Biodegradable polyester nonwoven fabric and nonwoven fabric product comprising same

Abstract

The present invention addresses the problem of providing: a biodegradable polyester nonwoven fabric that quickly decomposes even in seawater while maintaining a hole diameter required for a filter or the like; and a nonwoven fabric product comprising the same.　The biodegradable polyester nonwoven fabric contains 20% by weight or more of undrawn fibers comprising an aliphatic polyester resin having a fineness of 0.1 dtex or more and having a heating crystallization peak temperature of 100°C or less, the fibers containing a phosphite ester-based decomposition accelerator. The biodegradable polyester nonwoven fabric preferably contains drawn fibers and is preferably marine biodegradable. Nonwoven fabric products using the nonwoven fabric according to the present invention include tea bags, coffee filters, soup stock bags, containers, packages, masks, filters, sanitary articles, wipers, wet towels, and the like.

Description

Biodegradable polyester nonwoven fabric and nonwoven fabric products made from it

[0001] The present invention relates to a highly biodegradable polyester nonwoven fabric product. More specifically, the present invention relates to a biodegradable polyester nonwoven fabric that quickly decomposes in seawater while maintaining the pore size required for filters, etc., and a nonwoven fabric product made of the same.

[0002] Known biodegradable nonwoven fabrics are those made from cellulose-based natural fibers or cellulose-based artificial fibers, as described in Patent Documents 1 and 2. However, they tend to lack strength, and such nonwoven fabrics are difficult to apply to fields such as filters, where pore size control is required.

[0003] For example, in order to increase the strength of nonwoven fabric, measures such as increasing the basis weight or performing heat pressing are available, but in either case, there is a problem in that when trying to increase strength, the voids become smaller and the pore diameter becomes increasingly smaller.

[0004] Furthermore, when nonwoven fabrics are used in the form of bags for containers, packaging, etc., a method of heat-sealing the nonwoven fabric by thermal fusion is often used, but such a method could not be applied to cellulosic fibers.

[0005] Furthermore, from the viewpoint of biodegradability, for example, aliphatic polyester fibers are used in Patent Document 3. However, although they exhibit a certain degree of biodegradability in aerobic environments where bacteria are present in large quantities, such as soil or compost, their biodegradability is not satisfactory in anaerobic environments where bacteria are scarce, such as low-temperature seawater.

[0006] JP-A-7-243179 JP-A-4-57951 JP-A 2002-177148

[0007] The present invention solves the above-mentioned conventional problems and aims to provide a biodegradable polyester nonwoven fabric that quickly decomposes in seawater while maintaining the pore size required for filters, etc., and a nonwoven fabric product made of the same.

[0008] The biodegradable polyester nonwoven fabric of the present invention has the following characteristics to solve the problems.

[0009] 1. A biodegradable polyester nonwoven fabric characterized by containing 20% ​​by weight or more of undrawn fibers made of an aliphatic polyester resin, having a fineness of 0.1 dtex or more, containing a phosphite ester-based decomposition accelerator and having a temperature-rising crystallization peak temperature of 100°C or less. 2. The biodegradable polyester nonwoven fabric according to the above item 1, further containing drawn fibers made of an aliphatic polyester resin, having a fineness of 20 dtex or less. 3. The biodegradable polyester nonwoven fabric according to the above item 1 or 2, wherein the aliphatic polyester resin is a marine biodegradable resin. 4. The biodegradable polyester nonwoven fabric according to any one of the above items 1 to 3, wherein the aliphatic polyester resin contains 0.1 to 20% by weight of a phosphite ester-based decomposition accelerator. 5. A nonwoven fabric product made of the biodegradable polyester nonwoven fabric according to any one of the above items 1 to 4. 6. The nonwoven fabric product according to the above item 5, which is for use in food extraction. 7. The nonwoven fabric product according to the above item 6, which is one of a tea bag, a coffee filter, and a soup stock bag. 8. 6. The nonwoven fabric product according to claim 5, which is any one of a container, packaging, a mask, a filter, a sanitary product, a wiper, and a wet towel.

