JP2002030524A - Thermally bondable conjugate fiber, method for producing the same and nonwoven fabric and synthetic paper using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermally bondable conjugate fiber having a wide heat bonding and processing temperature range, a thermally bonded nonwoven fabric having tenacity of practical use and exhibiting excellent softness and a synthetic paper having excellent heat sealability. SOLUTION: A thermally bondable conjugate fiber is obtained by subjecting a fiber-forming resin comprising an ethylene-propylene copolymer having 5-15 mol% ethylene content and 3-6.5 randomness index (CSD) by 13C-NMR method as a first component and an olefin-based polymer having a melting point >=10 deg.C higher than that of the first component or its copolymer as a second component to conjugate spinning so as to expose the first component to at least a part of the surface of the fiber. This nonwoven fabric having excellent tenacity and softness is obtained by heat-treating a fiber web containing >=10 mass % of the thermally bondable conjugate fiber. This synthetic paper having excellent heat sealability is obtained from the thermally bondable conjugate fiber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-adhesive conjugate fiber which can provide a non-woven fabric having a wide heat-bonding temperature range, a large heat-bonding strength, and a soft touch when included in a non-woven fabric. The present invention relates to a production method, and a nonwoven fabric and synthetic paper containing the heat-adhesive conjugate fiber.

[0002]

2. Description of the Related Art In recent years, sanitary materials, packaging materials, filters,
BACKGROUND ART In various applications such as wet tissues, wipers, and battery separators, a heat-bonded nonwoven fabric in which at least a part of a low-melting-point component is heat-bonded between fibers with a heat-bondable conjugate fiber whose surface is exposed to the fiber is used. As the heat-adhesive composite fiber, a composite fiber in which a combination of a high melting point (core) component / a low melting point (sheath) component is polypropylene / polyethylene, polyester / polyethylene, or the like is widely used. Various other heat-adhesive conjugate fibers have been proposed and put to practical use. For example, JP-A-4-73214,
JP-A-5-9810 discloses a composite fiber comprising a combination of a polypropylene / ethylene-propylene copolymer, and JP-A-6-108310 discloses a composite fiber comprising a polypropylene / propylene-ethylene-butene-1 terpolymer. Composite fibers comprising combinations of the following have been proposed.
The present applicant also discloses in Japanese Patent Application Laid-Open No. 2000-45125 that polyester or the like is used as the first component (high melting point component),
A mixture of two kinds of ethylene-propylene copolymers is
A heat-adhesive conjugate fiber as a component (low melting point component) has been proposed.

[0003]

However, the above-mentioned conjugate fiber has the following problems. For example, composite fibers composed of a combination of polypropylene / polyethylene and polyester / polyethylene may not always have good compatibility with each other, and may cause separation between components (in the case of core-sheath composite fibers, separation between core and sheath). . When such peeling occurs, for example, when a nonwoven fabric is produced, the heat-adhesive conjugate fiber may not be able to sufficiently exhibit the bonding ability, and a nonwoven fabric having sufficient strength may not be obtained. On the other hand, a propylene-based composite fiber in which the combination of the high melting point component / the low melting point component is a polypropylene / ethylene-propylene copolymer or a polypropylene / ethylene-propylene-butene-1 terpolymer has good compatibility between the two components. Therefore, the problem of peeling does not easily occur, and excellent adhesive ability is exhibited. However, these fibers have a drawback that the heat processing temperature range is narrow because the melting point of the low melting point component is higher than that of polyethylene and is close to the melting point of polypropylene, which is the high melting point component.

The conjugate fiber described in Japanese Patent Application Laid-Open No. 4-73214 aims to eliminate this drawback by increasing the MFR ratio of the sheath component / core component to 2 to 10. However, if an attempt is made to achieve such an MFR ratio, spinnability and stretchability deteriorate, and inter-fiber fusion may occur during the manufacturing process, particularly during the spinning process.

JP-A-5-9810 and JP-A-6-9810
The conjugate fiber described in JP-108310A employs a resin having a low melting point, keeps the draw ratio low, and secures a difference in melting point between the core component and the sheath component. However,
When a propylene copolymer having a low melting point is used, there is a problem that fusion between fibers is easily caused during the spinning process. In addition, fibers made of such a propylene-based copolymer have no "stiffness" and tend to have poor card processability when producing a nonwoven fabric.

[0006] Although the composite fiber described in JP-A-2000-45125 is excellent in terms of surface resilience and cushioning property, its heat adhesiveness and the flexibility of a nonwoven fabric produced using the fiber are not necessarily sufficient. It was not something.

The present invention has been made in view of the above circumstances, and can provide a nonwoven fabric having a wide temperature range for heat bonding, exhibiting excellent adhesive ability, and having a soft touch, and having excellent heat sealing performance. It is an object of the present invention to provide a heat-adhesive conjugate fiber capable of providing a synthetic fiber having the following.

[0008]

The heat-adhesive conjugate fiber of the present invention comprises, as a first component, a fiber-forming resin containing an ethylene-propylene copolymer, and has a melting point of at least 10 ° C. higher than that of the first component. The composite or its copolymer is used as a second component, and the first component is a conjugate fiber exposed on at least a part of the fiber surface, and the ethylene-propylene copolymer contained in the first component has an ethylene content of 5%. was 15 mol%, and randomness index by ¹³ C-NMR method (CS
The above problem has been solved by using an ethylene-propylene copolymer in which D) is 3 to 6.5.

