JP5301891B2 - Process for producing pellets from crystalline lactic acid-based polyester film and pellets obtained by the process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing pellets which are not brought into contact with water during a production process, suppress fusion, blocking and bleed-out and have a uniform size, no reduction in weight-average molecular weight and excellent flowability between particles from a crystalline lactic acid-based polyester film comprising a crystalline lactic acid-based polyester resin and a liquid plasticizer. <P>SOLUTION: The method for producing pellets from a crystalline lactic acid-based polyester film comprises (A) a process for grinding a film including a crystalline lactic acid-based polyester resin and a liquid plasticizer in the mass ratio of 70:30-95:5 and having a melting calorie of 10-55 mJ/mg, (B) a process for melting a film ground in a resin temperature range in which 15-99% of the area at the low-temperature side in a melting peak area of the film is melted and extruding the melt to form a strand, (C) a process for cutting the strand to give pellets and (D) a process for independently floating the pellets in an air flow and cooling them. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a method for producing a pellet from a crystalline lactic acid-based polyester film and a pellet obtained by the production method.

  The film recovery granulation technique is a useful technique for reducing raw materials used and waste in film formation. The main flow of general recovery granulation is to pulverize a film, melt-extrude the pulverized film as a strand, and cut this to obtain pellets. The performance required for pellets obtained by recovery granulation is that the pellets are not fused and blocked, the weight average molecular weight of the pellets does not decrease, the plasticizer contained in the pellets does not bleed out, and the size is uniform. There are some things.

As a method of cutting strands in typical recovery granulation, a strand cut method, an underwater cut method, a water-cooled hot cut method, and an air-cooled hot cut method are employed. Among these, in the strand cutting method, the underwater cutting method, and the water cooling cutting method, the strand or the pellet immediately after cutting comes into contact with water, so that the resulting pellet is rapidly cooled and the pellet surface is solidified. Therefore, the possibility that the pellets are fused due to the residual heat during extrusion is reduced.
Patent Documents 1 and 2 disclose a technique for cooling a strand with water to obtain pellets.

JP-A-7-1447 JP 2007-152760 A

  In the methods disclosed in Patent Documents 1 and 2, water and resin come into contact with each other in the production process. For example, when the resin is a biodegradable lactic acid-based polyester resin, the resulting pellets may undergo hydrolysis over time. There is sex. In these methods, it is necessary to apply tension to the strand. However, the crystalline lactic acid polyester resin softened with a plasticizer has a disadvantage that the melt tension is low and the strand is frequently cut. Furthermore, when the pellets are put into the dryer to dry the moisture adhering to the pellets or the moisture absorbed in the pellets, there is a problem that the pellets are blocked by the heat of the dry air.

  On the other hand, when pellets are obtained by the air-cooled hot cut method, the resin does not come into contact with water at all, so the obtained pellets are not likely to undergo hydrolysis, but the strands and pellets are not cooled with water. The possibility of causing fusion due to residual heat during extrusion increases. Also, the pellets obtained by this method may cause blocking when drying moisture absorbed by a dryer. Furthermore, since the crystalline lactic acid-based polyester softened with a plasticizer has a low melt tension, if the strand surface is not solidified with water, there is a high possibility that the pellet will have poor cutting properties. Therefore, there is no conventional production method for obtaining pellets that are not fused by air cooling from a crystalline lactic acid polyester resin softened with a plasticizer.

  The problem to be solved by the present invention is that a crystalline lactic acid-based polyester film containing a crystalline lactic acid-based polyester resin and a liquid plasticizer can be fused, blocked and bleed-out without contact with water during the production process. An object of the present invention is to provide a method for producing a pellet which is suppressed, has a uniform size, does not have a decrease in weight average molecular weight, and has good fluidity between particles.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors contain a crystalline lactic acid-based polyester resin and a liquid plasticizer in a mass ratio of 70:30 to 95: 5 and have a heat of fusion. In the crystalline lactic acid-based polyester film of 10 to 55 mJ / mg, the above-mentioned problem is obtained by combining a step of obtaining a strand by extruding in a specific temperature range and a step of obtaining a pellet by floating in an air stream and cooling. As a result, the present invention has been completed.

That is, this invention provides the pellet obtained by the method of manufacturing a pellet from the following crystalline lactic acid-type polyester films, and its manufacturing method.
[1]
A method for producing pellets from a crystalline lactic acid-based polyester film,
(A) a step of pulverizing the film containing a crystalline lactic acid polyester resin and a liquid plasticizer in a mass ratio of 70:30 to 95: 5 and having a heat of fusion of 10 to 55 mJ / mg;
(B) a step of melting and extruding a film pulverized in a resin temperature range in which an area of 15 to 99% on the low temperature side melts in the melting peak area of the film, and forming a strand;
(C) a step of cutting the strand to obtain a pellet;
(D) a step of cooling the pellets by independently floating them in an air stream;
Manufacturing method.
[2]
Said (C) is a manufacturing method as described in said [1] which is a process of blowing the air to the part to cut and cutting the said strand.
[3]
The production method according to [1] or [2], wherein (D) is a step of cooling in an air flow of 0 to 30 ° C.
[4]
Said (D) is a manufacturing method as described in any one of said [1]-[3] which is the process of making it float independently and cooling for 5 seconds or more.
[5]
The pellet obtained by the manufacturing method as described in any one of said [1]-[4].

  According to the present invention, a crystalline lactic acid-based polyester containing a crystalline lactic acid-based polyester resin and a liquid plasticizer in a mass ratio of 70:30 to 95: 5 and having a heat of fusion of 10 to 55 mJ / mg. From film, without contact with water during recovery granulation, fusion, blocking and bleed out of the obtained pellets are suppressed, the size is uniform, the weight average molecular weight does not decrease, and the flow between particles It is possible to provide a method for producing pellets with good properties.

  Hereinafter, the best mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

  The method for producing pellets from the crystalline lactic acid-based polyester film of the present embodiment includes (A) a crystalline lactic acid-based polyester resin and a liquid plasticizer in a mass ratio of 70:30 to 95: 5, and A step of pulverizing the film having a heat of fusion of 10 to 55 mJ / mg, (B) melting and extruding the pulverized film in a resin temperature range in which an area of 15 to 99% on the low temperature side melts in the melting peak area of the film Forming a strand, (C) cutting the strand to obtain a pellet, and (D) a step of cooling the pellet independently by floating in an air stream.

  The crystalline lactic acid-based polyester resin used in the present embodiment is a lactic acid-based polyester resin having a heat of fusion of 5 mJ / mg or more.

