KR20200099486A - Biodegradable polyester resin composition with improved compatibility - Google Patents

Abstract

The present invention relates to a polyester resin composition with improved compatibility. More particularly, the present invention relates to a biodegradable polyester resin composition that improves compatibility between incompatible polyester resins having a large difference in the coefficient of thermal expansion, and significantly improves mechanical properties such as tear strength and elongation, and to a manufacturing method thereof.

Description

Biodegradable polyester resin composition with improved compatibility {BIODEGRADABLE POLYESTER RESIN COMPOSITION WITH IMPROVED COMPATIBILITY}

The present invention relates to a biodegradable polyester resin composition with improved compatibility, and more particularly, to improve compatibility between incompatible polyester resins having a large difference in thermal expansion coefficient, and significantly improve mechanical properties such as tear strength and elongation. It relates to a biodegradable polyester resin composition and a method of manufacturing the same.

With the recent rapid increase in the amount of plastic products used, environmental pollution problems caused by disposal of them after use are serious. Accordingly, development for application to various fields such as various containers and packaging papers using biodegradable polyester resins has been actively made. These biodegradable polyester resins are environmentally friendly because they are decomposed into low-molecular substances due to the enzyme action of microorganisms existing in the environment, and finally decomposed into water and carbon dioxide.

As a biodegradable polyester resin, polylactic acid (PLA), which is inexpensive and has good mechanical properties, is the most widely known, but it is applied to various fields due to the problem of low tear strength and elongation and easily damaged by impact. There are restrictions on the following.

In addition, polylactic acid has poor bubble stability, and thus there is a problem in that a hole is formed in a portion having a thin thickness during blow molding for producing a film. The blow molding is a widely used process due to its high production speed and low cost, but it is impossible to commercialize and commercialize it due to the limitations of blow molding of polylactic acid.

In order to compensate for the disadvantages of conventional polylactic acid, a study to improve the low physical properties of polylactic acid by blending with polybutylene adipate terephthalate (PBAT), another polyester resin with high tear strength and elongation It is being done.

However, other polyester resins, including polybutylene adipate-terephthalate copolymer, have a relatively high cost and very low compatibility with polylactic acid, making it difficult to achieve the desired physical properties, so that the vulnerability of polylactic acid cannot be improved. There is a problem that the polylactic acid biodegradable film is easily torn.

In order to improve this incompatibility problem, research has been attempted to lower the interfacial tension between PLA and PBAT by introducing various compatibilizers such as epoxy, peroxide and isocyanate in the PLA/PBAT blend, but the compatibility between the two resins is still possible. It is not enough, so it is difficult to apply.

On the other hand, polylactic acid and polybutylene adipate-terephthalate copolymer exhibit a slight difference in the coefficient of thermal expansion (CTE).In the case of polylactic acid, the coefficient of thermal expansion varies greatly depending on the temperature range, and from room temperature to 140 At °C, the average coefficient of thermal expansion is 199 ppm/℃. Further, in the case of the polybutylene adipate-terephthalate copolymer, the thermal expansion coefficient tends to increase linearly with temperature, and the average thermal expansion coefficient is 278 ppm/°C at room temperature to 170°C.

This difference in coefficient of thermal expansion causes voids due to the difference in shrinkage between the two resins as the polylactic acid and polybutylene adipate-terephthalate copolymer are blended at high temperature and then cooled to room temperature. Accordingly, polybutylene adipate-terephthalate copolymer, which is a dispersed phase, is dispersed in polylactic acid, which is a continuous phase in the blend, to form a sea-island structure on a plane, but a polybutylene adipate-terephthalate copolymer As the dispersed phase separates, the surface becomes coarse and even shows the form of a crushed blend.

As described above, when the dispersed phase in the polymer blend is separated from the continuous phase and pores are generated along the interface, the occurrence of cracks is very easily induced along the pore direction and the tear strength of the blend is significantly lowered, resulting in a decrease in physical properties. .

That is, in the past, research has focused on increasing the compatibility between the resin and the polylactic acid resin used to improve the physical properties of polylactic acid by introducing various compatibilizing agents, but these studies have been conducted in the incompatibility between two resins with low compatibility. It didn't ultimately solve the problem.

The present inventor minimizes the generation of voids in the blend by adjusting the average coefficient of thermal expansion of the two resins having incompatibility to a similar level, thereby improving the compatibility between the two resins with low compatibility, and remarkably improving mechanical properties such as tear strength. It was found that it could be made and the present invention was completed.

