JP2007009008A - Heat-resistant polylactic acid-based resin composition, and its molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid-based resin composition having excellent moldability and heat resistance, and to provide a molded article comprising the composition. <P>SOLUTION: This polylactic acid-based resin composition comprising 1 to 99 pts.wt. of a polyolefin and 10 to 99 pts.wt. (the total amount of both the components is 100 pts.wt.) of a polylactic acid-based resin, is characterized in that the ratio of poly L-lactic acid having L-lactic acid units to poly D-lactic acid having D-lactic acid units in the polylactic acid-based resin is 99/1 to 50/50. The polylactic acid-based resin composition is molded. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a polylactic acid-based resin composition comprising a polylactic acid-based resin and a polyolefin using poly-L-lactic acid having an L-lactic acid unit and poly-D-lactic acid having a D-lactic acid unit as the polylactic acid-based resin. The present invention relates to a resin composition and a molded article having excellent heat resistance obtained therefrom.

  In recent years, depletion of fossil raw materials represented by crude oil has been regarded as a problem. Therefore, plants have attracted attention as a raw material for plastics that can replace fossil raw materials. Polylactic acid is particularly attracting attention because it uses lactic acid obtained by fermentation from corn and other cereal resources as a raw material and is excellent in moldability and rigidity. However, since polylactic acid has low heat resistance, its application development has been limited. Polylactic acid has a glass transition point (Tg) of about 60 ° C., and its heat resistance in an amorphous state is 60 ° C. or less. Therefore, it has been pointed out that it tends to cause whitening, deformation, etc. under daily use environment. ing. In addition, polylactic acid has crystallinity, and heat resistance is greatly improved by crystallization exceeding 60 ° C. However, since the crystallization rate is slow, a post-crystallization step is required, and the like, However, it has been pointed out that a different molding method is required and the cost becomes high.

  Various improvements in polylactic acid crystallization speed and, in turn, heat resistance have been made. In particular, improvement of the crystallization rate using a racemic crystal of polylactic acid is well known. Since lactic acid constituting polylactic acid has an asymmetric carbon, D-lactic acid and L-lactic acid which are optical isomers exist. A strong interaction acts between poly-D-lactic acid containing only D-lactic acid as a constituent and poly-L-lactic acid containing only L-lactic acid as a constituent. Racemic crystals with a high conversion rate are formed. Patent Document 1 discloses a polylactic acid resin composition having a good moldability by promoting the formation of racemic crystals by melt-mixing poly L-lactic acid and poly D-lactic acid having a specific molecular weight. However, even with such a method, the formation rate of racemic crystals is not sufficiently satisfactory, and a polylactic acid resin composition having excellent heat resistance cannot be obtained.

Patent Document 2 discloses a resin composition containing a polylactic acid resin and a polyacetal resin and having excellent crystallization characteristics and heat resistance. However, polyacetals are weak against acids and have the disadvantage that they decompose and emit odor when blended with polylactic acid.
JP 2003-096285 A JP 2003-253106 A

  An object of the present invention is to provide a polylactic acid resin composition having improved heat resistance and excellent moldability, and a molded product thereof.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have determined that poly L-lactic acid and D-lactic acid unit comprising a polyolefin and a polylactic acid-based resin and having an L-lactic acid unit in the polylactic acid-based resin. It has been found that a polylactic acid-based resin composition having improved heat resistance and excellent moldability can be obtained by including the poly-D-lactic acid having the present invention.

  That is, the present invention is a polylactic acid comprising 1 to 90 parts by weight of a polyolefin (A) and 10 to 99 parts by weight of a polylactic acid resin (B) (provided that the total of (A) and (B) is 100 parts by weight). The ratio of poly L-lactic acid (B-1) having an L-lactic acid unit and poly D-lactic acid (B-2) having a D-lactic acid unit in the polylactic acid resin (B) A polylactic acid resin composition having a ratio of 99/1 to 50/50 is provided.

