JP2013076192A - Polyolefin composite fiber and nonwoven fabric made thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefin composite fiber derived from a biomass-originated material as a raw material with performance equivalent to the conventional one, thereby suppressing the consumption of petroleum resources and suppressing the net increase of carbon dioxide after disposal, and to provide a nonwoven fabric made thereof.SOLUTION: A polyolefin composite fiber comprises two polyolefins with different melting temperatures, which are derived from a biomass-originated component as a raw material comprising radioactive carbon (carbon 14) by means of the accelerator mass spectrometer (AMS). In the two polyolefins, a polyolefin with lower melting temperature composes at least a part of an outer circumference of the cross section of a fiber while a polyolefin with higher melting temperature composes the other part of the cross section of the fiber.

Description

  The present invention relates to a composite short fiber derived from biomass and a nonwoven fabric using the same.

  Nonwoven fabrics made of composite fibers made from polyolefins such as polyethylene and polypropylene have excellent mechanical properties and chemical stability. Nonwoven fabrics made of these are sanitary materials such as diapers and napkins, tea packs, It is widely used for household materials such as wipers and industrial materials such as battery separators and filters.

  By the way, polyolefins are conventionally made from valuable fossil resources such as petroleum. In addition, when discarded by incineration, carbon originally contained in fossil resources is released into the air as carbon dioxide, so the newly generated carbon dioxide increases the greenhouse effect, resulting in global warming. It is one of the causes.

  On the other hand, the plant which is the origin of biomass can make biomass, such as starch and cellulose, by photosynthesis from solar energy, carbon dioxide, and water (for example, refer patent documents 1 and 2). Synthetic fibers and non-woven fabrics made thereof can also reduce the amount of petroleum resources used if such biomass is used as a starting material. In addition, even if carbon dioxide is emitted after incineration, carbon dioxide in the environment is originally absorbed and fixed by plants, which affects the balance of carbon dioxide in the atmosphere. It can be considered as carbon neutral, which is not given (or suppresses the net increase of carbon dioxide).

  Therefore, for example, a composite fiber using a biomass-derived polyolefin in a part of the fiber cross section has been proposed (see, for example, Patent Document 3). Aromatic polyesters are used as constituents other than biomass-derived polyolefins, but in the current commercial technology, aromatic polyesters must use at least part of raw materials derived from fossil resources. However, it is insufficient from the viewpoint of the carbon neutral. A composite fiber using biomass-derived polylactic acid for the core and biomass-derived polyolefin for the sheath has also been proposed (see, for example, Patent Document 4). According to this technique, the content of the biomass-derived substance in the composite fiber can be increased, but it is difficult to obtain a material that satisfies the performance such as mechanical characteristics and durability.

JP 2009-091694 A JP 2008-150759 A JP 2011-038207 A JP 2010-066532 A

  The present invention has been made against the background of the above prior art, and its purpose is to use a composite fiber containing a biomass-derived substance at a high content rate, while maintaining the same features as a conventional polyolefin composite fiber. It is to suppress the consumption of resources and to suppress the net increase of carbon dioxide in the atmosphere accompanying incineration and disposal.

  As a result of investigations to solve the above problems, the above object is achieved by a composite fiber using two kinds of polyolefins each having a different melting point and a nonwoven fabric using the same, both of which are made of biomass-derived raw materials. That is, at least a part of the fiber cross section is made of a low melting point olefin, and the other part of the fiber cross section is a composite fiber made of a polyolefin having a melting point higher than that of the polyolefin, the accelerator mass in the composite fiber This is achieved by including biomass-derived carbon as measured by radioactive carbon (carbon 14) measurement using a spectrometer (AMS).

  That is, the present invention is a composite fiber comprising two types of polyolefins having different melting points from a biomass-derived component containing radioactive carbon (carbon 14), and having a relatively low melting point in the two types of polyolefins. This is a composite fiber characterized in that the polyolefin constitutes at least a part of the outer periphery of the fiber cross section, and a nonwoven fabric comprising the same, and the present invention can solve the above problems.

The conjugate fiber of the present invention is a conjugate fiber made of polyolefin, and contains radioactive carbon (carbon 14) measured by an accelerator mass spectrometer (AMS). Preferably, the polyolefin is a biomass-derived carbon 14 based on the concentration (100%) of radioactive carbon (carbon 14, ¹⁴ C) in the circulating carbon as of 1950 as measured using an accelerator mass spectrometer (AMS). The ratio is 70% or more. The composite fiber and the non-woven fabric using the composite fiber according to the present invention greatly contribute to the suppression of the depletion of petroleum resources when used as a general-purpose material. The increase in the atmosphere can be greatly suppressed.

