JP2011046005A - Poly(lactic acid)-based heat-resistant container and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a poly(lactic acid)-based heat-resistant container, in which the container excellent in heat resistance and impact resistance can be manufactured by thermal molding in a shorter cycle than heretofore. <P>SOLUTION: A resin composition containing at least poly(lactic acid) (A), a block copolymer (B) of poly(lactic acid) and an aliphatic polyester and talc (C) is extruded to prepare a primary sheet 14 having relative crystallinity Xc of 40 to 55%. The relative crystallinity Xc of the master roll sheet is set to 60 to 70% by heating the primary sheet at 85 to 125°C with a heating section 21 of a thermoforming machine 20. Successively the heated master roll sheet is subjected to vacuum molding and/or pressure molding with a molding section 22 of the thermoforming machine 20 and a molding is held in a metal mold in a heating state as it is, thereby the primary sheet is formed into a container shape and the relative crystallinity Xc of the obtained container is set to 75% or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a polylactic acid-based heat-resistant container and a resultant polylactic acid-based heat-resistant container. In particular, the present invention relates to a method for producing a polylactic acid-based heat-resistant container by thermoforming a polylactic acid-based raw sheet.

  Polylactic acid (lactic acid polymer) is harmless to animals and plants and humans, is biodegradable and thermoplastic, and is relatively inexpensive, so it is a material resin for various environmentally friendly containers and packaging materials. It is attracting attention as. However, since polylactic acid generally has a low crystallization speed, it is difficult to crystallize in a short time only by thermoforming the raw sheet, and it is difficult to achieve both productivity and heat resistance. In addition, polylactic acid alone has the disadvantage of being inferior in impact resistance. For this reason, there is a technology for improving productivity and improving heat resistance of molded products by adding crystal nucleating agents such as talc and silica to polylactic acid to promote crystallization of polymers during injection molding and thermoforming. Various proposals have been made. Various techniques for improving the impact resistance of a molded product finally obtained by blending a polyester resin or other modified resin with polylactic acid have been proposed.

Among the above technical trends, Patent Document 1 states that “a method for producing a polylactic acid-based molded product that can be molded in a production cycle of the same level as a general-purpose resin product and has excellent heat resistance and impact resistance. Is disclosed. The method of Patent Document 1 includes the following steps.
1) Polylactic acid 85 to 97% by mass with a D-form content of 5 mol% or less and a residual lactide content of 0.1 to 0.6% by mass, and an aliphatic having a single tensile elastic modulus of 40 to 1000 MPa Resin containing 100 mass parts of resin components containing 3-15 mass% of polyester resin and / or aliphatic aromatic polyester resin, and 1-25 mass parts of talc having an average particle size of 0.1-10 μm as a crystal nucleating agent Using a sheet comprising the composition;
2) The absolute value of the amount of heat of crystal melting ΔHm when the sheet was measured with a differential scanning calorimeter at a temperature rising condition of 20 ° C./min under conditions of 100 to 120 ° C. and 5 to 30 seconds in advance. Pre-crystallization so that the crystallization index, which is the difference from the absolute value of the heat-up crystallization heat amount ΔHc generated by crystallization during warming, is | ΔHm | − | ΔHc | = 10 to 15 J / g;
3) Molding and crystallization of the pre-crystallized sheet using a molding die heated to 90 to 130 ° C. so that the crystallization index is | ΔHm | − | ΔHc | ≧ 25 J / g. Make it.

JP 2006-212897 A

However, the technique of Patent Document 1 does not necessarily enable a polylactic acid-based molded product to be manufactured in a short cycle. For example, in paragraph 0049 of Patent Document 1,
“(Example 1)
First, the sheet A was precrystallized. That is, the sheet A is brought into close contact with a 300 mm diameter roll heated to a surface temperature of 118 ° C. rotating at a constant speed for 26.5 seconds, and then the sheet A is peeled from the heating roll via a water-cooled cooling roll. Thus, a precrystallization sheet having a crystallization index of 13.3 J / g was obtained. A box-shaped container having a length of 230 mm, a width of 200 mm, and a depth of 24 mm was molded using the obtained pre-crystallized sheet as a material, using a hot plate pressure forming machine and an aluminum mold (HMR-3B). The heating hot plate temperature (heating softening temperature) at the time of molding is 120 ° C., the mold surface temperature is 117 ° C., the heating time (heating softening time) required for molding is 3.5 seconds, and the mold is released after molding. The required crystallization time was 7.5 seconds and the shot cycle was 13.0 seconds. The molded semi-finished product was punched with a cutting blade using a Thomson blade to obtain a molded product. The obtained molded product had a crystallization index of 29.18 J / g and good heat resistance. 』
As described above, in the technique of Patent Document 1, in order to pre-crystallize the sheet A, a step of bringing the sheet A into close contact with a heating roll having a diameter of 300 mm for 26.5 seconds is necessary. Also, the shot cycle required 13.0 seconds even in the subsequent pressure forming using a hot plate pressure forming machine and an aluminum mold.

