JPS63243324A - Heat bonding fiber and nonwoven fabric thereof - Google Patents

Abstract

PURPOSE:To obtain the titled nonwoven fabric, having soft feeling and high tenacity and useful as diapers, etc., by using a low-density copolymer of ethylene with octene-1 having specific physical properties as a sheath component and a blend structure thereof with crystalline polypropylene as a core component. CONSTITUTION:A heat bonding fiber obtained by carrying out melt conjugate spinning using (A) linear low-density polyethylene which is a low-density copolymer of ethylene and octene-1 and 1-15wt.% octene-1 content having 0.900-0.940g/cm<3> density, 5-100g/10min melt index measured by the method of ASTM D-1238 (E) and >=25cal/g heat of melting as a sheath component and a blend structure of 99-50wt.% component (A) with 1-50wt.% crystalline polypropylene having <=20g/10min melt flow rate measured by the method of ASTM D-1238 (L) as a core component. The resultant heat bonding fiber is then formed into a web by a conventional method and heat-treated to afford the aimed nonwoven fabric.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to thermal adhesive fibers and nonwoven fabrics thereof.

(Prior Art) In the production of nonwoven fabrics, methods for adhering fibers to each other include a method of entangling fibers such as a needle punch method, and a method of using various adhesives as a binder.

In applications such as disposable diapers and covering paper for sanitary absorbent materials, the demand for which has increased rapidly in recent years, various physical properties such as a soft texture that feels good on the skin, a light basis weight, and high tensile strength are required. Ru. In order to satisfy these requirements as much as possible, a nonwoven fabric production method using a binder method is mainly adopted. As the binder method, a method in which an adhesive solution is attached to a web has been mainly adopted, but there are problems such as the need for energy to remove the solvent of the adhesive solution and the poor working environment.

In order to solve these problems, a method has been proposed in which fibers having a lower melting point than the fibers constituting the web are mixed into the web as a binder, and the fibers constituting the web are bonded together by heat treatment. For example, as a binder for non-woven fabrics with high strength and good texture,
No. 1-10583 discloses a composite fiber whose composite components are fiber-forming polymers having different melting points. Also 1
The polyethylene fibers normally used in composite components are low-density polyethylene (LDPE) and high-density polyethylene (H
DPE), but when these polyethylenes are used, the resulting nonwoven fabric has a hard texture and cannot provide a soft feel. In order to compensate for this drawback, recently, Japanese Patent Application Publication No. 6
Linear low-density polyethylene (hereinafter referred to as "linear low density polyethylene") obtained by copolymerizing ethylene and octene-1 as disclosed in JP-A No. 0-209010 and JP-A No. 60-194113.

It is called L-LDPE. ) has come to be used as a nonwoven fabric binder due to its soft texture and low melting point.

(Problems to be Solved by the Invention) The present inventors previously proposed Japanese Patent Application No. 61-23623.

L-LD with limited density, melt index, and heat of fusion
We proposed a nonwoven fabric made of thermally bonded fibers with PE as a sheath component and polyethylene terephthalate as a core component.

The obtained nonwoven fabric has a soft texture and a low basis weight.

Moreover, although it was highly strong, peeling phenomenon was observed in some areas at the interface between L-LDPE and polyethylene terephthalate, resulting in problems such as poor durability and the inability to increase the spinning speed.

An object of the present invention is to provide thermally bonded fibers and nonwoven fabrics thereof that have good fiber and nonwoven fabric properties and good spinnability.

(Means for Solving the Problems) The present inventors have conducted intensive research to solve the above problems, and as a result, have arrived at the present invention.

That is, the present invention is a low-density copolymer of ethylene and octene-1, which has an octene-1 content of 1 to 15% by weight, a density of 0.900 to 0.940 g/cd, and a melt index of ASTM D-1238. Measured by method (E): 5 to 100 g/10 minutes, heat of fusion is 25 cal
Linear low density polyethylene (A) consisting of /g or more is 99
~50% by weight, melt flow rate is ASTM D-1
A blend structure (C) consisting of 1 to 50% by weight of crystalline polypropylene (B) smaller than 20 g 710 min as measured by the method of 238 (L) and the above (A) and (B) as a core component, and the above line The gist of the present invention is to provide a thermally adhesive fiber characterized by having a cross-sectional shape composed of low-density polyethylene (A) as a sheath component, and a nonwoven fabric made of the thermally adhesive fiber.

