JP2010121131A - Natural fiber-reinforced polylactic acid resin composition and molded article using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a natural fiber-reinforced polylactic acid resin composition which has excellent property balance among hydrolysis resistance, mechanical strength, and heat resistance. <P>SOLUTION: The natural fiber-reinforced polylactic acid resin composition includes (A) 50-95 mass% of a first polylactic acid resin; and (B) 5-50 mass% of a natural fiber surface-treated with a second polylactic acid resin. The second polylactic acid resin includes a different isomer from the first polylactic acid resin. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a natural fiber reinforced polylactic acid resin composition and a molded article using the same.

  Until recently, the research direction of polymer materials has mainly been led by the development of tough special polymer materials and the safety of polymer materials.

  However, since the problem of environmental pollution due to waste polymer has emerged as a social problem all over the world, there is a need for an environmentally friendly polymer material. The environmental affinity polymer is roughly classified into a photodegradable polymer and a biodegradable polymer. A polymer material that is completely biodegradable in the environment has a main chain structure and contains functional groups that can be decomposed by microorganisms. Of these, aliphatic polyester polymers are most studied because they have excellent processability and easy adjustment of degradation characteristics. In particular, polylactic acid (PLA) is 70,000 tons worldwide. A market of scale has been formed, and its application range has been expanded to fields where general plastics such as food packaging materials and containers and electronic product cases were used. To date, the main uses of polylactic acid resins have been disposable products that utilize the biodegradable properties of polylactic acid, such as food containers, wraps, and films. Polylactic acid is currently being produced by Natureworks, USA.

  However, conventional polylactic acid resins are inferior in moldability, mechanical strength, and heat resistance, so in the case of thin film products, they are easily damaged, have low resistance to temperature, and when the external temperature rises above 60 ° C, There is a problem that deformation occurs in the form. In addition, polylactic acid has a low hydrolysis resistance, so that it does not exhibit a resistance of 48 hours or more in a high temperature and high humidity environment and is degraded.

  On the other hand, since the crystallinity is improved by melt-mixing L-polylactic acid and D-polylactic acid, the heat resistance and mechanical strength are improved as compared with the case where L-polylactic acid or D-polylactic acid is used alone. The physical properties are much improved.

  Such a mixed form of L-polylactic acid and D-polylactic acid is called a stereo complex. Improvements in physical properties using such a stereo complex are proposed in the following Non-Patent Documents 1 to 3 and Patent Documents 1 to 6 below. Among these, Patent Document 5 discloses a glass fiber reinforcement method using a stereo complex and glass fiber, and Patent Document 6 discloses a natural fiber reinforcement method using a stereo complex and natural fiber. ing.

JP 2005-187630 A JP 2003-096285 A JP 2000-0117163 A JP 2007-045915 A JP 2006-265486 A JP 2006-045428 A

Macromolecules 20,904 (1987) Macromolecules 28, 5230 (1995) Macromolecules 26, 6918 (1993)

  However, the conventionally proposed stereocomplex composition does not have sufficient performance, and the glass fiber reinforcement method presented in Patent Document 5 has an excellent effect of improving strength, but has a low biomass content. There are disadvantages.

  In addition, the natural fiber reinforcing method presented in Patent Document 6 does not exhibit satisfactory performance because the adhesive force between natural fibers and polylactic acid is not sufficient. In this method, polylactic acid and natural fiber are simply mixed and used. Therefore, considering the defect of natural fiber itself and the insufficient adhesion at the interface between natural fiber and polylactic acid resin, It is difficult to expect physical properties such as mechanical strength.

  Then, an object of this invention is to provide the natural fiber reinforced polylactic acid resin composition which has the physical property balance which was excellent in hydrolysis resistance, mechanical strength, and heat resistance.

  The present invention includes (A) 50 to 95% by mass of a first polylactic acid resin; and (B) 5 to 50% by mass of a natural fiber surface-treated with a second polylactic acid resin. A natural fiber reinforced polylactic acid resin composition comprising isomers different from the first polylactic acid resin.

  The present invention also includes (A) 50 to 95% by mass of a first polylactic acid resin; and (B) 5 to 50% by mass of a natural fiber surface-treated with a second polylactic acid resin, from 240 ° C. to a crystallization temperature. When observing under isothermal conditions after quenching, the spherulite crystals are formed on the surface of the natural fiber before the part other than the surface of the natural fiber, and the growth rate is faster, natural fiber reinforced polylactic acid A resin composition is provided.

  The crystallization temperature may be 100 to 180 ° C. The spherulite crystal is preferably a stereocomplex spherulite crystal, and the crystallization temperature is preferably 140 to 180 ° C.

  The first polylactic acid resin and the second polylactic acid resin are preferably L-polylactic acid (PLLA) resin, D-polylactic acid (PDLA) resin, L, D-polylactic acid resin, and combinations thereof, respectively. Selected from the group consisting of The L-polylactic acid (PLLA) resin preferably contains 95% by mass or more of repeating units derived from L-lactic acid. The D-polylactic acid (PDLA) resin preferably contains 95% by mass or more of repeating units derived from D-lactic acid.

  The natural fiber surface-treated with the second polylactic acid resin can be obtained, for example, by in-situ synthesis of the second polylactic acid resin on the surface of the natural fiber. Alternatively, the second polylactic acid resin and the natural fiber may be obtained by melt mixing using a batch mixer. As another method, it can be prepared by impregnating the surface of the natural fiber with the second polylactic acid resin using a continuous impregnation apparatus.

  The natural fiber surface-treated with the second polylactic acid resin is preferably such that the second polylactic acid resin and the natural fiber are in the range of 1: 0.1 to 1:10 (second polylactic acid resin: natural fiber). Having a mass ratio.

  The natural fiber is preferably a bast fiber. Moreover, preferably, 70 mass% or more of cellulose is included. Furthermore, the average length is preferably 0.01 to 100 mm, and the average diameter is preferably 0.001 to 50 μm.

