TW202216900A - Polylactic acid resin composition and application thereof - Google Patents

Abstract

A polylactic acid resin composition includes a polylactic acid resin, a carbon fiber, a carbon black, a nucleating agent and a coupling agent. The content of the polylactic acid resin ranges between 75-95 wt%. The content of the carbon fiber ranges between 2-9 wt%. The content of the carbon black ranges between 0-9 wt%. The content of the nucleating agent ranges between 0.001-5 wt%. The content of the coupling agent ranges between 0.001-5 wt%. The total weight percentage of components (a), (b), (c), (d) and (e) is defined as 100wt%.

Description

Polylactic acid resin composition and its application

The present invention relates to a biodegradable polylactic acid resin composition and its application, in particular to an electronic device tray comprising the above polylactic acid resin composition.

In recent years, in view of the global warming problem, plastics formed from natural plants as raw materials are attracting attention. Polylactic Acid (PLA) resin is biodegradable and available from renewable resources such as cornstarch, and thus is an environmentally friendly polymer. However, it is recognized that PLA resins have poor physical properties, such as: low heat resistance, poor surface resistance values, and poor mechanical properties. On the other hand, PLA resin exhibits low crystallization rate and low crystallinity, so that products formed from PLA may not have sufficient Heat Deflection Temperature (HDT) and impact strength. Therefore, it is difficult to use PLA resins as antistatic materials and/or industrial trays.

Electronic trays, such as integrated circuit (IC) trays, may be used to house, handle, and transport IC packages. For suitable IC trays for use in manufacturing processes such as reflow and IC shipping, certain properties are required, such as HDT, impact strength and surface resistance values, among others. Currently, there is still a need for an environmentally friendly IC tray with desirable properties. Typical IC trays are primarily formed from polyphenylene ether (PPE), which is a petrochemical product and is not biodegradable in normal environments. PPE-based IC trays can release greenhouse gases and damage the environment when burned. Therefore, there is a need for an environmentally friendly IC tray with high HDT, high impact strength and low sheet resistance value.

In some embodiments, the present invention provides a polylactic acid resin composition comprising polylactic acid resin, carbon fiber, carbon black, a nucleating agent and a coupling agent. Wherein, (a) the content of polylactic acid resin is between 75-95wt%; (b) the content of carbon fiber is between 2-9wt%; (c) the content of carbon black is between 0-9wt%; (d) the content of nucleating agent is between 0.001-5wt%; and (e) the coupling agent content is between 0.001-5wt%, wherein the content is based on the total weight of components (a), (b), (c), (d) and (e) 100wt %count.

In some embodiments, the present invention further provides a tray for electronic components, which includes polylactic acid resin, carbon fiber, carbon black, a nucleating agent, and a coupling agent. Wherein, (a) the content of polylactic acid resin is between 75-95wt%; (b) the content of carbon fiber is between 2-9wt%; (c) the content of carbon black is between 0-6wt%; (d) the content of nucleating agent is between 0.001-5wt%; and (e) the coupling agent content is between 0.001-5wt%, wherein the content is based on the total weight of components (a), (b), (c), (d) and (e) 100wt %count.

[polylactic acid]

In some embodiments of the present invention, the polylactic acid (PLA) may be a homopolymer of lactic acid. Lactic acid exists as optical isomers, namely L-lactic acid (L-form) and D-lactic acid (D-form). For some embodiments of the present invention, PLA can be prepared from one or both of these optical isomers. For the purpose of obtaining PLA with high melting temperature ( _Tm ) and high glass transition temperature ( _Tg ), it is desirable to use one of these optical isomers as the main component. For example, in PLA, the L-form of lactic acid may be present in an amount of not less than about 80 mol% or not greater than about 20 mol%; such as in PLA, the L-form of lactic acid may be present in an amount of not less than about 85 mol% or not greater than About 16 mol%; or the L-form of lactic acid, such as in PLA, may be present in an amount of no less than about 90 mol% or no more than about 12 mol%, with the remainder corresponding to or including the D-form of lactic acid.