Korean Patent Application Publication No. 10-2015-0089091

It is an object of the present invention to provide a polyester resin composition with remarkably improved compatibility by improving compatibility between incompatible polyester resins having a large difference in coefficient of thermal expansion, and more specifically, exhibiting excellent biodegradability and tear strength, It is to provide a polyester resin composition excellent in mechanical properties such as elongation.

In addition, it is an object of the present invention to provide a polyester resin composition having improved bubble stability, excellent blow moldability and high productivity.

It is also an object of the present invention to provide a method for producing the polyester resin composition and a polyester molded article manufactured using the same.

The present invention for achieving the above object provides a polyester resin composition comprising an aliphatic biodegradable polyester, an aromatic polyester copolymer, and a thermal expansion coefficient modifier.

In one aspect of the present invention, the aliphatic biodegradable polyester and the aromatic polyester copolymer may have a difference in the average coefficient of thermal expansion at 25 to 140°C of 50 ppm/°C or more.

In one aspect of the present invention, the aliphatic biodegradable polyester and the aromatic polyester copolymer may have a difference in glass transition temperature of 60°C or more.

In one aspect of the present invention, the weight ratio of the aliphatic biodegradable polyester and the aromatic polyester copolymer may be 5:5 to 9:1.

In one aspect of the present invention, the thermal expansion coefficient modifier may be any one or a mixture of two or more selected from the group 4 metal alkoxide group.

In one aspect of the present invention, the thermal expansion coefficient modifier may be any one or a mixture of two or more selected from titanium alkoxide.

In one aspect of the present invention, the content of the thermal expansion coefficient modifier may be 0.01 to 5 parts by weight based on 100 parts by weight of the mixed resin of the aliphatic biodegradable polyester and the aromatic polyester copolymer.

In one aspect of the present invention, the polyester resin composition may further include a triglyceride as a thermal expansion coefficient modifier.

In one aspect of the invention, the glass transition temperature of the aromatic polyester copolymer may be -60 to 25 ℃.

In one aspect of the present invention, the polyester resin composition may be a polyester resin composition in which aliphatic biodegradable polyester forms a continuous phase and has a sea-island structure.

In addition, the present invention comprises the steps of preparing a polyester masterbatch composition comprising an aromatic polyester copolymer and a thermal expansion coefficient modifier; And mixing an aliphatic biodegradable polyester in the masterbatch composition.

In one aspect of the present invention, the content of the thermal expansion coefficient modifier may be 0.1 to 10 parts by weight based on 100 parts by weight of the aromatic polyester copolymer.

In addition, the present invention provides a polyester molded article manufactured by extrusion or injection of the polyester resin composition, and the polyester molded article may have remarkably excellent tear strength compared to a molded article manufactured from aliphatic biodegradable polyester.

The polyester resin composition according to the present invention has superior mechanical strength such as tear strength and shrinkage compared to the conventional aliphatic biodegradable polyester resin, and can overcome problems in use due to the low physical properties of the aliphatic biodegradable polyester resin. It has the advantage of not causing environmental pollution by being completely biodegradable in the state.

In addition, the polyester resin composition according to the present invention has a remarkably improved compatibility by controlling the thermal expansion coefficient of the incompatible polyester resin having a large difference in thermal expansion coefficient to a similar level, thereby ultimately solving the incompatibility problem between different resins. Rather, it has the advantage of showing remarkably improved physical properties.

In addition, as the polyester resin composition according to the present invention exhibits excellent blow moldability by improving conventional low bubble stability, it has an advantage of excellent productivity and applicability.

1 is a SEM photograph of a cross section of a polyester resin according to an embodiment of the present invention.
2 is an SEM photograph of a cross section of a polyester resin according to an embodiment of the present invention.
3 is a SEM photograph of a cross section of a polyester resin according to a comparative example of the present invention.

Hereinafter, the present invention will be described in more detail through specific examples or examples including the accompanying drawings. However, the following specific examples or examples are only one reference for describing the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

In addition, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. The terms used in the description in the present invention are merely intended to effectively describe specific embodiments and are not intended to limit the present invention.

In addition, the glass transition temperature used in the specification and the appended claims means that it is measured by differential scanning calorimetry (DSC) at a rate of 5°C/min unless otherwise defined.

In addition, the coefficient of thermal expansion used in the specification and the appended claims means those defined according to ASTM D696, unless otherwise specified.

