Marine biodegradable polyester resin molded article and method for producing the same

Abstract

The marine degradable polyester resin composition of the present invention, which is a resin composition comprising mainly a polyester and containing a phosphite degradation accelerator, is characterized in that the phosphite degradation accelerator is a compound represented by chemical formula (I). Furthermore, it is preferred that the phosphite degradation accelerator is a dialkyl pentaerythritol diphosphite, that the polyester resin composition is an aliphatic polyester, or that the polyester resin composition is poly-L-lactic acid or poly-D-lactic acid having an optical purity of 90% or higher. The polyester resin molded body of the present invention is characterized by being made of the aforesaid marine degradable polyester resin composition.

Description

Technical Field

[0001] The present invention relates to an ocean-degradable polyester resin composition and a molded article made therefrom.

Background Art

[0002] In recent years, various plastics such as bottles and fiber scraps have flowed into the ocean, which not only affects the ecosystem but also raises concerns about affecting humans through bioaccumulation and the like. For example, a large number of cases of ghost fishing (accidental ingestion or entanglement on the body) have been observed in marine organisms (such as marine mammals, sea turtles, seabirds, fish, etc.). Although plastics are crushed and subdivided in the natural environment as a pre-stage of decomposition, some marine organisms mistake the subdivided plastics for plankton and accidentally ingest or absorb them, which not only inhibits the absorption of nutrients but may even cause death. In addition, plastics may adsorb harmful substances and be incorporated into the food chain, and there are also concerns about the subsequent impact on humans due to bioaccumulation.

[0003] To prevent these, although various efforts such as charging for plastic vinyl bags have spread, they are still insufficient.

[0004] As an approach from the material for this problem, the development of ocean-degradable plastics as alternative materials that decompose rapidly in the ocean has attracted attention. For example, there is a private organization that presents "plastic having a decomposition rate of 90% in 6 months in seawater at 30°C" as an index of ocean-degradable plastics and is active.

[0005] However, the improvement of this "decomposition rate in seawater at 30°C" is more difficult than the improvement of the decomposition property in soil or compost. This is because there are few bacteria and the like that decompose plastics in the sea, and there are adverse conditions such as low oxygen concentration in the sea.

[0006] Currently, the only known resins that decompose in the sea are copolymer resins using 3-hydroxybutyrate-3-hydroxyhexanoic acid as a monomer, and starch-based polymers. While many biodegradable polymers have been shown to decompose in soil and compost, achieving high decomposition in water, especially seawater, remains a major challenge.

[0007] In particular, improving the biodegradability of polyester resins, which have excellent physical properties and versatility and have been widely used as films, fibers, and injection-molded products, has been difficult.

[0008] For example, polylactic acid, a type of polyester resin, is made from lactic acid or its derivatives obtained from plant-derived raw materials, and is therefore known as an environmentally friendly polymer material that is biodegradable in soil.

[0009] However, polylactic acid, especially its homopolymers, has high crystallinity and glass transition temperatures, and low biodegradability by water and enzymes, resulting in a problem of slow decomposition in the natural environment. These aliphatic polyesters exhibit relatively rapid hydrolysis only in high-temperature environments such as compost. However, particularly in high molecular weight polymers, they do not easily decompose in water or seawater at low temperatures of around 30°C.

[0010] Patent Document 1 discloses a method for promoting decomposition by adding organic carboxylic acids and organic carboxylate salts to polylactic acid. However, although the decomposition rate improved under an 80°C × 90%RH environment, the decomposition rate was insufficient under environments where there was almost no decrease in molecular weight, such as seawater at 30°C. Patent Document 2 proposes a composition in which a copolymer of malic acid or aspartic acid and polylactic acid is blended with polylactic acid. However, although a rapid weight reduction was observed under a high-temperature alkaline environment, the effect was significantly reduced under a neutral environment of pH 7.4.

[0011] Until now, no polyester composition had been found that exhibited high biodegradability even in anaerobic environments with few bacteria, such as seawater at 30°C. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Japanese Patent Publication No. 2002-256142 [Patent Document 2] International Publication No. 2018 / 079662 Brochure [Overview of the project] [Problems that the invention aims to solve]

[0013] The present invention aims to solve the above-mentioned conventional problems and provide a marine biodegradable polyester resin composition that decomposes rapidly even in low-temperature seawater. [Means for solving the problem]

[0014] The marine biodegradable polyester resin composition of the present invention is a resin composition mainly composed of polyester, and is characterized in that it contains a phosphite ester-based decomposition accelerator, wherein the phosphite ester-based decomposition accelerator is a compound represented by the following general formula (I).

