Resin composition and method for producing same

Abstract

Provided is a resin composition containing a biomass filler surface-treated with a silane coupling agent. The resin composition comprises a biomass filler containing calcium carbonate and protein derived from biomass; and a thermoplastic resin. The biomass filler is surface-treated by reacting a carboxy group, an amino group, or a hydroxy group contained in the protein contained in the biomass filler with an alkoxy group of the silane coupling agent.

Description

Resin Composition and Method for Producing the Same

[0001] The present disclosure relates to a resin composition excellent in strength and environmental compatibility, and a method for producing the same, using a biomass filler and a thermoplastic resin as raw materials.

[0002] Amid the deepening of global environmental problems such as climate change and ocean pollution, the generation of energy by burning fossil fuels and the use of products such as plastics made from fossil fuels are being reexamined, and the realization of a decarbonized society has become a major challenge for society as a whole. Among these, reducing the use of plastics derived from fossil fuels and replacing them with bio-based resources as much as possible directly leads to reducing the use of fossil fuels, and if bio-based resources can be decomposed in nature, it is expected to contribute to preventing ocean pollution and the like. Even when combustion treatment is carried out as the final disposal, if it is derived from living organisms, the material balance in the biosphere, including carbon and other constituent elements, does not change, and the increase of greenhouse gases such as carbon dioxide in the atmosphere is also suppressed.

[0003] Under such a background, technologies that incorporate bio-based fillers into plastics to reduce the use of fossil fuels will become even more important in the future. For example, as a method of mixing highly hydrophobic polypropylene and cellulose having a hydrophilic surface, Patent Document 1 discloses a method of carboxymethylating cellulose fibers and complexing them with a polymer having an amino group or an acid-modified polyolefin resin.

[0004] Among thermoplastic resins, so-called engineering plastics such as polyamide, which are excellent in strength, have particularly poor wettability with cellulose and are difficult to complex. Patent Document 2 discloses that when polyamide and cellulose fibers are complexed, polyphenylene ether is added to promote homogeneous complexation and increase strength.

[0005] Patent Document 3 also discloses heat resistance improvement of cellulose fiber by acetylating hydroxyl groups on the surface of cellulose fibers, and strength improvement by protecting cellulose fibers from damage by heating during complexation.

[0006] Furthermore, as an inorganic filler with excellent heat resistance, Patent Document 4 discloses a resin composition with excellent rigidity and impact resistance obtained by blending calcium carbonate and talc with styrene resin.

[0007] WO2014 / 087767, WO2021 / 080010, Japanese Patent Publication No. 2021-187885, Japanese Patent Publication No. 2008-195883

[0008] Although efforts to increase the strength of resins by using calcium carbonate as a filler are known, as described above, the affinity between the surface of calcium carbonate, a type of metal salt, and the resin is low, resulting in insufficient strength of the composite resin. Furthermore, even when attempting to use silane coupling agent treatments, which are widely used to improve the affinity between resins and fillers, the surface of calcium carbonate does not have hydroxyl groups that can chemically adsorb silane coupling agents. Therefore, silane coupling agents are not an effective means of improving affinity, and sufficient strength improvement cannot be expected.

[0009] In view of the foregoing, this disclosure is the result of the inventors' diligent efforts and aims to provide a resin composition containing a biomass filler surface-treated with a silane coupling agent.

[0010] The resin composition according to this disclosure comprises a biomass filler containing biomass-derived calcium carbonate and protein, and a thermoplastic resin, wherein the biomass filler is surface-treated by a reaction between a carboxyl group, an amino group, or a hydroxyl group contained in the protein contained in the biomass filler and an alkoxy group of a silane coupling agent.

[0011] A method for producing a resin composition according to this disclosure includes the steps of surface-treating a biomass filler containing calcium carbonate and protein with a silane coupling agent, and stirring and kneading a powder mixture of a thermoplastic resin and the surface-treated biomass filler while heating and melting it.

