TWI609044B - Polylactic acid composition - Google Patents

Description

Polylactic acid composition

The present invention relates to a raw plastic composition, and more particularly to a polylactic acid composition having the advantages of heat resistance, impact resistance, and no characteristic processing.

Traditional plastic materials are made from petroleum. They are widely used in all aspects of daily life because of their light weight, easy processing, durability, and toughness. However, the plastic material has a stable structure and is not easily broken down by external environmental factors, making plastic waste a burden on the environment. At present, the disposal methods of plastic waste include landfill method and incineration method. After the plastic waste is buried, it will reduce the service life of the landfill in the short term because it is not easy to decompose. In the long run, the natural water seepage layer of the soil will be blocked and the land will be desertified, which will seriously affect the environmental ecology. When treated by incineration, plastic waste can almost disappear without occupying the land. However, in the process of incineration, harmful gases such as dioxin will be produced, which will also damage the environment.

With the increasing attention to environmental issues, the use and development of biodegradable plastics that can be decomposed by microorganisms in the natural environment has also received much attention. Among them, polylactic acid (PLA, also known as polylactide), in addition to having biodegradable properties without damaging the environment, it has the characteristics of convenient processing and good mechanical properties, and its monomer It can be completely converted from renewable resources such as corn or sugar beets without worrying about the source of raw materials, and its production cost is also relatively low.

However, the crystallization rate of polylactic acid is slow and it is difficult to crystallize during the molding process, so that the heat distortion temperature of the molded product of polylactic acid is low, resulting in heat resistance. Insufficient sex, difficult to apply to higher temperature environments. If the crystallinity of the polylactic acid can be effectively increased, the heat distortion temperature of the molded article of the polylactic acid can be increased to increase the heat resistance, thereby increasing the application range of the polylactic acid.

Specifically, the processing cycle of polylactic acid can be completed in one minute through the injection molding process of a general cold mold, but the heat distortion temperature of the molded article is only about 55 to 60 ° C, and the Taiwan Patent Certificate No. I364362 discloses A method for producing a heat-resistant polylactic acid molded article, which comprises adding a nucleating agent to a polylactic acid raw material, and then forming a preliminary molded product, and then heat-treating the preliminary molded article to thereby improve crystallinity of the primary molded article, The polylactic acid product having higher heat resistance is obtained, that is, the heat resistance of the polylactic acid is improved mainly by means of secondary processing.

However, it takes time to perform secondary processing, and additional cost is required, which causes shortcomings in overall process time and cost, but does not meet industrial requirements.

In view of the above-mentioned shortcomings of the prior art, it is an object of the present invention to provide a polylactic acid composition which has better heat resistance and impact resistance after being subjected to secondary processing after molding, thereby saving process time and cost. advantage.

In order to achieve the foregoing object, the technical means adopted by the present invention is to provide a polylactic acid composition comprising: a polylactic acid mixture comprising 60 to 95% by weight of L-type polylactic acid material and 5 to 40% by weight. a D-type polylactic acid material; a polymer blend, which is a polyester polymer blend or a polyether type a polymer blend having a polymer chain having at least one functional group capable of forming a hydrogen bond; a nucleating agent selected from the group consisting of an aromatic acid salt compound, a fatty acid metal salt, an inorganic filler, and a combination thereof And a compatibilizing agent comprising a peroxide or an unsaturated reactive functional compound.

Optical purity: a mixture of compounds that are optical isomers, and the pure state of a compound in the mixture, the ratio of the optical rotation of the former to the optical rotation of the latter.

The polylactic acid composition of the present invention has the advantages that it can have high heat resistance without secondary processing, saves time and cost, and can simultaneously have high impact resistance, so that it can be applied in a wider range.

Further, the functional group which is liable to form a hydrogen bond is a carboxyl group, an alcohol group, an ether group, an amine group or a guanamine group.

Further, the unsaturated reactive functional compound is an unsaturated carboxylic acid ester compound, an epoxy compound, a polyunsaturated polyester compound or a polyvalent guanamine compound.

