JP2003171544A - Lactic acid resin composition, peroxide-modified lactic acid resin composition, and their molded items - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lactic acid resin composition and a peroxide-modified lactic acid resin composition, both excellent in processability and physical properties in addition to biodegradability inherent in a lactic acid resin; and molded items obtained from them. <P>SOLUTION: The lactic acid resin composition comprises 100 pts.mass lactic acid resin and 0.05-5.0 pts.mass organic peroxide having a 1-hr half-life temperature (Th1) of 70-200°C and, preferably, a hydrogen abstraction coefficient (ε) of 10-60. The peroxide-modified lactic acid resin composition is prepared by subjecting the lactic acid resin composition to a reaction by a specific means so as to satisfy the relation represented by the equation: D2/D1=1.10-3.0 (wherein D1 is the polydispersity of the composition before the reaction; and D2 is that after the reaction). Molded items are prepared from these compositions. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a lactic acid-based resin composition excellent in moldability, a peroxide-modified lactic acid-based resin composition, and a molded product obtained by molding and processing them.

[0002]

2. Description of the Related Art In recent years, due to an increase in environmental problems, it has been demanded that when a plastic product is discarded in a natural environment, it is decomposed / disappeared with time and finally does not adversely affect the natural environment. Conventional plastics are stable in the natural environment for a long period of time and have a low bulk specific gravity, so problems such as promoting the shortening of the life of waste landfills and impairing the natural landscape and living environment of wild animals and plants are pointed out. It had been.

Therefore, biodegradable plastic materials are attracting attention today. It is known that biodegradable plastics gradually disintegrate / decompose in soil or water due to hydrolysis or biodegradation, and finally become harmless decomposition products by the action of microorganisms. Examples of biodegradable plastics that have been put into practical use include polylactic acid, aliphatic polyester, modified PVA, cellulose ester compounds, starch modified products, and blends thereof. Each biodegradable plastic material has its own unique characteristics, and its application can be expanded according to these characteristics. Among them, lactic acid-based resin is one of the few hard resins, and polyethylene terephthalate (PET) and polystyrene ( P
Substitution of hard resin such as S) and ABS is expected.

However, lactic acid-based resins have the drawbacks of relatively low melt tension, poor strain hardening, and poor workability. Due to the relatively low melt tension and strain hardening, for example, bubbles are not stable in blown film molding, drawdown of the sheet occurs during preheating in sheet molding, and parison is deformed in blow molding. In addition, there have been problems such as a large amount of foam breakage in foam molding.

To increase the melt tension, increase the molecular weight,
An improved method such as copolymerizing a branching polyfunctional monomer may be considered, but an increase in the molecular weight increases the melt viscosity more than necessary, and the productivity such as the extrusion discharge amount decreases, while the branching polyfunctional monomer is used. Is not easy to obtain industrially.

Regarding the attempt to increase the melt tension by adding a peroxide, in JP-A-11-2865 in foam molding.
No. 70 discloses a composition of a blend of a lactic acid-based resin and another aliphatic polyester resin, which is disclosed in Japanese Patent Application Laid-Open No. 01-26658. It was not specified, and it was not necessarily effective in improving moldability.

[0007]

That is, the object of the present invention is to provide a lactic acid-based resin composition having excellent processability and physical properties in addition to the biodegradability inherent to the lactic acid-based resin, and peroxide modification. The present invention provides a lactic acid-based resin composition and a molded product made of them.

