JP5398180B2 - Lignin-containing microfibrillated plant fiber and method for producing the same - Google Patents

Description

  The present invention relates to a microfibrillation technology for pulp.

The plant structure is mainly composed of cellulose, hemicellulose and lignin. In the fine structure of a plant structure, about 40 cellulose molecules are usually bonded by hydrogen bonds to form cellulose microfibrils having a width of several nm (usually about 4 to 5 nm). Then, to form a cellulose fine fibers (cellulose micro fibrillation Li Le flux) gathered several cellulose microfibrils. Hemicellulose is present in the gaps between the cellulose microfibrils and around the cellulose microfibrils. And lignin is filled in the gap between cellulose microfibrils.

  Cellulose microfibrils have high strength and low density, and from the viewpoint of environmental load in recent years, attempts have been made to extract cellulose microfibrils or cellulose fine fibers from plant raw materials and use them. For example, a fiber reinforced resin is known that improves the physical properties by blending a synthetic fiber such as aramid fiber into the resin. As this fiber, cellulose fine fiber (microfibrillated cellulose) or cellulose microfiber taken out from plant materials is known. Attempts have been made to use fibrils. Moreover, the utilization as a wood cement molded object containing a microfibrous cellulose is also tried (for example, refer patent document 1).

On the other hand, in the fields of papermaking and pulp industries, effective utilization of each component has been attempted by separating lignin, hemicellulose, cellulose and the like from plant raw materials. For this reason, methods for separating non-crystalline components such as lignin and hemicellulose have also been developed. For example, the Kraft pulp method, the soda pulp method, the sulfite pulp method, etc., which are heated under pressure with a mixed solution of sodium hydroxide and sodium sulfide. First, a method of treating with an aqueous solution of ammonium oxalate after treating with a sodium hypochlorite solution (possible even under normal pressure) has been performed. In the case of producing microfibrillated cellulose from plant raw materials, the same idea as in the papermaking and pulp industries is the center, and amorphous components such as lignin and hemicellulose are treated with chemical treatments known in the papermaking and pulp industries. This was removed by appropriately changing treatment to obtain a so-called crude pulp, which was mechanically defibrated (for example, with a grinder, mortar, high-pressure homogenizer, etc.) to produce microfibrillated cellulose. Since components such as lignin and hemicellulose are known to bind to each other or bind to and adhere to cellulose fibers, etc., the presence of these components was thought to prevent successful defibration. The removed crude pulp was used as a raw material for microfibrillation.
JP 2005-059513 A

  However, the microfibrillated cellulose produced from the lignin-removed product is minute and has a large specific surface area, and has many hydroxyl groups on the surface, so the drainage and dehydration properties are poor, making it difficult to use in aqueous systems. .

Furthermore, since the microfibrillated cellulose produced from the lignin-removed product has hydrophilicity mainly derived from cellulose, it is not compatible with a resin that is inherently hydrophobic. For this reason, when it tried to manufacture a fiber reinforced resin by mix | blending microfibrillated cellulose with resin as it was, the dispersibility of a fiber worsened and the improvement of the physical characteristic of resin obtained was suppressed. Therefore, in order to improve the drainage and dispersibility of fibers, processing of reducing the hydrophilicity of textiles, addition of a third component was necessary.

  In addition, lignin is produced as a by-product of the process of removing lignin, but lignin has low usage and various uses are being explored, but it is actually used as a combustion raw material (black liquor) in the paper and pulp industries. It has been used only for other purposes. Thus, since lignin is difficult to reuse, lignin by-product is not preferable.

  Accordingly, the present invention relates to a method for producing microfibrillated plant fibers that do not require lignin removal, microfibrillated plant fibers from which lignin has not been removed, molded products of the plant fibers, and resins containing the plant fibers. The purpose is to provide moldings. As a result of intensive studies to achieve the above object, the present inventor has obtained the following knowledge. Chemicals (eg, sodium hydroxide, sodium sulfide, sodium hypochlorite, ammonium oxalate, etc.) do not completely remove lignin from plant materials, and lignin is not removed or part of lignin The microfibrillation containing lignin and hemicellulose by steaming and mechanically defibrating the pulp from which the lignin has been removed, for example, pulp containing about 2 to 70% by weight of lignin relative to the weight of cellulose Plant fiber is obtained, the decomposition temperature of the microfibrillated plant fiber is higher than that of ordinary microfibrillated cellulose substantially free of lignin, and the hydrophilicity of the microfibrillated plant fiber is substantially equal to that of lignin. Compared with ordinary microfibrillated cellulose that does not contain Is excellent in drainage and dewaterability of the fiber, facilitates treatment in aqueous systems, has excellent fiber dispersibility when blended in resin, and is very useful as a fiber of fiber reinforced resin (physical strength Contribute to improvement).

