JP2008031375A - Lactate-based resin composition, method for molding thermally molded article and thermally molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lactate-based resin composition which can form a thermally molded article excellent in heat resistance and productivity, to provide a thermally molded article, and to provide a method for producing the thermally molded article. <P>SOLUTION: This lactate-based resin composition comprises 100 pts.wt. of a lactate-based resin (A) and 0.005 to 10 pts.wt. of a moldability-improving agent (B). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lactic acid resin composition, a thermoformed article produced from the composition, and a method for producing the same. More specifically, the lactic acid resin composition having improved thermoformability, a molded body and a sheet comprising the composition, a thermoformed body obtained by secondary molding of the sheet, and excellent productivity of the thermoformed body. It relates to a manufacturing method.

  Conventionally, polystyrene, polyvinyl chloride, polypropylene, and polyethylene terephthalate resin have been used as materials for molded articles made of plastic. Some molded articles produced from such resins are excellent in transparency, but if they are disposed of incorrectly, the amount of dust increases. Furthermore, since it hardly decomposes in the natural environment, it remains in the ground semipermanently when buried.

  On the other hand, lactic acid resins such as polylactic acid and copolymers of lactic acid and other hydroxycarboxylic acids have been developed as thermoplastic resins having biodegradability. Lactic acid-based resins are 100% biodegradable within a few months to one year in the body of an animal, and when placed in soil or seawater, they begin to degrade in a few weeks in a moist environment, and from several years to several years. It disappears over the years, and its decomposition products have the property of becoming lactic acid, carbon dioxide and water that are harmless to the human body.

  A molded body of such a lactic acid resin (for example, a molded body such as a ball having a three-dimensional shape, an unstretched film or sheet having a two-dimensional shape, an unstretched filament having a one-dimensional shape, The yarn is usually amorphous immediately after molding, and is transparent because there are almost no crystals having a size equal to or larger than the wavelength of light causing light scattering.

  However, this transparent molded body is generally inferior in heat resistance because it has a low glass transition temperature (Tg) and is amorphous. For example, an amorphous polylactic acid container is excellent in transparency but has low heat resistance, and therefore cannot be used for storing hot water or heating in a microwave oven, and its application is limited. Further, in order to improve heat resistance, by filling in a mold kept near the crystallization temperature at the time of molding, or by heat-treating (annealing) the amorphous molded body after molding, When the degree of conversion is increased, usually, crystals (for example, spherulites) having a size equal to or larger than the wavelength of light that causes light scattering rapidly grow, and the formed body becomes opaque.

  Therefore, it has been studied to improve the heat resistance of the sheet or molded article by adding a crystal nucleating agent to the lactic acid resin to promote crystallization, but without inhibiting the transparency of the resin itself. It was difficult to improve heat resistance.

Japanese Patent Laid-Open No. 2002-146170 (Patent Document 1) discloses that a plasticizer and a crystal nucleating agent are essential components, and a specific crystallinity is imparted to a plasticized polylactic acid resin, thereby realizing practicality. It is described that a high film can be obtained, and JP 2004-204143 A (Patent Document 2) discloses a technique related to a composition comprising a biodegradable polyester and a layered silicate and a molded body using the composition. Although disclosed, it has been difficult to produce a thermoformed article excellent in heat resistance with excellent production efficiency by any method.
JP 2002-146170 A JP 2004-204143 A

  The present invention is intended to solve the above-described problems in the prior art, and is a lactic acid resin composition capable of forming a thermoformed article excellent in heat resistance and productivity, a molded article comprising the composition, and a thermoformed article. Another object of the present invention is to provide a method for producing a thermoformed article having excellent heat resistance and productivity.

  More specifically, a lactic acid resin composition that can be uniformly heated and softened in a short time by preheating at the time of molding, a molded body such as a sheet comprising the composition and a multilayer sheet, and secondary molding of the sheet or multilayer sheet It is an object of the present invention to provide a thermoformed article obtained by the method and a production method excellent in productivity of the thermoformed article.

  The present inventors can improve the heat absorption capacity of the lactic acid resin composition by adding a specific additive to the lactic acid resin composition, and a sheet comprising such a lactic acid resin composition. It has been found that a thermoformed article having excellent heat resistance can be obtained with excellent production efficiency by secondary molding, and the present invention has been completed.

The lactic acid resin composition of the present invention is characterized by containing 100 parts by weight of a lactic acid resin (A) and 0.005 to 10 parts by weight of a moldability improver (B).
As the moldability improving agent (B), a compound represented by the following formula (1) is preferable.

  The method for producing a thermoformed article of the present invention comprises a step of heat-softening a sheet comprising the lactic acid resin composition and then molding the sheet by a vacuum forming method, a pressure forming method or a vacuum / pressure forming method. Yes.

  The thermoformed article of the present invention is preferably produced by the production method.

  Since the lactic acid-based resin composition of the present invention can be heated and softened uniformly in a short time by preheating at the time of molding, the molded body, sheet and multilayer sheet comprising the composition, and the sheet or multilayer sheet can A thermoformed article excellent in heat resistance and productivity obtained by subsequent molding can be produced.

  Further, according to the method for producing a thermoformed article of the present invention, the lactic acid resin composition as a raw material can be uniformly heat-softened in a short time by preheating at the time of molding, so that the thermoformed article having excellent heat resistance. Can be manufactured with excellent production efficiency.

Hereinafter, a lactic acid resin composition according to the present invention, a molded body comprising the composition, a sheet and a multilayer sheet, a thermoformed body obtained by secondary molding of the sheet or the multilayer sheet, and production of the thermoformed body The method will be described in detail. The sheet in the present invention has a thickness of 10
It means both a sheet and a film of about μm to 10 mm.

[Lactic acid resin composition]
The lactic acid resin composition of the present invention contains 100 parts by weight of the lactic acid resin (A) and 0.005 to 10 parts by weight of the moldability improver (B).

