JP2010270183A - Polylactic acid-based oriented sheet, method for manufacturing the same, and formed product obtained by forming polylactic acid-based oriented sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid-based oriented sheet that has good heat resistance and transparency while simultaneously having well-balanced practical impact resistance and moldability, a method for manufacturing the same, and a formed product obtained by forming the polylactic acid-based oriented sheet. <P>SOLUTION: The polylactic acid-based oriented sheet is obtained by at least performing uniaxial orientation of a resin composition containing a polylactic acid-based resin (A) and a methacrylate-based resin (B). A blending ratio of the polylactic acid-based resin (A) to the methacrylate-based resin (B) in the resin composition, (A):(B) is 75:25 to 45:55 (mass ratio). Average values of surface orientation degrees (ΔP) and orientation relaxation stress (ORS) of the oriented sheet obtained in the longitudinal direction and the width direction satisfy formula (1) ΔP≥(4.6-0.072X)/1,000 and formula (2) ORS≤5.5 MPa. The formed product is obtained by forming the polylactic acid-based oriented sheet. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polylactic acid-based stretched sheet excellent in heat resistance, impact resistance and moldability, a method for producing the same, and a molded body obtained by molding the polylactic acid-based stretched sheet.

  In recent years, it has been recognized by general consumers that the use of plastic products containing various biodegradable polymers is preferable from the viewpoint of environmental protection and the use of plant-derived materials from the viewpoint of saving petroleum resources. As a result, attempts to use biodegradable polymers and plant-derived polymers as raw materials have also been widely applied to industrial products.

In particular, polylactic acid is a plant-derived and biodegradable polymer, and among biodegradable polymers, it has a relatively high melting point, toughness and transparency, and is recognized as a practically superior polymer. Has been.
However, polylactic acid is deficient in heat resistance as compared with general-purpose synthetic resins. Therefore, various methods for mixing polylactic acid and other thermoplastic resins have been reported as methods for improving the heat resistance of polylactic acid.

For example, by selecting polymethacrylate having a specific molecular weight as a thermoplastic resin, this polymethacrylate and polylactic acid can be uniformly melt-kneaded, resulting in polylactic acid containing improved heat resistance A resin composition is disclosed (for example, see Patent Document 1).
However, a sheet obtained by stretching a polylactic acid-containing resin composition disclosed in Patent Document 1 may lack impact resistance and lack practicability as a package.

In order to improve this problem, a polylactic acid resin composition containing a polylactic acid resin having a weight molecular weight of 50,000 or more and a polymethacrylate is stretched to form a film, and then subjected to a heat treatment. It is disclosed that when the crystallinity of a film is increased, the rigidity of the film at a high temperature can be maintained (see, for example, Patent Document 2).
However, when the film obtained by this technique is subjected to a process such as deep drawing, for example, it is difficult to obtain a molded product having the desired mold reproducibility due to its high rigidity, In addition, the molded article may have insufficient impact resistance at room temperature, and is difficult to handle as compared with general-purpose polyester products.

JP-A-2005-171204 Japanese Patent Laying-Open No. 2005-036054

  In view of the above circumstances, the problem to be solved by the present invention is a polylactic acid-based stretched sheet having a good balance between practical impact resistance and formability and good heat resistance and transparency, and a method for producing the same In addition, an object of the present invention is to provide a molded article obtained by molding the polylactic acid-based stretched sheet.

  As a result of intensive studies to solve the above problems, the present inventors have obtained a sheet obtained by stretching a resin composition containing a polylactic acid resin and a methacrylate resin in a specific ratio in at least one axial direction. The inventors found that a sheet having excellent heat resistance, impact resistance and mold reproducibility during molding can be obtained when the degree of plane orientation and orientation relaxation stress satisfy a specific relational expression, and the present invention has been completed.

That is, the present invention is a polylactic acid-based stretched sheet formed by at least uniaxially stretching a resin composition containing a polylactic acid-based resin (A) and a methacrylate-based resin (B),
The blending ratio (A) :( B) of the polylactic acid resin (A) and the methacrylate resin (B) in the resin composition is 75:25 to 45:55 (mass ratio), and the resulting stretching The average values in the longitudinal direction and the width direction of the sheet orientation degree (ΔP) and orientation relaxation stress (ORS) are expressed by the following formulas (1) and (2).
ΔP ≧ (4.6-0.072X) / 1000 (1)
ORS ≦ 5.5 MPa (2)
[However, X in the above formula (1) represents the content (% by mass) of the methacrylate resin (B) in the resin composition, and 25 ≦ X ≦ 55. ]
The present invention provides a polylactic acid-based stretched sheet characterized by satisfying the above requirements, and a molded body formed by molding the same.

