JP2016113557A - Method of producing polylactic resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing polylactic resin composition in which the occurrence of a die line is suppressed, in addition which has excellent durability and heat stability.SOLUTION: The method of producing polylactic resin composition containing polylactic resin, acryl/styrene copolymer having epoxy group, and carbodiimide compound is provided which comprises: a step (1) of mixing polylactic resin and acryl/styrene copolymer having epoxy group to prepare mixture; and a step (2) of further mixing the mixture obtained in the step (1) with carbodiimide compound, and in which concentration of carboxyl group terminus in the mixture obtained in the step (1) is 20 mmol/kg or less.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing a polylactic acid resin composition. More specifically, the present invention relates to a method for producing a polylactic acid resin composition that can be suitably molded into a molded product such as a clear case or a tray for daily necessities, cosmetics, home appliances, and the like.

  Polylactic acid resin is inexpensive because L-lactic acid as a raw material is produced by fermentation using sugar extracted from corn, straw, etc., and the carbon dioxide emission is extremely low because the raw material is derived from plants. In addition, due to the characteristics of the resin such as high rigidity and high transparency, its use is currently expected.

  For example, in Patent Document 1, phosphono fatty acid ester (component B) as a residual catalyst deactivator is blended with polylactic acid (component A), and a phosphate metal salt (component C) is used as a crystal nucleating agent. Furthermore, by using an impact modifier (component D), the thermal stability of the matrix resin is improved by the deactivation effect of the phosphono fatty acid ester (component B), and the impact resistance is increased synergistically. It is disclosed that a polylactic acid composition excellent in stability, particularly wet heat stability, and impact resistance can be obtained. Moreover, by using the above composition, it is possible to reduce the amount of end-capping agent (E component) added in order to exhibit a certain wet heat stability, and it is derived from the end-capping agent (E component) malodor and odor-causing substances. It has been reported that mold contamination, which seems to be possible, can be reduced. Here, as the terminal blocking agent, a carbodiimide compound, an epoxy compound, an oxazoline compound, and an oxazine compound are listed. An example in which other raw materials containing 1 part by weight of a carbodiimide compound and 0.5 parts by weight of an epoxy group-containing acrylic-styrene copolymer are mixed together and then melt-kneaded is disclosed.

JP 2010-1111734 A

  However, when a conventional polylactic acid resin composition is prepared using an extruder with a T-die, a die line is generated, and the appearance of the resulting sheet becomes poor.

  The present invention relates to a method for producing a polylactic acid resin composition, in which generation of die lines is suppressed, and further, durability and thermal stability are excellent.

The present invention relates to a method for producing a polylactic acid resin composition comprising a polylactic acid resin, an acrylic / styrene copolymer having an epoxy group, and a carbodiimide compound, wherein the production method comprises step (1): polylactic acid resin and Step (2) of preparing a mixture by mixing an acrylic / styrene copolymer having an epoxy group: a step of further mixing a carbodiimide compound with the mixture obtained in the step (1), It is related with the manufacturing method of the polylactic acid resin composition whose carboxyl group terminal concentration of the mixture obtained by 20 is 20 mmol / kg or less.

  The polylactic acid resin composition obtained by the production method of the present invention has an excellent effect that generation of die lines is suppressed, and further, durability and thermal stability are excellent.

The production method of the polylactic acid resin composition of the present invention includes the following steps (1) to (2), that is, the blending order of the acrylic / styrene copolymer having an epoxy group and the carbodiimide compound to the polylactic acid resin is specified. Furthermore, it is characterized in that the carboxyl group terminal concentration of polylactic acid in the middle is a specific content.
Step (1): Mixing a polylactic acid resin and an acrylic / styrene copolymer having an epoxy group to prepare a mixture Step (2): Further mixing a carbodiimide compound with the mixture obtained in the step (1). Step (1) and step (2) may be either continuous or non-continuous. For example, after the mixture obtained in step (1) is temporarily stored, step (2) is performed. However, it is included in the production method of the present invention.

