JPH0482952A - Production of ultra-fine filament nonwoven fabric - Google Patents

Abstract

PURPOSE:To efficiently obtain the subject product excellent in tenacity and having a remarkably high uniformity, a fine surface morphology and a dense structure at a low cost by producing a web from a two component conjugate filament having a special structure and subsequently treating the resultant web using a group of rolls having a high linear pressure. CONSTITUTION:A two component conjugate filament consisting of a segment composed of (A) a polymer component and (B) another polymer component incompatible with (A) component and having a melting point different from that of (A) component by 30-150 deg.C and having plural convex lens-shaped cross sections and satisfying formulae, (R1/R0)>1, (R2/R0)>=1 and (L/H)>=1 where (R0), (R1), (R2), (L) and (H) show respectively radius of circumcircle of component (A) on cross section perpendicular to fiber axis, radius of circumcircle of component (B), radius of curvature of circular arc at convex lens-shaped part of component (B) in contact with component (A), arc length of circular arc and thickness of convex lens-shaped part is subjected to melt spinning. The spun fiber is then drawn and piled up and the resultant web is subsequently treated using a group of high linear pressure rolls. Fibers of component (B) are separated from the conjugate fiber thereby to form separated filaments followed by heat bonding between the obtained separated filaments using the lower melting component.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for producing a nonwoven fabric made of ultrafine long fibers, and more specifically, to a method for producing a nonwoven fabric made of ultrafine long fibers having a delicate surface morphology and a dense structure. This relates to a manufacturing method.

(Prior Art) Nonwoven fabrics have conventionally been used for various purposes such as clothing, industrial materials, civil engineering and construction materials, agricultural and horticultural materials, life-related materials, and medical and sanitary materials. Among these, nonwoven fabrics made of long fibers are widely used because they have a higher tenacity than nonwoven fabrics made of short fibers, and are superior in productivity. Many attempts have been made to obtain a nonwoven fabric made of long fibers that has a delicate and dense structure on one surface. For example, Japanese Patent Publication No. 44-240.9, Japanese Patent Publication No. 52-30629, and Japanese Patent Publication No. 62-413.
Publication No. 16 discloses a method of obtaining a nonwoven fabric composed of fine fibers by subjecting a sheet to chemical treatment to dissolve or remove a portion of the polymer constituting the fibers. There is. Also.

Japanese Patent Publication No. 1-47585 and Japanese Patent Publication No. 1-47586
The publication discloses a method of obtaining a nonwoven fabric made of ultrafine fibers by treating a sheet with a high-pressure water jet, splitting the fibers into ultrafine fibers, and three-dimensionally entangling the fibers. '-47579 discloses a method for obtaining a nonwoven fabric made of ultrafine fibers by washing the nonwoven fabric with water to remove water-soluble components. However, these methods of producing nonwoven fabrics have the problem that the production process is complicated and that the production cost is high because it is necessary to remove the polymer. Furthermore, Japanese Patent Publication No. 531010 discloses a method for obtaining a nonwoven fabric made of ultrafine fibers by puffing a sheet and splitting the fibers;

There is a problem in that the constituent fibers are partially damaged.

(Problems to be Solved by the Invention) The present invention aims to solve the above-mentioned problems and provide a method that can efficiently produce a nonwoven fabric made of ultra-thin long fibers having a delicate surface morphology and a dense structure. It is.

(Means for Solving the Problems) As a result of intensive studies to solve the above problems, the inventors have found
We have arrived at the present invention. In other words, the present invention is as follows.

a polymer component A, which is incompatible with the polymer component A;
and a segment having two or more convex lens-shaped cross sections made of a polymer component B having a melting point difference of 30 to 150° C. with the polymer component A.

Radius of the circumscribed circle of the polymer component A in the cross section perpendicular to the fiber axis R62 Radius of the circumscribed circle of the polymer component B R1° The radius of curvature R29 The arc length of the arc and the thickness H of the convex lens-shaped portion are as shown in (■) below.

