JPH08127993A - Wet nonwoven fabric and its production - Google Patents

Abstract

PURPOSE: To obtain wet nonwoven fabric having high strength and excellent printability and resistant to see-throughness by forming a web from reticular fibrid short fibers and treating the web with a hot calender roll. CONSTITUTION: Each of an olefin polymer such as high-density polyethylene and an ester polymer such as polyethylene terephthalate is kneaded with 0.1-5wt.% of talc powder as a crystal uncleation agent and the polymers are dissolved in methylene chloride to disperse the talc and obtain a spinning dope having a polymer concentration of 5-30wt.%. The dope is extruded within 90min after the preparation through a nozzle at 150-240 deg.C under >=40kg/cm2<2> pressure into a region having temperature and pressure lower than those of the spinning process. The reticular fibers composed of essentially continuing olefin and ester fibrid fibers are cut to form short fibers. The short fibers are beaten and formed by a paper-making process to form a wet web. The web is treated with a hot calender roll to obtain nonwoven fabric having self-fused contact points of the fibrid short fibers over the whole surface of the web.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wet type nonwoven fabric composed of short fibrid fibers formed by connecting ultrafine fibril fibers and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a nonwoven fabric, a dry nonwoven fabric obtained by a dry method and a wet nonwoven fabric obtained by a wet method are known. All of the non-woven fabrics mainly consist of synthetic fibers as constituent fibers, but various methods of manufacturing non-woven fabrics that can improve the flexibility and the filtration efficiency by making the fineness of the constituent fibers finer are proposed. Has been done. For example,
As a method for producing a dry non-woven fabric with ultrafine fibers as constituent fibers, a non-woven fabric obtained by a spunbond method using a deformed nozzle is constructed by a mechanical method such as needle punching or kneading or a high-pressure water flow method. A method of splitting fibers and a so-called melt blown method of extruding a molten polymer from a spinning nozzle and pulling and thinning it with a heating fluid are known. However, the method using the odd-shaped nozzle increases the nozzle cost and complicates the process. In addition, the melt blown method surely gives extremely thin fibers, but since it is made finer at the polymer stage, stretch orientation,
It has the drawback that the crystallization is low and the strength of the resulting nonwoven fabric is extremely low.

A so-called flash spinning method has been conventionally known as a method for producing a dry non-woven fabric having ultrafine fibers as constituent fibers. The flash spinning method is, as described in U.S. Pat. No. 30,815,19, a spinning solution in which a polymer is dissolved in a low boiling point solvent is discharged from a spinning nozzle (discharge hole), and a low melting point solvent is instantaneously added. It is vaporized to precipitate the polymer, and the precipitated polymer is super-stretched by an explosive force due to vaporization to form ultrafine fibers,
The ultrafine fibers are interconnected to form a three-dimensional network structure, and form a substantially continuous network fiber,
The net-like fibers are accumulated to produce a non-woven fabric. For example, a polyolefin non-woven fabric produced by flash spinning using an olefin polymer as a polymer is lightweight and is used as a material for envelopes and the like. However, this polyolefin-based non-woven fabric has a low modulus, does not have a feeling of use / wearing and has a unique slimy feel, and has a limit in being used for general purposes. Also,
The polyester non-woven fabric produced by using an ester polymer as a polymer has low strength and is difficult to put into practical use.

On the other hand, regarding the method for producing a wet-laid nonwoven fabric having ultrafine fibers as constituent fibers, the beating degree of the synthetic pulp which is the constituent fibers is increased, and the synthetic pulp is crushed to make its fineness as small as possible. Alternatively, it is only attempted to reduce the fineness of synthetic short fibers for papermaking. However, when the beating degree is increased, the fiber length of the synthetic pulp is shortened, and there is a disadvantage that a high-strength wet non-woven fabric cannot be obtained. In addition, the finer the fineness of the synthetic short fibers for papermaking, the lower the strength of the obtained wet-laid nonwoven fabric. The advantage of the wet non-woven fabric having ultrafine fibers as constituent fibers is that the printability is improved because it is difficult to pass through even with a low basis weight, in addition to improving the flexibility and improving the filtration efficiency. To be

[0005]

Therefore, the present inventors have conducted various studies to develop a novel wet-laid nonwoven fabric having ultrafine fibers as constituent fibers. First, the present inventors
A study was conducted on the use of reticulated fibers obtained by a conventionally known flash spinning method as a raw material fiber of a wet non-woven fabric. However, since the reticulated fiber obtained by the flash spinning method using an olefin polymer has a relatively high strength, it is difficult to form a fibrid-like fiber suitable for papermaking even after repeated beating. there were. Further, the reticulated fiber obtained by a flash spinning method using an ester-based polymer is too low in strength, and when it is beaten, it tends to be a fibril fiber alone, and it is difficult to make a fibrid fiber suitable for papermaking. Met. In addition, the fibril fiber means each ultrafine fiber that constitutes the reticulated fiber obtained by the flash spinning method. In addition, the fibrid-like fiber means a fiber in which some of the fibril fibers are connected to each other and are in the form of pulp fibers having a large number of whiskers. Therefore, fibrid fibers are obtained by cutting the reticulated fibers in the longitudinal, lateral, and height directions, and each reticulated fiber or one fiber in the fibrid fibers is called a fibril fiber. .

Further, by performing beating under strict conditions, even if a good fibrid fiber is obtained from an olefin-based reticulated fiber or an ester-based reticulated fiber, the fineness (diameter) of each fibril fiber is further reduced. That was difficult. This is because when the flash spinning method is adopted using an olefin polymer, a good reticulated fiber can be obtained under the condition of a specific range, and the reticulated fiber is constituted only within this specific range. This is because the fineness of the fibril fiber cannot be adjusted. This also applies when an ester polymer is used as the polymer.

Therefore, in the present invention, a plurality of polymers having poor compatibility are mixed in the spinning solution used in the flash spinning method, the spinning solution is discharged from the discharge hole, the solvent is vaporized, and the fibril fiber is formed. When the polymer is formed, the polymer having poor compatibility is divided into the components which are independent of each other, so that the fibril fiber to be formed is further finely divided.
Then, since fibril fibers are divided when they are formed, crystallization of the fibril fibers is not sufficiently promoted, and for the purpose of avoiding this, an inorganic powder to be a crystal nucleating agent is mixed in the polymer. The purpose is to obtain a sufficiently crystallized high-strength fibril fiber. Further, the present invention, the reticulated fiber obtained by the flash spinning method, as a fibril fiber connected body composed of a polymer having poor compatibility, when the reticulated fiber is beaten, the fibril fibers are easily released from the connection. The purpose is to make it easier to obtain fibrid fibers suitable for papermaking.

[0008]

Means for Solving the Problems That is, the present invention comprises an olefin-based fibril fiber containing an olefin-based polymer as a main component and an ester-based fibril fiber containing an ester-based polymer as a main component, And, the olefin-based fibril fiber and / or the ester-based fibril fiber contains an inorganic powder that can be a crystal nucleating agent,
The present invention relates to a wet non-woven fabric, which is composed of fibrid short fibers, and in which the contact points between the fibrous short fibers are self-fused over the whole, and a method for producing the same.