First, a blend structure of the core components of the thermal adhesive fiber of the present invention (
L-LDPE constituting C) and the sheath component consists of a linear low-density copolymer of ethylene and octene-1, and it is important that the content of octene-1 is 1 to 15% by weight. When the content of octene-1 is less than 1% by weight, the resulting thermally bonded fiber becomes hard, resulting in poor feel in products such as nonwoven fabrics. In addition, the content of octene-1 is 15% by weight.
If it exceeds, spinning becomes difficult.

It is difficult to obtain fibers with a fineness of 8 denier or less.

Note that L-LDPR is particularly preferably a copolymer of ethylene and octene-1, but other α-olefins such as butene-1, hexene-1 or octene-1 are also preferred.
A mixture of octene-1 and hexene-1 can also be used within the above range of octene-1 content.

Next, L-LDPH+7) Density is 0.940
If it exceeds g/CIa, the degree of crystallinity will increase and the texture of the obtained fiber will become hard, which is not preferable. On the other hand, 0.9
If it is less than 0.92g/c/, it is difficult to obtain high-performance fibers in terms of yarn quality performance, and in particular from the viewpoint of yarn quality performance and texture.
0 to 0.940 g/cj is preferred.

In the present invention, the above L-LDPE and polypropylene (hereinafter referred to as "polypropylene") are used.

It is called PP. ), but the melt index (hereinafter referred to as MI value) of L-LDPR is lower than the ASTM D- 123
8(E), it is necessary to be in the range of 5 to 100 g/10 minutes. If the MI value is less than 5 g/10 minutes, the deformation of the discharged yarn during melt spinning will not be smooth, and it will be susceptible to melt fracture, ballast effect, etc., and as a result, high-speed spinning will be difficult. Also, M
If the I value exceeds 100 g/10 minutes, the viscosity will be so low that a diameter ring will occur and the performance of the obtained fiber will be poor. Furthermore, if the melt viscosity with PP is too wide, the discharged yarn will break just below the spinneret, resulting in a serious drawback. Therefore, the MI value of the above L-LDPE is 5 to 10.
0 g/10 minutes is required, and a more preferable MI value is in the range of 40 to 70 g/10 minutes.

L-LDPf! The heat of fusion, which is a measure of the crystallinity of
If it is less than 5 cal/g, the spinning properties will be poor and high speed spinning will not be possible. Here, the heat of fusion was measured by the first-order method. PerkinElmer product osc-2C
Using a mold, 5 mg of a sample is taken and measured at a heating rate of 20° C./min, and the DSC curve obtained by raising the temperature from room temperature is determined according to the device manual.

Next, the PP to be blended with the L-LDPE is isotactic polypropylene, and its melt flow rate (hereinafter referred to as MF value) is ASTM D-1.
238(L), it is necessary that the amount is 20 g/10 minutes or less. That is, the MF value is 20g/10
If it exceeds 10 minutes, the blending with L-LDPE will not be smooth and a uniform structure will not be formed, because the polypropylene segments flow too much in the L-LD Japanese acid component and form a linear shape in the fiber axis direction. As a result, the melt elasticity of the spun yarn becomes extremely high, so in order to reduce yarn breakage during spinning, it is necessary to keep the spinning speed low. Also, L-LDPE! : PP The blending ratio with PP also affects the spinning properties. By setting the ratios of L-LDPE and PP to 99 to 50% by weight and 1 to 50% by weight, respectively, L-LDPE and PP can be blended smoothly and appropriate melt elasticity can be obtained.

When the amount of PP in L-LDPti is less than 1%, no improvement in yarn-spinning properties is observed due to blending, and L-LDPt!
It will be the same as the individual spinning performance. On the other hand, if it exceeds 50% by weight, it will become rich in PP, making it difficult to improve flow characteristics through blending and making it difficult to obtain thin fibers.

