JP2002146170A - Crystalline polylactic acid resin composition and film and sheet using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasticized poly (lactic acid) resin composition that shows good blocking resistance, opening properties and bleed-out resistance in both of the case where the film is produced from the resin composition and where the molded products are used, and provide the film and sheets produced from the resin composition. SOLUTION: The objective poly (lactic acid) resin composition comprises (A) a crystalline poly (lactic acid) resin, (B) a plasticizer and (C) a crystal- nucleating agent as essential components and has the glass transition temperature of <=30 deg.C, the temperature-falling crystallization heat of >=10 J/g and the temperature-falling crystallization peak temperature of >=80 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polylactic acid resin composition. More specifically, the present invention relates to a polylactic acid resin composition having degradability in a natural environment and having improved flexibility, elongation, impact resistance and anti-blocking property, and a film and sheet comprising the same.

[0002]

2. Description of the Related Art In recent years, as the amount of plastic used has increased,
The waste disposal is regarded as a problem. Conventionally, methods of treating plastic waste include landfill and incineration. In the case of landfill disposal, plastic waste remains in its original form semi-permanently, causing problems such as shortage of landfills and destruction of nature.
On the other hand, when plastics are incinerated, the heat of combustion is high and the incinerators are easily damaged, causing pollution problems such as generation of harmful substances.

Under such circumstances, so-called biodegradable plastics, which can be decomposed and consumed in a natural environment by microbial decomposition or the like and converted into carbon dioxide or water and reduced to the natural environment, have attracted attention. As such biodegradable plastics, various plastics such as polycaprolactone, polybutylene succinate, polyhydroxyvalerate, and polylactic acid have reached a practical stage. Among them, polylactic acid has recently attracted attention as a plant-derived plastic, that is, petroleum-saving plastic, because it uses lactic acid obtained as a raw material by biologically fermenting a starch source that is refined through photosynthesis by plants such as corn. Polylactic acid is widely used in various applications as a material that has excellent transparency, heat resistance, rigidity and mold resistance compared to conventional biodegradable plastics, and also has practical durability. It is attached to. However, polylactic acid has the drawback that it is hard and brittle, such as high rigidity, low flex resistance, and low impact resistance due to its molecular structure. Fields requiring flexibility and elongation, such as various soft films In the field of sheets and seats, improvements were desired. Conventionally, as a method for improving the flexibility of polylactic acid,
Copolymerization, blending of flexible polymers, and plasticizing techniques with plasticizers have been attempted. As an example of softening by copolymerization, JP-A-7-173266 discloses a technique of copolymerizing a lactic acid component, another hydroxycarboxylic acid component and a polyhydric alcohol component. However, in the improvement by copolymerization, the crystallinity of polylactic acid is impaired, so that there is a problem that a film is blocked or heat resistance is impaired.

On the other hand, flexible polymer blends such as polybutylene succinate, polyethylene succinate and polycaprolactone have high biodegradability and high flexibility, as described in JP-A-8-245866. A method of mixing a polymer may be used. However, most of these flexible polymers have poor compatibility with polylactic acid and required a large amount of addition to provide sufficient flexibility. As a result, there is a problem in that characteristics that are advantages of polylactic acid, such as durability and mold resistance, are impaired.

Various studies have been made in the past on plasticization with a plasticizer. US Pat. No. 5,076,983 discloses a method using lactide, which is a cyclic dimer of lactic acid, as a plasticizer. According to this method, although a plasticizing effect can be obtained, there is a problem that sublimation of the mixed lactide causes smoke and contamination of the molding machine during melt molding. In addition, polylactic acid containing a large amount of lactide is easily decomposed due to low hydrolysis resistance, and there is a problem that only a molded article having low durability can be obtained even in ordinary use.

JP-A-4-335060 discloses phthalic acid esters, aliphatic dibasic acid esters, phosphoric acid esters, hydroxy polycarboxylic acid esters, fatty acid esters, polyhydric alcohol esters, epoxy plasticizers, polyester plasticizers. A composition obtained by mixing a plasticizer comprising an agent or a mixture thereof with a polylactic acid-based resin is shown. JP-A-11-181262 discloses a lactic acid-based polymer composition containing an ether ester-based plasticizer. Also, Japanese Patent Application Laid-Open Nos. Hei 7-118513 and
Japanese Patent No. 283557 discloses a lactic acid-based polymer composition comprising a lactic acid-based polymer containing polylactic acid as a main component and a polyester-based plasticizer. According to these publications,
It is said that by mixing a plasticizer having high compatibility with polylactic acid at a high concentration, sufficient flexibility can be imparted to polylactic acid. However, since the methods described in these publications all aim at lowering the glass transition temperature of polylactic acid by plasticization, in order to impart practically sufficient flexibility, the glass transition temperature must be set to the actual value. It was necessary to be near or lower than the operating temperature. When such a composition having a low glass transition temperature is put to practical use as a film or sheet, there is a problem that blocking tends to occur during the production process or use of the composition or film. Therefore, it has been difficult to industrially produce commercially valuable films and sheets for the compositions obtained by the methods described in the above publications.

As a general solution to the above problem, there is known a method of adding inorganic particles for imparting blocking resistance to a film or sheet. An example of filling biodegradable plastic with inorganic particles is disclosed in
Japanese Patent Application Laid-Open No. 70696/1995 describes a method in which calcium carbonate having an average particle diameter of 20 μm or less or hydrous magnesium silicate (talc) is mixed with a biodegradable plastic such as polylactic acid or polycaprolactone by 10 to 40% by mass.
However, this publication does not mention the provision of flexibility by plasticization, and its purpose is to promote decomposition after disposal by adding a large amount of inorganic particles rather than as a blocking measure. .