That is, the present invention provides the following microfibrillated plant fibers, molded products thereof, resin molded products containing the plant fibers, and methods for producing them.
Item 1. A microfibrillated plant fiber obtained by mechanically defibrating pulp containing 2 to 70% by weight of lignin with respect to cellulose weight.
Item 2. Item 2. The microfibrillated plant fiber according to Item 1, wherein the mechanical fibrillation treatment is a grinding treatment.
Item 3. Item 3. The microfibrillated plant fiber according to Item 1 or 2, wherein the cellulose microfibril and / or cellulose microfibril bundle has a structure in which hemicellulose and / or lignin is covered.
Item 4. Item 4. The microfibrillated plant fiber according to Item 3, wherein the periphery of the cellulose microfibril and / or the cellulose microfibril bundle is a structure coated with hemicellulose and lignin in this order.
Item 5. At least one chemical modification pulp selected from the group consisting of mechanical defibration the pulp is esterified treated pulp to be subjected, etherified treated pulp, acetalization processes pulp and lignin pulps aromatic ring is treated in Item 5. The microfibrillated plant fiber according to any one of Items 1 to 4, which is
Item 6 . Item 6. A microfibrillated plant fiber molded body obtained by molding the microfibrillated plant fiber according to any one of Items 1 to 5.
Item 7. Item 6. A resin molded article containing the microfibrillated plant fiber according to any one of Items 1 to 5.
Item 8. A method for producing microfibrillated plant fibers, wherein a pulp containing 2 to 70% by weight of lignin is mechanically defibrated with respect to cellulose weight.
Item 9 . Item 9. The method according to Item 8, wherein the defibrating is a grinding treatment.
Item 10 . After evaporation a solution of the pulp with water, the production method according to claim 8 or 9 is to fibrillation treatment.
Item 11. The pulp subjected to mechanical defibration is at least one chemically modified pulp selected from the group consisting of esterified pulp, etherified pulp, acetalized pulp and pulp treated with lignin aromatic rings. The manufacturing method in any one of claim | item 8-10.

  In the present invention, since lignin is not completely removed chemically, it is presumed that the matrix portion composed of lignin and hemicellulose filling between the microfibrillated cellulose is broken and microfibrinated (microfibrillated). . Therefore, the microfibrillated plant fiber obtained by the production method of the present invention retains a structure composed of cellulose, hemicellulose and protolignin (lignin in a state existing in the plant tissue) inherent in the plant raw material. Presumed to be. Specifically, the microfibrillated plant fiber of the present invention has a structure in which hemicellulose and / or lignin coats part or all of the periphery of cellulose microfibrils and / or cellulose microfibril bundles, in particular, cellulose microfibrils and / or Alternatively, it is presumed that hemicellulose covers the periphery of the cellulose microfibril bundle and further has a structure in which this is covered with lignin (FIG. 1). However, it is presumed that there will also be a portion where hemicellulose and / or lignin is removed and the hemicellulose or cellulose fiber length is exposed on the surface.

  In the present invention, the average fiber diameter of the microfibrillated plant fiber is preferably 4 nm to 400 nm, more preferably 4 nm to 200 nm, and even more preferably 4 nm to 100 nm. Further, the microfibrillated plant fiber of the present invention is intricately intertwined with fibers. The relationship between the lignin content and the cellulose content in the microfibrillated plant fiber of the present invention is as follows: lignin is 2 to 70% by weight, preferably 5 to 60% by weight, more preferably 10 to 50% by weight, based on the weight of cellulose. is there. The content of lignin in the microfibrillated plant fiber of the present invention is preferably 1 to 40% by weight, more preferably 3 to 35% by weight, and still more preferably 5 to 35% by weight. Since the microfibrillated plant fiber of the present invention does not remove lignin in the pulp that is the raw material, the lignin content in the pulp and the lignin content in the microfibrillated plant fiber are almost the same. Similarly, the relationship between the cellulose content and the lignin content in the pulp and the relationship between the cellulose content and the lignin content in the microfibrillated plant fiber are almost the same.

Incidentally, JP 2001-342353, degreased wood flour in (ethanol: benzene = 1 2 solution) was defatted wood powder, sorbed phenol derivative was added an acetone solution of phenol derivatives, phosphorus Although a composition obtained by acid treatment is described, this composition differs from the microfibrillated plant fiber of the present invention in that it is not microfibrillated and protolignin is not present.

  The pulp used in the present invention is different from the pulp used in the production of conventional microfibrillated cellulose, and it is necessary that the lignin is not completely removed. The lignin content in the pulp is 1 to 40% by weight, preferably 3 to 35% by weight, more preferably 5 to 35% by weight. The relationship between the lignin content and the cellulose content in the pulp is such that lignin is 2 to 70% by weight, preferably 5 to 65% by weight, more preferably 10 to 60% by weight, based on the weight of cellulose.

  As a plant raw material for supplying pulp used in the present invention, a plant raw material for supplying pulp that has been used in the production of conventional microfibrillated cellulose can be widely used. For example, wood, bamboo, hemp, Examples include jute, kenaf, crop waste, cloth, recycled pulp, and waste paper. Preferred are wood, bamboo, hemp, jute, kenaf, and crop residue.

  The method of pulping the plant material is not limited as long as the lignin in the plant material is not completely removed and the pulp content is about 2 to 70% by weight with respect to the cellulose content in the pulp. Applicable. For example, a mechanical pulping method for mechanically pulping plant materials can be applied. Examples of the mechanical pulp (MP) obtained by the mechanical pulping method include groundwood pulp (GP), refiner mechanical pulp (RMP), thermomechanical pulp (TMP), and chemithermomechanical pulp (CTMP).

  In addition, chemical pulp (CP, (CP, (P)) obtained by chemically or mechanically and mechanically pulping plant raw materials by chlorine treatment, alkali treatment, oxygen oxidation treatment, sodium hypochlorite treatment, sulfite treatment, etc. Even kraft pulp (KP), sulfite pulp (SP), semi-chemical pulp (SCP), chemi-ground pulp (CGP), chemimechanical pulp (CMP) does not completely remove lignin and contains a certain amount The pulp may be used as a pulp in the present invention, and the pulp may be subjected to chemical modification treatment commonly used in the pulp field as necessary, for example, esterification treatment, etherification treatment, acetal. Examples include pulps treated with pulps treated with aromatic rings of lignin, etc. Esterification, etherification The acetalization treatment mainly includes esterification, etherification, and acetalization treatment of hydroxyl groups present in cellulose, hemicellulose, and lignin, and treatment of the aromatic ring of lignin is desirable for the aromatic ring of lignin. Introducing the above substituents.

