Synthetic resin composition, synthetic resin molded product, and helmet

Abstract

To obtain a synthetic resin composition and a synthetic resin molded article having a unique texture and excellent strength while effectively utilizing shells as a resource. [Solution] The synthetic resin composition of the present invention is a synthetic resin composition containing synthetic resin and crushed shells in a mass ratio of 98:2 to 25:75, where the crushed shells contain finely crushed shells having an average particle size of 1 μm or more but less than 100 μm and coarsely crushed shells having an average particle size of 100 μm or more but not more than 3000 μm in a mass ratio of 97:3 to 40:60. The synthetic resin molded product of the present invention is obtained by molding the synthetic resin composition into a predetermined shape.

Description

[Technical Field]

[0001] The present invention relates to a synthetic resin composition, a synthetic resin molded product, and a helmet. [Background technology]

[0002] A large amount of shells are generated as waste from marine resources such as scallops, oysters, and pearl oysters. These shells are piled up on land while waiting to be disposed of by landfill or other means, but securing a place to pile up the shells and their impact on the environment are problems. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-75964 Summary of the Invention [Problem to be solved by the invention]

[0004] As a measure to utilize shells as a resource, it has been proposed to obtain synthetic resin molded products with excellent strength by adding crushed scallop shells to synthetic resins (see, for example, Patent Document 1). However, such conventional synthetic resin molded products containing crushed scallop shells have the same texture as ordinary synthetic resin molded products, and do not have a unique texture in terms of appearance and feel.

[0005] The problem to be solved by the present invention is to effectively utilize seashells as a resource and to obtain a synthetic resin molded product having a unique texture and excellent strength. [Means for solving the problem]

[0006] The synthetic resin composition according to the present invention, which has been made to solve the above problems, comprises: A synthetic resin composition containing a synthetic resin and crushed shells in a mass ratio of 98:2 to 25:75, The crushed shells contain finely crushed shells having an average particle size of 1 μm or more and less than 100 μm and coarsely crushed shells having an average particle size of 100 μm or more and 3000 μm or less in a mass ratio of 97:3 to 40:60.

[0007] Here, the average particle size means the volume average diameter, which is measured by, for example, a laser diffraction / scattering method. [Effects of the Invention]

[0008] By using the synthetic resin composition of the present invention having the above-mentioned constitution, it is possible to effectively utilize seashells as a resource and to obtain synthetic resin molded articles having a unique texture and excellent strength. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a flowchart showing a process for producing a synthetic resin composition according to one embodiment of the present invention. [Figure 2] 1 is a perspective view showing a helmet according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] As a result of extensive research into solving the above problems, the inventors discovered that by adding two types of crushed shells with different particle sizes to a synthetic resin in a predetermined ratio, a synthetic resin composition having a unique texture and excellent strength could be obtained, leading to the present invention.

[0011] That is, a synthetic resin composition according to one embodiment of the present invention is a synthetic resin composition containing synthetic resin and crushed shells in a mass ratio of 98:2 to 25:75 (preferably 97:3 to 45:55), and the crushed shells contain finely crushed shells having an average particle size of 1 μm or more but less than 100 μm (preferably 10 μm or more but 30 μm or less) and coarsely crushed shells having an average particle size of 100 μm or more but 3000 μm or less in a mass ratio of 97:3 to 40:60 (preferably 90:10 to 70:30).

[0012] Furthermore, in a synthetic resin composition according to one embodiment of the present invention, the coarsely ground shell material preferably comprises a first coarsely ground material having an average particle size of 100 μm or more but less than 1000 μm, and a second coarsely ground material having an average particle size of 1000 μm or more but less than 3000 μm, and the mass ratio of the first coarsely ground material to the second coarsely ground material is preferably 1:99 to 99:1.

[0013] The synthetic resin composition of this embodiment can be produced by a production method including a shell pulverization production step in which the finely pulverized shells and the coarsely pulverized shells are obtained by pulverizing shells, and a synthetic resin composition production step in which the finely pulverized shells and the coarsely pulverized shells are added to and mixed with a molten synthetic resin to obtain a synthetic resin composition (Figure 1).

