JP2009161658A - Flame-retardant polylactic acid composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a flame-retardant polylactic acid composition which contains a polylactic acid enabling an environmental load to be reduced even upon manufacture and abandonment and can provide a molded article having flame retardant properties and excellent toughness. <P>SOLUTION: The polylactic acid resin composition contains the polylactic acid (A), a metal hydrate (B), a flexible component (C), a plasticizer (D) and a carbonizing agent (E), wherein the carbonizing agent (E) includes a phenol novolak resin having 110 to 220°C softening point. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a flame retardant polylactic acid composition, and more particularly to a flame retardant polylactic acid composition having excellent toughness.

  In recent years, polylactic acid resin, which is a bioplastic, has attracted attention as an alternative to petroleum raw materials, and its practical application has been actively performed in various applications, and in part, it has already been commercialized. The use period is short, such as containers and packaging and agricultural films, and the initial characteristics are used for a long period of time, such as applications that assume disposal, housings for home appliances and OA equipment, and automotive parts. There is a wide variety of applications up to high functionality that can be retained.

  However, since polylactic acid is a flammable resin, it can cause disasters that threaten people's safety. Therefore, it is used for applications that require high flame resistance, such as home appliances, OA equipment housings, and automobile parts. In some cases, flame retardant measures are necessary. In addition, it is important for practical use that the molded body has not only high flame retardancy but also toughness (large bending fracture strain).

  Regarding the flame retardancy of polylactic acid, a method in which a halogen-based flame retardant such as a bromine compound having a high flame retardancy efficiency is blended with the resin is considered. However, when a halogen-based flame retardant is added to a polycarbonate resin, which is a typical polyester resin, repeated melting and kneading for the purpose of reuse deteriorates the resin, resulting in flame retardancy and impact resistance. There is a problem that the physical properties such as the above decrease. When a halogen-based flame retardant is used for polylactic acid having the same ester bond, there is a concern that the physical properties are lowered when melt kneading is repeated as in the case of the polycarbonate resin.

  As a countermeasure for flame retardancy of polylactic acid, for example, at least one flame retardant additive selected from polylactic acid, phosphorus compounds, hydrate compounds (metal hydrates such as aluminum hydroxide) and silica compounds There has been reported a biodegradable resin composition (Patent Document 1) using Generally, phosphorus compounds are easy to plasticize a resin and are extremely effective in improving the fluidity of the resin. However, on the other hand, the heat resistance and mechanical properties with the deflection temperature under load (HDT) or the like of the resin composition as an index may be reduced due to the effect of plasticization.

  On the other hand, a flame retardant additive (Patent Document 2) in which a metal hydrate having reduced alkali components that cause thermal decomposition of polylactic acid and a phenolic resin as a carbonizing agent has been reported. According to this, when about 50% by mass of an inorganic flame retardant such as aluminum hydroxide is added, and in addition to that, a low molecular weight phenol resin or the like is used as a carbonizing agent, the flame retardancy of polylactic acid can be further enhanced. It is shown. Moreover, since the toughness of the resin composition is greatly reduced when a metal hydrate is added to polylactic acid, it has been shown that a known soft component or plasticizer may be used in combination as a countermeasure.

  However, the resin composition described in Patent Document 2 has a problem that it cannot be used for applications that require large toughness such as housings of home appliances, OA equipment, and automobile parts. The reason is that, since the soft component and the plasticizer are flammable materials, the flame retardancy of the composition is lowered when the amount of addition is increased in order to improve the toughness of the composition. For this reason, in order to apply polylactic acid to said use, it was a subject to develop the method which can improve the toughness of a composition, without increasing a soft component and a plasticizer.

  Further, if the flame retardancy of the composition is further improved, it is desirable because the applicable applications are expanded. However, increasing the amount of the metal hydrate and reducing the amount of the softening component and the plasticizer as countermeasures against them are undesirable because they cause the toughness of the molded body of polylactic acid to decrease. Therefore, it is an object to develop a method capable of improving the flame retardancy of the composition without increasing the amount of metal hydrate or reducing the amount of the soft component or plasticizer.