  In the present invention, the lignin-containing pulp is mechanically ground or beaten with a refiner, a twin-screw kneader (double-screw extruder), a high-pressure homogenizer, a medium stirring mill, a stone mill, a grinder, a vibration mill, a sand grinder or the like. As a result, the fiber is defibrated or refined into microfibrillated plant fibers. A preferable temperature in the defibrating treatment is 0 to 99 ° C, more preferably 0 to 90 ° C. It is desirable that the pulp that is the raw material for the defibrating process has a shape (for example, a powder form) suitable for the defibrating process. In addition, it is advantageous in terms of reducing the defibrating energy when the pulp is steamed with steam (for example, heated in a pressure cooker in the presence of moisture) prior to the defibrating treatment.

  A preferable defibrating method is grinding (grinding). As the grinder, a stone mill type grinder is preferable. The grinding may be performed until the fiber diameter reaches a desired size.

The microfibrillated plant fiber of the present invention is also excellent in moldability. On the other hand, conventional microfibrillated cellulose is readily solidified coagulation by drying, molding the dried for between cellulose binds with strong hydrogen bonding is difficult. On the other hand, since the microfibrillated plant fiber of the present invention contains lignin having thermoplasticity, it can be thermoplasticized by heating to form a molded article even after drying and solidification. For example, after the microfibrillated plant fiber is dehydrated and appropriately dried, a microfibrillated plant fiber molded product can be produced while adjusting the shape in the mold.

  Moreover, the microfibrillated plant fiber of this invention can be mix | blended with resin similarly to the conventional microfibrillated cellulose, and can be used as a fiber composite resin. The content of the microfibrillated plant fiber in the resin containing the microfibrillated plant fiber is usually 1 to 99% by weight, preferably 3 to 90% by weight.

The material of the resin is not particularly limited. For example, polylactic acid, polybutylene succinate, vinyl chloride resin, vinyl acetate resin, polystyrene, ABS resin, acrylic resin, polyethylene, polyethylene terephthalate, polypropylene, fluororesin, amide resin, acetal resin, polycarbonate, cellulose plastic, polyglycolic acid, poly-3-hydroxybutyrate, poly-4-hydroxybutyrate, polyhydroxy shea Barireto, polyethylene adipate, polycaprolactone, polypropiolactone polyesters of lactones such as, polyethers such as polyethylene glycol, polyglutamic acid, polyamide polylysine, thermoplastic resins such as polyvinyl alcohol, phenol resins, urea resins, melamine resins, unsaturated polyester resins, Epo Shi resins, can be used a diallyl phthalate resin, polyurethane resin, silicon resin, and thermosetting resins such as polyimide resin, but are not limited to be used in combination singly or two or more. Preferred are biodegradable resins such as polylactic acid and polybutylene succinate, phenol resins, and epoxy resins.

  Examples of biodegradable resins include L-lactic acid, D-lactic acid, DL-lactic acid, glycolic acid, malic acid, succinic acid, ε-caprolactone, N-methylpyrrolidone, trimethylene carbonate, paradioxanone, 1,5- Examples include homopolymers such as dioxepan-2-one, hydroxybutyric acid, and hydroxyvaleric acid, copolymers, and mixtures of these polymers. One kind can be used alone, or two or more kinds can be used in combination. Preferred biodegradable resins are polylactic acid, polybutylene succinate, and polycaprolactone, and more preferred are polylactic acid and polybutylene succinate.

  The method of blending the microfibrillated plant fiber with the resin is not particularly limited, and a method of blending ordinary microfibrillated cellulose with the resin can be adopted. For example, a method of sufficiently impregnating a resin monomer solution with a sheet or molded body composed of microfibrillated plant fibers and polymerizing with heat, UV irradiation, a polymerization initiator, or the like, or a polymer resin solution or resin powder dispersion In addition to a method of sufficiently impregnating and drying, a method of sufficiently dispersing microfibrillated plant fibers in a resin monomer solution and polymerizing with heat, UV irradiation, a polymerization initiator, or a polymer resin solution or resin powder dispersion In addition to a method of sufficiently dispersing in a liquid and drying, a method of kneading and dispersing microfibrillated plant fibers in a heat-melted resin liquid, press molding, extrusion molding, injection molding, or the like. However, since the microfibrillated plant fiber of the present invention is hydrophobized by the presence of lignin as compared to the conventional microfibrillated cellulose, it is much more compatible with hydrophobic resins. As a result, the dispersibility of the fibers in the resin is excellent. For this reason, the compounding to resin is easy and the mechanical strength of the fiber reinforced resin obtained is also improved.

  In blending microfibrillated plant fibers into resins, surfactants, starches, polysaccharides such as alginic acid, natural proteins such as gelatin, glue, casein, inorganic compounds such as tannin, zeolite, ceramics, and metal powder, coloring Agents, plasticizers, fragrances, pigments, flow regulators, leveling agents, conductive agents, antistatic agents, ultraviolet absorbers, ultraviolet dispersants, and deodorants may be added.