  Furthermore, this invention provides the manufacturing method of the polylactic acid-type stretched sheet which has the said specific performance.

  The polylactic acid-based stretched sheet of the present invention solves the problems of impact resistance of conventional polylactic acid-based stretched sheets and mold reproducibility during molding, and is the same as general-purpose polyester-based stretched sheets and styrene-based stretched sheets. It has a certain degree of heat resistance, moldability and strength. Therefore, the polylactic acid-based sheet of the present invention containing a large amount of biodegradable polymer can be used for various general-purpose packaging bodies, which is preferable from the viewpoint of environmental protection.

It is a graph which shows the relationship between a methacrylate resin content rate (mass%) and a plane orientation degree ((DELTA) P) regarding an Example and a comparative example. It is a graph which shows the relationship between the sheet ORS average value (MPa) of an Example, and the protrusion height (mm) at the time of shaping | molding.

  Hereinafter, the present invention will be described in detail.

  The polylactic acid-based stretched sheet of the present invention is a sheet obtained by stretching at least uniaxially a resin composition containing a polylactic acid-based resin (A) and a methacrylate-based resin (B).

  The polylactic acid-based resin (A) used in the present invention is a polymer containing 85% by mass or more of lactic acid monomer units, and is polylactic acid, or lactic acid and other hydroxycarboxylic acid, aliphatic cyclic ester, dicarboxylic acid. It is a copolymer of an acid or a diol, or a composition of these polymers containing 85% by weight or more of a lactic acid monomer unit.

  Lactic acid can be used by mixing L-lactic acid and D-lactic acid, but is composed of either isomer of L-lactic acid or D-lactic acid from the viewpoint of excellent heat resistance of the obtained stretched sheet. Specifically, it is preferable that the D-form content (molar ratio of D-lactic acid to the total mass of lactic acid used as a raw material) is 2.0 mol% or less or 98.0 mol% or more.

  The production method of the polylactic acid resin (A) used in the present invention is not particularly limited, and various polymerization methods such as a direct polymerization method from lactic acid or a ring-opening polymerization method via lactide, etc. Can be used.

The methacrylate resin (B) used in the present invention is a homopolymer of a methacrylic ester such as cyclohexyl methacrylate, t-butyl cyclohexyl methacrylate, or methyl methacrylate, or these methacrylic esters and other monomers. And a copolymer.
Examples of the monomer copolymerizable with the methacrylic acid ester include other methacrylic acid alkyl esters, acrylic acid alkyl esters, styrene, vinyltoluene, α-methylstyrenes, N-phenylmaleimide, and N-cyclohexylmaleimide. And unsaturated carboxylic acid anhydrides such as maleic anhydride, and unsaturated acids such as acrylic acid, methacrylic acid and maleic acid.

Since the methacrylate resin (B) is used in combination to improve the lack of heat resistance of the polylactic acid resin (A), the methacrylate resin (B) alone has excellent heat resistance. For example, it is preferable that the Vicat softening temperature [value measured according to ASTM D1525 (weight 49 N, temperature increase rate 2 ° C./min)] be 105 ° C. or higher.
Furthermore, the weight average molecular weight (polystyrene conversion value using gel permeation chromatography) of the methacrylate resin (B) is preferably in the range of 50,000 to 200,000 from the viewpoint of processability and strength of the resin. More preferably, it is in the range of 7 to 150,000.

  Moreover, it does not specifically limit as a manufacturing method of methacrylate-type resin (B), The thing obtained by various methods, such as block polymerization, solution polymerization, suspension polymerization, can be used.

In the present invention, the polylactic acid-based stretched sheet is a resin composition containing a polylactic acid-based resin (A) and a methacrylate-based resin (B), and the polylactic acid-based resin (A) and the methacrylate-based resin (B). It is essential that the blending ratio (A) :( B) is 75:25 to 45:55 (mass ratio).
When the blending ratio of the polylactic acid-based resin (A) exceeds 75% by mass, the heat resistance of the obtained polylactic acid-based stretched sheet is not at a practical level, and the blending ratio of the polylactic acid-based resin (A) is 45% by mass. If it is less than that, it will lack practicality as a plant-derived polymer or biodegradable polymer.

In the present invention, the polylactic acid-based resin (A) and the methacrylate-based resin (B) are used in the above blending ratio, but other resins and various additives may be used in combination as necessary. .
Examples of the various additives include an antistatic agent, an antioxidant, an ultraviolet absorber, a lubricant, an antiblocking agent, and a heat stabilizer.

