JP2011506778A - Composite fiber having low-temperature processability, nonwoven fabric and molded body using the same - Google Patents

Abstract

It has low-temperature processability, shrinkage is suppressed, has good thermal adhesiveness, has excellent card-passing processability when processed into a nonwoven fabric, and obtains a bulky and well-formed nonwoven fabric A composite fiber is provided. In addition, the present invention provides a bulky non-woven fabric and a molded article having excellent low-temperature processability. A first component containing at least 75% by mass of an ethylene / α-olefin copolymer having a melting point of 70 to 100 ° C. and a second component containing crystalline polypropylene are a composite fiber having a parallel section, In the fiber cross section perpendicular to the fiber axis, the first component occupies 55 to 90% of the outer periphery of the fiber, and the boundary line between the first component and the second component curves convexly toward the first component side. A composite fiber, wherein the area ratio of the first component to the second component (first component / second component) is in the range of 70/30 to 30/70; A non-woven fabric obtained by a non-woven fabric treatment; a molded product obtained using the above composite fiber.
[Selection] Figure 1

Description

  The present invention relates to a composite fiber having low temperature processability during heat processing and having good thermal adhesiveness while suppressing shrinkage. Moreover, this invention relates to the nonwoven fabric and molded object which were excellent in the bulkiness and feel using the said composite fiber.

  Conventionally, various composite fibers having low-temperature processability have been proposed, and an ethylene / α-olefin copolymer that easily adjusts the melting point is used as a component constituting the composite fiber. For example, a sheath core type and a parallel type composite using a “mixture” of a polyethylene resin having a low melting point of 90 to 125 ° C. and a polyethylene resin having a high melting point of 120 to 135 ° C. as one component of the composite component A fiber has been proposed (see, for example, Patent Document 1). In addition, latent crimpable conjugate fibers using “each” of a component containing an ethylene / α-olefin copolymer and a component containing a polyester resin as one component of a composite component have been proposed (for example, Patent Documents). 2).

However, conventional conjugate fibers having low-temperature processability still leave room for improvement in practice. For example, the composite fiber proposed in Patent Document 1 substantially uses a polyethylene resin having a high melting point of 120 to 135 ° C. for stability of productivity while using a polyethylene resin having a low melting point of 90 to 125 ° C. In particular, since it is “mixed” in the range of 30% by mass or more and used as one component of the composite fiber, the low-temperature workability is impaired and it cannot be said that it is sufficient. Patent Document 2 relates to a latent crimpable composite fiber that utilizes the property that a composite fiber containing an ethylene / α-olefin copolymer as a component easily contracts during heat treatment. Shrinkable conjugate fibers are not suitable for obtaining a nonwoven fabric with good formation in which shrinkage is suppressed.
In addition, such a conjugate fiber having latent crimping property utilizes a difference in shrinkage between a plurality of constituent components, and such a component easily peels after heat treatment, and is a non-woven fabric. If the adhesive component that melts and other components that do not melt are peeled off during processing, the fibers made of the adhesive component and the fibers made of other components that do not melt are mixed in the nonwoven fabric. When there are many portions that do not contribute to the strength of the nonwoven fabric, there may be a problem that the strength of the nonwoven fabric does not come out.
Thus, what was proposed as a fiber which has low temperature workability until now needed further improvement in the point of low temperature workability, the formation of a nonwoven fabric, and intensity | strength.

International Publication No. 00/36200 Pamphlet Japanese Patent Laid-Open No. 2006-233381

  The object of the present invention is to have low-temperature processability and to suppress shrinkage, to have good thermal adhesiveness, and to pass through the card especially when processing into a non-woven fabric, particularly when card processing is performed. An object of the present invention is to provide a composite fiber that can obtain a non-woven fabric that is excellent in bulk, is bulky, and has good texture. Another object of the present invention is to provide a non-woven fabric and a molded article that are excellent in low-temperature processability, are bulky, and have a good texture.

As a result of intensive studies, the inventor has identified a specific ethylene / α-olefin copolymer as a component that contributes to the low-temperature processability of the composite fiber, that is, a component having a lower melting point that is exclusively softened and melted during heat treatment. It has been found that the above-mentioned problems can be achieved by a composite fiber that constitutes a specific parallel-type cross section in which a specific amount or more of a coalescence is included, which is a first component, and a component that includes crystalline polypropylene is a second component.
Accordingly, in the present invention, the first component containing at least 75% by mass of the ethylene / α-olefin copolymer having a melting point of 70 to 100 ° C. and the second component containing crystalline polypropylene constitute a parallel section. In the fiber cross section perpendicular to the fiber axis, the first component occupies 55 to 90% of the outer periphery of the fiber, and the boundary between the first component and the second component is directed toward the first component side. A composite having a convexly curved curve and an area ratio (first component / second component) between the first component and the second component in the range of 70/30 to 30/70 Fiber.

In the embodiment of the present invention, the ethylene / α-olefin copolymer used has a molecular weight distribution (Mw / Mn) of 1.5 to 2.5, a density of 0.87 to 0.91 g / cm ³ , and ASTM. According to D-1238, an ethylene / α-olefin copolymer having a melt index (MI) of 10 to 35 g / 10 min measured under conditions of a temperature of 190 ° C. and a load of 21.2 N can be mentioned.
The composite fiber can exhibit a heat shrinkage of 50% or less when heat treated at 100 ° C. for 5 minutes.
The composite fiber of the present invention can be processed into a non-woven fabric to produce a non-woven fabric, and the composite fiber of the present invention is processed or the nonwoven fabric obtained from the composite fiber of the present invention is processed to form a molded body. It can be.
Accordingly, the present invention is further directed to a nonwoven fabric obtained by subjecting the composite fiber to a nonwoven fabric treatment, a molded body obtained using the composite fiber, and a molded body obtained using the nonwoven fabric. .
Examples of the non-woven fabric treatment include a hot air bonding method and a hot water bonding method.

  The composite fiber of the present invention has a component containing at least 75% by mass of an ethylene / α-olefin copolymer having a melting point of 70 to 100 ° C. as a first component, and in the fiber cross section perpendicular to the fiber axis, The boundary line with the second component occupies 55 to 90% of the outer periphery of the fiber, and a curve that curves convexly toward the first component side is drawn, and the area ratio with the second component (first component / first component) 2 component) has a parallel section configured to be in the range of 70/30 to 30/70. Since the first component containing this ethylene / α-olefin copolymer mainly covers the fiber surface, it exhibits good thermal adhesion at a heat treatment temperature of 100 ° C. or less. That is, it has good low temperature workability. In addition, since the second component containing crystalline polypropylene is exposed on a part of the fiber surface, the height of surface friction peculiar to ethylene / α-olefin copolymers can be reduced, and a lubricant or the like can be added. Even if it is not added or is added in a small amount, stable production in the fiber production process is possible, and in particular, when card processing is performed, fiber permeability in the card process is good.

  In a general two-component parallel cross-sectional shape combined with a half-moon shape, there is concern about separation between components. In the parallel section of the composite fiber of the present invention, the first component containing the ethylene / α-olefin copolymer occupies 55 to 90% of the length of the peripheral surface, and the boundary line with the second component is on the first component side. A curve that curves in a convex shape toward the surface and is configured so that the area ratio (first component / second component) to the second component is in the range of 70/30 to 30/70. In particular, when card processing is performed, preferable workability is exhibited without impairing the fiber permeability in the card process and the strength of the nonwoven fabric after processing into a nonwoven fabric. Further, in the general two-component parallel type cross-sectional shape combined with the half-moon shape, there is a point that shrinkage is likely to occur due to heat treatment, but the conjugate fiber of the present invention has a specific ethylene / α-olefin copolymer as the first. It is considered that shrinkage is effectively suppressed by adopting a specific fiber cross-sectional shape as a component.

  The nonwoven fabric obtained by using the conjugate fiber of the present invention is bulky and soft, and has little shrinkage during heat treatment, so there is almost no width (reduction in width with respect to the flow direction of the nonwoven fabric), and productivity and formation are good. It is. Moreover, since the composite fiber of this invention uses the component containing melting | fusing point 70-100 degreeC ethylene / alpha-olefin copolymer as an active ingredient, the heat processing at 100 degrees C or less is attained. Therefore, since it becomes possible to use a medium such as steam or hot water when forming the nonwoven fabric of the conjugate fiber of the present invention or molding processing, depending on the application, environment, and situation, from a wide range of options, Appropriate nonwoven fabric forming conditions and molding process conditions can be selected.

It is the schematic which illustrates the shape of the parallel type cross section of the composite fiber of this invention.

