JP2000248164A - Lactic acid series composition and its molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lactic acid series composition for retaining a high loss angle tangent at not less than a room temperature and being stable with time by comprising a lactic acid series polymer having branching or network structure constructed with a main chain structure component containing a lactic acid component of not less than a specific amount and a plasticity component, thereby forming the composition having a specific dynamic viscoelastic property value. SOLUTION: A lactic acid series composition comprises a main chain structure component containing a lactic component of at least 50% based on the weight fraction and a plasticity component, in a dynamic viscoelastic measurement (JISK7198A), a transition temperature being not more than 30 deg.C, and in a temperature range of from the transition temperature to 150 deg.C, a dynamic storage elastic modulus being 1×104-1×108 Pa and a loss tangent being 0.1-3.0. The composition is obtained by melt mixing and polymerizing the lactic acid series polymer and the plasticity component at a temperature of 100-180 deg.C. As the lactic acid series polymer is used the material having a weight-average molecular weight of at least 10,000. As the plasticizer is preferable the material having a weight-average molecular weight of 100-5,000 and a solubility parameter value of 9.0-11.0. A molding is particularly preferable to use for a vibration damper, a vibration insulator, and an impact absorber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The composition of the present invention can be used for various applications such as packaging materials, industrial materials, industrial supplies, containers, etc., and particularly for films, tapes and sheets requiring transparency and flexibility. It is suitable as a material. Further, since the flexible component is contained in the branched chain, it has stability over time, has a wide rubber-like elastic region and is excellent in shock absorption, and is very suitable for use as a vibration damping material, a vibration damping material, or a shock absorbing material. Although it is not particularly limited as a vibration damping material / vibration damping material, by shaping it into a sheet or the like, the vibration of a bearing part of a rotating shaft, an automobile, a machine tool, a ship, a building material, an acoustic material, etc. It can be used as a countermeasure for the noise generated. Alternatively, it can be used as a sound absorbing and insulating material and a vibration reducing material by using it as an interior material in a car or a building.

The use of a damper or a vibration isolator containing the composition according to the present invention can also be applied to applications such as seismic resistance of buildings and micro vibrations such as internal combustion driving devices. Although it is not particularly limited as a shock absorbing application, it can be used for a bridge girder of a road bridge, a side wall of a road or a quay, a floor / wall of a building, a shock absorbing portion of a vehicle, etc. Use of the composition of the present invention or a molded article of the present invention for a part to be subjected to repeated impacts such as application to encapsulation, application to canes and sports equipment, application to tools and equipment such as hammers, etc. It is possible to reduce the impact. Furthermore, because of the biodegradability, the problem of waste such as conventional plastics is reduced.

[0003]

2. Description of the Related Art In recent years, from the viewpoint of protection of the natural environment, biodegradable polymers that can be decomposed in the natural environment and molded products thereof have been demanded, and studies on naturally degradable resins such as aliphatic polyesters have been actively conducted. . In particular, the lactic acid-based polymer has a glass transition point of 60 ° C and a melting point of 170 to 180 ° C, and has high thermal stability and excellent transparency.・ It is expected to spread.

It is known that a lactic acid-based polymer has a very large loss angle tangent of 2.0 to 3.0 at its glass transition point and has a unique property as compared with general-purpose resins. However, the glass transition point of the homopolymer was around 60 ° C., and its properties were not sufficiently utilized near room temperature. In order to bring out the characteristics, a method of preparing a copolymer or blending other components can be considered. However, in the case of copolymerization, if copolymerization is performed at a composition ratio necessary to sufficiently lower the glass transition point, the copolymer will have a random block structure and the block length of the lactic acid component will be shorter, so it will be compared with the homopolymer. As a result, the properties of the lactic acid polymer deteriorate, and it is difficult to obtain a sufficient loss tangent value. When blending other components, a method of adding a plasticizer for the purpose of lowering the glass transition point can be considered, but simply blending causes bleed-out of the plasticizer, and there is a problem in stability over time. Was.

