in order to obtain a more flexible long-fiber nonwoven fabric, and have found that the following points have not been taken into consideration. That is, the had not been considered at all for the low melting component of the composite length O維used. Since this low melting point component acts as an adhesive in the spot fusion bonding area, it has been conventionally selected on the basis of a low melting point and high adhesive strength. However, in the area other than the spot fusion zone, this low melting point component also forms a part of the long fiber, and therefore affects the flexibility of the long fiber itself.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

In the nonwoven fabric according to the present invention, the composite long fibers described above are used as constituent fibers, and the composite long fibers are bonded to each other by melting and solidifying the first component. In order to obtain such a nonwoven fabric, for example, the following method can be adopted. First, the composite long fibers are spun by the composite melt spinning method, and then the composite long fibers are accumulated on a moving wire mesh conveyor to form a fibrous web. Then, this fiber web, by partially heating at intervals, or throughout the fibrous web and more heating by blowing hot air, to melt the first component, by subsequently solidifying the first component, The long fibers are bonded to each other.
At this time, the heating temperature is generally set to a temperature equal to or higher than the melting point of the first component and lower than the melting point of the second component. When the melting point is lower than the melting point of the first component, the first component does not melt, the long fibers cannot be bonded well to each other, and a high-strength nonwoven fabric tends to be difficult to obtain. Further, when the temperature is higher than the melting point of the second component, both the first component and the second component are melted, the fiber form is broken, and it tends to be difficult to obtain a nonwoven fabric having good flexibility. As described above, the nonwoven fabric according to the present invention is obtained.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

The basis weight of the non-woven fabric according to the present invention is a matter that can be arbitrarily determined, but is generally 10 g / m ^{2 to} 30 g.
/ M ² is preferable. Unit weight is 10g / m ²
If it is less than the above range, the nonwoven fabric is too thin and difficult to handle, or is not suitable for use as a surface material of a disposable diaper. On the other hand, when the fabric weight exceeds 30 g / m ² , the nonwoven fabric tends to be thick and the flexibility tends to decrease. As described above, the nonwoven fabric according to the present invention can be suitably used mainly as a surface material for sanitary materials such as disposable diapers and sanitary napkins, and can also be used as a base cloth for wiping cloth and a material for clothing.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction content]

Comparative Example 1 Using only the second component (core component), isotactic polypropylene, used in Example 1a, the spinning temperature was 23.
Melt spinning was performed at 0 ° C. to obtain a non-composite type long fiber having a fineness of 2 denier. This non-composite type long fiber was processed in the same manner as in Example 1a,
A fiber web having a basis weight of 23 g / m ² was obtained. Then, this fibrous web was introduced between the pair of rolls used in Example 1a to obtain a non-woven fabric in which the total area of the spot fusion bonded area was 5%. At this time, the temperature of the hot embossing roll was 150 ° C.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location D04H 3/03 A 7199-3B 3/14 A 7199-3B // D01F 6/30 7199-3B

Claims (1)

1. A first component comprising an ethylene-propylene random copolymer having an ethylene content of 2 to 5% and a melting peak temperature of 155 ° C. or lower, and isotactic polypropylene. A non-woven fabric comprising composite long fibers formed with a second component as constituent fibers, and by melting and solidifying the first component, the composite long fibers are bonded to each other. 2. A composite long filament having a core-sheath structure, wherein the first component is a sheath component and the second component is a core component.
The non-woven fabric described. 3. A composite continuous filament having a parallel structure in which each of the first component and the second component has a half-moon-shaped cross section, and the first component and the second component are joined to each other. Non-woven fabric.