JP2005029601A - Injection molding material, its manufacturing method and injection molded article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding material which reduces discoloration and is free from a foreign odor due to scorching of vegetable fibers in melt kneading when made into a molded article, and reduces an adverse affect to the environment and the like, its manufacturing method, and an injection molded article. <P>SOLUTION: The injection molding material has an aliphatic polyester as the major component and comprises 70-99.5 mass% thermoplastic plastic which has biodegradability and a melt flow rate (MFR) at 190°C under a load of 2.16 kgf of ≥4.0 (g/10 min) and 0.5-30 mass% vegetable fibers obtained by retting. The method for manufacturing the injection molding material comprises mixing a thermoplastic plastic having biodegradability with vegetable fibers obtained by retting and heat-kneading the resulting mixture at a specific temperature. The injection molded article is obtained by injection molding comprising a step of injecting the injection molding material at a specific temperature. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to an injection molding material containing a biodegradable thermoplastic having an aliphatic polyester as a main component, a method for producing the same, and an injection molded product. In addition, the present invention relates to an injection molding material that has less adverse effects on the environment, a manufacturing method thereof, and an injection molded product obtained by injection molding the injection molding material.
[0002]
[Prior art]
In recent years, resin molding in which molding materials composed of various resin materials alone or in combination are molded into a required shape for members, parts, etc. constituting many industrial products according to required functions, performance, properties, etc. The product is used.
These resin molded products are rarely preserved, and most of them are used when industrial products that incorporate the resin molded products are disposed of and discarded, or the resin molded products themselves perform their functions. After that, it is finally discarded. However, when a conventional resin molded product is discarded, it is difficult to be decomposed in the natural environment, which is one factor that pollutes the environment.
[0003]
Therefore, in recent years, molded articles using materials that are decomposed in a natural environment have been studied. For example, a molded product obtained from a composition obtained by mixing biodegradable polylactic acid with an inorganic fiber reinforcing material such as glass fiber in order to improve the heat resistance and rigidity of the molded product is known. In the composition containing such a biodegradable resin, even if the biodegradable resin is biodegraded, the inorganic fiber reinforcing material and the like mixed with the composition are not decomposed in a natural environment. Therefore, there is still a high possibility that the inorganic fiber reinforcing material will adversely affect the environment and the human body.
As a technique for improving the adverse effects on the environment caused by the inorganic fiber reinforcing material, it comprises 100 parts by mass of a biodegradable thermoplastic resin and 1 to 100 parts by mass of plant cellulose fibers selected from Manila hemp, sisal hemp or New Zealand hemp. A composite material characterized by this has been proposed (see Patent Document 1).
[0004]
Although composite materials containing vegetable fibers such as plant cellulose fibers can reduce the adverse effects on the environment to some extent, some biodegradable thermoplastic resins used have a new problem of coloration and off-flavor generation in melt-kneading.
That is, in order to use plant cellulose fibers or the like as a reinforcing material for biodegradable thermoplastic resins, it is necessary to heat the biodegradable thermoplastic resin to a molten state and knead the plant cellulose fibers or the like. And in order to sufficiently knead the fibers, it must be carried out at a temperature at which the fluidity of the molten resin can be sufficiently secured, and further, when heat resistance that can withstand practical use is required for a molded product made of a biodegradable thermoplastic resin. Usually, a melt kneading temperature of 150 ° C. or higher is required. However, since plant cellulose fibers and the like are mainly composed of cellulose, when the melt kneading temperature exceeds 170 ° C., the progress of coloring due to the “burning” of the plant cellulose fibers and the occurrence of a strange odor is recognized, and when molded products are obtained. Coloring and off-flavor generation were inevitable.
[0005]
[Patent Document 1]
JP 2001-335710 A
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide an injection molding material that is less colored when formed into a molded product due to scorching of vegetable fibers in melt-kneading, has no off-flavor, and has less adverse effects on the environment.
The present invention also relates to a method for producing an injection-molded material, which is less colored when it is formed into a molded product due to scorching of vegetable fibers in melt-kneading, and has less adverse effects on the environment, etc., and this material is injected. An object of the present invention is to provide an injection molded product obtained by molding.
[0007]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found that plant fibers obtained by refining by letting hardly cause scorching due to heat, and in melt kneading of a thermoplastic material (composition) containing the plant fibers. It has been found that coloring of the material and a molded product obtained from the material and generation of a strange odor can be suppressed. Further, heat having a melt mass flow rate (hereinafter, simply referred to as “MFR (190 / 2.16)”) at a temperature of 190 ° C. and a load of 2.16 kgf is 4.0 (g / 10 min) or more. It has been found that when a plastic plastic is used, melt kneading and the like can be performed at a lower temperature, and similarly, coloring of materials and molded products and generation of off-flavors can be suppressed.
