Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-10-25
2003-02-04
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S047000, C524S156000
Reexamination Certificate
active
06515054
ABSTRACT:
BACKGROUND OF THE INVENTION
A. Technical Field
The present invention relates to a biodegradable resin composition and its molded product. Specifically, the invention relates to a biodegradable composition and its molded product wherein the composition comprises a biodegradable resin.
B. Background Art
In recent years, as social demands for environmental preservation rise, biodegradable resins that are degradable by microorganisms etc. attract more and more attention. Specific examples of the above biodegradable resins include melt-moldable aliphatic polyesters such as poly(hydroxybutyrate), polycaprolactone, poly(lactic acid) and polybutylene succinate.
However, of the above conventional aliphatic polyesters, biodegradable resins producible by microorganisms, for example, poly(hydroxybutyrate), involve an extremely high cost, and further, biodegradable resins obtainable by chemical synthetic processes, such as polycaprolactone, poly(lactic acid) and polybutylene succinate, are also 2 to 3 times as expensive as olefinic resins etc. which are widely used. It is the existing circumstance that these problems on the cost deteriorate the wide usability of the biodegradable resins.
In recent years, in order to cope with such problems of the above biodegradable resins on the cost, studies are made about biodegradable resin compositions which are designed to involve low costs by mixing the biodegradable resins with inexpensive organic or inorganic fillers to increase the amounts of the compositions. Arts in which, of the fillers, starches having an effect to accelerate the biodegradation rate are used attract attention.
However, blending the above biodegradable resin with the filler needs an agent or process for promoting their compatibility, for example, surface-treating the filler, because, in the case where the compatibility between the biodegradable resin and the filler is poor, the mechanical strength of the resultant blend might so inferior that this blend might be difficult to apply to various uses of molded products, and further because some blending processes deteriorate the biodegradable resin.
To solve these problems, many processes are proposed in which processes starches are used as fillers and blended with the biodegradable resin.
For example, JP-A-512010/1998 proposes a process which comprises the steps of synthesizing a thermoplastic starch from a starch, sorbitol, and glycerol and then blending this thermoplastic starch with a biodegradable resin. However, this process has problems in that blending an active-proton-containing compound, such as sorbitol or glycerol, with a biodegradable resin of the polyester structure at high temperature deteriorates the biodegradable resin. Furthermore, this process is insufficient to compatibilize the biodegradable resin and the starch.
JP-A-207047/1994 proposes a process which comprises the step of blending a starch and a cellulose ester together. However, this process has problems in that a blend, obtained by this process, exhibits a fracture elongation merely less than 200% and is therefore a material poor in the mechanical strength.
JP-A-211959/1998 proposes a process in which an ethylene oxide adduct of acetylene glycol is used when blending corn starch and a biodegradable resin together. However, this process has problems in that blending an active-proton-containing component (included in the acetylene glycol compound) with a biodegradable resin of the polyester structure at high temperature deteriorates the biodegradable resin. Furthermore, this process is insufficient to compatibilize the biodegradable resin and the corn starch.
JP-A-330954/1995 proposes a process which comprises the steps of introducing polyethylene glycol as a diol component formable into an aliphatic polyester to synthesize a hydrophilicity-enhanced aliphatic polyester and then blending it with a starch. However, it is difficult to say that the synthesis of the diol-component-introduced aliphatic polyester for the purpose of only enhancing the compatibility with the starch is an easy process. Furthermore, this process disarranges the crystal structure and therefore decelerates the crystallization rate in the molding step.
JP-A-152602/1998 proposes a process in which polyethylene glycol is used when blending a starch and a biodegradable resin together. However, this process has problems in that, in the case where the blending step is carried out using a high hydrophilic polymer such as polyethylene glycol, the resultant blend feels sticky to the touch due to moisture, or the biodegradable resin deteriorates with the passage of time due to water absorbed into polyethylene glycol, and further in that polyethylene glycol is so hydrophilic as to merely have low compatibility with the biodegradable resin.
JP-A-158485/1998 and JP-A-313063/1994 propose a process in which a low-molecular aliphatic polyester is added when blending a high-molecular aliphatic polyester and a starch together. However, it is difficult to say that the synthesis of two kinds of high-molecular and low-molecular aliphatic polyesters for the purpose of only enhancing the compatibility with the starch is an easy process. Furthermore, this process is applicable only to specific aliphatic polyesters and therefore poor in the wide usability.
JP-A-331315/1993 and JP-A-188671/1996 propose a process which comprises the step of blending an aliphatic polyester with a pasty starch which is prepared by adding water to a starch. However, this process has problems in that water acts as active proton to deteriorate (hydrolyze) the biodegradable resin. Furthermore, this process is insufficient to compatibilize the biodegradable resin and the starch.
JP-A-271694/1994 proposes a process which comprises the step of blending a starchy polymer, a poly(vinyl alcohol), and a nonionic surfactant wherein the starchy polymer has a water content of 5 to 30 weight %. However, this process has problems in that water in the starchy polymer acts as active proton to deteriorate (hydrolyze) the biodegradable resin. Furthermore, this process is insufficient to compatibilize the biodegradable resin and the starchy polymer.
SUMMARY OF THE INVENTION
A. Object of the Invention
In order to solve the above problems, an object of the present invention is to provide a biodegradable resin composition and its molded product wherein the biodegradable resin composition exhibits excellent biodegradability and excellent mechanical strength, and further, is inexpensive, easy to process by molding, and usable for a wide range of purposes.
B. Disclosure of the Invention
Considering such existing circumstances, the present inventors diligently studied to solve the above-mentioned problems. As a result, they found that the moldability and the mechanical strength are enhanced by adding an anionic surfactant to a resin composition which comprises a biodegradable resin and a filler, and further that the mechanical strength is greatly enhanced if the anionic surfactant is particularly a sulfonic-acid-group-containing anionic surfactant.
Thus, a biodegradable resin composition, according to the present invention, comprises a biodegradable resin, a filler, and an anionic surfactant.
A molded product, according to the present invention, is a molded product from the above biodegradable resin composition according to the present invention.
These and other objects and the advantages of the present invention will be more fully apparent from the following detailed disclosure.
DETAILED DESCRIPTION OF THE INVENTION
There is no especial limitation in the biodegradable resin in the present invention if this resin is a thermoplastic resin having biodegradability. Specific examples of the biodegradable resin include: high-molecular aliphatic polyesters; and biodegradable polymers containing aromatic dicarboxylic acids as essential structural units.
The number-average molecular weight of the high-molecular aliphatic polyester in the present invention is not especially limited, but is, for example, in the range of 10,000 to 100,000, preferably in the range of 2
Atsumi Yoshiko
Itoh Hiroshi
Matsushita Teruki
Nippon Shokubai Co. , Ltd.
Rajguru U. K.
Roylance Abrams Berdo & Goodman L.L.P.
Seidleck James J.
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