JP2014227452A - Polylactic acid-based resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polylactic acid-based resin having excellent fire retardancy without melting and kneading a fire retardant.SOLUTION: A polylactic acid-based resin is formed by coupling a polylactic acid (A) and polyester (B) containing a phosphorus atom through a covalent bond, (i) has a number average molecular weight of (B) of 1,000 or more, (ii) has an average degree of polymerization of (B) of 3 or more, and (iii) has a content of the phosphorus atom in the polylactic acid-based resin of 0.5-2.0 mass%. A method for producing a polylactic acid-based resin includes a step of polymerizing lactide in the presence of a polymerization catalyst by using the polyester (B) containing the phosphorus atom as an initiator.

Description

  The present invention relates to a polylactic acid resin.

  In recent years, biodegradable polyester resins have attracted attention from the viewpoint of environmental conservation. Among them, polylactic acid resin, polyethylene succinate resin, polybutylene succinate resin and the like are low in cost and highly useful because they can be mass-produced. In particular, polylactic acid resin can be industrially produced using plants such as corn and sweet potato as raw materials, and even if incinerated after use, the balance between the carbon dioxide absorbed during growth of the raw materials and the carbon dioxide generated by incineration Since it can be removed, it is particularly useful.

  In many cases, application of polylactic acid resin to electrical products requires a high level of flame retardancy, that is, performance of UL94 standard V-1 or higher.

  As a polylactic acid resin imparted with flame retardancy, for example, Patent Document 1 discloses a polylactic acid resin obtained by melt-kneading a polylactic acid resin, a polylactic acid-based flame retardant copolymer, and an anti-drip agent. In addition, it is disclosed that a polylactic acid-based flame retardant copolymer is obtained by depolymerizing a polylactic acid resin with a phosphorus atom-containing glycol and extending the chain. Patent Document 2 discloses a polylactic acid resin in which an organic phosphorus compound, a hydrogenated styrene elastomer, and talc are contained in a polylactic acid resin.

JP 2009-227784 A JP 2010-275348 A

  However, the polylactic acid-based resin of Patent Document 1 needs to be melt-kneaded with polylactic acid not containing a flame retardant after preparing a polylactic acid-based flame retardant copolymer, and the manufacturing process is complicated. . In addition, polylactic acid-based flame retardant copolymer itself has a low molecular weight when the depolymerization amount of phosphorus atom-containing glycol is increased to improve flame retardancy. Its properties were low and its use was limited. On the other hand, since it is difficult for the polylactic acid resin of Patent Document 2 to uniformly disperse the flame retardant in the polylactic acid resin, there is a problem that the flame retardancy varies or the flame retardant bleeds out. .

  An object of the present invention is to provide a polylactic acid-based resin having excellent flame retardancy without melting and kneading a flame retardant.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors polymerized lactide using a specific phosphorus atom-containing polyester as an initiator, so that the flame retardant was excellent without being melt-kneaded. It has been found that a polylactic acid resin having flame retardancy can be obtained, and the present invention has been achieved.

The gist of the present invention is as follows.
(1) A polylactic acid resin in which a polylactic acid (A) and a polyester (B) containing a phosphorus atom are bonded via a covalent bond,
(I) The average degree of polymerization of (B) is 3 or more,
(Ii) In (B), the number of repeating units having a phosphorus atom-containing monomer as a constituent component is 2 or more. (Iii) The content of phosphorus atoms in the polylactic acid resin is 0.5 to 2.0 mass%.
A polylactic acid resin characterized by
(2) The method for producing a polylactic acid-based resin according to (1), comprising a step of polymerizing lactide using a polyester (B) containing a phosphorus atom as an initiator in the presence of a polymerization catalyst.
(3) A molded product obtained by molding the polylactic acid resin according to (1).

  ADVANTAGE OF THE INVENTION According to this invention, the polylactic acid-type resin which has the outstanding flame retardance can be provided, without melt-kneading a flame retardant. The polylactic acid-based resin of the present invention does not bleed out because the polylactic acid and the phosphorus atom-containing polyester are bonded via a covalent bond.

  The polylactic acid-based resin of the present invention is a resin formed by bonding polylactic acid (A) and a polyester (B) containing a phosphorus atom via a covalent bond.

  Polylactic acid (A) is comprised from what polymerized lactide. Lactide includes L-lactide, which is a cyclic dimer of L-lactic acid, D-lactide, which is a cyclic dimer of D-lactic acid, meso-lactide obtained by cyclic dimerization of D-lactic acid and L-lactic acid, D- It is selected from one or more of DL-lactide, which is a mixture of lactide and L-lactide.