The secondary composite filaments satisfying the formulas (1) and 3 are melt-spun, and the spun secondary composite filaments are taken up by a take-up means consisting of an air sucker and placed on a collection surface such as a web conveyor. The fibers made of the polymer component B are separated at least in part from the composite filaments by treating the web with a roll group consisting of two or more rolls with wire pressure, thereby splitting the fibers. Production of an ultra-thin long-fiber nonwoven fabric, characterized in that the fibers are at least partially thermally bonded by fibers made of long fibers and made of a polymer component with a lower melting point of either the polymer component A or the polymer component B. The gist is the method.

R+ /Ro >1 ■R2
/Ro≧1 ■L /H≧1
Next, the present invention will be explained in detail.

In the present invention, the incompatible polymer components and B both have fiber-forming ability and can be melt-spun using a conventional melt-spinning device. Examples of combinations of polymer components A and B include polyester and polyamide, polyester and polyolefin, polyamide and polyolefin, and examples of the polyester polymer include polyethylene terephthalate, polybutylene terephthalate, and the like. Polyesters such as copolymerized polyesters whose main component is

Examples of polyamides include polyamides such as nylon 6, nylon 46, nylon 66, nylon 610, and copolymerized nylons containing these as main components.

Examples of the polyolefin type include polyolefins such as polypropylene, high density polyethylene, linear low density polyethylene, and ethylene/propylene copolymer. Also, for one polymer component A and B.

In each case, additives such as customary matting agents, heat stabilizers, pigments or polymer crystallization promoters may be added.

First, the method for producing the ultrafine long fiber nonwoven fabric of the present invention is as follows.

Two or more convex lens shapes made of the polymer component A and a polymer component B that is incompatible with the polymer component A and has a melting point difference of 3° to 150° C. A two-component composite filament composed of segments having a cross section is melt-composite-spun using a conventional melt-composite spinning device. As the spinneret device, a composite spinneret device having a structure in which two or more molten polymer components B are guided from the outer periphery of an introduction hole for the molten polymer component A is used. The number of segments into which the polymer component A divides the polymer component B, that is, the number of segments having a convex lens-shaped cross section made of the polymer component B, is preferably 2 or more, since the more ultrafine fibers can be obtained, If the amount is too large, the cross-sectional structure will be such that segments made only of polymer component B are adhered to each other, and the problem arises that fiber splitting and peeling cannot be performed in the subsequent process.

Normally, it is best to limit the number to about 16. Further, the segment made of the polymer component B needs to have a convex lens-shaped cross section; in this case.

Since the contact circumference of the segment consisting only of the polymer component B in contact with the polymer component A becomes relatively short, splitting performance is improved when splitting the two-component composite continuous fiber in a subsequent step.

Next, the melt-spun two-component composite long fibers are taken up by a taking-up means such as an air sucker, and deposited on a collection surface such as a web conveyor, and the web is rolled onto a smooth-surfaced roll heated at high line pressure. Depending on the group, a segment consisting of one polymer bottom portion B is peeled off from the composite filament by heat treatment at a temperature lower than the melting point of the polymer component on the lower melting point side, whichever is polymer component A or polymer component B. The fibers are made into long fibers, and at the same time, the fibers are at least partially thermally bonded using fibers made of a polymer component having a lower melting point of either the polymer bottom portion A or the polymer component B. In addition, the web is treated with a group of unheated rolls with a smooth surface under high line pressure, and -7 polymer component B is
The segment consisting of is peeled from the composite filament to produce a split filament, and then heat treated with a heating roll at a temperature below the melting point of the polymer component on the lower melting point side of either polymer component A or polymer component B. By doing so, the fibers may be at least partially thermally bonded by the fibers made of the polymer component on the lower melting point side. A heated embossing roll can also be used instead of a heated roll with a smooth surface. By heat-treating the web using a heated embossing roll at a temperature below the melting point of either polymer component A or polymer component B, the lower melting point polymer component is removed. A nonwoven web is obtained by at least partially thermally adhering the fibers with the fibers of The segments made of polymer component B may be peeled from the composite filaments to produce split filaments. Note that the obtained nonwoven fabric may be subjected to a softening process to improve the flexibility of the nonwoven fabric.