The present invention has been made based on the above findings.
[0008]
That is, the present invention has (1) biodegradability, which is mainly composed of aliphatic polyester, and has a melt mass flow rate (MFR) of 4.0 (g / 10 min) or more at a temperature of 190 ° C. and a load of 2.16 kgf. An injection molding material containing 70 to 99.5% by mass of thermoplastic plastic and 0.5 to 30% by mass of vegetable fiber obtained by letting is provided.
In the present invention, MFR (190 / 2.16) is a value when measured according to method A (manual cutting method) or method B (automatic cutting method) of JIS K7210-1999. Note that the shape of the sample is not particularly limited.
[0009]
The MFR (190 / 2.16) of the thermoplastic is preferably 4.5 (g / 10 min) or more, and more preferably 5.0 (g / 10 min) or more.
Further, the thermoplastic is preferably 80 to 95% by mass, more preferably 85 to 90% by mass, and the plant fiber is preferably 5 to 20% by mass, and 10 to 15% by mass. More preferably.
[0010]
In the present invention, the aliphatic polyester includes aliphatic / aromatic polyesters in addition to aliphatic polyesters.
The aliphatic polyester is preferably biodegradable, and at least one of the aliphatic polyesters preferably has a melting point or a flow start temperature of 150 ° C. or higher. The aliphatic polyester is more preferably polylactic acid, and the vegetable fiber is preferably kenaf fiber. Moreover, the number average fiber length of the vegetable fiber is preferably 0.5 to 10 mm, and more preferably 0.7 to 5 mm, from the viewpoint of excellent dispersibility in thermoplastics.
[0011]
In the present invention, the melting point of the aliphatic polyester is a value measured by differential scanning calorimetry (DSC). Specifically, about 20 mg of an aliphatic polyester sample is heated at a temperature rising rate of 10 ° C./min. It is the temperature at the top of the crystal melting endothermic peak when it is allowed to occur. The flow start temperature of the aliphatic polyester is a value measured by a capillary rheometer. Specifically, the temperature is lowered while extruding a sample (aliphatic polyester) dissolved at a shear rate of 60 (1 / sec). The temperature when the pressure sensor installed on the sample inlet side of the die measures 10 MPa.
[0012]
The material of the present invention preferably further contains 30 parts by mass or less of inorganic fine particles with respect to 100 parts by mass in total of the thermoplastic plastic and the vegetable fiber.
[0013]
In addition, the present invention has (2) biodegradability in which the main component is aliphatic polyester, and the melt mass flow rate (MFR) at a temperature of 190 ° C. and a load of 2.16 kgf is 4.0 (g / 10 min) or more. 70 to 99.5% by mass of thermoplastic plastic and 0.5 to 30% by mass of vegetable fiber obtained by letting are mixed and heated and kneaded at a kneading temperature not lower than the flow start temperature of the thermoplastic plastic and not higher than 230 ° C. An injection molding material manufacturing method for obtaining an injection molding material is provided.
Further, in the method for producing an injection molding material, the inorganic fine particles of 30 parts by mass or less with respect to a total of 100 parts by mass of the thermoplastic plastic and the plant fiber in the mixture of the thermoplastic plastic and the plant fiber. May be mixed.
[0014]
Furthermore, the present invention includes (3) an injection molding including a step of adjusting the cylinder temperature to a temperature range of not less than the flow start temperature of the thermoplastic plastic and not more than 230 ° C. and injecting the injection molding material according to the above (1). An injection molded product obtained by the above is provided.
In the above (3), the melt-kneading step may be performed together with the injection step (in the process or continuously before and after the step), or the melt-kneading step may be performed separately from the step. The melt kneading temperature in the melt kneading step is preferably adjusted to the above cylinder temperature (from the flow start temperature of the thermoplastic plastic to 230 ° C. or lower).
The resulting injection-molded product has little coloration caused by plant fiber and no odor.
[0015]
In the present invention, the flow start temperature of the thermoplastic can be measured by the same method and conditions as the measurement of the flow start temperature of the aliphatic polyester.
[0016]
In this specification, for the sake of convenience, the kneading for producing the injection molding material is referred to as “heat kneading”, and the kneading in the injection molding is referred to as “melt kneading”, but there is no particular difference between the two.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described below.
