Okara powder for resin kneading and okara-containing resin

Abstract

To provide okara powder for resin kneading and an okara-containing resin, which can be stably kneaded and compounded with a resin, suppress deterioration of a resin molding property and generation of unpleasant odors during molding, and be suitably used for an okara resin product in various fields such as an injection molded product, press molded product, sheet molded product, extrusion molded product, and blow molded product.SOLUTION: A technology improves a kneading and compounding suitability by classifying an okara particle contained in an okara powder for resin kneading so that a cumulative 90% particle diameter D90 is 90 μm or less, thereby preventing a decrease in resin molding property due to addition of okara. Furthermore, the okara particles are uniformly dispersed throughout an okara-containing resin kneaded with the okara powder for resin kneading, resulting in a product with an aesthetically pleasing appearance. The resin can be suitably used in a wide range of products, including an injection-molded product, press-molded product, sheet-molded product, extrusion-molded product, blow-molded product, and inflation-molded product.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a soybean pulp powder for kneading with resin, which is to be kneaded with resin and used. More specifically, the present invention relates to a soybean pulp powder for kneading with resin, which can be stably kneaded and compounded with resin, which can suppress a decrease in the moldability of resin due to the addition of soybean pulp, and which can improve the unpleasant odor generated during the molding of soybean pulp into resin. [Background technology]

[0002] In recent years, as fossil fuel resource depletion and global environmental problems have become serious, the use of biomass has been promoted worldwide with the aim of preventing global warming by reducing waste and carbon dioxide, and creating a recycling-oriented society. Japan's "Plastic Resource Recycling Strategy" sets out a roadmap to introduce approximately 2 million tons of biomass plastics by 2030, in order to reduce the energy and CO2 emissions associated with plastic incineration through the widespread use of biomass plastics.

[0003] Currently, the soy pulp produced during the tofu manufacturing process is recycled in part for use as food, animal feed, fish feed, and fertilizer, but much of it is disposed of as waste. In recent years, research has been progressing on composite materials made from soy pulp and resin in order to make effective use of soy pulp as biomass.

[0004] For example, Patent Document 1 proposes a method for imparting functionality such as antibacterial properties or improved strength by mixing a thermosetting or thermoplastic resin with edible biomass such as soybean pulp, bran, coffee bean pulp, soybean pulp, soy sauce dregs, or beer pulp while heating at around 150°C, and then molding the mixture using any molding method. However, because the true specific gravities of the edible biomass and the resin differ, the greater the amount of edible biomass mixed, the more difficult it is to mix the edible biomass and the resin to a state where they do not peel off.

[0005] In response to this, Patent Document 2 discloses a method for producing resin pellets by uniformly kneading soy pulp and resin without adding a compatibilizer, by retaining an appropriate amount of moisture and oil in soy pulp, thereby suppressing the generation of static electricity during kneading and molding, and increasing the affinity with resin.

[0006] However, in Patent Document 2, increasing the okara mixing ratio increases the likelihood of strand breakage during the process of cutting the resin extruded from the kneader's discharge port into pellets using a pelletizer, resulting in a significant management burden for the operator. Furthermore, okara is a biomass that significantly reduces the moldability of resins, resulting in limited flexibility in the shape of the molded product. In particular, when thinning the resin using inflation molding or other methods, the amount of okara added is extremely limited from the perspective of moldability and okara resin film strength. In particular, it is difficult to incorporate okara in an amount of 5 wt% or more (calculated as bone dry weight) for okara resin films with thicknesses of 50 μm or less. Furthermore, when okara is blended with resin, heating during the molding process generates a distinctive, burnt odor, similar to the smell of okara and resin, which can be unpleasant during molding and when using the molded product. Therefore, further improvements in the kneading stability and moldability of okara-containing resins are needed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 10-145055 [Patent Document 2] Patent No. 7349083 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above-mentioned conventional drawbacks, the present invention is based on a novel concept and has an object to provide an okara powder for resin kneading and an okara-containing resin that can be stably kneaded and compounded with resin, suppresses a decrease in resin moldability and the generation of unpleasant odors during molding, and can be suitably used in okara resin products in a variety of fields, such as injection-molded products, press-molded products, sheet-molded products, extrusion-molded products, and blow-molded products. [Means for solving the problem]

[0009] In view of the above object, as a result of extensive research, the present inventors have discovered that the use of soybean pulp adjusted to a predetermined particle size range can improve the kneading stability and moldability of soybean pulp-containing resins, and have arrived at the present invention. That is, the problems of the present invention can be solved by the following configuration.

[0010] The first invention is a soy pulp powder for resin kneading, which is to be kneaded into a resin and used, characterized in that the soy pulp particles contained in the soy pulp powder for resin kneading have a cumulative 90% particle diameter D90 of 90 μm or less.

[0011] A second aspect of the present invention is the soy pulp powder for use in kneading with a resin, wherein the soy pulp particles contained in the soy pulp powder for use in kneading with a resin have a median diameter D50 of 20 μm or more and 45 μm or less.

[0012] The third invention is a soy pulp-containing resin containing the soy pulp powder for resin kneading, characterized in that the soy pulp-containing resin contains 1 wt% or more and 80 wt% or less of the soy pulp powder for resin kneading.

[0013] The fourth invention is an okara resin product containing the okara powder for resin kneading, characterized in that the okara resin product contains 1 wt% or more and 80 wt% or less of the okara powder for resin kneading.

[0014] A fifth aspect of the present invention is the soybean pulp resin product, wherein an aggregation rate S2 of the soybean pulp particles in the soybean pulp resin product is 5% or less.

[0015] The sixth invention of the present invention is an okara resin film containing the okara powder for resin kneading, characterized in that the okara resin film contains 1 wt% or more and 80 wt% or less of the okara powder for resin kneading.