In the present invention, the polylactic acid resin composition preferably has the following characteristics.
1. The polyolefin (A) is a propylene-based polyolefin (A1).
2. The cooling crystallization temperature of the polyolefin (A) is 100 ° C. or higher and 140 ° C. or lower.
3. The L-polylactic acid (B-1) having a polylactic acid-based resin (B) having an L-lactic acid unit and the poly-D-lactic acid (B-2) having a D-lactic acid unit are in a block form via a covalent bond and / or A polylactic acid copolymer (B-3) having a structure bonded in a graft form and / or a random form is included.
4). The ratio of the molecular weight of the poly L-lactic acid (B-1) having an L-lactic acid unit and the poly D-lactic acid (B-2) having a D-lactic acid unit in the polylactic acid resin (B) is 0.1 to 0.1. 1.4.

  The resin composition comprising the polyolefin and the polylactic acid resin according to the present invention provides a polylactic acid resin composition having excellent heat resistance. Molded articles formed from the resin composition can be applied to fields where conventional polylactic acid has insufficient heat resistance. In addition, the polylactic acid-based resin composition is excellent in moldability as compared with conventional polylactic acid.

  The term “polylactic acid resin (B)” used in the present invention means a polymer containing at least 50 mol% of L-lactic acid units and / or D-lactic acid units and a polymer containing the same as a main component. It is synthesized by polycondensation of lactic acid or ring-opening polymerization of lactide, which is a cyclic dimer of lactic acid. Copolymerized with other monomers copolymerizable with lactic acid.

  The terms “poly-L-lactic acid (B-1) having an L-lactic acid unit” or “poly-D-lactic acid (B-2) having a D-lactic acid unit” used in the present invention are L-lactic acid units or D- means a polymer containing 80 mol% or more, preferably 90 mol% or more, and more preferably 95 mol% or more of D-lactic acid units, and is a polycondensation of lactic acid or a cyclic dimer of lactic acid. It is synthesized by ring-opening polymerization of lactide. Copolymerized with other monomers copolymerizable with lactic acid.

  The polylactic acid-based resin (B) is composed of a poly-L-lactic acid (B-1) having an L-lactic acid unit and a poly-D-lactic acid (B-2) having a D-lactic acid unit, which are block-like, graft-like, The polylactic acid copolymer (B-3) connected at random may be included. The poly L-lactic acid (B-1) having an L-lactic acid unit and the poly D-lactic acid (B-2) having a D-lactic acid unit each preferably have a molecular weight of 10,000 to 500,000, and more preferably a molecular weight of 15,000. 1,000 to 300,000.

  The term “polyolefin (A)” used in the present invention means a polymer composed of a repeating unit derived from an olefin having 2 to 20 carbon atoms, specifically having 2 to 2 carbon atoms. An olefin homopolymer or copolymer selected from 20 olefins. When this polyolefin segment has stereoregularity, it may be either isotactic polyolefin or syndiotactic polyolefin.

  Examples of the olefin having 2 to 20 carbon atoms include linear or branched α-olefins, cyclic olefins, aromatic vinyl compounds, conjugated dienes, and nonconjugated dienes. Specific examples of the linear or branched α-olefin include ethylene, propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3 -Methyl-1-pentene, 3-ethyl-1-pentene, 4,4-dimethyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4-ethyl-1-hexene , 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene, etc., 2 to 20, preferably 2 to 10 carbon atoms Can be mentioned.

  Examples of the cyclic olefin include those having 3 to 20 carbon atoms, preferably 5 to 15 such as cyclopentene, cycloheptene, norbornene, 5-methyl-2-norbornene, tetracyclododecene, and vinylcyclohexane. Examples of the aromatic vinyl compound include styrene, α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, o, p-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, p- Mono or polyalkyl styrenes such as ethyl styrene are mentioned.