The difference in melting point between polymer component A and polymer component B in the present invention needs to be 30 to 150°C.

The melting point of a polymer as used in the present invention is measured using a PerkinElmer Differential Calorimeter DS (Model 2), with a sample amount of approximately 5 mg and a scanning speed of 20°C/min, according to the manual of the device. It was determined from the DSC curve obtained by

If the melting point difference between polymer component A and polymer component B is less than 30°C, the nonwoven fabric will shrink due to heat when the web is thermally bonded with a heating roll, resulting in a decrease in dimensional stability and poor texture of the nonwoven fabric. Or.

This is not preferable because it causes ILFI problems such as narrowing the bonding temperature range during thermal bonding and making temperature control difficult. If the melting point difference exceeds 150°C, thermal deterioration of the polymer component on the lower melting point side will be accelerated, which is not preferable. In addition.

If the web is thermally bonded with a heated roll whose surface temperature is higher than the melting point of the polymer component on the low melting point side, the resulting nonwoven fabric will be film-like or have a hard surface, which is not necessarily desirable.

To form a web, the melt-spun fiber bundle is cooled.

It is possible to use drawn continuous fibers obtained by drawing or highly oriented undrawn continuous fibers obtained by high-speed spinning.

The process from spinning to web formation may be a continuous process, and
The web may be created from separately produced drawn filaments or highly oriented undrawn filaments. The web is created by taking these long fibers with a taking means such as an air sucker, forcibly charging them with a charging device to spread the fibers, and depositing them on a collecting surface of a moving web conveyor, etc. do.

The high line pressure roll group as used in the present invention is composed of two or more rolls, and usually a pair of rolls to a multi-stage roll group of up to 10 rolls in total can be used. If the number of rolls is too large, the equipment investment cost will increase, which is not preferable. The linear pressure of the roll group is an important factor in peeling off the segments consisting of the dipolymer acid component B from the composite filaments to produce split filaments, and the stress of shearing, elongation, compression, etc. Peel off the segment consisting of.

This linear pressure is usually preferably at least about 20 kg/cm, although it depends on the splitting properties of the composite long fibers. 20
If it is less than kg/cm, the segments made of the polymer component B cannot be sufficiently peeled off, which is not preferable.

Next, regarding the secondary composite long fibers in the present invention.

explain.

Figures 1 and 2 are cross-sectional views for explaining the structure of the secondary composite filament according to the present invention, and Figures 3 and 4 are examples of secondary composite filaments that satisfy the constituent requirements of the present invention. FIG. In Figures 1 and 2, l Ro is the polymer component A in the cross section perpendicular to the fiber axis of the secondary composite filament.
The radius of the circumcircle.

R1 is the radius I of the tangent circle of the polymer component B, R2 is the radius of curvature of the arc that is in contact with the polymer component A in the convex lens-shaped portion made of the polymer component B, L is the arc length of the arc, and H is the convex lens. This is the thickness of the shaped part. Ro.

R, , R2, L and H were determined by actual measurements based on a cross-sectional photograph of the fiber cross-section magnified 1000 times.

In the ultrafine long fiber nonwoven fabric of the present invention, R8. R1, R2, L and H are the following 1, 2 and 3
It is necessary to satisfy the formula.

R+ / Ro > 1 ゛
■R2/ Ro≧1 ■L
/H≧1 ■If R, /R, is R, /Ro≦1, or R2/RO is R2/
When Ro11 is used, 1 When the polymer component A and the polymer component B are separated.

Unless the treatment is performed using a group of rolls with extremely high linear pressure and smooth surfaces, it will be difficult to separate and split the polymer component A and the polymer component B, which is not preferable. R1/Ro is R1/RO
>1. And even if R2/R,, is R2/Ro≧1,
When L/H is L/H<1, depending on the selection of polymer acid content A and polymer component B, polymer component A and polymer component A may be mixed in the step of taking up the secondary composite filament yarn with an air sucker. Combined component B
This is undesirable because the fibers are peeled off and the spreadability of the fibers decreases when forming into a web, making it impossible to obtain a uniform web.