  Hereinafter, the present invention will be described in detail. The present invention is a composite fiber composed of two types of polyolefins having different melting points. Among the two types of polyolefins, the low melting point polyolefin constitutes at least a part of the outer periphery of the fiber cross section, and has a melting point higher than that of the low melting point polyolefin. High-polyolefin is a composite fiber that constitutes the other part of the fiber cross section, and the biomass-derived carbon in the composite fiber is measured by radioactive carbon (carbon 14) measurement using an accelerator mass spectrometer (AMS) described later. Is included. Polyolefins used in the present invention are high density polyethylene (HDPE), medium density polyethylene, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), atactic polypropylene, isotactic polypropylene, syndiotactic polypropylene, Ethylene / propylene copolymer, polybutadiene, polystyrene, polyacrylonitrile, polyvinyl alcohol, polyvinyl acetate, polyvinyl chloride, polyacrylic acid, polyacrylic acid ester (methyl ester, ethyl ester, propyl ester, butyl ester, hexyl ester, etc. ), Polymethacrylic acid, polymethacrylic acid (methyl ester, ethyl ester, propyl ester, butyl ester, hexyl ester, etc.). These components include the above-mentioned other types of polyolefins, polyesters such as polyethylene terephthalate or polybutylene terephthalate, polyamides such as nylon 6,6, polyethers, polyether esters, Polymers such as ether ester amide, polymethylene oxide, polyphenylene ether or polyether imide or various other additives as required, for example, heat stabilizer, hydrophilic agent, antifoaming agent, color adjuster, antioxidant, Additives such as ultraviolet absorbers, infrared absorbers, antistatic agents, antistatic agents, antibacterial agents, fluorescent whitening agents, plasticizers or impact resistance agents may be copolymerized or mixed. In other words, for these purposes, alkali metal compounds, alkaline earth metal compounds, aluminum compounds, carbon compounds such as carbon black or carbon nanotubes, germanium compounds, titanium compounds, chromium compounds, manganese compounds, iron compounds, cobalt compounds, Inorganic compounds such as nickel compounds, copper compounds, zinc compounds, palladium compounds, silver compounds, tin compounds, boron compounds, silicone compounds, sulfur compounds, halogen compounds, phosphorus compounds, antimony compounds, aliphatic hydrocarbon compounds, alicyclic rings Aromatic hydrocarbon compound, aromatic hydrocarbon compound, aliphatic amino compound, aromatic amino compound, nitro compound, nitroso compound, azo compound, urea compound, urethane compound, amide compound, ether compound, thioether compound, epoxy Compounds, carboxylic acid compounds, in a range of 0.01ppm~10.0% by weight of one or two or more relative to the weight of the polyolefin of ester compounds such as organic compounds, may be mixed and blended.

  Among these compounds, examples of alkali metal compounds include lithium fluoride, lithium chloride, lithium bromide, lithium hydroxide, lithium formate, lithium acetate, lithium propionate, lithium butyrate, lithium stearate, and trilithium citrate. , Dilithium hydrogen citrate, lithium dicitrate, lithium gluconate, lithium succinate, dilithium oxalate, lithium hydrogen oxalate, lithium malonate, lithium glutarate, lithium adipate, lithium suberate, lithium azelate , Lithium sebacate, lithium phthalate, lithium hydrogen phthalate, lithium isophthalate, lithium hydrogen isophthalate, lithium terephthalate, lithium terephthalate, lithium metaphosphate, lithium malate, trilithium phosphate, phosphoric acid water Dilithium, lithium dihydrogen phosphate, lithium nitrite, lithium benzoate, lithium hydrogen tartrate, lithium heavy oxalate, lithium biphthalate, lithium bitartrate, lithium bisulfate, lithium nitrate, lithium carbonate, lithium hydrogen carbonate, lactic acid Lithium, lithium sulfate, lithium hydrogen sulfate, sodium fluoride, sodium chloride, sodium bromide, sodium iodide, sodium hydroxide, sodium formate, sodium acetate, sodium propionate, sodium butyrate, sodium stearate, trisodium citrate, Disodium hydrogen citrate, sodium dihydrogen citrate, sodium gluconate, sodium succinate, disodium oxalate, sodium hydrogen oxalate, sodium malonate, sodium glutarate, sodium adipate, sodium Sodium phosphate, sodium azelate, sodium sebacate, sodium phthalate, sodium hydrogen phthalate, sodium isophthalate, sodium hydrogen isophthalate, sodium terephthalate, sodium hydrogen terephthalate, sodium metaphosphate, sodium malate, triphosphate Sodium, disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium nitrite, sodium benzoate, sodium hydrogen tartrate, sodium bioxalate, sodium biphthalate, sodium bitartrate, sodium bisulfate, sodium nitrate, sodium carbonate, Sodium hydrogen carbonate, sodium lactate, sodium sulfate, sodium hydrogen sulfate, potassium fluoride, potassium chloride, potassium bromide, potassium iodide, potassium alum, potassium hydroxide, gi Potassium acetate, potassium acetate, potassium propionate, potassium butyrate, potassium stearate, tripotassium citrate, dipotassium hydrogen citrate, potassium dihydrogen citrate, potassium gluconate, potassium succinate, dipotassium oxalate, hydrogen oxalate Potassium, potassium malonate, potassium glutarate, potassium adipate, potassium suberate, potassium azelate, potassium sebacate, potassium phthalate, potassium hydrogen phthalate, potassium isophthalate, potassium hydrogen isophthalate, potassium terephthalate, terephthalic acid Potassium hydrogen, potassium metaphosphate, potassium malate, tripotassium phosphate, dipotassium hydrogen phosphate, potassium dihydrogen phosphate, potassium nitrite, potassium benzoate, potassium hydrogen tartrate, potassium heavy oxalate, heavy hydrogen Potassium rurate, potassium bitartrate, potassium bisulfate, potassium nitrate, potassium carbonate, sodium potassium carbonate, potassium bicarbonate, potassium lactate, potassium sulfate, potassium hydrogen sulfate, rubidium chloride, rubidium chloride, rubidium bromide, rubidium hydroxide, Rubidium formate, rubidium acetate, rubidium propionate, rubidium stearate, tribidium citrate, dirubidium citrate, rubidium dicitrate, rubidium gluconate, rubidium succinate, dirubidium oxalate, rubidium hydrogen oxalate, phthalate Rubidium phosphate, rubidium isophthalate, rubidium terephthalate, trirubium phosphate, dirubidium hydrogen phosphate, rubidium dihydrogen phosphate, rubidium nitrite, rubidium benzoate, rubidium nitrate, Acid rubidium bicarbonate, rubidium, lactic rubidium, rubidium sulfate, hydrogen rubidium sulfate, cesium chloride, cesium hydroxide, cesium acetate, cesium carbonate, cesium benzoate, cesium nitrate, can be exemplified cesium sulfate or lactate cesium. From these compound groups, a single type of compound may be used, or a plurality of types of compounds may be used in combination.

