Composite resin composition, and production method of non-edible modified biomass

Abstract

To improve mixing property of a thermoplastic resin with a biomass and to improve lowering of fluidity in molding due to heightening of melt viscosity of a composite resin composition, being a problem in molding, by making an active hydrogen contained in a non-edible biomass with a controlled particle diameter react with a monoisocyanate with a long chain functional group or an acid anhydride with a long chain functional group so as to introduce long chain functional groups in the biomass via a urethane bond or an ester bond.SOLUTION: In a composite resin composition produced by kneading a non-edible biomass having a volume-average particle diameter controlled to 50 micrometers or less, or a non-edible modified biomass having a functional group introduced by a monoisocyanate or an acid anhydride after controlling the volume-average particle diameter, and 10-80 mass% of a biopolymer or a thermoplastic resin derived from a petroleum-derived raw material, the non-edible biomass is uniformly dispersed in the thermoplastic resin so that an increase in the melt viscosity is suppressed, and the fluidity important for resin molding is greatly improved.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for producing modified biomass and a method for producing a composite resin composition containing the modified biomass.

Background Art

[0002] Research and development of carbon-neutral materials with an awareness of circular economy are being promoted worldwide. Wood-Plastic Composite (WPC) produced by kneading biomass materials mainly composed of inedible plants and thermoplastic resins such as polyethylene and polypropylene, and then injection molding or extrusion molding the pellets is one of them.

[0003] As the biomass material for WPC, wood powder obtained by pulverizing wood mainly composed of cellulose to 100 to 300 micrometers is used. As the thermoplastic resin, polypropylene (PP), polyethylene (PE), polystyrene (PS), etc. are used because the wood powder as a filler starts thermal decomposition when it exceeds 200°C, and WPC is produced by extrusion molding, injection molding, etc.

[0004] For the production of WPC, performance called moldability such as fluidity is very important. However, biomass such as wood has high hydrophilicity because it is mainly composed of cellulose having a hydroxyl group, and it is difficult to be uniformly dispersed in a highly hydrophobic thermoplastic resin, leading to an increase in the melt viscosity which is an index of fluidity.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Non-Patent Documents

[0006]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] Due to the recent increase in biomass power generation, the problem of securing wood powder has become apparent. In recent years, the non-edible parts of agricultural crops or unused biomass have been increasing. Although they are reused in abandoned bamboo groves, farmland restoration, livestock bedding, etc., the advanced utilization (higher added value) of rice husk resources, which is costly in collection and transportation, is also desired.

[0008] In order to achieve carbon neutrality, increasing the proportion of biomass (biomass content) in the composite resin composition has been studied. When simply increasing the biomass content, the hydroxyl groups present on the biomass surface increase, causing the biomass to aggregate and preventing uniform mixing with the thermoplastic resin. As a result, the melt viscosity of the composite resin composition increases, leading to a decrease in fluidity during molding. As a countermeasure, a method of improving the miscibility by acid-modifying a part of the structure of the thermoplastic resin has been proposed. For example, in Japanese Patent Application Laid-Open No. 2002-38018, maleic acid-modified polypropylene is blended to enhance the miscibility between wood powder and synthetic resin used in the composition for synthetic wood, but it is insufficient for improving the fluidity of the composite resin composition.

Means for Solving the Problems

[0009] The present invention reacts the active hydrogen contained in inedible biomass with controlled particle size with a monoisocyanate having a long-chain functional group or an acid anhydride having a long-chain functional group, and introduces the long-chain functional group into the biomass via a urethane bond or an ester bond, thereby improving the miscibility of the thermoplastic resin and the biomass and improving the decrease in fluidity during molding due to the increase in the melt viscosity of the composite resin composition, which was a problem during molding.

[0010] Furthermore, based on the finding that by using biopolyethylene or polylactic acid, which are bioplastics, as the thermoplastic resin, a composite material with a higher biomass content can be obtained more efficiently.