Lactic acid resin (A);
The lactic acid resin (A) is a polymer containing 50 mol% or more of lactic acid units, preferably 75 mol% or more, more preferably 100%.
(1) polylactic acid, or lactic acid-other aliphatic hydroxycarboxylic acid copolymer,
(2) a lactic acid-based polymer containing a polyfunctional polysaccharide and a lactic acid unit,
(3) A lactic acid-based polymer containing an aliphatic polyvalent carboxylic acid unit, an aliphatic polyhydric alcohol unit and a lactic acid unit, and (4) a mixture thereof. Among these, in view of transparency and heat resistance during use, polylactic acid and lactic acid-other aliphatic hydroxycarboxylic acid copolymers are preferable, and polylactic acid is more preferable. Lactic acid includes L-lactic acid and D-lactic acid. In the present invention, the term lactic acid means both L-lactic acid and D-lactic acid unless otherwise specified.

  As the raw material for the lactic acid resin (A), lactic acids and hydroxycarboxylic acids are used. As lactic acid, L-lactic acid, D-lactic acid, a mixture thereof, or lactide which is a cyclic dimer of lactic acid can be used. In order to express high crystallinity, it is preferable that the content of one of the L-lactic acid unit and the D-lactic acid unit is large in the lactic acid resin using lactic acid as a raw material. Specifically, the content of one of the L-lactic acid unit or the D-lactic acid unit in the lactic acid unit is preferably 90% or more, more preferably 95% or more, and particularly preferably 98% or more.

  Moreover, as hydroxycarboxylic acid which can be used together with the said lactic acid, C2-C10 hydroxycarboxylic acid is preferable. Specifically, glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 6-hydroxycaproic acid and the like can be preferably used. Further, a cyclic ester intermediate of hydroxycarboxylic acid, for example, glycolide, which is a dimer of glycolic acid, and ε-caprolactone, which is a cyclic ester of 6-hydroxycaproic acid, can also be used. Mixtures of lactic acids and hydroxycarboxylic acids as raw materials can be used in various combinations so that the lactic acid content in the resulting copolymer is 50% or more, preferably 75% or more.

  In order to obtain the lactic acid resin (A), a publicly known method can be used. For example, a method of directly dehydrating polycondensation of the raw material, a method of ring-opening polymerization of a cyclic dimer of the lactic acid or hydroxycarboxylic acid, for example, a cyclic ester intermediate such as lactide, glycolide, or ε-caprolactone, etc. Is mentioned.

In the case of production by direct dehydration polycondensation, it is suitable for the present invention by polymerizing a mixture of lactic acids or lactic acids and hydroxycarboxylic acids as raw materials, preferably by azeotropic dehydration condensation in the presence of an organic solvent. A high-molecular weight lactic acid resin having high strength can be obtained. In particular, it is preferable to use a phenyl ether solvent as the organic solvent, remove water from the solvent distilled by azeotropic distillation, and return the substantially anhydrous solvent to the reaction system.

The weight average molecular weight (Mw) of the lactic acid resin (A) is preferably 30,000 to 5,000,000, more preferably 50,000 to 1,000,000, further preferably 100,000 to 300,000, and particularly preferably 100,000 to 250,000. is there. Moreover, the dispersity (Mw / Mn) is 2 to 10, preferably 2 to 8, more preferably 2 to 6, still more preferably 2 to 4, particularly preferably 2 to 3.5. When the weight average molecular weight (Mw) and dispersity (Mw / Mn) of the lactic acid resin are in the above ranges, a lactic acid resin composition that can be molded at a high speed during crystallization can be obtained. In addition, you may mix other resin other than the said lactic acid-type resin (A) in the range which does not impair the objective of this invention to the lactic acid-type resin composition of this invention.

Moldability improver (B);
The moldability improver (B) is an infrared absorber or far infrared absorber that can improve the heat absorption ability of the lactic acid resin and has the maximum absorption wavelength in the near infrared to far infrared region.

  As the moldability improver (B), those which are not decomposed at the molding temperature when added to lactic acid resin and melt-kneaded, when molded into a sheet, or after thermoforming, are preferable. Those that absorb less are preferred.

(Infrared absorber)
Examples of infrared absorbers include organic infrared absorbers and inorganic infrared absorbers.

  Examples of the organic infrared absorber include anthraquinone compounds, cyanine compounds, phthalocyanine compounds, naphthalocyanine compounds, nitroso compounds and metal complex salts thereof, squarylium compounds, thiol nickel complex compounds, triallylmethane compounds, Organic colorants such as naphthoquinone compounds and amino compounds are exemplified, and compounds represented by the following formula (1) are preferred.

These compounds are used alone or in combination of two or more.
In addition, the compound represented by the above formula (1) is

3 to 16 of the 16 hydrogen atoms inside, 13 on average

It is a compound substituted with.
As the inorganic infrared absorber, for example, inorganic fine particles that at least partially absorb near-infrared rays having a wavelength of 700 nm to 2000 nm, among which inorganic oxide fine particles having a metal belonging to groups 3A, 4A, and 5A are used. Particularly preferred are inorganic oxide fine particles doped with metals belonging to the groups 3A, 4A and 5A. Specifically, for example, metal oxides such as indium oxide, tin oxide, germanium oxide, and zinc oxide doped with metals belonging to 3A, 4A and 5A groups, indium oxide doped with tin Particularly preferred are (ITO), tin oxide doped with antimony (ATO), germanium oxide doped with gallium, and the like. In addition, carbon black, antimony oxide, tin oxide doped with indium oxide, oxides of metals belonging to Group 4, 5, or 6 of the periodic table, carbides, borides, and the like can be given.

These organic and inorganic infrared absorbers can be used singly or in combination of two or more.
Although the addition amount of an infrared absorber changes with kinds, it is 0.005-10 weight part with respect to 100 weight part of lactic acid-type resin (A), Preferably it is 0.01-10.0 weight part, More preferably 0.1 to 5.0 parts by weight.

(Far infrared absorber)
As the moldability improver (B), a compound exhibiting maximum absorption in the far infrared region, that is, a far infrared absorber may be used. Specifically, as the far infrared absorber, a far infrared ray of 4000 nm to 25000 nm is used. Examples include particles of organic compounds and inorganic compounds that absorb light in the region. These can be used alone or in combination of two or more.