That is, there is a demand for the development of a polylactic acid composition with improved flame retardancy and toughness without increasing the amount of metal hydrate and without changing the amount of the soft component or plasticizer added.
JP 2003-192925 A WO2005 / 061626

  An object of the present invention is to provide a flame retardant containing a polylactic acid capable of reducing the environmental load at the time of production and disposal, having a flame retardancy, and having an excellent toughness. It is in providing a functional polylactic acid composition.

  The inventors of the present invention have conducted extensive research on the flame retardancy of polylactic acid by employing a phenol novolac resin. Regarding the mechanism of improving the flame retardancy of a polylactic acid composition by a phenol novolac resin, as described in Patent Document 2, a phenol novolac resin having a low molecular weight is added to polylactic acid together with a metal hydrate as described in Patent Document 2. It has been found that carbides and melted resins derived from novolac resins are combined with metal hydrates and the resulting metal oxides to form a unique composite layer. This composite layer captures the decomposition gas (containing combustible gas) of the resin component in the polylactic acid composition, suppresses the diffusion of the decomposition gas to the outside, and inhibits the spread of the resin. In addition, it forms a heat-insulating layer that expands by trapping moisture generated by the thermal decomposition of metal hydrates and decomposition gas of the resin component, and can effectively block the heat of ignition, resulting in the flame retardancy of the composition. It is thought that it can be improved.

  As a result of research, the present inventors have found that when a phenol novolac resin having a high molecular weight and a low molecular weight component is used, the amount of carbide generated is increased as compared with the case of adding a conventional low molecular weight phenol novolac resin. I found out that I can. Increasing the amount of carbide increases the trapping power of the flammable cracked gas generated from the resin component of the polylactic acid composition, thereby suppressing the diffusion of the cracked gas to the outside and suppressing the spread of the resin. The effect and the effect of forming a heat-insulating layer that can block heat of ignition by expanding by capturing moisture and resin component decomposition gas generated by the thermal decomposition of metal hydrate, resulting in flame retardancy of the composition The knowledge that can be improved than before.

  Moreover, it discovered that the toughness of the molded object obtained became high by adding the phenol novolak resin which was high molecular weight and reduced the low molecular weight component to polylactic acid. The reason for this is that when a high molecular weight phenol novolak molecule dissolves between the polylactic acid molecules and the polylactic acid crystallizes, it is placed across multiple crystals of polylactic acid, resulting in a grain boundary of the crystal. It is conceivable that the disposition at the grain boundary of the polylactic acid can be suppressed by arranging the connection so that the bending fracture strain of the obtained molded body is increased. The effect of such toughness improvement is that the conventional low molecular weight phenol novolac resin has insufficient molecular chain length and could not be arranged to connect the crystal grain boundaries of polylactic acid. It was obtained for the first time by a phenol novolac resin having a high molecular weight and a reduced low molecular weight component, and obtained the knowledge that the toughness of the molded body can be greatly improved. Based on these findings, the present invention relating to a polylactic acid composition excellent in flame retardancy and toughness has been completed.

  That is, the present invention is a polylactic acid resin composition containing polylactic acid (A), metal hydrate (B), soft component (C), plasticizer (D), and carbonizing agent (E), The carbonizing agent (E) relates to a polylactic acid composition containing a phenol novolac resin having a softening point of 110 ° C. or higher and 220 ° C. or lower.

  The polylactic acid composition of the present invention contains a polylactic acid capable of reducing the environmental burden even during production or disposal, and obtains a molded article having flame retardancy and excellent toughness. Can do.

  The polylactic acid composition of the present invention is a polylactic acid resin composition containing polylactic acid (A), metal hydrate (B), soft component (C), plasticizer (D), and carbonizing agent (E). The carbonizing agent (E) includes a phenol novolac resin having a softening point of 110 ° C. or higher and 220 ° C. or lower.

