KR101804429B1 - Polylactic acid resin film - Google Patents

Abstract

The present invention relates to a poly (lactic acid) resin film which can be usefully used for packaging because it exhibits biodegradability peculiar to poly (lactic acid) resin, exhibits optimized physical properties such as excellent flexibility and mechanical properties.
Wherein the poly (lactic acid) resin film comprises a hard segment including a predetermined poly (lactic acid) repeating unit; And a soft segment including a polyurethane polyol repeating unit in which certain polyether polyol repeating units are linearly linked through a urethane bond, wherein a total Young's modulus in the longitudinal direction and in the width direction is from 350 to 750 kgf / Mm < 2 >, and the total initial tensile strength in the longitudinal direction and the width direction is not less than 20 kgf / mm < 2 >.

Description

[0001] POLYLACTIC ACID RESIN FILM [0002]

The present invention relates to a poly (lactic acid) resin film. More specifically, the present invention relates to a poly (lactic acid) resin film which can be usefully used for packaging because it exhibits biodegradability peculiar to poly (lactic acid) resin, exhibits optimized physical properties such as excellent flexibility and mechanical properties.

Crude oil-based resins such as polyethylene terephthalate, nylon, polyolefin, or flexible polyvinyl chloride (PVC) are still widely used as materials for various applications such as packaging materials. However, such a crude oil-based resin has no biodegradability and thus has a problem of causing environmental pollution such as discharging a large amount of carbon dioxide, which is a global warming gas, during disposal. In addition, as the petroleum resources are gradually getting depleted, the use of biomass-based resins, typically polylactic acid resins, showing biodegradability has been widely studied.

However, since such a poly (lactic acid) resin is insufficient in heat resistance and mechanical properties compared to a crude oil-based resin, there is a limit to the field or application to which it can be applied. Particularly, attempts have been made to apply poly (lactic acid) resin as a packaging material for packaging films and the like, but such applications are limited due to the low flexibility of the poly (lactic acid) resin.

In order to overcome the limitations of such a polylactic acid resin, a method of adding a low molecular weight softener or plasticizer to a polylactic acid resin, or introducing a plasticizer obtained by addition polymerization of a polyether-based or aliphatic polyester- .

However, even if a packaging film or the like containing a poly (lactic acid) resin is obtained by these methods, it is a fact that there is a limit in improving the flexibility in most cases. In addition, the plasticizer or the like not only bleeds out over time, but also has a disadvantage that haze of the packaging film is increased and transparency is lowered. In addition, in the case of concentrating only on the improvement of flexibility, mechanical properties or blocking resistance are largely lowered, and most of them are unsuitable for use in packaging.

For this reason, while exhibiting biodegradability peculiar to polylactic acid resin, it exhibits optimized physical properties such as excellent flexibility and mechanical properties, and accordingly, development of a film material that can be preferably used for packaging applications is continuously required.

Accordingly, it is an object of the present invention to provide a poly (lactic acid) resin film which exhibits biodegradability peculiar to poly (lactic acid) resin, but exhibits optimized physical properties such as excellent flexibility and mechanical properties.

The present invention relates to a hard segment comprising a polylactic acid repeat unit represented by the following formula (1): And polyurethane polyol repeating units having polyether polyol repeating units linearly connected to each other through a urethane bond and having a polyether polyol repeating unit represented by the following formula (2), wherein the sum of the Young's moduli in the longitudinal direction and the width direction is 350 To 750 kgf / mm < 2 >, and an initial tensile strength sum in the longitudinal direction and the transverse direction of at least 20 kgf / mm < 2 &

[Chemical Formula 1]

(2)

In the general formulas (1) and (2), A is a linear or branched alkylene group having 2 to 5 carbon atoms, m is an integer of 10 to 100, and n is an integer of 700 to 5000.

Hereinafter, a poly lactic acid resin film according to a specific embodiment of the invention will be described.

According to one embodiment of the invention, there is provided a hard segment comprising a polylactic acid repeat unit of the formula 1: And polyurethane polyol repeating units having polyether polyol repeating units linearly connected to each other through a urethane bond and having a polyether polyol repeating unit represented by the following formula (2), wherein the sum of the Young's moduli in the longitudinal direction and the width direction is 350 To 750 kgf / mm < 2 >, and an initial tensile strength sum in the longitudinal direction and the transverse direction of 20 kgf / mm < 2 &

[Chemical Formula 1]

(2)

In the general formulas (1) and (2), A is a linear or branched alkylene group having 2 to 5 carbon atoms, m is an integer of 10 to 100, and n is an integer of 700 to 5000.

The poly (lactic acid) resin, which is a main component of such a film, basically contains the poly (lactic acid) repeating unit represented by the above formula (1) as a hard segment. In addition, the poly (lactic acid) resin includes a polyurethane polyol repeating unit as a soft segment. The polyurethane polyol repeating unit is a repeating unit in which the polyether polyol repeating units represented by the above-mentioned formula (2) are urethane bonds (-C (= O) ) In a linear manner.

These polylactic acid resins and films basically exhibit biodegradability specific to biomass-based resins as they contain polylactic acid repeating units as hard segments. Further, as a result of the experiments conducted by the inventors of the present invention, it has been found that, by including the polyurethane polyol repeating unit as a soft segment, the polylactic acid resin exhibits greatly improved flexibility and also provides a film exhibiting excellent transparency and low haze value It turned out.

In addition, the film made of the poly (lactic acid) resin was subjected to a test with a width of 10 mm and a length of 150 mm using an Instron 1123 UTM universal testing machine at a temperature of 20 ° C and a relative humidity of 65% under the conditions of a stretching speed of 300 mm / The total Young's modulus in the longitudinal direction and the width direction is 350 to 750 kgf / mm 2, preferably 450 to 650 kgf / mm 2, preferably 500 to 600 kgf / mm 2, And has a tensile strength total of 20 kgf / mm 2 or more, preferably 20 to 60 kgf / mm 2. The physical properties of such a film can be attributed to the structural characteristics of the poly (lactic acid) resin described above.

In particular, the poly (lactic acid) resin is obtained by reacting a polyether polyol repeating unit with a diisocyanate compound to form a polyurethane polyol repeating unit in which a plurality of polyether polyol repeating units are linearly linked to a urethane bond, Block copolymers. As the polylactic acid resin includes the block copolymer thus obtained, the film containing the block copolymer can exhibit optimized properties in terms of various physical properties such as flexibility and mechanical properties, and for example, the above- The initial tensile strength sum range can be met. The excellent physical properties of such a film may also be attributed to an optimized production method or form (for example, a biaxially stretched film or the like) of a film described later using the polylactic acid resin.

On the other hand, as the film meets a certain Young's modulus total range, such films may exhibit flexibility and stiffness that are optimized for applications such as packaging. On the other hand, when the Young's modulus sum is excessively low, spreading or loosening occurs in the process of film formation and processing of the film, and handling property, process permeability, slit processability or shape retention property may become poor. In addition, when the wrap film is used, the releasability of the film may be insufficient due to insufficient slip of the film, and efficient packaging may be difficult due to deformation of the film before wrapping an article or food such as a container. On the contrary, when the Young's modulus is excessively high, the flexibility of the film is low and the stiffness is too high, so that when the film is folded during packaging, the folding line remains unchanged, resulting in bad appearance, It may not be deformed depending on the shape of the article or the food, which may cause difficulty in packaging.

And, when the film is subjected to a tensile test under the same conditions as the above Young's modulus, the film satisfies the specific initial tensile strength sum range described above. If the initial tensile strength is lower than this, the handling property of the film becomes poor, and even after packaging, the film may be easily broken and the contents may be damaged. Alternatively, the film of one embodiment may exhibit excellent mechanical properties that can be preferably used for applications such as packaging, as the film satisfies a specific initial tensile strength sum range.

