KR101553333B1 - Process for preparing polylactide resin - Google Patents

Abstract

The present invention relates to a process for producing a low molecular weight polylactide resin which can be used in medical and pressure sensitive adhesives, and more particularly to a process for producing a lactide monomer by ring-opening polymerization in the presence of an organometallic catalyst and a cocatalyst in the presence of an aliphatic alcohol having 8 to 18 carbon atoms Molecular weight polylactide resin having a short polymerization time and a low glass transition temperature (Tg) and a low melting temperature (Tm), and a low molecular weight polylactide resin prepared from the low molecular weight polylactide resin.

Description

PROCESS FOR PREPARING POLYLACTIDE RESIN [0002]

The present invention relates to a method for producing a low molecular weight polylactide resin which can be used in medical and pressure sensitive adhesives. More particularly, the present invention relates to a method for producing a low molecular weight polylactide resin, The present invention relates to a method for producing a low molecular weight polylactide resin exhibiting thermal properties different from those of a resin.

The polylactide (or polylactic acid) resin is a kind of resin containing a repeating unit represented by the following formula (1). Because these polylactide resins are biomass-based, unlike existing crude oil-based resins, it is possible to utilize recycled resources and produce less CO _{2, which} is a global warming gas, , Biodegradable by moisture and microorganisms at the time of landfilling, and has appropriate mechanical strength similar to that of conventional crude oil-based resins.

[Chemical Formula 1]

Such polylactide resins have been mainly used for disposable packaging / containers, coatings, foams, films / sheets and fibers. In recent years, polylactide resins have been mixed with conventional resins such as ABS, polycarbonate or polypropylene It is becoming more and more active to use it for semi-permanent use such as a mobile phone exterior material or an automobile interior material. Particularly, the polylactide resin has been widely used for various applications such as food containers, bottles, trays and films, and medical materials, pressure-sensitive adhesives, cushioning materials, and nonwoven fabrics.

Generally, as a method for producing a polylactide resin, there is a method of directly condensing lactic acid or ring opening polymerization of an lactide monomer under an organometallic catalyst. Among them, direct condensation polymerization from lactic acid is advantageous in that lactic acid is used as a raw material at a relatively low price. However, the direct polycondensation method has a problem that the polymerization conversion is low and the molecular weight of the final polymerized product is low due to the hydrolysis of the polymeric polymer chain by the water generated in the polycondensation process. On the other hand, the ring-opening polymerization method of lactide monomers has a disadvantage in that it is necessary to use lactic acid to lactide monomer to use raw materials, but it is commercially applied because polymerization is relatively simple and mass production is possible.

However, in the conventional production process of the polylactide resin, there is a problem that the conversion rate is as low as 40% to 60% and the residual monomer content is as high as 40% to 60% in mass production of the low molecular weight polylactide resin .

The present invention is intended to provide a method for effectively producing a low molecular weight polylactide resin usable for medical products and films.

The present invention also provides a low molecular weight polylactide resin produced by the above method.

The present invention includes ring-opening polymerization of a lactide monomer in the presence of an organometallic catalyst and a cocatalyst in the presence of an aliphatic alcohol having 8 to 18 carbon atoms, wherein 0.001 to 0.015 part by weight of an organometallic catalyst and 100 parts by weight of a cocatalyst 0.1 to 10 parts by weight based on 100 parts by weight of the polylactide resin.

The present invention also provides a polylactide resin produced by the above method.

Hereinafter, a method for producing a polylactide resin according to a specific embodiment of the present invention and a polylactide resin produced by the method will be described in detail. It is to be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

&Quot; Including "or" containing ", unless the context clearly dictates otherwise throughout the specification, refers to any element (or component) including without limitation, excluding the addition of another component .