In the present invention, an olefin polymer and an ester polymer are used to obtain a reticulated fiber made of fibril fiber by a flash spinning method. The olefin polymer used at this time includes polyethylene, polypropylene,
An ethylene-based copolymer, a propylene-based copolymer, an ethylene-vinyl alcohol-based copolymer and the like are adopted. When an ethylene-based polymer such as polyethylene is adopted among these polymers, ASTM-D
It is preferable to adopt a melt index value of 0.3 to 30 g / 10 minutes measured by the method of -1238E. When the melt index value is less than 0.3 g / 10 minutes, the viscosity of the spinning mixed solution is excessively increased, and the fineness of the fibril fiber obtained by flash spinning tends to increase. Also, the melt index value is 30 g /
When it exceeds 10 minutes, the strength of the obtained reticulated fiber is lowered, so that it becomes difficult to obtain fibrid short fibers suitable for papermaking by beating, or even if the fibrid short fibers are obtained, the wet non-woven fabric becomes slimy. Feeling and tackiness occur, and handling tends to be poor. When a propylene polymer such as polypropylene is used, it is preferable to use a polymer having a melt flow rate value of 1 to 40 g / 10 minutes measured by the method of ASTM-D-1238L. Melt flow rate value is 1g
If it is less than / 10 minutes, the viscosity of the spinning mixed solution is too high, and the fineness of the resulting fibril fiber tends to increase. In addition, the melt flow rate value is 40 g / 10
If the amount exceeds the minute, the strength of the obtained reticulated fiber decreases, so that it becomes difficult to obtain fibrid short fibers suitable for papermaking by beating, or even if fibrid short fibers are obtained, a wet nonwoven fabric has a slimy feel. Or tackiness occurs, and the handling tends to be poor.

When an ethylene-vinyl alcohol copolymer is used as the olefin polymer, it is preferable to employ one having the following copolymerization ratio. That is, the ethylene-vinyl alcohol copolymer is a crystalline polymer in which ethylene and vinyl alcohol are randomly copolymerized, and the copolymer having a copolymerization ratio of ethylene of 20 to 70 mol% is used. It is particularly preferable that it is 30 to 50 mol%. In addition to ethylene, vinyl alcohol is most preferably used alone, but a small amount of vinyl-based monomer may be mixed with vinyl alcohol. When the repeating unit consisting of ethylene is less than 20 mol%, that is, when the repeating unit of vinyl alcohol is more than 80 mol%, the flexibility of the obtained nonwoven fabric tends to decrease. Further, when the repeating unit consisting of ethylene exceeds 70 mol%, that is, when the vinyl alcohol-based repeating unit is less than 30 mol%, the ratio of hydroxyl groups in the olefin polymer becomes relatively small, and the obtained fibrid is obtained. The hydrophilicity of the short staple fibers tends to decrease, and the slurry of the short fibrous fibers tends to be difficult to obtain. The ethylene-vinyl alcohol copolymer can also be obtained by saponifying an ethylene-vinyl acetate copolymer. In this case, the saponification degree is preferably about 95% or more. When the saponification degree is low, the crystallinity of the ethylene-vinyl alcohol-based copolymer tends to decrease,
Crystallization of the obtained fibril fiber is not sufficiently improved, and the softening point or melting point becomes too low, which may cause troubles in the subsequent self-fusion process, for example. When an ethylene-vinyl alcohol copolymer is used, it is usually preferable to use one having a number average molecular weight of about 8,000 to 30,000.

As the ester-based polymer used in the present invention, polyethylene terephthalate, polybutylene terephthalate, etc. are adopted, and isophthalic acid, phthalic acid, glutaric acid, adipic acid, sulfoisophthalic acid, diethylene glycol, propylene are mainly used as the main component. Also used are those in which glycol, 1,4-butanediol, 2,2-bis (4-hydroxyethoxyphenyl) propane, etc. are copolymerized as copolymerization components in the range of up to 40 mol%. Regarding the viscosity of the ester polymer used in the present invention, it is preferable to employ one having a relative viscosity [η _rel ] of about 1.3 to 1.8. That is, as the ester-based polymer, the relative viscosity [η _rel ] is about 1.3 to 1.6 and the relative viscosity [η _rel ] is 1.7.
Even high-viscosity polyester resins produced by solid-state polymerization, which is a degree, are favorably adopted. In particular,
The higher the viscosity of the ester polymer, the higher the strength of the resulting nonwoven fabric. The relative viscosity [η _rel ] was measured with a solution in which a solvent having a mixing ratio of tetrachloroethane and phenol of 1/1 (weight ratio) was used, and the concentration of the ester polymer was 0.5% at a temperature of 20 ° C. It was done.

In the present invention, the olefin polymer and the ester polymer are dissolved in a solvent. In the flash spinning method, a spinning solution in which a polymer is dissolved is discharged into the atmosphere through a discharge hole to precipitate the polymer.Therefore, the solvent dissolves the polymer at low temperature and low pressure. It is preferable to employ a material that is difficult to dissolve and in which the polymer is easily dissolved under high temperature and high pressure. That is, as the solvent used in the present invention, it is preferable to employ a solvent that does not easily dissolve the olefin polymer and the ester polymer at low temperature and low pressure, and easily dissolves both polymers at high temperature and high pressure. Examples of such solvents include aromatic hydrocarbons such as benzene and toluene, butane, pentane, and aliphatic hydrocarbons such as isomers and homologues thereof, alicyclic hydrocarbons such as cyclohexane, and unsaturated hydrocarbons. Hydrogen, trichloromethane, methylene chloride, carbon tetrachloride, chloroform, 1,1
-Dichloro-2,2-difluoroethane, 1,2-dichloro-1,1-difluoroethane, halogenated hydrocarbons such as methyl chloride and ethyl chloride, alcohols, ethers, ketones, nitriles, amides, fluoro Carbons and the like can be used alone or in combination. In particular, in recent years, the use of a solvent that destroys the ozone layer must be avoided in the midst of calls for global environmental problems. From this point as well, methylene chloride, 1,1-dichloro-2,2-difluoroethane, It is preferable to use 1,2-dichloro-1,1-difluoroethane or the like.

The olefin polymer and the ester polymer are dissolved using the above solvent to obtain a spinning mixed solution. When a spinning mixed solution is obtained using an olefin polymer and an ester polymer, the ratio of both polymers used may be in any range, but in general, the olefin polymer: Ester polymer = 5-9
It is 5:95 to 5 (parts by weight). Then, when obtaining the spinning mixed solution, an inorganic powder that can serve as a crystal nucleating agent is dispersed in the spinning mixed solution. As the inorganic powder, any powder may be used as long as it does not react with the solvent or dissolve in the solvent. Particularly, it is preferable to adopt talc, calcium carbonate, titanium oxide, silica, magnesium oxide or the like.