Therefore, the poly (lactic acid) resin film of one embodiment exhibits biodegradability, but exhibits various physical properties such as excellent flexibility and mechanical properties, and therefore can be preferably used for packaging and the like.

Hereinafter, the film of one embodiment will be described in more detail. First, the poly (lactic acid) resin as the main component of the film will be described in detail, and then the film including the poly (lactic acid) resin will be described in detail.

In the polylactic acid resin contained in the film, the polylactic acid repeating unit represented by formula (1) contained in the hard segment is a repeating unit constituting a poly (lactic acid) homopolymer. Such polylactic acid repeating units can be obtained by a method for producing polylactic acid homopolymers well known to those skilled in the art. For example, L-lactide or D-lactide, which is a cyclic double monomer, is produced from L-lactic acid or D-lactic acid and ring-opening polymerization is carried out, or L-lactic acid or D- Among them, poly (lactic acid) repeating units having a higher polymerization degree can be obtained through ring-opening polymerization, which is preferable. The poly (lactic acid) repeating unit may be prepared by copolymerizing L-lactide and D-lactide at a certain ratio so as to exhibit noncrystallinity. In order to further improve the heat resistance of the film containing the polylactic acid resin, L-lactide, or D-lactide. More specifically, the polylactic acid repeating unit can be obtained by ring-opening polymerization using an L-lactide or D-lactide raw material having an optical purity of 98% or more. If the optical purity is less than the above range, the melting temperature (Tm) Can be lowered.

The polyurethane polyol repeating units contained in the soft segment have a structure in which the polyether polyol repeating units of formula (2) are linearly linked via a urethane bond (-C (= O) -NH-). More specifically, the polyether polyol repeating units are obtained by ring-opening (co) polymerization of a monomer such as an alkylene oxide and have a hydroxy group at the terminal thereof. The terminal hydroxyl group reacts with the diisocyanate compound to form the urethane bond C (= O) -NH-), and the polyether polyol repeating units are linearly connected to each other via the urethane bond to form the polyurethane polyol repeating unit. By including such a polyurethane polyol repeating unit in a soft segment, the flexibility of the film containing the polylactic acid resin can be greatly improved. Such a polyurethane polyol repeating unit makes it possible to provide a film exhibiting excellent physical properties without lowering the heat resistance, blocking resistance, mechanical properties or transparency of the poly (lactic acid) resin or the film containing the poly (lactic acid) resin.

On the other hand, a poly (lactic acid) -based copolymer having a soft segment in which a polyester polyol repeating unit is linked by a urethane bond has been known. However, such a polylactic acid copolymer has a problem that the transparency of the film is lowered and the haze value is increased due to low compatibility of the polyester polyol and the polylactic acid. In addition, such a polylactic acid copolymer has a wide molecular weight distribution and an excessively low glass transition temperature, so that the melt property is poor and the film extruded state is poor, and the mechanical properties, heat resistance and blocking resistance of the film are also insufficient.

Then, a polylactic acid copolymer in which a polyether polyol repeating unit is copolymerized with a polylactic acid repeating unit in a branched form using a trifunctional or higher isocyanate compound, or a copolymer obtained by copolymerizing the above polyether polyol repeating unit and poly Polylactic-type copolymers in the form of chain-extended by a urethane reaction have also been previously known. However, also in these previously known poly (lactic acid) copolymers, the block size of the polylactic acid repeating unit corresponding to the hard segment is small and the glass transition temperature is too low, so that the heat resistance, mechanical properties and blocking resistance of the film are insufficient, There are still problems such that the molecular weight distribution is wide and the melting property is poor and the film extrusion state is poor.

On the contrary, the polylactic acid resin (i.e., one included in the film of one embodiment), in which a plurality of polyether polyol repeating units comprise a polyurethane polyol repeating unit and a polylactic acid repeating unit linearly connected via a urethane bond, The present invention provides a film exhibiting excellent flexibility by a polyurethane polyol repeating unit, exhibits an optimized glass transition temperature, has a small molecular weight distribution, and contains a poly (lactic acid) repeating unit in a large segment size, so that the film has excellent mechanical properties, And blocking resistance. Thus, it has been found that the poly (lactic acid) resin contained in the film of one embodiment solves all the problems of previously known copolymers, thereby providing a film having excellent physical properties and greatly improved flexibility.

The polyether polyol repeating unit and the diisocyanate compound are reacted so that the molar ratio of the isocyanate group of the compound of the terminal hydroxyl group: diisocyanate compound of the polyether polyol repeating units is 1: 0.50 to 1: 0.99, A repeating unit can be formed. Preferably, the reaction molar ratio of the isocyanate group of the terminal hydroxyl group: diisocyanate compound of the polyether polyol repeating units is 1: 0.60 to 1: 0.90, more preferably 1: 0.70 to 1: 0.85.

As described in more detail below, the polyurethane polyol repeating unit has a hydroxyl group at the end thereof, and therefore can act as an initiator in the polymerization process for the formation of the polylactic acid repeating unit. However, if the molar ratio of the hydroxyl group to the isocyanate group is excessively high, the number of terminal hydroxyl groups of the polyurethane polyol repeating unit is insufficient (OHV <3), and the polyurethane polyol repeating unit may not function properly as an initiator. When the molar ratio of the hydroxyl group to the isocyanate group is too low, the number of terminal hydroxyl groups in the polyurethane polyol repeating unit becomes too large (OHV > 21), making it difficult to obtain polyanhydride repeating units and poly lactic acid resins having a high molecular weight.

On the other hand, the polyether polyol repeating unit may be, for example, a repeating unit of a polyether polyol (co) polymer obtained by ring-opening (co) polymerization of at least one alkylene oxide. Examples of the alkylene oxide include ethylene oxide, propylene oxide, butylene oxide, and tetrahydrofuran. Examples of the polyether polyol repeating unit obtained by the reaction include repeating units of polyethylene glycol (PEG); Repeating units of poly (1,2-propylene glycol); Repeating units of poly (1,3-propanediol); Repeating units of polytetramethylene glycol; Repeating units of polybutylene glycol; A repeating unit of a polyol which is a copolymer of propylene oxide and tetrahydrofuran; A repeating unit of a polyol which is a copolymer of ethylene oxide and tetrahydrofuran; Or a repeating unit of a polyol which is a copolymer of ethylene oxide and propylene oxide. Considering flexibility imparted to the poly (lactic acid) resin film, affinity with the poly (lactic acid) repeating unit and humidifying property, the polyether polyol repeating unit may be a repeating unit of poly (1,3-propanediol) or polytetramethylene glycol , And the polyether polyol repeating unit may have a number average molecular weight of 400 to 9000, preferably 1000 to 3000. [

The diisocyanate compound capable of bonding with the terminal hydroxyl group of the polyether polyol repeating unit to form a urethane bond can be any compound having two isocyanate groups in the molecule. Examples of such diisocyanate compounds include 1,6-hexamethylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 1,3-xylene diisocyanate, 1,4-xylene diisocyanate, , 5-naphthalene diisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, 3,3'-dimethyl-4,4'-diphenylmethane diisocyanate, 4,4'- bisphenylenediisocyanate, hexamethylene di Isocyanate, isophorone diisocyanate, or hydrophenylmethane diisocyanate. In addition, various diisocyanate compounds well known to those skilled in the art can be used without limitation. However, it is preferable to use 1,6-hexamethylene diisocyanate in view of imparting flexibility to the poly (lactic acid) resin film.