  Examples of the conjugated diene include 1,3-butadiene, isoprene, chloroprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 4-methyl-1,3-pentadiene, 1,3-pentadiene, and 1,3-hexadiene. , 1,3-octadiene and the like having 4 to 20, preferably 4 to 10 carbon atoms. Non-conjugated dienes include, for example, 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 1,4-octadiene, 1,5-octadiene, 1,6-octadiene, 1,7-octadiene, 2 -Methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, 7-methyl-1,6-octadiene, 4-ethylidene-8-methyl-1,7-nonadiene, 4,8-dimethyl-1 , 4,8-decatriene (DMDT), dicyclopentadiene, cyclohexadiene, dicyclooctadiene, methylene norbornene, 5-vinyl norbornene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 5-isopropylidene -2-norbornene, 6-chloromethyl-5-isopropylene-2-norbornene, 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2 -5 carbon atoms such as norbornadiene 0, preferably include the 5 to 10.

  The term “propylene-based polyolefin (A1)” used in the present invention means a polyolefin containing at least 50 mol% of propylene units as a polymer constituent unit. As the number of propylene units increases, the crystallinity of the propylene-based polyolefin (A1) improves, and the heat resistance of the polylactic acid-based resin composition improves. A preferable range of the propylene unit is 60 mol% or more and 100 mol% or less, and more preferably 70 mol% or more and 100 mol% or less.

  The polylactic acid resin composition according to the present invention comprises 1 to 90 parts by weight of polyolefin (A) and 10 to 99 parts by weight of polylactic acid resin (B) (however, the total of (A) and (B) is 100 parts by weight) The ratio of poly-L-lactic acid (B-1) having an L-lactic acid unit and poly-D-lactic acid (B-2) having a D-lactic acid unit in the polylactic acid resin (B) is It is a resin composition which is 99 / 1-50 / 50. The ratio of poly L-lactic acid (B-1) to poly D-lactic acid (B-2) is preferably 98/2 to 40/60, more preferably 97/3 to 30/70.

  In addition to polyolefin and polylactic acid resins, this resin composition includes a crosslinking agent, a crosslinking accelerator, a crosslinking aid, a softener, a tackifier, an anti-aging agent, a foaming agent, a processing aid, an adhesion promoter, An additive such as an inorganic filler, an organic filler, a crystal nucleating agent, a heat stabilizer, a weather stabilizer, an antistatic agent, a colorant, a lubricant, a flame retardant, and an antiblooming agent may be contained. Further, secondary modification such as crosslinking and foaming may be performed.

  Moreover, in addition to polyolefin and a polylactic acid-type resin, the compatibilizer which improves compatibility of both may be added. By containing the compatibilizing agent, the compatibility between the polyolefin resin and the polylactic acid resin is improved, and a resin composition in which both are well dispersed is obtained. The improvement in compatibility and dispersibility can be confirmed, for example, by observing the cross section of the resin composition with an electron microscope or the like. By adding the compatibilizing agent, it can be confirmed that the phase of either the polyolefin resin or the polylactic acid resin has a size (diameter, thickness, etc.) of 20 μm or less. In the preferred case, it is 10 μm or less. By adding a compatibilizing agent, for example, an improvement in impact strength is expected.

  In particular, when a polylactic acid resin composition having improved heat resistance is obtained, a polyolefin (A) having a high crystallization rate selected from polyethylene, isotactic polypropylene, isotactic block polypropylene and the like (Mw: 5) 1,000 to 1,000,000) is used. Moreover, the higher the temperature-lowering crystallization temperature of the polyolefin (A), the more crystallization of polylactic acid is induced and the heat resistance is improved. The temperature-falling crystallization temperature is preferably 80 ° C. or higher and 140 ° C. or lower, more preferably 100 ° C. or higher and 140 ° C. or lower, and further preferably 110 ° C. or higher and 140 ° C. or lower.

