JPH0457950A - Production of superfine staple fiber nonwoven fabric - Google Patents

Abstract

PURPOSE:To efficiently obtain the subject nonwoven fabric having soft hand by subjecting a conjugate staple fiber web of a polyolefinic polymer component and a noncompatible component having a higher melting point than that of the aforementioned component to fiber splitting and entangling treatment and then carrying out fusing treatment. CONSTITUTION:Melt undrawn fiber yarn of a polyolefinic polymer component and a noncompatible polymer component having a melting point higher than that of the aforementioned component by at least 20 deg.C is bundled, drawn, mechanically crimped and cut to prepare a web 1 from the resultant staple fiber. The resultant web 1 is then subjected to fiber splitting and entangling treatment with liquid columnar streams 3 to provide <=0.7 denier single fiber size by (partial) peeling of the polyolefinic polymer component. After drying, interstices between the staple fibers are (partially) bonded with staple fiber of the polyolefinic polymer component in a heat-treating machine 6.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a nonwoven fabric, and more specifically,
The present invention relates to a method for producing an ultrafine short fiber nonwoven fabric that has a soft texture and can be suitably used for medical hygiene materials.

(Prior Art) In recent years, short fiber nonwoven fabrics have been used for medical sanitary materials, particularly for disposable diapers, sanitary napkins, and the like.

Since these short fiber nonwoven fabrics are usually composed of short fibers having a single filament fineness of about 165 denier, they have a problem of poor texture, that is, they feel hard to the touch when used. In order to improve the texture,
Attempts have been made to obtain a nonwoven fabric made of ultrafine short fibers having a single filament fineness of about 0.5 denier. For example, JP-A-62-
In Publication No. 133164.

A method is disclosed for obtaining a nonwoven fabric composed of ultrafine staple fibers by treating composite staple fibers with a high-pressure liquid stream to split and fibrillate them. however.

This method for producing a nonwoven fabric does not improve spreadability because it uses ultrafine short fibers with a single filament fineness of about 0.5 denier.

It is difficult to increase the opening speed, and therefore productivity is significantly reduced. This has the problem of increased production costs. In addition, although the obtained nonwoven fabric has a soft feel due to the formation of entanglements between the short fibers due to the high-pressure liquid flow treatment, it has a problem of low tenacity because the short fibers are not thermally bonded. ing.

(Problems to be Solved by the Invention) The present invention solves the above problems and makes it possible to efficiently produce an ultrafine short fiber nonwoven fabric that has a flexible texture and can be suitably used for medical sanitary materials. It is intended to provide a method.

(Means of agreement for solving the problem) The present inventors have conducted intensive studies to solve the above problem, and as a result, 1.
We have arrived at the present invention. In other words, the present invention is as follows.

Melting a bicomponent composite fiber consisting of a polyolefin polymer component A and a polymer component B that is incompatible with the polyolefin polymer component A and has a melting point at least 20° C. higher than the melting point of the polymer component A. After composite spinning, the undrawn fiber yarns of the spun bicomponent composite fibers are collected and bundled to form an undrawn fiber yarn bundle.9Then, the obtained undrawn fiber yarn bundle is stretched. After applying mechanical crimping, the fibers are cut into a predetermined fiber length to obtain two-component composite staple fibers, a web is created using the two-component composite staple fibers, and the resulting web is treated with a high-pressure liquid columnar flow. At least a portion of the segment made of the low melting point polymer component A is exfoliated from the composite short fibers to produce split short fibers with a single filament fineness of 0.7 denier or less, and three-dimensional entanglement is caused between the short fibers. The short fibers made of the low melting point polymer component A are bonded at least partially by the short fibers made of the low melting point polymer component A by applying heat treatment at a temperature higher than the melting point of the low melting point polymer component A. The gist of the present invention is a method for producing an ultrafine short fiber nonwoven fabric characterized by the following.

Next, one aspect of the present invention will be explained in detail.

