JP2003231798A - Lactic acid resin composition and sheet product of the same, and bag product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lactic acid sheet product having biodegradable properties, physical properties similar to an OPP (oriented polypropylene film), good heat- resistant properties and wet-heat durability, and to provide a lactic acid resin composition used for producing the same. <P>SOLUTION: The lactic acid resin composition comprises 67-96 mass% of a lactic acid resin as a main component and 4-33 mass% of a plasticizer having a boiling point of 220°C or more at atmospheric pressure or 170°C or more at 5-10 Torr. The lactic acid sheet product comprised of the lactic acid resin composition is prepared by being stretched at least in one direction, and preferably has a storage modulus at 20°C of 500-3,000 MPa and a heat shrinkage after heating for 15 minutes at 120°C of 10% or less in both TD and MD. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lactic acid-based resin composition, a sheet-shaped product and a bag-shaped product thereof, and particularly to a lactic acid-based resin composition mixed with a plasticizer, a sheet-shaped product thereof and a lactic acid-based resin sheet-shaped product. The present invention relates to a bag-shaped product formed from a product.

[0002]

2. Description of the Related Art Plastic products are often discarded after use, and disposal such as incineration and landfill is a problem. In other words, ordinary plastics are stable in the natural environment for a long period of time and have a low bulk specific gravity, which promotes the shortening of the life of landfills for waste, and damages the natural landscape and the living environment of wild animals and plants. Was pointed out. Therefore, research is being conducted on materials that decompose and disappear over time in a natural environment. Biodegradable plastics are currently drawing attention as such materials. It is known that biodegradable plastics gradually disintegrate and decompose in soil or water by hydrolysis or biodegradation, and finally become harmless decomposition products by the action of microorganisms. Biodegradable plastics that have begun to be put into practical use include polylactic acid, aliphatic polyesters, modified PVA, cellulose ester compounds, starch modified products, and blends thereof. In particular, lactic acid-based resins have good cost performance, It has received a great deal of attention because it can be obtained from a source material.

Lactic acid-based resins utilize the characteristics of high rigidity and transparency, and as a substitute for polystyrene (PS), polyethylene terephthalate (PET), etc., as disclosed in Japanese Patent Laid-Open No. 7-207041, among others. It has begun to be used in the field of stretched films. On the other hand, propylene stretched film (OPP), which is widely used as a general-purpose film, is used for food packaging and other electronic, medical,
It is widely used in various packaging films for chemicals, cosmetics, etc., agricultural films, industrial protective films, adhesive tapes, etc., and has flexibility in film, good fusing seal strength, and heat resistance in secondary processing and practical use. Characteristics such as wet heat durability are required. However, a film made of a lactic acid-based resin is too hard or has a too low fusion-cut seal strength as a substitute for OPP. Japanese Patent Application Laid-Open No. 8-501584 and Japanese Patent Application Laid-Open No. 7-177826 disclose techniques for improving flexibility and the like by adding a plasticizer to a lactic acid resin. However, these techniques are not practical because they have poor heat resistance (thermal dimensional stability) and poor wet heat durability. Further, the suitability for a fusing and sealing machine was not good for producing the fusing and sealing bag.

[0004]

The present invention has been made to solve the above problems, and an object of the present invention is to be similar to OPP in addition to the biodegradability inherent in lactic acid resins. It is intended to provide a sheet-like material and a bag having physical properties and excellent heat resistance and wet heat resistance, and a lactic acid-based resin composition used for producing these.

[0005]

The lactic acid-based resin composition of the present invention contains 67% by mass to 96% by mass of a lactic acid-based resin as a main component and has a boiling point of 220 ° C. or higher at normal pressure, or 5 Torr or more. Boiling point at 10 Torr is 170 ° C
It is characterized by containing 4% by mass to 33% by mass of the above plasticizer. Here, the plasticizer may be diglycerin tetraacetate. Further, a carbodiimide compound can be mixed within the range of 0.1% by mass to 10% by mass with respect to 100% by mass of the total amount of the lactic acid resin and the plasticizer. The lactic acid-based resin sheet-like product of the present invention is a sheet-like product comprising the lactic acid-based resin composition, and is characterized by being stretched in at least one direction. Here, the storage elastic modulus at 20 ° C. is 500 MPa to 3,0.
It is preferably 00 MPa, and the heat shrinkage rate after heating at a temperature of 120 ° C. for 15 minutes is preferably 10% or less for both TD and MD. Further, the weight average molecular weight retention of the lactic acid-based resin after being stored for 4 weeks in an atmosphere having a temperature of 40 ° C. and a humidity of 80% RH can be 80% or more. The bag-shaped product of the present invention is characterized by being formed using a steam lactic acid-based resin sheet-shaped product.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The lactic acid-based resin composition of the present invention comprises 67% by mass of the lactic acid-based resin.
96 mass% and 4 mass% -33 mass% of plasticizers are contained as a main component. However, the total amount of lactic acid resin and plasticizer is 10
Mix so that it becomes 0 mass%. If the mixing amount of the plasticizer is less than 4% by mass, the softening of the sheet material does not proceed, and if it is more than 33% by mass, the viscosity becomes too low when the sheet material is melt extruded, and heat resistance cannot be obtained. The problem arises. Therefore, when the amount of the plasticizer mixed is out of the above range, the characteristics as a sheet-like material similar to OPP are not imparted.