  The D-form content of the polylactic acid-based resin of the present invention is preferably 1.0 mol% or less or 99.0 mol% or more with respect to 100 mol% of the lactic acid component constituting the polylactic acid. By setting the D-form content of the polylactic acid-based resin within the above range, the melting point can be improved and the isothermal crystallization rate index during cooling can be reduced. The D-form content of the lactide to be used is not particularly limited as long as the D-form content of the obtained polylactic acid resin can be within the above range. The D-form content of the lactide used with the polylactic acid-based resin may be slightly different because the lactide may undergo a very small amount of racemization during the polymerization. The D-form content of the polylactic acid resin is more preferably 0.6 mol% or less or 99.4 mol% or more.

  In order to polymerize a high molecular weight polylactic acid resin, the amount of free acid contained in lactide is preferably 30 meq / kg or less, more preferably 20 meq / kg or less, and 10 meq / kg or less. More preferably, it is most preferably 5 meq / kg or less. By setting the amount of free acid to 30 meq / kg or less, degradation of the polymer by the free acid during polymerization can be suppressed.

  The polyester (B) containing a phosphorus atom needs to have a hydroxyl group at both ends. In order to have a hydroxyl group at both ends, a polyester may be produced by a known direct esterification method or transesterification method described later. If it does not have a hydroxy group at both ends, it cannot act as an initiator.

  The number average molecular weight of the polyester (B) containing a phosphorus atom needs to be 1000 or more, preferably 5000 or more, more preferably 5000 to 50000, and more preferably 10000 to 40000. Further preferred. When the number average molecular weight is less than 1000, the number average molecular weight of the obtained polylactic acid-based resin is low, and the mechanical strength in the case of forming a molded body is not preferable. On the other hand, when the molecular weight exceeds 50,000, the moldability may be lowered.

  The polyester (B) containing a phosphorus atom is composed of a dicarboxylic acid component and a glycol component, or is composed of a dicarboxylic acid component, a glycol component, and a hydroxycarboxylic acid component.

  For the polyester (B) containing a phosphorus atom, it is necessary to copolymerize a monomer containing a phosphorus atom with one or more components of a dicarboxylic acid component, a glycol component, and a hydroxycarboxylic acid component. Among the monomers containing a phosphorus atom, examples of the dicarboxylic acid component include 2- (9,10-dihydro-9-oxa-10-oxide-10-phosphophenanthren-10-yl) methylsuccinic acid <HCA- IA>. Examples of the glycol component include 10- (2,5-dihydroxyphenyl) -10H-9-oxa-10-phosphaphenanthrene-10-oxide <HCA-HQ>, diphenylphosphinyl hydroquinone <PPQ>, [3-hydroxymethyl phosphinyl, mono (2-hydroxyethyl) ester], n-butyl-bis (3-hydroxypropyl) phosphite oxide. Examples of the hydroxycarboxylic acid component include 2-carboxyethyl (phenyl) phosphinic acid. HCA-IA and HCA-HQ are from Sanko Co., PPQ is from Hokuko Sangyo Co., Ltd. [3-hydroxymethyl phosphinyl, mono (2-hydroxyethyl) ester] is from Clarinant Co., Ltd., n-butyl- Bis (3-hydroxypropyl) phosphite oxide can be obtained from Nippon Kagaku Kogyo Co., Ltd., and 2-carboxyethyl (phenyl) phosphinic acid can be obtained from Hichem. Among monomers containing a phosphorus atom, HCA-IA is preferable because of its high heat resistance, reactivity, and versatility.

  HCA-IA comprises 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide <HCA> and itaconic acid <IA> from 1: 0.9 to 1: 1.2 (moles). The ratio can be obtained by reacting at a temperature of 150 to 180 ° C. for 1 to 3 hours.

  In addition, about the monomer with low polymerizability among the monomers containing a phosphorus atom, you may add alkylene glycol, such as ethylene glycol and propylene glycol, to the terminal beforehand.

  Examples of the dicarboxylic acid other than the monomer containing a phosphorus atom include phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, 4,4′-dicarboxybiphenyl, 5-sodium sulfoisophthalic acid, and 5-hydroxy-isophthalic acid. Oxalic acid, malonic acid, succinic acid, glutaric acid, pimelic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid Acid, heptadecanedioic acid, octadecanedioic acid, nonadecanedioic acid, eicosanedioic acid, docosanedioic acid, dimer acid, hydrogenated dimer acid, fumaric acid, maleic acid, itaconic acid, mesaconic acid, citraconic acid, 1,4-cyclohexane Dicarboxylic acid, 1,2-cyclohexanedicarboxylic acid 1,3-cyclohexane dicarboxylic acid, 2,5-norbornene dicarboxylic acid. These may be anhydrides.