  Since the polylactic acid resin has a carboxyl group in the terminal structure, durability can be improved by blocking its reactivity. Therefore, a reaction method using a compound having an epoxy group or a carbodiimide compound as a reaction blocking agent is generally known. However, it was found that when both the compounds were reacted at the same time, it was difficult to react the two compounds in a balanced manner due to the difference in reactivity. Therefore, in the present invention, the compound having an epoxy group is reacted once until the terminal carboxyl group concentration reaches a specific amount, and then the carbodiimide compound is reacted to block the terminal carboxyl group of the polylactic acid resin. It is estimated that durability and thermal stability can be improved. In addition, by reacting the polylactic acid resin with a compound having an epoxy group, and then reacting the remaining terminal carboxyl group, sufficient entanglement occurs between molecules of the obtained polylactic acid resin composition, resulting in a swell ratio. It is presumed that an excellent effect is achieved that the generation of die lines is suppressed and the occurrence of die lines is also suppressed. A polylactic acid resin composition obtained by reacting only a carbodiimide compound or only a compound having an epoxy group has low moldability. Moreover, it is presumed that the compound having an epoxy group is a copolymer of acrylic, thereby improving the compatibility with the polylactic acid resin and improving the reactivity with the polylactic acid resin. . Further, it is presumed that by copolymerizing styrene there, the stability (moisture absorption resistance, thermal stability) of the compound having an epoxy group is improved and handling is facilitated. However, these assumptions do not limit the present invention.

<Process (1)>
In step (1), a polylactic acid resin and an acrylic / styrene copolymer having an epoxy group are mixed to prepare a mixture. Here, the carboxyl group terminal density | concentration of the obtained mixture is 20 mmol / kg or less, It is characterized by the above-mentioned.

[Polylactic acid resin]
Examples of the polylactic acid resin include commercially available polylactic acid resins such as those manufactured by Nature Works: Nature Works PLA / 3001D, 4032D, 2500HP, and 3100HP, as well as polylactic acid resins synthesized from lactic acid and lactide. From the viewpoint of strength and transparency, a polylactic acid resin having an optical purity of 90% or more is preferable. For example, a polylactic acid resin (4032D, 2500HP, etc.) manufactured by Nature Works with a relatively high molecular weight and high optical purity is preferable.

  In the present invention, from the viewpoint of the strength and transparency of the polylactic acid resin composition, as the polylactic acid resin, a stereocomplex comprising two types of polylactic acid obtained by using lactic acid components mainly composed of different isomers. Polylactic acid resin may be used.

  In addition, the polylactic acid resin in the present invention may contain a biodegradable polyester resin other than the polylactic acid resin or a non-biodegradable resin such as polypropylene as a polymer alloy by blending with the polylactic acid resin. In the present specification, “biodegradable” means a property that can be decomposed into a low molecular weight compound by a microorganism in nature. Specifically, JIS K6953 (ISO 14855) “controlled aerobic composting conditions”. This means biodegradability based on the “Aerobic and Ultimate Biodegradation and Disintegration Test”.

  From the viewpoint of biodegradability, the content of the polylactic acid resin is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and more preferably 95% by mass or more in the polylactic acid resin composition. Even more preferred.

[Acrylic / styrene copolymer having epoxy group]
In the present invention, an acrylic / styrene copolymer having an epoxy group is used from the viewpoint of reactivity with a polylactic acid resin and from the viewpoint of suppression of die line generation (moldability). The epoxy group is preferably a glycidyl group from the viewpoint of ease of synthesis and economy. Specific examples of such compounds include “JONCRYL ADR4370S” (glycidyl group-containing acrylic / styrene copolymer, weight average molecular weight 6700, epoxy equivalent 285 g / mol) manufactured by BASF, “JONCRYL ADR4368CS” (glycidyl group-containing acrylic). / Styrene copolymer, weight average molecular weight 6700, epoxy equivalent 285 g / mol), “JONCRYL ADR4368F” (glycidyl group-containing acrylic / styrene copolymer, weight average molecular weight 6700, epoxy equivalent 285 g / mol), “JONCRYL ADR4300S "(Glycidyl group-containing acrylic / styrene copolymer, weight average molecular weight 5500, epoxy equivalent 445 g / mol)," ARUFON UG4035 "manufactured by Toa Gosei Co., Ltd. (glycidyl group-containing acrylic / Tylene copolymer, weight average molecular weight 11000, epoxy equivalent 556 g / mol), “ARUFON UG4040” (glycidyl group-containing acrylic / styrene copolymer, weight average molecular weight 11000, epoxy equivalent 480 g / mol), “ARUFON UG4070” (Glycidyl group-containing acrylic / styrene copolymer, weight average molecular weight 9700, epoxy equivalent 714 g / mol). These can be used alone or in combination of two or more.

  The weight average molecular weight of the acrylic / styrene copolymer having an epoxy group is preferably 4,000 or more, more preferably 5,000 or more, and 6,000 from the viewpoints of suppression of die line generation, durability, and thermal stability. The above is more preferable, 15,000 or less is preferable, 12,000 or less is more preferable, and 8,000 or less is more preferable. In the present specification, the weight average molecular weight of the acrylic / styrene copolymer having an epoxy group can be measured according to a known measurement method, for example, the GPC method.

