Ultraviolet permeation suppressing material containing lignocellulose nanofibers

Abstract

To provide an ultraviolet transmission suppressing material containing a lignocellulose nanofiber having a high ultraviolet transmission suppressing effect, no toxicity and a low environmental load.SOLUTION: The ultraviolet transmission suppressing material contains lignocellulose nanofibers (LCNF).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an ultraviolet transmission inhibitor containing lignocellulose nanofibers. [Background technology]

[0002] Cellulose has recently been utilized as a renewable resource. Nanocellulose fibers, obtained by micronizing cellulose, have been incorporated into resins and other materials to improve mechanical strength. Examples of nanocellulose fibers include long-fiber cellulose nanofibers (CNF) and short-fiber, needle-shaped cellulose nanocrystals (CNC). Other well-known nanocellulose fibers include bacterial cellulose nanofibers produced by cellulose-producing bacteria such as acetic acid bacteria, and chitin and chitosan nanofibers, which are different from cellulose. Nanocellulose fibers can be obtained by chemical or mechanical defibration of cellulose extracted from wood, a combination of these processes, or synthesis using cellulose-producing bacteria such as acetic acid bacteria. Chemical defibration processes include TEMPO oxidation, phosphate esterification, and enzymatic hydrolysis. Mechanical defibration processes include high-pressure homogenization, microfluidization, grinder grinding, freeze-pulverization, high-shear kneading, and ball mill grinding.

[0003] Patent Document 1 describes a method for producing a resin material reinforcement, which includes the steps of mixing water, microcellulose fibers containing nanocellulose fibers, and a filler surface-treated with fatty acids while applying shear force, drying the mixture, and pulverizing the solid content after drying. According to this method, the resin material reinforcement can be easily produced by preventing the microcellulose fibers from aggregating during the drying process, and when the resin material reinforcement is blended into a resin material, the strength of the resin material can be significantly improved compared to conventional methods. However, there have been no reports of the ability to effectively suppress UV transmission.

[0004] Meanwhile, Patent Document 2 describes a polyolefin resin composition obtained by adding (B) talc surface-treated with an organic silane compound, (C) a hindered amine stabilizer, and (D) an ultraviolet absorber to (A) a polyolefin. According to this document, a polyolefin resin composition with excellent weather resistance can be provided by using talc surface-treated with an organic silane compound, a hindered amine stabilizer, and an ultraviolet absorber in combination. However, the ultraviolet absorbers used are toxic, and in some cases require neutralization to reduce the environmental impact upon disposal, so a safer ultraviolet absorber has been desired. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-144614 [Patent Document 2] Japanese Patent Application Publication No. 6-220261 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made to solve the above-mentioned problems, and aims to provide an ultraviolet light transmission inhibitor containing lignocellulose nanofibers that has a high ultraviolet light transmission inhibitory effect, is non-toxic, and has a low environmental impact. [Means for solving the problem]

[0007] The above problems are solved by providing an ultraviolet transmission inhibitor containing lignocellulose nanofibers (LCNF).

[0008] In this case, it is preferable that the composition further contains a filler, and the mass ratio of the filler to the LCNF (filler / LCNF) is 0.3 / 1 to 12 / 1.

[0009] A resin composition containing the ultraviolet transmission suppressor is a preferred embodiment, a resin pellet containing the ultraviolet transmission suppressor is a preferred embodiment, a coating material containing the ultraviolet transmission suppressor is a preferred embodiment, and a paint containing the ultraviolet transmission suppressor is also a preferred embodiment. [Effects of the Invention]