The lactic acid type resin used in the present invention is poly (L-lactic acid) whose structural unit is L-lactic acid, and whose structural unit is D-
Poly (D-lactic acid) which is lactic acid, a copolymer whose structural unit is both L-lactic acid and D-lactic acid, that is, poly (DL-lactic acid)
Lactic acid), a mixture thereof, and even a copolymer with another hydroxycarboxylic acid unit such as α-hydroxycarboxylic acid, a copolymer with an aliphatic diol / aliphatic dicarboxylic acid. May be However, the composition ratio of D-lactic acid (D-form) and L-lactic acid (L-form) of the lactic acid resin is L
Body: D body = 100: 0 to 90:10, or L body:
It is preferable that D-form = 0: 100 to 10:90.
If the composition ratio of the D body and the L body is out of this range, it is difficult to obtain the heat resistance of the sheet-shaped material.

In the present invention, lactic acid-based resins having different copolymerization ratios of L-form and D-form may be blended. In this case, the average value of the copolymerization ratio of the L-form and the D-form of a plurality of lactic acid-based resins may be set within the above range. L body or D
By blending the homopolymer of the body with the copolymer, it is possible to balance the difficulty of bleeding and the development of heat resistance.

Other hydroxycarboxylic acid units copolymerized with the lactic acid-based resin include optical isomers of lactic acid (D-lactic acid for L-lactic acid, L-lactic acid for D-lactic acid),
Glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxy-n-butyric acid, 2-hydroxy-3,3
-Dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-
Examples thereof include bifunctional aliphatic hydroxycarboxylic acids such as methyl lactic acid and 2-hydroxycaproic acid, and lactones such as caprolactone, butyrolactone and valerolactone. Examples of the aliphatic diol copolymerized with the lactic acid-based resin include ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol and the like. Further, examples of the aliphatic dicarboxylic acid include succinic acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid and the like.

The weight average molecular weight of the lactic acid resin is 50,000 to 4
It is preferably in the range of 0,000, and more preferably 100,000 to 250,000. When the weight average molecular weight of the lactic acid resin is less than 50,000, practical physical properties are difficult to be expressed, and when it is more than 400,000, the melt viscosity may be too high, resulting in poor moldability.

As a method for polymerizing the lactic acid-based resin, any known method such as condensation polymerization method and ring-opening polymerization method can be adopted. For example, in the condensation polymerization method, L-lactic acid, D-lactic acid, or a mixture thereof can be directly subjected to dehydration condensation polymerization to obtain a lactic acid-based resin having an arbitrary composition. Further, in the ring-opening polymerization method, a lactic acid-based resin can be obtained by using lactide, which is a cyclic dimer of lactic acid, and a catalyst selected as appropriate while using a polymerization modifier and the like.
L-lactide, which is a dimer of L-lactic acid, is lactide.
-D-lactide, which is a dimer of lactic acid, and DL-lactide composed of L-lactic acid and D-lactic acid, and lactic acid having any composition and crystallinity by mixing and polymerizing these as needed. A system resin can be obtained.

Further, in order to improve heat resistance and the like, a small amount of a copolymerization component can be added, and a non-aliphatic dicarboxylic acid such as terephthalic acid or an ethylene oxide adduct of bisphenol A can be added. Aliphatic diols and the like can also be used. Furthermore, for the purpose of increasing the molecular weight, a small amount of a chain extender such as a diisocyanate compound, an epoxy compound or an acid anhydride can be used.