[0016] A seventh aspect of the present invention is an okara resin film produced by inflation molding, wherein the okara resin film contains 1 wt % to 30 wt % of the okara powder for resin kneading. [Effects of the Invention]

[0017] According to the first invention, by making the cumulative 90% particle diameter D90 of the okara particles 90 μm or less, it is possible to obtain an okara powder for kneading with resin, which can be stably kneaded and compounded with resin, suppress the characteristic unpleasant odor generated during molding, and improve the moldability of the okara-containing resin.

[0018] According to the second invention, by adjusting the median diameter D50 of the okara particles to 20 μm or more and 45 μm or less, the okara particles can be kneaded and compounded with the resin more stably, and the moldability of the okara-containing resin can be improved.

[0019] According to the third invention, by blending the okara powder for resin kneading of the present invention in an amount of 1 wt% to 80 wt% in an okara-containing resin, the okara powder can be stably kneaded and compounded with the resin, the characteristic unpleasant odor generated during molding can be suppressed, and the moldability of the okara-containing resin can be further improved.

[0020] According to the fourth invention, by blending the okara powder for resin kneading of the present invention in an amount of 1 wt% to 80 wt% in an okara resin product, it is possible to stably knead and compound the resin, suppress the characteristic unpleasant odor that occurs during molding, and improve moldability.

[0021] According to the fifth invention, by blending the okara powder for resin kneading of the present invention and setting the aggregation rate S2 of the okara particles contained in the okara resin product to 5% or less, the okara particles are dispersed uniformly throughout the resin, and an okara resin product with excellent appearance can be obtained.

[0022] According to the sixth invention, by blending the okara powder for resin kneading of the present invention in an okara resin film at 1 wt% or more and 80 wt% or less, the okara powder can be kneaded and compounded more stably with the resin, the characteristic unpleasant odor generated during molding can be suppressed, and the moldability of the okara-containing resin can be further improved.

[0023] According to the seventh invention, by blending the soy pulp powder for resin kneading of the present invention in an inflation-molded film at 1 wt % or more and 30 wt % or less, it becomes possible to mold a thin film of 50 μm or less, which was difficult to mold with resins using conventional soy pulp. [Brief explanation of the drawings]

[0024] [Figure 1] This is a stereomicroscope photograph (200x magnification) of okara powder, which is made by drying raw okara generated during the tofu manufacturing process. [Figure 2] 1 is a flowchart showing an example of a process for producing soy pulp powder for kneading with a resin according to the present invention. [Figure 3] FIG. 2 is a diagram showing the particle size distribution of the okara powder of Example 1. [Figure 4] FIG. 1 is a diagram showing the particle size distribution of the okara powder of Comparative Example 1. [Figure 5] FIG. 1 is a diagram showing the particle size distribution of the okara powder of Comparative Example 2. [Figure 6] FIG. 10 is a diagram showing the particle size distribution of the okara powder of Comparative Example 3. [Figure 7] FIG. 1 is a diagram showing the particle size distribution of the okara powder of Example 2. [Figure 8] FIG. 10 is a diagram showing the particle size distribution of the okara powder of Comparative Example 4. [Figure 9] FIG. 1 is a schematic diagram of a kneader used to produce pellets containing soy pulp in the examples. [Figure 10] FIG. 1 is a view showing photographs of films produced using the soy pulp powders of Example 1, Comparative Example 1, and Comparative Example 2. [Figure 11] FIG. 1 shows stereomicroscope photographs of films produced using the soybean pulp powders of Example 1, Comparative Example 1, and Comparative Example 2, and binarized images of the stereomicroscope photographs. [Figure 12] 1 is a graph showing the breaking strain of a polyethylene resin containing soybean pulp. [Figure 13] 1 is a graph showing the elastic modulus of a polyethylene resin containing soybean curd refuse. [Figure 14] 1 is a diagram showing stereomicroscope images of the test pieces of Example 1, Comparative Example 1, and Comparative Example 2. FIG. [Figure 15] FIG. 2 is a diagram showing binarized images of the test pieces of Example 1, Comparative Example 1, and Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0025] The soy pulp powder for kneading with resin and the soy pulp-containing resin of the present invention will be described in detail below.

[0026] In this specification, "okara" is defined as a processed product made from the residue obtained by squeezing soy milk from whole soybeans, and is different from processed soybeans such as defatted soybeans. In this specification, the particle size of okara particles refers to the volume-average particle size measured by laser light scattering (laser diffraction), and the values ​​of the cumulative 10% particle size D10, median size D50, cumulative 90% particle size D90, and cumulative 95% particle size D95 refer to the cumulative percentage of frequency measured by volume. In this specification, the aggregation rate of okara particles before kneading the okara powder for resin kneading with resin is defined as "aggregation rate S1," and the aggregation rate of okara particles after kneading the okara powder for resin kneading with resin is defined as "aggregation rate S2."

[0027] (1) Okara powder for kneading resin The soy pulp powder for resin kneading of the present invention is composed of an aggregate of dried soy pulp particles and has a particle size distribution in which the cumulative 90% particle size D90 is 90 μm or less.Furthermore, the soy pulp powder for resin kneading of the present invention preferably has a median size D50 of 20 μm or more and 45 μm or less.

[0028] Raw okara, which is the raw material for okara powder for resin kneading, is the residue left over when soy milk is squeezed out during the process of producing tofu from whole soybeans, and is generated in large quantities during the tofu production process. Figure 1 shows a stereomicroscope photograph (200x magnification) of okara powder made by drying raw okara generated during the tofu production process. As shown in Figure 1, okara powder made by drying raw okara contains many coarse okara particles with a particle size of over 150 μm, and there is a large variation in the size of the okara particles. In addition, the oil contained in the okara makes it sticky, causing the okara particles to clump together.

[0029] In the present invention, by thoroughly classifying the okara particles so that the particle size distribution of the okara particles falls within a predetermined range, it becomes easier to blend the particles uniformly into resin, and it is possible to obtain an okara powder for kneading with resin that is less likely to cause problems with the strength and moldability of the finished okara resin product.