  The natural fiber reinforced polylactic acid resin composition of the present invention is impact reinforced with respect to 100 parts by mass of the total amount of the (A) first polylactic acid resin and the natural fibers surface-treated with the (B) second polylactic acid resin. You may further contain 0.01-30 mass parts of agents. The impact reinforcing agent is preferably a reactive olefin copolymer in which a reactive group selected from the group consisting of maleic anhydride, glycidyl methacrylate, oxazoline, and combinations thereof is grafted to an olefin rubber; rubber A core-shell copolymer in which an unsaturated compound is grafted to a porous polymer; and a mixture thereof.

  The natural fiber reinforced polylactic acid resin composition is composed of hydrolysis resistance, flame retardant, flame retardant auxiliary, organic reinforcing agent, inorganic reinforcing agent, antibacterial agent, heat stabilizer, antioxidant, mold release agent, light stabilizer. , Compatibilizers, inorganic additives, surfactants, coupling agents, plasticizers, admixtures, stabilizers, lubricants, antistatic agents, flameproofing agents, antiseptics, colorants, UV blockers, fillers, cores One or more additives selected from the group consisting of a forming agent, an adhesive preparation, a pressure-sensitive adhesive, and a mixture thereof may be further included.

  The natural fiber reinforced polylactic acid resin composition is composed of a polycarbonate resin, a polyolefin resin, a polyester resin, a nylon resin, a rubber-modified vinyl graft copolymer resin, a polyacetal, a polymethyl methacrylate, and a combination thereof. It may further include one or more selected thermoplastic resins.

  The present invention also provides a molded article produced using the natural fiber reinforced polylactic acid resin composition.

  The natural fiber reinforced polylactic acid resin composition according to an embodiment of the present invention has a balance of physical properties excellent in hydrolysis resistance, mechanical strength, and heat resistance, so that it can be used for automobile parts, mechanical parts, electrical and electronic parts, computers, and the like. It is useful for office equipment and miscellaneous goods.

It is the schematic which shows the natural fiber reinforced polylactic acid resin composition by one Embodiment of this invention. It is the schematic which shows the natural fiber reinforced polylactic acid resin composition by one Embodiment of this invention. It is the schematic which shows the natural fiber reinforced polylactic acid resin composition by one Embodiment of this invention. It is the schematic which shows the natural fiber reinforced polylactic acid resin composition by one Embodiment of this invention. It is the schematic which shows the natural fiber reinforced polylactic acid resin composition by one Embodiment of this invention. It is the schematic which shows the natural fiber reinforced polylactic acid resin composition by one Embodiment of this invention. It is the schematic which shows the natural fiber reinforced polylactic acid resin composition by one Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, and the present invention is not limited by the following embodiments.

  Unless otherwise stated herein, “(meth) acrylate” is meant to include both “acrylate” and “methacrylate”. In addition, “(meth) acrylic acid alkyl ester” means to include both “acrylic acid alkyl ester” and “methacrylic acid alkyl ester”, and “(meth) acrylic acid ester” means “acrylic acid ester”. And “methacrylic acid ester”.

  The natural fiber reinforced polylactic acid resin composition according to one embodiment of the present invention includes (A) a first polylactic acid resin and (B) a natural fiber surface-treated with a second polylactic acid resin.

  Hereinafter, each component contained in the natural fiber reinforced polylactic acid resin composition according to an embodiment of the present invention will be specifically described.

(1) First polylactic acid resin and second polylactic acid resin Generally, a polylactic acid resin, which is a biodegradable resin, is a polyester resin produced by an ester reaction using lactic acid obtained by degrading corn starch as a monomer. Therefore, it is easy to obtain commercially.

  The first polylactic acid resin and the second polylactic acid resin are preferably L-polylactic acid (PLLA) resin, D-polylactic acid (PDLA) resin, L, D-polylactic acid resin, and combinations thereof, respectively. Selected from the group consisting of

  The L-polylactic acid (PLLA) resin includes, for example, 95% by mass or more of repeating units derived from L-lactic acid and 5% by mass or less of repeating units derived from D-lactic acid. Preferably, it contains 98 to 99.99% by mass of repeating units derived from L-lactic acid and 0.01 to 2% by mass of repeating units derived from D-lactic acid. The D-polylactic acid (PDLA) resin includes, for example, 95% by mass or more of repeating units derived from D-lactic acid and 5% by mass or less of repeating units derived from L-lactic acid. Preferably, it contains 98 to 99.99% by mass of repeating units derived from D-lactic acid and 0.01 to 2% by mass of repeating units derived from L-lactic acid. When L-polylactic acid resin and D-polylactic acid resin each contain 95% by mass or more of repeating units derived from L-lactic acid and 95% by mass or more of repeating units derived from D-lactic acid, heat resistance, molding And a physical property balance excellent in resistance to hydrolysis and hydrolysis can be obtained.

  That is, the first polylactic acid resin and the second polylactic acid resin each contain different isomers. In the present specification, “including isomers different from each other” means that one of the first polylactic acid resin and the second polylactic acid resin includes a repeating unit derived from L-lactic acid and the other is derived from D-lactic acid. Means containing repeating units. Therefore, in addition to the case where the main components of the first polylactic acid resin and the second polylactic acid resin are isomers different from each other, the components of the isomers in which the main components are the same isomer but at least one are different. Including the case of having. In this case, there are various combinations of natural fiber reinforced polylactic acid resin compositions composed of natural fibers surface-treated with the first polylactic acid resin and the second polylactic acid resin, and some examples are illustrated. 1A to G.

  1A to 1G are conceptual views showing examples of natural fiber reinforced polylactic acid resin compositions according to an embodiment of the present invention.

  In FIGS. 1A to G, the matrix corresponds to the first polylactic acid resin (1), and the line shown on a part of the surface of the natural fiber (3) represents the second polylactic acid resin (5).