For the purpose of imparting impact resistance and cold resistance to the lactic acid-based resin, an aliphatic polyester resin having a glass transition temperature (Tg) of 0 ° C. or less, an aliphatic aromatic polyester resin, etc., are added to the lactic acid-based resin. It is also possible to blend the same amount or less. As the aliphatic polyester resin, an aliphatic polyester resin other than a lactic acid-based resin, for example, an aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic dicarboxylic acid, an aliphatic polyester obtained by ring-opening polymerization of cyclic lactones, a synthetic Examples include aliphatic polyesters. The aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic dicarboxylic acid is an aliphatic dicarboxylic acid such as ethylene glycol, 1,4-butanediol and 1,4-cyclohexanedimethanol which are aliphatic diols. It can be obtained by condensation polymerization of one or more selected from succinic acid, adipic acid, suberic acid, sebacic acid and dodecanedioic acid. If desired, the desired polymer can be obtained by jumping up with an isocyanate compound or the like. Further, in order to enhance heat resistance and mechanical strength, an aromatic monomer component such as terephthalic acid can be copolymerized in the range of 50 mol% or less as the dicarboxylic acid component. Examples thereof include Easter Bio manufactured by Eastman Chemical Co., and Ecoflex manufactured by BASF. Examples of the aliphatic polyester obtained by ring-opening polymerization of cyclic lactones include aliphatic polyesters obtained by polymerizing one or more kinds selected from cyclic monomers such as ε-caprolactone, δ-valerolactone, β-methyl-δ-valerolactone and the like. Is mentioned. Examples of synthetic aliphatic polyesters include cyclic acid anhydrides and oxiranes, for example,
Examples thereof include copolymers of succinic anhydride and ethylene oxide, propylene oxide and the like.

In the present invention, the "sheet-like material" means a sheet or film. According to JIS definition, a sheet is a thin product that generally has a small thickness for its length and width, and a flat film. A film is extremely thin compared to its length and width, and its maximum thickness is arbitrary. Limited thin flat product, usually supplied in roll form (JIS K 6900). Therefore, it can be said that a film has a particularly thin thickness among the sheets.
However, since the boundary between the sheet and the film is not clear and it is difficult to clearly distinguish them, in the present invention, as described above,
The term "sheet material" is used as a concept that includes both sheets and films.

From the viewpoint of compatibility and biodegradability, the plasticizer used in the present invention is preferably selected from at least one compound selected from the compounds represented by the following (1) to (10). _{(1) H 5 C 3 (} OH) 3-n (OOCCH 3) n 0 <n ≦ 3 This monoacetate glycerin, diacetate or triacetate - a preparative, may be a mixture thereof. However, n is preferably close to 3. (2) Glycerin alkylate (alkyl group has 2 carbon atoms
˜20, which may have a residue of a hydroxyl group) or diglycerin tetraalkylate. Examples thereof include glycerin tripropionate, glycerin tributyrate, diglycerin tetraacetate, and modified acetylated monoglyceride (PL009 manufactured by Riken Vitamin Co., Ltd.). (3) Ethylene glycol alkylate (the alkyl group has 1 to 20 carbon atoms, and a hydroxyl group residue may be present). For example, ethylene glycol diacetate and the like can be mentioned. (4) A polyethylene glycol alkylate having an ethylene repeating unit of 5 or less (the alkyl group has 1 to 20 carbon atoms, and a hydroxyl group residue may be present). Examples thereof include diethylene glycol monoacetate and diethylene glycol diacetate. (5) Aliphatic monocarboxylic acid alkyl ester (alkyl group has 1 to 20 carbon atoms). For example, butyl stearate and the like can be mentioned. (6) Aliphatic dicarboxylic acid alkyl ester (the alkyl group has 1 to 20 carbon atoms and may have a residue of a carboxyl group). For example, di (2-ethylhexyl) adipate, di (2-ethylhexyl) azelate and the like can be mentioned. (7) Aromatic dicarboxylic acid alkyl ester (the alkyl group has 1 to 20 carbon atoms and may have a residue of a carboxyl group). Examples thereof include dibutyl phthalate and dioctyl phthalate. (8) Aliphatic tricarboxylic acid alkyl ester (the alkyl group has 1 to 20 carbon atoms, and may have a residue of a carboxyl group). For example, citric acid trimethyl ester and the like can be mentioned. (9) A low molecular weight aliphatic polyester having a weight average molecular weight of 20,000 or less. Examples thereof include succinic acid and an ethylene glycol / propylene glycol condensate (sold by Dainippon Ink and Chemicals, Inc. under the trade name of “Polysizer”). (10) Natural fats and oils and their derivatives. Examples thereof include soybean oil, epoxidized soybean oil, castor oil, tung oil, and rapeseed oil.