  A preferred combination of the microfibrillated plant fiber and the resin is a microfibrillated plant fiber obtained by a grinder treatment from chemi-thermomechanical pulp, and the lignin weight% relative to the cellulose weight is 30 to 65 wt% (particularly 40 to 65 wt%). %) And a thermoplastic resin such as polybutylene succinate and polypropylene. The content of the microfibrillated plant fiber in the thermoplastic resin is usually preferably 2 to 70% by weight (particularly 20 to 60% by weight).

  Another preferred combination of microfibrillated plant fiber and resin is microfibrillated plant fiber obtained by biaxial defibration treatment from sulfite pulp or kraft pulp, and the lignin weight% with respect to the weight of cellulose is 2 to 50 wt%. % (Particularly 4 to 30% by weight) and a biodegradable resin such as polylactic acid or a thermoplastic resin such as polypropylene. The content of the microfibrillated plant fiber in the biodegradable resin or thermoplastic resin is usually preferably 2 to 70% by weight (particularly 20 to 60% by weight).

  As described above, a fiber-reinforced resin molded product can be produced. The resin molded product of the present invention is a resin molded product excellent in mechanical strength, particularly toughness, as compared with a resin molded product containing conventional microfibrillated cellulose. In addition, when the microfibrillated plant fiber of the present invention is used as the fiber, compared with the case of using the microfibrillated cellulose, since it contains a lot of lignin, it has excellent heat resistance and can be molded at a higher temperature. is there. The resin molded product of the present invention can be molded in the same manner as other moldable resins, and can be molded by, for example, extrusion molding or injection molding. The molding conditions may be applied by appropriately adjusting the molding conditions of the resin as necessary.

  According to the present invention, a microfibrillated plant fiber containing a relatively large amount of lignin and hemicellulose can be obtained. In addition, the decomposition temperature of the microfibrillated plant fiber is higher than that of ordinary microfibrillated cellulose. Use in aqueous systems such as low water control of the microfibrillated plant fiber compared to ordinary microfibrillated cellulose, which makes it excellent in drainage and dewaterability, and facilitates sheeting from a water-dispersed state. In addition, it is excellent in compatibility with the resin and can be easily blended as a fiber reinforced resin fiber, contributing to improvement in physical strength.

  EXAMPLES Hereinafter, although an Example etc. demonstrate this invention in detail, this invention is not limited to these. Hereinafter, the microfibrillated plant fiber may be referred to as MFPF, the microfibrillated cellulose may be referred to as MFC, and the chemithermomechanical pipe may be referred to as CTMP.

<Example 1>
(1) Manufacture of microfibrillated plant fiber from chemithermomechanical pulp Chemithermomechanical pulp (CTMP; conifer chemisermomechanical pulp Q250B60, B70, and B80 from Nippon Paper Industries Co., Ltd.) Suspended in water and sufficiently stirred to make a 1 wt% slurry, which was ground by a grinder (stone mill) to obtain microfibrillated plant fibers (MFP). The grinding process was performed only once. The microfibrillated cellulose thus obtained was once freeze-dried. The amount of vanillin obtained from the lignin content and the lignin content of MFPF was determined. Separately, the fine content was also measured. The results are shown in Table 1.

As shown in Table 1, in the microfibrillated plant fiber of the present invention, both the lignin content and the amount of vanillin are in the general range of conifers, and the plant raw materials lignin, cellulose, and hemicellulose are almost denatured or removed. Not suggested. In addition, the manufacturing conditions, measurement constant conditions, etc. in this example are as follows.
[grinder]
Serendipeter MKCA6-3 (Masuyuki Sangyo Co., Ltd.)
Whetstone: MKG-C80 # (Diameter 15cm)
Rotation speed: 1500rpm
Temperature: Room temperature (25 ° C)
[Lignin quantification method]
Measurement of Klason lignin content Wood-containing polysaccharides were made water-soluble by acid hydrolysis, and lignin was separated and quantified as water-insoluble substances by acid-catalyzed degeneracy reaction.

  About 1 g of a pulp sample was dried and its weight (S) was weighed. This sample was placed in a 100 ml beaker, 15 ml of 72% sulfuric acid was added, and the contents were sufficiently stirred with a glass rod to make the contents uniform. In a thermostatic chamber (20 ° C.), the mixture was allowed to stand for 2 hours with appropriate mixing. Thereafter, 560 ml of distilled water was added to the contents and transferred to a 1 L beaker. In order to keep the liquid volume constant, the mixture was boiled for 2 hours while appropriately adding distilled water. After standing to cool, the mixture was filtered through a 1G3 glass filter weighed in advance and washed with 500 m of mature distilled water. It dried for 24 hours with the ventilation dryer of 110 degreeC, and calculated the weight (W) of the obtained water-insoluble precipitate. The lignin content (L) was calculated according to the following formula.

Lignin content L (%) = W / S × 100
[Cellulose determination method]
About 1 g of a pulp sample was dried and its weight (S) was weighed. Add 30 ml of sodium sulfite and boil for 10 minutes, then filter. As an exposure step, add 30 ml each of calcium hypochlorite with 10% effective chlorine and 20% concentrated sulfuric acid and let stand for 10 minutes. These boiling, washing and bleaching were repeated and finally washed with warm water and ether and then dried for 24 hours with a blow dryer at 110 ° C., and the weight (W) of the obtained water-insoluble precipitate was calculated. The cellulose content (C) was calculated according to the following formula.

Cellulose content C (%) = W / S × 100
Lignin weight% with respect to cellulose weight = lignin content L / cellulose content C × 100
[Vanillin quantification method]
Vanillin produced by oxidative degradation of lignin by alkaline nitrobenzene oxidation was quantitatively analyzed by gas chromatography.

