JP4808367B2 - Method for producing polylactic acid-based molded body - Google Patents

Description

実施例１〜７で得られた成形体としての容器は、熱湯を注いでも全く変形せず、耐熱性に優れたものであった。また耐衝撃性も優れていた。
【００６５】
比較例１は、タルクを全く使用しなかったため、熱処理した容器の結晶化が不十分で、熱湯を注いだ際に一瞬で変形してしまった。
比較例２は、タルクの添加量が多すぎたため、容器自体が脆く、成形中あるいは成形後における容器の割れが観察された。
【００６６】
比較例３は、ポリ乳酸の光学純度が低かったため、熱処理や結晶核剤を添加することにより結晶化を促しても、ポリ乳酸の結晶化が不十分で、耐熱性に劣る容器であった。
【００６７】
比較例４は、ガラス転移温度０℃以下の芳香族・脂肪族共重合ポリエステル（Ｂ）を使用しなかったため、落球高さが低く、耐衝撃性に劣った容器であった。
比較例５は、ガラス転移温度０℃以下の芳香族・脂肪族共重合ポリエステル（Ｂ）の配合量が多過ぎたため、耐衝撃性に優れるものの、結晶化速度が著しく遅く、このため成型サイクル時間を要することになって工業的な生産の観点から問題であった。
【００６８】
比較例６は、金型内での熱処理温度が１６０℃と高く、ポリ乳酸の融点付近であったため、結晶核が融解してしまい、このため得られた容器は十分結晶化しておらず、したがって耐熱性に劣ったものであった。
【００６９】
比較例７は、金型内での熱処理時間が１００℃とポリ乳酸分子が結晶化するに要する温度まで上がっておらず、処理時間を長くしても結晶化が不十分であり、このため｜ΔＨｍ｜−｜ΔＨｃ｜が９．０Ｊ／ｇにしかならず、耐熱性に劣る容器しか得られなかった。
【００７０】
【発明の効果】
本発明によれば、光学純度と残留ラクチド量とを厳密に調整したポリ乳酸とガラス転移温度が０℃以下の芳香族・脂肪族ポリエステルとタルクとを所定の混合範囲としてシート状物を形成し、このシート状物を真空成形に代表される一般的な成形法によって成形するに際し、成形中の金型内で所定の条件にて熱処理するため、得られる生分解性の成形体の熱的性質は、（｜ΔＨｍ｜−｜ΔＨｃ｜）≧２５Ｊ／ｇとなり、結晶化速度が０．０１０ｍｉｎ^-1以上となり、かつ、厚み５００μｍ当たりの落球高さが２０ｃｍ以上となって、従来のポリ乳酸による成形体では不可能であった熱湯にも耐えうる耐熱性と耐衝撃性を兼ね備えたものとすることができる。
【００７１】
このようにして得られるポリ乳酸系成形体は、耐熱性と耐衝撃性が必要とされる容器、例えば弁当用トレー、どんぶり、皿、コップなどに好適に使用できる他に、夏季の倉庫保管中や運搬中においても変形しないため、蓋材や建材、ボード、文具、ケース、キャリアテープ、プリペイドカード、ＩＣカードなどのカード類、ＦＲＰなど様々な用途にも適用できる。[0001]
BACKGROUND OF THE INVENTION
  The present inventionMethod for producing polylactic acid-based molded bodyAbout.
[0002]
[Prior art]
  In recent years, biodegradable polymers that are decomposed by microorganisms and the like have attracted attention with increasing social demands for environmental protection. Specific examples of biodegradable polymers include aliphatic polyesters such as polybutylene succinate, polycaprolactone and polylactic acid, and aliphatic-aromatic copolymers such as terephthalic acid / 1,4 butanediol / adipic acid copolymer. Examples thereof include polyesters that can be melt-molded, such as polymerized polyesters.
[0003]
  Among the above-mentioned aliphatic polyesters, polylactic acid widely distributed in nature and harmless to animals, plants and animals and animals has a melting point of 140 to 175 ° C. and sufficient heat resistance, and is a relatively inexpensive thermoplastic raw material. Expected to be a degradable resin.
[0004]
  However, when this polylactic acid is simply molded into a sheet or container, the polylactic acid crystals are almost completely melted by the heat history during molding, and only those having poor heat resistance can be obtained.
