KR101777447B1 - Polylactic acid copolymer from plasticizer having end-functional group and composition comprising the same - Google Patents

Abstract

TECHNICAL FIELD The present invention relates to a poly (lactic acid) copolymer having a high crystallization rate and a composition comprising the poly (lactic acid) copolymer. The poly (lactic acid) copolymer of the present invention, which is produced by melt reaction of a poly (lactic acid) And is superior in heat resistance, so that it can be applied to various molded articles requiring heat resistance such as disposable articles, kitchen containers, electric / electronic parts, and automobile parts.

Description

TECHNICAL FIELD [0001] The present invention relates to a polylactic acid copolymer produced by using a plasticizer having a terminal functional group and a composition comprising the polylactic acid copolymer,

TECHNICAL FIELD The present invention relates to a poly (lactic acid) copolymer prepared using a plasticizer having a terminal functional group and a composition comprising the same, and more particularly, to a poly (lactic acid) copolymer and a composition containing the same that exhibit excellent crystallization speed, excellent processability and heat resistance .

Many of the petroleum derived plastics have a wide range of applications, from basic necessities to aerospace materials, with easy control of mechanical properties and thermal stability. However, when these plastics are disposed of in the environment, they are not decomposed and accumulate. In addition, when incinerating plastic waste, it emits harmful by-products and releases large amounts of carbon dioxide, accelerating environmental pollution and global warming.

Due to such environmental problems, studies on environmentally friendly plastics, that is, biodegradable plastics which are decomposed by plastics made of plant raw materials or microorganisms, have actively been studied. Among the eco-friendly plastics currently under consideration are polyhydroxybutyrate, polycaprolactone, polylactic acid, aliphatic polyesters, and bio-polyethylene, among which the most widely studied are commercially available polymers, It is a heritage.

Polylactic acid is a comparatively hard polymer and has a flexural modulus similar to that of general-purpose plastics, but lacks heat resistance and is not easily molded. These drawbacks have limitations that can not be applied to fields requiring high heat resistance. As a result, studies have been made to compensate for poor physical properties of polylactic acid by mixing polylactic acid with petroleum-based plastics such as polypropylene or polycarbonate. In many cases, however, the content of polylactic acid does not exceed 50 wt% There is a difficulty to say.

In order to ensure high heat resistance and moldability of the polylactic acid, there is a method of improving the degree of crystallization of the polymer. In order to increase the crystallinity of poly (lactic acid) at present, a method of increasing the temperature of the mold during injection molding and lengthening the cooling time in the mold is common, but there is a disadvantage that the molding cycle is prolonged. In order to reduce the cooling time, a method of accelerating the crystallization rate of poly (lactic acid) (hereinafter also referred to as crystallization degree) by adding a crystal nucleating agent is known. The crystal nucleating agent acts as a primary crystal nucleus of the crystalline polymer to accelerate crystal growth, to make the crystal size smaller and to increase the crystallization rate. As the crystal nucleus of the poly (lactic acid) resin, inorganic particles composed of talc and / or boron nitride, amide compounds, sorbitol derivatives, and phosphate ester metal salts are known, but their effectiveness is inadequate or their price is low.

According to Non-Patent Documents 1 and 2, a method of adding a nucleating agent and a plasticizer is proposed as another method for increasing the crystallization degree and the crystallization speed of poly (lactic acid). Unlike the method of adding an excess amount of plasticizer in order to impart flexibility to the polymer, the method is a method of increasing the crystallization speed by increasing the mobility of the polymer chain by adding a certain amount of plasticizer (anti-plasticization). In detail, although the crystallization rate of poly (lactic acid) was significantly lowered by mixing poly (lactic acid) and talc with polyethylene glycol, the crystallization rate was not sufficiently fast. Also, even if polyethylene glycol is used in an amount of 5% by weight or less, there is a disadvantage in that injection molding is not easy due to severe surface run-off.

In order to reduce the surface runoff phenomenon of polyethylene glycol, as disclosed in Korean Patent Laid-Open Nos. 10-2012-0035729 and 7,351,785, polyethylene glycol is added during polymerization of poly (lactic acid) to form a poly (lactic acid) -polyethylene glycol copolymer Is generated. However, when a copolymer is formed through polymerization, a long reaction time is required, a large amount of an organic solvent harmful to the human body must be used, and the reaction condition needs to be finely controlled. In addition, there is no mention of the crystallization degree and the crystallization rate. The object of the present invention is to provide flexibility in the production of a poly (lactic acid) film, and a problem that crystallinity is lowered by using a high content of polyethylene glycol.