  In the conjugate fiber of the present invention, a component containing an ethylene / α-olefin copolymer is a first component. The ethylene / α-olefin copolymer is composed of ethylene and α-olefin. Specific examples of the α-olefin include linear α-olefins such as propylene, butene-1, pentene-1, hexene-1, heptene-1, and octene-1. Of these, butene-1 and octene-1 are preferable, and octene-1 is more preferable. The α-olefin content in the ethylene / α-olefin copolymer is preferably 30 mol% or less, and more preferably 20 mol% or less. The α-olefin content is usually 1 mol% or more. The content in this case refers to the molar ratio percentage of ((α-olefin) / (α-olefin + ethylene)). If the α-olefin content is too high, solidification is delayed in the fiber production process, and inter-fiber fusion or the like tends to occur and productivity tends to be impaired. When the α-olefin content is within 30 mol%, the fiber has sufficient rigidity, and in particular, when card processing is performed, the fiber permeability in the card process is good.

The melting point of the ethylene / α-olefin copolymer to be used is 70 to 100 ° C., preferably 80 to 100 ° C. With a melting point of 70 ° C. or higher, interfiber fusion can be prevented. For example, when a treatment agent such as an antistatic agent applied to the fiber surface in the fiber production process is dried, problems such as interfiber fusion occur. It becomes difficult and good productivity is exhibited. Moreover, when the melting point is 100 ° C. or lower, the processing temperature when processing the fiber into a nonwoven fabric or a molded body can be set to 100 ° C. or lower, and steam or hot water can be used as a heat treatment medium. This makes it possible to select a processing method using a relatively low temperature medium. In addition, it is not necessary to be concerned about the influence on other components that are not originally melted constituting the fiber, which is preferable.
The melting point mentioned here is the melting peak temperature when the ethylene / α-olefin copolymer is measured by a differential scanning calorimeter (DSC). When a plurality of melting peaks are confirmed, the temperature of the largest melting peak is taken as the melting point, and when melting peaks having a plurality of similar sizes are found, the lower melting peak temperature is taken as the melting point.

  The molecular weight distribution (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) and the number average molecular weight (Mn) of the ethylene / α-olefin copolymer, is preferably 1.5 to 2.5, more preferably 1.7-2.3. If the molecular weight distribution (Mw / Mn) is in the range of 1.5 to 2.5, the spinnability in the fiber production process will be good, and a composite fiber having sufficient strength in terms of fiber properties can be obtained. ,preferable.

The density of the ethylene / α-olefin copolymer is preferably 0.87 to 0.91 g / cm ³ , particularly preferably 0.88 to 0.90 g / cm ³ . When the density of the ethylene / α-olefin copolymer is 0.87 g / cm ³ or more, the surface viscosity when the copolymer is processed into fibers is moderate, and the fiber is less likely to stick during fiber production. It is suitable to be used as a main constituent of On the other hand, when the density is 0.91 g / cm ³ or less, the melting point of the ethylene / α-olefin copolymer is relatively low and is 100 ° C. or less, which is suitable as the ethylene / α-olefin copolymer used in the present invention. .

  The melt index (MI) of the ethylene / α-olefin copolymer is preferably 10 to 35 g / 10 min, more preferably 15 to 30 g / 10 min, in view of stable production in the fiber production process. Here, MI is a value measured under conditions of 190 ° C. and a load of 21.2 N according to ASTM D-1238.

The ethylene / α-olefin copolymer to be used may be a single type or a mixture of two or more types.
Various additives can be blended in the ethylene / α-olefin copolymer used in the present invention as long as the object of the present invention is not impaired. For example, lubricants, heat stabilizers, antioxidants, weathering stabilizers, antistatic agents, colorants and the like. Preferable examples of the lubricant include fatty acid amides such as oleic acid amide and erucic acid amide, fatty acid esters such as butyl stearate, polyolefin waxes such as polyethylene wax and polypropylene wax, and metal soaps such as calcium stearate. Particularly preferably used are fatty acid amides such as oleic acid amide, erucic acid amide, stearic acid amide, and behenic acid amide.

The first component in the conjugate fiber of the present invention is made of the above ethylene / α so that steam or hot water can be used as a heat medium at the time of forming into a non-woven fabric or molding so that it can be involved in thermal bonding at low temperatures. -It must contain an effective amount of an olefin copolymer. The content of the ethylene / α-olefin copolymer is 75% or more, preferably 85% or more, and particularly preferably 100% as a resin raw material, based on the mass of the first component. It is preferable that the ethylene / α-olefin copolymer is 75% by mass or more in the first component because the performance of the ethylene / α-olefin copolymer can be mainly exhibited.
In addition to the ethylene / α-olefin copolymer, the ethylene / α-olefin copolymer may be included in the first component under the condition that 75% or more of the ethylene / α-olefin copolymer is included on the mass basis of the first component. Examples of a good resin material include low density polyethylene, high density polyethylene, ethylene / vinyl acetate copolymer, and propylene copolymer. These are a method of uniformly mixing in advance in the state of a resin, and a method of feeding from an feed port in the middle of an extruder when an ethylene / α-olefin copolymer is melted and extruded in a fiber production process Can be mixed together.

The composite fiber of the present invention uses a component containing crystalline polypropylene as the second component. This crystalline polypropylene is a propylene homopolymer or a copolymer of propylene and a small amount of α-olefin (usually 2% by mass or less). As such crystalline polypropylene, Ziegler Natta catalyst or metallocene catalyst is used. There is a general-purpose polypropylene obtained by using.
The crystalline polypropylene in the present invention has a melting point of 150 to 165 ° C., preferably 155 to 165 ° C., a melt mass flow rate (MFR = 230 ° C., 21.2 N) of 0.1 to 80 g / 10 min, and further 3 to 40 g. Those within the range of / 10 min are preferred.
The second component constituting the conjugate fiber of the present invention contains crystalline polypropylene and, as long as the effect is not significantly impaired, mixing with a propylene / α-olefin copolymer, melt mass flow rate (MFR), A mixture of crystalline polypropylenes having different physical properties such as molecular weight distribution (Mw / Mn) can be suitably used. If necessary, other thermoplastic resins, inorganic substances such as titanium dioxide, calcium carbonate and magnesium hydroxide, various additives (flame retardants, heat stabilizers, antioxidants, weather stabilizers, antistatic agents, Colorants etc. may be added. In the second component constituting the conjugate fiber of the present invention, it is generally appropriate that crystalline polypropylene accounts for at least 75% by mass.

In the conjugate fiber of the present invention, a first component containing an ethylene / α-olefin copolymer and a second component containing crystalline polypropylene constitute a parallel-type cross section having a specific structure.
In the fiber cross section perpendicular to the fiber axis, 55 to 90% of the outer periphery of the fiber is occupied by the first component including the ethylene / α-olefin copolymer, and 45 to 10% is occupied by the second component including crystalline polypropylene. is there. When the first component including the specific ethylene / α-olefin copolymer occupies 55% or more of the outer periphery of the fiber, heat treatment at 100 ° C. or less is possible, and the second component including crystalline polypropylene is the fiber. By occupying 10% or more of the outer periphery, crystalline polypropylene continuously appears on the fiber surface, reducing inter-fiber friction, metal friction, and viscosity when ethylene / α-olefin copolymer is used on the fiber surface. The spinnability and, when card processing is performed, the card processability is good. In particular, in the fiber cross section perpendicular to the fiber axis, the first component including the ethylene / α-olefin copolymer occupies 60 to 80% of the outer periphery of the fiber, and the second component including crystalline polypropylene occupies 40 to 20%. Is preferred.