In other embodiments of the present invention, the PLA may be a copolymer of lactic acid and a hydroxycarboxylic acid component other than lactic acid. The hydroxycarboxylic acid component other than lactic acid may be, for example, glycolic acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxycaproic acid, or hydroxyheptanoic acid.

PLA can be formed by polycondensation methods using the above-mentioned monomers, or by ring-opening polymerization methods using the corresponding cyclic dimers or compounds of the above-mentioned monomers (eg, lactide, which is a cyclic dimer of lactic acid).

In some embodiments of the present invention, the weight average molecular weight ( _Mw ) of PLA can be at least any one of: about 10,000 g/mol, about 20,000 g/mol, about 30,000 g/mol, about 40,000 g/mol mol and about 50,000 g/mol; and can be up to any of the following: about 160,000 g/mol, about 200,000 g/mol, about 250,000 g/mol, about 300,000 g/mol, about 400,000 g/mol, and about 500,000 g/mol. For example, the weight average molecular weight of PLA can be from about 30,000 g/mol to about 250,000 g/mol.

In some embodiments of the present invention, based on the total weight of components (a), (b), (c), (d) and (e) being 100 wt %, the content of the polylactic acid resin ranges from 75 to 95 wt %. For example, the content of the polylactic acid resin may be 75, 77, 80, 83, 85, 87, 89, 90, 92, 93, 94 or 95 wt %. [Nucleating agent]

In some embodiments, nucleating agents can be used to improve the nucleation arrangement of PLA crystals and increase the crystallization rate and crystallinity of PLA. Increasing the crystallization rate and crystallinity of PLA can increase HDT and impact strength. In some embodiments of the present invention, a nucleating agent that can increase the crystallization rate and crystallinity of PLA can be used in the resin composition. In some embodiments, the nucleating agent comprises metal carbonates (eg, alkaline earth metal carbonates, such as calcium carbonate or barium carbonate), ester derivatives of citric acid (eg, acetyltributyl citrate), metal silicates (eg hydrated magnesium silicates such as talc), amino acids (eg glycine or L-alanine), poly(amino acids) (eg polyglycine), heterocyclic organic compounds (eg N-amino) phthalimide), metal oxides such as titanium dioxide, or a combination of two or more thereof. In some embodiments, the nucleating agent is L-alanine.

In some embodiments of the present invention, based on the total weight of components (a), (b), (c), (d) and (e) as 100 wt %, the content of the nucleating agent is 0.001-5 wt %. For example, the nucleating agent may be present in an amount of 0.001, 0.005, 0.1, 0.5, 1, 1.5, 2, 3, 4, or 5 wt%. [filler]

Fillers can be added to resin compositions for a variety of purposes, such as reducing cost, improving mechanical strength, or adjusting the appearance of the final product. Different fillers are selected for different purposes. It has been found that some fillers may be beneficial for one property of the resin composition but may be detrimental for another property of the resin composition. In addition, the addition of fillers such as rubber and plasticizers may adversely affect the thermal stability of the resin composition.

In some embodiments of the present invention, fillers suitable for use in the PLA resin compositions of the present invention comprise inorganic fillers. The inorganic fillers may include carbon-containing fillers. Carbon-containing fillers include carbon fibers, carbon black, or other suitable materials.

Carbon fiber is a high-strength reinforcing material, which can improve the impact strength of the PLA resin composition and reduce the surface resistance of the PLA resin composition. Through the combination of nucleating agent and carbon fiber, a synergistic effect can be produced, so that the biodegradable PLA resin composition can be improved in impact strength properties; It is easy to generate static electricity accumulation problems. In some embodiments of the present invention, adding carbon fibers to PLA can increase the electrical conductivity of PLA, thereby achieving antistatic effect (for example, surface resistance <10 ¹² ohm/sq).

In some embodiments of the present invention, based on the total weight of components (a), (b), (c), (d) and (e) as 100 wt %, the content of carbon fiber is less than 10 wt %, for example, it may be between 2 -9wt%. For example, the content of carbon fiber may be 2, 3, 4, 5, 6, 7, 8 or 9 wt %. In some embodiments of the present invention, it is found that increasing the content of carbon fiber can reduce the surface resistance value; however, when the content of carbon fiber is greater than or equal to 10wt%, although the surface resistance value can be reduced to below 10 ¹² ohm/sq, however, PLA resin The carbon fibers in the composition may be released, which may easily cause defects such as cracks on the surface of the molded product.