[Polylactic acid (A)]
Examples of the polylactic acid (A) used in the flame retardant polylactic acid composition of the present invention include extracts obtained from biomass raw materials, derivatives or modified products thereof, monomers, oligomers obtained from biomass raw materials, and derivatives thereof. Alternatively, in addition to a polycondensation product synthesized using a modified product, a synthesis product using a raw material other than a biomass raw material may be used. The polylactic acid (A) may be poly L-lactic acid, poly D-lactic acid, or a copolymer thereof, such as lactic acid and other monomers such as hydroxycarboxylic acid having ester forming ability with lactic acid. A copolymer may be included. Examples of such hydroxycarboxylic acid include glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypentanoic acid, hydroxycaproic acid, and the like. These polylactic acids may have a side chain or a crosslinked structure. These polylactic acids may have any molecular weight, and may have a low molecular weight in order to increase fluidity, or may have a high molecular weight in order to increase melt tension.

  The flame retardant polylactic acid composition of the present invention may contain a resin component other than the polylactic acid. Such a resin component may be any of petroleum-derived resins, biomass-derived polymer compounds, and the like, and may be contained within a range that does not impair flame retardancy and toughness in the flame-retardant polylactic acid composition of the present invention. it can. Examples of petroleum-derived resins include polypropylene, polystyrene, ABS, nylon, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, urea resin, melamine resin, alkyd resin, acrylic resin, unsaturated polyester resin, diallyl phthalate resin, epoxy resin, Silicone resin, cyanate resin, isocyanate resin, furan resin, ketone resin, xylene resin, thermosetting polyimide, thermosetting polyamide, styrylpyridine resin, nitrile terminal resin, addition curable quinoxaline, addition curable polyquinoxaline Examples thereof include thermosetting resins such as resins. When using a thermosetting resin, it is preferable to use a curing agent or a curing accelerator necessary for the curing reaction. Examples of the polymer compound derived from biomass other than polylactic acid include esters such as polybutylene succinate obtained from succinic acid obtained from a saccharide contained in corn, straw or the like as a starting material. In addition, starch, amylose, cellulose, cellulose ester, chitin, chitosan, gellan gum, carboxyl group-containing cellulose, carboxyl group-containing starch, polysaccharides such as pectinic acid and alginic acid, and thermosetting resins using plant materials such as lignin are also used. can do. Polybutylene succinate can also be used as the soft component (C) described below.

  In addition, examples of the biomass-derived polymer compound include polybutoxyhydroxyalkanoate (trade name: Biopol, etc., manufactured by Zeneca) which is a polymer of hydroxybutyrate and / or hydroxyvalerate synthesized by microorganisms. Can do.

[Metal Hydrate (B)]
The metal hydrate (B) has a function of cooling the polylactic acid composition by an endothermic action when decomposing by heating, or diluting a combustible gas generated from the polylactic acid composition by water vapor generated at that time. For example, those that decompose at a temperature of 210 ° C. or higher, which is the upper limit temperature during kneading and molding of the polylactic acid composition, are preferred. Examples of the metal hydrate (B) include aluminum hydroxide, magnesium hydroxide, dosonite, calcium aluminate, hydrated gypsum, calcium hydroxide, zinc borate, barium metaborate, borax, kaolin clay, and calcium carbonate. The surface of these surfaces treated with an epoxy resin, a phenol resin, or the like, or the one obtained by solidifying a metal can be used. Of these, aluminum hydroxide is particularly preferable because it has a high endothermic effect and is excellent in flame retardancy.

  The 50% by mass particle size of the metal hydrate (B) is preferably in the range of 0.5 μm or more and 20 μm or less. When the metal hydrate (B) has such a particle size, the dispersibility in the polylactic acid composition is good, and the effect of improving flame retardancy is obtained. If the 50% by mass particle size of the metal hydrate (B) is 0.5 μm or more, the viscosity of the polylactic acid composition can be prevented from increasing and the moldability can be prevented from being lowered. Suppressing the increase in shear force applied to the polylactic acid composition, and as a result, anti-drip agents such as polytetrafluoroethylene (PTFE), and glass fibers added for the purpose of improving heat resistance and impact resistance It is possible to suppress damage to inorganic and organic fibrous materials such as resin fibers and improve flame retardancy and mechanical properties. When the 50% by mass particle size of the metal hydrate (B) is 20 μm or less, the surface properties of the resulting molded article are excellent, and irregularities are generated on the surface, so that deterioration in design properties can be suppressed.