The present invention is based on a thermoplastic plastic having a biodegradability, which is composed mainly of an aliphatic polyester and has a melt mass flow rate (MFR) of 4.0 (g / 10 min) or more at a temperature of 190 ° C. and a load of 2.16 kgf. It is an injection molding material (hereinafter referred to as “material of the present invention”) containing 99.5% by mass and 0.5 to 30% by mass of vegetable fiber obtained by letting.
[0018]
The biodegradable thermoplastic used in the material of the present invention is mainly composed of aliphatic polyester, and has a melt mass flow rate MFR (190 / 2.16) of 4.0 at a temperature of 190 ° C. and a load of 2.16 kgf. (G / 10 min) or more.
When the MFR (190 / 2.16) of the thermoplastic is 4.0 (g / 10 min) or more, kneading with the vegetable fiber described later is performed at a relatively low temperature (for example, higher than the flow start temperature of the thermoplastic). 230 ° C. or lower), and it is possible to effectively suppress the coloring of the molded product and the generation of off-flavors caused by the plant fiber. MFR (190 / 2.16) is preferably 4.5 (g / 10 min) or more, and more preferably 5.0 (g / 10 min) or more, in that it is more excellent in suppressing effect.
The upper limit of the MFR (190 / 2.16) is not particularly limited as long as it can satisfy physical and mechanical characteristics when formed into a molded product.
[0019]
The MFR (190 / 2.16) of the thermoplastic can be adjusted by the MFR (190 / 2.16) of an aliphatic polyester described later or another polymer mixed with the polyester, or a mixing ratio thereof.
In the present invention, MFR (190 / 2.16) is a value when measured according to method A (manual cutting method) or method B (automatic cutting method) of JIS K7210-1999. Note that the shape of the sample is not particularly limited.
[0020]
Thermoplastics are biodegradable. Thereby, the material of the present invention containing the thermoplastic plastic is less likely to adversely affect the environment and the human body even if the molded product is disposed of.
In order to impart biodegradability to the thermoplastic, it is preferable to use a biodegradable aliphatic polyester as the main component.
[0021]
The thermoplastic plastic is composed mainly of an aliphatic polyester described later, and may contain other resin components in addition to the aliphatic polyester. In this case, the aliphatic polyester is preferably contained in an amount of 50% by mass or more, and more preferably 55% by mass or more, based on the total mass of the thermoplastic plastic including the aliphatic polyester. The other resin component is preferably biodegradable.
[0022]
In the present invention, the aliphatic polyester as the main component of the thermoplastic includes aliphatic / aromatic polyester in addition to the aliphatic polyester. The aliphatic polyester is not particularly limited, but preferably has biodegradability. Moreover, it is preferable that at least 1 type of aliphatic polyester is 150 degreeC or more in the melting | fusing point or flow start temperature at the point of the heat resistance of the molded article obtained.
[0023]
In the present invention, the melting point of the aliphatic polyester is a value measured by differential scanning calorimetry (DSC). Specifically, about 20 mg of an aliphatic polyester sample is heated at a heating rate of 10 ° C./min. It is the temperature at the top of the crystal melting endothermic peak. The flow starting temperature of the aliphatic polyester is a value measured by a capillary rheometer, specifically, the temperature is lowered while extruding a sample (aliphatic polyester) dissolved at a shear rate of 60 (1 / sec), This is the temperature when the pressure sensor installed on the sample inlet side of the die measures 10 MPa.
[0024]
Examples of such aliphatic polyesters include polylactic acid, polycaprolactone (PCL), polybutylene succinate (PBS), polyhydroxybutyric acid (polyhydroxybutyrate (PHB)), polyethylene succinate (PES), poly ( Butylene succinate / adipate), poly (butylene succinate / carbonate) and the like.
Examples of the aliphatic / aromatic polyester include poly (butylene succinate / terephthalate), poly (butylene adipate / terephthalate), poly (tetramethylene adipate / terephthalate), and the like.
Among these, polylactic acid and polyhydroxybutyric acid are preferable, and polylactic acid is more preferable in terms of easy availability and excellent biodegradability, and excellent heat resistance.
These polyesters can use 1 type (s) or 2 or more types, Moreover, what is generally marketed can be used without a restriction | limiting in particular.
[0025]
The polylactic acid is preferably a homopolymer of L-lactic acid, a copolymer of L-lactic acid and D-lactic acid, a copolymer of L-lactic acid and hydroxycarboxylic acid, or a mixture thereof.