[0012] According to the resin composition of this disclosure, the biomass filler is surface-treated by a reaction between the carboxyl group, amino group, or hydroxyl group contained in the protein of the biomass filler and the alkoxy group of the silane coupling agent. This enhances the interaction between the thermoplastic resin and the biomass filler, thereby enabling a high-strength resin composition.

[0013] This figure shows the initial state of the reaction between chitin and 3-glycidoxypropyltrimethoxylan, and a structural formula of a portion of the reaction product. Table 1 shows the parts by weight of each raw material and the evaluation results of the bending strength in Examples 1 to 6 and Comparative Examples 1 to 3.

[0014] The resin composition according to the first embodiment comprises a biomass filler containing biomass-derived calcium carbonate and protein, and a thermoplastic resin, wherein the biomass filler is surface-treated by a reaction between a carboxyl group, an amino group, or a hydroxyl group contained in the protein contained in the biomass filler and an alkoxy group of a silane coupling agent.

[0015] The resin composition according to the second embodiment is, in the first embodiment, the surface treatment is performed with an alkoxysilane, the alkoxysilane being an alkoxysilane represented by the chemical formula YnSi(OR)4-n, where n is an integer from 1 to 3, Y is at least one of the group consisting of a glycidoxypropyl group, a styryl group, an acrylate group, a methyl methacrylate group, a vinyl group, a thiolpropyl group, and an aminopropyl group, and R may be any alkyl group having 1 to 5 carbon atoms.

[0016] The resin composition according to the third embodiment is, in the first embodiment, the surface treatment is performed with an alkoxysilane, the alkoxysilane being an alkoxysilane represented by the chemical formula Si(OR1)x(R2)4-x, where x is an integer from 2 to 4, R1 is any alkyl group having 1 to 5 carbon atoms, and R2 is any organic functional group having 1 to 10 carbon atoms.

[0017] In the fourth embodiment, the resin composition is characterized in that, in the first or second embodiment, the surface treatment is performed with an alkoxysilane, and the alkoxysilane may be at least one selected from the group consisting of 3-glycidoxydoxypropyltrimethoxysilane, 3-glycidoxydoxypropyltriethoxysilane, 3-glycidoxydoxypropylmethyldimethoxysilane, and 3-glycidoxydoxypropylmethyldiethoxysilane.

[0018] In the fifth embodiment, the resin composition is characterized in that, in the first or second embodiment, the surface treatment is performed with an alkoxysilane, and the alkoxysilane may be n-hexyltrimethoxysilane.

[0019] In the sixth embodiment, the resin composition may, in any of the first to fifth embodiments, contain a biomass filler derived from seashells or eggshells.

[0020] In the seventh embodiment, the resin composition is such that the shell may be a scallop or an oyster.

[0021] In the eighth embodiment of the resin composition, the calcium carbonate content may be 20% by weight or more and 70% by weight or less, in any of the first to seventh embodiments described above.

[0022] In the ninth embodiment, the resin composition may be a polyamide in any of the first to eighth embodiments described above, where the thermoplastic resin is a polyamide.

[0023] In the resin composition according to the tenth embodiment, the polyamide may be at least one selected from the group consisting of nylon 6, nylon 66, a polyamide polymer of sebaciac acid and metaxylylenediamine, a polyamide polymer of sebaciac acid, metaxylylenediamine and paraxylylenediamine, a polyamide polymer of sebaciac acid, paraxylylenediamine and paraxylylenediamine, and poly(metaxylyleneadipamide).

[0024] A method for producing a resin composition according to the eleventh embodiment includes the steps of surface-treating a biomass filler containing calcium carbonate and protein with a silane coupling agent, and stirring and kneading a powder mixture of a thermoplastic resin and the surface-treated biomass filler while heating and melting it.

[0025] The resin compositions and methods for producing the same according to embodiments of this disclosure will be described in detail below.