[0005] JP-A-8-199052 and JP-A-8-199052
JP-A-199053 and JP-A-8-283557 disclose compositions containing a (poly) ester plasticizer using an ether bond-containing glycol such as polyethylene glycol. And high stability with time. In addition, there was a problem in the melting characteristics in forming a film or the like. US Patent 5180
No. 765 discloses a composition in which a low molecular weight product of lactic acid or lactide which is a raw material of a lactic acid polymer is added as a plasticizer as a plasticizer. However, there is a problem in stability over time because the temperature is reduced and decomposition is promoted.

[0006]

As described above, it has heretofore been difficult to prepare a composition having stability over time and maintaining a high loss tangent in a temperature range of room temperature or higher.

[0007]

Means for Solving the Problems In order to solve such a problem, the present inventors have made intensive studies and found that a lactic acid-based polymer is used as a main chain and a transition temperature represented by a plasticizer is shifted to a lower temperature. A composition was found that shows a stable value in a temperature range of room temperature or higher without lowering the loss angle tangent value of the lactic acid-based polymer by chemically bonding the component to a side chain or a cross-linked chain. It has also been found that this composition has stability over time.

That is, the present invention provides a lactic acid-based composition having a high loss angle tangent and being stable with time, particularly suitable for damping / vibration-proofing materials and shock absorbing materials, and a molded product thereof. It is to provide. More specifically, in the present invention, the transition temperature is 30 ° C. in the dynamic viscoelasticity measurement (JIS K7198A method).
A lactic acid-based composition having a dynamic storage modulus of 1 × 10 ⁴ to 1 × 10 ⁸ Pa and a loss angle tangent of 0.1 to 3.0 in a temperature range from the transition temperature to 150 ° C. is there.
The transition temperature of the dynamic storage modulus according to the JIS K7198A method refers to the temperature at which the composition or molded article is physically deformed softly, and is a polymer composition having the same composition or a molding obtained from the same polymer composition. Even in the case of a product, a different value is obtained for each composition or molded product depending on the degree of crystallization and the state of crystallization. In this point, it is different from the glass transition temperature which is a value specific to the polymer.

The transition temperature is 30 ° C. or less, preferably 10 ° C.
Below 30 ° C, at room temperature below the transition point
Because of the temperature range, flexible properties below the transition point are needed.
This is because there is a problem in stability in a high temperature range. Ma
The dynamic storage modulus is 1 × 10^Four~ 1 × 10⁸Pa, good
Preferably 1 × 10 ^Five~ 1 × 10⁸Pa, loss angle tangent is
It is 0.1 to 3.0, preferably 0.2 to 1.5. This
Beyond these ranges, flexible damping materials, shock absorbing applications and
This is because sufficient characteristics cannot be obtained. And even this
These values must be stable against temperature changes. value
If the change is large, the characteristics will change due to changes in the operating temperature
Because it will.

According to the present invention, a lactic acid-based polymer and a plastic component
The present invention relates to a lactic acid-based composition that is melt-mixed at 00 to 180 ° C and polymerized. Furthermore, the present invention relates to a molded article of the composition obtained by the present invention. Hereinafter, the lactic acid polymer and the plastic component used in the present invention will be described step by step. The lactic acid polymer in the present invention, in addition to lactic acid homopolymer,
Lactic acid copolymers and blended polymers are also included. Lactic acid homopolymers include L-lactide composed of two L-lactic acids, D-lactide composed of D-lactic acid, and L-lactide.
Any of three types of lactide cyclic dimerized lactide, meso-lactide composed of lactic acid and D-lactic acid, may be used as a main raw material, and can be obtained by performing a polymerization reaction in the presence of a catalyst. A copolymer containing only L-lactide or D-lactide can be crystallized to obtain a high melting point copolymer. In the copolymer of the present invention, even better properties can be obtained by combining these three lactides. A lactic acid copolymer is a lactic acid monomer or lactide copolymerized with another copolymerizable component.
Such other components include dicarboxylic acids having two or more ester bond-forming functional groups, polyhydric alcohols,
Examples include hydroxycarboxylic acids, lactones and the like, and various polyesters, various polyethers, and various polycarbonates composed of these various components.