[0009] The heat-adhesive conjugate fiber of the present invention has an ethylene content of an ethylene-propylene copolymer contained in a first component exposed to at least a part of the fiber surface, ie, a low-melting component (or a heat-adhesive component). Is specified as described above, and the temperature at which the low-melting point component is melted is made suitable for nonwoven fabric production or the like without impairing the spinnability. Also,
By specifying the randomness index (CSD) of the ethylene-propylene copolymer by the ¹³ C-NMR method (also simply referred to as “randomness index (CSD)”) as described above, the range of the thermal bonding processing temperature of the fiber is obtained. And also
The nonwoven fabric produced using the obtained fibers has a soft touch.

Here, "the first component is exposed on at least a part of the fiber surface" means that the first component occupies at least a part of the circumference of the fiber cross section. In the heat-adhesive conjugate fiber of the present invention, the first component is preferably 20 to 100%, more preferably 50 to 100% of the circumference of the fiber cross section.
And most preferably 100%.

In the heat-bonding conjugate fiber of the present invention, the ethylene-propylene copolymer (hereinafter referred to as E) contained in the first component is used.
Ethylene copolymer content of 5 to 15 mol
l%, preferably 7 to 10 mol%. here,
The ethylene content refers to a value measured for a spun filament obtained by spinning a polymer before fiber formation under the same spinning conditions as those for forming a conjugate fiber. If the ethylene content is less than 5 mol%, the adhesiveness is poor,
The range of the heat bonding temperature tends to be narrow. If the ethylene content exceeds 15 mol%, fusion between fibers may occur during the fiber production process, and the softening point may become too low, causing fusion to the net during production or processing of the nonwoven fabric, or heat. There is a tendency that processability is inferior, for example, adhesion to a roll occurs.

The randomness index (CSD) of the EP copolymer by ¹³ C-NMR method is a parameter indicating the randomness of the ethylene-propylene copolymer, and the smaller the randomness index (CSD), the smaller the random copolymer index. Become closer to The larger the randomness index (CSD), the closer to a block copolymer.

In the present specification, the randomness index (CSD) by ¹³ C-NMR is defined as “New Edition Polymer Analysis Handbook” (Kinokuniya Shoten, 1995) based on ¹³ C-NMR spectra measured under the following measurement conditions. Issued) 615-6
According to page 18, ethylene-ethylene chain fraction (E
E), the chain fraction of propylene-propylene (PP), and the chain fraction of ethylene-propylene (EP) are determined, and these are calculated from the following equation (1).

1. Measurement conditions (1) Measuring device: EX270 manufactured by JEOL Ltd. (2) Preparation of test solution: prepared by dissolving 300 mg of sample in a mixed solvent of 2 ml of O-dichlorobenzene and 0.5 ml of deuterated benzene (3) Standard Material: Tetramethylsilane (4) Measurement temperature: 130 ° C (5) 13C nuclear resonance frequency: 60 MHz (6) Repeated measurement integration time: 15 hours

2. Formula for calculating randomness index (CSD) CSD = EE [PP / (EP / 2) ² ] ... (1) (where EE is the chain fraction of ethylene-ethylene, PP is the chain fraction of propylene-propylene) , EP is ethylene-
Shows the chain fraction of propylene)

In the conjugate fiber of the present invention, the randomness index (CSD) of the ethylene-propylene copolymer contained in the first component is from 3 to 6.5, and is from 3.5 to 6.5.
The following is preferred. Here, the randomness index (CSD) refers to a value measured for a spun filament obtained by spinning a polymer before fiber formation under the same spinning conditions as those for forming a composite fiber. Randomness index (CS) measured for spun filaments
D) is a randomness index (C) of the polymer before fiber formation.
SD) tends to be larger. This is because the polymer is kneaded and heated inside the extruder, so that the copolymer molecules (EP) of ethylene and propylene are cut by the action of mechanical force and heat, and the chain fraction of ethylene-propylene is reduced. Is estimated to decrease. Therefore, the randomness index (CSD) within the above range
Can be obtained by selecting a polymer having a smaller randomness index (CSD) than the above range as a polymer before forming a fiber, and fibrillating the polymer in accordance with a production method described later. Specifically, an EP copolymer having a randomness index (CSD) of 2 to 5.5 measured before fiber formation is
If the polymer constituting the first component is selected and spun, the composite fiber of the present invention in which the randomness index (CSD) of the EP copolymer contained in the first component is 3 to 6.5 can be obtained. .

When the randomness index (CSD) of the EP copolymer as the first component of the conjugate fiber is less than 3, a nonwoven fabric having a soft touch cannot be obtained. Randomness index (CSD)
Exceeds 6.5, the resulting fiber has a large thermal shrinkage and a large rubbery elasticity, so that it is inferior in the processability and the range of the thermal bonding temperature tends to be narrow. .

The EP copolymer having a randomness index (CSD) of 2 to 5.5 measured before fiber formation has a randomness index (CSD) of 2 to 5.5 measured before fiber formation.
5.5 and a mixture of two or more EP copolymers having a randomness index (CSD) of 2 to 5.5 measured before fiber formation. The randomness index (CSD) measured before fiber formation is 2-5.
The EP of No. 5 is, for example, PM940M manufactured by Monter-SDK Sunrise Co., Ltd.