[0026] (Embodiment 1) <Resin Composition> The resin composition according to Embodiment 1 comprises a biomass filler containing biomass-derived calcium carbonate and protein, and a thermoplastic resin. The biomass filler is surface-treated by a reaction between a carboxyl group, an amino group, or a hydroxyl group contained in the protein contained in the biomass filler and an alkoxy group of a silane coupling agent.

[0027] In the resin composition according to Embodiment 1, for example, terminal functional groups or parts of the skeletal structure of the thermoplastic resin react or interact with the functional groups of the silane coupling agent that surface-treats the biomass filler. This strengthens the interaction between the thermoplastic resin and the biomass filler, resulting in a high-strength resin composition with fewer defects that could trigger fracture.

[0028] <Raw Materials> <Thermoplastic Resin> The thermoplastic resin is not limited to any particular type; it should be one that deforms upon thermal melting by heating and can be mixed with biomass filler. It may also be a mixture of multiple thermoplastic resins. Examples of thermoplastic resins include polyethylene, polyvinyl chloride, polypropylene, polystyrene, acrylonitrile butadiene styrene, acrylonitrile styrene, polymethyl methacrylate, polybutylene terephthalate, polyethylene terephthalate, polyamide, polyoxymethylene, polyvinyl alcohol, polyphenylene ether, polycarbonate, polyphenylene sulfide, aromatic polyether ketone, polyimide, polyamide polymer of sebaciac acid and metaxylylenediamine, polyamide polymer of sebaciac acid, metaxylylenediamine and paraxylylenediamine, poly(metaxylylene adipamide), etc. In particular, materials with a softening temperature of 150°C to 250°C are preferred due to their ease of melting during manufacturing and their thermal stability during use.

[0029] Furthermore, it is preferable that the thermoplastic resin has reactivity with the chemically active site of the silane coupling agent, and from this viewpoint, it is preferable that it has amino groups, hydroxyl groups, carboxyl groups, thiol groups, or ester structures, amide structures, urea structures, amine structures, or cyano structures. From the above viewpoint, polyamides and polyesters are particularly preferred as thermoplastic resins, and particularly preferred specific examples include the polyamides nylon 6, nylon 66, and poly(metaxylylene adipamide), and from the viewpoint that the thermoplastic resin itself contains naturally derived sebacic acid as a raw material, polyamide polymers of sebacic acid and metaxylenediamine, polyamide polymers of sebacic acid, metaxylenediamine and paraxylenediamine, and polyamide polymers of sebacic acid, paraxylenediamine and paraxylenediamine. Furthermore, as for polyamides, it is preferable to select one with a high glass transition temperature from the viewpoint that it is possible to suppress the decrease in strength under high temperature conditions. Specifically, it is preferable that the glass transition temperature exceeds 50°C. Therefore, polyamide polymers of sebaic acid and metaxylylenediamine, polyamide polymers of sebaic acid, metaxylylenediamine and paraxylylenemine, polyamide polymers of sebaic acid, paraxylylenediamine and paraxylylenemine, and poly(metaxylylene adipamide) can be suitably used because their glass transition temperatures are 60°C, 63°C, 73°C, 75°C, and 85°C, respectively. Among these, poly(metaxylylene adipamide) is particularly suitable from the viewpoint of having a glass transition temperature exceeding 80°C. Furthermore, poly(metaxylylene adipamide) is preferred because it is a polymer that also possesses flame retardancy due to having a benzene ring in its structure.

[0030] <Biomass Filler> Figure 1 shows the initial state of the reaction between chitin and 3-glycidoxypropyltrimethoxylan, and a structural formula showing a portion of the reaction product. As a biomass filler, for example, the following known naturally derived materials can be used. That is, calcium carbonate powder obtained by crushing shellfish such as scallops, surf clams, and oysters, coral shells, eggshells, etc., or calcium oxide powder obtained by calcining and crushing can be used. Because these biomass fillers are biomass, they contain proteins such as conchiolin and chitin. These protein complexes such as conchiolin and chitin act as adsorption reaction sites for the silane coupling agent. For example, as shown in Figure 1, the hydroxyl groups, etc., that these possess can bond with silanol groups produced by hydrolysis of the alkoxy groups of the silane coupling agent through a dehydration condensation reaction. As a result, a biomass filler surface-treated with a silane coupling agent can be obtained.

