KR20090073933A - Polyactic acid composition - Google Patents

Abstract

A polylactic acid resin composition is provided to increase compatibility with natural fiber and polylactic acid resin by using a chain extender, to ensure high viscosity, excellent mechanical strength and heat resistance, and to improve surface gloss and color of molded products. A polylactic acid resin composition comprises a polylactic acid resin 10-80 parts by weight, a rubber-modified vinyl-based graft copolymer resin 10-70 parts by weight and natural fiber 5-50 parts by weight. The polylactic acid resin composition includes a chain extender. The polylactic acid resin comprises an L-isomer 95-100 weight% and a D-isomer D 0-5 weight% based on the total weight of the polylactic acid resin. The rubber-modified vinyl-based graft copolymer resin is prepared by graft-polymerizing an aromatic vinyl compound 50-95 parts by weight and a vinyl cyanide compound 5 -50 parts by weight to an elastomer 40-70 weight%.

Description

Polylactic acid resin composition {POLYACTIC ACID COMPOSITION}

The present invention relates to a polylactic acid resin composition having improved mechanical strength and heat resistance. More particularly, the present invention relates to a polylactic acid resin composition which improves the compatibility of natural fiber and polylactic acid resin with a chain extender and increases the viscosity of the composition to improve mechanical strength and heat resistance. Eggplant relates to a polylactic acid composition.

Until recently, research directions for polymer materials were mainly led to the development of robust special purpose polymer materials and the safety of polymer materials. However, as the problem of environmental pollution caused by waste polymers is becoming a social problem all over the world, the necessity of environmentally friendly polymer materials is required.

Such environmentally friendly polymers can be broadly classified into photodegradable and biodegradable polymers. The double biodegradable polymers have functional groups capable of being decomposed by microorganisms in the main chain structure.

Among these polymers, aliphatic polyester polymers are the most researched as biodegradable polymers because of their excellent processability and easy control of decomposition properties. Especially, polylactic acid (PLA) forms a market of 150,000 tons in the world. In addition, the scope of application is expanding to the field where general plastics such as food packaging materials, containers, and electronics cases were used. To date, the main use of polylactic acid resins is in disposable products utilizing the biodegradable properties of polylactic acid, such as food containers, wraps, films and the like. These polylactic acids are currently being produced by Natureworks in the US and Toyota in Japan.

However, existing polylactic acid resins are easily broken in the case of thin film products due to lack of moldability, mechanical strength and heat resistance, and have low temperature resistance. .

Japanese Patent Publication Nos. 2005-220177, 2005-200517, and 2005-336220 disclose techniques for mixing glass fibers to improve heat resistance and mechanical strength at the same time, but glass fibers are not biodegradable after disposal. There is a disadvantage.

In order to solve this problem, a method of increasing heat resistance and the like using a composition including an acrylonitrile-butadiene-styrene (ABS) resin in a polylactic acid resin has been proposed. Styrene-based thermoplastic resins such as acrylonitrile-butadiene-styrene resins have excellent impact resistance, mechanical strength, surface properties and processability, and are widely used in electric / electronic products, automotive interior / exterior parts, and general goods. In particular, maleimide-based ABS is useful in various automotive interior / exterior materials for which heat resistance and moldability are enhanced and heat resistance is required. Japanese Patent Laid-Open Nos. 1999-279380 and 2006-070224 also describe methods using a composition comprising an acrylonitrile-butadiene-styrene resin in a polylactic acid resin, but the heat resistance performance is not as expected. I couldn't.

An object of the present invention is to provide an environmentally friendly polylactic acid resin composition having improved moldability, mechanical strength and heat resistance.

However, technical problems to be achieved by the present invention are not limited to the above-mentioned problems, and other technical problems will be clearly understood by the average technician from the following description.

In order to achieve the above object, according to an embodiment of the present invention (A) polylactic acid resin; (B) rubber modified vinyl graft copolymer resin; And (C) provides a polylactic acid resin composition comprising a natural fiber.

According to another embodiment of the present invention, a pellet is provided using the polylactic acid resin composition.

According to another embodiment of the present invention provides a molded article prepared from the polylactic acid resin composition.

Other specific details of embodiments of the present invention are included in the following detailed description.

The polylactic acid resin composition according to the present invention improves the surface gloss and color of molded products such as automobiles, mechanical parts, electrical and electronic parts, office equipment, and sundries, and has excellent heat resistance while having mechanical strengths higher than those available for molded products. .

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, by which the present invention is not limited and the present invention is defined only by the scope of the claims to be described later.

