JPH06257011A - Polyolefinic grid fiber - Google Patents

Abstract

PURPOSE:To obtain grid fiber having high strength and high modulus, comprising fibrils of a polyethylenic polymer and fibrils of a polypropylene-based polymer. CONSTITUTION:The polyolefinic grid fiber comprises fibrils A of a polyethylenic polymer and fibrils B of a polypropylene-based polymer in the ratio of 5:95-95:5 by weight and has >=50wt.% total of both fibrils. The polyolefinic grid fiber is obtained by dissolving both the polymers in a solvent of the same bath at high temperature under high pressure to give a solution, subjecting the solution as a spinning solution to flash spinning.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin-based reticulated fiber having a high strength and a high modulus, which contains a fibril composed of a polyethylene polymer and a fibril composed of a polypropylene polymer.

[0002]

2. Description of the Related Art Conventionally, as ultrafine fibers, fibers obtained by melt spinning a two-component filament in which two different polymers are arranged in a sea-island type and removing one polymer with a solvent,
A fiber obtained by a so-called melt blown method in which a molten polymer is extruded from a spinning hole and pulled at a high speed by a high temperature air flow is known. However, in the former two-component filaments, one polymer is removed with a solvent, so the obtained ultrafine fibers consist of a single polymer, and the polymer is dissolved and removed during the production of this filament. Although the latter filament is indeed an ultrafine fiber, it is necessary to draw and thin the polymer in the molten state immediately after discharge when manufacturing this filament. Stretch orientation and crystallization do not proceed sufficiently, and thus the strength of the obtained fiber is not improved.
On the other hand, as an ultrafine mesh fiber, US Pat.
No. 9 discloses a technique for obtaining the above-mentioned fibers by a so-called flash-spinning method in which a solution obtained by dissolving a thermoplastic polymer in a specific solvent under high temperature and high pressure is further pressurized to an autogenous pressure or higher and spun into the atmosphere. It is disclosed. However, since this reticulated fiber is composed of a single thermoplastic polymer,
The drawbacks inherent to polymers limit the application of the product. For example, when a polyethylene-based polymer is used as the thermoplastic polymer, the resulting reticulated fiber has a low modulus, and when the reticulated fiber is used as a fabric, the feeling of wearing when used is poor, and the polyethylene-based heavy polymer is used. There is a problem that the slimy feeling peculiar to coalescence is not eliminated. On the other hand, when a polypropylene-based polymer is used as the thermoplastic polymer, the obtained reticulated fiber has high modulus, but has low strength and inferior light resistance.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and is a high-strength and high-modulus fabric containing a fibril made of a polyethylene-based polymer and a fibril made of a polypropylene-based polymer. The present invention aims to provide a polyolefin-based reticulated fiber suitable as a material for knitting, dry non-woven fabric, synthetic pulp, wet non-woven fabric and the like.

[0004]

The present inventors have arrived at the present invention as a result of extensive studies to solve the above problems. That is, the present invention relates to a fibril A made of a polyethylene polymer and a fibril B made of a polypropylene polymer.
The subject matter is a polyolefin-based reticulated fiber containing and satisfying the following formulas (1) and (2). 5/95 ≦ [A (wt%) / B (wt%)] × 100 ≦ 95/5 (1) A (wt%) + B (wt%) ≧ 50 (wt%) ... (2)

Next, the present invention will be described in detail. The reticulated fiber of the present invention comprises a fibril A made of a polyethylene polymer and a fibril B made of a polypropylene polymer. A fibril A made of a polyethylene-based polymer which is one of the constituent elements of the reticulated fiber of the present invention.
The term "fiber-forming low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene" or "copolymerized polyethylene in which other components are copolymerized with ethylene as the main component," and its melting point Is 100 ° C. or higher. If the melting point of these polymers is less than 100 ° C., they will be melted even by boiling water, and the practicality of fibril A will deteriorate. In addition, the higher the density of these polymers, the more the module thereof is improved when fibril A is used,
Moreover, the slimy feel and tackiness of the fibril A are reduced, which is preferable.

The fibril B, which is a polypropylene-based polymer which is another constituent of the reticulated fiber of the present invention, is mainly composed of fiber-forming crystalline polypropylene or propylene, which is a copolymer of other components. It is made of polymerized polypropylene or the like and has a melting point of 100 ° C. or higher. If the melting point of these polymers is less than 100 ° C., they will be melted even by boiling water, and the practicality of fibril B will deteriorate.