Preferably, the content of the polylactic acid mixture is 100 parts by weight, the content of the polymer blend is 0.1 to 49 parts by weight, and the content of the nucleating agent is 0.1 to 15 parts by weight, and the compatibilization is carried out. The content of the agent is from 0.1 to 5 parts by weight.

Most preferably, the content of the polylactic acid mixture is 100 parts by weight, the content of the polymer blend is 0.5 to 15 parts by weight, and the content of the nucleating agent is 0.5 to 5 parts by weight, and the compatibilization is carried out. The content of the agent is from 0.2 to 2 parts by weight.

Preferably, in the polylactic acid mixture, the L-type polylactic acid material has L-type polylactic acid having an optical purity of 95% or more, and the D-type polylactic acid material has D-type polylactic acid having an optical purity of 95% or more.

Most preferably, in the polylactic acid mixture, the L-type polylactic acid material has an L-type polylactic acid having an optical purity of 98% or more, and the D-type polylactic acid material has a D-type polylactic acid having an optical purity of 98% or more.

Preferably, the polylactic acid mixture has a molecular weight of from 80,000 to 300,000, and most preferably, the polylactic acid mixture has a molecular weight of from 120,000 to 200,000.

Preferably, the molecular weight of the L-type polylactic acid of the L-type polylactic acid material of the polylactic acid mixture is between 100,000 and 300,000, and the molecular weight of the D-type polylactic acid of the D-type polylactic acid material of the polylactic acid mixture is between Between 60,000 and 200,000; optimally, the molecular weight of the L-type polylactic acid is between 120,000 and 200,000, and the molecular weight of the D-type polylactic acid is between 70,000 and 150,000.

The technical means adopted by the present invention for achieving the intended purpose are further explained below in conjunction with the preferred embodiments of the present invention.

A preferred embodiment of the polylactic acid composition of the present invention comprises a polylactic acid mixture, a polymer blend, a nucleating agent and a compatibilizing agent.

The foregoing polylactic acid mixture is composed of 60 to 95% by weight of L-type polylactic acid material and 5 to 40% by weight of D-type polylactic acid material, and the L-type polylactic acid material has L-shaped poly with optical purity of 95% or more. Lactic acid, the D-type polylactic acid material having a D-type polylactic acid having an optical purity of 95% or more; preferably, the L-type polylactic acid material has an optical purity of 98% The above L-type polylactic acid, and the D-type polylactic acid material has a D-type polylactic acid having an optical purity of 98% or more; further, the higher the proportion of the D-type polylactic acid material is added, the easier it is to form a stereo-compound (stereo- Complex PLA), but the narrower the processing window, the higher the processing difficulty, and the optical purity of L-type polylactic acid and D-type polylactic acid can promote the formation rate of the stereocomplex.

In addition, when the polylactic acid mixture is applied to different processes, the molecular weight thereof needs to be in a specific range in order to balance the properties required for practical application and processing; for example, when used in an extrusion molding process, a polylactic acid mixture is used. The molecular weight preferably ranges from 80,000 to 300,000; if the molecular weight of the polylactic acid mixture is less than 80,000, it is difficult to have properties required for practical applications such as mechanical properties, heat resistance properties, etc., thereby The molded article is easily broken; if the molecular weight of the polylactic acid mixture is higher than 300,000, it is difficult to have the properties required for processing (for example, the viscosity is too high), and further, if the processing parameters are reluctantly adjusted (for example, processing) The temperature) is processed to have additional disadvantages (such as a shortened service life) for the molded article; optimally, the molecular weight of the polylactic acid mixture is between 120,000 and 200,000.

Further, the molecular weight of the L-type polylactic acid of the L-type polylactic acid material of the polylactic acid mixture is between 100,000 and 300,000, and the molecular weight of the D-type polylactic acid of the D-type polylactic acid material of the polylactic acid mixture is between 60,000. Between 200,000; optimally, the molecular weight of the L-type polylactic acid is between 120,000 and 200,000, and the molecular weight of the D-type polylactic acid is between 70,000 and 150,000.

