Biodegradable polyester resin and method for producing the same

Abstract

To provide a biodegradable polyester resin which has improved degradability under the natural environment.SOLUTION: A biodegradable polyester resin is composed of a dicarboxylic acid component and a diol component. In the total acid components, 35 mol% or more of an aliphatic dicarboxylic acid component is contained, and 1 ppm or more of a sulfur component is contained. The biodegradable polyester resin preferably contains 20 mol% or more of an aliphatic diol component in the total diol components. The aliphatic diol component is preferably ethylene glycol and / or 1,4-butanediol.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a biodegradable polyester resin and a method for producing the same. Background Art

[0002] Polyester resins are widely used in various fields because they are lightweight, easy to process, and inexpensive. Polyester resins hardly decompose in the natural environment and remain in the ground semi-permanently even when buried. As a result, problems such as damage to the landscape and destruction of the living environment of marine organisms have occurred due to discarded polyester products. To solve these problems, recycling systems for polyester resins such as a separate waste collection system, a returnable system, and a deposit system are being introduced, but they have not been sufficiently penetrated to end-users at present.

[0003] As a resin that can solve environmental problems, a so-called biodegradable polyester resin that is decomposed by enzymes of microorganisms existing in nature is known. Examples of biodegradable polyester resins include polylactic acid, polyethylene succinate, polybutylene succinate, etc., and these are used in a wide range of applications such as packaging containers, tableware, stationery, garbage bags, sundries, etc.

[0004] For example, Patent Document 1 discloses a molded article made of a biodegradable resin containing polylactic acid as an essential component and containing polybutylene succinate adipate or polybutylene adipate terephthalate.

[0005] Japanese Patent Application Laid-Open No. 2005-350530 Summary of the Invention

[0006] In recent years, society's awareness of natural environment protection has been increasing further. For example, in order to suppress the adverse effects on marine organisms by microplastics caused by the disposal of plastic products into the ocean, a biodegradable polyester resin with even better degradability in the natural environment is desired.

[0007] This invention was made in view of the above background, and aims to provide a biodegradable polyester resin with improved decomposition properties in the natural environment.

[0008] The present inventors, in order to solve the above problems, have diligently studied and arrived at the present invention. That is, the gist of the present invention is as follows (1) to (9): (1) A biodegradable polyester resin comprising a dicarboxylic acid component and a diol component, wherein the total acid component contains 35 mol% or more of an aliphatic dicarboxylic acid component and 1 ppm or more of a sulfur component. (2) The biodegradable polyester resin of (1), wherein the total diol component contains 20 mol% or more of an aliphatic diol component. (3) The biodegradable polyester resin of (1) or (2), wherein the aliphatic diol component is ethylene glycol and / or 1,4-butanediol. (4) Any of the biodegradable polyester resins of (1) to (3), wherein the upper limit of the sulfur component content is 500 ppm or less. (5) Any of the biodegradable polyester resins of (1) to (4), which do not contain catalyst-derived metal components. (6) Any biodegradable polyester resin from (1) to (5) that has a retention rate of 60% or less of the intrinsic viscosity after being treated in water at 60°C for 7 days. (7) Any biodegradable polyester resin from (1) to (6) that has a retention rate of 70% or less of the number-average molecular weight after being treated in an environment of 60°C and 85% RH humidity for 7 days. (8) Any biodegradable polyester resin from (1) to (7) that has a degree of biodegradation of 60% or more after 80 days under conditions of seawater temperature of 30°C ± 2°C in a marine biodegradation test (ASTM D6691). (9) A method for producing a biodegradable polyester resin according to any of (1) to (8), wherein an organic sulfonic acid compound is used as a polymerization catalyst. (10) A fiber composed of a biodegradable polyester resin according to any of (1) to (8).

[0009] The biodegradable polyester resin of the present invention, by containing a specific amount of sulfur component, not only exhibits biodegradability but also improves its ability to decompose under moist heat, making it more susceptible to hydrolysis. As a result, biodegradation and hydrolysis by microorganisms proceed, further enhancing its decomposition capabilities in natural environments. Brief explanation of the drawing [Figure 1] An example of a schematic cross-section of a segmented composite form composed of the biodegradable polyester resin of the present invention is shown. [Figure 2] Another example of a schematic cross-section of a segmented composite form composed of the biodegradable polyester resin of the present invention is shown. Modes for carrying out the invention

[0011] The present invention will now be described in detail. The biodegradable polyester resin of the present invention is composed of a dicarboxylic acid component and a diol component. Of the total acid components constituting the polyester resin, the content of the aliphatic dicarboxylic acid component is 35 mol% or more, preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 100 mol%. If it is less than 35 mol%, the crystallinity becomes too high, and the moist heat decomposition and biodegradability decrease.

[0012] Examples of aliphatic dicarboxylic acid components include oxalic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, pimelic acid, suberic acid, azelaic acid, undecanediic acid, dodecanediic acid, tridecanediic acid, tetradecanediic acid, pentadecanediic acid phthalic acid, and others.

[0013] In particular, oxalic acid, succinic acid, glutaric acid, adipic acid, or sebacic acid are preferred because they are readily available as plant-derived raw materials and have superior biodegradability, succinic acid, adipic acid, and sebacic acid are more preferred, and succinic acid and adipic acid are even more preferred.