  The epoxy equivalent of the acrylic / styrene copolymer having an epoxy group is preferably 50 g / mol or more, more preferably 100 g / mol or more, and 200 g / mol or more from the viewpoints of suppression of die line generation, durability, and thermal stability. Is more preferably 1,000 g / mol or less, more preferably 800 g / mol or less, still more preferably 600 g / mol or less, and even more preferably 400 g / mol or less. In the present specification, the epoxy equivalent of the acrylic / styrene copolymer having an epoxy group can be measured according to a known measuring method, for example, potentiometric titration.

  The content of the copolymer is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, with respect to 100 parts by mass of the polylactic acid resin, from the viewpoint of suppression of die line generation and durability. .3 parts by mass or more is more preferable, 1.0 part by mass or more is further more preferable, and from the viewpoint of thermal stability, 5.0 parts by mass or less is preferable, 3.0 parts by mass or less is more preferable, and 1.5 parts by mass. Part or less is more preferable, and 0.8 part by mass or less is even more preferable.

(Mixing method)
In the step (1), the raw materials mentioned above are mixed, but the mixing method is not particularly limited and can be performed by a usual method. Examples thereof include a melt-kneading method in which an acrylic / styrene copolymer having an epoxy group and other components described later are mixed as necessary while melting a polylactic acid resin using an extruder or the like. In addition, the raw materials can be subjected to melt kneading after being uniformly mixed in advance using a Henschel mixer, a super mixer, or the like.

(Mixer)
As the mixer used in the step (1), for example, a known melt kneader such as a closed kneader, a single or twin screw extruder, an open roll type kneader, and the like can be used. From the viewpoints of generation suppression, durability, and thermal stability, a single-screw or twin-screw extruder is preferable, and a twin-screw extruder is more preferable.

(Mixing temperature)
For example, when melt-kneading using an extruder, the mixing temperature is preferably 200 ° C. or higher when the discharge rate is less than 40 kg / h from the viewpoint of suppression of die line generation, durability, and thermal stability. The temperature is preferably 250 ° C. or lower, more preferably 230 ° C. or lower, and still more preferably 210 ° C. or lower. When the discharge rate is 40 kg / h or more and less than 160 kg / h, the resin temperature is preferably 220 ° C. or more, more preferably 230 ° C. or more, further preferably 240 ° C. or more, preferably 280 ° C. or less, more preferably Is 270 ° C. or lower, more preferably 260 ° C. or lower. When the discharge rate is 160 kg / h or more, the resin temperature is preferably 230 ° C. or more, more preferably 240 ° C. or more, further preferably 250 ° C. or more, preferably 280 ° C. or less, more preferably 270 ° C. or less. It is. In this specification, the resin temperature is the resin temperature in the barrel, exhibits the same temperature as the barrel set temperature, and can be actually measured by a contact thermometer.

(Mixing time)
The mixing time depends on the resin temperature at the time of mixing, but is preferably 10 seconds or longer, more preferably 20 seconds or longer, still more preferably 30 seconds or longer, from the viewpoint of die line generation suppression and durability, and heat stability. From the viewpoint of property, it is preferably 100 seconds or shorter, more preferably 70 seconds or shorter, and even more preferably 50 seconds or shorter.

  The mixture thus obtained has a carboxyl group terminal concentration of 20 mmol / kg or less, but preferably 19 mmol / kg or less, more preferably 18 mmol / kg or less, from the viewpoint of suppression of die line generation, durability, and thermal stability. More preferably, it is 17 mmol / kg or less, preferably 8 mmol / kg or more, more preferably 10 mmol / kg or more, still more preferably 12 mmol / kg or more. In order for the carboxyl group terminal concentration to be 20 mmol / kg or less, it can be adjusted by adjusting the resin temperature at the time of mixing and the mixing time (the length of the kneading part and the discharge amount). In this specification, carboxyl group terminal concentration can be measured in accordance with the method as described in the below-mentioned Example.

<Process (2)>
In step (2), a carbodiimide compound is further mixed with the mixture obtained in step (1).

[Carbodiimide compound]
Examples of the carbodiimide compound include a polycarbodiimide compound and a monocarbodiimide compound.