  The polylactic acid-based stretched sheet of the present invention is a sheet obtained by using the resin composition mixed at the above-described blending ratio and stretching it at least uniaxially. The stretching direction of the sheet may be either the longitudinal direction or the width direction, but is preferably the longitudinal direction in the manufacturing process. In order to adjust the degree of orientation of the obtained sheet, the sheet is preferably biaxially stretched in the longitudinal direction and the width direction.

In the polylactic acid-based stretched sheet of the present invention, the average value in the longitudinal direction and the width direction of the degree of plane orientation (ΔP) and orientation relaxation stress (ORS) is expressed by the following formulas (1) and (2).
ΔP ≧ (4.6-0.072X) / 1000 (1)
ORS ≦ 5.5 MPa (2)
[However, X in the above formula (1) represents the content (% by mass) of the methacrylate resin (B) in the resin composition, and 25 ≦ X ≦ 55. ]
It is essential to satisfy.
Those not satisfying these relational expressions lack the balance between the impact resistance and formability of the stretched sheet and are not practical.

The plane orientation degree (ΔP) of the sheet is a numerical value defined by the refractive index of the sheet measured with an Abbe refractometer or the like. The refractive index in the longitudinal direction of the sheet is nMD, the refractive index in the width direction is nTD, When the refractive index in the thickness direction is nZD, it is expressed by the following relational expression (4).
ΔP = (nMD + nTD) / 2−nZD (4)

  If it is difficult to measure the refractive index due to the fact that the sheet is opaque, it can be obtained by other methods. Examples of such methods include X-ray, infrared spectroscopy, and Raman spectroscopy. Can be mentioned. In particular, the ATR method of infrared spectroscopy can be preferably used because the state of orientation of the sheet surface can be easily measured. In this case, using a sheet whose refractive index can be measured with an Abbe refractometer or the like, the correlation between the sheet surface orientation coefficient and the surface orientation degree measured by other methods is obtained, and the target sheet is obtained. By converting into the plane orientation coefficient, the plane orientation degree of the target sheet can be obtained.

  A sheet that does not satisfy the relational expression (1) is likely to cause problems particularly in terms of impact resistance and strength.

Further, the orientation relaxation stress (ORS) of the sheet is the maximum value of the stress that develops at a sheet temperature of 120 ° C. by dry heating in accordance with ASTM D1504.
A sheet that does not satisfy the relational expression (2) is likely to cause a problem particularly in terms of mold reproducibility during molding.

  In the case of a biaxially stretched sheet, these ORS conditions may be that a target sheet may be obtained by satisfying one stretching direction, but it is easy to form various shapes under relatively wide thermoforming conditions. From a certain point of view, it is more preferable that the ORS condition is satisfied in the two stretching directions.

Furthermore, in the polylactic acid-based stretched sheet, the crystallinity expressed by the following formula (3) is 16 J / g or less, so that the moldability is excellent, and in particular, application to a deep-drawn molded body is possible. It is preferable from the point.
Crystallinity = heat of crystal melting (ΔHm) −heat of crystallization (ΔHc) (3)

In addition, the amount of heat of crystal melting and the amount of heat of crystallization in the above formula (3) are determined as follows.
That is, according to JIS-K7122, the sample was heated by a differential scanning calorimeter from 30 ° C. to 200 ° C. under a temperature rising rate of 10 ° C./min and a nitrogen gas flow rate of 50 ml / min. A DSC curve is prepared, and the crystallization heat quantity (ΔHc) is obtained from the crystallization exothermic peak area at the time of temperature rise in the drawn DSC curve, and the crystal melting heat quantity (ΔHm) (J / g) is obtained from the crystal melting endothermic peak area. Asked.

  Although it does not specifically limit about the thickness of the polylactic acid-type stretched sheet of this invention, 70-500 micrometers from viewpoints, such as the handleability at the time of processing a molded object, and the intensity | strength and transparency as a molded object. It is preferable to make it become the range of 100-300 micrometers.