On the other hand, the above-mentioned poly (lactic acid) resin contained in the film of one embodiment may include a block copolymer in which the poly (eth) acid repeating unit of the hard segment is bonded to the polyurethane polyol repeating unit of the soft segment. More specifically, in such a block copolymer, the terminal carboxyl group of the polylactic acid repeating unit may form an ester bond with the terminal hydroxy group of the polyurethane polyol repeating unit. For example, the chemical structure of such a block copolymer can be represented by the following general formula 1:

[Formula 1]

Polyester repeating unit (L) -Ester-polyurethane polyol repeating unit (E-U-E-U-E) -Ester-

In the general formula (1), E represents a polyether polyol repeating unit, U represents a urethane bond, and Ester represents an ester bond.

Since the polyurethane polyol repeating unit and the polyurethane polyol repeating unit are combined with each other, the polyurethane polyol repeating unit or the like for imparting flexibility can be prevented from being bleed out. In addition, The physical properties such as transparency, mechanical properties, heat resistance, blocking resistance and the like can be excellent. Particularly, as the poly (lactic acid) repeating unit and the polyurethane polyol repeating unit have a block copolymer form, the glass transition temperature (Tg) and the melting temperature (Tm) of the poly (lactic acid) resin are optimized, The heat resistance and the like can be further improved.

However, it is not necessary that all of the polylactic acid repeating units included in the polylactic acid resin is in the form of a block copolymer bonded to the polyurethane polyol repeating units, and at least a part of the polylactic acid repeating units But may be in the form of a poly (lactic acid) homopolymer. In this case, the polylactic acid resin may be in the form of a mixture comprising the block copolymer described above and a polylactic acid repeating unit not bonded to the polyurethane repeating unit, that is, a polylactic acid homopolymer.

On the other hand, the poly (lactic acid) resin is preferably a poly (lactic acid) resin having a weight average molecular weight of 80 to 100,000, 95% by weight of the soft segment and 5 to 20% by weight of the soft segment, preferably 82 to 92% by weight of the hard segment and 8 to 18% by weight of the soft segment, 90% by weight of the soft segment, and 10 to 15% by weight of the soft segment.

If the content of the soft segment is excessively high, it may become difficult to provide a poly (lactic acid) resin having a high molecular weight, and mechanical properties such as strength of the film may be deteriorated. In addition, the glass transition temperature is lowered, so that slipping, handleability, form retention, blocking resistance and the like may be deteriorated during packaging using a film. On the other hand, if the content of the soft segment is too low, there is a limit to improve the flexibility of the poly (lactic acid) resin and the film thereof. Particularly, the glass transition temperature of the poly (lactic acid) resin is excessively high, so that the flexibility of the film may be deteriorated. In addition, since the polyurethane polyol repeating unit of the soft segment is difficult to act as an initiator, It may not be manufactured.

The poly (lactic acid) resin may further contain a phosphorus stabilizer and / or an antioxidant to inhibit oxidation or pyrolysis of the soft segment or the like during its production. Examples of the antioxidant include Hindered phenol antioxidants, amine antioxidants, thio antioxidants, and phosphite antioxidants. The kinds of each of these stabilizers and antioxidants are well known to those skilled in the art.

In addition to these stabilizers and antioxidants, the polylactic acid resin may contain various known plasticizers, ultraviolet stabilizers, coloring inhibitors, matting agents, deodorants, flame retardants, antiwear agents, antistatic agents, release agents, antioxidants, Ion exchangers, coloring pigments, inorganic or organic particles, and the like.

Examples of the plasticizer include phthalate ester plasticizers such as diethyl phthalate, dioctyl phthalate and dicyclohexyl phthalate; Aliphatic dibasic acid ester plasticizers such as di-n-butyl adipate, di-n-octyl adipate, di-n-butyl sebacate and di-2-ethylhexyl azelate; Phosphate ester plasticizers such as diphenyl-2-ethylhexyl phosphate and diphenyloctyl phosphate; Tributyl acetyl citrate, tri-2-ethylhexyl acetyl citrate, tributyl citrate, and other hydroxycarboxylic acid ester plasticizers; Fatty acid ester-based plasticizers such as methyl acetyl ricinoleate and methyl stearate; Polyhydric alcohol ester plasticizers such as glycerin triacetate; Epoxidized soybean oil, epoxylated amami-oil fatty acid butyl ester, and epoxy-based stearyl epoxy stearate. Examples of the coloring pigment include inorganic pigments such as carbon black, titanium oxide, zinc oxide and iron oxide; Organic pigments such as cyanine pigments, phosphorus pigments, quinone pigments, lineron pigments, isoindolinone pigments, and thioindigo pigments. Inorganic or organic particles may be further added to improve the anti-blocking property of other films. Examples of the inorganic or organic particles include silica, colloidal silica, alumina, alumina sol, talc, mica, calcium carbonate, polystyrene, polymethylmethacrylate, And the like. In addition, various additives known to be usable in the polylactic acid resin or the film thereof can be included, and the specific kind and the method of obtaining it are known to those skilled in the art.

For example, the block copolymers contained therein may have a number average molecular weight of 50,000 to 200,000, preferably a number average molecular weight of 50,000 to 150,000. The poly (lactic acid) resin may have a weight average molecular weight of 100,000 to 400,000, preferably 100,000 to 320,000. Such a molecular weight may affect the workability and mechanical properties of the poly (lactic acid) resin described above. When the molecular weight is too small, the melt viscosity may be excessively low when melt-processed by a method such as extrusion, which may result in deterioration of workability in a film or the like, and mechanical properties such as strength may be deteriorated even if processing into a film is possible. On the other hand, when the molecular weight is excessively high, the melt viscosity during melt processing is too high and the productivity as a film may be greatly reduced.

The molecular weight distribution (Mw / Mn) defined by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn) of the polylactic acid resin such as the block copolymer contained therein is preferably 1.60 to 2.20, May have a value of 1.80 to 2.15. Since the poly (lactic acid) resin exhibits such a narrow molecular weight distribution, it exhibits an appropriate melt viscosity and melting property when it is melt processed by a method such as extrusion, and can exhibit excellent film extrusion state and processability. In addition, the film containing the poly (lactic acid) resin can exhibit excellent mechanical properties such as strength. On the other hand, when the molecular weight distribution is excessively narrowed (decreased), the melt viscosity at the processing temperature for extrusion and the like is excessively large, so that processing as a film may be difficult. Conversely, when the molecular weight distribution becomes too large Or the melt viscosity is too small, so that it is difficult to form the film into a film itself or the film extrusion state may be poor.

In addition, the polylactic acid resin, for example, the block copolymer contained therein, may have a glass transition temperature (Tg) of 25 to 55 DEG C, preferably a glass transition temperature (Tg) of 30 to 55 DEG C. As the glass transition temperature range is shown, the flexibility and stiffness of the film containing the poly (lactic acid) resin are optimized, so that such a film can be used for packing and the like very advantageously. If the glass transition temperature of the poly (lactic acid) resin is excessively low, the flexibility of the film may be improved. However, as the stiffness becomes too low, the slipping, handling, Blocking property may be deteriorated, which may make the application as a packaging material undesirable. On the other hand, if the glass transition temperature is too high, the flexibility of the film is low and the stiffness is too high, so that the film is easily folded and the mark is not lost or the adhesion to the product is poor when wrapped. Furthermore, noise may be generated severely during packaging of the film, which may limit its application as a packaging material.

The polylactic acid resin may have a melting temperature (Tm) of 160 to 178 ° C, preferably 165 to 175 ° C. If the melting temperature is too low, the heat resistance of the film containing the poly (lactic acid) resin may be deteriorated. If it is too high, a high temperature is required in the melt processing by extrusion or the like, or the viscosity becomes too high, . However, the above-mentioned poly (lactic acid) resin enables to provide a packaging film showing excellent physical properties including heat resistance as well as excellent flexibility, as well as excellent melt processability, by optimizing the glass transition temperature and the like with such melting temperature.