  As monocarbodiimide compounds, diphenylcarbodiimide, di-2,6-dimethylphenylcarbodiimide, di-2,6-diethylphenylcarbodiimide, di-2,6-diisopropylphenylcarbodiimide, di-2,6-ditert-butylphenyl Carbodiimide, di-o-tolylcarbodiimide, di-p-tolylcarbodiimide, di-2,4,6-trimethylphenylcarbodiimide, di-2,4,6-triisopropylphenylcarbodiimide, di-2,4,6-tri Aromatic monocarbodiimide compounds such as isobutylphenylcarbodiimide; Alicyclic monocarbodiimide compounds such as di-cyclohexylcarbodiimide and di-cyclohexylmethanecarbodiimide; Di-isopropylcarbodiimide and di-octadecylcar Aliphatic mono carbodiimide compounds such diimide, and the like.

  Specific examples of the polycarbodiimide include poly (4,4′-diphenylmethanecarbodiimide), poly (p-phenylenecarbodiimide), poly (m-phenylenecarbodiimide), poly (diisopropylphenylcarbodiimide), and poly (triisopropylphenylcarbodiimide). ) And other alicyclic polycarbodiimides such as poly (dicyclohexylmethanecarbodiimide).

  You may use the said carbodiimide compound individually or in combination of 2 or more types. Among these, di-2,6-diisopropylphenylcarbodiimide and poly (dicyclohexylmethanecarbodiimide) are preferable from the viewpoint of suppression of die line generation, durability, and thermal stability, and di-2 is preferable from the viewpoint of thermal stability. More preferred is 6,6-diisopropylphenylcarbodiimide.

  The content of the carbodiimide compound is preferably 0.05 parts by mass or more, more preferably 0.1 parts by mass or more, with respect to 100 parts by mass of the polylactic acid resin, from the viewpoint of suppressing the occurrence of die lines and durability. More preferred are parts by mass or more, even more preferred are 1.0 parts by mass or more, and from the viewpoint of thermal stability, 5.0 parts by mass or less are preferred, 3.0 parts by mass or less are more preferred, and 1.5 parts by mass or less. Is more preferable, and 0.8 mass part or less is still more preferable. In addition, when using two or more carbodiimide compounds, the total usage-amount is meant.

  Moreover, the mass ratio of the acrylic / styrene copolymer having an epoxy group and the carbodiimide compound (copolymer / carbodiimide compound) is 0.25 to 4 from the viewpoint of suppression of die line generation, durability, and thermal stability. Is preferable, 0.5-2 is more preferable, and 0.75-1.25 is still more preferable.

  In the present invention, the above components are used, but as long as the effects of the present invention are not impaired, other components than the above include plasticizers, hydrolysis inhibitors, lubricants, crystal nucleating agents (organic crystal nucleating agents, inorganic Crystal nucleating agent), filler (inorganic filler, organic filler), flame retardant, antioxidant, ultraviolet absorber, antistatic agent, antifogging agent, light stabilizer, pigment, antifungal agent, antibacterial agent, foaming An agent or the like can be used. Similarly, other polymer materials and other resin compositions can be used as long as the effects of the present invention are not impaired. These components may be used in either step (1) or step (2). Moreover, the amount of use can also be set suitably according to a well-known technique.

(Mixing method)
In the step (2), the carbodiimide compound is mixed with the mixture obtained in the step (1), but the mixing method is not particularly limited and can be performed by a usual method. Examples thereof include a melt-kneading method in which a carbodiimide compound and, if necessary, other components are mixed while melting the mixture obtained in step (1) using an extruder or the like.

(Mixer)
The mixer used in step (2) is not particularly limited as long as the components can be mixed, and the same mixer as used in step (1) can be used.

(Mixing temperature)
For example, when melt-kneading using an extruder, the mixing temperature is preferably 160 ° C. or higher, more preferably 170 ° C. or higher, and more preferably 170 ° C. or higher, from the viewpoint of suppression of die line generation, durability, and thermal stability. Is a temperature of 175 ° C or higher, preferably 220 ° C or lower, more preferably 200 ° C or lower, still more preferably 190 ° C or lower, and even more preferably 185 ° C or lower.

(Mixing time)
The mixing time depends on the resin temperature at the time of mixing, but is preferably 5 seconds or more, more preferably 10 seconds or more, still more preferably 20 seconds or more, and thermal stability from the viewpoint of suppression of die line generation and durability. From the viewpoint of properties, it is preferably 70 seconds or shorter, more preferably 50 seconds or shorter, and further preferably 30 seconds or shorter.

  In addition, you may dry the obtained melt-kneaded material according to a well-known method.

  Thus, the polylactic acid resin composition in the present invention is obtained. The carboxyl group in the obtained polylactic acid resin composition is one in which end-capping with both an acrylic / styrene copolymer having an epoxy group and a carbodiimide compound has been sufficiently performed, suppressing the occurrence of die line, durability, and From the viewpoint of thermal stability, the carboxyl terminal concentration is preferably 5 mmol / kg or less, more preferably 3 mmol / kg or less, and from the viewpoint of suppression of die line generation and durability, preferably 2 mmol / kg or less, more preferably 1 mmol. / Kg or less.