In addition, the aromatic polyester copolymer used in the specification and the appended claims, unless otherwise specified, refers to a copolymer collectively referred to as polyester derived from different aromatic monomers or polyester derived from a mixture of aliphatic and aromatic monomers. it means.

In addition, the singular form used in the specification and the appended claims may be intended to include the plural form unless otherwise indicated in the context.

The present invention relates to a polyester resin composition that significantly improves compatibility between polyester resins having incompatibility so as to exhibit excellent blow moldability and excellent mechanical properties such as tear strength and biodegradability.

The polyester resin composition according to the present invention includes an aliphatic biodegradable polyester, an aromatic polyester copolymer, and a thermal expansion coefficient regulator.

The aliphatic biodegradable polyester used in the present invention exhibits a biodegradable property that is degraded by microorganisms or water, and any aliphatic polyester having known biodegradability can be used without limitation.

The total number of carbon atoms of the aliphatic repeating unit constituting the aliphatic biodegradable polyester may be 2 to 15. Specific examples, polylactic acid, polyglycolic acid, polycaprolactone, polybutylene adipate, polyethylene succinate, polybutylene succinate (polybutylene succinate), poly3-hydroxybutyrate, and the like may be exemplified, but are not limited thereto.

As the aliphatic biodegradable polyester, polylactic acid, which is preferably inexpensive and excellent in heat resistance and transparency, may be used.

Specifically, the polylactic acid (PLA) is a monomer derived from D-lactide, L-Lactide, or D,L-lactide (D,L-Lactide). It is polymerized from, and can be used as a polylactic acid homopolymer and a copolymer with other aliphatic a-hydroxy acid (AHA) by adjusting the content of the monomer according to the use, and the weight average molecular weight is 10,000 to 1 ,00,000 g/mol, specifically 50,000 to 500,000 g/mol, but is not limited thereto.

In addition, the aromatic polyester copolymer used in the present invention may be used without limitation as long as it is an aromatic polyester copolymer known to compensate for the low physical properties of the aliphatic biodegradable polyester. Specifically, the aromatic polyester copolymer may be an aliphatic/aromatic biodegradable polyester copolymer, and the total number of carbon atoms of the repeating unit containing an aromatic substituent included in the aliphatic/aromatic biodegradable polyester copolymer may be 6 to 30 days. have.

Specific examples include polybutylene adipate-co-terephthalate (PBAT) and polybutylene adipate-butylene succinate terephthalate copolymer (polybutylene adipate-co-butylene succinate terephthalate, PBAST). ) And the like may be illustrated. The aliphatic/aromatic biodegradable polyester copolymer has a relatively high price compared to the aliphatic biodegradable polyester, but has excellent tensile strength, moisture resistance, and processability.

As the aromatic polyester copolymer, a polybutylene adipate-terephthalate copolymer having excellent tensile strength, tear strength, durability and workability while preferably exhibiting biodegradability may be used.

Specifically, when the polybutylene adipate-terephthalate copolymer is used together with polylactic acid, it is effective to improve mechanical properties such as low elongation and tear strength while maintaining excellent biodegradability of polylactic acid.

The weight average molecular weight of the polybutylene adipate-terephthalate copolymer may be 10,000 to 500,000 g/mol, specifically 20,000 to 100,000 g/mol. As the polybutylene adipate-terephthalate copolymer has the weight average molecular weight, the film prepared from the polyester resin composition according to the present invention can have mechanical properties such as appropriate tear strength, and at the same time have good biodegradability. Can represent.

The polybutylene adipate-terephthalate copolymer includes a butylene adipate repeating unit and a butylene terephthalate repeating unit as repeating units forming a main chain, in a molar ratio of 1:9 to 9:1, specifically 3:7. To 7:3.

In one aspect of the present invention, the thermal expansion coefficient modifier remarkably improves the compatibility between the aliphatic biodegradable polyester and the aromatic polyester copolymer having incompatibility and imparts excellent mechanical properties to the polyester resin composition, metal alkoxide group Any one or a mixture of two or more selected from may be used.

Specifically, the metal alkoxide may be a Group 4 metal alkoxide, and as a specific example, titanium ethoxide, zirconium ethoxide, zirconium propoxide, titanium propoxide, titanium isopropoxide, zirconium isopro Foxside, titanium butoxide, titanium t-butoxide, zirconium butoxide and zirconium t-butoxide may be exemplified, but are not limited thereto.