[0011] By reacting the active hydrogen contained in inedible biomass with controlled particle size, such as cellulose and chitin (chitin, chitosan), with a monoisocyanate having a functional group and an acid anhydride having a functional group, the modified inedible biomass is uniformly dispersed in the thermoplastic resin during kneading. As a result, the melt viscosity of the composite resin composition decreases, and good moldability in extrusion molding and injection molding can be ensured.

[0012] In addition, the present invention is also effective not only for modifying biomass but also for adjusting the hydrophilicity of plastics such as polyvinyl alcohol having a hydroxyl group in the molecule.

Brief Description of the Drawings

[0013]

Figure 1

Embodiments for Carrying Out the Invention

[0014] The definitions and meanings of the terms and notations in this specification are shown below. [Grinding] The pulverization technology is classified into coarse pulverization (several centimeters), medium pulverization (several millimeters to several hundred micrometers), fine pulverization (100 micrometers to several tens of micrometers), and ultrafine pulverization (less than several micrometers) according to the fineness of the pulverized powder, and the pulverization is carried out in a dry or wet manner. In the present invention, considering the productivity during kneading with the thermoplastic resin after pulverization, fine pulverization to ultrafine pulverization was carried out by a dry method.

[0015] [Biomass] The inedible biomass used in the present invention preferably has a hydroxyl group or an amino group that reacts with isocyanate. For example, wood such as hardwood and softwood, construction-generated wood, residues from sawmills, rice straw, wheat straw, rice husks, bamboo, residues of resource crops (sugarcane, corn, rapeseed, etc.), and inedible and unused biomass obtained from crab shells and shrimp shells can be mentioned. These may be used alone or in combination of two or more.

[0016] [Modification of Biomass] In the present invention, the active hydrogen of natural polysaccharides present in biomass such as cellulose, chitin, and chitosan is reacted according to the following [Chemical Formula 1] or [Chemical Formula 2] to produce a modified biomass in which a part of the hydrophilic biomass is hydrophobized. [Chemical Formula] [Chemical Formula]

[0017] R 1 is the backbone of a natural polymer present in biomass such as cellulose, chitin, and chitosan, and R 2 is a methyl group, ethyl group, butyl group, t-butyl group, hexyl group, octyl group, 2-ethylhexyl group, dodecyl group, lauryl group, octadecyl group, benzyl group, cyclohexyl group, phenyl group, etc., and R 3 represents an acyl group such as a propionyl group, butyryl group, valeryl group, caproyl group, caprylyl group, lauroyl group, or benzoyl group. It has long been known, as shown in Non-Patent Documents 1 and 2, that the hydroxyl groups in cellulose react with isocyanates and acid anhydrides.

[0018] However, it has not been known that by introducing hydrophobic functional groups into cellulose via urethane bonds, the miscibility with highly hydrophobic thermoplastic resins can be improved, the dispersibility of the modified biomass can be enhanced, and the melt viscosity, which significantly affects fluidity in the molding of the composite resin composition obtained by kneading, can be reduced.

[0019] [Monoisocyanate having a functional group] According to the reaction of [Chemical Formula 1] above, examples of monoisocyanates having a functional group that reacts with the hydroxyl groups of biomass include methyl isocyanate, ethyl isocyanate, butyl isocyanate, t-butyl isocyanate, hexyl isocyanate, octyl isocyanate, 2-ethylhexyl isocyanate, dodecyl isocyanate, lauryl isocyanate, octadecyl isocyanate, benzyl isocyanate, cyclohexyl isocyanate, phenyl isocyanate, etc. These may be used alone or in combination of two or more.

[0020] [Aprotic solvent] Examples of aprotic solvents required when reacting biomass with isocyanate having a functional group include acetone, ethyl acetate, dichloromethane, tetrahydrofuran (THF), dimethylformamide (DMF), acetonitrile, dimethyl sulfoxide (DMSO), etc. These solvents can be used alone or in combination of two or more.

