JPH0770899A - Heat-bonded nonwoven cloth and its production - Google Patents

Abstract

PURPOSE:To provide a heat-bonded nonwoven cloth composed of fine-denier core-sheath conjugate polyolefin short fibers, having high strength and bulkiness, extremely excellent water-retainability and good ground texture and giving excellent feeling to the skin. CONSTITUTION:This heat-bonded nonwoven cloth is composed of core-sheath conjugated short fibers consisting of a sheath part composed mainly of an ethylene-based polymer and a core part composed of a propylene-based polymer, having a single fiber fineness of 0.2-1de and bonded with each other at contacting points of the fibers. The cloth is free from characteristic slimy feeling of polyethylene, has extremely excellent ground texture and gives excellent feeling to the skin and, accordingly, it is suitable for medical and hygienic uses e.g. for disposable diaper, sanitary napkin, etc. The cloth has chemical resistance and excellent water-retainability and is suitable as a separator for dry cell. It is applicable to a wide variety of fields such as agricultural and horticultural materials, life-relating materials such as packaging material and filter, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-bonded non-woven fabric composed of polyolefin-based fine and core-sheath type composite short fibers and a method for producing the same. This non-woven fabric has high strength, bulkiness, and extremely excellent water retention, and does not have the slimy feeling peculiar to polyethylene, and has a very good texture,
Has a good texture. Therefore, it is particularly suitable for medical hygiene materials such as disposable diapers and sanitary napkins. Moreover, since it has chemical resistance and is excellent in water retention, it is particularly suitable as a separator for dry batteries.
In addition, it can be suitably used in a wide range of applications such as agricultural and horticultural materials, packaging materials and filters as daily life related materials.

[0002]

2. Description of the Related Art Conventionally, heat-bonded short-fiber nonwoven fabrics have been used for various purposes such as clothing, industrial materials, civil engineering and construction materials, agricultural and horticultural materials, life-related materials, medical hygiene materials, etc. There is.

[0003] Nonwoven fabrics for medical hygiene materials such as disposable diapers and coated papers for sanitary absorbents, which have been rapidly increasing in demand in recent years, are required to have a soft and soft texture. Further, the demand for non-woven fabrics for electrical and electronic-related equipment is expanding, and in this field, non-woven fabrics are also required to have good chemical resistance and excellent water retention. In order to satisfy these required qualities as much as possible, a production method of a nonwoven fabric by a thermal bonding method such as a thermal-through type or an embossing type is mainly adopted.

These non-woven fabrics are obtained by using composite fibers containing a fiber-forming polymer having different melting points as a composite component,
Japanese Patent Publication No. 42-21318, Japanese Patent Publication No. 44-2254
No. 7, JP-B-52-12830, JP-B-61
It is publicly known in the publication such as -10583.

[0005]

The low melting point component of conventionally used composite type heat-bondable fibers for nonwoven fabrics is usually
Polyester or polyethylene is used. Nonwoven fabrics composed of composite heat-bonded fibers containing polyethylene as a low-melting point component have a unique slimy feel to polyethylene, which makes some people feel uncomfortable, and polyethylene itself has poor spinnability, resulting in fineness. However, there was a problem that the above fiber could not be obtained.

The inventors of the present invention previously disclosed in Japanese Patent Laid-Open No. 03-1
No. 93958 proposes a spunlace nonwoven fabric made of ultrafine polyolefin core / sheath composite short fibers.
Since the non-woven fabric is processed by the spunlace method, the softness is not impaired, but since it is a perforated non-woven fabric, there is a problem that the use is limited such as being unsuitable for a dry battery separator and other uses. there were.

The object of the present invention is to solve the above-mentioned problems and to provide a non-woven fabric having a very good texture and a good texture.
Moreover, it is to provide a polyolefin-based heat-bonded non-woven fabric having practical performance, chemical resistance and water retention.

[0008]

The inventors of the present invention have reached the present invention as a result of intensive research to solve the above problems. That is, the present invention provides (1) a core-sheath type having an ethylene-based polymer as a main component and a propylene-based polymer as a core, and having a single yarn fineness of 0.2 to 1 denier. A heat-bonded non-woven fabric, which is composed of composite short fibers and is bonded at the points of contact between the fibers, and (2) a sheath part mainly composed of an ethylene polymer and a core part of a propylene polymer. In addition, a card web composed of core-sheath type composite short fibers having a single yarn fineness of 0.2 to 1 denier is heat-treated with hot air so as to satisfy the following formula, and at a contact point between fibers. Method for producing heat-bonded non-woven fabric characterized by bonding, heat treatment temperature T (° C) Tm1 ≤ T <Tm2-10 heat treatment time t (min) 0.1 ≤ L / v, L /
v = t Tm1: melting point (° C.) of ethylene polymer in the sheath Tm2: melting point (° C.) of propylene polymer in the core L: heat treatment zone length (m) v: heat treatment rate (m / min) ) And are the gist.

Next, the present invention will be described in detail. First, the core-sheath type composite short fibers constituting the nonwoven fabric of the present invention will be described. The sheath portion of the core-sheath type composite staple fiber is mainly composed of an ethylene polymer, and specifically, a blend structure of an ethylene polymer and a propylene polymer, or a copolymer of propylene is used. It is composed of a polymerized ethylene-based copolymer.

For example, when the sheath portion is made of a single component of low density polyethylene, the non-woven fabric has a slimy feeling, which is a problem. Further, when the sheath portion is composed of a single component of high-density polyethylene, the spinnability is reduced and it becomes difficult to obtain fine fibers. On the other hand, by adopting a blended structure or a copolymerized structure as in the present invention, it is possible to prevent the occurrence of slimy feeling due to the influence of polypropylene even when low density polyethylene is applied. However, since the spinnability can be improved, fibers with a fineness can be obtained.

