KR20060024876A - Novel clay/polylactide nanocomposite with improved shear thining property and preparation thereof - Google Patents

Abstract

The present invention relates to novel clay / polylactide nanocomposites using melt kneading of polylactide-modified clay and linear polylactide, and a method of manufacturing the same. More specifically, (1) preparing a modified clay by introducing polylactide by ring-opening polymerization reaction into a layered clay having a hydroxyl group on the surface; And (2) melt kneading the clay prepared in (1) and the high molecular weight polylactide to produce a novel clay / polylactide nanocomposite. The novel clay / polylactide nanocomposite produced is improved. Shear thinning.

Polylactide * nanocomposite * shear thinning * ring-opening polymerization * melt kneading

Description

Novel Clay / Polylactide Nanocomposite with Improved Shear Thining Property and Preparation Thereof}             

1 is a graph showing the rheological properties at 210 ℃ of the clay / polylactide nanocomposite Clay- g -PLL-h / PL prepared in Example 2 of the present invention and pure polylactide.

Figure 2 is a graph showing the rheological characteristics at 210 ℃ of the clay / polylactide nanocomposite Clay- g -PLL-l / PL and pure polylactide prepared in Comparative Example 2 of the present invention.

3 is Clay-g-PLL-h / PL and Cloisite ^? Of 3wt% clay content in the clay / polylactide nanocomposites prepared in Example 2 and Comparative Example 3 of the present invention; A graph showing the rheological properties of 30B / PL, and pure polylactide at 210 ° C.

FIG. 4 is a graph showing the rheological properties of clay-g-PLL-h / PL and commercialized OPP grade polypropylene in the clay / polylactide nanocomposite prepared in Example 2 of the present invention.

5 is Clay-g-PLL-h / PL and 3wt% clay content of 3 wt% clay in the clay / polylactide nanocomposite prepared in Example 2 and Comparative Example 3 of the present invention ^. TEM picture of 30B / PL.

6 is Cloisite ^? And Clo- g-PLL-h / PL and 3 wt% clay content of 3 wt% clay in the clay / polylactide nanocomposites prepared in Example 2 and Comparative Example 3 of the present invention ^. The WAXD pattern of 30B / PL is shown.

The present invention relates to novel clay / polylactide nanocomposites using melt kneading of polylactide-modified clay and linear polylactide, and a method of manufacturing the same. More specifically, (1) preparing a modified clay by introducing polylactide by ring-opening polymerization reaction into a layered clay having a hydroxyl group on the surface; And (2) melt kneading the clay prepared in (1) and the high molecular weight polylactide to produce a novel clay / polylactide nanocomposite. The novel clay / polylactide nanocomposite produced is improved. Shear thinning.

Polylactide is a biodegradable, biocompatible aliphatic polyester, which has been used mainly for medical purposes such as drug delivery media, tissue engineering supports, and sutures. However, recently, polylactide has been recognized as an alternative to general purpose plastics such as polyethylene, polypropylene, polystyrene, etc. due to the recognition of the biodegradability, excellent mechanical strength, and environmentally friendly materials of the polymer itself.

However, polylactide has significant limitations in practical applications due to the poor processability, robustness, etc. of the material itself despite some of the above advantages. In particular, the weak melt processability of polylactide, such as low shear thinning and pyrolysis, is the biggest problem in application to general purpose plastics, and existing polymer processing equipment such as extruders and injection molding machines that are currently commercialized can be easily used. There is no problem.

Thus, researches to modify polylactide have been actively conducted in order to solve the above problems, and most representative examples thereof include branched polylactide synthesis and clay / polylactide nanocomposite production.

In the case of the former branched polylactide, the shear thinning property is improved, but there are disadvantages in that it cannot solve gas permeability and low heat distortion temperature, which are other problems of the polylactide. Therefore, recent researches for improving melt processability, gas permeability and heat distortion temperature of polylactide are focused on the preparation of clay / polylactide nanocomposite materials.

The method of preparing the clay / polylactide nanocomposite is largely divided into two methods. The first is a method using a polymerization method, and the second is a method using a melt kneading method.

When the clay / polylactide nanocomposite is prepared using the former polymerization method, the polylactide ends are fixed to the surface of the clay, and thus, even when the clay content is relatively low, it may exhibit considerable shear thinning phenomenon. Due to the heterogeneous reaction conditions and the high melting temperature of the polylactide, the molecular weight of the polylactide bonded to the clay surface may be relatively small, resulting in a decrease in mechanical properties. In addition, when the latter melt kneading method is used, the mechanical strength can be maintained due to the use of the already synthesized polylactide. However, the polylactide chain and the surface of the clay are only physically interacted with each other to generate a significant shear thinning phenomenon. There is a disadvantage that a relatively high clay content is required to represent.

