JPH0571057A - Production of polypropylene based conjugate staple fiber and nonwoven fabric - Google Patents

Abstract

PURPOSE:To obtain the title conjugate staple fiber having excellent stretchability, bulkiness and flexibility by subjecting two kinds of polypropylene based copolymers to melt conjugate spinning and then thermally stretching the spun yarn under specific conditions and further applying crimping treatment and finishing lubricant thereto. CONSTITUTION:(A) a propylene based copolymer component obtained by subjecting 92-97wt.% propylene to random copolymerization with 3-8wt.% ethylene and (B) a polypropylene based copolymer component obtained by copolymerizing 97-100wt.% propylene with 0-3% ethylene are used are conjugating components and these components are subjected to melt conjugate spinning under conditions of 15g to 45g/min melt flow value, 1/1 to 6/1 melt flow value ratio and 2-10m/min discharged liner rate. Then the obtained undrawn conjugate fiber is drawn while heating at >=50 deg.C and temperature not to melt fibers each other and the drawn conjugate fiber is further subjected to crimping treatment and a finishing lubricant is applied thereto and the conjugate fiber is dried and cut into prescribed length to efficiently obtain the objective staple fiber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene-based composite staple fiber suitable for obtaining a nonwoven fabric excellent in stretchability, bulkiness and flexibility and a method for producing the nonwoven fabric.

[0002]

2. Description of the Related Art Conventionally, as a nonwoven fabric made of a thermoplastic synthetic composite fiber, a nonwoven fabric made of a composite fiber in which a plurality of polymer components having different melting points are arranged in parallel type or core-sheath type has been widely used. The non-woven fabric composed of this composite fiber utilizes the latent crimp property which is the characteristic of the heterogeneous composite fiber,
Stretchability is imparted by developing crimps during the processing of non-woven fabrics, and it is mainly used as a material for medical and hygiene materials such as supporters, pad materials and diapers. For example, Japanese Examined Patent Publication (Kokoku) No. 55-26203 discloses a composite fiber composed of a three-dimensional copolymer containing butene-1, and Japanese Laid-Open Patent Publication No. 1227553/1990 discloses a copolymer containing butene-1. A non-woven fabric composed of a composite fiber composed of is proposed. However, this non-woven fabric is not only poor in stretchability and bulkiness but also hard in texture although it is improved in thermal adhesiveness because it is made of a three-dimensional copolymer containing butene-1. Also, Japanese Patent Publication Sho 52-
Japanese Patent No. 37097 proposes a composite fiber composed of a polypropylene polymer and a polyethylene polymer.
The non-woven fabric made of this composite fiber has a problem that fluff is generated on the non-woven fabric surface due to peeling between the two components at the time of producing the non-woven fabric, and the quality of the product is deteriorated. Furthermore, Japanese Patent Laid-Open No. 2-1
Japanese Patent Publication No. 91720 proposes a composite fiber composed of a polypropylene polymer and an ethylene-propylene random copolymer, and a method for producing the same. This composite fiber is stretched by reducing the Q value (weight average molecular weight / number average molecular weight) of the polypropylene polymer to develop a spiral crimp. However, since the polypropylene polymer has a small Q value in this conjugate fiber, the heat treatment temperature range during crimping treatment is limited and process control is difficult. Had a problem that its quality deteriorated.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and is excellent in stretchability, bulkiness and flexibility, and is suitable for obtaining a non-woven fabric suitable for medical hygiene materials. And a method capable of efficiently producing a nonwoven fabric.

[0004]

The present inventors have arrived at the present invention as a result of intensive studies to solve the above problems. That is, the present invention includes 1) a polypropylene-based copolymer component A in which 92% by weight or more and 97% by weight or less of propylene and 3% by weight or more and 8% by weight or less of ethylene are randomly copolymerized, and 97% by weight or more and 100% by weight. % Propylene and 0% to 3% by weight
A melt flow rate value of a composite short fiber of 15 g / 10 min or more and 45 g / 10 when the following polypropylene-based copolymer component B copolymerized with ethylene is used as a composite component
The melt flow rate value ratio (B / A) of the polymer component A and the polymer component B after melting is set to 1/1 to
6/1 and the melt linear component of polymer component A and polymer component B are set to 2-10 m / min for the discharge linear velocity, and the resulting unstretched composite fiber is 50 ° C. or more and the temperature at which the fibers do not fuse to each other. Of the polypropylene-based short fiber, which is characterized in that it is heat-stretched at Production method,

2) A polypropylene system in which 92% by weight or more and 97% by weight or less of propylene and 3% by weight or more and 8% by weight or less of ethylene are randomly copolymerized, and the Q value (weight average molecular weight / number average molecular weight) is 8 or less. Copolymer component A, 9
7 wt% to 100 wt% propylene and 0 wt%
When a polypropylene-based copolymer component B having a Q value (weight average molecular weight / number average molecular weight) of 5 or more and 8 or less is copolymerized with ethylene of 3% by weight or less and 3% by weight or less, and a composite short fiber is obtained. Melt flow rate value is 15g / 1
The melt flow rate value ratio (B / A) of the polymer component A and the polymer component B after melting is 1/1 to 6/1 and is 0 to 45 g / 10 min. Melt composite spinning was performed at a discharge linear velocity of A and the polymer component B of 2 to 10 m / min, and the obtained undrawn composite fiber was heat drawn at a temperature of 50 ° C. or higher and at a temperature at which the fibers were not fused to each other, and then obtained. A method for producing a polypropylene-based short fiber, which comprises subjecting a stretched composite fiber to crimping treatment, applying a finishing oil agent, drying the cut composite fiber, and cutting the composite fiber into short fibers,

3) A polypropylene system in which 92% by weight or more and 97% by weight or less of propylene and 3% by weight or more and 8% by weight or less of ethylene are randomly copolymerized, and the Q value (weight average molecular weight / number average molecular weight) is 8 or less. Copolymer component A, 9
7 wt% to 100 wt% propylene and 0 wt%
When a polypropylene-based copolymer component B having a Q value (weight average molecular weight / number average molecular weight) of 5 or more and 8 or less is copolymerized with ethylene of 3% by weight or less and 3% by weight or less, and a composite short fiber is obtained. Melt flow rate value is 15g / 1
The melt flow rate value ratio (B / A) of the polymer component A and the polymer component B after melting is 1/1 to 6/1 and is 0 to 45 g / 10 min. Melt composite spinning was performed at a discharge linear velocity of 2 to 10 m / min of A and the polymer component B, and the resulting undrawn composite fiber was hot-drawn at a temperature of 50 ° C. or higher and at a temperature at which the fibers were not fused to each other. )
To (3), the drawn composite fiber is then subjected to a crimping treatment, a finishing oil agent is applied thereto, dried, and cut into a predetermined length to obtain a short fiber. (1) The birefringence of the copolymer component A portion and the birefringence of the copolymer component B portion of the composite short fiber before heat treatment are both 0.02 or more, (2) ) The crystal volume of the composite short fibers before heat treatment measured by the wide-angle X-ray diffraction method is 100,000Å ³ or less, (3) the long period of the composite short fibers before heat treatment measured by the small-angle X-ray scattering method is 130Å Be less than,