In the case where the sheath has a blend structure,
The ethylene-based polymer and the propylene-based polymer are not compatible with each other, but by finely blending and dispersing the propylene-based polymer in the ethylene-based polymer, the spinnability of the ethylene-based polymer in the sheath portion is improved, Moreover, peeling of the core-sheath layer due to the propylene-based polymer of the core can be eliminated.

Examples of the ethylene-based polymer include linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, high-density polyethylene, and ethylene-based copolymerized ethylene.

Examples of the propylene-based polymer include polypropylene and copolymerized propylene mainly containing propylene. The mixing ratio (weight ratio) of the ethylene polymer (denoted as a) and the propylene polymer (denoted as b) of the blend, that is, the blend ratio a / b, is 99.5.
/0.5 to 75/25 is preferable. If the weight ratio of the propylene-based polymer is high, the characteristics of the propylene-based polymer are strengthened and the spinnability is deteriorated, which is not good.
On the other hand, when the amount of the propylene-based polymer is less than the above range, it becomes difficult to uniformly mix, the spinnability is not improved, and it becomes difficult to obtain a fine fiber, and peeling from the core portion occurs, It is not good because the slimy feeling peculiar to polyethylene appears and the applications are limited. Therefore, the mixing ratio is more preferably 95/5 to 80/20.

When the sheath portion is a copolymer, it is preferable that the copolymerization is so-called random copolymerization from the viewpoint of improving the spinnability. In the case of this copolymer, similarly to the case of the blend structure, it is possible to prevent the occurrence of slimy feeling of polyethylene and to improve the spinnability, so that a fiber having a fineness can be obtained. You can do it. In the case of this copolymer, the reason why the spinnability is improved is not clear, but peeling of the core-sheath layer from the propylene polymer of the core component can be eliminated by the copolymerization of propylene with the ethylene polymer. It is thought to be because. That is, it is considered that the ethylene-based polymer and the propylene-based polymer are a combination of components that are incompatible with each other, but by copolymerizing propylene, affinity is imparted and peeling of the core-sheath layer can be eliminated. To be

The ethylene copolymer may be copolymerized with 0.2% by weight or more of propylene. If the copolymerization amount of propylene is too large, the spinnability is lowered, the properties of polypropylene become too strong, and the melting point is greatly lowered, which is not preferable. On the other hand, if the amount of propylene copolymerized is too small, the properties of polyethylene become stronger and a slimy feeling appears, or peeling occurs between the sheath and core portions, which is not preferable. Therefore, it is preferably 0.5 to 5% by weight.

On the other hand, in any of the cases where the sheath portion is the blend structure and the copolymer, examples of the propylene-based polymer constituting the core portion include polypropylene and copolymerized propylene mainly containing propylene. .

The composite ratio (weight ratio) of the core-sheath type composite fibers is required to be sheath / core = 3/1 to 1/3. When the weight ratio of the sheath portion is large, the heat-adhesive component is increased, the fiber strength is lowered, and when the heat-bonded nonwoven fabric is spread, the texture becomes hard and the bulkiness is insufficient, which is not preferable.
Further, when the weight ratio of the core portion becomes large, the fiber strength becomes high, but when expanded into a heat-bonded nonwoven fabric, insufficient adhesion between fibers occurs, which causes a problem that the strength of the nonwoven fabric decreases, which is not preferable. The composite form may be a general concentric core-sheath structure, an eccentric core-sheath structure, or an irregular cross-section.

The single yarn fineness of the fiber according to the present invention is 1 denier.
Must be less than or equal to This is because as the single yarn fineness decreases, the number of fibers per constituent non-woven fabric increases, and bulkiness and flexibility can be improved. The lower limit is about 0.2 denier from the current spinneret accuracy.

In the core-sheath type composite fiber, it is preferable that the birefringence of the sheath portion and the core portion are both 0.030 or more, and the maximum heat shrinkage stress of the fiber is 0.015 g / denier or less. The birefringence of a fiber means the degree of crystal orientation of the fiber itself, and the larger the value, the higher the orientation. If the birefringence of both the sheath portion and the core portion is less than 0.030, the orientation of the fibers is reduced, so that the fiber strength and the fiber modulus are reduced, and a bulky and high-strength heat-bonded nonwoven fabric cannot be obtained. From this, the birefringence is more preferably 0.035 or more. The birefringence referred to here is treated with a Carl Zeiss Jena interference microscope using a mixed liquid of liquid paraffin and α-bromonaphthalene as an encapsulant to obtain a polymer component and a core of the sheath portion of the composite fiber. The birefringence of each of the parts and the polymer component is measured.

Next, the maximum heat shrinkage stress of the fiber is an index of the shrinkage force during the heat treatment, and the larger the value, the higher the shrinkage of the fiber. Fibers for heat-bonded non-woven fabrics are especially
If the shrinkage force is high at the time of heat-bonding, the texture, thickness, and width of the obtained non-woven fabric will change, which is a problem. Therefore, the smaller the maximum heat shrinkage stress, the more stable the quality of the non-woven fabric can be obtained. From this, more preferably 0.0
It is preferably 10 g / denier or less.

Next, a method for producing the core-sheath type composite fiber will be described. This fiber can be produced by melt-composite spinning, and this melt-composite spinning can be carried out using an ordinary composite spinning device. In the melt composite spinning, a core-sheath type spinneret may be used, and the composite spinning may be generally performed at a spinning temperature of 200 ° C to 280 ° C.