  Referring to FIGS. 1A and 1B, the first polylactic acid resin (1) and the second polylactic acid resin (5) are respectively PLLA and PDLA in FIG. 1A, and PDLA and PLLA in FIG. 1B, respectively. In either case, the isomers are different from each other.

  When the second polylactic acid resin (5) has isomers different from the first polylactic acid resin (1), the first polylactic acid resin (1) and the second polylactic acid resin (5) are melt-mixed. Thus, a stereo complex can be formed. The crystallinity is improved by the formation of the stereo complex, and physical properties such as heat resistance and mechanical strength can be greatly improved as compared with the case where a general PLA resin is used alone.

  More preferably, L-polylactic acid resin is used as the first polylactic acid resin (1) as shown in FIG. 1A, and D-polylactic acid is used as the second polylactic acid resin (5) for surface treatment of natural fibers (3). Resin is used. This is because a D-polylactic acid resin film is formed on the surface of the natural fiber, so that the stereocomplex can be more efficiently induced and a greater improvement in physical properties can be obtained.

  Referring to FIG. 1C, the first polylactic acid resin (1) includes PLLA and PDLA, and the second polylactic acid resin (5) includes PLLA and PDLA. Referring to FIG. 1D, the first polylactic acid resin (1) includes PLLA and PDLA, and the second polylactic acid resin (5) includes PLLA. Referring to FIG. 1E, the first polylactic acid resin (1) includes PLLA and PDLA, and the second polylactic acid resin (5) includes PDLA.

  Even in such a case, it can be considered that the second polylactic acid resin has different isomers from the first polylactic acid resin. Therefore, the first polylactic acid resin and the second polylactic acid resin It can be melt mixed to form a stereocomplex.

  Referring to FIG. 1F and FIG. 1G, the first polylactic acid resin (1) and the second polylactic acid resin (5) are both PLLA in FIG. 1F and PDLA in FIG. Isomer.

  That is, according to one embodiment of the present invention, L-polylactic acid resin and natural fiber surface-treated with L-polylactic acid resin can be mixed and used, and D-polylactic acid resin and D-polylactic acid can be used. A natural fiber surface-treated with a resin can be mixed and used.

  Each of PLLA and PDLA preferably has 5% by mass or less of repeating units derived from D-lactic acid and 5% by mass or less of repeating units derived from L-lactic acid. In this case, a stereocomplex can also be formed when the same isomers are used, such as PLLA and PLLA, and PDLA and PDLA.

  In this way, when natural fibers are surface-treated with L-polylactic acid resin or D-polylactic acid resin and mixed, L-polylactic acid resin or D-polylactic acid resin and natural fibers are simply mixed and used. In comparison with the above, the adhesion between the natural fiber and the polylactic acid resin is improved, and further improvement in physical properties such as heat resistance and mechanical strength can be expected.

  The polylactic acid resin is not particularly limited in molecular weight or molecular weight distribution as long as it can be molded. For example, a resin having a weight average molecular weight of 50,000 g / mol or more can be used, preferably 90, The thing of 000-500,000 g / mol can be used. When the weight average molecular weight of the polylactic acid resin is within the above range, the natural fiber reinforced polylactic acid resin composition can have a physical property balance excellent in mechanical strength and heat resistance.

  1st polylactic acid resin (A) by one Embodiment of this invention is 50- with respect to the total amount of 1st polylactic acid resin (A) and the natural fiber (B) surface-treated with 2nd polylactic acid resin. Although it is contained in an amount of 95% by mass, it is preferably contained in an amount of 60 to 90% by mass. When the content of the first polylactic acid resin is within the above range, heat resistance and mechanical strength are excellent, and environmental compatibility can be expected.

(2) Natural fiber A natural fiber is contained in a polylactic acid resin as a reinforcing agent, and is produced, for example, from a wood part of a plant trunk and a flexible bast part in a bast part. Fibers can be used.

  The bast fiber is useful as a polymer composite material. Examples of the bast fiber include flax, cannabis, jute, kenaf, ramie, and curua. Etc.

  As the natural fiber, for example, cellulose containing 70% by mass or more, preferably 95% by mass or more can be used. In general, the cell membrane of fiber cells is mainly composed of cellulose, lignin, and semicellulose. However, if the lignin and semicellulose are sufficiently removed so that the cellulose is contained in an amount of 70% by mass or more, it is heat resistant. Property and mechanical strength can be improved, and in particular, the problem that the lignin is thermally decomposed during molding to discolor the product can be improved.

  The natural fiber has, for example, an average length of 0.01 to 100 mm, preferably 0.1 to 10 mm. When the average length of the natural fibers is within the above range, mechanical strength such as tensile strength, flexural strength, flexural modulus and the like is improved, and excellent workability and external characteristics can be expected.

  The natural fiber has, for example, an average diameter of 0.001 to 50 μm, preferably 0.01 to 20 μm. If the average diameter of the natural fiber is within the above range, the processability and surface gloss are excellent.

  Because natural fibers are not easy to supply at the time of resin extrusion, it is difficult to add a large amount of natural fibers. In order to overcome such problems, a natural batch is manufactured with a polymer in a batch mixer using a batch mixer, or a master batch is manufactured through compression molding. Since it has a defect due to the porosity of the fiber itself, it is difficult to greatly improve the adhesive force between the natural fiber and the resin.

  In order to overcome such a problem, for example, by treating the surface of the second polylactic acid resin with the surface of the natural fiber, the second polylactic acid resin present on the surface of the natural fiber and the second polylactic acid resin having other isomers. A stereocomplex with 1 polylactic acid resin is formed. Thereby, the strength of the surface of the natural fiber can be maximized and the defect of the natural fiber itself can be overcome.

  Such surface treatment is preferably performed by one of the following three methods.

  In the first method, as shown in the following reaction formula 1, a D, D-lactide monomer is synthesized with a second polylactic acid resin on the surface of the natural fiber using —OH group present in the natural fiber as an initiator. In this way, the wettability between the polylactic acid resin and the natural fiber is improved.

