JP2004315724A - Composition containing polylactic acid and molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition giving a molded article having excellent mechanical properties while keeping biodegradability, moldable with a short cycle time and generating little toxic gas in incineration. <P>SOLUTION: Fired shell powder is used as a component of the composition containing polylactic acid. The composition containing polylactic acid preferably further contains a flame retardant. The invention further provides a molded article produced by melting, molding and cooling the composition containing polylactic acid. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to a plastic composition having a small impact on the global environment.
[0002]
[Prior art]
At present, with increasing interest in the global environment, biodegradable plastics that are completely degraded and digested by microorganisms in soil have attracted attention.
[0003]
Several patent applications have already been filed for molded articles using such plastics (for example, see Patent Documents 1 to 3). These molded products are particularly used as films and packaging materials, and biodegradable plastics have already been introduced into LSI trays and embossed tapes used for transporting LSIs.
[0004]
In recent years, introduction to electric appliances and computers has been considered. Biodegradable plastic has already been used for some parts of personal computers, and it is expected that it will be applied to more parts including housings in the near future.
[0005]
Among biodegradable plastics, polylactic acid is excellent in transparency, hardness, moldability, biodegradability, and the like, and is expected to be applied in various fields.
[0006]
Although polylactic acid has such excellent properties, there is a problem that elasticity such as flexural modulus is not sufficient for application to OA equipment and the like. Also, due to its biodegradability properties, it has poor durability as compared with commonly used plastics such as ABS.
[0007]
As another problem, polylactic acid is a crystalline resin, and in order to impart sufficient strength to a molded product, for example, cooling molding is performed while maintaining a mold temperature near a crystallization temperature (100 to 110 ° C.). Although it is necessary, since the glass transition temperature of polylactic acid is as low as about 60 ° C., there is a problem that the molded product is soft and deformed at the time of taking out from the mold as it is. In this case, in order to cool to 60 ° C. or less, it is conceivable to maintain the crystallization temperature for a long time, but the molding cycle time becomes long, which is not preferable in view of mass production.
[0008]
In addition, since polylactic acid has poor flame retardancy, it is often necessary to add a flame retardant. However, depending on the type of flame retardant, a toxic gas is generated during combustion.
[0009]
In the above description, the term “plastic” is used. However, more strictly, the term “plastic” includes a case where the plastic is composed of a plurality of plastics and a case where it is a composition with components other than plastic.
[0010]
[Patent Document 1]
JP-A-3-290461 (Claims)
[0011]
[Patent Document 2]
Japanese Patent Application Laid-Open No. 4-16952 (Claims)
[0012]
[Patent Document 3]
JP-A-4-325526 (Claims)
[0013]
[Problems to be solved by the invention]
An object of the present invention is to solve the above-mentioned problems and to provide a composition which has biodegradability and can provide a molded article having excellent mechanical properties. Another object of the present invention is to provide a composition capable of shortening the molding cycle time while maintaining such characteristics. It is another object of the present invention to provide a composition which has flame retardancy and hardly generates toxic gas during combustion. Still other objects and advantages of the present invention will become apparent from the following description.
[0014]
[Means for Solving the Problems]
According to one aspect of the present invention, there is provided a polylactic acid-containing composition containing polylactic acid and baked shell powder.
[0015]
According to still another aspect of the present invention, the above-mentioned polylactic acid-containing composition is melted, shaped, and cooled, and a molded product or polylactic acid is melt-blended with at least a calcined shell powder, and shaped. And a molded product obtained by cooling.
[0016]
According to these aspects, it is possible to achieve the above-mentioned problems in biodegradability, mechanical properties, molding cycle time, and behavior during combustion.
[0017]
In any of the above embodiments, the baked shell powder is scallop shell powder, the amount of the baked shell powder is 1 to 30% by weight of the total composition, and the average particle diameter of the baked shell powder is 0. It is preferred that the thickness be in the range of 0.1 to 100 μm and further contain a flame retardant.
[0018]
The shape of the molded product is preferably a film shape or a three-dimensional shape, and the application is preferably an electric product.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described using examples and the like. It should be noted that these examples and the like and the description illustrate the present invention, and do not limit the scope of the present invention. It goes without saying that other embodiments can also belong to the category of the present invention as long as they conform to the gist of the present invention.
[0020]
By using a polylactic acid-containing composition containing polylactic acid and baked shell powder, it is possible to give a molded article having excellent biodegradability and various properties.