[0031] Furthermore, the longest part length of a single particle of these biomass filler powders can be, for example, approximately 50 nm to 500 μm. If it is smaller than 50 nm, aggregation becomes severe, making dispersion difficult during heat melt mixing. If it is larger than 500 μm, it is prone to clogging in the mold channel during molding, reducing fluidity and making molding difficult. From the viewpoint of achieving both suppression of aggregation and suppression of fluidity reduction, a length of 100 nm to 100 μm is preferable. In addition, the biomass filler may be pre-coated with fatty acids, resin acids, cationic surfactants, lignin, etc. If it is coated, it is preferable from the viewpoint of improving compatibility with the thermoplastic resin mentioned above and facilitating uniform dispersion. The amount of biomass filler added can be 20% by weight to 90% by weight. If it is less than 20% by weight, the effect of increasing strength cannot be sufficiently achieved, and if it is greater than 90% by weight, the resin component ratio becomes too low, which is undesirable as it causes a decrease in fluidity due to aggregation of biomass fillers. From the perspective of ensuring high strength and fluidity, a concentration of 40% to 60% by weight is even more preferable.

[0032] Compared to calcium carbonate obtained by conventional inorganic synthesis, biomass fillers contain carboxyl and amino groups derived from proteins, as described above. Therefore, when atomic absorption spectrometry is performed, carbon and nitrogen derived from these functional groups are detected. In particular, in the case of biomass fillers obtained from scallop shells, the cross-section forms an inner layer with a leaf-like structure, an intermediate layer with a cross-lamellar structure, and an outer layer, and such layered structures can sometimes be observed in biomass fillers. The protein described above has a structure in which columnar calcium carbonate crystals of calcite, which constitute the inner layer, are arranged, and the protein is continuously inserted between these crystals.

[0033] Furthermore, when the biomass filler is eggshell, it contains a cuticle layer made of polysaccharides that covered the outside of the egg, pores, outer eggshell membrane, inner eggshell membrane, papillary segments adjacent to the outer eggshell membrane, and papillary nuclei at the tips of the papillary segments. A columnar structure of calcium carbonate deposits can be observed starting from the papillary nuclei. Among these, the eggshell membrane is composed of protein, and the amino groups, carboxyl groups, and hydroxyl groups contained in these proteins react with silane coupling agents, thereby treating the surface of the biomass filler.

[0034] <Alkoxysilane> For example, reactive alkoxysilanes or non-reactive alkoxysilanes can be used as alkoxysilanes for surface treatment of biomass fillers.

[0035] <Reactive Alkoxysilanes> Here, the reactive alkoxysilane is an alkoxysilane represented by the chemical formula YnSi(OR)4-n, where n is an integer from 1 to 3, from the viewpoint of having a reactive organic functional group. Y can be, for example, a glycidoxypropyl group, a styryl group, an acrylate group, a methyl methacrylate group, a vinyl group and its derivatives, a thiolpropyl group, or an aminopropyl group. Furthermore, a reaction induction method such as a photoreaction, a thermal reaction, or a combination thereof can be appropriately selected. In addition, two or more of these functional groups may be used in combination. In particular, thiolpropyl groups and aminopropyl groups can polymerize glycidoxypropyl groups, and therefore can be suitably mixed and used with glycidoxypropyl groups. R is not limited, but can be an alkyl group having 1 to 5 carbon atoms, and specifically, examples include methoxysilane, ethoxysilane, propoxysilane, butoxysilane, diethoxydimethoxysilane, etc. Among these, methoxysilane and ethoxysilane are preferred from the viewpoint of easy hydrolysis and easy reaction control.

