JP3410075B2 - Crystalline polylactic acid resin composition, film and sheet using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art With the increase in the amount of plastics used in recent years,
The waste treatment is regarded as a problem. Conventionally, methods such as landfill and incineration have been adopted as methods for treating plastic waste. In the case of landfill disposal, plastic waste remains in the soil semi-permanently in its original form, causing problems such as shortage of landfill and natural destruction.
On the other hand, when plastics are incinerated, the combustion heat is high and the incinerator is easily damaged, and it causes pollution problems such as generation of harmful substances.

Under such circumstances, so-called biodegradable plastics, which can be decomposed and consumed by microbial decomposition in a natural environment and converted into carbon dioxide gas or water, can be reduced to the natural environment. As such biodegradable plastics, various plastics such as polycaprolactone, polybutylene succinate, polyhydroxyvalerate and polylactic acid have already reached the practical stage. Among them, polylactic acid has recently been attracting attention as a plant-derived plastic, that is, a petroleum-saving plastic, since lactic acid obtained by biofermenting a starch source purified by plants such as corn through photosynthesis is used as a raw material. Polylactic acid has excellent transparency, heat resistance, rigidity, and mold resistance compared to conventional biodegradable plastics, and is also widely used as a material with practical durability. I'm sick of it. However, polylactic acid has the drawback of being so rigid and brittle that it has high rigidity due to its molecular structure, low bending resistance, low impact resistance, etc., and it is a field requiring flexibility and elongation, such as various soft films. Improvements have been desired in the field of seats and seats. As a method for improving the flexibility of polylactic acid, conventionally,
Copolymerization, blends of flexible polymers, and plasticizing techniques with plasticizers have been tried. As an example of softening by copolymerization, JP-A-7-173266 discloses a technique of copolymerizing a lactic acid component with another hydroxycarboxylic acid component and a polyhydric alcohol component. However, the improvement by copolymerization has a problem that the crystallinity of polylactic acid is impaired, resulting in blocking of the film and impaired heat resistance.

On the other hand, regarding the flexible polymer blend, as described in JP-A-8-245866, polybutylene succinate, polyethylene succinate, polycaprolactone and the like have biodegradability and high flexibility. The method of mixing a polymer is mentioned. However, most of these flexible polymers have poor compatibility with polylactic acid, and a large amount of them has been required to impart sufficient flexibility. As a result, there has been a problem that the characteristic features of polylactic acid, such as durability and mold resistance, are impaired.

Various studies have been made in the past regarding plasticization by a plasticizer. US Pat. No. 5,076,983 discloses a method in which lactide, which is a cyclic dimer of lactic acid, is used as a plasticizer. Although a plasticizing effect can be obtained by this method, there is a problem that sublimation of the mixed lactide causes smoke and contamination of the molding machine during melt molding. Further, polylactic acid containing a large amount of lactide has a problem that it is easily decomposed due to its low hydrolysis resistance, and only a molded product having low durability can be obtained even in ordinary use.

JP-A-4-335060 discloses phthalic acid ester, aliphatic dibasic acid ester, phosphoric acid ester, hydroxy polycarboxylic acid ester, fatty acid ester, polyhydric alcohol ester, epoxy plasticizer, polyester plasticizer. A composition obtained by mixing a plasticizer comprising an agent or a mixture thereof with a polylactic acid resin is disclosed. JP-A-11-181262 discloses a lactic acid-based polymer composition containing an ether ester-based plasticizer. Further, JP-A-7-118513 and JP-A-8-185513
JP-A-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 sufficient flexibility can be imparted to polylactic acid by mixing a plasticizer having a high compatibility with polylactic acid in a high concentration. However, all of the methods described therein are intended to lower the glass transition temperature of polylactic acid by plasticizing, and therefore, in order to impart practically sufficient flexibility, the glass transition temperature is not It had to be near or below 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 was difficult to industrially produce a film or sheet having a commercial value for the composition obtained by the method described in the above publication.

As a general remedy for the above problems, there is known a method of adding inorganic particles for imparting blocking resistance to a film or sheet. As an example of filling biodegradable plastic with inorganic particles, Japanese Patent Application Laid-Open No. H05-53242
JP-A-70696 discloses a method in which biodegradable plastics such as polylactic acid and polycaprolactone are mixed with calcium carbonate having an average particle diameter of 20 μm or less and hydrous magnesium silicate (talc) in a mass ratio of 10 to 40%.
However, this publication makes no mention of imparting flexibility by plasticization, and the purpose thereof is not to prevent blocking but to promote decomposition after disposal by adding a large amount of inorganic particles. .