[0015] [ka]

[0016] (In general formula (I), R is an alkyl group, an aryl group, or a hydrogenated bisphenol A skeleton, and these may be the same or different. n is an integer in the range of 1 to 20.) Furthermore, it is preferable that the phosphite-based decomposition accelerator is dialkyl pentaerythritol diphosphite, the polyester resin composition is an aliphatic polyester, or the polyester resin composition has an optical purity of 90% or more and is poly-L-lactic acid or poly-D-lactic acid. Also, it is preferable that the number average molecular weight of the resin composition is 50,000 or more, the acid value of the resin composition is 300 eq / ton or less, and the content of the phosphite-based decomposition accelerator is 0.01 to 5% by mass.

[0017] Another polyester resin molded body of the present invention is characterized by being composed of the above-described marine-degradable polyester resin composition. Furthermore, it is preferable that the storage strength retention rate on land after 5 months of the resin molded body is 60% or more, the shape of the polyester resin molded body is a fiber or a film, and when the shape is a fiber, the initial strength of the fiber is 1.5 cN / dtex or more.

[0018] A masterbatch of another polyester resin composition of the present invention is the above-described marine-degradable polyester resin composition, and is characterized in that the content of the phosphite-based decomposition accelerator is 5 to 20% by mass. Or, it is a method for producing a polyester resin molded body, characterized by adding this masterbatch to a polyester resin and melt-molding it. Furthermore, it is preferable that the shape of the polyester resin molded body is a fiber or a film.

Advantages of the Invention

[0019] The present invention provides a marine-degradable polyester resin composition that decomposes rapidly even in low-temperature seawater.

Modes for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described in detail.

[0021] The marine-degradable polyester resin composition of the present invention is a resin composition mainly composed of polyester. Here, "mainly" means that 50% by mass or more of the whole is its constituent component, and further preferably, it is a polyester resin in which 70% by mass or more, particularly 90% by mass or more and 100% by mass or less are the main components.

[0022] Examples of the polyester resin include polymers or copolymers obtained by polycondensing one or more selected from dicarboxylic acids or their ester-forming derivatives, diols or their ester-forming derivatives, hydroxycarboxylic acids or their ester-forming derivatives, and lactones. Preferably, a polyester composed of a hydroxycarboxylic acid or its ester-forming derivative is exemplified, and more preferably, an aliphatic polyester composed of a hydroxycarboxylic acid or its ester-forming derivative is exemplified.

[0023] Regarding the hydroxycarboxylic acid or its ester-forming derivative, and lactone, which are preferred constituent components of the polyester of the present invention, examples of the hydroxycarboxylic acid include glycolic acid, lactic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, hydroxybenzoic acid, p-hydroxybenzoic acid, 6-hydroxy-2-naphthoic acid, and their ester-forming derivatives. Examples of the lactone include caprolactone, valerolactone, propiolactone, undecalactone, 1,5-oxepan-2-one, and the like.

[0024] Examples of polymers whose main component is a preferred aliphatic hydroxycarboxylic acid include polycondensates or copolymers of glycolic acid, lactic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyvaleric acid, and hydroxycaproic acid. Among these, polyglycolic acid, polylactic acid, poly3-hydroxycarbon butyric acid, poly4-polyhydroxybutyric acid, poly3-hydroxyhexanoic acid, or polycaprolactone, and copolymers thereof are particularly preferred. Poly-L-lactic acid, poly-D-lactic acid, stereocomplex polylactic acid, and racemic polylactic acid are especially preferred.

[0025] Furthermore, the polyester of the present invention is an aliphatic polyester, and it is particularly preferable that the aliphatic polyester is at least one selected from the group consisting of poly-L-lactic acid, poly-D-lactic acid, racemic polylactic acid, and polyglycolic acid.

[0026] Furthermore, the dicarboxylic acids or their ester-forming derivatives and diols or their ester-forming derivatives that can be used as constituent components of the polyester resin of the present invention are described below.

[0027] Examples of dicarboxylic acids or ester-forming derivatives include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, and 2,6-naphthalenedicarboxylic acid; aliphatic dicarboxylic acids such as oxalic acid, succinic acid, and adipic acid; or alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid. Alternatively, ester-forming derivatives of these dicarboxylic acids are also preferred.

[0028] Furthermore, examples of diols or their ester-forming derivatives include aliphatic glycols with 2 to 20 carbon atoms, such as ethylene glycol and 1,3-propanediol; long-chain glycols with molecular weights of 200 to 100,000, such as polyethylene glycol and poly-1,3-propylene glycol; and aromatic dioxy compounds such as hydroquinone and bisphenol A. Alternatively, these may be ester-forming derivatives of these diols.

[0029] The polyester components described above can be used not only as the main polyester components but also as secondary copolymer components. In this case, the copolymer components other than the main polyester component are preferably in the range of 0 to 10 mol%, more preferably in the range of 0 to 5 mol%, and particularly preferably in the range of 0 to 2 mol%, based on the total repeating units of the polyester.