[0010] The present invention can provide an ultraviolet light transmission inhibitor containing lignocellulose nanofibers that has a high ultraviolet light transmission inhibitory effect, is non-toxic, and has a low environmental impact. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a graph showing the results of measuring the light transmittance of the polypropylene sheets obtained in Example 1 and Comparative Examples 1 and 2. FIG. [Figure 2] FIG. 1 is a graph showing the results of measuring the light transmittance of the polypropylene sheets obtained in Examples 1 to 5. [Figure 3] FIG. 2 is a graph showing the results of a tensile test conducted after a weather resistance test using the polypropylene pellets obtained in Example 1 and Comparative Example 2. [Figure 4] FIG. 1 shows the results of a tensile test conducted after a weather resistance test using polypropylene pellets obtained in Example 6 and Comparative Example 3. [Figure 5] FIG. 1 shows the results of measuring the light transmittance of an LCNF-containing varnish and varnish alone. [Figure 6] FIG. 1 is a diagram showing regions A to F of a circular iron plate coated with red paint in a metal halide test. [Figure 7] FIG. 1 is a diagram showing the results of observation under a polarizing microscope in the evaluation of dispersibility. DETAILED DESCRIPTION OF THE INVENTION

[0012] The UV suppressor of the present invention is characterized by containing lignocellulose nanofibers (hereinafter sometimes abbreviated as "LCNF"). In addition to LCNF, other nanocellulose fibers are known, including cellulose nanofibers (CNF), cellulose nanocrystals (CNC), bacterial cellulose nanofibers, and, although not cellulose, chitin nanofibers and chitosan nanofibers. However, the inventors' extensive research has revealed that the inclusion of LCNFs results in a UV suppressor with enhanced UV suppression. Comparing the examples and comparative examples in the UV acceleration test described below, the polypropylene pellets of Comparative Example 2, which does not contain LCNF, and the polypropylene pellets of Comparative Example 1, which contains CNF, showed a decrease in number-average molecular weight Mn after the UV acceleration test. The ratio of weight-average molecular weight Mw to number-average molecular weight Mn (Mw / Mn dispersity) was larger than that of blank PP, indicating a broader molecular weight distribution. This suggests that the UV acceleration test decomposed the polypropylene to produce low-molecular-weight polypropylene. In contrast, the polypropylene pellets of Example 1 containing LCNF did not show a decrease in molecular weight after the UV accelerated test, and the Mw / Mn (dispersity) remained almost unchanged compared to the blank PP, demonstrating a high UV transmission suppression effect. The inventors have demonstrated that adding the UV transmission inhibitor of the present invention to a resin or the like suppresses UV penetration into the resin or the like, thereby suppressing UV degradation (decomposition and deterioration of mechanical properties) of the resin or the like.

[0013] The LCNF used in the present invention can be obtained by known methods such as high-pressure homogenizer, microfluidizer, grinder milling, freeze-pulverization, high-shear kneading, ball mill milling, and water jet milling. LCNF contains a certain amount of lignin, which distinguishes it from lignin-free CNF. The lignin content of the LCNF is preferably 1 to 80% by mass, more preferably 2 to 70% by mass, and even more preferably 3 to 60% by mass. The LCNF used in the present invention contains cellulose and hemicellulose in addition to lignin. The cellulose content of the LCNF is preferably 15 to 80% by mass, more preferably 20 to 70% by mass, and even more preferably 30 to 60% by mass. The hemicellulose content of the LCNF is preferably 5 to 40% by mass, more preferably 8 to 35% by mass, and even more preferably 12 to 30% by mass. The LCNF used in the present invention may further contain certain amounts of ash and organic solvent-soluble components. The ash content of the LCNF is preferably 0.01 to 3 mass%, more preferably 0.05 to 2 mass%, and even more preferably 0.1 to 1.5 mass%. The organic solvent soluble content of the LCNF is preferably 0.1 to 10 mass%, more preferably 0.5 to 8 mass%, and even more preferably 1 to 5 mass%.

[0014] The fiber width (fiber thickness) of the LCNF used in the present invention is preferably 2 nm to 50 μm, more preferably 5 nm to 30 μm, even more preferably 10 nm to 10 μm, and particularly preferably 15 nm to 1 μm. The fiber length of the LCNF used in the present invention is preferably 10 nm to 5 mm, more preferably 50 nm to 2 mm, even more preferably 100 nm to 1 mm, and particularly preferably 500 nm to 500 μm.