Carbon fibers of various suitable lengths and/or particle sizes can be used. In some embodiments, the carbon fibers have a length (eg, an average length) of about 0.01 mm to about 800 mm, such as about 0.01 mm, about 1 mm, about 10 mm, about 50 mm, about 100 mm, about 200 mm, about 300 mm mm, about 400 mm, about 500 mm, about 600 mm, about 700 mm, or about 800 mm. In some embodiments, the particle size (eg, average particle size) of the carbon fibers is about 0.01 μm to about 100 μm, such as about 0.01 μm, about 1 μm, about 10 μm, about 20 μm, about 30 μm, about 40 μm, About 50 μm, about 60 μm, about 70 μm, about 80 μm, about 90 μm, or about 100 μm.

In some embodiments of the present invention, carbon black may be added as desired. Carbon black can reduce the surface resistance value of the PLA resin composition, and the cost is lower than that of carbon fiber.

In some embodiments of the present invention, it is found that the effect of using carbon black alone is not as good as that of using the same amount of carbon fiber alone, and the HDT, surface resistance value and mechanical strength of the resulting molded product are all poor. However, in some embodiments, it is found that when carbon black and carbon fiber are used together, the two can exert a synergistic effect, and can reduce the surface resistance value to below 10 ¹² ohm/sq without causing cracks on the surface of the molded product. In some embodiments, the surface resistance value can be even further reduced to below 10 ¹⁰ ohm/sq without cracking the surface of the molded product. In some embodiments of the present invention, the PLA resin composition of the present invention may optionally include carbon black, wherein the total weight of components (a), (b), (c), (d) and (e) is 100 wt % The content of carbon black is less than 10 wt %, for example, it can be between 0 and 9 wt %. For example, the content of carbon black may be 0, 1, 2, 3, 4, 5, 6, 7, 8 or 9 wt%. In other embodiments of the present invention, based on the total weight of components (a), (b), (c), (d) and (e) being 100 wt %, the content of carbon black is less than 7 wt %. At 0-6 wt%, it helps to increase the impact strength to about 1.5 kg-cm/cm or higher and maintain the surface resistance value below 10 ¹² ohm/sq. In some embodiments, the PLA resin composition includes both carbon fibers and carbon black, and the carbon fibers and The total content of carbon black is less than 15 wt%, eg, less than or equal to 14 wt%, less than or equal to 13 wt%, less than or equal to 12 wt%.

Carbon blacks of various suitable lengths and/or particle sizes can be used. In some embodiments, the carbon black has a length (eg, an average length) of about 0.01 mm to about 800 mm, such as about 0.01 mm, about 1 mm, about 10 mm, about 50 mm, about 100 mm, about 200 mm, about 300 mm, about 400 mm, about 500 mm, about 600 mm, about 700 mm or about 800 mm. In some embodiments, the particle size (eg, average particle size) of the carbon fibers is about 0.01 μm to about 100 μm, such as about 0.01 μm, about 1 μm, about 10 μm, about 20 μm, about 30 μm, about 40 μm, About 50 μm, about 60 μm, about 70 μm, about 80 μm, about 90 μm, or about 100 μm. [Coupling Agent]

In the PLA resin composition of some embodiments of the present invention, PLA is an organic material, and the filler is an inorganic material. Unlike organic materials, which can form bonds with each other through functional groups, inorganic materials generally do not form strong bonds with organic materials, which may result in poor compatibility and adhesion between PLA and inorganic fillers. In order to solve this problem, a coupling agent can be used to modify the surface of the inorganic filler, and the inorganic filler can be bonded to the organic material through the dual reactivity of the coupling agent. Coupling agents can also be used in organic fillers to further improve the compatibility and adhesion between PLA and organic fillers. In some embodiments, the filler is bonded (eg, covalently bonded) to the PLA via a coupling agent.