In the composite fiber of the present invention, the first component has a randomness index (CSD) of 3 to 6.5.
It is preferable to consist only of the P copolymer. When the first component contains a fiber-forming resin other than the EP copolymer having a randomness index (CSD) of 3 to 6.5, the mixing ratio is preferably less than 50 mass%. If it exceeds 50 mass%, the effect of the present invention cannot be obtained.

Other fiber-forming resins contained in the first component include EP having a randomness index (CSD) of less than 3.
There are olefinic polymers or copolymers such as copolymers, polypropylene, high density polyethylene, low density polyethylene and linear low density polyethylene. The mixing ratio of the other fiber-forming resin is selected according to the type of the resin.
For example, an EP copolymer, low density polyethylene or linear low density polyethylene having a randomness index (CSD) of less than 3 is less than 50 mass%, more preferably 20 mass%.
It is advisable to mix below. Polypropylene or high-density polyethylene is less than 10 mass%, more preferably 5 mass%
It is advisable to mix below.

The nonwoven fabric and synthetic paper of the present invention contain at least 10% by mass of the heat-adhesive conjugate fiber of the present invention,
At least a part of the heat-adhesive conjugate fiber is melted and heat-bonded. When the content of the heat-adhesive conjugate fiber of the present invention is less than 10 mass% in the nonwoven fabric of the present invention,
It is difficult to impart sufficient strength to the nonwoven fabric. Since the nonwoven fabric and synthetic fiber of the present invention have a practically strong and soft touch, they are suitable for sanitary materials, packaging materials, filters, wet tissues, wipers, battery separators, and the like.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the heat-adhesive conjugate fiber of the present invention, the first component has an ethylene content of 5 to 15 mol%.
And the randomness index (CSD) is 3-6.5.
Is a fiber-forming resin containing the ethylene-propylene copolymer. The first component preferably has a melting point of 120 to 150 ° C. and an MFR of 1 to 100. More preferably, the melting point is 125 to 140 ° C and the MFR is 10 to 50.

In this specification, the melting point is JIS-
MFR refers to the melting point before fiber production measured by the DSC method according to K-7122, and the MFR is the MFR before fiber production measured at 230 ° C and 21.2 N (2.16 kgf) according to ASTM-D-1238. Point. When the resin used as the first component and / or the second component is a mixture, the melting point of the first component is the same as that of the EP copolymer whose randomness index (CSD) contained in the first component is 3 to 6.5. Melting point,
The melting point of the second component refers to the melting point of the resin that is the main component of the second component (the resin most contained in the second component in terms of mass%).

If the melting point is less than 120 ° C., fusion between fibers may occur during the fiber production process, or adhesion to a net or a roll may occur during nonwoven fabric processing. Melting point is 1
If the temperature exceeds 50 ° C., the difference in melting point from the second component becomes small, so that the temperature range of the heat bonding processing becomes narrow. Also, when the difference in melting point between the first component and the second component is small and the heat bonding processing temperature approaches the melting point of the second component, the second component is also melted or softened in the process of manufacturing the nonwoven fabric, so that the nonwoven fabric becomes hard and the tactile sensation is increased. It tends to be worse.

When the MFR is less than 1, the spinnability is poor, and
If it exceeds 00, fusion between fibers may occur during the fiber production process.

The first component may be mixed with a known nucleating agent such as an inorganic substance (for example, calcium carbonate, talc, etc.) of 15 mass% or less. Mixing the crystal nucleating agent has the advantage that fusion between fibers in the fiber production process can be prevented and a soft nonwoven fabric with a soft touch can be obtained. The first component includes other additives such as antistatic agents, pigments, matting agents, heat stabilizers, light stabilizers, flame retardants, antibacterial agents, lubricants, plasticizers, and softeners. One or more kinds of additives can be mixed according to the use or the like.

In the heat-adhesive conjugate fiber of the present invention, the second
The component is an olefin-based polymer or a copolymer thereof having a melting point higher by at least 10 ° C. than the melting point of the first component. The second component more preferably has a melting point 20 ° C. or more higher than the melting point of the first component.

The olefin polymer and the copolymer thereof as the second component of the heat-adhesive conjugate fiber of the present invention have good compatibility with the EP copolymer contained in the first component, and peeling between the components is possible. Since it does not easily occur, the rubbery elasticity of the first component is not emphasized after forming the fiber. Furthermore, since the olefin polymer and its copolymer are softer than the hard polyester resin such as polyethylene terephthalate or polybutylene terephthalate, the resin itself is softer.
By using this, the fiber itself can be made flexible, and the flexibility of the nonwoven fabric containing the fiber can be further improved.

The olefin polymer used as the second component or the copolymer thereof has a melting point of 150 to 250 ° C.
FR is preferably 5 to 60. Specifically, the second component is preferably polypropylene, polymethylpentene, an ethylene-vinyl alcohol copolymer, or the like, or a mixture thereof. In particular, crystalline polypropylene is preferably used as the second component because of its excellent fiber-forming properties.

The second component may also contain various additives as necessary. Specifically, one or more additives selected from an antistatic agent, a pigment, a matting agent, a heat stabilizer, a light stabilizer, a flame retardant, an antibacterial agent, a lubricant, a plasticizer, a softener and the like. May include.

