JP2008308613A - Polylactic acid-based resin composition, and preform and blow-molded bottle comprising the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polylactic acid-based resin composition, a preform and a blow-molded bottle excellent in transparency and heat resistance. <P>SOLUTION: The polylactic acid-based resin composition contains a polylactic acid (A), a lactic acid-based copolymer (B) containing a lactic acid component by 30 to 70 mass%, and an amide-based crystal nucleating agent (C) having at least one hydroxy group, wherein the mass ratio (A/B) ranges 50/50 to 95/5, the content of (C) is 0.01 to 5 parts by mass with respect to 100 parts by mass total of (A) and (B), and the composition satisfies the following conditions (i) to (iii). They are: (i) the crystallization peak temperature is 60 to 120°C in the measurement by DSC at a temperature rising rate of 20°C/minute; (ii) the period until an exothermic peak in an isothermal crystallization curve at 75°C in a temperature rising process measured by DSC exhibits the peak top is not longer than 10 minutes, and the absolute crystallization heat is 5 to 25 J/g; and (iii) the period until an exothermic peak in an isothermal crystallization curve at 130°C in a temperature falling process measured by DSC exhibits the peak top is not shorter than 5 minutes. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polylactic acid resin composition excellent in transparency and heat resistance, a preform, and a blow molded bottle.

  In recent years, biodegradable polymers that are decomposed by microorganisms and the like have attracted attention with increasing social demands for environmental protection. Specific examples of biodegradable polymers include aliphatic polyesters such as polyethylene succinate, polybutylene succinate, polycaprolactone, polylactic acid, and copolymers of terephthalic acid / 1,4 butanediol / adipic acid. -Polyester which can be melt-molded, such as aromatic copolymerized polyester, may be mentioned. Among the aliphatic polyesters, polylactic acid is one of the resins having good transparency and the highest glass transition temperature (Tg), and can be mass-produced from plant-derived raw materials such as corn and sweet potato. However, it is cheap and can contribute to reducing the amount of petroleum raw materials used. However, when used as a storage container such as a beverage container, there is a problem that heat resistance is low.

  Polylactic acid generally has a low crystallization speed, so even if the mold is set in the crystallization temperature range, crystallization does not proceed sufficiently during the process, and as a result, a molded product with an accurate dimension may not be obtained. Even when a molded product was obtained, the transparency was lost due to crystallization, or the heat resistance was poor.

Therefore, a method of crystallizing a molded body made of polylactic acid to impart heat resistance has been developed. For example, Patent Documents 1 and 2 disclose a method for promoting crystallization by adding a bisamide compound to polylactic acid. Patent Document 3 discloses a resin composition sheet composed of polylactic acid, a polylactic acid copolymer, and an amide compound.
However, the resin compositions disclosed in Patent Documents 1 and 2 have a problem that crystallization is too fast and blow molding cannot be performed, or even when molding is performed, whitening occurs and transparency is impaired. Further, the amide compound used in Patent Document 3 is inferior in compatibility with the resin, and there is a problem that the transparency of the resin composition and the molded product obtained therefrom is impaired.
Japanese Patent No. 3411168 JP-A-2005-179619 JP 2004-149692 A