On the other hand, the above-mentioned poly (lactic acid) resin can be produced by ring-opening (co) polymerization of a monomer such as at least one alkylene oxide to form a (co) polymer having a polyether polyol repeating unit; Reacting the (co) polymer with a diisocyanate compound in the presence of a catalyst to form a (co) polymer having a polyurethane polyol repeating unit; (D or L-lactic acid), or ring-opening polymerization of lactide (D or L-lactide) in the presence of a (co) polymer having the polyurethane polyol repeating unit &Lt; / RTI &gt;

Particularly, a (co) polymer having a polyurethane polyol repeating unit in which the polyether polyol repeating units are linearly linked via a urethane bond is reacted with a (co) polymer having a polyether polyol repeating unit and a diisocyanate compound And then polymerizing it with lactic acid or lactide, a polylactic acid resin having excellent physical properties as described above and a block copolymer included therein can be produced. On the other hand, in the case of introducing a polyester-based polyol repeating unit other than the polyether-based polyol repeating unit or by first polymerizing the polyether-based polyol with lactic acid or the like in a different sequence of reaction and then extending the chain, And a polylactic acid resin containing the block copolymer are difficult to produce.

The amount of the (co) polymer having a polyurethane polyol repeating unit corresponding to the molecular weight of the whole poly (lactic acid) resin, the molecular weight of the polyether polyol (co) polymer or the content of the soft segment, It becomes a main factor that makes polylactic acid resin having one excellent physical property to be produced. However, the appropriate range of the molecular weight of the polylactic acid resin or the content of the soft segment has already been described above, and thus a further detailed description thereof will be omitted.

The method for producing such a poly (lactic acid) resin will be described in more detail as follows.

First, a monomer such as at least one alkylene oxide is ring-opened (co) polymerized to form a (co) polymer having a polyether polyol repeat unit. This is a method for producing a polyether polyol You can proceed accordingly.

Thereafter, the (co) polymer having the polyether polyol repeating unit, the diisocyanate compound and the urethane reaction catalyst are charged in the reactor, heated and stirred to perform the urethane reaction. By this reaction, two isocyanate groups of the diisocyanate compound and a terminal hydroxyl group of the (co) polymer are bonded to each other to form a urethane bond. As a result, a (co) polymer in which polyether polyol repeating units have polyurethane polyol repeating units in a linearly linked form via the urethane bond can be formed, which is included as a soft segment of the above-mentioned polylactic acid resin. At this time, the polyurethane polyol (co) polymer is formed in such a manner that the polyether polyol repeating units (E) are linearly bonded in the form of EUEUE through a urethane bond (U) to have polyether polyol repeating units at both terminals .

The urethane reaction can be carried out in the presence of a conventional tin catalyst, for example, Stannous Octoate, Dibutyltin Dilaurate, Dioctyltin Dilaurate and the like. In addition, the urethane reaction can be carried out under the reaction conditions for the production of a conventional polyurethane resin. For example, after a diisocyanate compound and a polyether-based polyol (co) polymer are added in a nitrogen atmosphere, the urethane reaction catalyst is added thereto and reacted at a reaction temperature of 70 to 80 ° C for 1 to 5 hours to obtain a polyurethane- (Co) polymer can be produced.

Then, lactic acid (D or L-lactic acid) is subjected to condensation polymerization in the presence of the (co) polymer having the polyurethane polyol repeating unit, ring-opening polymerization of lactide (D or L-lactide) The polylactic acid resin, particularly the block copolymer contained therein, can be prepared. That is, when such a polymerization reaction is carried out, a poly (lactic acid) repeating unit contained as a hard segment is formed to produce the poly (lactic acid) resin. At this time, the polyurethane polyol repeating unit is bonded to at least a part of the poly A block copolymer may be formed. As a result, a known polylactic acid copolymer prepared by preparing a prepolymer in which a polyether polyol and a poly (lactic acid) are bonded to each other and then lengthening the prepolymers with a diisocyanate compound, or a polyol compound obtained by linking the prepolymers with a trifunctional or higher isocyanate compound (Which is included in the film of one embodiment) may be formed, which exhibits a different structure and physical properties from known branched copolymers which have been reacted with the above-mentioned block copolymer. Particularly, such a block copolymer may contain a block (hard segment) in which the polylactic acid repeating units are bonded to each other in a relatively large unit (molecular weight), so that the film formed of the poly (lactic acid) resin containing the block copolymer has a narrow molecular weight distribution, Thereby exhibiting excellent mechanical properties and heat resistance. On the other hand, the above-mentioned known copolymers have a structure in which polyunsaturated repeating units having a small unit (molecular weight) are alternately arranged randomly with a polyether polyol repeating unit or the like, and thus the resulting film has properties such as the glass transition temperature And the mechanical properties and heat resistance are insufficient.

Meanwhile, the lactide ring-opening polymerization reaction may be carried out in the presence of a metal catalyst including an alkaline earth metal, a rare earth metal, a transition metal, aluminum, germanium, tin or antimony. More specifically, such metal catalysts can be in the form of carboxylates, alkoxides, halides, oxides or carbonates of these metals. Preferably, as the metal catalyst, tin octylate, titanium tetraisopropoxide or aluminum triisopropoxide may be used.

The above-mentioned poly (lactic acid) resin may exhibit more flexibility while exhibiting biodegradability of the poly (lactic acid) resin, as it includes a block copolymer having a specific hard segment and a soft segment bonded thereto. Also, the soft segment for imparting flexibility can be minimized to be bleed out, and the degradation of mechanical properties, heat resistance, transparency or haze characteristics of the film can be greatly reduced by the addition of such a soft segment.

Further, since the poly (lactic acid) resin is produced so as to have a predetermined glass transition temperature and optionally a predetermined melting temperature, a film or the like obtained therefrom can exhibit optimized flexibility and stiffness as a packing material, And the blocking resistance and the heat resistance are further improved. Therefore, such a poly (lactic acid) resin can be very suitably applied to a packaging material such as a film.

Hereinafter, the film of one embodiment including the above-described poly (lactic acid) resin will be described in detail. Since the film contains the above-described poly (lactic acid) resin, the film exhibits excellent flexibility and stiffness as well as excellent mechanical properties, heat resistance, blocking resistance and transparency, and is therefore highly desirable for packaging applications in various fields Can be used.

Such a film may have various thicknesses depending on each use, and may have a thickness of 5 to 500 mu m. For example, when it is used as a packaging film such as a wrap film or an envelope, it has a thickness of 5 to 100 mu m, preferably 7 to 50 mu m, more preferably 7 to 30 mu m Thickness.

The film may have a weight change rate of 3 wt% or less, preferably 0.01 to 3.0 wt%, more preferably 0.05 to 1.0 wt% when treated in a hot air oven at 100 캜 for 1 hour. These properties can reflect the excellent heat resistance and anti-bleed out characteristics of the film. If the weight change rate is 3 wt% or more, the dimensional stability of the film becomes poor, which means that the plasticizer, the residual monomer, the additive or the like are bleed out, and these components can contaminate the package contents.

The film may have a haze of 3% or less and a transmittance of 85% or more, preferably a haze of 2% or less, a transmittance of 90% or more, more preferably a haze of 1% The transmittance may be 92% or more. If the haze is too large or the transmittance is too low, the contents can not easily be distinguished during packaging of the film, and the printed image is hard to appear clearly when the multilayer film using the printing layer is applied.