4) A polypropylene copolymer component A in which 92% by weight or more and 97% by weight or less of propylene and 3% by weight or more and 8% by weight or less of ethylene are randomly copolymerized, and 9
7 wt% to 100 wt% propylene and 0 wt%
The melt flow rate value is 15 g / 10 min or more and 45 g / 10 min or less when a composite short fiber is formed by using a polypropylene-based copolymer component B in which 3% by weight or less of ethylene is copolymerized as a composite component. The melt flow rate value ratio (B / B) of the polymer component A and the polymer component B after melting
A) is 1/1 to 6/1, and the melt linear spinning is performed at a discharge linear velocity of the polymer component A and the polymer component B of 2 to 10 m / min. The drawn composite fiber is heat-stretched at a temperature at which the fibers do not fuse with each other, and then the resulting stretched composite fiber is subjected to a crimping treatment, a finishing oil agent is applied, and the product is dried and cut into predetermined lengths to obtain short fibers. A card web was prepared using 50% by weight or more of the composite short fibers, and the card web was placed on a porous support member.
After the web is subjected to a fluid entanglement treatment with a fluid jet having a pressure of less than 30 kg / cm ² , the pressure is 50 kg / cm ^2.
The web is subjected to a fluid entanglement treatment by the above fluid jet to three-dimensionally entangle the composite short fibers constituting the web, and then the web is subjected to a dry heat treatment to remove water and form a composite short fiber. A method for producing a non-woven fabric, characterized by expressing crimps,

5) Polypropylene system in which 92% by weight or more and 97% by weight or less of propylene and 3% by weight or more and 8% by weight or less of ethylene are randomly copolymerized, and Q value (weight average molecular weight / number average molecular weight) is 8 or less. Copolymer component A, 9
7 wt% to 100 wt% propylene and 0 wt%
When a polypropylene-based copolymer component B having a Q value (weight average molecular weight / number average molecular weight) of 5 or more and 8 or less is copolymerized with ethylene of 3% by weight or less and 3% by weight or less, and a composite short fiber is obtained. Melt flow rate value is 15g / 1
The melt flow rate value ratio (B / A) of the polymer component A and the polymer component B after melting is 1/1 to 6/1 and is 0 to 45 g / 10 min. Melt composite spinning was performed at a discharge linear velocity of A and the polymer component B of 2 to 10 m / min, and the obtained undrawn composite fiber was heat drawn at a temperature of 50 ° C. or higher and at a temperature at which the fibers were not fused to each other, and then obtained. The drawn composite fiber is subjected to a crimping treatment, a finishing oil is applied thereto, and then dried, cut into a predetermined length to form a short fiber, and then a card web is prepared using 50% by weight or more of the obtained composite short fiber. After placing this card web on a porous support member and subjecting the web to fluid entanglement with a fluid jet having a pressure of less than 30 kg / cm ² , the pressure is 50 kg / cm ^2.
The web is subjected to a fluid entanglement treatment by a fluid jet of 3 cm ² or more to three-dimensionally entangle the composite short fibers constituting the web, and then the web is subjected to a dry heat treatment to remove water and the composite short fibers. A method for producing a non-woven fabric, characterized by expressing crimps in fibers,

6) Polypropylene system in which 92% by weight or more and 97% by weight or less of propylene and 3% by weight or more and 8% by weight or less of ethylene are randomly copolymerized, and the Q value (weight average molecular weight / number average molecular weight) is 8 or less. Copolymer component A, 9
7 wt% to 100 wt% propylene and 0 wt%
When a polypropylene-based copolymer component B having a Q value (weight average molecular weight / number average molecular weight) of 5 or more and 8 or less is copolymerized with ethylene of 3% by weight or less and 3% by weight or less, and a composite short fiber is obtained. Melt flow rate value is 15g / 1
The melt flow rate value ratio (B / A) of the polymer component A and the polymer component B after melting is 1/1 to 6/1 and is 0 to 45 g / 10 min. Melt composite spinning was performed at a discharge linear velocity of 2 to 10 m / min of A and the polymer component B, and the resulting undrawn composite fiber was hot-drawn at a temperature of 50 ° C. or higher and at a temperature at which the fibers were not fused to each other. )
A composite fiber satisfying (3) to (3) is obtained. Then, the drawn composite fiber obtained is subjected to crimping treatment, applied with a finishing oil agent, dried and cut into a predetermined length to obtain a short fiber, which is then obtained. A card web is prepared using 50% by weight or more of the composite short fibers, the card web is placed on a porous support member, and the web is subjected to a fluid entanglement treatment by a fluid jet having a pressure of less than 30 kg / cm ^2. The pressure is 50kg / c
The web is subjected to a fluid entanglement treatment with a fluid jet of m ² or more to three-dimensionally entangle the composite short fibers constituting the web, and then the web is subjected to a dry heat treatment to remove water and the composite short fibers. The following conditions (4) to (6) for the fiber
And a crimp is expressed. (1) The birefringence of the copolymer component A portion and the birefringence of the copolymer component B portion of the composite short fiber before heat treatment are Both are 0.02 or more, (2) the crystal volume of the composite short fiber before heat treatment measured by the wide-angle X-ray diffraction method is 100,000 Å ³ or less, (3) measured by the small-angle X-ray scattering method The long period of the composite short fibers before heat treatment is less than 130Å, (4) the birefringence of the copolymer component A portion and the birefringence of the copolymer component B portion of the composite short fibers after heat treatment are both before the above heat treatment. Lower than the birefringence of the copolymer component A portion and the birefringence of the copolymer component B portion of the composite staple fiber of (5), (5) Crystal volume of the composite staple fiber after heat treatment measured by wide-angle X-ray diffractometry Is 200000Å ³ or more, (6) The gist is that the long period of the composite short fibers after heat treatment measured by the small angle X-ray scattering method is 130 Å or more.

Next, the present invention will be described in detail. First, the method for producing the composite staple fiber of the present invention will be described. In the method of the present invention, first, a polypropylene-based copolymer component A in which 92% by weight or more and 97% by weight or less of propylene and 3% by weight or more and 8% by weight or less of ethylene are randomly copolymerized,
A composite staple fiber composed of 97 wt% or more and 100 wt% or less propylene and 0 wt% or more and 3 wt% or less ethylene-based polypropylene-based copolymer component B is produced.

The polymer component A is obtained by copolymerizing 92% by weight or more and 97% by weight or less of propylene and 3% by weight or more and 8% by weight or less of ethylene, has fiber-forming properties and can be melt-spun with good spinnability. Is. The copolymerization of ethylene has a great influence on the melting point lowering and heat shrinkability of the copolymer, lowers the melting point of the copolymer in proportion to the copolymerization amount, and increases the heat shrinkability. If the amount of this copolymer is less than 3% by weight, the melting point of the copolymer will be less likely to drop, and the crimping property will decrease when the composite short fibers are heat-treated, and the heat shrinkage will also decrease, such being undesirable. However, if the amount of the copolymerization exceeds 8% by weight, the rate of production of by-products soluble in the polymerization solvent (hydrocarbon) increases during the polymerization and the productivity decreases, which is industrially uneconomical and is not preferable. Therefore,
The copolymerization amount is 3% by weight or more and 8% by weight or less, preferably 3.2% by weight or more and 7.0% by weight or less, and particularly preferably 3.5% by weight or more and 6.0% by weight or less. Good. The polymer component A is 3% by weight or more and 8% by weight or more.
The following ethylene and 92% by weight or more and 97% by weight or less of propylene are randomly copolymerized. This random copolymerization is extremely important in terms of uniform heat shrinkage properties and spinnability of the copolymer. Block copolymerization is another type of copolymerization. In this copolymerization, the structure part of ethylene exists in the block structure of polypropylene as a block unit, so that the heat shrinkage property of the copolymer becomes non-uniform and This is not preferable because it causes a problem that the threadiness is extremely lowered.