  An object of the present invention is to solve the above problems and provide a polylactic acid resin composition, a preform, and a blow molded bottle that are excellent in transparency and heat resistance.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above problems can be solved by controlling the crystallization rate of the polylactic acid-based resin, which has led to the present invention. That is, the gist of the present invention is as follows.
(1) Polylactic acid containing polylactic acid (A), a lactic acid copolymer (B) containing 30 to 70% by mass of a lactic acid component, and an amide crystal nucleating agent (C) having at least one hydroxyl group It is a system resin composition, Comprising: Mass ratio (A / B) of (A) and (B) is 50 / 50-95 / 5, and with respect to a total of 100 mass parts of (A) and (B) , (C) content is 0.01 to 5 parts by mass, and satisfies the following (i) to (iii).
(I) The crystallization peak temperature when measured with a differential scanning calorimeter (DSC) at a rate of temperature increase of 20 ° C./min is 60 to 120 ° C.
(Ii) The time (t _max 1) until the exothermic peak of the isothermal crystallization curve at 75 ° C. in the temperature rising process measured by DSC shows the peak top is 10 minutes or less, and the absolute amount of crystallization heat (ΔH) The value is 5-25 J / g.
(Iii) The time (t _max 2) until the exothermic peak of the isothermal crystallization curve at 130 ° C. in the temperature lowering process measured by DSC shows the peak top is 5 minutes or more.
(2) The polylactic acid-based resin composition according to (1), wherein the mass ratio (A / B) of the above (A) and (B) is 50/50 to 90/10.
(3) The polylactic acid resin composition as described in (1) or (2), wherein the haze of a 2 mm thick molded piece injection molded at 180 ° C. is 15% or less.
(4) A preform comprising the polylactic acid resin composition according to any one of (1) to (3) above.
(5) The preform according to (4), wherein the mouth is crystallized.
(6) A blow molded bottle comprising the polylactic acid resin composition according to any one of (1) to (3) above.
(7) The blow molded bottle according to (6), wherein the mouth is crystallized.
(8) The blow molded bottle as described in (6) or (7) whose haze of a trunk | drum is 10% or less.
(9) containing polylactic acid (A), a lactic acid copolymer (B) containing 30 to 70% by mass of a lactic acid component, and an amide crystal nucleating agent (C) having at least one hydroxyl group, The mass ratio (A / B) between A) and (B) is 50/50 to 95/5, and the content of (C) is 0 with respect to a total of 100 parts by mass of (A) and (B). In a method of manufacturing a preform from a polylactic acid resin composition in an amount of 0.01 to 5 parts by mass and then blow-molding the preform after the preform is heated, the blow-molded bottle is simultaneously formed with the blow molding. Is maintained in a mold at 70 to 130 ° C and / or after blow molding, the blow molded bottle is maintained at a temperature of 70 to 130 ° C.
(10) The method for producing a blow-molded bottle according to (9), wherein the mouth is heated and crystallized before blow molding or after blow molding.

  According to the present invention, a blow-molded bottle that can be crystallized by heating at a practical molding cycle time without impairing transparency during blow molding, and has excellent transparency and heat resistance after crystallization. Can be provided.

Hereinafter, the present invention will be described in detail.
The polylactic acid resin composition of the present invention comprises polylactic acid (A), a lactic acid copolymer (B) containing 30 to 70% by mass of a lactic acid component, and an amide crystal nucleating agent having at least one hydroxyl group ( C).

In the present invention, as polylactic acid (A), poly L-lactic acid, poly D-lactic acid, poly DL-lactic acid which is a copolymer of L-lactic acid and D-lactic acid, or a mixture thereof can be used.
The melting point of the preform or blow molded product obtained by mixing with the lactic acid copolymer (B) is preferably 160 ° C. or higher. When the melting point of the preform or blow molded article is less than 160 ° C., the heat resistance may be inferior. By the way, the melting point of polylactic acid (A) varies depending on the copolymerization ratio of L-lactic acid and D-lactic acid. When the content of D-lactic acid increases, the crystallinity of polylactic acid itself decreases and the melting point decreases. Therefore, as a method for setting the melting point of the preform or blow molded body to 160 ° C. or higher, a method using mainly polylactic acid (A) having a D-lactic acid content of 2 mol% or less can be mentioned. A melting point of 160 ° C. or higher is obtained by partially mixing polylactic acid having a D-lactic acid content of 10% or more and a substantially amorphous polylactic acid with a D-lactic acid content of 2 mol% or less. It is possible to control the crystallinity and the crystallization speed while having the above, and is effective as a method for obtaining desired crystallinity.

  The weight average molecular weight of the polylactic acid (A) is preferably in the range of 50,000 to 300,000, more preferably 80,000 to 250,000, and most preferably 100,000 to 200,000. When the weight average molecular weight of the polylactic acid (A) is less than 50,000, the melt viscosity is too low, and the resulting blow molded article is inferior in mechanical properties. When the weight average molecular weight exceeds 300,000, the melt viscosity Becomes too high and molding becomes difficult.

  In the present invention, the lactic acid copolymer (B) needs to contain 30 to 70% by mass of the lactic acid component, and preferably contains 30 to 60% by mass. When the content of the lactic acid component is less than 30% by mass, the compatibility with the polylactic acid (A) is poor and it is difficult to obtain a transparent preform or blow molded article. If the content exceeds 70% by mass, the effect of accelerating the crystallization rate of polylactic acid (A) is small, the heat treatment time required for crystallization is long, the practicality is inferior, and the transparency when crystallized is also high. Inferior.

In the lactic acid copolymer (B), the copolymer component other than the lactic acid component is preferably a polyester or polyether composed of a dicarboxylic acid and a diol.
The dicarboxylic acid component is not particularly limited, but oxalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, dodecanedioic acid, dimer acid, terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid , 5-sodium sulfoisophthalic acid, maleic anhydride, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, dicarboxylic acids such as cyclohexanedicarboxylic acid, 4-hydroxybenzoic acid, and ε-caprolactone. From the aspect of compatibility with polylactic acid, dicarboxylic acids having 10 or less carbon atoms are preferred.