  Examples of the glycol other than the monomer containing a phosphorus atom include ethylene glycol, diethylene glycol, triethylene glycol, 1,4-butanediol, polyethylene glycol, polytetramethylene glycol, 1,5-pentanediol, and 1,7-heptane. Diol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, tricyclodecanedi Examples include methanol, spiroglycol and dimer diol.

  Examples of the hydroxycarboxylic acid other than the monomer containing a phosphorus atom include oxirane, glycolic acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxyisobutyric acid, and 2-hydroxy-2-methylbutyric acid. 2-hydroxyvaleric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 6-hydroxycaproic acid, 10-hydroxystearic acid, 4- (β-hydroxy) ethoxybenzoic acid, β- Examples include propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone.

  The polyester (B) containing a phosphorus atom may be copolymerized with a tri- or higher functional alcohol as long as the amount is small. Examples of the trifunctional or higher functional alcohol include trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, α-methylglucose, mannitol, and sorbitol.

  In the polyester (B) containing a phosphorus atom, the average degree of polymerization needs to be 3 or more, preferably 15 or more, more preferably 30 or more, and further preferably 45 or more. . When the average degree of polymerization is less than 3, the number average molecular weight of the obtained polylactic acid-based resin is decreased, and the mechanical strength when formed into a molded body is not preferable. The average degree of polymerization can be determined by dividing the number average molecular weight of (B) by the average molecular weight of the repeating unit.

  The average molecular weight of the repeating unit refers to a value obtained by summing up the weighted average values of the molecular weights of the residues of the monomers used in accordance with the composition ratio (molar ratio). Specifically, when the polyester (B) containing a phosphorus atom is composed only of a dicarboxylic acid component and a glycol component, the composition ratio is calculated by setting each of the dicarboxylic acid component and the glycol component to 100 mol%. When the polyester (B) containing a phosphorus atom is composed of a dicarboxylic acid component, a glycol component, and a hydroxycarboxylic acid component, the total of the dicarboxylic acid component and the hydroxycarboxylic acid component and the total of the glycol component and the hydroxycarboxylic acid component Is 100 mol% and the composition ratio is calculated. And when using trifunctional or more alcohol, trifunctional or more alcohol is calculated as a part of glycol component replaced.

  The polyester (B) containing a phosphorus atom is produced by a known production method such as a direct esterification method or a transesterification method. In addition, after synthesizing a monomer containing a phosphorus atom and using it as a copolymerization component of (B), for example, when synthesizing HCA and IA and using HCA-IA as a copolymerization component of (B) It is preferable to synthesize a monomer containing a phosphorus atom in advance and then introduce other raw materials other than the monomer containing a phosphorus atom to perform esterification. When the above synthesis is performed simultaneously during the direct esterification step, the color tone may be extremely poor depending on the reaction temperature.

Examples of the direct esterification method include a method in which a monomer raw material is introduced into a reaction vessel, an esterification reaction is performed, and then a polycondensation reaction is performed. In the esterification reaction, the reaction is performed by heating and melting at a temperature of 160 ° C. or higher for 4 hours or longer in a nitrogen atmosphere. In the polycondensation reaction, the polycondensation reaction proceeds under a reduced pressure of 130 Pa or less until a desired molecular weight is reached at a temperature of 220 to 280 ° C. A catalyst may be used in the esterification reaction and polycondensation reaction. Examples of the catalyst include titanium compounds such as tetrabutyl titanate, metal acetates such as zinc acetate and magnesium acetate, and organic tin compounds such as antimony trioxide, hydroxybutyltin oxide, and tin octylate. The amount of the catalyst, the acid component per mol, preferably in a 0.1 × ^{10 -4} ~100 × ¹⁰ -4 mol. In addition, in order to increase the amount of hydroxy groups of the polyester (B) containing phosphorus atoms, a tri- or higher functional alcohol may be further added following the polycondensation reaction, and the depolymerization reaction may be performed in an inert atmosphere. .

  In the polylactic acid resin of the present invention, the mass ratio (A / B) of the polylactic acid (A) and the polyester (B) containing a phosphorus atom is preferably 95/5 to 60/40, 7.5 /92.5 to 70/30 is more preferable. When the mass ratio of (A) exceeds 95 mass% with respect to the total of (A) and (B), the flame retardancy of the polylactic acid-based resin may not be improved. On the other hand, when the mass ratio of (A) is less than 60% by mass with respect to the total of (A) and (B), the number average molecular weight of the molecular chain of the polylactic acid-based resin is small, so that a molded body is obtained. In some cases, the mechanical strength may be low.

