JP3886817B2 - Biodegradable composite materials and biodegradable plastic moldings - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a composite material of a natural fiber and a biodegradable plastic, particularly a biodegradable composite material having a high strength, and a molded product obtained by molding the composite material.
[0002]
[Prior art]
In recent years, biodegradable plastics have attracted attention for reducing environmental impact. However, commercially available biodegradable plastics have limited applications due to their considerably lower mechanical strength compared to what are called engineering plastics. For this reason, attempts have been made to make up for the lack of strength by adding reinforcement, but in this case, the reinforcement itself is meaningless unless it is biodegradable. For example, in addition to plant natural fibers such as bamboo, jute, kenaf, etc. Animal natural fibers are used. However, the present situation is that the reinforcing effect expected by mixing these natural fibers is not obtained.
[0003]
The inventors of the present invention have conducted research focusing on this point, and in the case of a composite material in which natural fibers are simply mixed, the plastic of the base material and the natural fibers of the reinforcing material are separated when stress is applied. And found that the reinforcing effect is not exhibited. This is considered to be because the adhesiveness at the interface between the biodegradable plastic and the natural fiber is insufficient and the molded product is not sufficiently integrated.
[0004]
[Problems to be solved by the invention]
Based on the above research results, the present invention has been made to provide a biodegradable composite material that can exhibit high mechanical strength by enhancing the adhesion between the biodegradable plastic and the natural fiber. Is.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the biodegradable composite material of the present invention has a plant natural fiber treated with a surface treatment agent that reacts with OH groups in order to crosslink between OH groups of cellulose, and an ester structure. It is a blend of biodegradable plastics, and a cross-linking treatment between OH groups is performed using glyoxal or trimethoxymethylmelamine as a surface treatment agent.
[0006]
In the above case, the blending ratio of the plant natural fiber to the biodegradable plastic is selected in the range of 0.5 to 51 wt%.
[0007]
As plant-derived natural fibers, plant fibers such as bamboo, jute, kenaf, and mitsumata can be used, but bamboo is particularly suitable because it grows quickly and is highly productive and has sufficient production in Japan. Material.
[0008]
As the surface treatment agent, glyoxal or trimethoxymethylmelamine used in the papermaking process as a surfactant is used.
[0009]
Moreover, the biodegradable plastic used as a base material of a composite material should just have ester structures, such as aliphatic polyester , for example, well-known biodegradable plastics marketed, such as a polybutylene succinate, can be used suitably.
[0010]
In the present invention, bamboo fibers having a diameter of 30 to 100 μm and a length of 200 to 800 μm are used. Moreover, since bamboo fiber has a peculiar color and smell, in addition to using it as it is, it can use the thing decolored or colored, and the thing deodorized or scented.
[0011]
A composite material using such bamboo fibers can be molded by an injection molding method, whereby a molded product having a desired shape can be obtained.
[0012]
As described above, in the present invention, the surface treatment agent is prepared by mixing the plant natural fiber obtained by crosslinking between the OH groups of cellulose with glyoxal or trimethoxymethylmelamine and the biodegradable plastic having an ester structure. The wettability of the fiber surface is improved by the interaction between the OH group of cellulose crosslinked and activated by the chemical reaction caused by the ester group of the biodegradable plastic, and the interfacial adhesion is enhanced, so that both are fully integrated. Turn into. Therefore, a biodegradable composite material having high mechanical strength after molding can be obtained.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to two examples.
[0014]
In the first embodiment, polybutylene succinate (Bionore # 1020 manufactured by Showa Polymer Co., Ltd.) is used as a base plastic, and an average diameter of about 70 μm and an average length of about 500 μm obtained by pulverization as a reinforcing material. Bamboo fibers (manufactured by Suehiro Sangyo Co., Ltd.) and glyoxal as surface treatment agents were used.
[0015]
First, a treatment liquid diluted to 1 wt% with a 40 wt% glyoxal aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) and a treatment liquid diluted to 2 wt% were prepared. Air dried at room temperature. This dipping may be carried out by any method other than dipping because the treatment solution only needs to sufficiently penetrate and get wet with the bamboo fibers.