The reticulated fiber of the present invention contains the fibril A made of the polyethylene polymer and the fibril B made of the polypropylene polymer so as to satisfy the above formulas (1) and (2). is there. In the reticulated fiber of the present invention, the content ratio of fibril A and fibril B [A (wt%) / B (wt%)] × 100 is [5/9
5], that is, when the fibril A is less than 5 relative to the fibril B95, the strength and the modulus of the obtained reticulated fiber are lowered, which is not preferable. On the other hand, when the content ratio exceeds [95/5], that is, when the fibril A exceeds 95 with respect to the fibril B5, the modulus of the obtained reticulated fiber is lowered, and when the reticulated fiber is used to fabricate, for example, Is unfavorable because it is weak and the feeling of wearing becomes poor. Therefore, in the present invention, this content ratio is 5 /
95-95 / 5, preferably 15-85-85 / 1
5, and particularly preferably 25/75 to 75/25. Further, in the reticulated fiber of the present invention, when the content ratio of the fibril A and the fibril B, that is, [A (wt%) + B (wt%)] is less than 50 wt%, the present invention has high strength and high strength. Since it has a high modulus, it is impossible to obtain a reticulated fiber suitable as a material for the above-mentioned use.

The reticulated fiber of the present invention is composed of two kinds of polymers as described above, and fibrils A and B having an equivalent diameter of 0.01 to 10 μm are continuously gathered to form a three-dimensional reticulated structure. It has a net-like structure. The smaller the equivalent diameter of these fibrils A and B,
When the obtained reticulated fiber is used to form, for example, a woven fabric, a knitted fabric, or a non-woven fabric, the denseness and the flexibility can be improved, and in particular, the non-woven fabric can also reduce the bactericidal property while sufficiently retaining the moisture permeability. Therefore, it is preferable that the equivalent diameter of the fibrils A and B is 0.01 to 10 μm, and particularly the denseness, flexibility, or high moisture permeability /
When low bactericidal property is required, it is preferably 0.01 to 0.1 μm.

In the present invention, the reticulated fiber contains the above-mentioned two kinds of fibrils A and B in a content ratio of 50% by weight or more. The fibril to be mixed is a thermoplastic polymer having a fiber-forming property, which is soluble in a solvent for dissolving the polyethylene-based polymer and the polypropylene-based polymer and can be flash-spun. Polymers such as polyethylene-based polymers different from those used for fibrils A and B, polypropylene-based polymers such as copolymers thereof, polyethylene terephthalate-based polymers, polybutylene terephthalate-based polymers or polyester-based copolymers thereof Polymer,
Alternatively, a fibril made of a thermoplastic polymer such as an ethylene vinyl alcohol polymer may be used.

The reticulated fiber of the present invention can be obtained, for example, from US Pat.
It can be efficiently produced by the so-called flash spinning method as described in JP-A-227794. That is, the polyethylene-based polymer and the polypropylene-based polymer, or if necessary, the polyethylene-based polymer and the polypropylene-based polymer and the other thermoplastic polymer as described above, in a solvent of the same bath at high temperature and high pressure. The solution obtained by dissolving below was used as a spinning solution, which was spun into the atmosphere through a spinning hole having a pressure drop chamber while further pressurizing it above autogenous pressure, and the solvent was instantaneously vaporized immediately after spinning. Form a reticulated fiber structure. Solvents used for preparing the solution include aromatic hydrocarbons such as benzene and toluene,
Aliphatic hydrocarbons such as butane, pentane, hexane, heptane, octane or their isomers and homologues, alicyclic hydrocarbons such as cyclohexane, methylene chloride, carbon tetrachloride, chloroform, 1,1-dichloro-2 , 2 difluoroethane, 1,2-dichloro-1,1 difluoroethane, methyl chloride, ethyl chloride, halogenated hydrocarbons such as fluorocarbons, alcohols, esters, ethers,
Ketone, nitrile, amide, sulfur dioxide, carbon disulfide,
Unsaturated hydrocarbons such as nitromethane or mixtures of the solvents mentioned above can be used. Methylene chloride as a solvent, 1,1-dichloro-2,2 difluoroethane,
The use of 1,2-dichloro-1,1 difluoroethane is preferable because it does not harm the global environment as seen when conventional freon is used as a solvent.