2N-NaOH solution (4 ml) and nitrobenzene (0.24 ml) are added to 100 mg of a sample (lyophilized microfibrillated plant fiber) and heated at 170 ° C. for 2 hours in an autoclave. Vanillin was extracted from the reaction solution, acetylated, and quantitatively analyzed by gas chromatograph (Shimadzu GC-18A type).
[Quantitative analysis of constituent sugars]
The alditol acetate method was applied. That is, the sample was acid-hydrolyzed (after reducing the released monosaccharides, the produced alditol was acetylated and quantitatively analyzed by gas chromatography.

72% sulfuric acid (0.3 ml) is added to 80 mg of a sample (lyophilized microfibrillated plant fiber) and left at 30 ° C. for 1 hour. Thereafter, water (8.4 ml) is added and heated in an autoclave at 120 ° C. for 1 hour. The reaction solution was adjusted to pH 5.5-5.3 using saturated Ba (OH) ₂ and sodium borohydride (NaBH ₄ ) was added to reduce monosaccharides in the aqueous solution to obtain alditol. The resulting alditol was mixed with 2 ml of acetic anhydride and 0. After adding 1 ml and acetylating, it was quantitatively analyzed by gas chromatograph (Shimadzu GC-18A type).
(2) Manufacture of sheet-like MFPF (hot press sheet)
The microfibrillated plant fiber (MFP) obtained above was poured (cast) into a Teflon (registered trademark) petri dish and dried in a dryer at 105 ° C. to obtain a sheet-like MFPF.

  The sheet-like MFPF thus obtained was observed with an electron microscope (upper left 2000 times in FIG. 2, upper right 20000 times in FIG. 2).

Furthermore, the microfibrillated plant fiber (MFP) obtained above was freeze-dried, and the obtained solid was pulverized with an analytical pulverizer (R-8, Nihon Riken Kikai Co., Ltd.) to obtain a powder. The obtained powder (about 2 g) was put into a round mold with φ = 50 mm and pressed at 19 MPa for 15 minutes to obtain a sheet having a thickness of about 1 mm. The produced sheets were each dried at 110 ° C. for 2 hours and then hot pressed under the conditions of 200 ° C., 130 MPa, and 5 minutes. After pressing, neither cooling nor removal was performed.
(3) Manufacture of MFPF-blended polybutylene succinate (PBS) resin The MFPF slurry treated with a grinder was mixed with lab plast mill (mixing temperature: 130) with PBS fine powder (average particle size 13, 1 μm) and fiber content 10% by weight. C., kneading time: 5 minutes), and the resulting kneaded product is formed into a sheet (thickness: about 35 .mu.m) by hot pressing (NF-50 type, 20 MPa, 130.degree. C., manufactured by Shindo Metal Industry Co., Ltd.). An MFPF-containing PBS resin was obtained.
<Example 2>
Production of MFPF from delignified (low chlorite treated (weak)) lignin-rich pulp 30 g of CTMP was dispersed in 570 ml of distilled water and heated to 50 ° C. Next, 6 g of sodium chlorite was added and stirred well with a glass rod. Further, about 1 ml of acetic acid was added, and the pH was adjusted to 4 to 5 with a pH test paper. On the way, it was kept for 1 hour with stirring. After completion of the reaction, the reaction solution was removed by filtration, further dispersed in 1 L of distilled water and filtered. This operation was performed 4 times in total. The obtained chlorite-treated pulp was dispersed in 3 L of distilled water, treated with the same grinder as in Example 1, and microfibrillated to produce MFPF. Except for these, a composite with a hot press sheet and PBS resin was prepared in the same manner as in Example 1.
<Example 3>
Production of MFPF from alkali-treated lignin-rich pulp 20 g of CTMP was dispersed in 2 L of 5% aqueous sodium hydroxide and stirred at room temperature for 6 hours. After completion of the reaction, the reaction solution was removed by centrifugation at 300 rpm for 3 minutes. The obtained precipitate was dispersed in 1 L of 5% acetic acid aqueous solution, and neutralized by centrifugation at 300 rpm for 3 minutes. Further, the obtained precipitate was dispersed in 2 L of distilled water and filtered. This operation was repeated until the filtrate became neutral.

The obtained alkali-treated pulp was dispersed in 2 L of distilled water, treated with the same grinder as in Example 1, and microfibrillated to produce MFPF. Except for these, a hot press sheet was prepared in the same manner as in Example 1.
<Example 4>
Production of MFPF from acetylated lignin-rich pulp 10 g of CTMP was dispersed in 1 L of distilled water and dehydrated by filtration. The filter residue was dispersed in acetic acid 800 ml, and acetic anhydride 82m l, and 60% perchloric acid 4.6 m l was added pressure, and stirred at room temperature for 1 hour. About 100 ml of distilled water was added to terminate the reaction, and the reaction solution was removed by filtration. Further, the dispersion was dispersed in 2 L of distilled water and filtered, and this operation was repeated until the filtrate became neutral to obtain an acetylated pulp. Separately, 10 g of CTMP was used in the same manner to obtain an acetylated pulp, which was combined with the previously obtained acetylated pulp to obtain about 20 g of acetylated pulp in total.