The coupling agent can be a silane coupling agent, a titanate coupling agent, or a combination thereof. Various suitable silane coupling agents and titanate coupling agents can be selected. Examples of silane coupling agents suitable for use in some embodiments of the present invention include, but are not limited to, trimethoxysilane, triethoxysilane, or combinations thereof. According to some embodiments of the present invention, the silane coupling agent may be 3-acryloyloxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, or a combination thereof. Examples of titanate coupling agents suitable for use in some embodiments of the present invention include, but are not limited to: titanium di(cumylphenylate) oxyacetate, bis(dioctyl oxophosphate) base) di(dioctylphosphato) ethylene titanate or a combination thereof.

The coupling agent can be added to the PLA resin composition in various appropriate amounts, and can be adjusted depending on the filler content. In some embodiments, based on the total weight of components (a), (b), (c), (d) and (e) as 100 wt %, the content of the coupling agent is 0.001-5 wt %. For example, the coupling agent may be present in an amount of 0.001, 0.005, 0.1, 0.5, 1, 1.5, 2, 3, 4, or 5 wt%. [polylactic acid resin composition]

In some embodiments of the present invention, the PLA resin composition can be prepared by a variety of suitable methods. In some embodiments, the PLA resin composition is prepared by: (1) mixing a PLA resin with a nucleating agent to form a first mixture, (2) mixing a filler and a coupling agent to form a second mixture, and (3) ) adding the second mixture to the first mixture (or otherwise mixing the first mixture with the second mixture) to prepare the PLA resin composition.

The PLA resin composition can be applied as an antistatic material. When the PLA resin composition is used as an antistatic material, a slight sacrifice of impact strength can be tolerated, focusing on the improvement of surface resistance. For example, if the surface resistance value of the antistatic material is less than 10 ¹² ohm/sq, and the impact strength is greater than 1.3 kg-cm/cm, it can be evaluated as an excellent antistatic material.

The PLA resin composition can be further processed into final products such as lids for electronic products (eg mobile phones or computers), food containers or trays, or trays for industrial components. In some embodiments, the PLA resin composition may be kneaded by a twin-screw extruder, and then injected with an injection molding machine at a temperature ranging from about 150°C to about 200°C to form a tray. The tray can be further baked to relieve stress and stabilize the tray size.

Products made from the PLA resin compositions of some embodiments of the present invention are biodegradable, such that the products can be decomposed in the natural environment, eg, by microorganisms. In some embodiments, the PLA resin composition may have a degree of decomposition of about 70 wt % or higher in about 90 days in the natural environment.

In some embodiments, the PLA resin composition is processed into a biodegradable antistatic material. In other embodiments, the biodegradable antistatic material has a degree of decomposability of about 70 wt % or more in the natural environment after about 90 days. In other embodiments, the biodegradable antistatic material has an impact strength of about 1.3 kg-cm/cm or more (eg, about 1.4 kg-cm/cm or more, about 1.5 kg-cm/cm or more high); an HDT of about 125°C or higher (eg, about 128°C or higher, about 130°C or higher, about 130°C or higher, about 135°C or higher); and a surface resistance value of about 10 ¹² ohm/sq or less (eg, about 10 ¹¹ ohm/sq or less, about 10 ¹⁰ ohm/sq or less, about 10 ⁹ ohm/sq or less, about 10 ⁸ ohm/sq or less, about 10 ⁷ ohm/sq or less, about 10 ⁶ ohm/sq or less, about 10 ⁵ ohm/sq or less, or about 10 ⁴ ohm/sq or less, and can be as low as about 10 ³ ohm/ sq or less). Furthermore, in some embodiments, the surface of the resulting antistatic material has no or only some microcracks.