Accordingly, the present inventors have studied to solve the above problems, and when the polymerization method and the melt kneading method are applied simultaneously under optimum conditions, the novel clay / polylactide nanocomposite that maintains mechanical properties while improving shear thinning phenomenon It has been found that the present invention can be prepared to complete the present invention.

Accordingly, it is an object of the present invention to provide novel clay / polylactide nanocomposites with improved shear thinning properties.

Another object of the present invention is to provide a method for preparing the clay / polylactide nanocomposite.

In order to achieve the above object, the novel clay / polylactide nanocomposite of the present invention (1) to prepare a modified clay by introducing polylactide by ring-opening polymerization reaction to the layered clay having a hydroxyl group on the surface ; And (2) melt kneading the clay prepared in (1) and the high molecular weight polylactide to produce a novel clay / polylactide nanocomposite.

In the present specification, the "shear scavenging phenomenon" means a rheological property of a polymer whose composite viscosity decreases as the shear rate increases in log-log coordinates due to its pseudoplastic properties. .

Hereinafter, the present invention will be described in more detail.

Hereinafter, a method for preparing the novel clay / polylactide nanocomposite of the present invention will be described in more detail at each step.

(1) preparing a modified clay by introducing polylactide in a ring-opening polymerization reaction into a layered clay having a hydroxyl group on its surface;

The most characteristic feature of the present invention is a method for producing clay with polylactide, wherein the number average molecular weight of polylactide grafted on the surface of the modified clay to enhance shear thinning is 15,000 g / mol. Should be ideal. This is the molecular weight range for properly using the chain entanglement phenomenon and slip phenomenon. Therefore, in the present invention, the clay surface is first activated with an initiator for ring-opening polymerization to first induce the initiator to be located only on the clay surface, and after the activation of clay, the lactide is added to increase the reaction temperature and allow the ring-opening polymerization to proceed for a predetermined time. By reacting only on the clay surface, it is possible to produce modified clay grafted polylactide on the clay surface.

In the step (1), after the clay having a hydroxyl group on the surface is pretreated using a ring-opening polymerization catalyst in order to increase the reaction yield, the lactide-based monomer is added to the pretreated clay, and then the reaction system is heated to raise the clay surface. Carry out the reaction. At this time, since the molecular weight of the polylactide is affected by the polymerization temperature, the higher the temperature rise temperature is preferable as the boiling point of the solvent. In addition, since the molecular weight of the polylactide to be polymerized is determined according to the number of molecules of the activated hydroxyl group and the number of molecules of the monomer, the content of the monomer depends on the number of molecules of the hydroxyl group activated on the clay surface.

Specific examples of the lactide-based monomers include L-lactide, D-lactide, DL-lactide, racemic lactide, and the like.

In addition, the ring-opening polymerization catalyst used in the above is a tin (tin), aluminum (Al), rare earth (rare earth) catalyst, it can be used as one or a mixture thereof. The content of the catalyst is used in an amount of 0.01 to 1.0 mol% of the monomer added to the ring-opening polymerization.

The number average molecular weight of the polylactide grafted on the surface of the modified clay produced by the method of step (1) is 15,000 g / mol or more.

(2) melt kneading the clay prepared in (1) and the high molecular weight polylactide to prepare a novel clay / polylactide nanocomposite;

The number average molecular weight of the polylactide used in step (2) is 50,000 g / mol or more.

The novel clay / polylactide nanocomposites prepared above contain 0.1-10% by weight of clay.

Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited only to these examples.

Example 1 Preparation of Clay with Surface Modified with Polylactide (I)

In order to modify the clay into a structure suitable for the present invention, Cloisite ^? 30B and the L-lactide monomer are reacted with tin (II) octoate as a catalyst.

First, dry Cloisite ^® dispersed in 240 ml of xylene dehydrated in the glove box ^. 0.3 mmol of tin (II) octoate was added to 4.32 g of 30B, followed by stirring at 50 ° C. for 1 day. 43.2 g of L-lactide was added to the activated clay, and then the ring temperature polymerization reaction was performed for 7 days after raising the reactor temperature to 135 ° C.