Examples of the inorganic compound include carbon black, antimony oxide, tin oxide doped with indium oxide, and oxides, carbides or borides of metals belonging to Group 4, Group 5 or Group 6 of the periodic table.

More specifically, for example, inorganic compounds containing at least one atom selected from Si, Al, Mg, Ca and Li can be mentioned, and the following compounds can be exemplified;
Magnesium oxide, calcium oxide, aluminum oxide, silicon oxide, lithium hydroxide, magnesium hydroxide, calcium hydroxide, aluminum hydroxide, magnesium carbonate, calcium carbonate, calcium sulfate, magnesium sulfate, aluminum sulfate, lithium phosphate, calcium phosphate, silicic acid Magnesium, calcium silicate, aluminum silicate, calcium aluminate, magnesium aluminate, sodium aluminosilicate, potassium aluminosilicate, calcium aluminosilicate, kaolin, clay, talc, mica, zeolite, hydrotalcite compound, lithium aluminum composite hydroxide Aluminum / lithium / magnesium composite carbonate compound, aluminum / lithium / magnesium composite silicate hydroxide compound, magnesium / aluminum Beam-silicon complex hydroxide, magnesium aluminum silicon composite sulfate compounds, magnesium aluminum silicon composite carbonate compound, a metal complex hydroxide salt containing plural kinds anion.

These inorganic compounds may be obtained by dehydrating crystal water.
As said inorganic compound, the compound which has a refractive index substantially equivalent to the refractive index of lactic acid-type resin is preferable.

    In addition, the surface of the inorganic compound particles is composed of a higher fatty acid such as stearic acid, a higher fatty acid metal salt such as an alkali metal oleate, an organic sulfonic acid metal salt such as an alkali metal dodecylbenzenesulfonate, a higher fatty acid amide, It may be coated with a fatty acid ester or wax.

The said inorganic compound can be used individually by 1 type or in combination of 2 or more types.
The average particle size of the inorganic compound is preferably in the range of 0.01 to 15 μm, more preferably 0.05 to 10 μm, and still more preferably 0.1 to 10 μm.

  The addition amount of the far-infrared absorber is within the range of 0.005 to 10 parts by weight with respect to 100 parts by weight of the lactic acid resin (A), and the sheet (unheated sheet) made of the lactic acid resin composition described later. The total light transmittance in the far infrared region (4000 nm to 25000 nm) (average value of the values measured with a color difference meter color computer SM6-IS-2B (trade name, manufactured by Suga Test Machine Co., Ltd.) in accordance with JIS K 7150) In terms of a measured value with a sheet having a thickness of 1500 μm, it is 0% or more and 40% or less, preferably 20% or less, more preferably 10% or less, and the transmittance in the visible light region (around 380 nm to 780 nm). (Typically, the total light transmittance at 555 nm) is similarly converted to a measured value of a sheet having a thickness of 1500 μm, and is 60% or more and 100% or less, preferably 70% or more. It is desirable to adjust so that.

Other additives;
In the lactic acid resin composition of the present invention and a molded body comprising the composition, in particular, a sheet and a thermoformed body, a crystal nucleating agent, a crystallization accelerator, an antiblocking agent, a lubricant, a mold release agent, and other additives as necessary. (Plasticizers, antistatic agents, antifogging agents, ultraviolet absorbers, antioxidants, etc., impact resistance improvers) may be included. These may be added singly or in combination.

(Crystal nucleating agent)
The crystal nucleating agent is present in the lactic acid resin composition of the present invention, becomes a crystal nucleus when heat-treated under certain conditions, and as a result, promotes crystallization of the lactic acid resin, and / or Alternatively, the effect of maintaining the transparency by reducing the crystal size of the lactic acid resin is exhibited. Examples of the crystal nucleating agent include inorganic crystal nucleating agents and organic crystal nucleating agents described below, and one of these may be used alone, or a combination of both may be used.

  The total amount of the crystal nucleating agent added is 0.05 to 3 parts by weight, preferably 0.1 to 2.0 parts by weight, more preferably 0.1 to 0.1 parts by weight with respect to 100 parts by weight of the lactic acid resin (A). 1.0 part by weight.

(Inorganic crystal nucleating agent)
The inorganic crystal nucleating agent can be used without any limitation as long as it has an effect of increasing the crystallization speed of the crystalline lactic acid resin, and examples thereof include silicate compounds such as talc, kaolin and clay. .

The addition amount of the inorganic crystal nucleating agent is 0.05 to 3 parts by weight, preferably 0.1 to 2.0 parts by weight, and more preferably 0.1 to 1 part with respect to 100 parts by weight of the lactic acid resin (A). 0.0 part by weight.
(Organic crystal nucleating agent)
The organic crystal nucleating agent used in the present invention is an aliphatic carboxylic acid amide having an amide bond.

  Specifically, aliphatic carboxylic acid monoamides having 8 to 30 carbon atoms such as capric acid amide, stearic acid amide, oleic acid amide, erucic acid amide, behenic acid amide, methylene bis stearic acid amide, ethylene bis lauric acid amide , Ethylene biscapric amide, ethylene bis oleic acid amide, ethylene bis stearic acid amide, ethylene bis erucic acid amide, ethylene bis behenic acid amide, ethylene bis isostearic acid amide, ethylene bis hydroxy stearic acid amide, butylene bis stearic acid Amide, hexamethylene bis oleic acid amide, hexamethylene bis stearic acid amide, hexamethylene bis behenic acid amide, aliphatic carboxylic acid bis amide such as hexamethylene bishydroxy stearic acid amide, etc. And fatty acid amide having an amide bond within.

  The organic crystal nucleating agent may be used alone or in combination of two or more. When the lactic acid resin (A) is polylactic acid, ethylene bis stearamide, ethylene bis laurate, ethylene bis oleate, and hexamethylene bis behenate are preferred. The lactic acid resin (A) is a copolymer of lactic acid and other aliphatic hydroxycarboxylic acid, or a copolymer containing lactic acid units, other aliphatic polyvalent carboxylic acid units and aliphatic polyhydric alcohol units. In the case of coalescence, aliphatic carboxylic acid monoamides such as stearic acid amide, oleic acid amide and erucic acid amide are preferred.