[0005]
  Therefore, many attempts to impart heat resistance to polylactic acid have been reported. For example, in Patent Document 1, injection molding was attempted by adding ordinary talc, silica, calcium lactate, etc. as a nucleating agent to a lactic acid-based polymer. However, the crystallization rate was slow and the molded product was brittle, so that it was practically usable. Therefore, such a lactic acid-based polymer has a low crystallization rate even if it is used for general injection molding, blow molding, and compression molding using ordinary talc, silica and the like. In addition, it is described that the practical heat resistance of the obtained molded product is as low as 100 ° C. or less, and there are restrictions on the use.
[0006]
  In Patent Document 2, polyglycolic acid and its derivatives are added as polynuclear agents to poly L-lactide and the like, thereby shortening the injection molding cycle time by increasing the crystallization speed, and exhibiting excellent mechanical properties. It is described that the product which has can be obtained.
[0007]
  However, in Patent Document 1, when injection molding was attempted without actually adding a nucleating agent to the lactic acid-based polymer, molding was not possible under the condition that the mold temperature as disclosed in Patent Document 2 was Tg or higher. It is stated that.
[0008]
  Patent Document 3 discloses a method in which wax is used as a crystal nucleating agent and a crystallization accelerator, and a molded product is heat-treated at a crystallization temperature, or a method in which a mold is held at a crystallization temperature for a predetermined time. Yes. However, in this method, although the heat resistance up to about 80 ° C. has been improved, the heat resistance at a temperature higher than that, particularly at a temperature of 100 ° C. or higher, particularly for microwave ovens, is insufficient.
[0009]
  On the other hand, as a method for imparting heat resistance and impact resistance without using a crystal nucleating agent, Patent Document 4 discloses that the degree of crystal orientation and crystallinity are obtained by stretching an unstretched sheet 1.5 to 5 times. A technique for improving the above is disclosed. However, since this method results in a stretched sheet, further stretching is required when processing into a container such as a tray. However, a stretched sheet is inferior in stretchability and is not suitable for deep drawing. Therefore, the application is limited.
[0010]
[Patent Document 1]
          JP-A-8-193165
[0011]
[Patent Document 2]
          JP-A-4-220456
[0012]
[Patent Document 3]
          JP-A-11-106628
[0013]
[Patent Document 4]
          Japanese Patent Laid-Open No. 9-25345
[0014]
[Problems to be solved by the invention]
  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve such problems and to obtain a molded body obtained by heat-treating a sheet made of polylactic acid and a crystal nucleating agent and having excellent heat resistance and impact resistance.
[0015]
[Means for Solving the Problems]
  As a result of intensive studies for improving the heat resistance and impact resistance of the conventional polylactic acid molded body as described above, the present inventors have obtained a glass transition temperature of 0 ° C. or less to polylactic acid having high crystallinity.Aromatic / aliphatic copolyesterAnd blending talc with an average particle diameter of 1 to 8 μm in a certain range, extruding to form a sheet, and then carrying out heat treatment under certain conditions to improve the crystallinity of polylactic acid and the presence of a flexible component Based on the above, the inventors have found that the heat resistance and impact resistance are remarkably improved, and that the crystallization speed is improved from the viewpoint of the molding cycle until the industrial production becomes possible.
[0016]
  That is, the present inventionCrystalline polylactic acid resin (A) having an optical purity of 95% or more and a residual lactide content of 0.1 to 0.4% by mass, and an aromatic / aliphatic copolymer polyester (B) having a glass transition temperature of 0 ° C. or less And talc (C) having an average particle diameter of 1 to 8 μm, the mixing ratio of (A) and (B) is (A) / (B) = 97/3 to 80/20 mass%, A resin composition (excluding those containing a flame retardant) blended so that the mixing ratio is 5 to 20% by mass with respect to the total amount of the composition is formed into an unstretched sheet by extrusion molding, and then a molding die , And heat forming at a processing temperature of 110 to 150 ° C. and a processing time of 1 to 30 seconds at the same time in a molding die while forming by any one of vacuum forming, pressure forming, vacuum pressure forming and press forming. The gist is to do.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the present invention will be described in detail.
  The crystalline polylactic acid resin (A) used in the present invention needs to have an optical purity of 95% or more.
[0021]
  There are two types of optically active substances in the polylactic acid monomer, namely D-lactic acid and L-lactic acid. Currently, L-lactic acid is industrially produced in large quantities and at low cost, and L-polylactic acid (PLLA) derived from L-lactic acid is generally used also in polylactic acid. The crystallinity of polylactic acid varies depending on the content of L-lactic acid or D-lactic acid. For example, when the optical purity L of the lactic acid monomer is defined as the following formula 1, the larger L is, that is, the higher the optical purity is. Crystallinity increases.
