JP2003342452A - Injection molding - Google Patents

Abstract

(57) [Problem] To provide a biodegradable injection-molded article having excellent impact resistance and heat resistance without substantially impairing the biodegradability inherent in lactic acid-based resins. SOLUTION: The injection molded article is an injection molded article composed of a resin composition containing a lactic acid-based resin, an aliphatic polyester other than the lactic acid-based resin, and a plasticizer, and has a solubility parameter of a component constituting the resin composition ( SP value) is an inequality
SP value of lactic acid-based resin> SP value of aliphatic polyester other than lactic acid-based resin> SP value of plasticizer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biodegradable injection-molded article, and more particularly to a biodegradable injection-molded article having excellent impact resistance and heat resistance.

[0002]

2. Description of the Related Art Due to increasing environmental problems in recent years, when plastic products are discarded in the natural environment, they will decompose over time.
It is beginning to be demanded that it disappears and eventually 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 resin materials have attracted attention. Biodegradable resin can be used in soil or water,
Hydrolysis and biodegradation gradually cause disintegration / decomposition,
It is known that the action of microorganisms will eventually result in a harmless decomposed product. Also, waste can be easily treated by composting.

Biodegradable resins that have been put into practical use include aliphatic polyesters, modified PVA, cellulose ester compounds, starch modified products, and blends thereof. Each of these biodegradable resin materials has its own characteristic, and it can be considered to be used in accordance with this characteristic. Of these, aliphatic polyesters have begun to be widely used because of their wide range of properties and processability similar to general-purpose resins. In addition, among the aliphatic polyesters, lactic acid-based resins are excellent in transparency, rigidity, heat resistance, etc., and therefore, have attracted attention in the field of film packaging and injection molding as substitute materials for polystyrene and polyethylene terephthalate.

However, since lactic acid-based resins are inherently brittle, it is very difficult to use them in applications requiring impact resistance. For example, in the field of sheets and films, it is generally known that the impact resistance can be improved by blending an aliphatic polyester other than a lactic acid resin. However, in an injection-molded article, a sufficient impact resistance improving effect cannot be obtained only by blending polylactic acid with an aliphatic polyester.

Japanese Patent Laid-Open No. 2000-273207 discloses that
A method of improving impact resistance by blending a lactic acid-based resin, an aliphatic polyester other than the lactic acid-based resin, and a plasticizer is disclosed. However, in this method, the plasticizer lowers the glass transition temperature of the lactic acid-based resin and impairs heat resistance.
Moreover, the effect of the plasticizer on the impact resistance is not clear,
A sufficient impact resistance improving effect cannot be obtained.

Further, Japanese Patent Application Laid-Open No. 11-116784 discloses a method for improving impact resistance by adding a fatty acid ester to polylactic acid and crystallizing it.
However, in this method, the fatty acid ester acts as a nucleating agent to improve impact resistance, while it acts as a plasticizer, resulting in a marked decrease in heat resistance. In addition, since the elastic modulus at room temperature decreases, it cannot be used for applications requiring hardness.

[0007] Normally, molded articles used as home electric appliance parts and vehicle parts are required to have impact resistance depending on their applications. Therefore, Izod impact strength (notch) measured according to JIS K-7110 23k) is 15k
A resin having a J / m ² or more is selected. Similarly, from the viewpoint of heat resistance, the storage elastic modulus E'in dynamic viscoelasticity measurement is 1 G.
A resin is selected that has a temperature of decreasing to Pa of 55 ° C. or higher.

[0008]

An object of the present invention is to provide a biodegradable injection-molded article having excellent heat resistance and impact resistance.

[0009]

The present inventors have completed the present invention as a result of intensive studies in view of such a current situation. That is, the injection-molded article of the present invention is an injection-molded article composed of a resin composition containing a lactic acid-based resin, an aliphatic polyester other than the lactic acid-based resin, and a plasticizer, and has solubility parameters of components constituting the resin composition ( SP
Value) is in the relationship of SP value of lactic acid resin> SP value of aliphatic polyester other than lactic acid resin> SP value of plasticizer.

