JPH0860441A - Thermally fusible conjugate fiber and thermally fusible nonwoven fabric - Google Patents

Abstract

PURPOSE: To obtain a surface material for sanitary materials such as sanitary napkin and paper diaper, excellent in strength of nonwoven fabric, high recovery of bulkiness and weave characteristics hardly forming nep (small fiber mass) and having soft touch feeling and a thermally fusible nonwoven fabric widely used as the surface material for sanitary materials. CONSTITUTION: This thermally fusible conjugate fiber is composed of the first component comprising a crystalline polypropylene and the second component consisting mainly of polyethylene and the second component is arranged as parallel type or eccentric sheath-core type so as to continuously exist on at least one part of fiber surface in longitudinal direction and has threedimensional latent crimp having 4-16 tops/inch, 1.0-2.0 denier single yarn fineness and 20-40mm apparent cut length.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing heat-fusible composite fibers and a heat-fusible nonwoven fabric. More specifically, it is widely used as a surface material for sanitary materials such as sanitary napkins and disposable diapers, and a surface material for sanitary materials, which has excellent nonwoven fabric strength, high bulkiness and recovery properties, and formation properties with little nep (small fiber lumps). The present invention relates to a heat-fusible nonwoven fabric and a method for producing a heat-fusible composite fiber.

[0002]

2. Description of the Related Art Nonwoven fabrics such as sanitary napkins and surface materials for sanitary materials such as disposable diapers have become more sophisticated in performance in recent years due to diversification, and the nonwoven fabric strength can be maintained with as little weight as possible and bulkiness. A high recovery rate, less nep (small fiber mass) as a formation characteristic, and a soft texture are required. In order to satisfy these, production of a bulky nonwoven fabric obtained by heat-sealing the heat-fusible conjugate fiber in which the Q value of the first component, preheating at a specific temperature, draw ratio, crimp number, crimp elastic modulus, etc. are specified. The method is known from Japanese Patent Publication No. 1-37055.

However, as a surface material for sanitary materials, it is still insufficient, there are problems in the opening (card) process, many neps (small fiber lumps) deteriorate the texture, the bulkiness recovery rate is small, and the strength is high. It was a non-woven fabric with no texture. Further, development of a non-woven fabric that solves all of these is desired.

[0004]

Means for Solving the Problems The present inventor has arrived at the invention described below as a result of intensive studies for improving the above-mentioned drawbacks. That is, the present invention comprises a first component made of crystalline polypropylene and a second component mainly made of polyethylene, and the second component is arranged in parallel so that at least a part of the fiber surface is continuously present in the longitudinal direction. Or it is arranged in an eccentric sheath core type and has a three-dimensional actual crimp of 4 to 16 ridges / inch,
Single yarn fineness 1.0 to 2.0d, apparent cut length 20 to 4
A 0 mm heat-fusible composite fiber, a spinning process of spinning with a parallel type or an eccentric sheath core type spinneret,
The maximum drawing ratio of 0.60 at a temperature of 0 ° C or higher and 130 ° C or lower
Through a drawing process of drawing at 0.85 times, a crimping process of cooling the drawn yarn to a temperature equal to or lower than a preheating temperature and a crimping process, and an annealing process of annealing at a temperature of 80 ° C. to 120 ° C. after cooling. A method for producing a heat-fusible conjugate fiber, comprising 50% by weight or more of the heat-fusible conjugate fiber or the heat-fusible conjugate fiber obtained by the above-mentioned production method, and further comprising a second component of the conjugate fiber. It is a heat-fusion nonwoven fabric in which the intersections of fibers are heat-fused by heat fusion, and the above-mentioned heat-fusion nonwoven fabric is used to obtain a thickness of 1 m.
It is a sanitary material surface material of m or more.

First in the heat-fusible composite fiber of the present invention
The crystalline polypropylene used as a component is a general term for a crystalline polymer containing propylene as a main component, and among them, not only a homopolymer of propylene but also ethylene, butene-
A copolymer with 1 or 4-methylpentene-1 and the like are included. The polyethylene mainly used as the second component is a general term for a polymer containing ethylene as a main component, such as a high-pressure process polyethylene or a medium- and low-pressure process polyethylene. -1, or a copolymer (EVA) with vinyl acetate, etc., but the melting point of this polyethylene is 20 ° C. higher than the melting point of the crystalline polypropylene which is the first component.
It is preferably lower than the above. Various stabilizers, fillers, pigments and the like usually used for polyolefin fibers can be added to the above crystalline polypropylene and polyethylene within the range not impairing the object of the present invention.