The dicarboxylic acids include succinic acid, adipic acid, azelaic acid, sebacic acid, terephthalic acid, isophthalic acid and the like. Examples of polyhydric alcohols include aromatic polyhydric alcohols such as those obtained by adding ethylene oxide to bisphenol, ethylene glycol, propylene glycol, butanediol, hexanediol, octanediol, glycerin, sorbitan, trimethylolpropane, neomethyl Aliphatic polyhydric alcohols such as pentyl glycol, diethylene glycol,
Examples include ether glycols such as triethylene glycol, polyethylene glycol, and polypropylene glycol. Examples of hydroxycarboxylic acids include glycolic acid, hydroxybutylcarboxylic acid, and others described in
And those described in US Pat. Examples of the lactone include glycolide, ε-caprolactone glycolide, ε-caprolactone, β-propiolactone, δ-butyrolactone, β- or γ-butyrolactone, pivalolactone, and δ-valerolactone.

The lactic acid polymer is synthesized by a conventionally known method. That is, direct dehydration condensation from a lactic acid monomer as described in JP-A-7-33861, JP-A-59-96123, and Proceedings of the Society of Polymer Discussion, Vol. 44, pp. 3198-3199, or lactic acid cyclic dimer It can be synthesized by ring-opening polymerization of lactide. When performing direct dehydration condensation, any lactic acid of L-lactic acid, D-lactic acid, DL-lactic acid, or a mixture thereof may be used. or,
When performing ring-opening polymerization, L-lactide, D-lactide, DL-lactide, or any of these lactides may be used. When the lactic acid component in the lactic acid polymer main chain is 50% or less by weight, its transparency and
It is not preferable because characteristics unique to polylactic acid such as heat resistance and biodegradability are lost. Furthermore, the weight average molecular weight is 10
When the molecular weight is less than 000, high elasticity cannot be obtained and decomposition is promoted.

Lactide synthesis, purification and polymerization procedures are described, for example, in US Pat. No. 4,057,537, Published European Patent Application No. 261572, Polymer Bulletin, 14, 49.
1-495 (1985) and Makromol Chem., 187, 1611-16
28 (1986). The catalyst used for this polymerization reaction is not particularly limited, but a known lactic acid polymerization catalyst can be used. For example, tin compounds such as tin tin lactate, tin tartrate, tin dicaprylate, tin dilaurate, tin dipalmitate, tin distearate, tin dioleate, tin α-naphthoate, tin β-naphthoate, and tin octylate , Powdered tin, tin oxide; zinc dust, zinc halide, zinc oxide,
Organic zinc compounds, titanium compounds such as tetrapropyl titanate, zirconium compounds such as zirconium isopropoxide, antimony compounds such as antimony trioxide, bismuth compounds such as bismuth (III) oxide, aluminum oxide, and aluminum isopropoxy And aluminum-based compounds such as aluminum. Among them, a catalyst composed of tin or a tin compound is particularly preferable from the viewpoint of activity. The amount of these catalysts used is, for example, in the case of performing ring-opening polymerization, 0.001 to 5% by weight based on lactide.
It is about. The polymerization reaction can be usually carried out at a temperature of 100 to 220 ° C in the presence of the above catalyst, depending on the type of the catalyst. It is also preferable to carry out two-stage polymerization as described in JP-A-7-247345.

As the plastic component used in the present invention, a plasticizer generally used for plasticizing polylactic acid or a modified product of polylactic acid can be used. As examples of such plasticizers, many plasticizers widely used for vinyl chloride polymers can be used, but preferably, phthalate esters, adipic esters, glycolic acid derivatives, ether ester derivatives, glycerin derivatives, alkyl A single or a plurality of mixtures selected from phosphate esters, dialalkylates, diesters, tricarboxylic esters, polyesters, polyglycol diesters, alkyl alkylate diesters, aliphatic diesters, alkylate monoesters, citrates, and aromatic hydrocarbons Can be used. More specifically, the plastic component is preferably a single or a plurality of mixtures selected from dimethyl phthalate, diethyl phthalate, ethylphthalylethyl glycolate, triethylene glycol diacetate, ether ester, tributyl acetylcitrate, and triacetin. .