[0014] To the extent that the effects of the present invention are not impaired, acid components other than aliphatic dicarboxylic acid components may be included. Examples of such acid components include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 5-(alkali metal) sulfoisophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, or their ester-forming derivatives, as well as unsaturated aliphatic dicarboxylic acids such as fumaric acid, maleic acid, itaconic acid, or their ester-forming derivatives.

[0015] In the biodegradable polyester resin of the present invention, it is preferable that the total diol components contain 20 mol% or more of aliphatic diol components, more preferably 30 mol% or more, even more preferably 50 mol% or more, even more preferably 80 mol% or more, and particularly preferably 100 mol%. If the content of aliphatic diol components in the total diol components is less than 20 mol%, the crystallinity may become too high, which may reduce the moist heat decomposition and biodegradability.

[0016] Examples of aliphatic diol components include ethylene glycol, 1,4-butanediol, 1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,4-butylene glycol, 1,5-pentanediol, and 1,6-hexanediol. Among these, ethylene glycol and 1,4-butanediol are preferred because they are readily available as plant-derived raw materials and have superior biodegradability.

[0017] Examples of diol components other than aliphatic diols include polyalkylene glycols such as polyethylene glycol, triethylene glycol, and polytetramethylene glycol, hydroquinone, 4,4'-dihydroxybisphenol, 1,4-bis(β-hydroxyethoxy)benzene, bisphenol A, 2,5-naphthalenediol, and aromatic diols such as glycols obtained by adding ethylene oxide to these diols.

[0018] The biodegradable polyester resin of the present invention may contain components having three or more ester-forming groups. Examples of components having three or more ester-forming groups include at least one three- or more polyfunctional compound selected from three or more polyhydric alcohols; three or more polyhydric carboxylic acids or their anhydrides, acid chlorides, or esters; and three or more hydroxycarboxylic acids or their anhydrides, acid chlorides, or esters.

[0019] Examples of polyhydric alcohols with three or more functionalities include glycerin, trimethylolpropane, and pentaerythritol. These may be used individually or in combination of two or more.

[0020] Examples of polycarboxylic acids with three or more functionalities or their anhydrides include trimesic acid, propanetricarboxylic acid, trimellitic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, and cyclopentatetracarboxylic anhydride. These may be used individually or in combination of two or more.

[0021] Examples of hydroxycarboxylic acids with three or more functionalities include malic acid, hydroxyglutaric acid, hydroxymethylglutaric acid, tartaric acid, citric acid, hydroxyisophthalic acid, and hydroxyterephthalic acid. These may be used individually or in combination of two or more.

[0022] The content of components having three or more ester-forming groups is preferably 0.01 mol% to 2.0 mol% of the total acid components constituting the biodegradable polyester resin of the present invention. If it exceeds 2.0 mol%, the crosslinking of the polymer may proceed excessively, which can lead to problems such as difficulty in stably extracting strands, deterioration of moldability, and impairment of various physical properties, and is therefore undesirable.

[0023] The biodegradable polyester resin of the present invention contains 1 ppm or more of sulfur. By containing 1 ppm or more of sulfur, the polyester resin of the present invention has improved moist heat decomposition properties in addition to biodegradability by microorganisms, and becomes more susceptible to hydrolysis. As a result, biodegradation by microorganisms and hydrolysis proceed, further improving its decomposition properties in the natural environment. The sulfur content is preferably 1 to 500 ppm, more preferably 5 to 300 ppm, even more preferably 10 to 200 ppm, and particularly preferably 15 to 150 ppm. If it exceeds 500 ppm, the resin may have a low degree of polymerization, the molecular weight may not increase sufficiently, and it may have inferior moldability and strength. Furthermore, if hydrolysis proceeds too far, a significant decrease in strength may occur when it is made into molded articles or fibers, and it may not be suitable for practical use. The sulfur component is preferably derived from an organic sulfonic acid compound used as a polymerization catalyst in the manufacturing method described later.

[0024] The biodegradable polyester resin of the present invention may be obtained using an organic sulfonic acid compound in combination with a metal catalyst as a polymerization catalyst, but it is preferable that it be obtained without using a metal catalyst. That is, it is preferable that the biodegradable polyester resin of the present invention does not contain metal components derived from the catalyst. Examples of metal catalysts include compounds such as germanium, antimony, titanium, zinc, aluminum, iron, magnesium, potassium, calcium, sodium, manganese, nickel, and cobalt.

[0025] The biodegradable polyester resin of the present invention may contain ether-bonded diols such as diethylene glycol and triethylene glycol. This increases the hydrophilicity of the resin and further improves its biodegradability. The content of ether-bonded diols is preferably 20 mol% or less, and more preferably 1 to 15 mol%, of the total diol components.

[0026] The biodegradable polyester resin of the present invention may contain an antioxidant. The content of the antioxidant is not particularly limited, but for example, it is 0.1 to 1.0% by mass in the biodegradable polyester resin.

[0027] Examples of the antioxidant include hindered phenol-based antioxidants and the like. Examples of the hindered phenol-based antioxidant include 2,6-di-t-butyl-4-methylphenol, n-octadecyl 3-(3’,5’-di-t-butyl-4’-hydroxyphenyl)propionate, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, 4,4’-butylidenebis-(3-methyl-6-t-butylphenol), triethylene glycol-bis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate], 3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1’-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane, etc. Among them, tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane is preferable in terms of effect and cost.