On the other hand, as an attempt to improve the blocking property of a plasticized polylactic acid resin composition, JP-A-8-34 discloses
No. 913 discloses that 90% by mass or more of SiO ₂ is contained in 100 parts by mass of a mixture of a polylactic acid resin and a plasticizer selected from the group consisting of a polyhydric alcohol ester and a hydroxy polycarboxylic acid, and the average particle size is 100% by mass. A composition comprising 0.1 to 5 parts by weight of a blocking agent having a thickness of 7 to 50 nm and 0.1 to 2 parts by weight of a lubricant is disclosed. This publication states that the film made of the plasticized polylactic acid resin composition has improved blocking resistance. However, in the examples, it is only shown that such effects are obtained for stretched films.For example, in the case of a film or sheet that is not substantially stretched such as an inflation film, it is described in this publication. Some methods were not sufficient to improve blocking resistance.

Further, Japanese Patent Application Laid-Open No. 11-116788 discloses a composition in which a plasticizer is mixed with a polymer component comprising a mixture of polylactic acid and an aliphatic polyester having a melting point of 80 ° C. to 250 ° C. According to this publication, a film excellent in bleed resistance and blocking resistance can be obtained only when a specific aliphatic polyester resin and SiO ₂ as inorganic particles are used in combination with the plasticized composition of polylactic acid. The present inventors have conducted detailed verification of the examples in this publication, and as a result, in the blocking resistance test described in Japanese Patent Application Laid-Open No. 11-116788, it was confirmed that the blocking resistance was improved. The effect is not sufficient, and in the method described in the examples, when the film formed into a tube is folded by a pinch roll when forming the film, blocking occurs between the folded two-layer film in the tube shape. However, it was found that it was difficult to open the tube and peel off the two layers of the film. In particular, when the degree of plasticization is large and the glass transition temperature of the composition is equal to or lower than room temperature, this phenomenon becomes more remarkable, and the method described in this publication can prevent blocking of the film that occurs during molding. Did not. Further, the film obtained according to Example 1 of JP-A-11-116788 shows almost no crystallization immediately after molding, and when left for a long period of time, changes in physical properties due to post-crystallization and plasticizers due to post-crystallization. Bleed-out was observed, and there was a problem in practice. As described above, in the prior art, there were various problems in industrially producing a plasticized polylactic acid resin composition as a practical film or sheet.

[0010]

The problem to be solved by the present invention is to improve the drawback of polylactic acid, which is hard and brittle, and to have problems such as bleed-out and blocking during both production and use. It is an object of the present invention to provide a plasticized polylactic acid resin composition and a film or sheet comprising the same.

[0011]

Means for Solving the Problems The present inventors have made various studies to solve the above-mentioned problems, and as a result, have obtained the following findings. There are two types of optically active isomers of polylactic acid, namely, D-lactic acid and L-lactic acid. At present, L-lactic acid is industrially produced in large quantities at low cost, and L-polylactic acid (PLLA) derived from L-lactic acid is generally used for polylactic acid. The crystallinity of polylactic acid changes depending on the content of L-lactic acid or D-lactic acid. For example, when the optical purity L of a lactic acid monomer is defined as Formula 1, the crystallinity increases as L increases, that is, as the optical purity increases. To increase. Optical purity = | M (L) -M (D) | Formula 1 M (L): mol% of L-lactic acid unit with respect to all lactic acid units constituting polylactic acid resin M (D): polylactic acid resin Mol% of D-lactic acid unit with respect to all lactic acid units constituting M (L) + M (D) = 100

Generally, the optical purity is 100%, for example, 100%.
Even when PLLA is polymerized from a monomer composed of a% L-lactic acid component, since the racemization of the monomer occurs partially due to the thermal history in the polymerization and the subsequent melt molding, the optical purity of PLLA used industrially is 98%. The neighborhood is said to be the upper limit. Therefore, this is the most highly crystalline composition practically among polylactic acids. However, the crystallization rate of PLLA comprising such a high-purity L-lactic acid component is relatively low, and the supercooling property in the cooling crystallization process is very high. In particular, polylactic acid requires a polymer having a relatively high molecular weight to obtain practical strength and durability, and a polymer having a weight average molecular weight of 100,000 or more as a guide. Is even more pronounced. Therefore, when polylactic acid is rapidly cooled and solidified by contact with a cast roll or cold air in melt molding of a film or sheet, crystallization hardly occurs,
Generally, only a molded article having a substantially amorphous structure can be obtained.

In the case of plasticized crystalline polylactic acid, the crystallization rate tends to be slightly improved because the mobility of the molecular chains is increased by plasticization. Crystallization hardly occurs during the cooling and solidification process, and immediately after molding, only a substantially amorphous structure is obtained. It is for this reason that in the prior art, the problem of blocking is observed in films and sheets made of a composition whose glass transition temperature has dropped to around room temperature due to plasticization. Also, JP-A-11-1167
No. 88, a flexible polyester resin and S
When iO ₂ is used in combination, although the blocking resistance is slightly improved due to the surface effect of the crystalline flexible polyester particles and SiO ₂ particles dispersed in the polylactic acid matrix having a substantially amorphous structure, It hardly contributes to crystallization during the cooling and solidification process, and the film or sheet immediately after molding still has a problem of blocking. Further, the composition thus formed has a Tg
Is near or below room temperature, post-crystallization occurs when left for a long time, and changes in physical properties and bleed-out are likely to occur.