  The total addition amount of the organic crystal nucleating agent is 0.05 to 3 parts by weight, preferably 0.1 to 2.0 parts by weight, more preferably 0.1 to 0.1 parts by weight with respect to 100 parts by weight of the lactic acid resin (A). 1.0 part by weight.

(Crystallization accelerator)
The crystallization accelerator refers to an agent that increases the crystal growth rate when the lactic acid resin composition of the present invention is crystallized by any method (for example, heat treatment). The crystallization accelerator is preferably one that does not substantially impair the transparency of the lactic acid resin (A).

Examples of the crystallization accelerator include phthalic acid derivatives such as di-n-octyl phthalate, di-2-ethylhexyl phthalate, dibenzyl phthalate, diisodecyl phthalate, ditridecyl phthalate, and diundecyl phthalate, and isophthalates such as dioctyl isophthalate. Acid derivatives, adipic acid derivatives such as di-n-butyl adipate and dioctyl adipate, maleic acid derivatives such as di-n-butyl maleate, citric acid derivatives such as tri-n-butyl citrate, monobutyl itaconate, etc. Itaconic acid derivatives, oleic acid derivatives such as butyl oleate, ricinoleic acid derivatives such as glyceryl monoricinoleate, phosphate esters such as tricresyl phosphate and trixylenyl phosphate, polyethylene adipate, polyacrylate acetylcitric acid Hydroxypolycarboxylic acid esters such as tributyl, polyhydric alcohol esters such as glycerin triacetate and glycerin tripropionate, polyalkylene glycol derivatives such as polyethylene glycol and polypropylene glycol, benzyl-2- (2-methoxyethoxy) ethyl = Examples include adipart.

  Among these, citric acid derivatives, polyalkylene glycol derivatives, hydroxy polyvalent carboxylic acid esters, and polyhydric alcohol esters that can increase the crystallization rate with a small amount and are easily available are preferably used.

  Specifically, polyethylene glycol, ATBC (trade name; manufactured by Jay Plus Co., Ltd.), Dyphaty 101 (trade name; manufactured by Daihachi Chemical Co., Ltd.), Riquemar PL-710 (trade name; Riken Vitamin Co., Ltd.) ) And Lactosizer GP-4001 (trade name; manufactured by Arakawa Chemical Co., Ltd.) and the like can be preferably used because they are inexpensive and easily available and have a high crystallization promoting effect.

  The addition amount of the crystallization accelerator is 0.1 to 7 parts by weight, preferably 0.5 to 7 parts by weight, more preferably 1 to 5 parts by weight with respect to 100 parts by weight of the lactic acid resin (A). More preferably, it is 1 to 3 parts by weight.

  In general, when a large amount of an organic crystal nucleating agent is added, the dispersed particle size becomes large due to aggregation of the organic crystal nucleating agent, and the number of nucleating agents that work effectively decreases, thereby reducing the effect of promoting crystallization. In the present invention, by adding the crystallization accelerator in an amount within the above range, aggregation of the added organic crystal nucleating agent can be prevented, and a large crystallization promotion effect can be obtained in a short time while maintaining transparency.

(Anti-blocking agent)
As the anti-blocking agent, a publicly known one can be used.
The anti-blocking agent is 0.01 to 3 parts by weight, preferably 0.05 to 2 parts by weight, more preferably 0.05 to 1 part by weight, based on 100 parts by weight of the lactic acid resin (A). Used in If the addition amount is too small, the effect of the anti-blocking agent is hardly exhibited. Conversely, if the addition amount is too large, the appearance of the film, particularly transparency may be lowered.

(Lubricant)
As a lubricant used for a molded body made of the lactic acid resin composition of the present invention, for example, a sheet, a publicly known and publicly available material can be used. For example, aliphatic hydrocarbon lubricants such as liquid paraffin, microcrystalline wax, natural paraffin, synthetic paraffin and polyethylene; fatty acid lubricants such as stearic acid, lauric acid, hydroxystearic acid, hydrogenated castor oil; lead stearate, calcium stearate, Examples thereof include metal soap lubricants that are fatty acid metal salts having 12 to 30 carbon atoms such as calcium hydroxystearate; long-chain ester waxes such as montan wax; and composite lubricants obtained by combining these.

The lubricant is used in an amount of 0.1 to 2 parts by weight, preferably 0.2 to 1.5 parts by weight, more preferably 0.3 parts by weight per 100 parts by weight of the lactic acid resin (A). Part to 1 part by weight. If the addition amount is too small, the resulting molded product, for example, the slipping property of the sheet may not be expressed. Conversely, if the addition amount is too large, the formability of the sheet is lowered and the flatness of the resulting sheet is low In some cases, the transparency may be lowered.

  When a lubricant and an antiblocking agent are used in combination, the amount used is 0.2 to 7 parts by weight of the total amount of lubricant and antiblocking agent with respect to 100 parts by weight of the lactic acid resin. The above range is not exceeded. When there are too few lubricants and antiblocking agents, the durable effect of a weather resistance is not expressed, and when there are too many, shaping | molding may become unstable or the external appearance of a film may be inferior.

(Release agent)
In this invention, in order to improve the moldability at the time of a shaping | molding process, a well-known and publicly used release agent can also be added. There is no restriction | limiting as a mold release agent used unless the characteristic of the lactic acid-type resin composition of this invention is impaired. Examples thereof include silicon derivatives, Teflon (registered trademark) derivatives, aliphatic carboxylic acids, aliphatic carboxylic acid metal salts, and aliphatic alcohols. In particular, silicon derivatives and aliphatic carboxylic acids having a high release agent effect are preferable.

  As the silicon derivatives, dimethyl silicone oil is particularly preferable, and the solution viscosity is 0.5 to 500,000 centistokes, preferably 1 to 10,000 centistokes, more preferably 5 to 5000 centistokes, and further preferably 5. ~ 1000 centistokes. Examples thereof include KF96 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd.), KF69 (trade name; manufactured by Shin-Etsu Chemical Co., Ltd.), and KMP110 (trade name: manufactured by Shin-Etsu Chemical Co., Ltd.).

