US20070043148A1

US20070043148A1 - Biodegradable resin composition

Info

Publication number: US20070043148A1
Application number: US11/489,841
Authority: US
Inventors: Young-kwan Yi; Sang-Hwan Lee
Original assignee: ELECSYS Co Ltd; YOUNG-KWAN YI
Current assignee: ELECSYS Co Ltd; YOUNG-KWAN YI
Priority date: 2005-07-20
Filing date: 2006-07-20
Publication date: 2007-02-22
Also published as: TW200708554A; WO2007011119A1; KR20070010837A

Abstract

This invention provides a biodegradable resin composition and a biodegradable molding using the same and in particular, it not only have satisfactory biodegradability, processability and properties required for biodegradable resins by comprising cellulose diacetate as a main component but also can lower manufacturing costs and prevent environmental contamination by preparing the biodegradable resins by reusing a cause factor of environmental contamination.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a biodegradable resin composition and a biodegradable molding using the same and more particularly, it relates to a biodegradable resin composition comprising cellulose diacetate as a main component, which can not only satisfy the biodegradability, processability and properties required for a biodegradable resin but also lower manufacturing costs and prevent environmental contamination by producing the biodegradable resin by reusing a cause factor of environmental contamination and a biodegradable molding using the same.
2. Description of Related Art
As plastics are light and strong and they are easy to be processed and not easily degraded, their consumption from industrial materials to disposable products and wrapping materials is continuously increasing. Hard wastes including such plastics are disposed by landfill or incineration after their use, or reused by recycling them. However, the disposal of wastes by landfill, incineration, etc. gives rise to environmentally severe damage. Accordingly, to solve the environment issue, various biodegradable plastics that keep their function and structure during their use but can be degraded into water and carbon dioxide by microorganism once wasted are being produced.
For example, U.S. Pat. Nos. 5,234,977, 5,256,711, 5,264,030, 5,292,782, 5,334,634, 5,461,093, 5,461,094, 5,569,692, 5,616,671, 5,696,186, 5,869,647, and 5,874,486 disclose methods of preparing biodegradable plastics by mixing a starch which is inexpensive and easily biodegradable with common resins such as polyethylene, polypropylene and polystyrene, and polyester-based matrix resins. However, as the starch is added, a plasticizer is to be added, which causes discoloring and bad fume during processing and the properties of the plastics are remarkably deteriorated.
Further, U.S. Pat. Nos. 4,133,784 and 4,337,181 disclose methods of preparing films by adding pregelatinized starches to ethylene-acrylic acid copolymers. However, the ethylene-acrylic acid copolymers are expensive and the properties of the produced films are extremely fragile for practical use, and their biodegradability is not good.
Further, U.S. Pat. Nos. 5,254,607, 5,256,711 and 5,258,430 disclose the use of a pregelatinized starch, but they require a separate apparatus for adding water and a plasticizer in a large amount so as to pregelatinize starch and also, the degradability of the ethylene-vinyl alcohol copolymers which are synthetic resins used to increase properties and dimension stability has not been verified.
Also, Korean Patent Laid-Open Nos. 1994-0011542, 1994-0011556, and 1994-0011558 attempted reaction extrusion by use of an organic acid catalyst and binding agent to induce the chemical binding of starch and polyethylene. However, unreacted coarse monomers are likely to remain, and in the case that the content of the starch is more than 30%, mechanical properties are remarkably reduced, and the polyethylene which is used as a matrix resin is not degraded and remains.
Hence, researches about methods of preparing biodegradable resins using cellulose derivatives have been conducted and especially, the researches about the biodegradable resins using cellulose acetate among the cellulose derivatives have been mainly performed.
The cellulose acetate, a conversion form into an acetic ester of cellulose, has been known to be inherently biodegradable but in fact, its biodegradability is not good. Thus, although molding products comprising the cellulose acetate are laid under the grounds, they maintain the prototype of the molding products until 1 or 2 years and it takes considerably long time for the molding products to be completely biodegraded. Also, the molding products are sometimes landfilled as wastes, or left in nature environment, not being recovered as wastes.
Accordingly, researches about methods for improving the biodegradability of the cellulose acetate are in progress. Japanese Patent Laid Open No. 6-199901 discloses a method of regulating the biodegradability of the cellulose acetate by adding an acid compound having a higher acid dissociation constant than acetic acid to the cellulose acetate. However, in this method, at the point when the acid compound is added to the cellulose acetate, the cellulose acetate is chemically hydrolyzed by the influence of the acid compound and this hydrolysis reaction generates acetic acid, which gives strong acetic acid odor to the cellulose acetate products.
Therefore, studies about methods of preparing biodegradable plastics using different kinds of cellulose derivatives other than the cellulose acetate have been incessantly conducted and more progressive studies are in need.