The conjugate fiber of the present invention further draws a curve in which the boundary line between the first component and the second component curves convexly toward the first component side in the fiber cross section perpendicular to the fiber axis. By having this structure, the length of the boundary line between the first component and the second component is increased, that is, between the two components compared to a composite fiber having a general parallel cross-sectional structure in which both components in a semicircular shape are simply joined. Further, when the first component has a structure in which the second component is wrapped, the peeling of the second component from the conjugate fiber is suppressed.
In particular, in the fiber cross section perpendicular to the fiber axis, two intersections where the boundary line between the first component and the second component that draws a curve curved in a convex shape toward the first component side intersects the outer circumference of the fiber are a and b. , A point where a straight line passing through a point c that bisects a line segment ab connecting a and b and extending in a direction perpendicular to the line segment ab intersects the boundary line between the first component and the second component is d, When the point intersecting the fiber outer periphery on the second component side is represented by e, the boundary line is the first so that the relationship between the length of the line segment cd and the length of the line segment ce satisfies the relationship of cd ≧ 0.8ce. It is preferable to have a structure that curves convexly toward the one component side. Further preferable is cd ≧ ce, more preferable is cd ≧ 1.5ce, and particularly preferable is the case where the relationship of cd ≧ 2ce is satisfied. Property is improved.
Further, when the boundary line between the first component and the second component that draws a curve that curves in a convex shape toward the first component side is regarded as a part of the outer periphery of a circle or ellipse drawn by the outer periphery of the second component, It is preferable that the length (g) of the boundary line exceeds 50% of the total outer circumferential length (h) of the circle or ellipse to be drawn by the second component, and more preferably 60% or more. is there. In particular, when both ends of the diameter or major axis of the circle or ellipse to be drawn by the second component are present in the fiber cross section perpendicular to the fiber axis of the composite fiber, and the length is f, the first When the length of the line segment ab connecting the two intersection points a and b where the boundary line between the component and the second component intersects the outer periphery of the fiber is in a relationship of f> ab, the second component is In the cross section, since a composite structure that exhibits an anchor function with respect to the first component can be formed, the anti-separation effect of the second component can be extremely effectively enhanced.

The two components constituting the composite fiber of the present invention are the fiber and the point that the ratio of the first component / second component = 70/30 to 30/70 maintains the cross-sectional shape in the area in the fiber cross section perpendicular to the fiber axis. It is also preferable from the viewpoint of stability during production and the balance between strength and elongation when processed into a nonwoven fabric, and a ratio of 60/40 to 40/60 is more preferable.
The conjugate fiber of the present invention can be produced using a conventionally known parallel type composite die. For example, it can be produced using a parallel type composite spinneret described in JP-A-48-11417 and JP-A-52-74011.

In order to form the cross-sectional shape of the composite fiber of the present invention using the parallel composite die, the first component containing the ethylene / α-olefin copolymer and the second component containing crystalline polypropylene are melted. It is necessary to balance fluidity (viscosity, etc.), and the melt index (MI) and melt mass flow rate (MFR) of the two components are taken into account and adjusted according to the conditions during fiber production. For example, for the first component containing an ethylene / α-olefin copolymer, the fluidity (viscosity) at the time of melting at a temperature of about 190 ° C. is measured, and fibers can be produced from fluctuations in the melt fluidity (melt viscosity). Select the temperature range for fluidity (viscosity) and set the extrusion temperature as the fiber production condition. Similarly, measure the fluidity (viscosity) at a temperature around 230 ° C for the second component containing crystalline polypropylene. When the extrusion temperature is selected, when the extrusion temperature is selected such that the melt fluidity (melt viscosity) of the first component is relatively greater than the melt fluidity (melt viscosity) of the second component, each component is equal. When it extrudes with a pressure, the ratio of the 1st component which covers a fiber surrounding surface in a fiber cross section will increase relatively. For example, although the temperature dependence (increase tendency) of the fluidity (viscosity) at the time of melting differs depending on the resin used, it cannot be generally stated, but the melt index (MI) of the first component and the melt mass flow rate of the second component When the ratio of (MFR) is 1.5 to 3 times the ratio of the melt index (MI) of the first component to the melt mass flow rate (MFR) of the second component, the cross-sectional shape of the composite fiber of the present invention is formed. Easy to do. Particularly preferred is a ratio of 1.8 to 2.5. The higher this ratio is, the easier it is to have a structure in which the first component wraps the second component, so the proportion of the second component occupying the outer periphery of the fiber decreases. Moreover, even if it is the same extrusion temperature and melt viscosity, the ratio with respect to the fiber outer periphery of the 1st component in a fiber cross section and a 2nd component can be increased / decreased by changing resin discharge amount ratio. This means that the area ratio in the fiber cross section perpendicular to the fiber axis is changed. For example, in the same manufacturing conditions, the area ratio of the second component in the fiber cross section perpendicular to the fiber axis is relatively When it becomes higher, the ratio of the second component to the outer periphery of the fiber tends to increase.
In order to produce the conjugate fiber of the present invention, an ordinary melt spinning method can be employed in addition to selecting the extrusion temperature and the resin discharge amount as described above.

  A treatment agent may be applied to the surface of the conjugate fiber of the present invention for the purpose of improving process stability during fiber production. The treatment agent is mainly an antistatic agent, and there are other hydrophilic agents that further improve the wettability of the fiber surface. Components include alkyl phosphates and their ethylene oxide adducts, sorbitan fatty acid ester ethylene oxide adducts, Examples include glycerin fatty acid ester and polyoxyethylene-modified silicone. A simple substance or an arbitrary mixture of these components is used as a treating agent.

The composite fiber of the present invention has a heat shrinkage rate of 50% or less, preferably 30% or less, particularly preferably 20% or less when heat-treated at 100 ° C. for 5 minutes.
The heat shrinkage referred to here is the composite fiber of the present invention is fed into a card machine as a staple fiber, and the fiber web collected at the card exit (which has become a sheet with the fibers tangled) is cut into a fixed shape, The heat treatment is performed at 100 ° C. for 5 minutes, and the size difference (decrease) before and after the treatment is expressed as a percentage (%).
In the present invention, the heat shrinkage rate is specifically determined by cutting the composite fiber of the present invention into an arbitrary length of 30 to 65 mm to form a staple fiber, which is put into a miniature card machine, and has a basis weight of 200 g / An m ² fibrous web is made. The fiber web is cut using a paper pattern of 250 mm × 250 mm in the fiber flow direction (MD) and the direction perpendicular to the flow direction (CD), and then left for 10 minutes to perform heat treatment. Immediately before, the MD length of the cut fiber web is measured, and then heat treatment is performed at 100 ° C. for 5 minutes in a circulating hot air oven. The MD length is measured again after the heat treatment, and is a value obtained by the following formula.
Thermal contraction rate (%) = {(L ₀ −L) / L ₀ } × 100
L ₀ : Length of MD before heat treatment L: Length of MD after heat treatment The smaller this value, the less shrinkage of the fiber web when making into a nonwoven fabric, stable processing is possible, and a good texture nonwoven fabric Obtainable.
In addition, the measurement conditions of heat shrink shown here do not specify or limit the processing conditions, heat treatment conditions, nonwoven fabric forming conditions, usage methods, and the like of the conjugate fiber of the present invention.

  Conventionally known composite fibers having a parallel cross-sectional structure by a combination of resins, in the heat treatment process in the fiber production, it is easy to express the crimp derived from the cross-sectional structure and their resin configuration, as a result, The effect of improving the bulkiness as a fiber is achieved. In particular, when a heat treatment is performed in a state in which the degree of freedom of the fibers is increased, such as a fiber web that is an aggregate of fibers cut to a desired length for making a nonwoven fabric, the fibers themselves tend to contract. Therefore, what was bulky in the state of the fiber web contracted greatly after the nonwoven fabric processing, and it was often impossible to maintain the bulkiness. Further, in the fiber web, various devices are made to make the basis weight uniform, but the spot weight is not completely eliminated, and in addition, the degree of freedom of the fibers in the fiber web is distributed, and the degree thereof is Since it is slightly different, shrinkage is likely to occur from a portion with a higher degree of freedom during the heat treatment in forming the nonwoven fabric. Therefore, the more shrinkable part converges the surrounding fibers to become a lump, and the part where the fibers are reduced due to the convergence is reduced in the basis weight, so that the unevenness of the basis weight is extremely noticeable throughout the nonwoven fabric, and is uniform. It was difficult to obtain a non-woven fabric.

On the other hand, the first component containing the ethylene / α-olefin copolymer is perpendicular to the fiber axis even though the conjugate fiber of the present invention has a parallel-type cross-sectional structure composed of two components. Ethylene / α having a cross-sectional shape that occupies 55 to 90% of the outer periphery of the fiber in the fiber cross section, and has a cross-sectional shape arranged to wrap around the second component containing crystalline polypropylene, and has a melting point of 70 to 100 ° C. An olefin copolymer, preferably a molecular weight distribution (Mw / Mn) of 1.5 to 2.5, a density of 0.87 to 0.91 g / cm ³ , and a melt index (MI) of 10 to 35 g / 10 min. By using a certain ethylene / α-olefin copolymer, the shrinkage during heat treatment can be stabilized while maintaining the benefits of improving the bulkiness due to the latent crimp imparted by adopting the parallel cross-sectional structure. It from becoming possible to suppress 50% or less is a range that can be a nonwoven fabric or molding Te.
It is unclear why the composite fiber of the present invention in which a specific resin structure and a specific composite structure are combined can exhibit such an excellent shrinkage suppression mechanism. By using the above specific ethylene / α-olefin copolymer, combining it with crystalline polypropylene, and making it a fiber having a specific fiber cross-sectional shape, surprisingly the shrinkage is suppressed, On the other hand, it was unexpected that a non-woven fabric having excellent bulkiness, which is generally considered to be a contradictory performance, good texture, and excellent heat treatment characteristics at a low temperature of 100 ° C. or less was obtained.