The particle size of the inorganic powder is preferably 5 μm or less. If the particle size exceeds 5 μm, it tends to be difficult to obtain fibril fibers with a finer fineness, or the filtration filter in the spinneret having a plurality of discharge holes tends to be clogged, resulting in spinning. Operability tends to decrease. Therefore, the particle size of the inorganic powder is preferably 5 μm or less, more preferably 4 μm or less, and most preferably 3 μm or less. The particle size of the inorganic powder was determined from photographs taken and observed with an electron microscope at a magnification of 5000 times.

The bulk specific volume of the inorganic powder is preferably from 2 to 10 cc / g, more preferably from 3 to 9 cc / g, most preferably from 3 to 8 cc / g. The bulk specific volume is
It is the volume of the inorganic powder per unit weight. The larger the bulk specific volume, the larger the surface area of the inorganic powder and the greater the effect as a crystal nucleating agent. If the bulk specific volume of the inorganic powder is 2 cc / g or less, the effect as a crystal nucleating agent is halved, and therefore the addition amount of the inorganic powder (content in the polymer) must be increased, There is a tendency for the strength of the fibril fibers to be reduced. Further, it is difficult to produce an inorganic powder having a bulk specific volume of more than 10 cc / g, and if such an inorganic powder is to be obtained, the cost of the inorganic powder will increase, and the cost of the resulting nonwoven fabric will also increase. Become.

The quantitative ratio of the inorganic powder to be dispersed in the spinning mixed solution is preferably 0.1 to 5% by weight, and preferably 0.1 to 2% by weight, based on the weight of both polymers. More preferable. That is, [weight of inorganic powder / (weight of both polymers +
The weight of the inorganic powder)] × 100 is 0.1 to 5% by weight.
Is preferable, and 0.1 to 2% by weight is more preferable. If the mixing ratio of the inorganic powder is less than 0.1% by weight, the effect as a crystal nucleating agent is reduced, and the strength of the obtained fibril fiber tends not to be sufficiently improved,
Consequently, the strength of the non-woven fabric tends not to be sufficiently improved.
Further, if the mixing ratio of the inorganic powder exceeds 5% by weight, a large amount of the inorganic powder is contained in the fibril fiber, and the strength of the fibril fiber tends to decrease. Further, a large amount of inorganic powder adheres to the vicinity of the discharge hole for discharging the spinning mixed solution, which tends to deteriorate the operability.

Using the olefin polymer, ester polymer, solvent and inorganic powder described above, a spinning mixture solution is prepared in which both polymers are dissolved in the solvent and the inorganic powder is dispersed in the solvent. . The spinning mixed solution is prepared, for example, by introducing an olefin polymer, an ester polymer and an inorganic powder into a solvent and dissolving the olefin polymer and the ester polymer. Further, the olefin polymer is previously kneaded with 0.1 to 5% by weight of inorganic powder, and the ester polymer is also previously kneaded with 0.1 to 5% by weight.
It can also be prepared by kneading the inorganic powder by weight% and dissolving both the polymers kneaded with the inorganic powder in a solvent. Furthermore, a mixture of an olefin-based polymer and an ester-based polymer is added with 0.1 to 5 in advance.
It may also be prepared by kneading wt% of inorganic powder and dissolving this in a solvent.

In order to dissolve both polymers in the solvent, it is generally necessary to raise the temperature, and it is necessary to heat to 150 to 240 ° C. That is, in order to keep the state in which both polymers are dissolved in the solvent, it is general to keep the spinning mixed solution at a temperature of 150 to 240 ° C. If the holding temperature of the spinning mixed solution exceeds 240 ° C., the olefin polymer or the like may be decomposed, the obtained fibril fiber tends to be colored, or the strength of the fibril fiber tends to decrease. Further, when the temperature of the spinning mixed solution is less than 150 ° C., even if the spinning mixed solution is discharged from the discharge hole to the atmospheric atmosphere at room temperature, the temperature does not decrease so much that the precipitation of the polymer hardly occurs explosively. It is difficult to form a reticulated fiber composed of fibril fiber, and a tubular fiber having a hollow portion is likely to be formed. Both polymers are sufficiently dissolved in the solvent,
It is needless to say that the temperature of the spinning mixed solution may be maintained at a temperature lower than 150 ° C. or higher than 240 ° C. when the reticulated fiber having good physical properties can be obtained.

In the spinning mixed solution in which both polymers are dissolved in a solvent, the polymer concentration is preferably 5 to 30% by weight. Here, the polymer concentration is represented by [(weight of olefin-based polymer + weight of ester-based polymer) / weight of spinning mixed solution] × 100. When the polymer concentration is less than 5% by weight, it tends to be difficult to obtain substantially continuous reticulated fibers even when the spinning mixed solution is discharged from the discharge holes by the flash spinning method. In the present invention, since a substantially continuous reticulated fiber is cut into a certain length and then beaten to obtain a fibrid-like short fiber, a substantially continuous reticulated fiber is obtained by a flash spinning method. There is no need to get Therefore, the polymer concentration may be less than 5% by weight to obtain reticulated short fibers which are not substantially continuous by the flash spinning method. However, it is preferable to obtain a substantially continuous reticulated fiber by the flash spinning method in terms of later handling. On the other hand, when the polymer concentration exceeds 30% by weight, it becomes difficult to obtain a reticulated fiber composed of fibril fibers, and a tubular fiber containing bubbles tends to be obtained.

On the other hand, the solvent concentration of the spinning mixed solution is 70 to
It is preferably set to 95% by weight. When the solvent concentration is less than 70% by weight, the solution viscosity of the spinning mixed solution becomes too high, and the dissolution of the polymer is likely to be nonuniform, and it is difficult to obtain a reticulated fiber composed of fibril fibers and voids are formed. A tubular fiber is likely to be generated. Further, if the solvent concentration exceeds 95% by weight, it becomes difficult to obtain substantially continuous reticulated fibers. In the present invention, since it is not necessary to obtain a substantially continuous reticulated fiber, the solvent concentration should be 9%.
When the content is 5% by weight or less, reticulated short fibers may be obtained.
As described above.

When the spinning mixture solution is prepared, it is preferable to add and inject an inert gas such as nitrogen or carbon dioxide into a closed container containing the spinning mixture solution. The additional injection of inert gas, even before making the spinning mixture,
It may be after creation. When the temperature is raised to dissolve the polymer in the solvent, it may be before or after the temperature rise. In particular, if an inert gas is added and injected before the temperature is raised, it is possible to prevent deterioration of the polymer, improve the temperature rising rate, improve the solubility of the polymer in a solvent, etc., and obtain it by the flash spinning method. It is possible to make the fineness of the fibril fiber constituting the reticulated fiber finer, and as a result, it is possible to obtain a wet non-woven fabric having improved filtration efficiency and excellent printability.