  The polylactic acid-based resin of the present invention can be produced by melt ring-opening polymerization of lactide in the presence of a polymerization catalyst using a polyester (B) containing a phosphorus atom as an initiator. Further, if necessary, a low polymer may be taken out during the melt ring-opening polymerization, and this may be subjected to solid phase polymerization.

  Examples of the polymerization catalyst used for the melt ring-opening polymerization include compounds containing tin, aluminum, zinc, calcium, titanium, germanium, manganese, magnesium, and rare earth elements. From the viewpoint of a small amount, a compound containing tin or aluminum is preferable. Examples of the compound containing tin or aluminum include stannous chloride, stannous bromide, stannous iodide, stannous sulfate, stannic oxide, stannous myristate, stannous octoate, tin stearate. , Tetraphenyltin, tin methoxide, tin ethoxide, tin propoxide, tin butoxide, diethoxytin, dinonyloxytin, aluminum acetylacetonate, aluminum isopropoxide, aluminum butoxide, and aluminum-imine complex. Among these, tin myristate, tin octylate, tin stearate, tin methoxide, tin ethoxide, tin propoxide, tin butoxide, diethoxytin, and dinonyloxytin are preferable, and tin octylate is more preferable from the viewpoint of high catalytic activity. The addition amount of the polymerization catalyst is preferably 0.001 to 1 part by mass, and 0.003 to 0.1 part by mass with respect to 100 parts by mass in total of the polyester (B) containing lactide and phosphorus atoms. More preferably, it is more preferably 0.003 to 0.02 parts by mass. By setting the addition amount of the polymerization catalyst to 0.001 to 1 part by mass, a resin with less coloring can be obtained at an appropriate polymerization rate.

  The reaction temperature of the melt ring-opening polymerization is preferably 170 to 230 ° C, more preferably 170 to 210 ° C, and further preferably 180 to 200 ° C. By setting the reaction temperature to 170 to 230 ° C., a resin with less coloring can be obtained at an appropriate polymerization rate.

  The reaction vessel for carrying out the melt ring-opening polymerization is not particularly limited, and a vertical reactor and a horizontal reactor equipped with a helical ribbon blade, a high-viscosity stirring blade and the like can be used alone or in parallel. In addition, the reaction vessel may be a continuous type, a batch type or a semi-batch type, or a combination thereof.

  In the melt ring-opening polymerization, the polyester (B) containing a phosphorus atom is preferably melted at a temperature lower than the polymerization temperature or polymerized after being dissolved in a melt of lactide. When polymerization is performed without dissolving (B) in lactide or melting, polymerization is performed in a non-uniform state, and it may be difficult to control the polymerization reaction.

  When a low polymer is taken out in the middle of the melt ring-opening polymerization and solid-phase polymerized, the low polymer is crystallized in advance at a temperature not lower than the glass transition temperature of the low polymer and lower than the melting point from the viewpoint of preventing fusion. It is preferable to keep it.

  The reaction temperature of the solid phase polymerization is preferably at least the glass transition temperature of the low polymer and less than the melting point. The reaction temperature may be raised stepwise as the polymerization proceeds.

  Although it does not specifically limit as reaction container which performs a solid phase polymerization, For example, a vertical reactor, a horizontal reaction container, a tumbler, and a rotary kiln are mentioned.

  In solid phase polymerization, in order to efficiently remove water generated during solid phase polymerization, the reaction may be performed under reduced pressure or under an inert gas stream.

  The obtained polylactic acid-based resin can usually be used after being processed into pellets or rods.

  Usually 1% by mass or more of lactide remains in the polylactic acid resin obtained by melt ring-opening polymerization. These lactides can be removed by a known lactide weight loss method. Examples of the lactide weight loss method include a method of vacuum devolatilization in a single-screw or multi-screw extruder, a method of vacuum devolatilization in a reaction vessel, and a method of acetone treatment. Among these, a method of acetone treatment is preferable.

  Acetone treatment is to wash the polylactic acid resin after polymerization with acetone. Specifically, the mass ratio of the polylactic acid resin and acetone is 1: 1 to 1: 3, and stirring is performed for 30 minutes or more with a stirring blade or the like. The temperature during stirring is preferably 0 to 60 ° C, more preferably 10 to 40 ° C, and further preferably 20 to 30 ° C. When the temperature at the time of stirring exceeds 60 degreeC, since the boiling point of acetone is exceeded, volatilization of acetone becomes large. When the temperature is lower than 0 ° C., it is necessary to cool acetone, which is disadvantageous in cost. The stirring speed of the stirring blade is preferably 50 to 1000 rpm, more preferably 100 to 500 rpm, and further preferably 150 to 300 rpm. When the stirring speed exceeds 1000 rpm, the stirring speed is too high, and the generation of dust may increase due to the violent collision of the resins. On the other hand, when the stirring speed is less than 50 rpm, the amount of lactide extracted into acetone decreases, and the treatment time may be long. In addition, when this acetone washing | cleaning process is repeated in multiple times, the removal efficiency of an unreacted lactide will improve especially.