[0022]
        Optical purity = | M (L) −M (D) |
However, M (L) is mol% of L-lactic acid units with respect to all lactic acid units constituting the polylactic acid resin, and M (D) is mol% of D-lactic acid units with respect to all lactic acid units constituting the polylactic acid resin. , M (L) + M (D) = 100.
[0023]
  In general, even when PLLA is polymerized from a monomer comprising an optical purity of 100%, for example, 100% L-lactic acid component, the racemization of the monomer partially occurs due to the thermal history in the polymerization and subsequent melt molding, so it is used industrially. It is said that the upper limit of the optical purity of PLLA is around 98%. Therefore, this is the most highly crystalline composition in practical use among polylactic acids. However, even in PLLA composed of such a high-purity L-lactic acid component, the crystallization rate is relatively slow and the supercooling property in the cooling crystallization process is very high.
[0024]
  In particular, in order to obtain substantial strength and durability, a polymer having a relatively high molecular weight is used as polylactic acid. As a guideline, a polymer having a weight average molecular weight of 100,000 or more, preferably 150,000 to 300,000 is used. Is good.
[0025]
  On the other hand, in order to impart heat resistance to the finally obtained polylactic acid-based molded product, in addition to promoting crystallization (crystallization rate) of polylactic acid itself, the crystallinity of polylactic acid after molding is improved. It is necessary to let For this purpose, it is necessary for the polylactic acid itself to have the ability to be highly crystalline. For this purpose, it is necessary that the polylactic acid resin has an optical purity of 95% or more, preferably 96%. That's it. Polylactic acid resin with an optical purity of less than 95% decreases the crystallinity of polylactic acid itself, and does not crystallize sufficiently even when talc is added as a crystal nucleating agent or heat treatment, and the required heat resistance Cannot be obtained.
[0026]
  In general, it is known that lactide present in polylactic acid resin promotes hydrolysis of polylactic acid when the amount is too large, but low molecular weight lactide crystallizes more than high molecular weight polylactic acid. This lactide crystallization facilitates the crystallization of polylactic acid. Therefore, defining an appropriate amount of lactide contained in polylactic acid is an effective item for the purpose of promoting crystallization and imparting heat resistance. That is, the amount of residual lactide is preferably in the range of 0.1 to 0.6% by mass and more preferably in the range of 0.1 to 0.4% by mass with respect to the entire resin. If the amount of residual lactide is less than 0.1% by mass, the amount is too small as an initiator for promoting crystallization of polylactic acid, making it difficult to use. Moreover, when it exceeds 0.6 mass%, the effect | action which accelerates | stimulates hydrolysis will become strong and is not preferable.
[0027]
  Of the present inventionObtained by manufacturing methodIn the polylactic acid-based molded article, an aromatic / aliphatic copolymer polyester (B) having a glass transition temperature of 0 ° C. or lower is essential as a constituent component.
  Since this (B) component has a glass transition temperature of 0 ° C. or lower, it has flexibility even at room temperature. Dispersion of such components in the polylactic acid resin has a function of absorbing external impact as in the case of dispersing rubber. That is, it contributes to improvement of impact properties. Specific examples of the component (B) include aromatic / aliphatic copolyesters which are copolyesters having an aliphatic diol.
[0028]
  Aliphatic diolExamples thereof include ethylene glycol, propylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. And the component (B)The above componentsIs selected by polycondensation. If necessary, the structure can be jumped up and long-chain branched using an isocyanate, an acid anhydride, an epoxy compound, an organic peroxide, or the like.
[0029]
  In the present invention, the mixing ratio of the component (A) and the component (B) needs to be (A) / (B) = 97/3 to 80/20% by mass, preferably (A) / (B ) = 97/3 to 85/15% by mass, more preferably (A) / (B) = 95/5 to 85/15% by mass. When the mixing ratio of the component (B) is less than 3% by mass, the external impact cannot be absorbed and the impact resistance is inferior. On the other hand, when the mixing ratio of the component (B) exceeds 20% by mass, the impact resistance is remarkably improved, but the crystallization of polylactic acid itself is hindered and the heat resistance is poor. At the same time, the crystallization rate itself becomes slow, so that a molding cycle in actual production takes time, resulting in poor productivity.