Non-Patent Document 1: Polymer, 48, 6855 (2007)

Non-Patent Document 2: Society of Plastics Engineers, DOI: 10.1002 / spepro.002983

It is an object of the present invention to solve the problems of the prior art as described above, and it is an object of the present invention to provide a plasticizer, which is modified with a reactive functional group at a terminal having a difference in solubility parameter of 10 or less, Which is produced by a molten reaction without the use of an organic solvent harmful to human body.

It is also an object of the present invention to provide a composition comprising a polylactic acid copolymer having a high degree of crystallinity and a high crystallization rate and excellent in injection molding by adding a crystallization nucleating agent to the polylactic acid copolymer.

The poly (lactic acid) copolymer according to the present invention is prepared by the melt reaction of a poly (lactic acid) and a plasticizer whose terminal is modified with a reactive functional group, and the plasticizer is contained in an amount of 0.05 to 25% by weight.

In the polylactic acid copolymer according to the present invention, the polylactic acid may be L-poly lactic acid or D-poly lactic acid.

The weight average molecular weight of the poly (lactic acid) is preferably 10,000 g / mol or more. If the weight average molecular weight is less than 10,000 g / mol, the processability is deteriorated and the physical properties of the injected product are poor.

In the polylactic acid copolymer according to the present invention, the plasticizer having the terminal modified with a reactive functional group is a substance having a difference in solubility parameter with poly (lactic acid) of 10 or less, and is selected from the group represented by the following formulas But it is not limited to the plasticizers of the following formulas.

[Chemical Formula 1]

Wherein R ₁ and R ₃ are each independently an epoxy, isocyanate, anhydride, carbodiimide or hydroxyl group, R ₂ is hydrogen, a C ₁ to C ₈ alkyl or alkenyl group, or a C ₆ to C ₈ An aryl group, l is an integer of 0 to 200, and m is an integer of 0 to 200. Also, the positions of l and m may be interchanged.)

(2)

Wherein R ₄ and R ₈ are each independently an epoxy, isocyanate, anhydride, carbodiimide or hydroxyl group, R ₅ to R ₇ are each independently hydrogen, a C ₁ to C ₈ alkyl group or an alkenyl group, C ₆ -C ₈ An aryl group, x is an integer of 0 to 100, y is an integer of 1 to 200, and z is an integer of 0 to 100.)

(3)

Wherein R ₉ and R ₁₀ are represented by - (R ₁₁ O) _r R ₁₂ , wherein R ₁₁ is C ₁ -C ₆ alkylene and R ₁₂ is an epoxy, isocyanate, anhydride, carbodiimide , A hydroxy group, a hydrogen, a C ₁ -C ₈ alkyl group or an alkenyl group, or C ₆ -C ₈ An aryl group, o and p are integers of 0 to 8, q is an integer of 0 to 100, and r is an integer of 0 to 6.)

[Chemical Formula 4]

Wherein R ₁₃ to R ₁₆ are represented by - (R ₁₇ O) _v R ₁₈ wherein R ₁₇ is C ₁ -C ₆ alkylene and R ₁₈ is an epoxy, isocyanate, anhydride, carbodiimide , A hydroxy group, a hydrogen, a C ₁ -C ₈ alkyl group or an alkenyl group, or C ₆ -C ₈ S, t and u are an integer of 0 to 8, and v is an integer of 0 to 6.)

In the polylactic acid copolymer according to the present invention, the content of the plasticizer is 0.05 to 25% by weight, preferably 1 to 20% by weight, more preferably 2 to 10% by weight based on the total weight of the polylactic acid copolymer If the amount is less than 0.05% by weight, the crystallization rate of the copolymer lowers, which is undesirable. If the amount exceeds 25% by weight, the crystallization rate is increased rather than the stiffness of the polylactic acid is lowered. It is not preferable.

The poly (lactic acid) copolymer according to the present invention can be obtained by melt extrusion reaction of the poly (lactic acid) and the plasticizer. During the melt reaction with the poly (lactic acid), the copolymer or carboxyl group of the poly (lactic acid) .

The temperature of the melting reaction is from 160 to 250 ° C, preferably from 170 to 220 ° C, more preferably from 180 to 200 ° C. If the melting reaction temperature is less than 160 ° C, the polylactic acid resin does not melt, , The rate of the bonding reaction with the functional group of the plasticizer slows down. When the temperature exceeds 250 ° C, the decomposition of the poly (lactic acid) accelerates, the crystallization rate of the obtained resin lowers, and yellowing becomes undesirably undesirable.