[0008]

DISCLOSURE OF THE INVENTION The inventors of the present invention have made intensive studies in view of the present situation as a result, and as a result, completed the invention of high effect. The invention according to the present application is the invention described in the following (1) to (5). (1) 100 parts by mass of lactic acid-based resin and 1 hour half-life temperature T
Organic peroxide having h1 of 70 to 200 ° C. of 0.05 to
A lactic acid-based resin composition comprising 5.0 parts by mass. (2) 100 parts by mass of lactic acid resin and 1 hour half-life temperature T
h1 is 70 to 200 ° C., hydrogen abstraction coefficient ε is 10 to 6
A lactic acid-based resin composition comprising 0.05 to 5.0 parts by mass of an organic peroxide that is 0. (3) reacting the lactic acid-based composition by a predetermined means,
When the polydispersity of the lactic acid resin before the peroxide reaction is D1 and the polydispersity of the lactic acid resin after the peroxide reaction is D2, D2 / D1 = 1.10 to 3.0. Oxide-modified lactic acid resin. In the present invention, the predetermined means is heating,
Means such as radiation irradiation. (4) A film made of the above peroxide-modified lactic acid resin,
Molded bodies such as sheets, sheet molded bodies, foamed sheets, foamed sheet molded bodies, blow molded bodies, injection molded bodies, mold foamed bodies, fibers, pipes, plates and plate molded bodies. (5) 50 to 97 parts by mass of lactic acid-based resin, 3 to 50 parts by mass of aliphatic polyester having glass transition temperature Tg of 0 ° C. or lower, and / or aliphatic aromatic polyester, and 1-hour half-life temperature Th1 of 70 to 200 ℃, Hydrogen abstraction coefficient ε
A composition comprising 0.05 to 5.0 parts by mass of an organic peroxide having a content of 10 to 60. (6) A film formed by reacting the lactic acid-based resin composition by a predetermined means such as heating or irradiation with radiation,
Molded bodies such as sheets, sheet molded bodies, foamed sheets, foamed sheet molded bodies, blow molded bodies, injection molded bodies, mold foamed bodies, fibers, pipes, plates and plate molded bodies.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The lactic acid-based resin in the present invention means poly (L-lactic acid) whose structural unit is L-lactic acid, poly (D-lactic acid) whose structural unit is D-lactic acid, and L-lactic acid and D-lactic acid whose structural unit is L-lactic acid. It refers to certain poly (DL-lactic acid) or a mixture thereof, and may be a copolymer with α-hydroxycarboxylic acid or diol / dicarboxylic acid.

The lactic acid-based resin can be polymerized by condensation polymerization,
Any known method such as ring-opening polymerization method can be adopted. For example, in the polycondensation method, L-lactic acid, D-lactic acid, or a mixture thereof can be directly dehydrated and polycondensed to obtain a lactic acid resin having an arbitrary composition.

In the ring-opening polymerization method, a polylactic acid-based polymer can be obtained by using lactide, which is a cyclic dimer of lactic acid, and a catalyst selected as necessary while using a polymerization regulator and the like. it can. L-lactide is a dimer of L-lactic acid.
Lactide, D-lactide, which is a dimer of D-lactic acid, and DL-lactide composed of L-lactic acid and D-lactic acid,
A lactic acid-based resin having an arbitrary composition and crystallinity can be obtained by mixing these as required and polymerizing.

Furthermore, if necessary, for example, to improve heat resistance, a small amount of a non-aliphatic dicarboxylic acid such as terephthalic acid and / or a non-aliphatic diol such as an ethylene oxide adduct of bisphenol A is used as a copolymerization component. You may use. Furthermore, a small amount of a chain extender such as a diisocyanate compound, an epoxy compound or an acid anhydride can be used for the purpose of increasing the molecular weight.

The above-mentioned other hydroxy-carboxylic acid units copolymerized with the lactic acid-based resin include optical isomers of lactic acid (D-lactic acid for L-lactic acid and L-lactic acid for D-lactic acid).
-Lactic acid), glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-methyllactic acid, Examples thereof include bifunctional aliphatic hydroxy-carboxylic acids such as 2-hydroxycaproic acid and lactones such as caprolactone, butyrolactone and valerolactone.

Examples of the aliphatic diol copolymerized with the lactic acid resin include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid and dodecanedioic acid.