The heat-adhesive conjugate fiber of the present invention preferably has a structure in which the first component is exposed on at least a part of the fiber surface. Examples of the conjugate fiber having such a structure include core-sheath conjugate fibers, side-by-side conjugate fibers, split conjugate fibers, and sea-island conjugate fibers arranged concentrically or eccentrically. The fiber cross-sectional shape of the heat-adhesive conjugate fiber of the present invention may be any of a circular shape, an irregular shape, and a hollow shape. In particular, concentric core-sheath composite fibers are convenient because they have many thermal bonding points and can sufficiently exhibit a thermal bonding effect.

Composite ratio of first component / second component (volume ratio)
Is preferably from 8/2 to 2/8. More preferably, it is 7/3 to 3/7. When the composite ratio exceeds 8/2, heat shrinkage increases. If the composite ratio is less than 2/8, a nonwoven fabric having sufficient strength cannot be obtained when a nonwoven fabric is produced using this fiber.

The fineness of the heat-adhesive conjugate fiber of the present invention is not particularly limited, and may be appropriately selected according to the use. For example, when the heat-adhesive conjugate fiber of the present invention is used to produce a low-weight nonwoven fabric (10 to 80 g / m ² ) such as a sanitary material or a wet tissue, the heat-bonding nonwoven fabric has a good tactile feel. The fineness of the conductive composite fiber is preferably 0.5 to 4 dtex.

Next, an example of the method for producing the heat-adhesive conjugate fiber of the present invention will be specifically described. First, as the first component,
One or more EP copolymers having an ethylene content of 5 to 15 mol% and a randomness index (CSD) of 2 to 5.5 (preferably 2.5 or more and 5.5 or less) are prepared. Mix with other fiber-forming resins as needed,
The raw material resin of the first component. As the second component, an olefin-based polymer or copolymer having a melting point higher by at least 10 ° C. than the melting point of the first component is prepared.

Using a known melt spinning machine, a spinning temperature of 200
Extruding the first component and the second component at ~ 350 ° C, taking-up speed of 100 ~ 1500m / min, taking-up fineness of 1 ~ 75dtex
Is produced. When the spinning temperature of the first component is lower than 200 ° C., the melted resin has a high melt viscosity, and thus the yarn breaks easily. The spinning temperature of the first component is 3
If the temperature exceeds 50 ° C., the melt viscosity is low, so that the spun filaments are easily fused to each other, and the spinnability is reduced due to thermal decomposition of the resin. The preferred spinning temperature of the first component is 230
３００300 ° C. When the spinning temperature of the first component is set within this range, the E contained in the first component of the obtained conjugate fiber is reduced.
The CSD of P can be within the desired range. If the spinning temperature of the second component is less than 200 ° C., the melt viscosity of the melted resin is high, so that yarn breakage is likely to occur. When the spinning temperature of the second component exceeds 350 ° C., the spinnability is reduced due to thermal decomposition of the resin. When, for example, a highly crystalline polypropylene is used as the second component, a preferable spinning temperature of the second component is 230 to 300 ° C.

As described above, the take-up fineness of the spun filament is preferably 1 to 75 dtex. When the take-up fineness of the spun filament is less than 1 dtex, yarn breakage or the like occurs and productivity is reduced. Spun filament take-up fineness of 7
If it exceeds 5 dtex, it becomes difficult to obtain a heat-adhesive conjugate fiber having a small fineness. When forming a nonwoven fabric with the heat-adhesive conjugate fiber of the present invention, in order to improve the texture of the nonwoven fabric, the take-up fineness of the spun filament should be 3 to 20 dtex.
It is preferable that

Next, the spun filament is drawn to obtain a drawn filament. The stretching treatment is performed at a stretching temperature of 30.
It is preferably carried out at a temperature of up to 95 ° C. and a stretching magnification of 2 to 5 times. More preferred stretching ratio is 2.5 to
It is 4.5 times. If the draw ratio is less than 2 times, the obtained fibers themselves do not have "stiffness", and the card permeability at the time of producing a fibrous web is reduced, and the productivity of the nonwoven fabric is reduced. Also,
If the stretching ratio is less than 2 times, the strength of the single fiber may be insufficient, and the strength of the nonwoven fabric may decrease. Stretch ratio is 5
If the ratio is more than twice, productivity may decrease due to, for example, yarn breakage during stretching, and further, thermal bonding between fibers may be insufficient when producing a nonwoven fabric. The stretching method is
Any of a wet stretching method performed in warm water or hot water or a dry stretching method may be used.

In the production process of the heat-adhesive conjugate fiber of the present invention, an annealing treatment is carried out at a temperature of 60 to 120 ° C. before, during or after the drawing treatment. Is preferred. The annealing treatment is performed in a tensioned or relaxed state using dry heat, wet heat or steam heat. The annealing treatment enhances the crystallinity of the fiber to impart “stiffness” to the fiber, and contributes to the improvement of the processability such as the card passability of the fiber during the production of the nonwoven fabric. Further, the texture of the nonwoven fabric can be adjusted by the annealing treatment conditions.