By injecting such an inert gas, the spinning mixed solution can be maintained at least under autogenous pressure. The autogenous pressure is a pressure spontaneously generated by the volume of the container, the amount of the inert gas injected, and the temperature in the container. The volume of the container is within a certain range for accommodating a desired amount of the spinning mixed solution, and the temperature within the container is within a certain range depending on the spinning temperature. , Generally determined by the amount of inert gas injected into the container. Autogenous pressure is generally 40 kg
Is preferably to / cm ² or more, thus mixing the spinning solution is preferably maintained under 40 kg / cm ² or more autogenous pressure. In addition to this self-generated pressure, another pressure may be applied to the spinning mixed solution. In this way, the spinning mixed solution maintained under at least a high pressure equal to or higher than the autogenous pressure passes through the pressure drop chamber and is discharged (that is, flash) to a pressure region (generally, atmospheric region) substantially lower than that. Spun) to obtain a substantially continuous reticulated fiber.
When the holding pressure of the spinning mixed solution is less than 40 kg / cm ² (general autogenous pressure), the change in pressure during flash spinning is too small, the explosive force is lowered, and the orientation of the fibril fiber constituting the reticulated fiber is reduced. It becomes low, and it tends to be difficult to obtain a high-strength reticulated fiber. In addition, there is a tendency that the discharge of the spinning mixed solution becomes uneven, and it becomes difficult to stably obtain the reticulated fiber in which a large number of fibril fibers are connected. In addition,
The upper limit of the holding pressure of the spinning mixed solution may be any value, but it is preferably about 120 kg / cm ² from the viewpoint of suppressing the decrease in the viscosity of the polymer.

The spinning mixed solution maintained at a predetermined temperature and a predetermined pressure is then flash-spun and discharged. However, the solution is discharged within 90 minutes after the polymer is dissolved and discharged as shortly as possible. preferable. If the polymer is dissolved and then discharged for more than 90 minutes, the ester polymer is likely to be colored or thermally decomposed, and the strength of the obtained fibril fiber and the strength of the obtained nonwoven fabric tend to be lowered. Further, when the spinning mixed solution is discharged in a state where the dissolution of the polymer has not progressed sufficiently, clogging occurs in the filtration filter in the spinneret, or it becomes difficult to obtain a uniform reticulated fiber, which eventually leads to a uniform It tends to be difficult to obtain such short fibrid-like fibers.

In the spinning mixed solution, in addition to the olefin polymer, the ester polymer, and the inorganic powder, a matting agent, a light-proof agent, a heat-resistant agent, a pigment, and a fiber-spreading agent used in ordinary fiber formation. It is preferable to add a weathering agent, an ultraviolet absorber, a heat storage agent, a stabilizer and the like. Particularly, it is preferable to add a surfactant to the spinning mixed solution. That is, in the present invention, the olefin-based polymer and the ester-based polymer, which are incompatible with each other, are dissolved in a solvent, and therefore both polymers are easily separated into a dissolved solution phase. That is, it is easy to separate into two phases, a solution phase in which the olefin polymer is mainly dissolved and a solution phase in which the ester polymer is mainly dissolved. When a surfactant is added to prevent the phase separation, the spinning mixed solution can be stably maintained in an emulsified state. As the surfactant, it is preferable to use a nonionic surfactant, for example, monoesters such as lauric acid, stearic acid and oleic acid, and polyoxyethylene adducts such as lauryl alcohol, stearyl alcohol and oleyl alcohol. Etc. are preferably used. The more homogeneously the olefin polymer and the ester polymer are dissolved in the spinning mixed solution, the more reticulated fibers composed of fibril fibers having an extremely small fineness can be obtained.

The spinning mixed solution prepared as described above is discharged from the discharge holes by the flash spinning method to obtain substantially continuous reticulated fibers or substantially discontinuous reticulated short fibers. That is, the spinning mixed solution is discharged from the discharge hole,
By the instantaneous and explosive vaporization of the solvent under the low pressure and the low temperature, the reticulated fiber or the reticulated short fiber composed of the ultra-stretched and highly oriented fibril fiber can be obtained.
This instantaneous and explosive vaporization is the vaporization force due to the instantaneous velocity, and the solvent vaporizes at once in a time of 0.1 seconds or less, the process is extremely short, and the concentration of the polymer increases. Occurs, and finally only the polymer precipitates.
Then, the precipitated polymer is cooled by vaporization, subjected to super-stretching and highly oriented, and becomes a reticulated fiber or reticulated short fiber made of ultrafine fibril fiber. Therefore, the reticulated fiber or reticulated short fiber obtained by the method according to the present invention has a three-dimensional reticulated structure in which a fibril fiber mainly containing an olefin polymer and a fibril fiber mainly containing an ester polymer are used. Are connected so that Here, the meaning that the olefin polymer is the main component in the fibril fiber means that the olefin polymer is more mixed than the mixing ratio of the olefin polymer and the ester polymer in the spinning mixed solution. It means that the ratio is large, and that the ester-based polymer is the main component in the fibril fiber means
This means that the mixing ratio of the ester polymer is higher than the mixing ratio of the olefin polymer and the ester polymer in the spinning mixed solution. The diameter of the fibril fiber is extremely small, and is generally 0.01 to
It is about 10 μm.

The substantially continuous reticulated fiber obtained as described above is cut into a fixed length to obtain reticulated short fibers.
In the flash spinning method, it is also possible to directly obtain the substantially discontinuous short mesh fibers by decreasing the polymer concentration. The fiber length of the reticulated short fibers is generally preferably 50 mm or less. When the fiber length of the reticulated short fibers exceeds 50 mm, the reticulated short fibers are likely to become entangled with the shaft during beating with a beating machine, which tends to make uniform beating difficult.

The reticulated short fibers can be beaten using a conventionally known beating machine. In this case, the bath ratio, the number of flybars, the number of revolutions, the beating load, and the beating time may be selected as optimum conditions according to the machine used. Generally, the conditions are such that the bath ratio is 1:10 to 1000 (reticulated short fibers: water), the number of flybars is 27 in the upper part / 7 in the lower part, and the rotation speed is about 500 rpm. Further, the beating load is sequentially changed from 0 to 10 kg, and the beating time is preferably about 10 minutes.
When the reticulated short fibers are beaten under such conditions, the mutual connection of the fibril fibers is released, and the fibrous short fibers in which a large number of the fibril fibers are connected in a whisker shape can be obtained. The form of this fibrid-like short fiber is, schematically speaking, a form in which a net is randomly cut at various points. In addition, the reticular short fibers are those in which olefinic fibril fibers and ester fibril fibers, which are poorly compatible, are interconnected so as to form a three-dimensional network structure, so that they can be easily beaten by a beater. Fibrillated short fibers composed of fibril fibers with an extremely small fineness as the connection between fibril fibers is released and the division of the part where olefinic fibril fibers and ester fibril fibers are integrated progresses. Is obtained. The fibrillar short fibers obtained by beating are composed of fibril fibers having a fiber diameter of about 0.01 to 1 μm, and have a form such as pulp fibers in which the fibril fibers are connected in a whisker shape. The fiber length of the fibril-like short fibers is about 5
It is about mm or less.