The polymer component B is 97% by weight or more and 10% or more.
Propylene of 0% by weight or less and ethylene of 0% by weight or more and 3% by weight or less are copolymerized, and it has fiber-forming properties and can be melt-spun with good spinnability. As described above, the copolymerization of ethylene has a great influence on the melting point lowering and heat shrinkability of the copolymer, lowers the melting point of the copolymer in proportion to the copolymerization amount, and increases the heat shrinkability. In this polymer component B, it is necessary to suppress lowering of melting point and increase of heat shrinkability. That is, when the difference in melting point and heat shrinkage characteristics between the polymer component A and the polymer component B becomes too small,
When the composite short fibers are heat-treated, the crimp developability decreases, which is not preferable. Therefore, this copolymerization amount is 0% by weight.
3% by weight or less, preferably 2.5% by weight or less,
Particularly preferably, it is 2% by weight or less.

In the present invention, melt-composite spinning can be carried out using a normal melt-composite spinning apparatus. In the melt composite spinning, the copolymer component A having a melt flow rate value of 5 g / 10 min or more and 40 g / 10 min or less and the copolymer component B having a melt flow rate value of 15 g / 10 min or more and 80 g or more are used. / 10 minutes or less,
It is necessary to carry out melt spinning so that the melt flow rate value of the composite staple fiber obtained by compounding both polymers is 15 g / 10 min or more and 45 g / 10 min or less. The melt flow rate value of this composite short fiber is ASTM D 1238.
It is measured by the method described in (L), and when the melt flow rate value is less than 15 g / 10 minutes,
The heat shrinkage stress of the composite short fibers increases, and the crimping force and the stretching force,
The bulkiness can be increased, but not only the spinnability of the polymer but also the thermal drawability in the next step is reduced, and the polypropylene polymer is decomposed because the spinning temperature during melt spinning is set high. A large amount of gas is generated and the environment of the spinning chamber is deteriorated, which is not preferable. On the other hand, when the melt flow rate value exceeds 45 g / 10 minutes, the heat shrinkage force of the composite short fibers decreases, so that a nonwoven fabric excellent in stretchability and bulkiness cannot be obtained, and the polymerization of the polypropylene-based polymer It is not preferable because it decomposes too slowly and a large amount of gas is generated to deteriorate the environment of the spinning chamber. Therefore, this melt flow rate value is 15 g / 10 minutes or more and 45 g /
10 minutes or less, preferably 18g / 10 minutes or more 40g
/ 10 minutes or less, particularly preferably 20 g / 10 minutes or more 35
It is preferably g / 10 minutes or less.

In the melt composite spinning, the melt flow rate value ratio (B / A) of the polymer component A and the polymer component B is
Should be 1/1 to 6/1. The melt flow rate value ratio referred to here is a sample obtained by individually collecting the melt-measured polymers before composite spinning, cooling them once, and making them into chips, according to ASTM D 1238.
It is measured and calculated by the method described in (L). In the present invention, the polymer component A having a large amount of ethylene copolymerization is defined as the high shrinkage component, and the melt flow rate value ratio (B
/ A) is 1/1 to 6/1, that is, it is important that the polymer component A has a higher viscosity than the polymer component B. When the melt flow rate value of the polymer component B is less than 1 relative to the melt flow rate value of the polymer component A, the heat shrinkability of the composite staple fiber is lowered, which is not preferable. On the other hand, if the melt flow rate value of the polymer component B exceeds 6, when melt-spinning is performed using both components, kneeing frequently occurs on the spinneret surface and spinnability is deteriorated, which is not preferable. Therefore, the melt flow rate value ratio is set to 1/1 to 6/1, preferably 1.2 / 1 to 5.0 / 1, and particularly preferably 1.5 / 1 to 4.0 / 1. Is good.

In the melt composite spinning, the Q value (weight average molecular weight / number average molecular weight) of the polymer component A after melting is preferably 8 or less. The Q value is the ratio of the weight average molecular weight and the number average molecular weight of the polymer, which is determined by gel permeation chromatography, and the individually melt-measured polymers are individually collected before composite spinning, It is a value measured using a cooled polymer as a sample. It is known that the polypropylene polymer is easily deteriorated by the influence of heat and shear during melt spinning, and the Q value after melt spinning is lower than that before spinning. The Q value shows the width of the molecular weight distribution and has a great influence on the manufacturing suitability and processing suitability of the composite fiber. That is, when the Q value is large and the molecular weight distribution is wide, the temperature range of heat treatment for developing crimps or imparting elasticity to the composite fiber is wide, and a nonwoven fabric having bulkiness and elasticity can be stably obtained. be able to. However, if the Q value becomes large and the width of the molecular weight distribution becomes too wide, the yarn cooling during melt spinning becomes poor and the spinnability decreases. Therefore, this Q value is 8
Or less, preferably 7.5 or less, particularly preferably 7.
It is preferable to set it to 0 or less.

The Q value (weight average molecular weight / number average molecular weight) of the polymer component B after melting is preferably 5 or more and 8 or less. As described above, this Q value shows the width of the molecular weight distribution, and has a great influence on the manufacturing suitability and processing suitability of the composite fiber. In particular, the Q value of the polymer component B should be more limited than the Q value of the polymer component A. The polymer component B is a high melting point component of the composite fiber and represents the fiber module when crimping occurs, and the width of the molecular weight distribution is particularly important. That is, when the Q value is less than 5, the molecular weight distribution of the polymer is narrowed and the shrinkage rate of the composite fiber is lowered. For example, when crimping is applied to the composite fiber without applying the stuff abox, the actual crimp Is less likely to pass through the card process, which is most commonly used for web formation, and it is also difficult to pass through the nonwoven web or nonwoven fabric after passing the card process, such as embossing rollers or hot air dryers. Stable production of high-quality non-woven fabrics that have a high bulk and stretchability by narrowing the heat treatment temperature range for developing crimps and imparting stretchability by performing heat treatment using the above heat treatment equipment I can't. Furthermore, since the toughness of the composite fiber is reduced, it is not possible to obtain a nonwoven fabric having excellent bulkiness and flexibility. On the other hand, when the Q value exceeds 8, the width of the molecular weight distribution of the polymer becomes too wide, the cooling of the yarn during melt spinning becomes poor, and the spinnability decreases, and a fine composite fiber can be obtained. It will be difficult. Therefore, this Q
The value is 5 or more and 8 or less, preferably 5.3 or more and 7.8 or less, and particularly preferably 5.5 or more and 7.5 or less.

Further, in the melt composite spinning, it is necessary to set the discharge linear velocity of the polymer component A and the polymer component B to 2 to 10 m / min. The discharge linear velocity here means the discharge amount Q (g / min) of the single spinning hole of the molten polymer, and the density ρ (g of the same polymer.
/ Cm ³ ) and the spinning hole diameter d (mm), and is calculated by the following equation (a). Discharge linear velocity (m / min) = 4Q / (πρd ² ) ... (a) Normally, the composite fiber made of different polymers is melted. When spinning, the spinnability is greatly affected by the difference in the spinnability range due to the difference in the melt flow rate between the polymers to be combined and the melting temperature limited by the high viscosity component, and the appropriate discharge depending on the type of the polymer. It is necessary to select the linear velocity. Therefore, in the present invention, it is necessary to set the discharge linear velocity to 2 to 10 m / min in order to obtain good spinnability, and if the discharge linear velocity is outside this range, the spinnability is deteriorated. Preferably 3-9 m /
Min, particularly preferably 4 to 8 m / min.

In the present invention, the composite ratio (B / A) of the composite fibers
(Weight ratio) is not particularly limited, but is usually 75/25 to 2
5/75 is preferable, and 50/50 is particularly preferable because crimp developability is improved. Moreover, the composite form is a general parallel structure, a concentric or eccentric type core-sheath structure, or an irregular cross-section type, but considering the improvement of heat shrinkability and crimp developability, the parallel structure is desirable. .. When using a core-sheath structure, the eccentricity defined by the following equation (b) is preferably 15 or more. Eccentricity = (distance between center of single fiber and center of core component) × 100 / (radius of single fiber) ≧ 15 ... (B) When the eccentricity is less than 15, the crimp developability deteriorates, and a nonwoven fabric excellent in stretchability and bulkiness cannot be obtained, which is not preferable. A matting agent, a lightproofing agent, a heatproofing agent, a pigment or the like which is usually used for fibers can be added to both the components as long as the effects of the present invention are not impaired.