For example, when the heat-adhesive conjugate fiber of the present invention is to be obtained in the form of staple fiber or short fiber for airlay, a predetermined amount of a fiber treatment agent may be added to the obtained drawn filament, if necessary. A crimp is given by the crimping device. After crimping, 60-120
An annealing treatment is performed at a temperature of ° C. for several seconds to about 30 minutes. When performing the annealing treatment after attaching the fiber treatment agent, it is more preferable to set the annealing treatment temperature to 80 to 115 ° C., set the treatment time to 5 minutes or more, and perform the annealing treatment and simultaneously dry the fiber attachment agent. . By setting the temperature of the annealing treatment low, a strong nonwoven fabric can be obtained, and by setting the temperature of the annealing treatment high, a soft nonwoven fabric can be obtained. After the annealing process, the filament is cut to a predetermined length according to the use or the like.

When the heat-adhesive conjugate fiber of the present invention is used as a short fiber for synthetic paper, a predetermined amount of a heat treatment agent is adhered, cut to a length of 2 to 20 mm depending on the application, and the moisture content is reduced to 0%.
It is good to adjust to ~ 50 mass%. In order to increase the paper strength and heat-sealing strength of the synthetic fiber paper, the short fibers for synthetic fiber paper are preferably produced without performing an annealing treatment after the stretching treatment. Therefore, when the moisture content of the short fiber for synthetic fiber paper is reduced or set to 0%, it is preferable to carry out the drying treatment at a temperature as low as possible. The thus obtained thermoadhesive conjugate fiber of the present invention can be used, for example, for producing the nonwoven fabric or synthetic fiber paper of the present invention.

Next, the nonwoven fabric of the present invention will be described together with its production method. The nonwoven fabric of the present invention prepares a fibrous web so as to contain at least 10 mass% of the thermoadhesive conjugate fiber of the present invention, heat-treats the fibrous web, and at least a part of the surface of the thermoadhesive conjugate fiber (namely, the first Component) is melted and the fibers are thermally bonded to each other. The nonwoven fabric of the present invention has excellent strength and a soft touch. This is because the heat-adhesive conjugate fiber of the present invention is used as an adhesive component. Since the thermoadhesive conjugate fiber of the present invention has a wide thermobonding processing temperature range and can heat-bond the fibers at a temperature sufficiently lower than the melting point of the second component, the second heat
There is no decrease in the feel of the nonwoven fabric due to melting or softening of the components, and therefore, the nonwoven fabric of the present invention can achieve both a practically strong and soft touch.

The fibers contained in the nonwoven fabric of the present invention other than the heat-adhesive conjugate fiber of the present invention may be conventional fibers used in the production of nonwoven fabrics. As such fibers, specifically, natural fibers such as cotton, silk, wool, hemp, pulp, regenerated fibers such as rayon, acrylic fibers, polyester fibers, polyamide fibers, polyolefin fibers, and synthetic fibers such as polyurethane fibers are used. A plurality of types of fibers are selected according to the application and the like. The heat-adhesive conjugate fiber of the present invention is suitable for producing a nonwoven fabric in combination with a polyolefin-based fiber composed of polyethylene, polypropylene or an ethylene-propylene copolymer, and particularly, a polypropylene or an ethylene-propylene copolymer or the like. Good adhesion to propylene-based fibers consisting of It goes without saying that the nonwoven fabric of the present invention may be composed only of the heat-adhesive conjugate fiber of the present invention.

In producing the nonwoven fabric of the present invention, the form of the fiber web is not particularly limited, and a parallel web, a cross web and a semi-random web made of staple fibers, a long fiber web made of spunbond, and a short fiber are made by wet papermaking. It can be arbitrarily selected from a wet web and a dry web obtained by an air lay method according to the use and the like. Two or more different types of webs may be laminated and subjected to heat treatment. Alternatively, the nonwoven may be a meltblown nonwoven. When importance is placed on the flexibility of the nonwoven fabric, it is preferable to manufacture the nonwoven fabric using a fibrous web made of staple fibers. In addition, in order to entangle the fibers, the fiber web may be subjected to secondary processing such as needle punching or high-speed fluid flow treatment as necessary before and / or after the heat treatment.

After forming the fibrous web, the fibrous web is subjected to a heat treatment to melt and bond at least a part of the heat-adhesive conjugate fiber. The heat treatment method (the method for thermally bonding the fiber web) can be arbitrarily selected from known heat treatment methods such as a hot air blowing method and a hot roll method. In particular, the thermocompression bonding method using an embossing roll is a preferable heat treatment method in the case where importance is placed on the flexibility of the nonwoven fabric because heat bonding can be performed at a lower temperature and the pressing area is small.

The heat treatment conditions such as the heat treatment temperature differ depending on the heat treatment method. For example, when the hot air blowing method is employed, the heat treatment temperature is set to a temperature equal to or higher than the melting point of the first component and lower than the melting point of the second component, and preferably lower than the melting point of the second component −10 ° C. When a thermocompression bonding method using an embossing roll is adopted, the pressure between the rolls is preferably 15
0 to 1500 N / cm, and the heat treatment temperature T ° C is preferably (melting point of the first component −20) ° C ≦ T <(melting point of the second component −15) ° C, and more preferably (the melting point of the first component). Melting point−15) ° C. ≦ T <(melting point of second component−25) ° C.