  By using acetone as a solvent, unreacted lactide can be extracted and at the same time the crystallization rate of the polylactic acid resin can be improved.

  Acetone is a relatively inexpensive solvent and is advantageous in terms of cost, and it is possible to extract not only lactide but also low molecular weight oligomers in polylactic acid resin.

  The lactide content of the polylactic acid resin of the present invention is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, and further preferably 0.07% by mass or less. Preferably, it is most preferable to set it as 0.05 mass% or less. By setting the content of lactide to 0.2% by mass or less, smoke generation during molding can be suppressed, and hydrolysis of the molded body by the lactide monomer can be suppressed.

  The melting point of the polylactic acid resin of the present invention is preferably 150 to 180 ° C, more preferably 160 to 180 ° C. The melting point of the polylactic acid-based resin of the present invention greatly depends on the D-form content of the polylactic acid-based resin, and the melting point is adjusted by setting the D-form content to 1.0 mol% or less, or 99.0 mol% or more. Becomes higher.

  The content of phosphorus atoms in the polylactic acid resin of the present invention is required to be 0.5 to 2.0 mass% with respect to 100 mass% of the polylactic acid resin, and 0.8 to 1.5 mass%. % Is preferred. When the phosphorus atom content is less than 0.5% by mass, the flame retardancy of the polylactic acid resin cannot be improved. On the other hand, when the phosphorus atom content is more than 2.0% by mass, the number average molecular weight of the obtained polylactic acid-based resin is decreased, and the mechanical strength when formed into a molded product is decreased, which is not preferable.

  As long as the effects of the present invention are not impaired, the polylactic acid-based resin of the present invention further includes a heat stabilizer, an antioxidant, a flame retardant, a crosslinking agent, a crystal nucleating agent, a foam nucleating agent, a terminal blocking agent, a dispersing agent, You may mix | blend additives, such as a filler, a pigment, a weathering agent, a plasticizer, a lubricant, a mold release agent, an antistatic agent, and an impact modifier. These additives may be used alone or in combination. In addition, the method of mix | blending these additives with the polylactic acid-type resin of this invention is not specifically limited.

  Examples of the heat stabilizer and the antioxidant include phosphorus compounds, hindered phenols, hindered amines, sulfur compounds, copper compounds, alkali metal halides, and mixtures thereof.

  Examples of the crosslinking agent include organic peroxides, bifunctional or higher (meth) acrylic acid ester compounds, bifunctional or higher epoxy compounds, bifunctional or higher vinyl compounds, and mixtures thereof.

  Examples of the crystal nucleating agent include inorganic crystal nucleating agents such as talc, kaolin, and clay, sorbitol compounds, benzoic acid and metal salts of those compounds, phosphate ester metal salts, rosin compounds, ethylenebisoleic acid amide, methylenebis. Acrylic acid amide, ethylene bisacrylic acid amide, hexamethylene bis-9,10-dihydroxystearic acid bisamide, p-xylylene bis-9,10 dihydroxystearic acid amide, decanedicarboxylic acid dibenzoyl hydrazide, hexanedicarboxylic acid dibenzoyl hydrazide, 1 , 4-Cyclohexanedicarboxylic acid dicyclohexylamide, 2,6-naphthalenedicarboxylic acid dianilide, N, N ′, N ″ -tricyclohexyltrimesic acid amide, trimesic acid tris (t-butylamide), 1,4- Chlohexanedicarboxylic acid dianilide, 2,6-naphthalenedicarboxylic acid dicyclohexylamide, N, N'-dibenzoyl-1,4-diaminocyclohexane, N, N'-dicyclohexanecarbonyl-1,5-diaminonaphthalene, ethylenebisstearic acid Examples thereof include organic crystal nucleating agents such as amide, N, N′-ethylenebis (12-hydroxystearic acid) amide, octanedicarboxylic acid dibenzoyl hydrazide, dimethyl potassium sulfoisophthalate, and dimethyl barium sulfoisophthalate.

  Examples of the foam nucleating agent include titanium oxide, talc, kaolin, clay, calcium silicate, silica, sodium citrate, calcium carbonate, diatomaceous earth, calcined perlite, zeolite, bentonite, glass, limestone, calcium sulfate, aluminum oxide, titanium oxide. , Magnesium carbonate, sodium carbonate, ferric carbonate, and polytetrafluoroethylene powder.