Next, the ultrafine long fiber nonwoven fabric obtained by the method of the present invention will be explained.

The ultrafine long fiber nonwoven fabric obtained by the method of the present invention is composed of a monopolymer acid component A and a segment having two or more convex lens-shaped cross sections consisting of a polymer component B that is incompatible with the polymer component A. The second-order composite long fibers constituted by
Split fibers consisting only of secondary composite filaments with segments of polymer component B partially exfoliated from the secondary composite filaments and the polymer component A developed by splitting the secondary composite filaments. It is composed of long fibers and split long fibers composed only of the polymer component B.

The ultrafine long fiber nonwoven fabric in the present invention has a splitting ratio of segments consisting of monopolymer acid component B of 30% or more and 95% or less. This fiber splitting ratio means that Ro+R, , R2, L and H satisfy the above formulas 1, 2 and 3, and the segment consisting of the polymer component B from the secondary composite long fibers. Partially exfoliated secondary composite long fibers, split long fibers composed only of the polymer component A developed by splitting the secondary composite long fibers, and composed only of the polymer component B Select 10 arbitrary locations on a nonwoven fabric composed of split filaments, magnify the cross section of the nonwoven fabric 100 times and take a cross-sectional photograph.Next, in the 10 cross-sectional photographs, peel off from the composite filaments. Determine the total number of segments of polymer component B present and the total number of segments of polymer acid component B present,
It is calculated.

It represents the ratio (%) of the total number of exfoliated segments of polymer component B to the total number of segments of polymer component B present.

In the ultrafine long fiber nonwoven fabric of the present invention, the splitting ratio is preferably 30% or more and 95% or less.

If the fiber splitting ratio is less than 30%, it is not preferable because a nonwoven fabric having a delicate surface morphology and a dense structure cannot be obtained.

Further, the split long fibers are composed only of the polymer component B developed by splitting the composite long fibers.

It is preferable that the single yarn fineness is 0.8 denier or less. Even if the splitting ratio is 30% or more.

The single filament fineness of the split filament consisting of polymer component B is 0.
If it exceeds 8 denier, it becomes difficult to obtain a nonwoven fabric with a delicate surface and a dense structure, and the smaller the single yarn fineness is, the more it is possible to obtain a nonwoven fabric with a delicate surface and a dense structure.

Monopolymer acid content B in the two-component composite filament referred to in the present invention
The number of segments with a convex lenticular cross section consisting of
It is necessary that there are two or more.

If the number of segments is one, the composite filaments may be crimped depending on spinning conditions or drawing conditions, and the spreadability of the fibers decreases when forming into a web, making it impossible to obtain a uniform web.

In the method of the present invention, 1 type of polymer to be combined 9
Polymer composite ratio, spinning conditions, and stretching conditions.

By selecting various post-processing conditions such as peeling and splitting conditions, adhesion conditions, and softening processing, it is possible to obtain an ultrafine long fiber nonwoven fabric depending on the purpose of use.

(Example) Next, the present invention will be specifically described based on Examples. In addition, various characteristics in the examples were measured by the following methods.

Intrinsic viscosity: Measured at a temperature of 20°C using a mixed solution of equal weights of phenol and tetrachloroethane as a solvent.

Melt index: Measured by ASTM D 1238 E method.

Melting point: Determined from a DSC curve obtained by measuring a sample amount of about 5 mg at a scanning rate of 20° C./min using a PerkinElmer differential scanning calorimeter model DSC-2.

Prepare a measurement sample piece of nonwoven fabric with a tensile strength of 3 cm in width and 10 cm in length in the vertical and horizontal directions.
It was measured by the strip method described in 96.