[0030] Now, the polyester of the present invention is preferably composed mainly of the above components, but from the viewpoint of controlling decomposition in low-temperature water, it is also preferable to use two or more of these aliphatic polyesters in combination. In particular, polylactic acid is preferred as the main component, and a combination of polylactic acid and polyglycolic acid is particularly preferred. In that case, the polylactic acid that is the main component is preferably 50% or more of the total mass, and further, from the viewpoint of ease of controlling decomposition, it is preferable that it be 70% or more by mass, and more preferably 80% or more by mass and less than 100%. Here, the polylactic acid has a main chain consisting of lactic acid units, and the lactic acid monomers that contribute to the composition are preferably in proportion to 90 to 100 mol%, more preferably 95 to 100 mol%, and even more preferably 98 to 100 mol% of the monomers constituting the polylactic acid.

[0031] Incidentally, 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 mainly 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 in this way, it is possible to further improve the decomposition properties at low temperatures. In terms of ratio, it is preferable that the other lactic acid unit is 20 mol% or less relative to the main lactic acid unit. Furthermore, it is preferable that it be 0.1 to 15 mol%, and more preferably 1 to 15 mol%. If one is not present at all, the decomposition properties in water at low temperatures may decrease. On the other hand, if there is too much, the crystallinity of the polylactic acid may be lost, which may improve the decomposition properties in water at low temperatures, but on the other hand, it may become difficult to process into fibers or various molded articles.

[0032] In this invention, it is preferable to use polylactic acid with a high proportion of L-lactic acid units. Generally, the content of the main L-lactic acid or D-lactic acid in the polylactic acid resin is called optical purity, and it is preferable that the optical purity is 90% or more, more preferably 95% or more, and even more preferably 98-100%.

[0033] Furthermore, in the marine biodegradable polyester resin composition of the present invention, it is preferable that the number average molecular weight of the resin composition is 50,000 or more. More preferably, the number average molecular weight is in the range of 60,000 to 120,000, and particularly preferably in the range of 65,000 to 100,000. Being within this range makes it possible to produce a polyester resin composition that has high initial physical properties while still being highly biodegradable in the marine environment. Here, the number average molecular weight is the value obtained by measuring by gel permeation chromatography (GPC) and converting it to standard polystyrene equivalent.

[0034] The weight-average molecular weight of the polyester used is preferably between 30,000 and 500,000 in order to achieve a balance between the mechanical properties and moldability of the final molded article. More preferably, it is in the range of 50,000 to 350,000, and particularly preferably between 100,000 and 250,000.

[0035] Furthermore, the marine biodegradable polyester resin composition of the present invention preferably has an acid value of 300 eq / ton or less. More preferably, the acid value of the resin composition is in the range of 10 to 250 eq / ton, and particularly 20 to 200 eq / ton.

[0036] Furthermore, for a polyester resin molded article made from another marine-degradable polyester resin composition of the present invention, which will be described later, it is preferable that the acid value of the molded article is 100 eq / ton or less. Moreover, it is preferable that the acid value of the molded article is in the range of 10 to 75 eq / ton, and particularly 15 to 50 eq / ton.

[0037] By defining the range in this way, the polyester resin composition of the present invention has been made possible to have high initial physical properties while still being highly biodegradable in marine environments.

[0038] Such polyesters can be produced by conventionally known methods. For example, if the polyester is polylactic acid, it can be produced by methods such as ring-opening polymerization of L-lactide or D-lactide or mixtures thereof in the presence of a metal-containing catalyst, solid-phase polymerization of low molecular weight polylactic acid containing a metal-containing catalyst, or direct polymerization by dehydration condensation of lactic acid.

[0039] The marine biodegradable polyester resin composition of the present invention contains a phosphite ester-based decomposition accelerator, the molecular formula of which is a compound represented by the following general formula (1).

[0040] [ka]

[0041] (In general formula (I), R is an alkyl group, an aryl group, or a hydrogenated bisphenol A skeleton, and these may be the same or different. n is an integer in the range of 1 to 20.) Such phosphite esters are preferably compounds having a pentaerythritol diphosphite component, and among these, dialkylpentaerythritol diphosphite is preferred. More specifically, examples include distearyl pentaerythritol diphosphite, diisodecyl pentaerythritol diphosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, bis(2,4-di-t-butyl-6-methylphenyl)pentaerythritol diphosphite, bis(2,6-di-t-butyl-4-methylphenyl)pentaerythritol diphosphite, bis(2,4,6-tri-t-butylphenyl)pentaerythritol diphosphite, and mixtures thereof.

[0042] Among the compounds containing the pentaerythritol diphosphite component that are commonly used, examples 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.

[0043] In the present invention, the phosphite esters used must have appropriate heat resistance, and among the above, dialkylpentaerythritol diphosphite is preferred. In particular, the alkyl group is preferably a compound with 8 to 36 carbon atoms. Furthermore, it is preferable that the alkyl group has 10 to 24 carbon atoms, and most preferably distearyl pentaerythritol diphosphite with 18 carbon atoms. If the alkyl group has too few carbon atoms, the phosphite esters tend to become liquid, resulting in poor handling. For ease of handling, solid phosphite esters are generally preferred.