In the case where the sheath portion is a blend structure, the ethylene polymer (a) as one component of the blend which is the sheath component includes linear low density polyethylene, low density polyethylene and medium density as described above. polyethylene,
Examples thereof include high-density polyethylene or copolymerized ethylene mainly composed of ethylene. The melt index value of this ethylene polymer (a) is 10 to 50 g / 10.
Must be minutes. When it is less than 10 g / 10 minutes, the melt viscosity is too high and the spinnability is lowered. Also,
The means for raising the spinning temperature to lower the apparent melt viscosity is not preferable because a large amount of smoke is generated and the working environment is deteriorated. Furthermore, when blending with a propylene-based polymer, there arises a problem that microdispersion becomes impossible. On the other hand, when the melt index value exceeds 50 g / 10 minutes, the melt viscosity becomes too low, resulting in a decrease in fiber strength and a decrease in spinnability, which is a problem.

As the propylene-based polymer (b) which is the other component as the blend of the sheath component, polypropylene or a copolymerized propylene mainly containing propylene as mentioned above can be mentioned. The melt flow rate value of this propylene polymer (b) is
It is necessary to be 5 to 45 g / 10 minutes. Outside this range, a uniform microblend structure with the ethylene polymer cannot be obtained. That is, the melt flow rate is 5
If it is less than g / 10 minutes, the dispersibility in the ethylene polymer decreases. Further, if it exceeds 45 g / 10 minutes, the dispersibility of the ethylene polymer in the propylene polymer decreases. This is because it is a combination of polymers which are incompatible with each other. Therefore, 5-45g / 10
Minutes, but more preferably 10 to 40 g / 10 minutes.

The mixing ratio (weight ratio) a / b of the ethylene-based polymer (a) and the propylene-based polymer (b) of the blend of the sheath component is 99.5 as in the case of the fiber itself.
/0.5 to 75/25 is preferable, and 95/5 to 80/2
0 is more preferable.

When the sheath is a copolymer, it is necessary to use an ethylene copolymer in which propylene is copolymerized as described above, as the ethylene copolymer which is the sheath component. That is, in order to prevent the slimy feel of polyethylene and improve the spinnability, it is necessary to copolymerize propylene. Since the spinnability can be improved, finer fibers can be obtained. Further, the ethylene component of the sheath component and the propylene polymer of the core component are a combination of components which are incompatible with each other, but by copolymerizing propylene, an affinity is imparted, that is, between the core component and Since the peeling between the core and sheath layers can be eliminated,
The spinnability and physical properties of the composite fiber can be improved.

This ethylene-based copolymer may be copolymerized with 0.2% by weight or more of propylene, more preferably 0.5 to 5% by weight, as in the case of the fiber itself. . In addition to this propylene, butene, pentene,
Hexene, octene and the like may be copolymerized within the range not departing from the scope of the present invention.

The density of the ethylene copolymer of the sheath component is not particularly limited, but is 0.92 to 0.96 g / cm.
³ is enough. The melt index value of the ethylene polymer as the sheath component needs to be 10 to 50 g / 10 minutes. When it is less than 10 g / 10 minutes, the melt viscosity is too high and the spinnability is lowered. Further, in the means for raising the spinning temperature to lower the apparent melt viscosity, a large amount of smoke is generated and the working environment is deteriorated, which is not preferable. On the other hand, if the melt index value exceeds 50 g / 10 minutes, the melt viscosity is too low, and the strength of the fiber is lowered and the spinnability is lowered, which is a problem.

On the other hand, as the core component, the propylene-based polymer may be applied regardless of whether the sheath portion is the blend structure or the copolymer. That is, examples of the polymer to be applied include polypropylene and copolymerized propylene mainly containing propylene. The melt flow rate of this propylene-based polymer is 5 to 45.
It needs to be g / 10 minutes.

Outside of this range, there arises a problem that the spinnability is lowered due to the difference in the loosening effect between the layers of the fiber sheath and core. That is, when the melt flow rate value is less than 5 g / 10 minutes, the melt viscosity becomes extremely high, and thus the spinnability decreases. Even if the apparent melt viscosity is lowered by increasing the spinning temperature, the same thing can be said because the melt viscosity of the sheath also largely decreases, and moreover, smoke generation increases and the environment of the spinning chamber is deteriorated, which is a problem. Become. Also,
When it exceeds 45 g / 10 minutes, the modulus of the fiber is lowered and only fibers without stiffness are obtained. Further, when applied to a heat-bonded nonwoven fabric, there is a problem that the bulkiness is greatly reduced. Therefore, it is better to set it to 5 to 45 g / 10 minutes,
It is more preferably 40 g / 10 minutes.

In the composite spinning, the Q value (weight average molecular weight / number average molecular weight) after melting of the ethylene polymer component (a) as the sheath component 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 individual melt-measured polymers are individually collected before composite spinning. The measured values are obtained by using the cooled polymer as a sample. It is known that the thermoplastic polymer is easily deteriorated by the influence of heat and shearing force applied 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,
A stable composite fiber can be obtained, and when it is applied to a heat-bonded nonwoven fabric, the heat treatment temperature range becomes wider,
A non-woven fabric with stable quality can be obtained. However, when 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 deteriorates. Therefore, the Q value is preferably 8 or less, and 7.
0 or less is more preferable.

On the other hand, the Q value (weight average molecular weight / number average molecular weight) after melting of the propylene polymer component of the sheath component and the core component is preferably 2 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 and processing suitability of the composite fiber. In particular, this propylene-based polymer component is a high melting point component of the composite fiber and represents the fiber modulus, and the width of the molecular weight distribution is particularly important. That is, when the Q value is less than 2, the molecular weight distribution is narrowed and the shrinkage ratio of the composite fiber is lowered, which is a preferable direction, but the crimp retention property when crimping the composite fiber is lowered. , Most commonly used for web formation
It becomes difficult to successfully pass through the drive process. Further, when the nonwoven web or nonwoven fabric after the carding process is subjected to heat treatment using a heat treatment device such as an embossing roller or a hot air dryer to thermally bond the fibers, the heat treatment temperature range is narrowed and bulkiness is increased. It is impossible to stably obtain a high-quality non-woven fabric that has Furthermore, since the toughness of the composite fiber is lowered, 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 yarn cooling during melt spinning becomes poor, the spinnability deteriorates, and a fine composite fiber can be obtained. It will be difficult. Therefore, this Q value is 2 or more and 8
It is preferably not more than 3 and preferably not more than 7.