[0015] In a preferred embodiment, the ultraviolet transmission suppressor of the present invention further contains a filler, and the mass ratio of the filler to the LCNF (filler / LCNF) is 0.3 / 1 to 12 / 1. Having the mass ratio (filler / LCNF) within this range has the advantage of preventing aggregation of the LCNF and of obtaining a uniform composition when the ultraviolet transmission suppressor is mixed with a resin or the like. The mass ratio (filler / LCNF) is more preferably 0.5 / 1 to 10 / 1, even more preferably 0.8 / 1 to 8 / 1, particularly preferably 1 / 1 to 6 / 1, and most preferably 1.2 / 1 to 4 / 1.

[0016] Examples of fillers that can be used include fillers that are incorporated into molded articles made from synthetic resin materials such as rubber or plastic, and fillers that are incorporated into synthetic resin compositions such as paints. Examples include calcium carbonate, talc, silica, clay, wollastonite, potassium titanate, zonolite, titanium oxide, and magnesium oxide. Among these, fillers that have been surface-treated with a fatty acid and / or a fatty acid salt are preferred. For example, a slurry obtained by mixing a filler with water is stirred while being heated to about 50 to 70°C, and a fatty acid and / or a fatty acid salt is added thereto and further stirred. This mixture is pressed, dehydrated, and then dried, and can be used. The filler may be treated with other components in addition to the fatty acid and / or fatty acid salt. Examples of other components include a silane coupling agent.

[0017] The fatty acid may be either saturated or unsaturated, but saturated fatty acids are preferred because unsaturated fatty acids are prone to oxidation and deterioration. Fatty acids with a low carbon number tend to have a stronger odor. For this reason, fatty acids preferably have 6 or more carbon atoms, more preferably 10 or more. Because a high carbon number increases the melting point, fatty acids with a high carbon number tend to have a carbon number of 30 or less, more preferably 24 or less. Examples of fatty acids include caproic acid, decanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, and oleic acid. Examples of fatty acid salts include sodium salts of the above fatty acids and potassium salts of the above fatty acids.

[0018] By making the particle size of the filler approximately the same as the fiber width of the LCNF, it becomes possible to mix the filler and LCNF uniformly during the mixing process. This makes it possible to obtain a uniform composition when blended into a resin material, etc. The average particle size of the filler is preferably 2 to 100 μm, and more preferably 2 to 50 μm. The average particle size of the filler refers to the particle size at 50% of the cumulative value in the particle size distribution determined by laser diffraction / scattering.

[0019] When the ultraviolet transmission suppressor of the present invention further contains a filler, a preferred embodiment is to obtain a mixture by wet-mixing a paste-like LCNF and the filler while applying shear force. Dry mixing can result in the LCNF diffusing into the air. Wet mixing can prevent the LCNF from diffusing into the air and reducing yield. The application of shear force allows the LCNF and the filler to be uniformly mixed. It is believed that the application of shear force physically bonds the LCNF and the filler to each other and integrate them. Mixing while applying shear force can be performed using a mixer, ball mill, stone-type mill such as a mass colloider, or homogenizer.

[0020] In a preferred embodiment, after obtaining the mixture, a drying step is carried out to reduce the moisture content of the mixture and obtain a dried product. The drying method is not particularly limited, and examples thereof include a method in which the mixture is placed in any container and the container is stored in a warm air dryer. A vacuum dryer may be used instead of the warm air dryer. Using a vacuum dryer can lower the boiling point and reduce the moisture content in a shorter time.

[0021] After obtaining the dried product, a pulverization step can be carried out to suitably obtain the ultraviolet transmission suppressor of the present invention. The pulverization method is not particularly limited, and for example, pulverization can be simply carried out using a device such as a mixer, a pin mill, a roller mill, or a hammer mill. By pulverizing using any method, the ultraviolet transmission suppressor of the present invention in powder form can be easily obtained.

[0022] The ultraviolet transmission suppressor of the present invention can be blended with various materials. For example, the ultraviolet transmission suppressor of the present invention can be blended with resins such as polyolefin resins such as polyethylene and polypropylene; polyester resins such as polyethylene terephthalate and polybutylene terephthalate; polyamide resins such as nylon; polystyrene resins; epoxy resins; acetal resins; and fluorine-based resins to produce resin compositions or resin pellets. Therefore, a resin composition blended with the ultraviolet transmission suppressor is a preferred embodiment, and a resin pellet blended with the ultraviolet transmission suppressor is also a preferred embodiment.