The polyethylene-based polymer is AS
The melt index measured by the method described in TM-D-1238 (E) is 0.3 g / 10 minutes or more and 30 g /
The polypropylene-based polymer having a melt flow rate of 1 g / 10 or less measured by the method described in ASTM-D-1238 (L) is used for 10 minutes or less.
It is preferable to use one having a length of at least 40 g / 10 min. The melt index of the polyethylene polymer is 0.
If it is less than 3 g / 10 min and the melt flow rate value of the polypropylene-based polymer is less than 1 g / 10 min, the melt viscosity of the solution obtained by dissolving the polymer in the solvent is remarkably increased and the ultrafine fibrils A and B are obtained. Is difficult to obtain, which is not preferable. On the other hand, when the melt index of the polyethylene-based polymer exceeds 30 g / 10 minutes and the melt flow rate of the polypropylene-based polymer exceeds 40 g / 10 minutes, the degree of polymerization is too low to follow the spinning speed during flash spinning. However, the spun fibers have a short fiber-like or substantially powdery form, and even if ultrafine fibers A and B could be obtained, their strength is not improved. In this case, the slimy feeling and the tackiness increase, and also in the case of the fibril B, the tackiness increases and the handling property decreases, which is not preferable. As for the other thermoplastic polymers to be mixed with these polymers as necessary, it is advisable to appropriately select the degree of polymerization that can follow the spinning speed at the time of flash spinning, as described above. In the present invention, the above-mentioned two kinds of polymers, other thermoplastic polymers which are mixed as necessary, or a spinning solution prepared by dissolving these in a solvent are used in the matting agent usually used for fibers. Agents, light-proof agents, heat-resistant agents, pigments, fiber-opening agents, ultraviolet absorbers, heat storage agents, stabilizers, etc. can be added as long as the effects of the present invention are not impaired.

Taking into consideration the spinnability in flash-spinning using this spinning solution and the characteristics of the obtained reticulated fiber, these are the autogenous pressure or the nitrogen content of the polymerization degree of the polymer in the spinning solution and the temperature of the solvent. Since it depends on the pressure state, etc., the concentration of the polyethylene-based polymer and the polypropylene-based polymer, or the concentration of these polymers and other thermoplastic polymers to be mixed with them, as needed, is generally determined. Although it is difficult to specify, it is preferable to specify 5% by weight or more and 30% by weight or less of the total polymer and 95% by weight or more and 70% by weight or more of the solvent. If the concentration of this total polymer is less than 5% by weight,
It is difficult to obtain fibers having a continuous structure of fibrils. On the other hand, if the concentration of the polymer exceeds 30% by weight, the concentration of the polymer becomes too high and the dissolution becomes non-uniform, so that fine fibrils can be obtained. In addition, the spun fiber cannot be obtained as a fiber having a high-strength fibril, in which the fibrils are bonded to each other at their side faces and have a hollow structure having a cavity inside. Not preferable.

When preparing a spinning solution, all the above-mentioned polymers are used as solutes, and these are filled with a solvent in a dissolution apparatus, and a solution is prepared while heating and kneading, and the obtained solution is used as a spinning solution. As the melting device, an autoclave which has been used most widely in the past, or a continuous melting device including, for example, an extruder and a kneading device arranged continuously with the extruder can be used. When the temperature of the spinning solution is increased and kneaded in the dissolving device, the spinning pressure is further increased by pressurizing with an inert gas such as nitrogen or carbon dioxide having a purity of 99% by weight or more and not containing oxygen. It is possible and preferable. The gas of nitrogen or carbon dioxide is a so-called inert gas, which is hardly dissolved in the spinning solution used in the present invention and does not adversely affect the polymer, so that a substantial pressure is applied to the spinning solution. be able to. Further, when the spinning solution is prepared in the dissolving apparatus, nonionic surface active agents such as monoesters of lauric acid, stearic acid, oleic acid, etc., lauryl alcohol, stearyl alcohol, oleyl alcohol, etc. are prepared in the solution. Surface active agents such as polyoxyethylene adducts can also be added. By adding this surfactant, the spinning solution can be stably maintained in an emulsified state.

The dissolution time for dissolving all the polymers in the solvent in the dissolution apparatus is preferably 5 minutes or more and 90 minutes or less. When the dissolution time during dissolution exceeds 90 minutes, the thermal decomposition of the polypropylene-based polymer in the spinning solution becomes severe and the strength of the fibril B is not improved. On the other hand, when the dissolution time is less than 5 minutes, All of them are not preferable because the dissolution of all the polymers becomes insufficient and it becomes difficult to obtain fibers composed of uniform fibrils, or the filters are clogged during spinning.

The temperature at which the spinning solution is dissolved, that is, the melting temperature, and the temperature at which the spinning is performed, that is, the spinning temperature, are all such that all the polymer is sufficiently dissolved in the solvent, and the spinning solution is flash-spun to produce fine fibers. The temperature is not particularly limited as long as it is a temperature at which fibers having an aggregated and three-dimensionally reticulated structure can be obtained, but if it is intentionally specified, it is preferably 150 ° C or higher and 230 ° C or lower. . This melting temperature or spinning temperature is 150
If the temperature is lower than ℃, it is not possible to obtain ultrafine fibrils because the whole polymer is not uniformly dissolved in the solvent. On the other hand, if the melting temperature or spinning temperature exceeds 230 ℃, thermal decomposition of the polypropylene polymer occurs. The strength of the obtained fibril B is not improved, and coloring occurs even if the strength is maintained, which is not preferable.