After completion of the reaction, the reaction was precipitated in excess of diethyl ether and the precipitate was filtered to remove unreacted L-lactide. The unreacted precipitate was dispersed in tetrahydrofuran, centrifuged at 4000 rpm for 5 minutes, the supernatant was separated and the precipitate was washed with tetrahydrofuran. After repeating the centrifugation and washing three times, the precipitate was dried in a vacuum oven for 60 days at 60 ℃ to remove the residual solvent. Next, the purified composite was characterized using TGA, GPC and the like, the results are shown in Table 1 below.

Ring-opening polymerization test results of clay- g -PLL-h Code Clay content ^a [wt%] M _n of Poly (l-lactide) ^b [g / mol] PDI ^b Formation d ^c [wt%] Clay- g -PLL-h 9.6 21,600 1.42 99> a) measurement by TGA b) ion exchange with 0.1 M LiCl, measurement by GPC using polystyrene reference material c) centrifugation three times, and then vacuum drying

<Comparative Example 1> Preparation of clay having a surface modified with polylactide (II)

Dried Cloisite ^® dispersed in 240 ml xylene removed with water in the glove box ^. 3.9 mmol of tin (II) octoate was added to 4.32 g of 30B, followed by stirring at 50 ° C. for 1 day. Next, 43.2 g of L-lactide was added to the activated clay, and then the ring temperature polymerization reaction was performed for 3 days after raising the reactor temperature to 135 ° C.

After completion of the reaction, the reaction was precipitated in excess of diethyl ether and the precipitate was filtered to remove unreacted L-lactide. The unreacted precipitate was dispersed in tetrahydrofuran, centrifuged at 4000 rpm for 5 minutes, the supernatant was separated and the precipitate was washed with tetrahydrofuran. After repeating the centrifugation and washing three times, the precipitate is dried in a vacuum oven at 60 ℃ to remove the residual solvent for at least one day. The purified composite was characterized using TGA, GPC, etc., the results are shown in Table 2 below.

Ring-opening polymerization test results of clay- g -PLL-l Code Clay content ^a [wt%] M _n of Poly (l-lactide) ^b [g / mole] PDI ^b Production rate ^c [wt%] Clay- g -PLL-l 9.7 9,400 1.25 99> a) measurement by TGA b) ion exchange with 0.1 M LiCl, measurement by GPC using polystyrene reference material c) centrifugation three times, and then vacuum drying

Example 2 Melt Kneading of Modified Clay and Polylactide (I)

The clay modified in Example 1 was melt kneaded with the dried high molecular weight polylactide, and the preparation conditions thereof are shown in Table 3.

Melt-kneading Conditions of Clay- g -PLL-h and Polylactide Code Clay forms Clay content [wt%] Mixing speed [rpm] Mixing time [min] Mixing temperature [℃] Clay- g -PLL-h / PL ^a Clay- g -PLL-h 0.5, 1.3 ^b 40 15 180 a) Cargill-Dow polylactide [Code: CDpoly, M _n : 85,000, PDI: 2.3, d -lactide: 6.6%] b) wt% of Clay- g -PLL-h are 5, 10, 30 respectively

Comparative Example 2 Melt Kneading of Modified Clay and Polylactide (II)

The clay modified by Comparative Example 1 was melt kneaded with the dried high molecular weight polylactide, and the preparation conditions thereof are shown in Table 4.

Melt-kneading Conditions of Clay- g -PLL-l and Polylactide Code Clay form Clay content [wt%] Mixing speed [rpm] Mixing time [min] Mixing temperature [℃] Clay- g -PLL-l / PL ^a Clay- g -PLL-l 0.5, 1, 3 ^b 40 15 180 a) Cargill-Dow polylactide [Code: CDpoly, M _n : 85,000, PDI: 2.3, d -lactide: 6.6%] b) wt% of Clay- g -PLL-l are 5, 10, 30 respectively

Comparative Example 3 Melt Kneading of Unmodified Clay and High Molecular Weight Polylactide

Cloisite ^? 30B was melt kneaded with the dried high molecular weight polylactide, and its preparation conditions are shown in Table 5.

Cloisite ^? Melt kneading condition of 30B and polylactide Code Clay form Clay content [wt%] Mixing speed [rpm] Mixing time [min] Mixing temperature [℃] Clay / PL ^a Cloisite ^? 30B 1, 3 40 15 180 a) Cargill-Dow polylactide [Code: CDpoly, M _n : 85,000, PDI: 2.3, d -lactide: 6.6%]

Example 3 Rheological Properties of Modified Clay / Polylactide Nanocomposite and High Molecular Weight Polylactide (I)

In order to measure the rheological properties of the nanocomposite prepared in Example 2 and high molecular weight polylactide, the resin was compressed at 190 ° C. in a press to prepare disk-shaped specimens of 1.5 cm in diameter and 0.5 cm in thickness. The prepared specimen was mounted on a 25 mm parallel plate with a thickness of 1 mm using a rotatable viscometer (ARES, Rheometric Scientific). When the temperature of the viscometer reached a set temperature, the experiment was performed under constant tensile and dynamic shear conditions of 10%. Rheological characteristics test results are shown in Figure 1 below.