  The object of the present invention is to provide a polylactic acid heat-resistant container excellent in heat resistance and impact resistance by thermoforming a shorter cycle than before without requiring a precrystallization step with a heating roll as in Patent Document 1. It is to provide a method for producing a polylactic acid heat-resistant container that can be produced continuously or intermittently. Another object is to provide such a polylactic acid heat-resistant container.

The first invention of the present application is a method for producing a polylactic acid heat-resistant container,
I) A resin composition containing at least polylactic acid (A), a block copolymer (B) of polylactic acid and an aliphatic polyester, and talc (C) having an average particle diameter of 2 to 10 μm is formed into a sheet by extrusion molding. A preparation process for preparing an original sheet having a relative crystallinity Xc of 40 to 55% and a crystallization peak temperature Tc of 95 ° C. or less,
II) Using the thermoforming machine provided with the heating part which heats an original fabric sheet, and the shaping | molding part which has a metal mold | die for performing vacuum forming and / or pressure forming on the heated original fabric sheet, the said original fabric sheet is used. A process of thermoforming,
By heating the original sheet within a temperature range of 85 to 125 ° C. in the heating section of the thermoforming machine, the relative crystallinity Xc of the original sheet is set to 60 to 70%, and then the heat In the molding part of the molding machine, the heated original sheet is subjected to vacuum forming and / or pressure forming, and the molded product is held in a heated mold as it is, so that the original sheet is formed into a container shape. And the relative crystallinity Xc of the obtained container is 75% or more,
A thermoforming process,
Here, when the crystallization heat generation amount when the differential scanning calorimetry is performed on the sample under the temperature rising condition of 10 ° C./min is ΔHc and the melting endotherm is ΔHm, the relative crystallinity Xc is
Xc = 100 × (| ΔHm | − | ΔHc |) / | ΔHm |
It is represented by these, It is a manufacturing method of the polylactic acid type heat-resistant container characterized by the above-mentioned.

In the second invention of the present application, a raw sheet obtained by forming a resin composition containing at least polylactic acid (A), a block copolymer (B) of polylactic acid and an aliphatic polyester and talc (C) into a sheet is heated. A polylactic acid heat-resistant container obtained by molding,
Of the 100% by mass of the resin composition, the block copolymer (B) accounts for 3 to 9% by mass, the talc (C) accounts for 5 to 20% by mass, and the remainder is the polylactic acid (A) and The polylactic acid-based heat-resistant container is characterized in that it is occupied by other additives and has a relative crystallinity Xc of 75% or more.

  According to the method for producing a polylactic acid-based heat-resistant container of the present invention, a polylactic acid-based heat-resistant container having excellent heat resistance, impact resistance and rigidity can be produced continuously or intermittently in a shorter cycle than before by thermoforming. Can do. Moreover, in the thermoforming process using a thermoforming machine, it is possible to effectively prevent deformation when the molded product is released from the molding die.

  The polylactic acid-based heat-resistant container of the present invention exhibits excellent heat resistance even at an assumed use temperature of 90 ° C., and no elution or off-flavour occurs from the container even at the assumed use temperature, and the protection performance of the container contents ( Excellent impact resistance.

The figure which shows an example of the sheet extrusion molding machine by T-die method. The figure which shows an example of a vacuum and pressure type thermoforming machine. The molded article (a bowl-shaped container) in an Example etc. is shown, (a) is a top view, (b) is a front view. The graph which shows an example of differential scanning calorimetry.

Hereinafter, preferred modes for carrying out the present invention will be described.
The method for producing a polylactic acid heat-resistant container according to the present invention includes a preparation process for preparing an original sheet and a thermoforming process for thermoforming the original sheet using a thermoforming machine.

(Preparation of the original fabric sheet)
The raw sheet contains polylactic acid (A), a block copolymer (B) of polylactic acid and aliphatic polyester, talc (C) having an average particle diameter of 2 to 10 μm, and other additives (D). A resin composition is formed into a sheet by extrusion molding.

  Examples of usable polylactic acid (A) include poly L-lactic acid, poly DL-lactic acid which is a copolymer of L-lactic acid and D-lactic acid, or a mixture thereof. In addition, it is preferable that D body content rate in polylactic acid is 3 mol% or less. If the D-form content exceeds 3 mol%, the crystallinity of polylactic acid itself is lowered, and sufficient crystallinity can be obtained even if a crystal nucleating agent is added or a predetermined heat treatment is performed as described later. There is a risk of not.

  The weight average molecular weight (Mw) of the polylactic acid (A) is preferably in the range of 150,000 to 250,000, more preferably 160,000 to 200,000. When the polylactic acid has a weight average molecular weight of less than 150,000, the raw sheet obtained because the melt viscosity is too low is inferior in mechanical properties. On the other hand, when the weight average molecular weight of polylactic acid exceeds 250,000, the melt viscosity becomes too high, and it becomes difficult to form a sheet by melt extrusion molding of the resin composition.

  Further, the polylactic acid (A) alone preferably has a relative crystallinity Xc of 35% or more and a crystallization heat generation ΔHc of 10 J / g or more. The measurement of the crystallization calorific value ΔHc of commercially available polylactic acid was performed as follows. That is, a commercially available polylactic acid (for example, pellets) was heated at 220 ° C. for 15 minutes to be completely melted once, and then rapidly cooled with cold water close to 0 ° C. to return to near room temperature and brought into an amorphous state. The amorphous polylactic acid was subjected to differential scanning calorimetry with a differential scanning calorimeter (DSC) under a temperature rising condition of 10 ° C./min, and the crystallization calorific value ΔHc was measured (JIS (Japanese Industrial Standards). ) See K7122.