  As the 50% by mass particle diameter, a measurement value measured by particle size distribution measurement by a laser diffraction scattering method can be adopted.

  When the metal hydrate (B) has an alkali metal content of 0.2% by mass or less, the molecular weight of the polylactic acid decreases during kneading and molding when added to the polylactic acid composition. This is preferable because hydrolysis resistance is improved, and the decrease in flame retardancy of the polylactic acid composition can be suppressed as a result.

  The content of the metal hydrate (B) in the polylactic acid composition is particularly preferably in the range of 39.5% by mass or more and 70% by mass or less because flame retardancy and moldability are good. If the content of the metal hydrate (B) is 39.5% by mass or more, sufficient flame retardancy is obtained, and if it is 70% by mass or less, sufficient fluidity is obtained, and high formability. Even a thin-walled molded body that requires a good molding can be performed.

[Flexible component (C)]
The flexible component (C) is preferably an organic substance having a lower elastic modulus at room temperature than the polylactic acid (A). Such an organic substance is preferably a polymer having a unit capable of being compatible with polylactic acid and a unit exhibiting flexibility. Examples of the flexible component (C) include a copolymer composed of three component monomers of lactic acid, glycols, and linear saturated dicarboxylic acid. Examples of the copolymer glycols include ethylene glycol, propylene glycol, and diethylene glycol. Examples of the linear saturated dicarboxylic acid of the copolymer unit include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid and the like. As the soft component (C), in addition to the above, acrylics such as polybutylene succinate, copolymers of butylene succinate and lactic acid, polycaprolactone, copolymers of caprolactone and lactic acid, natural rubber, polymethyl methacrylate (PMMA), etc. -Based resin, block copolymer having two or more segments selected from polyester segment, polyether segment and polyhydroxycarboxylic acid segment, block copolymer having polylactic acid segment, aromatic polyester segment and polyalkylene ether segment , Polymers based on unsaturated carboxylic acid alkyl ester units, polyethylene succinate, polyethylene adipate, polypropylene adipate, polybutylene adipate, polyhexamethylene adipate, polybutylene Aliphatic polyesters, such as succinate adipate, may be used polyethylene glycol and esters thereof.

  The content of the soft component (C) in the polylactic acid composition is such that the mass ratio with the polylactic acid (A) is in the range of 95: 5 to 50:50, preferably in the range of 92: 8 to 70:30. It is preferable because a molded body having toughness can be obtained.