(In Reaction Formula 1, n is the degree of polymerization.)
The second method is a method of melt-mixing the second polylactic acid resin and natural fibers using a batch mixer.

  The third method is a method of sufficiently impregnating the surface of natural fibers with the second polylactic acid resin using a continuous impregnation apparatus. This is because, using the continuous impregnation apparatus, the natural fiber roving of the preheated continuous phase is passed through the melted second polylactic acid resin impregnation tank, and the second polylactic acid resin is interposed between the natural fibers inside the roving. Is first impregnated, and the natural fiber roving impregnated with the second polylactic acid resin is cooled and then second impregnated with the second polylactic acid resin.

  The first method is a method by chemical impregnation, and compared with the methods by the second and third physical impregnations, since the stereo complex is formed on the surface of the natural fiber when the stereo complex is formed, The bonding strength between the polylactic acid resin and the natural fiber is further increased, and thereby physical properties such as heat resistance, mechanical strength, and impact strength are further improved.

The second and third physical impregnation methods have the same degree of crystallinity (X _c ) and stereocomplex ratio (R _{sc / L} ) as the first method, but when mixed, natural fibers are used. Since the second polylactic acid resin is likely to be liberated and the binding force between the polylactic acid resin and the natural fiber may be relatively weak, the physical properties tend not to be improved as compared with the first method.

  In addition, since the third method, that is, impregnation in a continuous process, the dispersion of natural fibers in the resin is more efficiently performed than in the case of the second method, that is, impregnation with an arrangement type. , Better physical properties can be obtained.

  In the natural fiber (B) surface-treated with the second polylactic acid resin, the second polylactic acid resin and the natural fiber are, for example, 1: 0.1 to 1:10 (second polylactic acid resin: natural fiber). And preferably has a mass ratio of 1: 1. If the mass ratio of the second polylactic acid resin and the natural fiber is within the above range, crystallization with the first polylactic acid resin can be effectively induced and more efficiently dispersed in the first polylactic acid resin.

  The natural fiber (B) surface-treated with the second polylactic acid resin is based on the total amount of the first polylactic acid resin (A) and the natural fiber (B) surface-treated with the second polylactic acid resin. For example, it is contained in an amount of 5 to 50% by mass, preferably 10 to 40% by mass. If the content of the natural fiber surface-treated with the second polylactic acid resin is within the above range, the mechanical strength and processability can be improved.

(3) Impact Reinforcing Agent The natural fiber reinforced polylactic acid resin composition according to an embodiment of the present invention may further include an impact reinforcing agent in order to further reinforce the increase in viscosity with impact strength.

  As the impact reinforcing agent, those having excellent affinity with polylactic acid resin are preferable. For example, one or more selected from the group consisting of reactive olefin copolymers, core shell copolymers, and mixtures thereof are used. Can do.

  Examples of the reactive olefin copolymer include olefin rubber such as ethylene / propylene rubber, isoprene rubber, ethylene / octene rubber, ethylene-propylene-diene terpolymer (EDPM), and maleic anhydride. , Glycidyl methacrylate, oxazoline, and a copolymer selected from the group consisting of a combination thereof may be 0.1 to 5% by mass grafted.

  As a method of grafting a reactive group onto the olefin copolymer, a known method can be appropriately used.

  Examples of the core-shell copolymer include a rubber polymer obtained by polymerizing a monomer selected from the group consisting of a diene monomer, an acrylic monomer, a silicone monomer, and a combination thereof. , An acrylic monomer, an aromatic vinyl monomer, an unsaturated nitrile monomer, a polymer formed from one or more of these monomers, and an unsaturated compound selected from the group consisting of combinations thereof Can be a core-shell copolymer formed by grafting.

  Examples of the diene monomer include C4 to C6 diene monomers such as butadiene and isoprene. Of these, butadiene is preferably used. Specific examples of the rubbery polymer obtained by polymerizing the diene monomer include butadiene rubber, acrylic rubber, styrene / butadiene rubber, acrylonitrile / butadiene rubber, isoprene rubber, ethylene-propylene-diene terpolymer. (EPDM).

  Examples of the acrylic monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, hexyl (meth) ) Acrylate and the like. In this case, for example, ethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, 1,3-butylene glycol di (meth) acrylate, 1,4-butylene glycol di (meth) acrylate, allyl (meth) acrylate A curing agent such as triallyl cyanurate can be used.

  Examples of the silicone monomer include hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, trimethyltriphenylcyclotrisiloxane, tetramethyltetraphenylcyclotetrasiloxane, One or more cyclosiloxane compounds selected from the group consisting of octaphenylcyclotetrasiloxane and combinations thereof can be used. At this time, for example, a curing agent such as trimethoxymethylsilane, triethoxyphenylsilane, tetramethoxysilane, tetraethoxysilane, or the like can be used.

  The rubber average particle size of the rubbery polymer is preferably 0.4 to 1 μm from the viewpoint of maintaining impact resistance and colorability balance.

  The rubbery polymer is included in an amount of, for example, 30 to 90% by mass with respect to the total amount of the impact reinforcing agent. If it is in the said range, it is excellent in compatibility with a polylactic acid resin, As a result, the outstanding impact reinforcement effect is shown.

  Among the unsaturated compounds, examples of the acrylic monomer include (meth) acrylic acid alkyl esters, (meth) acrylic acid esters, anhydrides, alkyl or phenyl N-substituted maleimides, and combinations thereof. One or more selected can be used. Here, the alkyl means C1-C10 alkyl, and specific examples of the (meth) acrylic acid alkyl ester include methyl (meth) acrylate, ethyl (meth) acrylate, propyl ( Examples thereof include meth) acrylate and butyl (meth) acrylate, and preferably methyl (meth) acrylate can be used. Moreover, as said anhydride, an acid anhydride can be used, for example, Preferably, carboxylic acid anhydrides, such as maleic anhydride and itaconic anhydride, can be used.