Polylactic acid resin composition according to an embodiment of the present invention, (A) polylactic acid resin; (B) rubber modified vinyl graft copolymer resin; And (C) natural fibers.

Hereinafter, each component included in the polylactic acid resin composition according to an exemplary embodiment of the present invention will be described in detail.

(A) polyactic acid (PLA) resin

In general, polylactic acid is a polyester resin produced by ester reaction using lactic acid as a monomer obtained by decomposing corn starch, and is easily commercially available.

In the polylactic acid resin composition of the present invention, the content of the polylactic acid resin is 10 to 80 parts by weight depending on the target biomass content and physical properties. Can be used as a range.

The polylactic acid used in the present invention is composed of L-isomers, D-isomers, or L, D-isomers, and these polylactic acid resins may be used alone or in combination. Preferably, the polylactic acid resin preferably contains 95 wt% or more of L-isomer in terms of balance of heat resistance and moldability, and more preferably 95 to 100 wt% of L-isomer in consideration of hydrolysis resistance, and D It is preferable to use a polylactic acid resin composed of 0 to 5% by weight of isomers.

In addition, the D-isomer is It is preferably contained in 0.1 to 5% by weight, and if the molding process is possible, there is no particular limitation on the molecular weight or molecular weight distribution, but using a weight average molecular weight of 80,000 or more to blend together by raising the viscosity of the polylactic acid resin to a predetermined level or more Balanced dispersion with resin and phase stability can be induced. Preferably the weight average molecular weight is 90,000 to 500,000 It is preferable to use polylactic acid resin.

The polylactic acid resin is contained in 10 to 80 parts by weight, preferably 25 to 60 parts by weight. When the content of the polylactic acid resin is less than 10 parts by weight, it is difficult to manufacture a master batch with natural fibers, and the workability may be reduced. When the content of the polylactic acid resin exceeds 80 parts by weight, the content of natural fibers and rubber-modified vinyl graft copolymer resin is limited. It can be difficult to achieve the desired mechanical properties.

(B) Rubber modified vinyl graft copolymer resin

The rubber-modified vinyl graft copolymer resin is (b1) (b11) styrene, α-methylstyrene, halogen or alkyl substituted styrene, C1-C8 methacrylic acid alkyl esters, C1-C8 acrylic acid alkyl esters, or these 50 to 95 parts by weight of a mixture of (b12) and 5 to 95% by weight of a monomer mixture consisting of 5 to 50 parts by weight of acrylonitrile, methacrylonitrile, maleic anhydride or a mixture thereof (b2) butadiene rubber, acrylic rubber, From the group consisting of ethylene / propylene rubber, styrene / butadiene rubber, acrylonitrile / butadiene rubber, isoprene rubber, terpolymer (EPDM) of ethylene-propylene-diene, polyorganosiloxane / polyalkyl (meth) acrylate rubber composite It is prepared by graft polymerization with 5 to 95% by weight of one or a mixture thereof selected.

The C1-C8 methacrylic acid alkyl esters or C1-C8 acrylic acid alkyl esters are esters obtained from monohydryl alcohols containing 1 to 8 carbon atoms, respectively, as alkyl esters of methacrylic acid or acrylic acid. Specific examples of these include methacrylic acid methyl ester, methacrylic acid ethyl ester, methacrylic acid propyl ester, acrylic acid ethyl ester or acrylic acid methyl ester.

Preferred examples of the rubber-modified vinyl-based graft copolymer (B) include butadiene rubber, acrylic rubber, or styrene / butadiene rubber in the form of a mixture of styrene, acrylonitrile and optionally (meth) acrylic acid alkyl ester monomers. The copolymerized thing is mentioned.

Examples of other preferred rubber-modified vinyl-based graft copolymers include those obtained by graft copolymerization of a monomer of (meth) acrylic acid methyl ester to butadiene rubber, acrylic rubber, or styrene / butadiene rubber.

In one embodiment of the present invention is prepared by graft polymerization of 60 to 30% by weight of a monomer mixture consisting of 50 to 95 parts by weight of aromatic vinyl compound and 5 to 50 parts by weight of vinyl cyanide compound to 40 to 70% by weight of the rubbery polymer.

An example of the most preferred rubber modified graft copolymer in the present invention is an ABS graft copolymer.

In the manufacture of the graft copolymer, the particle diameter of the rubber particles is preferably in the range of 0.05 to 4 μm in order to improve impact resistance and surface properties of the molded product.