The above-mentioned film may be provided with properties required for a food packaging material such as heat sealing property, gas barrier property such as water vapor, oxygen or carbonic acid gas, releasing property, printing property and the like, To this end, it is also possible to blend a compound of the polymer having such properties into a film, or to coat at least one surface of the film with a thermoplastic resin such as an acrylic resin, a polyester resin, a silicone resin, an antistatic agent, a surfactant, . As another method, another film having a function such as a polyolefin-based sealant or the like may be co-extruded to form a multilayer film. Or may be produced in the form of a multilayer film by other methods such as adhesion or lamination.

On the other hand, the above-mentioned film can be formed, for example, in the form of a biaxially stretched film by applying a sequential biaxial stretching method or a simultaneous biaxial stretching method to the above-mentioned poly (lactic acid) resin, At this time, in the stretched film forming process, the polylactic acid resin is melt-extruded by a sheet-form extruder equipped with a T-die, and the sheet-like melt extrudate is cooled and solidified to obtain an unstretched film. Direction and the width direction.

The stretching conditions of the film can be suitably adjusted according to heat shrinkage characteristics, dimensional stability, strength, Young's modulus and the like. For example, in terms of strength and flexibility of the finally produced film, it is preferable that the stretching temperature is controlled to be not lower than the glass transition temperature of the polylactic acid resin and not higher than the crystallization temperature. In addition, the stretching ratio may be in the range of 1.5 to 10 times in the length and width directions, respectively, and the length and width direction stretching ratios may be adjusted differently.

After the stretched film is formed by such a method, the film is finally manufactured through heat fixation. It is preferable that the heat fixation is performed at 100 ° C or more for 10 seconds or more for the strength and dimensional stability of the film.

The above-mentioned film not only has excellent flexibility and transparency even when stored for a long period of time, but also can exhibit mechanical properties such as sufficient strength and anti-bleed out characteristics. In addition, it can exhibit biodegradability peculiar to polylactic acid resin. Therefore, such a film can be suitably applied as packaging materials in various fields. For example, sanitary films, lamination films, shrinkable labels, and matte films for snack packaging, such as consumer packaged goods or grocery packages, envelopes, refrigerated / frozen food packaging, shrinkable over-wrapping films, Bundle bundle films, sanitary napkins or baby products In addition, it can be widely used as packing material for industrial materials such as agricultural multi-film, automobile paint film protective sheet, garbage bag and compost bag.

As described above, according to the present invention, it is possible to provide a polylactic acid resin which exhibits biodegradability peculiar to the polylactic acid resin, but also has excellent flexibility and stiffness, excellent mechanical properties, heat resistance, transparency, anti-blocking property and anti- May be provided. Therefore, such a poly (lactic acid) resin film can be suitably applied as a packaging material in various fields to replace the packaging film obtained from the crude oil-based resin, and contributes greatly to prevention of environmental pollution.

Best Mode for Carrying Out the Invention Hereinafter, the function and effect of the present invention will be described in more detail through specific examples of the present invention. It is to be understood, however, that these embodiments are merely illustrative of the invention and are not intended to limit the scope of the invention.

* Property Definition and Measurement Method: Definition and measurement method of each property in the following embodiments are as summarized below.

(1) NCO / OH: terminal hydroxyl group of an isocyanate group of a diisocyanate compound (for example, hexamethylene diisocyanate) / polyether polyol repeating unit (or (co) polymer) for formation of polyurethane polyol repeating unit "

(2) OHV (KOH mg / g): The polyurethane polyol repeating unit (or (co) polymer) was dissolved in dichloromethane and acetylated, and acetic acid produced by hydrolysis thereof was titrated with 0.1N KOH methanol solution . This corresponds to the number of hydroxyl groups present at the end of the polyurethane polyol repeat unit (or (co) polymer).

(3) Mw and Mn (g / mol) and molecular weight distribution (Mw / Mn): The poly lactic acid resin was dissolved in Chloroform at a concentration of 0.25% by weight and subjected to Gel permeation chromatography (Viscotek TDA 305, Column: Shodex LF804 * 2ea), and weight average molecular weight (Mw) and number average molecular weight (Mn) were calculated as polystyrene as a standard material. Molecular weight distribution values were calculated from the Mw and Mn thus calculated.

(4) Tg (glass transition temperature, 占 폚): Measured by heating the sample at 10 占 폚 / min after melting and quenching the sample using a differential scanning calorimeter (TA Instruments). The midline value of the tangent line and the baseline near the endothermic curve was defined as Tg.

(5) Tm (melting temperature, 占 폚): Using a differential scanning calorimeter (manufactured by TA Instruments), the sample was subjected to melt quenching and then heated to 10 占 폚 / min. The maximum value of the melting endothermic peak of the crystal was defined as Tm.

(6) Content of polyurethane polyol repeating units (wt%): The content of polyurethane polyol repeating units contained in each produced poly (lactic acid) resin was quantified using a 600 MHz nuclear magnetic resonance (NMR) spectrometer.

(7) Extruded state: Poly (lactic acid) resin was extruded in a single screw extruder having a diameter of 30 mm equipped with a T die for the production of unstretched sheet at a temperature of 200 to 250 DEG C at an extrusion temperature, drum were cast by electrostatic force. At this time, the melt viscosity of the discharged material on the sheet was measured using a Physica Rheometer manufactured by Physica, USA. Specifically, through the use of a 25 mm parallel plate type shear force applying device, the complex viscosity (Pa · s) of the molten resin at the shear rate (1 / s) = 1 while maintaining the initial temperature of the discharged material s) was measured with the above-mentioned Physica Rheometer, and the state of melt viscosity (extrusion state) was evaluated according to the following criteria.

⊚: Good melt spinning speed and good winding on a cooling drum. ◯: Melt viscosity is slightly low, but winding is possible. ◯: Winding is not possible due to too low melt viscosity.

(8) Initial Tensile Strength (kgf / mm 2) MD, TD: A film sample having a length of 150 mm and a width of 10 mm was aged in an atmosphere of a temperature of 20 ° C and a humidity of 65% RH for 24 hours and UTM ) Using a universal testing machine, tensile strength was measured at a stretching speed of 300 mm / min and a distance between grips of 100 mm. The averages of the 5 tests in total were expressed as the results. The longitudinal direction of the film was indicated by MD, and the transverse direction by TD.

(9) Elongation (%) MD, TD: The elongation at break of the film under the same condition as the tensile strength of the above (6) was measured. The longitudinal direction of the film was indicated by MD, and the transverse direction by TD.

(10) F5 (kgf / mm &lt; 2 &gt;) MD, TD: The tangent of the tangent line at the point of stress at the time of 5% strain is obtained from the stress-strain curve obtained in the above (6) % The value of the stress at the time of elongation was obtained, and the average value of the test of 5 times in total was expressed as a result value. The longitudinal direction of the film was indicated by MD, and the transverse direction by TD.

(11) F100 (kgf / mm &lt; 2 &gt;) MD: The slope of the tangent line at the point of stress at the time of 100% deformation in the stress-strain curve obtained by the tensile test of the above (6) The value of the stress at the time of the test was obtained, and the average value of the test of the total of 5 times was expressed as a result value. Only the longitudinal MD of the film was measured.

(12) Young's modulus (kgf / mm &lt; 2 &gt;) MD, TD: The same specimen as the tensile test described in (6) above was subjected to a stretching speed of 300 mm / min using a UTM (INSTRON) universal testing machine according to ASTM D638, Young's modulus was measured. The averages of the 5 tests in total were expressed as the results. These values of the Young's modulus, particularly the Young's modulus measured in the length and width directions, correspond to the flexibility of the film, and the lower the Young's modulus value is, the better the flexibility. The longitudinal direction of the film was indicated by MD, and the transverse direction by TD.

(13) Wavy pattern (horizontal line): When the film is extruded by compounding two kinds of resin or resin and plasticizer having different molecular weights, the degree of the wave pattern generated by the difference in melt viscosity is measured by the following And evaluated according to the standards.