[Plasticizer (D)]
The plasticizer (D) broadly includes a “lubricant” having a releasing effect, and penetrates between the molecules of the polylactic acid (A) and the polymer added as necessary, so that the molecules between the polymers. A compound that weakens the force and facilitates movement of the molecular chain is preferable. Specific examples of the plasticizer (D) include dimethyl adipate, dibutyl adipate, diisobutyl adipate, bis (2-ethylhexyl) adipate, diisononyl adipate, diisodecyl adipate, bis (butyl diglycol) adipate, bis (butyl diglycol) Adipate, bis (2-ethylhexyl) azelate, dimethyl sebacate, dibutyl sebacate, bis (2-ethylhexyl) sebacate, bis (2-ethylhexyl) sebacate, diethyl succinate, bismethyldiethylene glycol adipate, benzyl-2- (2- Aliphatic dibasic acid esters such as methoxyethoxy) ethyl adipate, ditridecyl phthalate, dinormal octyl phthalate, diisononyl phthalate, dimethyl phthalate, diethyl Phthalate esters such as tarate, dibutyl phthalate, bis (2-ethylhexyl) phthalate, di-n-octyl phthalate, diisodecyl phthalate, butyl benzyl phthalate, diisononyl phthalate, ethyl phthalyl ethyl glycolate, tri-normal octyl trimellitate, tri Trimellitic acid esters such as isodecyl trimellitate and tris (2-ethylhexyl) trimellitate, trimethyl phosphate, triethyl phosphate, tributyl phosphate, tris (2-ethylhexyl) phosphate, tris (butoxyethyl) phosphate, triphenyl phosphate, tricres Zyl phosphate, trixylenyl phosphate, cresyl diphenyl phosphate, 2-ethylhexyl diphenyl phosphate Phosphoric acid esters such as methyl acetyl ricinoleate, aliphatic polyesters such as poly (1,3-butanediol adipate), polyglycerin acetates, epoxidized polyesters such as epoxidized soybean oil, epoxidized linseed Oil, epoxidized linseed oil fatty acid butyl, glyceryl triacetate, acetate ester such as 2-ethylhexyl acetate, sulfonamide such as N-butylbenzenesulfonamide, chlorinated paraffin, liquid paraffin such as alkylnaphthene hydrocarbon, n-paraffin, etc. Paraffin wax, polyethylene waxes such as low molecular weight polyethylene, partially oxidized polyethylene, octyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol Fatty alcohols such as cole, fatty acids such as linolenic acid, linoleic acid, oleic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, hydroxy fatty acids such as castor oil derived from 12-hydroxystearic acid, methyl stearate Fatty acid esters such as octyl stearate, stearyl stearate, ethylene glycol monostearate, ethylene glycol distearate, methyl 12-hydroxystearate, stearyl 12-hydroxystearate, ethylene glycol mono-12-hydroxystearate, mono- Hydroxy fatty acid esters such as propylene glycol 12-hydroxystearate, stearylamide, N-hydroxyethyl-ricinoleylamide, N-hydroxyethyl-12-hydro Cysteallylamide, N, N′-ethylene-bis-oleylamide, N, N′-ethylene-bis-ricinoleylamide, N, N′-ethylene-bis-octadecadienylamide, N, N′- Ethylene-bis-12-hydroxystearylamide, N, N'-ethylene-bis-stearylamide, N, N'-hexamethylene-bis-ricinoleylamide, N, N'-hexamethylene-bis-12-hydroxy Examples thereof include fatty acid amides such as stearylamide and N, N′-xylylene-bis-12-hydroxystearylamide, and aliphatic soaps.

  In order to obtain sufficient flame retardancy, the content of the plasticizer (D) in the polylactic acid composition is preferably 5% by mass or less.

[Carbonizer (E)]
The carbonizing agent (E) includes a phenol novolac resin having a softening point of 110 ° C. or higher and 220 ° C. or lower. The phenol novolac resin is a copolymer of phenol and formaldehyde, and the phenol novolac resin having such a softening point generates a large amount of carbides by heating, water vapor generated from the metal hydrate (B), It has a function of capturing a flammable decomposition gas generated from lactic acid and expanding it to inhibit diffusion to the outside and to form a heat insulating layer capable of blocking the heat of ignition. If the softening point of the phenol novolac resin is 110 ° C. or higher, the molecule of the phenol novolac resin has a molecular chain with a length that can connect the grain boundaries of polylactic acid, and the toughness is improved in the resulting molded article. Can do. On the other hand, if the softening point of the phenol novolac resin is 220 ° C. or lower, the dispersibility of the phenol novolac resin in polylactic acid is good, and the phenol novolac resin is uniformly dispersed in the composition, thereby improving flame retardancy. it can. It is preferable that the softening point of the phenol novolac resin is 120 ° C. or higher and 150 ° C. or lower because the above-described effect can be obtained more remarkably. The reason why the phenol novolac resin is specified by its softening point is that the softening point tends to increase as the molecular weight increases. The molecular weight of the phenol novolak resin having the softening point is preferably a high molecular weight and low molecular weight component reduced, and the weight average molecular weight in terms of standard polystyrene in the gel filtration chromatography measurement is 1500 or more, and the number average molecular weight is , 800 or more.

  Here, as the softening point, a measured value measured by a method in accordance with JIS K 6910 can be adopted, and the temperature at the time when slight infiltration or disintegration is observed in the inner wall of the capillary tube of the melting point measuring device and the contact portion of the sample. It can be.

  Since the phenol novolac resin is easily oxidized and discolored, it is preferable to use an antioxidant together in applications where design properties are required. One of the causes of coloring of the phenol resin is that the phenolic hydroxyl group is changed to quinone. For this reason, when the designability is required for the molded body, it is preferable to use the phenol novolac resin after protecting the hydroxyl group of the phenol novolac resin with a protective group. Examples of the protecting group include glycidylation and ethylene oxideation.