The method for preparing the graft copolymer is well known to those skilled in the art, and any one of emulsion polymerization, suspension polymerization, solution polymerization, or bulk polymerization may be used. Under the above-mentioned aromatic vinyl monomer, it is preferable to carry out emulsion polymerization or block polymerization using a polymerization initiator.

The rubber-modified vinyl graft copolymer resin is included in 10 to 70 parts by weight, preferably 30 to 60 parts by weight. When the content of the vinyl-based copolymer resin is less than 10 parts by weight, the impact strength may be lowered. If the content of the vinyl copolymer resin is greater than 70 parts by weight, the biomass is lowered, which is not preferable in terms of environment.

(C) natural fiber

The natural fiber is a reinforcing agent, and includes a bast fiber prepared from the bast of the flexible of the wood and the bast of the plant stem.

The bast fiber may include flax, hemp, jute, kenaf, ramie, curaua, and the like.

The average length of the natural fiber is preferably 1 to 100mm. If the average length of the natural fiber is less than 1mm, the effect of improving the strength is not obtained, if it exceeds 100mm, the moldability may be lowered.

In addition, the average diameter of the natural fiber is preferably 0.1 to 50㎛. When the average diameter of the natural fiber is 0.1 to 50㎛, there is an advantage that the gloss of the surface of the molded article is improved.

In the present invention, in order to improve the adhesion (wetting) between natural fibers and polylactic acid resin, the natural fibers may be subjected to surface treatment such as silane coupling agent treatment, plasma treatment, alkali treatment, and the like. Can be.

The natural fiber is included in 5 to 50 parts by weight. The effect of improving mechanical strength and heat resistance can be obtained within the above range, and it is more preferable to use it in the range of 5 to 20 parts by weight. When the content of the natural fiber is less than 5 parts by weight, the synergistic effect of the mechanical strength is insignificant, and when it exceeds 50 parts by weight, the moldability may be reduced.

(D) chain extender

The polylactic acid resin composition of the present invention may further include (D) a chain extender in addition to the (A) polylactic acid resin, (B) vinyl copolymer resin, and (C) natural fiber.

Hereinafter, the chain extender (D) will be described in detail.

The chain extender is preferably a functional group capable of reacting both the hydroxy or carboxyl end group of the polylactic acid resin and the hydroxyl group of the natural fiber, which can improve the compatibility of the natural fiber.

It is preferable to use what contains an epoxy functional group as said functional group.

The chain extender is a copolymer having an epoxy functional group bonded to the main chain, and the content of the epoxy functional group in the copolymer is 0.1 to 40 mol%, more preferably 10 to 20 mol% with respect to the copolymer. to be. It is preferred that the main chain is a copolymer selected from the group consisting of polyethylene, polypropylene, siloxane, aromatic vinyl monomers, vinyl cyanide monomers, and combinations thereof.

As the aromatic vinyl monomer, styrene substituted with an alkyl group having 1 to 4 carbon atoms such as α-methylstyrene, styrene substituted with halogen, and the like can be preferably used. As said vinyl cyanide monomer, acrylonitrile, methacrylonitrile, etc. can be used preferably. As said aromatic vinyl monomer, it is more preferable to use styrene, and it is more preferable to use acrylonitrile as a vinyl cyanide monomer.

The content of the chain extender is 0.01 to 5 parts by weight based on 100 parts by weight of the mixture of (A) + (B) + (C). When the content of the chain extender is 0.01 to 5 parts by weight, mechanical strength and heat resistance may be improved, and the melt extruder viscosity may be lowered to a level at which mixing is performed.

The polylactic acid resin composition according to the present invention may further include an additive. The additive is selected from the group consisting of antioxidants, weathering agents, release agents, colorants, sunscreens, fillers, nucleating agents, plasticizers, flame retardants, and mixtures thereof.

As said antioxidant, a phenol type, a phosphite type, a thioether type, or an amine type antioxidant can be used preferably.

As said weathering agent, a benzophenone type or an amine type weathering agent can be used preferably.

As the mold release agent, a fluorine-containing polymer, silicone oil, a metal salt of stearyl acid, a metal salt of montanic acid, a montanic acid ester wax, or a polyethylene wax can be preferably used.

As said coloring agent, dye or a pigment can be used preferably.

Titanium oxide or carbon black may be preferably used as the sunscreen.

As the filler, silica, clay, calcium carbonate, calcium sulfate, or glass beads can be preferably used.

As the nucleating agent, talc or clay can be preferably used.