The fineness of the conjugate fiber of the present invention is not particularly limited. Considering the physical properties of the components constituting the composite fiber and the process stability during production, a fineness suitable for processing the composite fiber into a nonwoven fabric or a molded body may be selected. For example, it is desirable to select in the range of 1 to 5 dtex for applications such as cosmetic puffs and drug-coated sheets that directly touch the human skin, and for liquid holding material applications such as printer ink cartridges, 1 to 10 dtex. The range is suitable, and the range of 1 to 20 dtex is suitable for the use of liquid volatile materials such as the fragrance core of household fragrances.
The length of the composite fiber of the present invention is not particularly limited, and may be a long fiber or a short fiber. In the case of cutting into short fibers, the cut length can be appropriately selected according to the fineness, processing method and application of the composite fiber. As a staple fiber, when passing through a card process, it is preferable to set it as 20-125 mm, and in order to obtain the further favorable card | curd permeability and the formation of a fiber web, it is preferable to set it as 25-75 mm. Moreover, when making the composite fiber of this invention into a nonwoven fabric by the airlaid method, it is preferable to set it as 3-25 mm as a chop for airlaid.

  The composite fiber of the present invention preferably has crimps in order to open the fiber bundle and obtain a bulky fiber web or nonwoven fabric. The number of crimps to be applied and the type of crimps can be appropriately selected according to the fineness and cut length of the composite fiber, and the processing method and application. For example, when a composite fiber (staple fiber) having a fineness of 3.3 to 6.6 dtex and a cut length of 38 to 45 mm is used as a fiber web by the carding method, the number of crimps is 10 to 25/25 mm. Preferably, when a composite fiber (air laid chop) having a fineness of 3.3 to 6.6 dtex and a cut length of 3 to 6 mm is used as a fiber web by the air laid method, the number of crimps is 5 to 15 threads / 25 mm. It is preferable to apply in a range. Examples of the crimp type include a zigzag shape and a spiral structure.

In order to process the conjugate fiber of the present invention into a non-woven fabric, it is preferable to use a technique of forming a non-woven fabric by performing a heat treatment after forming a fiber web. Examples of the fiber web forming method include a carding method in which a card machine is passed, or an airlaid method in which fibers are put into a cylindrical drum provided with slits, and the fibers are rotated and accumulated on a conveyor. Yes, but not limited to these methods. When these forming methods are used, other fibers can be blended as long as the effects of the present invention are not significantly impaired. Examples of fibers that can be blended include rayon and cotton for improving water retention, and hollow fibers containing polyethylene terephthalate as a component for further increasing the bulk of a nonwoven fabric.
After forming a fiber web with a desired basis weight by these fiber web forming methods, when the fiber web is heat treated to form a nonwoven fabric, before performing the heat treatment, the fibers in the fiber web are removed by water flow, compressed air, or needle. Strength improvement and texture can be changed by using a spunlace method or a needle punch method.
Examples of the heat treatment method include a hot air bonding method, a hot water bonding method, and a hot roll bonding method. Especially, as a heat processing method performed after forming the composite fiber of this invention in a fiber web, a hot air bonding method and a hot water bonding method are preferable.

The hot air bonding method is a method in which heated air is passed through a fiber web to soften and melt the low melting point component of the composite fiber to bond the fiber entangled portion, and crush a certain area like the hot roll bonding method. Since it is not an adhesion method that impairs the bulkiness, it is an adhesion method suitable for providing a nonwoven fabric that is bulky and has a good texture and texture.
This hot air bonding method is a bonding method suitable for obtaining a non-woven fabric that is bulky and has a good texture. Conventionally, in particular, when a composite fiber web cut with short fibers having a parallel section of a general half-moon shape composed of two components is heat-treated by a hot air bonding method, the degree of freedom of the fiber web on the conveyor is increased. Since it is high, shrinkage tends to be larger than other bonding methods, and it is difficult to obtain a nonwoven fabric with a good texture and texture. On the other hand, the composite fiber of the present invention can be suitably used particularly in this hot air bonding method because shrinkage due to heat treatment for making a nonwoven fabric is effectively suppressed. It is possible to provide a nonwoven fabric with excellent texture while maintaining the superiority of the resulting bulkiness.

The hot water bonding method is a method in which hot water or steam passes through the fiber web to soften and melt the low melting point component of the composite fiber and bond the fiber entangled portions. In the conjugate fiber of the present invention, the first component containing an ethylene / α-olefin copolymer having a melting point of 70 ° C. to 100 ° C. occupies a majority of the fiber peripheral surface. It is possible to apply a hot water bonding method to be heat treatment. The medium used in this bonding method is relatively inexpensive, such as hot water or steam, and does not require special equipment. By treating with such a medium, the composite fiber of the present invention is formed simultaneously with making a nonwoven fabric. Most of the treatment agent applied to the surface can be washed off. The treatment agent applied to the fiber surface is indispensable in the production process of composite fibers (such as staple fibers and airlaid chops), but depending on the application, it may be unnecessary or obstructed after making into a non-woven fabric or molding process. It may become. For example, food protective sheets, packaging materials and trays that come into direct contact with food, cosmetic puffs that impregnate cosmetics, and sticks for applying drugs to affected areas. There are techniques to configure the fiber surface treatment agent with safe food additives and components equivalent to it, and methods to remove the treatment agent by providing a washing process after becoming a non-woven fabric or molded product. Even if the treatment agent is composed of components, it does not eliminate the influence on cosmetics and drugs, and in order to maintain stable performance as a product, it is desirable that the treatment agent remains as little as possible on the nonwoven fabric or the molded body. Further, after the processing into a non-woven fabric or a molded body, the further washing step is an addition of equipment and time, which is disadvantageous in terms of cost.
Therefore, for such applications as described above, a nonwoven fabric or a molded body which is bulky and has been effectively reduced to such an extent that the treatment agent is hardly attached or the amount of the treatment agent attached does not cause the above-mentioned problems can be obtained at low cost. The industrial fiber of the present invention, which can adopt the hot water bonding method, is extremely significant in that it can be efficiently provided. Most preferably, the composite fiber of the present invention is made into a non-woven fabric by hot water bonding method and molded, or once formed into a non-woven fabric by heat treatment by hot air bonding method, it is molded by hot water bonding method.

The basis weight of the nonwoven fabric when the conjugate fiber of the present invention is processed into a nonwoven fabric can be appropriately selected depending on the purpose of use. For example, in the food packaging material applications, it is desirable to select the range of 20 to 50 g / m ^2, preferably be selected in the range of 30 to 150 g / m ² in applications such as cosmetic puffs and drugs impregnated sheet, For applications such as sticks for drug application, a range of 50 to 250 g / m ² is suitable.
Moreover, bulkiness of the nonwoven fabric in the case of the composite fiber of the present invention is processed into a nonwoven fabric, calculated in specific volume, 20 cm ³ / g or more of easily obtained, also preferably 30 cm ³ / g or more of Obtainable.

  When the conjugate fiber of the present invention is processed into a nonwoven fabric, other nonwoven fabrics, fiber webs, thermoplastic films, sheets and the like may be laminated on the nonwoven fabric according to the purpose. Examples thereof include a low melting point breathable film, a laminate with an apertured film or an apertured nonwoven fabric, and a laminate with an elastic nonwoven fabric made of an elastomer or another ethylene / α-olefin copolymer.

In the present invention, the “molded product” refers to a processed product obtained by processing the composite fiber of the present invention without passing through the non-woven fabric process, and a processed product obtained by processing through the non-woven fabric process. . When processed without a non-woven fabric process, a fiber web with a desired basis weight obtained by a carding method or the like is formed into a sliver shape, put into a specific mold, and heat-treated in that state. Can be obtained. When processing through a non-woven fabric forming step, the composite fiber of the present invention is made into a fiber web having a desired basis weight by a carding method or an airlaid method, etc., and this is once made into a non-woven fabric by a hot air bonding method or the like, and the obtained non-woven fabric is formed into a desired nonwoven fabric. After being overlapped or cut so as to have a basis weight or thickness, they can be further integrated by using a hot air bonding method or a hot water bonding method to obtain a “molded body”. In addition, after making the nonwoven fabric using the conjugate fiber of the present invention, the nonwoven fabric is overlaid or cut so as to have a desired basis weight and thickness, put into a specific mold and combined and subjected to heat treatment in that state, A “molded body” can also be obtained.
The “molded product” obtained using the conjugate fiber of the present invention can be easily subjected to secondary processing such as cutting a part thereof or further performing heat treatment.
The composite fiber of the present invention includes a cosmetic puff, a drug application sheet, a heat-dissipating sheet, a food tray, a cushioning material, a cushioning material, a core material such as a home fragrance, a liquid retaining material such as a humidifier, a seedling sheet, a wiper, It can use suitably for the use of.

