JP7733508B2 - Molding resin material and its manufacturing method - Google Patents

Description

The present invention relates to a molding resin material containing woody biomass roasted material, a thermoplastic resin such as polypropylene, polyethylene, or polylactic acid, and an acid-modified polyolefin, and a method for producing the same.

Biomass materials are attracting attention as industrial resources. Biomass materials are materials derived from living organisms such as plants. Because biomass materials are organic, they emit carbon dioxide when burned. However, the carbon contained in them comes from carbon dioxide absorbed from the atmosphere through photosynthesis during the biomass growth process, so it is safe to say that the use of biomass materials does not increase the amount of carbon dioxide in the atmosphere overall. This property is called carbon neutral.

Against the backdrop of global warming and other global environmental issues, there is an urgent need to conserve resources, recycle waste materials to turn them into raw materials, and promote environmental circulation, as exemplified by biodegradable plastics. In Japan, the revised Recycling Act and the Green Purchasing Act have been enacted, and there is a growing need for products that comply with these laws.

In this context, incorporating biomass materials into resin molded products, which are widely used in everything from automotive parts to everyday items, will help put the carbon-neutral concept into practice. For example, Patent Document 1 describes a composite material containing carboxymethylated cellulose nanofibers, a polymer compound with primary amino groups, an acid-modified polyolefin, and a polyolefin. Patent Document 2 describes a cellulose composite material containing wood pulp and a polymer matrix. Patent Document 3 describes a method for producing a wood-flour-containing resin injection-molded product by mixing wood flour and random polypropylene resin and using an injection molding machine.

International Publication No. WO2014/087767 Special Publication No. 2019-512591 JP 2010-138337 A

However, simply mixing "woody biomass" and "polypropylene" and then heating, melting, and molding them poses several problems, including the inability to mix uniformly with polypropylene due to the hydrophilic nature of the woody biomass, the resin body being shredded at the outlet of the device used to inject the mixture of woody biomass and polypropylene, and the surface of the resulting molded article not being smooth.

For example, Patent Document 1 describes the use of carboxymethylated cellulose nanofibers, but in order to carboxymethylate the cellulose and further improve uniform dispersion with the polyolefin resin, it is necessary to add a polymer compound with a primary amino group and an acid-modified polyolefin, which increases costs.

The objective of the present invention is to provide a molding resin material containing woody biomass at low cost, in which the woody biomass and thermoplastic resin are uniformly mixed and which is less likely to break or crack during molding, such as injection.

The inventors discovered that by mixing pulverized woody biomass roasted material with thermoplastic resins such as polypropylene, polyethylene, and polylactic acid, and further with acid-modified polyolefin, and then heating and kneading the mixture, a molding resin material with excellent moldability can be obtained, leading to the completion of the present invention.

The present invention includes, but is not limited to, the following:
(1) A molding resin material containing 40 to 90% by mass of pulverized woody biomass roasted material having an average particle size of 100 μm or less, and further containing a thermoplastic resin and an acid-modified polyolefin.
(2) The molding resin material according to (1), wherein the weight average molecular weight of the acid-modified polyolefin is 9,000 to 45,000.
(3) The molding resin material according to (1) or (2), wherein the acid-modified polyolefin has an acid value of 26 to 70.
(4) The molding resin material according to any one of (1) to (3), wherein the content of the acid-modified polyolefin in the molding resin material is 0.1 to 10% by mass.
(5) The molding resin material according to any one of (1) to (4), which contains, as the thermoplastic elastomer, any one of a styrene-butadiene block copolymer, an ethylene-octene copolymer, and a propylene-ethylene copolymer.
(6) The molding resin material according to any one of (1) to (5), wherein the thermoplastic resin includes a polyolefin resin.
(7) The molding resin material according to any one of (1) to (6), wherein the thermoplastic resin includes a polypropylene resin.
(8) The molding resin material according to any one of (1) to (7), wherein the thermoplastic resin contains a biodegradable resin.
(9) A method for producing a molding resin material, comprising a step of heating and kneading pulverized woody biomass roasted material, a thermoplastic resin, and a thermoplastic elastomer.
(10) The method according to (9), wherein the molding material is continuously produced by processing with a twin-screw kneading extruder in the heating and kneading step.