[0044] Furthermore, if phosphite esters contain bisphenol A-based components in addition to pentaerythritol diphosphite, their heat resistance tends to decrease, making them more prone to breakage during processes such as spinning for fiber production. While the presence of phenolic components tends to improve heat resistance, it also tends to inhibit marine biodegradability. Additionally, phosphite esters containing bisphenol A-based or phenolic components are also a cause for concern due to their chronic toxicity to aquatic environments.

[0045] Furthermore, the phosphite ester-based decomposition accelerator used in the present invention preferably has a thermal decomposition temperature of 170°C or higher. A preferred range for the thermal decomposition temperature is 400°C or lower, and more preferably in the range of 200 to 350°C. Here, the thermal decomposition temperature is defined as the temperature at which the weight decreases by 5% or more. By setting such a high thermal decomposition temperature, the material is less likely to decompose in subsequent processing steps such as fiber molding or film molding, thus maintaining high initial physical properties.

[0046] The marine biodegradable polyester resin composition of the present invention is a resin composition mainly composed of polyester, and is characterized by containing the above-mentioned phosphite ester-based decomposition accelerator.

[0047] Furthermore, the amount of phosphite ester-based decomposition accelerator added to the resin composition is preferably 0.01% by mass or more, and more preferably 0.01 to 5% by mass. It is even more preferable that the amount is in the range of 0.1 to 2% by mass, and particularly in the range of 0.3 to 1% by mass. If the amount of these agents added is too small, the effect of increasing the decomposition rate will be reduced, and if it is too large, moldability will be poor or thermal stability will deteriorate.

[0048] The preferred amount of additives mentioned above can also be defined by the amount of phosphorus atoms. It is preferable that the concentration of phosphorus atoms in the resin composition be 0.001% by mass or more, and more preferably in the range of 0.01 to 1.0% by mass. A range of 0.02 to 0.4% by mass is particularly preferred, and a range of 0.03 to 0.2% by mass is particularly preferred. If the amount of these agents added is too small, the effect of increasing the decomposition rate will be reduced, and if it is too large, the moldability will be poor or the thermal stability will deteriorate.

[0049] Furthermore, the marine biodegradable polyester resin composition of the present invention may be used with any known additives and fillers, as long as the effects of the invention are not lost. For example, it is preferable to include fillers, release agents, antistatic agents, plasticizers, impact resistance modifiers, etc.

[0050] Despite exhibiting excellent marine biodegradability at low temperatures, the marine biodegradable polyester resin composition of the present invention does not significantly impact marine ecosystems or other environmental aspects during decomposition due to its monomer components.

[0051] Furthermore, the marine biodegradable polyester resin composition of the present invention exhibits excellent hydrolysis properties. In particular, when the polyester component is polylactic acid, hydrolysis rapidly and significantly reduces the number-average molecular weight of polylactic acid in the initial stages, accelerating subsequent microbial degradation.

[0052] Incidentally, unlike other biodegradable plastics, polylactic acid is known to undergo a two-stage / two-mode degradation mechanism: first, its molecular weight is reduced by hydrolysis, and then it is completely broken down into carbon dioxide and water by microorganisms. For example, it is expected that microbial degradation will be accelerated by reducing the number-average molecular weight of polylactic acid to 20,000 at an early stage.

[0053] The marine biodegradable polyester resin composition of the present invention is effectively decomposed even in the ocean under low temperature and low oxygen concentration conditions, as well as under high temperature and high oxygen concentration conditions such as those found in composting. The ambient temperature range of 0 to 50°C, and more particularly the range of 5 to 35°C, is where the effects of the present invention are most pronounced.

[0054] Furthermore, it is preferable that the marine biodegradable polyester resin composition of the present invention exhibits a rate of increase in the number of main chain breaks of 5 (eq / ton / month) or more after immersion in low-temperature seawater (30°C) for 60 days. More preferably, the rate is in the range of 8 to 100 (eq / ton / month), and particularly preferably in the range of 10 to 50 (eq / ton / month). (Here, one month is defined as 30 days.) Furthermore, it is preferable that the present invention has a high storage strength retention rate when used on land. More specifically, it is preferable that the storage strength retention rate on land after 5 months (150 days) in an environment of room temperature 25°C and humidity 60% is 60% or more. Moreover, it is preferable that it has a strength retention rate of 80-100%, and especially 90-99%.

[0055] Another polyester resin molded article of the present invention is made from the marine biodegradable polyester resin composition of the present invention. Furthermore, it is preferable that the molding method be melt molding.

[0056] Preferred melt molding methods include known methods such as injection molding, extrusion molding, vacuum molding, pressure molding, and blow molding. The resulting shape can be pellets, fibers, fabrics, fiber structures, films, sheets, or nonwoven sheet fabrics. Furthermore, it is also preferable to process pellets, fibers, or films by crushing, cutting, or shredding them to produce powder.