[0014] The finely ground shells and the coarsely ground shells may be obtained by crushing the shells separately in the crushed shell production step, or the coarsely ground shells may be obtained by roughly crushing the shells to obtain the coarsely ground shells, and then a portion of the coarsely ground shells may be further crushed to obtain the finely ground shells. The coarsely ground shells may be obtained by crushing the shells using, for example, a hammer crusher or a jaw crusher, and the finely ground shells may be obtained by crushing the shells or the coarsely ground shells using, for example, a roller mill or a vibro mill, but are not limited to these. Alternatively, in the crushed shell production step, the shells may be crushed using a predetermined means to obtain shell powders of various particle sizes, which may then be grouped (i.e., classified) based on size to obtain the finely ground shells and the coarsely ground shells.

[0015] The type of shells is not limited, but shells such as scallop, oyster, clam, abalone, or pearl oyster can be used, and it is particularly desirable to use scallop shells, which are discarded in large quantities.

[0016] If the shells are derived from marine shells, it is preferable to obtain the crushed shells by immersing the shells in fresh water for a predetermined period (e.g., 1 to 3 years) to remove salt and then crushing them. It is also preferable to disinfect the shells by boiling or the like before crushing them.

[0017] In the shell pulverization production step, the shells may be pulverized after being fired, but it is preferable to obtain the finely pulverized shells and the coarsely pulverized shells by pulverizing unfired shells, which allows organic components (e.g., proteins) attached to the shells to be effectively utilized as components of the synthetic resin composition according to this embodiment.

[0018] The finely ground shells contained in the synthetic resin composition according to this embodiment function primarily as a reinforcing material that improves the mechanical properties (e.g., flexural modulus) of a synthetic resin molded article obtained from the synthetic resin composition, and the coarsely ground shells function primarily as a design-imparting material that affects the appearance, texture, feel, and other design aspects of the molded article. The synthetic resin composition according to this embodiment has the finely ground shells and the coarsely ground shells added to the synthetic resin in the above-mentioned ratio, so that a synthetic resin molded article can be obtained that has a matte appearance and a smooth (or rough) feel that imitates the texture of shells, while also having appropriate mechanical properties (e.g., flexural modulus).

[0019] Furthermore, the greater the proportion of finely pulverized shells in the pulverized shells (finely pulverized shells + coarsely pulverized shells) contained in the synthetic resin composition, the stronger the synthetic resin molded product will be, and the greater the proportion of coarsely pulverized shells, the closer the appearance and feel of the synthetic resin molded product will be to the texture of shellfish. Therefore, in order to obtain a synthetic resin molded product that requires strength, it is recommended to increase the proportion of finely pulverized shells in the pulverized shells (finely pulverized shells + coarsely pulverized shells) contained in the synthetic resin composition. On the other hand, in order to obtain a synthetic resin molded product with a texture and feel closer to that of a seashell, it is recommended to increase the proportion of coarsely pulverized shells in the pulverized shells contained in the synthetic resin composition. In short, the respective proportions of finely pulverized shells and coarsely pulverized shells in the synthetic resin composition can be adjusted depending on the properties (strength, appearance, texture, etc.) required of the molded product, the shape and size of the molded product, the type of synthetic resin contained in the synthetic resin composition, etc.

[0020] The type of synthetic resin is not particularly limited, but it is desirable to use thermoplastic resins such as polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), ABS resin, polyamide (PA), polycarbonate (PC), polylactic acid (PLA), polyacetal (POM), polybutylene terephthalate (PBT), or polyethylene terephthalate (PET). Furthermore, it is desirable to use waste plastic (recycled plastic) recovered from discarded home appliances and the like as the synthetic resin. This allows the synthetic resin composition according to this embodiment to be made almost entirely of waste materials, thereby contributing to reducing carbon dioxide emissions and waste in the environment.

[0021] A synthetic resin molded product according to one embodiment of the present invention is obtained by molding the synthetic resin composition into a predetermined shape. The predetermined shape may be a planar shape (e.g., a sheet) or a three-dimensional shape. As described above, by appropriately adjusting the proportion of ground shell material and the proportions of finely ground shell material and coarsely ground shell material contained in the synthetic resin composition, a synthetic resin molded product having excellent strength and a texture, appearance, and feel similar to that of a seashell can be obtained. In particular, by making the synthetic resin molded product have a matte appearance and a smooth (or rough) feel, it is possible to make users aware that the molded product contains seashells, which is expected to have an educational effect on waste issues.