The pressure for flash-spinning the spinning solution depends on the concentration of all polymers, the amount of solvent, the amount of nitrogen injected, etc., but is not limited to any particular value.
It is preferably not less than kg / cm ^{2 and not} more than 160 kg / cm ² . The strength of the fiber is expressed by sufficiently stretching and orienting the molecular chains of the polymer. Therefore, the flash spinning method, that is, the spinning solution is spun through a spinning hole having a pressure drop chamber, and immediately after spinning, the solvent is used. In the method of instantaneously evaporating the solvent to form a reticulated fiber structure, this stretching and orientation is performed by the explosive force that accompanies the instantaneous evaporation of the solvent immediately after spinning. The explosive force is the vaporizing force when the solvent is instantly vaporized, and usually means the force when the solvent vaporizes at once in 0.1 second or less. Therefore, the spinning pressure is preferably 40 kg / cm ² or more and 160 kg / cm ² or less, and when the spinning pressure is less than 40 kg / cm ² , the explosive force at the time of flash spinning using the spinning solution is decreased and the fiber is reduced. Orientation is insufficient and the strength is not improved, and the spinning state becomes non-uniform, making it difficult to obtain highly fibrillated reticulated fibers in a stable manner, while the pressure is 160 kg / When it exceeds cm ² , the viscosity of the polymer in the spinning solution is lowered and the strength of the fibril is not improved, either of which is not preferable.

[0017]

The reticulated fiber of the present invention comprises ultrafine fibers A and B composed of a polyethylene polymer and a polypropylene polymer which are incompatible with each other.
Regarding the fact that polyethylene-based polymers and polypropylene-based polymers are incompatible with each other, in order to evaluate the compatibility, for example, “New Values of the Sol
ubility Parameters from Vapor Pressure Data ”, J.
When the compatibility of the polymer is calculated from the molecular formula by the Hoy method described in Paint Technol. 42, 76 (1970), the calculated value is 9.0 for the polyethylene polymer and 7.8 for the polypropylene polymer. It is evaluated as a mutually incompatible combination. In the reticulated fiber of the present invention, since the fibrils A and B composed of the above-mentioned two polymers which are incompatible with each other are independently contained, the properties of both polymers are independent in the ultrafine reticulated fiber. Will be expressed. Moreover, when the reticulated fiber is obtained by the flash-spinning method, a solution containing at least 50% by weight of the above-mentioned two types of incompatible polymers is used as a spinning solution, so that finer fibrils can be formed than ever before. is there.

[0018]

EXAMPLES Next, the present invention will be specifically described based on Examples. The measurement and evaluation of various characteristics in the examples were carried out by the following methods. Melting point of polymer: Differential scanning calorimeter D manufactured by Perkin Elmer
The melting point was defined as the temperature at which the exothermic value of the melting and absorption heat curve measured using the SC-2 type at a temperature rising rate of 20 ° C./min. Melt index (g / 10 minutes): ASTM D 1
It was measured by the method described in 238 (E). Melt flow rate value (g / 10 minutes): ASTM D
It was measured by the method described in 1238 (L). Fiber fineness (denier): The fineness was determined according to the method described in JIS L-1090. Tensile strength (g / denier) of fiber: Tensilon UTM-4-1-100 manufactured by Toyo Baldwin Co., Ltd. was used, and 20 times / 5 cm of twist was added to each of 20 samples having a sample length of 10 cm, and a gripping interval was 5 cm and a tensile force was applied. The tensile strength was measured at a speed of 5 cm / min, and the average value of the obtained tensile strengths was converted to the fineness per unit weight to obtain the fiber strength (g / denier). Tensile elongation of fiber (%): Tensilon UTM-4-1-100 manufactured by Toyo Baldwin Co., Ltd. was used to measure the above 20 samples at a tensile rate of 5 cm / min. The tensile elongation (%) of the fiber was used. Fiber module (g / denier): A tensile test was conducted in the same manner as the measurement of tensile strength, and JIS L-1013 was used.
The initial tensile resistance was measured according to the method for measuring initial tensile resistance described in 7.10, and the average value of the obtained resistances was taken as the module (g / denier) of the fiber. Specific surface area (m ² / g) of fiber: The specific surface area (m ² / g) of the fiber was determined by the BET nitrogen adsorption method using a nitrogen adsorption device BELSORP28 type manufactured by Bell Japan.