[0010] According to the present invention, it is possible to provide a biodegradable polyester nonwoven fabric that rapidly decomposes in seawater while maintaining the pore size required for filters, etc., and a nonwoven fabric product made thereof. Furthermore, this nonwoven fabric product has high heat-sealability and excellent shape retention.

[0011] Hereinafter, embodiments of the present invention will be described in detail.

[0012] The biodegradable polyester nonwoven fabric of the present invention is a nonwoven fabric formed from polyester fibers mainly made of polyester resin. The polyester fibers are mainly made of polyester resin, and more specifically, it is preferable that at least 50% by weight, preferably 70% by weight or more, and particularly 90% by weight to 100% by weight of the polyester fibers are mainly made of polyester resin.

[0013] The biodegradable polyester nonwoven fabric of the present invention must contain at least 20 wt.% of unstretched fibers, based on the total weight of the nonwoven fabric, made of an aliphatic polyester resin, having a fineness of 0.1 dtex or greater, containing a phosphite ester-based decomposition accelerator, and having a temperature-rising crystallization peak temperature of 100°C or less. Furthermore, the fineness of the unstretched fibers is preferably 20 dtex or less, more preferably in the range of 2.5 to 15 dtex, and particularly preferably in the range of 5 to 10 dtex. If the fineness is too small, the fabric tends to be too dense, making it difficult to secure voids. If the fineness is too large, the pore size tends to be too large, making it difficult to control the filter pore size. Furthermore, the content of unstretched fibers is more preferably 25 to 80%, and particularly preferably 30 to 70%. If the unstretched fibers made of an aliphatic polyester resin are too thin or too few, the nonwoven fabric tends to be unable to maintain its strength. On the other hand, if the amount is too large, the voids in the nonwoven fabric tend to become small and the required pore size cannot be obtained, and therefore, in order to obtain the required pore size, an appropriate single fiber fineness is important.

[0014] Furthermore, polyester fibers other than unstretched fibers made of aliphatic polyester resin and having a fineness of 0.1 dtex or more are preferably drawn fibers made of aliphatic polyester resin. The drawn fibers preferably have a single fiber fineness of 20 dtex or less. A range of 1 to 10 dtex, particularly 2 to 5 dtex, is more preferred. The single fiber fineness of the drawn fibers is preferably smaller than that of unstretched fibers made of stretched aliphatic polyester resin, and is preferably 60% or less, and even more preferably in the range of 20 to 40%, of the single fiber fineness of the unstretched fibers. As with unstretched fibers, if the fineness is too small, the fibers tend to be too dense and voids cannot be secured, while if the fineness is too large, the pore size tends to be too large, making it difficult to control the filter pore size.

[0015] The unstretched fibers preferably have an elongation of 60% or more, more preferably 150 to 300%. Stretched fibers that can be used in addition to the unstretched fibers preferably have an elongation of less than 60%, more preferably in the range of 20 to 50%.

[0016] Furthermore, undrawn fibers do not crystallize during fiber formation, resulting in the presence of many amorphous portions, which flow due to the heat generated during nonwoven fabric formation, thereby exhibiting an adhesive effect. It is important that the undrawn fibers of the present invention have a temperature-rise crystallization peak (Tci) measured by differential scanning calorimetry (DSC), which indicates that they exhibit adhesiveness during thermal processing, i.e., that they provide the strength required for a nonwoven fabric. The temperature-rise crystallization temperature must be 100°C or lower, and is preferably higher than the glass transition temperature, more preferably in the range of 75°C to 95°C, and particularly preferably in the range of 80°C to 90°C.

[0017] Furthermore, various fiber materials can be used as fibrous components other than the polyester fibers that make up the biodegradable polyester nonwoven fabric of the present invention, and it is also preferable to mix or add, for example, wood pulp, natural pulp, synthetic pulp mainly composed of aramid or polyethylene, or synthetic or semi-synthetic fibers containing components such as nylon, acrylic, vinylon, rayon, etc. It is particularly preferable to use a biodegradable fiber material for paper in combination.