Examples of the hydroxycarboxylic acid include glycolic acid, 3-hydroxybutyric acid, 4-hydroxyvaleric acid, 6-hydroxycaproic acid and the like.
In general, polylactic acid has optical isomers such as D-form and L-form, but only L-form can be biodegraded. Polylactic acid is industrially produced by subjecting starch, which is a natural product, to lactic acid fermentation to obtain lactic acid and polymerizing it, and an isomerization reaction occurs in this process. Therefore, polylactic acid usually contains a small amount of D-form as an impurity. If the content of D-form is high, that is, the purity of L-form is low, crystallization of polylactic acid may be inhibited and the heat resistance of the molded product may not be sufficient. Therefore, polylactic acid used in the present invention has L-form purity. It is preferably 88% or more, more preferably 95% or more, and particularly preferably 97% or more.
Specific examples of the polylactic acid include those commercially available from Mitsui Chemicals under the trade name LACEEA.
[0026]
The molecular weight or the like of the aliphatic polyester is not particularly limited, and can be arbitrarily selected according to the characteristics required for the molded product. The molecular weight of polylactic acid is not particularly limited, but can be arbitrarily selected depending on the mechanical strength of the molded product, the water content during injection molding, and the like, as will be described later.
[0027]
As other resin components, various commonly used resins are not particularly limited and can be arbitrarily selected according to the use for which the material of the present invention is used, but preferably have biodegradability.
Examples of other resin components include aromatic polyesters having biodegradability such as modified polyethylene terephthalate, modified starch (modified starch), cellulose acetate, chitosan and the like.
These other resin components can be used singly or in combination of two or more, and commercially available ones can be used without particular limitation.
[0028]
The thermoplastic is a mixture of an aliphatic polyester and the other resin component, a dispersion of the other resin component in the aliphatic polyester, or a copolymer of the aliphatic polyester and the other resin component. It may be.
The thermoplastic plastic is preferably a mixture of an aliphatic polyester and the above-mentioned other resin components in terms of excellent productivity.
[0029]
The compounding ratio of the thermoplastic plastic containing aliphatic polyester as a main component is 70 to 99.5% by mass with respect to the total amount of the thermoplastic plastic and vegetable fibers described later. If it is this range, kneading | mixing of a thermoplastic plastic and vegetable fiber can be performed easily, and injection molding can also be performed easily.
The blending ratio is preferably 80 to 95% by mass, and more preferably 85 to 90% by mass in terms of easier kneading and injection molding.
[0030]
The vegetable fiber used for the material of the present invention is not particularly limited as long as it is obtained by letting, and examples thereof include kenaf fiber, bamboo fiber, agave fiber, hemp fiber, or a mixture thereof.
When the vegetable fiber obtained by letting is used, it is possible to suppress coloring of the molded product and generation of a strange odor due to the burning of the vegetable fiber in the heat kneading with the thermoplastic plastic and the melt kneading of the injection molding.
Among plant fiber, kenaf fiber is more preferable because it is easily available and can sufficiently prevent coloring and off-flavour.
[0031]
In general, letting is a method in which plant fibers are immersed in rivers, ponds, etc., and the pectin in the fibers is decomposed by microorganisms in the soil and water to refine the fibers. Can be arbitrarily selected.
[0032]
The number average fiber length of these plant-based fibers is preferably 0.5 to 10 mm, more preferably 0.7 to 5 mm, from the viewpoint of ease of dispersion in the thermoplastic plastics. .
[0033]
A commercial item may be used for the said vegetable fiber, and the number average fiber length may be cut and adjusted by arbitrary methods.
In addition, although the diameter of the said vegetable fiber is not specifically limited, For example, it is preferable that it is 0.2 mm or less, and it is more preferable that it is 0.1 mm or less.
[0034]
The plant fiber can be subjected to a known surface treatment in order to improve the affinity with the thermoplastic. Examples of the surface treatment include physical surface treatment such as plasma discharge treatment and corona discharge treatment, chemical surface treatment using an alkali hydroxide, a coupling agent, and the like. These processes may be performed alone or in any combination.
[0035]
The blending ratio of the vegetable fiber is 0.5 to 30% by mass with respect to the total amount of the thermoplastic and the vegetable fiber. If it is this range, the intensity | strength of the molded article obtained from the material of this invention can be strengthened, and generation | occurrence | production of coloring and a bad smell can be suppressed. The blending amount is preferably 5 to 20% by mass, and more preferably 10 to 15% by mass in terms of excellent effects due to these effects.