[0028] The biodegradable polyester resin of the present invention may contain an anti-coloring agent. Examples of the anti-coloring agent include phosphorus compounds such as phosphorous acid, phosphoric acid, polyphosphoric acid, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tridecyl phosphite, trimethyl phosphate, tridecyl phosphate, triphenyl phosphate, etc. These phosphorus compounds may be used alone or in combination of two or more.

[0029] The biodegradable polyester resin of the present invention may contain a crystallization nucleating agent. Examples of the crystallization nucleating agent include carbon black, calcium carbonate, synthetic silicic acid and silicate, zinc white, high-site clay, kaolin, basic magnesium carbonate, mica, talc, quartz powder, diatomaceous earth, dolomite powder, titanium oxide, zinc oxide, barium sulfate, calcium sulfate, alumina, calcium silicate, boron nitride, etc., and low molecular weight organic compounds having metal salts of carboxyl groups, for example, metal salts of octylic acid, toluic acid, heptanoic acid, pelargonic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, cerotic acid, montanic acid, mellitic acid, benzoic acid, p-tert-butylbenzoic acid, terephthalic acid, monomethyl terephthalate, isophthalic acid, monomethyl isophthalate, etc.

[0030] The content of the crystallization nucleating agent is preferably 0.1 to 5 parts by mass, more preferably 1 to 2 parts by mass, based on 100 parts by mass of the biodegradable polyester resin. If it is less than 0.1 part by mass, a predetermined effect may be difficult to obtain, and if it exceeds 5 parts by mass, the effect is saturated and uneconomical and may not be preferable.

[0031] The intrinsic viscosity of the biodegradable polyester resin of the present invention is preferably 1.0 to 2.0 from the viewpoint of excellent moldability into containers, fibers, films, etc. and strength when formed into molded products.

[0032] The biodegradable polyester resin of the present invention is excellent in hydrothermal decomposability. As an index of hydrothermal decomposability, the retention rate of the intrinsic viscosity after treatment in water at 60°C for 7 days is preferably 60% or less, more preferably 50% or less, and even more preferably 40% or less. Details of the calculation method of the retention rate of the intrinsic viscosity will be described later in the examples.

[0033] The number-average molecular weight of the biodegradable polyester resin of the present invention is preferably 20,000 or more, more preferably 40,000 or more, and even more preferably 60,000 or more. If the number-average molecular weight is less than 40,000, it tends to be difficult to mold it into containers, fibers, films, etc., or the strength of the molded product may be insufficient.

[0034] The biodegradable polyester resin of the present invention preferably has a number-average molecular weight retention rate of 70% or less, more preferably 60% or less, and even more preferably 30% or less, when treated for 7 days at a temperature of 60°C and a humidity of 85% RH, as another indicator of its moist heat decomposition properties. The lower limit of this retention rate is preferably 5%, more preferably 10%, and even more preferably 14%. If it is less than 5%, hydrolysis may proceed too much, which may cause a decrease in strength when used in molded articles or fibers. Details of the method for calculating the number-average molecular weight retention rate will be described later in the examples.

[0035] The biodegradable polyester resin of the present invention preferably has a biodegradability of 60% or more, more preferably 70% or more, and even more preferably 75% or more, as an indicator of biodegradability in marine biodegradability tests (ASTM D6691). The biodegradability is measured after 80 days under conditions of a seawater temperature of 30°C ± 2°C, and the details of the calculation method will be described later in the examples.

[0036] The biodegradable polyester resin of the present invention preferably has a glass transition temperature of -50 to 30°C. Furthermore, it is preferable that its crystal melting point be 80 to 140°C.

[0037] An example of a method for producing the biodegradable polyester resin of the present invention is described below. For example, using the above-mentioned acid component and diol component as raw materials, an esterification or transesterification reaction is carried out by a conventional method at a temperature of 200 to 260°C, followed by the addition of a polymerization catalyst, and a polycondensation reaction is carried out at a temperature of 230 to 280°C, preferably 240 to 280°C, under a reduced pressure of 5 hPa or less.

[0038] The molar ratio (G / A) of glycol component (G) to dicarboxylic acid component (A) in the polyester resin raw material is preferably 1.00 to 2.00, and more preferably 1.05 to 1.50. If it is less than 1.00, the esterification or transesterification reaction may not proceed sufficiently, and the polycondensation reaction may not proceed easily. On the other hand, if it exceeds 2.00, the polycondensation reaction may require a long time.

[0039] Furthermore, depending on the purpose and application, an acid component or a diol component may be added to the polymer obtained by the polycondensation reaction, and a depolymerization reaction may be carried out at a temperature of 240 to 280°C.