The sheath / core composite ratio (weight ratio) at the time of producing the core-sheath composite fiber is the same as that of the core-sheath composite fiber itself.
3/1 to 1/3 is required. Furthermore, in the melt-composite spinning, the discharge linear velocities of the ethylene polymer component and the propylene polymer component in the sheath component are 1.7 to 5.8.
It is preferably m / min / denier. The discharge linear velocity here means the single-hole discharge amount Q (g / min) of the molten polymer,
Melt density ρ (g / cm ³ ) of the polymer, spinning hole diameter d (m
m) and the target single yarn fineness D (denier) are calculated by the following equation (i). The melt density ρ is a melt indexer manufactured by Toyo Seiki Co., Ltd., a core component polymer or a sheath component polymer is used as a sample, and the core component is set for each of the samples by setting the temperature to a spinning temperature. The melt density of the polymer and the melt density of the sheath component polymer were obtained by the following equation (ii), and the obtained melt densities of the respective samples were weighted averaged.

Discharge linear velocity (m / min / denier) = 4 Q / (πρd ² ) / D ... (i) Melt density (g / cm ³ ) = FR × t / s × L ... (Ii) FR: Applied load using polymer melted at spinning temperature as a sample
Flow rate value measured under the condition of 2160g (g / 10
Min) s: Average cross-sectional area of piston and cylinder x 600 (c
m ² ) L: piston moving distance (cm) t: time required for the piston to move the distance L (seconds) Normally, when melt-spinning a composite fiber composed of different polymers, melt flow between the polymers to be combined is performed. -The spinnability is greatly influenced by the difference in the spinnability range due to the rate difference and the melting temperature limited by the high viscosity component, and it is necessary to select an appropriate discharge linear velocity according to the type of the polymer. Therefore, in order to obtain good spinnability, the discharge linear velocity is 1.7 to
It is preferably 5.8 m / min / denier, and when a fiber having a fineness is obtained, the spinnability tends to decrease when the discharge linear velocity is out of this range. That is, if it is less than 1.7 m / min / denier, yarn breakage is likely to occur. Also, 5.8m
If it exceeds / min / denier, the nozzle spinner face is contaminated, and the spinning tension is lowered to make uniform cooling difficult, resulting in a decrease in spinnability. Therefore, it is preferably 2.0 to 5.0 m / min / denier, and particularly preferably 2.5 to 4.0 m / min / denier.

A matting agent, a light-proofing agent, a heat-resistant agent, a pigment or the like usually used for fibers is added to both the sheath and core components as long as the effects of the present invention are not impaired. be able to.

Next, the unstretched conjugate fiber obtained by melt-composite spinning is heat-stretched at a temperature of 50 ° C. or higher and at a temperature at which the fibers do not fuse with each other. The hot stretching can be performed using a normal heat stretching device. It is generally known that when a thermoplastic synthetic fiber is stretched, it is heat-stretched at a glass transition temperature or higher.
Heat drawing is performed at the above temperature. If the stretching temperature is lower than 50 ° C., the stretching tension will be too high and the stretchability will decrease. In addition, the stretching temperature is at most lower than the temperature at which the fibers start to fuse together. If the drawing temperature becomes too high and the fibers start to fuse to each other, yarn breakage occurs in the drawing process and the operability is reduced, or the uniformity of the product is reduced and the quality is reduced, which is not preferable. . Therefore, the stretching temperature is 50 ° C. or higher and the temperature at which the fibers are not fused to each other, preferably 60 to 100 ° C.

Next, when a crimping treatment is applied to the obtained stretched composite fiber, a crimping device such as a stuffer type crimping device is usually used. Subsequent to the crimping treatment, a finishing oil agent is applied to the fibers, dried, and then cut into a predetermined length to obtain short fibers. The fiber length in this case is usually 32 to
A range of 76 mm applies.

In order to produce this fiber, the single fiber fineness of the composite staple fiber must be 1 denier or less.
When the monofilament fineness exceeds 1 denier, the flexibility of the nonwoven fabric is reduced, or the ethylene- and propylene-based melt polymer is insufficiently cooled during melt spinning, resulting in fusion between filaments. It is not preferable because it is generated and the spinnability is lowered.

The heat-bonded nonwoven fabric of the present invention needs to be composed of an aggregate in which the above-mentioned composite fibers are stretched and oriented. This is because when the conjugate fiber is stretched and oriented, brittleness of the conjugate fiber due to heat treatment in the nonwoven fabric manufacturing process is reduced, which leads to quality stability of the nonwoven fabric.

Further, the nonwoven fabric according to the present invention needs to be bonded at the bonding points of the fibers. This is necessary in order to maintain the shape of the non-woven fabric, and the fibers are bonded by fusion at the bonding points between the fibers of the web aggregate made of the composite fiber. That is, the sheath component of the core-sheath type composite fiber is melt-bonded at the contact point between the fibers. Moreover, since the sheath component has an affinity with the core portion, peeling does not occur between the core and sheath components, and since it is composed of ultrafine fibers, there are many constituent fibers, and there are many melt-bonded portions at the contact points of the fibers. As a result, the non-woven fabric form is strongly retained, has high strength, is bulky, and is a distinctive non-woven fabric.