  The aliphatic carboxylic acids are aliphatic carboxylic acids having 8 to 30 carbon atoms, preferably aliphatic carboxylic acids having 10 to 26 carbon atoms, and more preferably aliphatic carboxylic acids having 12 to 22 carbon atoms.

  The release agent is 0.01 part by weight to 1 part by weight, preferably 0.05 part by weight to 0.8 part by weight, and more preferably 0.1 part by weight with respect to 100 parts by weight of the lactic acid resin (A). Used in amounts ranging from parts to 0.5 parts by weight.

(Impact resistance improver)
In the present invention, in order to improve the impact resistance of the molded product, a publicly known impact resistance improver can be added. The impact resistance improver is not limited as long as the characteristics of the lactic acid resin composition of the present invention are not impaired. Examples thereof include impact resistance improvers having biodegradability and non-biodegradable thermoplastic elastomers. In particular, an impact resistance improving agent having biodegradability is preferable.

  Examples of the biodegradable impact resistance improver include Pramate PD-150 (trade name; manufactured by Dainippon Ink Chemical Co., Ltd.) and Puramate PD-350 (trade name; manufactured by Dainippon Ink Chemical Co., Ltd.). Non-biodegradable thermoplastic elastomers include, for example, TAFMER (trade name; manufactured by Mitsui Chemicals), syndiotactic polypropylene, ethylene-propylene-diene rubber, styrene-butadiene-butylene-styrene SBBS rubber, and imino modification. Examples include SBBS rubber, styrene-ethylene-butylene-styrene-based SEBS rubber, olefin-based elastomer or rubber such as imino-modified SEBS rubber, and silicon-based rubber such as metabrene (trade name: manufactured by Mitsubishi Rayon Co., Ltd.).

The above impact resistance improvers may be used alone or in combination of two or more. The addition amount of the impact resistance improver can be appropriately selected depending on the application, but is 0.1 to 20 parts by weight, preferably 1 part by weight, based on 100 parts by weight of the lactic acid resin (A). -15 parts by weight, more preferably 3 parts by weight to 10 parts by weight.

<Method for producing lactic acid resin composition>
The lactic acid resin composition of the present invention comprises a lactic acid resin (A) and a moldability improver (B), and if necessary, a crystal nucleating agent, a crystallization accelerator, an antiblocking agent, a lubricant, a release agent, It can be obtained by mixing other additives such as impact modifiers. The mixing of each component can apply a publicly known method and a kneading technique. For example,
(1) Powdery or pellet-like lactic acid resin (A), moldability improver (B), and other additives as needed are mixed together in a ribbon blender, and then mixed with a twin-screw extruder. A method of extruding pellets while heating and melting;
(2) When the powdered or pelleted lactic acid resin (A) is formed into an extruded pellet, the moldability improver (B) and other additives as necessary are extruded by a side feed or a liquid injection pump. Adding and mixing in the cylinder of
(3) After forming a pellet (masterbatch) obtained by extruding pellets by extruding the moldability improver (B) and other additives as necessary to a high concentration, the masterbatch is in the form of powder or pellets. A method of processing a molded article by diluting with a lactic acid resin (A) by dry blending;
(4) A method in which the above methods are combined and mixed may be mentioned.

  In addition, when adding a moldability improving agent (B) and other additives as necessary as a master batch, it may be added as a master batch for each additive or as a master batch of two or more additives. There are no restrictions on the method. When added as a master batch, the mixing ratio with the lactic acid resin (A) is such that the weight ratio of the master batch / lactic acid resin (A) is 1/100 to 1/2, preferably 1/50 to 1 /. 3, more preferably 1/30 to 1/5, particularly preferably 1/30 to 1/10.

[Molded body]
The molded article of the present invention comprises a lactic acid resin composition comprising the lactic acid resin (A) and the moldability improving agent (B) described above, and other additives as required.

  The molded article of the present invention is produced from the above-described lactic acid resin (A) and moldability improver (B), and a lactic acid resin composition containing other additives as required. For example, an injection molding method, an extrusion molding method, a blow molding method, a profile extrusion molding method, an inflation molding method, or a press molding method can be applied.

<Sheet>
The sheet of the present invention comprises a lactic acid resin composition containing the lactic acid resin (A) and moldability improver (B) described above, and other additives as required, and is a known and publicly used extruder or extruder. Can be manufactured with technology. Moreover, a stretched sheet can be produced by stretching as necessary.

  Since the sheet of the present invention comprising the lactic acid-based resin composition contains the moldability improver (B), it has excellent heat absorption capability. A molded article having a suitable thickness can be obtained, and a thermoformed article can be produced with excellent production efficiency even when a sheet having a relatively high degree of crystallinity is used.

  Further, since the formability improver (B) is dispersed in the sheet of the present invention, when heat is applied to the sheet, not only the sheet surface but also the inside thereof is heated uniformly. The sheet of the invention is considered to be excellent in thermoformability.

  The surface of the sheet comprising the lactic acid resin composition of the present invention is coated with a layer having functions such as antistatic property, antifogging property, tackiness, gas barrier property, adhesion and easy adhesion as necessary. Can be formed. For example, the antistatic layer can be formed by applying an aqueous coating solution containing an antistatic agent to one or both sides of the sheet and drying it. In addition, a layer having functions such as antistatic property, antifogging property, adhesiveness, gas barrier property, adhesion, and easy adhesion can be obtained by laminating other resin and other sheet, if necessary, on the above sheet. Can be formed. At that time, known methods such as extrusion lamination and dry lamination can be used.

<Multilayer sheet>
The multilayer sheet of the present invention comprises at least one sheet of a lactic acid resin composition comprising a lactic acid resin (A), a moldability improving agent (B), and other additives as required. . The layer other than the sheet made of the lactic acid resin composition described above may be, for example, a biodegradable polyester or other general-purpose resin, and can be appropriately selected depending on the purpose.