The weight-average molecular weight of the lactic acid resin is preferably in the range of 50,000 to 400,000, preferably 100,000 to
It is 250,000. When the weight average molecular weight of the lactic acid resin is less than 50,000, practical physical properties are difficult to be expressed, and when it exceeds 250,000, the melt viscosity may be too high, resulting in poor moldability.

The lactic acid-based resin composition according to the first aspect of the present invention contains an organic peroxide having a 1-hour half-life temperature (Th1) of 70 to 200 ° C. relative to 100 parts by mass of the lactic acid-based resin. This is a resin composition containing 05 to 5.0 parts by mass.

The lactic acid-based resin composition according to the second aspect of the present invention has a one-hour half-life temperature (Th1) of 70 to 200 ° C. and a hydrogen abstraction coefficient (ε) with respect to 100 parts by mass of the lactic acid-based resin. Organic peroxide of 10 to 60 0.05 to 5.
It is a resin composition containing 0 parts by mass.

Organic peroxide means hydrogen peroxide (HO--
It is a derivative of OH) and has a structure in which one or two hydrogen atoms of hydrogen peroxide are replaced by organic free radicals, and one or more peroxide bonds (O- It is a compound characterized by having O).

Known types of peroxides include ketone peroxides, diacyl peroxides, hydroperoxides, dialkyl peroxides, peroxyketals, alkyl peresters, and carbonates. There is.

However, in order to improve the moldability of the lactic acid-based resin, it is necessary to select a compound having a specific performance among them. That is, the one-hour half-life temperature (T
h1) is 70 to 200 ° C., preferably 100 to 160
It is essential to choose an organic peroxide that is in ° C. Further, it is preferable to select an organic peroxide having a hydrogen abstraction coefficient (ε) of 10 to 70, preferably 10 to 60, and more preferably 20 to 60.

Here, the one-hour half-life temperature (Th1) is the temperature at which half of the initial weight of the peroxide decomposes in 1 hour due to heat. 1 hour half-life temperature (Th1) is 70
If the temperature is lower than 0 ° C, the peroxide decomposes even at room temperature, which is not preferable for safety and product life. Also, when reacting with a lactic acid-based resin, the exothermic reaction is too rapid, causing thermal decomposition of the resin, local reaction to form a gel in the resin, and conversely loss of heat before reaction with the resin. It is not preferable to use it. 20
When the temperature is higher than 0 ° C, the denaturing reaction is difficult to proceed under general conditions. 1-hour half-life temperature (Th1) is 70-
As the organic peroxide having a temperature of 200 ° C., those which satisfy such a condition may be appropriately selected from commercial products. For example, the product name “PERKADOX BC” manufactured by Kayaku Akzo Co., Ltd.
(Th1 = 132 ° C.) is commercially available.

1-hour half-life temperature (Th1) for lactic acid resin
Moldability can be improved by kneading an organic peroxide having a temperature of 70 to 200 ° C. It is considered that when a predetermined organic peroxide is kneaded with the lactic acid resin, a cross-linking reaction occurs, and as a result, the viscosity in the linear region increases.

In the present invention, the hydrogen abstraction coefficient (ε) means that when an organic peroxide at a concentration of 0.2 mol / L in n-pentadecane is decomposed by heating at a half-life temperature of 15 minutes for 30 minutes. It is a relative comparison numerical value of the amount of n-pentadecane dimer produced. However, the amount when 2,2′-azobis (isobutyronitrile) was used was 1. When the hydrogen abstraction coefficient (ε) is less than 10, it is difficult to obtain the effect of improving the moldability of the lactic acid resin. In addition, organic peroxides exceeding 70 are difficult to synthesize and are not easily available including cost.