The heat-fusible conjugate fiber of the present invention is a conjugate fiber spun from a conjugate fiber side-by-side type or an eccentric sheath-core type spinneret, and the conjugate fiber second component has a length of at least a part of the fiber surface. It is necessary to continuously exist in the direction, and it is preferable to cover the fiber surface as widely as possible. Further, since the heat-fusible composite fiber generates crimps by utilizing the difference in elastic contraction of the two components, in the case of the sheath-core structure, the core component has an eccentric sheath-core as shown in FIG. The mold structure is preferable, and the center of the core component is preferably deviated from the center of the outer diameter of the composite component by 5 to 15%. Such a composite fiber can be obtained by a conventionally known melt spinning method of a parallel type or a sheath-core type in which the second component is a sheath component. There is no particular limitation on the ratio of the composite of both components, but it is preferable that the second component is 40 to 70% by weight.

The heat-fusible conjugate fiber of the present invention is preferably a fiber having a three-dimensional crimp and substantially no so-called latent crimp, which does not cause crimp during the heat treatment for forming a nonwoven fabric described later. When the fiber has substantially no latent crimp, it is possible to avoid shrinkage due to development of latent crimp that occurs during heat treatment for forming a nonwoven fabric. The number of crimps of the heat-fusible conjugate fiber of the present invention is 4 to 16 ridges / inch, preferably 6 to 14 ridges / inch. If the number of crimps is less than 4 threads / inch, it may be wound around the cylinder of the card machine. If the number of crimps exceeds 16 threads / inch, the opening will be poor and nep will occur when forming the nonwoven fabric. The thing is not targeted.

The heat-fusible conjugate fiber of the present invention needs to have a single yarn fineness of 1.0 to 2.0 d. When it is less than 1.0 d, the number of crimps becomes fine and problems such as nep occurrence occur. If it exceeds 2.0 d, the texture tends to be hard and the recovery rate of the non-woven fabric tends to be poor.

The apparent cut length of the heat-fusible composite fiber of the present invention is 20 to 40 mm, preferably 25 to 35 mm. When it is less than 20 mm, the migration of the fibers in the card machine is poor, which causes troubles such as winding around the walker, and when it is more than 40 mm, the entanglement of the fibers becomes strong and nep occurs. The heat-fusible conjugate fiber of the present invention preferably has an apparent cut length / cut length ratio of 50 to 70%. When it is less than 50%, the migration of the fiber inside the card machine is poor, causing troubles such as wrapping around the cylinder etc. Nep, and when it exceeds 70%, the entanglement of the fiber becomes strong and the cause of wrapping at the tea kine etc. Next to
The card process itself becomes impossible.

The method for producing the heat-fusible conjugate fiber of the present invention comprises a spinning step of spinning with a parallel type or an eccentric sheath core type spinneret,
A drawing process of drawing the spun undrawn yarn at a temperature of 90 ° C. or higher and 130 ° C. or lower at 0.60 to 0.85 times the maximum draw ratio, and a crimping process in which the drawn yarn is cooled to a preheating temperature or lower and crimped. After the process and cooling, it is annealed at a temperature of 80 ° C to 120 ° C
It goes through the annealing step of ringing.

In the spinning step, the first component made of crystalline polypropylene and the second component mainly made of polyethylene are spun, and the second component is arranged in parallel so that at least a part of the fiber surface is continuously present in the longitudinal direction. Spinning with a mold or an eccentric sheath core spinneret. In the drawing temperature step, the spun undrawn yarn is preheated to the drawing temperature. When the stretching temperature is less than 90 ° C, the number of crimps becomes fine, and when it exceeds 130 ° C,
It is not preferable because the fusion of the fibers with polyethylene occurs remarkably. When the draw ratio is 0.60 times or less than the maximum draw ratio, the difference in elastic shrinkage between the two components for generating crimp is reduced, and no crimp occurs. This is not preferable because the difference in shrinkage is large, the crimp cycle is short, the number of crimps is large, and the apparent cut length is short. Here, the maximum draw ratio means the draw ratio at which fluff begins to occur in the tow when the draw ratio is gradually increased.