Examples of the diol component include ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, cyclohexanedimethanol, and triethylene. Examples include glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide adducts of bisphenol A and bisphenol S, and the like. From the viewpoint of compatibility with polylactic acid, diol acids having 10 or less carbon atoms are preferred.
Among them, it is preferable that a polyether component such as ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butanediol, or polyethylene glycol, polypropylene glycol, polytetramethylene glycol is copolymerized. It is preferable that the weight average molecular weight of ether is 200-5000. By copolymerizing a polyether component having a specific weight average molecular weight, flexibility can be imparted to polylactic acid without lowering the compatibility with polylactic acid.

  Further, a small amount of trifunctional compounds such as trimellitic acid, trimesic acid, pyromellitic acid, trimethylolpropane, glycerin, pentaerythritol and the like may be used. Two or more of these copolymer components may be used in combination.

  The lactic acid copolymer (B) is crystalline and preferably has a melting point of 130 ° C. or higher, particularly 140 ° C. or higher. When the melting point is less than 130 ° C., the difference between the crystallization temperature range of the polylactic acid (A) and the crystallization temperature range of the lactic acid copolymer (B) increases, and the effect of improving the crystallization rate at the time of temperature rise is obtained. Get smaller. Moreover, the heat resistance after crystallization may be inferior.

  It is known that the amount of residual lactide present in the polylactic acid (A) and / or lactic acid-based copolymer (B) promotes hydrolysis of the polylactic acid (A) when the amount is too large. In the present invention, the amount of residual lactide in the resin composition is not particularly limited, but it is preferably 0.6% by mass or less from the viewpoint of suppressing decomposition of the molded product. If the amount of residual lactide exceeds 0.6% by mass, crystallization is promoted but the action of promoting hydrolysis is enhanced, which is not preferable.

  In the polylactic acid resin composition of the present invention, the mass ratio (A / B) of the polylactic acid (A) and the lactic acid copolymer (B) needs to be 50/50 to 95/5. 50/50 to 85/15. When the polylactic acid (A) component is less than 50% by mass, the glass transition temperature and the melting point are lowered, the handling property of the amorphous preform is inferior, and the heat resistance is lowered even if the blow molded article is crystallized. On the other hand, when the polylactic acid (A) component exceeds 95% by mass, the effect of improving the crystallization rate is small and the practicality of the molding process is inferior.

  In the polylactic acid resin composition of the present invention, the amide crystal nucleating agent (C) having at least one hydroxyl group is added in an amount of 0 to 100 parts by mass of the total of polylactic acid (A) and lactic acid copolymer (B). It is necessary to contain 0.01 to 5 parts by mass, preferably 0.05 to 2 parts by mass, and more preferably 0.1 to 1 part by mass. If the content of the amide-based crystal nucleating agent (C) is less than 0.01 parts by mass, the effect of promoting crystallization is poor. On the other hand, if it exceeds 5 parts by mass, the transparency is impaired or the workability is reduced. In addition, the crystallization rate is not preferable because it is out of an appropriate range, causing poor appearance or causing coloring.

In the present invention, the amide crystal nucleating agent (C) having at least one hydroxyl group has good compatibility with the polylactic acid (A) and the lactic acid copolymer (B), and the polylactic acid (A) and The polylactic acid resin composition comprising the lactic acid copolymer (B) is selected to increase the crystallization speed and maintain transparency when crystallized.
Specific examples of the amide crystal nucleating agent (C) include ricinoleic acid amide, hydroxystearic acid amide, N-hydroxyethyl-ricinoleic acid amide, N-hydroxyethyl-12-hydroxystearic acid amide, N , N′-ethylene-bis-ricinoleic acid amide, N, N′-ethylene-bis-12-hydroxystearic acid amide, N, N′-hexamethylene-bis-ricinoleic acid amide, N, N′-hexamethylene- Examples thereof include bis-12-hydroxystearic acid amide and N, N′-xylylene-bis-12-hydroxystearic acid amide.
Among these, N, N′-ethylene-bis-12-hydroxystearic acid amide, N, N′-hexamethylene bis-ricinoleic acid amide, N, N′-hexamethylene bis-12-hydroxystearic acid amide, N N'-xylylenebis-12-hydroxystearic acid amide is preferably used.
These amide crystal nucleating agents may be used alone or in combination.