As can be seen in Figure 1, the shear thinning properties of the nanocomposite when the molecular weight of the polylactide chemically bonded to the surface of the clay is greater than the chain entanglement molecular weight of the polylactide (~ 9,000 g / mol) is about 3wt% It can be seen that the clay content of is significantly improved. This is inferred to be due to a unique rheological phenomenon that occurs when the polylactide chain on the clay surface is entangled with the chain of polylactide as a substrate.

Comparative Example 4 Rheological Properties of Modified Clay / Polylactide Nanocomposite and High Molecular Weight Polylactide (II)

In order to measure the rheological properties of the nanocomposite prepared in Comparative Example 2 and the high molecular weight polylactide, the resin was compressed at 190 ° C. in a press to prepare disk-shaped specimens of 1.5 cm in diameter and 0.5 cm in thickness. The prepared specimen was mounted on a 25 mm parallel plate with a thickness of 1 mm using a rotatable viscometer (ARES, Rheometric Scientific). When the temperature of the viscometer reached a set temperature, the experiment was performed under constant tensile and dynamic shear conditions of 10%. Rheological characteristics test results are shown in Figure 2 below.

As can be seen in FIG. 2, in the case where the molecular weight of the polylactide chemically bonded to the clay surface is similar to the chain entanglement molecular weight of the polylactide (˜9,000 g / mol), the viscosity of the nanocomposite is increased even though the clay is added It can be seen that the viscosity of the pure polylactide is lower than that of the polylactide, and that the polylactide chains on the clay surface do not entangle with the matrix of the polylactide substrates, causing severe chain slippage under stressful conditions, thereby acting as a plasticizer in all areas. Infer by doing.

Comparative Example 5 Rheological Properties of Modified Clay / Polylactide Nanocomposites, Unmodified Clay / Polylactide Nanocomposites, and High Molecular Weight Polylactide

In order to measure the rheological properties of the nanocomposites prepared in Example 2 and Comparative Example 3 and high molecular weight polylactide, the resin was compressed at 190 ° C. in a press to prepare disc shaped specimens of 1.5 cm diameter and 0.5 cm thickness. It was. The prepared specimen was mounted on a 25 mm parallel plate with a thickness of 1 mm using a rotatable viscometer (ARES, Rheometric Scientific). When the temperature of the viscometer reached a set temperature, the experiment was performed under constant tensile and dynamic shear conditions of 10%. The rheological test results are shown in FIG. 3.

As can be seen in Figure 3, for the same clay content, the nanocomposite prepared in Example 2 showed a better shear thinning phenomenon than the nanocomposite prepared in Comparative Example 3, which is the impact of clay on the rheological properties The result is a complex reflection of the effect of chain entanglement between the polylactide chemically bonded to the clay surface and the high molecular weight polylactide as a substrate on the rheological properties.

Comparative Example 6 Rheological Properties of Modified Clay / Polylactide Nanocomposites, High Molecular Weight Polylactide, and Commercialized OPP Grade Polypropylene

In order to measure the rheological properties of the clay / polylactide nanocomposite prepared in Example 2 and the polypropylene of the OPP grade commercialized by Honam Petrochemical, the resin was compressed at 190 ° C. in a press to 1.5 cm in diameter and 0.5 cm in thickness. Disk-shaped specimens were prepared. The prepared specimen was mounted on a 25 mm parallel plate with a thickness of 1 mm using a rotatable viscometer (ARES, Rheometric Scientific). When the temperature of the viscometer reached a set temperature, the experiment was performed under constant tensile and dynamic shear conditions of 10%. Rheological characteristics test results are shown in Figure 4 below.

As can be seen in FIG. 4, the nanocomposite prepared in Example 2 exhibited better shear thinning than commercially available OPP grade polypropylene, which was chemically bound to clay surface and clay effects on rheological properties. The effect of chain entanglement between the polylactide and the high molecular weight polylactide as a substrate on the rheological properties is a result of a complex reflection.