In the crimping process, the drawn yarn is cooled to a temperature not higher than the drawing temperature, and the drawn yarn is drawn in a tension state by a take-up roll of a nip roll or the like to be in a relaxed state so that crimps are developed. At this time, if the temperature exceeds the stretching temperature,
Insufficient crimping. In the annealing process, after crimping,
The heat-fusible composite fiber in which crimps are developed is 80 ° C. or higher and 120 ° C.
Anneal at the following temperatures for about 0.5-30 minutes. If the annealing temperature is lower than 80 ° C., latent crimps may occur during processing of the nonwoven fabric, and if it is 120 ° C. or higher, the crimps generated due to the difference in elastic shrinkage tend to be elongated and the apparent cut length becomes large, which is not preferable. The heat-fusible composite fiber of the present invention is often used as a staple after being cut into a predetermined length in order to easily process it into a nonwoven fabric.

The heat-fusible nonwoven fabric of the present invention may contain the above-mentioned heat-fusible composite fiber in an amount of 50% by weight or more, and may be 100% by weight. The heat-bonded nonwoven fabric is obtained as a nonwoven fabric by heating the web and heat-bonding the web by a conventional carding method, air-lay method, or dry pulp method.
The heat-fusible nonwoven fabric of the present invention includes, as fibers other than the above-mentioned heat-fusible composite fibers, polyester, polyamide, polypropylene, polyethylene, other synthetic fibers, natural fibers such as cotton and wool, and fibers such as rayon. Less than 50% by weight may be mixed. At this time, the heat fusible composite fiber is 5
It is necessary that 0% by weight or more is mixed. When the content of the heat-fusible composite fibers is less than 50%, the heat-bonding points at the intersections of the fibers are small, so that not only high nonwoven fabric strength cannot be obtained, but also the desired bulkiness and recoverability cannot be obtained. The thing is not targeted.

Examples of the method of heating and heat fusion include a method of hot air dryer, suction band dryer, and the like. With this, the second component of the composite fiber is heat fused to heat the intersection of the fibers, It becomes a non-woven fabric. The heat treatment temperature is a temperature above the melting point of the second component of the composite fiber and below the melting point of the first component, which is about 120-155 ° C. The processing time is about 5 seconds or more when using a dryer or the like. The sanitary material surface material of the present invention is a sanitary material surface material having a thickness of 1 mm or more, which uses the above-mentioned heat-bonded nonwoven fabric. Especially bulky property is 1
It is desirable that the recovery rate be 50 mm or more and the recovery rate be 50 mm or more. When the thickness is less than 1 mm and the recovery rate is less than 50%, a soft texture cannot be obtained, so such a material is not targeted.
Here, the thickness to say, applying a load of 50gf per 1cm ² 24 hours, then allowed to stand for one hour at no load, to recover the thickness refers to the thickness was measured by applying a load of 2gf per 1cm ² a (mm) , Recovery rate is 50kg per cm ^2.
The difference between the thickness measured by applying a load of f over 24 hours and the thickness after being left for 1 hour without a load and the measured thickness is shown in percentage (%).

[0015]

EXAMPLES The present invention will be specifically described below with reference to examples. The measuring methods or definitions of the physical property values shown in the examples are collectively shown. Number of crimps: Measured according to JIS L1015 (Chemical fiber staple test method) 7.12.1. Single yarn fineness: Measured according to JIS L1015 (Chemical fiber staple test method) 7.5.1, Method A.