  For polylactic acid having a relative crystallinity Xc of less than 35% or a crystallization exotherm ΔHc of less than 10 J / g, a desired relative crystallinity (40 to 55%) and a desired crystallization peak temperature Tc (95 ° C. It becomes difficult to obtain an original fabric sheet having the following). That is, when the relative crystallinity Xc is less than 35% or the crystallization heat generation amount ΔHc is less than 10 J / g, the crystallization rate of polylactic acid itself is slow, and thus the target relative crystallinity Xc is reached in each molding process. There is a possibility that the time until is too long.

Incidentally, the relative crystallinity Xc is the degree of crystallization of the system when the maximum crystallinity that can be reached by the system to be measured (resin system) is regarded as 100% relative crystallinity ( It is an index indicating whether it is in (relative degree). The relative crystallinity Xc can be measured by a differential scanning calorimeter (DSC). In the present invention, the resin when the differential scanning calorimetry is performed on the sample (resin system) under a temperature rising condition of 10 ° C./min. When the crystallization exotherm of the system is ΔHc and the melting endotherm of the resin system is ΔHm,
Xc = 100 × (| ΔHm | − | ΔHc |) / | ΔHm |
(Unit:%) (see JIS (Japanese Industrial Standards) K7122).

As shown in the following chemical formula 1, the block copolymer (B) of polylactic acid and aliphatic polyester used in the present invention comprises a polylactic acid segment (B1) and an aliphatic polyester segment (B2). Lactic acid type block copolymer.

The polylactic acid segment (B1) in the block copolymer (B) is a part that exhibits an affinity for polylactic acid. In this sense, the polylactic acid segment (B1) is preferably composed of polylactic acid having the same chemical structure as the polylactic acid (A). On the other hand, the aliphatic polyester segment (B2) in the block copolymer (B) is a portion that contributes particularly to improvement in impact resistance and flexibility after forming into a sheet. In the present invention, the aliphatic polyester segment (B2) is preferably made of polypropylene sebacate (see Chemical Formula 2).

  The weight average molecular weight of the block copolymer (B) of polylactic acid and aliphatic polyester is preferably in the range of 60,000 to 120,000. Further, the block copolymer (B) preferably has a relative crystallinity Xc of 40% or higher and a crystallization peak temperature of 95 ° C. or lower. In addition, about the relative crystallinity degree Xc and crystallization peak temperature of a block copolymer (B), like the case of the said polylactic acid, it returns to an amorphous state once, with respect to the block copolymer of the amorphous state. It measured by performing differential scanning calorimetry by the differential scanning calorimeter (DSC) on the temperature rising conditions of 10 degree-C / min.

  In the block copolymer (B) having a relative crystallinity of less than 40% or a crystallization peak temperature of more than 95 ° C., a desired relative crystallinity (40 to 55%) and a desired crystallization peak temperature Tc ( It becomes difficult to obtain an original sheet having 95 ° C. or less. That is, under the condition that the relative crystallinity Xc is less than 40% or the crystallization peak temperature is over 95 ° C., the crystallization rate of the block copolymer (B) is slow, which inhibits the crystallization of polylactic acid. The time until the target relative crystallinity Xc is reached in each molding process may be too long.

  In the present invention, talc (C) is used as a crystal nucleating agent for polylactic acid. The average particle size of talc that can be used is in the range of 2 to 10 μm. If the average particle size is less than 2 μm, poor dispersion or secondary aggregation may occur, and the effect as a crystal nucleating agent may not be sufficiently obtained. On the other hand, if the average particle size exceeds 10 μm, there is a risk of adversely affecting the physical properties of the sheet when formed into a sheet, and consequently adversely affecting the physical properties of the molded product (for example, the impact resistance of the molded product is reduced). .

  Examples of other additives (D) contained in the resin composition include colorants such as pigments. When talc is contained in the resin composition, the sheet tends to be colored in gray. Therefore, it is preferable to add a colorant such as a pigment in order to compensate for lack of designability due to gray coloring. Examples of usable colorants include titanium oxide (white colorant) and carbon black (black colorant). As additives (D) other than the colorant, plasticizers, ultraviolet absorbers, light stabilizers, antistatic agents, antioxidants, mold release materials, moisture proofing materials, oxygen barrier agents, etc. are impaired in the properties of the resin composition. You may add to a resin composition within the range which does not exist.

  In the said resin composition, the block copolymer (B) of the said polylactic acid and aliphatic polyester occupies 3-9 mass% among the whole (100 mass%), and the said talc (C) is 5-20. The polylactic acid (A) and the other additive (D) account for the remainder. When the content of the block copolymer (B) is less than 3% by mass, the effect of modifying the resin composition by the block copolymer (B) can not be expected so much, and the impact resistance in the form of a sheet or a container is deteriorated. This can cause inconveniences. On the other hand, when the content of the block copolymer (B) exceeds 9% by mass, problems such as a decrease in rigidity in the form of a sheet or a container may occur. Further, when the content of talc (C) is less than 5% by mass, the effect as a crystal nucleating agent cannot be sufficiently exhibited. On the other hand, if the content of talc (C) exceeds 20% by mass, the content of talc is too high, making sheeting difficult, and even if sheeting is possible, the molded product is very Product quality will be adversely affected, such as fragility.