In the present invention, the unstretched composite fiber obtained by melt-composite spinning is then heat-stretched at a temperature of 50 ° C. or higher and at a temperature at which the fibers do not fuse together. The hot drawing can be performed using a normal hot drawing apparatus. Usually, when drawing a thermoplastic synthetic fiber, it is known to heat draw at a glass transition temperature or higher, but in the present invention, heat draw is performed at a temperature of 50 ° C. or higher, which is considerably higher than the glass transition temperature. If the stretching temperature is lower than 50 ° C., the stretching tension becomes too high, the stretchability is lowered, and the stretching apparatus becomes expensive, which is not preferable. Further, in the present invention, the drawing temperature is set to be lower than the temperature at which the fibers start to be fused even though the drawing temperature is high. If the drawing temperature becomes too high and the fibers start to fuse together, yarn breakage will occur in the drawing process and the operability will decrease, or the product uniformity will decrease and the quality will decrease, which is not desirable. .. Therefore, the stretching temperature is 50 ° C. or higher and the temperature at which the fibers are not fused to each other, and preferably 70 to 120 ° C.
It is good to say

Next, the obtained stretched composite fiber is subjected to crimping treatment. The crimping treatment can be performed using a crimping device such as a normal stuffer type crimping device.
Subsequent to this crimping treatment, a finishing oil agent is applied to the fibers, dried, and then cut into a predetermined length to obtain short fibers.

In the present invention, the single fiber fineness of the composite short fibers is 6
It is better to set it to denier or less. When the monofilament fineness exceeds 6 denier, the flexibility of the nonwoven fabric decreases, or when melt spinning, the polypropylene-based melt polymer is insufficiently cooled and fusion occurs between filaments, resulting in poor spinnability. It is not preferable because

The composite short fibers obtained by the method of the present invention have a dry heat shrinkage of 35% or more under the conditions of a temperature of 120 ° C. and an initial load of 2 mg, and the number of crimps is 60/25 mm after heat treatment at a temperature of 120 ° C. The above crimps are developed. The dry heat shrinkage of the composite short fibers contributes to the stretching force due to the diameter increase of the fibers themselves and the conversion force to the crimped form, and the number of crimps after heat treatment is the number of crimps of the untreated fibers. The increase in the amount contributes to the stretchability and bulkiness. The higher the dry heat shrinkage rate and the number of crimps after heat treatment, the greater the stretchability and bulkiness. This dry heat shrinkage rate is 120 ° C and initial load is 2
The composite short fiber obtained by the method of the present invention is 35% under the above temperature and load conditions.
It is possible to obtain a nonwoven fabric that exhibits the dry heat shrinkage ratio described above, and that the number of crimps is 60 crimps / 25 mm or more by heat treatment at the above temperature, and that is excellent in stretchability and bulkiness.
If the dry heat shrinkage is less than 35% and the number of crimps after the heat treatment is less than 60 pieces / 25 mm, a nonwoven fabric excellent in stretchability and bulkiness cannot be obtained, which is not preferable. In addition,
The composite short fibers obtained by the method of the present invention have a temperature of 120 ° C.
And the dry heat shrinkage ratio measured under the condition of the initial load of 50 mg is 3
When it is 0% or more, a high degree of shrinkage is exhibited even under a high elongation stress, and an instantaneous recoverability is exhibited in the fiber, which is more preferable.

The composite short fibers obtained by the method of the present invention are 3
It has a strength of g / denier or more, and when a non-woven fabric is made from composite short fibers, and the obtained non-woven fabric is used as a material for medical hygiene materials such as diapers, raw cotton falls off and adheres to the skin. It does not cause a feeling of strangeness, and does not cause problems such as the fiber absorbent being exposed inside or outside the diaper. Also, when used as a supporter, a knee drop phenomenon may occur,
It will not be damaged.

The composite short fibers obtained by the method of the present invention have both birefringence of the copolymer component A portion and the birefringence of the copolymer component B portion of the composite short fibers before heat treatment of 0.02 or more,
The birefringence of the copolymer component A portion and the birefringence of the copolymer component B portion of the composite short fiber after heat treatment are both the birefringence and the copolymer of the copolymer component A portion of the composite short fiber before the heat treatment. It is lower than the birefringence of the component B part. This birefringence was treated with a Karlzeus-Jena interference microscope, using a mixed solution of liquid paraffin and α-bromonaphthalene as an encapsulant, and the obtained composite fiber was used as a sample for polymer component A and polymer component B. The birefringence is measured respectively. Birefringence is generally used as an index showing the orientation of fibers. The composite fiber has a certain orientation, and when heat treatment is applied to the fiber, the heat shrinkage becomes extremely large, but at this time, the orientation is alleviated at once and the birefringence decreases. This means that substantial shrinkage brings about a structural change of the fiber, and this thermal shrinkage makes it possible to obtain a fiber structure exhibiting great stretchability. When the birefringence is low, the heat shrinkage does not increase even when heat treatment is performed because the orientation of the fibers is low, and thus it is not possible to obtain a fiber structure exhibiting a large elasticity.

The composite short fibers obtained by the method of the present invention have a crystal volume of 100,000 Å ³ or less before heat treatment, which is measured by the wide-angle X-ray diffraction method, and are measured by the wide-angle X-ray diffraction method. The crystal volume of the composite short fibers after heat treatment is 200,000Å ³ or more. This crystal volume is obtained by a wide-angle X-ray diffraction method, and is an α-type unit cell (a = 6.65Å, b = 20.96Å, c = 6.
50Å, β = 99.2 °) a-axis direction, b-axis direction and c
Crystal planes L (110), L (130) corresponding to the axial direction
And the following Scherrer using the surface spacing of L (003)
The apparent crystal size L (hkl) is obtained by the equation (c) and the product of these crystal sizes is calculated. Crystal size [L (hkl)] = Kλ / β cos θ (c) K = 0.9, λ = 1.5418, β = [[each crystal plane Half-width (deg)] ² −0.67 ² ] ^{1/2 If} the crystal volume of the fiber before heat treatment exceeds 100000Å ³ , the crystal volume is too large, so that crystal growth is expected even if the fiber is heat treated. Therefore, the heat shrinkage does not increase, so that a fiber structure exhibiting a large elasticity cannot be obtained, which is not preferable. On the other hand, if the crystal volume of the fiber after the heat treatment is less than 200,000Å ³ , the crystal volume is not sufficiently large and a stable fiber structure cannot be obtained, which is not preferable.