For the beating of the reticulated short fibers, a conventionally known beating machine may be used, or a crusher used for producing powder may be used. In particular, it is preferable to use a wet crusher that crushes in water because fusion between the reticulated short fibers can be prevented. After beating as described above, if necessary, the fibrid-like short fibers are disintegrated using a disintegrator.
The conditions for disaggregation by a disintegrator are: bath ratio 1: 20-200
0 (Fibrid short fiber: water), rotation speed 100-75
About 00 rpm is preferable. If the bath ratio is less than this range (the amount of water is less), the fibrous short fibers are further cut, the fiber length becomes shorter, and the fibril fibers fall off, so that the strength of the obtained wet-laid nonwoven fabric decreases. A tendency arises. Further, if the bath ratio is larger than this range (there is more water), the disaggregation and dispersion of the fibrid-like short fibers do not proceed, so that a wet non-woven fabric having a uniform texture tends to be difficult to obtain. When the bath ratio is large, the disaggregation of the fibrid-like short fibers is promoted by increasing the rotation speed, and a wet non-woven fabric having a uniform texture can be obtained.

After the fibrid short fibers are obtained, a slurry in which the fibrid short fibers are dispersed in water is obtained. This slurry can be prepared by further adding water to the fibrous short fibers containing water after beating. Further, after the beating, if the water is sufficient, the beating can be used as it is as a slurry. At this time, in order to uniformly disperse the fibrid short fibers in water, it is preferable to add a dispersant such as a surfactant or a thickener. When this slurry is put into a paper machine to make paper, a wet web containing water is formed on a conveyor such as a short-mesh, a long-mesh, and a round-mesh. As the paper machine, any conventionally known paper machine such as a suspended short-net paper machine, a fourdrinier paper machine, and a round-net paper machine can be used. Further, the slurry concentration may be appropriately selected according to the target weight of the wet non-woven fabric.
That is, when the slurry concentration is low, a wet fabric having a low basis weight can be obtained, and when the slurry concentration is high, a wet fabric having a high basis weight can be obtained. Here, the slurry concentration is the content ratio of the fibrid-like short fibers in the slurry. In addition, it is preferable to add a dispersant such as a surfactant or a thickener so that the fibrous short fibers are uniformly dispersed not only when the slurry is prepared but also in the beating step and the disaggregation step.

After forming the wet web, the water content in the wet web is removed. In order to remove the water content, it may be dehydrated by performing suction (suction) from the back surface of the conveyer such as a braid, or by pressing with a mangle roller or the like and squeezing. If the removal of water is incomplete by dehydration alone, the water may be removed by placing the wet web on the surface of the heating roller to remove water, or hot air may be blown onto the wet web to dry. Water may be removed. After removing water from the wet web, heat is applied to the entire surface of the wet web using a heating roller or hot air to soften or melt the fibrid short fibers, and at the contact points between the fibrid short fibers. The self-adhesive force self-bonds the fibrid short fibers to each other to obtain a wet-laid nonwoven fabric. The drying for removing the water content in the wet web and the application of the heat for self-fusing the fibrous short fibers to each other may be simultaneously performed by using a heating roller or hot air.

As a method for applying heat to the entire surface of the wet web, for example, a calendering method in which the wet web is passed between a pair of rollers equipped with at least one heated calender roller is adopted. As the calender roller, a pair of rollers made of a combination of one kind or two kinds selected from the group consisting of steel roller, cotton roller, rubber roller and resin roller is generally used. When a steel roller is used, it is preferable to coat the roller surface with a heat resistant resin such as fluorinated ethylene resin or rubber. This is to prevent an abnormal luster from appearing on the surface of the obtained wet-laid nonwoven fabric.
In addition, before passing through the calender roller, the wet web may be temporarily pressed with a resin roller or the like, or a multi-step calendering method in which the calender roller is passed through the calender roller twice or more to gradually fuse the web. May be adopted. As a method of applying heat to the entire surface of the wet web, for example, a method of applying heat by hot air in advance and then passing the wet web between a pair of rollers equipped with a calender roller at room temperature (unheated) is used. May be adopted.

When at least one heated calender roller is used, the temperature of the heated calender roller is not lower than the temperature of [melting point of olefin polymer-40 ° C], and [melting point of ester polymer-10]. [° C.] is preferable. More specifically, the proportion of the olefin polymer in the wet web is 20% by weight or more (that is, the proportion of the ester polymer is less than 80% by weight).
If so, it is preferable that the temperature is not lower than the melting point of the olefin-based polymer -40 ° C and lower than the temperature of the melting point of the ester-based polymer -10 ° C, and the ratio of the olefin-based polymer in the wet web. Is less than 20% by weight, it is preferably at least the melting point of the olefin polymer and less than the temperature of [melting point of ester polymer-10 ° C]. When the calender roller is heated to a temperature lower than such a temperature range, the degree of fusion bonding at the contact points between the fibrid short fibers becomes low, the resulting non-woven fabric frequently has fluffs, or the strength of the non-woven fabric is lowered. A tendency arises. On the other hand, when the calender roller is heated to a temperature higher than such a temperature range, the obtained nonwoven fabric may be colored or may be formed into a film over the whole. The linear pressure applied to the wet web passing between the pair of calender rollers is preferably about 1.0 to 20 kg / cm. Linear pressure is 1.
When it is less than 0 kg / cm, the degree of fusion at the contact points between the fibrid-like short fibers becomes low, the resulting non-woven fabric frequently has fluffs, or the strength of the non-woven fabric is extremely reduced, and the form of the non-woven fabric is obtained. It tends to be impossible to maintain. Further, the wet web is apt to slip on the calender roller, and it tends to be difficult to carry out uniform fusion throughout. On the other hand, if the linear pressure exceeds 20 kg / cm, the resulting nonwoven fabric tends to form a film over the entire surface, and the resulting nonwoven fabric tends to have a poor texture.

As described above, the wet non-woven fabric according to the present invention is obtained. The wet fabric of the present invention may have any unit weight (g / m ² ), but generally it is preferably about 10 to 100 g / m ² .
The wet nonwoven fabric is used as it is or after being dyed in a subsequent step, as a material for various products.
Examples of products made from this wet non-woven fabric include filtration filters, floppy disk sleeves, synthetic paper for printing, mounts and shoji paper.

