JP5062991B2 - Resin composition - Google Patents

Description

  The present invention relates to a polylactic acid resin composition excellent in heat resistance and impact resistance.

  Generally, as a raw material for molding, polypropylene (PP), acrylonitrile-butadiene-styrene resin (ABS), polyamide (PA6, PA66), polyester (PET, PBT), polycarbonate (PC) and other resins (hereinafter, General purpose resin) is used. However, molded articles produced from such resins are excellent in moldability and mechanical strength, but become discarded by disposal and are hardly decomposed in the natural environment. It remains in.

  On the other hand, in recent years, biodegradable polyester resins such as polylactic acid have attracted attention from the viewpoint of environmental conservation. Among the biodegradable resins, polylactic acid, polyethylene succinate, polybutylene succinate and the like are inexpensive and are highly useful because they can be mass-produced. Furthermore, polylactic acid can be produced using plants such as corn and sweet potato as raw materials.

  However, polylactic acid has usefulness such as transparency, but compared to general-purpose resins, it has a low practical heat resistance as it is, and its impact resistance is low due to its high rigidity. .

  Numerous methods have been proposed for improving these, such as the use of various additives, crosslinking by radiation, etc., alloying with other resins, and blending of reinforcing fibers. However, these do not only cost the chemicals used, but also complicate the manufacturing process. Also, the use of petroleum-derived substances is not preferable from the viewpoint of environmental protection, which is one of the original purposes of using polylactic acid resin. .

On the other hand, many methods of blending naturally derived plant fibers with polylactic acid have been proposed. For example, Patent Document 1 describes an example in which waste paper powder or the like is blended, but the heat distortion temperature is less than 140 ° C. (0.45 MPa load), and the effect is not sufficient. Further, in this document, 15% or more of other resins or impact resistance improvers are blended in order to improve the impact resistance at a low level, which is not preferable from the viewpoint of environmental conservation.
Japanese Patent Laid-Open No. 2005-23260

  The present invention is intended to solve the above-mentioned problems and to provide a polylactic acid resin composition excellent in heat resistance and impact resistance.

  As a result of intensive studies to solve the above problems, the present inventor has found that a polylactic acid resin composition containing powdered cellulose and plant fibers in a polylactic acid resin solves the above problems. The invention has been reached.

That is, the gist of the present invention is as follows.
(1) A polylactic acid resin composition comprising a polylactic acid resin (A), dried sugar squeezed pulp (B), and powdered cellulose (C).
(2) The content of the dried sugar radish pomace (B) is 20 to 40 parts by mass with respect to a total of 100 parts by mass of the polylactic acid resin (A) and the dried sugar radish pomace (B), and the powder Content of cellulose (C) is 5-15 mass parts, The polylactic acid resin composition as described in (1) characterized by the above-mentioned.
(3) The sugar radish pomace dry pulp (B) is melt-kneaded with a polylactic acid resin in a state where the fiber bundle average minor axis is 1.0 mm or less (1) to (2) The polylactic acid resin composition according to any one of the above.
(4) The polylactic acid resin composition according to any one of (1) to (3), wherein the average particle size of the powdered cellulose (C) is 20 μm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the resin composition excellent in heat resistance and impact resistance can be provided. By using this resin composition for various molded products that require heat resistance and impact resistance, the range of use of polylactic acid resin, which is a low environmental load material, can be greatly expanded, and the industrial utility value is extremely high.

Hereinafter, the present invention will be described in detail.
The resin composition of the present invention comprises a polylactic acid resin (A), sugar radish pomace dried pulp (B), and powdered cellulose (C).

  As the polylactic acid resin (A), poly (L-lactic acid), poly (D-lactic acid), and a mixture or copolymer thereof can be used in terms of heat resistance and moldability. In consideration of degradability, it is preferable to use poly (L-lactic acid) as a main component.

In the present invention, any plant-derived fiber can be used as the sugar radish pomace dry pulp (B), and the production raw material and production process are not particularly limited. In particular, a large heat resistance improvement effect can be obtained by using a material containing dried pulp that has been extracted after extracting sugar from sugar beets.

It is preferable that the addition amount of sugar radish pomace dry pulp (B) is 20-40 mass parts with respect to 100 mass parts combining polylactic acid resin (A) and sugar radish pomace dry pulp (B). . If the amount is less than 20 parts by mass, a sufficient effect on heat resistance may not be obtained. Conversely, if the amount is more than 40 parts by mass, impact resistance may be reduced, and pelletization after melt-kneading may occur. May be difficult.

The sugar radish pomace dry pulp (B) preferably has a fiber bundle average minor axis of 1.0 mm or less at the time of melt kneading with the polylactic acid resin (A), and preferably 0.5 mm or less. More preferred. If a longer diameter than this is used, a sufficient effect may not be obtained with respect to heat resistance.