The polylactic acid-based stretched sheet of the present invention can be obtained by uniformly mixing a solution in which each of the above components is dissolved in a solvent, removing the solvent from the solution, and then forming a film. It is preferable to employ a melt film-forming method, which is a practical production method, without requiring a step such as solvent removal.
The melt film-forming method is a method for producing a sheet by melting and kneading each component. The melt film forming method is not particularly limited, and after obtaining a resin composition using various commonly used mixers such as a kneader, a roll mill, a Banbury mixer, a single-screw or twin-screw extruder, it is melted. Examples thereof include a method in which the mixed resin is introduced into a slit-shaped base, extruded into a sheet shape on a cooling casting drum, and a sheet is obtained using a T-die method, a touch roll casting method, or the like. Among these melt film forming methods, from the viewpoint of productivity, a method of forming a sheet using a single-screw extruder or a twin-screw extruder is preferable, and in terms of mixing properties, a sheet is formed using a twin-screw extruder. The method is further preferred.

Further, the mixing order of the resins is not particularly limited. For example, after the polylactic acid resin (A) and the methacrylate resin (B) are dry blended, a method of using a melt kneader or a polylactic acid resin ( Examples thereof include a method of preparing a master batch in which A) and a methacrylate resin (B) are melt-kneaded, and then melt-kneading the master batch and the polylactic acid resin (A), and then forming a film.
In addition, if necessary, a method in which other additives are melt-kneaded at the same time, or a master batch in which the polylactic acid resin (A) and other additives are melt-kneaded in advance are prepared. You may use the method of melt-kneading resin (A) and methacrylate-type resin (B).

  Moreover, it is preferable that the temperature at the time of melt-kneading each component is in the range of 180 ° C. to 260 ° C., and from the viewpoint of preventing deterioration of the polylactic acid resin (A), and the polylactic acid resin (A) From the viewpoint of kneadability of the methacrylate resin (B), the temperature at which each component is melt-kneaded is more preferably in the range of 200 ° C to 230 ° C.

The draw ratio of the polylactic acid-based stretched sheet is 1.3 to 8.0 times in at least one direction, preferably 1.7 to 6.0 times, more preferably 1.5 to 4.0 times. is there.
The stretching temperature is in the range of 70 to 95 ° C. from the viewpoint that a polylactic acid-based stretched sheet that satisfies the above formulas (1) and (2) can be easily obtained.
The polylactic acid-based stretched sheet is preferably cooled below the stretching temperature from the viewpoint of preventing the orientation due to stretching from being relaxed after stretching and from the viewpoint of preventing the deterioration of formability due to the progress of crystallization. It is more preferable to cool at 0C.

A preferable example of the stretching conditions for the polylactic acid-based stretched sheet is to produce a 210 μm polylactic acid-based stretched sheet that has been roll-stretched 2.0 to 2.5 times and then tenter-stretched 2.0 to 2.5 times. The tenter stretching temperature is 70 to 90 ° C, and the cooling temperature is 40 to 60 ° C.
Moreover, when changing a draw ratio from 2.5 times to 3.0 times, in order to obtain the same ORS sheet, it is preferable to raise the drawing temperature by 2 to 7 ° C. as a rough guide.

  In addition, when the surface of the polylactic acid-based stretched sheet is coated with a surfactant or the like in order to impart antistatic properties or antifogging properties to the obtained polylactic acid-based stretched sheet, at least one surface of the polylactic acid-based stretched sheet is suitable An aqueous solution of a surfactant or the like adjusted to a proper concentration is applied by various methods such as a squeeze roll coater, an air knife coater, a knife coater, a spray coater, a gravure roll coater, and a bar coater, and then the applied aqueous solution is dried. In particular, from the viewpoint of improving the uniformity of the coating film, it is preferable to apply a surfactant or the like by the above method after corona treatment of the sheet surface. The strength of the corona treatment is preferably adjusted so that the contact angle with water is 80 to 30 °, more preferably 70 to 35 °. The preferred upper limit of the contact angle between the surface of the sheet and water is a value for improving the uniformity of the coating film, and the preferred lower limit of the contact angle is a value for preventing blocking when the sheet is rolled up. It is.

The polylactic acid-based stretched sheet obtained above can be formed into a molded body by thermoforming. As the thermoforming method, a hot plate contact heat forming method, a vacuum forming method, a vacuum / pressure forming method, a plug assist forming method, or the like is preferably used. The hot plate contact heating molding method is particularly preferable from the viewpoint of the uniformity of the thickness of the molded body and the production efficiency of the molded body, but when the transparency is particularly important, the vacuum molding method by indirect heating or the vacuum / pressure molding method is used. In addition, when performing deep drawing, a plug assist molding method can be employed.
The molding of the polylactic acid-based stretched sheet using these molding methods may be performed continuously using a sheet roll, or may be molded every shot using a cut plate sheet.
Hereinafter, an example of preferable molded object manufacturing conditions is given.