[0030] Conventionally, the average particle size of okara has been adjusted to 100 μm or less before being kneaded with resin, but the use of okara-containing resins has been limited because adding okara to resins significantly reduces the moldability of the resin. In contrast, the okara powder for resin kneading of the present invention allows for more stable kneading and compounding and can suppress the decrease in moldability caused by the addition of okara, thereby opening up new possibilities for the use of okara-containing resins.

[0031] (particle size of okara powder for resin mixing) The okara powder for resin kneading of the present invention is okara that has been subjected to classification so that the particle size distribution of the okara particles has a cumulative 90% particle size D90 of 90 μm or less. The okara powder for resin kneading of the present invention further preferably has a median diameter D50 of 20 μm or more and 45 μm or less. A median diameter D50 of less than 20 μm is undesirable because the okara particles tend to scatter when kneaded with the resin, which may reduce operability. Furthermore, a median diameter D50 of more than 45 μm is undesirable because the strength of the resulting okara resin product is reduced. In the present invention, classification is preferably performed so that the median diameter D50 is 22 μm or more and 40 μm or less, and particularly preferably 25 μm or more and 35 μm or less.

[0032] The soybean pulp powder for resin kneading of the present invention preferably has a narrow particle size distribution. In the present invention, soybean pulp particles with a particle size exceeding 100 μm and agglomerates of agglomerated soybean pulp particles cause a decrease in the strength and moldability of the finished soybean pulp resin product. Therefore, in the classification step, it is preferable to remove as many agglomerates of soybean pulp particles with a particle size exceeding 100 μm and agglomerates of agglomerated soybean pulp particles as possible.

[0033] The okara powder for resin kneading preferably has a cumulative 90% particle diameter D90 of 90 μm or less, more preferably 80 μm or less, and particularly preferably 70 μm or less. By making the cumulative 90% particle diameter D90 90 μm or less, it can be stably kneaded and compounded with resin, suppressing a decrease in the moldability of the okara-containing resin, and making it less likely that defects will occur in the appearance of the finished okara resin product, thereby further improving the physical properties of the okara-containing resin. In addition, it can suppress the unpleasant burnt odor that occurs when the okara-containing resin is heated and melted during molding.

[0034] The okara powder for resin kneading of the present invention preferably has a cumulative 95% particle diameter D95 of 100 μm or less, more preferably 90 μm or less, and particularly preferably 85 μm or less.The okara powder for resin kneading of the present invention preferably has a cumulative 99% particle diameter D99 of 200 μm or less, more preferably 150 μm or less, and particularly preferably 135 μm or less.

[0035] Furthermore, the okara powder for resin kneading of the present invention preferably has a cumulative 10% particle diameter D10 of 6 μm or more, more preferably 8 μm or more, and particularly preferably 10 μm or more. If the cumulative 10% particle diameter D10 is less than 6 μm, the okara particles may easily scatter when kneading the okara with a resin, which may reduce operability, and this is not preferred.

[0036] Furthermore, if the value obtained by dividing the cumulative 90% particle diameter D90 by the median diameter D50 (D90 / D50) is 1.0 or more and 3.0 or less, the strength of the resulting resin molded product is more likely to be satisfactory and moldability is more excellent, which is preferable. The upper limit of the D90 / D50 value is more preferably 2.5, even more preferably 2.2, and particularly preferably 2.0. Meanwhile, the lower limit of the D90 / D50 value is more preferably 1.1, even more preferably 1.3, and particularly preferably 1.5.

[0037] (Agglomeration rate S1 of soy pulp powder for resin mixing) In the okara powder for resin kneading of the present invention, if okara particles aggregate, the okara will not be uniformly dispersed in the finished okara resin product, resulting in color unevenness and a loss of aesthetic appeal. The aggregation rate S1 of the okara particles contained in the okara powder for resin kneading of the present invention is 5% or less, preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. In this specification, the aggregation rate S1 of the okara powder for resin kneading is defined as the area ratio of aggregated okara particles among 200 okara particles randomly selected from the okara powder in scanning electron microscope observation. That is, the aggregation rate S1 is the ratio of the total area Y of aggregated okara particles to the total area X of the 200 randomly selected okara particles, and is calculated by S1 = Y / X × 100 (%). The area of ​​each okara particle can be calculated by image analysis of a scanning electron microscope photograph.

[0038] (Manufacturing process of okara powder for resin kneading) An example of the manufacturing process for okara powder for resin kneading is shown in Figure 2. The raw okara remaining after soy milk is extracted from whole soybeans usually contains around 75 wt% moisture and cannot be used in a grinder as is. Therefore, first, the okara is dried in a drying process until the moisture content is around 5 wt% to prepare dried okara (Step S1).

[0039] In the subsequent grinding step, the dried okara is ground to prepare ground okara (step S2). In the grinding step, the okara particles are preferably ground to have a median diameter D50 of 30 μm or more and 50 μm or less. For grinding the dried okara, a known grinder such as a roll grinder, a collision grinder, or a ball mill grinder can be used.

[0040] Because the pulverized okara obtained by pulverization in the pulverization step has a large variation in the size of the okara particles, the okara particles are classified in the classification step so that the cumulative 90% particle diameter D90 is 90 μm or less (step S3). Okara is sticky due to the oil contained in the okara itself, which can clog sieves and cause the okara particles to easily aggregate, making it a powder that is difficult to classify. The method for classifying okara can be any known classification method, such as sieving or air classification, and is not particularly limited. However, taking into account the sticky nature of okara, thorough classification can be performed by repeating the classification process multiple times or adjusting the water content and oil content of dried okara until the cumulative 90% particle diameter D90 is 90 μm or less, thereby obtaining the okara powder for kneading with resin of the present invention.

[0041] The order of the drying step (step S1) and the pulverization step (step S2) is not particularly limited, and the drying step (step S1) may be performed after the pulverization step (step S2), or the drying step (step S1) and the pulverization step (step S2) may be performed simultaneously. For example, normal raw soybean pulverization may be performed in a slurry state, dried, and then classified.

