TWI472575B - Modified polylactic acid composition - Google Patents

Description

Modified polylactic acid composition

The present invention relates to a polylactic acid, and more particularly to a modified polylactic acid composition which can improve the heat resistance and toughness of polylactic acid and shorten the molding cycle of polylactic acid.

At present, oil prices are rising, and environmental protection issues are receiving increasing attention. Especially in terms of resource conservation and environmental protection such as carbon dioxide reduction, the use and development of bioplastics are receiving more and more attention.

The general biopolymer can be divided into the following two categories: 1. Biomass polymer: The finished product is not biodegradable, but some or all of the raw materials used are natural renewable resources, called raw material plastic, and its application fields are mainly automobile and electronics. With consumer goods, etc.; 2. Biodegradable polymer: A biodegradable product made of biodegradable plastics, called biodegradable plastics. Its application areas are food packaging containers and utensils, mainly referred to as "single use" products.

Polylactic acid is the most used in bioplastics and has the widest range of applications. The polylactic acid is PLA, that is, Poly-lactic-acid, which is a lactide polyester. Polylactic acid has the following advantages: A. The production of polylactic acid can reduce the use of fuel resources by more than 65%, and achieve the reduction standard of greenhouse gas emissions; B. Polylactic acid can be decomposed into carbon dioxide and water in 47 days in the composting field; C. When polylactic acid is incinerated in a waste treatment system of an incinerator, the environmental load is lower than that of conventional plastics.

However, the general polylactic acid also has the following disadvantages to be improved: (A) low glass transition point (Tg); (B) slow crystallization rate; (C) low toughness. At present, the methods for solving the disadvantages of polylactic acid include: A. Low glass transition point: 1. Adding fiber: adding glass fiber (GF), carbon fiber (CF) or kenaf fiber, however, the fiber must be added to a certain amount to have an effect, which will result in an increase in the specific gravity of the product, a decrease in fluidity, and a decrease in formability; Nano method: If adding montmorillonite, although a small amount can be added, the cost of montmorillonite is high (about 400-800 yuan per kilogram), and the safety of the treatment agent used for treating montmorillonite must also be considered. ;B. Slow crystallization rate: 1. Adding filler: it must be added to a certain amount to have an effect, and it will also cause an increase in the proportion of the product, a decrease in fluidity, and a decrease in formability; Nano method: such as adding montmorillonite, but there are cost and safety concerns as mentioned above; Addition of crystal nucleating agent: usually the effect is not good, and some are colored, resulting in poor product selling; C. Low toughness: 1. Adding a plasticizer: adding a natural oil such as glycerin or a plasticizer such as dioctyl phthalate (DOP), however, a surface bleeding problem occurs, and the heat resistance of the product is also lowered; Gluing method: such as adding a plastic substrate such as polycarbonate (PC) or acrylonitrile-butadiene-styrene (ABS) copolymer, however, the amount of addition is not low, resulting in a decrease in the raw material composition of the product; The addition of the elastomer: however, the amount of the elastomer substrate added is not low, resulting in a decrease in the product's biomass component and a lower temperature resistance.

In view of the shortcomings of the method for solving the disadvantages of polylactic acid at the present stage, the object of the present invention is to provide a modified polylactic acid composition which can improve the heat resistance and toughness of polylactic acid and shorten the molding cycle of polylactic acid. Without significantly affecting the physical properties of polylactic acid.

In order to achieve the above object, the modified polylactic acid composition of the present invention comprises: 100 parts by weight of a polylactic acid or a polylactic acid copolymer; and 0.1 to 5 parts by weight of a coupling agent, the coupling agent having one or more a compound capable of reacting with polylactic acid, and the functional group reactive with polylactic acid is isocynate, oxazoline, epoxy, or aziridine ( Aziridine) or carbamide.

Preferably, the modified polylactic acid composition of the present invention comprises 0.1 to 1 part by weight of a coupling agent.

Preferably, the coupling agent carries two or more functional groups reactive with polylactic acid.

Preferably, the functional group reactive with polylactic acid is an epoxy group.

Preferably, the coupling agent is epoxidized soybean oil or epoxy linseed oil.

Preferably, the coupling agent is formed into a master-batcher with a pigment and then a polylactic acid or polylactic acid copolymer to form a composition.

Specific achievable effects of the present invention include: 1. The present invention utilizes a coupling agent having a functional group reactive with polylactic acid to react with polylactic acid, thereby forming a chain extending effect of the modified polylactic acid, so that the modified polylactic acid composition formed has high heat resistance and The toughness characteristics and the molding cycle are shorter than the unmodified polylactic acid.

2. In the present invention, since the dose of the coupling agent is maintained in an appropriate range, the raw material cost is not greatly increased, and there is no problem that the conventional additive is added to the polylactic acid, so that the modified polylactic acid composition formed by the present invention is not easily affected. Defects in the appearance of the finished product.