Regarding the solubility parameter (SP) value,
Generally, it is known that those having close SP values have high compatibility. Since the lactic acid-based polymer has an SP value of about 9.7,
A plasticizer having a P value of 9.0 to 11.0 is preferred. More preferably, it is 9.5 to 10.5. In particular, a higher SP value than a lactic acid-based polymer tends to have higher compatibility than a lower lactic acid-based polymer. If it is smaller than 9.0 or larger than 11.0, the compatibility is poor and the transparency is reduced.

The weight average molecular weight of the plastic component is from 100 to 50.
00 is preferable, and 200-3000 is more preferable. When the weight average molecular weight is less than 100, a sufficient plasticizing effect cannot be obtained, and when it is more than 5,000, a sufficient plasticizing effect cannot be obtained, and the molecular properties of the plasticizer become remarkable, and heat resistance and transparency are reduced. Is not preferred. The amount of the plastic component is not particularly limited, but is 1 to 500 parts by weight, preferably 5 to 100 parts by weight, based on 100 parts by weight of the lactic acid polymer. If the amount of the plasticizer is less than 5 parts by weight, the softening temperature of the lactic acid-based polymer cannot be sufficiently lowered, and if the amount is more than 100 parts by weight, the efficiency of the copolymerization reaction decreases. Specifically, for example,
As a compounding example effective for plasticizing the lactic acid-based polymer, dimethyl phthalate 10 to 10 parts by weight of the lactic acid-based polymer is used.
100 parts by weight, and / or diethyl phthalate
100 parts by weight can be used. Alternatively, similarly, as triacetin and / or triethylene glycol diacetate and ether ester, R made by Asahi Denka Kogyo KK
S1000 may be used. By using these plastic components, while maintaining the transparency and hue of the lactic acid composition,
Its softening temperature can be lowered. As a result, the color of the copolymer can be kept good, and a sufficient plastic effect can be imparted to the molded article.

The lactic acid polymer has a weight average molecular weight of 10,000 or more, preferably 50,000 to 30.
It is 0000.

Next, the manufacturing method will be described in order. A lactic acid polymer and a plastic component are melt-mixed in advance. A known method can be used to plasticize the lactic acid polymer with a plastic component. For example, 10 to 50 parts by weight of dimethyl phthalate and 10 to 50 parts by weight of diethyl phthalate are added to 100 parts by weight of the lactic acid polymer.
It is obtained by extruding at 180 ° C., stirring and melting and mixing under a nitrogen atmosphere. When the lactic acid polymer and the plastic component are melt-mixed in advance, it is preferably performed in a dry nitrogen stream, for example, at 180 ° C. in order to prevent water from being mixed.
The temperature of the melt mixing is preferably equal to or higher than the melting temperature of the lactic acid polymer. If the melting temperature is too high, the plastic component is volatilized and reduced, and the physical properties of the composition become insufficient. It is preferable to carry out within the range. Next, a branched / crosslinked structure is prepared from the obtained mixture. As a method of initiating the branching / crosslinking reaction, a method of adding a radical initiator such as a peroxide, or a method in which the wavelength is 400 nm or less and the intensity is 120
A known method such as a method of irradiating an electron beam of mW / cm ² or more can be used. For example, a reaction is carried out by adding 0.1 to 10 parts by weight of peroxide to 100 parts by weight of the mixture.

When the lactic acid polymer and the plastic component are melt-mixed, a branching / crosslinking reaction can occur simultaneously. For example, when using a biaxial horizontal reactor for the polymerization reaction, a lactic acid polymer and a plastic component may be added simultaneously with a radical initiator or the like, and the above-mentioned electron beam is applied when the lactic acid-based polymer and the plastic component are melted and mixed. Irradiation may be performed to effect a mixed reaction. Further, it is also possible to melt and mix the lactic acid-based polymer and the plastic component, and to perform a reaction by irradiating an electron beam again to a material to which a reaction initiator such as acrylic acid is added.