[0042] (Ingredients of okara powder for resin mixing) The soybean pulp powder for kneading with a resin of the present invention comprises proteins, oils, sugars, dietary fiber, ash, moisture, and the like.

[0043] From the viewpoint of effectively utilizing waste soybean refuse, the soybean refuse powder for kneading with resin of the present invention preferably has substantially the same composition ratio as dried soybean refuse obtained by drying ordinary soybean refuse obtained in the process of producing tofu from whole soybeans. The composition of the soybean refuse powder for kneading with resin that is preferred in the present invention is as follows.

[0044] Protein: 20wt% to 25wt% Oil content: 10wt% or more and 15wt% or less Carbohydrates: 5wt% or more and 10wt% or less Dietary fiber: 43wt% to 55wt% Ash content: 3wt% or more and 4wt% or less Water: 1wt% or more and 8wt% or less

[0045] The moisture content of the okara powder for resin kneading of the present invention is not particularly limited, but from the viewpoint of preventing mold growth and aggregation of okara particles, the moisture content of the okara powder for resin kneading during storage is preferably 8 wt% or less, and more preferably 3 wt% or more and 6 wt% or more.

[0046] However, within the scope of the present invention, it is not precluded from producing okara powder for kneading with resin having a component composition different from that of ordinary okara by subjecting the okara to degreasing treatment, chemical treatment, etc. For example, in the drying step (step S1), the oil content of the okara may be controlled by performing a heat treatment at a high temperature to volatilize part of the oil contained in the okara.

[0047] The soybean-derived oil contained in the okara powder for resin kneading improves compatibility with the resin during the kneading process and is an essential component for uniform kneading, with approximately 50% of the oil consisting of linoleic acid, an unsaturated fatty acid. The oil content of the okara powder for resin kneading is preferably 1 wt% to 20 wt%, more preferably 10 wt% to 15 wt%, and most preferably 12 wt% to 14 wt%. An oil content of less than 1 wt% is undesirable because it can lead to uneven kneading with the resin and significant peeling of the okara particles from the resin.

[0048] On the other hand, if the oil content of the okara powder for resin kneading is more than 20 wt%, the okara particles are likely to clog the sieve mesh during the classification process, causing clogging of the sieve and also causing the okara particles to re-agglomerate after the classification process.Furthermore, this is undesirable because there is a concern that the oil will bleed from the molded product and cause corrosion of machinery such as injection molding machines.

[0049] (2) Soybean pulp-containing resin Next, the okara-containing resin containing the okara powder for resin kneading of the present invention will be described. In the kneading step, the okara powder for resin kneading and a resin are kneaded to produce the okara-containing resin and the okara resin pellets. In this specification, the product obtained after heating, melting, and kneading the mixture of the okara powder for resin kneading and the resin is referred to as a "kneaded product," the product obtained by cooling the kneaded product is referred to as an "okara-containing resin," the okara-containing resin pelletized is referred to as an "okara resin pellet," the okara-containing resin molded into a shape of a "okara resin product," and the okara-containing resin molded into a film shape is referred to as an "okara resin film."

[0050] (Resin material) The resin that can be blended with the soybean pulp powder for resin kneading of the present invention is not particularly limited, and examples that can be used include thermoplastic resins, thermosetting resins, elastomers, biodegradable resins, etc.

[0051] Examples of thermoplastic resins include polyethylene, polypropylene, polystyrene, ABS resin, polyvinyl chloride, and polyethylene terephthalate. Examples of elastomers include olefin-based elastomers, unsaturated aliphatic elastomers, hydrogenated unsaturated aliphatic elastomers, amide-based elastomers, ester-based elastomers, styrene-based elastomers, and urethane-based elastomers. Examples of thermosetting resins include phenolic resins, urea resins, and melamine resins. Examples of biodegradable resins include polylactic acid, polyglycolic acid, polybutylene succinate, polybutylene adipate, polyethylene terephthalate succinate, and polyvinyl alcohol. Two or more of these resins may be used in combination.

[0052] In the present invention, by using a biodegradable resin as the resin, it becomes possible to dispose of the soy pulp resin product containing the soy pulp powder for resin kneading of the present invention in the soil, ocean, etc. without incineration.

[0053] In the present invention, it is preferable to use a thermoplastic resin having a melting point of 220°C or less. Resins having a melting point exceeding 220°C undergo significant thermal decomposition of the okara during melt-kneading with the okara powder for resin kneading of the present invention. Furthermore, the resin to be blended with the okara powder for resin kneading of the present invention preferably has a melt flow rate (MFR) of 1.0g / 10 min to 50g / 10 min, more preferably 2.0g / 10 min to 40g / 10 min, and even more preferably 3.0g / 10 min to 35g / 10 min.

[0054] The okara-containing resin of the present invention may contain additional components in addition to the okara powder for resin kneading and the resin. In a typical embodiment, the additional components may include a filler for reinforcing strength, a flame retardant (e.g., triphenyl phosphate, aluminum hydroxide, magnesium hydroxide, calcium hydroxide), a pigment (e.g., titanium dioxide, zinc oxide, iron oxide), etc. Examples of fillers for reinforcing strength include organic fillers such as cellulose (e.g., derived from wood waste), and inorganic fillers such as talc and cement waste. The weight ratio of the additional components in the okara-containing resin of the present invention to the okara-containing resin is 30 wt% or less, typically 20 wt% or less.

[0055] (Kneading process) The content of okara powder for resin kneading in the okara-containing resin is preferably 80 wt% or less, calculated as an absolute dry weight. If the content of okara powder for resin kneading in the okara-containing resin is greater than 80 wt%, okara particles tend to peel off from the okara-containing resin, and the strength of the okara resin pellets is low, making it difficult to use the okara-containing resin in practical applications. Therefore, the content of okara powder for resin kneading in the okara-containing resin can be 80 wt% or less, preferably 75 wt% or less, more preferably 65 wt%, and even more preferably 50 wt% or less. While there is no particular lower limit for the content of okara powder for resin kneading in the okara-containing resin, it is preferable to include at least 1 wt% or more. From the viewpoint of effectively utilizing okara as a biomass filler, it is preferable to increase the okara content up to the molding limit.