[0018] Furthermore, the aliphatic polyester resin used to form the unstretched and / or stretched fibers in the biodegradable polyester nonwoven fabric of the present invention is preferably a marine degradable resin. Here, the marine degradable resin is a resin that exhibits high biodegradability even in an anaerobic environment with few bacteria, such as seawater at 30°C.

[0019] In general, examples of polyester resins include polymers or copolymers obtained by polycondensation of dicarboxylic acids or their ester-forming derivatives with one or more selected from diols or their ester-forming derivatives, hydroxycarboxylic acids or their ester-forming derivatives, and lactones. In the present invention, however, it is important to use an aliphatic polyester made from hydroxycarboxylic acids or their ester-forming derivatives in order to achieve biodegradability.

[0020] More specifically, the hydroxycarboxylic acids or ester-forming derivatives thereof, and lactones include, as hydroxycarboxylic acids, glycolic acid, lactic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and ester-forming derivatives thereof. As lactones, caprolactone, valerolactone, propiolactone, undecalactone, 1,5-oxepan-2-one, etc.

[0021] Among these, preferred examples include polyglycolic acid, polylactic acid, poly(3-hydroxycarboxylic acid), poly(4-polyhydroxybutyric acid), poly(3-hydroxyhexanoic acid), polycaprolactone, and copolymers thereof. In particular, it is preferred that the aliphatic polyester is any one selected from the group consisting of poly(L-lactic acid), poly(D-lactic acid), racemic poly(lactic acid), and polyglycolic acid.

[0022] As the polyester resin constituting the biodegradable polyester nonwoven fabric of the present invention, it is also preferable to use a combination of two or more of these aliphatic polyesters, particularly from the viewpoint of controlling decomposition in low-temperature seawater. Polylactic acid is particularly preferred as the main component, and a combination of polylactic acid and polyglycolic acid is particularly preferred. In this case, the main component, polylactic acid, preferably accounts for 50% or more of the total mass, and from the viewpoint of ease of decomposition control, it is more preferred that it accounts for 70% or more by weight, and particularly 80% or more but less than 100% by weight.

[0023] Lactic acid units include L-lactic acid units and D-lactic acid units, which are optical isomers of each other. When the main polyester of the present invention is polylactic acid, it is preferable that its main chain is primarily a combination of L-lactic acid units and D-lactic acid units. By using a polylactic acid resin in which L-lactic acid units and D-lactic acid units coexist, it is possible to further improve degradability at low temperatures. The ratio of the other lactic acid units to the main lactic acid units is preferably 20 mol% or less. It is more preferably 0.1 to 15 mol%, and even more preferably 1 to 15 mol%. Complete absence of either lactic acid unit may result in reduced degradability in low-temperature water. Furthermore, if the ratio is too high, the crystallinity of the polylactic acid may be lost, potentially improving degradability in low-temperature water, but it may also be difficult to process into fibers, various molded articles, etc.

[0024] In the present invention, it is preferable to use polylactic acid with a high ratio of L-lactic acid units. Generally, the content of L-lactic acid or D-lactic acid, which is the main component of a polylactic acid resin, is referred to as optical purity, and the optical purity is preferably 90% or more, more preferably 95% or more, and even more preferably 98 to 100%.

[0025] Furthermore, the aliphatic polyester used in the present invention preferably has a number-average molecular weight of 50,000 or more. Furthermore, the number-average molecular weight is preferably in the range of 60,000 to 200,000, and particularly 65,000 to 150,000. By having the number-average molecular weight in this range, it is possible to obtain a polyester resin composition that has high initial physical properties and yet is highly marine degradable. Here, the number-average molecular weight is a value measured by gel permeation chromatography (GPC) and converted into standard polystyrene.

[0026] Such polyesters can be produced by conventionally known methods. For example, when the polyester is polylactic acid, it can be produced by a method of ring-opening polymerization of L-lactide, D-lactide, or a mixture thereof in the presence of a metal-containing catalyst, a method of solid-state polymerization of low-molecular-weight polylactic acid containing a metal-containing catalyst, or a direct polymerization method of dehydration condensation of lactic acid.