The obtained pulp was dispersed in 2 L of distilled water, treated with a grinder, and microfibrillated to produce MFPF. Except for these, a composite with a hot press sheet and PBS resin was prepared in the same manner as in Example 1.
<Example 5>
Manufacture of a composite resin of microfibrillated cellulose (MFC) and polylactic acid Nippon Paper Industries' lignin-containing sulfite pulp (solid content 25.1%, lignin amount: 5.2 % with respect to cellulose) 79.7 g (pulp Content 20 g) was dispersed in an aqueous solution so as to have a solid content concentration of 3%, and then 80 g of polylactic acid (trade name Lacia H100, manufactured by Mitsui Chemicals) was added to the aqueous solution and stirred for 2 hours.

  The obtained pulp / polylactic acid suspension was suction filtered using a filter paper having a diameter of 18.5 cm and air-dried. The obtained pulp / polylactic acid mixed sheet was peeled off from the filter paper and placed in a technobel twin-screw extruder (screw diameter: 15 mm) to simultaneously disentangle pulp and mix pulp and polylactic acid. The speed of rotation is 400 / min and the defibration time is 60 minutes.

The obtained mixture of microfibrillated cellulose and polylactic acid was melt-kneaded in a lab plast mill (manufactured by Toyo Seiki; MODEL 30C 150). The kneading conditions were 180 ° C. and a rotation speed of 40 RPM for 15 minutes. The obtained mixture was press-molded with a molding machine (Kanto Metal Industry Co., Ltd.). The molding conditions are 180 ° C. and 0.5 MPa for 5 minutes, and then 2 MPa for 10 minutes. Thereby, a press-molded product was obtained.
<Example 6>
After dispersing 224.2 g (pulp content 50 g) of NUKP (solid content: 22.3%, cellulose content: 14.3 % with respect to cellulose) in an aqueous solution so as to have a solid content concentration of 3%, 44.4 g of polypropylene (manufactured by Nippon Polypro, trade name: MA4AHB) and maleic acid-modified polypropylene (trade name: H1000, manufactured by Toyo Kasei Kogyo) were added to the aqueous solution and stirred for 2 hours. The obtained pulp / polypropylene / maleic acid-modified polypropylene mixed solution was suction filtered using a filter paper having a diameter of 18.5 cm and air-dried. The obtained pulp / polypropylene / maleic acid-modified polypropylene mixed sheet is peeled off from the filter paper and placed in a technovel twin-screw extruder (screw diameter: 15 mm), and the pulp is defibrated and mixed with the pulp and polypropylene / maleic acid-modified polypropylene. At the same time. The speed of rotation is 400 / min and the defibration time is 60 minutes.

A mixture of the obtained microfibrillated cellulose, polypropylene, and maleic acid-modified polypropylene was melt-kneaded in a lab plast mill (manufactured by Toyo Seiki; MODEL 30C 150). The kneading conditions were 180 ° C. and a rotation speed of 40 RPM for 15 minutes. The obtained mixture was press-molded by a press with a molding machine (Kanto Metal Industry Co., Ltd.). The molding conditions are 180min 0.5MPa for 5min, then 2MPa for 10min. Thereby, a press-molded product was obtained.
<Comparative Example 1>
Lignin-removed (chlorinated acid treatment (strong)) lignin-removed undefibrated pulp Chemi-thermomechanical pulp used in Example 1 (CTMP; Chemi-thermomechanical pulp Q250B60, B70 of softwood made by Nippon Paper Industries Co., Ltd.) 3 types of B80) were suspended in an equal amount of water and stirred sufficiently to obtain a 1 wt% slurry. However, unlike Example 1, it was cast into a Teflon (registered trademark) petri dish without being ground by a grinder (stone mill grinder) and dried in a dryer at 105 ° C. to form a sheet. The lignin was removed by “lignin removal treatment” described later to obtain a cellulose sheet.

  Lignin removal was performed as follows. 5 g of the above-mentioned dried cast sheet was placed in a solution of 300 ml of distilled water, 2 g of sodium chlorite, and 0.4 ml of glacial acetic acid, and heated in a hot water bath at 70-80 ° C. for 1 hour with occasional stirring. After 1 hour, 2 g of sodium chlorite and 0.4 ml of glacial acetic acid were added again and heated in the same manner.

After this repeated treatment is performed four times, the lignin-removed undefibrated pulp sheet is obtained by washing with 3 L of cold water and 300 ml of acetone. Other than this, a hot press sheet was prepared in the same manner as in Example 1.
<Comparative example 2>
Production of MFC from Delignified (Chlorous Acid Treated (Strong)) Pulp 50 g of CTMP obtained in Example 1 was dispersed in 570 ml of distilled water and heated to 80 ° C. Next, 10 g of sodium chlorite was added and mixed well with a glass rod. Further, about 2 ml of acetic acid was added, and the pH was adjusted to 4 to 5 with a pH test paper. On the way, it was kept for 1 hour with stirring. Subsequently, the same amount of sodium chlorite and acetic acid were added, and the same operation was performed. This operation was performed 5 times in total. After completion of the reaction, the reaction solution was removed by filtration, further dispersed in 2 L of distilled water and filtered. This operation was performed 4 times.