[0056] The soybean pulp powder for resin kneading of the present invention is preferably adjusted to an appropriate moisture content before being kneaded with the resin to prevent the soybean pulp particles from scattering due to static electricity when kneaded with the resin. At the time of kneading with the resin, the moisture content of the soybean pulp powder for resin kneading is preferably 1 wt% or more but less than 20 wt%, more preferably 2 wt% or more but less than 10 wt%, and most preferably 3 wt% or more but less than 6 wt%. If the moisture content of the soybean pulp powder for resin kneading is less than 1 wt%, scattering may occur during mixing, resulting in a large variation in the mixing ratio. If the moisture content of the soybean pulp powder for resin kneading is greater than 20 wt%, the heat of vaporization of water vapor during heating may be so large that the resin may not melt sufficiently, and, particularly in the case of resins having ester bonds, there may be a significant decrease in molecular weight due to hydrolysis.

[0057] In the kneading step, the okara powder for resin kneading and the resin are placed in a kneader and heated, melted, and kneaded. A known kneader can be used for the kneading step. At this time, the oil contained in the okara prevents phase separation between the resin and the okara, resulting in a uniform kneading of the okara powder for resin kneading and the resin. Normally, when kneading food biomass or inorganic fillers that have low compatibility with resins, a compatibilizer or the like is added to improve uniformity. However, in the present invention, the okara particles are classified to a predetermined particle size range, and the oil originally contained in the okara acts as the compatibilizer, making it possible to achieve uniform kneading without the need for the separate addition of a commonly used compatibilizer.

[0058] When the soy pulp powder for resin kneading and the resin are heated, melted, and kneaded, the kneading temperature is preferably 160°C or higher and 220°C or lower, more preferably 160°C or higher and 200°C or lower, and most preferably 170°C or higher and 190°C or lower. If the kneading temperature is lower than 160°C, the resin will not melt sufficiently, and if the kneading temperature is higher than 220°C, thermal decomposition of the soy pulp will be significant, which may make it difficult to obtain a desirable soy pulp-containing resin. In a preferred embodiment, the kneading step can be carried out so that the molecular weight of the resin after kneading is increased compared to the molecular weight of the resin before kneading. The kneaded product obtained by heating, melting, and kneading the soy pulp powder for resin kneading and the resin is extruded, cut, and cooled to obtain a pellet-shaped soy pulp-containing resin.

[0059] In the kneading process, strands of the soybean pulp-containing resin are discharged from the discharge port. Immediately after discharge, the strands of the soybean pulp-containing resin are transferred to a pelletizer. The shape of the discharge port is not particularly limited, but a circular shape is most preferable. Furthermore, when the shape of the discharge port is circular, the diameter of the discharge port is preferably 1 mm or more and less than 10 mm, more preferably 2 mm or more and less than 6 mm, and most preferably 3 mm or more and less than 5 mm. If the diameter of the discharge port is less than 1 mm, the discharged strands are likely to be cut, and if the diameter is greater than 10 mm, the strands are likely to be cut, which may reduce the operability of the subsequent cooling and cutting processes.

[0060] The cooling method for the strand-shaped okara-containing resin in the cooling process can be any known cooling method, without particular limitation, such as a method of blowing air using a blower or the like (air-cooling method), a method of immersing in water (water-cooling method), or a method of contacting with a cooling block (cooling block contact method).

[0061] The distance from the discharge port to the pelletizer (hereinafter referred to as the cooling distance) is preferably 1 m or more and 10 m or less, more preferably 2 m or more and 6 m or less, and most preferably 3 m or more and 5 m or less. If the cooling distance is less than 1 m, the okara-containing resin may not be sufficiently cooled, which may make subsequent cutting difficult.

[0062] (3) Okara resin products The pellet-shaped okara-containing resin thus obtained can be molded into various okara resin products by known molding methods such as injection molding, press molding, extrusion molding, sheet molding, blow molding, and inflation molding. In okara resin products made from okara-containing resins, the resin is melted once and then solidified, and can be characterized by forming an interconnected network structure. In okara resin products made from okara-containing resins, the okara particles can maintain their shape before and after kneading.

[0063] (Agglomeration rate S2 of okara particles in okara resin products) Aggregated soybean pulp particles cause uneven color in soybean pulp resin products, so it is preferable that the soybean pulp particles contained in the soybean pulp resin product are uniformly present without agglomeration.

[0064] In the present invention, the agglomeration rate S2 of okara particles in a okara resin product is 5% or less, preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. In the present specification, the agglomeration rate S2 of okara particles in a okara resin product can be automatically calculated using an image processing device based on the color unevenness of the surface of the okara resin product. For example, a microscope image is taken of the surface of the okara resin product, in which the brightness of the aggregated areas where okara particles are aggregated is high and the brightness of the peripheral areas is low. A threshold is set between the brightness of the peripheral areas of the aggregated areas and the brightness of the central areas of the aggregated areas, and the microscope image is binarized. The agglomeration rate S2 of okara particles in the okara resin product can be calculated based on the area of ​​the aggregated areas (e.g., the number of pixels) in the binarized image.

[0065] (Soybean pulp resin film) The okara-containing resin of the present invention can be molded into a film using known methods such as T-die molding, inflation molding, calendar molding, and skiff molding. The okara-containing resin of the present invention has good moldability and can be molded into a thin film having a thickness of 50 μm or less by inflation molding, which was difficult with conventional okara. When the okara-containing resin of the present invention is used to mold a film, the resin kneaded with the okara powder for resin kneading of the present invention is preferably a polyethylene resin, and preferably a polyethylene resin having a melt mass-flow rate (MFR) of 0.8 g / 10 min to 12.0 g / 10 min.