In the present embodiment, the heat of fusion means the heat of fusion in the DSC (Differential Scanning Calorimetry) method.
The amount of heat of fusion of the crystalline lactic acid-based polyester resin can be measured by using DSC (Seiko Electronics Co., Ltd., DSC22C system) for the sample resin. Specifically, the resin is finely cut and weighed to 5 mg in an aluminum pan, and is measured at 50 ° C./minute from 0 ° C. to about 200 ° C. (in the measurement of lactic acid polyester resin, the predicted value of the melting point of the resin + 50 ° C.) The temperature is raised, held for 1 min, then lowered to 0 ° C. at 50 ° C./min, held for 1 min, and then again raised to 200 ° C. at 10 ° C./min. The amount of heat indicated by the endothermic peak and the area surrounded by the base line (melting peak area) appearing in the second temperature raising process can be measured as the heat of fusion.

In the present embodiment, the crystalline lactic acid-based polyester resin is preferably a resin containing 70% by mass or more of the following polymers with respect to the entire resin in the composition.
Examples of the polymer include a polymer composed only of lactic acid, a polymer of lactic acid and an aliphatic hydroxycarboxylic acid, or a copolymer of a lactic acid polymer and an aliphatic diol-aliphatic carboxylic acid polymer.
There are no particular restrictions on the polymerization method, copolymerization ratio, structure and the like. Two or more of these polymers may be blended and used.
From the viewpoints of heat resistance and transparency, a resin containing 90% by mass or more of a polylactic acid resin, which is a polymer composed only of lactic acid, with respect to the entire crystalline lactic acid-based polyester resin is preferable. Examples of the polylactic acid resin include “Naturworks (registered trademark, the same applies hereinafter)” series of Cargill Dow.

  In this embodiment, the other component contained in the crystalline lactic acid-based polyester resin includes an aromatic polyester obtained by condensing an appropriate amount of an aromatic carboxylic acid to an aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic carboxylic acid. Aliphatic aliphatic polyesters, copolymers of ethylene and vinyl acetate, and other examples include carbodiimide compounds.

  In the present embodiment, the crystalline lactic acid-based polyester resin preferably has a melting point of 130 ° C. or higher from the viewpoint of heat resistance when a film is produced from the recovered pellets. The upper limit of the melting point is not particularly limited, but the melting point of the crystalline lactic acid polyester resin is preferably 250 ° C. or lower.

In the present embodiment, the melting point means the crystal melting peak temperature in the DSC (Differential Scanning Calorimetry) method.
Specifically, the melting point can be measured by using a DSC (manufactured by Seiko Electronics Co., Ltd., DSC22C system) as a sample resin. Specifically, the resin is finely cut and weighed to 5 mg in an aluminum pan, and is measured at 50 ° C./minute from 0 ° C. to about 200 ° C. (in the measurement of lactic acid polyester resin, the predicted value of the melting point of the resin + 50 ° C.). Increase the temperature, hold for 1 min, then decrease the temperature to 0 ° C. at 50 ° C./min, hold for 1 min, then increase the temperature again to 200 ° C. at 10 ° C./min, endotherm during this second temperature increase process The peak can be measured as the melting point.

The liquid plasticizer used in the present embodiment refers to a plasticizer having a melting point of 45 ° C. or lower. The liquid plasticizer can be appropriately selected from known plasticizers. The molecular weight is 200 to 2000 and / or the SP value is 6 to 13 (SP value is calculated by the following formula, SP value = dΣG / M d: density, G: mol so as to mix well with the crystalline lactic acid polyester resin. It is preferably a liquid plasticizer having a polar group containing a nitrogen atom or an oxygen atom, which is a traction force constant (M: molecular weight).
When the molecular weight is 200 or more, the plasticizer molecule is too small from the space between the polymer chains of the crystalline lactic acid-based polyester resin, and does not fall off. If the molecular weight is 2000 or less, the plasticizer molecule is too large between the polymer chains, so that it cannot enter.
If the SP value is in the range of 6 to 13, the SP value of the crystalline lactic acid-based polyester resin is close to that of the crystalline lactic acid-based polyester resin, so that it is well mixed with the crystalline lactic acid-based polyester resin.
It is preferable to have a polar group containing a nitrogen atom or an oxygen atom because the affinity with the polymer chain is increased.
Examples of the liquid plasticizer include glycerin fatty acid ester, citrate ester, and epoxidized vegetable oil. These may be used alone or in combination of two or more.
Since the crystalline lactic acid-based polyester resin is considered to be biodegradable, a liquid plasticizer having biodegradability is preferably used, preferably glycerin fatty acid ester or epoxidized vegetable oil.

The glycerin fatty acid ester is not particularly limited, and examples thereof include monoglyceride, diglyceride, triglyceride, acetylated monoglyceride, and polyglycerin fatty acid esters such as diglycerin, triglycerin, and tetraglycerin. Among them, acetylated monoglyceride is more preferable from the viewpoint of good compatibility with crystalline lactic acid-based polyester resin and high plasticizing ability, and more preferable is a mixture of glycerol monocaprylate acetate and glycerol monocaprate acetate (hereinafter abbreviated). It may be described as “DACG”). Specific examples of DACG include “Riquemar (registered trademark, the same shall apply hereinafter) PL019” (manufactured by Riken Vitamin Co., Ltd.).
Epoxidized vegetable oils include epoxidized soybean oil, epoxidized linseed oil, epoxidized tung oil, epoxidized castor oil, epoxidized safflower oil, etc. Among them, high stability and transparency of resin containing plasticizer From this point, epoxidized soybean oil (hereinafter sometimes abbreviated as “ESO”) is preferable. Specific examples of ESO include trade name “Newsizer (registered trademark, the same shall apply hereinafter) 510R” (manufactured by NOF Corporation).
Examples of the citrate ester include triethyl citrate, tributyl citrate, dibutyl acetyl citrate, tributyl acetyl citrate, among others, acetyl acetyl from the viewpoint of good compatibility with crystalline lactic acid polyester resin and high stability. Tributyl citrate (hereinafter sometimes abbreviated as “ATBC”) is preferred. Specific examples of ATBC include “ATBC” (manufactured by Asahi Kasei Finechem Co., Ltd.).

  The crystalline lactic acid-based polyester film (hereinafter sometimes abbreviated as “film”), which is a raw material for pellets in the present embodiment, has a mass ratio of 70 to 70%. : A film containing 30 to 95: 5 and having a heat of fusion of 10 to 55 mJ / mg. The film preferably has a performance of an adhesion work of 0.7 to 2.5 mJ. When the adhesion work amount is within the above range, the film has good adhesion to the surface, and therefore the film can be suitably used as food packaging or the like.

The mass ratio of the crystalline lactic acid-based polyester resin and the liquid plasticizer contained in the film is in the range of 70:30 to 95: 5.
If the ratio of the crystalline lactic acid-based polyester resin is higher than 70:30, the amount of the liquid plasticizer is not excessive with respect to the amount of the crystalline lactic acid-based polyester resin, so the crystalline lactic acid-based polyester resin and the liquid plasticizer are good. The film can be stably formed. Moreover, the problem that the bleedability of the obtained pellet does not occur does not occur.
If the ratio of the crystalline lactic acid-based polyester resin is lower than 95: 5, the amount of the liquid plasticizer is not excessively small relative to the amount of the crystalline lactic acid-based polyester resin, and the film can obtain appropriate flexibility. Film formation can also be performed stably.