[0027] To further improve biodegradability, the polyester used in the present invention contains a phosphite-based decomposition accelerator, preferably a phosphite-based decomposition accelerator represented by the following general formula (I):

[0028]

[0029] (In general formula (I), R represents an alkyl group, an aryl group, or a hydrogenated bisphenol A skeleton, and may be the same or different. n represents an integer ranging from 1 to 20.)

[0030] Such phosphorous ester compounds are preferably compounds having a pentaerythritol diphosphite component, and more preferably dialkyl pentaerythritol diphosphites. More specific examples of compounds having a pentaerythritol diphosphite component include distearyl pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, tetrakis(2,6-di-t-butylphenyl)4,4'-biphenylene phosphite, and hydrogenated bisphenol A-pentaerythritol phosphite polymer.

[0031] In particular, dialkyl pentaerythritol diphosphites are preferred because they have appropriate heat resistance. Furthermore, compounds having an alkyl group with a carbon number in the range of 8 to 36 are preferred, and those having a carbon number of 10 to 24 are particularly preferred, with distearyl pentaerythritol diphosphite having 18 carbon atoms being most preferred. If the alkyl group has too few carbon atoms, the phosphites tend to be liquid and difficult to handle. In terms of ease of handling, solid phosphites are generally preferred.

[0032] Furthermore, when phosphites contain bisphenol A-based components in the portion other than pentaerythritol diphosphite, heat resistance tends to decrease, and thread breakage tends to occur, for example, during the spinning process for fiberization. Furthermore, when phenol-based components are included, heat resistance tends to improve, but marine biodegradability tends to be hindered. Furthermore, phosphites containing bisphenol A-based or phenol-based components are also of concern due to their chronic toxicity to the aquatic environment.

[0033] Furthermore, the phosphite ester decomposition accelerator preferably used in the present invention preferably has a thermal decomposition temperature of 170°C or higher. A preferred range of the thermal decomposition temperature is 400°C or lower, and a more preferred range is 200 to 350°C. Here, the thermal decomposition temperature is a temperature at which the weight is reduced by 5% or more. By setting the thermal decomposition temperature at such a high temperature, the compound is less likely to decompose in subsequent processing steps such as fiber molding or film molding, and it becomes possible to maintain high initial physical properties.

[0034] The biodegradable polyester nonwoven fabric of the present invention is preferably primarily composed of fibers made of the marine biodegradable polyester resin described above, and the amount of the phosphite ester degradation accelerator preferably used is preferably 0.01% by weight or more, and more preferably 0.1 to 20% by weight, in the resin composition. A range of 0.2 to 15% by weight, and particularly 0.3 to 10% by weight, is even more preferable. If the amount of these agents added is too small, the effect of increasing the decomposition rate is reduced, while if it is too large, moldability or thermal stability tends to deteriorate.

[0035] Furthermore, other known additives and fillers may be added to the polyester fibers used in the biodegradable polyester nonwoven fabric of the present invention, and it is also preferable to contain, for example, a filler, a release agent, an antistatic agent, a plasticizer, an impact resistance improver, etc.

[0036] Such polyester fibers have excellent marine biodegradability at low temperatures, and even when decomposed, the monomer components and the like are less likely to have adverse effects on the marine ecosystem and other environmental aspects, making them excellent biodegradable polyester nonwoven fabrics.

[0037] Furthermore, the polyester fibers have excellent hydrolysis properties, and when the polyester component is polylactic acid, the number average molecular weight of the polylactic acid is rapidly and significantly reduced in the early stages by hydrolysis, accelerating subsequent microbial decomposition.

[0038] The decomposition mechanism of polylactic acid, which is preferably used in the present invention, is known to be different from that of other biodegradable plastics, in that the molecular weight is reduced by hydrolysis, and then the polylactic acid is completely decomposed into carbon dioxide and water by microorganisms in a two-stage / two-mode decomposition mechanism. For example, by reducing the number-average molecular weight of polylactic acid to 20,000 in the early stage, microbial decomposition can be accelerated.