As a preferred example of the metal alkoxide, it may be any one or a combination of two or more selected from titanium C1 to C4 alkoxide, and a specific example when using titanium butoxide with aliphatic biodegradable polyester and aromatic polyester copolymer, The effect of lowering the interfacial tension between the two resins of the aliphatic biodegradable polyester and aromatic polyester copolymer having incompatibility and preventing the generation of voids at the interface is excellent.

Specifically, when the difference in the coefficient of thermal expansion between the aliphatic biodegradable polyester and the aromatic polyester copolymer is large, pores are formed at the interface between the two polymers, leading to the occurrence of cracks along the pore direction, and thus physical properties such as tear strength. There is a problem that this remarkably deteriorates. However, as the polyester resin composition of the present invention contains the metal alkoxide, no voids occur at the interface despite the large difference in the coefficient of thermal expansion between the different polyester resins in the composition, and excellent dispersibility results in excellent elongation. And it has the advantage of showing the tear strength.

In one aspect of the present invention, the aliphatic biodegradable polyester and aromatic polyester copolymer has a difference in average coefficient of thermal expansion at 25 to 140°C of 50 ppm/°C or more, specifically 70 ppm/°C or more, and more specifically 80 ppm It may be above /℃.

In addition, the coefficient of thermal expansion of the aliphatic biodegradable polyester at 25 to 140°C may be 10 to 500 ppm/°C, specifically 30 to 400 ppm/°C, more specifically 50 to 300 ppm/°C, and the aromatic polyester copolymer The coalescence may be 10 to 500 ppm/°C, specifically 100 to 450 ppm/°C, and more specifically 200 to 400 ppm/°C.

In general, the volume of a solid increases as the temperature rises. On the contrary, when the temperature of the solid is released, the volume decreases as the temperature decreases. In this case, when the temperature of the solid increases by 1℃, the length of the solid is thermally expanded in a specific direction. It is defined as a coefficient, which has a close relationship with the glass transition temperature and shrinkage of an object.

Specifically, when the polymer is cooled to room temperature after thermal processing at a high temperature of 140° C. or higher, when the glass transition temperature of the polymer is above room temperature, the polymer shrinks significantly and exhibits a high shrinkage rate as the polymer is cooled to room temperature below the glass transition temperature.

On the other hand, when the glass transition temperature of the polymer is less than room temperature, the polymer shrinks gradually due to cooling and exhibits a low shrinkage rate.

That is, when two polymers having different coefficients of thermal expansion are thermally processed together and then cooled to room temperature, the difference in the glass transition temperature between the two polymers is large, and when the glass transition temperature of one polymer is above room temperature, the two polymers have a shrinkage ratio. There is a significant difference in the resulting polymer blend, which causes the generation of a large amount of voids at the interface due to the difference in shrinkage in the polymer blend.

However, in the polyester resin composition according to the present invention, by using an aliphatic biodegradable polyester, an aromatic polyester copolymer, and a thermal expansion coefficient modifier together, the average coefficient of thermal expansion of the two polymers is adjusted to a similar level, thereby minimizing the occurrence of voids. As a result, the compatibility between polymers is maximized, thereby having the effect of showing remarkably improved physical properties.

In one aspect of the present invention, the aliphatic biodegradable polyester and the aromatic polyester copolymer may have a difference in glass transition temperature of 60°C or higher, specifically 70°C or higher, and more specifically 80°C or higher.

In addition, the glass transition temperature of the aliphatic biodegradable polyester may be 25 to 170 °C, specifically 35 to 140 °C, more specifically 50 to 100 °C, and the glass transition temperature of the aromatic polyester copolymer is -60 to 25 It may be ℃, specifically -50 to 10 ℃, more specifically -40 to 0 ℃.

In the polyester resin composition of the present invention, since the aliphatic biodegradable polyester and the aromatic polyester copolymer each have the glass transition temperature and exhibit a large difference in the glass transition temperature within the above range, the compatibility between the two polymers is very poor. And, the incompatibility problem according to the coefficient of thermal expansion is ultimately solved, showing excellent compatibility without generating voids at the interface, and having an effect of improving excellent physical properties.

In one aspect of the present invention, the weight ratio of the aliphatic biodegradable polyester and the aromatic polyester copolymer may be 1:9 to 9:1, specifically 5:5 to 9:1, more specifically 6:4 to 9:1, more specifically 7:3 to 9:1 may be.