  Polylactic acid-based resin (B) having an optical purity of 80% or more of poly L-lactic acid (B-1) having an L-lactic acid unit and poly D-lactic acid (B-2) having a D-lactic acid unit From the viewpoint of increasing the crystallinity, it is preferably 90% or more, and more preferably 95% or more. In addition, the poly L-lactic acid (B-1) having an L-lactic acid unit and the poly D-lactic acid (B-2) having a D-lactic acid unit are linked in a block shape, graft shape or random shape. The crystallinity of the polylactic acid resin (B) is further increased. Moreover, the ratio of the molecular weight of the poly L-lactic acid (B-1) having a poly L-lactic acid unit and the poly D-lactic acid (B-2) having a D-lactic acid unit is preferably 0.05 to 2. More preferably, it is 0.1-1.4.

  As a method for preparing such a resin composition, any known method can be adopted. For example, polyolefin, polylactic acid resin, and if necessary, the above additives are melt-kneaded using an extruder, a kneader, or the like. Is mentioned.

  The molded product according to the present invention is formed from the above-described polylactic acid resin composition with improved heat resistance.

  Although the molding method of the molded product according to the present invention is not particularly limited, for example, it can be produced by a method such as calendar molding, extrusion molding, injection molding, blow molding, press molding, stamping molding or the like. The molding temperature is preferably 180 ° C. or higher and 250 ° C. or lower.

  In the extrusion molding, a conventionally known extrusion apparatus and molding conditions can be employed. For example, a molten resin composition using a single screw extruder, a kneading extruder, a ram extruder, a gear extruder, or the like. Can be formed into a sheet or film (unstretched) by extruding from a T-die or the like.

  The stretched film is obtained by stretching an extruded sheet or an extruded film (unstretched) as described above, for example, by a tenter method (longitudinal and transverse stretching or transverse and longitudinal stretching), a simultaneous biaxial stretching method, or a uniaxial stretching method.

  Filaments can be made, for example, by extruding the molten composition through a spinneret. Further, it may be prepared by a melt blown method. The injection-molded product can be manufactured by injection molding into various shapes using a conventionally known injection molding apparatus under known conditions. The blow molded product can be manufactured using a known blow molding apparatus and employing known conditions.

  In injection blow molding, the resin composition is injected into a parison mold at a resin temperature of 180 ° C. to 250 ° C. to form a parison, and then the parison is held in a mold having a desired shape, and then air is blown into the mold. A hollow molded article can be manufactured by wearing on. Examples of the press-molded product include a mold stamping molded product.

  EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this invention is not limited to these Examples.

In the present invention, various physical properties were measured by the following methods.
(A) Thermal deformation temperature Injection molding was performed using the obtained polylactic acid-based resin composition, and the obtained injection molded product (thickness 3.2 mm) was measured under conditions based on ASTM D648. The load was measured under the condition of 0.45 MPa.
(B) Using a DSC7 manufactured by PERKIN ELMER as the temperature-falling crystallization temperature DSC, the crystallization temperature was measured when the temperature was lowered to 30 ° C at a rate of 10 ° C / min after melting at 230 ° C for 5 minutes.
(C) Weight average molecular weight The weight average molecular weight was evaluated by gel permeation chromatography (GPC) under the following conditions using polystyrene as a standard.
Apparatus: ShoDex GPC system-11
Column: PLgeL 5 μm MIXED-C (manufactured by Polymer Laboratory)
Solvent: Chloroform Concentration: 1% by weight
Injection volume: 20 μL
Flow rate: 1.0 mL / min

[Production Example 1]
750 g of D-lactide, 13.95 g of lauryl alcohol, and 37.5 mg of tin octoate (0.75 g of 5 wt% xylene solution added) are placed in a 5000 mL separable flask and polymerized at 180 ° C. for 4 hours while flowing nitrogen. went. After completion of the polymerization, the reaction product was dissolved in 3000 mL of chloroform, precipitated in methanol, and stirred well to remove the remaining D-lactide and subjected to suction filtration. After rinsing with methanol and drying at 60 ° C. and 2 kPa for 24 hours, 714 g of poly D-lactic acid having a weight average molecular weight of 21,900 in terms of standard polystyrene was obtained.

[Production Examples 2 to 5]
Table 1 shows the results of polymerization in Production Example 1 with varying amounts of lauryl alcohol.