[0036]
It is preferable that the material of the present invention further contains inorganic fine particles because the strength of the molded product can be increased.
The inorganic fine particles are not particularly limited, but are preferably natural products or degradable inorganic fine particles in consideration of adverse effects on the environment and the human body. Examples of such inorganic fine particles include talc, kaolin, wollastonite, or a mixture thereof.
[0037]
The average particle diameter of these inorganic fine particles is preferably from 0.01 to 10 μm, more preferably from 0.1 to 5 μm, from the viewpoint of ease of dispersion in the biodegradable resin.
The average particle diameter of the inorganic fine particles is measured by a Coulter counter method.
[0038]
As the inorganic fine particles, commercially available products may be used, and the average particle size may be adjusted by pulverization with a pulverizer such as a ball mill.
[0039]
The shape of the inorganic fine particles is preferably fine particles, but is not particularly limited as long as the effects of the present invention are exhibited.
[0040]
The blending amount of the inorganic fine particles is preferably 30 parts by mass or less with respect to 100 parts by mass in total of the thermoplastic and the vegetable fiber. If it is this range, the intensity | strength of the molded article obtained from the material of this invention can be strengthened with a vegetable fiber. The compounding amount is more preferably 0.5 to 20 parts by mass, and more preferably 5 to 15 parts by mass, in that the strength can be further increased.
[0041]
The combination of the plant fiber and the inorganic fine particles in the material of the present invention is not particularly limited, and can be arbitrarily selected (combined).
[0042]
The material of the present invention contains the thermoplastic plastic and the vegetable fiber, preferably the inorganic fine particles. Besides these, a light-shielding filler such as carbon black, and slidability such as silicon oil. Improving agents, coloring agents such as pigments, antibacterial agents, antifungal agents, foaming agents, UV absorbers, flame retardants, antistatic agents, plasticizers, mold release agents (lubricants), reinforcing fibers, crystal nucleating agents and vegetable fiber Various additives such as an antioxidant and a radical trapping agent that prevent deterioration of the resin can be blended as necessary.
The amount of these additives and the like is not particularly limited.
[0043]
As described above, the material of the present invention is an injection-molding material that is less colored when it is formed into a molded product due to the burning of plant fibers in melt-kneading, has no off-flavor, and has less adverse effects on the environment. In addition, it can satisfy all of the problems in disposal processing, which are particularly required in recent years, the excellent appearance of molded products, and the suppression of off-flavors in molded products, and has great industrial utility value.
[0044]
The material of the present invention is, for example, mixed (kneaded) the above-mentioned components and, if necessary, additives and the like at room temperature or under heating using a twin-screw kneader, single-screw kneader, Banbury mixer, kneader, or the like. Can be manufactured. The mixing method and conditions at this time are not particularly limited. As a method for producing the material of the present invention, there is a method in which the thermoplastic plastic, the vegetable fiber and, if desired, inorganic fine particles are mixed and heated and kneaded at a kneading temperature not lower than the flow start temperature of the thermoplastic plastic and not higher than 230 ° C. It is preferable in that the obtained material has high uniformity and can suppress coloring and off-flavor of the molded product. In this case, the blending ratio and blending amount of each component are in the above-described range.
[0045]
When the heating and kneading temperature is higher than the flow start temperature of the thermoplastic, heating and kneading can be performed easily. When the heating and kneading temperature is 230 ° C. or less, coloring of the molded product due to deterioration of the plant fiber (burning), etc. Generation can be effectively suppressed. It is preferable that the melting point of the thermoplastic is higher than the melting point of the thermoplastic because it can be easily kneaded with heat, and the heating and kneading temperature is more effective in suppressing the coloring of the molded product with the vegetable fiber and the generation of a strange odor. Is preferably 220 ° C. or lower, and more preferably 210 ° C. or lower.
Here, the flow start temperature and melting point of the thermoplastic plastic can be measured by the same method and conditions as the measurement of the flow start temperature and melting point of the aliphatic polyester.
[0046]
As described above, the material of the present invention may be kneaded in advance, or may be kneaded by the above method at the time of injection molding using a kneading function (screw) of an injection molding machine.
[0047]
The material of the present invention may be in any form as long as it contains the above components. For example, each of the above components may be heat-kneaded and then formed into a strand shape, a pellet shape, or the like. Alternatively, each of the above components may be in a state of being heat-kneaded. B) it may be simply mixed.