The SP value of the lactic acid resin is 1
1.00 to 11.20 (cal / cm ³)^1/2, The lactic acid
SP value of aliphatic polyester other than the system resin is 10.0
1-10.99 (cal / cm³)^1/2, The plasticizer S
P value is 8.50 to 10.00 (cal / cm³)^1/2so
Can be The resin composition is a lactic acid-based resin.
The fat and the aliphatic polyester other than the lactic acid resin, 6
It is contained at a ratio within the range of 0:40 to 90:10, and
Of lactic acid-based resins and aliphatic polyesters other than lactic acid-based resins
0.5 to 6 parts by weight of plasticizer for 100 parts by weight in total
Parts can be compounded. Further, the resin composition is
In addition, an inorganic filler can be contained. Also, the above
The resin composition further contains a carbodiimide compound
be able to. The resin composition is a lactic acid resin.
And an aliphatic polyester other than lactic acid resin, and a plasticizer
And the total amount of the inorganic filler is 100 parts by mass,
Add 0.5 to 10 parts by mass of rubodiimide compound
You can In addition, the injection molded body should be in the range of 60 to 130 ° C.
It is preferable that the heat treatment is performed at the temperature of. Also,
Izod impact measured according to JIS K-7110
Impact strength is 15 kJ / m²And above, and storage elastic modulus
The temperature at which E ′ drops to 1 MPa is 55 ° C. or higher.
You can

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below. The lactic acid-based resin used in the present invention includes poly (L-lactic acid) whose structural unit is L-lactic acid, poly (D-lactic acid) whose structural unit is D-lactic acid, L-lactic acid and D-lactic acid whose structural unit is L-lactic acid. Which is a poly (DL-lactic acid) or a mixture thereof, and further, a copolymerization weight with other hydroxycarboxylic acid units such as α-hydroxycarboxylic acid and (aliphatic) diol / (aliphatic) dicarboxylic acid. It may be a combination. However, at this time, the DL structure of the lactic acid-based resin is L body: D body = 100: 0.
~ 90: 10, or L body: D body = 0: 100 to 1
It is preferably 0:90, and L-form: D-form = 100:
0-94: 6, or L-body: D-body = 0: 100-
It is more preferably 6:94. Outside this range, the heat resistance of the component is difficult to obtain, and the application may be limited. Typical lactic acid resins include Shimadzu's Lacty series, Mitsui Chemicals' LACEA series, and Cargill Dow's Nature Works series.

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 condensation polymerization method, L-lactic acid or D-lactic acid,
Alternatively, a lactic acid resin having an arbitrary composition can be obtained by directly subjecting the mixture to dehydration polycondensation. 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. L-lactide, which is a dimer of L-lactic acid, and 2 of D-lactic acid, are included in lactide.
There is D-lactide which is a monomer, and DL-lactide which is composed of L-lactic acid and D-lactic acid, and a lactic acid-based resin having an arbitrary composition and crystallinity is obtained by mixing and polymerizing these as needed. be able to.

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 may be used for the purpose of increasing the molecular weight.

The 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 50,000 to 4
It is preferably in the range of 0,000, and more preferably 100,000 to 250,000. When the weight average molecular weight of the lactic acid resin is less than 50,000, practical physical properties are hardly exhibited and 4
If it is more than 0,000, the melt viscosity tends to be too high, resulting in poor moldability.

Examples of the aliphatic polyester other than the lactic acid 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 cyclic lactones, and a synthetic aliphatic polyester. Examples thereof include polyester.

The aliphatic polyester obtained by condensing the aliphatic diol with the aliphatic dicarboxylic acid is an aliphatic diol such as ethylene glycol, 1,4-butanediol, or 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 and dodecanedioic acid, which are dicarboxylic acids. If desired, the desired polymer can be obtained by jumping up with an isocyanate compound or the like. As a concrete example,
Examples include Bionore series manufactured by Showa High Polymer Co., Ltd., Enpole manufactured by Ile Chemical Co., Ltd., and the like.

Typical examples of the aliphatic polyester obtained by ring-opening polymerization of the cyclic lactones include cyclic monomers ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone and the like. More than one type is selected and polymerized. As a specific example, cell green series manufactured by Daicel Chemical Industries, Ltd. can be mentioned.

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.

From the viewpoint of the effect of improving impact resistance, it is preferable that the aliphatic polyester other than the lactic acid resin has a glass transition temperature (Tg) of 0 ° C. or lower. The aliphatic polyester having a glass transition temperature (Tg) of 0 ° C. or lower is
It acts like a rubber on the lactic acid resin and imparts impact resistance to the injection-molded article of the present invention. Further, the plasticizer dissolves in the rubber-like component and swells the aliphatic polyester, whereby the impact resistance can be further enhanced.