[0021] [Urethanization catalyst] As the urethanization catalyst for reacting the inedible biomass with the monoisocyanate having a functional group, any catalyst that promotes the urethanization reaction can be used. For example, tertiary amines such as triethylenediamine, bis(2-dimethylaminoethyl) ether, and N,N,N’,N’-tetramethylhexamethylenediamine; metal carboxylates such as potassium acetate and potassium 2-ethylhexanoate; and organometallic compounds such as stannous octoate, dibutyltin dilaurate, and bismuth octoate. These catalysts can be used alone or in combination of two or more.

[0022] As the addition amount of the catalyst, 1.0 part by mass or less, preferably 0.7 part by mass or less, is appropriate with respect to 100 parts by mass in total of the inedible biomass, the monoisocyanate having a functional group, and the aprotic solvent.

[0023] [Fine pulverization] The inedible biomass was pulverized in a dry state using an impact mill and then classified with an 80-mesh sieve. The inedible biomass can be pulverized not only with an impact mill but also with a rotary mill, a vibration mill, a fluid energy mill, etc. Even finer inedible biomass can be obtained by performing cryogenic pulverization after classification.

[0024] [Conditions for urethanization reaction] The micronized inedible biomass and the urethanization catalyst were uniformly dispersed in an aprotic solvent whose temperature was adjusted to 50°C under a nitrogen atmosphere, and while stirring the whole system, they were reacted with the monoisocyanate having a functional group whose temperature was adjusted to 50°C or lower. The introduction of the functional group via the urethane group into the inedible biomass was confirmed by measuring the infrared absorption spectrum after the reaction.

[0025] [Thermoplastic resin] Examples of the thermoplastic resin that can be used in the present invention include general-purpose resins such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyester (PES), polyamide (nylon), polycarbonate (PC), polymethyl methacrylate (PMMA), and thermoplastic polyurethane (TPU).

[0026] For reducing environmental load, the use of bioplastics is effective. Bioplastics is a general term for biomass plastics made from renewable organic resources such as plants and biodegradable plastics that are ultimately decomposed into carbon dioxide and water by the action of microorganisms etc.

[0027] By using biomass plastics such as bio-polyethylene (bio-PE) made from sugarcane and bio-polypropylene (bio-PP) made from tall oil, it is possible to increase the biomass degree indicating the percentage value of the dry weight of the used biomass without degrading the performance of the composite resin composition.

[0028] On the other hand, when considering environmental pollution caused by discarded composite resin compositions, the use of biodegradable plastics such as polycaprolactone (PCL), polybutylene adipate terephthalate (PBAT), polybutylene succinate (PBS), polyethylene terephthalate succinate (PETS), etc. is effective.

[0029] It is also possible to use starch and starch mixtures, and polylactic acid (PLA) which have the properties of both biomass plastics and biodegradable plastics.

[0030] Polylactic acid has a glass transition point around 60°C. For improving the heat resistance of the composite resin composition, it is effective to add a crystal nucleating agent such as zinc organic phosphonate salt or use PLA in which organically modified clay is nano-dispersed.

[0031] [Mixing and Kneading] In the operation of uniformly dispersing filler materials, stabilizers, pigments, etc. in a thermoplastic resin, an extruder, kneader, Banbury mixer, etc. are used. In the present invention, for a thermoplastic resin, a non-edible biomass whose volume average particle diameter is controlled to 50 micrometers or less, and a modified biomass, the mixability is improved during kneading, and the biomass is uniformly dispersed in the thermoplastic resin without aggregation. Therefore, the apparent viscosity of the obtained composite resin composition decreases, and when molded by injection molding or the like, the moldability such as fluidity is greatly improved.

[0032] [Melt viscosity] As an index of the fluidity during molding, in accordance with JIS K7210-01, using a capillary rheometer flow tester CFT-500D manufactured by Shimadzu Corporation, the apparent viscosity serving as an index of the melt viscosity was measured by the constant temperature method.