  In addition, the swell ratio of the obtained polylactic acid resin composition is preferably 1.10 or more, more preferably 1.15 or more, and further preferably 1.20 or more, from the viewpoint of suppression of die line generation, and is economical. From this viewpoint, it is preferably 1.50 or less, more preferably 1.40 or less, and still more preferably 1.30 or less. In the present specification, the swell ratio is an index of the size of the die swell, and means that the larger the expansion, the larger the expansion at the outlet of the extrusion port, and it should be measured according to the method described in the examples below. Can do.

  In addition, the YI value of the obtained polylactic acid resin composition is preferably 1.0 or more, more preferably 1.5 or more, still more preferably 2.0 or more, from the viewpoint of productivity. From the viewpoint, it is preferably 7.0 or less, more preferably 6.5 or less, and still more preferably 6.0 or less. In addition, in this specification, YI value can be measured in accordance with the method as described in the below-mentioned Example.

  Since the obtained polylactic acid resin composition is excellent in secondary processability such as thermoformability, it is filled in an extruder, melted, and then extruded from a T-die to form a sheet-like molded body. The extruded sheet-like molded article can be immediately brought into contact with a cooling roll and then a heating roll to adjust the crystallinity of the sheet, and then cut into a sheet-like molded article.

The obtained sheet-like molded article is excellent in transparency, and has excellent durability and thermal stability. Therefore, as a packaging material for various uses such as daily necessities, cosmetics, and home appliances, blister packs, trays, lunch boxes, etc. Can be thermoformed into food containers such as lids, industrial trays used for transportation and protection of industrial parts, and the like. You may crystallize in the case of thermoforming. In the present specification, crystallization means a state of high crystallinity in which the relative crystallinity obtained by the following formula is preferably 80% or more, more preferably 90% or more.
Relative crystallinity (%) = {(ΔHm−ΔHcc) / ΔHm} × 100
Specifically, the relative crystallinity was raised from 25 ° C. to 200 ° C. at a rate of temperature increase of 15 ° C./min using a DSC apparatus (diamond DSC manufactured by PerkinElmer Co., Ltd.) at a rate of temperature increase of 15 ° C./min. After being held, the temperature was lowered from 200 ° C. to 25 ° C. at a temperature drop rate of −500 ° C./min, held at 25 ° C. for 1 minute, and further increased from 25 ° C. to 200 ° C. at a temperature rising rate of 15 ° C./min as 2ndRUN. The absolute value ΔHcc of the cold crystallization enthalpy of the polylactic acid resin observed at 1st RUN and the crystal melting enthalpy ΔHm observed at 2nd RUN can be used.

  Moreover, the following are mentioned as an apparatus suitable for using for the manufacturing method of this invention.

  Specifically, for example, an apparatus suitable for performing the step (1) is an extruder having a barrel and a screw having an outer diameter of D (mm) inserted through the barrel. Along with the longitudinal direction of the machine, at least one raw material supply port a and a kneading part a are provided in this order, and the kneading part a has a length of at least 20 D (mm) or more and the kneading part a is located. An extruder in which the set temperature of the barrel is 200 ° C. or higher and 280 ° C. or lower is exemplified. That is, when compared with the steps in the production method of the present invention, a raw material containing a polylactic acid resin and an acrylic / styrene copolymer having an epoxy group is supplied from a raw material supply port a, and the raw materials are mixed in a kneading part a. This is an apparatus for preparing a mixture (melt kneaded product). In the present specification, an apparatus suitable for performing the step (1) may be referred to as an apparatus (1).

  An apparatus suitable for carrying out the step (2) is an extruder having a barrel and a screw having an outer diameter of D (mm) inserted through the barrel, in the longitudinal direction of the extruder. And at least the raw material supply port b and the kneading part b in this order, and the length of the kneading part b is at least 10 D (mm) or more, and the set temperature of the barrel where the kneading part b is located is 160 ° C. or more. An extruder having a temperature of 220 ° C. or lower is used. That is, when compared with the steps in the production method of the present invention, the carbodiimide compound is supplied from the raw material supply port b, and the mixture obtained in step (1) and the carbodiimide compound are mixed in the kneading part b to obtain a melt-kneaded product. It is a device to prepare. In this specification, an apparatus suitable for performing the step (2) may be referred to as an apparatus (2).