[0036] Surface treatment with alkoxysilanes is generally carried out by dehydration condensation between silanol groups, which are generated by the hydrolysis of the alkoxy group, and hydroxyl groups present on the surface of the object. In the case of biomass fillers, dehydration condensation occurs between hydroxyl groups present in polypeptides such as conchiolin or chitin, which are contained as impurities in the calcium carbonate that is the main component of the biomass filler, and silanol groups, thereby surface-treating the biomass filler. Suitable resins for dispersing biomass fillers surface-treated with such reactive alkoxysilanes include polyesters having carboxyl groups at the ends, or polyamides having amino groups at the ends in addition to carboxyl groups. If polyamides have amino groups at the ends, and the silane coupling material has reactive organic functional groups, specifically epoxy groups, the epoxy groups and amino groups react to directly chemically bond the polyamides and fillers, which is preferable from the viewpoint of improving strength.

[0037] <Range of Silane Coupling Agent Addition> The amount of silane coupling agent to be added can be between 0.05% by weight and 5% by weight relative to 100% by weight of the biomass filler. If it is less than 0.05% by weight, the surface treatment of the biomass filler cannot be sufficiently performed, and if it is greater than 5% by weight, polymers will form between the silane coupling agents, which will become foreign matter and is therefore undesirable.

[0038] <Non-reactive alkoxysilane> Here, the non-reactive alkoxysilane can have 2 to 4 alkoxy groups x, and is represented by the chemical formula Si(OR1)x(R2)4-x (where x is an integer from 2 to 4). R1 ​​is preferably an alkyl group having 1 to 5 carbon atoms, as described above. R2 is not limited, but can be an organic functional group having 1 to 10 carbon atoms, for example. Functional groups with more than 11 carbon atoms cause greater steric hindrance, inhibiting polymerization when a sol-gel cured product is formed by polymerization, making polymer formation difficult. Specifically, R2 can be hydrocarbon groups such as methyl, ethyl, vinyl, propyl, butyl, hexyl, phenyl, cyclohexyl, octyl, decyl, and allyl groups, as well as γ-chloropropyl and fluorohydrocarbon groups in which hydrogen is replaced by fluorine, γ-mercaptopropyl, γ-methacryloyloxypropyl, and other substituted hydrocarbon groups. The second alkoxysilane may be a mixture of two or more alkoxysilanes that satisfy the above conditions. Similar to the case of reactive alkoxysilanes, dehydration condensation occurs between the silanol group produced by hydrolysis of the alkoxy group and the hydroxyl group present in the polypeptide such as conchiolin and chitin contained in the biomass filler, thereby surface-treating the biomass filler. The R2 of the non-reactive alkoxysilane makes the surface of the biomass filler a hydrophobic surface, improving its affinity with particularly hydrophobic thermoplastic resins. As the resin in which the biomass filler surface-treated with such non-reactive alkoxysilane is dispersed, mainly highly hydrophobic thermoplastic resins, specifically polyethylene, polyvinyl chloride, polypropylene, polystyrene, and acrylonitrile butadiene styrene can be suitably used. Furthermore, when a hexyl group is used as the alkoxysilane, the silane coupling material molecule does not become too large, making surface treatment easier. In addition, since the hexyl group is a saturated hydrocarbon, it has high compatibility with polypropylene, and since polypropylene is a resin with excellent moldability, this combination is particularly preferred.

[0039] <Method for producing the resin composition> The method for producing the resin composition according to Embodiment 1 includes the following two steps: i) A step of surface-treating a biomass filler containing calcium carbonate and protein with a silane coupling agent (surface treatment of biomass filler). ii) A step of heating and melting a powder mixture of a thermoplastic resin and the surface-treated biomass filler, while stirring and kneading (heating and melting, stirring, and kneading of the powder mixture).

[0040] The following explains the two processes described above in order.