  Lisinoleic acid and 12-hydroxystearic acid, which are raw materials for the amide-based crystal nucleating agent (C) that is preferably used, are fatty acids obtained by saponification and decomposition of castor oil, and are derived from plants. Contributes to reduced usage.

  In order to increase the crystallinity of the blow molded article in the present invention, it is more preferable that the chemical structure of the amide crystal nucleating agent (C) is a symmetric structure. Moreover, in order to improve compatibility with polylactic acid (A) and a lactic acid-type copolymer (B), it is preferable that carbon number in an amide type crystal nucleating agent (C) exists in the range of 4-60. .

The polylactic acid resin composition of the present invention must satisfy the following (i) to (iii).
(I) The crystallization peak temperature when measured with a differential scanning calorimeter (DSC) at a rate of temperature increase of 20 ° C./min is 60 to 120 ° C.
(Ii) The time (t _max 1) until the exothermic peak of the isothermal crystallization curve at 75 ° C. in the temperature rising process measured by DSC shows the peak top is 10 minutes or less, and the absolute amount of crystallization heat (ΔH) The value is 5-25 J / g.
(Iii) The time (t _max 2) until the exothermic peak of the isothermal crystallization curve at 130 ° C. in the temperature lowering process measured by DSC shows the peak top is 5 minutes or more.
In addition, the specific measuring method of the said crystallization peak temperature, _tmax1 , _tmax2 , and the absolute value of crystallization calorie | heat amount was described in the Example column.

  In the polylactic acid-based resin composition of the present invention, if the crystallization peak temperature measured by DSC at a rate of temperature increase of 20 ° C./min is less than 60 ° C., it is crystallized during heating to soften the preform. Therefore, the blow moldability may be inferior. In addition, when the crystallization peak temperature exceeds 120 ° C., it takes too much time to crystallize, resulting in inferior practicality of the molding process, and it tends to whiten after crystallization. The crystallization peak temperature is more preferably 60 ° C to 100 ° C.

In the polylactic acid-based resin composition of the present invention, when the time (t _max 1) until the exothermic peak of the isothermal crystallization curve at 75 ° C. in the temperature rising process reaches the peak top (t _max 1) exceeds 10 minutes, crystallization occurs. Is too slow to be practically similar to the above.
In addition, if the absolute value of the crystallization heat amount is less than 5 J / g, crystallization does not proceed sufficiently during blow molding, whereas if the absolute value of the crystallization heat amount exceeds 25 J / g, whitening tends to occur during crystallization. . In order to achieve both transparency and heat resistance, the absolute value of the amount of crystallization heat is more preferably 10 to 25 J / g.

Further, in the polylactic acid resin composition of the present invention, when the time (t _max 2) until the exothermic peak of the isothermal crystallization curve at 130 ° C. in the temperature lowering process reaches the peak top is less than 5 minutes, crystallization occurs. Is too fast, it is crystallized during preform molding, and whitening occurs. Therefore, not only the transparency is inferior, but also the subsequent blow process cannot be performed and the moldability may be inferior.

In the present invention, in addition to the specific range, it is preferable that the values of {(t _max 2) − (t _max 1)} and {(t _max 2) / (t _max 1)} are larger. Specifically, {(t _max 2) − (t _max 1)} is preferably 5 or more, more preferably 8 or more, and particularly preferably 15 or more. {(T _max 2) / (t _max 1)} is preferably 2 or more, more preferably 3 or more, and particularly preferably 5 or more.

In the present invention, as a method of setting the crystallization peak temperature, t _max 1, t _max 2 and the absolute value of the crystallization heat amount of the polylactic acid resin composition within the above ranges, polylactic acid (A And a method of adjusting the type and addition amount of the lactic acid copolymer (B) and the amide crystal nucleating agent (C), a method of adjusting the kneading conditions during melt mixing, and the like.

  In the polylactic acid resin composition of the present invention, the haze of a 2 mm-thick molded piece injection-molded at 180 ° C. is preferably 15% or less, more preferably 12% or less. In order to form a bottle with excellent transparency, the preform needs to be transparent. When the haze in the molded piece is 15% or more, the injection-molded preform is whitened, and as a result, it tends to be difficult to obtain a bottle with excellent transparency.

  In the resin composition of the present invention, an inorganic crystal nucleating agent such as layered silicate represented by talc, smectite, vermiculite, swellable fluorinated mica, etc. other than those prescribed in the present invention, unless the characteristics are impaired, Or you may contain another organic type crystal nucleating agent. The content is preferably in the range of 0.1 to 15% by mass. If the content is less than 0.1% by mass, the effect as a crystal nucleating agent cannot be sufficiently exerted, and if the content exceeds 15% by mass, the transparency is lowered or the molded product becomes brittle. I will give it. These inorganic and organic crystal nucleating agents may be used alone or in combination.