The range of heat of fusion required for the film is 10 to 55 mJ / mg, preferably 20 to 55 mJ / mg.
If the heat of fusion is 10 mJ / mg or more, the degree of crystallinity of the film is high, so when the strand is extruded, the crystals that had the crystallized film before melting remain in the strand without completely disappearing. . If the crystal in the strand remains without disappearing, the crystal grows with this as a nucleus, so the crystallization speed of the pellet obtained by cutting the strand is fast, and the pellet immediately after cutting is difficult to fuse. Moreover, since the degree of crystallinity of the obtained pellet is high, it becomes difficult to block due to the outside temperature and humidity.
If the heat of fusion is 55 mJ / mg or less, the extrusion of the strand does not become unstable.

  The heat of fusion of the film can be measured using DSC (Seiko Electronics Co., Ltd., DSC22C system) for the sample film. Specifically, it can be measured by the method described in the following examples.

The melting point of the film is preferably higher than 140 ° C. from the viewpoint of heat resistance.
The melting point of the film can be measured by using a DSC (Seiko Electronics Co., Ltd., DSC22C system) as a sample film. Specifically, it can be measured by the method described in the following examples.

The film production apparatus is not particularly limited as long as it is a known apparatus. The film can be produced by a molding method such as a tenter molding method, an inflation molding method, or a T-die molding method.
In the present embodiment, for example, a so-called tenter trim portion pinched with a clip when stretched by a tenter molding method, or both ends of a bubble cut off when peeling a bubble folded by an inflation molding method one by one The folding part is also called a film.

  Other components contained in the film of the present embodiment include an aromatic aliphatic polyester obtained by copolymerizing an aliphatic polyester obtained by condensing an aliphatic diol and an aliphatic carboxylic acid with an appropriate amount of an aromatic carboxylic acid, ethylene And vinyl acetate copolymer, and other examples include carbodiimide compounds.

(A) Step of crushing film In the present embodiment, the step of crushing the film is a step of finely cutting the film. The extruder screw can be stably supplied to the extruder by finely cutting a film including a tenter trim portion, which is a raw material for pellets, and folding portions at both ends of the bubble. In order to cut the film, it is pulverized using a plurality of steps as necessary. As a method of pulverizing the film, a method of pulverizing by combining pulverizers having different mesh sizes is used. For example, when using an apparatus in which a pulverizer and an extruder are integrated (hereinafter sometimes referred to as “pulverization granulator”), including the pulverizer of the pulverization granulator, It is preferable to grind in a two-stage process. Examples of the pulverizing granulator include a granulator manufactured by EREMA Co., Ltd., an agglomerator KAG500, and the like.

  The agglomerator KAG500 is a device that has both a unit for crushing a loaded film with two rotary blades and a unit for extruding the pulverized material into strands and cutting them into pellets with the rotary blades. However, if the film is pulverized with only two rotary blades, it takes a long time, the temperature in the pulverizer rises due to the shear heat of the film and the rotary blade, and the film may melt in the pulverizer. Further, if the film is directly fed into the pulverizer, clogging occurs in the pulverizer, and the film may not be able to contact the rotary blade. Therefore, it is more preferable to use a plurality of pulverizers in combination with a pulverizer.

  When the agglomerator KAG500 is used, the size of the film pulverized product is defined by the maximum length in the shape of the pulverized product entering the extruder. The maximum length of the pulverized film to be supplied when the strand is extruded is preferably 40 mm or less, more preferably 30 mm or less. If the maximum length is 40 mm or less, when the pulverized film is supplied to the extruder screw for recovery granulation, it can be smoothly supplied without clogging at the supply port.

(B) Step of forming a strand In the present embodiment, the step of forming a strand is a step of forming a strand that is a pellet precursor by melting and extruding the film pulverized in the step (A). . The resin temperature range required in the present embodiment is 15 to 99% on the low temperature side in the melting peak area of the film, preferably 40 to 95%, and more preferably 40 to 90%. Is the range that melts the area.

  In the present embodiment, the resin temperature range in which the area of 15 to 99% on the low temperature side in the melting peak area melts means the temperature range in the range shown in FIG. Then, the pulverized film is melted at a temperature within the temperature range. FIG. 1 is a diagram showing a resin temperature range in which an area of 15 to 99% on the low temperature side melts in the melting peak area.

In the present embodiment, the film is melted in a resin temperature range in which the area of 15 to 99% on the low temperature side melts in the melting peak area of the film, thereby forming a strand by extruding with the crystal nucleus remaining in the film. can do.
When the melting resin temperature range is 99% or less, all the crystals in the extruded strand are not lost. If this crystal remains in the strand without disappearing, the crystal grows with this as a nucleus, so the crystallization speed of the pellet obtained by cutting the strand is fast, and the pellets immediately after cutting are fused by the residual heat of extrusion. It becomes difficult to do. In addition, since the degree of crystallinity of the pellets increases, blocking becomes difficult even if the pellets that have been preheated and cooled during extrusion are heated again to the glass transition temperature or higher.
When the temperature range of the resin to be melted is 15% or more, the viscosity of the resin does not decrease excessively at the temperature of the resin, so that there is no problem that the screw is overloaded and the extruder stops.
In the present embodiment, the resin temperature range can be changed as appropriate depending on other additives and equipment conditions, but it is preferable to melt and extrude the film in a temperature range of about 140 to 150 ° C.

(C) The process of obtaining a pellet In this Embodiment, the process of obtaining a pellet is a process of cutting the strand extruded by the said process (B) with a rotary blade, and obtaining a pellet. The die for extruding the strand preferably has 4 to 10 holes of 3 to 8 mm. The diameter and number of the holes can be appropriately selected in consideration of the particle diameter of the obtained pellet. The strand is preferably cut with as few rotary blades as possible, and the rotational speed of the rotary blade is preferably high. This is to prevent the pellets from adhering to the rotating blade by centrifugal force by rotating the rotating blade at high speed.
The blade used for the rotary blade is preferably subjected to electroless nickel plating, more preferably, composite plating in which fine particles of Teflon are uniformly dispersed and co-deposited in electroless nickel, leaving a blade edge of 1 mm. Plating can prevent the cut pellets from adhering to the blade. The reason why plating is not performed with respect to 1 mm of the blade edge is that, when the blade edge is plated, the sharpness of the blade is deteriorated, resulting in a problem that the cutting property of the pellet is deteriorated.