SUMMARY OF THE INVENTION

In order to solve the problems of the prior arts, it is an object of the invention to provide a biodegradable resin composition comprising a cellulose (di)acetate as a main component, which satisfies the biodegradability, processability and properties required for a biodegradable resin and from which acetic acid odor is removed, and a biodegradable molding using the same.
Also, it is another object of the invention to provide a biodegradable resin composition which can lower the manufacturing costs of the biodegradable resin composition to be produced and prevent environmental contamination in advance by reusing a cause factor inducing environmental contamination and a biodegradable molding using the same.
It is still another object of the invention to provide a biodegradable resin composition capable of preventing environmental contamination because the container is degraded under the ground or in the air within a short period when landfilled after its use, a method of preparing a biodegradable molding using the same and the biodegradable molding.
To achieve the aforementioned objects, the present invention provides a biodegradable resin composition comprising a cellulose diacetate as a main component.
Preferably, the molecular weight of the cellulose diacetate is 10,000 to 500,000.
Also, more preferably, the biodegradable resin composition comprises:
a) 50 to 90 parts by weight of a cellulose diacetate; and
b) 10 to 50 parts by weight of a plasticizer.
Further, the invention provides a biodegradable molding prepared by kneading and extruding the biodegradable resin composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing of the biodegradability of a biodegradable film prepared by using an embodiment of the invention comprising cellulose diacetate, comparing with that of cellulose which is a standard material.
FIG. 2 is a graph showing the biodegradability of PLA which is a commonly used biodegradable material, comparing with that of cellulose which is a standard material.

DETAILED DESCRIPTION OF THE INVENTION

This invention is further described in detail.
The inventors found that a cellulose diacetate can be biodegraded and it has a remarkably low melting point and thus has an excellent processability while possessing superior properties and accordingly, they have completed the invention.
The biodegradable resin composition of the invention is characterized by comprising a cellulose diacetate that is a biodegradable resin, as a main component.
Preferably, the biodegradable resin composition of the invention comprises a cellulose diacetate and plasticizer, and biodegradable moldings can be prepared by evenly mixing the biodegradable resin composition and kneading and extruding the mixed composition.
The cellulose diacetate is contained in the biodegradable resin composition preferably in an amount of 50 to 90 parts by weight. Within the above ranges, satisfactory processability as a biodegradable resin composition as well as the properties of moldings can be obtained.
Preferably, the cellulose diacetate can be obtained from a waste cigarette filter which is a cause factor of environmental contamination, and the manufacturing costs of the biodegradable resin compositions can be remarkably lowered by preparing the biodegradable resin compositions by recycling the cellulose diacetate of the waste cigarette filters and environmental contamination can be prevented in advance.
The plasticizer used in the invention makes molding, injection, etc. easy when the biodegradable moldings are prepared and it improves glass transition temperature (Tg), tensile strength, Young's modulus, etc. of the cellulose diacetate.
For the plasticizers, triacetin (TA), triethyl citrate (TEC), or glycerin can be suitably used, epoxidized soybean oil (ESO) as a secondary plasticizer can be added thereto and preferably, it is preferable to use triacetin.
The plasticizer is contained in the biodegradable resin composition of the invention preferably in an amount of 10 to 50 parts by weight, and the above range is preferable in aspect of the easiness of molding and injection when the moldings are prepared.
The biodegradable resin composition comprising the above components may further comprise clay minerals such as montmorillonite and bentonite, additives such as a degradation catalyst or processing aid, etc. if necessary and their amount is preferably 0.1 to 10 parts by weight.
For the catalysts, a latent heat catalyst can be used to cause the ring opening polymerization of epoxidized soybean when the epoxidized soybean is contained as a plasticizer.
The clay minerals have excellent hygroscopic property due to their laminated structure and accordingly, they render the moldings prepared with the biodegradable resin composition of the invention to be readily degraded even in the water. In particular, the montmorillonite is preferably used as a clay mineral.
Also, when the clay minerals are used in the biodegradable resin composition of the invention, it is preferable to mix the clay minerals with the plasticizer and disperse them using an ultrasonic machine before they are added to the biodegradable resin composition.
Further, the invention may further comprise a natural vegetable fiber as a filling agent within the biodegradable resin composition in the preparation of the biodegradable resin composition. Specific examples of the natural vegetable fiber are coconut fiber, hemp fiber, ramie fiber, sisal fiber, henequen fiber, pineapple leaf fiber, cotton fiber, coier fiber, rice straw, etc. and it is preferable to have an average diameter of 10 to 500 μm or so. Also, the filling agent is contained preferably in an amount of 1 to 50 parts by weight of 100 parts by weight of the biodegradable resin composition, and in this case, it is advisable to maintain the content of the plasticizer in at least 10% by weight of the biodegradable resin composition. If the filling agent is used, mechanical strength can be complemented and the use of the natural vegetable fibers that are inexpensive can much lower the manufacturing costs of the biodegradable resin composition.
Further, the invention provides a biodegradable molding characterized in that it is prepared by kneading and extruding the biodegradable resin composition comprising the aforementioned components.
For the kneading and extrusion, conventional methods used to knead and extrude biodegradable resin compositions can be applied and for example, a twin screw extruder or batch mixer can be used.
Preferably, the temperature during the kneading process is 25˜120° C. as the melting point of the cellulose diacetate is low and more preferably, it is 25˜100° C.
Also, after kneaded at the above temperature, it can be molded into moldings preferably at the temperature of 160˜220° C. using a common extruder.
The biodegradable moldings prepared by the aforementioned method can be applied to films for semiconductor packaging, disposable products such as a variety of containers, cups, spoons, forks, knives, toothbrushes and straws, paper cups, melty coatings such as paper coatings for the manufacture of paper plates, mulching films, agriculture and gardening supplies such as plant ports, clips, etc. garbage bags, compost bags, shrink wrap films, wrapping films, medical supplies such as syringes for animal injection, mouthpieces for endoscope, modifiers for hard biodegradable plastics, golf tee, fish net, fishing line, bottles, a variety of stationery and so on.
The biodegradable resin composition in accordance with the invention is melted at a melting point remarkably lower than the melting point required in the manufacture of cellulose derivatives used as a substance of prior biodegradable plastics so that it is easy to be prepared into moldings and at the same time, it has properties equal to those of the moldings prepared by using the prior biodegradable resins. In addition, it can in advance prevent environmental contamination by reusing a cause factor of environmental contamination and remarkably lower the manufacturing costs of the biodegradable resin compositions. Also, as the biodegradable moldings prepared by using the biodegradable resin compositions of the invention can be degraded under the ground or in the air within a short period when landfilled after their use, they have an advantage in that they can prevent environmental contamination.
For better understanding of the present invention, preferred embodiments follow. The following examples are intended to merely illustrate the invention without limiting the scope of the invention.