In the case of using an aromatic polyester copolymer to improve the weak physical properties of the conventional aliphatic biodegradable polyester, the compatibility between the two polymers is very poor, so it is difficult to achieve the desired physical properties, and a known compatibilizer is essentially used. As the biodegradable polyester resin composition has a high aliphatic biodegradable polyester content in the above range, it exhibits excellent biodegradability, heat resistance, transparency and applicability, and at the same time, elongation, tear strength, and moldability are remarkably improved. There is an effect that can be applied to the field.

In one aspect of the present invention, the content of the group 4 metal alkoxide as the thermal expansion coefficient modifier is 0.01 to 5 parts by weight, specifically 0.05 to 3 parts by weight based on 100 parts by weight of the mixed resin of the aliphatic biodegradable polyester and aromatic polyester copolymer Parts, more specifically, may be used in 0.1 to 2 parts by weight. In the above range, the compatibility of the aliphatic biodegradable polyester and the aromatic polyester copolymer is more effectively improved, and excellent tear strength and elongation are exhibited.

In addition, the polyester resin composition of the present invention may have an aliphatic biodegradable polyester forming a continuous phase and having a sea-island structure.

Specifically, referring to FIG. 3, when two polymers having different coefficients of thermal expansion are thermally processed together and then cooled to room temperature, the difference in the glass transition temperature between the two polymers is large, and the glass transition temperature of one polymer is at least room temperature. In this case, the two polymers exhibit a remarkable difference in the shrinkage rate, and in this case, the generation of voids at the interface is caused by the difference in shrinkage rate between the two polymers. Accordingly, as the dispersed phase having a large coefficient of thermal expansion and a glass transition temperature of less than room temperature is cooled from a continuous phase with a relatively small coefficient of thermal expansion and a glass transition temperature of less than room temperature and a high shrinkage rate, it gradually separates, resulting in a large amount of voids at the interface of the two polymers. Is formed to show a rough surface.

In the case of the polyester resin composition of the present invention, referring to FIG. 1, although the aliphatic biodegradable polyester and the aromatic polyester copolymer have a relatively large difference in the coefficient of thermal expansion, the aromatic polyester copolymer has an aliphatic biodegradability. It is easily dispersed in the continuous polyester phase, has excellent dispersibility without formation of voids, and the aromatic polyester copolymer dispersed phase is dispersed in the aliphatic biodegradable polyester continuous phase to form a planar sea-island structure preferably Can be.

Accordingly, the problem of the incompatibility of the two polymers in the polyester resin composition of the present invention is ultimately solved to show excellent compatibility, and mechanical properties such as tear strength and elongation are remarkably improved.

In a preferred aspect of the present invention, the polyester resin composition may further include a triglyceride as a thermal expansion coefficient modifier.

Triglyceride is a substance in which 2 or 3 fatty acid molecules are bonded to one molecule of glycerin through an ester bond, and the total number of carbon atoms of the fatty acid molecule may be C6 to C30, and specifically C8 to C20.

Triglyceride may be used as a plasticizer in general, but it is known that the plasticization performance is poor in the blend of aliphatic biodegradable polyester and aromatic polyester copolymer, and it does not have the property of controlling the thermal expansion coefficient. However, when triglycerides are used together with a group 4 metal alkoxide, which is a thermal expansion coefficient modifier, when mixed with aliphatic biodegradable polyester and aromatic polyester copolymers under high temperature conditions, the ester bond of triglycerides is coherent with aliphatic biodegradable polyester and aromatic polyester. Ester bonds and exchange reactions of the coalescence may occur. In the case of aliphatic biodegradable polyester by transesterification between triglyceride and polyester, aliphatic biodegradable polyester having a branch structure can be produced, and aliphatic biodegradable polyester and aromatic polyester copolymer Branched polyesters bonded to each other can be produced.

The aliphatic biodegradable polyester of the branched structure induces a decrease in the glass transition temperature while reducing the volume fraction of the crystal structure and increasing the mobility of the polymer chain present in the amorphous structure compared to the aliphatic biodegradable polyester of the straight chain structure. The volume reduction rate may be reduced due to the decrease in temperature during the cooling process. Accordingly, the thermal expansion coefficient of the aliphatic biodegradable polyester mixed with the aliphatic biodegradable polyester having a branched structure can be adjusted to a level similar to that of the aromatic polyester copolymer, so that the generation of voids can be minimized.