The composite short fibers obtained by the method of the present invention have a long period of less than 130 Å before heat treatment measured by the small angle X-ray scattering method and a heat treatment measured by the small angle X-ray scattering method. The long period of the subsequent composite short fibers is 130Å
That is all. This long period is obtained by the wide-angle X-ray diffraction method, and the polymer component A and the polymer component B are
It shows the average length of the sum of the crystal part and the amorphous part in the state of being joined. In this composite short fiber, the long cycle of the composite short fiber before heat treatment is less than 130 Å, and a suitable crystal part and a suitable amorphous part are mixed. When the long period of the composite short fiber before heat treatment is 130 Å or more and the crystal part of the fiber is already largely grown, the fiber is approaching the structurally relaxed state, so the thermal shrinkage rate does not increase, and thus a large elasticity is exhibited. It is not preferable because it is not possible to obtain a fiber structure. Further, when the amorphous portion of the fiber is large, the heat shrinkage rate becomes large, but it is not preferable because the stability with time is poor. Therefore, the composite short fibers before heat treatment are in a state in which a suitable crystal part and a suitable amorphous part are mixed and the long cycle is 130
It is preferably less than Å. By suppressing the long cycle before the heat treatment, it is possible to promote the relaxation of the molecular chain structure of the fiber after the heat treatment and increase the heat shrinkage. Furthermore, in this composite short fiber, it is preferable that the long cycle of the composite short fiber after heat treatment is 130 Å or more. By the heat treatment, the crystal grows in the direction of the molecular chain axis due to the incorporation of the amorphous part into the crystal part, and the long period becomes 130 Å or more, so that a stable structure can be obtained. The term "heat treatment" as used herein means that the composite short fibers are subjected to free length treatment at a temperature of (melting point of polymer component B-40 ° C) or higher and lower than melting point of polymer component B.

The composite short fibers obtained by the method of the present invention have a crystallinity of the composite short fibers before heat treatment measured by a density method of less than 70%, and a composite short fiber after heat treatment measured by a density method. The crystallinity of the fiber is 70% or more. This crystallinity is measured by the density method and is calculated from the following equation (d). Crystallinity = (ρc / ρ) × [(ρ−ρa) / (ρc−ρa)] × 100 ... (D) ρc is the crystal density, ρa is the amorphous density, ρ is the density measurement value of the sample ρc = 0.360g / cm ³ , ρa = 0 0.8545 g
/ Cm ³ By subjecting this composite short fiber to a heat treatment to improve its crystallinity, a product with improved heat resistance can be obtained when the final product is made from this fiber.

Next, the method for producing the nonwoven fabric of the present invention will be described. In the method of the present invention, first, a web is prepared using the composite short fibers. First, the composite short fibers are used alone, or 50% by weight or more of the composite short fibers and 50% by weight or less of other materials are mixed and carded by a card machine to prepare a web having a predetermined basis weight. As the short fibers of other materials mixed with the composite short fibers, usual thermoplastic synthetic short fibers or natural fibers such as Kotton can be used. This web may be a parallel web arranged in the traveling direction of the card machine, a random web arranged randomly, or a semi-random web arranged in a medium degree of both depending on the arrangement degree of the constituent fibers. A laminated web in which the card web of the composite short fibers and the card web of another material are stacked may be used. In the present invention, since 50% by weight or more of the constituent fibers of the non-woven fabric is the composite short fibers, a non-woven fabric excellent in stretchability and bulkiness can be obtained.

Next, after placing the obtained card web on the porous support member, the web was subjected to a fluid entanglement treatment with a fluid jet having a pressure of less than 30 kg / cm ² , and then the pressure was 50 kg / cm ^2. The web is subjected to a fluid entanglement treatment with a fluid jet of cm ² or more to three-dimensionally entangle the composite short fibers constituting the web. The fluid entanglement treatment as referred to in the present invention is to arrange a plurality of orifices having a hole diameter of 0.05 to 1.0 mm in one row or a plurality of rows with a distance between orifices of 0.5 to 10 mm, and to apply high pressure from these orifices. The constituent fibers of the web are entangled with each other by a fluid jet ejected in a columnar shape. As the fluid, normal temperature water or hot water can be used. It is also possible to use water mixed with additives. When the fluid jet impinges on the web, a plurality of orifice heads having a plurality of orifices arranged in one row or a plurality of rows are provided in a direction perpendicular to the traveling direction of the webs stacked on the porous support member. In addition, it is advisable to reciprocate with the same amplitude as the distance between the orifices so that the columnar fluid jets collide uniformly. This fluid entanglement process may be performed at least twice. First
The fluid entanglement process for the second time is to pre-entangle the constituent fibers of the web by using a fluid jet having a pressure of less than 30 kg / cm ² and causing the fluid jet having the same pressure to collide with the web. When the pressure is 30 kg / cm ² or more, the constituent fibers of the web are not entangled with each other, and the constituent fibers are disturbed by the water flow, which causes unsightly spots on the web, which is not preferable. Then, the second fluid entanglement process is performed. In the second fluid entanglement process, the pressure is 50k.
By using a fluid jet of g / cm ² or more and colliding the fluid jet of the same pressure with the web, the pre-entanglement of the constituent fibers formed on the web by the first fluid entanglement treatment is further strengthened. It is for making something special. In this second treatment, the pressure is preferably 50 kg / cm ² or more, and when the pressure is less than 50 kg / cm ² ,
The entanglement of the constituent fibers does not become stronger, and sufficient strength cannot be obtained when used as a nonwoven fabric. In addition, when stronger entanglement is required, the second fluid entanglement process may be performed a plurality of times under the same condition. The porous support member on which the web is placed may be any one as long as the fluid jet passing through the web can be removed without resistance. In particular, the porous support member 200 made of wire mesh or synthetic fiber fabric is used. A porous member having a mesh size or less is preferable.

Next, subsequent to the fluid entanglement treatment, the moisture remaining in the web is dried and removed, and then a dry heat treatment is performed using a drying device such as a hot air circulation dryer to give the constituent fibers of the web. Develop crimps. The crimps have a number of crimps of 60/25 mm or more when heat-treated at a temperature of 120 ° C., thereby imparting stretchability and bulkiness to the nonwoven fabric. In the method of the present invention, the web may be subjected to dry heat treatment with a heat calender or a hot embossing roller after the water remaining in the web is removed by drying. The method of the present invention also includes subjecting a laminated web obtained by stacking another web, for example, a card web of Kottton to the web made of the above-mentioned composite short fibers to a fluid entanglement treatment.

The nonwoven fabric obtained by the method of the present invention has a practically sufficient strength when used as a nonwoven fabric because the composite short fibers constituting the nonwoven fabric are three-dimensionally entangled with each other. In addition, a high shrinkage force of which the dry heat shrinkage rate is 35% or more at a temperature of 120 ° C and an initial load of 2 mg, and a high crimping force of which the number of crimps after heat treatment is 120 pieces / 60 mm / 25 mm or more. Since it is composed of the above-mentioned composite short fibers, it has excellent elasticity and bulkiness, and also has a low apparent density of 0.10 g / cm ³ or less. Furthermore, the tensile modulus of the nonwoven fabric is 40% or more in both longitudinal and transverse directions at 20% and 50% elongation, and it has excellent stretchability in both longitudinal and transverse directions. Especially when it is used as a material for medical hygiene materials, it does not lose its shape. In the present invention, the basis weight of the non-woven fabric is preferably 10 g / m ² or more and 150 g / m ² or less in view of the characteristics required for its application.