Further, throughout the present specification, "lactide monomer" can be defined as follows. Generally, lactide can be divided into L-lactide composed of L-lactic acid, D-lactide composed of D-lactic acid, and meso-lactide composed of one L-form and one D-form. Also, a mixture of L-lactide and D-lactide at 50:50 is referred to as D, L-lactide or rac-lactide. It is known that when the polymerization is carried out using only L-lactide or D-lactide having high optical purity among these lactides, L- or D-polylactide (PLLA or PDLA) having a very high stereoregularity is obtained, It is known that lactide has a higher crystallization rate and higher crystallinity than a polylactide having a lower optical purity. However, the term "lactide monomer" is defined herein to include all types of lactide, regardless of the difference in properties of the lactide according to each type and the property difference of the formed polylactide therefrom.

And, throughout the present specification, the term "polylactide resin" is defined to refer collectively to a single polymer or copolymer containing repeating units of the following formula (1). Such a "polylactide resin" may be prepared by the ring-opening polymerization of the above-mentioned "lactide monomer" to form the following repeating unit. The polymer after completion of the ring- Can be referred to as the above-mentioned "polylactide resin ". Here, the term "lactide monomer" includes all types of lactide as described above.

[Chemical Formula 1]

The category of the polymer that can be referred to as the "polylactide resin" includes polymers in all states after the ring-opening polymerization and the formation of the repeating unit are completed, for example, A polymer contained in a liquid or solid resin composition before product molding, or a polymer included in a plastic or fabric finished with product molding, or the like. Therefore, throughout the present specification, the physical properties (acidity, weight average molecular weight, residual catalyst amount, etc.) of "polylactide resin" are defined as the physical properties of the polymer having any state after the ring- .

Further, throughout the present specification, the term "polylactide resin composition" is defined to include any composition that is contained in or prepared from the above-mentioned "polylactide resin " The category of the composition that can be referred to as such a "polylactide resin composition" includes not only a liquid or solid resin composition having a state such as a master batch or a pellet before molding the product, but also plastic or fabric after molding have.

According to one embodiment of the present invention, the organometallic catalyst and alcohols having a carbon number of 8 to 18, which is a co-catalyst, are used in a specific amount to shorten the process time for ring-opening polymerization of the lactide monomer, A method of effectively producing a low molecular weight polylactide resin exhibiting different thermal properties can be provided. Wherein the polylactide resin comprises ring-opening polymerization of a lactide monomer in the presence of an organic metal catalyst and a co-catalyst in the presence of an aliphatic alcohol having 8 to 18 carbon atoms, And 0.1 to 10 parts by weight of a co-catalyst.

The present inventors have found that by using an aliphatic alcohol having 8 to 18 carbon atoms as a cocatalyst together with an organometallic catalyst in the polymerization of a low molecular weight polylactide (PLA), the activity of the metal catalyst is increased to shorten the polymerization time, Molecular weight polylactide having a thermal characteristic different from that of the conventional resin can be produced by lowering the molecular weight of the resulting polymer. Thus, the present invention has been completed. Such a low molecular weight polylactide resin can be effectively applied to a medical field requiring excellent biostability and biodegradability or a film field requiring a further improved flexibility with a low glass transition temperature (Tg).

Molecular weight polylactide (PLA) for the development of new applications such as medical and pressure sensitive adhesives, etc. In the conventional continuous bulk polymerization method, lactide and a metal catalyst, which are monomers, are added to the reactor to polymerize, To remove the remaining lactide. However, the continuous bulk polymerization method has a disadvantage that the metal catalyst is used in excess and the polylactide is decomposed by the residual metal catalyst after polymerization and is harmful to the human body. Also, since the viscosity is very high, there is a problem that it stays at the volatilization step or the efficiency of volatilization drops. In order to solve this problem, it is possible to produce a low molecular weight polylactide having a thermal characteristic different from that of the conventional resin by decreasing the amount of the metal catalyst used and increasing the activity of the metal catalyst by using DDD (Dodecanol) . In the present invention, since the low molecular weight polylactide is produced through the continuous bulk polymerization and the volatilization process, the polymerization time is short, the purification process using a solvent is not required separately, the viscosity is low and the volatilization process is easy, It is advantageous to mass production.