[0034]

EXAMPLES Next, the present invention will be described more specifically based on examples. The measurement and evaluation of various characteristics in the examples were performed by the following methods. [Melting point of polymer]: The temperature that gives the extreme value of the melting absorption curve measured at a temperature rising rate of 20 ° C./min using a differential scanning calorimeter DSC-2 type manufactured by Perkin Elmer was taken as the melting point. [Specific surface area of non-woven fabric]: “BELS” manufactured by Nippon Bell Co., Ltd.
ORP28 "was used to measure the specific surface area by the BET nitrogen adsorption method, and the unit was converted to m ² / g to obtain the specific surface area of the nonwoven fabric. [Apparent density of non-woven fabric]: sample width 10 cm, sample length 10 cm
3. Prepare a total of 5 sample pieces, measure the basis weight of each sample, and then use a thickness measuring instrument manufactured by Daiei Kagaku Seiki Seisakusho 4.
A load of 5 g / cm ² was applied, the thickness was allowed to stand for 10 seconds, the thickness was measured, the apparent density was calculated by the following formula, and the average value was used as the apparent density of the nonwoven fabric. Apparent density (g / cm ³ )
= Basis weight (g / m ² ) / thickness (mm) / 1000 [Strength and elongation of non-woven fabric]: Tensilon UTM-4-1-100 manufactured by Toyo Baldwin Co., Ltd. was used and JIS L
It was measured according to the strip method described in -1096. That is, 10 sample pieces having a sample length of 20 cm and a sample width of 5 cm were prepared, and the maximum strength and elongation were measured under the conditions of a gripping interval of 10 cm and a pulling speed of 10 cm / min, and the average value was 100 g /
The value converted into the basis weight of m ² was taken as the strength and elongation of the nonwoven fabric. [Rigidity of non-woven fabric]: Prepare five sample pieces with a sample width of 5 cm and a sample length of 10 cm, bend each sample piece in the lateral direction to form a cylindrical shape (a cylindrical body having a height of the sample width), and its end portion. Was bonded to form a sample, and the sample was compressed in the height direction using Tensilon UTM-4-1-100 manufactured by Toyo Baldwin Co., Ltd. at a compression rate of 5 cm / min, and the stress at the maximum load (g ) Was measured and used as the rigidity of the nonwoven fabric. [Moisture Permeability of Nonwoven Fabric]: The moisture permeability (g / m ² / hr) was measured according to JIS L-1099-A-1 under the conditions of a temperature of 40 ° C. and a humidity of 90% RH.

Example 1 First, 600 g of high-density polyethylene having a melting point of 132 ° C., a density of 0.96 g / cm ³ , and a melt index value of 0.8 g / 10 minutes was prepared. On the other hand, 900 g of polyethylene terephthalate having a melting point of 256 ° C. and a relative viscosity [η _rel ] of 1.7 was prepared. Also, as a crystal nucleating agent, the particle size is 1
A talc powder having a bulk specific volume of 5 cc / g in μm was prepared. Then, 3 g of this talc powder was kneaded with high-density polyethylene, and 4.5 g of this talc powder was kneaded with polyethylene terephthalate. Then, each kneaded product and 6000 g of methylene chloride were filled in a 10-liter autoclave. At this time, 3 g each of isooctyl stearate and isostearyl ester were added as surfactants. After that, the autoclave was closed, and then nitrogen was injected into the autoclave so that the pressure became 50 kg / cm ^2, and stirring was started at an appropriate speed and heating was also started. 220 ℃ after reaching 100 ℃
Was reached for 25 minutes, and stirring was continued for 10 minutes while maintaining the temperature at 220 ° C. to obtain a uniform spinning mixed solution. At this time, the pressure in the autoclave is 10
A gauge pressure of 1 kg / cm ² was exhibited.

As described above, the temperature is 220 ° C. and the pressure is 1
Immediately after the spinning mixed solution held at 01 kg / cm ² was obtained, the three valves were opened to spun the mixture through the three discharging holes with pressure drop chambers having a discharge hole diameter of 0.65 mmφ and L / D = 1. The solution was discharged to obtain reticulated fibers. At this time, the pressure in the pressure drop chamber was 95 kg / cm ² . After the obtained reticulated fiber was made to collide with a rotary plate, the reticulated fiber was cut by a slot disk cutter to obtain a reticulated short fiber having a fiber length of 32 mm.
150 g of this short mesh fiber, 10 liters of water and 1 g of polyacrylic amide, which is a thickener, were weighed and put into a beating machine, a Niagara type test beater manufactured by Toyo Seiki Seisaku-sho, Ltd., to perform beating. The beating conditions were such that the number of flybars was 27 sheets at the top and 7 sheets at the bottom, and the rotation number was 500 rpm. Further, the beating load was sequentially changed to 0 kg, 1 kg, and 2 kg in three stages, and the beating time was 5 minutes each. The content rate of the fibrous short fibers in the beating liquid after the beating (concentration of short fibrid fibers) was 1.57%. 200 cc of this beating solution was collected and put into a paper machine. Furthermore, 6.8 liters of water and Sanmol LF, a surfactant
7 g (manufactured by Nichika Kagaku Co., Ltd.) was put into a paper machine and stirred to obtain a slurry, and then papermaking was performed to obtain a wet web. This wet web was introduced into a pressure machine, squeezed, dehydrated and stabilized in shape, and then passed through a hydraulic clearance calender machine having three pairs of rollers to give a basis weight of 50 g.
A wet non-woven fabric of / m ² was obtained. The upper rollers of this calender were all rollers made of urethane rubber on the surface, and the lower rollers were all heating rollers with a steel surface coated with fluorinated ethylene resin.
The temperatures from the first pair of heating rollers to the third pair of heating rollers were 105 ° C, 110 ° C, and 125 ° C, respectively. The linear pressure between each pair of rollers is 0.1
It was kg / cm, 0.5 kg / cm, 1.0 kg / cm.

The wet non-woven fabric obtained as described above is
It was composed of fibril-like short fibers composed of fibril fibers having a very fineness. And, the contact points between the fibrid-like short fibers are fused throughout, showing high strength and high rigidity,
The wet non-woven fabric was excellent in moisture permeability. The characteristic values and the like of this wet-laid nonwoven fabric were as follows. Apparent density: 0.40 g / cm ³ Specific surface area: 31 m ² / g Strength (MD, CD): 10.2 kg / 5 cm, 11.8 kg /
5 cm elongation (MD, CD): 4.5%, 4.6% Rigidity of non-woven fabric: 210 g Moisture vapor transmission rate: 280 g / m ² / hr

Example 2 400 g of polypropylene having a melting point of 162 ° C., a density of 0.910 g / cm ³ , and a melt flow rate value of 4 g / 10 minutes.
Prepared. On the other hand, melting point 256 ° C., relative viscosity [η _rel ]
1100 g of polyethylene terephthalate with a 1.6
Prepared. As a crystal nucleating agent, talc powder having a particle size of 1 μm and a bulk specific volume of 5 cc / g was prepared. Then, 2 g of this talc powder was kneaded with polypropylene, and 5.5 g of this talc powder was kneaded with polyethylene terephthalate. Then, each kneaded product and 6000 g of methylene chloride were filled in a 10-liter autoclave. At this time, 3 g each of isooctyl stearate and isostearyl ester were added as surfactants. After that, the autoclave was closed, and nitrogen was added to
Inject it into the autoclave so that it becomes 0 kg / cm ² ,
Stirring was started at a moderate speed and heating was started. It takes 30 minutes for the temperature to reach 200 ° C after reaching 100 ° C, and 1 while maintaining the temperature at 200 ° C.
The stirring was continued for 0 minutes to obtain a uniform spinning mixed solution. At this time, the pressure in the autoclave showed a gauge pressure of 98 kg / cm ² .