EXAMPLES

Example 1

After 70 parts by weight of cellulose diacetate having a molecular weight of 202,332 (Eastman Co., Ltd.), and 30 parts by weight of triacetin (Mw. 218.21, major component C₉H₁₄O₆), Dae Shin Chemical Ind. Co., Ltd.) as a plasticizer were evenly mixed, the mixture was kneaded for 3 hours at the temperature of 100° C. and melted in Haake rheocord system of 200° C. thereby to prepare a blending mixture.

Examples 2 to 8 and Comparative Examples 1 to 6

With the exception that the compositions and ratios as shown in Table 1 below were used, blending mixtures were prepared by carrying out the same method as above Example 1.

	TABLE 1


	Cellulose
	(Parts by	Plasticizer

	Weight)	TA	TEC	GC	ESO	BET

EX. 1	CDA ¹70	30
EX. 2	CDA ¹80	20
EX. 3	CDA ¹80		20
EX. 4	CDA ¹80			20
EX. 5	CDA ¹80	10			10
EX. 6	CDA ²80	20
EX. 7	CDA ²70	20			10
EX. 8	CDA ³80	20
EX. 9	CDA ³70			30
COM. EX. 1	CA 90					10
COM. EX. 2	CA 80					20
COM. EX. 3	CA 70					30
COM. EX. 4	pure PP
COM. EX. 5	pure PLA

Note
CDA¹: Cellulose (Di)Acetate(Mn ca. 202,332 g · mol⁻¹, 54.5 wt. % acetyl content, Tg 188° C., Eastman Co., Ltd)
CDA²: Recycling fabric CDA (SK)
CDA³: Recycling fiber CDA (SK)
CA: Cellulose acetate(Mn ca. 50,000 g · mol⁻¹, 39.7 wt. % acetyl content, Tg 188° C., Aldrich Co., Ltd.)
PP: Polypropylene (grade H1500, Hyundai)
PLA: Polylacetic acid (Mn 83,000 g · mol⁻¹, Mw 153000 g · mol⁻¹Cargill-Dow Co., Ltd.)
TA: Triacetin(Mw. 218.21), Dae Shin Chemical Ind. Co., Ltd.
TEC: Triethyl citrate(Mw. 276.29), Aldrich Co., Ltd.
ESO: ShinDongBang Coroperation
GC: Glycerin

The blending mixtures prepared by melting the biodegradable resin composition in Haake rheocord system in Examples 1 to 9 were extruded for 10 minutes at the melting points of the blending mixtures using Carver laboratory press equipped with a temperature control device thereby to prepare initial films having a width of 10 cm, a height of 10 cm and a thickness of 300 μm. The prepared films were cut into ones having a width of 0.5 cm and a height of 4 cm and their glass transition temperature and modulus were measured by Dynamic Mechanical Analyzer. The results are shown in Table 2 below.