The solubility parameter (SP value) of the plasticizer used in the present invention is preferably lower than the SP value of the aliphatic polyester other than the lactic acid resin, and S
Those having a P value in the range of 8.50 to 10.00 (cal / cm ³ ) ^1/2 are preferable. In the present invention, the SP value means the Fedors method [Polym. Eng. Sci. 1
4 (2) 152, (1974)] from the structural formula. Specific examples of the plasticizer preferably used in the present invention include adipic acid esters such as dimethyl adipate, diisobutyl adipate, di-2-ethylhexyl adipate, diisononyl adipate, diisodecyl adipate, dibutyl sebacate, di-2-ethylhexyl sebacate and the like. Sebacate, di-2-
Azelaic acid ester such as ethylhexyl azelate, phthalic acid ester such as dibutyl phthalate, diisononyl phthalate, di-2-ethylhexyl phthalate, diheptyl phthalate, diisodecyl phthalate, tributyl trimellitate, tri-2-ethylhexyl trimellitate, etc. Examples include meritic acid ester.

When the SP value of the plasticizer is larger than the SP value of the aliphatic polyester other than the lactic acid resin, the plasticizer is compatible with the lactic acid resin, and a large amount of the plasticizer is present in the lactic acid resin. Not only does the aliphatic polyester other than the swelling resin not swell, but also the lactic acid resin is plasticized, resulting in a decrease in heat resistance. Further, if the SP value of the plasticizer is less than 8.50, the compatibility of both the lactic acid resin and the aliphatic polyester other than the lactic acid resin decreases, and bleeding out on the surface of the injection-molded product easily occurs. Top problems are likely to occur.

The lactic acid-based resin, the aliphatic polyester other than the lactic acid-based resin, and the plasticizer contained in the resin composition according to the present invention are represented by the following inequality: SP value of lactic acid-based resin> fat other than lactic acid-based resin SP value of group polyester> SP of plasticizer
If selected so as to satisfy the value, the plasticizer is transferred to an aliphatic polyester other than the lactic acid-based resin, which has a higher SP value and higher compatibility than the lactic acid-based resin, and the aliphatic polyester swells. The impact resistance of the injection molded article obtained is improved. In the present invention, the SP value of the lactic acid resin is 11.
It is preferably in the range of 00 to 11.20 (cal / cm ³ ) ^1/2 . Further, SP values of aliphatic polyesters other than lactic acid-based resins are 10.01 to 10.99 (cal / c
It is preferably within the range of m ³ ) ^1/2 .

The mixing ratio of the lactic acid resin and the aliphatic polyester other than the lactic acid resin is 60: 40-9 by mass ratio.
It is preferably within the range of 0:10, and 65:35.
More preferably, it is within the range of 85:15. By blending the lactic acid-based resin and the aliphatic polyester other than the lactic acid-based resin in such a range, an injection molded article having excellent heat resistance and impact resistance can be obtained.

The amount of the plasticizer added is 0.5 to 100 parts by weight of the total amount of the lactic acid resin and the aliphatic polyester.
It is preferable to mix 6 parts by mass, and more preferably 1 to 5 parts by mass. By blending the plasticizer within such a range, the resulting injection-molded article can improve impact resistance without impairing heat resistance.

Regarding the heat treatment conditions for the injection-molded article of the present invention, the heat treatment temperature is preferably in the range of 60 to 130 ° C, and more preferably in the range of 65 to 90 ° C. If the heat treatment temperature is in the range of 60 ° C to 130 ° C,
The thermal movement of the plasticizer is large, and the plasticizer impregnated in the lactic acid-based resin is easily released outside the system due to crystallization of the lactic acid-based resin, so that the plasticizer is easily transferred to the aliphatic polyester. Then, the aliphatic polyester other than the lactic acid resin swells, and the impact resistance is improved. Further, since the plasticizer in the lactic acid-based resin is reduced, the plasticization of the lactic acid-based resin is restored and the glass transition temperature is improved, that is, the heat resistance is improved.