◎: No wave pattern (horizontal line) occurred, ○: Wave pattern (horizontal line) occurred within 3 points, ×: More than 5 wave patterns (horizontal line) occurred.

(14) Weight change rate (%) at 100 占 폚: The film sample was previously aged for 24 hours in an atmosphere of a temperature of 23 占 폚 and a humidity of 65% RH, and the weight before heat treatment was measured. Thereafter, the resultant was treated in a hot air oven at 100 ° C for 60 minutes, aged under the same conditions as before treatment, and then weighed. The results were calculated by weight ratios before and after the heat treatment before the treatment.

(15) Pin Hole Generation and Bleeding-Out Characteristics: After the heat treatment of the above (12), the surface of the film sample was observed to determine whether pin holes were generated. Further, the extent to which the low molecular weight plasticizer component was bleed out to the film surface due to tactile sensation was evaluated according to the following criteria in an A4 size film sample.

◎: No pin hole and bleed out, ○: No more than 5 pin holes or bleed out, but not too much. ×: More than 5 pin holes or bleed out occur.

(16) Haze (%) and Transmittance (%): The film sample was previously aged in an atmosphere of a temperature of 23 ° C and a humidity of 65% RH for 24 hours, and then, using a haze meter (Model: Japan NDH2000) according to JIS K7136 And the average value was calculated as a result.

(17) Blocking resistance: Using a COLORIT P type (manufactured by Coulter, Inc.) of a stamping foil, the antistatic surface of the film sample was matched with the printing surface and allowed to stand at a temperature of 40 캜 and a pressure of 1 kg / cm 2 for 24 hours, The blocking state of the antistatic layer and the printing surface was observed. Based on the observation results, the anti-blocking property between the antistatic layer (layer A) and the printed surface of the in-mold transfer film was evaluated on the basis of the following criteria. At this time, the practical performance is satisfied up to.

⊚: no change, ∘: slight surface change (less than 5%), ×: over 5% peeling

The raw materials used in the following Examples and Comparative Examples are as follows:

One. Polyether series Polyol  The repeating unit (or (co) polymer) or its corresponding material

- PPDO 2.4: poly (1,3-propanediol); Number average molecular weight 2,400

- PPDO 2.0: poly (1,3-propanediol); Number average molecular weight 2,000

- PPDO 1.0: poly (1,3-propanediol); Number average molecular weight 1,000

PTMEG 3.0: polytetramethylene glycol; Number average molecular weight 3,000

PTMEG 2.0: polytetramethylene glycol; Number average molecular weight 2,000

PTMEG 1.0: polytetramethylene glycol; Number average molecular weight 1,000

- PEG 8.0: polyethylene glycol; Number average molecular weight 8,000

- PBSA 11.0: aliphatic polyester polyols made from 1,4-butanediol and condensates of succinic acid and adipic acid; Number average molecular weight 11,000

2. Diisocyanate compound (or trifunctional or higher isocyanate)

- HDI: hexamethylene diisocyanate

- D-L75: Bayer Desmodur L75 (TRIMETHYLOL PROPANE + 3 Toluene diisocyanate)

3. Lactide monomers

- L-lactide or D-lactide: Optical purity of 99.5% or more from Purac

4. Antioxidants, etc.

- TNPP: Tris (nonylphenyl) phosphite

- U626: Bis (2,4-di-t-butylphenyl) Pentaerythritol Diphosphite

S412: Tetrakis [methane-3- (laurylthio) propionate] methane

- PEPQ: (1,1'-Biphenyl) -4,4'-Dlybisphosphonous acid tetrakis [2,4-bis (1,1-dimethylethyl) phenyl] ester

I-1076: octadecyl 3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate

O3: Bis [3,3-bis- (4'-hydroxy-3'-tert-butyl-phenyl) butanoic acid] glycol ester

A. Preparation of polylactic acid resins A to H

Components and contents of the reactants as shown in Table 1 below were charged together with the catalyst in an 8 L reactor equipped with a nitrogen gas introduction pipe, a stirrer, a catalyst inlet, an outlet condenser and a vacuum system. Dibutyltin dilaurate (130 ppm) was used as a catalyst. The urethane reaction was carried out under a nitrogen stream at 70 ° C for 2 hours, and 4 kg of L- (or D-) lactide was added thereto, followed by nitrogen flushing five times.

Thereafter, the temperature was raised to 150 ° C to completely dissolve the L- (or D-) lactide, and 120 ppm of the catalyst Tin 2-ethylhexylate was diluted with 500 ml of toluene to the total reactant content through the catalyst inlet. The reaction was carried out at 185 DEG C under a pressure of 1 kg of nitrogen for 2 hours, 200 ppm of phosphoric acid was added to the catalyst inlet and mixed for 15 minutes to inactivate the residual catalyst. The unreacted L- (or D-) lactide was then removed through a vacuum reaction until 0.5 torr was reached. The molecular weight, Tg, and Tm of the obtained resin were measured and shown in Table 1.

B. Preparation of poly lactic acid resin L

A polyol and 4 kg of L-lactide as shown in Table 1 were charged into an 8 L reactor equipped with a nitrogen gas introduction pipe, a stirrer, a catalyst inlet, an outlet condenser and a vacuum system and subjected to nitrogen flushing five times. The temperature was raised to 150 ° C to completely dissolve the L-lactide, and 120 ppm of the catalyst Tin 2-ethylhexylate was diluted with 500 ml of toluene through the catalyst inlet and added to the reaction vessel. Subsequently, the reaction was carried out at 185 ° C under a pressure of 1 kg of nitrogen for 2 hours, 200 ppm of phosphoric acid was added to the catalyst inlet and mixed for 15 minutes to inactivate the residual catalyst. Unreacted L-lactide was removed by vacuum reaction until 0.5 torr was reached. Table 1 shows the molecular weights, Tg and Tm of the obtained resin.

C. Preparation of poly (lactic acid) resin M

6 g of 1-Dodecanol and 4 kg of L-lactide as shown in the following Table 1 were fed into an 8 L reactor equipped with a nitrogen gas introduction pipe, a stirrer, a catalyst inlet, an outlet condenser and a vacuum system and subjected to nitrogen flushing five times . The temperature was raised to 150 ° C to completely dissolve the L-lactide, and 120 ppm of the catalyst Tin 2-ethylhexylate was diluted with 500 ml of toluene through the catalyst inlet and added to the reaction vessel. Subsequently, the reaction was carried out at 185 ° C under a pressure of 1 kg of nitrogen for 2 hours, 200 ppm of phosphoric acid was added to the catalyst inlet and mixed for 15 minutes to inactivate the residual catalyst. Unreacted L-lactide was removed by vacuum reaction until 0.5 torr was reached. Table 1 shows the molecular weights, Tg and Tm of the obtained resin.

D. Poly lactic acid  Manufacture of resin O

A PBSA polyol (polyester polyol) and HDI as shown in Table 1 were charged into an 8 L reactor equipped with a nitrogen gas introduction pipe, a stirrer, a catalyst inlet, an outlet condenser and a vacuum system, and nitrogen flushing was performed five times. Dibutyltin dilaurate (130 ppm) was used as a catalyst. The urethane reaction was carried out at 190 占 폚 for 2 hours in a nitrogen stream, 4 kg of L-lactide was added, L-lactide was completely dissolved at 190 占 폚 in a nitrogen atmosphere, 120 ppm of addition polymerization catalyst Tin 2-ethylhexylate and 1000 ppm of Dibutyltin dilaurate as an ester and / or ester amide exchange catalyst were diluted with 500 ml of toluene and added to the reaction vessel. The reaction was carried out at 190 DEG C under a pressure of 1 kg of nitrogen for 2 hours, 200 ppm of phosphoric acid was added to the catalyst inlet and mixed for 15 minutes to inactivate the residual catalyst. The unreacted L-lactide was then removed through a vacuum reaction until 0.5 torr was reached. The molecular weight, Tg, and Tm of the obtained resin were measured and shown in Table 1.