[0039] The biodegradable polyester nonwoven fabric of the present invention using such a polyester will be effectively decomposed even in the sea, where the temperature is low and the oxygen concentration is low, rather than in the high temperature and high oxygen concentration conditions of compost. The effects of the present invention are most pronounced in the ambient temperature range of 0 to 50°C, and more particularly in the range of 5 to 35°C.

[0040] The biodegradable polyester nonwoven fabric of the present invention is a nonwoven fabric made from the above-mentioned polyester resin in the form of fibers. The polyester resin used is preferably produced by directly mixing the main polyester resin composition and the phosphite decomposition accelerator and melt-kneading the mixture to produce a resin composition, or by first preparing a masterbatch containing 5 to 20% by weight of the phosphite decomposition accelerator.

[0041] Examples of kneading equipment for the polyester resin before spinning include known single- or multi-screw horizontal kneading equipment, such as a ruder or kneader. A low kneading temperature is preferred, and a rotation speed of 600 rpm or less, preferably in the range of 100 to 400 rpm, is preferable. To reduce thermal degradation, the discharged strand is preferably cooled by water.

[0042] Such polyester resins are further processed by conventional melt spinning and subsequent post-processing to form fibers, ultimately producing nonwoven fabrics. The melting temperature of the resin in the spinning process is preferably in the range of 170 to 250°C, and more preferably in the range of 190 to 230°C. The fibers can be produced by extruding filaments from a melt spinneret, and can be circular, irregular, solid, hollow, or other shapes.

[0043] The biodegradable polyester nonwoven fabric of the present invention contains, as the polyester fibers, 20% by weight or more of unstretched fibers made of aliphatic polyester resin and having a fineness of 0.1 dtex or more. The fiber length of the unstretched fibers is preferably in the range of 1 to 50 mm, and more preferably in the range of 2 to 10 mm. The tensile elongation is preferably in the range of 50 to 500%, and more preferably in the range of 80 to 300%. The tensile strength is preferably 0.5 cN / dtex or more, and more preferably in the range of 0.8 to 2.4 cN / dtex. By including such unstretched fibers, the nonwoven fabric of the present invention has excellent heat-sealing properties.

[0044] Furthermore, to increase the strength of the biodegradable polyester nonwoven fabric of the present invention, it is preferable to contain drawn polyester fibers obtained by further drawing the undrawn fibers. The initial strength of the drawn fibers is preferably 1.5 cN / dtex or more, and more preferably 2.0 to 5.0 cN / dtex. The single fiber fineness of these drawn fibers is preferably 20 dtex or less. Furthermore, it is preferably finer than the single fiber fineness of the undrawn fibers made of aliphatic polyester resin, and more preferably in the range of 1 to 10 dtex, and particularly preferably in the range of 2 to 5 dtex. The fiber length of the drawn fiber yarn is preferably in the range of 1 to 50 mm, and more preferably in the range of 2 to 10 mm. Furthermore, by reducing the difference in fiber length with the undrawn fibers, a more dense entanglement state is achieved. The tensile elongation is preferably in the range of 5 to 100%, and more preferably in the range of 15 to 60%. The strength is preferably 1.5 cN / dtex or more, and more preferably in the range of 2 to 8 cN / dtex. By including such drawn fibers, the nonwoven fabric of the present invention has excellent heat-sealing properties and also excellent bending properties.

[0045] Methods for forming the above-mentioned fibers into nonwoven fabric include, but are not limited to, papermaking, spunlace, airlaid, needle punch, thermal bond, chemical bond, spunbond, meltblowing, and electrospinning.

[0046] As a method for processing the biodegradable polyester nonwoven fabric of the present invention, a wet-laid nonwoven fabric manufacturing method by papermaking is particularly preferred.

[0047] Such a biodegradable polyester fiber nonwoven fabric of the present invention has a basis weight of 10 g / m ２ or more, and more preferably 20 to 500 g / m ２ In particular, the range is 30 to 100 g / m ２ The thickness is preferably within 10 mm, and more preferably within the range of 0.05 mm to 5 mm. The density of the nonwoven fabric is preferably 0.2 to 0.65 g / cm. ３ is preferably in the range of 0.30 to 0.45 g / cm ３ The range is preferred.