[0021]
When calcined shell powder is used together with polylactic acid as a filler, it has the effect of enhancing the flexural strength of the polylactic acid-containing composition, and thus the molded product, increasing the heat deformation temperature and improving the high-temperature rigidity. This leads to an improvement in the mechanical properties of the molded product, and the molded product can be taken out even at a relatively high temperature, so that the molding cycle can be shortened.
[0022]
The fired shell powder is harmless to the ecosystem and is not degraded by microorganisms, so that it does not cause an environmental burden. Oysters, pearl oysters and the like are also useful as shells of the raw material. Among them, scallop shell powder baked at 1050 ° C. has an antibacterial effect, so that a decrease in durability due to biodegradation of polylactic acid can be suppressed.
[0023]
Furthermore, scallop shell powder has a property of adsorbing various VOCs (harmful volatile substances), and can suppress generation of toxic gas during combustion.
[0024]
In Aomori Prefecture, approximately 50,000 tons of scallop shells are discarded annually due to scallop cultivation in Mutsu Bay, and disposal is a problem. However, since this can be used as a resource, costs can be reduced and waste can be reduced. It also leads to a solution.
[0025]
The amount of the baked shell powder is preferably 1 to 30% by weight based on the total composition of the polylactic acid-containing composition. If the amount is less than this, there is no effect. If the amount is too large, the mechanical strength is reduced and the appearance is problematic.
[0026]
The average particle size (diameter) of the baked shell powder is preferably in the range of 0.1 to 100 μm. If it is smaller than this, it becomes difficult to handle due to aggregation or the like. If it is larger than this, the mechanical strength is rather deteriorated. This average particle size can be measured by a particle size distribution measuring device using light scattering.
[0027]
As a specific method of obtaining such a baked shell powder, for example, scallop shells are collected, baked in a sintering furnace at 1050 ° C. for 3 to 24 hours, cooled, and then crushed, crushed, sieved, etc. A method for obtaining a baked shell powder having a predetermined average particle size can be exemplified. General firing conditions include a firing temperature of 700 to 2500 ° C. and a firing time of 1 to 48 hours.
[0028]
In addition, although the baked shell powder is non-flammable, it is often preferable to add a flame retardant since the polylactic acid-containing composition containing polylactic acid and the baked shell powder is still easily burned.
[0029]
Flame retardants for this purpose include halogen-based, phosphorus-based, silicone-based, and inorganic-based flame retardants, all of which can be used. These flame retardants may generate toxic gas during combustion, but the toxic gas is adsorbed by the burnt shell powder and generation thereof is suppressed.
[0030]
The above-mentioned polylactic acid-containing composition can be melted, shaped, and cooled to form a film or a three-dimensionally shaped product. In the case of a normal molded product, melting, shaping, and cooling are performed in this order, but shaping is not limited to between melting and cooling. This is because, for example, there may be a stretching operation after the film formation.
[0031]
For this melting, for example, a single-shaft, twin-shaft or the like extruder can be used. In this case, it is possible to further blend other components with the polylactic acid-containing composition according to the present invention. In addition, such a blend still belongs to the category of the polylactic acid-containing composition according to the present invention unless it is contrary to the gist of the present invention.
[0032]
The molding by melting, shaping, and cooling may include any molding method without departing from the spirit of the present invention. Typical examples include melt extrusion film formation, extrusion molding, and injection molding.
[0033]
In addition, from the viewpoint of a molded product, the molded product according to the present invention does not pass through the polylactic acid-containing composition according to the present invention, and is prepared by melt-blending polylactic acid together with at least calcined shell powder, shaping, and cooling. It is also possible to obtain.
[0034]
Also in such a case, the baked shell powder is scallop shell powder, the amount of the baked shell powder is 1 to 30% by weight of the total molded product, and the average particle diameter of the baked shell powder is 0. It is preferable that the thickness be in the range of 1 to 100 μm and further contain a flame retardant. In this case, it is also possible to blend other components. Of course, it is also possible to blend a polylactic acid-containing composition.
[0035]
In this case, a molded product can be directly obtained without producing pellets or the like of the polylactic acid-containing composition, which is often advantageous in terms of energy and cost. It is also possible to use a molded product, a defective product at the time of molding, or the like again as a polylactic acid-containing composition.