  As the carbonizing agent (E), in addition to the phenol novolac resin, a carbonizing agent that does not inhibit the function of the phenol novolac resin can be used. Specific examples of the carbonizing agent include cresol novolac resin, phenol xylene aralkyl type resin, phenol biphenylene aralkyl type resin, bisphenol A type phenol resin, bisphenol F type phenol resin, bisphenol S type phenol resin, dihydroxy ether type of biphenyl isomer. Phenol resin, naphthalene diol type phenol resin, phenol diphenyl ether aralkyl type resin, naphthalene-containing novolac resin, anthracene-containing novolak resin, fluorene-containing novolac resin, bisphenol fluorene-containing novolac resin, bisphenol F-containing novolac phenol resin, bisphenol A Contained novolac type phenolic resin, phenol biphenylene triazine type resin, phenol xylile Triazine type resin, phenol triazine type resin, trisphenylol ethane type resin, tetraphenylol ethane type resin, polyphenol type resin, aromatic ester type phenol resin, cyclic aliphatic ester-containing phenol resin, ether ester type phenol resin and phenoxy resin And so on. Other phenols include biphenol, xylenol, bisphenol A, bisphenol F, bisphenol S, catechol and catechol resin. Furthermore, a catechol biphenylene aralkyl resin or a catechol xylene aralkyl resin obtained by copolymerizing a catechol and an aromatic derivative can also be used. In addition, lignin and its analogs such as lignophenols may be used.

  The content of the phenol novolac resin in the polylactic acid composition is in the range of 0.1% by mass or more and 20% by mass or less, so that the amount of metal hydrate (B) used can be reduced. Since the fluidity | liquidity of a composition is provided and heat resistance can be provided to the molded object obtained in addition to a flame retardance and toughness, it is preferable. If the content of the phenol novolac resin is 0.1% by mass or more, the effect of improving flame retardancy and toughness can be obtained. If the content is 20% by mass or less, the heat resistance, particularly the deflection temperature under load (HDT) is reduced. Can be suppressed. Further, the content of the carbonizing agent other than the phenol novolac resin is preferably in the range of 0.1% by mass or more and 20% by mass or less in the polylactic acid composition, like the phenol novolac resin.

[Additive]
The polylactic acid composition may contain an additive as long as the function of the constituent substances is not inhibited. An example of such an additive is an anti-drip agent. The anti-drip agent has a function of suppressing drip (dripping) during combustion. As the drip inhibitor, organic fibers such as polytetrafluoroethylene (PTFE) and acrylic modified PTFE are preferable. When these anti-drip agents are used, the content of the anti-drip agent in the polylactic acid resin composition is preferably 1% by mass or less. When the content of these anti-drip agents is 1% by mass or less, the granulation property is good when producing pellets.

  Moreover, a high-strength fiber can be used as an additive. Impact strength can be improved by using high-strength fibers. Examples of the high-strength fibers include polyamide fibers such as aramid fibers and nylon fibers, polyester fibers such as polyarylate fibers and polyethylene terephthalate fibers, ultrahigh-strength polyethylene fibers, and polypropylene fibers. Examples of the inorganic fiber include carbon fiber, metal fiber, and glass fiber. Aramid fiber and polyarylate fiber are aromatic compounds, and have higher heat resistance than other fibers, high strength, and light color. Therefore, it is particularly preferable. The shape of the high-strength fiber is not circular in the fiber cross section, but has an ellipse, polygon, irregular shape, or uneven shape, a kind of wedge shape in which both end portions are thicker than the center portion, and part of the shape is constricted , Non-linearly crimped shapes, high aspect ratios, and small fiber diameters increase the bonding area with the resin, increasing the debonding effect between the fibers and the matrix resin, and pulling out the fibers. This is preferable because the friction at the time increases, the impact relaxation effect increases, and the impact strength improves.