[0048]
The present invention also provides an injection molded product obtained by injection molding of the material of the present invention. The material of the present invention is suitably used particularly as a molding method in the case of injection molding.
That is, an injection-molded article obtained by injection molding (process) including a step of injecting the material of the present invention by adjusting the cylinder temperature to a temperature range of not less than the flow start temperature of the thermoplastic plastic and not more than 230 ° C. is provided. The resulting injection-molded product has little coloration due to vegetable fibers, has an excellent appearance, and the generation of off-flavors is sufficiently suppressed.
[0049]
The injection molding is not particularly limited, except that one of the features is that the cylinder temperature in the injection process (injection process) is adjusted to a temperature not lower than the flow start temperature of the thermoplastic resin and not higher than 230 ° C. It is possible to select an injection molding method including a melting / metering process, a pressurized flow / molding process, an injection process, a solidification process, and a removal process.
Methods, conditions, etc. other than the cylinder temperature in the injection step are not particularly limited, and methods, conditions, etc. that are normally performed can be arbitrarily selected.
Along with the step of injecting (continuously before or after the step), a melt-kneading step of kneading the material of the present invention may be performed, or a melt-kneading step may be performed separately from the step. The melt kneading temperature in the melt kneading step is preferably adjusted to the above cylinder temperature (from the flow start temperature of the thermoplastic plastic to 230 ° C. or lower).
In the injection molding, the preferred ranges of the melt kneading temperature and the cylinder temperature, such as the method of melt kneading the material of the present invention (melt kneading step), are the same as those of the heat kneading described in the method for producing the material of the present invention.
Thereby, an injection molded product obtained from the material of the present invention can be manufactured.
[0050]
In order to improve the heat resistance of the molded product thus obtained, the injection molding may be followed by an annealing treatment or the like, and further a coating or plating treatment may be performed.
[0051]
In addition, in the case of using polylactic acid as the aliphatic polyester in the injection molding, it is preferable to adjust the molecular weight thereof as follows according to the mechanical strength required for the molded product, the moisture content at the time of injection molding, and the like. .
In general, a crystalline polymer has the property of being easily crystallized as its molecular weight is small, but the mechanical strength is also reduced with crystallization. When polylactic acid having a weight average molecular weight of less than 50000 is used, the resulting resin molded product has low mechanical strength and cannot be applied to applications requiring a certain level of strength. Moreover, when polylactic acid comes into contact with moisture in a molten state, it easily hydrolyzes and tends to cause a decrease in molecular weight. Therefore, if the moisture content of the material of the present invention or polylactic acid is sufficiently dried to about 50 ppm or less and then supplied to the molding machine, there is little decrease in molecular weight, but in order to obtain a dryness with a moisture content of about 50 ppm. Large-scale drying equipment is required, and management of the dried molding material becomes complicated.
Therefore, in the present invention, it is preferable to adjust the water content of the material of the present invention or polylactic acid to a specific range corresponding to the weight average molecular weight and L-form purity of the polylactic acid used. Thereby, a resin molded product can be obtained without performing any annealing treatment. By adjusting the moisture content of the molding material with a general-purpose vacuum dryer or the like, a decrease in molecular weight in the molding process can be suppressed to some extent.
A resin molded product obtained by injection molding using a polylactic acid having a weight average molecular weight of 50000 or more and less than 120,000 and adjusting the water content of the material of the present invention immediately before molding to less than 200 ppm is easily crystallized by annealing treatment. In addition, a material having a practically sufficient mechanical strength can be obtained. When the material of the present invention containing polylactic acid having a weight average molecular weight of 50,000 or more and less than 120,000 and having a moisture content of 200 ppm or more is directly heat-molded, it is hydrolyzed in the molding step and the molecular weight is lowered. For this reason, the intensity | strength of the obtained molded article becomes low and cannot apply to the use which requires a certain amount of intensity | strength.