[0023] The ultraviolet transmission suppressor of the present invention can also be blended with rubbers such as natural rubber, isoprene rubber, butadiene rubber, chloroprene rubber, acrylonitrile-butadiene copolymer rubber, ethylene-propylene-diene terpolymer rubber, urethane rubber, silicone rubber, fluorine-based rubber, etc., and can also be blended with thermoplastic elastomers such as styrene-based thermoplastic elastomers, olefin-based thermoplastic elastomers, urethane-based thermoplastic elastomers, polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, etc. Therefore, rubbers blended with an ultraviolet transmission suppressor are preferred embodiments, and thermoplastic elastomers blended with an ultraviolet transmission suppressor are also preferred embodiments.

[0024] Furthermore, the UV transmission suppressor of the present invention can be incorporated into paint. In the present invention, the term "paint" includes coating materials used as top coats. Therefore, a paint containing a UV transmission suppressor is a preferred embodiment, and a coating material containing a UV transmission suppressor is also a preferred embodiment. A preferred embodiment of the paint is that a resin, a solvent, or the like is incorporated as needed. Examples of resins include vinyl acetate resins, urethane resins, acrylic resins, polyester resins, epoxy resins, polyvinyl alcohol resins, and polyurea resins. Examples of solvents include water or aqueous solvents containing water as the main component; alcohol-based solvents such as methanol, ethanol, propanol, isopropanol, and butanol; polyhydric alcohol-based solvents such as ethylene glycol, diethylene glycol, thiodiethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol; aromatic hydrocarbon-based solvents such as toluene and xylene; ether-based solvents such as dimethyl ether, ethyl methyl ether, diethyl ether, tetrahydrofuran, and 1,4-dioxane; and nitrile-based solvents such as acetonitrile, propionitrile, and benzonitrile. The paint may be a paint containing a coloring pigment, or a clear paint that does not contain a coloring pigment, such as a varnish. Among these, a water-based paint containing a coloring pigment is a preferred embodiment, and a water-based clear paint used as a top coat is also a preferred embodiment. Other additives, such as plasticizers, dispersants, anti-settling agents, emulsifiers, thickeners, antifoaming agents, mildew inhibitors, preservatives, anti-skinning agents, and anti-sagging agents, may be added within a range that does not impair the effects of the present invention.

[0025] As described above, the ultraviolet transmission suppressor of the present invention can be incorporated into various materials, and therefore can be suitably used in a variety of applications where deterioration by ultraviolet rays is expected, such as agricultural resin sheets; automotive resin parts; everyday items such as clothespins and resin ropes; paints (including coating materials) for automobiles, building materials, stationery, etc.; sealants used on residential exterior walls; lubricants; and adhesives. When the ultraviolet transmission suppressor of the present invention is incorporated into various materials, poor dispersion is acceptable as long as the ultraviolet transmission suppression effect is not impaired. When used in applications where a good appearance is desired, a good dispersion state is preferred. [Example]

[0026] The present invention will be described in more detail below with reference to examples. The raw materials used in the following examples are as follows. [Raw materials] Lignocellulose nanofibers (LCNF; ash content 0.3% by mass, organic solvent soluble content 2.9% by mass, lignin 34% by mass, cellulose 47% by mass, hemicellulose 15% by mass) were used, Cellfim L100 manufactured by Mori Machinery Co., Ltd. The fiber width was 30 to 300 nm, and the fiber length was 100 μm or less. Cellulose nanofibers (CNF; lignin 0 mass%, cellulose 90 mass%, hemicellulose 10 mass%) used were Cellfim C500 manufactured by Mori Machinery Co., Ltd. The fiber width was 20 to 200 nm, and the fiber length was 500 μm or less. The filler surface-treated with fatty acid was Shiraishi Kogyo Co., Ltd.'s Hakuenka CC. This filler is calcium carbonate surface-treated with fatty acid, and the average particle size measured by laser diffraction and scattering is 21.1 μm. The particle size is larger than the catalog value, possibly because the filler is in the form of secondary agglomerates. The varnish (solid content 52.8%) used was a water-based urethane varnish manufactured by Washin Paint Co., Ltd.