In the present embodiment, when the strand extruded from the extruder is cut, it is preferable that air be blown onto the portion to be cut. The strand has a high residual heat immediately after being extruded from the extruder, and it is difficult to cut in that state. Therefore, the cutting property can be improved by blowing the cooled air to the portion to be cut. The range necessary for the temperature of the air to be blown is preferably 0 to 30 ° C, more preferably 0 to 20 ° C.
If the temperature of the air to be blown is within a range of 0 ° C. or higher, the surface of the die is not cooled by the blown air, so that the temperature can be adjusted well and the extrusion can be stably performed.
If the temperature of the air to be blown is within a range of 30 ° C. or less, the pellets have good cutability, so that the cut pellets adhere to the blade and then fuse with the cut pellets, or the cut pellet resin However, the problem that the pellet shape is deformed can be suppressed.

(D) Step of cooling pellets In the present embodiment, the step of cooling the pellets is independent so that the pellets immediately after being cut in the step (C) are not fused with other pellets in the air. It is a process of floating and cooling. It is preferable to maintain a state of floating independently for 5 seconds or more in the air flow. The pellet immediately after cutting the strand has a high residual heat, and if left in this state, the possibility of fusion increases. Therefore, it is more preferable to cool the pellet for 5 seconds or more in an air flow of 0 to 30 ° C.

Usually, in such a recovery granulation technique, strands or pellets immediately after cutting are rapidly cooled using a liquid medium such as water to prevent fusion due to residual heat immediately after extrusion.
In this embodiment, since extrusion is performed in a resin temperature range in which 15 to 99% of the DSC melting peak area of the pulverized product melts during extrusion, the crystals contained in the film are completely Will not disappear. Therefore, this crystal remains in the extruded strand and the cut pellet, and since crystallization proceeds with this as a nucleus during independent floating, compared with the case where the resin is extruded at a temperature at which the film crystal completely disappears, The pellet is rapidly crystallized, and the crystallization of the pellet surface is partially started immediately after the strand is cut. Therefore, it is possible to suppress fusion even if the pellets where residual heat remains are in contact with each other while they are floated independently in the air stream, and float independently in the air stream without using a liquid medium such as water. By doing so, it is possible to cool the pellet to a temperature at which it does not melt.

A preferred range for the temperature of the air in which the pellets float is from 0 to 30 ° C, more preferably from 0 to 20 ° C.
If the temperature of the air is in the range of 0 ° C. or higher, the pellets are overcooled, and the problem of dew condensation hardly occurs.
If the temperature of the air is within a range of 30 ° C. or lower, the problem of fusion can be suppressed because the pellets are sufficiently cooled.

The range of time required for floating the pellet is preferably 5 seconds or more, more preferably 5 to 60 seconds, and further preferably 10 to 40 seconds.
If the floating time is within the range of 5 seconds or more, the pellets are sufficiently cooled, so that the problem of fusion can be sufficiently suppressed.
If the floating time is in the range of 60 seconds or less, it is more preferable because the pellet is overcooled and the problem of dew condensation does not occur.

In this Embodiment, the size of a pellet should just follow the size of the pellet generally used practically, Preferably the maximum length of a pellet is 3-14 mm, More preferably, it is 5-10 mm.
If the maximum length of the pellet is 3 mm or more, the pellet diameter will be too small, and the pellet will fly up in the air transportation pipe during air transportation to the molding machine, making it difficult to efficiently transport it, and poor mixing with other raw materials Is preferable.
If the maximum length of the pellet is 14 mm or less, it is preferable that the pellet is not clogged at the outlet of the hopper and the supply stability to the molding machine is not lost.

  According to the method for producing pellets from the film of the present embodiment, fusion, blocking and bleed out of the obtained pellets are suppressed and the size is uniform without contact with water during recovery granulation. In addition, pellets with no decrease in weight average molecular weight and good fluidity between particles can be obtained.

  According to the pellet manufacturing method of the present embodiment, a pellet with suppressed fusion can be obtained. However, depending on conditions, there is a case where a maximum of 15% by mass of pellets having a maximum length exceeding 14 mm is melted by the residual heat immediately after extrusion. In order to remove these pellets, it is more preferable to install a sieve having a mesh size of 10 mm on a container in which the pellets are stored.

In the present embodiment, the fusion is a pellet obtained by cutting the columnar strand extruded from the extruder, contacted immediately after the cut, lose the mutual interface due to the residual heat at the time of extrusion, the pellets are connected, It means a state where it cannot be broken down into individual pellets even if force is applied to the pellets again.
The state in which the pellets in the present embodiment are fused means a state in which two or more pellets are connected by the residual heat during extrusion, and the maximum length of the connected pellets exceeds 14 mm. It is defined as the arrival pellet.

  In the present embodiment, as a fusion index, the mass% of the fused pellets with respect to the total amount of the obtained pellets is measured. A preferable range of the mass% of the fusion pellet is 15 mass% or less, more preferably 10 mass% or less. If the mass percentage of the fusion pellet is 15 mass% or less, the raw material supply spots to the molding machine do not occur. Further, the pellets are not caught between the screw and the cylinder in the extruder, and cannot enter the groove of the screw well, so that the conveyance failure does not occur.

In the present embodiment, blocking means that pellets that have been preheated and cooled at the time of extrusion lose their interfaces due to the outside air temperature, humidity, and pellet weight, and the pellets are connected to each other. It means a state where it cannot be broken down into pellets.
The state in which the pellets in the present embodiment are blocking means a state in which two or more pellets are connected by the outside temperature, humidity, and the weight of the pellets, and the maximum length of the connected pellets exceeds 14 mm. Is defined as a blocking pellet.

  In this Embodiment, the mass% of the blocking pellet with respect to the obtained pellet whole quantity is measured as a parameter | index of blocking. A preferable range of the mass% of the blocking pellet is 15% by mass or less, and more preferably 10% by mass or less. Similarly to the case of fusion, if the mass% of the blocking pellet is 15 mass% or less, the raw material supply unevenness to the molding machine does not occur. Further, the pellets are not caught between the screw and the cylinder in the extruder, and cannot enter the groove of the screw well, so that the conveyance failure does not occur.

  In this Embodiment, the mass% and blocking mass% of a fusion | melting pellet can be calculated | required by the method as described in a following example.

  In the present embodiment, the bleed out amount is a measure of the amount of liquid additive coming out of the pellet surface. If the bleed-out amount is large, the pellet surface may become sticky and the fluidity of the pellet may be impaired. In the present embodiment, crystallization of pellets proceeds immediately after extrusion, and crystallization is almost finished when cooling of the residual heat is completed. Therefore, even when the pellet is in an atmosphere of a temperature of 40 ° C. and a humidity of 70% RH, bleeding out due to rapid crystallization tends to be suppressed.