  In the present invention, a raw material containing a polylactic acid resin and an acrylic / styrene copolymer having an epoxy group is introduced from a raw material supply port a, and they are mixed in a kneading part a, and carbodiimide is supplied from the raw material supply port b. If the compound is charged and the mixture obtained in the kneading part a and the carbodiimide compound can be mixed in the kneading part b, the apparatus used in the step (1) and the apparatus used in the process (2) are continuous. A device having the above structure may be used, or a separate device may be used.

  The barrels of the device (1) and the device (2) can be of a known shape, and may have the same shape or different shapes. Also, the number is not particularly limited, and it is preferable that the temperature of each barrel can be set independently.

  The screw in the device (1) and the device (2) is not particularly limited as long as it is inserted through the barrel and has a kneading section described later, and may be the same or different. As the screw shape, a known one can be used, and the screw outer diameter D (mm) is preferably 10 from the viewpoint of die line generation suppression, durability, thermal stability, and productivity. A screw of ˜80 mm, more preferably 15 to 70 mm, and still more preferably 20 to 60 mm is mentioned. Moreover, the discharge amount of the kneaded product extruded by the screw depends on the resin temperature at the time of mixing, but preferably 5 kg from the viewpoints of suppression of die line generation, durability, thermal stability, and productivity. / H to 400 kg / h, more preferably 10 kg / h to 320 kg / h, still more preferably 20 kg / h to 300 kg / h, even more preferably 30 kg / h to 200 kg / h, still more preferably 50 kg / H to 200 kg / h.

  The total length L (mm) of the screw is calculated using the screw outer diameter D (mm), L / D, in terms of suppression of die line generation, durability, thermal stability, and productivity. Preferably, the length satisfies the relationship of 20 to 100, more preferably 30 to 90, still more preferably 35 to 80, and still more preferably 40 to 70, and has a length that allows the screw to be driven to perform melt kneading. If there is no particular limitation. The total length of the device (1) and the device (2) may be the same or different.

  Further, the kneading part is not particularly limited, and a known part, for example, a kneading disk can be used. Kneading with the kneading disk is performed with a clearance between the flight top of the disk mounted perpendicular to the screw shaft and the inner wall of the barrel. In the present invention, the kneading disk has a size corresponding to the outer diameter D (mm) of the screw. The shape of the disc is not limited. The kneading sections in the apparatus (1) and the apparatus (2) may be the same or different.

  The installation location of the raw material supply port a in the apparatus (1) is, for example, a position that is 0D (mm) of the outer diameter D (mm) of the screw when starting from the opposite end of the kneaded product discharge port of the extruder. preferable. When there are a plurality of raw material supply ports a, the interval is not particularly limited, and the raw material, that is, a position where a polylactic acid resin and an acrylic / styrene copolymer having an epoxy group can be charged so as to be kneaded in the kneading part a The supply port for the polylactic acid resin and the supply port for the acrylic / styrene copolymer having an epoxy group may be the same or different. In addition, as for the barrel in which the raw material supply port a exists, temperature is set to 10-30 degreeC, for example, and there is no limitation in particular as a shape of a supply port, A well-known thing can be used.

  The length of the kneading part a in the apparatus (1) is preferably 15D or more, more preferably 20D or more, further preferably 25D or more when the discharge amount is less than 40 kg / h, using the screw outer diameter D (mm) as an index. It is preferably 45D or less, more preferably 40D or less, still more preferably 35D or less. When the discharge rate is 40 kg / h or more and less than 160 kg / h, it is preferably 20D or more, more preferably 24D or more, still more preferably 28D or more, preferably 50D or less, more preferably 45D or less, still more preferably 38D or less. is there. When the discharge rate is 160 kg / h or more, it is preferably 25D or more, more preferably 28D or more, further preferably 30D or more, preferably 65D or less, more preferably 50D or less, and further preferably 40D or less.

  What is necessary is just to set the preset temperature of the kneading part a in an apparatus (1) similarly to the mixing temperature of the above-mentioned process (1).

  For example, when the starting point of the raw material supply port b in the apparatus (2) starts from the opposite end of the kneaded product discharge port of the extruder, it is possible to suppress the occurrence of die line, durability, thermal stability, and productivity. From the viewpoint of the above, the position of 0D to 50D (mm) of the outer diameter D (mm) of the screw is preferable. When there are a plurality of raw material supply ports b, the interval is not particularly limited as long as the raw material can be charged so that the raw material can be kneaded in the kneading part b. The temperature of the barrel in which the raw material supply port b exists is set to 160 to 220 ° C., for example, and the shape of the supply port is not particularly limited, and a known one can be used. In addition, when using an apparatus having a structure in which the apparatus (1) and the apparatus (2) are continuous, the installation location of the raw material supply port b is installed closer to the kneaded product outlet than the kneading part a in the apparatus (1). For example, when the opposite end of the kneaded product discharge port of the extruder is used as the starting point, the overall view of the die line suppression, durability, thermal stability, and productivity can be summarized as follows. A position that exceeds 20D (mm) of the diameter D (mm) and is 50 D (mm) or less is preferable, and a position that is 40 D (mm) or less is more preferable.