Total hand: Total hand is an index showing the flexibility of the fabric, and the slot width is 10ml11 according to the handle-o-meter method described in JIS L-1096.
It was measured as

Example 1 Melting point is 128°C, melt index value is 25g/10
Polyethylene polymer with a melting point of 258
A polyethylene terephthalate polymer having an intrinsic viscosity of 0.70 at °C was used as polymer component B, and a two-component composite filament was melt-spun through a spinneret having 200 composite spinning holes.

During melt spinning, the melting temperature of monopolymer acid component A was set at 230°C,
Single hole discharge rate 0.60 g/min.

The melting temperature of polymer component B was 285°C, the single hole discharge rate was 0,
60 g/min [ratio (weight ratio) of component A to component B was 1:1]. After cooling the spun long fiber yarn, 25 filaments each were passed through eight air suckers placed 120 cm below the spinneret, and drawn and drawn.
The fibers were taken up at a speed of 3500 m/min, forcibly charged with a charging device to open the fibers, and deposited on the surface of a moving web conveyor to obtain a web.

The cross-sectional shape of the obtained two-component composite filament is 5, consisting of monopolymer acid content A and monopolymer acid content B, as shown in Figure 3.
It was composed of a segment having a convex lenticular cross section. Ro, R, , R2, L and H are determined based on a cross-sectional photograph taken with the fiber cross-section magnified 1000 times, and R, /Ro.

When R2/Ro and L/H were calculated, R1/Ro
is 1.4, R2/Ro is 6.3. L/H was 2.5. In addition, this composite long fiber is not split.

The web was uniform.

Next, the obtained web was heated with a multi-stage 6
A nonwoven fabric was obtained by performing fiber splitting and heat bonding twice using a roll group consisting of individual rolls. The processing conditions are such that the surface temperature of the heating roll group is 115°C.

The line pressure was 100 kg/Cm.

The obtained nonwoven fabric had a basis weight of 50 g/rn', a tensile strength in the vertical direction of 5.2 kg/3 cm, a tensile strength in the horizontal direction of 3.8 kg/3 cm, and a total weight of 200 g. Select 10 arbitrary locations on the non-woven fabric, enlarge the cross-section of the non-woven fabric 100 times and take a photograph of the cross-section.

Among the 10 cross-sectional photographs, the total number of segments of polymer component B that has peeled off from the composite long fibers and the total number of segments of polymer component B that are present were determined and the 10% fiber ratio was determined, and the 100% fiber ratio was 80%. Met. In addition to the split filament long fibers composed only of the polymer component B, the nonwoven fabric includes secondary composite filaments with no exfoliated segments consisting of the bipolymer bottom portion B, and the secondary composite filaments. Secondary composite long fibers in which segments made of polymer component B are partially exfoliated from the long fibers, and split long fibers composed only of the polymer component A developed by splitting the secondary composite long fibers. was recognized. In addition, polymer component B expressed by splitting the composite long fibers
When we determined the fineness of split filament made of only
It was extremely thin at 0.31 denier. and,
This nonwoven fabric had a delicate surface morphology and a dense structure.

Comparative Example 1 Melting point: 132°C, melt index value: 15g/10
The secondary composite continuous fibers were melt-spun in the same manner as in Example 1 except that the polyethylene polymer was changed to polymer component A.
After cooling, the filament is passed through an air sucker and drawn by suction, drawn at a speed of 3,500 m/min, and forcibly charged with a charging device to open the fibers, deposited on the surface of a moving web conveyor, and the web is Obtained.

The cross-sectional shape of the obtained secondary composite filament is 5, consisting of a double polymer bottom portion A and a single polymer bottom portion B, as shown in FIG.
It was composed of a segment having a convex lenticular cross section. Based on the cross-sectional photograph taken of the fiber cross-section, R6+ R+ + R21L and H are determined, and R,/
When Ro, R2/Ro and L/H were calculated, R,/
Ro is 2. O, R2/Ro is 6.5. L/H was 0.7. Further, the composite long fibers were partially split, and the opening properties of the fibers were partially poor, resulting in a web lacking uniformity.