As described above, at a temperature of 200 ° C. and a pressure of 9
Immediately after the spinning mixed solution held at 8 kg / cm ² was obtained, three valves were opened to spun the mixture through the three discharging holes with pressure drop chambers with a discharge hole diameter of 0.65 mmφ and L / D = 1. The solution was discharged to obtain reticulated fibers. At this time, the pressure in the pressure drop chamber was 95 kg / cm ² . The pressure in the pressure drop chamber was 92 kg / cm ² . Using this reticulated fiber, 1
A wet nonwoven fabric having a basis weight of 50 g / m ² was obtained in the same manner as in Example 1 except that the temperatures from the pair of heating rollers to the pair of heating rollers were 115 ° C., 125 ° C., and 155 ° C., respectively. .

The wet non-woven fabric obtained as described above is
It was composed of fibril-like short fibers composed of fibril fibers having a very fineness. And, the contact points between the fibrid-like short fibers are fused throughout, showing high strength and high rigidity,
It was a wet non-woven fabric with no coloration and excellent moisture permeability. The characteristic values and the like of this wet-laid nonwoven fabric were as follows. Apparent density: 0.47 g / cm ³ Specific surface area: 29 m ² / g Strength (MD, CD): 8.8 kg / 5 cm, 9.3 kg / 5 cm Elongation (MD, CD): 4.5%, 4. 5% Rigidity of non-woven fabric: 195g Moisture vapor transmission rate: 263g / m ² / hr

Example 3 Instead of the polyethylene terephthalate used in Example 1, a polyester having a melting point of 247 ° C. and a relative viscosity [η _rel ] of 1.3 copolymerized with 5 mol% of sulfoisophthalic acid was used. , The holding temperature of the spinning mixed solution is 200 ° C.,
A wet nonwoven fabric was obtained under the same conditions as in Example 1 except that the holding pressure was 99 kg / cm ² and the pressure in the pressure drop chamber was 94 kg / cm ² .

The wet non-woven fabric obtained as described above is
It was composed of fibril-like short fibers composed of fibril fibers having a very fineness. And, the contact points between the fibrid-like short fibers are fused throughout, showing high strength and high rigidity,
It was a wet non-woven fabric with no coloration and excellent moisture permeability. The characteristic values and the like of this wet-laid nonwoven fabric were as follows. Apparent density: 0.39 g / cm ³ Specific surface area: 28 m ² / g Strength (MD, CD): 7.2 kg / 5 cm, 7.5 kg / 5 cm Elongation (MD, CD): 5.1%, 5. 2% Nonwoven fabric rigidity: 205 g Moisture vapor transmission rate: 278 g / m ² / hr

Example 4 Instead of the talc powder used in Example 1, calcium carbonate powder having a particle size of 1 μm was used, and 6 g of calcium carbonate powder was kneaded with high-density polyethylene, and 9 g of this calcium carbonate powder was polyethylene. A wet non-woven fabric was obtained under the same conditions as in Example 1 except that kneading was performed with terephthalate, the holding pressure of the spinning mixed solution was 102 kg / cm ² , and the pressure in the pressure drop chamber was 95 kg / cm ² .

The wet non-woven fabric obtained as described above is
It was composed of fibril-like short fibers composed of fibril fibers having a very fineness. And, the contact points between the fibrid-like short fibers are fused throughout, showing high strength and high rigidity,
It was a wet non-woven fabric with no coloration and excellent moisture permeability. Further, the strength and the rigidity were slightly inferior to the case where talc powder was used as the inorganic powder, but they were sufficiently satisfactory. The characteristic values and the like of this wet-laid nonwoven fabric were as follows. Apparent density: 0.40 g / cm ³ Specific surface area: 31 m ² / g Strength (MD, CD): 8.0 kg / 5 cm, 8.2 kg / 5 cm Elongation (MD, CD): 4.5%, 4. 6% Non-woven fabric rigidity: 175 g Moisture vapor transmission rate: 250 g / m ² / hr

Examples 5 to 8 and Comparative Example 1 High density polyethylene 6 having a melting point of 132 ° C., a density of 0.96 g / cm ³ , and a melt index value of 0.6 g / 10 minutes.
00g was prepared. On the other hand, melting point 256 ° C, relative viscosity [η
_rel ] is 1.4, polyethylene terephthalate 90
0 g was prepared. As a crystal nucleating agent, talc powder having a particle size of 1 μm and a bulk specific volume of 5 cc / g was prepared. And Table 1
The amount of talc powder shown in (1) was kneaded with high-density polyethylene and polyethylene terephthalate. Then, each kneaded product and 6000 g of methylene chloride were filled in a 10-liter autoclave. At this time, 3 g each of isooctyl stearate and isostearyl ester were added as surfactants. After that, Example 1
A non-woven fabric was manufactured under exactly the same conditions as described above, and the characteristic values of this non-woven fabric are shown in Table 1.

[0046]

[Table 1] In Table 1, 1) is the addition and kneading amount of talc powder to high-density polyethylene, and 2) is the addition and kneading amount of talc powder to polyethylene terephthalate.

As is clear from the results shown in Table 1, the non-woven fabric obtained by the method according to Comparative Example 1 which does not use talc powder is You can see that the power is low. In addition, since the wet non-woven fabric obtained by the method according to Example 8 uses too much talc powder, the wet non-woven fabric obtained by the method according to Examples 5 to 7 has extremely low strength. ing.
Furthermore, when the method according to Example 8 is adopted, talc powder is likely to adhere to the periphery of the discharge hole, complicated maintenance is required, and operability is poor.

Examples 9 to 14 and Comparative Examples 2 to 4 As shown in Tables 2 and 3, the amount of methylene chloride in the preparation of the spinning mixed solution was changed to change the polymer concentration, and the spinning was performed. The same conditions as in Example 1 except that the holding temperature of the mixed solution was changed, the time until the spinning mixed solution was discharged after the polymer was dissolved, or the pressure in the pressure drop chamber was changed. A non-woven fabric was obtained. The characteristic values and the like of this nonwoven fabric are shown in Tables 2 and 3. When the amount of methylene chloride as a solvent was changed, the size of the autoclave was also changed to match it.