  In addition, in the resin composition of the present invention, in order to further accelerate the crystallization rate of polylactic acid, a crosslinking agent such as an organic peroxide or a crosslinking aid is used in combination as needed, and polylactic acid is extremely light. It is also possible to perform crosslinking.

  As the crosslinking agent, n-butyl-4,4-bis-t-butylperoxyvalerate, dicumyl peroxide, di-t-butyl peroxide, di-t-hexyl peroxide, 2,5-dimethyl- Organic peroxides such as 2,5-di (t-butylperoxy) hexane and 2,5-dimethyl-2,5-t-butylperoxyhexyne-3, phthalic anhydride, maleic anhydride, trimethyladipine Acid, trimellitic anhydride, polyvalent carboxylic acid such as 1,2,3,4-butanetetracarboxylic acid, metal complex such as lithium formate, sodium methoxide, potassium propionate, magnesium ethoxide, bisphenol A type diglycidyl Ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, terf Epoxy compounds such as Le acid diglycidyl ester, diisocyanate, triisocyanate, hexamethylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, xylylene diisocyanate, and the like isocyanate compounds such as diphenylmethane diisocyanate. The addition amount of the crosslinking agent is preferably 0.01 to 20 parts by mass, more preferably 0.01 to 10 parts by mass, and 0.01 to 3 parts by mass with respect to 100 parts by mass of the resin composition. More preferably.

  Examples of the crosslinking aid include trimethacrylate, glycidyl methacrylate, normal-butyl methacrylate, hydroxypropyl monomethacrylate, and polyethylene glycol monomethacrylate. The addition amount of the crosslinking aid is preferably 0.02 to 20 parts by mass and more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the resin composition. If the addition amount of the crosslinking aid is less than 0.02 parts by mass, the effect of increasing the reactivity is low, and if it exceeds 20 parts by mass, it is not preferable in terms of cost.

  In order to improve the durability, at least one end-capping agent selected from the group consisting of a carbodiimide compound, an epoxy compound and an oxazoline compound may be added to the resin composition of the present invention. The amount of the end-capping agent added is preferably 0.01 to 5 parts by mass and more preferably 0.05 to 2 parts by mass with respect to 100 parts by mass of the resin composition.

  In the resin composition of the present invention, a plasticizer, an ultraviolet ray inhibitor, a light stabilizer, an antifogging agent, an antifoggant, an antistatic agent, a flame retardant, an anti-coloring agent, an antioxidant, and a filler are added as necessary. In addition, pigments, mold release agents, moisture-proofing agents, oxygen barrier agents and the like may be added or coated within a range that does not impair the properties of the blow molded bottle.

  The method for producing the resin composition of the present invention is not particularly limited, but all the raw materials may be dry blended and charged from a supply hopper of a molding machine, or previously pelletized by a known method such as melt kneading. You may supply a thing to a molding machine. In melt kneading, a general kneader such as a single screw extruder, a twin screw extruder, a roll kneader, or a Brabender can be used. In order to improve the dispersibility of additives, a twin screw extruder is used. It is preferable to use it.

The resin composition of the present invention can be molded into a bottle shape by various blow molding methods. Although it does not specifically limit as a blow molding method, the direct blow method which performs blow molding after shaping | molding a preform by extrusion molding, the injection blow molding method which performs blow molding after shaping | molding a preform (bottom parison) by injection molding, etc. Is mentioned.
The latter injection blow molding method includes a hot parison method (also referred to as a one-stage method) in which blow molding is continuously performed after preform molding, or a cold in which blow molding is performed by cooling the preform once and then heating it again. Any method of the parison method (also called a two-stage method) can be adopted.
The resin composition of the present invention is characterized in that the crystallization at the time of temperature decrease is slow and the crystallization at the time of temperature increase is fast, so that a transparent preform is formed in advance by injection molding, and the preform is reheated. It is particularly preferable to use a cold parison method in which blow molding is performed.

In the present invention, a preform obtained from a polylactic acid resin composition by a conventionally known method such as injection molding or extrusion molding is heated to 65 to 120 ° C., preferably 70 to 110 ° C., and blow molded. By doing so, a blow molded bottle can be obtained.
If the preheating temperature of the preform is too low, the softening is insufficient and blowing cannot be performed, and if the heating temperature is too high or the time is too long, the crystallization of the preform proceeds so much that the moldability and transparency are low. descend.
In addition, although the draw ratio in blow molding is not specifically limited, it is 5-15 times by (vertical draw ratio x transverse draw ratio), preferably 6-10 times.