  Examples of the alkaline earth metal compound are not particularly limited as long as they are within a range that can be selected from the same viewpoint as described above, but specifically, calcium chloride, calcium formate, calcium succinate, calcium butyrate Calcium oxalate, calcium phosphate, calcium nitrate, calcium acetate, calcium lactate, magnesium chloride, magnesium formate, magnesium succinate, magnesium butyrate, magnesium oxalate, magnesium phosphate, magnesium nitrate, magnesium acetate, magnesium lactate or magnesium sulfate, etc. It can be illustrated. These may be a single type of compound or a combination of a plurality of types of compounds. Among them, it is preferable to use a compound containing a sodium atom or a potassium atom, more specifically a sodium salt or a potassium salt. On the other hand, when viewed from the anion species side, among these, acetates and / or carbonates are preferred. Further, an alkali metal salt and an alkaline earth metal salt may be used in combination.

  Specifically, the polyolefin used in the present invention is polypropylene, high-density polyethylene, ethylene / propylene random copolymer, polyethylene obtained by block copolymerization or graft copolymerization of maleic anhydride and block copolymerization or grafting of maleic anhydride. Preferably, the polyolefin is at least one selected from the group consisting of copolymerized polypropylene. More specifically, the low melting point polyolefin polymer used in the present invention includes high-density polyethylene, ethylene / propylene random copolymer polyolefin, polyethylene obtained by block or graft copolymerization of the third component, and block or graft copolymerization of the third component. Preference is given to polypropylene. The third component in this case includes vinyl acetate, vinyl chloride, styrene, methyl acrylate, ethyl acrylate, isopropyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, acrylic acid, methacrylic acid, and maleic anhydride. it can. Among these, particularly selected from the group consisting of high-density polyethylene, ethylene / propylene random copolymer, polyethylene obtained by block copolymerization or graft copolymerization of maleic anhydride, and polypropylene obtained by block copolymerization of maleic anhydride. Polyolefins are preferred. In addition, a plurality of the above-mentioned polyolefin polymers may be selected and mixed for use. Preferred examples of the polyolefin having a higher melting point than the low melting point polymer include isotactic polypropylene and syndiotactic polypropylene.

  As a method for producing a biomass-derived polyolefin in the present invention, for example, in the case of polyethylene, bioethanol is produced by fermenting biomass-derived components (biomass resources) such as starch and sugar obtained from corn, sugarcane, sweet potato, etc. with microorganisms. Then, this is dehydrated to produce ethylene, and further polymerized to obtain 100% biomass-derived polyethylene. In the case of polypropylene, a method of producing biomass polypropylene by producing propylene by a metathesis reaction using the above bioethylene as a starting material and further polymerizing it can be mentioned. Another method for producing polypropylene is to produce 1,3-propylene glycol by changing the fermentation conditions for the above biomass resources, to obtain propylene by dehydrating it, and by a known polymerization method. By polymerizing, biomass-derived polypropylene can be obtained. About the manufacturing method of this 1, 3- propylene glycol, Japanese translations of PCT publication No. 10-507082 gazette, Japanese translations of PCT publication No. 11-502718 gazette, Japanese translation gazette 2001-504338 gazette, Japanese translation gazette 2002-514426 gazette It is known that it is described in JP 507022, JP-T 2006-512907, JP-T 2007-501324, JP-T 2007-502325, and the like. Further, a copolymer of polypropylene and polyethylene can be obtained by polymerizing a predetermined amount of a mixture of propylene and ethylene obtained as described above by a known method.

  Moreover, the polyolefin used for this invention can improve the function, maintaining a high biomass origin carbon ratio by carrying out graft copolymerization of modified groups, such as maleic anhydride, with respect to the said biopolyolefin. For example, the maleic anhydride graft copolymerized polyolefin is added with 0.1 to 5 parts by weight of a radical initiator with respect to 100 parts by weight of maleic anhydride, and one or more polymerization reactors or single screw extruders and / or two It can be obtained by melt kneading or modifying in a solvent using a screw extruder or the like.

  In addition, it is preferable that the abundance ratio of biomass origin carbon by the measurement of the radioactive carbon (carbon 14) in the composite fiber in this invention is 70% or more. If it is less than 70%, it is not preferable because it replaces the conventional material composed of petroleum-based resources with a material derived from biomass, which does not meet the gist of the present invention to achieve carbon neutrality as a synthetic fiber as a whole. In addition, as a method for producing a polyolefin having a biomass-derived carbon content of 70% or more and less than 100%, it may be produced by polymerizing an olefin consisting only of a biomass-derived olefin and a petroleum-based material, You may manufacture by blending the polyolefin chip | tip which consists only of a biomass-derived polyolefin chip | tip and a petroleum-type raw material. In the above polyolefin polymer, various additives for additives, fluorescent brighteners, stabilizers, flame retardants, flame retardant aids, ultraviolet absorbers, antioxidants, and coloring are used as long as the effects of the present invention are not impaired. A pigment or the like may be contained. These various additives may be added at the time of producing the polyolefin or immediately before spinning the composite fiber.

  Moreover, there is no special restriction | limiting about the molecular weight of these polyolefin, If it is the range of the molecular weight which can exhibit intensity | strength elongation sufficient to spin a composite fiber, it can employ | adopt without a restriction | limiting. Similarly, the MFR of these polyolefins can be used without any particular limitation.

  Here, in specifying the content ratio of the biomass-derived component in the present invention, the meaning of performing measurement of radioactive carbon (carbon 14) will be described below. Biomass-derived components are classified into three types: waste, unused, and resource crops, depending on the form of generation. Specifically, biomass resources include cellulosic crops (pulp, kenaf, wheat straw, rice straw, waste paper, papermaking residue, etc.), lignin, charcoal, compost, natural rubber, cotton, sugarcane, oil (rapeseed oil, cottonseed oil, soybean oil, Coconut oil, etc.), glycerol, carbohydrate crops (corn, potatoes, wheat, rice, cassava, etc.), bagasse, terpene compounds, pulp black liquor, garbage, wastewater sludge and the like. In addition, a method for producing a glycol compound from biomass resources is not particularly limited, but a biological treatment method utilizing the action of microorganisms such as fungi and bacteria, acid, alkali, catalyst, thermal energy or light energy, etc. Known methods such as a chemical treatment method used, or a physical treatment method such as miniaturization, compression, microwave treatment or electromagnetic wave treatment can be used.