In this way, by using the blend structure (C) consisting of the above (A) and (B) as a core component, the L-LD consisting of the above (A)
A thermally bonded fiber is produced using PE as a sheath component, and a conventionally known melt spinning device for composite spinning can be used. At spinning temperature, L-LDPED and PP
A temperature approximately midway between the single spinning temperatures is suitable, and the preferred temperature is 210 to 250°C, more preferably 2
When the temperature is 20°C to 240°C, the ratio of the core/sheath component is 10 to 9.
0% by weight, L-LDPR constituting the sheath component is 90-10
Preferably, it consists of % by weight, L-LDPI! If the content of the component is less than 10% by weight, the stability of the composite fiber cross section will be poor (
, and the texture of the obtained fiber is hard (unfavorable).
If the L-LDPED content exceeds 90%, the texture will be soft and the thermal adhesion will be good, but the spinning properties will be poor and high-speed spinning will not be possible. Fibers may have a cross section of irregular shapes such as a triangle or a square, or a hollow cross section instead of just a single circle, and fibers with a core-sheath structure are preferable, but fibers with a so-called multi-core structure instead of just one core component are preferable. May exist, but L-
In order to take advantage of the characteristics of LDPR, such as softness, low melting point, and functionality as a binder, in thermally bonded fibers, it is necessary that L-LDPR be present in the surface layer of the fibers. In addition, additives such as a moisture absorbent, a wetting agent, a pigment, a dye, a stabilizer, a flame retardant, etc. may be added during composite spinning for the purpose of imparting additional performance to the heat-adhesive fiber.

Next, in order to obtain the nonwoven fabric of the present invention, filaments or tows are manufactured using a melt spinning device for composite spinning, cut into short fibers, passed through a card machine to create a web, and then processed using a calendar roll to create a web of L-LDPE. A nonwoven fabric can be produced by thermocompression bonding at a temperature lower than the melting point. In addition, considering productivity, it is preferable to use a nonwoven fabric produced by the spunbond method, and the manufacturing method involves sucking and opening the fibers coming out of a nozzle using a high-speed suction gun, and colliding them against a moving conveyor-like wire gauze to form a web. 9. It is obtained by subsequently performing a compression heat treatment using an embossing roll. The nonwoven fabric of the present invention can also be produced by a conventional papermaking method in which nonwoven fabric fibers are canted into short fibers, dispersed in water, and then paper is made.

(Function) The thermal adhesive fiber in the present invention is a composite fiber in which a blend of L-LDPE and PP is used as a core component and L-LDPE alone is used as a sheath component, and the thermal adhesive fiber is particularly suitable for nonwoven fabric applications. Therefore, it is possible to obtain a product with improved spinnability and durability, which were drawbacks of the conventional method. The inventors of the present invention speculate as to the reason for this as follows.

First, the polymer used in the present invention is L-LDPR.
and PP, and PP and L-LD to maintain the fiber morphology.
In the blended structure (C) with PR, on the other hand, L-LDPB plays a role in providing a soft texture and thermally adhering fibers to each other, and the blending mechanism and composite fibers are based on a specific polymer. Only then can the object of the present invention be achieved. L-LDP as a blending mechanism
PP exists as an island component in the sea component of H, and it is thought that the size and shape of this island component in the molten state affects the silk-spinning properties.

In other words, if the melt viscosities of L-LDPE and PP are too close, the island components will be quite small, and since the shape of the islands is close to linear, the interaction between both molecules will be thick (and the melt elasticity in the blended state will be The size increases and the spinning properties deteriorate.

On the other hand, if the melt viscosities of L-LDPE and PP are significantly different, the island components will become too thick (too much) and the flow deformability will be poor.

In addition, the mixing ratio of L-LDPB having the above melt viscosity and PP is 99 to 50% by weight for L-LDPE and 1 to 1% by weight for PP.
By setting the amount to 50% by weight, the PP component can be present in a spindle-shaped form in the sea component L-LDPE.

It exhibits melt viscoelasticity suitable for high-speed spinning.

That is, compared to L-LDPE alone, by dispersing PP in a spindle shape in the matrix of L-LDPE, melt elasticity is suppressed and a spun yarn that can follow high-speed deformation can be obtained. If the dispersion state becomes linear, the contribution of the island component to the melt elasticity is large (no blending effect is observed, much different from the case of L-LDPR or PET alone).

It cannot follow high-speed deformation.

As described above, it is thought that the dispersion state of the polymer in the molten state becomes the optimal molten state for high-speed spinning and improves spinnability only by using a specially limited polymer blend of the present invention. moreover.

PET and L-LDPf! Composite spinning consisting of a core-sheath structure and a blend structure of L-LDPE and PP in the core.
Comparing the product of the present invention in which LDPR is used in the sheath part, the melt spinning temperature can be set lower because PET is not used, and therefore L-LDPB is used as before. It has been found that problems such as fouling of the nozzle cap, kneeling (nozzle bending), and yarn breakage, which were observed due to the excessive melting temperature, are significantly reduced.