In some embodiments, the PLA resin composition can be processed into pallets. In other embodiments, the impact strength of the pallet is about 1.5 kg-cm/cm or higher; the HDT is about 125°C or higher (eg, about 128°C or higher, about 130°C or higher, about 133°C or higher, about 135°C or higher); and a surface resistance value of about 10 ¹² ohm/sq or less (eg, about 10 ¹¹ ohm/sq or less, about 10 ¹⁰ ohm/sq or less, about 10 ⁹ ohm/sq or less, about 10 ⁸ ohm/sq or less, about 10 ⁷ ohm/sq or less, about 10 ⁶ ohm/sq or less, about 10 ⁵ ohm/sq or less or about 10 ⁴ ohm/sq or less, and can be as low as about 10 ³ ohm/sq or less). Trays, such as IC trays, are suitable for the electronics industry, which are specified to have high HDT, high impact strength, and low surface resistance values (eg, HDT of about 125°C or higher, impact strength of about 1.5 kg-cm/cm or higher and surface The resistance value is about 10 ¹² ohm/sq or less). Furthermore, in some embodiments, the surface of the resulting tray has no or only some microcracks. example

Some embodiments of the present invention are further explained with reference to the following examples and comparative examples; however, these embodiments do not limit the scope of the present invention. In the examples, polylactic acid (NatureWorks® 4032D), L-alanine (Merck Corporation), carbon fiber (TAIRYFIL® CS-2516), carbon black (CABOT® XC-72), and a coupling agent (ShinEtsu KBM-503) were used. The relative amounts of the components are described in Tables 1 and 2.

The PLA was uniformly mixed with L-alanine to prepare a first mixture. The carbon fibers and/or carbon black are mixed with the coupling agent to prepare a second mixture. The second mixture was added to the first mixture to prepare a PLA composition. The PLA resin composition is kneaded by a twin-screw extruder at a temperature range of about 160°C to about 195°C, and then injection molded with an injection molding machine at a temperature range of about 150°C to about 200°C.

The properties of each injection molded PLA resin composition were tested according to the ASTM methods described in Tables 3 and 4, and the results were recorded in Tables 3 and 4. The appearance evaluation of each injection-molded PLA resin composition was evaluated as poor (X) if there were obvious cracks in the appearance, and good (O) if there were no obvious cracks. The appearance evaluations are described in Table 5.

Table 1 Element Example 1 Example 2 Example 3 Example 4 Example 5 (a) polylactic acid 90 88 86 84 91 (b) L-Alanine 1 1 1 1 1 (c) Carbon Fiber (CF) 5 5 5 5 5 (d) Carbon Black (CB) 1 3 5 7 - (e) coupling agent 3 3 3 3 3 Table 2 Element Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 (a) polylactic acid 96 86 81 93 91 86 81.5 (b) L-Alanine 1 1 1 1 1 1 1.2 (c) Carbon Fiber (CF) - 10 15 - - - 12.2 (d) Carbon Black (CB) - - - 3 5 10 4 (e) coupling agent 3 3 3 3 3 3 1 table 3 method nature unit Example 1 Example 2 Example 3 Example 4 Example 5 ASTM D-638 Tensile Strength kg/cm ² 586 603 575 505 580 ASTM D-638 Elongation % 1.23 1.31 1.18 1.01 1.21 ASTM D-256 Impact strength kg-cm/cm 1.54 1.64 1.5 1.34 1.52 ASTM D-638 flexural strength kg/cm ² 902 987 884 805 890 ASTM D-638 flexural modulus kg/cm ² 89395 91412 87854 74289 88320 ASTM D-257 Surface resistance value ohm/sq 1.76E+11 7.94E+09 2.54E +4 152.32 9.89E+11 ASTM D-648 HDT °C 133 134 134 135 133 Table 4 method nature unit Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 ASTM D-638 Tensile Strength kg/cm ² 121 668 710 460 432 353 830 ASTM D-638 Elongation % 3.33 0.98 0.73 3.32 2.98 2.35 0.86 ASTM D-256 Impact strength kg-cm/cm 1.42 1.61 1.73 1.44 1.4 1.31 1.95 ASTM D-638 flexural strength kg/cm ² 686 1164 1268 695 636 588 1317 ASTM D-638 flexural modulus kg/cm ² 60856 106542 121452 62174 58472 56934 108200 ASTM D-257 Surface resistance value ohm/sq 3.24E+13 1.04E+4 291.68 1.12E+13 5.24 E+12 4.36 E+10 47000 ASTM D-648 HDT °C 130 138 142 130 123 111 137.9 table 5 Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 Appearance evaluation O O O O O O X X O O X X