[Production Example 6]
673 g of poly-D lactic acid produced in the same manner as in Production Example 3, 1346 g of L-lactide and 67.3 mg of tin octoate (added 1.35 g of 5 wt% xylene solution) were placed in a reaction vessel made of SUS and 3 L / min. While flowing nitrogen at a flow rate, polymerization was carried out at 140 ° C. for 30 minutes, 180 ° C. for 2 hours, and 210 ° C. for 2 hours. After completion of the polymerization, the reaction product was taken out from the bottom of the reaction kettle, cooled to room temperature, and then the polymer was pulverized. Thereafter, the polymer was added to 5 L of methanol, and the remaining L-lactide was removed by stirring well, followed by suction filtration. After rinsing with methanol and drying at 60 ° C. and 2 kPa for 24 hours, 1710 g of a polylactic acid copolymer of poly L-lactic acid and poly D-lactic acid was obtained.

[Example 1] (Preparation and molding of resin composition)
Prime Polypropylene Block Polypropylene as Polyolefin (registered trademark Prime Polypro, MFR at 230 ° C., 2.16 kgf load: 25 g / 10 min, specific gravity: 0.901, amount of components soluble in paraxylene at 23 ° C .: 10.8 %, Temperature drop crystallization temperature 118 ° C.) 50 parts by weight, polylactic acid manufactured by Mitsui Chemicals as poly L-lactic acid (registered trademark LACEEA: weight average molecular weight 170,000, L-lactic acid / D-lactic acid = 98.2 / 1.8) 25 parts by weight, 25 parts by weight of poly-D-lactic acid obtained in Production Example 1 (total of 100 parts by weight of the three), and 10 parts by weight of talc (made by Fuji Talc Co., Ltd .: Grade LMP-350) are mixed. Then, it was melt-kneaded and pelletized using a KZW15 twin screw extruder manufactured by Technobel Co., Ltd. under the conditions of a temperature of 220 ° C. and a rotation speed of 200 rpm. No odor or the like was generated during melt kneading, and kneading was possible without problems.

  The obtained resin composition was molded on a condition of a cylinder temperature of 230 ° C., a total holding pressure and injection of 10 s, a cooling temperature of 80 ° C. and 30 s with a 20 t injection molding machine, and an injection molded product was obtained. Resin fluidity and mold release during molding could be molded without any problems. The obtained injection molded product had a heat distortion temperature of 105 ° C.

[Examples 2 to 6]
Block Polypropylene made of prime polymer as polyolefin (registered trademark Prime Polypro, MFR at a temperature of 230 ° C., a load of 2.16 kgf: 25 g / 10 min, specific gravity: 0.901, amount of components soluble in paraxylene at 23 ° C .: 10.8 %, Temperature-falling crystallization temperature 118 ° C.), polylactic acid manufactured by Mitsui Chemicals (registered trademark LACEEA: weight average molecular weight 170,000, L-lactic acid / D-lactic acid = 98.2 / 1.8), and production The poly D-lactic acid obtained in Examples 2 to 6 was kneaded at the blending ratio shown in Table 1 in the same manner as in Example 1, pelletized, and injection molded. Table 1 shows the heat distortion temperature of the obtained injection-molded piece.

[Comparative Example 1]
Injection molding of Mitsui Chemicals polylactic acid (registered trademark LACEEA: standard polystyrene equivalent weight average molecular weight 170,000, L-lactic acid / D-lactic acid = 98.2 / 1.8) was carried out in the same manner as in Example 1. . The obtained injection-molded piece had a low crystallinity of polylactic acid and was deformed at the time of mold release, so that a molded piece could not be obtained.

[Comparative Example 2]
For 100 parts by weight of polylactic acid manufactured by Mitsui Chemicals (registered trademark LACEEA: weight average molecular weight of 170,000 L, L-lactic acid / D-lactic acid = 98.2 / 1.8) in the same manner as in Example 1, Ten parts by weight of talc (Fuji Talc Co., Ltd .: Grade LMP-350) was melt-kneaded, pelletized, and injection molded. The injection molded piece was easily deformed due to the low crystallinity of polylactic acid in the injection molded piece. The heat deformation temperature of the obtained injection molded product was 57 ° C.