  In the present embodiment, a preferable range of the bleed-out amount as a bleed index is 1000 ppm or less, more preferably 600 ppm or less at 40 ° C. for 14 days. If the amount of bleed-out is in the range of 1000 ppm or less, the fluidity of the pellet is good, and the pellet can be stably supplied to the molding machine. The bleed-out amount is measured after confirming that the temperature of the pellet obtained by cutting the strand is stabilized at 25 ° C. Pellets whose temperature was stabilized at 25 ° C. were allowed to stand for 14 days at a temperature of 40 ° C. and a humidity of 70% RH, and the amount of liquid plasticizer that bleeds from the pellet surface was measured.

  In the present embodiment, the bulk density is a value indicating the mass of pellets filled per unit volume. In this embodiment, it is used as a parameter indicating the degree of pellet fusion or blocking, and when the particle size of the pellet is uniform, it is also used as a parameter indicating the size of the particle size. When the pellets are fused or blocked, the number of pellets filled per unit volume is reduced, resulting in loose filling, and the bulk density tends to be reduced. In addition, when the size of the pellet is uniform, the smaller the pellet particle size, the larger the number of pellets filled per unit volume, resulting in dense packing. When the bulk density changes, the supply stability of the pellets to the molding machine is lost, and problems such as the resin extrusion amount becoming unstable occur.

In the present embodiment, the preferred range of the bulk density is 0.65 to 0.80 g / cm ³ , more preferably 0.70 to 0.80 g / cm ³ . When the bulk density is 0.65 g / cm ³ or more, pellets are not clogged at the outlet of the hopper, and supply stability to the molding machine is not lost. When the bulk density is 0.80 g / cm ³ or less, the pellet diameter does not become too small, and the pellets do not fly up in the air transportation pipe during air transportation to the molding machine, and can be efficiently transported. Moreover, when mixing and using with other raw materials, a raw material can be mixed uniformly.

In the present embodiment, the amount of decrease in the weight average molecular weight is a crystalline lactic acid polyester resin contained in a film before pulverization by gel permeation chromatography (hereinafter sometimes referred to as “GPC”). And the weight average molecular weight of the crystalline lactic acid-based polyester resin contained in the obtained pellet was measured, and the difference in the weight average molecular weight was calculated. Since heat is applied when forming a pellet from a film, the pellet has a thermal history once more than that of the film. Therefore, the pellet may have a weight average molecular weight lower than that of the film.
In this embodiment, in order to promote crystallization of pellets during recovery granulation, the resin temperature when granulating is set low so as not to lose all the crystals of the film pulverized product. For this reason, according to the method of this Embodiment, the fall of a weight average molecular weight tends to be suppressed.

  In the present embodiment, the preferred range of the weight average molecular weight reduction amount is 50,000 or less, more preferably 30,000 or less. When the decrease in weight average molecular weight is 50,000 or less, the crystalline lactic acid-based polyester resin contained in the pellet is hardly deteriorated compared to the pulverized film, and the film is formed again using the pellet. A film having the same physical properties can be obtained.

In this embodiment, the angle of repose is used as a parameter representing the fluidity between pellets. When the fluidity between the pellets deteriorates, problems such as hindering the supply stability to the molding machine occur. In the present embodiment, the shape of the pellet is not uneven, and the surface of the pellet is not uneven, and the bleed-out of the pellet surface is also suppressed, so that it tends to have an appropriate fluidity.
The angle of repose can be measured by the method described in the following examples.

  In the present embodiment, the preferred range of the angle of repose is 20 to 30 °. If the angle of repose is in the range of 20 ° or more, the slipping property between the pellets is not excessive, and the pellets can be stably supplied to the molding machine. If the angle of repose is within a range of 30 ° or less, the problem of poor fluidity of the pellet does not occur, and the pellet can be stably supplied to the molding machine.

  Hereinafter, the present embodiment will be described more specifically with reference to examples and comparative examples. However, the present embodiment is not limited to only these examples. The evaluation method and measurement method used in this embodiment are as follows.

  Table 1 shows the resin compositions of the films used in the examples and comparative examples.

＊１ 結晶性乳酸系ポリエステル樹脂１；結晶性ポリ乳酸樹脂（Ｄ体含量４質量％）、カーギル・ダウ社製、（商品名、Ｎａｔｕｒｅｗｏｒｋｓ ４０４２Ｄ）
＊２ 結晶性乳酸系ポリエステル樹脂２；結晶性ポリ乳酸樹脂（Ｄ体含量２質量％）、Ｄ４ＰＬＡ^*1とＤ１ＰＬＡ^*3を１：２の比でブレンドして調製した。
＊３ 結晶性乳酸系ポリエステル樹脂３；結晶性ポリ乳酸樹脂（Ｄ体含量１質量％）、カーギル・ダウ社製、（商品名、Ｎａｔｕｒｅｗｏｒｋｓ Ｈ４００）
＊４ 非結晶性乳酸系ポリエステル樹脂１；非結晶性ポリ乳酸樹脂（Ｄ体含量１２質量％）、カーギル・ダウ社製、（商品名、Ｎａｔｕｒｅｗｏｒｋｓ ４０６０Ｄ）
＊５ 非結晶性乳酸系ポリエステル樹脂２；非結晶性ポリ乳酸樹脂（Ｄ体含量１０質量％）、Ｄ１２ＰＬＡ^*4とＤ４ＰＬＡ^*1を３：１の比でブレンドして調製した。
＊６ 非結晶性乳酸系ポリエステル樹脂３；非結晶性ポリ乳酸樹脂（Ｄ体含量８質量％）、Ｄ１２ＰＬＡ^*4とＤ４ＰＬＡ^*1を１：１の比でブレンドして調製した。
＊７ 結晶性乳酸系ポリエステル樹脂４；乳酸系脂肪族ポリエステル樹脂、乳酸−セバシン酸−１，２プロパンジオール共重合体、大日本インキ化学（株）社製、（商品名、プラメート（登録商標）ＰＤ１５０）
＊８ 結晶性樹脂；エチル−ビニルアセテート（ＶＡ含量４６質量％）、三井・デュポンポリケミカル社製、（商品名、エバフレックス（登録商標）ＥＶ４５ＬＸ）
＊９ 非結晶性ポリエステル樹脂４；ポリブチレンアジペート／テレフタレート共重合体、ＢＡＳＦ社製、（商品名、エコフレックス（登録商標） ＦＢＸ７０１１）
＊１０ 液状可塑剤１；アセチル化モノグリセライド、理研ビタミン（株）社製、（商品名、リケマールＰＬ０１９）、融点 −９０℃
＊１１ 液状可塑剤２；アセチルクエン酸トリブチル、旭化成ファインケム（株）社製、（商品名、ＡＴＢＣ）、融点 −８０℃
＊１２ 液状可塑剤３；エポキシ化大豆油、日本油脂（株）社製、（商品名、ニューサイザー５１０Ｒ）、融点 約５℃