  The length of the kneading part b in the apparatus (2) is 10D (mm) when the screw outer diameter D (mm) is used as an index and the die line generation suppression, durability, thermal stability viewpoint and productivity viewpoint are combined. ) Or more, preferably 12 D (mm) or more, more preferably 15 D (mm) or more, preferably 40 D (mm) or less, more preferably 30 D (mm) or less, and even more preferably 20 D (mm) or less.

  What is necessary is just to set the preset temperature of the kneading part b in an apparatus (2) similarly to the mixing temperature of the above-mentioned process (2).

  As a commercially available product of an extruder suitably used in the present invention, a twin screw kneader (TEM-41SS, L / D = 60, D = 41, manufactured by Toshiba Machine), a twin screw kneader (TEX-28V, L / D) D = 42, D = 28, manufactured by Nippon Steel), twin-screw kneader (TEX-44αII, L / D = 52.5, D = 54, manufactured by Nippon Steel), twin-screw kneader (TEX-54αII, L / D = 52.5, D = 62, manufactured by Nippon Steel Works) and the like.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. The parts in the examples are parts by mass unless otherwise specified. “Normal pressure” indicates 101.3 kPa, and “normal temperature” indicates 25 ° C.

[Carboxyl group end concentration]
3 g of a sample is dissolved in 100 mL of chloroform, and 100 mL of benzyl alcohol and a small amount of phenol red are added thereto and titrated with a 0.02N potassium hydroxide ethanol solution. Here, chloroform is used as a solvent for dissolving the polylactic acid resin, 0.02N potassium hydroxide ethanol solution is used as a titration solvent, benzyl alcohol is used as a compatibilizing agent, and phenol red is used as an indicator.

Examples 1-15 and Comparative Examples 1-6
Preparation of polylactic acid resin composition As a polylactic acid resin composition, the composition raw materials shown in Tables 1 to 3 are melt-kneaded under the conditions shown in Tables 1 to 3 with the following twin screw extruder, and strand cutting is performed. The pellet of the polylactic acid resin composition was obtained. The obtained pellets were dried at 70 ° C. under reduced pressure for 1 day, and the water content was adjusted to 500 ppm or less. In Example 6, in step (1), the mixture was melt-kneaded using a biaxial kneader, and the obtained pellets were dried at 70 ° C. under reduced pressure for 1 day, so that the water content was 500 ppm or less. Thereafter, in the step (2), the mixture obtained in the step (1) was melt kneaded to obtain a polylactic acid resin composition.
In addition, the mixing time of process (1), (2) can be measured from the change of the color of resin using a colored pellet, for example.
Using this measurement method, the mixing time of Example 1 was measured and found to be 42 seconds in Step (1) and 23 seconds in Step (2).
<Twin screw extruder>
Examples 1-4, 8-15 and Comparative Examples 1-6
Twin screw kneader (TEM-41SS, L / D = 60, D = 41, manufactured by Toshiba Machine)
Example 5
Twin screw kneader (TEM-26SS, L / D = 60, D = 26, manufactured by Toshiba Machine)
Example 6
Twin-screw kneader (TEX-28V, L / D = 42, D = 28, manufactured by Nippon Steel Works)
Example 7
Twin-screw kneader (TEX-44αII, L / D = 52.5, D = 54, manufactured by Nippon Steel Works)

The obtained pellets or mixture was formed into a sheet having a width of 40 cm using a T-die extruder (500 mm T-die manufactured by Plastic Engineering Laboratory Co., Ltd.) under the following conditions.
<Extrusion conditions>
Cylinder temperature of biaxial kneading part: 180 ° C
T-die (outlet) temperature: 180 ° C
Extrusion speed: 8 kg / h (speed at which the cooling roll contact time is 34 seconds)
Cooling roll surface temperature: 25 ° C
Heating roll surface temperature: 80 ° C

  The properties of the obtained pellets or sheet-like molded bodies were evaluated according to the methods of Test Examples 1 to 3 below. The results are shown in Tables 1-3. In addition, the presence or absence of die line generation at the time of sheet forming is visually evaluated, and “5” indicates that there is no die line (the number of die lines: 0), and there is almost no die line (the number of die lines: 1 to 5). “4”, “3” if there are a few die lines (number of die lines: 6 to 10), “2” if there are die lines (number of die lines: 11 to 20), The number: the number exceeding 20) was defined as “1”.