When only the reaction initiator is introduced from the middle, the lactic acid polymer and the plastic component can be melt-kneaded in advance, so that the temperature at the point where the initiator is introduced can be lowered and the reaction can proceed slowly. And the reaction can be performed without lowering the activity of the initiator. The reaction temperature is in the range of 120 to 180 ° C. Reaction temperature 12
When the temperature is lower than 0 ° C., the reaction does not proceed sufficiently, and the reaction at a temperature higher than 180 ° C. is not preferable because the deterioration of the reaction initiator is promoted and the decomposition reaction of the lactic acid polymer by the reaction intermediate is promoted. In addition, the plastic component may be volatilized and may be lost, and the desired physical properties may not be obtained. In the case of using a biaxial horizontal reactor, for example, when the reaction is performed at 120 to 180 ° C., the residence time is 5 to 20 minutes, and the reaction proceeds sufficiently, depending on the relationship with the reaction temperature. A branched / crosslinked structure copolymer of a polymer and a plastic component can be obtained.

The obtained copolymer is a thermoplastic resin having a flexible property in which a plastic component is contained in the molecular structure. The molding temperature of this copolymer can be set lower than that of polylactic acid alone, and there is little molecular degradation during molding, and it is difficult to color, and a transparent molded article can be obtained. Further, since the molding temperature can be set low, the cooling time after molding can be shortened, and good moldability is exhibited. The flexibility of the copolymer can be controlled by appropriately changing the composition and the amount of the plastic component used. further,
By exposing under a reduced pressure in a molten state at the latter stage of the reaction or after the completion of the reaction, unreacted lactide monomers and reaction by-products remaining about 1 to 3% can be removed.

As a specific method of the decompression treatment, the latter half of the biaxial horizontal reactor is heated at 120 to 160 ° C. and 1 to 50 ° C.
It is possible to maintain the pressure at Torr, and to retain and devolatilize for 3 to 15 minutes. The lactide monomer and the copolymer from which by-products have been removed in this manner can provide an excellent copolymer having greatly improved stability over time. In a simple blend of a lactic acid polymer and a plastic component, the plastic component bleeds out of the system as the lactic acid polymer crystallizes, and the effect of lowering the transition point decreases. When unreacted substances and by-products cannot be sufficiently removed and remain, they may contribute as a hydrolysis accelerator.

The copolymer of the present invention can be prepared in a known reaction vessel in addition to the above-described two-axis horizontal reaction apparatus.
A vertical reaction vessel or a horizontal reaction vessel provided with a shaft or a plurality of shaft stirrers, a horizontal reaction vessel provided with a scraping blade of one or more shafts, or a kneader of one or more shafts, 1
A single or multiple-screw extruder or other reactor may be used alone, or a plurality of reactors may be connected in series or in parallel.

The composition of the present invention can be modified in various ways by adding a secondary additive. Examples of secondary additives include ultraviolet absorbers, pigments, colorants, various fillers, electrostatic agents, release agents, fragrances, antibacterial agents, nucleating agents, stabilizers such as antioxidants and regulators, and the like. , And other similar ones. Furthermore, it is also possible to add and use a plasticizer as a secondary plasticizer as needed.

In the present invention and the following examples, the weight average molecular weight of a polymer is measured by GPC analysis in terms of polystyrene, and the glass transition point, crystallization point, and melting point of the polymer are measured by a scanning differential calorimeter (DSC). Value. The dynamic viscoelasticity was measured by a dynamic viscoelasticity measuring device DVA-300 manufactured by Shimadzu Corporation in accordance with JIS K7198A method.