[0030]
  In the present invention, in order to promote crystallization, in addition to optimizing the polylactic acid resin itself as described above, the presence of talc as a crystal nucleating agent is essential.
  Talc as a crystal nucleating agent in the present invention has an average particle diameter of 1 to 8 μm, preferably 1 to 5 μm. Of the many crystal nucleating agents, talc is an inorganic substance that has the highest crystallization efficiency for polylactic acid, so it is not only optimal as a crystal nucleating agent, but also very inexpensive and is an inorganic substance that exists in nature. Since it is a substance, it is industrially advantageous and does not give a load to the global environment. If the average particle size of the talc is less than 1 μm, the dispersion as a flocculating agent or secondary agglomeration will occur and the effect as a crystal nucleating agent will not be sufficiently exhibited, and the resulting molded article will have insufficient heat resistance. When the average particle size exceeds 8 μm, talc becomes a defect in the molded body besides acting as a crystal nucleating agent, and thus adversely affects the physical properties and surface state of the obtained molded body.
[0031]
  Talc content isTo the total compositionIt is 1-30 mass%, Preferably it is 5-20 mass%, More preferably, it is 10-15 mass%. If it is less than 1% by mass, the content is too small and only a small amount of crystal nuclei are produced, and the effect as a crystal nucleating agent cannot be sufficiently exhibited, so that the heat resistance of the molded article becomes insufficient. When it exceeds 30% by mass, the content is excessively increased and the molded article becomes brittle, which adversely affects physical properties.
[0032]
  In order to disperse this crystal nucleating agent efficiently, a dispersing agent may be used. The dispersant is preferably excellent in compatibility with polylactic acid and excellent in wettability with the crystal nucleating agent. As such a substance, at least one selected from fatty acid amides such as erucic acid amide, stearic acid amide, oleic acid amide, ethylene bis-stearic acid amide, ethylene bis-oleic acid amide, and ethylene bislauric acid amide should be selected. However, it is important for efficiently increasing the crystallinity of the polylactic acid-based molded article.
[0033]
  (A), (B), (C) After each sheet is formed with the mixing ratio as described above and a heat treatment is applied to this sheet,Get the compact. This molded product has a difference in absolute value between a crystal melting heat amount ΔHm and a temperature rising crystallization heat amount ΔHc as measured by a suggested scanning calorimeter under a temperature rising condition of 20 ° C./min as a crystallization index ( | ΔHm | − | ΔHc |) ≧ 25 J / g is required. Preferably, (| ΔHm | − | ΔHc |) ≧ 29 J / g. Thus, in order to satisfy (| ΔHm | − | ΔHc |) ≧ 25 J / g, the optical purity of the polylactic acid used as described above, the amount of residual lactide, the average particle diameter of talc, and the addition ratio thereof are respectively set. In addition to optimization, it is necessary to perform a heat treatment described later.
[0034]
  When (| ΔHm | − | ΔHc |) is less than 25 J / g, it is not sufficiently crystallized, and can be obtained from ordinary polylactic acid when, for example, hot water (90 ° C.) is poured into a molded container. In a container, the container is thermally deformed and heat resistance is insufficient. However, such a phenomenon does not occur at 25 J / g or more.
[0035]
  In the present invention, heat treatment is an essential condition in the production of a molded body. However, it is impossible industrially to take a long time for the heat treatment. On the other hand, polylactic acid is known as a material having a very low crystallization rate. Therefore, it is necessary to provide a crystallization rate that can be adapted to an industrial molding cycle. In the present invention, the required molded body can be industrially produced by optimizing the details of the polylactic acid composition, crystal nucleating agent and heat treatment conditions. Of the present inventionObtained by manufacturing methodThe molded body has a crystallization rate at 130 ° C. of 0.010 min.^-1It is necessary to be above, 0.015 min^-1The above is preferable. The crystallization rate at 130 ° C is 0.010 min.^-1If it is less than 1, the crystallization speed is slow and unsuitable for a normal molding cycle, and the crystallization becomes insufficient, resulting in poor heat resistance. The crystallization rate at 130 ° C is 0.010 min.^-1To achieve the above, as described above, optimization of the optical purity of the polylactic acid used, optimization of the average particle size and mixing ratio of talc, and aromatic / aliphatic copolyester or fat After optimizing the mixing ratio of the group polyester and polylactic acid, it is necessary to perform a heat treatment in a mold at a treatment temperature of 110 to 150 ° C. and a treatment time of 1 to 30 seconds as described later.