  A raw sheet extrudes the above resin composition containing polylactic acid (A), a block copolymer (B) of polylactic acid and an aliphatic polyester, talc (C) and other additives (D). Manufactured by forming into a sheet by molding. As the extrusion molding method at that time, for example, a T-die method of extruding a melt-kneaded resin composition using a T-die is preferable.

  In the T-die method, as shown in FIG. 1, an extruder 10 provided with a T-die 11, a touch roll 12 and a cast roll 13 is used. In sheet forming, the resin composition prepared in the hopper of the extruder is melted and kneaded by the T die 11 heated to a temperature of 200 to 230 ° C. and extruded therefrom. The extruded sheet-like material is cooled by a cast roll 13 set to a temperature range of 30 to 50 ° C., and becomes an unstretched sheet having a thickness of about 150 to 1000 μm. This is wound up to complete a roll 14 of the original sheet.

  The raw sheet obtained by extrusion molding has a relative crystallinity Xc of 40 to 55% and a crystallization peak temperature Tc of 95 ° C. or lower. If the relative crystallinity Xc and the crystallization peak temperature Tc of the raw sheet are out of the above ranges, it becomes difficult to finally obtain a heat-resistant container having a relative crystallinity Xc of 75% or more.

(Thermoforming process of raw sheet)
The raw sheet is thermoformed using a thermoforming machine. As shown in FIG. 2, the thermoforming machine 20 includes a heating unit 21 that heats the original fabric sheet and a mold (not shown) that performs vacuum forming and / or pressure forming on the heated original fabric sheet. A section 22 and a cut press section 23 for separating the container molded by the molding section from the continuous raw fabric sheet are provided.

  In the first stage of thermoforming, the raw fabric sheet is heated within the temperature range of 85 to 125 ° C. (more preferably within the temperature range of 110 to 120 ° C.) by the heating unit 21 of the thermoforming machine. If the heating temperature at this time is less than 85 ° C., the relative crystallization degree Xc does not reach 60% because the crystallization rate is slow. On the other hand, when the heating temperature exceeds 125 ° C., the drawdown of the raw sheet increases, and the molded product is wrinkled during the next second stage of sheet forming. The heating time in this first stage is about 6 to 8 seconds (12 to 16 seconds for the total heating time) for two-shot heating.

  By heating the original sheet at a temperature of 85 to 125 ° C. for a predetermined time (relatively short time), the relative crystallinity Xc of the original sheet is set to 60 to 70%. By setting the relative crystallinity Xc of the raw sheet to 60 to 70% by this first stage heating, the heat resistance containers having a relative crystallinity Xc of 75% or more are finally compared in the next second stage. Can be obtained in a short time. If the relative crystallinity Xc of the raw sheet exceeds 70% by heating in the first stage, the degree of crystallization becomes too high, and sheet molding in the next second stage (mechanical molding of the sheet) Becomes very difficult.

  In the second stage of thermoforming, the raw sheet heated by the heating part 21 of the thermoforming machine is subjected to vacuum forming and / or pressure forming in the forming part 22 of the thermoforming machine, and then the molded product is used as it is. By holding it in a heated mold, the raw sheet is formed into a container shape, and the relative crystallinity Xc of the obtained container is set to 75% or more.

  The temperature of the molding die used for the second stage sheet molding is preferably 85 ° C. or higher and lower than 125 ° C. and lower than the sheet heating temperature in the first stage. If the mold temperature at this time is less than 85 ° C., the crystallization is slow or does not proceed and the relative crystallinity Xc does not reach 75% in a short time, and the desired heat resistance cannot be obtained. On the other hand, when the mold temperature is 125 ° C. or higher, the molded product is likely to be deformed when the molded product is released from the mold due to a decrease in rigidity of the molded product on or in the mold. When the mold temperature is equal to or higher than the sheet heating temperature, the adhesion of the molded product to the mold becomes excessively strong, and the molded product is likely to be deformed when the molded product is released from the mold. For this reason, for example, when the heating temperature of the raw sheet in the first stage of thermoforming is 110 to 120 ° C., the temperature of the molding die in the second stage of thermoforming is 85 to 110 ° C. It is preferable that

  In the forming part 22, the heated raw sheet is subjected to vacuum forming and / or pressure forming, and the molded product is held in a heated mold as it is, so that the original sheet is formed into a desired container shape. And the desired relative crystallinity Xc. Then, in the cut press part 23, a desired shape container is obtained by cut | disconnecting a sheet forming part from the continuous raw fabric sheet. The container thus obtained (polylactic acid-based heat-resistant container) is a container having a relative crystallinity Xc of 75% or more and has very excellent heat resistance. Regarding the correlation between the relative crystallinity degree Xc and the heat resistance temperature in the polylactic acid heat resistance container of the present invention, the heat resistance temperature is about 90 ° C. when the relative crystallinity degree Xc = 75%, and the relative crystallinity degree Xc = 80%. The experiment shows that the heat resistance temperature is about 110 ° C., the relative crystallinity Xc = 100%, and the heat resistance temperature is about 130 ° C.