[0066] Furthermore, when a thin film having a thickness of 50 μm or less is blown using the okara-containing resin of the present invention, the content of the okara powder for resin kneading is preferably 1 wt% or more and 30 wt% or less. A okara powder content of more than 30 wt% is not preferred because the strength of the okara resin film cannot be sufficiently ensured. The lower limit of the okara powder content is preferably 3 wt% or more, more preferably 5 wt% or more, even more preferably 10 wt% or more, and particularly preferably 15 wt% or more.

[0067] When a thin film is formed using the soybean pulp-containing resin of the present invention, the film thickness is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 40 μm or less, and particularly preferably 30 μm or less. [Example]

[0068] The present invention will be described in more detail with reference to the following examples, but is not limited to these examples. In the examples, the particle size of the okara particles was measured using a laser diffraction / scattering particle size distribution analyzer (manufactured by Horiba, Ltd., device name: LA-960).

[0069] (1) Preparation of okara powder for kneading with resin Okara powder for resin kneading was prepared according to the procedure shown in Figure 2. First, raw okara produced in the tofu production process was dried at 105°C for 12 hours to reduce the moisture content of the okara to 3.7%. The dried okara was pulverized using a collision pulverizer to an average particle size of 50 μm or less, and sieved several times through 100-mesh to 500-mesh sieves to obtain okara powder, which was designated Example 1 (classified okara).

[0070] The particle size distribution of the okara powder of Example 1 was measured using a laser diffraction / scattering particle size distribution analyzer. Figure 3 shows a particle size distribution chart of the okara powder of Example 1. The okara powder set aside after the pulverization process and before the classification process was designated Comparative Example 1 (pulverized okara), and the okara powder set aside before the pulverization process was designated Comparative Example 2 (unpulverized okara). Figure 4 shows a particle size distribution chart of the okara powder of Comparative Example 1, and Figure 5 shows a particle size distribution chart of the okara powder of Comparative Example 2. The moisture content of each okara powder was measured, and the moisture content was 3.78 wt% for Example 1, 4.18 wt% for Comparative Example 1, and 3.90 wt% for Comparative Example 2. Furthermore, using the same procedure, pulverized okara with a different particle size distribution (Comparative Example 3) and two types of classified okara with different particle size distributions (Example 2 and Comparative Example 4) were prepared. Figure 6 shows a particle size distribution chart of the okara powder of Comparative Example 3, Figure 7 shows a particle size distribution chart of the okara powder of Example 2, and Figure 8 shows a particle size distribution chart of the okara powder of Comparative Example 4. In Figure 6 (Comparative Example 3), two peaks (approximately 35 μm and approximately 600 μm) were observed, which is thought to be due to aggregation of the pulverized okara particles.

[0071] Table 1 shows the particle sizes of the okara powders of Examples 1 and 2 and Comparative Examples 1 to 4. The okara powders of Examples 1 and 2 have cumulative 90% particle diameters D90 of 64.5 μm and 54.1 μm, respectively, and therefore satisfy the requirements for the okara powder for kneading with resin of the present invention.

[0072] [Table 1]

[0073] Table 2 shows a component analysis table of the okara powders of Example 1, Comparative Example 1, and Comparative Example 2. From the component analysis table in Table 2, it can be seen that the okara powder for kneading with resin of Example 1 has substantially the same composition ratio as regular okara obtained in the process of producing tofu from whole soybeans.

[0074] [Table 2]

[0075] (2) Evaluation of the influence of soybean pulp powder for resin kneading on its kneading compounding suitability and moldability Using the soybean pulp powders of Examples 1 and 2 and Comparative Examples 1 to 4, evaluation tests were carried out to assess their suitability for kneading and compounding with various resins, and their effect on moldability.

[0076] (Production of pellets containing soybean pulp) Figure 9 shows the extrusion mixer (hereinafter referred to as the mixer) used to prepare the okara-containing pellets. Resin and okara powder for resin mixing were charged into the resin inlet hopper and okara inlet hopper, respectively, at the blending ratios shown in Table 3, and then introduced into the cylinder. The mixer's screw diameter was 26 mm, the screw rotation speed was 65 rpm, and the cylinder heaters (C1, C2, C3, and C4) were set to 150°C, 170°C, 175°C, and 180°C, respectively. The 3-mm diameter strands consisting of the okara powder and resin mixture emerging from the nozzle tip were then introduced into a pelletizer using a drawing device and cut into 3-mm intervals. The distance from the discharge outlet to the pelletizer (hereinafter referred to as the cooling distance) was set to 5 m. In this way, okara-containing pellets No. 1 to No. 21 containing okara powder were prepared.

[0077] Next, the okara-containing pellets No. 1 to No. 21 were hot-pressed at 180°C in a compression press and then rapidly cooled to form okara-containing resin films with a thickness of 0.2 mm. The okara powders of Examples 1 and 2 and Comparative Examples 1 to 4 were evaluated for their kneading and compounding suitability, moldability, odor during molding, appearance of the molded product, and odor of the molded product according to the following criteria. The results are shown in Table 3.

[0078] [Table 3]

[0079] [Evaluation criteria for kneading and compounding suitability] ◎: No strand breakage occurs during continuous production for 1 hour. Good: Strand breakage occurs 1 to 3 times during 1 hour of continuous production. △: Strand breakage occurs 4 to 9 times during continuous production for 1 hour. ×: Strand breakage occurs 10 or more times during continuous production for 1 hour.