In addition, a copolymer having a structure in which an aliphatic biodegradable polyester and an aromatic polyester copolymer are bonded to each other through glycerin present in triglycerides is preferably located at the interface of a sea-island structure to prevent the generation of voids. By minimizing and further maximizing the compatibility between polymers, toughness can be improved, and tear strength and elongation can be further improved.

The content of the triglyceride may be used in an amount of 0.1 to 20 parts by weight, specifically 0.5 to 10 parts by weight, more specifically, 1 to 5 parts by weight, based on 100 parts by weight of the mixed resin of the aliphatic biodegradable polyester and aromatic polyester copolymer. have.

The polyester resin composition according to the present invention can be used without limitation as long as it is an additive that is obviously used in the relevant technical field, for example, a plasticizer, a viscosity modifier, an inorganic filler, an antioxidant, an amide wax, a pigment, a flame retardant, an antistatic agent, Any one or two or more additives selected from antibacterial agents, biodegradation accelerators, thermal stabilizers, light stabilizers, weather stabilizers, ultraviolet absorbers, and anti-blocking agents may be further included. Each of the additives may be used in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the mixed resin of an aliphatic biodegradable polyester and an aromatic polyester copolymer.

A description will be given of a method for producing a polyester resin composition according to the present invention.

The method for preparing a polyester resin composition according to the present invention comprises the steps of preparing a polyester masterbatch composition comprising an aromatic polyester copolymer and a thermal expansion coefficient modifier; And mixing an aliphatic biodegradable polyester in the masterbatch composition.

The thermal expansion coefficient modifier contained in the polyester masterbatch composition remarkably improves the compatibility between the aliphatic biodegradable polyester and aromatic polyester copolymer having incompatibility and imparts excellent mechanical properties to the polyester resin composition. It may be to use any one or a mixture of two or more selected from the alkoxide group. Since the metal alkoxide coefficient of thermal expansion has been described in detail above, a detailed description will be omitted.

The content of the thermal expansion coefficient modifier in the polyester masterbatch composition may be 0.1 to 10 parts by weight, specifically 0.1 to 5 parts by weight based on 100 parts by weight of the aromatic polyester copolymer. When the above range of the thermal expansion coefficient modifier is included, the molded article manufactured from the polyester resin composition to be prepared afterwards exhibits improved tear strength, elongation, and moldability without reducing biodegradation properties.

Specifically, in the step of preparing the polyester masterbatch composition, the aromatic polyester copolymer and the thermal expansion coefficient modifier are used at 30 to 500 rpm using an internal mixer, a super mixer, or a ribbon blender. By mixing at 140 to 200 ℃, it may be carried out including the step of introducing and extruding the extruder.

In addition, the step of mixing the master batch composition and the aliphatic biodegradable polyester is introduced into a known extruder, for example, a single screw extruder, a co-rotating twin-screw extruder or a two-way rotating twin-screw extruder, and a temperature of 140 to 200°C at 30 to 500 rpm. Can be carried out under conditions.

In one aspect of the present invention, a method of preparing a polyester resin composition may be performed by further including triglyceride as a thermal expansion coefficient modifier.

When a triglyceride is further included as a thermal expansion coefficient modifier, the method for preparing a polyester resin composition according to an aspect is to prepare a polyester masterbatch composition comprising an aromatic polyester copolymer and a thermal expansion coefficient modifier selected from the metal alkoxide group Step to do; And mixing an aliphatic biodegradable polyester and a triglyceride in the masterbatch composition.

The step of preparing the polyester masterbatch composition and the step of mixing the masterbatch composition and the aliphatic biodegradable polyester may use the same mixing means and methods described above, and the triglyceride coefficient of thermal expansion has been described in detail above, so a detailed description will be omitted.

In addition, after the step of mixing the aliphatic biodegradable polyester in the master batch composition, after extruding the polyester resin composition, may include the step of cooling and drying.

In this case, the cooling temperature may be performed below the glass transition temperature of the aliphatic biodegradable polyester, and the drying time is preferably dried until the final moisture content becomes 500 ppm or less.

In addition, the polyester resin composition in the form of pellets prepared after drying may be prepared in the form of a film through a known molding method such as blow molding using a circular die having a gap of 0.5 to 2.5 mm.

In addition, when manufacturing a film through blow molding, the BUR has a good range of 0.8 to 3.0, and is manufactured at a speed of 10 to 25 m/min to produce a blown film having a thickness of 10 to 50 μm. It can be.