[0026]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples below, but the present invention is not limited to these examples. In this example, an experiment was conducted using the following lactic acid-based polymer, plasticizer, and peroxide. <Lactic acid polymer A (P1)> To 90 parts by weight of L-lactide, 10 parts by weight of D-lactide were added and melt-mixed under an inert gas atmosphere.
After polymerizing at 190 ° C. for 15 minutes while stirring with 24 parts by weight of a twin-screw kneader, the mixture was extruded with a nozzle having a diameter of 2 mm, cooled with water and cut to obtain a low-crystalline polylactic acid chip C1.
The chip C1 was treated in nitrogen at 120 ° C. and a pressure of 1.5 kg / cm ² for 12 hours to remove unreacted monomer (lactide), thereby obtaining a chip P1. The weight average molecular weight of the chip P1 is 168,000, and the remaining monomer (lactide) is
It was less than 0.5%. As a result of DSC measurement, the glass transition temperature was 55.3 ° C, the crystallization temperature was 144.9 ° C, and the melting point was 175.7 ° C.

<Lactic acid polymer B (P2)> To 75 parts by weight of L-lactide, add 25 parts by weight of D-lactide, melt and mix under an inert gas atmosphere, and add 0.24 part by weight of tin octylate as a ring-opening polymerization catalyst. Part, while stirring with a twin-screw kneader
After polymerization at 15 ° C for 15 minutes, the mixture was extruded with a nozzle having a diameter of 2 mm, cooled with water and cut to obtain an amorphous polylactic acid chip C2.
I got Chip C2 is heated at 120 ° C. under a pressure of 1.5 kg / c
The mixture was treated in nitrogen of m ² for 12 hours to remove unreacted monomer (lactide), thereby obtaining chip P2. The chip P2 had a weight average molecular weight of 117,000 and a residual monomer (lactide) of 1.5% or less. As a result of DSC measurement, the glass transition temperature was 51.7 ° C., and the crystallization temperature and melting point were not observed.

<Plastic component: triacetin (manufactured by Daihachi Chemical Industry Co., Ltd.) (S1)> Acid value: 0.05 or less, hue (APHA): 20 or less, molecular weight: 218, specific gravity (20/20 ° C.): 1 .160 ±
0.003, solubility parameter (HOY): 9.9

<Peroxide: Kayahexa AD40C (manufactured by Kayaku Akzo Co., Ltd.) (O1)> Content: 40%, active oxygen content: 4.4%, molecular weight: 29
0.44, 10 hour half-life temperature: 118 ° C., activation energy: 36.0 kcal / kmol (CAS No.
78-63-7)

(Example 1) 100 parts by weight of P1 and 40 parts by weight of S1 were sufficiently melt-mixed with a twin-screw extruder at 190 ° C., and 2.5 parts by weight of O1 was melt-mixed with P1. After the addition, the mixture was mixed and reacted for an average of 5 minutes, extruded with a nozzle having a diameter of 2 mm, cooled with water, and cut to obtain a lactic acid-based polymer chip (PC1). After vacuum drying the chip PC1 at 60 ° C. to make it absolutely dry, a business card large plate (1 mmt) was prepared by injection molding, and dynamic viscoelasticity was measured. FIG. 1 shows the results of the dynamic viscoelasticity measurement. According to this figure, the dynamic storage modulus is 1.5 × 10 ^{6 to} 1.2 × 10 ⁷ and the loss angle tangent is 0.15 to 10 ° C. in the temperature range from the transition temperature to 10 ° C. to 150 ° C. It turns out that it is 0.25.

Example 2 100 parts by weight of P2 and 40 parts by weight of S1 were sufficiently melt-mixed with a twin screw extruder at 190 ° C., and 2.5 parts by weight of O1 was melt-mixed with P2. After the addition, the mixture was reacted for an average of 5 minutes, extruded through a nozzle having a diameter of 2 mm, cooled with water, and cut to obtain a lactic acid-based polymer chip (PC2). After vacuum drying the chip PC2 at 60 ° C. to make it absolutely dry, a business card large plate (1 mmt) was prepared by injection molding, and dynamic viscoelasticity was measured. FIG. 2 shows the results of the dynamic viscoelasticity measurement. According to this figure, the dynamic storage modulus is 9.0 × 10 ^{4 to} 1.5 × 10 ⁶ in the temperature range from the transition temperature of 20 ° C. and from the transition temperature to 150 ° C., and the loss tangent is 0.3 to It turns out that it is 1.0.