[0080] [Evaluation criteria for formability] ○: The discharge pressure of the mixer is within +0.2 MPa compared to the resin before mixing with the okara (processing is possible while maintaining the same high moldability as the resin before mixing with the okara) △: The discharge pressure of the kneader is within +1.0 MPa compared to the resin before kneading with soy pulp (moldability is slightly reduced) ×: The discharge pressure of the kneader is more than +1.0 MPa compared to the resin before kneading with soy pulp (deterioration in moldability)

[0081] [Evaluation criteria for odor during molding] The burnt odor of the okara during molding was sensory evaluated by three evaluators who smelled the odor in the workplace immediately after the okara-containing pellets were hot-pressed. ◎: No odor is felt during molding. Good: There is almost no burnt smell of soy pulp during molding. △: An unpleasant odor is felt around the press during molding. ×: A strong unpleasant odor spreads around the press during molding.

[0082] [Evaluation criteria for the aesthetics of molded products] The bean-curd refuse-containing pellets were hot-pressed to obtain a film having a thickness of 0.2 mm. The appearance of the film was evaluated visually for aesthetic appearance. ◎: The soy pulp is uniformly dispersed in the molded product, and no color unevenness is observed. ◯: A small amount of agglomerated grains of soy pulp can be visually confirmed in the molded product. △: Agglomerated grains of soy pulp can be visually confirmed in the molded product. ×: Areas with a large amount of soy pulp and areas with a small amount of soy pulp can be visually confirmed in the molded product.

[0083] [Evaluation criteria for the odor of molded products] 〇: Smells like beans. △: Slightly unpleasant odor. ×: Unpleasant odor is felt.

[0084] Comparing the kneading and compounding suitability, no strand breakage occurred in Examples 1 and 2. On the other hand, strand breakage occurred in Comparative Examples 1 to 4, in which the cumulative 90% particle diameter D90 was 100 μm or more. This shows that by setting the cumulative 90% particle diameter D90 of the okara powder to 90 μm or less, kneading and compounding are facilitated and strand breakage can be suppressed. Furthermore, as the average particle diameter of the okara increases, the temperature of the head resin coming out of the nozzle of the extrusion kneader decreases, and strand breakage tends to occur more easily.

[0085] Comparing the discharge pressure (moldability) of the kneader, it was almost the same as the resin before mixing with the soy pulp powder in Examples 1 and 2. On the other hand, in Comparative Examples 1 to 4, the discharge pressure increased, and the moldability of the resin decreased due to the incorporation of the soy pulp powder.

[0086] Regarding the smell of okara, in the state of okara powder before kneading, Examples 1 and 2 had a stronger smell of okara than Comparative Examples 1 to 4. However, when the okara powder was kneaded into resin and molded, Examples 1 and 2 had almost no burnt smell of okara compared to Comparative Examples 1 to 4, and the unpleasant smell during molding and in the molded product was significantly improved.

[0087] Figure 10 shows photographs of films made from pellets No. 1 (classified okara from Example 1), No. 3 (pulverized okara from Comparative Example 1), and No. 4 (unpulverized okara from Comparative Example 2). When comparing the aesthetics of the films made from each okara powder, the films from Comparative Examples 1 to 4 had obvious color unevenness that could be visually confirmed, whereas the films from Examples 1 and 2 had excellent aesthetics with almost no color unevenness. The difference in dispersibility due to differences in particle size could be clearly determined by visual inspection, and when the particle size was small, the particles were dispersed uniformly across the entire film.

[0088] FIG. 11 shows stereomicroscope photographs of films made from pellets No. 1 (classified okara of Example 1), No. 3 (pulverized okara of Comparative Example 1), and No. 4 (unpulverized okara of Comparative Example 2), as well as binarized images of the stereomicroscope photographs. The binarized images were created using the image processing software "ImageJ," with the median brightness of the peripheral region of the aggregated portion and the central region of the aggregated portion set as a threshold value. The aggregation rate S2 of the okara particles in each film was calculated from the binarized images. The aggregation rate was 0.85% for the classified okara of Example 1, 25.08% for the pulverized okara of Comparative Example 1, and 69.52% for the unpulverized okara of Comparative Example 2, demonstrating that the okara powder of Example 1 has extremely high dispersibility.

[0089] (3) Aesthetic evaluation of injection molded products (Making a small item holder) Pellet No. 1 (okara content 63.8%) and pellet No. 7 (okara content 75%) were used to injection mold small containers using an injection molding machine (NESK, FE80S12ASE) with a clamping force of 80 ton. During the injection molding process for the small containers with okara content of 63.8% and 75%, there was almost no smell of burnt okara.

[0090] When the surface quality of the small containers with okara contents of 63.8% and 70% was visually observed, both containers had fine, even surfaces and excellent appearances. This indicates that the okara powder of Example 1 had okara dispersed uniformly in the molded product.

[0091] (4) Strength evaluation of injection molded products An evaluation test was conducted to examine the influence of the soy pulp powders of Example 1, Comparative Example 1, and Comparative Example 2 on the strength and moldability of a polyethylene resin containing soy pulp. Polyethylene (PE) (Japan Polyethylene Corporation, Harmolex "NC566A", MFR: 3.8 g / 10 min) was used as the polyethylene resin.

[0092] (Strength evaluation of injection molded products) The okara powder of Example 1 and PE were charged into the hopper of an extrusion kneader in a weight ratio of 50:50 and melt-kneaded at 170°C. The strand-like kneaded mixture of okara powder and PE discharged from the discharge port of the extrusion kneader was cut at 3 mm intervals to obtain okara-containing PE pellets. Similarly, okara-containing PE pellets were also produced using the okara powders of Comparative Examples 1 and 2.

[0093] (Preparation of test specimens) The okara-containing PE pellets obtained by the above method were used to prepare dumbbell-shaped test pieces in accordance with Japanese Industrial Standard (JIS) K7139 using an injection molding machine (manufactured by NSK Ltd., FE80S12ASE) with a clamping force of 80 ton.

[0094] (Strength evaluation of test specimens) The test specimens were subjected to strength and elongation tests using a composite material testing machine (Instron, 5966) under conditions of a chuck distance of 90 mm, a gauge length of 50 mm, and a crosshead speed of 5 mm / min, and the breaking strain and elastic modulus were evaluated. Figure 12 shows the results of the breaking strain, and Figure 13 shows the results of the elastic modulus evaluation.