  Examples of the terminal blocking agent include carbodiimide, oxazoline, and epoxy resin.

  Examples of the dispersant include industrial oils such as liquid paraffin, mineral oil, creosote oil, lubricating oil and silicone oil, vegetable oils such as corn oil, soybean oil, rapeseed oil, palm oil, linseed oil and jojoba oil, ionic And nonionic surfactants.

  Examples of the filler include talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminate, sodium aluminosilicate, magnesium silicate, glass balloon, and carbon black. , Zinc oxide, antimony trioxide, zeolite, hydrotalcite, metal fiber, metal whisker, ceramic whisker, potassium titanate, boron nitride, graphite, glass fiber, carbon fiber and other inorganic fillers, aramid fiber, vinylon fiber, polyimide Organic fillers such as fiber, starch, cellulose fine particles, wood powder, okara, fir shell, bran and the like can be mentioned.

  The polylactic acid-based resin of the present invention can be formed into various molded products by a molding method such as injection molding, blow molding, or extrusion molding.

  As the injection molding method, a general injection molding method can be employed, and foam injection molding, injection press molding, or the like can also be employed. The cylinder temperature during injection molding is preferably equal to or higher than the melting point (Tm) or the flow start temperature (Tf) of the polylactic acid resin, more preferably 180 to 230 ° C, and more preferably 190 to 220 ° C. Further preferred. If the cylinder temperature is too low, short shots may occur during molding, resulting in unstable molding or overload. On the other hand, when the cylinder temperature is too high, the polylactic acid-based resin may be decomposed and the mechanical strength of the resulting molded product may be lowered or colored. The mold temperature at the time of injection molding is preferably 20 ° C. or more lower than the glass transition temperature (Tg) of the polylactic acid resin. When crystallization is promoted in the mold for the purpose of increasing the heat resistance of the polylactic acid-based resin, it is preferably maintained at (Tg + 20 ° C.) to (Tm−20 ° C.) for a predetermined time and then cooled to Tg or less. . In the case of post-crystallization, it is preferable to directly cool to Tg or lower and then heat-treat again at Tg to (Tm−20 ° C.).

  Examples of the extrusion molding method include a T die method and a round die method. The extrusion temperature is preferably Tm or Tf or more, more preferably 180 to 230 ° C, and further preferably 190 to 220 ° C. If the extrusion temperature is too low, the molding becomes unstable and may be overloaded. On the other hand, if the extrusion temperature is too high, the polylactic acid-based resin may be decomposed, and the strength of the resulting molded product may be reduced or colored. The temperature of the die is preferably 140 to 220 ° C, and more preferably 160 to 200 ° C. Sheets, pipes, and the like can be produced by extrusion molding, but may be heat-treated at Tg to (Tg-20 ° C.) for the purpose of improving their heat resistance.

  Examples of the blow molding method include a direct blow method in which direct molding is performed, an injection blow molding method in which blow molding is performed after a preformed body (bottom parison) is molded by injection molding, and stretch blow molding. In addition, any of a hot parison method in which blow molding is continuously performed after molding of a preformed body, and a cold parison method in which blow molding is performed by once cooling and taking out the preformed body and then performing blow molding can be employed. The blow molding temperature is preferably (Tg + 20 ° C.) to (Tm−20 ° C.). If the blow molding temperature is less than (Tg + 20 ° C.), molding may become difficult, or the resulting container may have insufficient heat resistance. On the other hand, if the blow molding temperature exceeds (Tm−20 ° C.), uneven thickness may occur or blowdown may occur due to a decrease in viscosity.

  Since the polylactic acid resin of the present invention has excellent flame retardancy, electrification of PC casing parts and casings, mobile phone casing parts and casings, other OA equipment casing parts, connectors, etc. Resin parts for products; automotive plastic parts such as bumpers, instrument panels, console boxes, garnishes, door trims, ceilings, floors, panels around engines, agricultural materials such as containers and cultivation containers, and resin parts for agricultural machinery; Resin parts for fisheries business such as floats and processed fishery products containers; dishes and food containers such as dishes, cups and spoons; medical resin parts such as syringes and drip containers; drain materials, fences, storage boxes, construction switchboards, etc. Resin parts for housing, civil engineering and building materials; Resin parts for greening materials such as flowerbed bricks and flower pots; Resin parts for leisure and miscellaneous goods such as cooler boxes, fan fans and toys; Rupen, ruler, can be suitably used in stationery resin parts such clips or the like.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
1. Raw materials The raw materials used in Examples and Comparative Examples are as follows.
(1) Lactide / L-lactide manufactured by Tokyo Chemical Industry Co., Ltd., D-form content = 0.06 mol%, free acid amount = 3 meq / kg