It is one of the constituent components of the two-component composite staple fiber in the present invention. Polyolefin polymer component A has fiber-forming ability and 9
It can be melt-spun using ordinary melt-spinning equipment.1 For example, low-density polyethylene (LDPE), linear low-density polyethylene (LLDPB), high-density polyethylene (HDPB), polypropylene, ethylene or acrylic on propylene. Examples include modified polyethylene or modified polypropylene copolymerized with unsaturated carboxylic acids such as acids. On the other hand, polymer component B, which is another component, is a polyester polymer or polyamide polymer that is incompatible with the polyolefin polymer component A, and both have fiber-forming ability and are It can be melt-spun using a melt-spinning device 9. Examples of polyester polymers include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and copolyesters containing these as main components. Examples of the acid component of the copolymerized polyester include carboxylic acids such as isophthalic acid and adipic acid, and examples of the glycol component include glycols such as neopentyl glycol. In addition, polyamide polymers include nylon 6°, nylon 46
．． Nylon 66, nylon 610. Examples include polyamides such as nylon 12 or copolymerized nylons containing these as main components. Further, as long as both the polymer base components A and B exhibit incompatibility between the two components, the above-mentioned compounds may be used alone or in a mixture of two or more thereof. Note 1
Polymer components A and B may each contain one or more conventional additives such as matting agents, heat stabilizers, pigments or polymer crystallization promoters.

Polymer component B, which is one component of the composite short fibers referred to in the present invention, needs to have a melting point that is at least 20° C. higher than the melting point of polymer component A, which is another component. The melting point of a polymer as used in the present invention is measured using a differential calorimeter DSC-2 manufactured by PerkinElmer, according to the manual of the device, with a sample amount of approximately 5 mg and a scanning speed of 20°C/min. It was determined from the obtained DSC curve. If the melting point difference between polymer component B and polymer component A is less than 20°C, the thermal deformation temperature ranges of both components overlap, and when the web is heat treated in a heat treatment device, polymer component B with a high melting point will be deformed or This is not preferable because problems such as melting and deterioration of the strength and texture of the obtained nonwoven fabric occur.

The two-component composite short fiber as used in the present invention is composed of the polymer component A and the polymer component B. Figure 1 is a cross-sectional view showing an example of the two-component composite short fiber referred to in the present invention.
Figure 1 (C
) is an example in which two-polymer acid components A and B are arranged radially and alternately on the circumference, and FIG. 1(d) is an example in which monopolymer acids A and B are arranged radially and alternately on the circumference. , and has a hollow part.

Monopolymer acid content A in the two-component composite short fibers referred to in the present invention
The number of segments is two or more, preferably four or more. If the number of this segment is one, crimping may occur in the composite short fibers depending on spinning conditions or drawing conditions, and when forming into a web, the spreadability of the fibers decreases, making it impossible to obtain a uniform web. , undesirable. In addition, if the number of segments is large, the advantage of splitting will improve, but if there is too many segments, the cross-sectional structure will be such that segments made only of polymer component A are adhered to each other, making it difficult to split and peel them in the subsequent process. 1 Usually, 8
It is best to limit it to about 100 pieces.

The method for producing the ultrafine short fiber nonwoven fabric of the present invention is as follows.

The polymer component is incompatible with the polymer component A and at least 20° C. below the melting point of the polymer component A.
A bicomponent composite fiber made of polymer component B having a high melting point is melt-composite-spun using a normal melt-composite spinning device, and the undrawn fiber yarn of the spun bicomponent composite fiber is taken up by a roll. The fibers are pulled out using a bow-cutting means such as the above, and then bundled to form an undrawn fiber yarn bundle. Next, the obtained undrawn fiber yarn bundle is drawn and mechanically crimped, and then cut into a predetermined fiber length to obtain a two-component composite short fiber.