As described above, one aspect of the present invention has the above-mentioned structure, has the soft texture, dry touch, and low-temperature heat adhesive properties characteristic of L-LDPH, and has a blended structure made of PP and L-LDPE.
It has better high-speed spinning properties than spinning alone, and the spinning temperature can be lowered compared to conventional composite spinning with PET, causing fewer troubles during spinning.

(Example) Hereinafter, a specific example of the present invention will be explained with reference to Examples.

The physical properties measured in Examples were evaluated by the methods described below.

(11 tensile strength JIS L-1096 strip method width 30m5
．． The maximum tensile strength of a test piece with a length of 100 fins is measured.

(2) Measure with a slit width of 10 mm according to the total hand JIS L-1096 hand-o-meter method. A smaller number indicates more flexibility.

(3) Take a test piece with compression hardness and softness of 50 dragons x 100 fins, place this test piece in a cylindrical shape with a height of 50 fins and a circumference of 1001 m, and place it on a flat plate type load cell, and perform a cylindrical test at a speed of 50 mm/min. Compress the piece and measure the maximum load at that time. The smaller the load, the more flexible it is.

Example 1. Comparative Examples 1-2 Linear low density polyethylene (A) (L-LDPE) (
Octene-15% by weight, density 0.935g/aJ, M
I value (melt index) 43g/10min, heat of fusion 3
6cal/g) and isotactic polypropylene (B)
(PP) (density 0.905 g/cm3, MF value (melt flow rate)) 15 g/10 min] at a weight ratio of 75:2
Using a melt spinning device for composite spinning, a blend structure (C) blended at a ratio of 5:5 as a core component and linear low-density polyethylene (A) as a sheath component was prepared using a melt spinning device for composite spinning.The weight ratio was core/sheath = 50:
The spinning temperature of the blend structure (C) at a ratio of 230
°C, L-LDPII! (A) Spinning temperature: 220°C, spinneret: 0.4 mφ x 36 holes, discharge rate: 54 g/min.

Composite fibers were produced at a suction speed of 8,700 m/min. Table 1 shows the yarn properties of the obtained fibers. Next, contamination of the spinneret and operability (silk-spinning performance) were observed. As is clear from Table 0, the results are shown in Table 1.

In the case of the core-sheath composite fiber of the present invention, high-speed spinning was possible, the spinneret was less contaminated, and the spinning performance was good.

Table 1 ×...-m-・a) Next: L-LDPH
A heat-bonded fiber having a core-sheath structure of 100% L-LDPR and PET was created. The linear low density polyethylene (A) used in Example 1 was spun alone in a normal melt spinning machine at a temperature of 250°C, a spinneret of 0, 4 mmφ x 36 holes, a discharge rate of 54 g/min, and a suction speed of 8500 m/min. Thermal bonding fibers were produced by the air flow drawing method under conditions of 10 minutes. The yarn quality performance of the obtained fibers is shown in Table 1.Next, as in Example 1, staining of the spinneret and operability were observed, and the results are shown in Table 1.
As is clear from the table, it is necessary to perform the spinning at a fairly high temperature in order to perform high-speed take-up, and as a result, yarn bending is likely to occur (the spinning nozzle is often contaminated, and the spinning performance is also somewhat poor). (Comparative Example 1) The linear low density polyethylene (A) used in Example 1 was used as a sheath component, and PET ((η)-0,70 phenol/tetrachloroethane 1: measured at 1.20°C) was used as a core component. as PET
Spinning temperature 285℃, L-LDPII! spinning temperature 2
A composite fiber having a core-sheath structure was produced according to Example 1 except that the temperature was 20° C. and the suction speed was changed to 8650 m/min. The yarn quality performance of the obtained fibers is shown in Table 1.Next, the staining of the spinneret and the operability were observed, and the results were shown in Table 1.As is clear from Table 1, L-LDPI! The spinning temperature of Example 1 is
Since the yarn was more likely to bend, the spinneret was often contaminated, and the spinning properties were also somewhat poor.

(Comparative Example 2) Example 2. Comparative Examples 3 to 4 L-LDP using the blend structure (C) of Example 1 as a core component
A nonwoven fabric was produced by a spunbond method using H as a sheath component. In addition, the spinning conditions were performed according to Example 1. In other words, the fibers are opened by suction, collided with a moving wire mesh, and the fabric weight is 1.
A web of 0 g/m" was prepared and then subjected to compression heat treatment using an embossing roll to produce a nonwoven fabric. The performance results are shown in Table 2.

Table 2 Next, the polymers of Comparative Example 1 and Comparative Example 2 were used.