The aforementioned polymer blend is used to strengthen the phase of each formulation in the composition The interaction force increases the impact resistance, and is a polyester type polymer blend or a polyether type polymer blend, and the polymer chain has at least one functional group which is easy to form a hydrogen bond, and further, The functional group which is liable to form a hydrogen bond is a carboxyl group, an alcohol group, an ether group, an amine group or a guanamine group; for example, the polyester type polymer blend is polyhydroxybutyrate (PHB), poly Polybutylene succinate (PBS), polycaprolactone (PCL) or poly(butylene-adipate-co-terephthalate, PBAT), The polyether polymer blend is polyethylene oxide (PEO) or polyphenylene oxide (PPO).

The foregoing nucleating agent is selected from the group consisting of an aromatic acid salt compound, a fatty acid metal salt, an inorganic filler, and a combination thereof. For example, the aromatic acid salt compound is an aryl sulfonate or an aryl phosphate. a salt or the like; the fatty acid metal salt is zinc stearate or calcium stearate; and the inorganic filler is a monomer nucleating agent, a clay, a metal oxide or an inorganic salt; that is, a nano clay, Graphite, kaolin, mica, montmorillonite, cerium oxide, calcium carbonate, aluminum hydroxide, aluminum oxide, aluminum carbonate, calcium lactate, barium sulfate, glass fiber, shell powder, and the like.

The foregoing compatibilizing agent is any agent for strengthening the bonding force between the polylactic acid mixture and the polymer blend of the polylactic acid composition according to the present invention, and avoids phase separation between the polylactic acid mixture and the polymer co-mixture, In order to improve the compatibility between the formulations and thereby improve the overall mechanical properties, the compatibilizing agent contains a peroxide, an unsaturated reactive functional compound or a polyester type compound, wherein the unsaturated reactive functional compound is Unsaturated carboxylic acid ester compound (such as methyl acrylate compound), epoxy compound (eg, epoxidized soybean oil, epoxy linseed oil, etc.), polyunsaturated polyester compounds (eg, isocyanates) or polyamidamines (eg, stearin amide); further, when When the bulking agent contains a polyester type compound, a polyunsaturated polyester compound or a polyhydrazide compound, the compatibilizing agent can promote the polylactic acid mixture in addition to improving the compatibility of the polylactic acid mixture and the polymer mixture. Crystallization.

The preferred embodiment can be formed into particles and then formed into a finished product. The granulating device can use a uniaxial extruder, a biaxial extruder or other general plastic granulator, and can be stretched longitudinally or transversely. Or biaxial stretching to obtain a desired polylactic acid molded article.

The following examples are intended to illustrate the invention. The examples are not intended to limit the scope of the invention in any way, but are intended to indicate how to practice the materials and methods of the invention.

<Example 1>

In this embodiment, the polylactic acid composition of the present invention is firstly kneaded and granulated, and the obtained polylactic acid composition particles are pressed into a sheet by an extrusion molding machine, and then uniaxially or biaxially stretched into a molded article. The relevant parameters and steps are detailed as follows: 100 parts by weight of the polylactic acid mixture, 0.5 parts by weight of the polyester type polymer blend, 0.5 parts by weight of the nucleating agent, and 0.2 parts by weight of the compatibilizing agent are supplied to The twin-screw kneader performs kneading granulation to obtain particles of a polylactic acid composition; the polylactic acid mixture is composed of a weight percentage of 60 L-type polylactic acid material and a weight percentage of 40 D-type polylactic acid material. The L-type polylactic acid of the L-type polylactic acid material has an optical purity of 98% or more and a molecular weight of 200,000, and the D-type polylactic acid material D-type polylactic acid has an optical purity of 98% or more and a molecular weight of 150,000. Among them, the twin-screw kneader is provided by Taiwan Yajing Machinery Co., Ltd., and its screw aspect ratio (L/D) At 32, the compression ratio is 2.5:1 and the operating temperature is 160 to 180 °C.