From these facts, the present inventors have found that using a plasticized polylactic acid resin composition, it has blocking resistance both during production and during use, and changes in physical properties due to post-crystallization. It has been found that the following requirements are necessary in order to industrially provide films and sheets having no bleed-out. (1) To have improved blocking resistance,
The plasticized polylactic acid composition must have appropriate crystallinity. (2) When processing into films and sheets by melt molding,
It is necessary to cause appropriate crystallization in the process of cooling and solidifying the plasticized polylactic acid composition from a molten state.

The present inventors have conducted intensive studies to satisfy the above requirements. As a result, by imparting specific crystallization characteristics to the plasticized polylactic acid composition, the polylactic acid composition is resistant to both production and use. A method for industrially providing a film or sheet having a blocking property and exhibiting no change in physical properties or bleed-out due to post-crystallization has been found.
That is, the present invention is specified by the matters described in [1] to [6] below. [1] (A) crystalline polylactic acid-based resin, (B) plasticizer,
(C) A highly crystalline polylactic acid resin composition comprising a crystal nucleating agent as an essential component and satisfying the following conditions. (1) Glass transition temperature ≦ 30 ° C. (2) 1 g of polylactic acid resin component by differential scanning calorimetry when cooled at a rate of 20 ° C./min from a molten state
ΔHc ≧ 10 (J / g) (3) The crystallization peak temperature by a differential scanning calorimeter when cooled from the molten state at a rate of 20 ° C./min is represented by T
Tcc ≧ 80 ° C. [2] The crystalline polylactic acid-based resin is a mixture of a polylactic acid resin (P1) having an optical purity of 90% or more and a polylactic acid resin (P2) having an optical purity of less than 90%, The highly crystalline polylactic acid resin composition according to [1], wherein the mass fraction of P1 to the total mass of P1 and P2 is 30 to 100% by mass. [3] The highly crystalline polylactic acid resin composition according to [1] or [2], wherein the nucleating agent is talc. [4] A film or sheet mainly comprising the polylactic acid resin composition described in [1] to [3]. [5] (A) a crystalline polylactic acid-based resin, (B) a plasticizer,
(C) A film or sheet comprising a crystal nucleating agent as an essential component and satisfying the following conditions. (1) Glass transition temperature ≦ 30 ° C. (2) 1 g of polylactic acid resin component by differential scanning calorimetry when cooled at a rate of 20 ° C./min from a molten state
ΔHc ≧ 10 (J / g) (3) The crystallization peak temperature by a differential scanning calorimeter when cooled from the molten state at a rate of 20 ° C./min is represented by T
Tcc ≧ 80 ° C. [6] The film or sheet according to [4] or [5], which is produced by an inflation method.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the present invention, lactic acid which is a raw material of polylactic acid is L
-Lactic acid, D-lactic acid, DL-lactic acid or a mixture thereof. When a cyclic dimer of lactic acid is used as a raw material, L-lactide, D-lactide, meso-lactide or a mixture thereof is used. The following method is mentioned as a method for producing polylactic acid used in the present invention. For example, as a method of directly performing dehydration polycondensation using lactic acid as a raw material, there is a method disclosed in US Pat. No. 5,310,865. Also cyclic dimer of lactic acid (lactide)
The method disclosed in US Pat. No. 2,758,987 may be mentioned as a method for subjecting the compound to ring-opening polymerization.

The polylactic acid used in the present invention has a weight average molecular weight of 80,000 to 1,000,000, preferably 10
Those having a molecular weight of 10,000 to 500,000, more preferably 120,000 to 300,000 are used. If the molecular weight is smaller than this range, mechanical properties, melt processability and durability are impaired. On the other hand, if it is larger than this range, the viscosity at the time of melting becomes too large, so that melt processing becomes difficult.

Since the polylactic acid used in the present invention needs to have crystallinity, it is preferable that the polylactic acid contains a polylactic acid having an L-lactic acid component or a D-lactic acid component as a main component. Specifically, optical purity L ≧ 90 (%)
It is desirable to contain polylactic acid which is Unless polylactic acid having an optical purity of 90% or more is contained, crystallinity sufficient to suppress blocking cannot be obtained, which is not preferable. Further, the polylactic acid used in the present invention may contain a low-crystalline or amorphous polylactic acid component in order to suppress bleed-out which is likely to occur when a plasticizer is added at a high concentration. That is, the polylactic acid used in the present invention is a highly crystalline polymer (P1) having an optical purity of 90% or more.
And a low-crystalline or non-crystalline polylactic acid (P2) having an optical purity of less than 90%. Furthermore, since the low crystalline or amorphous polylactic acid P2 tends to deteriorate in color tone after melt processing as the monomer having low optical purity is used, the optical purity L in the range of 50% ≦ L ≦ 90% is used. It is preferably used. The mixing ratio of the highly crystalline polylactic acid P1 and the low crystalline or amorphous polylactic acid P2 is such that P1: P2 is 100: 0.
The range of ３０30: 70 is preferred. If the mixing ratio of P1 is smaller than this, sufficient crystallinity cannot be obtained, and problems such as blocking occur.

In the polylactic acid used in the present invention, other aliphatic hydroxydicarboxylic acids, aliphatic diols and aliphatic dicarboxylic acids may be copolymerized as long as the composition exhibits the properties specified in the present invention. .