The obtained chlorite-treated pulp was dispersed in 2 L of distilled water, treated with the same grinder as in Example 1, and microfibrillated to produce MFC. This MFC was poured into a Teflon (registered trademark) petri dish (cast) and dried in a dryer at 105 ° C. to obtain a sheet-like microfibrillated cellulose (MFC). This sheet-like MFC (Comparative Example 2) was observed with an electron microscope (lower left side of FIG. 2 5000 times, lower right side of FIG. 2 30000 times). From the comparison between the upper and lower stages of FIG. 2, it was confirmed that the cellulose fibers were filled with lignin in the sheet shown in the upper stage. Except for these, a composite with a hot press sheet and PBS resin was prepared in the same manner as in Example 1.
<Comparative Example 3>
Production of a composite resin of microfibrillated cellulose (MFC) and polylactic acid using delignified (chlorinated acid (strong)) pulp In the same manner as in Comparative Example 2, 50 g of CTMP was dispersed in 570 ml of distilled water and heated to 80 ° C. Next, 10 g of sodium chlorite was added, stirred well with a glass rod, about 2 ml of acetic acid was further added, and the pH was adjusted to 4-5 with pH test paper. On the way, it was kept for 1 hour with stirring. Subsequently, the same amount of sodium chlorite and acetic acid were added, and the same operation was performed. This operation was performed 5 times in total. After completion of the reaction, the reaction solution was removed by filtration, further dispersed in 2 L of distilled water and filtered. This operation was performed 4 times.

  The obtained chlorite-treated pulp was dispersed in 2 L of distilled water, treated with the same grinder as in Example 1, and microfibrillated to produce MFC. After this MFC was dispersed in an aqueous solution so as to have a solid content concentration of 3%, 80 g of polylactic acid (trade name Lacia H100, manufactured by Mitsui Chemicals) was added to the aqueous solution and stirred for 2 hours. The obtained pulp / polylactic acid suspension was suction filtered using a filter paper having a diameter of 18.5 cm and air-dried. The obtained pulp / polylactic acid mixed sheet was peeled off from the filter paper and placed in a technobel twin-screw extruder (screw diameter: 15 mm) to simultaneously disentangle pulp and mix pulp and polylactic acid. The speed of rotation is 400 / min and the defibration time is 60 minutes.

The obtained mixture of microfibrillated cellulose and polylactic acid was melt-kneaded in a lab plast mill (manufactured by Toyo Seiki; MODEL30C150). The kneading conditions were 180 ° C. and a rotation speed of 40 RPM for 15 minutes. The obtained mixture was press-molded with a molding machine (Kanto Metal Industry Co., Ltd.). The molding conditions are 180 ° C. and 0.5 MPa for 5 minutes, and then 2 MPa for 10 minutes. Thereby, a press-molded product was obtained.
<Comparative Example 4>
Production of composite resin of NBKP microfibrillated cellulose (MFC) and polypropylene NBKP (solid content 23.6%, lignin content: 0% with respect to cellulose) 211.9 g (pulp content 50 g) made from Oji Paper A press-molded product was produced in the same manner as in Example 6 except that it was dispersed in an aqueous solution so as to have a partial concentration of 3%.
<Comparative Example 5>
Nippon Paper's lignin-free kraft pulp (solid content 30.0%, lignin content: 0% with respect to cellulose) is dispersed in an aqueous solution to a solid content concentration of 3%, and then a high-pressure homogenizer from SMT Co., Ltd. Using LAB1000, MFPF was manufactured by homogenizer treatment (15-pass circulation) at a pressure of 500 kg / m ² . Except for these, a hot press sheet was prepared in the same manner as in Example 1.
<Test example>
The following analysis was performed using the cellulose, the hot press sheet, the composite with PBS resin, and the composite with PLA or PP obtained in Examples and Comparative Examples. The test results are shown in Table 2.

The test method in this example is as follows.
[Pyrolysis temperature measurement]
Measurement was performed under the following conditions using about 3 mg of a sample. TGA2050 (TA Instruments) was used as a measuring device, held at 110 ° C. for 10 minutes, and then heated to 500 ° C. at 10 ° C./min.
[Degree of acetylation] (Applicable only to MFPF of Example 4)
About 0.2 g of the sample of Example 4 was dried for 24 hours with a blow dryer at 110 ° C., and the weight (S) after drying was weighed. Methanol 15m1 / distilled water 5ml was added and stirred at 70 ° C. 30 min. 10 ml of 0.5N NaOH was added, and the mixture was further stirred at 70 ° C. for 15 minutes, and subsequently stirred at room temperature for 24 hours. Thereafter, titration with 0.2N HCl was performed to determine the amount of 0.2N-HCl required (A (ml)). Furthermore, the same operation as described above was performed using untreated pulp (weight after drying: S ′), and the amount of 0.2N—HCl (A ′ (ml)) required for titration was determined. The degree of acetylation was determined using the following formula. In addition, each sample prepared 5 pieces, and let the average value be acetylation degree.

Amount of NaOH consumed by the sample (mol) = (0.5 × 100 × 1 / 1000−0.2 × A × 1/1000) / S = X
Amount of NaOH consumed by untreated pulp (mol1 / g) = (0.5 × 100 × 1 / 1000−0.2 × A ′ × 1/1000) / S ′ = Y
Amount of NaOH consumed by the acetyl group of the sample (mol) = (XY) × S = Z
Degree of acetylation (%) = Z × 60 / S × 100
[density]
The sample was cut into a size of 35 mm × 5 mm. Five of them were prepared for each sample and dried under vacuum conditions at 50 ° C. for 24 hours. The density of each sample was calculated from the weight after drying.
[Equilibrium moisture content]
The sample was cut into a size of 35 mm × 5 mm, and five samples were prepared for each sample and dried under a vacuum condition at 50 ° C. for 24 hours. After drying, each sample was weighed and allowed to stand for 2 days in an atmosphere of 20 ° C. and 47% RH to adjust the humidity. The weight after conditioning was measured, and the equilibrium water content was calculated.
[Hot water resistance]
The sample was cut into a size of 10 mm × 5 mm, and five samples were prepared and dried under a vacuum condition at 50 ° C. for 24 hours. After drying, the weight and thickness were measured and immersed in warm water at 50 ° C. for 5 minutes. After elapse of a predetermined time, it was taken out and lightly wiped off moisture on the surface, and then the weight and thickness were measured, and the rate of increase thereof was calculated.
[Measurement of bending Young's modulus and bending strength of sheet-like molded product]
According to JIS K 7203 (plastic bending test method), the bending properties of the sheet-like MFPFs obtained in Examples 1, 2, 4, 5, and 6 and the sheets obtained in Comparative Examples 2, 3, and 4 are 3 Measured by point bending.