  In the present invention, as the powdered cellulose (C), various materials such as purified wood cellulose powder, kenaf fiber powder, and cotton linter can be used, and there are no limitations on the starting material.

  The average particle size of the powdered cellulose (C) is 20 μm or less, preferably 15 μm or less. If powdered cellulose having a larger particle diameter than this is used, there may be cases where sufficient effects cannot be obtained for improving impact resistance and heat resistance.

It is preferable that the addition amount of powdered cellulose (C) is 5-15 mass parts with respect to 100 mass parts which match | combined the dry pulp (B) which squeezed sugar radish (A) and sugar radish . If the amount is less than 5 parts by mass or exceeds 15 parts by mass, sufficient effects may not be obtained for improving the impact resistance.

The means for mixing the polylactic acid resin (A), the sugar radish pomace dry pulp (B), and the powdered cellulose (C) is not particularly limited, and examples thereof include a melt kneading method using a general extruder. . In order to improve the kneading state, it is preferable to use a twin screw extruder. The kneading temperature is preferably in the range of (melting point of polylactic acid resin + 5 ° C.) to (melting point of polylactic acid resin + 100 ° C.), and the kneading time is preferably from 20 seconds to 30 minutes. When the temperature is lower than this range or for a short time, kneading or reaction becomes insufficient, and conversely, when the temperature is high or for a long time, the resin may be decomposed or colored. In blending, a dry blend, or a method of supplying powdered cellulose or dried pulp squeezed with sugar radish using a powder feeder is preferred.

As long as the properties of the resin composition of the present invention are not greatly impaired, pigments, heat stabilizers, antioxidants, weathering agents, flame retardants, plasticizers, lubricants, mold release agents, antistatic agents, fillers, crystals A nuclear material etc. can be added.
Examples of heat stabilizers and antioxidants include hindered phenols, phosphorus compounds, hindered amines, sulfur compounds, copper compounds, and alkali metal halides.
As the flame retardant, a halogen-based flame retardant, a phosphorus-based flame retardant, and an inorganic flame retardant can be used. However, in consideration of the environment, it is desirable to use a non-halogen flame retardant. Non-halogen flame retardants include phosphorus flame retardants, hydrates of metal compounds (aluminum hydroxide and magnesium hydroxide), N-containing compounds (melamine and guanidine), inorganic compounds (borate and molybdenum compounds). Is mentioned.
Inorganic fillers include talc, calcium carbonate, zinc carbonate, wollastonite, silica, alumina, magnesia, calcium silicate, sodium aluminate, calcium aluminate, sodium aluminosilicate, magnesium silicate, glass balloon, carbon black, oxidized Zinc, antimony trioxide, zeolite, hydrotalcite, metal fiber, metal whisker, ceramic whisker, potassium titanate, boron nitride, graphite, carbon fiber and the like can be mentioned.
Examples of the inorganic crystal core material include talc and kaolin. Examples of the organic crystal core material include a sorbitol compound, benzoic acid and a metal salt of the compound, a phosphate metal salt, and a rosin compound.
In addition, the method of mixing these with the resin composition of this invention is not specifically limited.

  In molding the resin composition of the present invention, it is preferable to adopt an injection molding method. In addition to a general injection molding method, gas injection molding, injection press molding, or the like can also be employed. As an example of injection molding conditions suitable for the resin composition of the present invention, the cylinder temperature is equal to or higher than the melting point or flow start temperature of the resin composition, preferably 180 to 280 ° C, optimally in the range of 200 to 270 ° C, Further, it is appropriate that the mold temperature is not higher than (melting point-20 ° C.) of the resin composition. If the molding temperature is too low, the operability becomes unstable, such as short-circuiting in the molded product, and overload tends to occur. Conversely, if the molding temperature is too high, the resin composition will decompose and the resulting molded product Problems such as a decrease in strength and coloring are likely to occur, both of which are not preferred.

  The heat resistance of the resin composition of the present invention can be enhanced by promoting crystallization. As a method for this purpose, for example, there is a method of promoting crystallization by cooling in a mold at the time of injection molding. In that case, the mold temperature is not less than (glass transition temperature + 20 ° C.) of the resin composition. , (Melting point −20 ° C.) or lower, and after maintaining for a predetermined time, it is preferable to cool to the glass transition temperature or lower. Further, as a method for promoting crystallization after molding, it is preferable that the glass is directly cooled to the glass transition temperature or lower and then heat-treated again at the glass transition temperature or higher and (melting point−20 ° C.) or lower.