On the other hand, as an attempt to improve the blocking property of the plasticized polylactic acid resin composition, JP-A-8-34
No. 913 discloses that 100 parts by mass of a mixture of a polylactic acid resin and a plasticizer selected from the group consisting of polyhydric alcohol esters and hydroxypolycarboxylic acids contains 90% by mass or more of SiO _{2 and} has an average particle size of A composition in which 0.1 to 5 parts by mass of an anti-blocking agent having a thickness of 7 to 50 nm and 0.1 to 2 parts by mass of a lubricant are mixed is disclosed. According to this publication, the blocking resistance of a film made of a plasticized polylactic acid resin composition is improved. However, in Examples, it is only shown that such an effect is obtained for a stretched film, and in the case of a film or sheet that is not substantially stretched, such as an inflation film, it is described in this publication. The method described above was not sufficient to improve the blocking resistance.

Further, Japanese Patent Application Laid-Open No. 11-116788 discloses a composition in which a plasticizer is mixed with a polymer component composed of a mixture of polylactic acid and an aliphatic polyester having a melting point of 80 to 250 ° C. According to this publication with respect to plasticized compositions of the polylactic acid, a film excellent in bleed resistance and blocking resistance only when a combination of Si0 ₂ as a specific aliphatic polyester resin and the inorganic particles are to be obtained. As a result of detailed verification of the examples of this publication, the inventors of the present invention confirmed that the blocking resistance was improved in the blocking resistance test described in JP-A-11-116788. The effect is not sufficient, and in the method described in the example, when the tube-shaped film is folded by a pinch roll when forming the film, blocking occurs between the folded tubular two-layer films. However, it has been found that it is difficult to open the tube and peel off the two layers of film. Particularly when the degree of plasticization is large and the glass transition temperature of the composition is room temperature or lower, this phenomenon becomes more remarkable, and the method described in this publication cannot prevent the blocking of the film that occurs during molding. There wasn't. Further, the film obtained in Example 1 of JP-A No. 11-116788 has almost no crystallization immediately after molding, and changes in physical properties due to post-crystallization when left for a long time and a plasticizer due to post-crystallization. Bleed out was seen, and there was a problem in practice. As described above, the conventional techniques have 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 disadvantage of polylactic acid, which is hard and brittle, and to find problems such as bleed-out and blocking both during production and during use. An object of the present invention is to provide a plasticized polylactic acid resin composition, and a film or sheet made of the same.

[0011]

Means for Solving the Problems As a result of various studies to solve the above problems, the present inventors have obtained the following findings. There are two kinds of optically active substances, that is, D-lactic acid and L-lactic acid, in the monomer of polylactic acid. Currently, L-lactic acid is industrially produced in large quantities and at low cost, and L-polylactic acid (PLLA) derived from L-lactic acid is generally used also in polylactic acid. The crystallinity of polylactic acid changes depending on the content rate of L-lactic acid or D-lactic acid. For example, when the optical purity L of the lactic acid monomer is defined as Formula 1, the crystallinity increases as L increases, that is, the optical purity increases. To increase. Optical purity = | M (L) -M (D) | ... Formula 1 M (L): mol% of L-lactic acid units to all lactic acid units constituting the polylactic acid resin M (D): polylactic acid resin Mol% of D-lactic acid unit 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 consisting of% L-lactic acid component, the racemization of the monomer partially occurs due to the heat history in the polymerization and the subsequent melt molding, and therefore the optical purity of PLLA industrially used is 98%. It is said that the vicinity is the upper limit. Therefore, this is the most highly crystalline composition in practical use among the polylactic acids. However, even in PLLA composed of such a high-purity L-lactic acid component, the crystallization rate is relatively slow, and the supercooling property in the cooling crystallization process is very high. In particular, for polylactic acid, in order to obtain practical strength and durability, it is necessary to use a polymer having a relatively high molecular weight, and as a guide, a polymer having a weight average molecular weight of 100,000 or more. Is even more pronounced. Therefore, in the melt molding of a film or sheet, when polylactic acid is rapidly cooled and solidified by contact with a cast roll or cold air, crystallization hardly occurs,
Generally, only a molded product 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 chain is increased by the plasticization, but nevertheless, the crystallization rate is rapidly increased in the molding of the film or sheet. Almost no crystallization occurs during the cooling and solidification process, and only a substantially amorphous structure is obtained immediately after molding. This is the reason why in the prior art, a film or sheet made of a composition whose glass transition temperature is lowered to around room temperature due to plasticization has a problem of blocking. In addition, JP-A-11-1167
As disclosed in Japanese Patent No. 88, a flexible polyester resin and S
When iO ₂ is used in combination, although the blocking resistance is slightly improved by the surface effect of the crystalline flexible polyester particles or SiO ₂ particles dispersed in the polylactic acid matrix having a substantially amorphous structure, the blocking resistance of the film or sheet is improved. 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 molded in this way has Tg
Is around room temperature or below room temperature, and therefore, after being left for a long period of time, post-crystallization occurs, and changes in physical properties and bleed-out easily occur.