This invention makes it possible to stably produce a highly viscous molding resin material containing ground woody biomass roasted material that does not break or crack during injection molding. Furthermore, by increasing the blending ratio of woody biomass roasted material, it is possible to obtain a molding resin material with excellent carbon neutrality.

The roasted product of the present invention can be obtained, for example, by roasting pulverized woody biomass with a size of 50 mm or less under conditions of an oxygen concentration of 10% or less and a material temperature of 240 to 350°C.

The present invention uses torrefied woody biomass. Both broadleaf and coniferous trees can be used as the raw material for woody biomass. Specific examples of broadleaf trees include, but are not limited to, eucalyptus, rubber tree, beech, linden, birch, poplar, acacia, oak, sugar maple, Asian elm, paulownia, magnolia, willow, ash, phillyraeoides phillyraeoides, oak, sawtooth oak, horse chestnut, zelkova, beech, dogwood, and ash. Coniferous trees include cedar, spruce, larch, Japanese black pine, Abies sachalinensis, dwarf pine, yew, juniper, spruce, and Japanese spruce. Examples include Japanese yew, Japanese holly, fir, Japanese sawara, Douglas fir, Asunaro, Japanese cypress, Japanese hemlock, Japanese hemlock, Hinoki cypress, yew, Japanese yew, spruce, yellow cedar, Douglas fir, Sitka spruce, Radiata pine, Eastern spruce, Eastern white pine, Western larch, Western fir, Western hemlock, and tamarack.

Among these, Eucalyptus wood and rubber tree (Hevea brasiliensis) are preferred. Examples of Eucalyptus include Eucalyptus (hereafter abbreviated as E.) calophylla, E. citriodora, E. diversicolor, E. globulus, E. grandis, E. urograndis, E. gummifera, E. marginata, E. nesophila, E. nitens, E. amygdalina, E. camaldulensis, E. delegatensis, E. gigantea, E. muelleriana, E. obliqua, E. regnans, E. sieberiana, E. viminalis, E. marginata, etc.

In the present invention, the form of the woody biomass used as the raw material is not limited, and suitable materials include wood chips, bark, sawdust, and sawdust. In a preferred embodiment, woody biomass having a size of 50 mm or less can be used as the raw material. For example, woody biomass can be adjusted to a size of 50 mm or less by crushing it, and it is preferable to use woody biomass crushed to a size of 1 mm to 50 mm as the raw material. In the present invention, the size of the crushed woody biomass is determined by sieving it according to the size of the circular holes in a sieving box. When crushing woody biomass, it is preferable to crush it using, for example, a hammer mill or a knife-cutting type biomass fuel chipper.

In this invention, torrefaction of woody biomass is used. Torrefaction generally refers to a process in which wood is heated in a low-oxygen atmosphere at a temperature lower than that used in carbonization. While the temperature used in typical wood carbonization processes is 400-700°C, in this invention, torrefaction is carried out at 240-350°C. By torrefaction, a solid fuel with a higher energy density than the starting material is obtained.

The roasting conditions in this invention are an oxygen concentration of 10% or less and a material temperature of 240-350°C. Here, the material temperature during roasting refers to the temperature of woody biomass near the outlet of the roasting treatment device. In this invention, roasting is performed under conditions of an oxygen concentration of 10% or less; however, if the oxygen concentration exceeds 10%, the material yield and calorific yield may decrease. Furthermore, if the material temperature is below 240°C, it becomes difficult to grind the roasted material to small particle sizes, and if it exceeds 350°C, the material yield and calorific yield decrease. The material temperature is preferably 240-330°C, and even more preferably 250-320°C. Hemicellulose undergoes significant thermal decomposition around 270°C, while cellulose and lignin undergo significant thermal decomposition around 355°C and 365°C, respectively. Therefore, it is presumed that by setting the roasting temperature to 170-350°C, hemicellulose is preferentially thermally decomposed, making it possible to produce a molding resin material that achieves both material yield and pulverizability.