[0036]
In addition, such a molded product, furthermore, a molded product formed using the polylactic acid-containing composition according to the present invention as a raw material, from the viewpoint of the composition, is still a polylactic acid-containing composition according to the present invention. It goes without saying that it belongs to the category.
[0037]
Other resins can coexist in the polylactic acid-containing composition according to the present invention. In order to ensure the biodegradability of the polylactic acid-containing composition, it is preferable that the other resin is also a biodegradable resin. In the present invention, "biodegradability" when it is referred to as "biodegradable resin" or "biodegradable" can be appropriately determined according to the actual situation. For example, if the JIS standard is equal to or higher than a predetermined level, biodegradability may be determined, or the required level of biodegradability may be reduced by placing importance on mechanical properties.
[0038]
Examples of the biodegradable resin other than the polylactic acid according to the present invention include polycaprolactone, polyhydroxybutyrate, polybutylene succinate, polybutylene adipate / terephthalate copolymer, and resins containing these as components. Since such a biodegradable resin is rich in flexibility, by mixing with a relatively hard and brittle polylactic acid-based resin, it is possible to improve the flexibility of the composition while ensuring biodegradability, and to improve the molded article. Strength and impact resistance can be improved.
[0039]
The amount of addition of these resins is not particularly limited as long as the characteristics are not limited, but as a ratio of the biodegradable resin other than polylactic acid to the total of polylactic acid and the biodegradable resin other than polylactic acid. , Preferably 0 to 70% by weight.
[0040]
In the present invention, a plasticizer such as polyester or polyether may be added and used as needed. If the biodegradability requirement is high, those derived from plants and organisms are recommended.
[0041]
When the strength needs to be improved, a filler such as glass fiber or carbon fiber may be appropriately used. These fillers may be coated with polylactic acid, or may be surface-treated with a silane coupling agent or the like.
[0042]
In addition to the additives described above, other additives can be contained according to the purpose, and such a composition may be preferable in some cases. For example, as a substance capable of suppressing hydrolysis of the polylactic acid-containing composition, a carboxylic acid that is a terminal functional group of a polyester resin, and a compound having reactivity with a hydroxyl group, such as a carbodiimide compound, an isocyanate compound, and an oxazoline-based compound. Can be illustrated. Similarly, a weather resistance improver, an antioxidant, a heat stabilizer, a plasticizer, a crystal nucleating agent, a lubricant, a release agent, a colorant, a compatibilizer, and the like can be blended.
[0043]
The molded product according to the present invention is useful as a housing or a part of an electric appliance such as an OA electric appliance or an electronic product.
[0044]
【Example】
Next, examples and comparative examples of the present invention will be described in detail. In addition, various measurements were performed as follows.
[0045]
(1) Flexural modulus According to the method of JIS K7171.
[0046]
(2) Load deflection temperature Measured under a load of 0.46 MPa according to the method of JIS K7191.
[0047]
(3) Biodegradability test According to the method of JIS K6953.
[0048]
(4) Combustion test According to the method of UL standard.
[0049]
[Example 1]
The following were used as raw materials of the polylactic acid-containing composition. Each raw material was dried in an electric furnace at 100 ° C. for 2 hours.
[0050]
-Polylactic acid Laissia H-100J manufactured by Mitsui Chemicals, Inc. was used.
[0051]
Scallop shell powder Scallop shell powder (magnacaps) obtained from Asada Shokai was used after passing through a sieve having a sieve of 50 μm.
[0052]
-Phosphorus-based flame retardant Exolit AP 750 manufactured by Clariant was used.
[0053]
A mixture of 60% by weight of polylactic acid, 20% by weight of scallop shell powder and 20% by weight of flame retardant was melt-kneaded while maintaining the temperature at 180 ° C. in an injection molding machine, and injection molding was performed.
[0054]
A metal mold for obtaining a plate-like molded product used in the above test was used.
[0055]
The mold was kept at 100 ° C. for 1 minute and cooled. The molded product could be taken out without deformation when opening the mold.
[0056]
[Comparative Example 1]
Example 1 was repeated except that talc 20% by weight was used instead of the scallop shell powder.
[0057]
The mold was held at 100 ° C. for 1 minute and tried to be removed, but the molded product was deformed when the mold was opened. This is because the molded article lacks high-temperature rigidity. However, even if a lower temperature mold is used, the molded product is not sufficiently cured. It is necessary to crystallize by holding at 100 ° C. for 1 minute or more.