[0040] An organic sulfonic acid compound is used as the polymerization catalyst. This allows the resulting biodegradable polyester resin to contain sulfur components within a specific range. To easily control the sulfur content within a specific range, the amount of organic sulfonic acid compound added is preferably 0.1 × 10⁻⁴ moles or more, and more preferably 1 × 10⁻⁴ to 20 × 10⁻⁴ moles, per mole of the acid component constituting the biodegradable polyester resin. If the amount of organic sulfonic acid compound added is less than 1 × 10⁻⁴ moles, the sulfur component in the resulting polyester resin may be insufficient. Conversely, if it exceeds 20 × 10⁻⁴ moles, the sulfur component in the resulting polyester resin will be too high, and hydrolysis and thermal decomposition during polymerization may be accelerated, reducing polymerizability, which may result in insufficient molecular weight increase or even failure to obtain the resin itself.

[0041] Examples of organic sulfonic acid compounds include benzenesulfonic acid, m- or p-benzenedisulfonic acid, 1,3,5-benzenetrisulfonic acid, o-, m- or p-sulfobenzoic acid, benzaldehyde-o-sulfonic acid, acetophenone-p-sulfonic acid, acetophenone-3,5-disulfonic acid, o-, m- or p-aminobenzenesulfonic acid, sulfanilic acid, 2-aminotoluene-3-sulfonic acid, phenylhydroxylamine-3-sulfonic acid, phenylhydrazine-3-sulfonic acid, 1-nitronaphthalene-3-sulfonic acid, thiophenol-4-sulfonic acid, anisole-o-sulfonic acid, and 1,5-na Phthalenedisulfonic acid, o-, m- or p-chlorobenzenesulfonic acid, o-, m- or p-bromobenzenesulfonic acid, o-, m- or p-nitrobenzenesulfonic acid, nitrobenzene-2,4-disulfonic acid, nitrobenzene-3,5-disulfonic acid, nitrobenzene-2,5-disulfonic acid, 2-nitrotoluene-5-sulfonic acid, 2-nitrotoluene-4-sulfonic acid, 2-nitrotoluene-6-sulfonic acid, 3-nitrotoluene-5-sulfonic acid, 4-nitrotoluene-2-sulfonic acid, 3-nitro-o-xylene-4-sulfonic acid, 5-nitro-o-xylene-4-sulfonic acid, 2-nitro-m-xylene n-4-sulfonic acid, 5-nitro-m-xylene-4-sulfonic acid, 3-nitro-p-xylene-2-sulfonic acid, 5-nitro-p-xylene-2-sulfonic acid, 6-nitro-p-xylene-2-sulfonic acid, 2,4-dinitrobenzenesulfonic acid, 3,5-dinitrobenzenesulfonic acid, o-, m- or p-fluorobenzenesulfonic acid, 4-chloro-3-methylbenzenesulfonic acid, 2-chloro-4-sulfobenzoic acid, 5-sulfosalicylic acid, 4-sulfophthalic acid, 2-sulfobenzoic anhydride, 3,4-dimethyl-2-sulfobenzoic anhydride, 4-methyl-2-sulfobenzoic anhydride, 5-methoxy-2-sulfobenzoic acid Aromatic anhydride, 1-sulfonaphthoic acid anhydride, 8-sulfonaphthoic acid anhydride, 3,6-disulfophthalic acid anhydride, 4,6-disulfoisulfalic acid anhydride, 2,5-disulfoterephthalic acid anhydride, methanesulfonic acid, ethanesulfonic acid, methionic acid, cyclopentanesulfonic acid, 1,1-ethanedisulfonic acid, 1,2-ethanedisulfonic acid, 1,Examples include 2-ethanedisulfonic acid anhydride, 3-propanedisulfonic acid, β-sulfopropionic acid, isethionic acid, nithionic acid, nithionic acid anhydride, 3-oxy-1-propanesulfonic acid, 2-chloroethanesulfonic acid, phenylmethanesulfonic acid, β-phenylethanesulfonic acid, α-phenylethanesulfonic acid, ammonium chlorosulfonate, methyl benzenesulfonate, ethyl p-toluenesulfonate, ethyl methanesulfonate, dimethyl 5-sulfosalicylate, trimethyl 4-sulfophthalate, and salts thereof. In particular, from the viewpoint of versatility, 2-sulfobenzoic anhydride, o-sulfobenzoic acid, m-sulfobenzoic acid, p-sulfobenzoic acid, 5-sulfosalicylic acid, benzenesulfonic acid, o-aminobenzenesulfonic acid, m-aminobenzenesulfonic acid, p-aminobenzenesulfonic acid, p-toluenesulfonic acid, p-toluenesulfonic acid, methyl p-toluenesulfonate, 5-sulfoisophthalic acid, and their salts are preferred.

[0042] In the manufacturing method of the present invention, by using an organic sulfonic acid compound as a polymerization catalyst, a specific amount of sulfur can be incorporated into the polyester resin, resulting in a polyester resin that exhibits biodegradability. If an organic sulfonic acid compound is not used and only other polymerization catalysts (for example, metal catalysts) are used, the sulfur content cannot be kept within a specific range, and a polyester resin with excellent biodegradability cannot be obtained.

[0043] The biodegradable polyester resin of the present invention exhibits excellent decomposition in the natural environment. Its applications are not particularly limited, but examples include molded articles, fibers, sheets, films, adhesives, and resin solutions.