  Among the unsaturated compounds, as the aromatic vinyl monomer, for example, one or more selected from the group consisting of styrene, C1-C10 alkyl-substituted styrene, halogen-substituted styrene, and combinations thereof can be used. . Specific examples of the alkyl-substituted styrene include o-ethyl styrene, m-ethyl styrene, p-ethyl styrene, α-methyl styrene and the like.

  Among the unsaturated compounds, as the unsaturated nitrile monomer, for example, one or more selected from the group consisting of acrylonitrile, methacrylonitrile, ethacrylonitrile, and combinations thereof can be used.

  The core-shell copolymer can be easily prepared by a person having ordinary knowledge in the technical field to which the present invention belongs.

  The impact reinforcing agent is, for example, 0.01 to 30 parts by mass with respect to 100 parts by mass of the total amount of (A) the first polylactic acid resin and (B) the natural fibers surface-treated with the second polylactic acid resin. Preferably, it is contained in a content of 1 to 10 parts by mass. When the content of the impact reinforcing agent is within the above range, a high impact reinforcing effect can be obtained, and mechanical strength such as tensile strength, flexural strength, flexural modulus can be improved.

(4) Other additives The natural fiber reinforced polylactic acid resin composition according to an embodiment of the present invention may further include other additives.

  Examples of the additive include hydrolysis resistance, flame retardant, flame retardant auxiliary, organic reinforcing agent, inorganic reinforcing agent, antibacterial agent, heat stabilizer, antioxidant, release agent, light stabilizer, and compatibilization. Agents, inorganic additives, surfactants, coupling agents, plasticizers, admixtures, stabilizers, lubricants, antistatic agents, flame retardants, antiseptics, colorants, UV blockers, fillers, nucleating agents, One or more selected from the group consisting of an adhesive preparation, a pressure-sensitive adhesive, and a mixture thereof can be used.

As the antioxidant, for example, a phenol type, a phosphate type, a thioether type or an amine type antioxidant can be used. As the mold release agent, for example, fluorine-containing polymer, silicone oil, metal salt of stearic acid, metal salt of montanic acid, montanic acid ester wax or polyethylene wax can be used. Moreover, as said antiseptic, a benzophenone type or an amine type antiseptic can be used, for example. As the colorant, for example, a dye or a pigment can be used. As the ultraviolet blocking agent, for example, titanium oxide (TiO ₂ ) or carbon black can be used. As the filler, for example, glass fiber, carbon fiber, silica, mica, alumina, clay, calcium carbonate, calcium sulfate, or glass beads can be used. If such filler is added, mechanical strength and Physical properties such as heat resistance can be improved. Further, as the nucleating agent, for example, talc or clay can be used. Hydrolysis-resistant agent, flame retardant, flame retardant auxiliary, organic reinforcing agent, inorganic reinforcing agent, antibacterial agent, heat stabilizer, light stabilizer, compatibilizer, inorganic additive, surfactant, coupling agent, plasticizer As the admixture, stabilizer, lubricant, antistatic agent, flameproofing agent, adhesive preparation, and pressure-sensitive adhesive, known materials can be appropriately used.

  The additive may be included in an appropriate content within a range that does not inhibit the physical properties of the natural fiber reinforced polylactic acid resin composition, but preferably 40 parts by mass with respect to 100 parts by mass of the natural fiber reinforced polylactic acid resin composition. Hereinafter, it may be contained in a content of preferably 0.1 to 20 parts by mass.

  The natural fiber reinforced polylactic acid resin composition of the present invention can be used by further mixing a thermoplastic resin.

  The thermoplastic resin is not particularly limited, but a group consisting of polycarbonate resin, polyolefin resin, polyester resin, nylon resin, rubber-modified vinyl graft copolymer resin, polyacetal, polymethyl methacrylate, and combinations thereof. One or more selected more can be used.

  The polycarbonate resin can be prepared, for example, by a reaction between a dihydric phenol and phosgene in the presence of a molecular weight regulator and a catalyst. Or what was prepared by ester interchange reaction of a dihydric phenol and a carbonate precursor can be used. Moreover, when preparing the said polycarbonate resin, you may further use a polyfunctional aromatic compound or a bifunctional carboxylic acid. Specific examples of the dihydric phenol include 2,2-bis (4-hydroxyphenyl) propane (bisphenol A).

  Examples of the rubber-modified vinyl-based graft copolymer resin include a butadiene rubber, an acrylic rubber, or a styrene / butadiene rubber, and a mixture of styrene, acrylonitrile, and optionally a (meth) acrylic acid alkyl ester monomer. Examples include those obtained by graft copolymerization, or those obtained by graft copolymerization of a monomer of (meth) acrylic acid alkyl ester with butadiene rubber, acrylic rubber, or styrene / butadiene rubber. Preferably, an ABS (acrylonitrile-butadiene-styrene) graft copolymer is used.

  The natural fiber reinforced polylactic acid resin composition may be included in an amount of, for example, 10 to 90% by mass with respect to the total amount of the mixture of the natural fiber reinforced polylactic acid resin composition and the thermoplastic resin. Is contained in a content of 30 to 70% by mass. When the content of the natural fiber reinforced polylactic acid resin composition is within the above range, high environmental compatibility can be obtained and the advantages of the thermoplastic resin can be expressed.

In the natural fiber reinforced polylactic acid resin composition as described above, when a stereocomplex is formed by the first polylactic acid resin and the second polylactic acid resin being different isomers, the natural fiber reinforced polylactic acid resin The crystallinity (X _c ) of the composition can be in the range of 30 J / g or more. The crystallinity is ΔH _L (L-polylactic acid resin) which is a calorific value generated at a melting point of 140 to 170 ° C. while raising the temperature to 250 ° C. at 10 ° C./min using a differential scanning calorimeter (DSC). And the total amount of ΔH _sc (stereocomplex crystal peak), which is the amount of heat generated at a melting point of 195 to 250 ° C.