Nonwoven fabrics were produced using the spunbond method in accordance with Example 2, except that the spinning conditions were the same as in Comparative Examples 1 and 2, respectively. The performance results are shown in Table 2. When examining the texture and tensile strength of the obtained nonwoven fabric, 1. The total hand value of Example 2 of the present invention showed a texture similar to that of a nonwoven fabric made of L-LDPE alone.9 In terms of strength, the core-sheath value of PET and L-LDPE was It can be seen that the improvement is comparable to that of composite fibers. From these results, it is clear that the present invention is superior not only in terms of practical feel and strength but also in terms of operability.

Example 3. Comparative Example 5 The blend structure (C) used in Example 1 was added as a core component,
L-LDPR was used as the sheath component, and the composite ratio was 50:50. Spinning temperature L-LDPE 220°C, blend structure 230
°C, spinneret 0.4mmφ x 200 holes, discharge amount 400g
undrawn fibers were produced at a spinning speed of 1,600 m/min, then stretched at a drawing temperature of 100°C and a draw ratio of 3.1 times, and crimped in a stuff-in box to obtain a fiber length of 5.
I cut it into one piece.

The yarn properties of the obtained short fibers were as follows: single yarn fineness: 3.5 den;
+Fiber length: 51 Soft strength: 3.6 g/d, elongation: 33%, number of crimps: 24 crimps/inch.

Crimping rate: 11%, crimp elasticity: 60%, crimp elongation rate: 12.5
%, exhibits excellent stapling properties, and can be further spun and drawn.

The operability of the crimping process was also good.

Next, feed the obtained staple to a card machine and
/ m ” web, and then pressure-thermal bonding was performed using a calendering machine at a temperature below the melting point of L-LDPH.
A nonwoven fabric was produced. When the physical properties of the obtained nonwoven fabric were examined, it was found to have a tensile strength of 1.0 kg/3 cm and a compression hardness/softness of 10 g.

For the purpose of comparison with the present invention, the blend structure of Example 3 was replaced with high density polyethylene 0IDPE) (density 0.9
61g/aJ, M I value 35g/10min, heat of fusion 67
cal/g) and isotactic polypropylene (P P
) (same polymer as Example 1, density 0.905 g/c
d, M F value of 15 g/10 min) and a blend ratio of 75:25. Composite fibers were produced with a core/sheath ratio of 50:50, but uneven blending occurred during the spinning stage, resulting in frequent yarn breakage, and it was not even possible to obtain undrawn fibers.

(Effects of the Invention) The heat-adhesive fiber of the present invention has a soft feel and is excellent in strength, so it is ideal for the inner part of disposable diapers. Additionally, unlike conventional L-LDPR alone or composite fibers of L-LDPE and PET, there is less nozzle contamination during spinning, which shortens return time.

It is widely used in the fields of nonwoven fabrics, woven fabrics, and knitted fabrics that require thermal bonding because the nozzle installation period can be extended and it is excellent in terms of operation.

Claims (3)

[Claims] (1) A low-density copolymer of ethylene and octene-1, with an octene-1 content of 1 to 15% by weight and a density of 0.
900-0.940g/cm^3, melt index is 5-1 as measured by the method of ASTM D-1238 (E)
00 g/10 minutes, linear low density polyethylene (A) having a heat of fusion of 25 cal/g or more is 99 to 50% by weight, and the melt flow rate is 20 g/10 minutes as measured by the method of ASTM D-1238 (L). It is composed of 1 to 50% by weight of small crystalline polypropylene (B), a blend structure (C) consisting of the above (A) and (B) as a core component, and the above linear low density polyethylene (A) as a sheath component. A thermal adhesive fiber characterized by having a cross-sectional shape. (2) The heat-adhesive fiber according to claim 1, wherein the fiber has a single filament fineness of 8 denier or less. (3) A low-density copolymer of ethylene and octene-1, with an octene-1 content of 1 to 15% by weight and a density of 0.
900-0.940g/cm^3, melt index is 5-1 as measured by the method of ASTM D-1238 (E)
00 g/10 minutes, linear low density polyethylene (A) having a heat of fusion of 25 cal/g or more is 99 to 50% by weight, and the melt flow rate is 20 g/10 minutes as measured by the method of ASTM D-1238 (L). It is composed of 1 to 50% by weight of small crystalline polypropylene (B), a blend structure (C) consisting of the above (A) and (B) as a core component, and the above linear low density polyethylene (A) as a sheath component. A nonwoven fabric made of thermally bonded fibers having a cross-sectional shape.