In the present invention, the content of radioactive carbon (C14) in the polyolefin composite fiber is defined as the standard (the value is set to 100%) of ¹⁴ C, which is radioactive carbon, in all the carbon atoms constituting the polyolefin. In this case, the weight ratio of ¹⁴ C concentration is shown. The radioactive carbon ¹⁴ C is preferably based on the concentration of ¹⁴ C in the circulating carbon as of 1950. The concentration of ¹⁴ C which is the radioactive carbon can be measured by the following measurement method (radiocarbon concentration measurement). That is, the concentration measurement of ¹⁴ C is carried out by an accelerator mass spectrometry (AMS) combining a tandem accelerator and a mass spectrometer (specifically, ¹² C, ¹³ C) contained in a sample to be analyzed. , ¹⁴ C.) is physically separated using an atomic weight difference by an accelerator, and the abundance of each isotope atom is measured.

In 1 mole of carbon atoms (6.02 × 10 ²³ ) there are about 6.02 × 10 ^{11 14} C, which is about one trillionth of a normal carbon atom. ¹⁴ C is called a radioisotope and its half-life regularly decreases at 5730 years. It takes 26,000 years for all of these to collapse. Therefore, fossil fuels such as coal, oil, and natural gas, which are considered to have passed over 26,000 years after carbon dioxide in the atmosphere has been taken into plants and immobilized, are initially fixed. All of the ¹⁴ C elements that were also included in the are collapsed. Therefore, in the 21st century, ^14C elements are not contained at all in fossil fuels such as coal, oil and natural gas. Therefore, chemical substances produced using these fossil fuels as a raw material do not contain any ¹⁴ C element. On the other hand, ¹⁴ C is a cosmic ray that undergoes a nuclear reaction in the atmosphere, is constantly generated, and balances with the decrease due to radiation decay. The amount of ¹⁴ C is constant in the earth's atmospheric environment.

On the other hand, when carbon dioxide in the atmosphere is taken in and immobilized by plants or animals that eat it, ¹⁴ C is not replenished in the taken-in state, and the half-life of ¹⁴ C Accordingly, the ¹⁴ C concentration decreases at a constant rate with time. Therefore, by analyzing the ¹⁴ C concentration in the glycol compound, it is possible to easily determine whether the raw material is a fossil resource such as a fossil fuel or a glycol compound that uses a biomass resource as a raw material. Also this ¹⁴ C concentration was ¹⁴ C-concentration in the circulating carbon in natural time 1950 with modern standard reference, it is common practice to use the criteria for the ¹⁴ C concentration is 100%. The current ¹⁴ C concentration measured in this way is about 107 pMC (percent modern carbon), and the plastic used as a sample is made of a 100% natural (biological) material. In other words, it is known to show a value of about 107 pMC. This value corresponds to the bio-ization rate 100% mentioned above. On the other hand, it is also known that when this ¹⁴ C concentration is measured using chemical substances derived from fossil fuels such as petroleum, it shows almost 0 pMC. This value corresponds to the bio-ization rate 0% mentioned above. By using these values, it becomes possible to calculate a mixing ratio of a compound derived from a natural resource (a compound derived from a biomass resource)-a compound derived from a fossil resource. Furthermore, it is preferable to use an oxalic acid standard issued by NIST (National Institute of Standards and Technology) as the standard standard reference for the ¹⁴ C concentration. The specific radioactivity of carbon in this oxalic acid ( ¹⁴ C radioactivity intensity per gram of carbon) is separated for each carbon isotope, corrected to a constant value for ¹³ C, and corrected for attenuation from 1950 AD to the measurement date The value subjected to is used as the standard ¹⁴ C concentration value.

Further, ¹⁴ C atoms are added. In the upper part of the atmosphere, the reaction in which cosmic rays (neutrons) collide with nitrogen atoms to generate 14 carbon atoms continues, and since this circulates throughout the atmosphere, In the carbon dioxide, it is measured that carbon 14 is contained at a constant ratio [average value 107 pMC (percent modern carbon)]. On the other hand, the 14 carbon atoms confined in the ground are deviated from the above-mentioned circulation. Therefore, only the reaction of returning to the nitrogen atom occurs with a half-life of 5,370 years while emitting radiation. Almost no 14 carbon atoms remain in the fossil raw materials. Therefore, by measuring the concentration of carbon 14 in the target sample and performing a reverse calculation using the content ratio of carbon 14 in the air [107 pMC] as an index, the ratio of biomass-derived carbon in the carbon contained in the sample is calculated. Can be sought. In the conjugate fiber of the present invention, it is defined that the ratio (ratio) of the biomass-derived carbon is preferably 70% ≧.

The detailed analysis method of the ¹⁴ C concentration in each organic compound first requires pretreatment of the organic compound. Specifically, the carbon contained in the organic compound is oxidized and converted into carbon dioxide. Further, the obtained carbon dioxide is separated from water and nitrogen, and the carbon dioxide is subjected to a reduction treatment and converted into graphite which is solid carbon. The obtained graphite is irradiated with a cation such as Cs ⁺ to generate carbon negative ions. Subsequently, the carbon ion was accelerated using a tandem accelerator, the charge was converted from a negative ion to a positive ion, and the orbits of ¹² C ³⁺ , ¹³ C ³⁺ , and ¹⁴ C ³⁺ were separated and separated by a mass spectrometry electromagnet. ¹⁴ C ³⁺ is measured with an electrostatic analyzer.