Examples of the biodegradable polyester include (1) polylactic acid and lactic acid-other aliphatic hydroxycarboxylic acid copolymer, (2) lactic acid resin containing polyfunctional polysaccharide and lactic acid unit, and (3) fat. A lactic acid resin containing an aliphatic polycarboxylic acid unit, an aliphatic polyhydric alcohol unit and a lactic acid unit, and (4) a lactic acid resin of a mixture thereof;
An aliphatic polyester composed of an aliphatic polyhydric carboxylic acid and an aliphatic polyhydric alcohol such as polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, and derivatives thereof;
Examples thereof include biodegradable polyesters such as polyethylene terephthalate adipate, polybutylene terephthalate adipate, and aliphatic polyester carbonate. In particular, in the case of transparency, safety, price, and rigidity required for the secondary molded body described later, such as a container, polylactic acid can be preferably used.

  The layer structure of the multilayer sheet of the present invention is not particularly limited as long as the layer (x) composed of the lactic acid resin composition of the present invention is included in at least one layer. For example, layer (x) / layer ( It is possible to take a structure such as a two-layer structure of y), a three-layer structure of layer (x) / layer (y) / layer (x), layer (y) / layer (x) / layer (y), etc. What is necessary is just to select suitably according to the use of a sheet | seat.

  For example, when a multilayer sheet is formed into a thermoformed body to be described later, the layer structure of the multilayer sheet has a mold temperature higher than the glass transition temperature (Tg) of the layer in contact with the mold. When the layer in contact with the mold is polylactic acid (Tg = about 60 ° C.) and the mold temperature is 60 ° C. or higher, the layer (x) made of the lactic acid resin composition of the present invention is at least composed of a surface layer. preferable.

  For example, when a layer composed of the lactic acid resin composition of the present invention is used as an outermost layer to form a two-layer sheet, a layer (x) / layer (y), a three-layer sheet, a layer (x) / layer ( It is possible to take a layer structure such as y) / layer (x).

  Moreover, when adding the additive mentioned above, it can add to all the layers or only an inner layer, an outer layer, or an intermediate | middle layer, and can select suitably according to the objective. For example, in order to impart the slipperiness of the sheet, it is preferable to add a lubricant or an antiblocking agent only to the innermost layer, and the slippery can be efficiently expressed in a relatively small amount.

Regarding the layer thickness structure, in the case of a two-layer structure, the ratio x / y of the layer (x) / layer (y) thickness is 0.05 to 0.95 / 0.95 to 0.05, preferably 0. .2 to 0.8 / 0.8 to 0.2, more preferably 0.3 to 0.7 / 0.7 to 0.3. In the case of a three-layer structure, layer (x) /
The ratio x / y / x of the layer (y) / layer (x) thickness is 0.05 to 0.6 / 0.05 to 0.9 / 0.05 to 0.6, preferably 0.05 to 0.5 / 0.2 to 0.7 / 0.05 to 0.5, more preferably 0.1 to 0.4 / 0.3 to 0.5 / 0.1 to 0.4.

The multilayer sheet of the present invention can be produced by a publicly known extruder or extrusion technique. Moreover, a stretched sheet can be produced by stretching as necessary.
The multilayer sheet of the present invention is preferably formed into a sheet by a melt extrusion method using an extruder equipped with a T die. At this time, different resin compositions may be bonded after being formed into separate sheets, or may be co-extruded using an extruder equipped with a multi-manifold die or a feed block. Moreover, a multilayer stretched sheet can be produced by stretching the obtained multilayer sheet in the flow direction by roll stretching. Furthermore, it may be stretched in the transverse direction by tenter stretching, or may be heat-treated under tension after transverse stretching.

  In the multilayer sheet of the present invention, a layer having functions such as antistatic property, antifogging property, tackiness, gas barrier property, adhesion and easy adhesion may be formed on the surface of the multilayer sheet as necessary by coating. it can. For example, the antistatic layer can be formed by applying an aqueous coating solution containing an antistatic agent to one side or both sides of a multilayer sheet and drying. In addition, the multilayer sheet of the present invention may be laminated with other resins and other sheets as necessary to provide functions such as antistatic properties, antifogging properties, tackiness, gas barrier properties, adhesion, and easy adhesion. A layer having can be formed. At that time, known methods such as extrusion lamination and dry lamination can be used.

[Thermoforming body]
The thermoformed article of the present invention is formed by thermoforming an amorphous or moderately crystallized sheet comprising the lactic acid resin composition of the present invention or a multilayer sheet containing the sheet, while crystallizing it before or during molding. It is excellent in moldability (moldability) as compared with the case where the moldability improver (B) is not added.

  In order for the thermoformed body obtained from the sheet or multilayer sheet of the present invention to have sufficient heat resistance, the sheet made of the lactic acid resin composition of the present invention to which a crystal nucleating agent has been added, has a melting point from the glass transition temperature or higher. For example, when the lactic acid resin is polylactic acid, the temperature is 60 ° C to 130 ° C, preferably 70 ° C to 120 ° C, more preferably 80 ° C to 110 ° C, still more preferably 80 ° C to 100 ° C. It is desirable to heat and crystallize highly.

The crystallinity at this time is 20% or more, preferably 20% to 45%, more preferably 20% to 40%, still more preferably 25% to 40%, and particularly preferably 25% to 35%.
By performing secondary molding after setting the crystallinity of the sheet made of the lactic acid resin composition within the above range, a thermoformed article having excellent molding processability and sufficient heat resistance can be obtained. Moreover, since the said crystallinity can be achieved in a very short time by using the lactic acid-type resin composition of this invention, a thermoforming body can be obtained with the outstanding production efficiency.

  The method of heating the sheet or multilayer sheet of the present invention varies depending on various thermoforming methods as described later, for example, a method of heating by radiant heat of a heater, a method of heating by contacting a heated metal plate or the like. Can be mentioned. Further, the heating time differs depending on the heating method, and may be any time as long as it is a time for heating the sheet to the above-described preferable temperature range.