[0041] <Surface Treatment (Surface Modification) of Biomass Filler> Multiple methods can be used for the first step, which is the surface treatment of the biomass filler. For example, a dispersion liquid may be prepared by dispersing the biomass filler in a solvent such as water or alcohol, and a specified amount of alkoxysilanes may be added dropwise to the dispersion liquid while stirring, and then the solvent may be evaporated while heating the dispersion liquid in a heating furnace. Alternatively, surface modification may be performed by stirring and mixing the biomass filler and alkoxysilanes in a known dry blending device such as a Henschel mixer. The amount of alkoxysilanes used for surface modification is not limited, but it can be 0.1% by weight or more and 2% by weight or less relative to the weight of the biomass filler. If the amount is less than 0.1% by weight, the amount of alkoxysilanes is too small, and the effect of the reaction or interaction with the resin composition due to surface modification is insufficient. If the amount is more than 2% by weight, aggregates may be formed due to the reaction of alkoxysilanes with each other, which may hinder the uniform dispersion of the biomass filler. As described above, by using biomass fillers whose surfaces are modified with reactive or non-reactive alkoxysilanes, a high-strength resin composition can be obtained through strong interaction between the surface of the biomass filler and the thermoplastic resin.

[0042] <Heating, melting, stirring, and kneading of powder mixture (compounding method)> The second step, heating, melting, stirring, and kneading of the powder mixture (compounding method), may involve mixing a specified amount of thermoplastic resin and surface-treated biomass filler to form a mixture, which may then be heated, melted, kneaded, and cooled. First, to mix, each component may be weighed into a container or bag and mixed manually using a spatula or a rod-shaped jig that can be used for stirring. Alternatively, a rotary mixer such as a Henschel mixer may be used to mix the components substantially uniformly. Mixing may also be done by physical mixing. From the viewpoint of ease of the above mixing process, the thermoplastic resin is preferably in powder or pellet form. Next, heating, melting, and kneading can be carried out using a single-screw (uniaxial) kneader, twin-screw kneader, roll kneader, kneader, Banbury mixer, etc. for the substantially uniformly mixed mixture. Furthermore, heating, melting, and kneading can be performed in combination. After heating, melting, and kneading, the mixture can be cooled to a temperature at which pulverization is possible to obtain a resin composition. Furthermore, other additives such as pigments and flame retardants can be added to the mixture during heating, melting, and kneading, depending on the application.

[0043] According to the method for producing the resin composition of Embodiment 1, during the heating and melting process, the functional groups of the silane coupling agent used to surface-treat the biomass filler can be reacted or interacted with, for example, terminal functional groups or a part of the skeletal structure of the thermoplastic resin. This strengthens the interaction between the thermoplastic resin and the biomass filler, resulting in a high-strength resin composition with fewer defects that could trigger fracture.

[0044] When the resin composition manufactured in this way is molded and applied, for example, to industrial parts, the biomass content is higher than that of conventional resin molded articles due to the inclusion of biomass fillers, contributing to a reduction in environmental impact. At the same time, because the biomass fillers are surface-treated, they strongly interact with the thermoplastic resin, resulting in an excellent molded article that achieves both environmental friendliness and high strength. For example, a resin composition that is a composite of an engineering plastic such as polyamide and a biomass filler can be provided.

[0045] Hereinafter, the embodiments will be specifically described.

[0046] (Embodiment 1) As a thermoplastic resin, 59.7 parts by weight of poly(meta-xylylene adipamide), which is a kind of polyamide (Mitsubishi Gas Chemical Company, Inc., Nylon MXD6, hereinafter referred to as Nylon MXD6), and 39.8 parts by weight of a surface-modified biomass filler were prepared.