[0057] Furthermore, these molded bodies can be suitably used in various applications such as housings, gears and other electrical and electronic components, building materials, civil engineering materials, agricultural materials, automotive parts (interior and exterior parts, etc.), and everyday parts.

[0058] Furthermore, the molded article can also be in the form of a fiber, and it is possible to form fibers or fiber structures by conventional melt spinning and subsequent post-processing. The melting temperature is preferably in the range of 170 to 250°C, and more preferably in the range of 190 to 230°C. It can then be manufactured by extruding it from a melt spinning die as monofilament or multifilament, and can be circular, irregularly shaped, solid, hollow, etc. Furthermore, it is preferable to perform stretching or other processes to achieve an initial fiber strength of 1.5 cN / dtex or higher, and more preferably 2.0 to 5.0 cN / dtex. At this time, the single fiber fineness of the fiber is preferably in the range of 1 to 10 dtex, and more preferably 2 to 5 dtex.

[0059] As a method for producing the marine biodegradable polyester resin composition and molded articles thereof according to the present invention, it is possible to directly mix the main polyester resin composition and the phosphite ester-based decomposition accelerator and melt-knead them to form the resin composition. However, it is also preferable to first form a masterbatch in which the phosphite ester-based decomposition accelerator content is 5 to 20% by mass.

[0060] In other words, the masterbatch of another polyester resin composition of the present invention is made from the above-mentioned marine biodegradable polyester resin composition of the present invention, and is characterized in that it contains 5 to 20% by mass of a phosphite ester-based decomposition accelerator.

[0061] Furthermore, it is preferable that the acid value of the masterbatch is 300 eq / ton or less. Moreover, it is preferable that the acid value of the masterbatch is in the range of 10 to 250 eq / ton, and particularly 20 to 200 eq / ton.

[0062] By setting the acid value within this range, it becomes possible to obtain an appropriate acid value in the polyester resin composition obtained from the masterbatch and in the molded articles made therefrom. This makes it possible to produce a polyester resin composition that has high initial physical properties while still being highly biodegradable in marine environments.

[0063] Furthermore, when the process goes through a masterbatch in this manner, it becomes possible to add a high concentration of phosphite ester-based decomposition accelerators, which helps to suppress the decrease in polymer molecular weight during kneading. A lower processing temperature during kneading is preferable, preferably in the range of 160 to 230°C. More preferably, it is in the range of 180 to 210°C. This makes it possible to suppress thermal degradation during processing and the decrease in polymer molecular weight.

[0064] Furthermore, when using polymers as raw materials or masterbatches as described above, it is preferable to dry them before processing and adjust the moisture content of the polymers or masterbatches.

[0065] The drying temperature of the raw material polymer is preferably in the range of 80 to 120°C, and the drying time is preferably in the range of 4 to 12 hours. Furthermore, the drying temperature is preferably in the range of 90 to 110°C, particularly 95 to 105°C. The drying time is preferably in the range of 6 to 10 hours, particularly 7 to 9 hours.

[0066] Furthermore, it is preferable to use a vacuum dryer for drying the masterbatch, as this makes it possible to more effectively suppress thermal decomposition. The drying temperature is preferably in the range of 60 to 100°C, and the drying time is preferably in the range of 4 to 10 hours. Moreover, the drying temperature is preferably in the range of 70 to 90°C, and more preferably in the range of 75 to 85°C. The drying time is preferably in the range of 5 to 9 hours, and more preferably in the range of 6 to 8 hours.

[0067] By going through such a drying process, it is preferable to adjust the moisture content of the raw polymer and masterbatch to a range of 100-1000 ppm, or even 50-500 ppm. By processing under these optimal conditions, the increase in the acid value in the raw materials and masterbatch can be more effectively suppressed.

[0068] Examples of kneading equipment used in subsequent processes include known single-screw or multi-screw horizontal kneading equipment, such as a ruder and a kneader. A low kneading temperature is preferred, and a rotation speed of 600 rpm or less, and more preferably in the range of 100 to 400 rpm, is preferred. To reduce thermal degradation, water cooling is preferred for cooling the discharged strands.

[0069] The concentration of the decomposition accelerator in the masterbatch is preferably 5 to 20% by mass, more preferably 5 to 15% by mass, and particularly preferably in the range of 5 to 10% by mass. If the concentration is too high, the decomposition accelerator may precipitate, depending on the solubility of the main component. The amount of phosphorus atoms in the masterbatch is preferably 0.1% by mass or more, more preferably in the range of 0.2 to 2% by mass, and particularly preferably in the range of 0.3 to 1% by mass.

[0070] As a method for producing the polyester resin molded article of the present invention, one particularly preferred method is to add the masterbatch described above to the polyester resin and melt-mold it. The resulting polyester resin molded article can take on various shapes as described above, but a fibrous or film shape is preferred. [Examples]

[0071] The present invention will be described in more detail below with reference to examples. Note that each item in the examples was measured by the following method.