In the present invention, the apparatus used for the roasting treatment is not particularly limited, but a rotary kiln and/or a vertical furnace is preferred. It is preferable to replace the atmosphere inside the apparatus with an inert gas such as nitrogen to adjust the oxygen concentration to 10% or less. The roasting treatment time is not particularly limited, but is preferably 1 to 180 minutes, more preferably 5 to 120 minutes, and even more preferably 10 to 60 minutes. When using a continuous apparatus, the residence time in the roasting apparatus can be controlled.

In the present invention, an externally heated roasting device may be used as the device for performing the roasting process. For example, an externally heated rotary kiln has a structure in which the inner kiln cylinder is partially or entirely covered by an outer kiln cylinder. Woody biomass is roasted within the inner kiln, and fuel is burned within the outer kiln to indirectly heat the woody biomass inside the inner kiln. The temperature within the outer kiln cylinder can be 400 to 800°C, with 450 to 750°C being preferred. If the temperature within the outer kiln cylinder is below 400°C, the pyrolysis of the woody biomass within the inner kiln cylinder will be insufficient, and the crushability of the resulting solid fuel will be reduced. On the other hand, if the temperature exceeds 800°C, the temperature of the woody biomass within the inner kiln cylinder will rise excessively, resulting in a decrease in the material yield and calorific yield of the resulting solid fuel.

The roasted product used in this invention preferably has a material yield of 60-90% and a calorific yield of 70-95% relative to the woody biomass raw material. Furthermore, the Hardgrove Grindability Index (HGI) specified in JIS M 8801:2004, which is an index of grindability, is preferably 25 or higher, and more preferably 30 or higher. The higher the HGI, the easier it is to grind. If the HGI is in the range of 25-70, it can be easily mixed with a thermoplastic resin and molded.

The roasted product used in the present invention may be formed into a molded product. That is, the pulverized starting material (roasted product) of woody biomass is molded into briquettes or pellets. Forming the product into a molded product makes it easier to handle and increases the density, thereby reducing transportation costs. The bulk density of the molded product after densification is preferably 500 kg/m3 or higher, and more preferably 600 kg/m3 or higher. Bulk density can be measured in accordance with JIS K 2151-6, "Bulk Density Test Method."

In the present invention, there are no particular limitations on the equipment used to mold the roasted material, but preferred examples include a briquette (manufactured by Kitagawa Iron Works), a ring die pelletizer (manufactured by CPM), and a flat die pelletizer (manufactured by Kahl or Dalton).

In the present invention, when the roasted material is molded, the moisture content of the roasted material is preferably 8 to 50%, and more preferably 10 to 30%. If the moisture content is less than 8%, blockages will occur inside the briquette or pelletizer, making it impossible to produce a stable molded product. If the moisture content exceeds 50%, molding will be difficult and the material will be discharged in a powder or paste form.

In the present invention, a binder may be added to the roasted product. There are no particular limitations on the binder, but suitable binders include organic polymers such as starch and lignin, inorganic polymers such as acrylic acid amide, and agricultural residues such as bran (residue generated during wheat flour production). From the perspective of efficiently utilizing woody biomass, it is desirable to add as few binders as possible; preferably, 50 parts by mass or less, and more preferably 20 parts by mass or less, per 100 parts by mass of the roasted product. However, adding more than 50 parts by mass does not mean that high density is impossible.

In the present invention, the roasted material is preferably pulverized before being kneaded with the thermoplastic resin. The average particle size of the pulverized material must be 100 μm or less, and 50 μm or less is more preferable. If the average particle size of the pulverized roasted material is greater than 100 μm, it becomes difficult to uniformly mix it with the resin, and problems such as the resin being shredded at the outlet of the device that ejects the mixture of pulverized material and resin, or transporting it to a cooling treatment device may occur. The average particle size is the 50% volume average particle size (D50) measured by laser light scattering (laser diffraction) and can be measured using a laser diffraction/scattering particle size distribution analyzer (Malvern Instruments, Instrument Name: Mastersizer 2000) or similar.