Preferred hot plate temperature conditions for molding the polylactic acid-based stretched sheet of the present invention by hot plate contact thermoforming are the mold reproducibility and molding cycle viewpoint (lower limit) of the molded product, and the transparency of the molded product. From the viewpoint (upper limit) of occurrence of raindrops and raindrops, the hot plate temperature is set to the Vicat softening temperature of the resin mixture +10 to 50 ° C, more preferably +15 to 40 ° C, and further preferably +20 to 35 ° C.
In addition, the heating time (the time for which the sheet is brought into contact with the hot plate in vacuum and / or compressed air and the total delay time until the sheet is vacuumed and / or compressed in order to extend the sheet to the mold) 0.5-15.0 seconds are preferable.

  The shape of the molded body is not particularly limited, such as container lids, trays, food packs, blister packs, other various packs, cases, etc., but the heat resistance and molding characteristic of the polylactic acid-based stretched sheet of the present invention and the molded body thereof From the viewpoints of properties, transparency of the molded product, and impact resistance, the lid of the container is particularly preferable, and among them, the lid of the food packaging container is particularly preferable.

  When the molded body comprising the polylactic acid-based stretched sheet of the present invention is used as a lid for a food packaging container, the container body is molded from the polylactic acid-based stretched sheet of the present invention, as well as a polypropylene non-foamed sheet, a polypropylene-based It is also preferable to use a foamed sheet, a polypropylene-based non-foamed sheet with filler, a polystyrene-based foamed sheet, a polystyrene-based non-foamed unstretched sheet, a crystallized polyester-based sheet, various plastic laminated sheets, paper, pulp, aluminum, etc. Can do.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. Unless otherwise specified, “part” and “%” are based on mass.

  The orientation relaxation stress, the plane orientation degree, and the crystallinity degree of the obtained sheet were measured by the following methods. Further, the physical properties of the sheet were evaluated by measuring heat resistance, mold reproducibility at the time of molding, impact resistance and plant-derived degree as follows.

(1) Orientation relaxation force (ORS)
In accordance with ASTM D-1504, the maximum value of the stress appearing on the sheet was measured at a sheet temperature of 120 ° C. by dry heating with an OS measuring instrument manufactured by Niri Kogyo Co., Ltd.

(2) Degree of plane orientation (ΔP)
Using a sodium light source D-line (wavelength 589 nm), the lengthwise refractive index (nMD), the widthwise refractive index (nTD), and the thicknesswise refractive index (nZD) of Atago Co., Ltd. Abbe refractometer 2T Was measured, and the degree of plane orientation (ΔP) was calculated from the following formula (4).
ΔP = (nMD + nTD) / 2−nZD (4)

(3) Crystallinity (ΔHm−ΔHc)
In accordance with JIS-K7122, a differential scanning calorimeter (DSC-60, manufactured by Shimadzu Corporation) was used to sample approximately 10 mg from 30 ° C. to 200 ° C., a heating rate of 10 ° C./min, and a nitrogen gas flow rate of 50 ml / min. The temperature was raised under the conditions. The heat of crystallization (ΔHc) is determined from the crystallization exothermic peak area at the time of temperature rise in the drawn DSC curve, and the heat of crystal melting (ΔHm) (J / g) is determined from the crystal melting endothermic peak area. The crystallinity was calculated from (5).
Crystallinity = ΔHm−ΔHc (J / g) (5)

(4) Heat resistance The heat resistance of the sheet was evaluated by measuring the shrinkage in the longitudinal direction and the width direction after leaving a 100 x 100 mm sheet test piece in a hot air dryer at a predetermined temperature for 10 minutes. . The shrinkage rate of the sheet was measured every 2 ° C., and the temperature at which the average value of the longitudinal direction and width direction shrinkage rates reached 2% was calculated as the 2% shrinkage temperature (° C.) of the sheet and evaluated according to the following criteria.

The evaluation of the heat resistance of the molded body made of a sheet was performed by molding a container having a depth of 27 mm and an opening of 95 mm × 95 mm by a molding method similar to the mold reproducibility evaluation described later. After standing in a hot air dryer for 5 minutes, the appearance was visually observed. This visual observation was performed every 5 ° C., and the upper limit of the temperature at which the molded body hardly deformed was regarded as the heat resistance temperature (° C.) of the molded body, and evaluated according to the following criteria.
A: 2% shrinkage temperature (° C.) of sheet, heat resistance temperature of molded body is 75 ° C. or more ○: 2% shrinkage temperature (° C.) of sheet, heat resistance temperature of molded body is 60 to less than 75 ° C. Δ: 2% shrinkage temperature (° C.), heat resistance temperature of molded body is less than 50 to 60 ° C. ×: 2% shrinkage temperature (° C.) of sheet, heat resistance temperature of molded body is less than 0 to 50 ° C.