From the above, the inventors of the present invention have used the plasticized polylactic acid resin composition to have blocking resistance both during production and during use, and change in physical properties due to post-crystallization. It has been found that the following requirements are necessary in order to industrially provide a film or sheet in which no bleedout or bleedout is observed. (1) In order to have improved blocking resistance,
The plasticized polylactic acid composition must have appropriate crystallinity. (2) When processed into a film or sheet by melt molding,
It is necessary to cause appropriate crystallization in the process in which the plasticized polylactic acid composition is cooled and solidified from the molten state.

The present inventors have conducted extensive studies to satisfy the above requirements, and 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. The inventors have found a method for industrially providing a film or sheet having a blocking property and showing no change in physical properties or bleed-out due to post-crystallization.
That is, the present invention is specified by the matters described in [1] to [6] below. [1] (A) Crystalline polylactic acid 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. (I) The crystalline polylactic acid resin (A) has an optical purity of 90%.
The above polylactic acid resin (P1) and a resin having an optical purity of less than 90%.
It is a mixture of polylactic acid resin (P2) and contains P1 and P2.
The mass fraction of P1 with respect to the total mass is 30 mass% or more, 1
It is less than 00 mass%. (II) The crystal nucleating agent (C) is talc, and its addition amount is
It is 13 mass% or more and 50 mass% or less in the composition. [ 2 ] Description of [1] characterized by satisfying the following conditions
Highly crystalline polylactic acid resin composition. (1) Glass transition temperature ≦ 30 ° C. (2) 1 g of polylactic acid resin component measured by a differential scanning calorimeter when cooled from a molten state at a rate of 20 ° C./min
ΔHc is the heating value for crystallization per unit time, ΔHc ≧ 10 (J / g) (3) The crystallization peak temperature measured by a differential scanning calorimeter when cooled from the molten state at a rate of 20 ° C./min is T
When expressed as cc, Tcc ≧ 80 ° C. [ 3 ] A film or sheet containing the polylactic acid resin composition described in [1] or [2] as a main component. [ 4 ] (A) Crystalline polylactic acid-based resin, (B) Plasticizer,
(C) A film or sheet comprising a crystal nucleating agent as an essential component and satisfying the following conditions. (I) The crystalline polylactic acid resin (A) has an optical purity of 90%.
The above polylactic acid resin (P1) and a resin having an optical purity of less than 90%.
It is a mixture of polylactic acid resin (P2) and contains P1 and P2.
The mass fraction of P1 with respect to the total mass is 30 mass% or more, 1
It is less than 00 mass%. (II) The crystal nucleating agent (C) is talc, and its addition amount is
It is 13 mass% or more and 50 mass% or less in the composition. [5] Description of [4] characterized by satisfying the following condition
A film or sheet on board. (1) Glass transition temperature ≦ 30 ° C. (2) 1 g of polylactic acid resin component measured by a differential scanning calorimeter when cooled from a molten state at a rate of 20 ° C./min
ΔHc is the heating value for crystallization per unit time, ΔHc ≧ 10 (J / g) (3) The crystallization peak temperature measured by a differential scanning calorimeter when cooled from the molten state at a rate of 20 ° C./min is T
When expressed as cc, Tcc ≧ 80 ° C. [6] The film or sheet according to any one of [3] to [5], which is produced by an inflation method.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
In the present invention, L as lactic acid which is a raw material of polylactic acid
-Lactic acid, D-lactic acid, DL-lactic acid or a mixture thereof may be mentioned, and when a cyclic dimer of lactic acid is used as a raw material, L-lactide, D-lactide, mesolactide or a mixture thereof may be mentioned. The method for producing polylactic acid used in the present invention includes the following methods. For example, the method disclosed in US Pat. No. 5,310,865 may be mentioned as a method for directly performing dehydration polycondensation using lactic acid as a raw material. Also a cyclic dimer of lactic acid (lactide)
Examples of the method for ring-opening polymerization of ## STR3 ## include the method disclosed in USP 2,758,987.