The heat treatment time for preventing the molded body from being deformed or shrunk is appropriately determined depending on the composition and the heat treatment temperature. For example, when the heat treatment temperature is 70 ° C., it is in the range of 15 minutes to 5 hours. It is preferable to perform the heat treatment within 10 seconds to 30 seconds when the heat treatment temperature is 130 ° C.
It is preferable to perform the heat treatment within the range of minutes. The method of heat treatment is to raise the temperature of the mold after injection molding to perform heat treatment in the mold, or to take out the injection-molded body from the mold without heat treatment and then use hot air, steam, hot water, far infrared rays. A method of performing heat treatment with a heater, an IH heater or the like can be mentioned. At this time, in order to prevent the deformation of the injection-molded body, it is preferable to fix it with a mold or a resin mold. Further, if heat treatment is performed in the packaged state, the productivity is improved.

In the present invention, by adding an inorganic filler to the resin composition, the effect of preventing deformation at the time of releasing from the mold and the effect of preventing shrinkage and warpage during heating can be obtained. The addition amount of the inorganic filler is preferably in the range of 5 to 30% by mass, and more preferably 10 to 20% by mass in the total amount of the resin composition.

Specific examples of the inorganic filler used in the present invention include talc, kaolin, calcium carbonate, bentonite, mica, sericite, glass flakes, graphite,
Magnesium hydroxide, aluminum hydroxide, antimony trioxide, barium sulfate, zinc borate, hydrous calcium borate, alumina, magnesia, wollastonite, xonotlite, sepiolite, whiskers, glass fibers, metal powder, beads, silica balloons, shirasu Examples thereof include balloons and organic balloons. Further, by treating the surface of the inorganic filler with titanic acid, a fatty acid, a silane coupling agent or the like, it is possible to improve the adhesiveness with the resin and improve the effect of the inorganic filler.

A molded article containing a large amount of an aliphatic polyester resin is hydrolyzed due to water vapor in the air or moisture in the contents or moisture from the outside during long-term storage or long-term use, resulting in deterioration of mechanical properties. There was a big problem in practice. In particular, in an atmosphere of high temperature and high humidity of 60 ° C. and 60% RH or more, decomposition may occur in a short period of time, and the molded body may decompose in several hours to several weeks. From the viewpoint of hydrolysis resistance, under an atmosphere of 85 ° C. and 80% RH,
70% molecular weight retention in 100-hour wet heat test
The above is practically preferable.

In order to impart hydrolysis resistance to the injection-molded article of the present invention, the total amount of lactic acid-based resin, aliphatic polyester resin other than lactic acid-based resin, plasticizer, and inorganic filler is 100 parts by mass. On the other hand, the carbodiimide compound is 0.5 to
It is effective to add within the range of 10 parts by mass. If the addition amount of the carbodiimide compound is within such a range,
The effect of improving the hydrolysis resistance is good, and the appearance of the molded product due to bleeding out of the carbodiimide compound does not deteriorate, and the mechanical properties do not deteriorate due to plasticization. Further, biodegradability and compost degradability are not impaired.

The carbodiimide compounds preferably used in the present invention include those having a basic structure of the following general formula. -(N = C = NR-) _n -In the formula, n represents an integer of 1 or more, and R represents an organic bond unit. Usually, n is appropriately set between 1 and 50. Examples of R include aliphatic, alicyclic and aromatic bond units.

Specifically, for example, poly (4,4'-diphenylmethanecarbodiimide), poly (p-phenylenecarbodiimide), poly (m-phenylenecarbodiimide), poly (tolylcarbodiimide), poly (diisopropylphenylenecarbodiimide), Poly (methyl-
Diisopropyl phenylene carbodiimide), poly (triisopropyl phenylene carbodiimide), etc., and these monomers are mentioned. In the present invention, the carbodiimide compounds may be used alone or in combination of two or more kinds.

In the resin composition, additives such as heat stabilizers, antioxidants, UV absorbers, light stabilizers, pigments, colorants, lubricants, nucleating agents, etc. are added to the extent that the effects of the present invention are not impaired. Can be prescribed.

Next, a method for molding an injection molded body according to the present invention will be described. The lactic acid-based resin, the aromatic-aliphatic polyester, the plasticizer, and, if necessary, the inorganic filler, the carbodiimide compound, and other additives can be mixed by putting the respective raw materials into the same injection molding machine. Injecting raw materials into an injection molding machine, mixing them, and then injection molding from the injection molding machine as it is, or extruding the dry-blended raw materials into a strand shape using a twin-screw extruder to create pellets, then injecting again There is a method of forming an injection molded body using a molding machine.