[0048] When the nonwoven fabric of the present invention is used for food extraction such as tea bags, the basis weight of the nonwoven fabric is 10 g / m ２ or more, and more preferably 20 to 60 g / m ２ The thickness is preferably within 0.5 mm, and more preferably within the range of 0.05 to 0.15 mm. The density of the nonwoven fabric is preferably 0.2 to 0.65 g / cm. ３ The range of 0.30 to 0.45 is more preferable.

[0049] The average pore size is preferably 20 to 60 μm, and more preferably 30 to 60 μm. Despite this pore size, the strength of the nonwoven fabric is preferably 2 N / 15 mm or more, and more preferably in the range of 2.5 to 5.0 N / 15 mm. In the present invention, it is possible to obtain such a nonwoven fabric by including specific unstretched fibers, and more preferably by using stretched fibers in combination.

[0050] The unstretched fibers made of aliphatic polyester resin, an essential component of the present invention, will now be described in more detail. These unstretched fibers serve as binder fibers in the nonwoven fabric, but the biodegradable nonwoven fabric of the present invention may also contain other binder fibers. The inclusion of binder fibers such as thermally adhesive fibers can improve the strength of the nonwoven fabric, its network structure, and bulkiness due to shrinkage. The binder fibers are preferably unstretched fibers or composite fibers.

[0051] In addition, various paper fiber materials can be used in small amounts and depending on the purpose. For example, wood pulp, natural pulp, synthetic pulp mainly composed of aramid or polyethylene, synthetic fibers or semi-synthetic fibers containing components such as nylon, acrylic, vinylon, and rayon may be mixed or added.

[0052] The biodegradable polyester nonwoven fabric of the present invention can be obtained, for example, by using the above-mentioned fibers to make paper using a Fourdrinier paper machine, a short wire paper machine, a cylinder paper machine, or the like, and then thermally bonding binder fibers such as unstretched fibers.

[0053] The biodegradable polyester nonwoven fabric of the present invention obtained in this manner is a biodegradable polyester nonwoven fabric that quickly decomposes even in seawater while maintaining the pore size required for filters and the like.

[0054] The marine biodegradable polyester nonwoven fabric of the present invention is ideally suited for use in nonwoven fabric products such as containers, packaging, masks, filters, sanitary products, wipers, and hand towels.

[0055] Furthermore, textile products using the biodegradable polyester nonwoven fabric of the present invention are excellent in biodegradability, thermal adhesion, and shape retention, making them particularly useful not only in sheet form but also as three-dimensionally molded textile products. The high heat-sealing and bending properties of the nonwoven fabric of the present invention allow it to maintain a small, flat shape during production, storage, and transportation, but to restore its three-dimensional shape during use, such as hot water extraction, ensuring a large internal space.

[0056] For example, the nonwoven fabric of the present invention has excellent biodegradability and is therefore suitable for use in food extraction, which is consumed in large quantities. Nonwoven fabric products for food extraction made from the biodegradable polyester nonwoven fabric of the present invention have excellent heat-sealing and bending properties, so they easily maintain their three-dimensional shape. This allows for a larger area of ​​contact with hot water during extraction, such as tea leaves, inside the nonwoven fabric, making it easier for the tea leaves to open, allowing for more effective extraction of active ingredients.

[0057] More specifically, it is effectively utilized as a nonwoven fabric product for food extraction, such as tea bags, coffee filters, or soup stock bags. For example, in the case of tea bags, the biodegradable polyester nonwoven fabric of the present invention can be heat-sealed to form a bag, resulting in double-chamber or single-chamber tea bags. In this case, the heat-sealing temperature is preferably 110°C or higher and 190°C or lower, and more preferably in the range of 110 to 140°C. The biodegradable polyester nonwoven fabric of the present invention contains unstretched fibers with a temperature-rising crystallization peak temperature of 100°C or lower, making it possible to perform heat sealing even at such relatively low temperatures. Alternatively, ultrasonic bonding can be performed, making it suitable for the production of tetrahedral (triangular) tea bags. From the viewpoint of three-dimensional shape retention, the nonwoven fabric is particularly effectively used as a double-chamber or tetrahedral tea bag.