The polylactic acid used in the present invention has a weight average molecular weight of 80,000 to 1,000,000, preferably 10
It is preferably from 10,000 to 500,000, more preferably from 120,000 to 300,000. When 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 and the melt processing becomes difficult, which is not preferable.

Since the polylactic acid used in the present invention is required to have crystallinity, it is desirable to contain polylactic acid containing L-lactic acid component or D-lactic acid component as a main component. Specifically, optical purity L ≧ 90 (%)
It is desirable to include polylactic acid which is If polylactic acid having an optical purity of 90% or more is not contained, sufficient crystallinity for suppressing 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 tends 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 amorphous polylactic acid (P2) having an optical purity of less than 90% are preferable. Further, since the low crystalline or amorphous polylactic acid P2 tends to have a poorer color tone after melt processing as a monomer having a lower optical purity is used, an optical purity L of 50% ≦ L ≦ 90% is preferable. It is preferably used. Mass of P1 with respect to total mass of P1 and P2
The fraction may be 30% by mass or more and less than 100% by mass.
is necessary. If the mixing ratio of P1 is smaller than this, sufficient crystallinity cannot be obtained and problems such as blocking occur.

The polylactic acid used in the present invention may be copolymerized with another aliphatic hydroxydicarboxylic acid, an aliphatic diol, or an aliphatic dicarboxylic acid within the range where the composition exhibits the characteristics 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, such as 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, 3 -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 acid include succinic acid, oxalic acid, malonic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid and dodecanedioic acid. To be These aliphatic dibasic acids can be used alone or in combination of two or more.

In the polylactic acid used in the present invention, a branched or crosslinked structure may be introduced by copolymerizing a polyfunctional reactive monomer within the range where the composition exhibits the characteristics specified in the present invention. . By introducing a branched or cross-linked structure, it is possible to improve the melting characteristics when the composition mixed with 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 a predetermined crystallization property. Specific examples of such biodegradable plastics include, for example, biodegradable aliphatic polyesters that can be produced by combining the above-mentioned aliphatic hydroxycarboxylic acid, aliphatic dihydric alcohol and aliphatic dibasic acid. Polymers may be mentioned. Preferred aliphatic polyester-based polymers include polyethylene oxalate, polybutylene oxalate, polyneopentyl glycol oxalate, polyethylene succinate, polybutylene succinate, polyhydroxybutyric acid and β-hydroxybutyric acid and β-hydroxyvaleric acid. Examples thereof include copolymers. As examples of other biodegradable plastics, a semi-aliphatic polyester-based polymer obtained by partially copolymerizing terephthalic acid and / or isophthalic acid with the above-mentioned aliphatic polyester-based polymer, and aliphatic diamine or fat to the above-mentioned aliphatic polyester Group aminocarboxylic acids,
Examples thereof include polyester amide-based polymers obtained by copolymerizing lactams, starch-based polymers, polyvinyl alcohol-based polymers, and cellulose acetate-based polymers.

As the plasticizer used in the present invention, a plasticizer excellent in compatibility with polylactic acid and plasticizing ability can be used. The plasticizer is not particularly limited, but is an aliphatic polycarboxylic acid ester derivative, an aliphatic polyhydric alcohol ester derivative, an aliphatic oxyacid ester derivative, an aliphatic polyether derivative, an aliphatic polyether polyvalent carboxylic acid ester derivative. And so on. These plasticizers may be used alone, or at least two kinds of plasticizers may be mixed and used.

The term "aliphatic polycarboxylic acid ester" refers to an ester compound composed of 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,
Di-2-ethylhexyl adipate, diisodecyl adipate, dibutyl sebacate, di-2-ethylhexyl sebacate and the like can be mentioned.

The aliphatic polyhydric alcohol ester refers to a compound composed of 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. Can be mentioned.

As the aliphatic oxyacid ester,
Examples thereof include methyl acetylricinoleate, propyl acetylricinoleate, butyl acetylricinoleate, and acetyltributylcitric acid.

Examples of the aliphatic polyether derivative include polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetramethylene glycol, and two or more kinds of monomers selected from ethylene glycol, propylene glycol, butylene glycol and tetramethylene glycol. And a copolymerized polyalkylene glycol. The degree of polymerization of these aliphatic polyethers is not particularly limited, but those having 2 to 50 are usually preferably used. One end hydroxyl group or both end hydroxyl groups of these aliphatic polyethers may be blocked by any substituent. For example, it may be end-capped with an alkoxy group such as methoxy, ethoxy and butoxy, or may be capped with an ester group such as methyl ester, ethyl ester, propyl ester, butyl ester, acrylic acid ester and methacrylic acid ester. .