The method for producing a polylactide resin of the present invention comprises ring-opening polymerization of a lactide monomer in the presence of an organometallic catalyst and a cocatalyst in the presence of an aliphatic alcohol having 8 to 18 carbon atoms, as described above.

As the organic metal catalyst, octylate tin _{(Sn (Oct) 2, 2} -ethylhexanoate), stearyl North dibutyltin dilaurate (stannous dibutyltin dilaurate), 1 such as stearyl North dioctyltin dilaurate (stannous dioctyltin dilaurate) Any catalyst known to be usable in the manufacture of polylactide resins may be used, but is not limited thereto.

The organometallic catalyst is used in an amount of 0.001 to 0.015 part by weight, preferably 0.0015 to 0.01 part by weight, more preferably 0.002 to 0.008 part by weight based on 100 parts by weight of the lactide monomer. The amount of the organometallic catalyst to be used should be 0.001 part by weight or more from the viewpoint of securing excellent polymerization activity and 0.015 part by weight or less from the viewpoint of preventing resin decomposition due to catalyst residues.

The aliphatic alcohol which can be used as a cocatalyst together with the organometallic catalyst has 8 to 18 carbon atoms, preferably 9 to 16 carbon atoms, more preferably 10 to 14 carbon atoms. The aliphatic alcohol should have a carbon number of 8 or more in view of the performance as a cocatalyst and should have a carbon number of 18 or less in terms of steric hindrance.

In addition, the aliphatic alcohol may have 1 to 3, preferably 2 to 3, hydroxyl groups in the molecule. The number of hydroxyl groups in the molecule of the aliphatic alcohol should be at least 1 in terms of securing the molecular weight controllability, and may be 3 or less in terms of ensuring improved mechanical properties of the final resin.

The aliphatic alcohol may be at least one of octanol, decanol, dodecanol, octadecanol, etc., and decanol, dodecanol, etc. may be used in terms of effective molecular weight control.

The aliphatic alcohol is used in an amount of 0.1 to 10 parts by weight, preferably 0.2 parts by weight or more, more preferably 0.3 parts by weight or more, based on 100 parts by weight of the lactide monomer. The amount of the aliphatic alcohol to be used should be 0.1 part by weight or more in view of improving the viscosity control efficiency of the polymerization resin and 10 parts by weight or less in view of ensuring improved mechanical properties of the final resin.

In the method for producing a polylactide resin of the present invention, the ring-opening polymerization reaction of the lactide monomer may proceed by bulk polymerization or solution phase polymerization. In the preparation of the polylactide according to the above embodiment, Both bulk polymerization and solution polymerization are possible.

Here, the bulk polymerization can be defined as a polymerization reaction in which substantially no solvent is used. In this case, substantially no solvent is used. The solvent is used in a small amount of solvent for dissolving the catalyst, for example, a used lactide monomer 1 up to a maximum of 1 mL of solvent per kg. When the ring-opening polymerization proceeds by bulk polymerization, the step for removing the solvent after polymerization can be omitted, and the decomposition or loss of the resin in the solvent removal step can be suppressed.

On the other hand, when the solution phase polymerization is carried out, usable solvents may be used without limiting the constitution as long as they can dissolve the lactide monomer and the organometallic catalyst. Specifically, toluene, xylene, chloroform, dimethyl chloride, diphenyl ether, or a mixed solvent of two or more of the above-mentioned solvents may be used, but the present invention is not limited thereto. When the solvent polymerization is carried out, the viscosity of the polymerization solution can be kept low when the polymerization reaction proceeds, which is advantageous in mixing and advantageous in terms of easy polymerization transfer and transfer.

On the other hand, the lactide monomer may be prepared from lactic acid. Such lactide monomers can also be any form of lactide, including all forms of lactide, such as L, L-lactide, D, L-lactide, D, D-lactide,

The ring-opening polymerization of the lactide monomer may be carried out at a temperature of 120 to 220 ° C, preferably 170 to 190 ° C. On the other hand, under the above-mentioned temperature condition, the polymerization reaction may proceed for 0.5 to 48.0 hours, preferably 1.0 to 10.0 hours, but is not limited to the above-mentioned time. The ring-opening polymerization of the lactide monomer can be carried out at a polymerization reaction temperature of 120 ° C or higher for 0.5 hours or longer in view of the improvement in conversion, and can be carried out at 220 ° C or lower for 48.0 hours or shorter in terms of ensuring excellent color of the resin.