The synthetic fiber paper of the present invention is prepared by preparing a wet web containing 10 mass% or more of the heat-adhesive conjugate fiber of the present invention, heat-treating the wet web, and at least a part of the surface of the heat-adhesive conjugate fiber (ie, It is obtained by melting the first component) and thermally bonding the fibers. The heat treatment is performed at a temperature equal to or higher than the melting point of the first component and lower than (the melting point of the second component−10) ° C.

The fibers contained in the synthetic fiber paper of the present invention other than the heat-adhesive conjugate fiber of the present invention may be conventional fibers used for producing synthetic fiber paper. As such fibers, specifically, natural fibers such as cotton, silk, wool, hemp, pulp, regenerated fibers such as rayon, acrylic fibers, polyester fibers, polyamide fibers, polyolefin fibers, and synthetic fibers such as polyurethane fibers are used. A plurality of types of fibers are selected according to the application and the like. The synthetic fiber of the present invention may be composed only of the heat-adhesive conjugate fiber of the present invention.

The synthetic fiber paper of the present invention has excellent heat sealing properties and can be used as heat seal paper. If the heat-sealing paper is used, a product having a joint (for example, a tea bag or a drainer pack) can be manufactured by forming the joint by a heat-sealing process. Such a product (for example, a tea bag) is prepared by forming the synthetic fiber paper obtained by the above-described method into a desired shape (for example, a bag shape), and then performing a heat sealing process with a heat sealing machine to form a joint. Manufactured. The heat sealing machine may be a known one, for example, a hot roll type and a stamp type are used. The heat sealing temperature is (melting point of first component−20) ° C. or higher,
(Melting point of second component + 40) ° C.

[0049]

EXAMPLES Hereinafter, the contents of the present invention will be specifically described with reference to examples. The strength and elongation of the obtained fiber, the specific volume of the nonwoven fabric, the tensile strength, the elongation at break, and the drape coefficient were measured as follows.

[Strength and Elongation of Fiber] According to JIS-L-1015, a load value and an elongation were measured using a tensile tester with a sample gripping distance of 20 mm, and a single fiber strength and a single fiber elongation were measured, respectively. Degree.

[Specific volume of nonwoven fabric] Thickness measuring machine (trade name:
Using a THICKNESS GAUGE model CR-60A (manufactured by Daiei Kagaku Seiki Seisaku-Sho, Ltd.), the thickness of the nonwoven fabric was measured under a load of 29.4 mN per 1 cm ^{2 of} the sample, and the specific volume was determined based on the thickness of the nonwoven fabric and the basis weight of the nonwoven fabric. Was calculated.

[Tensile strength and elongation at break of nonwoven fabric]
According to L-1096, a sample piece having a width of 5 cm and a length of 15 cm is gripped at an interval of 10 cm, stretched at a tensile speed of 30 cm / min using a constant-speed stretching type tensile tester, and the load value and the elongation rate at cutting Were defined as tensile strength and elongation at break, respectively. In addition, the sample piece was produced such that the width direction (CD direction) of the fiber web was the length direction of the sample piece.

[Drape coefficient of nonwoven fabric] JIS-L-1
It measured according to the 096-6.19.7-G method (drape coefficient).

[Example 1] Using a concentric core-sheath composite nozzle, as a sheath component (first component), the melting point was 138 ° C, the ethylene content was 9 mol%, and the randomness index (CSD).
Using a ethylene-propylene copolymer having a melting point of 3.03 (PM940M, manufactured by Montelusque Sunrise Co., Ltd.) and having a melting point of 165 ° C. as a core component (second component) of crystalline polypropylene (manufactured by Nippon Polychem Co., Ltd., SA03A) )
And the composite ratio (volume ratio) of the first component / the second component is 5 /
As 5, the spinning temperature of the sheath component was set to 250 ° C. and the spinning temperature of the core component was set to 300 ° C., and both components were melt-extruded, and 4.5 dtex was obtained.
Was obtained. This was stretched 2.7 times in warm water at 90 ° C. to give a 2.2 dtex drawn filament, and a fiber treatment agent was applied. Next, after mechanically crimping the filament with a stuffing box type crimper, annealing and drying are simultaneously performed in a relaxed state for about 15 minutes in a hot air penetration type dryer set at 110 ° C., and then The filament was cut to a fiber length of 45 mm to obtain a staple fiber.

Using the obtained staple fibers, a fibrous web having a basis weight of about 25 g / m ² was prepared using a parallel card. Next, the web was subjected to a thermocompression treatment to obtain a nonwoven fabric. The thermocompression bonding treatment was performed using an embossing roll having a circular embossing pattern and an embossing area of 20% and a flat roll, and setting the linear pressure between the embossing roll / flat roll to 500 N / cm. In this example, the processing temperature was set to 126 ° C., 128 ° C., 130 ° C., and the temperature (133 ° C.) required to obtain a non-woven fabric having a tensile strength of 7.8 N / 5 cm, and four types of non-woven fabrics were used. I got

Further, the randomness index (C) of the EP copolymer contained in the first component of the conjugate fiber used in this example
To determine SD), the EP copolymer used in this example was melt extruded at a spinning temperature of 250 ° C. to 4.5 dtex.
Was produced. The resulting filament has a CSD of 4.15 and an ethylene content of 9.3 mol.
l%.