[0036]
  In the present invention, in order to further accelerate the crystallization rate by the crystal nucleating agent, if necessary, a crosslinking agent such as an organic peroxide and a crosslinking aid are used in combination, and the resin composition is subjected to extremely light crosslinking. It is also possible.
[0037]
  Specific examples of the crosslinking agent include n-butyl-4,4-bis-t-butylperoxyvalerate, dicumyl peroxide, di-t-butyl peroxide, di-t-hexyl peroxide, 2,5 -Organic peroxides such as dimethyl-2,5-di (t-butylperoxy) hexane, 2,5-dimethyl-2,5-t-butylperoxyhexyne-3, phthalic anhydride, maleic anhydride Polyvalent carboxylic acids such as trimethyladipic acid, trimellitic anhydride, 1,2,3,4-butanetetracarboxylic acid, lithium formate, sodium methoxide,Metal complexes such as potassium propionate and magnesium ethoxide, epoxy compounds such as bisphenol A type diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, terephthalic acid diglycidyl ester, diisocyanates, tris Examples include isocyanate compounds such as isocyanate, hexamethylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, and diphenylmethane diisocyanate.
[0038]
  Specific examples of the crosslinking aid include trimethacrylate, glycidyl methacrylate, normal-butyl methacrylate, hydroxypropyl monomethacrylate, polyethylene glycol monomethacrylate and the like.
[0039]
  Of the present inventionObtained by manufacturing methodIn the molded body, it is necessary that the falling ball height for a thickness of 500 μm has a falling ball impact property of 20 cm or more. Here, the falling ball height for a thickness of 500 μm means that a box-shaped molded body formed of a sheet having a thickness of 500 μm is placed face down so that the bottom is placed on the top surface, and a 300 g iron ball is placed on this. Is [(height broken at a rate of once every two times) −5] cm.
[0040]
  If the falling ball height for a thickness of 500 μm is less than 20 cm, cracks may occur or cracks may occur when an external impact is applied during transportation of the molded body. Therefore, it is preferable that the falling ball height for a thickness of 500 μm is 30 cm or more.
[0041]
  In order to have a falling ball impact of 20 cm or more for a thickness of 500 μm, as described above, the glass transition temperature is 0 ° C. or less.Aromatic / aliphatic copolyester (B)It is necessary to mix 3% by mass or more with respect to the crystalline polylactic acid resin (A) having an optical purity of 95% or more.
[0042]
  Next, the present inventionObtained by manufacturing methodThe molecular weight retention rate of the molded body will be described. Here, the molecular weight retention is the weight average molecular weight (Mw) after the decomposition acceleration test in which the compact is left in a constant temperature and humidity chamber at 50 ° C. and 90% RH for 30 days, divided by the weight average molecular weight before leaving. A percentage value. It is preferable that a polylactic acid resin product having biodegradability usually does not decompose as much as possible during storage or use of a sheet or a molded product, but rapidly decomposes after use. For this reason, it is preferable that the molecular weight retention is 60% or more under the conditions of the accelerated decomposition test,70%More preferably, it is the above. When the molecular weight retention is less than 60%, it means that the decomposition rate is high, and decomposition is progressing during storage in a warehouse or the like, and it may not be able to endure actual use.
[0043]
  Of the present inventionObtained by manufacturing methodIf necessary, a plasticizer, an ultraviolet light inhibitor, a light stabilizer, an antifogging agent, an antifoggant, an antistatic agent, an anticoloring agent, an antioxidant, a filler, a pigment, and the like can be added to the molded body.
[0044]
  next,Production method of the present inventionAn example of the embodiment will be described.
  First, a polylactic acid resin (A) having an optical purity of 95% or more, an aromatic / aliphatic copolymer polyester (B) having a glass transition temperature of 0 ° C. or less, talc (C), and a dispersant as necessary. In a predetermined amount. In this case, the entire amount may be compounded with a biaxial kneading extruder, or only (A) and (C) may be compounded and (B) may be dry blended. All may be dry blended. Thereafter, it is melt-kneaded with a single-screw extruder or twin-screw extruder equipped with a T die and extruded from the T die, and an unstretched sheet is formed with a cast roll set to a temperature range of 30 to 50 ° C. Although the thickness of a sheet | seat can be suitably selected according to the intended purpose, 200-750 micrometers is preferable normally.
[0045]
  Next, when an unstretched sheet is formed by selecting any one of press molding, vacuum forming, pressure forming, and vacuum / pressure forming, it is formed while being heat-treated in a mold.