1-hour half-life temperature (Th1) is 70 to 20
Typical examples of the organic peroxide having a hydrogen abstraction coefficient (ε) of 10 to 70 at 0 ° C. include the following compounds. 1,1-di-t-butylperoxycyclohexane (T
h1 = 113 ° C., ε = 24 ° C.), t-butylperoxy-3,5,5-trimethylhexanoate (Th1 = 1
14 ° C, ε = 33), 2,2-di-t-butylperoxybutane (Th1 = 116 ° C, ε = 24), t-butylperoxyisopropyl carbonate (Th1 = 117).
C, ε = 40), t-butylperoxy-2-ethylhexyl carbonate (Th1 = 117 ° C., ε = 40),
t-amyl peroxybenzoate (Th1 = 118
C, ε = 39), t-butyl peroxyacetate (T
h1 = 119 ° C., ε = 43), 4,4-di-t-butylperoxyvaleric acid-n-butyl ester (Th1 = 12)
1 ° C, ε = 24), t-butylperoxybenzoate (Th1 = 122 ° C, ε = 49), 2,5-dimethyl-
2,5-di- (t-butylperoxy) hexane (Th
1 = 134 ° C., ε = 41), 1,3-bis- (t-butylperoxyisopropyl) benzene (Th1 = 134)
° C, ε = 55), t-butylcumyl peroxide (T
h1 = 136 ° C., ε = 41), di-t-butyl peroxide (Th1 = 141 ° C., ε = 49), 2,5-dimethyl-2,5-di- (t-butylperoxy) hexyne-3. (Th1 = 141 ° C., ε = 30) As an organic peroxide having a one-hour half-life temperature (Th1) of 70 to 200 ° C. and a hydrogen abstraction coefficient (ε) of 10 to 70, commercially available products may be used. You may select suitably what satisfy | fills. For example, Kayaku Akzo Co., Ltd. product name "Trigonox 22", "Trigonox 42",
"Trigonox D" etc. can be obtained commercially.

Here, 0.05 to 5.0 parts by mass, preferably 0.1 to 3.0 parts by mass of organic peroxide is added to 100 parts by mass of the lactic acid resin. When the amount of the organic oxide added is less than 0.05 parts by mass, it is difficult to improve the moldability of the lactic acid-based resin, and when it is greater than 5.0, the resin as a whole becomes crosslinked and the plasticity becomes poor, and conversely the processing is performed. Lose sex.

As a method for reacting the lactic acid-based resin composition, an extruder or a batch kneader is used, and the amount is 130 to 240.
It is common to melt knead while heating to ℃,
After low-temperature melt kneading at 80 to 130 ° C. or solution kneading, the mixture can be fixed in a mold and reheated in a hot-air stove, or can be reacted by irradiation with radiation. In this method, the peroxide and the lactic acid-based resin may be reacted after molding into an intermediate molded body. The intermediate molded product refers to a product such as an extruded sheet for obtaining a vacuum-formed product or a press-formed product from a sheet.

Next, in the present invention, the above composition is reacted by means such as heating and radiation irradiation. At this time, the polydispersity of the lactic acid resin before the peroxide reaction is set to D1, and the peroxide reaction is performed. If the polydispersity of the latter lactic acid-based resin is D2, D2 /
D1 = 1.10 to 3.0, preferably 1.3 to 2.2
It is important to control in the range of.

When D2 / D1 is less than the above range, it is difficult to improve the moldability of the lactic acid-based resin, and when it exceeds the above range, large and small gel-like substances are generated, which may impair the appearance and deteriorate the mechanical properties. is there. Further, even if the melt tension is increased, the strain-hardening property may be lowered, or bleeding of the oligomer may occur.

In order to control D2 / D1 within such a range, an organic peroxide having a one-hour half-life temperature (Th1) of 70 to 200 ° C. and a hydrogen abstraction coefficient (ε) of 10 to 60 is used. It is most important to use 5.0 parts by mass, but other than that, heating time, shear rate, moisture content,
The presence of a specific metal, the nature of the reaction residue of the peroxide, and the like are also strongly influenced, so that it is adjusted appropriately while observing D2.