In the present invention, it is preferable to hold the blow molded bottle in a mold at 70 to 130 ° C. simultaneously with the blow molding, or hold the blow molded bottle at an ambient temperature of 70 to 130 ° C. after blow molding. Is preferred. You may hold | maintain the blow bottle shape | molded with the 70-130 degreeC metal mold | die at the atmospheric temperature of 70-130 degreeC further.
Since the crystallization is promoted by holding the blow molded bottle at a mold temperature or atmospheric temperature of 70 to 130 ° C, more preferably 80 to 120 ° C for 1 second or more, and more preferably 3 seconds or more, blow molding is performed. The heat resistance and barrier properties of the bottle can be improved.
When the mold temperature or the ambient temperature is less than 70 ° C., the crystallization of polylactic acid does not proceed. On the other hand, when the temperature exceeds 130 ° C., the crystallization of polylactic acid becomes extremely slow, and the polylactic acid As the melting point approaches, the crystal may be melted. As a result, hardening due to crystallization is delayed, and it takes time to obtain the rigidity necessary for mold release, which is not preferable.

In the present invention, the mouth of the preform or blow molded bottle is preferably crystallized. By crystallizing the mouth portion, the mechanical strength and heat resistance of the mouth portion can be improved.
Examples of the method for crystallizing the mouth include a method in which the mouth is heated and crystallized before blow molding or after blow molding. As temperature to heat-crystallize, 60-130 degreeC is preferable and 70-120 degreeC is more preferable. Since the polylactic acid-based resin composition of the present invention is rapidly crystallized when the temperature is raised, the mouth of the preform or the mouth of the bottle can be crystallized at high speed.

  The shape and thickness of the preform and blow-molded bottle produced by the above method are not particularly limited, but for transparency, the thickness of the preform is preferably 10 mm or less, and 6 mm or less. More preferably, it is 5 mm or less. From the viewpoint of strength, the thickness of the blow molded bottle is preferably 0.1 mm or more, more preferably 0.1 to 5 mm, and further preferably 0.3 to 2 mm.

  Specific examples of blow-molded bottles include beverage cups and beverage bottles for dairy products, soft drinks, alcoholic beverages, etc., temporary storage containers for seasonings such as soy sauce, sauces, mayonnaise, ketchup, and cooking oil , Shampoo, rinse container, cosmetic container, agricultural chemical container and the like.

Next, the present invention will be specifically described by way of examples.
The raw materials of the resin compositions and the method for measuring the characteristic values in the examples and comparative examples are as follows.
(material)
(1) Polylactic acid (A): Nature Works 4032D, D-lactic acid content 1.4 mol%, weight average molecular weight (MW) = 160,000, Tg 59 ° C., Tm 167 ° C.
(2) Lactic acid-based copolymer (B): manufactured by Dainippon Ink and Chemicals, Pramate PD-350, lactic acid component content 50 mass%, Tm 154 ° C.
(3) Amide-based crystal nucleating agent (C): N, N′-ethylene-bis-12-hydroxystearic acid amide, WX-1 manufactured by Kawaken Fine Chemicals.

(Measurement method)
(1) Crystallization peak temperature:
Using DSC (DSC7 manufactured by Perkin Elmer), the temperature was raised from 25 ° C. to 200 ° C. at 20 ° C./min, and the temperature was maintained for 10 minutes. Thereafter, the temperature was lowered to −55 ° C. at −20 ° C./min, and again raised to 200 ° C. at 20 ° C./min. The top of the exothermic peak obtained during the second temperature increase was defined as the resin crystallization peak temperature.

(2) t _max 1 of crystallization at elevated temperature and heat of crystallization ΔH (J / g):
About the resin composition, it heated up at 200 degreeC / min to 200 degreeC using DSC, and maintained for 5 minutes. Thereafter, the temperature was lowered to 0 ° C. at −500 ° C./min and maintained for 5 minutes. Thereafter, the temperature was raised to 75 ° C. at 500 ° C./min, and the temperature was maintained to cause isothermal crystallization of the resin. In the isothermal crystallization curve obtained at this time, the time from when the isothermal crystallization temperature (75 ° C.) was reached until the exothermic peak due to crystallization showed the peak top was defined as t _max 1. It can be determined that the shorter the time, the faster the crystallization during temperature rise. The area surrounded by the exothermic peak and the baseline during isothermal crystallization was defined as ΔH (J / g).