Specific examples of the aliphatic hydroxycarboxylic acid include glycolic acid, lactic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid and 6-hydroxycaproic acid.
Further examples include cyclic esters of aliphatic hydroxycarboxylic acids, for example, lactide which is a dimer of lactic acid, glycolide which is a dimer of glycolic acid, and ε-caprolactone which is a cyclic ester of 6-hydroxycaproic acid. These can be used alone or in combination of two or more.

Specific examples of the aliphatic dihydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, 1,3-butanediol, 1,4-butanediol, and -Methyl-1,5 pentanediol, 1,6
-Hexanediol, 1,9-nonanediol, neopentyl glycol, polytetramethylene glycol,
1,4-cyclohexanediol and the like can be mentioned. These can be used alone or in combination of two or more.

Specific examples of the aliphatic dibasic acids include succinic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecandioic acid and dodecanedioic acid. Can be These aliphatic dibasic acids can be used alone or in combination of two or more.

The polylactic acid used in the present invention may have a branched or crosslinked structure by copolymerizing a polyfunctional reactive monomer as long as the composition exhibits the properties specified in the present invention. . The introduction of the branched or crosslinked structure can improve the melting properties when the composition containing the plasticizer is formed into a film or sheet.

The polylactic acid used in the present invention may be blended with other biodegradable plastics as long as the composition exhibits predetermined crystallization characteristics. Specific examples of such biodegradable plastics include, for example, aliphatic hydroxycarboxylic acids such as those described above, aliphatic polyesters having biodegradability that can be produced by combining aliphatic dihydric alcohols and aliphatic dibasic acids. Polymers. Preferred aliphatic polyester polymers include polyethylene oxalate, polybutylene oxalate, polyneopentyl glycol oxalate, polyethylene succinate, polybutylene succinate, polyhydroxybutyric acid and β-hydroxybutyric acid and β-hydroxyvaleric acid. And copolymers. Examples of other biodegradable plastics include a semi-aliphatic polyester polymer in which terephthalic acid and / or isophthalic acid are partially copolymerized in the above aliphatic polyester polymer, and an aliphatic diamine or a fatty acid in the above aliphatic polyester. Aromatic aminocarboxylic acids,
Examples thereof include a polyesteramide-based polymer, a starch-based polymer, a polyvinyl alcohol-based polymer, and a cellulose acetate-based polymer in which a lactam is copolymerized.

As the plasticizer used in the present invention, a plasticizer excellent in compatibility with polylactic acid and plasticizing ability can be used. Although there is no particular limitation on the plasticizer, aliphatic polycarboxylic acid ester derivatives, aliphatic polyhydric alcohol ester derivatives, aliphatic oxyacid ester derivatives, aliphatic polyether derivatives, aliphatic polyether polycarboxylic acid ester derivatives And the like. These plasticizers may be used alone, or at least two or more plasticizers may be used as a mixture.

The term "aliphatic polycarboxylic acid ester" refers to an ester compound comprising a saturated or unsaturated aliphatic polycarboxylic acid and a saturated or unsaturated aliphatic alcohol. For example, dimethyl adipate, diethyl adipate, di-butyl adipate, diisobutyl adipate,
Examples thereof include di-2-ethylhexyl adipate, diisodecyl adipate, dibutyl sebacate, and di-2-ethylhexyl sebacate.

The term "aliphatic polyhydric alcohol ester" means a compound comprising a saturated or unsaturated aliphatic polyhydric alcohol and a saturated or unsaturated aliphatic carboxylic acid. For example, ethylene glycol diacetate, ethylene glycol dibutyrate, diethylene glycol diacetate, triethylene glycol diacetate, polyethylene glycol diacetate, ethylene glycol dipropionate, diethylene glycol dipropionate, triethylene glycol dipropionate, polyethylene glycol dipropionate, Ethylene glycol dibutyrate, diethylene glycol dibutyrate, triethylene glycol dibutyrate, polyethylene glycol dibutyrate, ethylene glycol disebacate, diethylene glycol disebacate, triethylene glycol disebacate, polyethylene glycol disebacate,
Propylene glycol diacetate, propylene glycol dibutyrate, dipropylene glycol diacetate, tripropylene glycol diacetate, polypropylene glycol diacetate, propylene glycol dipropionate, dipropylene glycol dipropionate, tripropylene glycol dipropionate,
Polypropylene glycol dipropionate, propylene glycol dibutyrate, dipropylene glycol dibutyrate, tripropylene glycol dibutyrate,
Polypropylene glycol dibutyrate, propylene glycol disebacate, dipropylene glycol disebacate, tripropylene glycol disebacate, polypropylene glycol disebacate, glycerin triacetate, glycerin tripropionate, glycerin tributyrate, glycerin trisebacate, etc. No.

Examples of the aliphatic oxyacid ester include:
For example, methyl acetyl ricinoleate, propyl acetyl ricinoleate, butyl acetyl ricinoleate, acetyl tributyl citrate and the like can be mentioned.

Examples of the aliphatic polyether derivative include polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetramethylene glycol, and two or more monomers selected from ethylene glycol, propylene glycol, butylene glycol, and tetramethylene glycol. Copolymerized polyalkylene glycol represented by the following formula: The degree of polymerization of these aliphatic polyethers is not particularly limited, but usually 2 to 50 is preferably used. One or both terminal hydroxyl groups of these aliphatic polyethers may be blocked by any substituent. For example, the terminal may be blocked by an alkoxy group such as methoxy, ethoxy and butoxy, or may be blocked by an ester group such as methyl ester, ethyl ester, propyl ester, butyl ester, acrylate ester and methacrylate ester. .