It can be seen from Example 5 and Comparative Example 1 that the addition of carbon fiber helps to improve the mechanical strength and HDT, and can reduce the surface resistance value and improve the antistatic properties. From Comparative Examples 1 and 4 to 6, it can be seen that although the addition of carbon black can reduce the surface resistance value, its effect is not as good as that of carbon fiber, and in some cases, the deterioration of mechanical strength and the deterioration of HDT can be simultaneously observed. In addition, it is also found that when the carbon fiber or carbon black content of the PLA composition is too high, the appearance of the injection molded product of the PLA composition is prone to obvious cracks, which reduces its commercial use. For example, the carbon fiber content of Comparative Examples 2, 3, and 7 is greater than or equal to 10 parts by weight, the uniformity is poor, and the appearance of the PLA injection molding is not flat, or even cracks appear, and it is evaluated as poor; Comparative Example 6 contains too much carbon black (10 parts by weight or more), carbon black floats out in the molded product and accumulates on the surface, resulting in poor appearance evaluation.

Examples 1 to 4 further add carbon black in addition to carbon fiber, the results show that when carbon black and carbon fiber are used together, the two can play a synergistic effect, and the surface resistance value can be reduced to below 10 ¹² ohm/sq (even further reduced to 10 ¹⁰ ohm /sq or less) and will not crack the surface of the molded product; in addition, the molded product has excellent mechanical strength and HDT. As mentioned above, although Comparative Examples 2, 3, and 7 can reduce the surface resistance value to below 10 ¹⁰ ohm/sq, however, surface cracks occur due to excessive carbon fiber content; on the contrary, Examples 3 and 4 in this case have comparable surfaces Resistance value, but can retain less or no surface cracks, and can use less total carbon fiber and carbon black content. It can be known from Comparative Example 4 and Comparative Example 2 and Comparative Example 5 and Comparative Example 3 that carbon fiber helps to improve mechanical strength and HDT, and reduce surface resistance value. It can be known from Examples 1-5 that when the content of carbon fiber is less than 10wt% (eg, between 2-9wt%), and the content of carbon black is less than 10wt% (eg, between 0-9wt%), the surface resistance value of the PLA composition All are less than 10 ¹² ohm/sq, impact strength is greater than 1.3 kg-cm/cm, HDT is greater than 125°C (up to 133°C or higher), and the appearance of the injection molded product is evaluated as good, and can be used as an excellent antistatic Material. In particular, the surface resistance values of Examples 2-4 are all less than 10 ¹⁰ ohm/sq, and have very excellent antistatic properties. Among them, the surface resistance value of Example 4 reaches 152.32 ohm/sq, and has more excellent antistatic properties.

In addition, if the PLA composition is to be made into a tray for electronic parts, it needs to have good impact strength. For example, when its impact strength is greater than or equal to 1.5 kg-cm/cm, the PLA composition can be used as a Tray for electronic parts. It can be known from Examples 1, 2, 3, and 5 that when the content of carbon fiber is less than 10wt% (eg, between 2-9wt%), and the content of carbon black is less than 7wt% (eg, between 0-6wt%), its impact resistance is The strength is greater than 1.5 kg-cm/cm, and can be used to make trays for electronic parts.

In addition, if the PLA composition is to be made into a tray for electronic parts, a higher HDT is required. For example, when its HDT is greater than or equal to 125°C, the PLA composition can be used as a tray for electronic parts. tray. It can be seen from Examples 1 to 5 that their HDTs are all greater than or equal to 133°C, and have excellent HDTs.

In general, Examples 1-5 by containing a specific content of carbon fiber or further adding a specific content of carbon black, the PLA composition produced by it has good antistatic properties and can be used as an antistatic material, and among them Examples 1, 2, 3, The PLA composition of 5 can also be made into trays, which have suitable HDT and mechanical properties, and can be used in the electronic industry, such as IC trays.