In the case of polylactic acid, which is a representative aliphatic biodegradable polyester, there is a problem in that a hole is formed in a portion having a thin thickness during the process of blow molding to produce a film, so it is difficult to manufacture a film through blow molding. However, the polyester resin composition according to the present invention significantly reduces the problem of causing holes during molding through blow molding, and thus it is very easy to manufacture products such as films and bags, and the production speed is fast and various molded products at low cost. There is an advantage that can be manufactured.

In addition, when the polyester molded article according to the present invention is manufactured through the manufacturing step of the master batch composition, it has an effect of further improving the compatibility of the aliphatic biodegradable polyester and the aromatic polyester copolymer, and accordingly, the tear strength and The effect of remarkably improving the elongation at the same time is excellent.

In particular, in the case of including the above-described master batch composition manufacturing step, problems such as lowering of polymer molecular weight due to deterioration may generally be caused as two thermal processing processes occur until the final molded article is manufactured, but the manufacturing method of the present invention The masterbatch composition prepared by confirming that the weight average molecular weight of the aromatic polyester copolymer in the composition is rather increased, and thus can exhibit excellent mechanical properties without lowering the molecular weight due to deterioration.

In addition, the polyester molded article according to the present invention may be a polyester molded article manufactured from the method for producing a polyester resin composition as described above.

The polyester molded article according to the present invention may be manufactured by extrusion or injection of the polyester resin composition described above. The molded article may be manufactured through known means and is not limited to a specific shape and use.

In one aspect of the present invention, the polyester molded article is characterized in that the tear strength is significantly superior to the molded article made from aliphatic biodegradable polyester. As a specific example, as a molded article made from a polyester resin composition comprising a polylactic acid and polybutylene adipate-terephthalate copolymer exhibits excellent tear strength at least 1.5 times or more compared to a molded article made from a polylactic acid composition, The effect of preventing damage by impact is very excellent and has excellent durability.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples. However, the following Examples and Comparative Examples are only one example for describing the present invention in more detail, and the present invention is not limited by the following Examples and Comparative Examples.

(Material property evaluation)

1. Tear strength

It was measured with an elmendorf type tear strength tester according to KS M 3503.

2. Bubble stability

When forming the film, it must be produced without shaking from side to side while maintaining the bubble in an expanded state. At this time, the size of the bubble was not constant or the degree of shaking left and right was evaluated.

[Example 1]

Polylactic acid with a weight average molecular weight of 100,000 g/mol and a D-Lactide content of 1.4% by weight (PLA, glass transition temperature: 60°C) 75% by weight and a polybutylene adipate with a weight average molecular weight of 40,000 g/mol- Co-directional twin-screw extruder (diameter 48mm, L/D 40) by adding 0.11 parts by weight of titanium butoxide to 100 parts by weight of the mixed resin containing 25% by weight of terephthalate copolymer (PBAT, glass transition temperature: -30℃) Using an extrusion molding at 170 ℃ 50 rpm to prepare a polyester resin composition in the form of a pellet. After cooling the prepared polyester resin composition at -80°C for 5 hours, drying it in an oven at 80°C for 24 hours to make the moisture content less than 500 ppm, and then using a 55 mm single screw extruder (dice diameter 100 mm, die gap (dies gap) 1mm) was used to form a film having a thickness of 35 μm. At this time, the temperature of the dies was 170°C, the burr (BUR) was 2.8, and the film production speed was 15 m/min. As a result of evaluating the physical properties of the manufactured blow film, the tear strength was excellent and the bubble was stable. It was confirmed that it was maintained.

In addition, the prepared polyester resin composition was melt-extruded at 170° C., closely attached to a casting roll at 10° C., stretched at 85° C. 4.8 times the main contraction direction, and heat-set at 80° C., uniaxially stretching with a thickness of 45 μm. A polyester film was obtained. As a result of measuring the cross section of the prepared film by SEM, it was confirmed that it had a sea island structure as shown in FIG. 1.

[Example 2]

In Example 1, a blow film and a uniaxially stretched polyester film were prepared in the same manner as in Example 1, except that 35% by weight of polylactic acid and 65% by weight of a polybutylene adipate-terephthalate copolymer were used. Was prepared. It was confirmed that the produced blown film had excellent tear strength and bubble stability, and the uniaxially stretched polyester film had a sea island structure as shown in FIG. 2.