  In the conjugate fiber of the present invention, the low melting point polyolefin described above constitutes at least a part of the outer periphery of the fiber cross section, and the other part of the fiber cross section is made of a polyolefin having a higher melting point than the low melting point polyolefin. It is necessary to be a composite fiber having a form. Specifically, the core-sheath type, the concentric core-sheath type, the eccentric core-sheath type, the sea-island type, the side-by-side type, etc. are exemplified. It is preferable for making a formation. Also, the fiber cross-sectional shape is not limited to a round cross section, an elliptical cross section, a multi-leaf cross section such as a 3-8 leaf cross section, a deformed cross section such as a polygonal cross section such as a 3-8 octagon, and a round shape, an elliptical shape Alternatively, it may be a cross-sectional shape having a polygonal hollow of a triangle or more. In particular, the cross section and the Y-shaped section are preferable in terms of weight reduction and bulk increase of the nonwoven fabric. The single yarn fineness may be selected according to the purpose and is not particularly limited, but is generally preferably used in a range of about 0.01 to 500 dtex.

  The composite fiber of the present invention described above can be produced, for example, by the following method. Bio PP and bio PE polymers are separately discharged from a composite spinneret using a known spinning equipment and taken up at a speed of 100 to 2000 m / min while being cooled with cooling air to obtain an undrawn yarn. Subsequently, the undrawn yarn obtained is stretched in warm water at 70 to 100 ° C. or in steam at 100 to 125 ° C., crimped as necessary, and an oil agent according to the purpose and purpose is imparted. After performing the drying and relaxation heat treatment, it is cut into a predetermined fiber length to obtain the short fiber of the present invention. In this case, the oil agent may contain an amount that does not hinder the achievement of the object of the present invention, or a silicone compound that does not hinder the type.

  The composite fiber according to the present invention can be manufactured industrially at low cost with high productivity, and is suitable for applications such as dry nonwoven fabrics and wet nonwoven fabrics such as battery separators. It may be preferable to do this. That is, the composite fiber of the present invention adopts a core-sheath type composite fiber form, and the ratio of the weight average molecular weight of the core component to the weight average molecular weight of the sheath component measured by chromatography (core component weight average molecular weight / sheath component weight). In order to set the average molecular weight in the above-described range, it is preferable to reduce the weight average molecular weight of the core component and increase the weight average molecular weight of the sheath component. The weight average molecular weight of the core component is 100,000 to 160,000, and the weight average molecular weight of the sheath component is 40,000 to 40,000, provided that the core component weight average molecular weight / sheath component weight average molecular weight is 2.5 or less. A range of 80,000 is preferable, and a weight average molecular weight of the core component is preferably 120,000 to 150,000, and a weight average molecular weight of the sheath component is preferably 50,000 to 70,000.

  As a method of setting the ratio of the weight average molecular weight of the core component and the weight average molecular weight of the sheath component (core component weight average molecular weight / sheath component weight average molecular weight) of the conjugate fiber of the present invention to be within the above-mentioned range. For example, the following methods can be mentioned. By appropriately combining these methods, the weight average molecular weight ratio can be adjusted to a specific range of the present invention. The weight average molecular weight of both sheath core components measured by the chromatograph of the composite fiber of the present invention correlates with the melt flow rate (MFR) values of the core component resin and sheath component resin discharged from the spinneret, for example. When the weight average molecular weight is large, the MFR is small, and when the weight average molecular weight is small, the MFR is large. Therefore, it is preferable to decrease the weight average molecular weight of the core component and increase the weight average molecular weight of the sheath component. In other words, it is preferable to increase the MFR of the core component and decrease the MFR of the sheath component. Even when a resin material having a relatively low MFR is used, it is possible to increase the MFR of the resin discharged from the nozzle by adjusting the degree of molecular weight drop by changing the extrusion temperature during spinning. Therefore, the ratio of the above weight average molecular weight of the present invention (core component weight average molecular weight / sheath component weight average molecular weight) is 2.5 or less by appropriately selecting the MFR of the resin raw material for both sheath core components and the spinning extrusion conditions. Can be. The MFR of the resin raw material to be used is not particularly limited, but the MFR at 230 ° C. of the resin raw material of the core component is preferably 5 to 60 g / 10 min, and more preferably 8 to 40 g / 10 min. The extrusion temperature during spinning is not particularly limited, but is preferably in the range of 200 to 350 ° C, more preferably 260 to 330 ° C. Similarly, the MFR at 190 ° C. of the resin raw material for the sheath component is preferably 3 to 30 g / 10 min, more preferably 8 to 18 g / 10 min. The extrusion temperature during spinning is not particularly limited, but is preferably in the range of 180 to 300 ° C, more preferably 220 to 260 ° C.

  Generally, the drawability of an undrawn yarn obtained by melt spinning is strongly influenced by the stress that it receives during the spinning process. This is because the molecular chain is oriented along the fiber axis due to the stress acting on the spinning line, and the unstretched yarn in which the molecular chain is highly oriented by the high spinning line stress is low in elongation and stretched at a high magnification. I can't do it. Here, in the case of a composite fiber, it is necessary to consider the solidification temperature of both components. For example, in the case of a sheath-core type composite fiber, when one of the components is cooled to the solidification temperature in the spinning process, the deformability as the composite fiber is lost, and thus the other component cannot be deformed. That is, the component that solidifies at a lower temperature is solidified in a state where the composite fiber is not thinned, and in this case, a large stress does not act, and thus the molecular chain orientation of the component is kept low. Solidification of the polymer material is caused by glass transition or crystallization, but in the case of a polyolefin-based resin, the glass transition temperature is generally not more than room temperature, and thus solidification is caused by crystallization. The crystallization temperature tends to correlate with the melting point, and it can be said that the high melting point polyolefin resin has a higher crystallization temperature. That is, in the case of the sheath-core type composite fiber of the present invention, the high melting point component is arranged in the core and the lower melting point component is arranged in the sheath, so that the high melting point core component is solidified. Thus, the thinning of the composite fiber is completed, and then the sheath component having a low melting point is solidified. That is, the core component has a highly oriented unstretched yarn structure and the sheath component has a low orientation.