[0016]
The two types of bamboo fibers thus surface-treated are mixed with polybutylene succinate at a ratio of 10 wt%, and uniformly kneaded at a temperature of 135 ° C. using a biaxial extruder, and then inline screw type injection molding machine. A sample A1 using bamboo fiber molded at a screw temperature of 140 ° C. and treated with 1 wt% treatment liquid and sample A2 using bamboo fiber treated with 2 wt% treatment liquid were obtained. The temperature at the time of kneading and injection is set according to the melting point of polybutylene succinate , and when the base material is different, it is set according to the base material.
[0017]
FIG. 1 shows the results of a tensile test of these samples A1 and A2 and a sample A0 molded under the same conditions using bamboo fibers not treated with a treatment solution for comparison. The tensile test was performed using an Instron universal testing machine at a crosshead speed of 5 mm / min and a span distance of 115 mm.
[0018]
As is clear from FIG. 1, samples A1 and A2 have both improved mechanical strength and load compared to sample A0, and sample A2 shows a higher value than sample A1. Yes. These confirm that the surface treatment of bamboo fiber according to the present invention is effective and the intended purpose is achieved.
[0019]
In the second example, the base material and bamboo fiber are the same as in the first example, but trimethoxymethylmelamine was used as the surface treatment agent.
[0020]
First, prepare a treatment solution diluted to 1 wt% with a trimethoxymethylmelamine 80 wt% aqueous solution (Sumitex Resin M-3, manufactured by Sumitomo Chemical Co., Ltd.) and a treatment solution diluted to 2 wt%, respectively. Was immersed at room temperature and then air-dried at room temperature.
[0021]
The two kinds of surface-treated bamboo fibers were each mixed with polybutylene succinate at a ratio of 10 wt%, uniformly kneaded under the same conditions as in the first example, and formed into a dumbbell shape, and a 1 wt% treatment solution. Sample B1 treated with the above and Sample B2 treated with 2 wt% of the treatment liquid were obtained.
[0022]
FIG. 2 shows the results of a tensile test of these samples B1 and B2 and the above-described sample A0 under the same conditions as in the first example. As is clear from FIG. 2, although the samples B1 and B2 have almost the same elongation as the sample A0, the load is improved, and the sample B2 shows a higher numerical value than the sample B1. This second embodiment also confirms that the bamboo fiber treatment according to the present invention is effective and the intended purpose is achieved.
[0023]
When the fracture surface of each of the above samples was confirmed with a microscope, in sample A0 there were many gaps between the base plastic and bamboo fiber, whereas in samples A1 and A2 and samples B1 and B2, the gaps were Almost no occurrence was observed, and it was observed that the base material and bamboo fiber were integrated.
[0024]
In the above-described embodiment, bamboo fibers having an average diameter of about 70 μm and an average length of about 500 μm are used, but this provides the necessary strength and maintains sufficient fluidity without hindering injection molding. This is the selected value. If the bamboo fiber has an actual diameter of 30 to 100 μm and a length of 200 to 800 μm, even if the average value is different from the above, an injection molded product having a desired shape can be obtained without any particular problem. In consideration of the moldability and the strength of the molded product, it is desirable that the bamboo fiber has a diameter of 40 to 80 μm and a length of 400 to 600 μm. However, depending on the molding method and the type of fiber, the fiber diameter and length Even if it is outside the above range, it can be used.
[0025]
In FIG. 1, the sample having a higher concentration of the surface treatment agent has improved elongation and load. In FIG. 2, the sample having a higher concentration of surface treatment agent has improved elongation, and the higher the concentration of the surface treatment agent, the higher the result. Although it is good, the upper limit of the concentration at which the effect is obtained has not yet been sufficiently confirmed.