EXAMPLES Next, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited to a following example. In addition, the definition and the measuring method of the term used in this specification, especially an Example and a comparative example, and the following Tables 1-3 are as follows.
(1) Melt index MI: Measured under conditions of 190 ° C. and 21.2 N according to ASTM D-1238.
In addition, the numerical value shown in the table | surface is what measured resin. (Unit: g / min)
(2) Density The density was measured according to JIS K7112.
In addition, the numerical value shown in the table | surface is what measured resin. (Unit: g / cm ³ )

(3) Molecular weight distribution (Mw / Mn)
It is the ratio of the weight average molecular weight to the number average molecular weight, and is determined by gel permeation chromatography. It measured using "GPC-150C" made from Waters. (Column: Tosoh TSKgel GMH ₆ -HT 7.5cmI.D. × 60cm 1 pcs.)
In addition, the numerical value in a table | surface is the value measured about raw material resin.
(4) Melting point The temperature at which the resin melts is measured using a differential scanning calorimeter (DSC). (Unit: ° C)
Measurement was performed using DSC “Q-10” manufactured by TA Instruments. The resin was cut to a mass of 4.20 to 4.80 mg and filled into a sample pan and covered. Measurement was performed at a temperature increase rate of 10 ° C./min from 30 ° C. to 200 ° C. in an N ₂ purge to obtain a melting chart. The chart was analyzed to determine the melting peak temperature.
(5) Melt mass flow rate (MFR)
Measurements were performed at 230 ° C. and 21.2 N according to JIS K7210.
In addition, the numerical value shown in the table | surface is the value measured about raw material resin. (Unit: g / min)

(6) Fineness, fiber diameter This indicates the thickness of the fiber and is calculated from the weight per unit length. (Unit: dtex)
When the length of the fiber was sufficiently longer than 60 mm, the fiber bundle was cut into 60 mm, and the weight of 150 cut fibers was weighed using an electronic balance “AEL-40SM” manufactured by Shimadzu Corporation. The numerical value was multiplied by 1111 to obtain the fineness. When the length of the fiber was not sufficient, it was observed using a scanning electron microscope, 100 fibers were arbitrarily selected from the obtained images, and the diameters thereof were measured. The fineness was calculated from the average diameter and the specific gravity of the fiber.

(7) Observation of cross-sectional shape, such as occupancy ratio of first component relative to fiber cross-section outer circumference length Occupancy ratio (%) of first component relative to fiber perimeter length of fiber cross-section perpendicular to fiber axis and fiber cross-section perpendicular to fiber axis , The two intersections where the boundary line between the first component and the second component that draws a curve curved convexly toward the first component side intersects the outer circumference of the fiber are defined as a and b, and the line segment connecting the a and b A point where a straight line extending in a direction perpendicular to the line segment ab intersects with the boundary line between the first component and the second component passes through a point c that bisects ab into two, and intersects with the outer periphery of the fiber on the second component side. The ratio of the length of the fiber cd to the length of the line segment ce (cd / ce) when the point is e, and the first component and the first component that draw a curve that curves convexly toward the first component side When the boundary line with the two components is regarded as a part of the circumference of the circle or ellipse drawn by the outer periphery of the second component, The ratio (g / h) of the length g of this boundary line to the total outer circumferential length h of the circle or ellipse to be placed, and further the diameter or the major axis of the circle or ellipse to be drawn by the second component is the composite fiber As for the relationship between the diameter f or the length of the long axis and the length of the line segment ab when the cross section is present in the fiber cross section perpendicular to the fiber axis, the composite fiber is perpendicular to the length direction. And was observed and determined with an optical microscope or a scanning electron microscope.
Observation was performed using an optical microscope manufactured by NIKON or a scanning electron microscope “JSM-T220” manufactured by JEOL Datum. The length of the portion where each component was exposed on the fiber surface was measured from the obtained image, and calculated by applying the following equation. In the fiber cross section, the distinction between the first component and the second component can be confirmed by performing heat treatment in a state where the fiber is cut at right angles to the length direction. For example, the cut fiber is allowed to stand in an oven dryer at 100 ° C., the first component is softened and melted, and then observed with an optical microscope or a scanning electron microscope. Check if it exists.
Length of peripheral surface of first component (%) = (L ₁ / L) × 100
L ₁ : Length of the peripheral surface of the first component L: Total length of the peripheral surface of the fiber cross section

(8) Thermal contraction rate About a fiber web, the change (decrease rate) of the unit length before and behind heat processing is shown, and it calculates from ratio of change amount and unit length. (unit:%)
Using a 250 mm × 250 mm pattern paper, 200 g / m ² of the fiber web collected through the miniature card machine is used for each of the pattern in the fiber flow direction (MD) and the direction perpendicular to the flow direction (CD). Cut along. After standing for 10 minutes, the cut fiber web was then placed on kraft paper (350 mm × 700 mm) and the MD length was measured. Thereafter, the kraft paper was folded in half so that the top of the fiber web was lightly covered, and the kraft paper was placed in a SANYO convection oven (circulation hot air type) as it was and heat-treated at 100 ° C. for 5 minutes. After completion of the treatment, it was taken out from the dryer, allowed to cool at room temperature for 5 minutes, and the length of MD was measured again. The heat shrinkage rate was calculated by applying the following equation.
Thermal contraction rate (%) = {(L ₀ −L) / L ₀ } × 100
L ₀ : Length of MD before heat treatment L: Length of MD after heat treatment

(9) Weight per unit area Indicates the mass per unit of the nonwoven fabric and the fiber web, and is calculated from the mass of the nonwoven fabric or the fiber web cut out in a certain area. (Unit: g / m ² )
The nonwoven fabric cut out to 250 mm × 250 mm was lightened with an A & D company top plate electronic balance “HF-200”, and the numerical value was multiplied by 16 to calculate the basis weight.
(10) Bulkiness (specific volume)
Indicates the weight per unit volume of the nonwoven fabric, and is calculated from the basis weight measurement and the thickness measurement. (Unit: cm ³ / g)
The thickness of the non-woven fabric is measured under the conditions of an anvil load of 2 g / cm ² and a speed of 2 mm / sec using a “Digithic Nestor” manufactured by Toyo Seiki Seisakusho, and is calculated from the numerical value (mm) and the basis weight (g / m ² ). did.
(11) Texture This is a comprehensive judgment of the appearance of the non-woven fabric and the softness, strain, and swelling of the nonwoven fabric.
Judgment was made by a sensory test by a panelist. The evaluation was made according to three grades of “good”, “normal”, and “bad”.

Examples 1 to 6 and Comparative Examples 1 to 6 will be described below, and the results are summarized in Tables 1 to 3.
[Example 1]
The first component was an ethylene / α-olefin copolymer polymerized using a metallocene catalyst, and the α-olefin was octene-1, which was contained in the copolymer at 10 mol%. The density is 0.880, the melting point is 72 ° C., the melt index (MI) is 18 g / 10 min, and the molecular weight distribution (Mw / Mn) is 1.9. The second component is a crystalline polypropylene having a melt mass flow rate (MFR) of 8 g / 10 min and a melting point of 160 ° C.
Using these two components as constituent components, a parallel-type composite die is used, and the extrusion ratio (setting of 200 ° C. on the first component side and 260 ° C. on the second component side is set at a volume ratio of first component / second component = 50/50. (Temperature) was melt-spun. At the time of winding, an antistatic agent composed mainly of sorbitan fatty acid ester and ethylene oxide adduct of lauryl phosphate potassium salt was adhered. Spinnability was good. The obtained composite filament with a fineness of 6.5 dtex was stretched 1.7 times using a heating device equipped with a heating roll at 55 ° C., crimped with a crimping device, and then cut into 38 mm. A composite fiber (staple fiber) having a fineness of 4.4 dtex (fiber diameter: 25.2 μm) was obtained.