In any of the methods, it is necessary to consider the decrease in the molecular weight due to the decomposition of the raw materials, but it is preferable to select the latter for uniform mixing. In the present invention, for example, a lactic acid-based resin, an aliphatic polyester and a plasticizer are sufficiently dried to remove water, then melt-mixed using a twin-screw extruder and extruded into a strand shape to form pellets. However, in consideration of the fact that the melting point of the lactic acid-based resin changes depending on the composition ratio of the L-lactic acid structure and the D-lactic acid structure, and the melting point of the mixed resin changes depending on the mixing ratio of the aliphatic polyester, the melt extrusion temperature Is preferably selected as appropriate. In practice, a temperature range of 100-250 ° C is usually selected.

The pellets produced by the above method are sufficiently dried to remove water, and then injection molded. The injection molding method of the present invention is not particularly limited, but typical injection molding methods such as general injection molding method for thermoplastic resin, gas assist molding method and injection compression molding method can be adopted. . In addition to the above methods, an in-mold molding method, a gas press molding method, a two-color molding method, a sandwich molding method, PUSH-PULL, SCORIM and the like can be adopted according to other purposes.

The injection molding apparatus includes a general injection molding machine, a gas assist molding machine, an injection compression molding machine and the like, and molding dies and auxiliary equipment used for these, a mold temperature control device, a raw material drying device and the like. Composed. The molding conditions are preferably such that the temperature of the molten resin is 170 ° C. to 210 ° C. in order to avoid thermal decomposition of the resin in the injection cylinder.

When the injection molded body is obtained in an amorphous state, the mold temperature is set as low as possible in order to shorten the cooling time of the molding cycle (mold closing-injection-holding pressure-cooling-mold opening-unloading). It is preferable. Mold temperature is generally 15 ℃
It is ~ 55 ° C, and it is also desirable to use a chiller. However, when performing heat treatment outside the mold, shrinkage or warpage of the molded body,
In order to suppress the deformation, it is advantageous to raise the temperature within this range.

Further, in the case of the "inorganic filler filling system" in which the inorganic filler is added to the resin composition, when the filling amount of the inorganic filler is large, flow marks may occur on the surface of the molded product. At this time, the injection speed is preferably lower than the injection speed of the "unfilled system" in which the resin composition is not filled with the inorganic filler. For example, when a resin composition containing 15% by mass of talc is injection-molded with an injection molding machine having a screw diameter of 25 mm equipped with a plate mold having a thickness of 2 mm, if the injection speed is 30 mm / sec or less, molding without flow marks I got a body. In the case of unfilled resin, flow marks did not occur even at 50 mm / sec.

If sink marks are likely to occur, it is preferable that the holding pressure and the holding time are sufficient. For example, the holding pressure is preferably set in the range of 30 MPa to 100 MPa, and the holding time is appropriately set in the range of 1 second to 15 seconds depending on the shape and wall thickness of the molded body. When molding the above-mentioned plate having a thickness of 2 mm, the holding time is about 3 seconds.

In order to perform the heat treatment in the mold, the molten resin is filled in the heated mold and then held in the mold for a certain period of time. The mold temperature is preferably 60 ° C to 130 ° C, more preferably 70 ° C to 90 ° C.
If the mold temperature is lower than 60 ° C, it takes a long time for heat treatment,
The cycle becomes too long. On the other hand, if the temperature exceeds 130 ° C, deformation may occur at the time of release.

Since the injection-molded article of the present invention has excellent heat resistance, impact resistance, and hydrolysis resistance, it can be used for household appliances,
It can be used as automobile parts and other general molded products in the same manner as conventional resins. For example, according to the present invention, a calculator type molded body can be formed. FIG. 1A is a plan view of a calculator-type molded body which is one of the embodiments of the present invention, and FIG. 1B is a front view thereof. 1 to 6 are perforated portions of the through holes, 1 is a window portion for displaying calculation results,
Reference numerals 2 and 3 are key portions for numbers and the like, and reference numerals 4, 5 and 6 are portions for hooking.

[0045]

EXAMPLES The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto. The measured values shown in the examples were calculated by measuring under the following conditions. The SP values shown in the examples and comparative examples are based on the Fedors method [Poly
m. Eng. Sci. 14 (2) 152, (197
4)] is a value calculated from the structural formula.