The boiling point of the plasticizer at atmospheric pressure (1 atm) is preferably 220 ° C. or higher, more preferably 250 ° C. or higher. Alternatively, the boiling point at 5 to 10 Torr is preferably 170 ° C or higher, more preferably 180 ° C or higher. Boiling point at normal pressure is 2
When the boiling point is lower than 20 ° C. or lower than 170 ° C. at 5 to 10 Torr, the lactic acid-based resin is melted in relation to the melting point of the lactic acid-based resin having a ratio of D-form to L-form necessary for obtaining heat resistance. During extrusion processing, the plasticizer easily volatilizes at the extrusion temperature. Further, the solubility parameter (SP value) of the plasticizer is within the range of 9.0 to 11.0,
It is preferable from the viewpoint of compatibility with lactic acid resins. The plasticizer used in the present invention is diglycerin tetraacetate (boiling point of 5 Torr is 193 ° C., SP value is 10.3) from the viewpoint of difficulty in bleeding, hygiene, economy and the like.
Is particularly preferable.

In order to use the lactic acid type resin sheet material as a substitute for OPP, it is necessary to have wet heat resistance. A resin composition in which a plasticizer is added to a lactic acid-based resin is usually subjected to an attack of moisture in the air under an air atmosphere,
The decrease in the weight average molecular weight of the lactic acid resin progresses. Depending on the composition of the lactic acid-based resin and the type of plasticizer, stretching of the sheet-shaped material causes the crystallized structure to grow, making it difficult for the molecules to be attacked by water. Temperature 40 ° C, humidity 80% RH
The weight average molecular weight retention of the lactic acid-based resin after being stored for 4 weeks in the above atmosphere is 80% or more, which is practically no problem. The weight average molecular weight retention is a value obtained by dividing the weight average molecular weight after storage at a predetermined temperature and a predetermined humidity by the weight average molecular weight before storage as a percentage.

In order to further improve the wet heat durability, it is desirable to add 0.1 to 10 parts by mass of a carbodiimide compound to the resin composition with respect to 100 parts by mass of the total amount of the lactic acid resin and the plasticizer. A sheet-like material formed using such a resin composition has high wet heat durability. If the addition amount of the carbodiimide compound is 0.1 part by mass or more, the effect of improving the wet heat durability is sufficiently expressed, and if it is 10 parts by mass or less, the appearance of the sheet-like material and the mechanical properties are deteriorated due to bleeding out of the carbodiimide compound. Does not occur and the biodegradability is not significantly impaired. Examples of the carbodiimide compound include those having a basic structure represented by the following general formula. -(N = C = NR-) _n- However, in the said general formula, n shows an integer greater than or equal to 1. R represents another organic binding unit, and can be, for example, aliphatic, alicyclic, or aromatic. Further, when n is an integer of 2 or more, Rs of 2 or more may be the same or different. In order to prevent the hydrolyzability under high temperature and high humidity, n is preferably large, and particularly preferably n is in the range of 10 to 100. When n is less than 10, deactivation tends to occur quickly at high temperatures, and when n is greater than 100, cloudiness may occur when a plasticizer is added, the effect of improving hydrolysis resistance may be poor, and the manufacturing cost may increase. Further, when the purpose is to impart hydrolysis resistance in normal temperature air, n is preferably in the range of 1 to 30. Within such a range, the effect at low temperature can be obtained. Specifically, for example, poly (4,4'-
Diphenylmethanecarbodiimide), poly (p-phenylenecarbodiimide), poly (m-phenylenecarbodiimide), poly (tolylcarbodiimide), poly (diisopropylphenylenecarbodiimide), poly (methyl-diisopropylphenylenecarbodiimide), poly (triisopropylphenylenecarbodiimide), etc. , And these monomers. The carbodiimide compounds may be used alone or in combination of two or more.

As long as the effects of the present invention are not impaired, heat stabilizers, antioxidants, UV absorbers, light stabilizers, pigments, colorants,
Additives such as lubricants, nucleating agents, and inorganic fillers can be added.

Next, a method for producing the lactic acid-based resin sheet material of the present invention will be described. The lactic acid-based resin, the plasticizer, and the like can be mixed by putting the respective raw materials into the same extruder. There is a method of directly extruding from a die of an extruder to directly produce a film, or a method of extruding into a strand shape to produce pellets and then again producing the film by using an extruder. In any method, it is necessary to consider the decrease in molecular weight due to the decomposition of raw materials,
It is preferable to select the latter for uniform mixing. The melting extrusion temperature of the lactic acid resin is appropriately selected in consideration of the fact that the melting point changes depending on the composition ratio of L-lactic acid and D-lactic acid and the melting point of the resin composition changes depending on the mixing ratio of the plasticizer. It is preferable. Usually 100-25
A temperature range of 0 ° C is selected.