  In the present invention, as described above, the processing temperature is 110 to 150 ° C. and the processing time is 1 to 30 seconds as conditions for performing heat treatment after optimizing the details such as resin and crystal nucleating agent. is required. The treatment temperature of 110 to 150 ° C. is a temperature at which polylactic acid is most easily crystallized. Further, the treatment time of 1 to 30 seconds is a time that can be practically applied to a production cycle and can be crystallized without excess or deficiency. When the treatment temperature is less than 110 ° C., crystallization does not proceed sufficiently. On the other hand, when the treatment temperature exceeds 150 ° C., the crystallization rate becomes extremely slow, resulting in insufficient crystallization. Further, if the treatment time is less than 1 second, the time required for crystallization is insufficient, and if it exceeds 30 seconds, it does not adapt to a substantial molding cycle and causes problems in industrial production.
[0046]
【Example】
  Next, based on an Example, this invention is demonstrated concretely. However, the present invention is not limited to only these examples. In addition, the measurement of the various physical-property values in the following examples and comparative examples was implemented with the following method.
(1) Heat of crystal melting ΔHm and heat of crystallization ΔHc
  Using Pyrisl DSC manufactured by Perkin Elmer, 10 mg of the molded product was used as a test sample, and when the temperature was increased at a temperature increase rate of 20 ° C./min, the total heat amount of the peak appearing on the heat generation side was defined as the temperature increase crystallization heat amount ΔHc. The total heat quantity of the peak appearing on the endothermic side was defined as the crystal melting heat quantity ΔHm.
(2) Crystallization rate
  Using a Pyrisl DSC manufactured by PerkinElmer, Inc., the temperature was raised from 20 ° C. to 200 ° C. at 500 ° C./min, held for 5 minutes, further rapidly cooled to 130 ° C. at −500 ° C./min, and then until crystallization was completed It was measured. Thereafter, a value obtained by multiplying the reciprocal of the time until the crystallization fraction became 0.5 by the crystallization fraction 0.5 was taken as the crystallization speed.
(3) Heat resistance
  Using a single-shot indirect heating vacuum molding machine and mold CT Delican 15-11 (aluminum), a 150 mm long, 110 mm wide, 20 mm deep container is formed from the sheet, and 90 ° C. hot water is poured into the container. When the container is visually observed for deformation after a minute, it is evaluated as ◯ when the deformation is not good at all, and is evaluated as △ when it is slightly deformed, when it is slightly deformed. Was evaluated as x with poor heat resistance.
(4) Molecular weight retention
  The weight average molecular weight (Mw) after leaving the sample in a constant temperature and humidity chamber at 50 ° C. and 90% RH for 30 days was measured by a gel permeation chromatography (GPC) method using polystyrene as a standard substance in a THF solution. Lactic acid was measured using a styragel HR column and an ultrastyragel column and a refractometer as a detector, and the retention rate was calculated by the following formula.
[0047]
      Mw retention rate (%) = (Mw after 30 days / Mw before being left) × 100
(5) Impact resistance
  The box-shaped molded body after heat treatment formed with a sheet having a thickness of 500 μm is placed in a face-down state so that its bottom is placed on the upper surface, and a 300 g iron ball is placed on this from different heights every 5 cm. The sample was dropped vertically, and the impact resistance was evaluated by setting the height of the falling ball to (the height at which cracking occurred once every two times−5) cm.
Example 1
  Crystalline polylactic acid (A) (optical purity 97.2%, residual lactide amount 0.2% by weight, weight average molecular weight 200,000, manufactured by Cargill Dow: Nature Works), and aromatic having a glass transition temperature of 0 ° C. or less Aliphatic copolyester (B) (glass transition temperature-30 ° C., manufactured by BASF: Ecoflex F) is blended at a ratio of (A) / (B) = 90/10% by mass, and average 10% by mass of 2.75 μm particle size talc (manufactured by Hayashi Kasei Co., Ltd .: MW HS-T) was added to the total amount of the composition. And it melt-kneaded using the biaxial kneading extruder (made by Nippon Steel Works, type | model number TEX44 (alpha)), and produced the polylactic acid compound raw material at the extrusion temperature of 230 degreeC.
[0048]
  Next, this polylactic acid compound raw material was melt-extruded at an extrusion temperature of 215 ° C. using a single screw extruder having a screw diameter of 90 mm equipped with a T-die having a width of 1000 mm, and a thickness of 500 μm with a cast roll set at 40 ° C. An unstretched sheet was formed.