Next, a web is created using the two-component composite short fibers,
By treating the obtained web with a high-pressure liquid columnar flow, at least a portion of the segments made of the low melting point polymer component A are exfoliated from the composite short fibers, so that the single fiber fineness is 0.
．． The split short fibers are 7 denier or less, and at the same time, the short fibers are three-dimensionally entangled and integrated. When forming a web, the composite short fibers are opened using a fiber opening means such as a card, and the resulting web is deposited on a collecting surface of a moving net conveyor or the like. High-pressure liquid columnar flow treatment is a process in which a high-pressure liquid columnar flow collides with the web surface to split the two-component composite short fibers using stresses such as shearing, elongation, and compression, and at the same time create three-dimensional entanglements between the short fibers. They are integrated by combining them. The liquid used may be water at room temperature or warm water. A nozzle for injecting a liquid columnar flow has a hole diameter of 0.05 to 1. 0mm, preferably 0.1 to 0.4 mm. As for the injection pressure.

5-150kg/cTIG, preferably 10-10
It is best to set it to 0 kg/crlG. This injection pressure is 5
If kg/cnf is less than 0, the segments made of the polymer component A cannot be sufficiently exfoliated, which is not preferable. The distance between the nozzle and the web is 1-15 c
m is preferably set to 3 to 13 cm. If this interval becomes large, air will be mixed into the liquid columnar flow, reducing the effect of three-dimensional entanglement, which is not preferable.

Next, heat treatment is performed at a temperature higher than the melting point of the low melting point polymer component A, thereby forming the low melting point polymer component A.
A nonwoven fabric is obtained by at least partially adhering the short fibers using the short fibers. In addition.

The obtained nonwoven fabric may be subjected to a softening process to improve the flexibility of the nonwoven fabric. In the heat treatment, it is preferable to use a device that can sufficiently heat the inside of the web; for example, a hot air circulation dryer, an infrared heating device, etc. can be used. FIG. 2 is a process diagram showing an example of the manufacturing method of the present invention.

1 is a web, 2 is a net conveyor, 3 is a liquid columnar flow jet nozzle, 4 is a suction box, 5 is a dryer, 6 is a heat treatment machine, and 7 is a nonwoven fabric.

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

The ultrafine short fiber nonwoven fabric obtained by the production method of the present invention is
(a) two-component composite short fibers made of polymer component A and polymer component B that is incompatible with said polymer component A; and (b) segments made of polymer component A from said two-component composite short fibers. Partially exfoliated 2T&min. composite short fibers and (c) 2 above
The polymer component B expressed by splitting component composite short fibers
and (d) split short fibers consisting only of the polymer component A.

The ultrafine short fiber nonwoven fabric obtained by the production method of the present invention is
The splitting ratio of the segment consisting solely of the polymer component is at least 80%. This splitting ratio is <
(b) bicomponent conjugate short fibers in which the segments made of polymer component A are partially exfoliated from the bicomponent conjugate short fibers; and (8) division of the bicomponent conjugate short fibers. 10 arbitrary locations of the nonwoven fabric composed of the split short fibers made only of the polymer component B expressed by (d) split short fibers made only of the polymer component A were selected, and the cross section of the nonwoven fabric was It is calculated by taking an enlarged cross-sectional photograph and then taking into account the total number of segments to the polymer component that has peeled off from the composite short fibers and the total number of segments to the existing polymer component in the cross-sectional photograph. represents the ratio (%) of the total number of exfoliated segments of polymer component A to the total number of segments of polymer component A present.The ultrafine short fiber nonwoven fabric obtained by the production method of the present invention has a soft texture. Therefore, it is preferable that the splitting ratio is at least 80%, and this splitting ratio is 80%.
If it is less than %, the flexibility will be poor when made into a nonwoven fabric, which is not preferable.

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

It is preferable that the single yarn fineness is 0.7 denier or less, preferably 0.5 denier or less. Even if the splitting ratio is 80% or more, if the single fiber fineness of the splitting short fibers made of one polymer bottom portion A exceeds 0.7 denier, a nonwoven fabric with a flexible texture cannot be obtained. , undesirable.