  Hereinafter, examples of the present invention and examples to be compared (comparative examples) will be described, but before that, various physical property data measuring methods, heat stability, impact resistance and bending elastic modulus evaluation methods, and The material polymer used will be described.

(Physical property data from DSC measurement)
A differential scanning calorimeter (manufactured by Rigaku Corporation: DSC model 8230) was used to set a sample (about 5 mg) to be inspected and measured at a heating rate of 10 ° C./min. Then, as shown in FIG. 4, in the melting endothermic curve obtained from the measurement, the crystallization peak temperature Tc was obtained from the peak point of the exothermic side peak, and the crystallization exotherm ΔHc was obtained from the area of the exothermic side peak. Further, the melting peak temperature Tm was obtained from the peak point of the endothermic side peak, and the melting endotherm amount ΔHm was obtained from the area of the endothermic side peak. Then, the relative crystallinity Xc (unit:%) was calculated based on the following formula.
Xc = 100 × (| ΔHm | − | ΔHc |) / | ΔHm |

(Heat resistance stability)
In the examples and comparative examples described below, as shown in FIGS. 3A and 3B, the diameter D = 120 mm, the height h = 40 mm (also the depth), and the bottom surface thickness t = about 0. A 2 mm bowl-shaped container was molded. This bowl-shaped container was placed in an oven at a predetermined temperature and allowed to stand for 15 minutes, and then the dimensional change rate (specifically, the shrinkage rate) when returned to room temperature was measured. That is, when the diameter of the container before being put into the oven is D1, and the diameter of the container after being heated in the oven is D2, the dimensional change rate Yd (unit:%) is expressed as Yd = 100 × (D1−D2) / D1. , And calculated.
When the oven temperature is set to 70 ° C., 90 ° C., 100 ° C. and 110 ° C., and the dimensional change rate Yd is less than 1% even by the heat treatment for 15 minutes at each set temperature, at least at the temperature When the dimensional change rate Yd is 1% or more, the heat stability at that temperature is rejected (the table below). 4 was evaluated as “×”).

(Impact resistance)
Ten bowls (specimens) each having 150 g of a granular material put in a bowl-shaped container (see FIG. 3) molded in the examples and comparative examples described below and covered were prepared. Then, a drop test was performed in which each of these 10 specimens was freely dropped on a floor surface from a height of 1 m one by one in an examination room at a room temperature of about 20 ° C. In this drop test, when none of the 10 specimens were cracked, the impact resistance was evaluated as good (“◯” in Table 5 below), and 1 of 10 specimens was evaluated. If any one of the containers was cracked, the impact resistance was evaluated as poor (“x” in Table 5 below).

(Flexural modulus)
In the examples and comparative examples described below, the bowl-shaped container (see FIG. 3) as described above was molded, but a dish-shaped container (not shown) for measuring the flexural modulus was molded in exactly the same procedure. That is, in each example, a dish-shaped container having a length of 235 mm, a width of 200 mm, a depth of 25 mm, and a bottom surface thickness of t = about 0.2 mm is formed, and the flat bottom surface of the dish-shaped container is punched to obtain a 25 mm × 150 mm. A rectangular test piece was collected. And according to JIS (Japanese Industrial Standards) K7171 for each test piece, using the autograph made by Shimadzu Corporation, the bending elastic modulus (unit is in the measurement condition between fulcrums: 30 mm, bending speed: 20 mm / min) Pa) was measured (see Table 5).
The flexural modulus is an index indicating the high rigidity of the container. In the container of the present invention, if the flexural modulus is 5.00 GPa or more, the stiffness is good and the flexural modulus is less than 5.00 GPa. In some cases, it is evaluated as insufficient rigidity. In Table 5, the symbol “NG” indicating insufficient rigidity is attached to some comparative examples whose flexural modulus was less than 5.00 GPa.

(Material polymer used)
Through all the examples and comparative examples, the product name “Nature Works Polylactic Acid 4032D” manufactured by Nature Works LLC was used as the polylactic acid (A). Nature Works polylactic acid 4032D is a polylactic acid having a D-form content of 1.2 to 1.6 mol% and a weight average molecular weight (Mw) of about 180,000. The physical property data when this polylactic acid is measured by DSC alone is shown in Table 1 below.

  In Examples 1 to 4 and Comparative Examples 1 to 3, a product name “Plamate PD150” manufactured by DIC Corporation was used as a block copolymer (B) of polylactic acid and aliphatic polyester. In the plamate PD150, the polylactic acid segment (B1) is the Natureworks polylactic acid 4032D, and the aliphatic polyester segment (B2) is polypropylene sebacate (see Chemical Formula 2). The weight average molecular weight (Mw) of Puramate PD150 is about 90,000. The physical property data when this block copolymer is subjected to DSC measurement alone are shown in Table 1 below.