The poly (lactic acid) copolymer according to the present invention does not use an organic solvent harmful to the human body, and more than 90% by weight of the copolymer is made of a biodegradable material, so that the poly (lactic acid) copolymer has high environmental friendliness.

The poly (lactic acid) copolymer according to the present invention is characterized in that injection molding is easy and the molded product has excellent heat resistance. More specifically, the cycle time at injection molding is at least 100 times higher than that of ordinary polylactic acid, and the thermal deformation temperature of the injection molded product is at least 70 ° C, preferably at least 100 ° C, more preferably at least 110 ° C For example, 100 to 200 < 0 > C.

The poly (lactic acid) copolymer can be used for molding products in fields where heat resistance is importantly required, for example, office equipment such as automobile parts, electric / electronic parts, machine parts, and computers.

The polylactic acid copolymer composition according to the present invention is characterized by containing 0.01 to 5 parts by weight of a crystallization nucleating agent based on 100 parts by weight of the polylactic acid copolymer of the present invention.

Specific examples of the crystallization nucleating agent include polyglycolide, benzohydrazide derivative, talc, sodium stearate, calcium lactate, ethylenebis (12-hydroxystearylamide), terephthalimide derivative: NU-100), 1,4-cyclohexanedicarboxylic dianilide, and zinc phenylphosphate.

The amount of the crystallization nucleating agent used is preferably 0.01 to 5 parts by weight based on 100 parts by weight of the polylactic acid copolymer. If the amount is less than 0.01 part by weight, the crystallization rate is not fast, and if the amount is more than 5 parts by weight, The crystallization speed is not further accelerated, which is economically undesirable.

The polylactic acid copolymer composition according to the present invention can be produced by blending together a crystallization nucleating agent when a polylactic acid and a plasticizer are melt-reacted. At this time, in addition to the crystallization nucleating agent, conventional additives such as general lubricants, inorganic particles, heat stabilizers and antioxidants can be further blended.

The poly (lactic acid) copolymer composition according to the present invention has higher crystallinity and faster crystallization rate than general poly (lactic acid). More specifically, a crystallinity of 40% or more, it is preferred that when the inducing crystal formation at 110 ℃ crystallization rate _{(t 1/2) 15 ~} 30 seconds. The crystallinity by, while warming up to 10 ℃ / min up to 200 ℃ using a differential scanning calorimeter (DSC) peak melting point compared to the ΔH _m of calories is found in the 150 ~ 180 ℃ and poly a ΔH ° _m calculated melting heat of legacy Is the obtained value. The crystallization rate was maintained at 200 캜 for 3 minutes by raising the temperature up to 200 캜 to 200 캜 using a polarizing microscope and then the temperature was reduced to 110 캜 at a rate of 100 캜 / Is the measured value.

The poly (lactic acid) copolymer and the composition containing the same according to the present invention have a high crystallization rate, a high degree of crystallinity, a high heat resistance, and excellent injection molding.

1 is a graph showing the heat distortion temperature (HDT) according to the solubility parameter difference (delta) between the plasticizer and poly (lactic acid) used in the examples.

Hereinafter, the present invention will be described in more detail with reference to the following examples and comparative examples. However, these are for the purpose of illustrating the present invention, and the scope of the present invention is not limited thereto.

< Example  And Comparative Example >

Materials, production methods, injection methods and physical properties measurement methods used in Examples and Comparative Examples are as follows.

(1) Polylactic acid resin

As the L-poly lactic acid resin, 3251D manufactured by NatureWorks LLC was used.

(2) a plasticizer

The plasticizer used was one prepared by Nagase Chemtech, NJC and the like and modified with epoxy.

(3) Manufacturing method

The polylactic acid and the plasticizer, and optionally the crystallization nucleating agent, were melt-kneaded using a twin-screw extruder. At this time, the plasticizer was injected into an extruder having an extrusion temperature of 180 to 200 ° C by using a liquid feeder, and after melting and kneading, the plasticizer was obtained as a pellet using a pelletizer.

(4) Injection method

The pellets prepared according to the method of (3) above were dried at 80 DEG C for 4 hours or more, and then a cylinder temperature of 200 DEG C, a mold temperature of 110 DEG C and a molding cycle of 60 seconds were set using an injection molding machine. The specimens were obtained by injection molding.