The term "aliphatic polyether polyvalent carboxylic acid ester derivative" refers to a polyvalent ester compound composed of the above aliphatic polyether derivative and an aliphatic polyvalent carboxylic acid, and is represented by the chemical formula (I). (X-O-CO) -R- (CO-O-Y) ... (I) In formula (I), R represents a hydrocarbon group having 1 to 12 carbon atoms, and X and Y are as described above. An aliphatic polyether derivative is shown.
X and Y may be different or the same. Examples of the aliphatic polyether polycarboxylic acid ester include dimethyl diglycol succinate, diethyl diglycol succinate, dipropyl tyl diglycol succinate, dibutyl diglycol adipate,
Examples thereof include dimethyldiglycol adipate, diethyldiglycol adipate, dipropyltildiglycol adipate, and dibutyldiglycol adipate.

Since the plasticizing effect of the plasticizer differs depending on its type, there is no particular limitation on the amount added. An appropriate amount may be added depending on the type of 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 amount added is too small, sufficient flexibility cannot be obtained, and if the amount added is too large, melt processing becomes difficult and bleed out easily occurs, which is not preferable. Needless to say, the plasticizer used in the present invention is required 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 crystal nucleating agent is used to accelerate crystallization of polylactic acid in the cooling process. As such a crystal nucleating agent, natural or synthetic silicate compounds, titanium oxide, barium sulfate, tricalcium phosphate, calcium carbonate, sodium phosphate, etc. 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 swelling silicate, they may be treated with an organic compound such as onium salt. Silica containing SiO ₂ as a main component is not preferable because it has no effect as a crystal nucleating agent on the polylactic acid resin composition of the present invention. Generally, these crystal nucleating agents are more effective when they are uniformly dispersed in the resin composition and have less aggregation.
Therefore, these crystal nucleating agents may be surface-treated for the purpose of improving dispersibility.

The particle size of these crystal 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 deteriorate, which is not preferable. On the other hand, if the particle size is too small, the cohesiveness of the nucleating agent particles becomes strong, resulting in poor dispersion when kneading with the polylactic acid resin composition, which is not preferable.

The amount of the crystal nucleating agent used in the present invention is not particularly limited, but it is usually preferable to add it at a concentration of 3 to 50% by mass in the entire composition. Especially the crystal nucleating agent 5
Addition by mass% or more is more preferable because the crystallization promoting effect and the surface effect by the inorganic particles are synergistically exhibited when forming the film or sheet of the polylactic acid resin composition according to the present invention. Further, when it is 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 the film or sheet, which is more preferable. If the amount added is less than this, a sufficient effect cannot be obtained, and film blocking tends to occur. On the other hand, if the amount added is too large, the elongation and impact resistance of the film or sheet will decrease, which is not preferable.

The polylactic acid resin composition obtained by the present invention contains 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. Various additives 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 palmitoamide, N-stearyl erucic acid amide, N, N′-ethylenebisamide. Stearyl amide, N, N'-methylenebisstearylamide, methylol stearylamide, ethylenebisoleic acid amide, ethylenebisbehenic acid amide, ethylenebisstearic acid amide, ethylenebislauric acid, hexamethylenebisoleic acid amide, Hexamethylenebisstearic acid amide, butylenebisstearic acid amide, N, N'-dioleyl sebacic acid amide, N, N'-distearyl adipic acid amide, N,
N'-dioleyl adipate amide, N, N'- distearyl adipate amide, N, N'- distearyl sebacate amide, etc. are mentioned. You may use these individually or in mixture of 2 or more types. In particular, erucic acid amide is preferable because it has high compatibility with polylactic acid resin and is excellent in the effect of suppressing blocking and the effect of improving slipperiness.
The amount of the aliphatic carboxylic acid amide 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.
5 to 3 mass% is added.

In the present invention, defining the glass transition temperature and crystallization characteristics of the polylactic acid resin composition is an important requirement. The glass transition temperature (Tg) defined in the present invention is a differential scanning calorimeter (DSC) and is 7 mg ± 0.05 mg for a sample at 200 ° C. under nitrogen flow.
After melting for 3 minutes at -4 at a cooling rate of 300 ° C / min.
It is measured by quenching to 0 ° C. and then heating the sample at a heating rate of 20 ° C./min. If the Tg of the polylactic acid resin composition is too high, sufficient flexibility cannot be obtained at room temperature, which is not preferable. The lower the Tg, the more flexible it is when it is used in a low temperature environment. Therefore, the Tg needs to be 30 ° C. or lower, more preferably 20 ° C. or lower,
More preferably, it is 10 ° C. or lower.