  Moreover, surface treatment can be applied to the high-strength fibers as necessary in order to increase the affinity with the matrix resin or the entanglement between the fibers. As the surface treatment method, a treatment method that can be used for modifying the surface of the filler can be applied. For example, treatment with a coupling agent such as silane or titanate, ozone or plasma treatment, and alkyl phosphoric acid. Treatment with an ester type surfactant is effective.

  In addition to the high-strength fibers, plant fibers can also be used. Such plant fiber refers to a fiber derived from a plant, and specific examples include fibers obtained from wood, kenaf, bamboo, hemp, flax, etc., which are obtained by delignifying or depectining these. Pulp and the like can also be preferably used because they are less susceptible to thermal decomposition and discoloration. Since kenaf and bamboo have a high photosynthesis rate and fast growth and can absorb a large amount of carbon dioxide, it is preferable to use them as one of countermeasures for environmental problems such as global warming and forest destruction. Further, these fibers can act as a crystal nucleating agent for the resin and improve heat resistance such as increasing the deflection temperature under load of the polylactic acid composition. These fibers preferably have an average fiber length of 10 mm or less.

  Moreover, a hydrolysis-resistant inhibitor can be used as the additive. Since ester bonds contained in polyester resins such as polylactic acid are generally easily hydrolyzed, these hydrolysis can be suppressed by using a hydrolysis inhibitor. As the hydrolysis inhibitor, a compound having reactivity with a functional group containing active hydrogen contained in a polyester resin can be used. Examples of the functional group contained in the polyester resin include a carboxyl group, a hydroxyl group, an amino group, an amide group, and the like, and examples of the compound having reactivity with these functional groups include a carbodiimide compound described in Patent Document 2, Examples thereof include a carbodiimide compound having an aliphatic carbon chain, an isocyanate compound, and an oxazoline compound.

  As the additive, a flame retardant aid can be used. Examples of the flame retardant aid include a carbonization promotion catalyst that promotes carbonization of a resin component. Specifically, compounds such as zinc molybdate and zinc stannate, and these compounds, for example, are coated on the surface of talc. And the like.

  Further, if necessary, other flame retardants may be added as additives as long as the functions of the above substances are not impaired. Examples of the flame retardant include a nitrogen-based flame retardant and a phosphorus-based flame retardant. Specific examples include nitrogen-based flame retardants such as melamine and isocyanuric acid compounds, and phosphorus-based flame retardants such as red phosphorus, phosphoric acid compounds, and organic phosphorus compounds. These flame retardant aids and other flame retardants can be used by previously containing them in fibers or the like.

  In addition, as additives, inorganic fillers, reinforcing materials, colorants such as titanium oxide, stabilizers such as radical scavengers and antioxidants, antibacterial agents and fungicides can be used as necessary. Examples of the inorganic filler include silica, alumina, sand, clay, and iron slag. Examples of the reinforcing material include needle-like inorganic substances, and examples of the antibacterial agent include silver ions, copper ions, zeolites containing these, and the like.

  As a method for producing the polylactic acid composition of the present invention, each of the above components is melt-mixed by a known mixer, such as a tumbler, ribbon blender, uniaxial or biaxial kneader or the like, an extruder, a roll or the like. The method of mixing using a machine can be mentioned.

  As a method for producing a molded body using the polylactic acid composition of the present invention, an injection molding method, a film molding method, a blow molding method, a foam molding method, and the like can be used. A compression molding machine, a compression molding machine, etc. can be used. About the temperature at the time of these melt mixing and shaping | molding, it can select suitably in the range which is more than the melting temperature of the polylactic acid used as a matrix, and additives, such as a vegetable fiber and resin, do not thermally deteriorate.

  The present invention will be described in more detail with reference to the following examples, but the technical scope of the present invention is not limited thereto.

[Example 1]
[Preparation of polylactic acid composition]
Compositions were prepared using the raw materials shown in Table 1. 44% by mass of polylactic acid (A), 49.5% by mass of aluminum hydroxide as metal hydrate (B), 0.5% by mass of polytetrafluoroethylene as anti-drip agent, and ethylene bis as organic crystal nucleating agent 1% by mass of 12 hydroxystearylamide, 5% by mass of a phenol novolak resin having a softening point of 150 ° C. (referred to as “high molecular weight product” in the table) as a carbonizer (E), and the temperature of the composition is about 190 ° C. The mixture was melt-mixed using a set biaxial kneader to prepare pellets for injection molding.