(1) Impact resistance A No. 1 A test piece was prepared based on JIS K-7110, and the Izod impact strength in the edgewise direction at 23 ° C. was measured. The Izod impact strength was set to 15 kJ / m ² or more as a practical standard.

(2) Heat resistance Viscoelasticity spectrometer "VE" manufactured by Iwamoto Manufacturing Co., Ltd.
S-F3 "was used to increase the temperature at a vibration frequency of 10 Hz and a temperature of 0 ° C. at a temperature increase rate of 3 ° C./min, and the temperature when the storage elastic modulus E ′ was reduced to 1 GPa was measured. As a practical standard for heat resistance, a practical temperature was 55 ° C. or higher when the storage elastic modulus E ′ decreased to 1 GPa.

(3) Dimensional stability Using an injection molding machine "IS50E" manufactured by Toshiba Machine Co., Ltd., a calculator type amorphous molded body shown in FIG. 1 was obtained. The molding conditions at this time are: cylinder temperature 195 ° C., mold temperature 25 ° C., injection pressure 110 MPa, injection time 1.5 seconds, holding pressure 80 MP.
a, holding time 3.0 seconds, back pressure 10 MPa, screw rotation number 110 rpm. . After conditioning the molded body in the measurement room (temperature 23 ° C, humidity 50% RH) after molding,
The X and Y dimensions in the figure were measured. After that, the annealing treatment was performed under the designated heating condition (temperature and time). However, a constant temperature and constant humidity oven was used for the annealing treatment, and the compact was allowed to stand still without any load.
Immediately after the annealing treatment, the molded body was taken out and the condition was adjusted in the measuring chamber. After adjusting the condition for 24 hours, the X and Y dimensions were measured again, and the shrinkage rate due to the annealing treatment was calculated. A three-dimensional measuring machine was used for the measurement. When the contraction rate of both X and Y is less than 1.0%, the symbol is "○", and when the contraction rate of either X or Y is 1.0 or more and less than 2.0, the symbol is "△", X The symbol "x" indicates that the shrinkage ratios of Y and Y are both 2.0% or more.

(4) Weight-average molecular weight of aliphatic polyester biodegradable resin Using gel permeation chromatography, solvent chloroform, solution concentration 0.2 wt / vol%, solution injection amount 200 μL, solvent flow rate 1.0 mL / Minutes, the solvent temperature was measured at 40 ° C., and the weight average molecular weight of the lactic acid resin was calculated in terms of polystyrene. However, the weight average molecular weight of the standard polystyrene used is 2,000,000, 430
000, 110000, 35000, 10000, 40
00 and 600.

(5) Hydrolysis resistance A wet heat test was conducted under the conditions of 85 ° C. and 80% RH, and 100
The molecular weight retention rate after the lapse of time was calculated by the following formula.
The molecular weight retention rate was set to 70% or more as a practical standard.

[Equation 1]

Example 1 Cargill as a lactic acid resin
"Nature Works 4031D" made by Dow
(L-lactic acid / D-lactic acid = 98.5 / 1.5, weight average molecular weight 200,000) and “Bionole 3003” (polybutylene succinate 80 manufactured by Showa High Polymer Co., Ltd.) as an aliphatic polyester other than lactic acid-based resin. Mol% / adipate 20 mol% copolymer) and a plasticizer, Di-2 manufactured by Taoka Chemical Co., Ltd.
-Ethylhexyl adipate (DOA) was put into a 40 mmφ small-sized twin-screw extruder manufactured by Mitsubishi Heavy Industries, Ltd. at a mass ratio of 80: 20: 2, and compounded at 180 ° C to form a pellet. did. The obtained pellets are L100 mm × W100 mm × t using an injection molding machine “IS50E” (screw diameter 25 mm) manufactured by Toshiba Machine Co., Ltd.
Two types of plate materials with different thicknesses of 2 mm or 4 mm (hereinafter referred to as "3 mm plate" and "4 mm plate", respectively)
Was injection molded. The main molding conditions are as follows. 1) Temperature condition: Cylinder temperature (195 ° C), mold temperature (20 ° C) 2) Injection condition: Injection pressure (115 MPa), holding pressure (55 MPa) 3) Measuring condition: Screw rotation speed (65 rpm), back pressure ( Next, the injection-molded body was allowed to stand in a baking tester (“DKS-5S” manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.) and heat-treated at 70 ° C. for 3.5 hours. Izod impact strength using 4 mm plate and storage elastic modulus E'of 1 mm using 2 mm plate
The temperature when the temperature was lowered to a was measured. The results are shown in Table 1.