[0049]
  Furthermore, this sheet was vacuum-formed into a length of 150 mm, a width of 110 mm, and a depth of 20 mm using a single-shot indirect heating vacuum forming machine and a mold CT Delican 15-11 (made of aluminum) to produce a container as a molded body. . During the vacuum forming, heat treatment was performed by setting the inside of the mold at 140 ° C. and holding time of 5 seconds.
[0050]
  Table 1 shows various physical properties of the obtained molded body.
Example 2
  As the crystalline polylactic acid (A), polylactic acid (optical purity 96.0%, residual lactide content = 0.4 mass%, weight average molecular weight 190,000, manufactured by Cargill Dow, Inc .: Nature Works) was used. Other than that, an unstretched sheet and a vacuum molded container were obtained in the same manner as in Example 1. During the vacuum forming, the inside of the mold was heat-treated at 120 ° C. for 15 seconds.
[0051]
  Table 1 shows various physical properties of the obtained molded body.
Example 3
  Crystalline polylactic acid (A) / aromatic / aliphatic copolyester (B) having a glass transition temperature of 0 ° C. or lower = 85/15% by mass. Other than that, an unstretched sheet and a vacuum molded container were obtained in the same manner as in Example 1.
[0052]
  Table 1 shows various physical properties of the obtained molded body.
Example 4
  Talc (C) was mixed at 15% by mass with respect to the total amount of the composition. Other than that, an unstretched sheet and a vacuum molded container were obtained in the same manner as in Example 1.
[0053]
  Table 1 shows various physical properties of the obtained molded body.
Example 5
  Talc (C) having an average particle size of 4.1 μm (MICRON WHITE # 5000A manufactured by Hayashi Kasei Co., Ltd.) was used. Other than that, an unstretched sheet and a vacuum molded container were obtained in the same manner as in Example 1.
[0054]
  Table 1 shows various physical properties of the obtained molded body.
Example 6
  As shown in Table 1, the heat treatment conditions in the mold were changed to a temperature of 150 ° C. and a holding time of 3 seconds. Other than that, an unstretched sheet and a vacuum molded container were obtained in the same manner as in Example 1.
[0055]
  Table 1 shows various physical properties of the obtained molded body.
Example 7
  Crystalline polylactic acid (A) / aromatic / aliphatic copolyester (B) having a glass transition temperature of 0 ° C. or lower was set to 95/5 mass%. Further, as shown in Table 1, the heat treatment temperature condition in the mold was changed to a temperature of 130 ° C. and a holding time of 20 seconds. Other than that, an unstretched sheet and a vacuum molded container were obtained in the same manner as in Example 1.
[0056]
  Table 1 shows various physical properties of the obtained molded body.
Comparative Example 1
  Talc was not used. Other than that, an unstretched sheet and a vacuum molded container were obtained in the same manner as in Example 1.
[0057]
  Table 1 shows various physical properties of the obtained molded body.
Comparative Example 2
  The content of talc was changed to 40% by mass. Other than that, an unstretched sheet and a vacuum molded container were obtained in the same manner as in Example 1.
[0058]
  Table 1 shows various physical properties of the obtained molded body.
Comparative Example 3
  As the polylactic acid (A), polylactic acid (optical purity 80.0%, residual lactide amount = 0.5 mass%, weight average molecular weight 200,000, manufactured by Cargill Dow, Inc .: Nature Works) was used. Other than that, an unstretched sheet and a vacuum molded container were obtained in the same manner as in Example 1.
[0059]
  Table 1 shows various physical properties of the obtained molded body.
Comparative Example 4
  Glass transition temperature below 0 ° CAromatic / aliphatic copolyester (B)The same crystalline polylactic acid (A) and talc (C) as in Example 1 were used. Other than that, an unstretched sheet and a vacuum molded container were obtained in the same manner as in Example 1.
[0060]
  Table 1 shows various physical properties of the obtained molded body.
Comparative Example 5
  The mixing ratio of the crystalline polylactic acid (A) and the aromatic / aliphatic copolyester (B) having a glass transition temperature of 0 ° C. or lower was set to (A) / (B) = 70/30 mass%. Other than that, an unstretched sheet and a vacuum molded container were obtained in the same manner as in Example 1.
[0061]
  Table 1 shows various physical properties of the obtained molded body.