For example, when heating in an extruder for a long time, the presence of water, or the residue of peroxide becoming an acidic substance,
D2 / D1 tends to increase. In addition, there is a tendency for it to become smaller with high shear, heating for a short time, and radiation irradiation.

As described above, the lactic acid-based resin resin composition modified with peroxide (peroxide-modified lactic acid-based resin composition) has an increased melt tension, exhibits strain hardening properties, and is excellent in molding. To have sex. Therefore, the peroxide lactic acid-based resin composition is a film, sheet, sheet molded body, foamed sheet, foamed sheet molded body, blow molded body, injection molded body, mold foamed body, fiber, which requires melt tension during molding.
It is preferably used for pipes, plates, plate molded bodies and the like.

For example, the following effects are expected. 1) Bubbles are stable in blown film. 2) For sheets, prevent neckdown during extrusion casting. 3) The sheet molded body prevents drawdown during preheating and improves the thickness distribution of the molded body. 4) In the foamed sheet, the cell structure is made uniform and dense to prevent foam breakage. 5) In the foamed sheet molded body, drawdown at the time of preheating is prevented and the thickness distribution of the molded body is improved. 6) In the blow molded product, drawdown of the parison is prevented and the thickness distribution of the molded product is improved. 7) Prevent burr in the injection molded body. 8) In the foamed product, the cell structure is made uniform and dense, and foam breakage is prevented. 9) Fibers improve the spinnability during spinning and prevent yarn breakage. 10) For pipes, the shape stability during extrusion is improved. 11) The plate prevents drawdown during horizontal extrusion. 12) The plate molded body prevents drawdown during preheating and improves the thickness distribution of the molded body.

In the present invention, the lactic acid-based resin composition may be blended with an aliphatic polyester resin or an aliphatic aromatic polyester resin having a glass transition temperature Tg of 0 ° C. or lower.

Examples of the above-mentioned aliphatic polyester resin include an aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic dicarboxylic acid, an aliphatic polyester obtained by ring-opening polymerization of a cyclic lactone, and a synthetic aliphatic polyester. Can be mentioned.

The aliphatic polyester obtained by condensing the above aliphatic diol with an aliphatic dicarboxylic acid is an aliphatic diol such as ethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol, and an aliphatic polyester. It can be obtained by condensation polymerization of one or more selected from succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like which are dicarboxylic acids. If desired, the desired polymer can be obtained by jumping up with an isocyanate compound or the like. Examples of commercially available raw material pellets include Bionore manufactured by Showa High Polymer Co., Ltd., and the like.

In order to improve heat resistance and mechanical strength,
As the dicarboxylic acid component, 50 mol% or less of an aromatic monomer component such as terephthalic acid may be copolymerized. The resin copolymerized in such a form corresponds to the aliphatic aromatic polyester in the present invention. Examples of commercially available raw material pellets include Easter Bio manufactured by Eastman Chemical Co., and Ecoflex manufactured by BASF.

Typical examples of the aliphatic polyester obtained by ring-opening polymerization of the above cyclic lactones include cyclic monomers ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone and the like. More than one kind is selected and polymerized.

Examples of the synthetic aliphatic polyester include
Examples thereof include cyclic acid anhydrides and oxiranes, for example, copolymers of succinic anhydride and ethylene oxide, propylene oxide and the like.

When an aliphatic polyester resin or the like is blended with the lactic acid-based resin composition, the lactic acid-based resin and an aliphatic polyester and / or an aliphatic aromatic polyester having a glass transition temperature (Tg) of 0 ° C. or less, By using a lactic acid-based resin composition including an organic peroxide, not only the processability of the lactic acid-based resin but also the impact resistance and cold resistance can be improved. Further, addition of an organic peroxide improves mechanical strength and transparency as compared with a simple blend system of a lactic acid resin and an aliphatic polyester and / or an aliphatic aromatic polyester.