[0044] The molded articles, sheets, films, and fibers using the biodegradable polyester resin of the present invention are suitably used in a wide range of applications, such as packaging materials for liquids, powders, and solids of various foods, pharmaceuticals, and general merchandise, as well as agricultural materials and construction materials, and are particularly suitable for disposable applications. Specifically, it can be used in injection-molded products (e.g., trays for fresh food, fast food containers, coffee capsule containers, cutlery, outdoor leisure products, etc.), extruded products (e.g., fishing lines, fishing nets, vegetation nets, sheets for secondary processing, water-retaining sheets, etc.), hollow-molded products (bottles, etc.), agricultural mulch films, tunnel films, greenhouse films, sunshades, weed control sheets, ridge sheets, germination sheets, fumigation sheets for forestry, binding tapes including flat yarn, components such as back sheets and top sheets for sanitary materials such as diapers, packaging sheets, shopping bags, plastic bags, garbage bags, drainer bags, compost bags, etc., ropes, binding materials, and for medical use, surgical threads, sutures, crimped tapes, face masks, wet wipes, etc., and is particularly suitable for use in disposable applications.

[0045] The forms of fibers composed of the biodegradable polyester resin of the present invention include long fibers (continuous fibers) and short fibers. Long fibers may be monofilaments or multifilaments. Short fibers may be staple fibers or short-cut fibers. In addition, a split yarn is an example of a fiber form other than those described above.

[0046] When the fibers are in the form of long fibers (continuous fibers), they can be obtained by melt spinning, winding, and roller stretching using the biodegradable polyester resin of the present invention via the FDY method or POY method. Alternatively, using the spunbond method, the biodegradable polyester resin of the present invention can be melt-spun, and the numerous spun fibers can be deposited and collected on a net or the like to obtain a long fiber web. A nonwoven fabric can then be obtained by integrating the long fibers with each other through processes such as heat embossing or needle punching.

[0047] When the fibers are to be in the form of short fibers, the biodegradable polyester resin of the present invention can be used to melt-spin the fibers, then the bundled fibers can be heat-stretched at an appropriate ratio, and finally cut to the desired length to obtain short fibers.

[0048] When the short fibers are staple fibers, the fiber length is preferably about 20 to 150 mm, and the fibers are mechanically crimped. Such staple fibers can be used for dry nonwoven fabrics (e.g., thermal-through nonwoven fabrics, spunlace nonwoven fabrics, needle-punched nonwoven fabrics, airlaid nonwoven fabrics, nonwoven fabrics that are entangled by needle punching or spunlace and then heat-bonded, etc.) or for spinning yarn. Furthermore, dry nonwoven fabrics made from staple fibers can be suitably applied to various components such as hygiene products, diapers, and incontinence pads. When obtaining spinning yarn or dry nonwoven fabric, fibers other than those made from the biodegradable polyester resin of the present invention may be mixed in as appropriate.

[0049] If the short fibers are short-cut fibers, the fiber length should be approximately 2 to 20 mm, and they can be used for wet-laid nonwoven fabrics and synthetic paper. It is preferable that the short-cut fibers are not crimped, but rather treated with oils or other agents to provide water dispersibility. Wet-laid nonwoven fabrics composed of short-cut fibers are suitable for applications such as filters. When obtaining wet-laid nonwoven fabrics, other fibers besides those made from the biodegradable polyester resin of the present invention may be mixed in as appropriate.

[0050] Examples of characteristic values ​​for fibers made from the biodegradable polyester resin of the present invention include single fiber fineness of 0.5 to 25.0 decitex, strength of 0.1 to 6.0 cN / decitex, and elongation of 20 to 200%. The above physical properties can be adjusted by changing the conditions in the spinning and drawing processes depending on the application to which the fibers are used.

[0051] Examples of fiber cross-sectional forms include single-phase fibers composed solely of the biodegradable polyester resin of the present invention, single-phase fibers made by blending at least two resins with different constituent components of the biodegradable polyester resin of the present invention, composite fibers made by combining multiple resins with different constituent components of the biodegradable polyester resin of the present invention, and composite fibers made by combining the biodegradable polyester resin of the present invention with other resins. Furthermore, fibers with irregular cross-sectional shapes other than circular are also acceptable, as are hollow cross-sectional fibers having hollow portions. In the case of single-phase fibers, if they are made of a biodegradable polyester resin with a relatively low melting point (for example, 180°C or less) among the biodegradable polyester resins of the present invention, they can be used as fully melted type heat binder fibers.

[0052] Examples of composite fiber cross-sectional forms include side-by-side composite forms, core-sheath composite forms, sea-island composite forms, and morphologically divided composite forms. When forming composite forms, examples include combinations of different constituent resins of the biodegradable polyester resin of the present invention, combinations of the biodegradable polyester resin of the present invention with other biodegradable resins, and combinations of the biodegradable polyester resin of the present invention with other non-biodegradable resins. These combinations can be appropriately selected according to the required characteristics and applicable uses. Furthermore, considering the characteristics of the biodegradable polyester resin of the present invention, it is also preferable to select a biodegradable resin such as polylactic acid when combining it with other resins.