The grinder used to grind the roasted material may be any device capable of grinding organic materials, including, but not limited to, a ball mill, rod mill, bead mill, conical mill, disc mill, edge mill, hammer mill, mortar, pellet mill, VSI mill, Willy mill, roller mill, jet mill, mass colloider, etc.

The molding resin material of the present invention can be obtained by heating and kneading the above-mentioned roasted product, a thermoplastic resin, and an acid-modified polyolefin. A higher blend ratio of the roasted product in the molding resin material is preferable in order to achieve a high level of carbon neutrality. However, taking into consideration the manufacturing and strength of the resulting resin material and molded article, a blend ratio of 40% by mass or more and 90% by mass or less is preferred, and more preferably 50% by mass or more and 80% by mass or less.

The thermoplastic resin used in the present invention is preferably molded into granules for ease of handling, but any form is acceptable. It is also possible to use two or more types of thermoplastic resins simultaneously.

Thermoplastic resins include, but are not limited to, polyethylene and polypropylene, and any resin that can be plasticized and molded by heat can be used. Among these, polyethylene such as LDPE (low-density polyethylene) and polypropylene are preferred from the standpoint of moldability.

In the present invention, a biodegradable resin may be used as the thermoplastic resin. Examples of biodegradable resins with thermoplastic properties include, but are not limited to, polylactic acid (PLA), polybutylene succinate, polyethylene succinate, polyglycol, polycaprolactone, polyvinyl alcohol, etc.

In the present invention, by adding an acid-modified polyolefin, a molding resin material with high uniformity and adhesion can be produced when the roasted material and thermoplastic resin are kneaded.

The weight-average molecular weight of the acid-modified polyolefin is preferably 9,000 to 45,000, and more preferably 20,000 to 35,000. A weight-average molecular weight in the range of 9,000 to 45,000 improves the dispersibility of roasted wood biomass and increases tensile strength.

The acid value of the acid-modified polyolefin, measured in accordance with JIS K 0070, is preferably 26 to 70, and more preferably 40 to 60. An acid value in the range of 26 to 70 improves the dispersibility of roasted wood biomass and increases tensile strength.

Known acid-modified polyolefins can be used, including, but not limited to, maleic anhydride-modified polypropylene (UMEX 1001, 1010, manufactured by Sanyo Chemical Industries, Ltd.) and Modic (registered trademark) P908 (manufactured by Mitsubishi Chemical Industries, Ltd.).

The content of the acid-modified polyolefin in the molding resin material obtained by kneading is preferably 0.1 to 10% by mass, more preferably 0.3 to 5% by mass, and even more preferably 0.4 to 1% by mass.

In the present invention, by adding a thermoplastic elastomer, it is possible to stably produce a molding resin material with high viscosity that does not break or crack during injection molding, even when blended with ground woody biomass roasted material.

Thermoplastic elastomers used in the present invention include styrene-based thermoplastic elastomers. More specifically, examples include block copolymers such as styrene-butadiene-styrene (SBS) copolymer, styrene-isoprene-styrene (SIS) copolymer, styrene-ethylene-butylene-styrene (SEBS) copolymer, styrene-ethylene-propylene-styrene (SEPS) copolymer, and styrene-butadiene-butylene-styrene (SBBS) copolymer. These may be used alone or in combination of two or more.

Thermoplastic elastomers used in the present invention include polyolefin-based elastomers. More specifically, these include ethylene-butene copolymers, EPR (ethylene-propylene copolymers), modified ethylene-butene copolymers, EEA (ethylene-ethyl acrylate copolymers), modified EEA, modified EPR, modified EPDM (ethylene-propylene-diene terpolymers), ionomers, α-olefin copolymers, modified IR (isoprene rubber), modified SEBS (styrene-ethylene-butylene-styrene copolymers), halogenated isobutylene-paramethylstyrene copolymers, ethylene-acrylic acid modified products, ethylene-vinyl acetate copolymers, and acid-modified products thereof, as well as mixtures containing these as the main components. These may be used alone or in combination of two or more.