(Example) Next, the present invention will be specifically described based on Examples. Incidentally, various characteristics in the examples were measured by the primary method.

Phase, relative viscosity: What is the relative viscosity of the polyester polymer?

The measurement was carried out using a mixed solution of equal weights of phenol and ethane tetrachloride as a solvent, at a sample concentration of 0.5 g/100 m, and at a temperature of 20°C.

Relative viscosity: What is the relative viscosity of polyamide polymers?

Using sulfuric acid with a concentration of 96% by weight as a solvent, the sample concentration was 0.5g1
50-1 Measured at a temperature of 25°C.

Melt flow rate: Measured by STM D I238 L 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.

Tensile strength in vertical direction of non-woven fabric Width is 25 mm, length is 100 mm
An old measurement sample piece was prepared and measured using the strip method described in JIS L-1096.

A measurement sample piece having a compression stiffness width of 501 nXa and a length of 100 mm was prepared, and this sample piece was placed in a cylindrical shape with a height of 50-1 and a circumference of 100 mm on a flat plate type load cell.

The cylindrical sample piece was compressed at a speed of 50 rhymes/min, the maximum load was determined, and the obtained value was taken as the compression stiffness.

Fabric weight: Measured by the method described in JIS P-8142.

Example 1 Melting point: 130°C, melt flow rate: 20 g/
A 10-minute polyethylene polymer was used as polymer component A, a polyethylene terephthalate polymer with a melting point of 260°C and a relative viscosity of 1.38 was used as polymer component B, and the composite spinning hole was 319.
The bicomponent composite fibers were melt spun at a spinning temperature of 270° C. through a proprietary spinneret. 1 polymer component A during melt spinning
Single hole discharge rate of 0.26 g/min 1 Single hole discharge rate of polymer component B 0.21 g/min [ratio of component A and component B (
The volume ratio was 2:1]. After the spun composite fiber yarn was cooled, it was taken up by a take-up roll having a peripheral speed of 1000 m/min to obtain a package of undrawn fiber yarn. The obtained packages were collected and bundled to form a 100,000 denier tow, and stretched at a stretching temperature of 75° C. and a stretching ratio of 2.5.
Next, the fibers were mechanically crimped using a push-in crimper, and then cut to a length of 51 mm to obtain two-component composite short fibers. This short fiber has a single fiber fineness of 2 denier and is composed of one polymer component A and one polymer component B as shown in FIG. The combined component A had a petal-like cross-sectional shape.

Next, the 211ii composite short fibers were opened at a speed of 50 m/min using a roller card to obtain a basis weight of 40 g/m1.
After creating the web, as shown in Figure 2.

The resulting web was deposited on the surface of a moving net conveyor at a speed of 10 m/min and treated with two successive high-pressure water columns. This processing condition is such that the injection nozzle hole diameter is 0.15m.
m, the nozzle hole arrangement interval is 1.0IEl, and the number of nozzle hole rows is 2. The pressure of the first row of nozzle holes was 20 kg/m'G, the pressure of the second row of nozzle holes was 40 kg/m''G, and the distance between the nozzle and the web was 100 mm, and the injection treatment was performed from the web side. During treatment, used water was collected and removed using a suction box.

Continuing with the high-pressure water column flow treatment, the web was subjected to heat treatment using a dryer. What are the processing conditions?

The treatment temperature was 140° C. and the treatment time was 1 minute.

The obtained nonwoven fabric has a basis weight of 44 g1rd, a longitudinal tensile strength of 9.0 kg/3 cm, and a compression stiffness of 4.1.
It was g. Select 10 arbitrary locations on the nonwoven fabric, enlarge the cross section of the nonwoven fabric, take cross-sectional photographs, and then calculate the total number of segments of polymer component A that have peeled off from the composite staple fibers in the 10 cross-sectional photographs. When the total number of segments of polymer component A was determined and the 90% fiber ratio was determined, the 100% fiber ratio was 91%. This nonwoven fabric contains (d) split staple fibers made only of the polymer component A, and (i) two-component composite short fibers in which segments made of the polymer component A have not been peeled off at all.