[0022] The molding method for the synthetic resin molded product according to this embodiment is not particularly limited, but for example, injection molding can be suitably used.

[0023] The synthetic resin molded product according to this embodiment may be any article, but may be, for example, an article requiring strength, such as furniture such as a chair or a bench, a housing for an electrical appliance such as a personal computer, an automobile or automobile parts, or a helmet.

[0024] A helmet, which is an example of a synthetic resin molded product according to this embodiment, is shown in Figure 2. This helmet includes a main body 10 that covers the user's head and a chin strap 20 attached to the main body 10, and the main body 10 is made of the above-mentioned synthetic resin composition.

[0025] The surface of the main body 10 is provided with a plurality of ribs (protrusions) 11 extending in the front-to-rear direction. These ribs 11 mimic the structure of a scallop shell and serve to improve the strength of the main body 10. Furthermore, this biomimicry structure and the matte texture reminiscent of a seashell make it clear to the user that the helmet is made using a seashell. [Example]

[0026] The synthetic resin composition and synthetic resin molded article according to the present invention will be described in detail below using examples, but these examples do not limit the present invention, and various changes and modifications can be made without departing from the scope of the present invention.

[0027] [Experimental Example 1] Test pieces were prepared by injection molding using the synthetic resin compositions of Production Examples 1 to 5, and tests were conducted to evaluate the physical properties (mechanical properties) of tensile yield stress, bending stress, bending modulus, and impact strength. The results are shown in Table 1. In Table 1, all "%" represents "mass %." The same applies to Tables 2 to 4 described below.

[0028] [Table 1]

[0029] The synthetic resin composition of Production Example 1 consisted of 100% by mass of polypropylene (referred to as "PP" in Table 1). The synthetic resin compositions of Production Examples 2 to 4 were a mixture of 80% by mass of polypropylene and 20% by mass of crushed scallop shells. The synthetic resin composition of Production Example 5 was a mixture of 80% by mass of polypropylene and 20% by mass of calcium carbonate. The polypropylene contained in the synthetic resin compositions of Production Examples 1 to 5 was a commonly available commercial product. The calcium carbonate contained in the synthetic resin composition of Production Example 5 was a powder with an average particle size of 5 μm, and a commonly available commercial product was used. Meanwhile, the crushed scallop shells contained in the synthetic resin compositions of Production Examples 2 to 4 were discarded scallop shells obtained from Sarufutsu Village, Hakodate City, and Monbetsu City in Hokkaido, which were crushed to 30 μm, 15 μm, or 5 μm using a roller mill or vibro mill without calcination. The discarded scallop shells were left outdoors for 1 to 3 years after disposal, and those from which salt had been sufficiently removed were selected for use. In Experimental Examples 2 and 3 described below, the same polypropylene and crushed scallop shells were used.

[0030] Table 1 shows the MFR (melt flow rate) and density of the synthetic resin compositions of Production Examples 2 to 5. As can be seen from Table 1, although the synthetic resin composition of Production Example 1 had a lower density than the other Production Examples, there was no significant difference in MFR among Production Examples 1 to 5, and it was confirmed that the fluidity of the synthetic resin compositions during molding was equivalent.

[0031] Next, the synthetic resin compositions of Production Examples 1 to 5 were injection molded by known procedures to prepare test pieces, which were then subjected to physical property evaluation tests. The results showed that Production Examples 2 to 4, which contained pulverized scallop shells, were inferior to Production Example 1, which contained polypropylene only, in terms of tensile yield stress and impact strength, but were superior to Production Example 5, which contained calcium carbonate, and Production Examples 2 to 4 were superior to both Production Examples 1 and 5 in terms of flexural stress and flexural modulus. These results confirmed that pulverized scallop shells with average particle sizes of 5 μm, 15 μm, and 30 μm can function as reinforcing materials that contribute to improving the flexural stress and flexural modulus of molded articles.

[0032] [Experimental Example 2] Test pieces were prepared by injection molding using the synthetic resin compositions of Comparative Example 1 and Examples 1 to 4, and tests to evaluate the physical properties of tensile yield stress, bending stress, bending modulus, and impact strength were carried out in the same manner as in Experimental Example 1. The results are shown in Table 2.