[0052]
In addition, when polylactic acid having a large weight average molecular weight is used, the moisture content of the material of the present invention is adjusted to 1500 ppm or less that can be easily reached by a general-purpose hot air dryer or a shelf-type vacuum dryer. Thus, a desired resin molded product can be obtained by expecting a certain degree of molecular weight reduction, or by blending a crystal nucleating agent and adjusting the water content to heat molding. For example, using the material of the present invention in which a crystal nucleating agent is blended with polylactic acid having a weight average molecular weight of 120,000 or more and less than 200,000, the water content of the material of the present invention immediately before molding is 200 to 1500 ppm, or if necessary, the water content is less than 200 ppm The desired resin molded product can be obtained by adjusting to injection molding. When molding a molding material containing polylactic acid having a weight average molecular weight of 50,000 or more and less than 120,000 and an L-form purity of 88% or more, a reinforcing fiber and a crystal nucleating agent, it is preferable to adjust the moisture content to less than 200 ppm. Moreover, when injection molding the material of the present invention containing polylactic acid having a weight average molecular weight of 120,000 or more and less than 200,000 and L-form purity of 88% or more, a reinforcing fiber and a crystal nucleating agent, it is preferable to adjust the water content to 200 to 1500 ppm. . Furthermore, when molding the material of the present invention containing polylactic acid having a weight average molecular weight of 120,000 or more and less than 200,000 and L-body purity of 95% or more and reinforcing fibers, the moisture content is adjusted to 200 to 1500 ppm, and then injection molding is performed. It is preferable to crystallize by annealing treatment. As a result, crystallization of the obtained resin molded product easily proceeds and crystallization having sufficient mechanical strength is obtained. If the moisture content of the molding material exceeds 1500 ppm, polylactic acid is severely hydrolyzed in the molding process, the polylactic acid has a lower molecular weight than the expected molecular weight, and the physical properties of the resulting resin molded product are reduced. There is a possibility that a resin molded product having heat resistance, mechanical strength and the like cannot be obtained.
[0053]
The material of the present invention is suitably used as an injection molding material that is molded into the following molded product by injection molding.
The use of the molded article is not particularly limited, but is a structural member constituting a functional material, or a container, lid, and accompanying accessory used for storage, packaging, coating, protection, transportation, storage, form support, etc. It is preferably used as a part or a molded product that is molded in order to exhibit the function by loading the functional material.
Examples of the functional material include various recording materials.
Specific examples of the recording material include photographic photosensitive materials such as negative film, reversal film, photographic paper, monosheet or peel-apart instant photographic film; audio cassette tape, video cassette tape, floppy (registered trademark) ) Magnetic recording materials such as disks and magnetic tapes for computer data recording; optical recording materials such as CD, CD-R, CD-RW, DVD, DVD-R, DVD-RW, MD, and the like.
[0054]
The resin member for recording material used for various recording materials such as the above-mentioned photographic photosensitive material, magnetic recording material, and optical recording material is for storing, packaging, covering, protecting, conveying, storing, supporting the form, etc. The container used, the lid | cover, and its accompanying accessories, or the various members which load the said recording material and exhibit a function.
More specifically, as photographic photosensitive materials, for example, negative, reversal film containers, main bodies, lids or spools of various standards such as 135, 110, 120, 220, etc., or instant film film pack cases, etc. Various members such as a container body, a light shielding sheet, an elastic plate, a flexible light shielding sheet, a light shielding piece, a bottom light shielding sheet, a lens-equipped casing, and a mechanical part. . Examples of the magnetic recording material include an audio cassette tape, a video cassette tape, a computer data recording magnetic tape, a cassette housing for storing a floppy (registered trademark) disk and the like, and its constituent parts and a case for storing them. It is done. Further, examples of the optical recording material include a case for storing an MD cassette, CD, CD-R, CD-RW, DVD, DVD-R, DVD-RW, MD, and the like.
[0055]
【Example】
Hereinafter, the present invention will be described with specific examples, but the present invention is not limited to these specific examples.
[0056]
1. Material preparation and molding
<Example 1>
A letting kenaf obtained by refining a kenaf in accordance with a conventional method and cutting it to have a number average fiber length of 5 mm, and polylactic acid (Mitsui) with a melting point of 163 ° C. and an MFR (190 / 2.16) of 6.5 The pellets of LACEEA manufactured by Chemical Co., Ltd. were dried for 6 hours (90 ° C., 600 Pa) with a vacuum dryer.
85 parts by mass of the pellets and 15 parts by mass of the letting kenaf were mixed and heated and kneaded at 210 ° C. using a biaxial kneader, extruded into a strand, cooled with water, and pelletized to obtain the material of the present invention.
[0057]
<MFR measurement>
The MFR was measured using a MELT INDEXER (manufactured by Toyo Seiki) according to JIS K7210-1999 method B (automatic cutting method).
<Melting point measurement>
The melting point was measured by differential scanning calorimetry (DSC) by raising the temperature of polylactic acid 20 mg at a heating rate of 10 ° C./min, and the temperature at the top of the obtained crystal melting endothermic peak was taken as the melting point. .