[0072] (1) Number average molecular weight (Mn): The number-average molecular weight of the polymer was measured by gel permeation chromatography (GPC) and converted to the value equivalent to standard polystyrene.

[0073] During measurement, the following detector and column were used, and 10 μL of the sample solution was injected into the column using chloroform as the eluent at a temperature of 40°C and a flow rate of 1.0 mL / min. The sample solution was prepared by dissolving the sample in chloroform to a concentration of 2 mg / mL, and then filtering it through a 0.45 μm PTFE membrane filter.

[0074] Detector; differential refractometer; (Waters Corporation) "Waters 2414".

[0075] Columns used: Two "shodex GPC K-806L" columns manufactured by Showa Denko Corporation were connected in series.

[0076] (2) Measurement of phosphorus concentration: The phosphorus (P) concentration in the sample was measured by the following method. 200 mg of the sample was weighed into a decomposition container, 7 mL of nitric acid was added, the container was sealed, and the sample was decomposed using a wet decomposition apparatus (Perkin Eimer, Inc. "Multiwave 3000") at 700 W for 60 minutes. The phosphorus (P) concentration of the decomposed solution was measured using an ICP instrument (Agilent Agilent Technologies, Inc. "5100ICP-OES"). The P concentration was determined from a calibration curve created using commercially available phosphorus standard solutions for ICP.

[0077] (3) Acid value measurement The sample was dissolved in purified o-cresol under a nitrogen atmosphere, and then determined by neutralization titration with 0.05 N potassium hydroxide ethanol solution using bromocresol blue as an indicator. The result was 1 × 10⁻⁶ of the sample. 6 The total amount of carboxyl groups derived from the polymer and phosphite, which is a decomposition product of phosphite esters, was converted to a numerical value (eq / ton) of equivalent concentration.

[0078] (4) Rate of increase in the number of main chain breaks (evaluation of decomposition in low-temperature seawater): For the powdered resin composition, 100 mg of the powdered resin composition and 100 cc of natural seawater (collected at Matsuyama Port, Ehime Prefecture) were placed in a screw-cap bottle and shaken for 60 days at 30°C and 100 rpm using an AS ONE mix rotor (model number: VMRC-5). After 60 days, the resin composition was removed and filtered using filter paper (JIS, P3801:1995, type 5A standard). The resin composition remaining on the filter paper was dried overnight at room temperature under a vacuum of 133.3 Pa or less, and the number-average molecular weight was measured by GPC. Using the obtained number-average molecular weight, the number of main chain breaks in the resin composition was measured, and the rate of increase in the number of main chain breaks was determined using the following formulas 1 and 2.

[0079] For the fibrous resin composition, 5g of the resin composition, which was formed by knitting fibers into a tubular shape, and natural seawater (collected at Matsuyama Port, Ehime Prefecture) were placed in a 250cc screw-cap bottle and shaken at 30°C and 100rpm for 60 days. After 60 days, the resin composition was removed, dried overnight in a vacuum dryer, and the number-average molecular weight was measured by GPC. The rate of increase in the number of main chain cleavage was then determined using the following formulas 1 and 2, as described above.

[0080]

number

[0081]

number

[0082] (5) Fiber strength when stored on land: To evaluate hydrolysis resistance on land, the fibers were stored for 5 months at a room temperature of 25°C and a humidity of 60%RH. Fiber strength was measured and evaluated as the retention rate from the initial fiber properties. The fiber strength was measured under the conditions of a test length (distance between chucks) of 250 mm and a tensile speed of 200 mm / min. The initial fiber strength and the fiber strength after 5 months were compared to determine the retention rate of strength during storage on land. (6) Moisture content measurement The moisture content was determined by quantitatively measuring the amount of moisture under vaporization conditions of 180°C for 20 minutes using a Karl Fischer moisture meter (MKC-610) and a moisture vaporizer (APD-611) manufactured by Kyoto Electronics Manufacturing Co., Ltd., and then calculating the moisture content.

[0083] In the following embodiments, the following compounds were used as the "polyester resin" and "decomposition accelerator."