* 1 Crystalline lactic acid-based polyester resin 1; Crystalline polylactic acid resin (D-form content 4% by mass), manufactured by Cargill Dow, (trade name, Natureworks 4042D)
* 2 Crystalline lactic acid polyester resin 2; prepared by blending crystalline polylactic acid resin (D-form content 2% by mass), D4PLA ^{* 1} and D1PLA ^{* 3} in a ratio of 1: 2.
* 3 Crystalline lactic acid-based polyester resin 3; crystalline polylactic acid resin (D-form content: 1% by mass), manufactured by Cargill Dow, Inc. (trade name, Natureworks H400)
* 4 Amorphous lactic acid polyester resin 1; Amorphous polylactic acid resin (D-form content 12% by mass), manufactured by Cargill Dow, Inc. (trade name, Natureworks 4060D)
* 5 Amorphous lactic acid polyester resin 2; prepared by blending amorphous polylactic acid resin (D-form content 10% by mass), D12PLA ^{* 4} and D4PLA ^{* 1} at a ratio of 3: 1.
* 6 Amorphous lactic acid polyester resin 3; prepared by blending amorphous polylactic acid resin (D-form content 8 mass%), D12PLA ^{* 4} and D4PLA ^{* 1} at a ratio of 1: 1.
* 7 Crystalline lactic acid-based polyester resin 4; lactic acid-based aliphatic polyester resin, lactic acid-sebacic acid-1,2 propanediol copolymer, manufactured by Dainippon Ink & Chemicals, Inc. (trade name, Pramate (registered trademark) PD150)
* 8 Crystalline resin; ethyl-vinyl acetate (VA content 46% by mass), manufactured by Mitsui DuPont Polychemical Co., Ltd. (trade name, Everflex (registered trademark) EV45LX)
* 9 Amorphous polyester resin 4; polybutylene adipate / terephthalate copolymer, manufactured by BASF (trade name, Ecoflex (registered trademark) FBX7011)
* 10 Liquid plasticizer 1; acetylated monoglyceride, manufactured by Riken Vitamin Co., Ltd. (trade name, Riquemar PL019), melting point −90 ° C.
* 11 Liquid plasticizer 2; tributyl acetyl citrate, manufactured by Asahi Kasei Finechem Co., Ltd. (trade name, ATBC), melting point −80 ° C.
* 12 Liquid plasticizer 3: Epoxidized soybean oil, manufactured by Nippon Oil & Fats Co., Ltd. (trade name, Neusizer 510R), melting point: about 5 ° C.

(1) Heat of fusion, melting point The heat of fusion is the amount of heat that appears when a sample film is measured by DSC (DSC22C system, manufactured by Seiko Denshi Kogyo Co., Ltd.). The film was cut finely and weighed in 5 mg in an aluminum pan. The temperature was raised from 0 ° C. to 10 ° C./min. The amount of heat indicated by the melting peak area appearing in the temperature raising process was defined as the amount of heat of fusion. The endothermic peak was measured as the melting point (Tm).

(2) Melting peak area The melting peak area was defined as the area surrounded by the melting peak and the baseline.

(3) Angle of repose 200 g of pellets formed by cutting strands were transferred to a funnel having a discharge port with a diameter of 25 mm installed at a height of 10 cm from the floor surface in a state where the discharge port was closed. After all the pellets were transferred, the discharge port was opened and the pellets were dropped all at once, and the inclination angle of the pellet pile formed on the floor surface was measured.

(4) Bulk density The pellet was put into a 150 ml container until it was completely worn out, and the container was vibrated. Due to this vibration, the pellets were densely filled, so that a space for further pellets was created in the container. The operation of placing the pellets again in this space, vibrating the container, and placing the pellets in the empty space was repeated, and the pellets were filled up to the point where the container was completely worn out, leaving no space. The mass of the pellet filled to the point where the container was completely worn out was measured with a scale, and the bulk density was calculated by dividing the measured value by the volume of 150 ml.

(5) Amount of decrease in weight average molecular weight The film and the pellets obtained were each finely cut at room temperature, and 20 mg each was dissolved in 10 ml chloroform. Next, the obtained solution was filtered through a 0.45 μm filter made of PVDF to prepare a sample. The weight average molecular weight of this sample was measured using GPC (device: alliance 2695, detector: RI waters 2414, analytical column: LF-804 × 1, LF-G × 1). As measurement conditions, the temperature was 40 ° C., the flow rate was 1 ml / min, and the standard sample was polystyrene.
The difference in the weight average molecular weight between the film and the pellet was calculated as the amount of decrease in the weight average molecular weight.

(6) Mass% of fusion pellet
The mass% of the fused pellets with respect to the total amount of the pellets was measured as follows. In order to make it easy to distinguish 100 g of pellets made by cutting strands, place them on black paper, measure the pellets with a ruler, and connect two or more pellets to separate the fused pellets whose maximum length exceeds 14 mm did. The mass of the separated fused pellets was measured with a balance, and the mass% with respect to 100 g was determined by calculation.

(7) Mass% of blocking pellet
The mass% of the blocked pellets with respect to the total amount of the pellets was measured as follows. After removing the fused pellets from the pellets obtained by cutting the strands and stabilizing the temperature of the pellets at 25 ° C., 100 g of the pellets are placed in a cylindrical container with a radius of 25 mm, and a load of 10 g / cm ² from the top. And left in an atmosphere of 40 ° C. × 70% RH for 14 days. Then, in order to make it easy to distinguish, the pellet was placed on black paper, the pellet was measured with a ruler, two or more pellets were connected, and the connected pellets having a maximum length exceeding 14 mm were separated. The mass of the sorted pellet was measured with a balance, and the mass% with respect to 100 g was determined by calculation.

(8) Bleed-out amount After leaving 6 g of pellets with a stable temperature of 25 ° C. in an atmosphere of 40 ° C. and humidity 70% RH for 14 days, the amount of liquid plasticizer coming out of the pellet surface was quantified and put into pellets The mass% of the quantitative value with respect to the total amount of the liquid additive contained was calculated. Quantification of the amount of liquid plasticizer coming out of the pellet surface is performed by adding the pellet to methanol cooled to -78 ° C with dry ice, stirring and washing the pellet surface for 5 minutes, and adding the liquid contained in the methanol after washing The amount of the agent was measured using gas chromatography (apparatus: HP6890, manufactured by Agilent, analysis column: HP-1). As measurement conditions at this time, the analytical column temperature was raised from 180 ° C. to 300 ° C. at 10 ° C./min, the inlet temperature was 300 ° C., the detector temperature was 300 ° C., the injection volume was 2 μl, and the injection method was the split injection method (5: 1).