Test Example 1 <Durability>
The obtained sheet-like molded product is placed in a constant temperature and humidity machine (Platinum K series PL-3KPH, manufactured by Espec Co., Ltd.) at 80 ° C./75% RH. Measured. The longer the number of days, the better the durability.

Test Example 2 <Swell ratio>
The swell ratio of the obtained pellet was measured under the condition of 200 ° C./122 sec ⁻¹ using a capillograph (capillograph 1D, capillary diameter 1.0 mm, length 10 mm, manufactured by Toyo Seiki Seisakusho). A higher swell ratio indicates a better die line, preferably 1.10 or more, more preferably 1.15 or more, and still more preferably 1.20 or more.

Test Example 3 <Thermal stability>
The YI (Yellow Index) value of the obtained sheet-like molded product was measured with a color difference meter (SE2000, manufactured by Nippon Denshoku). It shows that it is excellent in thermal stability, so that a numerical value is low.

In addition, the raw material in Tables 1-3 is as follows.
[Polylactic acid resin]
NW4032D: Poly-L-lactic acid (optical purity 98.5%), manufactured by Nature Works [Epoxy group-containing acrylic / styrene copolymer]
Joncryl ADR4368CS: Glycidyl group-containing acrylic / styrene copolymer, Mw 6700, epoxy equivalent 285 g / mol, BASF ARUFON UG4040: Glycidyl group-containing acrylic / styrene copolymer, Mw 11000, epoxy equivalent 480 g / mol, Toagosei Co., Ltd. Manufactured [carbodiimide compound]
Carbodilite LA-1: Poly (dicyclohexylmethanecarbodiimide), isocyanate group content 2%, Nisshinbo Chemical Co. Bioadmid 100: Di-2,6-diisopropylphenylcarbodiimide, Rhein Chemie Carbodilite HMV15CA: Poly (dicyclohexylmethanecarbodiimide), isocyanate group 0% content, manufactured by Nisshinbo Chemical Co., Ltd.

  From the results of Tables 1 to 3, the polylactic acid resin composition prepared by the production method of the present invention is excellent in durability and thermal stability, and is excellent in that the generation of die lines is suppressed. I understand that.

  The polylactic acid resin composition obtained by the production method of the present invention can be suitably used for various applications such as food containers, packaging materials for daily necessities and home appliances, and trays for industrial parts.

Claims (5)

A method for producing a polylactic acid resin composition comprising a polylactic acid resin, an acrylic / styrene copolymer having an epoxy group, and a carbodiimide compound, wherein the production method comprises step (1): a polylactic acid resin and an epoxy group Step (2) of preparing a mixture by mixing an acrylic / styrene copolymer: The step obtained by step (1) includes a step of further mixing a carbodiimide compound with the mixture obtained in step (1). The manufacturing method of the polylactic acid resin composition whose carboxyl group terminal density | concentration of a mixture is 20 mmol / kg or less.   The manufacturing method of Claim 1 whose content of the acrylic / styrene copolymer which has an epoxy group is 0.05 to 5.0 mass parts with respect to 100 mass parts of polylactic acid resin.   The manufacturing method of Claim 1 or 2 whose content of a carbodiimide compound is 0.05 to 5.0 mass parts with respect to 100 mass parts of polylactic acid resin.   An extruder having a barrel and a screw having an outer diameter of D (mm) inserted through the barrel, the acrylic / styrene copolymer having a polylactic acid resin and an epoxy group along the longitudinal direction of the extruder One or more raw material supply ports a for supplying raw materials including coalescence, kneading part a for mixing the raw materials to prepare a mixture, at least in this order, and the kneading part a having a length of at least 20 D (mm) The manufacturing method according to any one of claims 1 to 3, wherein step (1) is performed using an extruder in which the set temperature of the barrel where the kneading part a is located is 200 ° C or higher and 280 ° C or lower.   An extruder having a barrel and a screw having an outer diameter of D (mm) inserted into the barrel, and a raw material supply port b for supplying a carbodiimide compound along the longitudinal direction of the extruder, the carbodiimide compound And kneading part b for mixing the mixture obtained in step (1) in this order, and the length of kneading part b is at least 10 D (mm) or more, and the barrel where kneading part b is located The manufacturing method in any one of Claims 1-4 which perform a process (2) using the extruder whose preset temperature is 160 degreeC or more and 220 degrees C or less.