Moreover, the ratio (R _{sc / L} ) of the stereocomplex of the natural fiber reinforced polylactic acid resin composition can exceed 0, and preferably has a range of 30% or more. If the stereo complex ratio (R _{sc / L} ) exceeds 0, it means that a stereo complex is formed. The ratio of the stereocomplex means the ratio occupied by the stereocomplex crystal in the crystal, and is a value calculated by the equation: ΔH _sc / (ΔH _sc + ΔH _L ) × 100.

  When the natural fiber reinforced polylactic acid resin composition according to the present invention is rapidly cooled from 240 ° C. to the crystallization temperature using liquid nitrogen and then observed under isothermal conditions, the spherulite crystals are preferably the surface of the natural fiber. It is formed earlier on the surface of the natural fiber and has a higher growth rate than other portions, specifically, the matrix portion. Here, the spherulite crystal means a spherical polycrystal in which several crystals are arranged radially at one point.

  Although the said crystallization temperature can be calculated | required previously by a differential scanning calorimeter, it is preferable that it is 100-180 degreeC. More preferably, when the second polylactic acid resin includes a different isomer from the first polylactic acid resin to form a stereo complex, the crystallization temperature is 140 to 180 ° C. The spherulite crystal observed at this time is called a stereocomplex spherulite crystal. In addition, when the first polylactic acid resin and the second polylactic acid resin contain the same isomer, the crystallization temperature may be 100 to 110 ° C.

  The growth rate of the spherulite crystal takes, for example, about 9 seconds for the surface of natural fibers and about 1 minute and 12 seconds for the matrix if the time required for the spherulite crystal particles to grow to 5 μm is measured. .

  As described above, whether or not the surface treatment of the natural fiber has been performed can be confirmed by whether or not spherulite crystals are present on the surface of the natural fiber.

  The natural fiber reinforced polylactic acid resin composition of the present invention can be produced by a known method for producing a resin composition. For example, the components and other additives can be mixed at the same time and then melt-extruded in an extruder to produce pellets.

  The present invention also provides a molded article produced by molding the natural fiber reinforced polylactic acid resin composition.

  The natural fiber reinforced polylactic acid resin composition is used for molded products in fields where mechanical strength and heat resistance are important, for example, automotive parts, mechanical parts, electrical and electronic parts, computers and other office equipment, and miscellaneous goods. In particular, it can be usefully applied to housings of electrical and electronic products such as televisions, computers, printers, washing machines, cassette players, audio, mobile phones and the like.

  Hereinafter, preferred embodiments of the present invention will be described. However, the present invention is not limited to the following examples.

  Each component used for manufacture of a natural fiber reinforced polylactic acid resin composition is as follows.

(1) Polylactic acid resin As L-polylactic acid resin, 4032D (containing D-isomer 1.2 to 1.6% by mass) manufactured by Natureworks, USA, and as D-polylactic acid resin, manufactured by Purac Of D, D-lactide (containing 99% by mass or more of D, D-lactide) was polymerized to have a weight average molecular weight of 50,000 g / mol.

(2) Natural Fiber A natural fiber produced from cannabis and having a cellulose component of 98% by mass, an average length of 5 mm, and an average diameter of 10 μm was used.

  The natural fiber was used after being surface-treated according to the following Production Examples 1 to 5.

Production Example 1
D-polylactic acid resin / cannabis masterbatch was prepared by placing dried cannabis into a reactor and ring-opening polymerization of D, D-lactide monomer.

  Specifically, in the ring-opening polymerization, first, cannabis and D, D-lactide monomer are introduced into a batch type mixer, mixed at 180 ° C. for about 5 minutes, and then twin screw extrusion connected to the mixer. Immediately fed to the machine, the reaction extrudate was produced in the form of pellets. Here, the input ratio of D, D-lactide monomer and cannabis was adjusted to have a mass ratio of 1: 1 in the final impregnated product.

At this time, tin octylate (Sn (Ot) ₂ ) and triphenylphosphine were mixed in an equimolar ratio as the polymerization catalyst. 500 moles of D, D-lactide monomer was added per mole of the polymerization catalyst. The obtained D-polylactic acid resin and natural fiber had a mass ratio of 1: 1 (D-polylactic acid resin: natural fiber).

  In order to remove the unreacted monomer from the mixture of the D-polylactic acid resin, the monomer, and the natural fiber thus produced, it was vacuum dried at 100 ° C.

Production Example 2
Each of the D-polylactic acid resin and the natural fiber is put into a batch mixer so that the mass ratio of 1: 1 (D-polylactic acid resin: natural fiber) is obtained. Manufactured.

Production Example 3
Each of the D-polylactic acid resin and the natural fiber was put into a continuous fiber impregnation apparatus so that the mass ratio of 1: 1 (D-polylactic acid resin: natural fiber) was reached. The lactic acid resin was sufficiently impregnated.

  After impregnating the long fiber type natural fiber roving into the D-polylactic acid molten resin, the fiber was passed in a straight line to obtain natural fibers surface-treated with the D-polylactic acid resin. The natural fibers were in the form of 3-50 mm pellets.

(3) Impact Reinforcing Agent 223-A (methyl methacrylate-butadiene ethyl acrylate copolymer) manufactured by Mitsubishi Rayon Co., Ltd. was used as an impact reinforcing agent.

Example 1
60% by mass of the first polylactic acid resin (L-polylactic acid resin) and 40% by mass of natural fibers surface-treated with the second polylactic acid resin (D-polylactic acid resin) produced in Production Example 1 After being dried for 4 hours under a vacuum, the mixture was extruded in a temperature range of 180 ° C. with an ordinary twin-screw extruder to produce an extrudate in the form of pellets.

Example 2
80% by mass of the first polylactic acid resin (L-polylactic acid resin) and 20% by mass of natural fibers surface-treated with the second polylactic acid resin (D-polylactic acid resin) produced in Production Example 1 were used. Except for, the same method as in Example 1 was used.

Example 3
The same procedure as in Example 1 was performed except that natural fibers surface-treated with the second polylactic acid resin (D-polylactic acid resin) in Production Example 2 were used.