In Comparative Example 4, as a polymer used in combination with polylactic acid (A), a product name “Ecoflex F” manufactured by BASF Corporation, which was used in Examples of Patent Document 1, was used. Ecoflex F are 1,4-butanediol _{(HO- (CH 2) 4 -OH} ), adipic acid _{(HOOC- (CH 2) 4 -COOH} ), terephthalic acid _{(HOOC-C 6 H 4 -COOH} ) It is a copolymerized aliphatic aromatic polyester (ie, polybutylene adipate terephthalate) and has a weight average molecular weight (Mw) of about 140,000. The physical property data when this aliphatic aromatic polyester is subjected to DSC measurement alone is shown in Table 1 below.

  Through all examples and comparative examples, as a talc (C), a product name “Microace P-8” (average particle size of 3.3 μm) manufactured by Nippon Talc Co., Ltd. was used. Further, as other additive (D), a white pigment (titanium oxide) manufactured by Sakai Chemical Industry Co., Ltd .: trade name “SH-1” was used.

Example 1
Polylactic acid (Nature Works polylactic acid 4032D) 79% by mass, polylactic acid / polypropylene sebacate block copolymer (Plamate PD150) 5% by mass, talc (Microace P-8) 15% by mass, pigment (titanium oxide) 1 A resin composition (100 mass%) was prepared by blending mass%. And the original fabric sheet was manufactured from the said resin composition by the T-die method. That is, the resin composition is melt-kneaded at a temperature of 220 to 230 ° C., and the molten resin composition is extruded under conditions of a touch roll temperature of about 39 ° C., a cast roll temperature of about 43 ° C., and a roll speed of 13 m / min. Thus, a 0.3 mm-thick original fabric sheet (see roll 14 in FIG. 1) was obtained. The raw sheet obtained in Example 1 had a crystallization peak temperature Tc = 87.0 ° C. and a relative crystallinity Xc = 48.6% (see Table 2 below).

  Next, a molded product was continuously formed from a roll-shaped raw fabric sheet using a vacuum / pressure space thermal contact molding machine. That is, the temperature of the heaters disposed above and below the raw sheet in the heating unit 21 of the thermoforming machine 20 is set to 290 to 350 ° C., and the raw sheet is heated in the heating unit 21 by two shots for about 6 seconds ( The part to be heated of the original fabric sheet was heated to about 118 ° C. by staying for a total of about 12 seconds. Incidentally, when a part of the raw sheet immediately after heating (and immediately before forming) was cut out and subjected to DSC measurement, the relative crystallinity was 66.2% (see Table 4 below).

  Subsequently, the heated portion of the raw sheet at about 118 ° C. is moved to the molding section 22 of the thermoforming machine 20, and the heated portion is placed on a mold having a surface temperature of 80 to 110 ° C. based on vacuum and pressure. A predetermined shape (a bowl shape in this example) was imparted to the sheet portion. The mold holding time at that time was 3.0 seconds. Then, the sheet | seat part by which vacuum and pressure forming were carried out was moved to the cut press part 23 of a thermoforming machine, and the molded article was cut off from the original fabric sheet with the cut press. The shot cycle of the continuous molding of the molded product in Example 1 was 6.8 seconds (see Table 5 below).

  As shown in FIGS. 3A and 3B, the obtained molded product is a bowl-shaped container having a diameter D = 120 mm, a height h = 40 mm, and a bottom surface thickness t = about 0.2 mm. When a portion of the bottom surface of the bowl-shaped container was cut out and subjected to DSC measurement, the relative crystallinity Xc was 100% (see Table 4 below). When the heat resistance stability of the bowl-shaped container of Example 1 was measured, the dimensional change Yd was less than 1% at any temperature of 70 ° C., 90 ° C., 100 ° C. and 110 ° C., and excellent heat resistance stability. (See Table 4 below). In addition, both impact resistance and flexural modulus were good (see Table 5 below).

(Example 2)
81% by mass of polylactic acid (Nature Works polylactic acid 4032D), 8% by mass of block copolymer of polylactic acid / polypropylene sebacate (Plamate PD150), 10% by mass of talc (Microace P-8), pigment (titanium oxide) 1 A resin composition (100 mass%) was prepared by blending mass%. And like Example 1, while producing the original fabric sheet from the said resin composition by the T-die method, the molded article was continuously shape | molded from the original fabric sheet using the vacuum and pressure space thermal contact molding machine.
Table 2 shows the physical property data of the original fabric sheet of Example 2. Table 4 shows the physical property data of the raw sheet and the molded product (bowl-type container) immediately after heating, and the evaluation results of the heat resistance stability. Table 5 shows the shot cycle, impact resistance, and flexural modulus of continuous molding of the molded article in Example 2.

(Example 3)
89% by mass of polylactic acid (Nature Works polylactic acid 4032D), 5% by mass of polylactic acid / polypropylene sebacate block copolymer (Plamate PD150), 5% by mass of talc (Microace P-8), pigment (titanium oxide) 1 A resin composition (100 mass%) was prepared by blending mass%. And like Example 1, while producing the original fabric sheet from the said resin composition by the T-die method, the molded article was continuously shape | molded from the original fabric sheet using the vacuum and pressure space thermal contact molding machine.
Table 2 shows the physical property data of the original fabric sheet of Example 3. Table 4 shows the physical property data of the raw sheet and the molded product (bowl-type container) immediately after heating, and the evaluation results of the heat resistance stability. Table 5 shows the shot cycle, impact resistance, and flexural modulus of continuous molding of the molded product in Example 3.