(2) Monomer containing phosphorus atom: HCA: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide manufactured by Sanko Co., Ltd.
IA: Iwata Chemical Industry, Itaconic acid PE100: Clariant PE100, 3-hydroxymethyl phosphinyl, mono (2-hydroxyethyl) ester PO4500: Nippon Chemical Industry PO-4500, n-butyl -Bis (3-hydroxypropyl) phosphite oxide

(3) Polyester containing phosphorus atom (B-1)
Sanko ME-100, HCA IA adduct with ethylene glycol added to both ends, molecular weight 434

・ (B-2)
A mixture composed of 215 parts by mass of HCA and 130 parts by mass of IA (HCA: IA = 100: 100 (molar ratio)) was charged into a reaction vessel equipped with a stirring blade and stirred at 150 rpm for 2 hours. An addition reaction was performed.
Thereafter, 478 parts by mass of (A-1) (135 moles when HCA is taken as 100 moles) was further added to the reaction vessel, and the mixture was stirred at a rotation speed of 100 rpm and controlled at 240 ° C. under a pressure of 0.35 MPa. Time esterification was performed.
After esterification, it was transferred to a polycondensation can and 0.4 parts by mass of tetrabutyl titanate monomer was added as a polymerization catalyst, and the pressure was gradually reduced to 1.3 hPa over 60 minutes, 1.3 hPa, 240 ° C. (B-2) was synthesized by performing a polycondensation reaction for 0.3 hour.

・ (B-3) to (B-8)
As shown in Table 1, a polyester was synthesized by performing the same operation as in the case of synthesizing (B-2) except that the type of the glycol component and the polycondensation time were changed.

  Table 1 shows production conditions, preparation composition, final composition and characteristic values of (B-2) to (B-8).

・ (B-9)
1-decanol made by Kishida Chemical

(3) Antioxidant / HP10
HP-10, 2,4,8,10-tetra-tert-butyl-6- (2-ethylhexyloxy) -6H, 12H-5,7-dioxa-6-phosphadibenzo [a, d, manufactured by ADEKA ] Cyclooctene

(4) Polymerization catalyst, tin octoate Stanokt manufactured by Yoshitomi Fine Chemicals

(5) Polylactic acid resin S-12
Toyota S-12, D content 0.1%, melting point 180 ° C

2. Analysis Method The measurement method and analysis method are as follows.

(1) Number average molecular weight (Mn)
The number average molecular weight in terms of polystyrene was measured using gel permeation chromatography (GPC) under the following conditions.
Liquid feeding unit: LC-10ADvp manufactured by Shimadzu Corporation
Ultraviolet-visible spectrophotometer: SPD-6AV manufactured by Shimadzu Corporation, detection wavelength: 254 nm
Column: VARIAN PLgel 5 μm MIXED-D 300 × 7.5 mm 2 used Solvent: Chloroform Measurement temperature: 35 ° C.
Flow rate: 1.0 mL / min

(2) D-form content After adding 0.3 g of polylactic acid resin to 6 mL of 1N potassium hydroxide / methanol solution and thoroughly stirring at 65 ° C., 450 μL of sulfuric acid is added and stirring is performed at 65 ° C. for decomposition. I let you. 5 mL of this decomposed product, 3 mL of pure water, and 13 mL of methylene chloride were mixed and shaken. After standing and separated, about 1.5 mL of the lower organic layer was collected and filtered with a HPLC disk filter having a pore size of 0.45 μm. Gas chromatography measurement was performed using HP-6890 Series GC system manufactured by Hewlett Packard. The ratio of the peak area of D-lactic acid methyl ester to the total peak area of lactate methyl ester was calculated, and this was defined as the D-form content (mol%).

(3) Residual lactide amount To 0.1 g of polylactic acid resin, 9 mL of methylene chloride and 1 mL of an internal standard solution (5000 ppm solution of 2,6-dimethyl-γ-pyrone) were added to dissolve the resin. To this solution, 40 mL of cyclohexane was added to precipitate the resin, and about 1.5 mL of the supernatant was collected. After filtration with a HPLC disk filter having a pore size of 0.45 μm, gas chromatography measurement was performed using 7890A GC System manufactured by Agilent Technologies.

(4) Melting point Using 7 mg of a polylactic acid resin as a sample, using a differential scanning calorimeter DSC-7 manufactured by PerkinElmer, the temperature was raised to 200 ° C. at a rate of temperature increase of 20 ° C./min in a nitrogen stream, and crystal melting The temperature at the peak top of the peak was taken as the melting point.