Example 4
The same procedure as in Example 1 was performed except that natural fibers surface-treated with the second polylactic acid resin (D-polylactic acid resin) in Production Example 3 were used.

Example 5
The same procedure as in Example 1 was performed except that an impact reinforcing agent was further used in Example 1. The impact reinforcing agent was used in an amount of 5 parts by mass with respect to 100 parts by mass of the total amount of natural fibers surface-treated with the first polylactic acid resin and the second polylactic acid resin.

Comparative Example 1
Without any surface treatment on natural fibers, 60% by mass of first polylactic acid resin (L-polylactic acid resin), 20% by mass of second polylactic acid resin (D-polylactic acid resin), and 20% by mass of natural fibers are individually provided. The same method as in Example 1 was carried out except that it was added.

Comparative Example 2
No surface treatment was performed on the natural fiber, and the same as in Example 1 except that 80% by mass of the first polylactic acid resin (L-polylactic acid resin) and 20% by mass of the natural fiber were individually added. Went in the way.

[Test example]
The pellets produced in Examples 1 to 5 and Comparative Examples 1 and 2 were dried at 80 ° C. for 4 hours or more, and then a cylinder temperature of 230 ° C., a mold temperature of 80 ° C., and molding using a 6 oz injection molding machine. Specimens were prepared by setting the cycle to 60 seconds and injection molding into ASTM dumbbell specimens. The prepared specimens were measured for physical properties by the following method, and the results are shown in Table 1 below.
1) Heat distortion temperature (HDT): Measured according to ASTM D648.
2) Tensile strength: measured in accordance with ASTM D638.
3) Flexural strength: Measured according to ASTM D790.
4) Flexural modulus: measured in accordance with ASTM D790.
5) IZOD impact strength: Measured according to ASTM D256 (thickness of specimen ¼ ″).
6) ΔH _L : The amount of heat corresponding to the melting point peak of L-polylactic acid crystals found at 140 to 170 ° C. was measured.
7) The temperature at which T _L : ΔH _L peak appears was measured.
8) ΔH _sc : The amount of heat corresponding to the melting point peak of the stereocomplex crystal found at 195 to 250 ° C. was measured.
9) The temperature at which T _sc : ΔH _sc peak appears was measured.
10) Crystallinity (X _c ): Using a differential scanning calorimeter (DSC) manufactured by TA instruments, taking a minimum of about 5 mg of the central portion from each specimen, avoiding the surface, up to 250 ° C. While increasing the temperature at 10 ° C./min, ΔH _L (crystal peak of L-polylactic acid) that is a heat amount generated at a melting point of 140 to 170 ° C. and ΔH _sc (a heat amount generated at a melting point of 195 to 250 ° C.). The total amount of the stereocomplex crystal peak) was calculated and shown.
11) Ratio of stereocomplex (R _{sc / L} ): Indicates the ratio occupied by the stereocomplex crystal in the crystal, and is a value calculated by the formula ΔH _sc / (ΔH _sc + ΔH _L ) × 100.
12) Confirmation of presence of spherulite crystals on the surface of natural fibers: In Examples 1 to 5 and Comparative Examples 1 and 2, whether or not the natural fibers were surface-treated depends on whether the surface of the natural fibers is spherulite crystals. Can be confirmed by whether or not there exists. Specifically, each sample was rapidly cooled with liquid nitrogen from 240 ° C. to the crystallization temperature (observed in the vicinity of 150 ° C., which can be measured in advance with a differential scanning calorimeter), and then in an isothermal state. If a shape in which spherulite crystals grow rapidly on the surface of the natural fiber is observed with an optical polarization microscope, it can be considered that the natural fiber is impregnated with a polylactic acid resin.
Growth of stereocomplex spherulite crystals is observed on the surface of natural fibers: ○
The growth of stereocomplex spherulite crystals cannot be observed on the surface of natural fibers: ×
The presence or absence of the growth was observed with an optical polarization microscope.

  In addition, after the specimen manufactured in Example 2 was rapidly cooled from 240 ° C. to 140 ° C. using liquid nitrogen, the spherulite crystal was observed, and as a result, the spherulite crystal particles grew to 5 μm. The natural fiber surface took about 9 seconds and the matrix took about 1 minute 12 seconds.

  As shown in Table 1, Examples 1 to 5 in which natural fibers were surface-treated with a polylactic acid resin were used in Comparative Examples 1 and 5 in which a polylactic acid resin and natural fibers were added separately without surface treatment of natural fibers. Compared with 2, it can be confirmed that the heat resistance, impact strength, and mechanical properties of tensile strength, flexural strength, and flexural modulus are all excellent.

  In particular, the excellent physical properties of Examples 1 to 5 using L-polylactic acid resin as the first polylactic acid resin and D-polylactic acid resin as the second polylactic acid resin are the basic resin L present in the matrix. -This is because the polylactic acid resin and the D-polylactic acid resin present in the natural fiber form a stereocomplex and the crystallization at this site is promoted.

  On the other hand, Comparative Example 1 using L-polylactic acid resin as the first polylactic acid resin and D-polylactic acid resin as the second polylactic acid resin and mixing natural fibers without any surface treatment is as follows. It can be confirmed that the heat resistance, impact strength, and mechanical strength all decrease and the crystallinity decreases. In addition, Comparative Example 2 using a mixture of L-polylactic acid resin and natural fibers not subjected to surface treatment also confirms that heat resistance, impact strength, and mechanical strength are all reduced. Can do.

  On the other hand, Examples 1 and 2 in which D-polylactic acid resin was formed on the surface of natural fiber according to Production Example 1 were obtained in Example 3 and Production Example 3 which were melt-mixed using Production Batch 2 using a batch mixer. Compared with Example 4 impregnated using a continuous impregnation apparatus, it can be confirmed that the heat resistance, impact strength, and mechanical properties are further excellent.