[0047] <Manufacture of surface-modified biomass filler> In this embodiment, the surface treatment of the surface-treated biomass filler was performed with an epoxy group-containing alkoxysilane by the following method. (1) 1.23 parts by weight of a scallop shell biomass filler (Hokkai Industry Co., Ltd. (scallop biomass filler k)) obtained by dry-crushing scallop shells as a biomass filler and 0.50 parts by weight of 3-glycidoxypropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd., KBM403) as an epoxy group-containing alkoxysilane as a surface treatment agent were prepared. (2) Cellulose fibers were put into a Henschel mixer, and 3-glycidoxypropyltrimethoxysilane was put into a syringe. While stirring the cellulose fibers in the Henschel mixer at a rotation speed setting of 1000 rpm, the needle of the syringe was inserted through the syringe hole provided in the lid of the Henschel mixer, and 3-glycidoxypropyltrimethoxysilane was injected therein. After the injection, the rotation was continued for another 10 minutes, and after the rotation was completed, the epoxy surface-modified biomass filler, that is, the scallop biomass filler surface-modified with epoxy in this embodiment, was recovered from the Henschel mixer.

[0048] (3) Poly(meta-xylylene adipamide) and the epoxy surface-modified scallop biomass filler were put into a single polyethylene bag, and the bag was manually shaken and mixed for 5 minutes. (4) While sequentially charging the mixture into the hopper portion of a twin-screw kneader set at 260°C, it was heated and melted and kneaded while extruding at a rotational speed of 100 rpm for the shaft, and the molten mixture from the discharge port was recovered to obtain the resin composition in this embodiment.

[0049] The resin composition used in this experiment was injection molded according to the following procedure. The resin composition was crushed into a powder using a pulverizer, and then dumbbell-shaped test specimens of the resin composition were prepared using an injection molding machine (Japan Steel Works 180AD) with the prepared powder. The conditions for preparing the dumbbell-shaped test specimens were a resin temperature of 240°C, a mold temperature of 80°C, an injection speed of 60 mm / s, and a holding pressure of 100 MPa. For measuring the elastic modulus and elongation at the breaking point, a multi-purpose dumbbell-shaped test specimen of JIS K7139 Type A1 was prepared.

[0050] (Example 2) This example is the same as Example 1, except that a biomass filler made from dry-milled oyster shells was used as the biomass filler.

[0051] (Example 3) This example is the same as Example 1, except that a biomass filler made by dry-grinding eggshells was used as the biomass filler.

[0052] (Comparative Example 1) This is the same as Example 1, except that no surface treatment was performed on the biomass filler, and 60 parts by weight of MXD6 was used as the thermoplastic resin and 40 parts by weight of scallop biomass filler K was used as the biomass filler.

[0053] (Comparative Example 2) This is the same as Example 1, except that 39.8 parts by weight of calcium carbonate, an inorganic material, was prepared instead of biomass filler.

[0054] (Example 4) This is the same as Example 1, except that 59.7 parts by weight of polypropylene was prepared as the thermoplastic resin, 39.8 parts by weight of scallop biomass filler (Tomoe Kogyo Co., Ltd. (Scallop Biomass Filler K)) which was obtained by dry grinding scallop shells was prepared as the biomass filler, and n-hexyltrimethoxysilane was prepared as the surface treatment agent.

[0055] (Comparative Example 3) This is the same as Example 4 except that no surface treatment was performed on the biomass filler.

[0056] (Example 5) This is the same as Example 1, except that 0.5 parts by weight of 3-aminopropyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd. KBM903) was prepared as an amino group-containing alkoxysilane as a surface treatment agent.

[0057] (Example 6) This is the same as Example 1, except that 0.5 parts by weight of n-hexyltrimethoxysilane (Shin-Etsu Chemical Co., Ltd. KBM903) was prepared as an amino group-containing alkoxysilane as a surface treatment agent.

[0058] (Evaluation of bending strength) The obtained dumbbell test specimens were subjected to a three-point bending test, and their bending strength was measured.