[0032]

EXAMPLES Next, the present invention will be specifically described based on Examples. The measurement and evaluation of various characteristics in the examples were carried out by the following methods. Melting point of polymer: Differential scanning calorimeter D manufactured by Perkin Elmer
The melting point was the temperature at which the exothermic value of the melting and absorption heat curve measured using a SC-2 type at a heating rate of 20 ° C./min. Melt flow rate value: ASTM D 1238 (L)
It was measured by the method described in. Tensile strength and elongation of fiber: Tensilon UTM-4-1-100 manufactured by Toyo Baldwin Co., Ltd. was used to measure a sample having a sample length of 20 mm at a tensile speed of 20 mm / min. Dry heat shrinkage ratio I of fiber: 15 single fibers in total as sample, length L ₁ (c) at initial load of 2 mg / denier for each single fiber
m) and then 1 in an air oven type heat treatment machine
The length L ₂ (cm) after heat treatment at 20 ° C. for 15 minutes was measured, the shrinkage rate was calculated by the following equation (e), and the average value was defined as the dry heat shrinkage rate I. Dry heat shrinkage I (%) = (L ₁ −L ₂ ) × 100 / L ₁ ... (e) Dry heat shrinkage II of fiber: 15 single fiber total As a sample, length L ₃ (c) at initial load of 50 mg / denier for each single fiber
m) and then 1 in an air oven type heat treatment machine
The length L ₄ (cm) after heat treatment at 20 ° C. for 15 minutes was measured, the shrinkage ratio was calculated by the following formula (f), and the average value was defined as the dry heat shrinkage ratio II. Dry heat shrinkage II (%) = (L ₃ −L ₄ ) × 100 / L ₃ ... (f) Tensile strength / elongation of nonwoven fabric: Tensilon UTM manufactured by Toyo Baldwin Co., Ltd. -4-1-100, JIS L-109
According to the strip method described in 6A, sample width 2.5c
A sample piece having a m and a sample length of 10 cm was measured at a tensile speed of 10 cm / min. Elongation elastic modulus of non-woven fabric: Tensilon UTM-4-1-100 manufactured by Toyo Baldwin Co., Ltd. was used, and JIS L-109 was used.
6 According to the method described in 6.13.1A, a sample piece having a sample width of 2.5 cm and a sample length of 10 cm was pulled at a pulling speed of 10 c.
Tensile test was performed at m / min and the elongation was 20% or 50%.
It was calculated from the ratio of the recovery growth to the constant growth at the time point%. Apparent density of non-woven fabric: sample width 10 cm, sample length 10 cm
Prepare a total of 5 sample pieces for each sample weight (g / g
After measuring m ² ), using a thickness measuring instrument manufactured by Daiei Kagaku Seiki Seisakusho, apply a load of 4.5 g / cm ² and measure the thickness (mm) after leaving for 10 seconds. The apparent density was calculated from (g), and the average value was used as the apparent density of the nonwoven fabric. Apparent density (g / cm ³ ) = (unit weight) × 10 ⁻³ / (thickness) ・ ・ ・ (g) Kneeing: The following two stages of kneeing occur in the spinning hole during melt spinning. It was evaluated by. ◯: The kneeing angle is less than 75 °, which causes no problem in operation. X: The kneeing angle is as large as 75 ° or more, which is a problem in operation. Smoke emission: The degree of smoke emission at the spinneret during melt spinning was evaluated by the following four grades by visual judgment. A: No smoke is observed. ○: Smoke emission is slightly observed. Fair: Smoke emission is observed considerably, but this does not pose a problem in operation. X: Extremely large amount of smoke is emitted, and smoke is accumulated near the spinneret, which is a problem in operation. Spinnability: The spinnability during melt spinning was evaluated according to the following three grades based on the occurrence rate of yarn breakage. ◯: Yarn break does not occur at all, and operability is good. △: 24 hours of yarn breakage, 16 spinning spindles
Occurs once per hit. ×: 24 hours of yarn breakage, 16 spinning spindles
It occurs more than once, which is a problem in operation. Stretchability: Stretchability was evaluated according to the following three grades based on the occurrence rates of yarn breakage and single yarn breakage. ◯: No yarn breakage or single yarn breakage occurred, and operability was good. Δ: 2 yarn breaks or single yarn breaks
Occurs once every 4 hours. X: Thread breakage or single thread breakage occurs twice or more per 24 hours, which is a problem in operation.

Examples 1 to 11 and Comparative Examples 1 to 9 A polypropylene copolymer having the Q value, the melt flow rate value and the melting point shown in Table 1 and having propylene and ethylene randomly copolymerized was used as the component A. , A polypropylene polymer having a Q value, a melt flow rate value, and a melting point shown in Table 1 or a polypropylene copolymer in which propylene and ethylene are randomly copolymerized or block copolymerized, is used as a component B, and a normal extruder-type melt extrusion is performed. After melting in a machine, using a spinneret with a spinning hole diameter of 0.5 mm and a number of holes of 300, the single hole discharge rate is 0.5 g / min, that is, the composite ratio (B / A) of component A and component B (weight) The ratio) is 1/1 and the melt-spun is carried out under the combinations and spinning temperature conditions shown in Table 2 and is drawn at a take-up speed of 1000 m / min to obtain an undrawn yarn of the parallel type composite filament yarn. Obtained. A plurality of the obtained unstretched yarns were bundled and hot-drawn as a tow. At the time of drawing, a two-stage hot roller drawing machine was used, and the drawing conditions were set to a drawing speed of 1
00m / min, first roller temperature 60 ° C, second roller temperature 9
0 ℃, 3rd roller temperature 25 ℃, maximum draw ratio of 80
Stretching was performed at a stretching ratio of%. Continuously after drawing, draw tow is supplied to the stuffed box to give 14 crimps / 25mm of crimp and a finishing oil is applied, then dried at a temperature of 70 ° C, cut into fiber length of 51mm, and single fiber fineness To obtain a raw cotton of a parallel type composite short fiber of 2 denier. Then, the obtained raw cotton was heat-treated at a temperature of 120 ° C. for 1 minute. In Table 1, a to h, yo and ta are ordinary homopolymers, ha to o and ka are random copolymers, and w is a block copolymer. Table 2 shows the combination of polymer components constituting the composite short fibers and the spinning temperature conditions, the characteristics of the obtained raw cotton and the results of the spinnability and stretchability are shown in Table 3, and the microstructures of the raw cotton and the heat-treated cotton. The measurement results of are shown in Tables 4 and 5.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

[0038]

[Table 5]

As is clear from Tables 2 and 3, raw cotton satisfying the requirements of the present invention has a temperature of 120 ° C. and an initial load of 2 m.
Dry heat shrinkage of 35% or more under g condition and temperature of 1
The number of crimps after heat treatment at 20 ° C. was 60 pieces / 25 mm or more, and it had high shrinkability and high crimpability. Also,
Melt flow rate value of short fiber is 15g / 10min or more 4
It was 5 g / 10 minutes or less, and the spinnability and drawability were good. In Comparative Example 1, since the melt flow rate value ratio (B / A) of the polymer component A and the polymer component B after melting exceeds 6/1, strong kneeing occurs in the spinning hole during melt spinning. , The spinnability decreased. In Comparative Example 2, the melt flow rate value ratio after melting was less than 1/1, and the spinnability was good, but the dry heat shrinkage ratio decreased. Comparative Example 3
In the case of ethylene, the random copolymerization amount of ethylene was small, and the dry heat shrinkage rate decreased. In Comparative Example 4, since the block copolymer having inferior spinnability was used as the polymer component B, the spinnability was lowered even though it was combined with the polymer component A.
In Comparative Example 5, the short fiber melt flow rate value is 45 g.
/ 10 minutes or more, the degree of polymerization of the polypropylene-based polymer was too low and decomposed to generate a large amount of gas, deteriorating the environment of the spinning chamber. In Comparative Examples 6 and 7, since the melt flow rate value of the short fibers was less than 15 g / 10 minutes, the spinnability and the drawability were lowered, and the spinning temperature had to be set high, the polypropylene polymer was It decomposed and generated a large amount of gas, which deteriorated the environment of the spinning chamber. In Comparative Example 8, the Q value of the polymer component B was high, the yarn cooling during melt spinning was poor, and the spinnability was lowered. In Comparative Example 9, the Q value of the polymer component B was low, the drawability was reduced, and the obtained short fibers were dried at a temperature of 120 ° C. and an initial load of 2 mg, and were subjected to heat treatment at a temperature of 120 ° C. The number of crimps was low. Further, as is clear from the measurement results of the fine structure of the fibers shown in Table 5, in Comparative Example 2 in which the long period before heat treatment is large and Comparative Example 3 in which the crystal volume is large, the dry heat shrinkage rate is low and the crimping property is low. Was not fully exerted.