The compounding ratio of each component (shown in parts by mass) is as follows: lactic acid resin: (aliphatic polyester and / or aromatic-aliphatic polyester): organic peroxide = 5
0 to 97: 3 to 50: 0.05 to 5.0 (parts by mass) is preferable. If the amount of lactic acid-based resin is greater than the range,
The desired effect of improving impact resistance and cold resistance is poor, and when it is small, rigidity and scratch resistance are poor.

Further, within a range not impairing the effects of the present invention,
Additives such as heat stabilizers, antioxidants, UV absorbers, light stabilizers, pigments, colorants, lubricants, nucleating agents, hydrolysis inhibitors, and inorganic fillers can also be formulated.

As a method of obtaining the composition,
Pre-compounding may be performed using a co-direction twin-screw extruder, kneader, Henschel mixer, or the like, or each raw material may be dry blended and directly charged into a molding machine. The molding machine is not particularly limited to achieve the present invention.

[0043]

EXAMPLES Examples will be shown below, but the present invention is not limited thereto. The measured values shown in the examples were calculated by measuring under the following conditions.

1) 1-hour half-life temperature (T
h) Benzene as a solvent, organic peroxide, 0.2mo
Prepare a 1 / L solution. Four 15 mL each of the sample solution is collected in a pressure resistance test tube. The four pressure vessels are replaced with nitrogen in advance, and the test tube containing the sample solution is placed in each pressure vessel and sealed. At the same time, the pressure vessel is placed in the glycerin bath which has been set to the measurement temperature assumed from the DSC measurement results. After 15 minutes, one pressure vessel is taken out of the glycerin bath, immediately immersed in ice water, and cooled. After cooling, the test tube was taken out from the pressure resistant container, and the active oxygen amount (A.O%) was measured by the iodometry method, and this is set to 0 hour. After that, the amount of active oxygen (A.O.%) is measured in the same manner at regular intervals (2 hours, 4 hours, 6 hours) to find the half-life at each temperature. The temperature is plotted on the horizontal axis and the half-life time is plotted on the vertical axis, and the one-hour half-life temperature Th is determined from the graph. The 15-minute half-life temperature was also read from the graph in order to determine the hydrogen abstraction coefficient shown below.

2) Hydrogen abstraction coefficient (ε) of organic peroxide An organic peroxide was dissolved in n-pentadecane at a concentration of 0.2 mol / L to prepare a sample solution. 20m of this sample solution
The mixture was collected in an L test tube, immersed in glycerin, and heated at a 15-minute half-life temperature for 30 minutes. The amount of n-pentadecane dimer produced at this time was measured, and the amount of n-pentadecane dimer produced when 2,2′-azobis (isobutyronitrile) was used was set to 1, and a relative numerical value was obtained.

3) D2 / D1 Gel permeation chromatography HLC-8120GPC manufactured by Tosoh Corporation, and GPC-80 of a chromatography column Shim-Pack series manufactured by Shimadzu Corporation.
0CP attached, solvent chloroform, solution concentration 0.2w
t / vol%, solution injection amount 200 μL, solvent flow rate 1.0
The measurement was performed at mL / min and a solvent temperature of 40 ° C. The number average molecular weight and weight average molecular weight of the lactic acid resin before and after the reaction were calculated in terms of polystyrene. The weight average molecular weight of the standard polystyrene used was 2,000,000, 670000,
110000, 35000, 10000, 4000, 6
00. The value obtained by dividing the weight average molecular weight by the number average molecular weight is the polydispersity index. The polydispersity before the organic peroxide reaction was D1, and the polydispersity after the reaction was D2, and D2 / D1 was calculated.