(5) Calculation of Solubility Parameter Difference (Δδ)

The difference in solubility parameter between the poly (lactic acid) and the plasticizer was calculated using the following equation with reference to Non-Patent Document 3 below. The unit of total solubility parameter δ is (cal / cm ³ ) ^1/2 , which can be calculated by E _coh (binding energy) and molar volume.

[Equation 1]

(F _d , F _p in the above formula 1 are the dispersion and polar group molar attraction contribution and E _h is the hydrogen bonding group contribution.) The values of F _d , F _p and E _h for the general structural formula are solubility parameter component The results of δ _{d, p, h} are used to predict the total solubility parameter value or to predict solubility with other materials.

Non-patented article 3: Propeties of Polymers (1990) -Van Krevelen

(5) Heat deformation temperature

The heat distortion temperature (HDT) was measured according to ASTM D648.

(6) Ease of injection molding

If the pellet obtained after the extrusion reaction is dried for more than 4 hours at 80 ° C and the injection molding time is 1 minute or less, injection molding is possible. If the injection molding cycle time is longer than 1 minute (Good), it was evaluated as x (defective) when insufficient crystallization was formed in the injection specimen and warpage occurred, or plasticizer outflow was severe and the mold was contaminated and injection was impossible.

7 time crystallization degree ranging from 50% (t _1/2; crystallization rate) Measurement

After the resin composition was melted at 200 占 폚, a thin film was formed on a slide glass and a glass cover was placed thereon. The slide glass was placed on a heating plate (Linkam Scientific Instruments Ltd.) preheated to a temperature of 110 캜, and the crystallization rate of the resin composition was observed with a polarizing microscope (Olympus BX51). More specifically, a polarized He-Ne laser having a wavelength of 632.8 nm was transmitted through the film to measure the degree of crystallization using the intensity of light subtracted as the resin crystallized (38-channel photodiode array of Hamamastu Photonics Co.) . The calculated by the following formula 1, the crystallinity (relative crystallinity Χ _c) with time was indicated in the graph the value as Χ _c against time, in seconds, the amount of time that the Χ _c the time 0.5 days t _1/2 Respectively.

[Equation 2]

(I) is the intensity of light at the time t, I (0) is the intensity of the light before the crystallization of the resin starts, and I _? Is the intensity of the light when the crystallization is completed. )

(8) Plasticizer dissolution test

The flexural strength measurement specimens were stored for 24 hours at a temperature of 80 ° C and a relative humidity of 50% in a thermo-hygrostat. When the plasticizer was eluted, it was rated as?, When the plasticizer was slightly eluted, it was evaluated as &amp; cir &amp;

Example  1 to 7 and Comparative Example  1 to 11

The compositions and physical properties of the compositions of Examples 1 to 7 and Comparative Examples 1 to 11 are shown in Table 1 below.

In Examples 1 to 7 and Comparative Examples 1 to 11 shown in Table 1, components and contents according to the composition shown in Table 1 below were mixed, followed by melt-kneading at 190 占 폚 in a twin-screw extruder. The pellet samples were dried at 80 DEG C for 4 hours or more, maintained at a temperature of 100 DEG C, maintained at 100 DEG C by injection molding, left at room temperature for 24 hours, and the physical properties of the pellets were measured by the same method as described above. The results are shown in Table 1 below.

In the case of Comparative Examples 9 to 11, examples in which no plasticizer is used.

[Table 1]

week)

1) Polylactic acid: Product name: 3251D, manufactured by NatureWorks

2) Plasticizer-1: Plasticizer having one or both ends modified with epoxy,

EX-141,145,171, 920,931,313,314,512,521,612,614,622, Nagase ChemteX Corporation

3) Plasticizer-2: Plasticizer having one or both ends modified with epoxy,

Trade name: E-PS, E-PO, manufactured by Nippon Chemical Co.

4) Plasticizer-3: Plasticizer with one end modified with epoxy

Code: WSD-158, Samsung Total for Experimental Production

4) a crystallization nucleating agent, a talc having a particle size of 3.5 ± 0.5 μm, a trade name: KC-5000C,

The chemical structures of the reactive plasticizers used in Examples 1 to 7 and Comparative Examples 1 to 8 are as follows.