Examples 12 to 18 and Comparative Examples 10 and 11 Same as Example 3 except that the spinneret having the spinning hole diameter shown in Table 6 was used and the single hole discharge rate was set as shown in Table 6. Then, the parallel type composite filament yarn was melt spun. The obtained results are shown in Table 6.

[0041]

[Table 6]

As is clear from Table 6, when the discharge linear velocities of the polymer component A and the polymer component B were 2 to 10 m / min, good spinnability and stretchability could be obtained.

Examples 19 to 21 and Comparative Examples 12 to 14 As shown in Table 7, the raw cottons obtained in the above Examples and Comparative Examples were supplied to a carding machine to prepare webs having the basis weight shown in Table 7. Then, it was transferred onto a conveyor made of an endless wire mesh of 90 mesh and moving at a speed of 2 m / min, and this web was subjected to the first fluid entanglement treatment. The first fluid entanglement treatment condition is to use water as the fluid,
Using an orifice head with a hole diameter of 0.1 mm and a distance between orifices of 1 mm arranged in a row, the distance between the orifice surface and the web is 5 cm, the movement amplitude of the orifice is 1 mm in the lateral direction, and the cycle is 10 round trips / second,
The water pressure of the water jet was set to 20 kg / cm ² . Following the first fluid entanglement treatment, the web was subjected to the second fluid entanglement treatment. The condition for the second fluid entanglement process was to use water as the fluid, use an orifice head with a hole diameter of 0.125 mm and a distance between the orifices of 1 mm arranged in two rows, and between the orifice surface and the web. Distance of 5c
m, the movement amplitude of the orifice head was 1 mm in the lateral direction, the cycle was 10 reciprocations / second, and the water pressure of the water jet was 75 kg / cm ² . In the above-mentioned orientation head, the orientation of the second row exists on each line extending vertically from the midpoint between the adjacent orientations of the first row, and the first and second rows are geometrically arranged. They are arranged in parallel. After the second fluid entanglement treatment, the third fluid entanglement treatment is performed under the same conditions as the second fluid entanglement treatment, and heat treatment is performed at a temperature of 120 ° C. for 1 minute using a hot air circulation dryer. To produce a non-woven fabric.
The performance of the obtained nonwoven fabric is shown in Table 7, and the measurement result of its fine structure is shown in Table 8.

[0044]

[Table 7]

[0045]

[Table 8]

As is apparent from Table 7, the non-woven fabric obtained by the method of the present invention has an apparent density of 0.10 g / cm ³ or less and is extremely bulky, and the non-woven fabric has a tensile strength of 20% and 50%. The elongation elastic modulus at the time of% elongation was 40% or more in both the longitudinal and lateral directions, which was extremely excellent in morphological stability. In Comparative Examples 12 to 14, the elongation elastic modulus at 50% elongation was less than 40% both in the longitudinal and transverse directions, and it was not possible to obtain a nonwoven fabric having sufficient stretchability.
Further, as is clear from the measurement results of the fine structure of the nonwoven fabric shown in Table 8, in Comparative Example 13 in which the long period before heat treatment is large and Comparative Example 14 in which the crystal volume is large, a nonwoven fabric having sufficient stretchability can be obtained. could not.

Examples 22 and 23 The polypropylene-based copolymer H shown in Table 1 was used as the component A, and the polypropylene polymers C and H shown in Table 1 were used as the component B. An undrawn yarn of a composite filament yarn was obtained. A plurality of the obtained unstretched yarns were bundled and hot-drawn as a tow. At the time of drawing, a two-stage hot roller drawing machine was used, and the drawing conditions were set to a drawing speed of 100 m /
Min, the first roller temperature was 55 ° C., the second roller temperature was 85 ° C., and the third roller temperature was 25 ° C., and stretching was performed at a stretching ratio of 80% of the maximum stretching ratio. Following drawing, the drawn tow was taken by a gear type reel, and after applying a finishing oil, it was dried at a temperature of 80 ° C. and cut into a fiber length of 51 mm. I got raw cotton. Table 9 shows the combinations of polymer components constituting the composite short fibers and the spinning temperature conditions, and Table 10 shows the properties of the obtained raw cotton and the spinnability and drawability.

[0048]

[Table 9]

[0049]

[Table 10]

As is clear from Tables 9 and 10, the raw cotton obtained by the method of the present invention has a temperature of 120 ° C. and an initial load of 2
41% dry heat shrinkage in mg condition and temperature 120
The number of crimps after heat treatment at ℃ was 83/25 mm, and it had high shrinkability and high crimpability. Further, the melt flow rate value of the short fibers was 28 g / 10 minutes, and the spinnability and the drawability were good. Moreover, it was possible to sufficiently develop the actual crimps in the composite fiber without using the stuffed box, and the card passing property was also good. In Example 23, the Q value of the polymer component B after melt spinning was low, the drawability was slightly lowered, and the obtained short fiber had a dry heat shrinkage ratio at a temperature of 120 ° C. and an initial load of 2 mg. The number of crimps after the heat treatment at a temperature of 120 ° C. was slightly low in all cases.

[0051]

EFFECT OF THE INVENTION The method for producing the composite staple fiber of the present invention uses the above specific polypropylene-based copolymer,
According to the present invention, it is possible to obtain a composite short fiber having high shrinkability, high crimpability, and high strength. Further, the method for producing a nonwoven fabric of the present invention uses the composite short fibers, and according to the present invention, it is excellent in stretchability, bulkiness and flexibility,
In particular, it is possible to obtain a nonwoven fabric that can be suitably used as a material for medical hygiene materials.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location D04H 1/54 A 7199-3B (72) Inventor Yoshimoto Miyamoto 23 Uji Kozakura, Uji-shi, Kyoto Unitika Incorporated Central Research Institute

Claims (6)