  The measuring instrument used for measuring the bending Young's modulus and bending strength is an Instron 3365 type (manufactured by Instron Corporation), and the sample has a thickness of 1 mm, a width of 4 mm, and a length of 8 cm. The results are shown in Table 2.

  From the results shown in Table 2 and FIG.

  It was confirmed that the MFPFs of Examples 1 to 4 had a thermal decomposition temperature higher by 13 ° C. or more than the MFC of the pulp containing almost no lignin of Comparative Example 2, and were remarkably excellent in thermal stability. In particular, MFPF (Example 4), which is an acetylated lignin-rich pulp, has a thermal decomposition temperature higher by 37 ° C. or more than the MFPFs of Examples 1 to 3, and particularly high thermal stability.

  An Example and a comparative example are contrasted. For example, Examples 1, 2, and 4 showed higher bending Young's modulus and bending strength than Comparative Example 2. In addition, Example 5 showed higher bending strength than Comparative Example 3 and Example 6 showed higher bending strength than Comparative Example 4.

  Also, the MFPF-containing PBS resin was more familiar with the resin (polybutylene succinate) than the MFC-containing PBS resin from which lignin was removed, and showed an increase in fracture strain of nearly 50%.

  From this result, it can be seen that the fibers are well bonded and the rigidity of the molded body is high. This is due to improved adhesion between fibers due to thermoplasticity of lignin.

  Only the density of Example 2 was lower than that of the comparative example, and the densities of the other examples were almost the same as those of the comparative example.

  The examples were clearly hot water resistant than the comparative examples. Therefore, it can be seen that in the examples, the hydrophobicity of the fibers is stronger than that of the comparative example due to the effect of containing lignin, and a molded article having better water resistance and moisture resistance than the comparative example is obtained.

The upper diagram is a schematic diagram showing the plant cell wall structure, and the lower diagram is a schematic diagram showing the basic structure of the plant fiber. In the upper figure, the plant cell wall shows that a plurality of layers having different orientations of cellulose microfibrils are laminated, and the line in the figure shows the orientation direction of the microfibrils. The following figure is an enlargement of a part thereof, Mfa indicates a cellulose microfibril amorphous region, Mfc indicates a cellulose microfibril crystal region, HC indicates hemicellulose, and a cross section indicates a cross section of the cellulose microfibril and its surroundings. The figure shows a longitudinal section showing a longitudinal section along a cellulose microfibril. If mimicking fiber reinforced plastic (FRP), it schematically shows that the periphery of microfibrils, which are reinforcing fibers, is covered in the order of matrix components, hemicellulose, and lignin. The upper row is an electron micrograph of the sheet-like MFPF (Example 2) (upper left 2000 times in FIG. 2, upper right 20000 times in FIG. 2). The lower row is a delignified sheet-like MFC electron microscope (5000 lower left in FIG. 2, 5000 right lower in FIG. 2). It is a graph showing the result of the tensile test of the molded product obtained in Example 1 and Comparative Example 2 in the test example, where the solid line (-) indicates the MFPF-containing PBS resin molded product (Example 1), and the broken line (...) indicates the MFPF. It is a PBS resin molded product (Comparative Example 2) containing a fiber that has been delignified. The vertical axis represents stress (MPa) and the horizontal axis represents strain (%).

Claims (11)

A microfibrillated plant fiber obtained by mechanically defibrating pulp containing 14.3 to 70% by weight of lignin with respect to cellulose weight. The microfibrillated plant fiber according to claim 1, wherein the mechanical fibrillation treatment is a grinding treatment. The microfibrillated plant fiber according to claim 1 or 2, having a structure in which hemicellulose and / or lignin is coated around cellulose microfibrils and / or cellulose microfibril bundles. The microfibrillated plant fiber according to claim 3, which has a structure in which the periphery of cellulose microfibril and / or cellulose microfibril bundle is coated in the order of hemicellulose and lignin. The pulp subjected to mechanical defibration is at least one chemically modified pulp selected from the group consisting of esterified pulp, etherified pulp, acetalized pulp and pulp treated with lignin aromatic rings. The microfibrillated plant fiber according to any one of claims 1 to 4. A microfibrillated plant fiber molded body obtained by molding the microfibrillated plant fiber according to any one of claims 1 to 5. The resin molding containing the microfibrillated plant fiber in any one of Claims 1-5. A method for producing a microfibrillated plant fiber comprising mechanically defibrating pulp containing 14.3 % to 70% by weight of lignin relative to the weight of cellulose. The production method according to claim 8, wherein the defibration is a grinding treatment. The method according to claim 8 or 9, wherein the pulp is digested with water and then defibrated. The pulp subjected to mechanical defibration is at least one chemically modified pulp selected from the group consisting of esterified pulp, etherified pulp, acetalized pulp and pulp treated with lignin aromatic rings. The manufacturing method according to any one of claims 8 to 10.