Next, the physical properties of the heat-bonded nonwoven fabric according to the present invention will be described. First, the strength of the nonwoven fabric will be described.
Since the nonwoven fabric of the present invention is composed of the ultrafine composite fibers, the contact points of the fibers are bonded in a state where the number of constituent fibers per unit weight is larger than that of the conventional fineness. Moreover, since the core portion and the sheath portion are not separated from each other, the binder component of the sheath portion sufficiently acts on the adhesion between the fibers, and the strength of the nonwoven fabric is increased. Therefore, in the present invention, the strength is preferably not less than 5 kg / 2.5 cm width, more preferably not less than 6 kg / 2.5 cm width.
This is regulated for practical purposes, 5 kg /
This is because if the width is less than 2.5 cm, it will interfere with general-purpose applications.

The bulkiness is the bulkiness of the nonwoven fabric, and the smaller the value, the higher the bulkiness. The nonwoven fabric according to the present invention has a bulk density of 0.03.
It is preferably 0.06 g / cm ³ . Bulk density is 0.06 g /
When it exceeds cm ³ , the nonwoven fabric cannot be said to be bulky, and the goodness of the ultrafine fibers cannot be utilized. The smaller the bulk density is, the higher the bulk is. However, the smaller the bulk density, the lower the Young's modulus of the single fiber itself, and therefore the bulk density tends to increase. Therefore, 0.03 g / cm
It is difficult to manufacture non-woven fabrics with a number of less than ³ from the current state.

The air permeability is the degree to which gas passes, and the smaller the value, the smaller the degree. The nonwoven fabric according to the present invention has an air permeability of 45 cc / cm ² · s.
The following are preferred. When the air permeability exceeds 45 cc / cm ² · s, the degree of passing gas is increased, and the heat insulating effect is lowered, and the dust removal performance is impaired, which is not preferable.

Next, regarding the coefficient of friction (MIU) of the non-woven fabric, the MIU of the non-woven fabric according to the present invention is preferably 0.18 or more. If the MIU is less than 0.18, the non-woven fabric becomes slippery easily, which causes various problems. For example, when applied as a coaster or a simple rug,
The non-woven fabric or the like is moved just by touching it, and problems such as damage to items are likely to occur.

Finally, water retention is the ability to retain water, and the higher the value, the better the retention of water. In the nonwoven fabric according to the present invention, the water retention is preferably 200% or more. If the water retention capacity is less than 200%, it cannot be said that the water retention capacity is good. For example, when applied to a dry battery separator, the electrolyte retention performance deteriorates, causing a problem.

The basis weight of the nonwoven fabric according to the present invention is not particularly limited, but when it is used as a medical hygiene material, it is 150 g / m 2.
² or less, 10 when used as a dry battery separator
0 g / m ² or less is usually applied.

Next, a method for manufacturing the nonwoven fabric according to the present invention will be described. First, the short fibers are prepared, and the short fibers are opened, weighed, and passed through a card machine to form a card web. The card machine is preferably a flat denier flat card machine. This is because in a general card machine with a rough needle gauge, many neps occur and the quality of the web deteriorates. This fibrous web is then bonded at the points of contact between the fibers to create a nonwoven fabric. Examples of the method for adhering the fibrous web at the contact points between the fibers include, for example, melt-bonding the sheath components of the constituent fibers by hot air of a heat-circulation heat treatment machine, a hot-air dryer, or the like and suppression thereof, and thereby contacting the fibers. A method of bonding at points can be used. As this heat treatment condition, the minimum control of hot air is necessary for melt-bonding the sheath components of the fibers constituting the web, but in the present invention, in the case of a heat circulation type heat treatment machine, the following conditions are essential. is there.

Heat treatment temperature T (° C.) Tm1 ≦ T ≦ Tm2-10 Heat treatment time t (min) 0.1 ≦ L / v, L / v
= T Tm1: Melting point (° C.) of ethylene-based polymer in the sheath portion Tm2: Melting point (° C.) of propylene-based polymer in the core portion L: Length of heat treatment zone (m) When the melting point is lower than the melting point of the polymer, the ethylene polymer does not melt and the fibers do not adhere to each other, so that the shape of the nonwoven fabric cannot be maintained.
Further, when the heat treatment temperature T exceeds a temperature 10 ° C. lower than the melting point of the propylene-based polymer of the core portion, the propylene-based polymer of the core portion is softened and the heat shrinkage of the constituent fiber itself is increased, and It becomes a non-woven fabric with a hard texture, and the effect of the present invention using ultrafine fibers cannot be seen. Therefore, a more preferable heat treatment temperature T (° C.) is Tm1-5 ≦ T ≦ T
m2-14, and most preferably Tm1-10 ≦ T.
≦ Tm2-18.

When the heat treatment time t is less than 0.1 minutes, the sheath component of the fibrous web is not melted uniformly and adhesion unevenness occurs, so that a uniform and strong nonwoven fabric cannot be obtained.

[0049]

EXAMPLES The present invention will be described in more detail below with reference to examples. In addition, the measuring method of the physical-property value shown in the following example is as follows. (1) Melt index value (hereinafter, simply abbreviated as MI value) It was measured by the method described in ASTM D1238 (E). (2) Tensile strength and elongation of fiber Tensilon UTM-4-1-10 manufactured by Toyo Boldwin Co., Ltd.
0 was used to measure a sample having a sample length of 20 mm under the condition of a tensile speed of 20 mm / min. (3) Tensile Strength of Nonwoven Fabric According to the slip method described in JIS L-1096, 10 test pieces having a width of 2.5 cm and a sample length of 10 cm were prepared.
The maximum strength was individually measured under the conditions of a tensile speed of 10 cm / min, and the average value was taken as the tensile strength. (4) Tensile elongation of nonwoven fabric The elongation at maximum tensile strength measured by the above method was defined as the tensile elongation. (5) Bulk density of non-woven fabric Prepare a total of 5 sample pieces having a sample width of 10 cm and a sample length of 10 cm, measure the basis weight (g / m ² ) of each sample piece, and then measure the thickness manufactured by Daiei Kagaku Seiki Seisakusho 4.5 g /
The thickness after applying a load of cm ² and leaving for 10 seconds (m
m) was measured, the bulk density was calculated by the following formula, and the average value was used as the bulk density of the nonwoven fabric.