[Claims] 1. A polypropylene-based copolymer component A in which 92% by weight or more and 97% by weight or less of propylene and 3% by weight or more and 8% by weight or less of ethylene are randomly copolymerized,
The melt flow rate value when a composite short fiber is obtained by using a polypropylene-based copolymer component B in which 0% by weight or more and 100% by weight or less propylene and 0% by weight or more and 3% by weight or less ethylene are copolymerized as a composite component 15g / 10 minutes or more 4
The melt flow rate value ratio (B / A) of the polymer component A and the polymer component B after melting was set to 5 g / 10 minutes or less.
Is 1 to 6/1 and the discharge linear velocity of the polymer component A and the polymer component B is 2 to 10 m / min. Is heat-stretched at a temperature that does not cause fusion, and then the resulting stretched composite fiber is subjected to crimping treatment, a finishing oil agent is applied, and then dried and cut into short fibers to obtain short fibers. Method for producing polypropylene-based short fibers. 2. A polypropylene system in which 92 wt% or more and 97 wt% or less of propylene and 3 wt% or more and 8 wt% or less of ethylene are randomly copolymerized, and a Q value (weight average molecular weight / number average molecular weight) is 8 or less. Copolymer component A, 9
7 wt% to 100 wt% propylene and 0 wt%
When a polypropylene-based copolymer component B having a Q value (weight average molecular weight / number average molecular weight) of 5 or more and 8 or less is copolymerized with ethylene of 3% by weight or less and 3% by weight or less, and a composite short fiber is obtained. Melt flow rate value is 15g / 1
The melt flow rate value ratio (B / A) of the polymer component A and the polymer component B after melting is 1/1 to 6/1 and is 0 to 45 g / 10 min. Melt composite spinning was performed at a discharge linear velocity of A and the polymer component B of 2 to 10 m / min, and the obtained undrawn composite fiber was heat drawn at a temperature of 50 ° C. or higher and at a temperature at which the fibers were not fused to each other, and then obtained. A method for producing a polypropylene-based short fiber, which comprises subjecting a stretched composite fiber to crimping treatment, applying a finishing oil, drying it, and cutting it into short fibers to obtain short fibers. 3. A polypropylene system in which 92% by weight or more and 97% by weight or less of propylene and 3% by weight or more and 8% by weight or less of ethylene are randomly copolymerized and Q value (weight average molecular weight / number average molecular weight) is 8 or less. Copolymer component A, 9
7 wt% to 100 wt% propylene and 0 wt%
When a polypropylene-based copolymer component B having a Q value (weight average molecular weight / number average molecular weight) of 5 or more and 8 or less is copolymerized with ethylene of 3% by weight or less and 3% by weight or less, and a composite short fiber is obtained. Melt flow rate value is 15g / 1
The melt flow rate value ratio (B / A) of the polymer component A and the polymer component B after melting is 1/1 to 6/1 and is 0 to 45 g / 10 min. Melt composite spinning was performed at a discharge linear velocity of 2 to 10 m / min of A and the polymer component B, and the resulting undrawn composite fiber was hot-drawn at a temperature of 50 ° C. or higher and at a temperature at which the fibers were not fused to each other. )
To (3), the drawn composite fiber is then subjected to a crimping treatment, a finishing oil agent is applied thereto, dried, and cut into a predetermined length to obtain a short fiber. Method for producing polypropylene-based short fibers. (1) The birefringence of the copolymer component A portion and the birefringence of the copolymer component B portion of the composite short fiber before heat treatment are both 0.02 or more, (2) measured by wide-angle X-ray diffractometry The crystalline volume of the composite short fiber before heat treatment is 100,000Å ³ or less, and (3) the long period of the composite short fiber before heat treatment measured by the small-angle X-ray scattering method is less than 130Å. 4. A polypropylene-based copolymer component A in which 92% by weight or more and 97% by weight or less of propylene and 3% by weight or more and 8% by weight or less of ethylene are randomly copolymerized,
The melt flow rate value when a composite short fiber is obtained by using a polypropylene-based copolymer component B in which 0% by weight or more and 100% by weight or less propylene and 0% by weight or more and 3% by weight or less ethylene are copolymerized as a composite component 15g / 10 minutes or more 4
The melt flow rate value ratio (B / A) of the polymer component A and the polymer component B after melting was set to 5 g / 10 minutes or less.
Is 1 to 6/1 and the discharge linear velocity of the polymer component A and the polymer component B is 2 to 10 m / min. Is heat-stretched at a temperature that does not cause fusion, and then the resulting stretched composite fiber is subjected to crimping treatment, applied with a finishing oil agent, dried, and cut into short fibers to give short fibers. A card web was prepared using 50% by weight or more of short fibers, the card web was placed on a porous support member, and the web was subjected to a fluid entanglement treatment with a fluid jet having a pressure of less than 30 kg / cm ² . After that, the web is subjected to a fluid entanglement treatment by a fluid jet having a pressure of 50 kg / cm ² or more to three-dimensionally entangle the composite short fibers constituting the web, and then the web is subjected to a dry heat treatment to obtain a moisture content. To remove the composite short fiber A method for producing a non-woven fabric, which comprises expressing crimps in 5. A polypropylene system in which 92 wt% or more and 97 wt% or less of propylene and 3 wt% or more and 8 wt% or less of ethylene are randomly copolymerized, and a Q value (weight average molecular weight / number average molecular weight) is 8 or less. Copolymer component A, 9
7 wt% to 100 wt% propylene and 0 wt%
When a polypropylene-based copolymer component B having a Q value (weight average molecular weight / number average molecular weight) of 5 or more and 8 or less is copolymerized with ethylene of 3% by weight or less and 3% by weight or less, and a composite short fiber is obtained. Melt flow rate value is 15g / 1
The melt flow rate value ratio (B / A) of the polymer component A and the polymer component B after melting is 1/1 to 6/1 and is 0 to 45 g / 10 min. Melt composite spinning was performed at a discharge linear velocity of A and the polymer component B of 2 to 10 m / min, and the obtained undrawn composite fiber was heat drawn at a temperature of 50 ° C. or higher and at a temperature at which the fibers were not fused to each other, and then obtained. The drawn composite fiber is subjected to a crimping treatment, a finishing oil is applied thereto, and then dried, cut into a predetermined length to form a short fiber, and then a card web is prepared using 50% by weight or more of the obtained composite short fiber. After placing this card web on a porous support member and subjecting the web to fluid entanglement with a fluid jet having a pressure of less than 30 kg / cm ² , the pressure is 50 kg / cm ^2.
The web is subjected to a fluid entanglement treatment by a fluid jet of 3 cm ² or more to three-dimensionally entangle the composite short fibers constituting the web, and then the web is subjected to a dry heat treatment to remove water and the composite short fibers. A method for producing a non-woven fabric, characterized in that fibers are crimped. 6. A polypropylene system in which 92% by weight or more and 97% by weight or less of propylene and 3% by weight or more and 8% by weight or less of ethylene are randomly copolymerized, and a Q value (weight average molecular weight / number average molecular weight) is 8 or less. Copolymer component A, 9
7 wt% to 100 wt% propylene and 0 wt%
When a polypropylene-based copolymer component B having a Q value (weight average molecular weight / number average molecular weight) of 5 or more and 8 or less is copolymerized with ethylene of 3% by weight or less and 3% by weight or less, and a composite short fiber is obtained. Melt flow rate value is 15g / 1
The melt flow rate value ratio (B / A) of the polymer component A and the polymer component B after melting is 1/1 to 6/1 and is 0 to 45 g / 10 min. Melt composite spinning was performed at a discharge linear velocity of 2 to 10 m / min of A and the polymer component B, and the resulting undrawn composite fiber was hot-drawn at a temperature of 50 ° C. or higher and at a temperature at which the fibers were not fused to each other. )
A composite fiber satisfying (3) to (3) is obtained. Then, the drawn composite fiber obtained is subjected to crimping treatment, applied with a finishing oil agent, dried and cut into a predetermined length to obtain a short fiber, which is then obtained. A card web is prepared using 50% by weight or more of the composite short fibers, the card web is placed on a porous support member, and the web is subjected to a fluid entanglement treatment by a fluid jet having a pressure of less than 30 kg / cm ^2. The pressure is 50kg / c
The web is subjected to a fluid entanglement treatment with a fluid jet of m ² or more to three-dimensionally entangle the composite short fibers constituting the web, and then the web is subjected to a dry heat treatment to remove water and the composite short fibers. The following conditions (4) to (6) for the fiber
And a method for producing a crimp, which is characterized by satisfying the requirements. (1) The birefringence of the copolymer component A portion and the birefringence of the copolymer component B portion of the composite short fiber before heat treatment are both 0.02 or more, (2) measured by wide-angle X-ray diffractometry The crystalline volume of the composite short fibers before heat treatment is 100,000Å ³ or less, (3) the long period of the composite short fibers before heat treatment measured by the small angle X-ray scattering method is less than 130Å, (4) heat treatment The birefringence of the copolymer component A portion and the birefringence of the copolymer component B portion of the subsequent composite short fiber are both the birefringence of the copolymer component A portion of the composite short fiber before the heat treatment and the copolymer component B. Lower than the birefringence of each part, (5) the crystal volume of the composite short fibers after heat treatment measured by wide-angle X-ray diffraction method is 200,000Å ³ or more, (6) measured by small-angle X-ray scattering method The long cycle of the composite short fibers after heat treatment is 130 That is greater than or equal to.