[0095] As shown in Figure 12, it was confirmed that the test specimens made using PE containing 50 wt% of classified okara from Example 1 were able to significantly suppress the decrease in breaking strain compared to the test specimens made using pulverized okara from Comparative Example 1.

[0096] Furthermore, as shown in Figure 13, it was confirmed that the pulverized okara of Comparative Example 1 had an elastic modulus similar to that of the unpulverized okara of Comparative Example 2, whereas the classified okara of Example 1 had a significantly improved elastic modulus.

[0097] (Agglomeration rate S2 of soybean pulp particles in the test piece) The aggregation rate S2 of okara particles in the test pieces of Example 1, Comparative Example 1, and Comparative Example 2 was evaluated. When the prepared dumbbell-shaped test pieces were observed as a whole under natural light, a 1 cm × 1.65 cm area with the greatest color unevenness was selected as the evaluation point. The evaluation point was observed under a microscope, and a microscopic image was taken in which the agglomerated areas where the okara particles were aggregated were brighter and the surrounding areas were brighter. Figure 14 shows the microscopic images of each test piece. While color unevenness was clearly visible in Comparative Examples 1 and 2, the classified okara of Example 1 produced a test piece with excellent appearance and almost no color unevenness.

[0098] Next, using the image processing software "ImageJ," the median value between the brightness of the peripheral region of the aggregated portion and the brightness of the central region of the aggregated portion was set as a threshold value, and the microscopic image was binarized. Figure 15 shows the binarized image of each test piece. The aggregation rate S2 of the okara particles in each test piece was calculated based on the proportion of the aggregated portion area (area of ​​the white portion) in the binarized image. The aggregation rate was 0.76% for the classified okara of Example 1, 8.39% for the pulverized okara of Comparative Example 1, and 39.04% for the unpulverized okara of Comparative Example 2. This indicates that the classified okara of Example 1 is uniformly present in the okara resin product with almost no aggregation.

[0099] (5) Evaluation of okara resin film by inflation molding Next, to evaluate the effect of soy pulp powder for resin mixing on film strength and moldability, soy pulp resin films were produced using PE containing soy pulp by inflation molding.

[0100] The okara-containing PE pellets containing 50 wt% of the okara powder of Example 1, polyethylene (Japan Polyethylene Corporation, Harmolex "NC566A", MFR: 3.8 g / 10 min), and polyethylene (Japan Polyethylene Corporation, Novatec "UF320", MFR: 0.9 g / 10 min) were mixed in a weight ratio of 30:20:50, and an okara resin film (Film No. 1) with a thickness of 30 μm and an okara content of 15 wt% was produced using an inflation molding machine. Similarly, okara resin films Nos. 2 to 4 were produced with the okara contents and film thicknesses shown in Table 4.

[0101] An attempt was made to produce an okara resin film using the okara powder of Comparative Example 2, but multiple small holes appeared in the okara resin film, making it impossible to blow-molde it into a 30 μm thick film (Film No. 3). This is thought to be due to the fact that the coarse particles and agglomerates of the okara particles reduce the moldability of the resin. With the classified okara of Example 2, no holes were observed, even when the okara content was increased to 25%, confirming that blow-molding was possible (Film No. 4).

[0102] [Table 4]

[0103] (Evaluation of the strength of okara resin film) The okara resin films of Films No. 1 and 2 were subjected to an Elmendorf tear strength test (TD) in accordance with Japanese Industrial Standards (JIS) K7128-2. When the okara content was 15%, the okara resin film produced using the pulverized okara of Comparative Example 1 had an Elmendorf tear strength (TD) of 30 N / mm (Film No. 2). In contrast, the okara resin film produced using the classified okara of Example 1 had an Elmendorf tear strength (TD) of 103 N / mm (Film No. 1), confirming that the film had sufficient strength to withstand practical use. [Industrial Applicability]

[0104] As explained above, the okara powder for resin kneading and the okara-containing resin of the present invention can be stably kneaded into a resin to form a composite, and can suppress the decrease in resin moldability caused by the addition of okara and the unpleasant odor during molding. Therefore, the powder can be suitably used in okara resin products in a variety of fields, such as injection-molded products, press-molded products, sheet-molded products, extrusion-molded products, blow-molded products, and inflation-molded products.

Claims

1. A soybean pulp powder for kneading with resin, which is to be kneaded with resin, The soy pulp powder for use in kneading with resins is characterized in that the soy pulp particles contained in the soy pulp powder for use in kneading with resins have a cumulative 90% particle diameter D90 of 90 μm or less.

2. 2. The soy pulp powder for use in kneading with resin according to claim 1, wherein the soy pulp particles contained in the soy pulp powder for use in kneading with resin have a median diameter D50 of 20 μm or more and 45 μm or less.

3. A soybean pulp-containing resin containing the soybean pulp powder for resin kneading according to claim 1, The soy pulp-containing resin contains the soy pulp powder for resin kneading in an amount of 1 wt % to 80 wt %.

4. A soy pulp resin product containing the soy pulp powder for resin kneading according to claim 1, The soy pulp resin product contains the soy pulp powder for resin kneading in an amount of 1 wt % to 80 wt %.

5. The aggregation rate S of the soybean pulp particles contained in the soybean pulp resin product ２ The soybean pulp resin product according to claim 4, characterized in that the content of soybean pulp is 5% or less.

6. A soybean pulp resin film containing the soybean pulp powder for resin kneading according to claim 1, The soy pulp resin film is characterized in that the soy pulp-containing polyethylene resin contains the soy pulp powder for resin kneading in an amount of 1 wt % to 80 wt %.

7. The soy pulp resin film according to claim 6, The soy pulp resin film is produced by inflation molding, The soy pulp resin film is characterized in that the soy pulp resin film contains the soy pulp powder for resin kneading in an amount of 1 wt % to 30 wt %.

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