Example 4 TEM image of modified clay / polylactide nanocomposite (I)

In order to take a TEM picture of the clay / polylactide nanocomposite prepared in Example 2, the flakes were made with a microtome device equipped with a diamond knife, and then Tecnai F20 equipment was used. The results are shown in Figure 5a.

As can be seen in FIG. 5A, the microstructure of the prepared clay / polylactide nanocomposite has a disordered intercalated structure.

Comparative Example 7 TEM image of modified clay / polylactide nanocomposite (II)

In order to take a TEM picture of the clay / polylactide nanocomposite prepared in Comparative Example 2 was used to make a slice with a microtome device equipped with a diamond knife Tecnai F20 equipment. The results are shown in Figure 5b below.

As shown in FIG. 5B, the microstructure of the prepared clay / polylactide nanocomposite has a disordered intercalated structure.

Comparative Example 8 TEM image of clay / polylactide nanocomposite

In order to take a TEM picture of the clay / polylactide nanocomposite prepared in Comparative Example 3 after the flakes were made with a microtome device equipped with a diamond knife, Tecnai F20 equipment was used. The results are shown in Figure 5c below.

As can be seen in Figure 5c it can be seen that the microstructure of the prepared clay / polylactide nanocomposite has a disordered intercalated structure.

Example 5 Cloisite ^? WAXD pattern of modified clay / polylactide nanocomposites with 30B

Cloisite ^? D / MAX-IIIC was used to obtain the WAXD pattern of the clay / polylactide nanocomposite prepared in Example 2, 30B, and the experimental conditions were 1.2 to 20 ^o at a room temperature of 1 ^o / min. Speed. The results are shown in Figure 6a below.

As can be seen in FIG. 6A, the prepared clay / polylactide nanocomposite disappeared when the clay interlayer peak of 2θ = 4.8 disappeared.

Comparative Example 9 WAXD pattern of modified clay / polylactide nanocomposite

In order to obtain the WAXD pattern of the clay / polylactide nanocomposite prepared in Comparative Example 2 was used D / MAX-IIIC equipment, the experimental conditions at each temperature range of 1.2 ~ 20 ^o at a rate of 1 ^o / min It was. The results are shown in Figure 6b below.

As can be seen in FIG. 6B, the prepared clay / polylactide nanocomposite showed that the clay interlayer peak of 2θ = 4.8 disappeared and the interlayer regularity of the clay disappeared.

Comparative Example 10 WAXD pattern of clay / polylactide nanocomposite

In order to obtain the WAXD pattern of the clay / polylactide nanocomposite prepared in Comparative Example 3 was used D / MAX-IIIC equipment, the experimental conditions at a temperature of 1.2 ~ 20 ^o at each temperature range of 1 ^o / min It was. The results are shown in Figure 6c below.

As can be seen in FIG. 6c, the prepared clay / polylactide nanocomposite disappeared because the clay intercalation peak of 2θ = 4.8 disappeared.

As described above, the present invention provides a composition and a method for producing the same, which can significantly increase the melt workability of the polylactide by maximizing the shear thinning phenomenon of the clay / polylactide nanocomposite even with a small amount of clay. The novel clay / polylactide nanocomposites provided by the present invention are expected to enable hollow fiber processing of polylactide due to increased shear thinning.

Claims (6)

(1) preparing a modified clay by pre-treating the hydroxyl group on the surface of the layered clay having a hydroxyl group on the surface by using a ring-opening polymerization catalyst, and introducing the lactide monomer to ring-opening polymerization; And (2) melt kneading the clay prepared in (1) and the high molecular weight polylactide to prepare a novel clay / polylactide nanocomposite; In the method of producing a novel clay / polylactide nanocomposite comprising: Method for producing clay / polylactide nanocomposites, characterized in that the number average molecular weight of the polylactide grafted on the surface of the modified clay prepared by the method of step (1) is 15,000g / mol or more The method of claim 1, wherein the catalyst of step (1) comprises at least one selected from the group consisting of tin, aluminum, and rare earths. Method for producing clay / polylactide nanocomposite, characterized in that it is used in an amount of mol%. The method of claim 1, wherein the monomer of step (1) is clay / polylac, characterized in that at least one selected from the group consisting of L-lactide, D-lactide, DL-lactide, and racemic lactide Method for preparing Tid nanocomposite. The method of claim 1, wherein the polylactide of step (2) has a number average molecular weight of 50,000 g / mol or more. Clay / polylactide nanocomposite prepared by the method of claims 1 to 4. The clay / polylactide nanocomposite of claim 5, wherein the nanocomposite contains 0.1 to 10% by weight of clay.

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