[0058] The present invention will be described in more detail below with reference to examples. The methods for measuring physical properties used in the examples are as follows.

[0059] (1) Heat-Rise Crystallization Temperature Using a differential scanning calorimeter (DSC), the temperature of an undrawn polyester fiber was measured by raising the temperature from 30° C. to 250° C. at a temperature rise rate of 10° C. / min.

[0060] (2) Fiber Fineness The fineness was expressed in dtex (decitex), which is the weight in grams per 10,000 meters.

[0061] (3) Basis Weight Basis weight was measured based on JIS P8124 (method for measuring metric basis weight of paper).

[0062] (4) Thickness The thickness was measured based on JIS P8118 (Method for measuring thickness and density of paper and paperboard). The measurement load was 75 g / cm. ２ Measurement was carried out with N=5, and the average value was calculated.

[0063] (5) Strength: Test was carried out based on JIS P8113 (tensile strength and testing methods for paper and paperboard). The MD direction of the rotary dryer was defined as the warp direction, and the CD direction was defined as the cross direction, and the average value of the strength in the warp and cross directions was defined as the tensile strength.

[0064] (6) Pore size: The average pore size was determined according to ASTM-F-316-86. The surface tension of the test liquid was 15.9 dynes / cm.

[0065] (7) Marine biodegradability A 10 cm square nonwoven fabric sample was placed in a container surrounded by a wire mesh and submerged in seawater. After 180 days, the wire mesh was removed, and the appearance of the sample was visually inspected. The degree of biodegradation was evaluated according to the following criteria: ◎: The shape of the sample has completely disappeared ○: The shape of the sample has changed so much that it is no longer recognizable △: Fragments of the sample remain ×: The shape of the sample remains completely

[0066] Example 1 A polyester resin (PLA; optical purity: 96% L-form, polylactic acid) having a number average molecular weight of 120,000 and a phosphorus-based decomposition accelerator (distearyl pentaerythritol diphosphite, phosphorus concentration: 7.6%, thermal decomposition temperature (5% weight loss temperature): 210°C) were mixed to a ratio of 99.0:1.0, and the mixture was melt-kneaded for 2 minutes using a microconical twin-screw compounder ("HAAKE MiniCTW" manufactured by ThermoFisher Scientific Inc.) at a set temperature of 190°C and a rotation speed of 100 rpm to obtain a resin composition.

[0067] This resin composition was melt-spun at a spinning temperature of 190°C and a spinning speed of 1500 m / min, and then cut without being stretched to obtain unstretched polyester fibers (fineness 7.3 dtex, strength 1.3 cN / dtex, elongation 228%, heating crystallization temperature 82°C).

[0068] The same resin composition was melt-spun at a spinning temperature of 190°C and a spinning speed of 2550 m / min, and then drawn at a draw ratio of 1.5, followed by heat setting at 150°C and winding up, followed by cutting into drawn polyester fibers (fineness 2.2 dtex, strength 3.5 cN / dtex, elongation 34%).

[0069] Unstretched polyester fibers with a fineness of 7.3 dtex and a fiber length of 5 mm were blended with stretched polyester fibers with a fineness of 2.2 dtex and a fiber length of 5 mm in a ratio of unstretched polyester fibers to stretched polyester fibers of 30:70, and a dispersant and an antifoaming agent were added to form a dispersed slurry. The slurry was made into paper using a TAPPI square paper machine (manufactured by Kumagai Riki Kogyo Co., Ltd., a square sheet machine of 250 mm square), dried at 120°C for 1 minute using a rotary dryer, and the resulting paper had a basis weight of 42 g / m. ２ , thickness 0.13 mm, density 0.32 g / cm ３ The composition and physical properties of the biodegradable polyester nonwoven fabric are shown in Table 1.

[0070] The resulting nonwoven fabric was heat-sealed at 140°C to create a double-chamber tea bag. This nonwoven fabric had excellent foldability when creating the tea bag, and its volume was small during storage and transportation. On the other hand, the volume of the tea bag expanded well when tea leaves were extracted with hot water, allowing the tea leaves to expand inside the tea bag, resulting in a black tea with a good flavor.