As the plasticizer, a polyester plasticizer, a glycerin plasticizer, a phosphate ester plasticizer, a polyalkylene glycol plasticizer, an epoxy plasticizer, etc. may be preferably used. have.

As the flame retardant, a bromine flame retardant, a phosphorus flame retardant, an antimony compound, a melamine compound, etc. may be preferably used.

The additive may be included as the remainder of the polylactic acid resin composition.

The chain extender is mixed with the polylactic acid resin and the natural fiber and processed to prepare a master batch, followed by further mixing the vinyl copolymer resin and the polylactic acid resin.

The master batch may be prepared using a batch type mixer, an extruder type mixer, or a long fiber fill.

In the present invention, by mixing the chain extender, polylactic acid resin and natural fibers to prepare a master batch, feeding is easy during extrusion, the advantage of increasing the viscosity of the mixture while improving the compatibility of polylactic acid and natural fibers Has

According to another embodiment of the present invention, the pellet may be prepared by a known method using the polylactic acid resin composition of the present invention. For example, after mixing the above-described composition and additives of the present invention, the melt extrusion may be carried out in an extruder to produce pellets.

According to another embodiment of the present invention, there is provided a molded article manufactured by molding the polylactic acid resin composition. The polylactic acid resin composition may be used in molded products in fields requiring durability, heat resistance, and transparency, for example, automobiles, mechanical parts, electrical and electronic parts, office equipment such as computers, and miscellaneous goods. In particular, it can be preferably applied to the housing of electrical and electronic products such as televisions, computers, printers, washing machines, cassette players, audio, mobile phones and the like.

The following presents specific embodiments of the present invention. However, the examples described below are merely for illustrating or explaining the present invention in detail, and the present invention is not limited thereto.

The specifications of (A) polylactic acid resin, (B) rubber-modified vinyl-based graft copolymer resin (C) natural fiber and (D) chain extender used in the following examples and comparative examples are as follows.

(A) polylactic acid resin

4032D manufactured by NatureWorks LLC, USA was used.

(B) Rubber modified vinyl graft copolymer resin

Butadiene rubber latex was added so that the butadiene content was 58 parts by weight based on the total amount of the monomers, 1.0 parts by weight of potassium oleate, cumene hydroperoxide, an additive necessary for a mixture of 31 parts by weight of styrene, 11 parts by weight of acrylonitrile, and 150 parts by weight of deionized water. An acrylonitrile-butadiene-styrene (ABS) graft copolymer was prepared by adding 0.4 parts by weight and 0.3 parts by weight of a t-dodecyl mercaptan chain transfer agent, and then maintaining it at 75 for 5 hours. A 1% sulfuric acid solution was added to the prepared ABS graft copolymer, solidified and dried to prepare a rubber-modified vinyl graft copolymer resin having a core-shell form having an average particle diameter of rubber of 0.3 μm in powder form. .

(C) natural fiber

In the embodiment of the present invention, the average length is 5mm, and the average content of cellulose is 98% by weight.

(D) chain extender

Kaneka Co., Ltd., MP-20® copolymer having 40% GMA (glycidyl methacrylate) bound to the polyethylene backbone was used.

(Example 1)

Natural fibers (NF-1), polylactic acid resins, and chain extenders Masterbatches were prepared by mixing 50: 50: 2 weight ratio. Separately, 30 parts by weight of polylactic acid resin and 50 parts by weight of rubber-modified vinyl graft copolymer resin were introduced into the main hopper, and 20 parts by weight of the prepared master batch was added to the side, and 40 parts by weight of polylactic acid resin and rubber-modified vinyl graft. 50 parts by weight of copolymer resin, 10 parts by weight of natural fiber content and 0.4 parts by weight of a chain extender were extruded in a conventional twin screw extruder at a temperature range of 200 to 230 ° C., and then the extrudate was prepared in pellet form. The prepared pellets were dried at 80 ° C. for 4 hours, and then, using an injection molding machine having an injection capacity of 6 Oz, a cylinder temperature of 230 ° C., a mold temperature of 80 ° C., and a molding cycle time of 60 seconds were set and ASTM dumbbell ( dumb-bell) injection molded into a specimen to prepare a physical specimen. The prepared physical property specimens are shown in Table 1 by measuring the physical properties by the following method.

Property evaluation method

(1) Heat deflection temperature (HDT): measured according to ASTM D648.

(2) Tensile strength: in accordance with ASTM D638 was measured at 5 mm / min cross head speed (cross head speed).