(Examples 2 and 3) In Example 1, "N
Nature Works 4031D "and Bionore 3
Injection was performed in the same manner as in Example 1 except that the compounding ratio of 003 and DOA was changed to 70: 30: 2 in Example 2 and 70: 30: 5 in Example 3, respectively, by mass ratio. A molded body was created. In addition, heat treatment was performed and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 4) In Example 1, dimethyl adipate (DMA) manufactured by Kurogane Kasei Co., Ltd. was used as a plasticizer, and the compounding ratio of "Nature Works 4031D", Bionole 3003 and DMA was measured. 7 by ratio
In the same manner as in Example 1 except that the time was changed to 0: 30: 2,
An injection molded body was obtained. In addition, heat treatment was performed and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

(Example 5) In Example 1, as the aliphatic polyester other than the lactic acid-based resin, polycaprolactone (manufactured by Daicel Chemical Industries, "Cell Green P-H") was used.
7)) and using "Nature Works 4031
An injection-molded article was obtained in the same manner as in Example 1 except that the compounding ratio of “D”, Cell Green P-H7, and DOA was changed to 70: 30: 2 by mass ratio. In addition, heat treatment was performed in the same manner as in Example 1, and evaluation was performed. The results are shown in Table 1.

[0055]

[Table 1]

(Examples 6 to 8) In Example 1, as the inorganic filler, Micro Ace L1 manufactured by Nippon Talc Co., Ltd. was used, and "Nature Works 4031D", Bionore 1003, Bionore 3003, DOA, and Microace L1 are listed. An injection-molded body was prepared in the same manner as in Example 1 except that the proportions (mass ratios) shown in 2 were used. In addition, heat treatment was performed in the same manner as in Example 1 to obtain impact resistance,
In addition to heat resistance, dimensional stability was evaluated. The results are shown in Table 2.
Shown in.

[0057]

[Table 2]

Comparative Example 1 Instead of the resin composition of Example 1, "Nature Works 4031D" was used.
An injection molded body was prepared in the same manner as in Example 1 except that was used. Moreover, it heat-processed similarly to Example 1, and evaluated. The results are shown in Table 3.

(Comparative Example 2) In Example 1, without adding a plasticizer, "Nature Works 4031D" was prepared.
An injection-molded article was prepared in the same manner as in Example 1 except that "Bionole 3003" was compounded at a mass ratio of 70:30. In addition, heat treatment is performed in the same manner as in Example 1,
An evaluation was made. The results are shown in Table 3.

(Comparative Example 3) DMP (SP value: 10.80) was used as a plasticizer, and "Nature Works" was used.
4031D ”, Bionole 3003, and DMP were compounded in a mass ratio of 70: 30: 5, and an injection-molded body was prepared in the same manner as in Example 1. In addition, heat treatment was performed in the same manner as in Example 1, and evaluation was performed. The results are shown in Table 3.

(Comparative Example 4) TEC (SP value: 11.46) was used as a plasticizer, and "Nature Works" was used.
4031D ”, Bionole 3003, and TEC were compounded in a mass ratio of 70: 30: 5, and an injection molded body was prepared in the same manner as in Example 1. In addition, heat treatment was performed in the same manner as in Example 1, and evaluation was performed. The results are shown in Table 3.

[0062]

[Table 3]

(Examples 9 and 10) "Microace L1" manufactured by Nippon Talc Co., Ltd. was used as an inorganic filler,
Stavaxol P manufactured by Rhein Chemie was used as a carbodiimide compound, and "Nature Works 40" was used.
31D "," Bionore 1003 "," Bionore 30 "
No. 03 ”, DOA,“ Microace L1 ”, and“ Stavaxol P ”were compounded in the proportions shown in Table 4, and an injection molded article was prepared in the same manner as in Example 1. Further, after the heat treatment was performed in the same manner as in Example 1, the above-mentioned hydrolysis resistance was evaluated. The results are shown in Table 4.