The aliphatic polyether polycarboxylic acid ester derivative refers to a polyvalent ester compound comprising the above aliphatic polyether derivative and an aliphatic polycarboxylic acid, and is represented by the chemical formula (I) or the like. (X—O—CO) —R— (CO—O—Y) (I) In the formula (I), R represents a hydrocarbon group having 1 to 12 carbon atoms, and X and Y represent the aforementioned groups. 1 shows an aliphatic polyether derivative.
X and Y may be different or the same. Examples of the aliphatic polyether polycarboxylic acid ester include dimethyl diglycol succinate, diethyl diglycol succinate, dipropyltyl diglycol succinate, dibutyl diglycol adipate,
Dimethyl diglycol adipate, diethyl diglycol adipate, dipropyltyl diglycol adipate, dibutyl diglycol adipate and the like can be mentioned.

Since the plasticizing effect of the plasticizer differs depending on the type, the amount of the plasticizer is not particularly limited. An appropriate amount may be added depending on the type of the plasticizer, and as a result, the glass transition temperature of the composition may be within the range specified in the present invention. Usually, 5 to 40% by mass, preferably 10 to 30% by mass, more preferably 15 to 25% by mass is added to the resin component in the polylactic acid resin composition. If the added amount is too small, sufficient flexibility cannot be obtained, and if the added amount is too large, melt processing becomes difficult or bleed-out easily occurs, which is not preferable. Needless to say, the plasticizer used in the present invention needs to have biodegradability in an environment such as soil or water, but it is desirable to use a plasticizer that is highly safe for the environment and organisms.

In the present invention, a nucleating agent is used to promote crystallization of polylactic acid during the cooling process. As such a crystal nucleating agent, a natural or synthetic silicate compound, titanium oxide, barium sulfate, tricalcium phosphate, calcium carbonate, sodium phosphate and the like are preferably used. Examples of the silicate compound include layered silicates such as kaolinite, halloysite, talc, smectite, vermiculite, and mica. These layered silicates may be swellable or non-swellable. In the case of swellable silicates, they may be treated with an organic compound such as an onium salt. Silica containing SiO ₂ as a main component is not preferred because the polylactic acid resin composition of the present invention does not have an effect as a crystal nucleating agent. In general, these nucleating agents are more effective as the dispersion in the resin composition is uniform and the aggregation is smaller.
Therefore, these nucleating agents may be subjected to surface treatment for the purpose of improving dispersibility.

The particle size of these nucleating agents is not particularly limited, but is 0.05 to 50 μm, preferably 0.1 to 20 μm.
m, more preferably 1 to 10 μm. If the particle size is too large, mechanical properties such as elongation at break and impact strength are undesirably reduced. On the other hand, if the particle diameter is too small, the cohesiveness of the nucleating agent particles is increased, which results in poor dispersion when kneaded with the polylactic acid resin composition, which is not preferable.

The amount of the nucleating agent used in the present invention is not particularly limited, but it is usually preferable to add the nucleating agent at a concentration of 3 to 50% by mass in the whole composition. In particular, 5
It is more preferable that the content be added in an amount of not less than mass%, because the crystallization promoting effect and the surface effect of the inorganic particles are synergistically exhibited when forming a film or sheet of the polylactic acid resin composition according to the present invention. Further, when added in an amount of 13% by mass or more, blocking is less likely to occur even when the glass transition temperature of the composition is lower than the environmental temperature at the time of producing a film or sheet. If the amount is less than this, a sufficient effect cannot be obtained, and blocking of the film is likely to occur. On the other hand, if the amount is too large, the elongation and impact resistance of the film or sheet are undesirably reduced.

The polylactic acid resin composition obtained according to the present invention may contain an antioxidant, an ultraviolet absorber, a heat stabilizer, a flame retardant, an internal release agent, an inorganic additive, an antistatic agent, a pigment, etc., depending on the purpose. Can be added. For example, in forming a film or sheet, an aliphatic carboxylic acid amide or the like is added to suppress blocking and improve slipperiness. Examples of such aliphatic carboxylic acid amides include stearic acid amide, oleic acid amide, erucic acid amide, behenic acid amide, N-oleyl palmitamide, N-stearyl erucic acid amide, N, N′-ethylenebis Stearylamide, N, N'-methylenebisstearylamide, methylol stearylamide, ethylenebisoleic acid amide, ethylenebisbehenic acid amide, ethylenebisstearic acid amide, ethylenebislauric acid, hexamethylenebisoleic acid amide, Hexamethylene bisstearic acid amide, butylene bisstearic acid amide, N, N'-dioleyl sebacic amide, N, N'-distearyl adipamide, N,
N'-dioleyl adipamide, N, N'-distearyl adipamide, N, N'-distearyl sebacamide, and the like. These may be used alone or in combination of two or more. In particular, erucamide is preferred because it has high compatibility with the polylactic acid resin, and has excellent blocking suppressing effect and slipperiness improving effect.
The amount of the aliphatic carboxylic acid amide to be added is not particularly limited, but is usually 0.05 to 10 with respect to the polylactic acid resin composition.
% By mass, preferably 0.1 to 5% by mass, preferably 0.1% by mass.
5 to 3% by weight are added.