(3) t _max 2 of crystallization during cooling and crystallization heat ΔH (J / g):
About the resin composition, it heated up at 200 degreeC / min to 200 degreeC using DSC, and maintained for 5 minutes. Thereafter, the temperature was lowered to 130 ° C. at −500 ° C./min, and the resin was crystallized isothermally while maintaining the temperature. In the isothermal crystallization curve obtained at this time, the time from reaching the isothermal crystallization temperature (130 ° C.) until the exothermic peak due to crystallization shows the peak top was defined as t _max 2. It can be determined that the longer this time is, the slower the crystallization is when the temperature is lowered. The area surrounded by the exothermic peak and the baseline during isothermal crystallization was defined as ΔH (J / g).

(4) Haze of resin composition:
Using an injection molding machine (IS-80G type manufactured by Toshiba Machine Co., Ltd.), resin temperature 180 ° C., mold temperature 15 ° C., injection pressure 60%, injection time 10 seconds, cooling time 10 seconds, interval 2 seconds, thickness 2 mm A color plate was molded. About this molded article, it measured using the Nippon Denshoku Industries Co., Ltd. NDH-2000 type turbidity / cloudiness meter.

(5) Haze of blow molded bottle:
A sample (thickness 0.4 mm) was cut out from the body portion of the blow molded bottle, and this sample was measured using an NDH-2000 turbidity / cloudiness meter manufactured by Nippon Denshoku Industries Co., Ltd.

(6) Formability:
(6-1) Mouth crystallization:
○: mouth crystallization can be performed within a cycle time without deformation.
X: Deformation occurs and mouth crystallization cannot be performed within the cycle time.
(6-2) Blow molding:
○: Stable blow molding with good productivity can be performed.
(Triangle | delta): Since mouth part crystallization was not able to be performed, blow molding cannot be performed with sufficient productivity.
X: Blow molding cannot be performed due to rupture.

(7) Heat resistance:
The blow molded bottle was heat-treated for 30 minutes in a 90 ° C. hot air dryer, and the appearance and shape before and after the heat treatment were compared and evaluated.
○: No change in appearance and shape before and after heat treatment.
X: Appearance and shape changed before and after heat treatment.

Example 1
[Production of Resin Composition A]
92.5 parts by mass of polylactic acid (A), 7.5 parts by mass of lactic acid copolymer (B), and 1.0 part by mass of amide-based crystal nucleating agent (C) were dry blended, and the screw diameter was 30 mmφ. Using a twin-screw extruder (PCM-30 manufactured by Ikegai Co., Ltd.), melt kneading was performed at 190 ° C., a screw rotation speed of 150 rpm, and a discharge rate of 100 g / min to obtain a resin composition A.
[Preform molding]
Using an injection blow molding machine (ASB-50, manufactured by Nissei ASB Machine), the resin composition A is melted at a temperature equal to or higher than the melting start temperature Tm or the flow starting temperature, and a plug having a diameter of 28 mm and a barrel thickness of 3.7 mm is obtained. Reform (bottomed parison) was obtained.
The main molding conditions are: resin drying temperature 60 ° C, drying time 12 hours or more, barrel temperature 150 ° C to 180 ° C, hot runner temperature 180 ° C, injection mold set water temperature 16 ° C, injection time 16 seconds, cooling time 25 seconds, The VP time is 1.1 seconds, the holding pressure is 3.7 MPa, the metering time is 2.8 seconds, the metering screw speed is 100 RPM, and the molding cycle is 49 seconds.
[Preform mouth crystallization]
Using the mouth crystallization apparatus (CM-2000 manufactured by Nissei ASB Machine), the mouth of the preform formed as described above was crystallized by heat treatment.
Main crystallization conditions are mouth heater setting 50-60%, mouth inner surface correction core setting temperature 40 ° C., correction core insertion depth 20.8 mm (from top of mouth), cycle 1600 / hour. .
[Molding of blow molded bottles]
The final mold was installed at the primary blow mold installation position of the blow molding machine HSO-6 (manufactured by Nissei ASB Machine) and used as a one blow machine. Here, one blow refers to a molding method in which only one blow mold is used in the process of re-heating the preform and performing blow molding. The preform after the mouth crystallization treatment was blow-molded with a 85 ° C. mold to obtain a blow-molded bottle having a capacity of 350 ml and a barrel thickness of about 0.4 mm. The heat resistance and haze of the obtained bottle are shown in Table 1.
Major molding conditions are preform reheat heater setting 32 to 43% (preform surface measured temperature 72 ° C), preform temperature 70 to 74 ° C after heating, primary blow mold set temperature 20 ° C, primary upper bottom mold The set temperature is 20 ° C., the primary blow time is 3 seconds, and the molding cycle is 7.5 seconds.