[Example 1]
The composition of A in Table 1 was sufficiently melt-kneaded by setting the resin temperature of the extruder kneading part to about 190 ° C. The liquid plasticizers DACG and ESO were injected from the liquid injection part provided in the cylinder of the extruder using a fixed liquid feed pump. The kneaded composition A was extruded as a resin composition from a T die provided at the tip of the extruder into a sheet. Next, an extruded sheet is led uniformly onto the roll surface having a mirror-finished smooth surface and placed on a cast roll having a surface temperature of 15 ° C. so that the roll surface is located within 3 mm from the die lip of the T die. This was rapidly cooled by contact.
Next, the sufficiently cooled extruded sheet was introduced into a roll type longitudinal stretching machine. The roll surface temperature in the stretching zone was 50 ° C., and the film was stretched 2.5 times in the machine direction due to the difference in rotational speed between the upstream and downstream rolls disposed in the stretching zone. The stretched film after the longitudinal stretching was immediately led to a cooling roll having a surface temperature of 15 ° C., and quickly cooled below the glass transition temperature. Thereafter, the stretched film was introduced into a tenter-type transverse stretching machine, stretched 4 times in the transverse direction at a stretching temperature of 55 ° C., and then continuously sent to the heat treatment step. This heat treatment step was performed by passing the film, which was tensioned in the vertical and horizontal directions, through a zone having an ambient temperature of 130 to 135 ° C. for about 8 seconds. Thus, a film of composition A having a DSC heat of fusion of 25 mJ / mg was obtained.

The portion of the film that had been chucked with the clips during transverse stretching was pulverized using a pulverizer manufactured by Horai Co., Ltd., a granulator manufactured by EREMA Co., Ltd., and an agglomerator KAG500. The size of the pulverized product was 60 mm or less at the maximum length after passing through a pulverizer manufactured by Horai Co., Ltd., and 30 mm or less after pulverization with an agglomerator KAG500. Next, the agglomerator KAG500 was used to extrude the pulverized film from a die having six holes with a diameter of 4 mm. The resin temperature at the time of extrusion was the resin temperature at which 50% melts in the melting peak area of the pulverized product. The number of revolutions of the extruder was 170 rpm with respect to the supply amount of the film ground product of 21 kg / h, and the agglomerator KAG500 was a single screw extruder (screw diameter: Φ37 mm, L / D = 10). Next, a 4 mm diameter strand extruded from the die was cut with a rotary blade to obtain a pellet. At this time, the speed of the rotary blade was 1420 rotations / min, and the blade was applied with a craniflon. Furthermore, the cooled air was sprayed on the part to be cut, and the pellets obtained by the cutting were floated independently in an air flow at 15 ° C. for 15 seconds.
The pellets thus obtained were measured for angle of repose, bulk density, weight average molecular weight reduction, fusion pellet mass%, blocking pellet mass%, and bleed-out amount. These results are shown in Table 2.

[Example 2]
A film having a composition B having a DSC heat of fusion of 28 mJ / mg was obtained in the same manner as in Example 1 except that the composition B was used in place of the composition A. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 49% melted in the DSC melting peak area of the pulverized product. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 3]
A film having a C composition having a DSC heat of fusion of 22 mJ / mg was obtained in the same manner as in Example 1 except that the composition C was used instead of the composition A. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 47% melts in the DSC melting peak area of the pulverized product. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 4]
A film having a composition D with a DSC heat of fusion of 30 mJ / mg was obtained in the same manner as in Example 1 except that the composition D was used in place of the composition A. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 52% melted in the DSC melting peak area of the pulverized product. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 5]
A composition E was used in place of the composition A, and a film having an E composition with a DSC heat of fusion of 35 mJ / mg was obtained in the same manner as in Example 1. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 45% melts in the DSC melting peak area of the pulverized product. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 6]
A composition F was used in place of the composition A, and a film having an F composition with a DSC heat of fusion of 22 mJ / mg was obtained in the same manner as in Example 1. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 50% melted in the DSC melting peak area of the pulverized product. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 7]
A film having a composition G having a DSC heat of fusion of 22 mJ / mg was obtained in the same manner as in Example 1 except that the composition G was used instead of the composition A. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 51% melts in the DSC melting peak area of the pulverized product. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 8]
The composition H was used in place of the composition A, and a film having an H composition with a DSC heat of fusion of 25 mJ / mg was obtained in the same manner as in Example 1. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 51% melts in the DSC melting peak area of the pulverized product. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 9]
Using composition I instead of composition A, a film of composition I having a DSC heat of fusion of 25 mJ / mg was obtained in the same manner as in Example 1. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 52% melted in the DSC melting peak area of the pulverized product. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 10]
Using composition A, a film of composition A having a DSC heat of fusion of 25 mJ / mg was obtained in the same manner as in Example 1. Using the same method as in Example 1 except for the temperature of the air blown at the time of cutting and the temperature of the air flow that floats the pellets immediately after cutting independently, granulate the chuck part of the clip in the obtained film. A pellet was obtained.
The temperature of the air sprayed at the time of cutting and the temperature of the air flow for independently floating the pellets immediately after the cutting were 10 ° C. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 11]
Using composition A, a film of composition A having a DSC heat of fusion of 25 mJ / mg was obtained in the same manner as in Example 1. Using the same method as in Example 1 except that air was not blown at the time of cutting, the chuck part of the clip of the obtained film was granulated to obtain pellets. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 12]
Using composition A, a film of composition A having a DSC heat of fusion of 25 mJ / mg was obtained in the same manner as in Example 1. Using the same method as in Example 1 except for the temperature of the air blown at the time of cutting and the temperature of the air flow that floats the pellets immediately after cutting independently, the chuck part of the clip is granulated in the obtained film. A pellet was obtained.
The temperature of the air sprayed at the time of cutting and the temperature of the air flow for independently floating the pellets immediately after the cutting were 20 ° C. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 13]
Using composition A, a film of composition A having a DSC heat of fusion of 25 mJ / mg was obtained in the same manner as in Example 1. Using the same method as in Example 1 except for the temperature of the air blown at the time of cutting and the temperature of the air flow that floats the pellets immediately after cutting independently, the chuck part of the clip is granulated in the obtained film. A pellet was obtained.
The temperature of the air blown at the time of cutting and the temperature of the air flow for independently floating the pellets immediately after the cutting were 35 ° C. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 14]
Using composition A, a film of composition A having a DSC heat of fusion of 25 mJ / mg was obtained in the same manner as in Example 1. Using the same method as in Example 1 except that the pellet immediately after cutting was floated independently in the air stream, the chuck part of the clip was granulated from the obtained film to obtain a pellet.
The time for the pellets immediately after cutting to float independently in the air stream was 3 seconds. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 15]
Using composition A, a film of composition A having a DSC heat of fusion of 25 mJ / mg was obtained in the same manner as in Example 1. Using the same method as in Example 1 except that the pellet immediately after cutting was floated independently in the air stream, the chuck part of the clip was granulated from the obtained film to obtain a pellet.
The time for the pellets immediately after cutting to float independently in the air stream was 10 seconds. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 16]
Using composition A, a film of composition A having a DSC heat of fusion of 25 mJ / mg was obtained in the same manner as in Example 1. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 70% melts in the DSC melting peak area of the pulverized product. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Example 17]
Using composition A, a film of composition A having a DSC heat of fusion of 25 mJ / mg was obtained in the same manner as in Example 1. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 90% was melted in the DSC melting peak area of the pulverized product. Table 2 shows the results obtained by performing the same measurements as in Example 1 on the obtained pellets.