Next, in the same manner as in Example 1, the resulting web was subjected to fiber splitting and thermal bonding twice using a group of heated rolls with smooth surfaces to obtain a nonwoven fabric.

The resulting nonwoven fabric has a splitting ratio as high as 90%.

Although it had a delicate surface morphology, it lacked uniformity.

Example 2 The web obtained in Example 1 was embossed using a heated embossing roll with a pressure contact area ratio of 12% to obtain a nonwoven sheet. What are the processing conditions?

The surface temperature of the heating embossing roll was 120℃, and the linear pressure was 3
It was set to 0 kg/cm.

Next, the obtained nonwoven sheet was subjected to a bending and wrinkle treatment.

The obtained nonwoven fabric had a basis weight of 60 g/m'', a tensile strength in the vertical direction of 12.6 kg/3 cm, a tensile strength in the horizontal direction of 5.0 kg/3 cm, and a total weight of 65 g. When we selected 10 arbitrary locations and calculated the 10% fiber ratio, the 10% fiber ratio was 95%.In addition to the 10% split fibers consisting only of the polymer component B, this nonwoven fabric also contained 9 fibers. A secondary composite filament from which segments made of the combined component B have not been peeled off at all; a secondary composite filament from which segments made of the polymer component B have been partially peeled from the secondary composite filament; Split filaments composed only of the polymer component A developed by splitting the composite filaments were observed.Furthermore, split filaments composed only of the polymer component B developed by splitting the composite filaments were observed. When the fineness of the split filament was determined, it was found to be extremely fine with a denier of OJ1.The nonwoven fabric had drapability and a delicate surface morphology.

(Effect of the invention) According to the method for producing an ultrafine long fiber nonwoven fabric of the present invention.

A secondary composite long fiber composed of a polymer component A and a polymer component B; a secondary composite long fiber in which a segment made of the polymer component B is partially peeled from the secondary composite long fiber;
Composed of split filament fibers composed only of polymer component A and split filament fibers composed only of polymer component B developed by splitting the secondary composite filaments, the fibers are excellent in strength and extremely uniform. It is possible to efficiently produce nonwoven fabrics with high surface resistance, delicate surface morphology, and dense structure at low cost.

The obtained nonwoven fabric can be suitably used as a material for medical hygiene materials.

[Brief explanation of the drawing]

Figures 1 and 2 are cross-sectional views for explaining the structure of the two-component composite filament according to the present invention, and Figures 3 and 4 show examples of the two-component composite filament that satisfies the constituent requirements of the present invention. 5 and 6 are cross-sectional views showing examples of two-component composite long fibers that do not satisfy the constituent requirements of the present invention. Patent applicant: Unitika Co., Ltd. Main 3 figures ■ 3 figures 4 prongs (2 k

Claims (1)

[Claims] (1) Polymer component A is incompatible with the polymer component A, and the melting point difference between the polymer component A and the polymer component A is 30 to 150.
The radius R_0 of the circumcircle of the polymer component A in the cross section perpendicular to the fiber axis,
The radius R_1 of the circumscribed circle of polymer component B, the radius of curvature R_2 of the arc that is in contact with polymer component A in the convex lens-shaped part made of polymer component B, the arc length L of the arc, and the thickness H of the convex lens-shaped part are as follows. Two-component composite filaments satisfying formulas 1, 2, and 3 are melt-spun, and the spun two-component composite filaments are taken up by a taking-up means consisting of an air suction device,
It is deposited on the collection surface of a web conveyor, etc. to form a web,
By treating the web with a roll group consisting of two or more rolls with high linear pressure, at least a portion of the fibers made of the polymer component B are exfoliated from the composite filaments to form split filaments, and the polymer component A method for producing an ultrafine long-fiber nonwoven fabric, which comprises at least partially thermally adhering the fibers using fibers made of a polymer component having a lower melting point than either polymer component A or polymer component B. R_1/R_0>1...1 R_2/R_0≧1...2 L/H≧1...3