In the present invention, it is an important requirement to define the glass transition temperature and the crystallization characteristics of the polylactic acid resin composition. The glass transition temperature (Tg) as defined in the present invention is defined as the following: A differential scanning calorimeter (DSC) is used to measure a sample at 7 mg ± 0.05 mg under nitrogen flow at 200 ° C.
At a cooling rate of 300 ° C./min.
After cooling rapidly to 0 ° C., the sample is heated at a rate of 20 ° C./min and measured. If the Tg of the polylactic acid resin composition is too high, it is not preferable because sufficient flexibility cannot be obtained when used at room temperature. As Tg is lower, sufficient flexibility is exhibited even when used in a low-temperature environment, so it is necessary that the temperature be 30 ° C or lower, more preferably 20 ° C or lower.
More preferably, the temperature is 10 ° C. or less.

The temperature-reduced crystallization calorie ΔHc and the temperature-reduced crystallization peak temperature Tcc defined in the present invention are as follows: 7 mg ± 0.05 mg of a sample using a differential scanning calorimeter under nitrogen flow.
The calorific value per 1 g of the polylactic acid resin component (J / g) and the crystallization peak temperature (° C.) that appear during the process of melting at 200 ° C. for 3 minutes and cooling to −40 ° C. at a cooling rate of 20 ° C./min. What is measured. When the heat of crystallization heat of cooling ΔHc of the polylactic acid resin composition is less than 10 J / g and the peak temperature of cooling crystallization Tcc is less than 80 ° C., sufficient crystallization does not occur in the process of cooling and solidifying the film or sheet, and the production It is not preferable because it becomes difficult to obtain a film or a sheet that does not cause blocking both at the time of use and at the time of use.

The method for producing the polylactic acid resin composition according to the present invention is not particularly limited, and any conventional melt kneading method such as a melt kneading method using a single or twin screw extruder or a melt kneading method using a roll may be used. Can be. As a melt kneading method using an extruder, for example, a mixture of all the polylactic acid resin, plasticizer, and crystal nucleating agent used in the present invention is simultaneously supplied and melt-kneaded by a single or twin screw extruder. Alternatively, the resin and the crystal nucleating agent may be quantitatively supplied from the first hopper port of the extruder, and the plasticizer may be quantitatively injected from the middle of the cylinder of the extruder by a quantitative pump. The resin composition kneaded in this way is extruded into strands, and after being cooled by a method such as a water bath,
It can be cut into pellets.

The resin composition according to the present invention is suitably used as a film or sheet. As in the case of the resin composition, the film or sheet has a glass transition temperature Tg ≦ 30 ° C.
It is preferable that the temperature drop crystallization heat quantity ΔHc ≧ 10 (J / g) and the temperature drop crystallization peak temperature Tcc ≧ 80 ° C. Although there is no particular limitation on the method for producing the film or sheet, any conventional molding method such as a T-die casting method, an air-cooled or water-cooled inflation method, a calendar method, and a hot press method can be applied. Among these, the air-cooled inflation method has a relatively slow cooling rate of the molten resin in the cooling and solidifying step after the melt extrusion as compared with the T-die casting method and the water-cooled inflation method, so that the crystallization of the composition in this step is difficult. It is preferable because it has an advantage that it is relatively easy to proceed, and there is an advantage that physical properties change with time and bleed-out due to blocking in a film production process and post-crystallization after product collection are less likely to occur. Further, since the apparatus is inexpensive and has high productivity, and the product is in a bag shape, it is suitable for producing bags such as packaging bags, garbage bags, and compost bags suitable for use. Further, a pinch roll for folding a tubular film during film formation by an inflation method can be cooled by cold water or the like. When a cooled roll is used, blocking which is likely to occur when the tube is folded is suppressed, and the opening property of the film may be improved.

The film or sheet made of the resin composition according to the present invention may be substantially unstretched or may be stretched uniaxially or biaxially. The film or sheet made of the resin composition according to the present invention may be non-porous or porous.

The film or sheet made of the resin composition according to the present invention may be used as a film made of another biodegradable plastic, a fiber, a nonwoven fabric, or a composite film or sheet which is composited with a biodegradable material such as paper. Can be.

The film or sheet comprising the resin composition according to the present invention may be subjected to corona treatment, coating,
Secondary processing such as embossing, printing, and bag making may be performed.
The film or sheet obtained by the above method may be subjected to a heat treatment as needed. Although there is no particular limitation on the method of the heat treatment, any conventional technique such as a hot air method or a hot roll method can be applied. By subjecting the film or sheet obtained by the present invention to heat treatment, crystallization is further promoted, and problems such as film elongation and slack due to tension often seen in the plasticized resin composition can be improved.

The use of the film or sheet obtained by the present invention is not particularly limited. For example, shopping bags, shopping bags, garbage bags, compost bags, wrap films, foods, cosmetics, pharmaceuticals, clothing, fertilizers, feeds, etc. Product packaging bags, freshness retention bags, deodorant bags, cleaning packaging bags,
Agricultural multi-film, agricultural watering, water supply tube, curing sheet, waterproof sheet, sandbag, clear file and other stationery films and sheets, passbook and other document case sheets, disposable hygiene products (diapers and sanitary products) Back sheet and the like.

[0044]

The present invention will be described below in detail with reference to examples. The specific method of the test described in this example is as follows.

(1) Weight Average Molecular Weight The weight average molecular weight of the polylactic acid resin composition prepared by the method described in Production Example 1 was determined by gel permeation chromatography (GPC) using LC10AD manufactured by Shimadzu Corporation. . The measurement was performed using a chloroform solvent at a column temperature of 40 ° C., and the weight average molecular weight was calculated by a polystyrene conversion method.