The preferred embodiment of the present invention may comprise 100 parts by weight of a polylactic acid or polylactic acid copolymer and 0.1 to 5 parts by weight of a coupling agent, which is also called a chain extender, which has more than one A compound capable of reacting with polylactic acid, and the functional group reactive with polylactic acid may be isocyanate, oxazoline, epoxy or aziridine. And carbamide; the reaction of polylactic acid with a coupling agent can be as follows: or

Preferably, the preferred embodiment of the present invention comprises 0.1 to 1 part by weight of a coupling agent. If the coupling agent is less than 0.1 part by weight, the chain extension effect is incomplete, and the molecular weight and melt viscosity of the composition cannot be improved. When the coupling agent is more than 5 parts by weight, the basic physical properties and mechanical strength of the molded article are lowered, and a large number of defective defects such as a gel are generated; preferably, the coupling agent is provided with two or more (including two) a functional group reactive with polylactic acid, such as a bifunctional coupling agent or a trifunctional coupling agent, the coupling agent may also be used in combination, such as a mixture of a difunctional coupling agent and a trifunctional coupling agent; Preferably, the functional group reactive with polylactic acid is an epoxy group, and the coupling agent having an epoxy group can react well with polylactic acid, and can also be used at a high temperature; preferably, if When the preferred embodiment is to be applied to a food packaging material, the coupling agent may be selected by the US Food and Drug Administration (FDA), such as epoxidized soybean oil or epoxy linseed oil; preferably, for coupling agent and polymerization The lactic acid can be fully reacted, and the coupling agent and the auxiliary agent can also be used. Made of materials such as masterbatch (masterbatch), then the polylactic acid composition is formed.

The preferred embodiment can be formed into particles and then formed into a finished product. The granulating device can use a single or double-axis extruder, a 10,000 horsepower machine, a kneader or other general plastic granulator, and the preferred embodiment can also be used. Directly made into finished products, such as injection molded film, sheet, bottle, foamed finished product and tube.

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:

Prepare 5 kg of commercially available polylactic acid (molecular weight: about 180,000) into a mixing tank, add a little processing oil and mix well, then put it into the Ethylene Chemicals with epoxy-based coupling product EPOLITE40E (epoxy equivalent: 135 G/eq (g/eq)) 10 g and EPOLITE 100F (epoxy equivalent: 150 g / equivalent (g / eq)) 15 g stirred evenly, using Kobe steel twin-screw extruder for granulation, screw diameter 43 mm The screw length to diameter ratio is 43, the temperature is set to 190 ° C, the screw rotation speed is 200 revolutions per minute (rpm), the vent hole is evacuated and the strip is water-cooled and pelletized, and the melt index of the obtained particles (Melt Index, MI) is one-third of the unmodified polylactic acid raw material, and the extrusion expansion ratio (%) is 0.45. After the particles are ejected from the test piece, the test piece is shortened compared to the unmodified polylactic acid raw material test piece. One-half, the heat distortion temperature (HDT) increased by 50 ° C, and the 173 ° C after the melting point was raised to 190 ° C, indicating that the finished product of the preferred embodiment has improved heat resistance and toughness, and the molding cycle is also shortened.

The preferred embodiment of the present invention utilizes a coupling agent having a specific functional group to react with polylactic acid to form a chain extending effect, so that the modified polylactic acid composition formed has characteristics of high heat resistance and toughness, and is formed. The cycle is also shorter than the unmodified polylactic acid. Further, since the dose of the coupling agent is kept in an appropriate range, the raw material cost is not greatly increased, and the formed modified polylactic acid composition is less likely to have defects affecting the appearance of the finished product.

The scope of application of the preferred embodiments of the present invention includes the following fields: a. Packaging field: film for packaging: such as plastic bags, label films, shrink films. Agricultural film: cover film, bagging. Food packaging box: hollow container (bottle), foam cushioning material, fishing box. b. Textile field: fiber applications such as clothes, masks, carpets, etc. c. Biomedical field: artificial bone nails, bone plates, drug release (such as diffusion control), wound dressing (artificial skin), wound closure (surgical suture, surgical supplies). d. Optoelectronics/Automotive: Replace existing plastic materials such as mobile phones, notebook cases, CDs, and automotive components.

Claims (3)

An improved polylactic acid composition comprising: 100 parts by weight of a polylactic acid or a polylactic acid copolymer; and 0.1 to 1 part by weight of a coupling agent having more than one reactable with polylactic acid A functional group-based compound which is reactive with polylactic acid is aziridine or carbamide. The modified polylactic acid composition according to claim 1, wherein the coupling agent has two or more functional groups reactive with polylactic acid. The modified polylactic acid composition according to claim 2, wherein the coupling agent is made into a master-batcher with a pigment, and then forms a composition with a polylactic acid or a polylactic acid copolymer.