The melt-molded biodegradable sheet material is
It is preferable to contact a rotating casting drum (cooling drum) for rapid cooling. It is preferable to appropriately select it depending on the mixing ratio of the lactic acid resin and the plasticizer and the properties of these resins. For example, the temperature of the casting drum is appropriately 60 ° C. or lower. If the temperature of the casting drum is 60 ° C. or lower, the disadvantage that the sheet-like material sticks to the casting drum and cannot be removed, or the crystallization of the polylactic acid portion is promoted and the sheet cannot be stretched does not occur. Therefore, it is preferable that the casting drum is cooled rapidly at a temperature of 60 ° C. or lower to render the polylactic acid portion substantially amorphous.

The obtained sheet material is stretched in at least one direction. The stretched film of the present invention can take any method as long as it is a usual stretched film molding method. The resin composition as a raw material may be pre-compounded in advance by using a same-direction twin-screw extruder, a kneader, a Henschel mixer, or the like, or after dry blending a lactic acid-based resin, a plasticizer or the like constituting the resin composition, It may be placed in an extruder. The liquid component such as the plasticizer may be blended at the same time when the solid component is blended, but may be injected from the vent port of the extruder by using a pump or the like separately from the solid component. As a stretching method, a roll stretching method in which a sheet material is stretched between two rolls having different peripheral speeds, or a tenter stretching method in which a sheet is gripped by a clip using a tenter and a row interval of clip rows is expanded The tubular method, the inflation method, and the like are appropriately used in combination as necessary. When biaxially stretching, a simultaneous stretching method or a sequential stretching method is adopted. The stretching condition is that the temperature of the sheet-like material is preferably 20 to 140 ° C.,
It is more preferably 40 to 110 ° C., and the draw ratio is preferably in the range of 1.5 to 5.0 times. Within such a range, troubles such as breakage and whitening of the sheet-like material and drawdown will not occur.

In order to further enhance the effects of the present invention, it is desirable that the sheet-shaped material is stretched and then heat-treated with a fixed width. The heat treatment conditions are preferably a temperature of 70 to 160 ° C., more preferably 90 to 140 ° C., particularly preferably 100 to 140 ° C., and a treatment time of 5 seconds to 5 seconds.
It is preferably within the range of minutes. When the temperature is lower than 70 ° C, it is difficult to obtain the heat treatment effect, and when the temperature is higher than 160 ° C, the sheet-like material is easily drawn down. If the treatment time is less than 5 seconds, it is difficult to obtain the heat treatment effect, and if the treatment time exceeds 5 minutes, the heat treatment equipment becomes large and the economical efficiency deteriorates.

A temperature of 12 is selected by selecting the ratio of the D and L forms of the lactic acid resin, selecting the type of plasticizer, stretching and heat treatment.
The heat shrinkage ratio after heat treatment at 0 ° C. for 15 minutes is TD, M
Both D can be 10% or less. When the heat shrinkage of the sheet material is 10% or less in TD and 10% or less in MD, heat resistance (heat dimensional stability) is excellent, and during secondary processing such as printing or bag making, or depending on the case, Does not cause the sheet-like material to shrink during storage or cause problems such as waviness and curling. Here, “TD” indicates the width direction (transverse direction) of the sheet-like material, and “MD” indicates the longitudinal direction (vertical direction) of the sheet-like material.

In the present invention, it is preferable that the storage elastic modulus (E ′) of the sheet-like material measured by dynamic viscoelasticity measurement at a frequency of 10 Hz and a temperature of 20 ° C. is in the range of 500 MPa to 3,000 MPa. Storage modulus (E ') is 5
When it is less than 00 MPa, it is excessively soft and easily deformed, so the sheet tension stretches due to roll tension during secondary processing such as printing and bag making, causing misalignment and curling, and lacking in self-supporting properties for product display effects. It may be inferior. Further, the storage elastic modulus E'is 3,000 MPa.
If it exceeds, it will be hard and difficult to stretch, so 2
Wrinkles are likely to occur during the next processing, and the product may feel dry during use. When obtaining properties and texture similar to OPP, the storage elastic modulus (E ') of the sheet material
Is preferably in the range of 500 MPa to 3,000 MPa. In order to control the storage elastic modulus (E ′) of the sheet-shaped product in such a range, it is most important to control the amount of the plasticizer within the range of 4 to 33% by mass. The storage elastic modulus can be kept within a predetermined range by appropriately adjusting the type of agent, the combination of molding processing conditions, and the like.