[0033] [Table 2]

[0034] The synthetic resin composition of Comparative Example 1 consists solely of polypropylene. Each of the synthetic resin compositions of Examples 1 to 4 consists of a mixture of polypropylene and crushed scallop shells with different average particle sizes. The ratios (mass%) of polypropylene and crushed scallop shells contained in each of the synthetic resin compositions of Examples 1 to 4 are shown in Table 2. Although not shown in Table 2, the synthetic resin composition of Example 4 contains 5 mass% of an elastomer additive.

[0035] In Table 2, "coarse scallop," "medium scallop," and "fine scallop" represent scallop shell finely ground products with average particle sizes of 1000 μm or more and 3000 μm or less, 100 μm or more and less than 1000 μm, and 10 μm or more and 30 μm or less, respectively. "Coarse scallop" and "medium scallop" correspond to the coarsely ground shell products of the present invention, and in particular, "coarse scallop" corresponds to the second coarsely ground product and "medium scallop" corresponds to the first coarsely ground product. Furthermore, "fine scallop" corresponds to the finely ground shell product of the present invention.

[0036] As can be seen from the results in Table 2, Examples 1 to 4 were inferior to Comparative Example 1 in terms of tensile yield stress and impact strength, but their bending stress was equal to or slightly inferior to that of Comparative Example 1, and their bending modulus was superior to that of Comparative Example 1. From this, it was inferred that adding crushed scallop shells to a synthetic resin composition can function as a reinforcing material that contributes to improving the physical properties of synthetic resin molded products, particularly the bending modulus.

[0037] [Experimental Example 3] Test pieces were prepared by injection molding using the synthetic resin compositions of Production Examples 6 to 13, and the effects of the crushed shells contained in the synthetic resin compositions on the design and strength of the synthetic resin molded products obtained from the synthetic resin compositions were investigated. The results are shown in Table 3.

[0038] [Table 3]

[0039] The synthetic resin compositions of Production Examples 6 to 12 consist of polypropylene and crushed scallop shells, and the synthetic resin composition of Production Example 13 contains 5 mass % of an elastomer additive in addition to polypropylene and crushed scallop shells.

[0040] In the "Strength" column of Table 3, "◯" indicates a strength that can be used for disaster prevention helmets, "×" indicates a strength that can be used for molded articles that are not subjected to impacts in normal use, such as ornaments, and "△" indicates a strength that is not sufficient for disaster prevention helmets but is better than "×". The ratios (mass%) of polypropylene and crushed scallop shells contained in the synthetic resin compositions of Production Examples 6 to 13 are shown in Table 3. As in Experimental Example 2, in Table 3, "coarse scallop," "medium scallop," and "fine scallop" indicate finely crushed scallop shells with average particle sizes of 1000 μm or more and 3000 μm or less, 100 μm or more and less than 1000 μm, and 10 μm or more and 30 μm or less, respectively.

[0041] As can be seen from Table 3, in Production Examples 6 and 7, which were synthetic resin compositions made from ground "fine scallops" and polypropylene, the surface of the molded product did not have a matte appearance reminiscent of the texture of a seashell (referred to as "grainy" in Table 3). On the other hand, in Production Examples 8 to 10, which were synthetic resin compositions made from ground "coarse scallops" and polypropylene, a coarse grainy texture was observed on the surface of the molded product. In Production Examples 11 and 12, which were synthetic resin compositions made from ground "medium scallops" and polypropylene, a fine grainy texture was observed. In Production Example 13, which was synthetic resin composition made from ground "coarse scallops" and "medium scallops" and polypropylene, both coarse and fine grainy textures were observed on the surface of the molded product. From the above, it was found that when the total ratio of ground "coarse scallops" and "medium scallops" to the synthetic resin composition was 3% by mass or more, a grainy texture was observed on the surface of the molded product, and these ground scallop shells are useful as design-imparting materials.

[0042] Furthermore, from the results in Table 3, it was inferred that if the synthetic resin composition contains pulverized scallop shells of "fine scallop," "medium scallop," and "coarse scallop," and the ratio of the total amount of these three types of pulverized scallop shells is 10 mass% or less, a molded product strong enough to be used as a disaster prevention helmet can be obtained.

[0043] When the synthetic resin composition of Production Example 13 was injection molded to actually produce the helmet shown in Figure 2, it was confirmed that the helmet had the physical properties required for a disaster prevention helmet.