  In addition, Example 4 shows more excellent physical properties than Example 3. This is because when impregnated using a continuous impregnation apparatus, the natural fiber in the resin is more melt-mixed using a batch mixer. This is probably because the dispersion is more efficient.

  In addition, all of Examples 1 to 4 including natural fibers surface-treated by the methods of Production Examples 1 to 3 are almost equivalent in crystallinity and stereocomplex ratio, but use chemical impregnation through polymerization. It can be confirmed that Examples 1 and 2 were further superior in heat resistance, impact strength, and mechanical properties as compared with Examples 3 and 4 using simple physical impregnation. In the case of physical impregnation, D-polylactic acid can be easily liberated from natural fibers at the time of compounding, but in the case of chemical impregnation, a stereocomplex is formed on the surface of natural fibers, so that resin and natural fibers This is thought to be due to a further increase in the binding force between the two.

  Normally, the polylactic acid resin composition containing natural fibers has a lower impact strength as more natural fibers are added. According to this example, Example 1 containing more natural fibers is more in comparison with Example 2. It can be confirmed that the impact strength is high. This is considered to be because the impact strength is improved by the crystal structure around the natural fiber supporting the natural fiber.

1 first polylactic acid resin,
3 Natural fiber,
5 Second polylactic acid resin.

Claims (17)

(A) 50 to 95% by mass of the first polylactic acid resin; and (B) 5 to 50% by mass of natural fibers surface-treated with the second polylactic acid resin.
The natural fiber reinforced polylactic acid resin composition, wherein the second polylactic acid resin contains isomers different from the first polylactic acid resin. (A) 50 to 95% by mass of the first polylactic acid resin; and (B) 5 to 50% by mass of natural fibers surface-treated with the second polylactic acid resin.
After rapid cooling from 240 ° C. to the crystallization temperature, when observed under isothermal conditions, spherulite crystals are formed on the surface of the natural fiber before the portion other than the surface of the natural fiber, and the growth rate is faster. Natural fiber reinforced polylactic acid resin composition.   The natural fiber reinforced polylactic acid resin composition according to claim 2, wherein the crystallization temperature is 100 to 180 ° C.   The natural fiber reinforced polylactic acid resin composition according to claim 2 or 3, wherein the spherulite crystal is a stereocomplex spherulite crystal, and the crystallization temperature is 140 to 180 ° C.   The first polylactic acid resin and the second polylactic acid resin are each composed of L-polylactic acid (PLLA) resin, D-polylactic acid (PDLA) resin, L, D-polylactic acid resin, and combinations thereof. The natural fiber reinforced polylactic acid resin composition according to any one of claims 1 to 4, which is further selected.   The L-polylactic acid (PLLA) resin contains 95 mass% or more of repeating units derived from L-lactic acid, and the D-polylactic acid (PDLA) resin contains 95 mass of repeating units derived from D-lactic acid. The natural fiber reinforced polylactic acid resin composition according to claim 5, comprising at least%.   The natural fiber surface-treated with the second polylactic acid resin is synthesized in-situ with the second polylactic acid resin on the surface of the natural fiber, and the second polylactic acid resin and the natural fiber are synthesized. It melt-mixes using a batch type mixer, or is obtained by making the surface of the said natural fiber impregnate the said 2nd polylactic acid resin using a continuous impregnation apparatus, The any one of Claims 1-6 obtained. Natural fiber reinforced polylactic acid resin composition.   The natural fiber surface-treated with the second polylactic acid resin has a mass ratio of the second polylactic acid resin and the natural fiber of 1: 0.1 to 1:10 (polylactic acid resin: natural fiber). The natural fiber reinforced polylactic acid resin composition according to any one of claims 1 to 7.   The natural fiber-reinforced polylactic acid resin composition according to claim 1, wherein the natural fiber is a bast fiber.   The natural fiber-reinforced polylactic acid resin composition according to any one of claims 1 to 9, wherein the natural fiber contains 70% by mass or more of cellulose.   The natural fiber reinforced polylactic acid resin composition according to any one of claims 1 to 10, wherein the natural fiber has an average length of 0.01 to 100 mm.   The natural fiber reinforced polylactic acid resin composition according to any one of claims 1 to 11, wherein the natural fiber has an average diameter of 0.001 to 50 µm.   It further comprises 0.01-30 parts by mass of impact reinforcement with respect to 100 parts by mass of the total amount of the (A) first polylactic acid resin and the natural fibers surface-treated with the (B) second polylactic acid resin. Item 15. The natural fiber-reinforced polylactic acid resin composition according to any one of Items 1 to 12.   The impact reinforcing agent is a reactive olefin copolymer in which a reactive group selected from the group consisting of maleic anhydride, glycidyl methacrylate, oxazoline, and combinations thereof is grafted to an olefin rubber; The natural fiber reinforced polylactic acid resin composition according to claim 13, selected from the group consisting of a core-shell copolymer grafted with an unsaturated compound in the coalescence; and a mixture thereof.   Hydrolysis-resistant agent, flame retardant, flame retardant auxiliary, organic reinforcing agent, inorganic reinforcing agent, antibacterial agent, heat stabilizer, antioxidant, mold release agent, light stabilizer, compatibilizer, inorganic additive, surface activity Agents, coupling agents, plasticizers, admixtures, stabilizers, lubricants, antistatic agents, flameproofing agents, antiseptics, colorants, UV blockers, fillers, nucleating agents, adhesive preparations, adhesives, and the like The natural fiber reinforced polylactic acid resin composition according to any one of claims 1 to 14, further comprising one or more additives selected from the group consisting of:   One or more thermoplastic resins selected from the group consisting of polycarbonate resins, polyolefin resins, polyester resins, nylon resins, rubber-modified vinyl graft copolymer resins, polyacetals, polymethyl methacrylates, and combinations thereof; The natural fiber reinforced polylactic acid resin composition according to any one of claims 1 to 15.   The molded article manufactured using the natural fiber reinforced polylactic acid resin composition of any one of Claims 1-16.

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