Examples

[0033] Hereinafter, the present invention will be specifically described based on examples, but the present invention is not limited to the following examples. Also, the definitions and notations of terms in the following examples are shown below.

[0034] [Biomass] (1) Bleached pulp: Chemical pulp produced by the kraft method. Pure cellulose fibers from which resins, lignin, hemicellulose, etc. have been removed (2) Rice husk: A by-product generated in the process of husking rice when making polished rice. Obtained through threshing and drying. (3) Wood chips: A mixture of softwood and hardwood. Used for biomass power generation (4) Bamboo: True bamboo, Moso bamboo, Phyllostachys glauca, Nüzhu, etc. classified by the Forestry Agency

[0035] [Pulverization of Biomass] Bleached pulp sheets, rice husks, wood chips, and bamboo cut into dimensions of about 2 to 3 centimeters were pulverized for 10 minutes using a high-speed mill HS-20 manufactured by Labo Net Co., Ltd., and a sieve with 80 mesh was attached to a vibrating sieve machine (KS-300), and samples were taken after classifying each biomass.

[0036] Further pulverized samples were obtained by freeze - pulverizing the samples that passed through an 80 - mesh sieve using a freeze - pulverizer JFC - 5000 manufactured by Nippon Kogaku Kogyo Co., Ltd. under dry conditions.

[0037] [Measurement of Biomass Particle Size] The particle sizes of the pulverized various biomasses were measured on a volume basis using a high - sensitivity fine - bubble measurement system SALD - 7500nano manufactured by Shimadzu Corporation.

[0038] [Modification of Biomass] To a 300 - mL four - necked flask, 13.7 g of micronized sun - dried pulp, 80.0 g of tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Corporation) as a solvent, and 0.04 g of triethylenediamine (manufactured by Tosoh Corporation, trade name TEDA) as a urethanization catalyst were added. Then, 25.0 g of octadecyl isocyanate (manufactured by Tokyo Chemical Industry) as a monoisocyanate was added dropwise while stirring under a nitrogen atmosphere, and the sun - dried pulp was reacted at 50 °C for 3 hours.

[0039] [Confirmation of Functional Group Introduction] After the reaction was completed, the solvent was removed by vacuum filtration, and the modified sun - dried pulp was completely dried. Then, the introduction of functional groups was confirmed using a microscopic Fourier transform infrared spectrophotometer (Nicolet iN10 manufactured by Thermo Fisher Scientific).

[0040] The measurement results are shown in Figure 1. Based on Non - Patent Document 3, when comparing the infrared absorption charts of sun - dried pulp and modified sun - dried pulp, absorption due to NH stretching vibration is confirmed at 3350 cm -1 for the modified sun - dried pulp. Also, absorption of carbonyl stretching vibration and NH bending vibration is observed at 1700 cm -1 and 1530 cm -1 , and the introduction of urethane groups into the sun - dried pulp was confirmed.

[0041] [Thermoplastic Resin] As the thermoplastic resin, polylactic acid resin (PLA), trade name: REVODE290 manufactured by ZHEJIANG HISUNBIOMATERIALS CO., LTD., and biomass-derived ethylene-butene copolymer (PEB), trade name: SHA7260 manufactured by Braskem, were used as biopolymers. Also, as the ether-based biomass thermoplastic polyurethane (BTPU), Milactran S380 (biomass content 40%) manufactured by Nippon Miraclan Co., Ltd. was used.

[0042] [Kneading] Using a continuous two-roll kneader (product name: Nidex) manufactured by Nippon Coke & Engineering Co., Ltd., the kneading of various biomasses and thermoplastic resins was carried out at temperatures of 170 °C for PLA and 140 °C for PEB for 15 minutes each.

[0043] [Melt Viscosity] As an index of the fluidity during molding, using a capillary rheometer flow tester CFT-500D manufactured by Shimadzu Corporation, in accordance with JIS K7210-01, the apparent viscosity (melt viscosity: Pa·s) was measured by the isothermal method with the test temperature set at 180 °C.