4) The strain-curable lactic acid-based resin composition was kneaded using SK KRC Kneader N90-1 manufactured by Kurimoto Seisakusho Co., Ltd. at 190 ° C. and 200 rpm, and the kneaded product was pressed with a 100 t press at 190 ° C. It was pressed for 10 minutes and gradually cooled. The press plate was cut into a size of width × length × thickness = 7 × 55 × 1.5 mm to obtain a sample for uniaxial extensional viscosity measurement. Using a RME manufactured by Rheometrics Co., Ltd., the uniaxial extensional viscosity of this sample was measured at 190 ° C. in a nitrogen atmosphere at a constant strain rate (0.5 sec ⁻¹ ). From the graph, the strain hardening degree was calculated by the following formula. Strain hardening degree = (η5-η1) / η1 where η1 = extension viscosity after 1 second of measurement time η5 = extension viscosity after 5 seconds of measurement time

5) Neck-in rate of extruded sheet The lactic acid-based resin composition was subjected to a 30 mmφ single screw extruder (l / d = 22) manufactured by Mitsubishi Heavy Industries, Ltd. equipped with a kneading zone, set temperature 190 ° C., rotation speed 30 rpm. With a discharge rate of 3 kg / h,
Width 200 mm, lip gap 1 mm from base to thickness 1
Sheet extrusion of 00 μm was performed. Adjust the take-up speed to make the sheet thickness 100 μm (take-off speed = about 4
m1), the seat width immediately after the mouth of the mouthpiece is set to L1,
The sheet width at a distance of 20 cm from the mouthpiece was L2, and the neck-in rate was calculated by the following formula. In general sheet molding, the neck-in rate is preferably 10% or less. Neck-in rate (%) = (L1-L2) / L1 × 10
0

6) Cell diameter of foamed sheet A lactic acid-based resin composition containing 1 part by mass of a foaming agent ACDA (azodicarbonamide) was added to a 30 mmφ single-screw extruder (l) manufactured by Mitsubishi Heavy Industries, Ltd. equipped with a kneading zone. / D = 22)
Then, a sheet having a thickness of 500 μm was extruded from a die having a width of 200 mm and a lip gap of 1 mm at a set temperature of 190 ° C., a rotation speed of 30 rpm, and a discharge rate of 3 Kg / h. The extruded sheet was cut with a cutter in the flow direction and observed with an optical microscope. The particle size of the foam cells was visually measured, and the average was calculated for 10 foam cells in the visual field. The overall state of the foam cells was also observed. In ordinary foamed extrusion sheet molding, it is preferable that the cell diameter is 100 μm or less, that the cell diameter is uniform and that there is no breakage.

7) Charpy impact strength A sample was placed 10 mm wide and 80 mm long in the longitudinal direction of the pipe.
Cut to a thickness of 4 mm, and a test was performed with a notch (notch type A) and edgewise using a Charpy impact tester manufactured by Yasuda Seiki Seisakusho based on JIS-K7111. The unit is KJ / m ² .

Example 1 Lacty 5000 manufactured by Shimadzu Corporation, which is homopolylactic acid as a lactic acid resin.
(Weight average molecular weight 200,000, polydispersity 2.0) was used.
To 100 parts by mass of this lactic acid resin, 0.4 part of lauroyl peroxide (manufactured by Nippon Kayaku Co., Ltd., trade name “Laurox”) (Th1 = 79 ° C., ε = 8) was added as an organic peroxide, and Kurimoto Seisakusho SK KRC Kneader N9 manufactured by Co., Ltd.
0-1 was kneaded at 190 ° C. and 200 rpm, the strand was extruded, quenched in a water tank, and then cut into strands to obtain pellets. The strain hardening degree, neck-in rate, and foam cell diameter were determined using the obtained pellets. The strain hardening degree was 4.8, the neck-in rate was 12%, and the foam cell diameter was 120 μm (uniform). .