(5) Moldability (mold reproducibility during molding)
The sheet formability was evaluated by measuring the height of the protrusion formed after the sheet was formed using a round hole mold having a diameter of 5 mm, and using this as the protrusion height (mm), based on the following criteria: evaluated. The higher the protrusion height, the easier the sheet is stretched during molding, which means that the shape of the mold can be reproduced well.
Here, the sheet is formed by hot plate contact heating molding method using a hot plate pressure forming machine HPT-100 manufactured by Wakisaka Engineering Co., Ltd., with a heating time of 1.2 seconds, a molding delay time of 1.5 seconds, and a molding time. 2.0 seconds, heating pressure 0.1 MPa, molding pressure 0.4 MPa, mold temperature 50 ° C. The hot plate temperature was set to an upper limit temperature at which no rounded pattern called raindrop was generated on the sheet.
◎: Projection height (mm) during molding is 2.0 mm or more ○: Projection height (mm) during molding is less than 1.5 to 2.0 mm △: Projection height (mm) during molding , 1.0 to less than 1.5 mm ×: protrusion height (mm) during molding is less than 1.0 mm

(6) Impact resistance The impact resistance of the sheet was evaluated according to JIS K7124 and JIS K5400 using a hemispherical core with a tip radius of 6.5 mm using a DuPont impact tester manufactured by Ueshima Seisakusho Co., Ltd. The impact strength (J) of the sheet was measured and evaluated according to the following criteria.
Evaluation of impact resistance of a molded article made of a sheet was performed by molding a container having a flat top surface portion having a depth of 23 mm and an opening portion of 169 mm × 112 mm by the same molding method as the above-described mold reproducibility evaluation. The impact strength (J) of the body top surface was measured and evaluated according to the following criteria.
◎: Impact strength (J) is 0.6 J or more ○: Impact strength (J) is less than 0.2 to 0.6 J △: Impact strength (J) is less than 0.1 to 0.2 J ×: Impact Strength (J) is less than 0.1J

(7) Degree of plant origin The content (mass%) of plant-derived materials such as polylactic acid resin was evaluated as the degree of plant origin according to the following criteria.
A: Degree of plant origin (mass%) is 70 mass% or more. O: Degree of plant origin (mass%) is less than 45-70 mass%. Δ: Degree of plant origin (mass%) is less than 20-45 mass%. : Degree of plant origin (mass%) is less than 20 mass%

Moreover, the following were used as polylactic acid-type resin and methacrylate-type resin.
Polylactic acid resin A1: PLA manufactured by Toyota Motor Corporation Toyota Eco-Plastic U'zS-12
Polylactic acid resin A2: PLA 4032D made by NatureWorks LLC
Methacrylate resin B1: PMMA Delpet 80N manufactured by Asahi Kasei Chemicals Corporation, Vicat softening temperature 109 ° C
Methacrylate resin B2: PMMA Delpet 80NH manufactured by Asahi Kasei Chemicals Corporation, Vicat softening temperature 109 ° C

[Example 1]
The polylactic acid resin (A1) and the methacrylate resin (B1) are supplied to a twin screw extruder (TEX30α-31.5BW-5V manufactured by Nippon Steel Works) having a screw with a diameter of 30 mm, and melted and kneaded. After extruding the sheet from the die and cooling and reheating the sheet with a roll, the sheet was stretched 2.0 times in the sheet flow direction (MD) due to the speed difference of the roll group. Further, the sheet was stretched 2.0 times in a direction orthogonal to the sheet flow direction (referred to as TD) by a tenter to obtain a sheet having a thickness of 0.18 to 0.33 mm.
Here, the stretching temperature (tenter atmosphere temperature) was set to 77 ° C., and the cooling temperature was set to 51 ° C. to obtain sheets having physical properties shown in Table 1.

[Example 2]
A sheet having physical properties shown in Table 1 was obtained in the same manner as in Example 1 except that the stretching temperature was 75 ° C and the cooling temperature was 55 ° C.

[Example 3]
A film having physical properties shown in Table 1 was obtained in the same manner as in Example 2 except that the polylactic acid resin A2 was used as the polylactic acid resin.

[Example 4]
Except that the cooling temperature was 70 ° C., a film was formed in the same manner as in Example 3 to obtain a sheet having physical properties shown in Table 1.