The lactic acid-based resin composition of the present invention is suitable as a raw material for a lactic acid-based resin sheet, and the formed lactic acid-based resin sheet of the present invention has physical properties similar to OPP.
It is suitable for fusing and sealing and can produce bag-shaped products. A biaxially stretched sheet of a lactic acid-based resin containing no plasticizer is too hard and difficult to stretch, so that it does not easily absorb wrinkles due to the dimensional difference and is easily wrinkled during bag making. It can be processed well without wrinkles during bagging. In addition, a sheet-shaped product obtained by biaxially stretching a lactic acid-based resin containing no plasticizer is unlikely to have a fusing seal strength, but the lactic acid-based resin sheet-shaped product of the present invention has a fusing seal strength comparable to that of OPP.

[0027]

EXAMPLES The present invention will be described in more detail with reference to the following examples. The present invention is not limited by the matters described below. The measured values and evaluations shown in the examples were measured under the following conditions.

(1) Storage elastic modulus (E ') Viscoelasticity spectrometer "VE" manufactured by Iwamoto Manufacturing Co., Ltd.
S-F3 ", vibration frequency 10Hz, temperature 20 ℃
The storage modulus of the MD of the sheet was measured. (2) Tensile Strength and Elongation A tensile test was performed based on JIS K 7127 to measure the strength and elongation when the sheet-like material broke. No. 2 test piece was used as the test sample, and the pulling speed was 100 mm
/ Min was measured 5 times and the average value was calculated. (3) Heat resistance (heat shrinkage) The sheet-like material piece was hung in an oven at 120 ° C for 15 minutes, and the heat shrinkage was calculated based on the following formula. However,
The length of the sheet material before heating in the oven was L1, and the length of the sheet material after the heat treatment was L2. Heat shrinkage rate (%) = (L1−L2) / L1 × 100 (4) Wet heat durability (weight average molecular weight retention rate) A sheet-shaped piece of which the weight average molecular weight of the lactic acid resin was measured in advance at a temperature of 80 ° C. Constant temperature and humidity chamber with humidity adjusted to 40% RH (Tabay Espec Co., Ltd., constant temperature and humidity chamber LH
-112) and allowed to stand for 4 weeks, and the weight average molecular weight retention rate was calculated based on the following formula. Weight average molecular weight retention rate is 80
% Or more is excellent in wet heat durability. (5) Weight average molecular weight of lactic acid based resin To gel permeation chromatography “HLC-8120GPC” manufactured by Tosoh Corporation, and “G” of chromatographic column Shim-Pack series manufactured by Shimadzu Corporation.
"PC-800CP" is attached, and chloroform is used as a solvent so that the solution concentration is 0.2 wt / vol% by mass.
The measurement was carried out at a solution injection amount of 200 μL, a solvent flow rate of 1.0 mL / min, and a solvent temperature of 40 ° C., and the weight average molecular weight of the lactic acid resin was calculated by polystyrene conversion. The weight average molecular weight of the standard polystyrene used was 2,000,000, 67.
50,000, 110,000, 35,000, 10,
00, 4,000 and 600. (6) Haze Based on JIS K 7105, the total light transmittance and the diffuse transmittance were determined and calculated using the following formulas. Haze (%) = diffuse transmittance / total light transmittance × 100 (7) Suitability for fusing seal bag making machine “HK65V” fusing seal bag making machine manufactured by Totani Giken Co., Ltd.
In, a sample in which a sheet having a width of 500 mm is wound into a roll is used, and the frontage is 100 mm and the length is 250 mm.
1000 pieces of the side-seal bag of were produced under the optimum conditions. The appearance of the obtained bag was visually observed and evaluated based on the following evaluation criteria. Evaluation criteria: ○ The bag without wrinkles or curls is 900-100.
A bag with no wrinkles and curls is 700-899
No more than 699 pouches without wrinkles or curls