Example 4
74% by mass of polylactic acid (Nature Works polylactic acid 4032D), 5% by mass of polylactic acid / polypropylene sebacate block copolymer (Plamate PD150), 20% by mass of talc (Microace P-8), pigment (titanium oxide) 1 A resin composition (100 mass%) was prepared by blending mass%. And like Example 1, while producing the original fabric sheet from the said resin composition by the T-die method, the molded article was continuously shape | molded from the original fabric sheet using the vacuum and pressure space thermal contact molding machine.
Table 2 shows the physical property data of the raw sheet of Example 4. Table 4 shows the physical property data of the raw sheet and the molded product (bowl-type container) immediately after heating, and the evaluation results of the heat resistance stability. Table 5 shows the shot cycle, impact resistance, and flexural modulus of continuous molding of the molded product in Example 4.

(Comparative Example 1)
Comparative Example 1 shows a case where the blending amount of the polylactic acid / polypropylene sebacate block copolymer (Plamate PD150) used in combination with polylactic acid is 2% by mass, which is lower than the lower limit of 3% by mass. That is, 82% by mass of polylactic acid (Nature Works polylactic acid 4032D), 2% by mass of block copolymer of polylactic acid / polypropylene sebacate (Plamate PD150), 15% by mass of talc (Microace P-8), pigment (titanium oxide) ) 1% by mass was added to prepare a resin composition (100% by mass). And like Example 1, while producing the original fabric sheet from the said resin composition by the T-die method, the molded article was continuously shape | molded from the original fabric sheet using the vacuum and pressure space thermal contact molding machine.
Table 3 shows the physical property data of the raw sheet of Comparative Example 1. Table 4 shows the physical property data of the raw sheet and the molded product (bowl-type container) immediately after heating, and the evaluation results of the heat resistance stability. Table 5 shows the shot cycle, impact resistance, and flexural modulus of the molded article continuous molding in Comparative Example 1.
Compared with Examples 1 to 4, in Comparative Example 1, the impact resistance was particularly lowered.

(Comparative Example 2)
Comparative Example 2 shows a case where the blending amount of the polylactic acid / polypropylene sebacate block copolymer (Plamate PD150) used in combination with polylactic acid is 11% by mass exceeding the upper limit of 9% by mass. That is, 73% by mass of polylactic acid (Nature Works polylactic acid 4032D), 11% by mass of polylactic acid / polypropylene sebacate block copolymer (Plamate PD150), 15% by mass of talc (Microace P-8), pigment (titanium oxide) ) 1% by mass was added to prepare a resin composition (100% by mass). And like Example 1, while producing the original fabric sheet from the said resin composition by the T-die method, the molded article was continuously shape | molded from the original fabric sheet using the vacuum and pressure space thermal contact molding machine.
Table 3 shows the physical property data of the raw sheet of Comparative Example 2. Table 4 shows the physical property data of the raw sheet and the molded product (bowl-type container) immediately after heating, and the evaluation results of the heat resistance stability. Table 5 shows the shot cycle, impact resistance, and flexural modulus of the molded article continuous molding in Comparative Example 2.
Compared with Examples 1 to 4, in Comparative Example 2, a decrease in flexural modulus (that is, a decrease in rigidity) was particularly observed.

(Comparative Example 3)
The comparative example 3 shows the case where the compounding quantity of a talc (microace P-8) is 2.5 mass% lower than 5 mass% which is the lower limit. That is, polylactic acid (Nature Works polylactic acid 4032D) 91.5% by mass, polylactic acid / polypropylene sebacate block copolymer (Plamate PD150) 5% by mass, talc (Microace P-8) 2.5% by mass, A resin composition (100% by mass) was prepared by blending 1% by mass of a pigment (titanium oxide). And like Example 1, while producing the original fabric sheet from the said resin composition by the T-die method, the molded article was continuously shape | molded from the original fabric sheet using the vacuum and pressure space thermal contact molding machine.
Table 3 shows the physical property data of the original fabric sheet of Comparative Example 3. Table 4 shows the physical property data of the raw sheet and the molded product (bowl-type container) immediately after heating, and the evaluation results of the heat resistance stability. Table 5 shows the shot cycle, impact resistance and flexural modulus of continuous molding of the molded product in Comparative Example 3.
In Comparative Example 3, the relative crystallization degree Xc of the raw fabric sheet did not reach 40% due to the small amount of talc, and high heat resistance was not obtained even after containerization by thermoforming. Moreover, the bending elastic modulus was lowered (that is, the rigidity was lowered), and the shot cycle could not be shortened.