E. Poly lactic acid  Manufacture of resin P

PEG, 3.6 kg of L-lactide and 0.4 kg of D-lactide as shown in the following Table 1 were fed into an 8 L reactor equipped with a nitrogen gas introduction pipe, a stirrer, a catalyst inlet, an outlet condenser and a vacuum system, Nitrogen flushing was performed. The temperature was raised to 150 ° C to completely dissolve the lactide. 120 ppm of the catalyst Tin 2-ethylhexylate was diluted with 500 ml of toluene through the catalyst inlet and added to the reaction vessel. Subsequently, the reaction was carried out at 185 ° C under a pressure of 1 kg of nitrogen for 2 hours, 200 ppm of phosphoric acid was added to the catalyst inlet and mixed for 15 minutes to inactivate the residual catalyst. Unreacted L-lactide was removed by vacuum reaction until 0.5 torr was reached. After this, 120 ppm of HDI and 130 ppm of dibutyltin dilaurate as shown in Table 1 below were diluted with 500 ml of toluene through a catalyst inlet and added to the reaction vessel. The reaction was carried out at 190 DEG C for 1 hour in a nitrogen atmosphere, and the molecular weights, Tg and Tm of the resin thus obtained are shown in Table 1.

F. Poly lactic acid  Manufacture of resin R

PEG, 3.6 kg of L-lactide and 0.4 kg of D-lactide as shown in the following Table 1 were fed into an 8 L reactor equipped with a nitrogen gas introduction pipe, a stirrer, a catalyst inlet, an outlet condenser and a vacuum system, Nitrogen flushing was performed. The temperature was raised to 150 ° C to completely dissolve the lactide. 120 ppm of the catalyst Tin 2-ethylhexylate was diluted with 500 ml of toluene through the catalyst inlet and added to the reaction vessel. Subsequently, the reaction was carried out at 185 ° C under a pressure of 1 kg of nitrogen for 2 hours, 200 ppm of phosphoric acid was added to the catalyst inlet and mixed for 15 minutes to inactivate the residual catalyst. Unreacted L-lactide was removed by vacuum reaction until 0.5 torr was reached. Subsequently, 120 ppm of D-L75 and 130 ppm of dibutyltin dilaurate as shown in Table 1 below was diluted with 500 ml of toluene through a catalyst inlet and added to the reaction vessel. The reaction was carried out at 190 DEG C for 1 hour in a nitrogen atmosphere, and the molecular weights, Tg and Tm of the resin thus obtained are shown in Table 1.

G. film Example  1 to 5, Comparative Example  Preparation of 1 to 2 and 6 to 8

The polylactic acid resins prepared in the above A to F were dried under reduced pressure at 80 ° C for 6 hours under a vacuum of 1 torr and then subjected to extrusion at a temperature of 30 ° C in a single screw extruder equipped with a T die And extruded. An unstretched film was produced by electrostatic casting or casting on a drum cooled to 5 ° C. This unstretched film was stretched three times in the longitudinal direction between the heating rolls under the stretching conditions shown in Table 2, and then the film stretched in the longitudinal direction was fixed with a clip, drawn into the tenter and stretched four times in the transverse direction, Heat treatment was performed at 120 캜 for 60 seconds. As a result, a biaxially stretched poly (lactic acid) resin film having a thickness of 20 mu m was obtained. The evaluation results of the obtained film are shown together in Table 2

H. Production of Film Example 6 and Comparative Examples 3 to 5

The resin mixture or polyol shown in Table 2 was dried under reduced pressure at 80 DEG C for 6 hours under a vacuum of 1 torr and then melted and kneaded at 190 DEG C in a biaxial kneading extruder to obtain a composition obtained by chipping. The composition was dried under reduced pressure at 80 DEG C for 6 hours under a vacuum of 1 torr, and then a biaxially oriented poly (lactic acid) resin film having a thickness of 20 mu m was prepared in the same manner as in the above method G. The evaluation results are also shown in Table 2.

Resin A Resin B Resin C Resin D Resin E Resin H Resin L Resin M Resin O Resin P Resin R PPDO 2.4 (g) 378.8 PPDO 2.0 (g) 114.6 PPDO 1.0 (g) 209.5 PTMEG 3.0 (g) 386.9 PTMEG 2.0 (g) 755.5 PTMEG 1.0 (g) 184.8 PEG 8.0 (g) 2400 800 800 PBSA 11.0 (g) 800 HDI (g) 13.1 21.2 30.5 15.2 44.4 5.38 9.5  10.1 D-L75 20 NCO / OH 0.60 0.80 0.90 0.50 0.70 0.55 0.8 0.7  0.85 OHV (KOH mg / g) 10 6 4 20 6 19 47 3 5.5  2.5 TNPP (g) 4 0.4 3 U626 (g) 2 3 3 PEPQ (g) 4 S412 (g) 2 I-1076 (g) One O3 (g) 2 L-lactide (g) 4,000 4,000 4,000 4,000 4,000 4,000 4000 3600 3600 D-lactide (g) 4,000 4,000 400 400 Polyurethane polyol repeating unit content (wt%) 10 10 6 5 17 4 39 0 18 18 17 Mw (g / mol) 148K 245K 315K 115K 149K 127K 26K 295K 65K 60K  85K Mn (g / mol) 75K 122K 148K 60K 70K 275K 14K 128K 185K 150K  421K Molecular weight distribution
(Mw / Mn) 1.97 2.01 2.13 1.92 2.13 2.17 1.86 2.30 2.85 2.50  4.95 Tg (占 폚) 49 42 54 55 31 62 15 65 18 22  12 Tm (占 폚) 170 168 172 173 164 176 130 176 85, 165 145  138

As shown in Table 1, the resins A to E were poly (1,3-propanediol) having a molecular weight of 1,000 to 2,400 or polytetramethylene glycol having a number average molecular weight of 1,000 to 3,000 in such a manner that NCO / , And 6-hexametylene diisocyanate to obtain a polyurethane polyol repeating unit (or (co) polymer) in which polyether polyol repeating units such as poly (1,3-propanediol) are linearly linked, And corresponds to a polylactic acid resin (block copolymer) obtained by using. Further, such a polylactic acid resin contains soft segments of the polyurethane polyol repeating units in an appropriate amount of 5 to 20% by weight.

In the poly (lactic acid) resin, the polyurethane polyol repeating unit (or (co) polymer) has a value of OHV of 3 to 20, and can preferably serve as an initiator in the polymerization process for the formation of the poly . The final polylactic acid resins A to E had a weight average molecular weight of 100,000 to 400,000, a molecular weight distribution of 1.80 to 2.15, a Tg of 25 to 55 ° C and a Tm of 160 to 178 ° C, It was confirmed that the film was suitable for melt viscosity.

On the other hand, in the resin H, the content and the amount of the polyurethane polyol repeating unit (or (co) polymer) as the soft segment are less than 5 wt%, and the glass transition temperature of the poly . Further, since the content and amount of the polyurethane polyol repeating unit (or (co) polymer) in the resin J were extremely high exceeding 20% by weight, the weight average molecular weight of the finally prepared poly (lactic acid) resin was less than 100,000, It was confirmed that the glass transition temperature was less than 25 占 폚.

Resin L was an attempt to produce a poly (lactic acid) resin by using polyethylene glycol having a molecular weight of 8,000 as an initiator in the ring-opening polymerization of L-lactide immediately without a urethane reaction. However, in such a case, the OHV of the initiator was high, so that a poly (lactic acid) resin having a desired weight average molecular weight could not be obtained. The resin L had a Tg of only 15 캜 and had a low polymerization conversion. When the film extrusion temperature was higher than 200 캜, the melt viscosity was so low that it was impossible to produce a film alone.