The cooling crystallization heat quantity ΔHc and the cooling crystallization peak temperature Tcc specified in the present invention are 7 mg ± 0.05 mg of sample using a differential scanning calorimeter, under nitrogen flow.
After being melted at 200 ° C. for 3 minutes and then cooled to −40 ° C. at a cooling rate of 20 ° C./min, the calorific value per 1 g of polylactic acid resin component (J / g) and the crystallization peak temperature (° C.) Measured. When the cooling crystallization heat amount ΔHc of the polylactic acid resin composition is less than 10 J / g and the cooling crystallization peak temperature Tcc is less than 80 ° C., sufficient crystallization does not occur in the cooling and solidifying process of the film or sheet, and the production It is not preferable because it becomes difficult to obtain a film or sheet that does not cause blocking during use or during 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-screw or twin-screw extruder and a melt-kneading method using a roll may be applied. You can Examples of the melt-kneading method using an extruder include melt-kneading using a single-screw or twin-screw extruder by simultaneously supplying a mixture of the polylactic acid resin, the plasticizer, and the crystal nucleating agent used in the present invention. 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 metering pump. The resin composition kneaded in this way is extruded in a strand shape, 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 preferably used as a film or sheet. The film or sheet has a glass transition temperature Tg ≦ 30 ° C., as in the case of the resin composition.
It is preferable that the cooling crystallization heat quantity ΔHc ≧ 10 (J / g) and the cooling crystallization peak temperature Tcc ≧ 80 ° C. The method for producing the film or sheet is not particularly limited, but any conventional molding method such as a T die casting method, an air-cooled or water-cooled inflation method, a calender method, and a hot press method can be applied. Among them, the air-cooled inflation method has a relatively slow cooling rate of the molten resin in the cooling and solidifying step after melt extrusion as compared with the T die-cast method and the water-cooled inflation method, so that the composition is crystallized in this step. This is preferred because it has a merit that it is relatively easy to proceed, and that changes in physical properties over time and bleed-out due to post-crystallization after the product is collected and blocking in the film production process are unlikely to occur. Further, since the device is inexpensive and has high productivity, and the shape of the product is a bag, it is suitable for producing bags such as packaging bags, garbage bags, and compost bags suitable for use. Further, the pinch roll that folds the tubular film at the time of film formation by the inflation method can be cooled with cold water or the like. When a cooled roll is used, blocking that tends to occur when the tube is folded is suppressed, and the openability 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 uniaxially or biaxially stretched. 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 can also be used as a film or sheet made of another biodegradable plastic, a composite film or sheet formed by combining with a biodegradable material such as paper or paper. You can

A film or sheet made of 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 heat-treated if necessary. The heat treatment method is not particularly limited, but 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 advanced, and problems such as film elongation and slack due to tension, which are often seen in plasticized resin compositions, can be improved.

The use of the film or sheet obtained by the present invention is not particularly limited, and examples thereof include shopping bags, shopping bags, garbage bags, compost bags, wrap films, foods, cosmetics, pharmaceuticals, clothes, fertilizers, feeds, etc. Product packaging bag, freshness keeping bag, deodorant bag, cleaning packaging bag,
Agricultural mulch film, agricultural sprinkler, water supply tube, curing sheet, water barrier sheet, sandbag, stationery film and sheet for clear file, document case sheet for passbook, disposable hygiene products (diapers and sanitary products) Examples include back sheets.

[0044]

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

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

(2) Glass transition temperature (Tg) Regarding the polylactic acid resin composition prepared by the method described in Production Example 1, the glass transition temperature (Tg) was determined using a DSC7 differential scanning calorimeter manufactured by Perkin Elmer. It was Thirty
After vacuum drying for 12 hours at ℃, 7mg ± 0.05m
A sample of g was accurately weighed and placed 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 temperature rising rate of 20 ° C./min to measure Tg.

(3) ΔHc, Tcc For the polylactic acid resin composition prepared by the method described in Production Example 1, ΔHc, Tcc was determined using a DSC7 differential scanning calorimeter manufactured by Perkin Elmer. After vacuum drying at 30 ° C. for 12 hours, a 7 mg ± 0.05 mg sample was accurately weighed and placed 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. ΔH (J / g) is the heat-down crystallization heat amount per 1 g of the polylactic acid resin component, and Tcc is the temperature-down crystallization peak temperature that appears in this cooling process.
It was measured as (° C).