Next, the particles of the polylactic acid composition are dried at 90 ° C to reduce the water content to less than 250 ppm, and then supplied to an extrusion molding machine at a processing temperature of 170 to 190 ° C, longitudinally stretched or transversely stretched or doubled. A polylactic acid molded article required for the shaft stretching process.

<Embodiment 2>

The methods, steps and components used in the examples are the same as in the first embodiment. However, the polylactic acid mixture of the present embodiment has a weight percentage of 70 of the L-type polylactic acid material and a weight percentage of 30 of the D-type polylactic acid material.

Further, the polylactic acid mixture of the present embodiment was 100 parts by weight, the polyester-type polymer blend to be added was 6 parts by weight, the nucleating agent was 3 parts by weight, and the compatibilizing agent was 1.2 parts by weight.

<Example 3>

The methods, steps and components used in the examples are the same as in the first embodiment. For the polylactic acid mixture of the present embodiment, the weight percentage of 80 is the L-type polylactic acid material and the weight percentage of 20 is the D-type polylactic acid material.

Further, the polylactic acid mixture of the present embodiment was 100 parts by weight, the polyester-type polymer blend to be added was 12 parts by weight, the nucleating agent was 5 parts by weight, and the compatibilizing agent was 1.8 parts by weight.

<Embodiment 4>

The methods, steps and components used in the examples are the same as in the first embodiment. However, the polylactic acid mixture of the present embodiment has a weight percentage of 90 The L-type polylactic acid material and the weight percentage 10 are the D-type polylactic acid materials.

Further, the polylactic acid mixture of the present embodiment was 100 parts by weight, the polyester type polymer blend to be added was 24 parts by weight, the nucleating agent was 12 parts by weight, and the compatibilizing agent was 2.4 parts by weight.

<Embodiment 5>

The methods, steps and components used in the examples are the same as in the first embodiment. However, the polylactic acid mixture of the present embodiment has a weight percentage of 95 of the L-type polylactic acid material and a weight percentage of 5 of the D-type polylactic acid material.

Further, the polylactic acid mixture of the present example was 100 parts by weight, the polyester-type polymer blend to be added was 48 parts by weight, the nucleating agent was 15 parts by weight, and the compatibilizing agent was 4.8 parts by weight.

<Comparative example>

Commercially available granulated polylactic acid plastic (manufactured by Natureworks LLC, product name 2003D), the heat distortion temperature, impact strength and elongation at break are shown in Table 1.

<heat resistance test>

The heat distortion temperature of each of Examples 1 to 5 was measured using a heat distortion temperature tester (HDT, manufactured by Hongda Instrument Co., Ltd.) to understand the heat resistance of each of the examples, and the higher the heat distortion temperature, the heat resistance of the test object. The better the nature; the test results are shown in Table 2.

As shown in Table 1 and Table 2, the heat distortion temperature of the comparative example is 55 ° C, and the heat distortion temperatures of Examples 1 to 5 are 126 ° C, 112 ° C, 105 ° C, 88 ° C and 72 ° C, respectively, showing the respective implementations. The examples all have better heat resistance than the comparative examples, and each embodiment can only save the process time and cost by merely performing the general molding process and eliminating the secondary processing by which the heat resistance is improved.

<Impact resistance test>

The impact tester (GT-7045, manufactured by High Speed Rail Technology Co., Ltd.) was used to perform Izod impact strength on Examples 1 to 5, respectively. The higher the impact strength, the better the impact resistance of the test object; The results are shown in Table 2.

As shown in Table 1 and Table 2, the impact strength of the comparative example is about 16 J/m, and the impact strength of Examples 1 to 5 is 45 J/m, 216 J/m, 342 J/m, 398 J/m and 453 J/m, respectively. It is shown that the impact strength of each of the examples is higher than that of the comparative examples, and the examples have better impact resistance.