(Comparative Example 4)
In Comparative Example 4, the aliphatic aromatic polyester (Ecoflex F) used in Patent Document 1 was used as a polymer used in combination with polylactic acid. That is, this corresponds to an example in which the block copolymer (Plamate PD150) in Example 1 is replaced with an aliphatic aromatic polyester (Ecoflex F). In addition, the procedure of the sheet | seat shaping | molding in the comparative example 4 and a thermoforming is in accordance with Example 1, and has gone through the procedure different from the Example of patent document 1. FIG. That is, 79% by mass of polylactic acid (Nature Works polylactic acid 4032D), 5% by mass of aliphatic aromatic polyester (Ecoflex F), 15% by mass of talc (Microace P-8), and 1% by mass of pigment (titanium oxide). The resin composition (100 mass%) was adjusted by mix | blending. And like Example 1, while producing the original fabric sheet from the said resin composition by the T-die method, the molded article was continuously shape | molded from the original fabric sheet using the vacuum and pressure space thermal contact molding machine.
Table 3 shows the physical property data of the raw sheet of Comparative Example 4. Table 4 shows the physical property data of the raw sheet and the molded product (bowl-type container) immediately after heating, and the evaluation results of the heat resistance stability. Table 5 shows the shot cycle, impact resistance and flexural modulus of continuous molding of the molded product in Comparative Example 4.
In Comparative Example 4, since the relative crystallinity Xc of Ecoflex F itself is as low as 17.8%, the relative crystallinity Xc of the original sheet after sheeting does not reach 40%, and the container is formed by thermoforming. Even after conversion, high heat resistance was not obtained. Moreover, the shot cycle could not be shortened.

  DESCRIPTION OF SYMBOLS 10 ... Extruder, 11 ... T die, 12 ... Touch roll, 13 ... Cast roll, 14 ... Raw material sheet roll, 20 ... Thermoforming machine, 21 ... Heating part, 22 ... Molding part, 23 ... Cut press part .

Claims (8)

A method for producing a polylactic acid-based heat-resistant container,
I) A resin composition containing at least polylactic acid (A), a block copolymer (B) of polylactic acid and an aliphatic polyester, and talc (C) having an average particle diameter of 2 to 10 μm is formed into a sheet by extrusion molding. A preparation process for preparing an original sheet having a relative crystallinity Xc of 40 to 55% and a crystallization peak temperature Tc of 95 ° C. or less,
II) Using the thermoforming machine provided with the heating part which heats an original fabric sheet, and the shaping | molding part which has a metal mold | die for performing vacuum forming and / or pressure forming on the heated original fabric sheet, the said original fabric sheet is used. A process of thermoforming,
By heating the original sheet within a temperature range of 85 to 125 ° C. in the heating section of the thermoforming machine, the relative crystallinity Xc of the original sheet is set to 60 to 70%, and then the heat In the molding part of the molding machine, the heated original sheet is subjected to vacuum forming and / or pressure forming, and the molded product is held in a heated mold as it is, so that the original sheet is formed into a container shape. And the relative crystallinity Xc of the obtained container is 75% or more,
A thermoforming process,
Here, when the crystallization heat generation amount when the differential scanning calorimetry is performed on the sample under the temperature rising condition of 10 ° C./min is ΔHc and the melting endotherm is ΔHm, the relative crystallinity Xc is
Xc = 100 × (| ΔHm | − | ΔHc |) / | ΔHm |
A process for producing a polylactic acid-based heat-resistant container, characterized by:   Of the 100% by mass of the resin composition, the block copolymer (B) accounts for 3 to 9% by mass, the talc (C) accounts for 5 to 20% by mass, and the remainder is the polylactic acid (A) and 2. The method for producing a polylactic acid heat-resistant container according to claim 1, wherein other additives are occupied.   The polylactic acid (A) according to claim 1 or 2, wherein the polylactic acid (A) has a relative crystallinity Xc of 35% or more and a crystallization calorific value ΔHc of 10 J / g or more. Manufacturing method of heat-resistant container.   The block copolymer (B) has a relative crystallinity Xc of 40% or more and a crystallization peak temperature Tc of 95 ° C or less. The manufacturing method of the polylactic acid-type heat-resistant container of description.   The polylactic acid heat-resistant container according to any one of claims 1 to 4, wherein the aliphatic polyester segment (B2) in the block copolymer (B) is made of polypropylene sebacate. Production method.   The polylactic acid segment (B1) in the block copolymer (B) is composed of polylactic acid having the same chemical structure as the polylactic acid (A). The manufacturing method of the polylactic acid-type heat-resistant container as described in a term. Polylactic acid (A), poly-lactic acid obtained by subjecting a raw sheet obtained by forming a resin composition containing at least a block copolymer (B) of polylactic acid and an aliphatic polyester and talc (C) to a sheet A lactic acid heat-resistant container,
Of the 100% by mass of the resin composition, the block copolymer (B) accounts for 3 to 9% by mass, the talc (C) accounts for 5 to 20% by mass, and the remainder is the polylactic acid (A) and A polylactic acid-based heat-resistant container characterized in that other additives occupy and the heat-resistant container has a relative crystallinity Xc of 75% or more.   Of the block copolymer (B), the polylactic acid segment (B1) is made of polylactic acid having the same chemical structure as the polylactic acid (A), and the aliphatic polyester segment (B2) is made of polypropylene sebacate. The polylactic acid heat-resistant container according to claim 7.

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