  When the undrawn yarn obtained in this way is drawn, the drawability of the core component that is highly oriented becomes rate-limiting, and the draw ratio is limited. In other words, it can be said that the stretchability of the sheath component that is low-oriented can be stretched only at a stretch ratio with a sufficient margin, that is, the strength expression of the sheath component is not sufficient. Here, it is important that the core component weight average molecular weight / sheath component weight average molecular weight of the composite fiber is 2.5 or less. This means that the weight average molecular weight of the core component is decreased and the weight average molecular weight of the sheath component is increased, that is, the MFR of the core component after nozzle discharge in the spinning process is increased and the MFR of the sheath component is decreased. . This makes it possible to control the degree of orientation of the core component and the sheath component of the undrawn yarn obtained in the spinning process so that the fiber strength is easily developed in the drawing process. When melt spinning is performed under such a resin composition and extrusion conditions, a large spinning line stress does not act on the core component, so molecular orientation is suppressed, and conversely, a large spinning line stress acts on the sheath component. As a result, molecular orientation is promoted.

  When the core component weight average molecular weight / sheath component weight average molecular weight of the composite fiber is 2.5 or less, it is possible to increase the MFR of the core component after nozzle discharge in the spinning process and to decrease the MFR of the sheath component. It leads to improvement of sex. As described above, in order to obtain an undrawn yarn that can be drawn at a high magnification, generally, a method of increasing the temperature of the discharged resin or decreasing the molecular weight of the discharged resin (increasing MFR) is employed. If the discharge resin temperature is remarkably increased or the molecular weight of the discharge resin is remarkably reduced, the tension is lowered directly under the nozzle, causing yarn swinging, which may lead to deterioration of spinnability. However, the MFR of the core component after nozzle discharge in the spinning process is increased so that the core component weight average molecular weight / sheath component weight average molecular weight of the heat-fusible conjugate fiber of the present invention is 2.5 or less. By adopting a resin configuration with a reduced MFR and extrusion conditions, the spinning line tension contracted by the core component is small, but the spinning line tension contracted by the sheath component is increased. This large tension acting on the sheath component leads to an increase in the overall tension of the composite fiber, which suppresses yarn fluctuations due to turbulence in the atmosphere and fluctuations in the speed of the cooling air, and minimizes deterioration of spinnability. And an undrawn yarn having excellent drawability can be obtained.

  This resin composition intended to suppress the orientation of the core component and promote the orientation of the sheath component, and the extrusion conditions are suitable as an undrawn yarn for obtaining a high-strength drawn fiber. This is because it is possible to stretch at a high magnification by suppressing the orientation of the core component that governs stretchability, and further, by enhancing the orientation of the sheath component in the unstretched yarn, it is possible to increase the strength expression by the stretching treatment. Because. The cross-sectional composite ratio of the core component and the sheath component is not particularly limited, but is preferably in the range of core / sheath = 40/60 to 70/30 vol%. When the ratio of the core component is high, the stretchability tends to slightly decrease, but the strength expression with respect to the draw ratio is increased, so the strength of the stretched fiber finally obtained is about the same. Become. Further, if importance is attached to suppression of thermal shrinkage of the drawn fiber, it is effective to increase the ratio of the core component. The fiber cross-sectional shape may be any of circular and elliptical round shapes, triangular and square square shapes, key shapes and different types such as an eight-leaf shape, and hollow shapes.

  Next, the nonwoven fabric using the conjugate fiber of the present invention will be described. In order to make the conjugate fiber of the present invention, preferably the short fiber, into a non-woven fabric, it is preferable to set the following fiber length according to the production of the web and impart crimp. For example, when the web is molded by the airlaid method, the fiber length is preferably 2 to 30 mm. By setting the fiber length to 2 mm or more, short fibers can be obtained industrially stably. Further, by setting the fiber length to 30 mm or less (or less than 30 mm), the fiber opening property is further improved and the web lump is hardly generated. A more preferable fiber length is 3 to 20 mm. Further, crimping may or may not be applied depending on the purpose of the nonwoven fabric. In other words, crimping may be imparted if the nonwoven fabric is desired to be bulky, and crimping may not be imparted if there is no need to improve the air opening property and discharge capacity. Shrink). Examples of crimp forms include a planar zigzag type, an omega type, and a spiral type. That is, the number of crimps is preferably 0 to 13/25 mm, and the crimp rate is preferably 0 to 15%. More specifically, when crimping is applied, it is preferable that the number of crimps is 3 to 13/25 mm, and the crimp rate is 3 to 15%. When the number of crimps is 13 peaks / 25 mm or less and the crimp rate is 15% or less, the air opening property is further improved. The short fibers of the present invention tend to have a smaller number of crimps and a lower crimp rate than conventional fibers, and are more easily controlled within the above range. In order to obtain bulkiness, it is preferable that the number of crimps is 3 peaks / 25 mm or more and the crimp rate is 3% or more. Further, the crimped form is more preferably a flat zigzag crimp or omega crimp included in a plane in terms of spreadability than a spiral three-dimensional crimp. By satisfying these configurations, the unopened component in the web molded by the airlaid method can be 5% by weight or less. A nonwoven fabric can be produced by heating the web thus obtained to melt at least a portion of the low-melting polyolefin and thermally bonding it to other fibers. When heating, a Yankee dryer, an embossing roll, or a calendar roll can be used. Also, depending on the use of the nonwoven fabric used, the adhesive may be attached to the fibers at any stage before or after the web molding, and the fibers may be bonded with the adhesive, or the fibers may be bonded by the needle punch method, water needle, etc. May be entangled to produce a nonwoven fabric.