(Example 1) First, a lactic acid resin was prepared. Purak Japan L-lactide (trade name "PURASORB L") 97kg and the company DL-
Lactide (trade name "PURASORB DL") 3kg
Then, 15 ppm of tin octylate was added, and the mixture was placed in a 500 L batch type polymerization tank equipped with a stirrer and a heating device. Then, the atmosphere is replaced with nitrogen, and the temperature is 185 ° C. and the stirring speed is 100 r.
Polymerization was carried out at pm for 60 minutes. The obtained melt was subjected to a 40 mmφ, same-direction twin-screw extruder manufactured by Mitsubishi Heavy Industries, Ltd. equipped with three stages of vacuum vents, and extruded into a strand at 200 ° C. to form pellets while degassing at a vent pressure of 4 torr, A lactic acid resin in the form of pellets was obtained. The obtained lactic acid-based resin had a weight average molecular weight of 200,000 and an L-form content of 98.
It was 6%. Next, the obtained lactic acid-based resin and diglycerin tetraacetate as a plasticizer (Riken Vinyl Co., Ltd.)
Manufactured by LIKEMAR PL710) and 87:13 (mass%)
And mixed at a temperature of 180 ° C. using a 40 mmφ small-sized same-direction twin-screw extruder manufactured by Mitsubishi Heavy Industries, Ltd. to form pellets. The pellets thus obtained were extruded at a barrel temperature of 200 ° C. through a T-die using a 110 mmφ single screw extruder manufactured by Mitsubishi Heavy Industries, Ltd., and rapidly cooled using a casting roll at 30 ° C. to obtain a 300 μm-thick sheet material. Obtained.
Subsequently, using a sequential biaxial tenter manufactured by Mitsubishi Heavy Industries, Ltd., a draw ratio of 2.5 was applied to MD and TD at a temperature of 50 ° C.
After stretching twice, heat treatment at 140 ° C for 15 seconds,
A stretched sheet having a film thickness of 50 μm was obtained. The resulting lactic acid-based resin sheet was measured and evaluated for storage elastic modulus (E ′), tensile strength and elongation, heat shrinkage, haze, suitability for fusing seal bag making machine. The results are shown in Table 1.

Example 2 Except that the lactic acid-based resin produced in Example 1 and diglycerin tetraacetate (Rikemar PL710 manufactured by Riken Vinyl Co., Ltd.) as a plasticizer were 84% by mass: 16% by mass. A lactic acid-based resin sheet material was prepared in the same manner as in Example 1. The lactic acid-based resin sheet material thus obtained was measured and evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Examples 3 and 4) The lactic acid resin produced in Example 1 and an acetylated monoglyceride modified product ("PL009" manufactured by Riken Vitamin Co., Ltd.) as a plasticizer,
A lactic acid-based resin sheet of Example 3 and Example 4 was prepared in the same manner as in Example 1 except that 5 Torr, a boiling point of 193 ° C., and an SP value of 9.70) were mixed at a ratio of 87:13 and 84:16, respectively. A substance was obtained. The same measurements and evaluations as in Example 1 were performed for each of the obtained sheet-shaped materials of Example 3 and Example 4. The results are shown in Table 1.

(Example 5) The lactic acid resin produced in Example 1 and glycerin triacetate as a plasticizer ("Triacetin" manufactured by Daihachi Chemical Co., Ltd., boiling point 258 ° C at normal pressure, SP value 10.24) A lactic acid-based resin sheet material of Example 5 was obtained in the same manner as in Example 1 except that and were mixed at a ratio of 93: 7. The same measurement and evaluation as in Example 1 were performed on the obtained sheet-shaped material of Example 5. The results are shown in Table 1.

(Comparative Examples 1 and 2) Comparative Example 1 and Comparative Example 2 were carried out in the same manner as in Example 1 except that the plasticizer addition amounts were changed to 3% by mass and 35% by mass, respectively. A sheet-like material having a film thickness of 50 μm was obtained. The same measurement and evaluation as in Example 1 were performed for each of the obtained sheet-shaped materials. The results are shown in Table 1.

[0034]

[Table 1]

(Example 6) The pellets obtained by compounding in Example 1 were mixed with stavaxol (trade name "Stavaxol P-100" manufactured by Bayer Co., Ltd., general formula).
-(N = C = NR-N = C = NR ') _n- ; Degree of polymerization
n≈28, R is a 2,5-diisopropylphenyl group,
A lactic acid-based resin sheet was obtained in the same manner as in Example 1 except that 2.0 parts by mass of R'is a phenyl group) was dry-blended. A wet heat durability test was performed on the obtained lactic acid resin sheet material. The results are shown in Table 2.

Example 7 The sheet-like material obtained in Example 1 was evaluated for wet heat durability and the weight average molecular weight retention rate was obtained. The results are shown in Table 2.

Comparative Example 3 The lactic acid resin produced in Example 1 was mixed with diglycerin tetraacetate (Rikemar PL710 manufactured by Riken Vinyl Co., Ltd.) as a plasticizer at 87:13 (mass%). Using a 40 mmφ small-sized same-direction twin-screw extruder manufactured by Mitsubishi Heavy Industries, Ltd.
Compounded at 80 ° C into pellet form. The obtained pellets were extruded at a barrel temperature of 200 ° C. through a T-die using a 110 mmφ single screw extruder manufactured by Mitsubishi Heavy Industries, Ltd., rapidly cooled to 30 ° C. using a casting roll, and an unstretched sheet having a film thickness of 50 μm. A substance was obtained. The obtained sheet-like material was evaluated for wet heat durability in the same manner as in Example 6. The results are shown in Table 2.