Comparative Example 6
  The same molding machine as in Example 1 was applied to an unstretched sheet produced in the same manner as in Example 1, but the heat treatment conditions were changed, and heat treatment was performed in a mold at 160 ° C. for 5 seconds. Subsequently, the container as a molded object was obtained like Example 1. FIG.
[0062]
  Table 1 shows various physical properties of the obtained molded body.
Comparative Example 7
  The same molding machine as in Example 1 was applied to an unstretched sheet produced in the same manner as in Example 1, but the heat treatment conditions were changed and heat treatment was performed in a mold at 100 ° C. for 1 minute. Subsequently, the container as a molded object was obtained like Example 1. FIG.
[0063]
  Table 1 shows various physical properties of the obtained molded body.
[0064]
[Table 1]

  Examples 1-7The container as a molded product obtained in the above was not deformed at all even when hot water was poured, and was excellent in heat resistance.The impact resistance was also excellent.
[0065]
  Comparative Example 1Since talc was not used at all, the heat-treated container was insufficiently crystallized and deformed instantly when hot water was poured.
  In Comparative Example 2, since the amount of talc added was too large, the container itself was fragile, and cracking of the container during or after molding was observed.
[0066]
  In Comparative Example 3, since the optical purity of polylactic acid was low, even if heat treatment or crystallization was promoted by adding a crystal nucleating agent, crystallization of polylactic acid was insufficient and the container was poor in heat resistance.
[0067]
  Comparative Example 4 has a glass transition temperature of 0 ° C. or lower.Aromatic / aliphatic copolymerizationSince polyester (B) was not used, the falling ball height was low and the container was inferior in impact resistance.
  Comparative Example 5 has a glass transition temperature of 0 ° C. or lower.Aromatic / aliphatic copolymerizationSince the blending amount of the polyester (B) was too large, the impact resistance was excellent, but the crystallization rate was remarkably slow, which required a molding cycle time, which was a problem from the viewpoint of industrial production.
[0068]
  In Comparative Example 6, since the heat treatment temperature in the mold was as high as 160 ° C. and was near the melting point of polylactic acid, the crystal nuclei were melted, and thus the obtained container was not sufficiently crystallized. It was inferior in heat resistance.
[0069]
  In Comparative Example 7, the heat treatment time in the mold was 100 ° C. and the temperature required for crystallization of polylactic acid molecules was not increased, and crystallization was insufficient even if the treatment time was increased. ΔHm | − | ΔHc | was only 9.0 J / g, and only a container having poor heat resistance was obtained.
[0070]
【The invention's effect】
  According to the invention, the optical purityAnd the amount of residual lactideA sheet-like material is formed by using polylactic acid, which is strictly adjusted, an aromatic / aliphatic polyester having a glass transition temperature of 0 ° C. or less, and talc within a predetermined mixing range, and this sheet-like material is generally represented by vacuum forming. When molding by typical molding method,In order to heat-treat under the predetermined conditions in the mold during molding,Biodegradable obtainedCompactThe thermal properties of (| ΔHm | − | ΔHc |) ≧ 25 J / g and the crystallization rate is 0.010 min.^-1The height of the falling ball per 500 μm thickness is 20 cm or more, and it has both heat resistance and impact resistance that can withstand hot water that was impossible with a conventional molded product of polylactic acid. Can do.
[0071]
  The polylactic acid-based molded product thus obtained can be suitably used for containers that require heat resistance and impact resistance, such as trays for lunch boxes, bowls, dishes, cups, etc. Since it is not deformed even during transportation, it can be applied to various uses such as lid materials, building materials, boards, stationery, cases, carrier tapes, prepaid cards, cards such as IC cards, and FRP.

Claims (1)

Crystalline polylactic acid resin (A) having an optical purity of 95% or more and a residual lactide content of 0.1 to 0.4% by mass, and an aromatic / aliphatic copolymer polyester (B) having a glass transition temperature of 0 ° C. or less And talc (C) having an average particle diameter of 1 to 8 μm, the mixing ratio of (A) and (B) is (A) / (B) = 97/3 to 80/20 mass%, A resin composition (excluding those containing a flame retardant) blended so that the mixing ratio is 5 to 20% by mass with respect to the total amount of the composition is formed into an unstretched sheet by extrusion molding, and then a molding die , And heat forming at a processing temperature of 110 to 150 ° C. and a processing time of 1 to 30 seconds at the same time in a molding die while forming by any one of vacuum forming, pressure forming, vacuum pressure forming and press forming. A method for producing a polylactic acid-based molded article.