[Example 5]
A film having physical properties shown in Table 1 was obtained in the same manner as in Example 3 except that the methacrylate resin B2 was used as the methacrylate resin and the cooling temperature was 54 ° C.

[Example 6]
A film having physical properties shown in Table 1 was obtained in the same manner as in Example 3 except that the stretching temperature was 72 ° C and the cooling temperature was 56 ° C.

[Example 7]
A sheet having physical properties shown in Table 2 was obtained in the same manner as in Example 2 except that the blending ratio of the methacrylate resin B1 was 35% by mass, the stretching temperature was 78 ° C., and the cooling temperature was 54 ° C.

[Example 8]
A sheet having physical properties shown in Table 2 was obtained in the same manner as in Example 2 except that the blending ratio of the methacrylate resin B1 was 50% by mass, the stretching temperature was 80 ° C., and the cooling temperature was 53 ° C.

[Example 9]
A sheet having physical properties shown in Table 2 was obtained in the same manner as in Example 8 except that the stretching temperature was 90 ° C and the cooling temperature was 56 ° C.

[Example 10]
A film having physical properties shown in Table 22 was obtained in the same manner as in Example 8 except that polylactic acid resin A2 was used as the polylactic acid resin and the cooling temperature was 43 ° C.

[Example 11]
Example 9 except that the draw ratio in the sheet flow direction (MD) was 2.5 times, the draw ratio in the direction perpendicular to the sheet flow direction (TD) was 2.5 times, and the cooling temperature was 63 ° C. Films were formed in the same manner to obtain sheets having physical properties shown in Table 2.

[Example 12]
A film having physical properties shown in Table 2 was obtained in the same manner as in Example 11 except that the polylactic acid resin A2 was used as the polylactic acid resin and the stretching temperature was 82 ° C.

[Comparative Example 1]
A sheet having physical properties shown in Table 3 was obtained in the same manner as in Example 1 except that the methacrylate resin was not blended, the stretching temperature was 70 ° C, and the cooling temperature was 70 ° C. The physical properties of the obtained sheet were inferior in heat resistance as shown in Table 3.

[Comparative Example 2]
A sheet having physical properties shown in Table 3 was obtained in the same manner as in Comparative Example 1 except that the draw ratio was 1.0 × 1.0 (non-stretched). As shown in Table 3, the physical properties of the obtained sheet were inferior in heat resistance, low in orientation, and inferior in impact resistance.

[Comparative Example 3]
Except that the blending ratio of the methacrylate resin B1 was 15% by mass, a film was formed in the same manner as in Example 2 to obtain a sheet having physical properties shown in Table 3. The physical properties of the obtained sheet were inferior in heat resistance as shown in Table 3.

[Comparative Example 4]
Except that the stretching temperature was 85 ° C. and the cooling temperature was 53 ° C., a film was formed in the same manner as in Example 1 to obtain sheets having physical properties shown in Table 3. As shown in Table 3, the physical properties of the obtained sheet were low in orientation and inferior in impact resistance.

[Comparative Example 5]
Except that the cooling temperature was 100 ° C., a film was formed in the same manner as in Example 1 to obtain a sheet having physical properties shown in Table 3. As shown in Table 3, the physical properties of the obtained sheet were high in crystallinity and inferior in mold reproducibility.

[Comparative Example 6]
Except that the cooling temperature was 110 ° C., a film was formed in the same manner as in Example 3 to obtain a sheet having physical properties shown in Table 3. As shown in Table 3, the physical properties of the obtained sheet were high in crystallinity and inferior in mold reproducibility. The sheet of Comparative Example 6 was not moldable.

[Comparative Example 7]
A film having physical properties shown in Table 3 was obtained in the same manner as in Example 6 except that the stretching temperature was 80 ° C. and the cooling temperature was 58 ° C. As shown in Table 3, the physical properties of the obtained sheet were high in crystallinity and inferior in mold reproducibility.

[Comparative Example 8]
Except that the stretching temperature was 83 ° C. and the cooling temperature was 58 ° C., a film was formed in the same manner as in Example 6 to obtain sheets having physical properties shown in Table 4. As shown in Table 4, the physical properties of the obtained sheet were high in crystallinity and inferior in mold reproducibility.

[Comparative Example 9]
Except that the cooling temperature was 105 ° C., a film was formed in the same manner as in Example 7 to obtain a sheet having physical properties shown in Table 4. As shown in Table 4, the physical properties of the obtained sheet were low in orientation and inferior in impact resistance.