(b) Two-component composite short fibers in which segments made of polymer component A are partially exfoliated from the two-component composite short fibers, and (c)
Split short fibers composed only of the polymer component B developed by splitting the two-component composite short fibers were observed.

Further, when the single fiber fineness of the split short fibers composed only of the polymer component A developed by splitting the composite short fibers was determined, it was found to be extremely fine at OJ7 denier. This nonwoven fabric had a soft touch.

Comparative Example 1 Two-component composite short fibers were obtained in the same manner as in Example 1, except that no heat treatment was performed, and the fibers were spread using a roller card to create a web with a basis weight of 40 g/m'. The resulting web was treated with a high-pressure water column twice in succession to obtain a nonwoven fabric.

The obtained nonwoven fabric has a basis weight of 38 g/g, a longitudinal tensile strength of 6.21 cg/3 cs, and a compression stiffness of 3.5.
g, and although it had excellent flexibility, it had low strength because the short fibers were not bonded.

Example 2 Melting point is 170°C, melt flow rate value is 50 g/
A 10-minute polypropylene polymer was used as polymer component A.

In the same manner as in Example 1 except that the melting temperature was 270°C, the bicomponent composite fiber was melt-spun and taken off with a take-off roll to obtain a package of undrawn fiber yarn. Gather and focus to make a 100,000 denier tow.
After stretching at a stretching temperature of 75°C and a stretching ratio of 2.5, and then mechanically crimp with a push-in crimper, the length was 51.
A two-component composite short fiber was obtained by cutting the fiber into 10 mm. This short fiber has a single fiber fineness of 2 denier and is composed of one polymer component A and one polymer component B as shown in FIG. The combined component A had a petal-like cross-sectional shape.

Next, in the same manner as in Example 1, the two-component composite short fibers were opened using a roller card to obtain a basis weight of 40 g/m''.
After creating the web, the speed of the obtained web is 10 m.
It was deposited on the surface of a net conveyor moving at a speed of 1/2 min and treated with two consecutive high-pressure water column flows.

Continuing with the high-pressure water column flow treatment, the web was subjected to heat treatment using a dryer. What are the processing conditions?

The treatment temperature was 170° C. and the treatment time was 1 minute.

The obtained nonwoven fabric has a basis weight of 43 g/m'', a longitudinal tensile strength of 9.4 kg/3 cti, and a compression stiffness of 4.
It was 9g. When 10 arbitrary points of the nonwoven fabric were selected and the 90% fiber ratio was determined, the 100% fiber ratio was 90%. This nonwoven fabric includes (d) split staple fibers made only of the polymer component A, (b) two-component composite short fibers with no exfoliated segments made of the polymer component A, and ( 0)
(c) a two-component conjugate short fiber in which a segment made of polymer component A is partially exfoliated from the two-component conjugate short fiber;
The polymer component B expressed by splitting component composite short fibers
It was recognized that split short fibers were composed only of Also,
When the single fiber fineness of the split short fibers composed only of the polymer component A developed by splitting the composite short fibers was determined,
It was extremely thin at 0.35 denier. and,
This nonwoven fabric had a soft touch.

Comparative Example 2 Two-component composite short fibers were obtained in the same manner as in Example 2, except that no heat treatment was performed, and the fibers were opened using a roller card to create a web with a basis weight of 40 g/m. The resulting web was treated with a high-pressure water column twice in succession to obtain a nonwoven fabric.

The obtained nonwoven fabric has a basis weight of 38 g/m', a longitudinal tensile strength of 6.8 kg/3 am, and a compression stiffness of 3.8.
g, and although it had excellent flexibility, it had low strength because the short fibers were not bonded.