[0059] Table 1 in Figure 2 shows the weight and flexural strength evaluation results for each raw material in Examples 1-6 and Comparative Examples 1-3. The following can be seen from Table 1 in Figure 2: A comparison between Example 1 and Comparative Example 1 shows that surface treatment of the biomass filler improves the strength of the resin composition. A comparison between Examples 1, 2, and 3 and Comparative Example 2 shows that the effect of surface treatment is greater on biomass filler than on calcium carbonate. A comparison between Example 1 and Comparative Example 1, and between Example 4 and Comparative Example 3, shows that by selecting an appropriate surface treatment agent according to the resin, it is possible to improve the strength of the resin composition compounded with biomass filler.

[0060] A comparison of Examples 1, 5, and 6 shows that treating the biomass filler with a silane coupling agent having functional groups such as epoxy groups or amino groups that react with impurities such as proteins contained in the biomass filler as a surface treatment agent significantly improves strength compared to treating it with a silane coupling agent that does not have functional groups. A comparison of Examples 7 and 8 with Reference Examples 1 and 2 shows that for higher strength, it is preferable for the amount of silane coupling agent added to be between 0.05 and 5% of the total weight of the filler and the silane coupling agent.

[0061] As described above, the resin composition according to this embodiment has excellent strength and can be applied to various industrial products that are in harmony with the environment.

Claims

1. A resin composition comprising a biomass filler containing biomass-derived calcium carbonate and protein, and a thermoplastic resin, wherein the biomass filler is surface-treated by a reaction between a carboxyl group, an amino group, or a hydroxyl group contained in the protein contained in the biomass filler and an alkoxy group of a silane coupling agent.

2. The resin composition according to claim 1, wherein the surface treatment is performed with an alkoxysilane, the alkoxysilane is an alkoxysilane represented by the chemical formula YnSi(OR)4-n, where n is an integer from 1 to 3, Y is at least one selected from the group consisting of a glycidoxypropyl group, a styryl group, an acrylate group, a methyl methacrylate group, a vinyl group, a thiolpropyl group, and an aminopropyl group, and R is any alkyl group having 1 to 5 carbon atoms.

3. The resin composition according to claim 1, wherein the surface treatment is performed with an alkoxysilane, the alkoxysilane is an alkoxysilane represented by the chemical formula Si(OR1)x(R2)4-x, where x is an integer from 2 to 4, R1 is any alkyl group having 1 to 5 carbon atoms, and R2 is any organic functional group having 1 to 10 carbon atoms.

4. The resin composition according to claim 1, wherein the surface treatment is performed with an alkoxysilane, and the alkoxysilane is at least one selected from the group consisting of 3-glycidoxydoxypropyltrimethoxysilane, 3-glycidoxydoxypropyltriethoxysilane, 3-glycidoxydoxypropylmethyldimethoxysilane, and 3-glycidoxydoxypropylmethyldiethoxysilane.

5. The resin composition according to claim 1, wherein the surface treatment is performed with an alkoxysilane, and the alkoxysilane is n-hexyltrimethoxysilane.

6. The resin composition according to any one of claims 1 to 5, wherein the biomass filler comprises calcium carbonate derived from seashells or eggshells.

7. The resin composition according to claim 6, wherein the seashell is a scallop or an oyster.

8. The resin composition according to any one of claims 1 to 7, wherein the calcium carbonate content is 20% by weight or more and 70% by weight or less.

9. The resin composition according to any one of claims 1 to 8, wherein the thermoplastic resin is a polyamide.

10. The resin composition according to claim 9, wherein the polyamide is at least one selected from the group consisting of nylon 6, nylon 66, a polyamide polymer of sebaciac acid and metaxylylenediamine, a polyamide polymer of sebaciac acid, metaxylylenediamine and paraxylylenediamine, a polyamide polymer of sebaciac acid, paraxylylenediamine and paraxylylenediamine, and polymetaxylylene adipamide.

11. A method for producing a resin composition, comprising the steps of: surface-treating a biomass filler containing calcium carbonate and protein with a silane coupling agent; and stirring and kneading a powder mixture of a thermoplastic resin and the surface-treated biomass filler while heating and melting it.