[Comparative Example 3]
Polylactic acid manufactured by Mitsui Chemicals (registered trademark LACEEA: weight average molecular weight 170,000, L-lactic acid / D-lactic acid = 98.2 / 1.8) as poly L-lactic acid in the same manner as in Example 1, 50 parts by weight, poly 50 parts by weight of poly-D-lactic acid obtained in Production Example 4 as D-lactic acid (however, the total of poly-L-lactic acid and poly-D-lactic acid is 100 parts by weight), and talc (manufactured by Fuji Talc Co., Ltd .: Grade LMP) -350) 10 parts by weight was melt-kneaded, pelletized, and injection molded. The injection molded piece was easily deformed due to the low crystallinity of polylactic acid in the injection molded piece. The heat deformation temperature of the obtained injection molded product was 58 ° C.

[Comparative Example 4]
Block Polypropylene manufactured by Prime Polymer Co., Ltd. as a polyolefin (registered trademark Prime Polypro, MFR at a temperature of 230 ° C., a load of 2.16 kgf: 25 g / 10 min, specific gravity: 0.901, amount of components soluble in paraxylene at 23 ° C .: 10. 50% by weight of 8%, crystallization temperature at 118 ° C.) and 50 parts by weight of polylactic acid (registered trademark LACEEA: weight average molecular weight of 170,000 L, L-lactic acid / D-lactic acid) in terms of standard polystyrene as poly L-lactic acid (However, a total of 100 parts by weight of polyolefin and poly-L-lactic acid) and 10 parts by weight of talc (Fuji Talc Co., Ltd .: Grade LMP-350) were melt-kneaded, pelletized, and injection molded. Resin fluidity and mold release during molding could be molded without any problems. The heat deformation temperature of the obtained injection molded product was 81 ° C.

  As is clear from the Examples and Comparative Examples, the moldability and heat resistance were obtained by blending and kneading the polyolefin, poly L-lactic acid having an L-lactic acid unit, and poly D-lactic acid having a D-lactic acid unit at a predetermined ratio. A polylactic acid resin composition having excellent properties can be obtained.

  A molded product made from a resin composition comprising a polyolefin, a poly-L-lactic acid having an L-lactic acid unit, and a poly-D-lactic acid having a D-lactic acid unit is excellent in heat resistance and is electronic, electrical, and communication. Can be used as equipment casings, containers, medical materials and other industrial materials.

Claims (5)

A polylactic acid resin composition comprising 1 to 90 parts by weight of a polyolefin (A) and 10 to 99 parts by weight of a polylactic acid resin (B) (provided that the total of (A) and (B) is 100 parts by weight) The ratio of poly L-lactic acid (B-1) having an L-lactic acid unit and poly D-lactic acid (B-2) having a D-lactic acid unit in the polylactic acid resin (B) is 99/1 to A polylactic acid resin composition, which is 50/50. The polylactic acid-based resin composition according to claim 1, wherein the polyolefin (A) is a propylene-based polyolefin (A1). 3. The polylactic acid resin composition according to claim 1, wherein the temperature-falling crystallization temperature of the polyolefin (A) is 100 ° C. or more and 140 ° C. or less. The polylactic acid-based resin (B) is a block in which a poly-L-lactic acid (B-1) having an L-lactic acid unit and a poly-D-lactic acid (B-2) having a D-lactic acid unit are covalently bonded and / or 4. The polylactic acid-based resin composition according to claim 1, comprising a polylactic acid copolymer (B-3) having a structure bonded in a graft form and / or a random form. 5. The ratio of the molecular weight of the poly L-lactic acid (B-1) having an L-lactic acid unit and the poly D-lactic acid (B-2) having a D-lactic acid unit in the polylactic acid resin (B) is 0.1 to 0.1. The polylactic acid resin composition according to claim 1, wherein the polylactic acid resin composition is 1.4.