Example 2 A nonwoven fabric was obtained in the same manner as in Example 1 except that the composite ratio (volume ratio) of the first component / the second component was set to 4/6. The processing temperature required to obtain a nonwoven fabric having a tensile strength of 7.8 N / 5 cm was 131 ° C.

Comparative Example 1 Melting point was 140 as a sheath component.
Example 1, except that an ethylene-propylene copolymer (Y2045GP, manufactured by Idemitsu Petrochemical Co., Ltd.) having an ethylene content of 7.0 mol% and a randomness index (CSD) of 1.53 was used. A nonwoven fabric was obtained in the same manner. The processing temperature required to obtain a nonwoven fabric having a tensile strength of 7.8 N / 5 cm was 139 ° C.

Further, the randomness index (C) of the EP copolymer contained in the first component of the composite fiber used in this comparative example
In order to measure SD), the EP copolymer used in this comparative example was melt-extruded at a spinning temperature of 250 ° C. to 4.5 dtex.
Was produced. The resulting filament has a CSD of 2.54 and an ethylene content of 6.8.
mol%.

Comparative Example 2 Melting point was 143 as a sheath component
The same as Example 1 except that an ethylene-propylene copolymer (manufactured by Nippon Polychem Co., Ltd., SX02R) having an ethylene content of 6.1 mol% and a randomness index (CSD) of 1.38 was used. To obtain a nonwoven fabric. The processing temperature required to obtain a nonwoven fabric having a tensile strength of 7.8 N / 5 cm was 141 ° C.

Further, the randomness index (C) of the EP copolymer contained in the first component of the conjugate fiber used in this comparative example
In order to measure SD), the EP copolymer used in this comparative example was melt-extruded at a spinning temperature of 250 ° C. to 4.5 dtex.
Was produced. The resulting filament had a CSD of 2.30 and an ethylene content of 6.1.
mol%.

Table 1 shows the performances of the fibers obtained in Example 1, Example 2, Comparative Example 1 and Comparative Example 2, and the nonwoven fabric produced using them. The drape coefficient of the nonwoven fabric was measured for a nonwoven fabric produced at a processing temperature of 130 ° C. and for a nonwoven fabric having a tensile strength of 7.8 N / 5 cm.

[0063]

[Table 1]

As shown in Table 1, each of the nonwoven fabrics of Examples 1 and 2 corresponding to the nonwoven fabric of the present invention has a higher tensile strength than the nonwoven fabrics of Comparative Examples 1 and 2 obtained at the same processing temperature. Had. The drape coefficients of the nonwoven fabrics of Examples 1 and 2 produced at a processing temperature of 130 ° C. are Comparative Example 1.
Although the drape coefficients of the nonwoven fabrics were higher than those of the nonwoven fabrics of Nos. 2 and 2, the nonwoven fabrics of the examples were not inferior in flexibility in view of their high strength. In addition, when nonwoven fabrics were produced so that the tensile strengths were the same, in each example, a nonwoven fabric having a predetermined strength could be obtained at a lower processing temperature than each comparative example. Therefore, each of the nonwoven fabrics of the examples is softer than the nonwoven fabric of the comparative example (ie,
Drape coefficient is small).

Example 3 A spun filament was prepared and stretched in the same manner as in Example 1, and then a fiber treating agent was applied to cut the fiber into 5 mm to obtain a heat-adhesive conjugate short fiber. The short fibers and NBKP (pulp) were mixed at a mass ratio of 5: 5 to prepare a fiber web, and the fiber web was subjected to a heat treatment at 145 ° C. for 30 seconds using a cylinder dryer to obtain a basis weight of 30 g / m ^2. Synthetic paper was obtained.

[Comparative Example 3] A spun filament was prepared and stretched in the same manner as in Comparative Example 1, and then a fiber treating agent was applied thereto to cut the fiber into 5 mm to obtain a heat-adhesive conjugate short fiber. A synthetic fiber paper having a basis weight of 30 g / m ² was obtained in the same manner as in Example 3 except that this short fiber was used.

[Comparative Example 4] A spun filament was prepared and stretched in the same manner as in Comparative Example 2, and then a fiber treating agent was applied thereto and cut to 5 mm to obtain a heat-adhesive conjugate short fiber. A synthetic fiber paper having a basis weight of 30 g / m ² was obtained in the same manner as in Example 3 except that this short fiber was used.

The heat-sealing properties of the synthetic fibers of Example 3, Comparative Examples 3 and 4 were evaluated by forming a heat-sealed portion according to the following method and measuring the peel strength of the heat-sealed portion.

(Heat sealing conditions) width 30 mm, length 70
Prepare two mm synthetic papers. Two sheets of synthetic paper are overlapped and heat-sealed at a position 50 mm from one end of the synthetic paper using a stamp-type heat sealer (TP701-13, heat seal tester, manufactured by Tester Sangyo Co., Ltd.) having a width of 5 mm. The heat treatment was performed to form a heat seal portion. The heat sealing process was performed at a temperature of 130 ° C., a pressure of 98 kPa, and a processing time of 1 second.

(Strength of Peeling) The ends of the two synthetic fiber papers on the side 50 mm apart from the heat-sealed portion were opened, and the width was 30 mm.
It was gripped at a grip interval of 10 mm, stretched at a pulling speed of 10 cm / min using a constant-speed stretching type tensile tester, and the load value at the time of cutting was defined as peel strength.