[0027] Example 1 [Ultraviolet transmission suppressing material] A paste-like LCNF with a water content of 90% by mass and a filler surface-treated with a fatty acid were mixed in a weight ratio of 40:60 using a mixer (Super Mixer, Model SMV-20, manufactured by Kawata Co., Ltd.) The mixture obtained by the mixing was dried with hot air in a hot air dryer (Box Dryer, manufactured by Matsui Mfg. Co., Ltd.) and pulverized at a rotation speed of 3600 rpm using a mixer (Super Mixer, Model SMV-20, manufactured by Kawata Co., Ltd.) to obtain a powdered ultraviolet transmission suppressor.

[0028] [Preparation of polypropylene pellets] Polypropylene raw material pellets were placed in a kneader, heated and kneaded to melt, and then 1 part by weight of maleic anhydride-modified polypropylene (Kayabrid 006PP, manufactured by Kayaku Akzo Co., Ltd.) was added as a compatibilizer per 100 parts by weight of polypropylene, followed by the ultraviolet transmission suppressor obtained in the example. The ultraviolet transmission suppressor was added in such an amount that the LCNFs accounted for 4% by mass of the total weight including the polypropylene, maleic anhydride-modified polypropylene, and ultraviolet transmission suppressor. The mixture was then further kneaded to produce LCNF-containing polypropylene pellets.

[0029] [Preparation of polypropylene sheets] The obtained pellets were set in a press and pressed at 180°C and 15 MPa for 2 minutes, and then immediately cooled to prepare a polypropylene sheet.

[0030] Examples 2 to 5 In Example 1, LCNF-containing polypropylene pellets were prepared so that the LCNF contents were 0.4 mass %, 1.2 mass %, 2 mass %, and 2.8 mass %, respectively, and polypropylene sheets were prepared using the pellets.

[0031] Example 6 LCNF-containing polyamide pellets were prepared in the same manner as in Example 1, except that raw material pellets of polyamide (nylon 6) were used instead of raw material pellets of polypropylene.

[0032] Comparative Example 1 Powder was obtained in the same manner as in Example 1, except that CNF was used instead of LCNF, and CNF-containing polypropylene pellets and a polypropylene sheet were produced.

[0033] Comparative Example 2 Polypropylene pellets and a polypropylene sheet were prepared in the same manner as in Example 1, except that no ultraviolet transmission suppressant was used.

[0034] Comparative Example 3 Polyamide pellets were prepared in the same manner as in Example 1, except that raw material pellets of polyamide (nylon 6) were used instead of raw material pellets of polypropylene, and no ultraviolet transmission suppressor was used.

[0035] [Measurement of transmittance of polypropylene sheet] The light transmittance of the polypropylene sheets of Examples 1 to 5 and Comparative Examples 1 and 2 was measured using an ultraviolet-visible-near-infrared spectrophotometer equipped with an integrating sphere ("V-750" manufactured by JASCO Corporation). The results are shown in Figures 1 and 2.

[0036] [UV acceleration test using a xenon weather meter] The polypropylene pellets obtained in Example 1 and Comparative Examples 1 and 2 were injection molded at 210°C to obtain molded articles (size: 60 mm × 80 mm × 5 mm). The molded articles were subjected to a 400-hour UV accelerated test using a xenon weather meter. The change in molecular weight after the accelerated test was measured using a high-temperature GPC apparatus (HLC-8321GPC / HT, detector RI). 1,2,4-Trichlorobenzene was used as the eluent. The measurement sample was dissolved in 1,2,4-trichlorobenzene and the insoluble matter was removed. The results are shown in Table 1. As can be seen from Table 1, the molded article made using the polypropylene pellets (LCNF-free) of Comparative Example 2 showed a decrease in molecular weight after the UV accelerated test. The Mw / Mn (dispersity) was larger than that of the blank PP, indicating a broader molecular weight distribution. This suggests that the UV accelerated test decomposed the polypropylene to produce low-molecular-weight polypropylene. Furthermore, the molded article made using the polypropylene pellets (containing CNF) of Comparative Example 1 showed a slight decrease in molecular weight after the UV accelerated test. On the other hand, the molecular weight of the molded article made from the polypropylene pellets (containing LCNF) of Example 1 did not decrease after the accelerated ultraviolet test. Therefore, it was found that the inclusion of LCNF exerts the effect of suppressing ultraviolet light transmission.