  Moreover, also when forming a web by a wet papermaking method, 2-30 mm is preferable for the fiber length for the same reason as the above, More preferably, it is 3-20 mm. Crimping may or may not be applied depending on the purpose of the nonwoven fabric. When it is desired to give bulkiness to the wet nonwoven fabric, crimps may be imparted, but from the viewpoint of dispersibility in water during wet papermaking, it is preferable not to impart crimps. After the web molding, a nonwoven fabric by a wet papermaking method can be produced by an operation such as heat bonding between fibers according to the above method.

  Furthermore, when forming a web by a card method, it is preferable that fiber length shall be 30-200 mm. By setting the fiber length to 30 mm or more, it becomes difficult for the web to break due to poor entanglement between the fibers. Further, by setting the fiber length to 200 mm or less, the spreadability on the card is improved, and the texture of the web is less likely to occur. The fiber length is more preferably 35 to 150 mm, and even more preferably in the range of 40 to 100 mm. In order to allow the card to pass through, it is preferable that crimps are imparted to the short fibers. In this case, the number of crimps is preferably 5 to 30 crests / 25 mm, and the crimp rate is preferably 3 to 30%. By setting the number of crimps to 30 crests / 25 mm or less and the crimping ratio to 30% or less, the spreadability on the card is improved, and the texture of the web is less likely to occur. Further, by setting the number of crimps to 5 crests / 25 mm or more and the crimping ratio to 3% or more, it is difficult to cause web breakage due to intertwining between fibers. The crimped form may be a conventionally known crimped form such as a three-dimensional crimp such as a planar zigzag type, an omega type, or a spiral shape.

  The composite fiber of the present invention may be used as a long fiber, or may be used as a spunbonded nonwoven fabric by subjecting the long fiber to a heat bonding treatment. Further, it may be used as a spun yarn by cutting it into a short fiber having a fiber length of about 5 to 150 mm by cutting it as a fiber bundle in which several thousand to several millions are assembled, You may use as a nonwoven fabric formed by the dry method etc. Moreover, although the composite fiber of this invention may be used independently, it is suitable also for the use used by mixing with another fiber. Accordingly, mixed spinning, twisting, fine spinning and twisting may be performed, and further, weaving and knitting may be used, or a mixed nonwoven fabric may be used. Other fibers mixed with the composite fiber of the present invention include synthetic fibers such as polyester, nylon, acrylic and aramid; cellulose fibers such as viscose rayon, cupra and polynosic; solvent-spun cellulose fibers such as lyocell; silk Cotton, hemp, wool and other animal fiber.

  The composite fiber of the present invention can be used for various applications by making it into a nonwoven fabric by the above-described technique or in the state of the composite fiber, and can be made into various fiber forms according to the application. For example, in the case of the fiber for card nonwoven fabric, the fiber form of the staple which gave the crimp is preferable. The composite fiber of the present invention has high fiber strength and heat-sealing power, and is considered particularly suitable because it can increase the bulk and strength of the nonwoven fabric and improve card productivity. The fineness, the number of crimps, and the fiber length are not particularly limited and can be appropriately selected. In the case of fibers for woven fabric filters, fibers for winding filters, fibers for woven fabric sheets, fibers for knitted nets, etc., the fiber form of filaments is preferred. The fineness is not particularly limited and can be appropriately selected. In the case of an airlaid nonwoven fabric, a shortcut chop is preferred. The fineness is not particularly limited, and may be crimped or may not be crimped. The fiber length can be appropriately selected in consideration of the type of processing machine, required physical properties, productivity, and the like. In the case of a fiber for concrete reinforcement or a fiber for papermaking nonwoven fabric, the fiber form of a shortcut chop is preferable. It may be crimped or may not be crimped, and the fiber length can be appropriately selected in consideration of processing methods, required physical properties, productivity, and the like. Although the fineness is not particularly limited, for example, in the case of a wet nonwoven fabric such as a battery separator, it is preferable that the fineness is small, preferably 2.2 dtex or less, more preferably 1.5 dtex or less. More preferably, it is 1.0 dtex or less. When a battery separator wet nonwoven fabric is produced using the sheath-core type heat-fusible conjugate fiber of the present invention, it has a high fiber strength, and also has a high heat-sealing power when made into a nonwoven fabric by heat treatment, This is particularly suitable because it has a high effect of preventing sharp hard objects such as metals from penetrating the nonwoven fabric.

  Hereinafter, the present invention will be described more specifically with reference to examples. The polymer physical properties and mechanical properties (general physical properties) in Examples and Comparative Examples were measured by the following methods.

(A) Melting point (Tm)
A thermal analyst 2200 manufactured by TA Instrument Japan Co., Ltd. was used, and the temperature was measured at a temperature rising rate of 20 ° C./min.

(B) Fineness Measured by the method described in JIS L 1015 7.5.1 Method A.

(C) Dry strength and dry elongation (nonwoven fabric)
It was measured by the method described in JIS L 1015: 2005 8.7.1 method.

(D) 120 degreeC dry heat shrinkage rate It measured at 120 degreeC by the method as described in JISL1015: 2005 8.15 b) method.

(E) Number of crimps and crimp rate Measured by the method described in JIS L 1015 7.12.

(F) Nonwoven fabric appearance The appearance of the molded web is observed and evaluated according to the following criteria.
Level 1: Unopened lumps and spotted spots (shading) are not seen, and the texture is uniform.
Level 2: Unopened lumps are not conspicuous, but spotted spots (shading) can be visually confirmed.
Level 3: Unopened lumps and spotted spots (shading) are conspicuous and the texture is uneven.