[0053] In a core-sheath composite form, if the core component is made of the biodegradable polyester resin of the present invention with a high melting point, and the sheath component is made of the biodegradable polyester resin of the present invention with a low melting point, it can be used as a heat-adhesive fiber in which the sheath component functions as a heat-adhesive binder component. Furthermore, if the core component is made of a polylactic acid resin with a melting point of about 170-180°C, and the sheath component is made of the biodegradable polyester resin of the present invention with a melting point of 160°C or lower, it can be used as a heat-adhesive fiber with biodegradability. It is preferable to mix the aforementioned fully melted type heat-adhesive fiber and the core-sheath composite form heat-adhesive fiber with a main fiber such as a fiber made of a resin with a high melting point or a natural fiber rather than a low melting point binder component to obtain spun yarn or nonwoven fabric.

[0054] Examples of the segmented composite form include combinations of different constituent resins of the biodegradable polyester resin of the present invention, combinations of the biodegradable polyester resin of the present invention with other biodegradable resins, and combinations of the biodegradable polyester resin of the present invention with other non-biodegradable resins. Examples of the segmented composite form include a cross-sectional form in which the region of one resin component is divided by the presence of the region of the other resin component, such as a form in which the two constituent resins are arranged radially, a form in which the two constituent resins are stacked in multiple stripes, and a multi-leaf form in which one resin is arranged in a core and the other resin is arranged around the core with numerous leaf parts.

[0055] In such a segmented composite fiber, by combining two constituent resins with poor compatibility, physical impact can be applied to the segmented composite fiber, causing delamination and separation at the interface between the two constituent resins, thereby obtaining a fine fiber composed solely of each constituent resin.

[0056] Figures 1 and 2 show examples of schematic cross-sections of a segmented composite morphology. Figure 1 is a four-lobed section, and Figure 2 is a petal-shaped section. In Figure 1, the four leaf sections arranged around the core component are divided by the core component. In Figure 2, one component is arranged radially in a petal-like form within the other component, and the other component is divided by the petal-like component.

[0057] The biodegradable polyester resin of the present invention may be divided into multiple units by other components and arranged accordingly, or the other components may be divided into multiple units by the biodegradable polyester resin of the present invention. Furthermore, the biodegradable polyester resins of the present invention may be combined with other biodegradable polyester resins that have poor compatibility, and the biodegradable polyester resin of the present invention may be divided into multiple units by other biodegradable polyester resins with different constituent components, or vice versa. The divided composite form may also be flat or have a hollow portion in the center.

[0058] Physical impact methods applied to the split composite fibers include physical impact during the process of applying mechanical crimp in the fiber manufacturing process, physical impact when creating a web using a cotton blending machine or carding machine, physical impact when nonwoventing the obtained web by needle punching or high-pressure water jet treatment, and impact on woven fabrics, nonwoven fabrics, etc. made from the fibers of the present invention by high-pressure water jet treatment, liquid jet treatment, air jet treatment, etc. In particular, nonwoven fabrics in which the fibers are three-dimensionally intertwined and split fibers are formed by needle punching or high-pressure water jet treatment are very dense and have a good texture, making them suitable for use in medical and sanitary materials such as face masks and diapers that come into contact with the skin.

[0059] Next, the present invention will be specifically described with reference to examples. The various characteristic values ​​in the examples were measured or evaluated as follows: (a) Glass transition temperature, crystal melting point The obtained polyester resin was measured using a PerkinElmer differential scanning calorimeter (Diamond DSC) in a nitrogen stream, at a temperature range of -70°C to 200°C, a heating (cooling) rate of 20°C / min, and a sample amount of 8 mg.

[0060] (b) Number-average molecular weight The number-average molecular weight of the polyester resin was measured in polystyrene equivalent using gel permeation chromatography (GPC) under the following conditions: Liquid delivery device: Shimadzu Nexera-i Plus Detector: Shimadzu differential refractive index detector RID-10A Column: SHODEX LF-404 Solvent: Chloroform Flow rate: 0.3 ml / min Measurement temperature: 40℃

[0061] (c) Intrinsic viscosity: Polyester resin was measured in a phenol / tetrachloroethane = 1 / 1 (weight ratio) mixed solvent at a concentration of 0.5 wt% at 20°C.

[0062] (d) Composition of polyester resin The polyester resin was dissolved in deuterated chloroform, and 1H-NMR was measured using a JEOL nuclear magnetic resonance spectrometer (JNM-ECZ). The copolymerization amount and content of each component were determined from the integrated intensity of the proton peaks of each component in the resulting chart.

[0063] (e) Sulfur and metal content: Polyester resin was melt-molded at 300°C to form a disc-shaped molded plate with a diameter of 3 cm and a thickness of 1 cm. The content was determined by quantitative analysis using the calibration curve method with a Rigaku ZSX Primus X-ray fluorescence analyzer.