In another embodiment of the present invention, the present invention provides a polylactide resin prepared by the above method. The polylactide resin may have a thermal characteristic different from the conventional resin by minimizing the residual metal content and lowering the molecular weight by using a higher aliphatic alcohol having 8 to 18 carbon atoms together with the organometallic catalyst.

The present inventors have found that a polylactide resin prepared by ring-opening polymerization of a lactide monomer using an aliphatic alcohol having 8 to 18 carbon atoms as a cocatalyst together with an organometallic catalyst in a specific optimized range of content, (Tg) and melting temperature (Tm), as well as excellent biostability and biodegradability with a low molecular weight, can be exhibited with low thermal properties. Such a low molecular weight polylactide resin can be effectively applied to a medical field requiring excellent biostability and biodegradability or a film field requiring a flexibility improved by a low glass transition temperature (Tg).

The polylactide resin has a weight average molecular weight of 1,000 to 200,000 g / mol, preferably 3,000 to 150,000 g / mol, more preferably 5,000 to 100,000 g / mol, and still more preferably 7,000 to 20,000 g / mol . The polylactide resin preferably has a number average molecular weight of 1,000 to 100,000 g / mol, preferably 2,000 to 70,000 g / mol, more preferably 3,000 to 50,000 g / mol, still more preferably 4,000 to 10,000 g / mol . In view of the mechanical properties of the final resin, the weight average molecular weight and the number average molecular weight of the polylactide resin may be 1,000 g / mol or more, respectively, and 20,000 g / mol or less and 10,000 g / mol or less .

The polylactide resin may have a glass transition temperature (Tg) of 40 to 60 占 폚, preferably 45 to 50 占 폚. In addition, the melting temperature (Tm) of the polylactide resin may be 140-180 ° C, and more preferably 145-165 ° C. The glass transition temperature (Tg) and the melting temperature (Tm) of the polylactide resin may be 40 ° C or higher and 140 ° C or higher, respectively, in terms of resin storage and handling, and 60 ° C or lower and 180 ° C or lower .

The polymerization of the low molecular weight polylactide resin according to the present invention as described above can achieve an excellent conversion rate as compared with the conventional polymerization method and minimize the residual monomer content in the polymer. When the process for producing a low molecular weight polylactide resin of the present invention is applied, a conversion rate of 85% or more or 85% to 99.99%, preferably 87% or more, more preferably 90% or more can be achieved. The residual monomer content in the thus prepared polymer may be 15% or less, or 0.01% to 15% or less, preferably 13% or less, more preferably 10% or less, and more preferably, the residual monomer The content may be made to be 1% or less.

In addition, unlike the conventional polymerization process, the present invention can synthesize both a high molecular weight polylactide resin and a low molecular weight polylactide resin, and is advantageous for mass production, and continuously proceeds from the polymerization to the volatilization step .

On the other hand, in another embodiment of the present invention, the present invention provides a polylactide resin composition comprising the above-mentioned polylactide resin.

Such a polylactide resin composition is expected to exhibit excellent biodegradation characteristics and flexible properties as it contains a low molecular weight polylactide resin and can be preferably used for future oriented materials such as medical materials or environmentally friendly films . In addition, the polylactide resin composition can be used for the production of biodegradable containers such as disposable containers, disposable forks, etc., or disposable articles due to excellent biodegradability characteristics and the like.

At this time, the polylactide resin composition may include a polylactide resin alone, or may include a polycarbonate resin, an ABS resin, a polypropylene resin, or the like. However, when used as an electronic product packaging or an automobile interior material, the polylactide resin composition is not limited in its constitution, but in consideration of a decrease in mechanical properties such as durability, % ≪ / RTI > by weight. In addition, when used in the production of a product requiring more biodegradability such as a disposable article, the composition is not limited thereto, but the composition preferably contains at least 60% by weight of polylactide resin, more preferably at least 80% by weight of polylactide resin can do.