Example 3 The procedure was the same as in Example 1 except that the polymer component B was a nylon 6 polymer (manufactured by Unitika Co., Ltd., trade name A1030BRF) with a melting point of 217°C and a relative viscosity of 3.09, and the melting temperature was 265°C. Then, the bicomponent composite fiber was melt-spun and taken off with a take-up roll to obtain a package of undrawn fiber yarn, and the obtained package was collected and bundled into a 100,000-denier tow, and the drawing temperature was set at 75°C. The fibers were stretched at a stretching ratio of 2.6, mechanically crimped using a push-in crimper, and then cut to a length of 51 mm to obtain two-component composite short fibers. This short fiber had a single fiber fineness of 2 denier, as shown in FIG. 1(a).

It consisted of a polymer component A and a polymer component B, and had a cross-sectional shape in which four polymer components A were added around the polymer component B in a petal shape.

Next, in the same manner as in Example 1, the two-component composite short fibers were opened using a roller card to give a basis weight of 40 g/
After creating a web of m', the resulting web is deposited on the surface of a moving net conveyor at a speed of 10 m/min,
Two consecutive treatments were carried out with high pressure water column flow.

Continuing with the high-pressure water column flow treatment, the web was subjected to heat treatment using a dryer. What are the processing conditions?

The treatment temperature was 140° C. and the treatment time was 1 minute.

The obtained nonwoven fabric has a basis weight of 47 g/m'', a longitudinal tensile strength of 8.6 kg/3 cm, and a compression stiffness of 4.8.
It was g. When 10 arbitrary points of the nonwoven fabric were selected and the 1-split fiber ratio was determined, the 2-split fiber ratio was 88%. Also.

When the single fiber fineness of the split short fibers composed only of the polymer component A developed by splitting the composite short fibers was determined,
It was extremely thin at 0.38 denier. and,
This nonwoven fabric was extremely soft to the touch.

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

It is composed of two-component composite short fibers and split short fibers developed by splitting the two-component composite short fibers, and the short fibers are at least partially adhered by the short fibers made of a low melting point polymer component. Strong and excellent.

Moreover, a nonwoven fabric having a soft texture can be efficiently produced at low cost.

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

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an example of the two-component composite short fiber according to the present invention, and FIG. 2 is a process diagram showing an example of the manufacturing method according to the present invention. 1: Web, 2: Net conveyor, 3: Liquid column underground jet nozzle. : Non-woven fabric

Claims (3)

[Claims] (1) A two-component composite consisting of a polyolefin polymer component A and a polymer component B that is incompatible with the polyolefin polymer component A and has a melting point at least 20°C higher than the melting point of the polymer component A. The fibers are melt-composite-spun, the undrawn fiber yarns of the spun bicomponent composite fibers are collected and bundled into undrawn fiber yarn bundles, and then the obtained undrawn fiber yarn bundles are collected. After being stretched and mechanically crimped, the fibers are cut into a predetermined fiber length to obtain two-component composite short fibers, a web is created using the two-component composite short fibers, and the obtained web is treated with a high-pressure liquid columnar flow. By doing so, at least a portion of the segment made of the low melting point polymer component A is peeled off from the composite short fibers to obtain split short fibers having a single filament fineness of 0.7 denier or less, and a three-dimensional structure is formed between the short fibers. By entanglement and integration, and then heat treatment at a temperature higher than the melting point of the low melting point polymer component A, the short fibers made of the low melting point polymer component A are used to at least partially connect the short fibers. A method for producing an ultrafine short fiber nonwoven fabric characterized by adhesion. (2) The ultrafine according to claim 1, wherein the polyolefin polymer component A constituting the two-component composite staple fiber is a polyethylene polymer or a polypropylene polymer, and the polymer component B is a polyester polymer or a polyamide polymer. A method for producing short fiber nonwoven fabric. (3) Claim 1 or 2, wherein the split short fibers are ultrafine short fibers with a single fiber fineness of 0.5 denier or less, which is composed only of the low melting point polymer component A developed by splitting the two-component composite short fibers. The method for producing the ultrafine short fiber nonwoven fabric described above.