(G) The mixing ratio sample of the biomass origin carbon by measurement of radioactive carbon (carbon 14) was subjected to an accelerator mass spectrometer (AMS) (a combination of a tandem accelerator and a mass spectrometer), and the content of carbon 14 was measured. Carbon dioxide in the atmosphere contains a certain amount of carbon 14 (because neutrons collide with nitrogen in the upper atmosphere to generate carbon 14), but fossil raw materials such as petroleum contain carbon 14. 14 (although carbon 14 emits radiation in the ground and changes to nitrogen with a half-life of 5,370 years). On the other hand, the abundance ratio of carbon 14 in the current atmosphere is measured to be a specific value [107 pMC (percent modern carbon) as an average value], and existing plants that carry out photosynthesis have carbon 14 at this ratio. It is known that it has been incorporated. Therefore, the ratio of biomass-derived carbon in the carbon contained in the sample can be determined by measuring the total carbon and carbon 14 content in the sample. (See formula below) Biomass-derived carbon content (%) = (Amount of carbon derived from biomass in sample / total amount of carbon in sample) × 100
Hereinafter, ethylene, propylene, polyethylene, and polypropylene containing carbon 14 are referred to as bioethylene, biopropylene, biopolyethylene [bioPE], and biopolypropylene [bioPP], and are produced from conventional petroleum-derived raw materials. Ethylene, propylene, polyethylene, and polypropylene not containing 14 are referred to as petroleum-derived ethylene, petroleum-derived propylene, petroleum-derived polyethylene [petroleum-derived PE], and petroleum-derived polypropylene [petroleum-derived PP].

[Example 1]
A bio-PE polymer (melting point: 130 ° C.) is fed to a known concentric core-sheath type composite spinneret separately at a weight ratio of 50/50 so that the bio-PP polymer (melting point: 160 ° C.) becomes a core, A 0.3 mm round hole capillary was extruded from a die having 1032H holes at a discharge rate of 700 g / min. This was air-cooled with cooling air at 30 ° C. and wound at 1150 m / min to obtain an undrawn yarn. This undrawn yarn was subjected to two-stage drawing, and 0.25% by weight of an oil agent composed of polyether / polyester copolymer / alkyl phosphate potassium salt = 95/5 (weight ratio) was added, and hot air at 105 ° C. After drying, the fiber length was cut to 5 mm. The fineness of the obtained short fiber was 2.2 dtex.
Using a square sheet machine manufactured by Kumagai Riki Kogyo Co., Ltd., the short fibers obtained by the above method and wood pulp are poured into water at a weight ratio of 80:20, and thoroughly stirred and mixed to disperse. A sheet having a size of about 25 cm × about 25 cm and a basis weight of 27 g / m ² was prepared. Next, the sheet was dried at room temperature for a whole day and night, and then heat treated for 5 minutes in a hot air circulating dryer at 140 ° C. to obtain a wet nonwoven fabric. The nonwoven fabric texture is level 1 and contains biomass-derived polyolefin. The results are shown in Table 1.

[Example 2]
A core-sheath short fiber and a nonwoven fabric were obtained in the same manner as in Example 1 except that bio-PE (melting point: 127 ° C.) obtained by graft copolymerization with 1% by weight of maleic anhydride was used as the sheath component. The evaluation results are shown in Table 1. The nonwoven fabric texture is level 1 and contains biomass-derived polyolefin. The results are shown in Table 1.

[Example 3]
A core-sheath short fiber and a nonwoven fabric were obtained in the same manner as in Example 1 except that an ethylene / propylene random copolymer polyolefin (melting point: 130 ° C.) composed of bioethylene and biopropylene was used as the sheath component. The nonwoven fabric texture is level 1 and contains biomass-derived polyolefin. The results are shown in Table 1.

[Comparative Example 1]
Short fibers and nonwoven fabric were obtained in the same manner as in Example 1 except that petroleum-derived PE (melting point: 130 ° C.) was used as the sheath component and petroleum-derived PP was used as the core component. The evaluation results are shown in Table 1. The nonwoven fabric texture is level 1, but does not contain biomass-derived polyolefin. The results are shown in Table 1.

  According to the present invention, while maintaining the same features as the conventional polyolefin conjugate fiber and the nonwoven fabric composed thereof, the consumption of petroleum resources is suppressed as compared with the conventional polyolefin conjugate fiber, and carbon dioxide in the atmosphere accompanying incineration and disposal It is possible to provide a composite fiber and a non-woven fabric that can suppress an increase in the number of fibers. The fibers and non-woven fabrics obtained by the present invention can be suitably used in a wide range of applications such as sanitary materials such as diapers and napkins, living materials such as tea packs and wipers, and industrial materials such as battery separators and filters. it can.

Claims (6)

  A composite fiber comprising two types of polyolefins having different melting points from a biomass-derived component containing radioactive carbon (carbon 14), and a relatively low melting point polyolefin crossing the fibers in the two types of polyolefins A composite fiber comprising at least a part of the outer periphery of the surface.   The polyolefin is at least selected from the group consisting of polypropylene, high-density polyethylene, ethylene / propylene random copolymer, polyethylene obtained by block copolymerization or graft copolymerization of maleic anhydride, and polypropylene obtained by block copolymerization or graft copolymerization of maleic anhydride. The composite fiber according to claim 1, which is a polyolefin selected from one kind. The ratio of carbon 14 based on the concentration (100%) of the radioactive carbon (carbon 14, ¹⁴ C) in the circulating carbon as of 1950 in all carbon atoms in the composite fiber is 70% by weight or more. The composite fiber in any one of -2.   A nonwoven fabric comprising the conjugate fiber according to any one of claims 1 to 3, wherein a web is molded by an airlaid method.   A nonwoven fabric comprising the composite fiber according to any one of claims 1 to 3, wherein a web is molded by a wet papermaking method.   A nonwoven fabric comprising the composite fiber according to any one of claims 1 to 3, wherein a web is molded by a card method.