[Comparative Example 10]
Except that the stretching temperature was 100 ° C. and the cooling temperature was 57 ° C., a film was formed in the same manner as in Example 9, and sheets having physical properties shown in Table 4 were obtained. As shown in Table 4, the physical properties of the obtained sheet were low in orientation and inferior in impact resistance.

[Comparative Example 11]
Except that the cooling temperature was 105 ° C., a film was formed in the same manner as in Example 9 to obtain sheets having physical properties shown in Table 4. As shown in Table 4, the physical properties of the obtained sheet were low in orientation and inferior in impact resistance.

[Comparative Example 12]
Except that the cooling temperature was 120 ° C., a film was formed in the same manner as in Example 9 to obtain a sheet having physical properties shown in Table 4. As shown in Table 4, the physical properties of the obtained sheet were low in orientation and inferior in impact resistance.

[Comparative Example 13]
A sheet having physical properties shown in Table 4 was obtained in the same manner as in Example 9 except that the draw ratio was 1.0 × 1.0 (non-stretched). As shown in Table 4, the physical properties of the obtained sheet were low in degree of orientation and inferior in impact resistance.

[Comparative Example 14]
A sheet having physical properties shown in Table 4 was obtained in the same manner as in Example 9 except that the blending ratio of the methacrylate resin B1 was 75% by mass and the stretching temperature was 110 ° C. The physical properties of the obtained sheet were inferior in plant origin as shown in Table 4.

Methacrylate-based resin content (% by mass) and degree of plane orientation (ΔP) of Examples 1 to 12 having good impact resistance and Comparative Examples 2 to 4 and Comparative Examples 9 to 11 having insufficient impact resistance A graph showing the relationship of) is shown in FIG.
From the result of the graph of FIG. 1, it was confirmed that the sheet satisfying ΔP ≧ (4.6-0.072X) / 1000 in the plane orientation degree (ΔP) has good impact resistance.

Moreover, the graph which shows the relationship between the sheet ORS average value (MPa) of Examples 1-12 and the protrusion height (mm) at the time of shaping | molding is shown in FIG.
From the results of the graph of FIG. 2, it was confirmed that when the ORS (MPa) was 5.5 MPa or less, the mold reproducibility at the time of molding was good.

The polylactic acid-based stretched sheet of the present invention has excellent heat resistance, impact resistance, and moldability, is useful as a polylactic acid-based stretched sheet for molding, and is suitable as a thermoformed container, particularly as a molded container lid. Can be used.

Claims (7)

A polylactic acid-based stretched sheet formed by at least uniaxially stretching a resin composition containing a polylactic acid-based resin (A) and a methacrylate-based resin (B),
The blending ratio (A) :( B) of the polylactic acid resin (A) and the methacrylate resin (B) in the resin composition is 75:25 to 45:55 (mass ratio), and the resulting stretching The average values in the longitudinal direction and the width direction of the sheet orientation degree (ΔP) and orientation relaxation stress (ORS) are expressed by the following formulas (1) and (2).
ΔP ≧ (4.6-0.072X) / 1000 (1)
ORS ≦ 5.5 MPa (2)
[However, X in the above formula (1) represents the content (% by mass) of the methacrylate resin (B) in the resin composition, and 25 ≦ X ≦ 55. ]
A polylactic acid-based stretched sheet characterized by satisfying Furthermore, the polylactic acid type | system | group stretched sheet of Claim 1 whose crystallinity degree represented by following formula (3) is 16 J / g or less.
Crystallinity = heat of crystal melting (ΔHm) −heat of crystallization (ΔHc) (3)   The polylactic acid type | system | group stretched sheet of Claim 1 or 2 whose D body content rate of the said polylactic acid-type resin (A) is 2.0 mol% or less or 98.0 mol% or more.   The polylactic acid stretched sheet according to any one of claims 1 to 3, wherein the methacrylate resin (B) has a Vicat softening temperature of 105 ° C or higher.   The polylactic acid-based stretched sheet according to any one of claims 1 to 4, wherein the stretched sheet has a thickness of 70 to 500 µm.   A molded article obtained by molding the polylactic acid-based stretched sheet according to any one of claims 1 to 5. At least one resin composition obtained by mixing a polylactic acid resin (A) and a methacrylate resin (B) at a blending ratio (A) :( B) of 75:25 to 45:55 (mass ratio) is used. A method for producing a polylactic acid-based stretched sheet characterized by stretching at a stretching ratio of 1.3 to 8.0 times and a stretching temperature of 70 to 95 ° C in the direction, and then cooling at a stretching temperature or lower.

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