[0049]

[Table 2]

[0050]

[Table 3]

The wet nonwoven fabrics obtained by the methods according to Examples 9 to 12 were satisfactory, with no coloring, high strength and good other properties. On the other hand, in the methods according to Comparative Examples 2 to 4, good reticulated fibers could not be obtained, and it was difficult to obtain wet nonwoven fabrics for the following reasons. That is,
In the method according to Comparative Example 2, the holding temperature of the spinning mixed solution was low, and the polymer was not sufficiently dissolved in the solvent. Therefore, reticulated fibers could not be obtained even by flash spinning. In the method according to Comparative Example 3, the holding temperature of the spinning mixed solution was too high, and the polymer dissolved in the solvent was decomposed, so that reticulated fibers could be obtained even by flash spinning. There wasn't. In the method according to Comparative Example 4, since the polymer concentration is too high, the fibers obtained by flash spinning become tubular fibers instead of reticulated fibers, and it is difficult to obtain fibrid-like short fibers that can be paper-formed even when beaten. there were. In the method according to Example 13, the polyester mixed polymer was decomposed mainly because the holding time of the spinning mixed solution was long, and the substantially continuous reticulated fiber could not be obtained. However, the fibrous short fibers could be obtained by beating the reticulated short fibers having non-uniform fiber length, and the wet non-woven fabric could be produced. In addition, the obtained wet-laid nonwoven fabric was colored due to the polyester polymer. In the method according to Example 14, it was not possible to obtain substantially continuous reticulated fibers because the polymer concentration of the spinning mixed solution was low, but Example 1 was used.
It was possible to fabricate a wet nonwoven fabric in the same manner as in No. 3.

Examples 15 to 18 In the hydraulic clearance calendering machine used in Example 1, the calender roller heating temperature and the linear pressure applied to the wet web by the pair of calender rollers were set as shown in Table 4. Example 1 except that it was changed
A wet non-woven fabric was obtained under the same conditions as above. The characteristic values and the like of this wet-laid nonwoven fabric are as shown in Table 4.

[0053]

[Table 4]

The wet non-woven fabrics obtained by the methods according to Examples 15 to 18 were satisfactory, with no coloring, high strength and good other properties.

[0055]

The method for producing a wet-laid nonwoven fabric according to the present invention uses a spinning mixed solution prepared by dissolving an olefin polymer and an ester polymer in a solvent and applies a flash spinning method to obtain reticulated fibers, The fibrid short fibers obtained by beating the reticulated fibers are made into paper. Since the olefin-based polymer and the ester-based polymer are incompatible with each other, both polymers are separated or divided immediately after flash spinning to form a fibril fiber. Therefore, it is a fibril fiber having a very fineness, and a fibril fiber having an olefin polymer as a main component and a fibril fiber having an ester polymer as a main component can be obtained, and both fibril fibers have a three-dimensional network structure. Thus, a reticulated fiber is obtained which is connected so that When this reticulated fiber is beaten, the connection between both fibril fibers is partially released, and fibrid short fibers having a form such as pulp fibers in which both fibril authorities are connected in a whisker shape are obtained.
Further, since the spinning mixed solution used in the present invention is mixed with an inorganic powder that can serve as a crystal nucleating agent, extremely fine fibril fibers are sufficiently crystallized, and although the fineness is fine, its strength is relatively high. It has become a thing.

[0056]

EFFECTS OF THE INVENTION Therefore, the wet non-woven fabric according to the present invention, which is produced by making such fibrid-like short fibers as a paper, has the fibrid-like short fibers formed of ultrafine and high-strength fibril fibers as constituent fibers, and Since the contact points between the short staple fibers are self-fused over the whole, they have the effect of high strength. Further, since the diameter of the fibril fibers constituting the fibrid short fibers is extremely thin, the gap between the fibrid short fibers is extremely small,
Fine dust can be satisfactorily removed, and the filtration efficiency is significantly improved. Further, since the fibril fiber is extremely fine, it is difficult to see through even a wet non-woven fabric having a low basis weight, and the printability can be improved.

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Claims (5)

[Claims] 1. An olefin fibril fiber containing an olefin polymer as a main component and an ester fibril fiber containing an ester polymer as a main component are connected to each other,
And the olefinic fibril fiber and / or the ester fibril fiber contains an inorganic powder capable of becoming a crystal nucleating agent, and is composed of fibrid short fibers, and further between the fibrid short fibers. A wet non-woven fabric, characterized in that the contact points are entirely self-bonded. 2. The wet non-woven fabric according to claim 1, wherein the olefin-based fibril fiber and the ester-based fibril fiber each contain 0.1 to 5% by weight of an inorganic powder that can serve as a crystal nucleating agent. 3. A spinning mixed solution in which an olefin polymer and an ester polymer are dissolved in a solvent, and an inorganic powder capable of serving as a crystal nucleating agent is dispersed, which is at a predetermined temperature and at least an autogenous pressure. The spinning mixed solution held below is discharged from a discharge hole to a region under a temperature and a pressure lower than the predetermined temperature and the autogenous pressure to form a substantially continuous reticulated fiber, and then the reticulated fiber is cut. To obtain reticulated short fibers, beat the reticulated short fibers to form fibrid short fibers, and then disperse the fibrid short fibers in a water bath to obtain a slurry. After forming a web and subsequently removing the water content contained in the wet web, heat is applied to the entire surface to self-melt the contact points between the fibrid-like short fibers over the whole. Wear A method for producing a wet non-woven fabric, comprising: 4. An olefin-based polymer and an ester-based polymer are mixed with 0.1 to 5% by weight of an inorganic powder capable of becoming a crystal nucleating agent, and the olefin-based polymer and the ester-based polymer are mixed in a solvent. The polymer is dissolved and the inorganic powder is dispersed to prepare a spinning mixture solution having a total polymer concentration of the olefin polymer and the ester polymer of 5 to 30% by weight. 4 at a temperature of ~ 240 ° C
While maintaining the pressure of 0 kg / cm ² or more, the spinning mixed solution is discharged from the discharge hole into the atmosphere within 90 minutes after the olefin polymer and the ester polymer are dissolved. To form a continuous reticulated fiber, and then cut the reticulated fiber to obtain a reticulated short fiber, beat the reticulated short fiber to form a fibrid short fiber, then, the fibrid short fiber By dispersing in a water bath to obtain a slurry, papermaking the slurry to form a wet web, subsequently removing water contained in the wet web, and then applying heat to the entire surface, A method for producing a wet non-woven fabric, characterized in that the contact points between the fibrid-like short fibers are self-fused over the whole. 5. A spinning mixed solution in which an olefin polymer and an ester polymer are dissolved in a solvent, and an inorganic powder capable of becoming a crystal nucleating agent is dispersed, under a predetermined temperature and a predetermined pressure. The spinning mixed solution held at is discharged from a discharge hole to a region under a temperature and a pressure lower than the predetermined temperature and the predetermined pressure to form a substantially discontinuous short fiber, and then the short short fiber. To form fibrid-like short fibers, and then the fibrid-like short fibers are dispersed in a water bath to obtain a slurry, and the slurry is formed into a wet web, and subsequently, in the wet web. A method for producing a wet non-woven fabric, characterized in that after the contained water is removed, heat is applied to the entire surface so that the contact points between the fibrid-like short fibers are entirely self-fused.