(Examples 2 to 4, Comparative Examples 1 to 3) As a lactic acid resin, homopolylactic acid, Lacty 5000 manufactured by Shimadzu Corporation (weight average molecular weight 200,000, polydispersity 2.0) Was used. To this lactic acid-based resin, the organic peroxides shown in Table 1 were added, and using Kurimoto Seisakusho's SK KRC Kneader N90-1, kneading was performed at 190 ° C. and 200 rpm, the strands were extruded, and after rapid cooling in a water tank, Strand cut to obtain pellets. The above evaluation was performed using the obtained pellets. The results of these evaluations are shown in Table 1.

[0053]

[Table 1]

Comparative Example 4 As an organic peroxide, t-butyl peroxybenzoate (Th1 = 122 ° C., ε =
Pelletization was tried in the same manner as in Example 1 except that 5.5 parts of 49) was added. However, the modification of the resin by the organic peroxide proceeded too much, the extruded melt became a gel, and stable strands could not be obtained, so that pelletization could not be performed. The strand D2 / D1 was 3.6.

Comparative Example 5 Lacty 5000 manufactured by Shimadzu Corporation and Easter Bio manufactured by Eastman Chemical Co. having a Tg of −30 ° C. were dry-blended at 8/2, a 25 mmφ base and DISK manufactured by Batten. Klaus Maffei 45m with type former
Subjected to mφ single screw extruder, extruded resin temperature 190 ° C, screw rotation speed 70 rpm, outer diameter 25 mmφ, wall thickness 4 mm
Extruded the pipe. The pipe was distorted due to its own weight, because the melt tension was insufficient and the pipe was distorted due to insufficient melt tension without being cooled with water at the mouth of the mouthpiece and only supported by a circular pipe with a shaping tool. The Charpy impact strength was 3.5 KJ / m ² .

Example 5 As the organic peroxide, 2,2
-Di-t-butylperoxybutane (Th1 = 116
C., .epsilon. = 24) was extruded in the same manner as in Comparative Example 4 except that 0.5 part by mass was added. As a result, the melt tension was high, the appearance of the pipe was not deformed, and it was round and good. It was The Charpy impact strength is 4.2 KJ / m
² , which was improved compared to the case where no organic peroxide was added.

[0057]

As described above in detail, according to the present invention, in addition to the biodegradability which lactic acid resin originally has,
It is possible to provide a lactic acid-based resin composition having excellent processability and physical properties, a peroxide-modified lactic acid-based resin composition, and a molded article made of them.

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Claims (6)

[Claims] 1. A lactic acid-based resin comprising 100 parts by weight of a lactic acid-based resin and 0.05 to 5.0 parts by weight of an organic peroxide having a 1-hour half-life temperature (Th1) of 70 to 200 ° C. Resin composition. 2. 100 parts by mass of a lactic acid-based resin and an organic peroxide having a 1-hour half-life temperature (Th1) of 70 to 200 ° C. and a hydrogen abstraction coefficient (ε) of 10 to 60.
A lactic acid-based resin composition comprising 0 parts by mass. 3. A lactic acid resin in an amount of 50 to 97 parts by mass, an aliphatic polyester having a glass transition temperature (Tg) of 0 ° C. or less, and / or an aliphatic aromatic polyester in an amount of 3 to 50 parts by mass, and a 1-hour half-life temperature. Organic peroxide having a (Th1) of 70 to 200 ° C. and a hydrogen abstraction coefficient ε of 10 to 60.
A lactic acid-based resin composition, characterized in that it is composed of 05 to 5.0 parts by mass. 4. The lactic acid-based resin composition according to claim 1 or 2 is reacted by a predetermined means, and the polydispersity of the lactic acid-based resin before the peroxide reaction is set to D1, and the lactic acid-based resin after the peroxide reaction. When the polydispersity of the resin is D2, D2 / D1 = 1.1
A peroxide-modified lactic acid-based resin composition, which is 0 to 3.0. 5. A molded article, which is formed by molding the peroxide-modified lactic acid-based resin composition according to claim 4. 6. A molded article, which is formed by reacting the lactic acid-based resin composition according to claim 3 by a predetermined means and then molding.