[0058]
This pellet (material) was further dried with a vacuum dryer for 6 hours (90 ° C., 600 Pa), then supplied to an injection molding machine, melt-kneaded with the cylinder temperature set at 210 ° C., and then set at 30 ° C. A test piece (length 100 mm, width 12 mm, thickness 2 mm) was molded into a mold.
This injection molding was performed 10 times to obtain 10 test pieces.
[0059]
<Example 2>
As inorganic fine particles, 10 parts by mass of talc (talc MS, average particle diameter 0.2 μm, manufactured by Nippon Talc Co., Ltd.) is used with respect to 100 parts by mass of polylactic acid pellets and letting kenaf. Similarly, the material of the present invention was obtained by mixing and heating and kneading at 210 ° C. Thereafter, injection molding was carried out in the same manner as in Example 1 to obtain 10 specimens.
[0060]
<Comparative Example 1>
The kenaf was chemically treated and refined according to a conventional method to obtain a chemically treated kenaf cut to have a number average fiber length of 5 mm. Specifically, the fiber was refined by digesting with sodium hydroxide.
Ten test pieces were obtained in the same manner as in Example 1 using the chemically treated kenaf.
[0061]
<Comparative example 2>
A polylactic acid having an MFR (190 / 2.16) of 2.0 measured in the same manner as in Example 1 was used.
Except that the heat kneading temperature, melt kneading temperature and cylinder temperature were adjusted to 240 ° C., injection molding was carried out in the same manner as in Example 1 to obtain 10 test pieces.
Since the polylactic acid has a small MFR (190 / 2.16) and low fluidity, it cannot be heated and kneaded unless the heating and kneading temperature is increased to 240 ° C.
[0062]
<Comparative Example 3>
Ten specimens were obtained in the same manner as in Example 1 using sisal hemp not subjected to the surface treatment described in Example 1 of Patent Document 1.
[0063]
2. Evaluation of molded products
<Appearance of molded product>
All the external appearances (coloring degrees) of the 10 samples of each molded product obtained above were visually evaluated.
As a result, the molded product obtained in Example 1 had a light brownish appearance (light brown) in all samples and had a sufficiently practical appearance. The molded product obtained in Example 2 had a milk coffee-like clean appearance due to the white color of talc in all samples.
The molded articles obtained in Comparative Examples 1 to 3 were dark brown and clearly inferior in appearance in all samples.
[0064]
<Odor of molded product>
Occurrence of off-flavors was confirmed for all 10 samples of each molded product obtained above.
The molded products obtained in Examples 1 and 2 could not be confirmed in all samples, but the molded products obtained in Comparative Examples 1 to 3 were burned with plant fiber in all samples. I felt a nasty smell.
[0065]
【The invention's effect】
As explained in detail, according to the present invention, the injection molding is less colored when formed into a molded product due to scorching of vegetable fibers in melt-kneading (heat-kneading), and has no off-flavor and has no adverse effect on the environment. Can provide material.

Claims (7)

70-99.5 mass of a thermoplastic resin having biodegradability, which is mainly composed of aliphatic polyester, and has a melt mass flow rate (MFR) of 4.0 (g / 10 min) or more at a temperature of 190 ° C. and a load of 2.16 kgf. %When,
An injection molding material containing 0.5 to 30% by mass of vegetable fiber obtained by letting. The injection molding material according to claim 1, wherein the aliphatic polyester is polylactic acid. The injection molding material according to claim 1 or 2, wherein the plant fiber is a kenaf fiber. The injection molding material according to any one of claims 1 to 3, wherein the vegetable fiber has a number average fiber length of 0.5 to 10 mm. Furthermore, the injection molding material in any one of Claims 1-4 which contain an inorganic fine particle 30 mass parts or less with respect to a total of 100 mass parts of the said thermoplastic plastic and the said vegetable fiber. 70-99.5 mass of thermoplastic plastics having biodegradability with aliphatic polyester as the main component and melt mass flow rate (MFR) at a temperature of 190 ° C. and a load of 2.16 kgf of 4.0 (g / 10 min) or more. % And vegetable fiber 0.5-30% by mass obtained by letting are mixed and heated and kneaded at a kneading temperature not lower than 230 ° C. of the thermoplastic plastic to obtain an injection molding material. Manufacturing method. An injection molding obtained by injection molding including a step of injecting an injection molding material according to any one of claims 1 to 5 by adjusting a cylinder temperature to a temperature range of not less than a flow start temperature of the thermoplastic plastic and not more than 230 ° C. Goods.