<Elongation test>

Each of Examples 1 to 5 was subjected to a tensile test using a tensile tester (Insrton 3369, manufactured by Instron Co., USA), and the elongation at break of each of the examples was measured. The elongation at break indicates that the test object was The ratio of the length that can be stretched before the fracture to the original length is usually expressed as a percentage. The higher the value of the elongation at break, the better the ductility of the test object, the better the processing performance. The test results are shown in Table 2. .

As shown in Tables 1 and 2, the elongation at break of the comparative examples was about 6%, and the elongations of Examples 1 to 5 were about 32%, 115%, 236%, 352%, and 486%, respectively. The elongation at break of each of the examples was higher than the elongation at break of the comparative examples, and the examples had better ductility.

In summary, the polylactic acid composition of the present invention has better heat resistance than commercially available polylactic acid without secondary processing, and can save time and cost, and at the same time, the polylactic acid composition of the present invention has a comparative advantage. The excellent impact resistance makes it a wider range of applications.

In addition, in order to make the polylactic acid composition have the advantages of better heat resistance, better impact resistance, and no need for secondary processing, it is further processed in a process for producing a molded article to facilitate processing; It can be mass-produced after being made into a molded article with better product stability (for example, long service life), and the foregoing examples are exemplified, preferably, mixed with polylactic acid. When the amount is 100 parts by weight, the content of the polyester type polymer blend is 0.5 to 25 parts by weight, the content of the nucleating agent is 0.5 to 5 parts by weight, and the content of the compatibilizing agent is 0.2 to 2 parts by weight.

Claims (8)

A polylactic acid composition comprising a polylactic acid mixture, a polymer blend, a nucleating agent and a compatibilizing agent; the polylactic acid mixture is composed of 60 to 95% by weight of L-type polylactic acid material Composition with 5 to 40% by weight of D-type polylactic acid material; the polymer blend is a polyester type polymer blend or a polyether type polymer blend, and the polymer of the polymer blend The chain has at least one functional group that readily forms a hydrogen bond; the nucleating agent is selected from the group consisting of an aromatic acid salt compound, a fatty acid metal salt, an inorganic filler, and a combination thereof; the compatibilizing agent contains a peroxide An unsaturated functional group compound or a polyester type compound; wherein the content of the polylactic acid mixture is 100 parts by weight, the content of the polymer blend is 0.1 to 49 parts by weight, and the content of the compatibilizing agent is 0.1. Up to 5 parts by weight. The polylactic acid composition according to claim 1, wherein the functional group of the polymer blend which is liable to form a hydrogen bond is a carboxyl group, an alcohol group, an ether group, an amine group or a guanamine group. The polylactic acid composition according to claim 1 or 2, wherein the unsaturated reactive functional compound of the compatibilizing agent is an unsaturated carboxylic acid ester compound, an epoxy compound, a polyunsaturated polyester compound or a poly-decylamine. Class of compounds. The polylactic acid composition according to claim 1 or 2, wherein the nucleating agent is contained in an amount of from 0.1 to 15 parts by weight based on 100 parts by weight of the polylactic acid mixture. The polylactic acid composition according to claim 1 or 2, wherein the polylactic acid is mixed The L-type polylactic acid material has an L-type polylactic acid having an optical purity of 95% or more, and the D-type polylactic acid material has a D-type polylactic acid having an optical purity of 95% or more. The polylactic acid composition according to claim 1 or 2, wherein the L-type polylactic acid material of the polylactic acid mixture has an L-type polylactic acid having an optical purity of 98% or more, and the D-type polylactic acid material has an optical purity of 98% or more. D type polylactic acid. The polylactic acid composition according to claim 1 or 2, wherein the polylactic acid mixture has a molecular weight of from 80,000 to 300,000. The polylactic acid composition according to claim 1 or 2, wherein the L-type polylactic acid of the L-type polylactic acid material of the polylactic acid mixture has a molecular weight of from 100,000 to 300,000, and the polylactic acid material of the polylactic acid mixture is D. The molecular weight of the D-type polylactic acid is between 60,000 and 200,000.