For example, in the case of vacuum forming or vacuum / pressure forming used for thermoforming, such as polyethylene terephthalate (PET) or polystyrene (PS), a heating method is generally used by radiant heat such as a ceramic heater, The heater temperature is 700 ° C., preferably 150 ° C. to 500 ° C., more preferably 200 ° C. to 500 ° C., further preferably 250 ° C. to 400 ° C., particularly preferably 300 ° C. to 400 ° C., from the glass transition temperature of the lactic acid resin composition. The heating time is 1 second to 60 seconds, preferably 1 second to 30 seconds, more preferably 1 second to 20 seconds, still more preferably 1 second to 10 seconds, and particularly preferably 1 second to 7 seconds.

  In addition, in the case of hot plate pressure forming used for thermoforming of stretched polystyrene (OPS) or the like, the heating method is generally a method of contacting a heated metal plate or the like, and the temperature of the metal plate or the like is 60 ° C to 200 ° C, preferably 70 ° C to 175 ° C, more preferably 80 ° C to 175 ° C, still more preferably 80 ° C to 150 ° C, and the heating time is 1 to 20 seconds, preferably 1 second to 15 seconds. More preferably, it is 1 second-10 seconds, More preferably, it is 1 second-5 seconds, Most preferably, it is 1 second-3 seconds.

  In order for the thermoformed product obtained from the sheet of the present invention to have sufficient transparency, a sheet made of the lactic acid resin composition of the present invention is made of a temperature between the glass transition temperature and the melting point, such as a lactic acid resin. In the case of polylactic acid, the haze after heating for 2 to 15 seconds at a temperature of 60 ° C. to 130 ° C. and highly crystallization is 15% or less, more preferably 10% to 1% when the sheet thickness is 450 μm, More preferably, it is desirable to prepare so as to be 7% to 1%, particularly preferably 5% to 1%.

  The thermoforming for obtaining the thermoformed product of the present invention is performed by contacting a mold set at a specific temperature during molding by a publicly known molding method such as vacuum molding, vacuum pressure forming, hot plate pressure forming, press molding or the like. While doing. At this time, crystallization may be performed simultaneously with molding. The thermoformed article of the present invention can be formed with a molding cycle equivalent to a general-purpose resin such as polystyrene (PS) or polyethylene terephthalate (PET).

  Here, in the case of a forming method using a forming machine such as a vacuum forming machine, a vacuum pressure forming machine, a hot plate pressure forming machine, etc., in order to highly crystallize while forming, after preheating the sheet in advance It is shaped by being brought into contact with a mold set in a specific temperature range, by vacuum forming, pressure forming or vacuum / pressure forming, and further by assisting with a plug.

  For example, when the lactic acid resin is polylactic acid, the sheet is preheated to 60 ° C to 130 ° C, preferably 70 ° C to 120 ° C, more preferably 80 ° C to 110 ° C, particularly preferably 85 ° C to 105 ° C. Then, it shape | molds, making it contact with the metal mold | die set to 60 to 130 degreeC, Preferably 70 to 125 degreeC, More preferably, 80 to 120 degreeC, More preferably, 90 to 110 degreeC.

  When the sheet temperature is within the above range, a thermoformed article having a good shape and high transparency can be obtained. Moreover, when the mold temperature is within the above range, the crystallization rate of the lactic acid resin composition is increased. As a result, the time for contact with the mold can be shortened, the molding cycle is shortened, and the productivity is increased.

  In addition, when molding using plug assist together, the temperature of the plug is similarly a specific temperature, preferably 40 ° C to 120 ° C, more preferably 50 ° C to 110 ° C, and further preferably 60 ° C to 110 ° C. Particularly preferably, it is more effective when set to 70 ° C to 100 ° C.

  The optimum temperature of the sheet, mold and plug is determined depending on the composition of the lactic acid resin composition, for example, the lactic acid resin (A) and the moldability improver (B), and other additives used as necessary. And changes with quantity.

Therefore, the optimum conditions for the mold and plug temperature can be appropriately set in consideration of the transparency, heat resistance, moldability and productivity of the molded body.
The time for which the sheet is brought into contact with the mold is 1 to 15 seconds, preferably 1 to 10 seconds, more preferably 1 to 7 seconds, and further preferably, in order to obtain a thermoformed article having substantially sufficient heat resistance. It takes 1 to 7 seconds, particularly preferably 1 to 4 seconds. When the contact time is within the above range, a thermoformed article having the desired heat resistance and transparency can be obtained with high productivity.

The molded body and thermoformed body (hereinafter simply referred to as “molded body”) made of the lactic acid resin composition of the present invention are excellent in volume retention. Specifically, the volume retention is 90% or more, more preferably 95% or more. Here, the volume retention in the present invention is determined by immersing the cup-shaped molded body in 90 ° C. warm water for 5 minutes, then taking out the cup-shaped molded body, and the amount of water (V1) filled in the cup-shaped molded body. ) And the amount of water (V0) filled in the cup-shaped molded body before immersion, and the following calculation formula:
Volume retention (%) = V1 / V0 × 100
Is calculated by

  The molded body made of the lactic acid resin composition of the present invention has a high deformation temperature by visual judgment when, for example, a cup-shaped molded body is held at a constant temperature for 2 hours in a thermostat, that is, heat shrink resistance. It has the characteristic that it is excellent in. The thermal deformation start temperature is preferably 55 ° C. or higher, more preferably 60 ° C. or higher, and still more preferably 65 ° C. or higher.

In the present invention, a molded article excellent in transparency can be obtained by appropriately selecting a crystal nucleating agent and a crystallization accelerator.
Transparency of the molded product of the present invention (in accordance with JIS K6714, Tokyo Denshoku Haze Met
er, measured in terms of thickness of 250 μm) is preferably 10% or less, more preferably 8% to 1%, still more preferably 7% to 1%, particularly preferably 6% to 1%. is there.

  Since the molded article of the present invention has high heat resistance while maintaining the high transparency characteristic of the lactic acid resin, for example, hot fill containers such as pudding, jam and curry containers, food trays, blister containers, and It can also be widely used in applications requiring transparency and heat resistance, such as general packaging containers such as clear cases.

[Example]
EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples at all.