[0037] [Table 1]

[0038] [Tensile test after weather resistance test] Test specimens (4 mm thick, 10 mm wide) were prepared using the polypropylene pellets obtained in Example 1 and Comparative Example 2, and the polyamide pellets obtained in Example 6 and Comparative Example 3, in accordance with JIS K7161-2:2014. Outdoor exposure tests (0, 7, 21, 35, 49, and 63 weeks) were conducted. Tensile tests were conducted in accordance with JIS K7161-1:2014 using a tension-compression testing machine (Shimadzu Corporation, "AGS-5KNG") at a test speed of 2 mm / min to determine stress, modulus, and elongation. The results are shown in Tables 2 and 3, and in Figures 3 and 4.

[0039] [Table 2]

[0040] [Table 3]

[0041] [Transmittance measurement after dispersion in varnish] Only the varnish was applied to a polypropylene plate, and the varnish was peeled off after drying. LCNF was added to the varnish so that the LCNF content was 0.5% by mass relative to the total amount of varnish, and the mixture was stirred with a brush to prepare an LCNF-containing varnish. This LCNF-containing varnish was applied to a polypropylene plate, and the LCNF-containing varnish was peeled off after drying. The light transmittance was measured using an ultraviolet-visible-near-infrared spectrophotometer equipped with an integrating sphere ("V-750" manufactured by JASCO Corporation). The results are shown in Figure 5.

[0042] [Color change after metal halide test] Varnishes containing 0.25 mass%, 0.5 mass%, 1 mass%, and 1.5 mass% LCNF were prepared. As shown in Figure 6, a circular iron plate coated with red paint was divided into regions A to F. Regions E and F were topcoated with a varnish containing LCNF, regions C and D were topcoated with varnish only, and regions A and B were not topcoated. Only regions B, C, and E were exposed to ultraviolet light at an irradiance of 150 mW / cm. 2 A metal halide test was carried out by irradiating the specimen with light at 1000 K for 24 hours, and the color of the surface of areas A to F was measured using a color reader ("CR-10" manufactured by Konica Minolta, Inc.). The results are shown in Table 4.

[0043] [Table 4]

[0044] [Evaluation of dispersibility] In Example 1, the material was pulverized after hot air drying at a rotation speed of 1800 rpm to obtain an insufficiently pulverized ultraviolet transmission suppressor as a powder. This powder was used to prepare polypropylene pellets so that the LCNF content was 4% by mass, and these pellets were used to prepare a poorly dispersed polypropylene sheet. Observation was performed using a polarizing microscope (Nikon Corporation, "ECLIPSE Ci-POL"). Observation was performed without a polarizing plate. The polypropylene sheets of Example 1 and Comparative Example 2 were also observed in the same manner. The results are shown in Figure 7. Aggregates of approximately 100 to 300 μm were observed in the poorly dispersed polypropylene sheet. On the other hand, aggregates of approximately 10 to 30 μm were observed in the polypropylene sheet of Example 1. No aggregates were observed in the polypropylene sheet of Comparative Example 2, which did not contain LCNF.

Claims

1. An ultraviolet light transmission inhibitor containing lignocellulose nanofibers (LCNF).

2. 2. The ultraviolet transmission suppressor according to claim 1, further comprising a filler, wherein the mass ratio of the filler to the LCNF (filler / LCNF) is 0.3 / 1 to 12 / 1.

3. A resin composition containing the ultraviolet transmission suppressor according to claim 1 or 2.

4. A resin pellet containing the ultraviolet transmission suppressor according to claim 1 or 2.

5. A coating material containing the ultraviolet transmission inhibitor according to claim 1 or 2.

6. A paint containing the ultraviolet transmission inhibitor according to claim 1 or 2.

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