[Reactive plasticizer of Example 1, WSD-158]

[Reactive plasticizer of Example 2, EX-141]

[Reactive plasticizer of Example 3, EX-145]

[Reactive plasticizer of Example 4, EX-171]

EX-920 (n = 3), EX-931 (n = 11)) of the reaction type plasticizers of Examples 5 and 6,

[Example 7: Reactive plasticizer, EX-313]

[Reactive plasticizer of Comparative Example 1, EX-314]

EX-512 (n = 2), EX-521 (n = 3)) of the reaction type plasticizers of Comparative Examples 2 and 3

EX-612 (WPE = 166), EX-614 (WPE = 167), EX-622 (WPE = 191)) of Comparative Examples 4,

[Reactive plasticizer of Comparative Example 7, E-PS]

[Reactive plasticizer of Comparative Example 8, E-PO]

In Table 1, Examples 1 to 8 show the heat resistance characteristics and the elution properties of the poly (lactic acid) copolymer composition prepared by using a plasticizer having a difference in solubility parameter with poly (lactic acid) of 10 or less and each having one or both terminals modified with epoxy . As shown in Table 1, the injection is easy the smaller solubility parameter difference from the poly (lactic acid) is smaller, faster crystallization rate (t _1/2), do not have a surface leakage phenomenon of unreacted plasticizers and polylactic acid terminus. Of particular importance is the fact that the difference in solubility parameters is an important criterion for determining elution.

In particular, poly (lactic acid) and the solubility parameter difference is the smallest in Example 1, the composition of the crystallization rate (t _1/2) is the fastest, heat distortion temperature was measured the highest at about 121 ℃, which thermal deformation of the general polylactic acid Which is much higher than the temperature of 56 ° C.

Meanwhile, as shown in FIG. 1, when the solubility parameter difference Δδ and the heat distortion temperature (HDT) are plotted, a certain pattern can be found. First, the smaller the difference in solubility parameter, the more the thermal deformation temperature tends to increase. The solubility parameter difference can be divided into the plasticizer dissolution zone and the plasticizer dissolution zone based on 10. It is preferable that the plasticizer is not costly, so it is desirable to select a plasticizer having a solubility parameter difference of 10 or less.

Claims (8)

Wherein the plasticizer has a difference in solubility parameter of 10 or less as compared with the polylactic acid,
Wherein the plasticizer having the terminal modified with a functional group is represented by the following chemical formula 3 or 4:
(3)

Wherein R ₉ and R ₁₀ are represented by - (R ₁₁ O) _r R ₁₂ , wherein R ₁₁ is C ₁ -C ₆ alkylene and R ₁₂ is an epoxy, isocyanate, anhydride, carbodiimide , a hydroxy group, is hydrogen, C ₁ ~ C ₈ alkyl group or a C ₂ ~ C ₈ alkenyl, or C ₆ ~ C ₈ aryl group, o and p is an integer of from 1 to 8, q is an integer from 1 to 100, and r is an integer of 0 to 6.)
[Chemical Formula 4]

Wherein R ₁₃ to R ₁₆ are represented by - (R ₁₇ O) _v R ₁₈ wherein R ₁₇ is C ₁ -C ₆ alkylene and R ₁₈ is an epoxy, isocyanate, anhydride, carbodiimide , a hydroxy group, hydrogen, C ₁ ~ C ₈ is an alkyl group or a C ₂ ~ C ₈ alkenyl, or C ₆ ~ C ₈ aryl group, s, t and u is an integer of from 1 to 8, v is an integer from 1 to 6 to be.). delete The poly (lactic acid) copolymer according to claim 1, wherein the poly (lactic acid) is L-poly (lactic acid) or D-poly (lactic acid). The polylactic acid copolymer according to claim 1, wherein the temperature of the melting reaction is 160 to 250 ° C. The polylactic acid copolymer according to claim 1, wherein the polylactic acid copolymer has a thermal deformation temperature of 100 ° C or more. A polylactic acid copolymer composition comprising 0.01 to 5 parts by weight of a crystallization nucleating agent based on 100 parts by weight of the polylactic acid copolymer according to any one of claims 1 to 5. The method according to claim 6, wherein the crystallization nucleating agent is selected from the group consisting of polyglycolide, benzohydrazide derivative, talc, sodium stearate, calcium lactate, ethylenebis (12-hydroxystearylamide), terephthalimide derivative -Cyclohexanedicarboxylic dianilide, and zinc phenylphosphate. The polylactic acid copolymer composition according to claim 1, The polylactic acid copolymer composition according to claim 6, wherein the polylactic acid copolymer composition has a crystallization rate of 40% or more and a crystallization speed (t _1/2 ) of 15 to 30 seconds when the crystal formation is induced at 110 ° C. Composition.

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