As used herein and not otherwise defined, the terms "substantially," "substantially," "approximately," and "about" are used to describe and take into account minor variations. When used in conjunction with an event or circumstance, a term can encompass both instances in which the event or circumstance occurs precisely as well as instances in which the event or circumstance occurs closely. For example, when used in conjunction with a numerical value, the term can encompass a variation range of less than or equal to ±10% of that numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to Equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. For example, if the first value is within a variation range of less than or equal to ±10% of the second value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ± 2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%, the first value may be "substantially" the same or equal to the second value.

As used herein, the singular terms "a/an" and "the" can include plural referents unless the context clearly dictates otherwise.

Amounts, ratios, and other numerical values are sometimes presented herein in range format. It is to be understood that such range formats are used for convenience and brevity, and should be flexibly construed to include not only the values expressly designated as the limits of the range, but also all individual values or subranges subsumed within the range, as if expressly Specify each numerical value and subrange generically.

While the invention has been described and illustrated with reference to specific embodiments of the invention, such description and illustration do not limit the invention. It will be clearly understood by those skilled in the art that various changes may be made and equivalent elements may be substituted in the embodiments without departing from the true spirit and scope of the invention as defined by the appended claims. The illustrations may not necessarily be drawn to scale. Due to variables in the manufacturing process and the like, differences may exist between the reproduction of the skill in the present invention and the actual device. There may be other embodiments of the invention not specifically described. The specification and drawings are to be regarded in an illustrative rather than a restrictive sense. Modifications may be made to adapt a particular situation, material, composition of matter, method or process to suit the object, spirit and scope of the invention. All such modifications are intended to be within the scope of the claims appended hereto. Although the methods disclosed herein have been described with reference to specific operations performed in a specific order, it is understood that such operations may be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of the present disclosure. Accordingly, unless specifically indicated herein, the order and grouping of operations are not limitations of the invention.

Claims (13)

A polylactic acid resin composition, comprising: (a) polylactic acid resin, its content is between 75-95wt%; (b) carbon fiber, its content is between 2-9wt%; (c) carbon black, its content is between 0-9wt%; (d) a nucleating agent in an amount of 0.001-5 wt%; and (e) coupling agent, its content is between 0.001-5wt%, The content is based on the total weight of components (a), (b), (c), (d) and (e) as 100 wt %. The polylactic acid resin composition according to claim 1, wherein the content of the carbon black is less than 7 wt%. The polylactic acid resin composition according to claim 1, wherein the total content of carbon fiber and carbon black is less than 15 wt%. The polylactic acid resin composition of claim 1, wherein the carbon fibers have a particle size ranging from about 0.01 μm to about 100 μm. The polylactic acid resin composition of claim 1, wherein the particle size of the carbon black is in the range of about 0.01 μm to about 100 μm. The polylactic acid resin composition according to claim 1, wherein the nucleating agent comprises metal carbonates, ester derivatives of citric acid, metal silicates, amino acids, poly(amino acids), heterocyclic organic compounds , at least one of metal oxides. The polylactic acid resin composition of claim 1, wherein the coupling agent comprises a silane coupling agent or a titanate coupling agent or a combination thereof. The polylactic acid resin composition according to claim 1, having the following characteristics: the surface resistance measured according to ASTM D-257 is less than 10 ¹² ohm/sq. A tray for electronic parts, comprising: (a) polylactic acid resin, its content is between 75-95wt%; (b) carbon fiber, its content is between 2-9wt%; (c) carbon black, its content is between 0-6wt%; (d) a nucleating agent in an amount of 0.001-5 wt%; and (e) coupling agent, its content is between 0.001-5wt%, The content is based on the total weight of components (a), (b), (c), (d) and (e) as 100 wt %. The pallet of claim 9, having an impact strength greater than 1.5 kg-cm/cm, measured in accordance with ASTM D-256. The tray of claim 9, having a surface resistance value of less than 10 ¹² ohm/sq as measured according to ASTM D-257. The tray of claim 9 having a surface resistance value of from about 152 ohm/sq to about 9.8×10 ¹¹ ohm/sq as measured in accordance with ASTM D-257. The pallet of claim 9 having a heat deflection temperature greater than about 125°C as measured in accordance with ASTM D-648.