Example 2
A resin composition B was obtained in the same manner as in Example 1 except that the composition shown in Table 1 was used. Using resin composition B, a preform and a blow molded bottle were obtained in the same manner as in Example 1. The heat resistance and haze of the obtained bottle are shown in Table 1.

Comparative Example 1
A resin composition C was obtained in the same manner as in Example 1 except that the composition shown in Table 1 was used. A preform was molded using the resin composition C in the same manner as in Example 1, but the crystallization at the time of temperature increase was slow, and the mouth crystallization could not be performed. Next, a blow molded bottle was obtained in the same manner as in Example 1 except that the mouth portion was not crystallized.
The main molding conditions are: preform reheat heater setting 32 to 43% (preform surface measured temperature 85 ° C), preform temperature after heating approximately 80 to 90 ° C, blow mold set temperature 20 ° C, upper bottom mold set temperature 20 ° C, blow time 3 seconds, molding cycle 7.5 seconds.

Comparative Example 2
A resin composition D was obtained in the same manner as in Example 1 except that the composition shown in Table 1 was used. A preform was molded using the resin composition D in the same manner as in Example 1. However, since the crystallization was rapid when the temperature was lowered, crystallization occurred during the preform molding, and a cloudy preform was obtained. . Next, blow molding was attempted in the same manner as in Comparative Example 1, but since crystallization had already occurred, even if the preform was preheated, it could not be stretched and ruptured to obtain a blow molded bottle. could not.

As shown in Table 1, the bottles made of the resin compositions A and B of the present invention had good moldability and heat resistance.
On the other hand, Resin Composition C containing no amide-based crystal nucleating agent was inferior in moldability because it could not be crystallized at the mouth, and had low heat resistance. In the resin composition D which does not contain a lactic acid-based copolymer, the characteristic value could not be within a specific range, so that the blow moldability was inferior.

Claims (10)

A polylactic acid resin composition containing polylactic acid (A), a lactic acid copolymer (B) containing 30 to 70% by mass of a lactic acid component, and an amide crystal nucleating agent (C) having at least one hydroxyl group The mass ratio (A / B) of (A) and (B) is 50/50 to 95/5, and (C) with respect to a total of 100 parts by mass of (A) and (B) (C ) Content of 0.01 to 5 parts by mass and satisfying the following (i) to (iii).
(I) The crystallization peak temperature when measured with a differential scanning calorimeter (DSC) at a rate of temperature increase of 20 ° C./min is 60 to 120 ° C.
(Ii) The time (t _max 1) until the exothermic peak of the isothermal crystallization curve at 75 ° C. in the temperature rising process measured by DSC shows the peak top is 10 minutes or less, and the absolute amount of crystallization heat (ΔH) The value is 5-25 J / g.
(Iii) The time (t _max 2) until the exothermic peak of the isothermal crystallization curve at 130 ° C. in the temperature lowering process measured by DSC shows the peak top is 5 minutes or more. 2. The polylactic acid resin composition according to claim 1, wherein the mass ratio (A / B) of (A) to (B) is 50/50 to 90/10. The polylactic acid resin composition according to claim 1 or 2, wherein the haze of a 2 mm thick molded piece injection-molded at 180 ° C is 15% or less. A preform comprising the polylactic acid resin composition according to any one of claims 1 to 3. The preform according to claim 4, wherein the mouth is crystallized. A blow molded bottle comprising the polylactic acid resin composition according to any one of claims 1 to 3. The blow-molded bottle according to claim 6, wherein the mouth is crystallized. The blow molded bottle according to claim 6 or 7, wherein the haze of the trunk is 10% or less. A polylactic acid (A), a lactic acid copolymer (B) containing 30 to 70% by mass of a lactic acid component, an amide crystal nucleating agent (C) having at least one hydroxyl group, and (A) The mass ratio (A / B) to (B) is 50/50 to 95/5, and the content of (C) is 0.01 to 100 parts by mass with respect to a total of 100 parts by mass of (A) and (B). In a method of producing a preform from 5 parts by mass of a polylactic acid-based resin composition, then heating the preform and then blow-molding to produce a blow-molded bottle, simultaneously with blow molding, A method for producing a blow-molded bottle, wherein the blow-molded bottle is held at a temperature of 70 to 130 ° C after being held in a mold at 130 ° C and / or after blow molding. The method for producing a blow-molded bottle according to claim 9, wherein the mouth portion is heated and crystallized before or after blow molding.