Bulk density (g / cm ³ ) = (weight per unit area) / (thickness) / 1000 (6) Air permeability of non-woven fabric A test piece was measured by a method of JIS-1096 using a Frazier type tester. The amount of air passing through (cc / cm ² / sec) was determined and displayed as the average value of 5 test pieces. (7) Using a non-woven MIU friction tester, KES-SE (manufactured by Kato-Tech), a piano wire having a diameter of 0.5 mm is bent into a U-shape, and ten weights are attached to the contact elements. Was applied with a force of 50 g, and the contact surface was pressed against the sample nonwoven fabric. This sample non-woven fabric is 2 cm horizontally at a constant speed of 0.1 cm / sec.
It was moved, and five friction coefficients in the moving region were measured in each of the vertical direction and the horizontal direction, and the average value thereof was calculated to be MIU. (8) Water retention of non-woven fabric Prepare three pieces of 25 cm x 25 cm sample pieces in advance,
After measuring the weight (W0) of this sample piece, place it in distilled water.
Soak for hours. Thereafter, the sample pieces were taken out and lightly ironed one by one with a glass rod, and the weight (W1) was measured again. Then, the water retention rate was calculated according to the following formula, and the water retention rate was displayed as an average value of three sample pieces.

Water retention rate (%) = 100 (W1−W0) / W0 (Example) As core-sheath type composite staple fiber A, the following A-1 was prepared in advance.
The fibers of A-8 were prepared.

A-1 An ethylene-based copolymer having a density of 0.951 g / cm ³ , a melting point of 129 ° C., a Q value of 4, a melt index value of 25 g / 10 minutes, and 1.5% by weight of propylene was randomly copolymerized. As sheath component, density 0.920 g / cm ³ , melting point 16
2 ° C, Q value 6.5, melt flow rate value 30g / 10
The propylene-based polymer as the core component was used as a core component and melted by a usual extruder-type extruder. Then, using a core-sheath type composite spinneret with a spinning hole diameter of 0.5 mm and a number of holes of 390, the single hole discharge rate was 0.11 g / min, that is, the ratio of the core component to the sheath component (weight ratio) was 1/1. Was melt-spun at a spinning temperature of 230 ° C. and taken at a take-up speed of 1100 m / min to obtain an unstretched yarn of a core-sheath type composite filament yarn.
Tens of the obtained undrawn yarns were converged to form a tow, which was subjected to hot drawing. At the time of stretching, a two-stage thermal roller stretching machine was used, and the stretching conditions were as follows: stretching speed: 100 m / min, first roller:
Stretching was performed at a temperature of 65 ° C., a second roller temperature of 90 ° C., and a third roller temperature of 25 ° C. at a draw ratio of 90% of the maximum draw ratio. After the drawing, the drawing tow is supplied to a stuffer box to provide crimps of 14 pieces / 25 mm, and then a finishing oil agent is added and dried at a temperature of 70 ° C. to obtain a single fiber fineness of 0.6 denier. A raw cotton of a core-sheath type composite short fiber having a fiber length of 38 mm was obtained. The strength and elongation of the obtained raw cotton is 3.8 g.
/ Denier, 88%.

A-2 Spin-stretching was carried out under the same conditions as in A-1, except that the single-hole discharge rate was 0.08 g / min.
A raw cotton of a core-sheath type composite short fiber having a fiber length of 32 mm was obtained.
The strength and elongation of the obtained raw cotton were 3.6 g / denier and 89%.

A-3 Spin-stretching was carried out under the same conditions as in A-1, except that the single hole discharge rate was 0.23 g / min.
A raw cotton of a core-sheath type composite short fiber having a fiber length of 38 mm was obtained.
The strength and elongation of the obtained raw cotton were 4.5 g / denier and 88%.

A-4 linear low density polyethylene having a density of 0.936 g / cm ³ , a melting point of 125 ° C., a Q value of 3, and a melt index value of 43,
Density 0.919 g / cm ³ , melting point 163 ° C., Q value 6.
0, a melt flow rate value of 15 g / min and a propylene-based polymer blended at a weight ratio of 90/10 were used as a sheath component, and had a density of 0.920 g / cm ³ , a melting point of 163 ° C., and Q.
A propylene-based polymer having a value of 6.0 and a melt flow rate value of 30 g / min was used as a core component. After melting these with an ordinary extruder-type extruder, the spinning hole diameter was reduced to 0.
Using a core-sheath type composite spinneret with a diameter of 5 mm and a number of holes of 300, the single-hole discharge rate was 0.11 g / min, that is, the composite ratio (polymerization ratio) of the core component and the sheath component was 1/1, and spinning was performed at 230 ° C. It was melt-spun at a temperature and taken up at a take-up speed of 1100 m / min to obtain an unstretched filament of a core-sheath type composite filament yarn. Dozens of the obtained undrawn yarns are converged into a tow, hot-drawn by the same method as the method of A-1 raw cotton, dried at a temperature of 70 ° C., and have a post-single fiber fineness of 0.6 denier. A raw cotton of a core-sheath type composite short fiber having a fiber length of 38 mm was obtained. The strength and elongation of the obtained raw cotton were 3.7 g / denier and 90%.