In addition, the polylactide resin composition may further include various additives previously contained in various resin compositions.

The polylactide resin composition may be a liquid or solid resin composition before molding the final product, or may be a plastic or a fabric in the final product state. The final plastic or fabric product or the like may be prepared by a conventional method ≪ / RTI >

In the present invention, matters other than those described above can be added or subtracted as required, and therefore, the present invention is not particularly limited thereto.

The present invention uses an aliphatic alcohol having a carbon number of 8 to 18 as a cocatalyst together with an organometallic catalyst in a specific content range optimized to reduce the ring opening monomer polymerization reaction time remarkably and to reduce the residual metal content A polylactide resin having a molecular weight can be effectively produced.

In particular, the low molecular weight polylactide prepared according to the present invention can realize excellent biostability and biodegradability, and can realize a thermal property having a low glass transition temperature (Tg) unlike conventional resins, And can exhibit very excellent performance in required eco-friendly films and the like.

FIG. 1 shows the result of differential scanning calorimetry (DSC) thermal analysis of a polylactide resin prepared according to Example 4 of the present invention.
2 shows the results of measurement of the molecular weights of the polylactide resins prepared according to Examples 1 to 4 of the present invention.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

Example  One

As shown in following Table 1, the monomer L- lactide 93.924 tablets twice a Sn (Oct) ₂ as an organometallic catalyst to the weight% (1,000 g) was added to 0.003 wt% (0.09369 g), and the co-catalyst dodecyl (DDP, 1-dodecanol) was refined once to prepare a reaction mixture containing 0.366 wt% (2.83 meq / mol, 3.6588 g) and polymerization was carried out at 185 ° C in a 2 L reactor. The mixture was stirred at a rate of 100 rpm at the time of polymerization. After the polymerization, the reaction mixture was transferred to a volatilizer and the unreacted monomers remaining in the reactant were recovered and removed at a temperature of 220 ° C to prepare a pelletized low molecular weight polylactide resin.

Example  2 to 4

As shown in the following Table 1, when the ratio of the monomer L-lactide to the organometallic catalyst Sn (Oct) ₂ (the molar ratio of the catalyst to the monomer) was changed and the amount of 1-dodecanol , A low molecular weight polylactide resin was prepared in the same manner as in Example 1.

Comparative Example  One

As shown in the following Table 1, except that the ratio of monomer L-lactide to Sn (Oct) _{2 as the} organometallic catalyst was different and the co-catalyst 1-dodecanol was not used, A low molecular weight polylactide resin was prepared.

The components, amounts used, process conditions and the like in the production method of the polylactide resin according to Examples 1 to 4 and Comparative Example 1 are as shown in Table 1 below.

division Catalyst: monomer mole ratio Monomer usage
(g) Organometallic catalyst Co-catalyst Kinds usage
(g) Kinds usage
(meq / mol) Example 1 30,000: 1 1,000 Sn (Oct) ₂ 0.0937 DDO 2.83 Example 2 40,000: 1 1,000 Sn (Oct) ₂ 0.0703 DDO 5 Example 3 50,000: 1 1,000 Sn (Oct) ₂ 0.0562 DDO 8.4 Example 4 60,000: 1 1,000 Sn (Oct) ₂ 0.0468 DDO 50 Comparative Example 1 30,000: 1 1,000 Sn (Oct) ₂ 0.0937 - -

Experimental Example

The properties of the polylactide resins prepared in Examples 1 to 4 and Comparative Example 1 were evaluated in the following manner.

(1) Measurement of molecular weight (Mw, Mn, PDI): The molecular weight (Mw, Mn) and the molecular weight distribution index (PDI: Mw / Mn) of the polymer were measured using Gel Permeation Chromatography (GPC) Mn) were measured.