(5) Bending strength Using an injection molding machine (trade name “IS-80G type” manufactured by Toshiba Machine Co., Ltd.), a test piece conforming to ISO178 was prepared while adjusting the mold surface temperature to 105 ° C.
The bending strength was measured according to ISO178 using the obtained test piece.
The bending strength is preferably 35 MPa or more, and more preferably 50 MPa or more.

(6) Flame retardancy Using an injection molding machine (trade name “IS-80G type” manufactured by Toshiba Machine Co., Ltd.), the mold surface temperature is adjusted to 105 ° C., and is determined by UL94 (Under Writers Laboratories Inc., USA). A test piece having a thickness of 0.8 mm was prepared in accordance with the standard.
Using the obtained test piece, flame retardancy was evaluated according to UL94.
The flame retardancy is preferably V-2 or more, and more preferably V-1 or V-0.
In Table 2, those not satisfying V-2 are indicated as “notV-2”.

(7) Bleed resistance The test piece obtained in (5) was subjected to wet heat treatment at 60 ° C. × 95% for 200 hours in a thermostatic oven. The surface of the test piece after the heat treatment was visually observed and evaluated in the following two stages.
○: The surface state has not changed.
X: The surface state has changed.

Example 1
92.5 parts by mass of lactide, 7.5 parts by mass of polyester (B-2) as an initiator, 0.4 part by mass of HP10 as an antioxidant, and 0.2 parts by mass of tin octylate as a polymerization catalyst are charged into a reaction vessel. Thereafter, the reaction vessel was purged with nitrogen. Stirring was started when the temperature was raised to 180 ° C. and the contents were melted after nitrogen substitution. Thereafter, the internal temperature was raised to 190 ° C. and polymerization was carried out for 6 hours.
The obtained resin was vacuum devolatilized at 140 ° C. and 5 hPa for 40 hours to remove residual lactide, thereby obtaining a polylactic acid resin.

Examples 2-12, Comparative Examples 1-6
Except changing the kind and amount of polyester to be used, and the amount of lactide as shown in Table 2, the same operation as in Example 1 was performed to obtain a polylactic acid resin.

  Table 2 shows the composition and characteristic values of the obtained polylactic acid resin.

Comparative Example 6
After putting 60 parts by mass of polylactic acid resin (S-12) and 40 parts by mass of PO4500 into the reaction vessel, the reaction vessel was purged with nitrogen. Stirring was started when the temperature was raised and the contents were melted after nitrogen substitution. Thereafter, the internal temperature was raised to 230 ° C. and depolymerized for 2 hours.
The temperature was lowered to 190 ° C., 30 parts by mass of cyclohexyl diisocyanate was slowly added, and the reaction was allowed to proceed for 30 minutes with stirring.
Thereafter, devolatilization was performed at 5 hPa for 30 minutes to remove residual lactide, and a polylactic acid resin was obtained.

  All of the polylactic acid-based resins of Examples 1 to 12 had a bending strength of 35 MPa or more, excellent mechanical strength, and flame retardancy of V-2 or more. Moreover, the bleed resistance was also excellent.

Since the polylactic acid resins of Comparative Examples 1 to 3 had a low molecular weight of the polyester as an initiator, the number average molecular weight of the obtained polylactic acid resins was low, and the bending strength was low.
Furthermore, since the polylactic acid-based resin of Comparative Example 1 had a low phosphorus atom content, the flame retardancy was low.
The polylactic acid resin of Comparative Example 4 had a low bending strength because the phosphorus atom content was too high.
Since the polylactic acid resin of Comparative Example 5 did not contain phosphorus atoms in the initiator polyester, the flame retardancy was low.
The polylactic acid resin of Comparative Example 6 is a retest of the polylactic acid flame retardant copolymer used in Cited Document 1. Since it was not polymerized using a polyester containing a phosphorus atom as an initiator, the bending strength was low.

Claims (3)

A polylactic acid resin in which polylactic acid (A) and polyester (B) containing a phosphorus atom are bonded via a covalent bond,
(I) The number average molecular weight of (B) is 1000 or more,
(Ii) The average degree of polymerization of (B) is 3 or more,
(Iii) The content of phosphorus atoms in the polylactic acid-based resin is 0.5 to 2.0% by mass
A polylactic acid resin characterized by The method for producing a polylactic acid-based resin according to claim 1, comprising a step of polymerizing lactide using the polyester (B) containing a phosphorus atom as an initiator in the presence of a polymerization catalyst. A molded article obtained by molding the polylactic acid resin according to claim 1.