A-5: A high density polyethylene having a density of 0.961 g / cm ³ , a melting point of 136 ° C., a Q value of 4, and a melt index value of 20 is used as a sheath component, and has a density of 0.920 g / cm ³ , a melting point of 163 ° C. and a Q value of 6 A propylene-based polymer having a melt flow rate of 30 g / min was used as a core component. After melting these with an ordinary extruder-type extruder, the spinning hole diameter was 0.5.
Using a core-sheath type composite spinneret with a diameter of 390 mm and a number of holes of 390, the single-hole discharge rate is 0.5 g / min, that is, the composite ratio (polymerization ratio) of the core component and the sheath component is 1/1, and spinning is performed at 230 ° C. It was melt-spun at a temperature and taken up at a take-up speed of 1100 m / min to obtain an unstretched filament of a core-sheath type composite filament yarn. Dozens of the obtained undrawn yarns are converged into a tow, hot-drawn by the same method as the method of the A-1 raw cotton, and dried at a temperature of 70 ° C.,
A raw fiber of a core-sheath type composite short fiber having a single fiber fineness of 2 denier and a fiber length of 51 mm was obtained. The strength and elongation of the obtained raw cotton is 4.7 g /
Denier was 91%.

A-6 An ethylene polymer having a density of 0.936 g / cm ³ , a melting point of 126 ° C., a Q value of 4, and a melt index value of 43 g / 10 min, and a density of 0.920 g / cm ³ , a melting point of 162 ° C., Q
A component obtained by blending a propylene polymer having a value of 6.5 and a melt flow rate of 15 g / 10 min at a weight ratio of 90/10 was used as a sheath component. Also, the density 0.920
g / cm ³ , melting point 162 ° C., Q value 6.5, melt flow
A propylene-based polymer having a rate value of 30 g / 10 minutes was used as a core component. These were melted by an ordinary extruder-type extruder, and then a core-sheath type composite undrawn yarn was collected under the same spinning conditions as the A-1 raw cotton. Sequentially, drawn according to A-1 raw cotton, single fiber fineness 0.6 denier, fiber length 38 m
m of core-sheath type composite short fiber was obtained. The strength and elongation of the obtained raw cotton were 3.9 g / denier and 89%.

A-7 An ethylene-based polymer having a density of 0.936 g / cm ³ , a melting point of 126 ° C., a Q value of 4, and a melt index value of 43 g / 10 min, a density of 0.920 g / cm ³ , a melting point of 162 ° C., and Q.
Conditions for producing A-6 raw cotton except that a propylene-based polymer having a value of 6.5 and a melt flow rate of 15 g / 10 min was blended at a weight ratio of 98/2 to form a sheath component. Using a single fiber fineness of 0.6 denier and a fiber length of 3
A raw cotton of 8 mm core-sheath type composite short fibers was obtained. The strength and elongation of the obtained raw cotton was 3.8 g / denier d, 88%.

A-8: Density: 0.951 g / cm ³ , melting point: 135 ° C., Q value: 4, melt index value: 25 g / 10 minutes, and 0.2% by weight of propylene was randomly copolymerized. The conditions for producing A-3 raw cotton were applied except that the components were used to obtain raw cotton of core-sheath type composite short fibers having a single fiber fineness of 1.0 denier and a fiber length of 38 mm. The strength and elongation of the obtained raw cotton was 3.5 g / 92% denier.

Examples 1 to 4 and Comparative Example 1 A-1 to A-5 were used as the core-sheath type composite short fibers, and these were supplied to a card machine (60-32 type) manufactured by Ikegami Machine Co., Ltd. to open the fibers. Then, a basis weight of 50 g / m ² card web was prepared. This card web was heat treated with hot air at a heat treatment temperature of 140 with a continuous heat treatment machine (heat treatment zone 160 cm) manufactured by Tsujii Dyeing Machine Industry.
The heat treatment was carried out under the conditions of ℃, hot air volume of 100 m ³ / min and heat treatment time of 25 seconds. Table 1 shows the physical properties of the obtained non-woven fabric.

[0061]

[Table 1]

As is clear from Table 1, in Examples 1 to 4, the smaller the single fiber fineness, the higher the tenacity,
It can be seen that a nonwoven fabric excellent in water retention can be obtained. In Comparative Example 1, since the single fiber fineness was large, the number of fibers constituting the nonwoven fabric was small, so that the nonwoven fabric had high air permeability and poor water retention.

Examples 5 and 6, Comparative Examples 2 to 4 After preparing a card web in the same manner as in Example 1, the same conditions as in Example 1 were used except that the heat treatment temperature and the heat treatment time were changed as shown in Table 2. I made a non-woven fabric. The obtained results are shown in Table 2.

[0064]

[Table 2]

As is clear from Table 2, the nonwoven fabric of Example 5 is high in strength and excellent in water retention. In Example 6, although the heat treatment time is long, there is a problem from the viewpoint of productivity, but it can be seen that the obtained nonwoven fabric has high strength and excellent water retention.

In Comparative Example 2, since the heat treatment temperature was too high, the core component constituting the fiber was softened, the shrinkage of the web was severe, and the texture was very hard, and it could not be said to be a non-woven fabric. In Comparative Example 3, since the heat treatment temperature was too low, the whole was not fused at the contact point of the fibers, and a nonwoven fabric having high tenacity could not be obtained. In Comparative Example 4, the heat treatment time was short and the web surface was fused at the fiber contact points, but the back surface was not fused and only fluff was obtained. Example 7 A raw fabric A-6 of core-sheath type composite short fibers was used to make a web under exactly the same conditions as in Example 1, and then a nonwoven fabric was made. The nonwoven fabric performance is shown below. It can be seen that the product of Example 7 is a non-woven fabric having obviously high strength and excellent water retention. In addition, the texture of the non-woven fabric was very excellent and the texture was good.