(4) Blocking resistance (4-a) Evaluation of opening property With respect to the film produced by the inflation method described in Production Example 2, the opening property of a folded tubular film was evaluated. The case where the mouth of the tube was easily opened was evaluated as ○, the case where there was some resistance when opening was evaluated as △, and the case where the tube was not opened at all was evaluated as ×. (4-b) Bleeding property and blocking property in a product state The film produced by the inflation method described in Production Example 2 is 80 in accordance with JIS Z0219.
The bleeding property and blocking property of the film were evaluated when the film was held under conditions of ° C and a load of 500 g. The case where no bleedout was observed was evaluated as ◯, the case where a slight bleedout was observed was evaluated as Δ, and the case where bleedout was significantly observed was evaluated as x. In addition, those in which blocking was not observed were marked with ◯, those in which blocking was slightly observed were marked with Δ, and those which were completely blocked were marked with x.

(Raw Materials Used) (Resin) In each of the examples and comparative examples, the following polylactic acid resins were used. (1) Polylactic acid resin PLA-1 (manufactured by Cargill Dow Polymers, trade name EcoPLA / 4030D, L-lactic acid component optical purity 98%, weight average molecular weight 200,000) (2) Polylactic acid resin PLA-2 (Cargill Dow Polymers, Inc.) Made, product 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, product 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, trade name EcoPLA / 4050D, L-lactic acid component optical purity 88%, weight average molecular weight 200,000) (5) Polybutylene sax Nate resin PBS (Showa High Polymer Co., Ltd., trade name Bionore # 1001) (Plasticizer) Examples and In Comparative Examples, the following were used as plasticizers. Acetyl tributyl citric acid (manufactured by Sanken Kako Co., Ltd., trade name A
TBC) Acetyl polyethylene glycol monomethyl ether (MPEG) (manufactured by Sanyo Kasei Co., Ltd., no trade name, polyethylene glycol skeleton molecular weight 400) dibutyl diglycol adipate (manufactured by Daihachi Chemical Co., Ltd., trade name BXA) (inorganic particles) Examples and comparison In the examples, the following were used as the inorganic particles. Talc (Talc manufactured by Hayashi Kasei, 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) As an organic nucleating agent, erucic acid amide (Nippon Yushi Co., Ltd., trade name Alflo P10) was used.

Production Example 1: Preparation of Composition For each of the Examples and Comparative Examples, the polylactic acid raw material, the plasticizer, the crystal nucleating agent, and the organic lubricant were melt mixed in the proportions shown in Table 1. A resin raw material, a crystal nucleating agent, and an organic lubricant were quantitatively supplied from a hopper port of the kneading machine using a biaxial melt kneading machine having a screw diameter of φ44 mm using a weight control type quantitative feeder. Further, the plasticizer is quantitatively supplied from the middle of the cylinder by using a constant amount injection pump, and the set temperature is set to 170.
The mixture was melt-mixed at ˜190 ° C., screw rotation speed 100 rpm, and total discharge amount 80 kg / h. The strand discharged from the nozzle was cooled in a cold water bath and pelletized by a starland cutter. The pelletized polylactic acid resin composition thus obtained was dried under reduced pressure at 50 ° C. for 8 hours,
It was subjected to a later film formation test.

Production Example 2: Formation of Film of Composition For each of Examples and Comparative Examples, an inflation film was formed using the polylactic acid resin composition prepared in Production Example 1 above. Screw diameter 45 mm equipped with a circular die with a diameter of 100 mm
Melt extrusion was performed at a set temperature of 180 ° C. The molten resin composition discharged from the die was expanded by air pressure and simultaneously formed into a tube while being air-cooled by an air ring. A film formed to have a film thickness of 25 μm and a film folding width of 350 mm is moved by a pair of pinch rolls installed on the die.
It was collected at a speed of 0 m / min. After a cooling time of about 7 seconds, the tube-shaped film was nipped by a pinch roll and wound by a winding machine for 1000 m. The composition was formed into a film in an environment where the temperature was adjusted to 25 to 30 ° C. The film thus obtained was subjected to various measurements.