[0026]
In the above-mentioned embodiment, bamboo fiber is blended in polybutylene succinate at a ratio of 10 wt%, but the blending ratio of plant natural fiber depends on the use of composite material, fiber type, biodegradable plastic type, etc. To select as appropriate. The mechanical strength of the obtained molded product naturally varies depending on the blending ratio of natural fibers, but if the blending ratio is in the range of 0.5 to 51 wt%, there is an effect of improving the strength, and in particular the blending ratio is 5 to 30 wt%. If so, a great improvement in strength can be expected. The above 51 wt% is an upper limit value that is recognized as a plastic in the standard, and technically, a higher blending ratio is possible.
[0027]
In addition, the base material plastic and the surface treatment agent are not limited to those in the examples, and other materials can be used as long as the properties are the same. Various materials such as an inhibitor, a flame retardant, and a colorant can be appropriately added. Moreover, since bamboo fiber has a peculiar color and smell, what was decolored or colored, and what was deodorized or perfumed can be used. These treatments can be carried out by appropriate means such as impregnating bamboo fibers into a colorant or fragrance solution.
[0028]
【The invention's effect】
As is clear from the above description, the biodegradable composite material of the present invention is a plant-derived natural material in which glyoxal or trimethoxymethylmelamine is used as a surface treatment agent that reacts with OH groups to crosslink between OH groups of cellulose. The fiber and the biodegradable plastic having an ester structure are uniformly blended. Therefore, the wettability of the fiber surface is improved by the interaction between the OH group of cellulose crosslinked and activated by the chemical reaction by the surface treatment agent and the ester group of the biodegradable plastic, and the adhesion at the interface is increased. Since the two are sufficiently integrated, a biodegradable composite material having mechanical strength almost equal to that of engineering plastic, usable for a wide range of applications, and having high practicality can be obtained.
[0029]
Bamboo fiber is used as a plant-derived natural fiber. Bamboo grows quickly and is highly productive, and it is relatively easy to obtain because there is sufficient production in Japan, and biodegradability with high mechanical strength. It becomes possible to manufacture the composite material at a low cost.
[0030]
Further, since glyoxal or trimethoxymethylmelamine generally used in the papermaking process is used as the surface treatment agent, it is easy to obtain.
[0031]
In addition, when polybutylene succinate commercially available as a biodegradable plastic is used, it is easy to obtain.
[0032]
Further, by using bamboo fibers having a diameter of 30 to 100 μm and a length of 200 to 800 μm, a molded product having a desired shape can be obtained by applying an injection molding method while ensuring a necessary strength.
[Brief description of the drawings]
FIG. 1 is a diagram showing the results of a tensile test of a molded product according to an embodiment of the present invention.
FIG. 2 is a diagram showing a result of a tensile test of a molded product according to another embodiment.
[Explanation of symbols]
A1, A2 Sample of molded product B1, B2 Sample of molded product in other embodiment A0 Sample of molded product according to prior art

Claims (8)

A blend of plant natural fibers treated with a surface treatment agent that reacts with OH groups to crosslink between OH groups of cellulose and a biodegradable plastic having an ester structure , wherein the surface treatment agent is glyoxal Or a biodegradable composite material characterized by being trimethoxymethylmelamine .   The biodegradable composite material according to claim 1, wherein the blending ratio of the plant natural fiber to the biodegradable plastic is 0.5 to 51 wt%.   The biodegradable composite material according to claim 1 or 2, wherein the plant natural fiber is bamboo fiber. The biodegradable composite material according to any one of claims 1 to 3 , wherein the biodegradable plastic is polybutylene succinate. The biodegradable composite material according to claim 3 or 4 , wherein the bamboo fiber has a diameter of 30 to 100 µm and a length of 200 to 800 µm. The biodegradable composite material according to claim 5, wherein the bamboo fiber is decolorized or colored. The biodegradable composite material according to claim 5, wherein the bamboo fiber is deodorized or flavored. A molded product of biodegradable plastic, characterized in that the biodegradable composite material according to any one of claims 5 to 7 is used and is molded into a desired shape by an injection molding method.

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