Example 1 A high-density polyethylene polymer having a melting point of 132 ° C., a density of 0.96 g / cm ³ and a melt index of 0.8 g / 10 min, a melting point of 162 ° C. and a density of 0.905 g / c
A crystalline polypropylene polymer having m ³ and a melt flow rate value of 5 g / 10 min, dry ice, and isooctyl stearate and isostearyl ester as surfactants were filled and closed in an autoclave, and then methylene chloride was added. Was poured into an autoclave and the solution was heated with moderate stirring. This solution has a polymer concentration of 15% by weight, a polyethylene polymer / polypropylene polymer weight ratio of 40/60, carbon dioxide gas of 15% by weight,
70% by weight of methylene chloride. The amount of the surface active agent added is 0.2% by weight based on the solution.
At this time, the internal temperature of the autoclave rises from 80 ° C
The temperature rising time until reaching 80 ° C. was 25 minutes.
Then, this solution was kneaded at a temperature of 180 ° C. for 30 minutes to obtain a uniform solution. At this time, the internal pressure of the autoclave is 9
It was 1 kg / cm ² G. Then, at this internal pressure, that is, the spinning pressure of 91 kg / cm ² G, the valve of the autoclave was immediately opened to have a pressure drop chamber having a hole diameter of 0.7 mm.
The spinning solution was spun into the atmosphere through a spinning hole having a pore length / pore diameter ratio of 1 to obtain a reticulated fiber composed of the polyethylene polymer and the polypropylene polymer. At this time, the pressure in the pressure drop chamber was 82 kg / cm ² G. The properties of the obtained reticulated fiber are shown in Table 1. In Table 1, PE is a polyethylene polymer, PP is a polypropylene polymer, MIX is a melt index, and MFR is a melt flow rate value. As is clear from Table 1, this reticulated fiber had a practical strength, a high modulus, and no coloring at all. Also, when the surface of the fiber was photographed with an electron microscope and the surface morphology was observed, this fiber
The fibrils had a structure in which a large number of fibrils having a fibril diameter of about 0.1 to 1.0 μm as a main body were aggregated and spread in a net shape.

Examples 2-6 and Comparative Examples 1-2 A high-density polyethylene polymer having a melting point of 132 ° C., a density of 0.96 g / cm ³ and a melt index of 0.6 g / 10 min, and a melting point of 162. ℃, density 0.905g / c
m ³ a and a melt flow rate value using a crystalline polypropylene polymer of 3 g / 10 min, except that the weight ratio of the polyethylene polymer / polypropylene polymer were changed as shown in Table 1 as in Example 1 Then, a reticulated fiber composed of the polyethylene polymer and the polypropylene polymer was obtained. At this time, the pressure in the pressure drop chamber is approximately 90 kg / c.
It was m ² G. The properties of the obtained reticulated fiber are shown in Table 1. The reticulated fibers of Examples 2 to 6 had a practical strength as shown in Table 1, a high modulus, and no coloring at all. In addition, when the surface of the fiber was photographed with an electron microscope and the surface morphology was observed, it was found that a large number of fibrils having a fibril diameter of about 0.1 to 1.0 μm gathered and spread in a mesh shape. It had a different structure. On the other hand, the reticulated fiber of Comparative Example 1 has a good fibril formation state, but has a low modulus because it is formed from the polyethylene polymer alone, and does not eliminate the slimy feeling peculiar to the polyethylene polymer. there were. Further, the reticulated fiber of Comparative Example 2 was not formed in a good fibril state and was slightly low in strength because it was formed from the polypropylene polymer alone.

[0021]

[Table 1]

[0022]

The reticulated fiber of the present invention contains fibrils made of a polyethylene polymer and fibrils made of a polypropylene polymer, has high strength and high modulus, and is used as long fibers. In some cases, as materials such as woven or knitted or dry non-woven fabric,
When long fibers are cut into short pieces and used as short fibers, they can be suitably used as materials such as synthetic pulp and wet non-woven fabric. For example, sound absorbing material, absorbent material, artificial leather, hygiene material, protection It can be used in applications such as clothes, curtains, sheets, wiping cloths, filters, house wraps, and paper.

Claims (1)

[Claims] 1. A polyolefin reticular fiber comprising fibril A made of a polyethylene polymer and fibril B made of a polypropylene polymer so as to satisfy the following formulas (1) and (2). 5/95 ≦ [A (wt%) / B (wt%)] × 100 ≦ 95/5 (1) A (wt%) + (B wt%) ≧ 50 (wt%) (2)