Examples 1 to 6 PL was used as the polylactic acid resin (P1) having an optical purity of 90% or more.
Using A-1, 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, a resin composition was prepared according to Production Example 1 at a mixing ratio shown in Table 1. did. Regarding the obtained resin composition, (1) weight average molecular weight, (2) glass transition temperature, (3)
The crystallization heat value 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 sampled for 1000 m. Regarding the obtained film,
The opening property of (4-a) film and the bleeding property and blocking property of (4-b) film were evaluated.

Example 7 PL was used as a polylactic acid resin (P2) having an optical purity of less than 90%.
Using the same raw materials as in Example 1 except that A-3 was used,
The resin composition and the film were produced with the mixing ratios shown in Table 1. Various evaluations were performed on the obtained resin composition and film.

Example 8 The same raw materials as in Example 1 were used except that ATBC was used as a plasticizer, and a resin composition and a film were prepared in the mixing ratio shown in Table 1. Various evaluations were performed on the obtained resin composition and film.

Example 9 The same raw materials as in Example 1 were used except that BXA was used as a plasticizer, and a resin composition and a film were produced at the mixing ratios shown in Table 1. Various evaluations were performed on the obtained resin composition and film.

Comparative Examples 1 to 5 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 carried out.

Comparative Examples 6 to 7 The same raw materials as in Example 1 were used except that silica was used as the crystal nucleating agent, and 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.

Comparative Example 8 The same raw material as in Example 1 was used except that only PLA-4 was used as the polylactic acid raw material, and a resin composition and a film were produced at the mixing ratios shown in Table 1. Various evaluations were performed on the obtained film.

[0059]

Comparative Example 9 A resin composition and a film were prepared using the raw materials shown in Table 1. Various evaluations were performed on the obtained resin composition and film. The results are shown in Table 1.

[0061]

[Table 1]

[0062]

INDUSTRIAL APPLICABILITY As in the present invention, by imparting a specific crystallinity to plasticized polylactic acid, it overcomes the disadvantage of polylactic acid that it is hard and brittle at room temperature, while it is being manufactured or used. Also, it becomes possible to industrially provide a highly practical film having good blocking resistance, excellent opening property and bleed-out resistance.
Further, by mixing and using polylactic acid resins having different monomer optical purities, that is, crystallinity in a specific range, a resin composition having crystallinity and bleed-out resistance and a film made of the same can be obtained.

Claims (6)

(57) [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: . (I) The crystalline polylactic acid resin (A) has an optical purity of 90%.
The above polylactic acid resin (P1) and a resin having an optical purity of less than 90%.
It is a mixture of polylactic acid resin (P2) and contains P1 and P2.
The mass fraction of P1 with respect to the total mass is 30 mass% or more, 1
It is less than 00 mass%. (II) The crystal nucleating agent (C) is talc, and its addition amount is
It is 13 mass% or more and 50 mass% or less in the composition. 2. A contract characterized by satisfying the following conditions :
The highly crystalline polylactic acid resin composition according to claim 1. (1) Glass transition temperature ≦ 30 ° C. (2) 1 g of polylactic acid resin component measured by a differential scanning calorimeter when cooled from a molten state at a rate of 20 ° C./min
ΔHc ≧ 1 where ΔHc is the heat value of crystallization per hit
0 (J / g) (3) The crystallization peak temperature measured by a differential scanning calorimeter when cooled from the molten state at a rate of 20 ° C./min is T
When cc, Tcc ≧ 80 ° C. 3. A film or sheet comprising the polylactic acid resin composition according to claim 1 or 2 as a main component. 4. 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. (I) The crystalline polylactic acid resin (A) has an optical purity of 90%.
The above polylactic acid resin (P1) and a resin having an optical purity of less than 90%.
It is a mixture of polylactic acid resin (P2) and contains P1 and P2.
The mass fraction of P1 with respect to the total mass is 30 mass% or more, 1
It is less than 00 mass%. (II) The crystal nucleating agent (C) is talc, and its addition amount is
It is 13 mass% or more and 50 mass% or less in the composition. 5. A contract characterized by satisfying the following conditions :
The film or sheet according to claim 4. (1) Glass transition temperature ≦ 30 ° C. (2) 1 g of polylactic acid resin component measured by a differential scanning calorimeter when cooled from a molten state at a rate of 20 ° C./min
ΔHc is the heating value for crystallization per unit time, ΔHc ≧ 10 (J / g) (3) The crystallization peak temperature measured by a differential scanning calorimeter when cooled from the molten state at a rate of 20 ° C./min is T
When cc, Tcc ≧ 80 ° C. 6. The film or sheet according to claim 3, which is produced by an inflation method.