About the 1st component, the density, melting | fusing point, melt index (MI), and molecular weight distribution (Mw / Mn) were measured based on the measuring method of said (1)-(4). About 2nd component, melting | fusing point and melt mass flow rate (MFR) were measured based on the measuring method of said (4) and (5). The results are shown in the item of constituents in Table 1. The fiber properties of the obtained composite fiber (staple fiber) were measured according to the measurement methods (6) and (7) above. The results are shown in the item of yarn quality in Table 1 together with a schematic diagram of the fiber cross section. In the fiber cross section in the direction perpendicular to the fiber axis, no separation between the components was observed. Furthermore, cd / ce = 7.5, f> ab, and g / h = 0.80.
100 g of the obtained conjugate fiber (staple fiber) was put into a 500 mm width miniature card machine to collect a fiber web. The fiber permeability in the card process was good. The thermal shrinkage of this fiber web was measured according to the measurement method of (8) above. The result is shown in the item of yarn quality in Table 1. Further, 50 g of the obtained composite fiber (staple fiber) was put into a 500 mm width miniature card machine to obtain a fiber web. This fiber web was processed using a hot air circulating through-air processing machine under the conditions of a set temperature of 98 ° C., a hot air wind speed of 0.8 m / sec, and a processing time of 12 sec. The physical properties of the obtained through-air nonwoven fabric were measured and evaluated according to the measurement methods (9) to (11) above. The results are shown in the item of physical properties of nonwoven fabric in Table 1.
Since the thermal shrinkage rate of the fiber web using the obtained composite fiber (staple fiber) has become a low value of 15%, it is bulky even in processing by the hot air bonding method, and a nonwoven fabric having a good texture and texture can be obtained. I was able to.

[Example 2]
The first component was an ethylene / α-olefin copolymer polymerized using a metallocene catalyst, and the α-olefin was octene-1, which was contained by 9 mol% in the copolymer. The density is 0.885, the melting point is 78 ° C., the melt index (MI) is 30 g / 10 min, and the molecular weight distribution (Mw / Mn) is 2.0. The second component is a crystalline polypropylene having a melt mass flow rate (MFR) of 16 g / 10 min and a melting point of 160 ° C.
Using these two components as constituent components, a parallel-type composite die is used, and the extrusion ratio (setting of 200 ° C. on the first component side and 260 ° C. on the second component side is set at a volume ratio of first component / second component = 50/50. (Temperature) was melt-spun. At the time of winding, an antistatic agent composed mainly of sorbitan fatty acid ester and ethylene oxide adduct of lauryl phosphate potassium salt was adhered. Spinnability was good. The obtained composite filament with a fineness of 10.2 dtex was stretched 1.7 times using a heating device equipped with a heating roll at 60 ° C., crimped with a crimping device, and then cut into 38 mm. A composite fiber (staple fiber) having a fineness of 7.0 dtex (fiber diameter: 31.7 μm) was obtained.

About the 1st component, the density, melting | fusing point, melt index (MI), and molecular weight distribution (Mw / Mn) were measured based on the measuring method of said (1)-(4). About 2nd component, melting | fusing point and melt mass flow rate (MFR) were measured based on the measuring method of said (4) and (5). The results are shown in the item of constituents in Table 1. The fiber properties of the obtained composite fiber (staple fiber) were measured according to the measurement methods (6) and (7) above. The results are shown in the item of yarn quality in Table 1 together with a schematic diagram of the fiber cross section. In the fiber cross section in the direction perpendicular to the fiber axis, no separation between the components was observed. Furthermore, cd / ce = 6.0, f> ab, and g / h = 0.75.
100 g of the obtained conjugate fiber (staple fiber) was put into a 500 mm width miniature card machine to collect a fiber web. The fiber permeability in the card process was good. The thermal shrinkage of this fiber web was measured according to the measurement method of (8) above. The result is shown in the item of yarn quality in Table 1. 50 g of the obtained composite fiber (staple fiber) was put into a 500 mm width miniature card machine to form fiber webs, and these fiber webs were set at a set temperature of 98 ° C. and hot air speed 0. Processing was performed under conditions of 8 m / sec and a processing time of 12 sec. The physical properties of the obtained through-air nonwoven fabric were measured and evaluated according to the measurement methods (9) to (11) above. The results are shown in the item of physical properties of nonwoven fabric in Table 1.
Since the thermal shrinkage rate of the fiber web using the obtained composite fiber (staple fiber) was as low as 17%, a nonwoven fabric that is bulky even in processing by the hot air bonding method and has a good texture and texture can be obtained. I was able to.

[Example 3]
The first component was an ethylene / α-olefin copolymer polymerized using a metallocene catalyst, and the α-olefin was octene-1, which was contained in the copolymer at 5 mol%. The density is 0.902, the melting point is 98 ° C., the melt index (MI) is 30 g / 10 min, and the molecular weight distribution (Mw / Mn) is 2.1. The second component is a crystalline polypropylene having a melt mass flow rate (MFR) of 16 g / 10 min and a melting point of 160 ° C.
Using these two components as constituent components, a parallel-type composite die is used, and the extrusion ratio (set by the first component side 200 ° C. and the second component side 260 ° C. at a volume ratio of first component / second component = 45/55) (Temperature) was melt-spun. At the time of winding, an antistatic agent composed mainly of sorbitan fatty acid ester and ethylene oxide adduct of lauryl phosphate potassium salt was adhered. Spinnability was good. The obtained composite filament with a fineness of 10.0 dtex was stretched 2.6 times using a heating device equipped with a heating roll at 70 ° C., crimped with a crimping device, and then cut into 38 mm. A composite fiber (staple fiber) having a fineness of 4.4 dtex (fiber diameter 25.0 μm) was obtained.

About the 1st component, the density, melting | fusing point, melt index (MI), and molecular weight distribution (Mw / Mn) were measured based on the measuring method of said (1)-(4). About 2nd component, melting | fusing point and melt mass flow rate (MFR) were measured based on the measuring method of said (4) and (5). The results are shown in the item of constituents in Table 1. The fiber properties of the obtained composite fiber (staple fiber) were measured according to the measurement methods (6) and (7) above. The results are shown in the item of yarn quality in Table 1 together with a schematic diagram of the fiber cross section. In the fiber cross section in the direction perpendicular to the fiber axis, no separation between the components was observed. Furthermore, cd / ce = 3.0, f> ab, and g / h = 0.70.
100 g of the obtained conjugate fiber (staple fiber) was put into a 500 mm width miniature card machine to collect a fiber web. The fiber permeability in the card process was good. The thermal shrinkage of this fiber web was measured according to the measurement method of (8) above. The result is shown in the item of yarn quality in Table 1. 50 g of the obtained composite fiber (staple fiber) is put into a 500 mm width miniature card machine to form a fiber web, and this fiber web is set at a set temperature of 98 ° C. and hot air wind speed 0. 0 using a hot air circulation type through air processing machine. Processing was performed under conditions of 8 m / sec and a processing time of 12 sec. The physical properties of the obtained through-air nonwoven fabric were measured and evaluated according to the measurement methods (9) to (11) above. The results are shown in the item of physical properties of nonwoven fabric in Table 1.
Since the thermal shrinkage rate of the fiber web using the obtained composite fiber (staple fiber) was as low as 28%, it is bulky even in processing by the hot air bonding method, and a nonwoven fabric having a good texture and texture can be obtained. I was able to.

[Example 4]
Spinning and drawing under the same conditions as in Example 3 and applying crimps with a crimping device, then cutting to 5 mm and a composite fiber having a fineness of 4.4 dtex (fiber diameter 25.0 μm) (Airlaid chop) was obtained.
200 g of the obtained composite fiber (airlaid chop) was put into an airlaid machine having one pair of forming heads, and a fiber web was formed by the airlaid method. The fiber dischargeability from the airlaid machine was good. This fiber web was subjected to hot air bonding using a hot air circulation type through-air processing machine under the conditions of a set temperature of 98 ° C., a hot air wind speed of 0.38 m / sec, and a processing time of 14 sec. The physical properties of the obtained through-air nonwoven fabric were measured and evaluated according to the measurement methods (9) to (11) above. The results are shown in the item of physical properties of nonwoven fabric in Table 1.
When the obtained composite fiber was processed into a fiber web by the airlaid method and processed by the hot air bonding method, it was bulky, shrinkage was suppressed, and a nonwoven fabric having a good texture and texture could be obtained.