[0044] Table 4 below summarizes the results of Experimental Examples 1 to 3, showing the relationship between the ratio of synthetic resin to crushed scallop shells contained in the synthetic resin composition and the physical properties (mechanical characteristics) and design of the molded products. In Table 4, the "item" column indicates the name of the synthetic resin composition (for example, "Basic Fine" indicates a basic synthetic resin composition containing crushed scallop shells, and "Physical Properties Emphasis 1" indicates a synthetic resin composition that can produce molded products with excellent physical properties). Each value in Table 4 indicates the proportion (mass%) of synthetic resin (PP) in the synthetic resin composition, or the proportion (mass%) of crushed scallop shells with average particle sizes of "fine," "medium," and "coarse." Note that "fine," "medium," and "coarse" correspond to the aforementioned "fine scallop," "medium scallop," and "coarse scallop." Table 4 reveals that by adjusting the ratio of the synthetic resin and crushed scallop shells contained in the synthetic resin composition, synthetic resin compositions suitable for molded products that emphasize physical properties and synthetic resin compositions suitable for molded products that emphasize design can be obtained.

[0045] [Table 4] [Explanation of symbols]

[0046] 10...Main body 11...Ribs 20...Chin strap

Claims

1. A synthetic resin composition containing a synthetic resin and crushed shells in a mass ratio of 98:2 to 25:75, The shell pulverized material contains finely ground shells having an average particle size of 10 μm or more and 30 μm or less and coarsely ground shells having an average particle size of 100 μm or more and 3000 μm or less in a mass ratio of 97:3 to 40:

60. A synthetic resin composition.

2. The mass ratio of the synthetic resin to the crushed shell material is 97:3 to 45:

55. The synthetic resin composition according to claim 1.

3. The mass ratio of the finely ground shells to the coarsely ground shells is 90:10 to 70:

30. The synthetic resin composition according to claim 1.

4. The coarsely pulverized shell material comprises a first coarsely pulverized material having an average particle size of 100 μm or more and less than 1000 μm, and a second coarsely pulverized material having an average particle size of 1000 μm or more and 3000 μm or less, and the mass ratio of the first coarsely pulverized material to the second coarsely pulverized material is 1:99 to 99:

1. The synthetic resin composition according to claim 1.

5. 2. The synthetic resin composition according to claim 1, wherein the ground shells are ground unburned shells.

6. A synthetic resin molded product obtained by molding the synthetic resin composition according to any one of claims 1 to 5 into a predetermined shape.

7. A helmet formed by molding a synthetic resin composition comprising synthetic resin and crushed shells in a mass ratio of 98:2 to 25:75, wherein the crushed shells comprise finely crushed shells having an average particle size of 1 μm or more and 100 μm or less and coarsely crushed shells having an average particle size of 100 μm or more and 10,000 μm or less in a mass ratio of 97:3 to 40:60, wherein the coarsely crushed shells consist of first coarsely crushed shells having an average particle size of 100 μm or more and less than 1,000 μm and second coarsely crushed shells having an average particle size of 1,000 μm or more and 3,000 μm or less, the mass ratio of the first coarsely crushed shells to the second coarsely crushed shells being 1:99 to 99:1, and wherein the helmet is provided with a plurality of ridges extending in the front-to-rear direction on its outer surface.

8. A shell pulverization process for pulverizing shells to obtain finely pulverized shells having an average particle size of 10 μm or more and 30 μm or less and coarsely pulverized shells having an average particle size of 100 μm or more and 3000 μm or less; a synthetic resin composition producing step of obtaining a synthetic resin composition by mixing the finely pulverized shell material and the coarsely pulverized shell material with a molten synthetic resin; and In the synthetic resin composition production step, the ratio of the mass of the synthetic resin to the total mass of the shell pulverized material, which is the sum of the mass of the finely pulverized shell material and the mass of the coarsely pulverized shell material added to the synthetic resin, is 98:2 to 25:75, and the ratio of the mass of the finely pulverized shell material to the mass of the coarsely pulverized shell material in the total mass of the shell pulverized material is 97:3 to 40:

60. A method for producing a synthetic resin composition.

9. In the shell pulverization step, the shells are pulverized in an unfired state to obtain the finely pulverized shells and the coarsely pulverized shells. A method for producing the synthetic resin composition according to claim 8.

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