[0064] (f) Retention rate of number-average molecular weight after treatment at 60°C × 85%RH for 7 days. Polyester resin was prepared as a powder with an average particle size of 200 μm or less, and 50 mg of this powder was used as the sample. It was treated for 7 days in a constant temperature and humidity chamber manufactured by Shimadzu Corporation under conditions of an internal temperature of 60°C and internal humidity of 85%. The number-average molecular weight of the treated sample was measured using the same method as in (b) above, and the retention rate of the number-average molecular weight was calculated using the following formula: Retention rate (%) = (Number-average molecular weight of the sample after testing × 100) / (Number-average molecular weight of the sample before testing)

[0065] (g) Intrinsic viscosity retention rate after treatment in water at 60°C for 7 days. 4g of polyester resin was placed in a metal container with 200mL of water, sealed, and heated to 60°C for 7 days. The intrinsic viscosity of the treated sample was measured using the same method as in (c) above, and the retention rate of the number-average molecular weight was calculated using the following formula: Retention rate (%) = (Intrinsic viscosity of the sample after testing × 100) / (Intrinsic viscosity of the sample before testing)

[0066] (h) Marine Biodegradation Test (ASTM D6691) Polyester resin was prepared as a powder with an average particle size of 200 μm or less, and 50 mg of this powder was used as a sample. In accordance with ASTM D6691, the amount of CO2 emitted 80 days after the start of the test was measured, and the degree of biodegradation was calculated using the marine biodegradation test. The test was conducted using seawater at a measurement temperature of 30 ± 2℃. The following criteria were used for evaluation: ◎: Biodegradation of 75% or more 〇: Biodegradation of 70% or more but less than 75% △: Biodegradation of 60% or more but less than 70% ×: Biodegradation of less than 60%

[0067] Example 1: 81.9 parts by mass of succinic acid and 56.0 parts by mass of ethylene glycol were supplied to an esterification reactor and reacted at a temperature of 200°C, a pressure of 50 hPa, and for 2 hours to obtain an oligomer (esterified product). The oligomer was transferred to a polymerization reactor, and 0.05 parts by mass of 5-sulfosalicylic acid as an organic sulfonic acid compound, which is a polymerization catalyst, and 0.0868 parts by mass of polyphosphoric acid as a phosphate compound were added. The reactor was then subjected to reduced pressure, and after 60 minutes, the final pressure was set to 0.9 hPa. A melt polycondensation reaction was carried out at a temperature of 280°C for 5 hours to obtain a biodegradable polyester resin.

[0068] Examples 2-21 and Comparative Examples 1-2 yielded polyester resins in the same manner as in Example 1, except that the acid component, diol component, component having three or more ester-forming groups, the amount of nucleating agent added, the amount of organic sulfonic acid compound used as a polymerization catalyst, the amount of metal catalyst added, and the reaction temperature and reaction time of the melt polycondensation reaction were changed as shown in Table 1.

[0069] Comparative Examples 3-6: Polyester resins were obtained in the same manner as in Example 1, except that an organic sulfonic acid compound was not added as a polymerization catalyst, a metal catalyst was used in the amounts shown in Table 1, and the amounts of acid and diol components were changed as shown in Table 1.

[0070] [Table 1] The abbreviations in Tables 1 and 2 refer to the following: SU: succinic acid, ADA: adipic acid, SEA: sebacic acid, TPA: terephthalic acid, EG: ethylene glycol, BD: butanediol, BAEO: ethylene oxide adduct of bisphenol A, DEG: diethylene glycol, TEG: triethylene glycol, SS: 5-sulfosalicylic acid, GeO2: germanium dioxide, TBT: tetrabutyl titanate, Sb2O3: antimony trioxide

[0071] Table 2 shows the resin composition and sulfur content of the polyester resins obtained in Examples 1-21 and Comparative Examples 1-6. [Table 2]

[0072] Table 3 shows the evaluation results of the polyester resins obtained in Examples 1-21 and Comparative Examples 1-6. [Table 3]

[0073] As is clear from Table 3, the biodegradable polyester resins of the present invention obtained in Examples 1 to 21 exhibited excellent moist heat decomposition and biodegradability.

[0074] As can be seen from Examples 8 to 10, the biodegradable polyester resin of the present invention exhibited excellent moist heat decomposition and biodegradability even when using an organic sulfonic acid-based catalyst and a metal-based catalyst in combination.

[0075] On the other hand, the polyester resin obtained in Comparative Example 1 had a low sulfur content due to the small amount of organic sulfonic acid compound added as a polymerization catalyst, resulting in poor moist heat decomposition and biodegradability.

[0076] The polyester resin obtained in Comparative Example 2 had a low content of aliphatic dicarboxylic acid components, resulting in high crystallinity and poor resistance to moist heat decomposition and biodegradation.

[0077] The polyester resins obtained in Comparative Examples 3 to 6 were inferior in terms of moist heat decomposition and biodegradability because only metal-based catalysts were used as polymerization catalysts.

[0078] Next, we will describe an example in which fibers were manufactured using the polyester resin obtained in the above example. The fiber properties were measured by the following methods: (1) Fiber fineness: The measurement was performed in accordance with JIS L1015 8.5.1 Method A, except that the measurement sample was cut to a length of 20 mm, 100 fibers were taken out and their mass was measured, and the number of measurements was 4. (2) Fiber strength and elongation: Measured in accordance with JIS L-1015 8.7.

[0079] Example 22 (Short Fibers) Using the biodegradable polyester resin obtained in Example 4, melt spinning was performed using a die with 1040 pores and a pore diameter of 0.22 mm, at a discharge rate of 440 g / min, a spinning temperature of 240°C, and a spinning speed of 700 m / min. Next, the obtained undrawn yarn was gathered to form a 50 ktex tow, which was then drawn at a drawing temperature of 65°C and a draw ratio of 3.1 times. Then, mechanical crimping was applied using a push-type crimper, and after applying a finishing oil, the fibers were cut to a length of 51 mm to obtain single-phase short fibers with a fineness of 2.4 dtex, a strength of 2.5 cN / dtex, and an elongation of 52%.