[Comparative Example 1]
The first component was an ethylene / α-olefin copolymer, and the α-olefin was octene-1, and 2 mol% was contained in the copolymer. The density is 0.913, the melting point is 107 ° C., the melt index (MI) is 30 g / 10 min, and the molecular weight distribution (Mw / Mn) is 3.0. The second component is a crystalline polypropylene having a melt mass flow rate (MFR) of 16 g / 10 min and a melting point of 160 ° C.
Using these two components as constituent components, a parallel-type composite die is used, and the extrusion ratio (setting of 200 ° C. on the first component side and 260 ° C. on the second component side is set at a volume ratio of first component / second component = 50/50. The composite fiber having a fiber cross-sectional structure in which a boundary line between the first component and the second component curved in a convex shape toward the first component side was produced by melt spinning under the condition of (temperature). At the time of winding, an antistatic agent composed mainly of sorbitan fatty acid ester and ethylene oxide adduct of lauryl phosphate potassium salt was adhered. Spinnability was good. The obtained composite filament with a fineness of 11.5 dtex was stretched 3.3 times using a heating device equipped with a heating roll at 70 ° C., crimped with a crimping device, and then cut into 38 mm. A composite fiber (staple fiber) having a fineness of 3.8 dtex (fiber diameter: 23.2 μm) was obtained.

About the 1st component, the density, melting | fusing point, melt index (MI), and molecular weight distribution (Mw / Mn) were measured based on the measuring method of said (1)-(4). About 2nd component, melting | fusing point and melt mass flow rate (MFR) were measured based on the measuring method of said (4) and (5). The results are shown in the item of components in Table 2. The fiber properties of the obtained composite fiber (staple fiber) were measured according to the measurement methods (6) and (7) above. The results are shown in the item of yarn quality in Table 2 together with a schematic diagram of the fiber cross section. Furthermore, in the fiber cross section in the direction perpendicular to the fiber axis, cd / ce = 3.5, f> ab, and g / h = 0.55.
100 g of the obtained conjugate fiber (staple fiber) was put into a 500 mm width miniature card machine to collect a fiber web. The fiber permeability in the card process was good. These fiber webs were measured for thermal shrinkage in accordance with the measurement method of (8) above. The results are shown in the item of yarn quality in Table 2. 50 g of the obtained composite fiber (staple fiber) was put into a 500 mm width miniature card machine to form fiber webs, and these fiber webs were set at a set temperature of 98 ° C. and hot air speed 0. Processing was performed under conditions of 8 m / sec and processing time of 12 sec. However, since the melting point of the ethylene / octene-1 copolymer, which is the first component, is high, the fiber entanglement point does not melt at the processing temperature of 98 ° C. could not. As described above, Comparative Example 1 was produced by a method similar to that described in Example 3 except that the melting point was 107 ° C., which was largely different from that described in Example 3. However, what was obtained was not a composite fiber that enables non-woven fabric processing and molding at a low temperature enough to adopt the hot water bonding method. Therefore, the expected evaluation of the shrinkage ratio of the fiber web at 100 ° C. on the assumption of low-temperature processing no longer makes sense for the measurement.

[Comparative Example 2]
The first component was an ethylene / α-olefin copolymer, and the α-olefin was propylene and butene, and the respective contents were 3 mol% and 3 mol% in the copolymer. The density is 0.897, the melting point is 81 ° C., the melt index (MI) is 4 g / 10 min, and the molecular weight distribution (Mw / Mn) is 2.0. The second component is a crystalline polypropylene having a melt mass flow rate (MFR) of 8 g / 10 min and a melting point of 160 ° C.
Using these two components as constituent components, a parallel-type composite die is used, and the extrusion ratio (set by the first component side at 220 ° C. and the second component side at 260 ° C. with a volume ratio of first component / second component = 50/50 (setting) (Temperature) was melt-spun. When winding, an antistatic agent mainly composed of sorbitan fatty acid ester and ethylene oxide adduct of lauryl phosphate potassium was adhered, but when the wound composite filament was confirmed, a little sticking occurred. . Although the agglutination was observed, the obtained composite filament with a fineness of 9.8 dtex was stretched 1.7 times using a heating device equipped with a heating roll at 60 ° C., and crimped by a crimping device. Thereafter, the resultant was cut to 38 mm to obtain a composite fiber (staple fiber) having a fineness of 6.8 dtex (fiber diameter: 31.1 μm).

About the 1st component, the density, melting | fusing point, melt index (MI), and molecular weight distribution (Mw / Mn) were measured based on the measuring method of said (1)-(4). About 2nd component, melting | fusing point and melt mass flow rate (MFR) were measured based on the measuring method of said (4) and (5). The results are shown in the item of components in Table 2. The fiber properties of the obtained composite fiber (staple fiber) were measured according to the measurement methods (6) and (7) above. The results are shown in the item of yarn quality in Table 2 together with a schematic diagram of the fiber cross section. Since the melt index (MI) of the first component is low, in the fiber cross section in the direction perpendicular to the fiber axis, the boundary line between the first component and the second component curves in a convex shape toward the second component side. I started drawing. Therefore, cd / ce could not be measured, and f and g / h could not be measured. Moreover, the peeling between components was seen.
100 g of the obtained conjugate fiber (staple fiber) was put into a 500 mm width miniature card machine to collect a fiber web. The fiber passing property in the carding process was not good because spots were generated in the fiber discharging property. The thermal shrinkage of this fiber web was measured according to the measurement method of (8) above. The results are shown in the item of yarn quality in Table 2. 50 g of the obtained composite fiber (staple fiber) was put into a 500 mm width miniature card machine to form fiber webs, and these fiber webs were set at a set temperature of 98 ° C. and hot air speed 0. Processing was performed under conditions of 8 m / sec and processing time of 12 sec. However, the shrinkage was large, the strength of the nonwoven fabric was low, and a nonwoven fabric with good texture and texture could not be obtained. The heat shrinkage rate of the fiber web using the obtained conjugate fiber was as high as 55%.

[Comparative Example 3]
The first component was an ethylene / α-olefin copolymer, and the α-olefin was propylene, and was contained in an amount of 15 mol% in the copolymer. The density is 0.863, the melting point is 50 ° C., the melt index (MI) is 21 g / 10 min, and the molecular weight distribution (Mw / Mn) is 2.0. The second component is a crystalline polypropylene having a melt mass flow rate (MFR) of 16 g / 10 min and a melting point of 160 ° C.
Using these two components as constituent components, a parallel-type composite die is used, and the extrusion ratio (set by the first component side at 220 ° C. and the second component side at 260 ° C. with a volume ratio of first component / second component = 50/50 (setting) (Temperature) was melt-spun. However, at the time of winding, the spun composite filament was stuck, and a spun composite filament that could be drawn could not be collected. Regarding the comparative example, the schematic diagram of the fiber cross section shown in Table 2 is something that was collected and observed from the glued composite spun filaments. Since the melt index (MI) of the first component is significantly lower than the melt mass flow rate (MFR) of the second component, the boundary line between the first component and the second component is present in the fiber cross section perpendicular to the fiber axis. Both the linear and so-called composite components had a half-moon-shaped composite cross section. In the fiber cross section in the direction perpendicular to the fiber axis, cd / ce = 0, and separation was observed between the composite components.
About the 1st component, the density, melting | fusing point, melt index (MI), and molecular weight distribution (Mw / Mn) were measured based on the measuring method of said (1)-(4). About 2nd component, melting | fusing point and melt mass flow rate (MFR) were measured based on the measuring method of said (4) and (5). The results are shown in the item of components in Table 2.

[Comparative Example 4]
As the first component, a blend of two resins was used. One was an ethylene / α-olefin copolymer, and the α-olefin was propene, which was contained in the copolymer at 12 mol%. The density is 0.870, the melting point is 75 ° C., the melt index (MI) is 1 g / 10 min, and the molecular weight distribution (Mw / Mn) is 1.9. The other was a propylene / α-olefin copolymer, and the α-olefin was ethylene and butene-1, and their contents were both 1 mol% in the copolymer. Its melting point is 128 ° C. and its melt mass flow rate (MFR) is 16 g / 10 min. The two resins were blended at a mass ratio of 20/80. Table 2 shows the physical properties of an ethylene / propene copolymer which is a resin having a lower melting point. The second component is a crystalline polypropylene having a melt mass flow rate (MFR) of 8 g / 10 min and a melting point of 160 ° C.
Using these two components as constituent components, a parallel-type composite die is used, and the extrusion ratio (set by the first component side 200 ° C. and the second component side 260 ° C. at a volume ratio of first component / second component = 50/50) The composite fiber having a fiber cross-sectional structure in which a boundary line between the first component and the second component curved in a convex shape toward the first component side was produced by melt spinning under the condition of (temperature). At the time of winding, an antistatic agent composed mainly of sorbitan fatty acid ester and ethylene oxide adduct of lauryl phosphate potassium salt was adhered. Spinnability was good. The obtained composite filament with a fineness of 9.7 dtex was stretched 2.6 times using a heating device equipped with a heating roll at 60 ° C., crimped with a crimping device, and then cut into 38 mm. A composite fiber (staple fiber) having a fineness of 4.4 dtex (fiber diameter 25.1 μm) was obtained.