[0044]

Table 1

[0045] From the results in Table 1, it was found that the finer the particle size of the biomass filler, the lower the apparent viscosity of the composite resin composition obtained after kneading. Also, it was clarified that even for biomass fillers having the same particle size, the apparent viscosity decreased significantly when a part of them was hydrophobized.

[0046] [Molding of Urethane-based Composite Resin Composition] For the urethane-based composite resin composition kneaded with Milactran S380 (BTPU) and rice husk and bamboo after passing through 80 mesh at ratios of 80 / 20 and 60 / 40 respectively, a test piece was created using a mold with dimensions of length x width x height = 170 mm x 120 mm x 3 mm under the condition of a mold temperature of 190 °C with a 15-ton hand press.

[0047] [Measurement of mechanical properties] In accordance with the test method for polyurethane-based thermoplastic elastomers of JIS K 7311, the mechanical properties (elongation, tensile strength) of the urethane-based composite resin composition were measured. The measurement results are shown in Table 2.

[0048]

Table 2

[0049] From the results in Table 2, it is possible to further improve the biomass content of the composite resin composition of the present invention by combining Miraclan S380 with a biomass content of 40% and biomass such as rice husks and bamboo. Also, when adding about 20% of inedible biomass, although the tensile strength decreases slightly, the elongation property improves. Further, it has been clarified that the elongation property can be further improved by introducing a long-chain alkyl group via a urethane bond into the inedible biomass.

Industrial applicability

[0050] The composite resin composition produced by kneading a biomass material centered on inedible plants of the present invention and a thermoplastic resin can be widely applied not only to interior and exterior building materials for housing as a wood plastic material but also to interior materials for automobiles.

Claims

1. A composite resin composition produced by kneading 20 to 90 mass% of non-edible biomass whose volume average particle size is controlled to 50 micrometers or less with 10 to 80 mass% of a biopolymer made of biomass plastic, biodegradable plastic, or a thermoplastic resin derived from petroleum-derived raw materials.

2. A composite resin composition produced by kneading 50 to 80 mass% of non-edible biomass whose volume average particle size is controlled to 50 micrometers or less with 20 to 50 mass% of a biopolymer made of biomass plastic, biodegradable plastic, or a thermoplastic resin derived from petroleum-derived raw materials.

3. 3. The composite resin composition according to claim 1, wherein the non-edible biomass is non-edible biomass containing cellulose and chitin (chitin, chitosan) having active hydrogen.

4. A method for producing non-edible modified biomass, comprising reacting active hydrogen of the non-edible biomass with a monoisocyanate or an acid anhydride in the presence of a catalyst in an aprotic solvent to introduce a functional group.

5. The method for producing non-edible denatured biomass according to claim 4, wherein the reaction is preferably a urethane reaction of non-edible biomass having a monoisocyanate and active hydrogen, which does not produce by-products.

6. 5. A method for producing inedible denatured biomass, wherein the monoisocyanate or acid anhydride according to claim 4 has a long-chain aliphatic hydrocarbon, an alicyclic hydrocarbon, and an aromatic group as a functional group.

7. The method for producing nonedible denatured biomass according to any one of claims 4 to 6, wherein the catalyst according to claim 4 is a tertiary amine, a tin compound, or a bismuth compound, and at least one of these is used.

8. The method according to any one of claims 4 to 6, wherein the non-edible biomass and the isocyanate are reacted in an aprotic polar solvent at 80°C or lower.

9. The method according to claim 7, wherein the non-edible biomass and the isocyanate are reacted in an aprotic polar solvent at 80°C or lower.

10. The method for producing non-edible denatured biomass according to claim 4, wherein after the non-edible biomass and the isocyanate are reacted, the aprotic polar solvent is removed by filtration under reduced pressure at room temperature.

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