(3) Flexural strength: Measured at a crosshead speed of 2.8 mm / min in accordance with ASTM D790.

(4) Flexural modulus: measured at a crosshead speed of 2.8 mm / min in accordance with ASTM D790.

(Example 2)

Except for changing the content of the polylactic acid resin and natural fibers as shown in Table 1 was carried out in the same manner as in Example 1.

(Example 3)

The same procedure as in Example 1 was conducted except that no chain extender was used.

(Example 4)

The same procedure as in Example 1 was conducted except that the content of the chain extender was changed as shown in Table 1.

(Example 5)

The same procedure as in Example 1 was conducted except that the content of the chain extender was changed as shown in Table 1.

(Example 6)

The same procedure as in Example 1 was conducted except that 5 parts by weight of NF-2 was used as the natural fiber.

(Comparative Example 1)

The same procedure as in Example 1 was conducted except that no natural fibers were used.

(Unit: parts by weight) Item Example Comparative example One 2 3 4 5 6 One (A) polylactic acid resin 40 35 40 40 40 40 40 (B) Rubber modified vinyl graft copolymer resin 50 50 50 50 50 50 50 (C) natural fiber 10 15 10 10 10 5 - (D) chain extender 0.4 0.4 - 0.1 1.0 0.4 - Heat Deflection Temperature (℃) 75 80 56.3 70 83 56.1 49.6 Tensile strength (kgf / ㎠) 441 453 375 421 462 403 343 Flexural strength (kgf / ㎠) 534 534 464 513 650 521 413 Flexural Modulus (kgf / ㎠) 28060 30080 26550 25641 32145 27510 20310

As shown in Table 1, Examples 1 to 6 it was confirmed that the heat distortion temperature significantly increased compared to Comparative Example 1. Examples 1 and 2 have improved heat resistance, and mechanical strengths such as tensile strength, flexural strength, and flexural modulus are also improved. In addition, it can be seen that when the chain extenders are used as in Examples 1, 2, and 4 to 6, mechanical properties are more improved.

As shown in Table 2, both the heat resistance and the mechanical strength of Comparative Example 1 in which no natural fiber was used at all were significantly lower than those in Example 1 using natural fiber.

In conclusion, the use of a chain extender in the mixture of natural fibers and polylactic acid significantly improves the mechanical strength and heat distortion temperature and improves the compatibility with the polylactic acid resin. From this, it can be seen that the adhesion between the natural fiber and the polylactic acid and the viscosity of the mixture have a great influence on the heat resistance.

The present invention is not limited to the above embodiments, but may be manufactured in various forms, and a person skilled in the art to which the present invention pertains has another specific form without changing the technical spirit or essential features of the present invention. It will be appreciated that the present invention may be practiced as. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims (10)

(A) polylactic acid resin; (B) rubber modified vinyl graft copolymer resin; And (C) natural fibers; Polylactic acid resin composition comprising a. The method of claim 1, The polylactic acid resin composition includes (A) 10 to 80 parts by weight of polylactic acid resin; (B) 10 to 70 parts by weight of rubber-modified vinyl graft copolymer resin; And (C) natural fiber 5 To 50 parts by weight Polylactic acid resin composition which consists of. The method of claim 1, The polylactic acid resin composition further comprises (D) a chain extender. The method of claim 3, Wherein the chain extender is included in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the mixture of (A) + (B) + (C). The method of claim 1, The polylactic acid resin is a polylactic acid resin composition comprising 95 to 100% by weight of L-isomer and 0 to 5% by weight of D-isomer with respect to the total weight of polylactic acid. The method of claim 1, The natural fiber is a bast fiber polylactic acid resin composition. The method of claim 1, The natural fiber is a polylactic acid resin composition which is treated with a silane coupling agent, plasma surface treatment or alkali surface treatment. The method of claim 1, The rubber-modified vinyl-based graft copolymer is prepared by graft polymerization of 60 to 30% by weight of a monomer mixture consisting of 50 to 95 parts by weight of an aromatic vinyl compound and 5 to 50 parts by weight of a vinyl cyanide compound to 40 to 70% by weight of a rubbery polymer. Polylactic acid resin composition. The method of claim 1 Wherein said chain extender comprises an epoxy functional group. The method of claim 1, The composition is a polylactic acid resin composition further comprises an additive selected from the group consisting of antioxidants, weathering agents, mold release agents, colorants, sunscreens, fillers, nucleating agents, plasticizers, adhesion aids, pressure-sensitive adhesives, and mixtures thereof. .