The details of the lactic acid resin (A), moldability improver (B) and the like used in this example are as follows.
<Lactic acid resin (A)>
a1: Polylactic acid (LACEA (registered trademark) H-400, manufactured by Mitsui Chemicals, weight average molecular weight (Mw); 210,000, dispersity (Mw / Mn); 3.2, L-form / D-form = 98.2 / 1.8, melting point 165 ° C.)
<Formability improver (B)>
b1: Hydrotalcite (Alkamizer, manufactured by Kyowa Chemical Industry Co., Ltd.)
b2: Compound represented by the following formula (1)

<Organic crystal nucleating agent>
EBL: Ethylene bis lauric acid amide (“Sripax L” manufactured by Nippon Kasei Co., Ltd.)
EBS: Ethylene bis-stearic acid amide (“Alflow H50S” manufactured by Nippon Oil & Fats Co., Ltd.) <crystallization accelerator>
c1: benzyl = 2- (2-methoxyethoxy) ethyl = adipate (Differty (registered trademark) 101, manufactured by Daihachi Chemical Co., Ltd.)
<Vacuum / Pneumatic forming machine>
FKS-0631-20 (manufactured by Asano Laboratory) was used.

[Example 1]
100 parts by weight of polylactic acid resin a1 (LACEA (registered trademark) H-400), 0.01 part by weight of moldability improver b1 (Alkamizer, manufactured by Kyowa Chemical Industry Co., Ltd.), organic crystal nucleating agent EBS (Alflow H50S) 0.5 parts by weight and 1 part by weight of a crystallization accelerator c1 (Dyfati (registered trademark) 101) were mixed with a Henschel mixer, and then pelletized under conditions of an extruder cylinder set temperature of 190 to 220 ° C.

  Subsequently, the obtained pellet was supplied to a T-die film forming machine (screw diameter 50 mm, die width 500 mm) in which the cylinder temperature was set to 220 ° C. The molten resin was extruded onto a cast roll whose temperature was adjusted to 30 ° C. to obtain a sheet having a thickness of 1200 μm. A part of this sheet was cut and subjected to measurement of haze (transparency A) and crystallinity (crystallinity A).

  The remainder of the 1200 μm-thick sheet is heated under conditions of a heater temperature of 350 ° C. and a preheating time of 7 seconds so that the sheet temperature becomes about 100 ° C., and then is vacuum-compressed using a mold and a plug held at room temperature. Thermoforming was performed to produce a cup-shaped molded body. The sheet temperature is a value measured with a non-contact thermometer attached to the vacuum / pressure forming machine. The mold shape is a cup-shaped mold having an upper diameter of 100 mm, a bottom diameter of 60 mm, a height of 150 mm, and a drawing ratio of 1.5, and an optimum mold holding time in which a good thermoformed body (cup) can be obtained. Was 5 seconds.

The physical properties of the sheet and the thermoformed body were measured and evaluated by the following methods. The results are shown in Table 1.
Physical properties of the sheet;
<Crystallinity A>
Using a differential thermal scanning calorimeter (Seiko Co., Ltd.), the amount of heat of crystallization (ΔHc) and the amount of heat of fusion (ΔHm) were measured when the test piece obtained from the sheet was heated at a rate of 10 ° C./min. The crystallinity A is calculated by the following formula:
Crystallinity A (%) = (heat of fusion−heat of crystallization) / 93 × 100
This is the value obtained in. “93” in the formula is the value of the perfect ideal crystal melting enthalpy (J / g) of polylactic acid.

<Transparency A (Haze)>
In accordance with JIS K6714, a thickness meter of 120 is used using a Haze Meter manufactured by Tokyo Denshoku Co., Ltd.
The value of the 0 μm sheet was determined.

Physical properties of thermoformed bodies;
<Moldability>
After heating the sheet having a thickness of 1200 μm while changing the preheating time so that the sheet temperature becomes 80 to 100 ° C. at a preheating heater temperature of 350 ° C., vacuum / pneumatic thermoforming is performed using a mold and a plug held at room temperature, The shape of the obtained molded body was observed. The evaluation criteria are as follows.

○: Good shape of mold shape △: Bad shape of mold shape
X: Molding is impossible
From the side surface of the obtained thermoformed body (cup), a cut sample of 5 cm long × 2 cm wide was collected. About this cut sample, thickness was measured and the haze was measured by the method similar to the said transparency A. FIG.

<Heat resistance>
Heat-resistant shrinkage After the obtained thermoformed body (cup) was held in a dryer at 65 ° C. for 2 hours, the degree of deformation was visually evaluated. The evaluation criteria were “AA” when there was no deformation and “BB” when the deformation was significant.

-Volume retention After the obtained thermoformed body (cup) was immersed in 60 degreeC warm water for 5 minutes, the cup was taken out. From the amount of water filled in the cup after immersion (V1) and the amount of water filled in the cup before immersion (V0), the following calculation formula:
Volume retention (%) = V1 / V0 × 100
The volume retention was determined.

[Examples 2-3, Comparative Examples 1-3]
As shown in Table 1, except that the lactic acid resin (A), the moldability improver (B), the crystal nucleating agent, the crystallization accelerator, and the mold temperature and sheet temperature in thermoforming were changed. In the same manner as in Example 1, preparation of a lactic acid resin composition, preparation of a sheet, preparation of a thermoformed article, and evaluation thereof were performed. The results are shown in Table 1.

  In addition, the description “≦ 60” of the volume retention ratio (%) of Comparative Examples 2 and 3 in Table 1 shows that when Comparative Examples 2 and 3 were re-examined, the shape of the thermoformed body (cup) was not reproducible, It shows that it was 60% even if the volume retention was high.

Claims (4)

  A lactic acid resin composition containing 100 parts by weight of a lactic acid resin (A) and 0.005 to 10 parts by weight of a moldability improver (B). The lactic acid resin composition according to claim 1, wherein the moldability improving agent (B) is a compound represented by the following formula (1).

  A method for producing a thermoformed article comprising a step of heat-softening a sheet comprising the lactic acid resin composition according to claim 1 or 2 and then molding the sheet by a vacuum forming method, a pressure forming method or a vacuum pressure forming method.   A thermoformed article obtained by the production method according to claim 3.