(2) Conversion measurement: Measured using a Varian Unity Inova 500 MHz nuclear magnetic resonance spectrometer (Varian).

(3) Measurement of Glass Transition Temperature (Tg): Measured using a differential scanning calorimeter (DSC) of mettle-toledo.

(4) Measurement of Melting Temperature (Tm): Measured using a differential scanning calorimeter (DSC) of Mettle-Toledo Corporation.

The evaluation results of the physical properties of the polylactide resins according to Examples 1 to 4 and Comparative Example 1 are shown in Table 2 below.

division Mw (g / mol) Mn (g / mol) PDI Conversion Rate (%) Tg (占 폚) Tm (占 폚) Example 1 113,000 68,000 1.66 95 57 167 Example 2 69,200 42,800 1.61 96 54 167 Example 3 49,900 29,200 1.71 97 50 162 Example 4 8,600 5,000 1.72 96 47 145 Comparative Example 1 199,100 119,100 1.67 95 59 168

1 shows the results of DSC thermolysis of the polylactide resin prepared in Example 4, and the results of molecular weight measurements of the polylactide resin prepared in Examples 1 to 4 are shown in FIG. 2 . As shown in the DSC analysis results of FIG. 1, it was found that the polylactide resin of Example 4 prepared using an aliphatic alcohol according to the present invention had a lowered glass transition temperature (Tg) due to a change in thermal properties. As shown in the graph of Fig. 2, it can be seen that the molecular weight of the polymerized PLA is lowered by increasing the amount of dodecanol (DDO) according to Examples 1 to 4.

As shown in Table 2, the polylactide resins of Examples 1 to 4 prepared using the aliphatic alcohol as a cocatalyst according to the present invention had a significantly lowered molecular weight, a glass transition temperature (Tg) and a melting temperature (Tm) of It is confirmed that it can be implemented. Particularly, the polylactides of Examples 1 to 4 had a weight average molecular weight (Mw) and a number average molecular weight (Mn) of 8,600 to 113,000 g / mol and 5,000 to 68,000 g / mol, respectively, To 1.71.

In addition, the polylactides of Examples 1 to 4 of the present invention exhibited an excellent degree of conversion of 95% to 97%, a glass transition temperature (Tg) and a melting temperature (Tm) 167 < [deg.] ≫ C.

On the other hand, as shown in the experimental results for Comparative Example 1, when the aliphatic alcohol was not applied, the weight average molecular weight (Mw) and the number average molecular weight (Mn) were 199,100 g / mol and 119,100 g / It can be seen that the polylactide resin having a molecular weight is not polymerized.

Claims (9)

Comprising ring-opening polymerization of a lactide monomer in the presence of an organometallic catalyst and a co-catalyst in the presence of an aliphatic alcohol having 8 to 18 carbon atoms, wherein 0.001 to 0.015 parts by weight of an organometallic catalyst and 0.1 to 10 parts by weight By weight of the polylactide resin. The method according to claim 1,
Wherein the organometallic catalyst is selected from the group consisting of tin (Oct) ₂ , 2-ethylhexanoate, stannous dibutyltin dilaurate, and stannous dioctyltin dilaurate Wherein the polylactide resin is a polylactide resin. The method according to claim 1,
Wherein the cocatalyst is a polylactide resin having 1 to 3 hydroxyl groups in the molecule. The method according to claim 1,
Wherein the co-catalyst is at least one selected from the group consisting of octanol, decanol, dodecanol, and octadecanol. The method according to claim 1,
Wherein the ring-opening polymerization is carried out at a temperature of 120 to 200 DEG C for 0.5 to 48 hours. 6. A polylactide resin produced by the process according to any one of claims 1 to 5 and having a weight average molecular weight of 1,000 to 113,000 g / mol and a number average molecular weight of 1,000 to 68,000 g / mol. delete delete The method according to claim 6,
Wherein the polylactide resin has a glass transition temperature (Tg) of 40 to 57 占 폚 and a melting temperature (Tm) of 140 to 167 占 폚.

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