[Example 3]

0.44 parts by weight of titanium butoxide was added to 100 parts by weight of polybutylene adipate-terephthalate copolymer (PBAT, glass transition temperature: -30°C) having a weight average molecular weight of 40,000 g/mol, and a coaxial twin screw extruder (diameter 48mm, L/D 40) extruded at 170°C at 50 rpm to prepare a polyester masterbatch composition in the form of pellets, cooled at -80°C for 5 hours and dried in an oven at 80°C for 24 hours to The content was set to be 500 ppm or less.

Then, 25% by weight of the dried masterbatch composition and 75% by weight of polylactic acid (PLA, glass transition temperature: 60°C) having a weight average molecular weight of 100,000 g/mol and a D-Lactide content of 1.4% by weight were mixed in the same direction. A polyester resin composition in the form of pellets was prepared by extrusion molding at 170° C. at 50 rpm using a twin screw extruder (diameter 48 mm, L/D 40), and after cooling and drying in the same manner as in Example 1, it was molded into a film. . As a result of evaluating the physical properties of the prepared film, it was confirmed that the film had a tear strength superior to that of Example 1 and that the bubble was very stable.

[Example 4]

In Example 1, a blow film and a uniaxially stretched polyester film were prepared in the same manner as in Example 1, except that 5 parts by weight of triglyceride were added and used. The produced blown film was found to have very good tear strength and bubble stability.

[Example 5]

In Example 3, the same as in Example 3, except that 7 parts by weight of triglyceride was mixed with respect to 100 parts by weight of polylactic acid, and 75% by weight of a mixture of polylactic acid and triglyceride was mixed in 25% by weight of the masterbatch composition. Carried out to prepare a film. As a result of evaluating the physical properties of the film, it was confirmed that the film had a tear strength superior to that of Example 3 and that the bubble was very stable.

[Comparative Example 1]

A blow film and a uniaxially stretched polyester film were prepared in the same manner as in Example 1, except that titanium butoxide was not used in Example 1. The produced blown film has a remarkably low tear strength, and the size of the blown film is changed as the bubble is shaken by 2 cm or more from side to side during bubble molding, so that it cannot be continuously produced.The uniaxially stretched polyester film is also as shown in FIG. It was confirmed that a structure was not formed and a large amount of voids were formed at the interface between the two polymers, indicating a rough surface.

Claims (13)

A polyester resin composition comprising an aliphatic biodegradable polyester, an aromatic polyester copolymer, and a thermal expansion coefficient regulator. The method of claim 1,
The aliphatic biodegradable polyester and the aromatic polyester copolymer has a difference in average coefficient of thermal expansion at 25 to 140°C of 50 ppm/°C or more. The method of claim 1,
The aliphatic biodegradable polyester and the aromatic polyester copolymer has a difference in glass transition temperature of 60°C or more. The method of claim 1,
The weight ratio of the aliphatic biodegradable polyester and the aromatic polyester copolymer is 5:5 to 9:1 polyester resin composition. The method of claim 1,
The polyester resin composition wherein the thermal expansion coefficient modifier is any one or a mixture of two or more selected from the group 4 metal alkoxide group. The method of claim 1,
The thermal expansion coefficient modifier is a polyester resin composition of any one or a mixture of two or more selected from titanium alkoxide. The method of claim 5,
The content of the thermal expansion coefficient modifier is 0.01 to 5 parts by weight based on 100 parts by weight of the mixed resin of the aliphatic biodegradable polyester and aromatic polyester copolymer. The method of claim 7,
The polyester resin composition further comprises a triglyceride as the coefficient of thermal expansion modifier. The method of claim 1,
The glass transition temperature of the aromatic polyester copolymer is -60 to 25 ℃ polyester resin composition. The method of claim 1,
The polyester resin composition is a polyester resin composition having an aliphatic biodegradable polyester forming a continuous phase and having a sea-island structure. Preparing a polyester masterbatch composition comprising an aromatic polyester copolymer and a coefficient of thermal expansion modifier; And
Mixing an aliphatic biodegradable polyester with the masterbatch composition;
A method for producing a polyester resin composition comprising a. The method of claim 11,
The content of the thermal expansion coefficient modifier is 0.1 to 10 parts by weight based on 100 parts by weight of the aromatic polyester copolymer method for producing a polyester resin composition. A polyester molded article obtained by extruding or injecting the polyester resin composition according to any one of claims 1 to 10.

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