[0058]
Then, after holding the mold at 100 ° C. for 1 minute, the mold was cooled to 50 ° C. over 5 minutes by water cooling, held at 50 ° C. for 1 minute, opened, and the molded product was taken out. As a result, a molded product having a normal shape was obtained, but it took 7 minutes to remove the molded product, and it is considered that productivity was deteriorated.
[0059]
Various tests were performed using the molded product of Example 1 and the molded product of Comparative Example 1.
[0060]
As a result, the flexural modulus increased from 3.5 GPa in Comparative Example 1 to 4.8 GPa in Example 1.
[0061]
The deflection temperature under load (0.46 MPa) was 101 ° C. in Example 1 compared to 68 ° C. in Comparative Example 1. This means that the high-temperature rigidity was improved by Example 1.
[0062]
In the biodegradability test, in the aerobic compost at 59 ° C., it took about 8 weeks in Example 1 to reduce the weight loss to 50% by weight, compared to about 2 weeks in Comparative Example 1. It was found that the brakes were moderately applied and the durability increased.
[0063]
As a result of the combustion test, both were UL94V at the V-2 level. However, it was visually confirmed that smoke emission was smaller in Example 1 than in Comparative Example 1. It is considered more secure.
[0064]
[Example 2]
The same experiment as in Example 1 was performed with the baked oyster shell powder, but similarly better results were obtained than in Comparative Example 1. However, although the amount of smoke was smaller than that of Comparative Example 1, it was larger than that of the baked scallop shell powder.
[0065]
From the contents disclosed above, the inventions shown in the following supplementary notes can be derived.
[0066]
(Supplementary Note 1) A polylactic acid-containing composition containing polylactic acid and baked shell powder.
[0067]
(Supplementary Note 2) The composition according to Supplementary Note 1, wherein the baked shell powder is scallop shell powder.
[0068]
(Supplementary Note 3) The polylactic acid-containing composition according to Supplementary Note 1 or 2, wherein the amount of the calcined shell powder is 1 to 30% by weight of the total composition.
[0069]
(Supplementary Note 4) The polylactic acid-containing composition according to any one of Supplementary Notes 1 to 3, wherein an average particle diameter of the baked shell powder is in a range of 0.1 to 100 µm.
[0070]
(Supplementary Note 5) The polylactic acid-containing composition according to any one of Supplementary Notes 1 to 4, further comprising a flame retardant.
[0071]
(Supplementary Note 6) A molded product obtained by melting, shaping, and cooling the polylactic acid-containing composition according to any one of Supplementary Notes 1 to 5.
[0072]
(Supplementary Note 7) A molded product obtained by melt-blending polylactic acid together with at least calcined shell powder, shaping, and cooling.
[0073]
(Supplementary Note 8) The molded product according to supplementary note 7, wherein the baked shell powder is scallop shell powder.
[0074]
(Supplementary Note 9) The molded article according to Supplementary Note 7 or 8, wherein an amount of the calcined shell powder is 1 to 30% by weight of the whole molded article.
[0075]
(Supplementary Note 10) The molded product according to any one of Supplementary Notes 7 to 9, wherein an average particle diameter of the baked shell powder is in a range of 0.1 to 100 µm.
[0076]
(Supplementary Note 11) The molded article according to any one of Supplementary Notes 7 to 10, further comprising a flame retardant.
[0077]
(Supplementary Note 12) The molded product according to Supplementary Notes 6 to 11, which has a film shape or a three-dimensional shape.
[0078]
(Supplementary Note 13) An electric product using the molded product according to Supplementary Notes 6 to 12.
[0079]
【The invention's effect】
According to the present invention, it is possible to provide a composition capable of providing a molded article having excellent mechanical properties while having biodegradability. Further, it is possible to provide a composition capable of shortening the molding cycle time while maintaining such characteristics. Further, it is possible to provide a composition having flame retardancy and hardly generating toxic gas during combustion.

Claims (5)

A polylactic acid-containing composition containing polylactic acid and baked shell powder. The polylactic acid-containing composition according to claim 1, further comprising a flame retardant. A molded product obtained by melting, shaping, and cooling the polylactic acid-containing composition according to claim 1 or 2. A molded product obtained by melt-blending polylactic acid together with at least baked shell powder, shaping, and cooling. The molded article according to claim 4, further comprising a flame retardant.