[0071]

[Table 2]

As shown in Table 2, in Example 3 corresponding to the synthetic fiber of the present invention, the peel strength of the heat-sealed portion was large,
It had excellent heat sealability.

Further, the following test was conducted to examine the strength of the heat seal portion formed on the synthetic fiber paper of the present invention. First, the synthetic fiber paper obtained in Example 3 and Comparative Example 3 was 50 mm × 5 mm.
It was cut into 0 mm squares. 2 pieces of synthetic paper cut into squares
The three sides were superposed and subjected to heat sealing using the heat sealing machine and joined to form a bag. The heat sealing process is performed at a temperature of 130 ° C., a pressure of 98 kPa, and a processing time of 1
Performed as seconds. Next, after 3 g of tea leaves were put into this bag, the remaining one side was subjected to a heat sealing treatment under the above conditions to produce a dee bag.

The obtained tea bag was put into a kettle containing boiling water and boiled down for about 10 minutes. As a result, no change was observed in the tea bag made of the synthetic fiber paper obtained in Example 3, but in the tea bag made of the synthetic fiber paper obtained in Comparative Example 3, the heat-sealed portion was broken and the tea leaves came out of the bag. Leaked.

[0075]

The heat-adhesive conjugate fiber of the present invention is characterized in that a specific ethylene-propylene copolymer is used as a heat-adhesive component and this is combined with an olefin polymer or its copolymer. Due to this feature, the heat-adhesive conjugate fiber of the present invention can exhibit heat-adhesive ability at a wide range of temperatures. By utilizing this property, a heat-bonded nonwoven fabric can be manufactured at a lower processing temperature than when using a conventional heat-bondable conjugate fiber, so that it can be compared with a conventional heat-bonded nonwoven fabric having the same strength. It is possible to obtain a nonwoven fabric having a softer touch. Further, if this property is utilized, it is possible to obtain a synthetic fiber paper having excellent heat sealing properties, that is, a synthetic fiber paper capable of forming a heat-sealed portion having high strength at a lower temperature.

Therefore, the non-woven fabric of the present invention which contains at least 10% by mass of the heat-adhesive conjugate fiber of the present invention and at least a part of the heat-adhesive conjugate fiber is melted and heat-bonded has high strength and Gives a soft touch.
Further, the heat-adhesive conjugate fiber of the present invention has a mass of at least 10 mass.
%, At least a part of the heat-adhesive conjugate fiber is melted, and the heat-bonded synthetic fiber of the present invention exhibits excellent heat sealability. Such nonwoven fabric and synthetic paper are suitable for sanitary materials, packaging materials, filters, wet tissues, wipers, battery separators, and the like.

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) 4L041 AA07 AA20 AA25 BA02 BA05 BA21 BA49 BA59 BD03 BD06 BD07 BD11 BD20 CA38 CA42 DD05 DD15 4L047 AA08 AA28 BA09 BB02 BB09 CB01 CB09 CC03 CC11 CC12 4L055 AA20 AF16 AF16 AF16 EA04 EA19 EA20 EA32 FA13 FA16 GA02 GA05 GA26 GA29 GA31

Claims (7)

[Claims] 1. A fiber-forming resin containing an ethylene-propylene copolymer is used as a first component, and has a melting point 10 times lower than that of the first component.
An olefin-based polymer or a copolymer thereof having a temperature of at least ° C is used as a second component, and the first component is a conjugate fiber exposed on at least a part of the fiber surface, and the ethylene-propylene copolymer contained in the first component is , Ethylene content is 5-15mo
A thermoadhesive conjugate fiber having a l% and a randomness index (CSD) of 3 to 6.5 determined by ¹³ C-NMR method. 2. The heat-adhesive conjugate fiber according to claim 1, wherein the olefin polymer of the second component is crystalline polypropylene. 3. The heat-adhesive conjugate fiber according to claim 1, wherein the first component is an ethylene-propylene copolymer. 4. A randomness index (CS) having an ethylene content of 5 to 15 mol% and a ¹³ C-NMR method.
A fiber-forming resin containing an ethylene-propylene copolymer having D) of 2 to 5.5 as a first component, and an olefin polymer having a melting point higher than that of the first component by 10 ° C. or more as a second component. A thermoadhesive conjugate fiber obtained by conjugate spinning such that the first component is exposed on at least a part of the fiber surface as a component. 5. An ethylene content of 5 to 15 mol% and a randomness index (CS) determined by ¹³ C-NMR method.
D) a fiber-forming resin containing an ethylene-propylene copolymer having 2 to 5.5 as a first component, and an olefin polymer having a melting point higher than that of the first component by 10 ° C. or more or a copolymer thereof as a second component. A method for producing a heat-adhesive conjugate fiber, wherein the first component is conjugate-spun so as to be exposed on at least a part of the fiber surface. 6. A non-woven fabric comprising at least 10 mass% of the heat-adhesive conjugate fiber according to claim 1, wherein at least a part of the heat-adhesive conjugate fiber is melted and heat-bonded. 7. A synthetic fiber paper containing at least 10 mass% of the heat-adhesive conjugate fiber according to claim 1, wherein at least a part of the heat-adhesive conjugate fiber is melted and heat-bonded.