[0084] <Polyester resin> PLA1; TotalCorbion's polylactic acid "LX-175" (optical purity: 96% L-isomer, number-average molecular weight: 120,000) ·PLA2; TotalCorbion's polylactic acid "L-130" (optical purity: 99% L-isomer, number-average molecular weight: 100,000) <Decomposition accelerator (phosphorus-based decomposition accelerator)> (Examples) PEP-8; Distearyl pentaerythritol diphosphite (PEP-8, manufactured by ADEKA Corporation, phosphorus concentration 7.6%, thermal decomposition temperature (5% weight loss temperature): 210℃) JPH-3800; Hydrogenated bisphenol A pentaerythritol phosphite polymer (manufactured by Johoku Chemical Industry Co., Ltd., "JPH-3800", number average molecular weight 2000, thermal decomposition temperature (5% weight loss temperature): 180℃) (Comparative example) ·JC-356; Diethyl(3,5-di-t-butyl-4-hydroxybenzyl)phosphonate (manufactured by Johoku Chemical Industry Co., Ltd., "JC-356") ·JC-228; Diethylbenzylphosphonate (JC-228, manufactured by Johoku Chemical Industry Co., Ltd.) ·JC-390; Diethyl octadecyl phosphonate (JC-390, manufactured by Johoku Chemical Industry Co., Ltd.) [Example 1] A polyester resin (PLA1) with a number-average molecular weight of 120,000 and a phosphorus-based decomposition accelerator (PEP-8) were mixed in a ratio of 99.0:1.0. The mixture was then melt-kneaded for 2 minutes at a set temperature of 190°C and a rotation speed of 100 rpm using a microconical twin-screw compounder (ThermoFisher Scientific Inc. "HAAKE MiniCTW") to obtain a resin composition. The obtained resin composition was obtained as a powder by freeze-grinding, and its decomposition in low-temperature seawater was evaluated. The evaluation results are shown in Table 1.

[0085] [Examples 2-4] A powdered resin composition was obtained in the same manner as in Example 1, except that the ratio of polyester resin (PLA1) to phosphorus-based decomposition accelerator (PEP-8) was changed to the ratio shown in Table 1. The evaluation results are also shown in Table 1.

[0086] [Example 5] A powdered resin composition was obtained in the same manner as in Example 1, except that the phosphorus-based decomposition accelerator (PEP-8) in Example 1 was replaced with "JPH-3800". The evaluation results are shown in Table 1.

[0087] [Example 6] A polyester resin (PLA1) with a number-average molecular weight of 120,000 was dried at 100°C for 8 hours to obtain a polyester resin (PLA1) with a moisture content of 200 ppm. The obtained polyester resin (PLA1) and a phosphorus-based decomposition accelerator (PEP-8) were mixed in a ratio of 95.0:5.0, and the mixture was melt-kneaded for 2 minutes at a set temperature of 190°C and a rotation speed of 100 rpm using a microconical twin-screw compounder (Thermo Fisher Scientific Inc. "HAAKE MiniCTW") to obtain a resin composition. The acid value of this resin composition was 108 eq / ton. The obtained resin composition was made into a powder by freeze-grinding, and its decomposition was evaluated in low-temperature seawater. The number-average molecular weight before the hydrolysis test was 95,800, while the number-average molecular weight after 2 months of hydrolysis was 17,800, and the rate of increase in the number of main chain cleavage was 22.9 eq / ton / month.

[0088] [Table 1]

[0089] [Example 7] A masterbatch pellet was prepared by melt-kneading a polyester resin (PLA1) with a number-average molecular weight of 120,000 and a phosphorus-based decomposition accelerator (PEP-8) in a ratio of 95:5 using a twin-screw extruder (manufactured by Technovel Co., Ltd.) at 190°C and 200 rpm. The obtained masterbatch pellet had a number-average molecular weight of 77,000 and a phosphorus concentration of 0.37 mass%. A pellet blend of the polyester resin (PLA1) with a number-average molecular weight of 120,000 and the above-obtained masterbatch pellet in a ratio of 90:10 was melt-spun at 195°C to obtain a fiber with a single fiber fineness of 2.9 dtex and 24 filaments, and its decomposition was evaluated in low-temperature seawater. The evaluation results are shown in Table 2.

[0090] [Examples 8 and 9] Except for changing the mixing ratio of the masterbatch pellets and polyester resin (PLA1) from Example 6 to the ratio shown in Table 1, a fiber with a single fiber fineness of 2.9 dtex and 24 filaments was obtained in the same manner as in Example 6. The evaluation results are shown in Table 2.

[0091] [Examples 10-12] Except for changing the base polymer described in Example 6 to a polyester resin (PLA2) with a number-average molecular weight of 100,000, fibers with a single fiber fineness of 2.9 dtex and 24 filaments were obtained in the same manner as in Examples 6 to 8. The evaluation results are shown in Table 2.

[0092] [Table 2]

[0093] [Example 13] A polyester resin (PLA1) with a number-average molecular weight of 120,000 was dried at 100°C for 8 hours to obtain a polyester resin (PLA1) with a moisture content of 200 ppm. The obtained polyester resin (PLA1) and a phosphorus-based decomposition accelerator (PEP-8) were melt-kneaded at 190°C and 200 rpm using a twin-screw extruder (manufactured by Technovel Co., Ltd.) in a ratio of 95.0:5.0 to prepare a masterbatch pellet. The number-average molecular weight of the obtained masterbatch pellet was 88,000, and the phosphorus concentration in the pellet was 0.40 mass%. The acid value in the masterbatch was 113 eq / ton.