[0064]

[Table 4]

As is clear from Tables 1 to 4, Examples 1 to 1
The injection molded product of No. 8 has an Izod impact strength of 15 kJ / m.
² or more, the storage elastic modulus E 'is temperature temperatures above 55 ℃, when reduced to 1 GPa, was found to have excellent impact resistance and heat resistance. Similarly, Examples 9 to 10 were also excellent in impact resistance and heat resistance. In addition, from Table 2, Examples 6 to 8 in which dimensional stability was evaluated
Was found to be of a practical level or better. Table 4
From Examples 9 to 1, the hydrolysis resistance was evaluated.
No. 0 had a molecular weight retention of 70% or more, and was found to have excellent hydrolysis resistance. Since the injection-molded articles of Examples 1 to 10 are biodegradable, they are also excellent from the viewpoint of environmental protection. On the other hand, as is clear from Table 3, the injection molded articles of Comparative Examples 1 and 2 had an Izod impact strength of less than 15 kJ / m ² and were found to be inferior in impact resistance. Further, it was found that the injection-molded articles of Comparative Examples 3 and 4 had a temperature of less than 55 ° C. when the storage elastic modulus E ′ was lowered to 1 GPa, and were inferior in heat resistance.

[0066]

Industrial Applicability According to the present invention, it is possible to provide a biodegradable injection-molded article having excellent impact resistance and heat resistance. In addition, it is possible to provide an injection-molded article that is further resistant to hydrolysis without substantially impairing the inherent biodegradability of the lactic acid resin.

[Brief description of drawings]

FIG. 1A is a plan view of an injection-molded article according to a first embodiment of the present invention, and FIG. 1B is a front view.

[Explanation of symbols]

1-6 Perforated part

Front page continued (51) Int.Cl. ⁷ Identification code FI theme code (reference) // C08L 101/16 C08L 101/16 (72) Inventor Jun Takagi 5-8 Mitsuyacho, Nagahama-shi, Shiga Mitsubishi Plastics Co., Ltd. Company's Nagahama factory F-term (reference) 4F071 AA43 AA81 AA83 AB03 AB18 AB21 AB26 AC10 AC12 AF01 AF23 AF45 AF53 AH07 AH12 BA01 BB05 BC03 BC10 4J002 CF032 CF181 CF191 DA027 DA067 DE077 DE127 DE007 DE077 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ047 DJ037 DJ047 FA037 FA047 FA087 FA107 FD017 FD026 GN00 GQ00 4J200 AA04 AA06 AA16 BA12 BA14 DA26 EA05 EA07 EA11

Claims (8)

[Claims] 1. An injection-molded article comprising a resin composition containing a lactic acid-based resin, an aliphatic polyester other than the lactic acid-based resin, and a plasticizer, wherein the solubility parameter (SP value) of the components constituting the resin composition is An injection-molded article having a relationship of SP value of lactic acid resin> SP value of aliphatic polyester other than lactic acid resin> SP value of plasticizer. 2. The SP value of the lactic acid resin is 11.00.
˜11.20 (cal / cm ³ ) ^1/2 , the SP value of the aliphatic polyester other than the lactic acid resin is 10.01 to 1
^{0.99 (cal / cm 3) 1/2} , SP value of the plasticizer is injected according to claim 1, wherein it is 8.50~10.00 (cal / cm ^{3) 1/2} Molded body. 3. The resin composition comprises a lactic acid resin and an aliphatic polyester other than the lactic acid resin, 60: 40-9.
The content of the lactic acid-based resin and the aliphatic polyester other than the lactic acid-based resin is 100 in the ratio of 0:10.
The injection-molded article according to claim 1, wherein 0.5 to 6 parts by mass of a plasticizer is blended with respect to parts by mass. 4. The injection-molded article according to claim 1, wherein the resin composition further contains an inorganic filler. 5. The injection-molded article according to claim 1, wherein the resin composition further contains a carbodiimide compound. 6. The carbodiimide compound is contained in an amount of 0.5 to 100 parts by mass based on 100 parts by mass of the lactic acid resin, the aliphatic polyester other than the lactic acid resin, the plasticizer, and the inorganic filler in the resin composition. The injection-molded article according to claim 5, wherein 10 parts by mass is added. 7. The injection-molded product according to claim 1, wherein the injection-molded product is heat-treated at a temperature within a range of 60 to 130 ° C. 8. The Izod impact strength measured according to JIS K-7110 is 15 kJ / m ² or more, and the temperature at which the storage elastic modulus E ′ drops to 1 MPa is 55.
The injection-molded product according to any one of claims 1 to 7, which has a temperature of not less than ° C.