[0080] Example 23 (Core-Sheath Type Composite Short Fiber) Poly-DL-lactic acid (PLA6202D, manufactured by NW Corporation), mainly composed of L-lactic acid with an L-lactic acid / D-lactic acid (copolymerization molar ratio) of 98.7 / 1.3, was placed in the core, and the biodegradable polyester resin obtained in Example 4 was placed in the sheath. A die with 1014 holes and a hole diameter of 0.35 mm was used, and melt spinning was performed at a spinning temperature of 240°C and a spinning speed of 700 m / min with a discharge rate of 428 g / min and a core-sheath mass ratio of 50 / 50. Next, the obtained undrawn yarn was gathered to form a 50 ktex tow and drawn at a drawing temperature of 75°C and a drawing ratio of 3.0 times. Next, mechanical crimping was applied using a push-type crimper, followed by the application of a finishing oil. The fibers were then cut to a length of 51 mm to obtain core-sheath type composite short fibers with a fineness of 2.4 dtex, a strength of 2.5 cN / dtex, and an elongation of 49%.

[0081] Example 24 (Split-type composite short fiber) Using poly-DL-lactic acid (PLA6202D, manufactured by NW Corporation) mainly composed of L-lactic acid with an L-lactic acid / D-lactic acid (copolymerization molar ratio) of 98.7 / 1.3 and the biodegradable polyester resin of Example 4, a 4-lobe composite spinneret (10¹⁴ holes) was used, resulting in a fiber cross-section of 4 lobes as shown in Figure 1 (5 divisions in total for both components). Poly-DL-lactic acid was placed in the lobe portion, and the biodegradable polyester resin of Example 4 was placed in the core portion. The composite ratio was set to core / lobe = 35 / 65 as a melt volume ratio. Melt spinning was performed under the conditions of a spinning temperature of 230°C, an extrusion rate of 485 g / min, and a spinning speed of 800 m / min to obtain undrawn split-type composite fibers. Next, the obtained undrawn yarn was drawn at a drawing temperature of 65°C and a drawing ratio of 2.90 times, then mechanically crimped using a push-type crimper, and after applying a finishing oil, it was cut to a fiber length of 51 mm to obtain split-type composite staple fibers with a fineness of 2.2 dtex, a strength of 2.9 cN / dtex, and an elongation of 41%.

[0082] Example 25 (Split-type composite short fiber) Using poly-DL-lactic acid (PLA6202D, manufactured by NW Corporation) mainly composed of L-lactic acid with an L-lactic acid / D-lactic acid (copolymerization molar ratio) of 98.7 / 1.3 and the biodegradable polyester resin of Example 4, a petal-shaped cross-section composite spinneret (850 holes) with 20 divisions (total of both components) as shown in Figure 2 was used. Poly-DL-lactic acid was arranged in the petal-shaped portion, and the biodegradable polyester resin of Example 4 was arranged in the non-petal-shaped region. Melt spinning was performed with a composite ratio of 50 / 50 as a melt volume ratio, a spinning temperature of 230°C, an extrusion rate of 550 g / min, and a spinning speed of 860 m / min to obtain undrawn split-type composite fibers. Next, the obtained undrawn yarn was drawn at a drawing temperature of 60°C and a drawing ratio of 2.50 times. Then, mechanical crimping was applied using a push-type crimper, and after applying a finishing oil, it was cut to a fiber length of 51 mm to obtain split-type composite staple fibers with a fineness of 3.3 dtex, a strength of 2.2 cN / dtex, and an elongation of 55%.

Claims

1. A polyester resin comprising a dicarboxylic acid component and a diol component, The total acid components contain 35 mol% or more of an aliphatic dicarboxylic acid component, and a biodegradable polyester resin containing 1 ppm or more of a sulfur component.

2. 2. The biodegradable polyester resin according to claim 1, wherein the biodegradable polyester resin contains 20 mol% or more of an aliphatic diol component in all diol components.

3. 3. The biodegradable polyester resin according to claim 1, wherein the aliphatic diol component is ethylene glycol and / or 1,4-butanediol.

4. The biodegradable polyester resin according to any one of claims 1 to 3, wherein the upper limit of the sulfur component content is 500 ppm or less.

5. The biodegradable polyester resin according to any one of claims 1 to 4, which does not contain a metal component derived from a catalyst.

6. The biodegradable polyester resin according to any one of claims 1 to 5, which has an intrinsic viscosity retention rate of 60% or less after treatment in water at a temperature of 60°C for 7 days.

7. The biodegradable polyester resin according to any one of claims 1 to 6, wherein the retention rate of the number average molecular weight after treatment for 7 days in an environment of a temperature of 60°C and a humidity of 85% RH is 70% or less.

8. The biodegradable polyester resin according to any one of claims 1 to 7, wherein the biodegradability after 80 days is 60% or more in a marine biodegradability test (ASTM D6691) under conditions of a seawater temperature of 30 ° C. ± 2 ° C.

9. 9. A method for producing the biodegradable polyester resin according to claim 1, wherein an organic sulfonic acid compound is used as a polymerization catalyst.

10. A fiber comprising the biodegradable polyester resin according to any one of claims 1 to 8.

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