[0094] As a base polymer, a polyester resin (PLA1) with a number-average molecular weight of 120,000 was dried at 100°C for 8 hours to obtain a polyester resin (PLA1) with a moisture content of 200 ppm. Meanwhile, the masterbatch pellets obtained above were also dried at 80°C for 6 hours to obtain masterbatch pellets with a moisture content of 100 ppm. This base polymer and the masterbatch pellets were blended in a 90:10 ratio and melt-spun at 195°C to obtain fibers with a single fiber fineness of 2.9 dtex and 24 filaments. The degradation of these fibers in low-temperature seawater was evaluated. The evaluation results are shown in Table 3.

[0095] [Examples 14-16] In Example 13, a polyester resin (PLA2) with a number-average molecular weight of 100,000 was used as the base polymer instead of the polyester resin (PLA1) with a number-average molecular weight of 120,000. The base polymer was then dried at 100°C for 8 hours to obtain a fiber with a moisture content of 160 ppm. The procedure was the same as in Example 13, except that a single fiber fineness of 2.9 dtex and 24 filaments were obtained.

[0096] The evaluation results are shown in Table 3.

[0097] [Table 3]

[0098] [Comparative Example 1] A powdered resin composition was obtained in the same manner as in Example 1, except that the phosphorus-based decomposition accelerator (PEP-8) was not used and the ratio was changed to 100% polyester resin (PLA1). The evaluation results are shown in Table 4.

[0099] [Comparative Examples 2-4] Powdered resin compositions were obtained in the same manner as in Example 1, except that the phosphorus-based decomposition accelerator (PEP-8) in Example 1 was replaced with "JC-356" (Comparative Example 2), "JC-228" (Comparative Example 3), and "JC-390" (Comparative Example 4). The evaluation results are shown in Table 4.

[0100] [Table 4]

Claims

1. A polyester resin molded article made from a marine biodegradable polyester resin composition, The polyester resin composition consists mainly of a resin composition made of polyester. It contains a phosphite ester-based decomposition accelerator, The phosphite ester decomposition accelerator is a compound represented by the following general formula (I), 【number】 (In general formula (I), R is an alkyl group, an aryl group, or a hydrogenated bisphenol A skeleton, and these may be the same or different. n is an integer in the range of 1 to 20.) The polyester resin composition is an aliphatic polyester, and its optical purity is 90% or higher, poly-L-lactic acid or poly-D-lactic acid. The number-average molecular weight of the resin composition is 60,000 to 120,000. The acid value of the resin composition is 10 to 250 eq / ton, The shape of the polyester resin molded body is that of multifilament fibers. Single fiber fineness is 1 to 10 dtex. The initial strength of the fiber is 1.5 to 5.0 cN / dtex. 5 g of the resin composition, formed by knitting the fibers into a tubular shape, and natural seawater were placed in a 250 cc screw-cap bottle, shaken at 30°C and 100 rpm for 60 days, and the number-average molecular weight was measured by GPC. The rate of increase in the number of main chain breaks after 60 days, calculated using the following formulas 1 and 2, was between 5 and 50 (eq / ton / Month). [Math 1] [Math 2] The strength retention rate after 150 days in a land environment with a room temperature of 25°C and 60% humidity is 75-99%. A marine biodegradable polyester resin molded article characterized by the above.

2. The marine biodegradable polyester resin molded article according to claim 1, wherein the phosphite ester-based decomposition accelerator is dialkylpentaerythritol diphosphite.

3. A marine biodegradable polyester resin molded article according to claim 1, wherein the content of the phosphite ester-based decomposition accelerator is 0.01 to 5% by mass.

4. It consists mainly of a resin composition made of polyester. It contains a phosphite ester-based decomposition accelerator, The phosphite ester decomposition accelerator is a compound represented by the following general formula (I), 【Chemistry 2】 (In general formula (I), R is an alkyl group, an aryl group, or a hydrogenated bisphenol A skeleton, and these may be the same or different. n is an integer in the range of 1 to 20.) The polyester resin composition is an aliphatic polyester, and its optical purity is 90% or higher, poly-L-lactic acid or poly-D-lactic acid. The number-average molecular weight of the resin composition is 60,000 to 120,000. Acid value of resin composition is 10 to 250 eq / ton A polyester resin composition which is A polyester resin is dried at 90-110°C for 6-10 hours to achieve a moisture content of 100-200 ppm, to which a phosphite ester-based decomposition accelerator is added. The content of the phosphite ester-based decomposition accelerator is 5 to 20% by mass. Furthermore, the masterbatch is dried at 70-90°C for 4-10 hours to obtain a moisture content of 50-100 ppm. The material was dried at 90-110°C for 6-10 hours to achieve a moisture content of 100-200 ppm. When added to polyester resins, Melt molding, The single fiber fineness is 1 to 10 dtex, and the multifilament fiber is a multifilament fiber. A method for producing a polyester resin molded article, characterized by the above.

Images