(2) Glass Transition Temperature (Tg) The glass transition temperature (Tg) of the polylactic acid resin composition prepared by the method described in Production Example 1 was determined using a DSC7 differential scanning calorimeter manufactured by Perkin Elmer. Was. 30
After drying under reduced pressure at 12 ° C. for 12 hours, 7 mg ± 0.05 m
g sample was accurately weighed and sealed in a sample holder. The sample was melted at 200 ° C. for 3 minutes under nitrogen flow, and then rapidly cooled to −40 ° C. at a cooling rate of 300 ° C./min.
From here, the sample was heated at a heating rate of 20 ° C./min, and Tg was measured.

(3) ΔHc, Tcc The ΔHc and Tcc of the polylactic acid resin composition prepared by the method described in Production Example 1 were determined using a DSC7 differential scanning calorimeter manufactured by Perkin Elmer. After drying under reduced pressure at 30 ° C. for 12 hours, a sample of 7 mg ± 0.05 mg was accurately weighed and sealed in a sample holder. The sample was melted at 200 ° C. for 3 minutes under nitrogen flow, and then cooled to −40 ° C. at a cooling rate of 20 ° C./min. The cooling heat of crystallization per 1 g of the polylactic acid resin component appearing in the cooling process is ΔH (J / g), and the cooling crystallization peak temperature is Tcc.
(° C.).

(4) Blocking Resistance (4-a) Evaluation of Opening Property The film prepared by the inflation method described in Production Example 2 was evaluated for the opening property of the folded tubular film. A tube whose mouth was easily opened was evaluated as ○, a tube having a slight resistance upon opening was evaluated as △, and a tube not opened at all was evaluated as ×. (4-b) Bleeding property and blocking property in a product state Regarding the film produced by the inflation method described in Production Example 2, it is 80 according to JIS Z0219.
The bleeding property and the blocking property of the film when the film was held at a temperature of 500 ° C. and a load of 500 g were evaluated.も の indicates no bleed-out, △ indicates slight bleed-out, and × indicates marked bleed-out. In addition, も の indicates that no blocking was observed, Δ indicates that some blocking was observed, and X indicates completely blocked.

(Raw Materials Used) (Resin) In each of Examples and Comparative Examples, the following was used as the polylactic acid resin. (1) Polylactic acid resin PLA-1 (manufactured by Cargill Dow Polymers, trade name EcoPLA / 4030D, optical purity of L-lactic acid component 98%, weight average molecular weight 200,000) (2) Polylactic acid resin PLA-2 (Cargill Dow Polymers Manufactured and trade name EcoPLA / 5039B, L-lactic acid component optical purity 60%, weight average molecular weight 200,000) (3) Polylactic acid resin PLA-3 (manufactured by Cargill Dow Polymers, trade name EcoPLA / 4060D, L-lactic acid component optical purity 80) %, Weight average molecular weight 200,000) (4) Polylactic acid resin PLA-4 (manufactured by Cargill Dow Polymers Co., Ltd., trade name EcoPLA / 4050D, optical purity of L-lactic acid component 88%, weight average molecular weight 200,000) (5) Polybutylene succinate Nate resin PBS (manufactured by Showa Polymer Co., Ltd., trade name: Bionore # 1001) (Plasticizer) Examples and In Comparative Examples, the following were used as plasticizers. Acetyl tributyl citric acid (trade name A, manufactured by Sanken Kako Co., Ltd.)
TBC) Acetyl polyethylene glycol monomethyl ether (MPEG) (manufactured by Sanyo Chemical Co., Ltd., no trade name, polyethylene glycol skeleton molecular weight: 400) dibutyl diglycol adipate (manufactured by Daihachi Chemical Co., trade name: BXA) (Inorganic particles) Examples and comparisons In the examples, the following were used as the inorganic particles. Talc (talc manufactured by Hayashi Kasei Co., Ltd., trade name: MW HS-T0.
5, average particle size 2.75 μm) Silica (silica manufactured by Fuji Silysia Ltd., trade name: Sylysia P)
310, average particle size 1.2 μm) (Organic lubricant) Erucamide (trade name: Alflow P10, manufactured by NOF Corporation) was used as an organic nucleating agent.

Production Example 1: Preparation of Composition For each of Examples and Comparative Examples, the above-mentioned polylactic acid raw material, plasticizer, crystal nucleating agent, and organic lubricant were melt-mixed in the proportions shown in Table 1. Using a biaxial melt kneader having a screw diameter of 44 mm, a resin raw material, a crystal nucleating agent, and an organic lubricant were quantitatively supplied from a kneader hopper opening by using a weight control type quantitative feeder. Further, a plasticizer is quantitatively supplied from the middle of the cylinder using a quantitative injection pump.
Melt mixing was performed at ~ 190 ° C, a screw rotation speed of 100 rpm, and a total discharge rate of 80 kg / h. The strand discharged from the nozzle was cooled in a cold water bath and then pelletized by a starland cutter. The pellet-shaped polylactic acid resin composition thus obtained was dried under reduced pressure at 50 ° C. for 8 hours,
It was subjected to a later filming test.