Preferred thermoplastic elastomers for use in the present invention include styrene-butadiene block copolymers, ethylene-octene copolymers, and propylene-ethylene copolymers. Styrene-butadiene block copolymers are particularly preferred. The above thermoplastic elastomers may also be modified with maleic anhydride, fumaric anhydride, or the like. In styrene-butadiene block copolymers, the styrene content is preferably 15 to 30% by mass.

The blending ratio of thermoplastic elastomer is preferably 1 to 20% by mass, and more preferably 3 to 10% by mass.

A molded article can be obtained by heat-treating the molding resin material of the present invention. The temperature when the molding resin material of the present invention is heat-treated (heated, melted, kneaded, etc.) is typically about 100 to 300°C, preferably about 110 to 250°C, and particularly preferably about 120 to 220°C. The molded article obtained by heat treatment can be molded into the desired shape using conventional resin molding methods.

In the manufacturing method of the molding resin material of the present invention, the roasted product and acid-modified polyolefin can be heated and kneaded using equipment commonly used in resin molding. For example, a common extruder or twin-screw kneading extruder can be used. The TEX series manufactured by The Japan Steel Works, Ltd. can be used as the twin-screw kneading extruder.

The molding resin material of the present invention can be used to produce a variety of molded articles. Molding can be performed using conventional methods used for molding thermoplastic resins, including, but not limited to, injection molding, extrusion molding, blow molding, molded parts, hollow molding, and foam molding.

The molding resin material of the present invention or the molded article obtained by molding it may contain organic and/or inorganic substances other than the thermoplastic resin and the roasted product. Examples of other components include alkalis such as sodium hydroxide, potassium hydroxide, magnesium hydroxide, and calcium hydroxide; inorganic fillers such as clay, talc, calcium carbonate, mycelium, titanium dioxide, and zinc oxide; organic fillers such as carbon black, graphite, and glass flake; dyes or pigments such as red iron oxide, azo pigments, and phthalocyanines; and property-modifying additives such as dispersants, lubricants, plasticizers, mold release agents, flame retardants, antioxidants (phenolic antioxidants, phosphorus antioxidants, and sulfur-based antioxidants), antistatic agents, light stabilizers, UV absorbers, metal deactivators, crystallization accelerators (nucleating agents), foaming agents, crosslinking agents, and antibacterial agents.

The molding resin material of the present invention can be molded for a variety of purposes and can be used as a substitute for plastic products. Molded articles obtained from the molding resin material of the present invention can be widely used, including, for example, trays, automobile parts, automobile dashboards and other interiors, airplane luggage compartments, structural components for transportation equipment, housings for home appliances, electrical appliance components, cards, various containers such as toner containers, building materials, seedling pots, agricultural sheets, writing implements, wooden products, household appliances, straws, cups, toys, sporting goods, port components, building components, generator components, tools, fishing gear, packaging materials, 3D printer models, pallets, food containers, tableware, cutlery (spoons, forks, etc.), chopsticks, and various sheets. When these products are no longer needed, they are disposed of. However, even if they are incinerated, emitting carbon dioxide, the roasted wood biomass content can be treated as not increasing the amount of carbon dioxide in the atmosphere.

The present invention will be explained in more detail below using experimental examples, but the present invention is not limited to these experimental examples. Unless otherwise specified, parts and percentages refer to parts by mass and percentages by mass, and numerical ranges are stated as including their endpoints.