(Comparative Example 1) 100 parts by weight of P1 and 40 parts by weight of S1 were melt-mixed with a twin-screw extruder at 190 ° C for an average of 5 minutes, extruded with a nozzle having a diameter of 2 mm, cooled with water, and cut. A lactic acid-based polymer chip (RP1) was obtained. After vacuum drying the chip RP1 at 60 ° C. to make it completely dry,
A business card large plate (1 mmt) was prepared by injection molding, and dynamic viscoelasticity was measured. FIG. 3 shows the results of the dynamic viscoelasticity measurement. From this figure, the transition temperature is 20 ° C.,
The dynamic storage modulus in the temperature range up to 50 ° C. is 8.0.
× 10 ^{5 to} 8.0 × 10 ⁶ , and the loss angle tangent is 0.1 to 0.
25.

(Comparative Example 2) 100 parts by weight of P2 and 40 parts by weight of S1 were melt-mixed with a twin screw extruder at 190 ° C for an average of 5 minutes, extruded with a nozzle having a diameter of 2 mm, water-cooled and cut. A lactic acid-based polymer chip (RP2) was obtained. After vacuum drying the chip RP2 at 60 ° C. to make it completely dry,
A business card large plate (1 mmt) was prepared by injection molding, and dynamic viscoelasticity was measured. FIG. 4 shows the results of the dynamic viscoelasticity measurement. From this figure, the transition temperature is 25 ° C.
In the temperature range up to 0 ° C., the dynamic storage modulus is 1.0 ×
10 ^{4 to} 1.8 × 10 ⁶ , loss angle tangent is 0.3 to 2.0
It turns out that it is. However, it can be seen that the temperature range is narrow, each value changes dramatically, and drawdown occurs in a temperature range of 90 ° C. or higher.

[0034]

According to the present invention, the lactic acid-based polymer exhibits a stable value in a temperature range of room temperature or higher without reducing the loss angle tangent value. This composition has stability over time.

[Brief description of the drawings]

FIG. 1 is a diagram showing the results of dynamic viscoelasticity measurement of Example 1.

FIG. 2 is a diagram showing the results of dynamic viscoelasticity measurement in Example 2.

FIG. 3 is a diagram showing the results of dynamic viscoelasticity measurement of Comparative Example 1.

FIG. 4 is a diagram showing the results of dynamic viscoelasticity measurement of Comparative Example 2.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) G10K 11/162 G10K 11/16 A 11/16 J F term (Reference) 3J048 AA01 AC01 BA01 BD01 4J002 CF002 CF191 CH002 ED026 EH006 EH046 EH056 EH086 EH096 EH146 EH156 EW046 FD026 GG01 GG02 GL00 GM00 5D061 AA06

Claims (4)

[Claims] 1. A dynamic viscoelasticity measurement (JI) comprising a branched or networked lactic acid-based polymer composed of a main chain structural component containing a lactic acid component having a weight fraction of 50% or more and a plastic component.
SK7198A method), the transition temperature is 30 ° C. or lower, and the dynamic storage modulus is 1 × 10 ⁴ to 1 × 10 ⁸ Pa and the loss angle tangent is 0.1 in the temperature range from the transition temperature to 150 ° C. A lactic acid-based composition of about 3.0. 2. A lactic acid-based polymer having a weight average molecular weight of 10,
000 or more and a weight average molecular weight of 100 to 5,0
A solubility parameter (SP) value of 9.0 to 11.0 at 00
2. The lactic acid composition according to claim 1, wherein the plastic component is 3. A plasticizer comprising a phthalic acid ester, an adipic acid ester, a glycolic acid derivative, an ether ester derivative, a glycerin derivative, an alkyl phosphate, a dialkylater, a diester, a tricarboxylate, a polyester, a polyglycol diester, an alkylalkylate diester, It is a single or a plurality of mixtures selected from aliphatic diesters, alkylator monoesters, citrates, and aromatic hydrocarbons.
3. The lactic acid composition according to 2. 4. A vibration damping material, a vibration damping material or a shock absorbing material comprising the composition according to claim 1.