Production Example 2: Film Formation of Composition For each of Examples and Comparative Examples, a blown film was formed using the polylactic acid resin composition prepared in Production Example 1 described above. Screw diameter 45 mm equipped with a cyclic die having a diameter of 100 mm
Was melt-extruded at a set temperature of 180 ° C. The molten resin composition discharged from the die was formed into a tube shape while being expanded by air pressure and simultaneously air-cooled by an air ring. A film formed so as to have a film thickness of 25 μm and a film fold width of 350 mm is applied to a pair of pinch rolls set on the upper part of the die.
It was picked up at a speed of 0 m / min. After a cooling time of about 7 seconds, the tubular film was nipped by a pinch roll and wound up by 1000 m by a winder. The composition was formed into a film in an environment controlled at 25 to 30 ° C. The film thus obtained was subjected to various measurements.

Examples 1 to 8 As a polylactic acid resin (P1) having an optical purity of 90% or more, PL
A-1, a resin composition was prepared using PLA-2 as a polylactic acid resin (P2) having an optical purity of less than 90%, MPEG as a plasticizer, and talc as a crystal nucleating agent at a mixing ratio shown in Table 1 according to Production Example 1. did. Regarding the obtained resin composition, (1) weight average molecular weight, (2) glass transition temperature, (3)
The crystallization heat ΔHc and the crystallization peak temperature Tcc were measured. Further, the obtained resin composition was formed into a film by an inflation method according to Production Example 2, and a film having a thickness of 25 μm was collected at a length of 1000 m. Regarding the obtained film,
(4-a) The opening property of the film and (4-b) the bleeding property and the blocking property of the film were evaluated.

Example 9 As a polylactic acid resin (P2) having an optical purity of less than 90%, PL
The same raw materials as in Example 1 were used except for using A-3,
Resin compositions and films were prepared at the mixing ratios shown in Table 1. Various evaluations were performed on the obtained resin composition and film.

Example 10 Using the same raw materials as in Example 1 except that ATBC was used as a plasticizer, a resin composition and a film were produced at the mixing ratio shown in Table 1. Various evaluations were performed on the obtained resin composition and film.

Example 11 Using the same raw materials as in Example 1 except that BXA was used as a plasticizer, a resin composition and a film were prepared at the mixing ratio shown in Table 1. Various evaluations were performed on the obtained resin composition and film.

Comparative Examples 1 to 3 Films were prepared in the same manner as in Example 1 except that the amounts of polylactic acid resin, plasticizer and talc added were changed to the mixing ratios shown in Table 1, and various evaluations were made.

Comparative Examples 4 and 5 The same raw materials as in Example 1 were used except that silica was used as a crystal nucleating agent, and resin compositions and films were prepared at mixing ratios shown in Table 1. Various evaluations were performed on the obtained resin composition and film.

Comparative Example 5 A resin composition and a film were prepared at the mixing ratios shown in Table 1 by using the same raw materials as in Example 1 except that only PLA-4 was used as the polylactic acid raw material. Various evaluations were performed on the obtained film.

Comparative Example 6 A resin composition and a film were prepared in the same mixing ratio as shown in Table 1, except that PLA-4 having an optical purity of 88% was used as the polylactic acid resin. Various evaluations were performed on the obtained resin composition and film.

Comparative Example 7 A resin composition and a film were prepared using the respective raw materials shown in Table 1. Various evaluations were performed on the obtained resin composition and film. Table 1 shows the results.

[0061]

[Table 1]

[0062]

According to the present invention, by imparting specific crystallinity to the plasticized polylactic acid, the disadvantage of polylactic acid, which is hard and brittle at room temperature, can be overcome, and it can be used in both production and use. This also makes it possible to industrially provide a highly practical film having good blocking resistance, and excellent openability and bleed-out resistance.
By mixing and using polylactic acid resins having different monomer optical purities, that is, crystallinity in a specific range, it is possible to obtain a resin composition having crystallinity and bleed-out resistance and a film comprising the same.

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Claims (6)

[Claims] 1. A highly crystalline polylactic acid resin composition comprising (A) a crystalline polylactic acid-based resin, (B) a plasticizer, and (C) a crystal nucleating agent as essential components and satisfying the following conditions. . (1) Glass transition temperature ≦ 30 ° C. (2) 1 g of polylactic acid resin component by differential scanning calorimetry when cooled at a rate of 20 ° C./min from a molten state
ΔHc ≧ 10 (J / g) (3) The crystallization peak temperature by a differential scanning calorimeter when cooled from the molten state at a rate of 20 ° C./min is represented by T
cc, Tcc ≧ 80 ℃ 2. The crystalline polylactic acid-based resin has an optical purity of 90.
% Or more of a polylactic acid resin (P1) and a polylactic acid resin (P2) having an optical purity of less than 90%, and P1 and P2
The high crystalline polylactic acid resin composition according to claim 1, wherein the mass fraction of P1 with respect to the total mass of the polylactic acid is 30 to 100 mass%. 3. The highly crystalline polylactic acid resin composition according to claim 1, wherein the nucleating agent is talc. 4. A film or sheet comprising the polylactic acid resin composition according to claim 1 as a main component. 5. A film or sheet comprising (A) a crystalline polylactic acid-based resin, (B) a plasticizer, and (C) a crystal nucleating agent as essential components and satisfying the following conditions. (1) Glass transition temperature ≦ 30 ° C. (2) 1 g of polylactic acid resin component by differential scanning calorimetry when cooled at a rate of 20 ° C./min from a molten state
ΔHc ≧ 10 (J / g) (3) The crystallization peak temperature by a differential scanning calorimeter when cooled from the molten state at a rate of 20 ° C./min is represented by T
cc, Tcc ≧ 80 ℃ 6. The film or sheet according to claim 4, which is produced by an inflation method.