[Preparation of sample for evaluation]
The obtained pellets for injection molding were dried at 100 ° C. for 7 hours or more, and using an injection molding machine in which the mold temperature was set to 100 ° C. and the barrel temperature was set to 190 ° C., the thicknesses were 1.6 mm and 3.2 mm. The sample was molded into a plate shape, and polylactic acid was crystallized in a mold to prepare a sample 1 for evaluating a polylactic acid molded article.

[Evaluation of flame retardancy]
The manufactured 1.6 mm-thick evaluation sample was subjected to a UL (Underwriter Laboratories) 94 standard vertical combustion test, and the flame retardancy was evaluated according to the criteria shown in Table 2. When it did not correspond to the criteria shown in Table 2, it was written as NOT. By the way, if the flame retardancy is arranged in order from good to bad, V-0, V-1, V-2, and NOT are obtained. The results are shown in Table 3.

[Evaluation of bending properties]
A three-point bending property was measured in accordance with JISK 7171 using a 3.2 mm-thick evaluation sample. The measurement conditions were a bending strength (MPa), a flexural modulus (GPa), and a bending fracture strain (%) with a distance between fulcrums of 50 mm. The results are shown in Table 3.

[Examples 2 to 12, Comparative Examples 1 to 11]
Samples for evaluation were prepared in the same manner as in Example 1 except that the raw materials shown in Tables 3 to 6 were used, and flame retardancy and bending characteristics were evaluated. The results are shown in Tables 3-6.

  From the results, it can be seen that the polylactic acid composition of the present invention is superior in flame retardancy as compared with conventional polylactic acid compositions. In the example in which the phenol novolak resin (hereinafter referred to as the phenol novolak resin (E)) used as the carbonizing agent (E) was added, the toughness was improved, whereas in the comparative example in which the conventional phenol novolak resin was added, It was found that no improvement in toughness was observed.

  Moreover, even when using high molecular weight type polylactic acid or modified polylactic acid partially incorporating a cross-linked structure as polylactic acid (A), Examples 4 to 6 using phenol novolac resin (E) It turns out that the polylactic acid composition excellent in the flame retardance and toughness is obtained compared with the comparative examples 5-7 using a phenol novolak resin.

  In order to obtain the effect of improving flame retardancy and toughness by using the phenol novolak resin (E) in the polylactic acid composition from Examples 4, 7 to 9, and Comparative Examples 5 and 8 to 10, metal hydroxide It turns out that it is necessary to use a thing (B), a soft component (C), and a plasticizer (D) together. Furthermore, it was excellent in flame retardancy and toughness by using a phenol novolak resin (E) having a softening point of 110 ° C. or higher and 220 ° C. or lower from Examples 4 and 10 to 12 and Comparative Examples 5 and 11. It turns out that a polylactic acid resin composition is obtained.

  The polylactic acid composition of the present invention is biodegradable and has flame retardancy and toughness in various fields such as electrical and electronic equipment such as housings of electrical appliances, building materials, automobile parts, daily necessities, medicine, and agriculture. It can be used to produce excellent and practical molded bodies.

Claims (4)

  A flame retardant polylactic acid composition comprising polylactic acid (A), metal hydrate (B), soft component (C), plasticizer (D), and carbonizing agent (E), wherein the carbonizing agent (E ) Comprises a phenol novolac resin having a softening point of 110 ° C. or higher and 220 ° C. or lower.   The flame retardant polylactic acid composition according to claim 1, wherein the metal hydrate (B) contains aluminum hydroxide having an alkali metal content of 0.2% by mass or less.   The flame retardant polylactic acid composition according to claim 1 or 2, wherein the flexible component (C) comprises a polymer having units capable of being compatible with polylactic acid and units exhibiting flexibility.   The plasticizer (D) contains a compound that penetrates between molecules of polylactic acid (A) to weaken intermolecular force between polymers and facilitates movement of molecular chains. The flame-retardant polylactic acid composition according to any one of the above.