Further, the resin M can be produced by introducing a polylactic acid resin (hereinafter referred to as &quot; polylactic acid resin &quot;) prepared by ring-opening polymerization of L-lactide using a small amount of 1-Dodecanol as an initiator, Resin. In the case of poly (lactic acid) resin, it was possible to produce film alone at a film extrusion temperature of 200 ° C or higher. However, it was confirmed that the polylactic acid resin had a broad molecular weight distribution of 2.30.

The resin O is not a polyether polyol repeating unit but a polyurethane formed from a polyester polyol repeating unit such as PBSA as a softening component in a resin, while a ring-opening polymerization catalyst and an ester exchange catalyst and / In the presence of at least one of a polyurethane and a lactide. In such a polylactic acid copolymer, the polyurethane is randomly introduced into a small segment size and is copolymerized with the polylactic acid repeating unit while the ester and / or ester amide exchange reaction takes place. This resin O has a broad molecular weight distribution of 2.85, Tg is excessively low as compared with the present invention, and Tm is also relatively low.

Finally, the resins P and R are prepared by firstly adding a lactide to a polyether polyol repeating unit, preparing a prepolymer in which the polyether polyol repeating unit and the poly (lactic acid) repeating unit are copolymerized and then chain-extending the prepolymer with a diisocyanate compound Copolymer (resin P) and a branched copolymer (resin R) obtained by reacting the prepolymers with an isocyanate compound having three or more functions. These resins P and R were found to have a broad molecular weight distribution of 2.50 and 3.91, a Tg lower than that of the present invention, and a relatively low Tm.

Referring to Table 2, Examples 1 to 5 show that the content of the softening component (polyurethane polyol repeating unit) in the poly (lactic acid resin) is 5 to 20 wt%, the weight average molecular weight is 100,000 to 400,000, the molecular weight distribution is 1.80 to 2.15, 25 to 55 占 폚 and Tm of 160 to 178 占 폚. In addition, Example 6 was also produced using a polylactic acid resin (resin E) and a general polylactic acid resin (resin M) belonging to the category of the present invention

The films of Examples 1 to 6 all have excellent mechanical properties such that the total initial tensile strength in the length and width directions is not less than 20 kgf / mm &lt; 2 &gt;, and the total Young's modulus in the length and width direction is as high as 350 to 750 kgf / It was confirmed that while the flexibility was maintained, the proper range was maintained, and the stiffness was also indicated at an appropriate level. It is preferable that the weight change ratio is 3 wt% or less when treated in a hot air oven at 100 캜 for 1 hour, the haze is 5% or less and the transmittance is 90% or more and the blocking resistance is also excellent, and transparency, haze, And excellent physical properties such as heat resistance.

On the other hand, the film of Comparative Example 1 made of a general poly (lactic acid resin) M has a Young's modulus of more than 750 kgf / mm &lt; 2 &gt; In addition, in the case of the film of Comparative Example 3 produced by using the resin M and the resin L together, the difference in melting point between the two resins was too large to be in an extruded state and a wave pattern was generated in the final film . In addition, a pin hole was formed on the film and the appearance of the film was poor. Also, the Tg of the resin L was too low to cause problems such as blocking resistance, and initial tensile strength and transmittance were also poor.

In Comparative Examples 4 and 5, poly (3, 3-propanediol) having a number average molecular weight of 2,400 and poly (1,3-propanediol) having a number average molecular weight of 11,000 were used as the plasticizer component -Butanediol and an aliphatic polyester polyol made of a condensate of succinic acid and adipic acid is simply mixed with resin M to form a film. In the films of Comparative Examples 4 and 5, the degree of dispersion of the plasticizer component in the resin was not perfect, the haze of the film was high, and after the lapse of time, the plasticizer component bleed out on the film surface.

Further, in Comparative Example 2, the resin H has a comparatively high glass transition temperature due to a low content of the soft segment. For this reason, the film obtained from the resin H has a total Young's modulus in the length and width direction exceeding 750 kgf / mm &lt; 2 &gt;

In addition, the film of Comparative Example 6 was made of a copolymer in which the polyester polyol repeating unit was introduced and the glass transition temperature was low so that the characteristics of the present invention were not satisfied. Although such a film exhibited relatively good flexibility due to random introduction of the polyurethane as a softening component into a small segment size, since the polylactic acid repeating unit is also introduced into a relatively small segment size, it exhibits poor heat resistance due to low Tg and Tm , It was confirmed that filming was difficult due to blocking problem. Further, it has been confirmed that the haze value of the film is high and low transparency due to the low miscibility of the polyester polyol and poly (lactic acid) used for the formation of the softening component, and it is confirmed by the ester and / It was found that the distribution was widened and the melting characteristics were uneven, resulting in poor film extrusion state and mechanical property deterioration.

The films of Comparative Examples 7 and 8 include a resin obtained by urethane reaction of a prepolymer obtained by addition polymerization of a lactide to a polyether polyol with a diisocyanate or an isocyanate compound having three or more functional groups. Property or film properties. These films were found to exhibit uneven melt viscosity and poor mechanical properties. Further, the blocking characteristics of the hard segment and the soft segment in the resin were lowered and showed low Tm and Tg, indicating poor heat resistance and difficulty in filming due to blocking problems.

Further, since the films of Comparative Examples 6 to 8 are required to use an excessive amount of catalyst during the production of the resin, it is considered that the decomposition of the polylactic acid resin is induced during the production or use of the film. The stability of the film was found to be poor.

Claims (11)

A hard segment comprising a polylactic acid repeat unit of Formula 1; And
A polyaspartic acid resin having a glass transition temperature (Tg) of 25 to 55 占 폚 and containing a soft segment containing a polyurethane polyol repeating unit having polyether polyol repeating units of the following formula Lt; / RTI &gt;
A total Young's modulus in the longitudinal direction and in the width direction of 350 to 750 kgf / mm 2 and an initial tensile strength sum in the longitudinal direction and the width direction of 20 kgf / mm 2 or more:
[Chemical Formula 1]

(2)

In the general formulas (1) and (2), A is a linear or branched alkylene group having 2 to 5 carbon atoms, m is an integer of 10 to 100, and n is an integer of 700 to 5000.
The film according to claim 1, wherein the poly (lactic acid) resin has a melting temperature (Tm) of 160 to 178 占 폚.
The film according to claim 1, wherein the polyether polyol repeating units are linearly connected via a urethane bond formed by the reaction of a terminal hydroxy group with a diisocyanate compound.
The film according to claim 3, wherein the polylactic acid resin comprises a block copolymer in which a terminal carboxyl group of a polylactic acid repeating unit contained in the hard segment is ester-bonded to a terminal hydroxy group of the polyurethane polyol repeating unit.
5. The polylactic acid resin composition according to claim 4, wherein the polylactic acid resin comprises the block copolymer; And a polylactic acid repeating unit not bonded to the polyurethane polyol repeating unit.
The film according to claim 1, wherein the poly (lactic acid) resin has a weight average molecular weight of 100000 to 400000.
The film of claim 1, wherein the polylactic acid resin comprises 80 to 95 weight percent of the hard segment and 5 to 20 weight percent of the soft segment.
The film according to claim 3, wherein the reaction molar ratio of the isocyanate group of the terminal hydroxyl group: diisocyanate compound of the polyether polyol repeating units is 1: 0.50 to 1: 0.99.
The film according to claim 1, which is used for packaging.
The film according to claim 1, having a biaxially oriented film form.
The film according to claim 1, having a thickness of 5 to 500 탆.