[Comparative Example 1]
A composition J was used in place of the composition A, and a film of composition J having a DSC heat of fusion of 4 mJ / mg was obtained in the same manner as in Example 1. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 50% melted in the DSC melting peak area of the pulverized product. Table 3 shows the results obtained by performing the same measurement as in Example 1 on the obtained pellets.

[Comparative Example 2]
Using composition K instead of composition A, a film having a composition of K having a DSC heat of fusion of 7 mJ / mg was obtained in the same manner as in Example 1. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 40% melts in the DSC melting peak area of the pulverized product. Table 3 shows the results obtained by performing the same measurement as in Example 1 on the obtained pellets.

[Comparative Example 3]
A film having an L composition having a DSC heat of fusion of 9 mJ / mg was obtained in the same manner as in Example 1 except that the composition L was used in place of the composition A. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 40% melts in the DSC melting peak area of the pulverized product. Table 3 shows the results obtained by performing the same measurement as in Example 1 on the obtained pellets.

[Comparative Example 4]
A film having an M composition having a DSC heat of fusion of 19 mJ / mg was obtained in the same manner as in Example 1 except that the composition M was used in place of the composition A. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 45% melts in the DSC melting peak area of the pulverized product. Table 3 shows the results obtained by performing the same measurement as in Example 1 on the obtained pellets.

[Comparative Example 5]
Using composition A, a film of composition A having a DSC heat of fusion of 25 mJ / mg was obtained in the same manner as in Example 1. Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 100% melts in the melting peak area of the pulverized product. Table 3 shows the results obtained by performing the same measurement as in Example 1 on the obtained pellets.

[Comparative Example 6]
Using composition A, a film of composition A having a DSC heat of fusion of 5 mJ / mg was obtained in the same manner as in Example 1 except for the draw ratio. The draw ratio was 1.5 times in length and 1.2 times in width.
Except for the resin temperature at the time of extrusion, the same method as in Example 1 was used, and among the obtained films, the chuck portion of the clip was granulated to obtain pellets.
The resin temperature at the time of extrusion was a resin temperature at which 40% melts in the melting peak area of the pulverized product. Table 3 shows the results obtained by performing the same measurement as in Example 1 on the obtained pellets.

[Comparative Example 7]
Using composition A, a film of composition A having a DSC heat of fusion of 25 mJ / mg was obtained in the same manner as in Example 1. The portion of the film that had been chucked with the clips during transverse stretching was pulverized using a pulverizer manufactured by Horai Co., Ltd., a granulator manufactured by EREMA Co., Ltd., and an agglomerator KAG500.
Next, the pulverized film was extruded from a die having 6 holes of 4 mm in diameter using a single screw extruder. The resin temperature at the time of extrusion was the resin temperature at which 50% melts in the melting peak area of the pulverized product. The number of revolutions of the extruder was 170 rpm with respect to the supply amount of the pulverized film of 21 kg / h to obtain a strand. The obtained strand was led to a water bath having a water temperature of 25 ° C., cooled, and then cut to obtain pellets. Table 3 shows the results obtained by performing the same measurement as in Example 1 on the obtained pellets.

From the results of Tables 2 and 3, the pellets of Examples 1 to 17 obtained by the production method of the present embodiment are suppressed in fusion, blocking and bleed out, uniform in size, and weight average molecular weight. The pellets were good in fluidity between particles.
On the other hand, the pellets obtained by the production methods of Comparative Examples 1 to 3 and 6 using a film having a heat of fusion of less than 10 mJ / mg experienced fusion and blocking. In addition, pellets with non-uniform sizes were obtained because the angle of repose was large and the bulk density was sparse.
In the pellet obtained by the production method of Comparative Example 4 using a film having a smaller proportion of the crystalline lactic acid-based polyester resin than 70:30, the pellets were fused together and the liquid plasticizer in the pellets bleeded out. In addition, pellets with non-uniform sizes were obtained due to the large angle of repose. Furthermore, the weight average molecular weight in the pellet was lowered.
The pellets obtained by the production method of Comparative Example 5 melted and extruded at a resin temperature that melted in excess of 99% in the melting peak area were fused and blocked. In addition, pellets with non-uniform sizes were obtained because the angle of repose was large and the bulk density was sparse.
In the pellet obtained by the production method of Comparative Example 7 in which the cut pellet was cooled by water cooling, the crystalline lactic acid polyester resin was hydrolyzed and the weight average molecular weight in the pellet was greatly reduced. In addition, bleedout of the liquid plasticizer occurred more than the pellets obtained in Examples 1-15.

According to the present invention, a crystalline lactic acid-based polyester containing a crystalline lactic acid-based polyester resin and a liquid plasticizer in a mass ratio of 70:30 to 95: 5 and having a heat of fusion of 10 to 55 mJ / mg. From film, without contact with water during recovery granulation, fusion, blocking and bleed out of the obtained pellets are suppressed, the size is uniform, the weight average molecular weight does not decrease, and the flow between particles It is possible to provide a method for producing pellets with good properties.
And according to this invention, the collection | recovery granulation method useful for reduction of a raw material to be used and a waste can be provided.

In the melting peak area, a resin temperature range in which an area of 15 to 99% on the low temperature side melts is shown.

Claims (5)

A method for producing pellets from a crystalline lactic acid-based polyester film,
(A) a step of pulverizing the film containing a crystalline lactic acid polyester resin and a liquid plasticizer in a mass ratio of 70:30 to 95: 5 and having a heat of fusion of 10 to 55 mJ / mg;
(B) a step of melting and extruding a film pulverized in a resin temperature range in which an area of 15 to 99% on the low temperature side melts in the melting peak area of the film, and forming a strand;
(C) a step of cutting the strand to obtain a pellet;
(D) a step of cooling the pellets by independently floating them in an air stream;
Manufacturing method.   The manufacturing method according to claim 1, wherein (C) is a step of blowing the air to a portion to be cut to cut the strand.   The manufacturing method according to claim 1 or 2, wherein (D) is a step of cooling in an air stream of 0 to 30 ° C.   The manufacturing method according to any one of claims 1 to 3, wherein (D) is a step of independently floating and cooling for 5 seconds or more.   The pellet obtained by the manufacturing method as described in any one of Claims 1-4.

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