  Specific examples of the molded body using the resin composition of the present invention include mobile phone strap parts, fan bones, buttons, golf tees, personal computer housing parts and housings, mobile phone housing parts and housings. In addition, resin parts for electrical appliances such as OA equipment casing parts, bumper, instrument panel, console box, garnish, door trim, ceiling, floor, engine resin parts for automobiles and the like. Moreover, it can also be set as a film, a sheet | seat, a hollow molded product, etc.

Hereinafter, the present invention will be described more specifically with reference to examples. The measuring method used for evaluation of the resin composition of an Example and a comparative example is as follows.
Thermal deformation temperature:
Based on ISO 75, the heat distortion temperature was measured with a load of 0.45 MPa. The heat distortion temperature preferably exceeds 140 ° C.
Charpy impact value:
Measured according to ISO 179. The Charpy impact value preferably exceeds 2.0 kJ / m ² .

Moreover, the various raw materials used for the Example and the comparative example are as follows.
Polylactic acid resin (A): 6201D manufactured by Cargill Dow
Sugar radish pomace dry pulp (B):
(B1) Hokkaido dairy industry sugar radish pomace dry pulp (fiber bundle average minor axis 1.0 mm)
(B2) The dried pulp pulverized (fiber bundle average minor axis 0.3 mm)
Powdered cellulose (C):
(C1) Nippon Paper Chemicals W-50GK (average particle size 45 μm)
(C2) W-10MG2 manufactured by the same company (average particle size 10 μm)

Example 1
Extruded in a state where 85 parts by mass of polylactic acid resin, 15 parts by mass of dried pulp (B1), and 10 parts by mass of powdered cellulose (C2) were sufficiently mixed using a twin screw extruder (TEM 37BS manufactured by Toshiba Machine Co., Ltd.) Extrusion was carried out while exhausting by a vacuum pump through a vent under the conditions of a barrel temperature of 200 ° C., a screw rotation speed of 130 rpm, and a discharge of 15 kg / h. The discharged resin was cut into pellets to obtain resin composition pellets.
After the pellets were dried with hot air at 80 ° C. for 24 hours, test pieces for measuring general physical properties (ISO type) were prepared using an IS-80G injection molding machine manufactured by Toshiba Machine Co., Ltd. and subjected to various measurements. The molding conditions were a cylinder temperature of 170 to 190 ° C. and a mold surface temperature of 100 ° C.

Examples 2-8 and Comparative Examples 1-2
Resin composition pellets were obtained in the same manner as in Example 1 except that the amount and type of polylactic acid resin (A), sugar radish pomace dry pulp (B), and powdered cellulose (C) were changed, and this was injection molded. Various physical properties were measured.

  Table 1 summarizes the evaluation results of Examples 1-8 and Comparative Examples 1-2.

  As is clear from Table 1, in Examples 1 to 8, it was found that a resin composition excellent in heat resistance and impact resistance was obtained. In Comparative Example 1, since powdered cellulose was not used, the impact resistance was inferior. Moreover, in the comparative example 2, since plant fibers other than powdered cellulose were not used, it resulted in inferior heat resistance.

Furthermore, in Examples 2, 3, 5, and 6, since the blending amount of sugar radish pomace dry pulp is 20 to 40 parts by mass, compared to Examples 1 and 4, in heat resistance or impact resistance More favorable results were obtained. In addition, in Examples 2, 3, 5, and 6, since the blending amount of powdered cellulose is 5 to 15 parts by mass, a more favorable result in impact resistance is obtained compared to Examples 7 and 8. It was. Furthermore, in Example 6, since a cellulose powder having an average particle size of 15 μm or less was used, more favorable results in impact resistance and heat resistance were obtained as compared with Examples 2 and 3. Moreover, in Example 5, since it used after grind | pulverizing the sugar radish pomace dried pulp and making the fiber bundle average short axis less than 0.5 mm, compared with Example 2, 3, 6, in heat resistance More favorable results were obtained.

Claims (4)

A polylactic acid resin composition comprising a polylactic acid resin (A), sugar radish pomace dried pulp (B), and powdered cellulose (C). The content of the dried sugar radish (B) is 20 to 40 parts by mass with respect to the total of 100 parts by mass of the polylactic acid resin (A) and the dried sugar radish (B). The polylactic acid resin composition according to claim 1, wherein the content is 5 to 15 parts by mass. Sugar beet pomace dried pulp (B) is according to any one of claims 1 to 2, characterized in that the fiber bundle average minor diameter is polylactic acid resin and melt kneading the following conditions 1.0mm Polylactic acid resin composition. The polylactic acid resin composition according to any one of claims 1 to 3 , wherein the average particle size of the powdered cellulose (C) is 20 µm or less.