[0038]

[Table 2]

As is clear from Table 1, the lactic acid resin sheet materials of Examples 1 to 5 have MD and TD elongations of 100% or more, respectively, and are excellent in breakage resistance, and the heat shrinkage rate is high. Was 10% or less in both MD and TD, and it was found that the heat resistance (thermal stability) was excellent. Moreover, it was found that the lactic acid-based resin sheet materials of Examples 1 to 5 had a haze of 15% or less and were excellent in transparency. further,
The lactic acid-based resin sheet materials of Examples 1 to 5 have a storage elastic modulus (E ′) in the range of 500 to 3,000 MPa,
It was found that the suitability for the fusing seal bag making machine was good. On the other hand, the sheet-shaped material of Comparative Example 1 has a storage elastic modulus (E ′) of 3,
It was found that the sheet-like material was less stretchable because it was larger than 000 MPa, and wrinkles were likely to occur during secondary processing. The lactic acid-based resin sheet material of Comparative Example 2 has a heat shrinkage rate of more than 10% in both MD and TD and has a problem of heat resistance. Further, since the storage elastic modulus (E ′) is less than 500 MPa, it is subjected to secondary processing. It was found that the sheet-like material was liable to be stretched and misaligned or curled, which was inferior to the suitability for the fusing seal bag making machine. Further, as is clear from Table 2, it was found that the lactic acid-based resin sheet material of the present invention has a storage elastic modulus of 80% or more and is excellent in wet heat durability. On the other hand, it was found that the unstretched sheet material of Comparative Example 3 was inferior in storage elastic modulus to the lactic acid resin sheet material of the present invention. The lactic acid-based resin sheet materials of Examples 2 to 4 were also evaluated for wet heat durability, and the weight average molecular weight retention was 80% or more.

[0040]

As is clear from the above description, the lactic acid-based resin sheet or bag-shaped product formed using the lactic acid-based resin composition of the present invention has physical characteristics similar to OPP. Excellent heat resistance (heat stability) and wet heat durability. Since the lactic acid-based resin composition of the present invention contains a polylactic acid-based resin and a plasticizer as main components, it has biodegradability and is biodegradable even when discarded in a natural environment, and does not adversely affect the natural environment. . In addition, the lactic acid-based resin composition of the present invention has a lower calorific value than the polyethylene-based resin or the like that has been conventionally used as a heat-shrinkable film. Therefore, even if incinerated, the incinerator is not easily damaged. That is, according to the present invention, a lactic acid-based resin composition, a sheet-shaped product, and a bag-shaped product, which have biodegradability that does not impose a load on the natural environment, have physical properties similar to OPP, and have excellent heat resistance and wet heat durability, are provided. It can be provided and can be applied to the packaging material and industrial material fields.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C08L 67/02 C08L 67/02 79/00 79/00 Z 91/00 91/00 F term (reference) 3E086 AA01 AB01 AC07 AD01 BA02 BA15 BA33 BB21 BB41 BB42 BB85 BB90 DA08 4F071 AA43 AA44 AA58 AC10 AE04 AF20Y AF53Y AF61Y AH04 BB02 BB06 BB07 BB08 BB09 BC01 4J002 AE052 CF032 CF181 CM052 EH036 EH046 EH056 EH096 EH146 FD022 FD026 FD033 GG02

Claims (7)

[Claims] 1. As a main component, 67 mass% of lactic acid-based resin
A lactic acid-based resin composition comprising 96% by mass and 4% by mass to 33% by mass of a plasticizer having a boiling point of 220 ° C. or higher at normal pressure or a boiling point of 170 ° C. or higher at 5 Torr to 10 Torr. object. 2. The lactic acid-based resin composition according to claim 1, wherein the plasticizer is diglycerin tetraacetate. 3. The carbodiimide compound is further mixed in the range of 0.1% by mass to 10% by mass with respect to 100% by mass of the total amount of the lactic acid resin and the plasticizer. The lactic acid-based resin composition described in 1. 4. A sheet-like material comprising the lactic acid-based resin composition according to claim 1, wherein the lactic acid-based resin composition is stretched in at least one direction. object. 5. The storage elastic modulus at 20 ° C. is 500 MP.
The lactic acid-based resin sheet material according to claim 4, wherein a heat shrinkage ratio after heating at 120 ° C. for 15 minutes is 10% or less for both TD and MD. 6. The weight average molecular weight retention of the lactic acid-based resin after being stored for 4 weeks in an atmosphere having a temperature of 40 ° C. and a humidity of 80% RH is 80% or more. The lactic acid-based resin sheet-like product described. 7. A bag-shaped product, which is formed by using the lactic acid-based resin sheet-shaped product according to any one of claims 4 to 6.