About the 1st component, the density, melting | fusing point, melt index (MI), and molecular weight distribution (Mw / Mn) were measured based on the measuring method of said (1)-(4). About 2nd component, melting | fusing point and melt mass flow rate (MFR) were measured based on the measuring method of said (4) and (5). The results are shown in the item of components in Table 2. The fiber properties of the obtained composite fiber (staple fiber) were measured according to the measurement methods (6) and (7) above. The results are shown in the item of yarn quality in Table 2 together with a schematic diagram of the fiber cross section. Furthermore, in the fiber cross section in the direction perpendicular to the fiber axis, cd / ce = 0.2 and g / h <0.5.
100 g of the obtained conjugate fiber (staple fiber) was put into a 500 mm width miniature card machine to collect a fiber web. The fiber permeability in the card process was good. About the obtained fiber web, the heat shrinkage rate was measured based on the measuring method of said (8). The results are shown in the item of yarn quality in Table 2. 50 g of the obtained composite fiber (staple fiber) was put into a 500 mm width miniature card machine to form fiber webs, and these fiber webs were set at a set temperature of 98 ° C. and hot air speed 0. Processing was performed under conditions of 8 m / sec and a processing time of 12 sec. However, the shrinkage was large, and a nonwoven fabric having a good texture and texture could not be obtained. The heat shrinkage ratio of the fiber web using the obtained conjugate fiber was as high as 65%.

[Comparative Example 5]
As the first component, a blend of two resins was used. One is low density polyethylene. The density is 0.918, the melting point is 105 ° C., the melt index (MI) is 24 g / 10 min, and the molecular weight distribution is 7.0. The other is an ethylene / vinyl acetate copolymer. The amount of vinyl acetate is 20% by mass, the density is 0.939, the melting point is 92 ° C., the melt index (MI) is 20 g / 10 min, and the molecular weight distribution (Mw / Mn) is 5.0. The two resins were blended at a mass ratio of 75/25. Table 3 shows the physical properties of an ethylene / vinyl acetate copolymer which is a resin having a lower melting point. The second component is a crystalline polypropylene having a melt mass flow rate (MFR) of 8 g / 10 min and a melting point of 160 ° C.
Using these two components as constituent components, a parallel-type composite die is used, and the extrusion ratio (setting of 200 ° C. on the first component side and 260 ° C. on the second component side is set at a volume ratio of first component / second component = 50/50. The composite fiber having a fiber cross-sectional structure in which a boundary line between the first component and the second component curved in a convex shape toward the first component side was produced by melt spinning under the condition of (temperature). At the time of winding, an antistatic agent composed mainly of sorbitan fatty acid ester and ethylene oxide adduct of lauryl phosphate potassium salt was adhered. Many yarn breaks occurred during spinning. The obtained composite filament with a fineness of 9.7 dtex was stretched 2.6 times using a heating device equipped with a heating roll at 60 ° C., crimped with a crimping device, and then cut into 38 mm. A composite fiber (staple fiber) having a fineness of 3.3 dtex (fiber diameter 21.5 μm) was obtained.

About the 1st component, the density, melting | fusing point, melt index (MI), and molecular weight distribution (Mw / Mn) were measured based on the measuring method of said (1)-(4). About 2nd component, melting | fusing point and melt mass flow rate (MFR) were measured based on the measuring method of said (4) and (5). The results are shown in the item of constituents in Table 3. The fiber properties of the obtained composite fiber (staple fiber) were measured according to the measurement methods (6) and (7) above. The results are shown in the item of yarn quality in Table 3 together with a schematic diagram of the fiber cross section. Furthermore, in the fiber cross section in the direction perpendicular to the fiber axis, cd / ce = 9.5, f> ab, and g / h = 0.86.
100 g of the obtained conjugate fiber (staple fiber) was put into a 500 mm width miniature card machine to collect a fiber web. The fiber passability in the carding process was not good because spots were generated in the fiber discharge. About the obtained fiber web, the heat shrinkage rate was measured based on the measuring method of said (8). The results are shown in the item of yarn quality in Table 3. 50 g of the obtained composite fiber (staple fiber) was put into a 500 mm width miniature card machine to form fiber webs, and these fiber webs were set at a set temperature of 98 ° C. and hot air speed 0. Processing was performed under conditions of 8 m / sec and a processing time of 12 sec. However, the shrinkage was large, and a nonwoven fabric having a good texture and texture could not be obtained.
The heat shrinkage rate of the fiber web using the obtained conjugate fiber was as high as 60%.

[Comparative Example 6]
Spinning and drawing under the same conditions as in Comparative Example 5 and applying crimps with a crimping device, then cutting to 5 mm and a composite fiber having a fineness of 3.3 dtex (fiber diameter 21.5 μm) (Airlaid chop) was obtained.
200 g of the obtained composite fiber (air laid chop) was put into an air laid machine having one pair of forming heads to form a fiber web by the air laid method. However, the fiber dischargeability from the air laid machine was not good. The obtained fiber web was hot-air bonded using a hot-air circulating through-air processing machine at a set temperature of 98 ° C., a hot-air wind speed of 0.38 m / sec, and a processing time of 14 sec. Although it was possible, shrinkage occurred, and a nonwoven fabric with good texture and texture could not be obtained. The results are shown in Table 3.

[Example 5]
The composite fiber (staple fiber) obtained in Example 3 was made into a fiber web by the carding method, and this fiber web was made into a rod-shaped sliver. The fiber web made into a sliver is filled into a cylindrical mold (10 mm × 10 mm × 60 mm) made of a 20 mesh wire net with a wire diameter of 0.29 mm, and in that state, 98 ° C. using a circulating through-air processing machine. Was subjected to hot air bonding under the conditions of a set temperature of 1, a hot air speed of 1.2 m / sec, and a processing time of 12 sec to obtain a rectangular parallelepiped fiber molded body. The obtained fiber molded body was excellent in cushioning properties.

[Example 6]
Using the composite fiber (air laid chop) obtained in Example 4, a fiber web having a basis weight of 50 g / m ² was obtained by the air laid method, and this fiber web was set at 98 ° C. using a circulating through-air processing machine. Then, hot air bonding was performed under conditions of a hot air speed of 0.38 m / sec and a processing time of 14 sec. The obtained through-air non-woven fabric was filled in a glass tube having an inner diameter of 8 mm, placed in boiling water as it was, and boiled for 2 minutes. After boiling, it was cooled to obtain a cylindrical fiber molded body. The obtained fiber molded body was moderately flexible and had little variation in fiber density, and was suitable for liquid retention.

  The composite fiber of the present invention comprises a parallel section with a first component containing an ethylene / α-olefin copolymer having specific properties and a second component containing crystalline propylene, Since it has processability and has a low thermal shrinkage rate, it is useful for producing a nonwoven fabric and a molded body that are bulky and have good texture and texture at a heat treatment temperature of 100 ° C. or less.

Claims (7)

  A first component containing at least 75% by mass of an ethylene / α-olefin copolymer having a melting point of 70 to 100 ° C. and a second component containing crystalline polypropylene are a composite fiber having a parallel section, In the fiber cross section perpendicular to the fiber axis, the first component occupies 55 to 90% of the outer periphery of the fiber, and the boundary line between the first component and the second component curves convexly toward the first component side. A composite fiber, wherein the area ratio of the first component to the second component (first component / second component) is in the range of 70/30 to 30/70. The molecular weight distribution (Mw / Mn) of the ethylene / α-olefin copolymer is 1.5 to 2.5, the density is 0.87 to 0.91 g / cm ³ , and the temperature is 190 ° C. according to ASTM D-1238. The composite fiber according to claim 1, wherein the melt index (MI) measured under a load of 21.2 N is 10 to 35 g / 10 min.   The composite fiber according to claim 1 or 2, wherein a heat shrinkage rate when heat-treated at 100 ° C for 5 minutes is 50% or less.   The nonwoven fabric obtained by making the conjugate fiber of any one of Claims 1-3 into a nonwoven fabric.   The nonwoven fabric according to claim 4, wherein the nonwoven fabric treatment is a hot air bonding method or a hot water bonding method.   The molded object obtained using the composite fiber of any one of Claims 1-3.   The molded object obtained using the nonwoven fabric of Claim 4 or 5.

Images