Notation 50 g / m ² Tensile strength 11.4 kg / 2.5 cm Tensile elongation 39% Bulk density 0.042 g / cm ³ MIU 0.20 Air permeability 20 cc / cm ² s Water retention 760% Example 8 Core-sheath type A web was prepared using the raw cotton A-7 of the composite short fibers under the same conditions as in Example 1, and then a nonwoven fabric was prepared. The nonwoven fabric performance is shown below. It can be seen that the material of Example 8 is a non-woven fabric having a significantly high strength and excellent water retention. In addition, the texture of the non-woven fabric was very excellent and the texture was good.

Notation 49 g / m ² Tensile strength 11.6 kg / 2.5 cm Tensile elongation 38% Bulk density 0.045 g / cm ³ MIU 0.35 Air permeability 21 cc / cm ² · s Water retention 765% Example 9 Core-sheath type A web was prepared using the raw cotton A-8 of the composite short fibers under the same conditions as in Example 1, and then a nonwoven fabric was prepared. The nonwoven fabric performance is shown below. It can be seen that the material of Example 9 is a non-woven fabric having a significantly high strength and excellent water retention. In addition, the texture of the non-woven fabric was very excellent and the texture was good.

Notation 49 g / m ² Tensile strength 9.2 kg / 2.5 cm Tensile elongation 37% Bulk density 0.032 g / cm ³ MIU 0.20 Air permeability 25 cc / cm ² · s Water retention 545%

[0070]

EFFECTS OF THE INVENTION The heat-bonded nonwoven fabric according to the present invention is composed of polyolefin-based fine-core core-sheath type composite short fibers, and therefore has high nonwoven fabric strength, bulkiness and extremely excellent water retention. In addition, since a fiber containing a specific ethylene polymer as a sheath component is used, it does not have a slimy feeling peculiar to polyethylene, has a very good texture, and has a good texture. Therefore, it is particularly suitable for medical hygiene materials such as disposable diapers and sanitary napkins. Moreover, since it has chemical resistance and is excellent in water retention, it is particularly suitable as a separator for dry batteries. In addition, it can be applied to a wide range of applications such as agricultural and horticultural materials, packaging materials and filters as daily life related materials.

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[Procedure amendment]

[Submission date] October 28, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 7

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0008

[Correction method] Change

[Correction content]

[0008]

The inventors of the present invention have reached the present invention as a result of intensive research to solve the above problems. That is, the present invention provides (1) a core-sheath type having an ethylene-based polymer as a main component and a propylene-based polymer as a core, and having a single yarn fineness of 0.2 to 1 denier. A heat-bonded non-woven fabric, which is composed of composite short fibers and is bonded at the points of contact between the fibers, and (2) a sheath part mainly composed of an ethylene polymer and a core part of a propylene polymer. In addition, a card web composed of core-sheath type composite short fibers having a single yarn fineness of 0.2 to 1 denier is heat-treated with hot air so as to satisfy the following formula, and at a contact point between fibers. Method for producing heat-bonded non-woven fabric characterized by bonding, heat treatment temperature T (° C) Tm1 ≤ T ≤ Tm2-10 heat treatment time t (min) 0.1 ≤ L / v, L /
v = t Tm1: melting point (° C.) of ethylene polymer in the sheath Tm2: melting point (° C.) of propylene polymer in the core L: heat treatment zone length (m) v: heat treatment rate (m / min) ) And are the gist.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Nobuo Noguchi 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Ltd. Central Research Institute

Claims (7)

[Claims] 1. A sheath portion containing an ethylene-based polymer as a main component,
It has a propylene-based polymer core and has a single yarn fineness of 0.
A heat-bonded non-woven fabric comprising 2-1 denier core-sheath type composite short fibers, which are bonded at the contact points between the fibers. 2. The heat-bonded nonwoven fabric according to claim 1, wherein the sheath portion is a blend structure of an ethylene polymer and a propylene polymer. 3. The mixing ratio of the ethylene polymer and the propylene polymer in the sheath is, by weight ratio, ethylene polymer / propylene polymer = 99.5 / 0.5 to 75/25. The heat-bonded non-woven fabric according to claim 2, wherein 4. The heat-bonded non-woven fabric according to claim 1, wherein the sheath portion is made of an ethylene polymer copolymerized with propylene. 5. The copolymerization ratio of propylene in the copolymer of the sheath part is 0.2% by weight or more and 5% by weight or less, and the copolymerization ratio of the ethylene polymer is 99.8% by weight or less and 95%. The heat-bonded non-woven fabric according to claim 4, wherein the heat-bonded nonwoven fabric is contained in an amount of not less than wt%. 6. Strength is 5 kg / 2.5 cm width or more, bulk density is 0.03 to 0.06 g / cm ³ , and air permeability is 45 cc.
/ Cm ² · s or less, the coefficient of friction (MIU) is 0.18 or more, the water retention is 200% or more, the thermal bonding nonwoven fabric according to any one of claims 1 to 3. 7. An ethylene-based polymer as a main component sheath portion,
It has a propylene-based polymer core and has a single yarn fineness of 0.
A heat-bonded non-woven fabric, characterized in that a card web composed of core-sheath type composite staple fibers of 2-1 denier is heat-treated with hot air so as to satisfy the following formula and bonded at the contact points of the fibers. Manufacturing method. Heat treatment temperature T (° C.) Tm1 ≦ T <Tm2-10 Heat treatment time t (min) 0.1 ≦ L / v, L /
v = t Tm1: melting point (° C.) of ethylene polymer in the sheath Tm2: melting point (° C.) of propylene polymer in the core L: heat treatment zone length (m) v: heat treatment rate (m / min) )