Apparent cut length: The length (mm) of the fiber without tension was measured without stretching the crimped staple or applying unnecessary force, and the average of 30 measured values was obtained. Bulk property: The resulting non-woven fabric is subjected to a load (50 gf / cm ² ) for 24 hours to measure the thickness (A), and then left for 1 hour without any load to recover the thickness, and a load of ² gf / cm ² is applied. (B) is measured and the recovery rate (thickness (B) -thickness (A)) / thickness (B) is calculated as a percentage (%). And the result is ○,
No was shown by x. Nonwoven fabric strength: In accordance with JIS L1085 (nonwoven fabric interlining test method), a test piece having a width of 5 cm is held at a grip interval of 10 cm,
Measured in the fiber direction (MD) and the direction perpendicular to it (CD) at a pulling speed of 30 ± 2 cm, the pass / fail judgment is MD strength 2500 g /
5cm or more, less than, CD strength 500g / 5cm
The above results were totaled, less than were rejected, and the results were indicated by o and x by. Number of neps: The number of neps in 1 m ^{2 of} non-woven fabric was counted, and the number was expressed as number / m ² , and 1 or less was total, 2 or more was unacceptable, and the unacceptability was indicated by ×, and unacceptable was indicated by ×. Feeling: Performing a sensory test by 5 panelists, excellent when all were judged to be soft, good when 3 or more were judged to be soft, and judged to be lacking in softness for 3 or more The case was evaluated as unsatisfactory, and excellent was indicated by ◯, good by Δ, and unacceptable by x. Web shrinkage: Cut the web into 25 cm squares and dry
After heating at 145 ° C. for 5 minutes under no load, the shrinkage in the fiber direction is obtained at three points, and the average value is shown, and if less than 10%,
10% or more was rejected, the result was indicated by ◯, and the rejection was indicated by x.

Examples 1 to 4, Comparative Examples 1 to 9 Polypropylene as the first component, polyethylene shown in Table 1 as the second component, a core-sheath type with a hole diameter of 0.6 mm and a number of holes of 350, and a parallel type spinneret. The composite fiber is spun using the above, drawn under the conditions shown in Table 1, and the first using a cutter of a predetermined length.
The staples shown in the table were obtained. The physical properties of these fibers are summarized in Table 1.

The obtained heat-fusible composite fiber staple is made into a web having a basis weight of 20 to 30 g / m ² by a carding machine, and the web is heated at a predetermined temperature of 135 to 140 ° C. for 5 seconds using a suction band dryer. A non-woven fabric was obtained which was treated to heat-weld the intersections of the heat-fusible fibers. The characteristics of the non-woven fabric are shown in Table 2. In Example 2 and Comparative Example 8 in Table 2, the staples of Example 1 and Comparative Example 3 in Table 1 were used.

[0019]

EFFECTS OF THE INVENTION The heat-fusible conjugate fiber of the present invention has high bulkiness recoverability, which has been impossible up to now, and good formation properties,
A non-woven fabric having high tenacity and a very soft touch feeling, and a fiber useful as a surface material for sanitary materials, and at the same time, all of these improvements were satisfied. As a result, it can be widely used for sanitary napkins, nonwoven fabrics such as paper diapers, and surface materials for sanitary materials.

[0020]

[Table 1]

[0021]

[Table 2]

[Brief description of drawings]

FIG. 1 is a sectional view of a composite fiber of the present invention.

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Claims (4)

[Claims] 1. A first component consisting of crystalline polypropylene and a second component consisting mainly of polyethylene,
The second component is arranged in a parallel type or an eccentric sheath-core type so that at least a part of the fiber surface is continuously present in the length direction, and
It has a three-dimensional actual crimp of 16 to 16 mountains / inch and a single yarn fineness of 1.
A heat-fusible composite fiber having an apparent cut length of 0 to 2.0 d and a cut length of 20 to 40 mm. 2. A spinning step of spinning with a parallel type or an eccentric sheath core type spinneret, and the spun undrawn yarn is drawn at a temperature of 90 ° C. or higher and 130 ° C. or lower at a maximum draw ratio of 0.60 to 0.85 times. 2. The heat fusible property according to claim 1, which has been subjected to a stretching step, a crimping step of crimping the drawn yarn to a temperature lower than a preheating temperature, and an annealing step of annealing at a temperature of 80 ° C. or higher and 120 ° C. or lower after cooling. Method for manufacturing conjugate fiber. 3. The heat-fusible conjugate fiber according to claim 1 or the heat-fusible conjugate fiber obtained by the production method according to claim 2 is contained in an amount of 50% by weight or more, and heat of the second component of the conjugate fiber is contained. A heat-fusion nonwoven fabric in which the intersections of fibers are heat-fused by fusion. 4. The heat-fusion non-woven fabric according to claim 3, which has a thickness of 1
Sanitary material surface material of mm or more.