[0071] (Examples 2 and 3) Biodegradable polyester nonwoven fabrics of Examples 2 and 3 were obtained in the same manner as Example 1, except that the ratio of unstretched polyester fiber to stretched polyester fiber in Example 1 was changed to 50:50 and 70:30. The configuration and physical properties are also shown in Table 1. Furthermore, as in Example 1, double-chamber tea bags were made using the obtained nonwoven fabric. As in Example 1, the volume was small during storage and transportation, and the tea leaves expanded inside the tea bag when extracted with hot water, resulting in black tea with a good flavor.

[0072] Example 4 As in Example 1, the dispersed slurry was made into paper using a TAPPI square paper machine (Kumagaya Riki Kogyo Co., Ltd., square sheet machine, 250 mm square), except that afterwards, it was dried using a rotary dryer at 80°C for 1 minute, and then hot-pressed using a calendar roll at 120°C, 2 m / min, and a linear pressure of 50 kgf / cm to obtain a biodegradable polyester nonwoven fabric. The composition and physical properties are also shown in Table 1. Furthermore, as in Example 1, double-chamber tea bags were made using the obtained nonwoven fabric. The volume was small during storage and transportation, and black tea with good flavor was obtained, but the tea leaves were slightly less flexible in hot water compared to Example 1.

[0073] (Comparative Example 1) A biodegradable polyester nonwoven fabric of Comparative Example 1 was obtained in the same manner as in Example 1, except that the unstretched polyester fiber of Example 1 was replaced with wood pulp (N-BKP). Due to the wood pulp containing a large amount of thin components, although the average pore size was of a certain value, the frequency of small pores was high, resulting in a nonwoven fabric with poor permeability. The composition and physical properties are also shown in Table 1.

[0074] (Comparative Example 2) A biodegradable polyester nonwoven fabric of Comparative Example 2 was obtained in the same manner as in Example 3, except that the unstretched polyester fiber of Example 3 was replaced with wood pulp (N-BKP). Although the strength was slightly improved by using wood pulp containing a large amount of fine components, the nonwoven fabric had a small pore size and poor permeability. The composition and physical properties are also shown in Table 1.

[0075]

[0076] (Comparative Example 3) A polyester nonwoven fabric was obtained in the same manner as in Example 1, except that it did not contain the unstretched polyester fibers of Example 1 and consisted only of stretched polyester fibers. The strength was insufficient, and a sheet-like nonwoven fabric could not be obtained.

[0077] The biodegradable polyester nonwoven fabric of the present invention rapidly decomposes in seawater while maintaining the pore size required for filters, etc. It can be effectively used in nonwoven fabric products such as food extract containers, packaging, masks, filters, sanitary products, wipes, and hand towels.

Claims

1. A biodegradable polyester nonwoven fabric characterized by containing 20% ​​by weight or more of unstretched fibers made of aliphatic polyester resin, having a fineness of 0.1 dtex or more, containing a phosphite ester-based decomposition accelerator, and having a peak temperature of crystallization upon heating of 100°C or less.

2. The biodegradable polyester nonwoven fabric according to claim 1, further comprising drawn fibers made of an aliphatic polyester resin and having a fineness of 20 dtex or less.

3. The biodegradable polyester nonwoven fabric according to claim 1, wherein the aliphatic polyester resin is a marine biodegradable resin.

4. The biodegradable polyester nonwoven fabric according to claim 1, wherein the aliphatic polyester resin contains 0.1 to 20% by weight of a phosphite decomposition accelerator.

5. A nonwoven fabric product made from the biodegradable polyester nonwoven fabric according to any one of claims 1 to 4.

6. The nonwoven fabric product according to claim 5, which is for use in food extraction.

7. The nonwoven fabric product according to claim 6, which is one of a tea bag, a coffee filter, and a soup stock bag.

8. The nonwoven fabric product according to claim 5, which is any one of a container, packaging, mask, filter, sanitary product, wiper, and wet towel.

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