[Example 1]
Wood chips of Eucalyptus eurograndis were crushed using a disc chipper. After crushing, the crushed chips with sizes of 1 to 50 mm were dried using a conveyor dryer (manufactured by Alvan Blanch Co., Ltd.) at a hot air temperature of 70°C for 3 hours to adjust the moisture content to 10%.
Next, roasting was carried out using a large rotary kiln-type carbonization furnace, with an oxygen concentration of 1% or less, and the material temperature of the ground chips in the carbonization furnace at 260°C for a residence time of 12 minutes, to obtain a roasted woody biomass product. After cooling, the roasted product was pulverized in a LabMill (manufactured by Osaka Chemical Co., Ltd.) to an average particle size of 50 µm.
Next, the pulverized roasted product, polypropylene (product name: J107G, manufactured by Prime Polymer, melt flow rate: 30 g/10 min), and acid-modified polyolefin (product name: UMEX 1010, acid value 52, molecular weight 30,000, manufactured by Sanyo Chemical Industries, Ltd.) were mixed in a blending ratio of 51:48.5:0.5, and the mixture was kneaded at 190°C for 6 minutes in a DSM Xplore Compounder 15 (manufactured by Leo Labo), molded at 190°C in the heating barrel (9 bar 2 s - 11 bar 0.5 s - 11 bar 24 s) and in a mold at 40°C to prepare a dumbbell of the molding resin material, and the physical properties were measured.
The average particle size of the pulverized roasted product was measured using a laser diffraction particle size measuring device (Mastersizer 3000, manufactured by Malvern), and the 50% particle size on a volume basis was taken as the average particle size.

[Example 2]
A molding resin material was produced in the same manner as in Example 1, except that a maleic anhydride-modified styrene-butadiene block copolymer (product name: M1943, styrene content 20%, manufactured by Asahi Kasei Corporation) was used as the thermoplastic elastomer, and the compounding ratio of the pulverized roasted product, polypropylene, acid-modified polyolefin, and thermoplastic elastomer was 51:43.6:0.4:5.

[Example 3]
A molding resin material was produced in the same manner as in Example 2, except that the compounding ratio of the ground roasted product, polypropylene, acid-modified polyolefin, and thermoplastic elastomer was 51:38.6:0.4:10.

[Comparative Example 1]
A molding resin material was produced in the same manner as in Example 1, except that no acid-modified polyolefin was added and the ground roasted product and polypropylene were mixed in a blending ratio of 50:50.

The tensile strength of the molding resin materials produced in Examples 1 to 3 and Comparative Example 1 was measured by the following method, and the results are shown in Table 1.
[Tensile strength measurement]:
A dumbbell according to JIS K 6251 was prepared using DSM Xplore Compounder 15 (manufactured by Leo Labo Co., Ltd.), and measurements were made at a tensile speed of 1 mm/min in accordance with JIS K 7161: Testing method for tensile properties of plastics.

As shown in Table 1, the molding resin materials of Examples 1 to 3, which contained acid-modified polyolefin, had higher breaking strain and higher tenacity than the molding resin material of Comparative Example 1, which did not contain thermal acid-modified polyolefin, demonstrating superior moldability.

Claims (9)

(a) pulverized woody biomass roasted material having an average particle size of 100 μm or less;
(b) a thermoplastic resin; and
(c) an acid-modified polyolefin;
A molding resin material containing
The molding resin material, wherein the content of pulverized woody biomass roasted material is 40 to 90% by mass, and the content of acid-modified polyolefin is 0.1 to 1% by mass. The molding resin material according to claim 1, wherein the weight-average molecular weight of the acid-modified polyolefin is 9,000 to 45,000. The molding resin material according to claim 1 or 2, wherein the acid-modified polyolefin has an acid value of 26 to 70. The molding resin material according to any one of claims 1 to 3, wherein the thermoplastic elastomer comprises a styrene-butadiene block copolymer, an ethylene-octene copolymer, or a propylene-ethylene copolymer. The molding resin material according to any one of claims 1 to 4, wherein the thermoplastic resin includes a polyolefin resin. The molding resin material according to any one of claims 1 to 5, wherein the thermoplastic resin includes a polypropylene resin. The molding resin material according to any one of claims 1 to 6, wherein the thermoplastic resin includes a biodegradable resin. A method for producing a molding resin material, comprising a step of heating and kneading (a) pulverized wood biomass roasted material, (b) a thermoplastic resin, (c) an acid-modified polyolefin, and (d) a thermoplastic elastomer,
The method according to any one of claims 1 to 4, wherein the content of the pulverized woody biomass roasted material in the molding resin material is 40 to 90% by mass, and the content of the acid-modified polyolefin is 0.1 to 1% by mass . The method according to claim 8, wherein the heating and kneading step continuously produces molding material processed in a twin-screw kneading extruder.