TABLE 2

Glass transition temperature (Tg) and

Young's modulus measured from MDA

Young's modulus

EX./COM. EX. Tg (° C.) (GPa)

EX. 1 97 1.50

EX. 2 108 1.55

EX. 3 138.5 1.72

EX. 4 146.9 1.64

EX. 5 141.9 1.91

EX. 6 89.9 1.34

EX. 8 92.8 1.34

COM. EX. 2 206.3 2.51
As shown in Table 2 above, the working Examples of the invention had remarkably lower Tg and Young's modulus than Comparative Example in which cellulose acetate was used and thus they could be very easily processed.
In addition, to measure mechanical properties of the working Examples of the invention and Comparative Examples, tensile specimen were prepared according to ASTM D1708 and ASTM D638, wherein the injection pressure was 750-900 psi, injection time was 3 seconds, the temperature of cylinder was 180-200° C. and cycle time was 2 min. The mechanical strength of the films prepared above was measured by the machine named LR30K-plus from LLOYD, Inc. 10 Specimen in each example were fabricated and then tested. The average value was taken and the results are shown in Table 3 below.

TABLE 3

Young's

Tensile Strength Elongation modulus

EX. (MPa) (%) (MPa)

EX. 1 72 8 2300

EX. 2 131 8 3671

EX. 4 90 5 2964

EX. 9 73 6 2254

COM. EX. 5 84 5 2633
As shown in Table 3 above, the biodegradable resin compositions of the inventions showed properties similar to Comparative Example 5 in which the prior biodegradable resin was used.
Also, in order to examine the biodegradability of the biodegradable resin compositions of the invention, the biodegradable resin composition of Example 2 was subject to experiment according to KS M 3100-1 (ISO 14855) provision, and the biodegradability test was carried out in composting conditions. The composition of Comparative Example 5 was tested likewise. As of cellulose which is a standard material and Example 2 and Comparative Example 5, their aerobic biodegradability and collapse rate were measured in the composting conditions and the quantity of the generated carbon dioxide was measured by titration.
FIG. 1 showed the biodegradability of Example 2 of the invention and cellulose which is a standard material over time and FIG. 2 showed the biodegradability of Comparative Example 5 and the cellulose which is a standard material over time.
As shown in FIG. 1 and FIG. 2, the biodegradable resin composition of the invention showed biodegradability almost equal to that of Comparative Example 5 wherein the commonly used biodegradable resin composition was used.
The biodegradable resin composition in accordance with the invention can remarkably lower the manufacturing costs when compared with the cellulose acetate which has been used as biodegradable plastic materials, can prevent environmental contamination by reusing the cause factor of environmental contamination, remarkably improves the properties, is easy to be prepared into moldings at a low temperature due to its low melting point, and has considerably improved properties when compared with prior biodegradable moldings using starch.

Claims

1. A biodegradable resin composition comprising a cellulose diacetate as a main component.

2. The biodegradable resin composition according to claim 1 wherein the cellulose diacetate is an ethyl cellulose having a molecular weight of 10,000 to 500,000.

3. The biodegradable resin composition according to claim 1 wherein the biodegradable resin composition comprises:

a) 50 to 90 parts by weight of a cellulose diacetate; and

b) 10 to 50 parts by weight of a plasticizer.

4. The biodegradable resin composition according to claim 1 wherein the plasticizer is selected from the group consisting of triacetin (TA), triethyl citrate (TEC), glycerin and a mixture thereof.

5. The biodegradable resin composition according to claim 1 wherein the cellulose diacetate is obtained from a waste cigarette filter.

6. The biodegradable resin composition according to claim 1 wherein the biodegradable resin composition further comprises a clay mineral, degradation catalyst or processing aid.

7. The biodegradable resin composition according to claim 1 wherein the biodegradable resin composition further comprises a natural vegetable fiber.

8. A biodegradable molding prepared by kneading, extruding and injecting the biodegradable resin composition of claim 1.

9. The biodegradable molding according to claim 8 wherein the biodegradable molding is a film for semiconductor packaging, container, cup, spoon, fork, knife, toothbrush, straw, paper cup, paper coating for the manufacture of paper plates, mulching film, plant port, clip, garbage bag, compost bag, shrink wrap film, wrapping film, syringe for animal injection, mouthpiece for endoscope, modifier for hard biodegradable plastics, golf tee, fish net, fishing line, bottles or stationery.