Fibrous material for thermoforming and composite material for thermoforming

Abstract

Provided are a fibrous material for thermoforming that contains an anion-modified pulp exhibiting thermoformability, and a composite material for thermoforming. A fibrous material for thermoforming according to an embodiment of the present invention includes an anion-modified pulp in which 45 mol % or more of the anionic group is an onium salt. The composite material for thermoforming according to said embodiment contains an anion-modified pulp in which 45 mol % or more of the anionic group is an onium salt, and a thermoplastic resin.

Description

Thermoforming fibrous materials and thermoforming composite materials

[0001] The present invention relates to a thermoforming fibrous material and a thermoforming composite material containing anionically modified pulp, and to a molded article obtained by thermoforming them.

[0002] In recent years, from the viewpoint of sustainability, materials using cellulose fibers, which are naturally occurring biomass, have been attracting attention. For example, Patent Document 1 describes a fiber-reinforced resin composition containing chemically modified cellulose nanofibers and a thermoplastic resin, and describes, as an example, a method of kneading the chemically modified pulp with the thermoplastic resin to defibrate the chemically modified pulp, thereby obtaining a resin composition containing the chemically modified cellulose nanofibers and the thermoplastic resin.

[0003] JP 2016-176052 A

[0004] Cellulose fibers are inherently not thermoformable. Therefore, they cannot be thermoformed unless they are added to a resin such as a thermoplastic resin. As mentioned above, it has been known to add chemically modified cellulose fibers to thermoplastic resins as a reinforcing material, but it has not been known that specific anion-modified pulp has thermoformability.

[0005] SUMMARY OF THE INVENTION Embodiments of the present invention aim to provide novel thermoformable fibrous materials and thermoformable composites that include anionically modified pulp that has thermoformability.

[0006] The present invention includes the following embodiments. [1] A thermoforming fibrous material comprising anion-modified pulp in which 45 mol % or more of the anionic groups are onium salts. [2] The thermoforming fibrous material according to [1], wherein the melting point of the modifier for converting the anionic groups to onium salts is 150°C or lower. [3] The thermoforming fibrous material according to [1] or [2], wherein the onium salt is a quaternary onium salt. [4] The thermoforming fibrous material according to any one of [1] to [3], wherein the anion-modified pulp has an amount of anionic groups of 0.5 to 3.0 mmol / g, measured after all of the anionic groups are in the acid form. [5] A molded product obtained by thermoforming the thermoforming fibrous material according to any one of [1] to [4].

[0007] [6] A thermoforming composite material comprising an anion-modified pulp in which 45 mol % or more of the anionic groups are onium salts, and a thermoplastic resin. [7] A molded article obtained by thermoforming the thermoforming composite material according to [6].

[0008] According to embodiments of the present invention, novel thermoformable fibrous materials and thermoformable composite materials can be provided that contain anionically modified pulp having thermoformability.

[0009] [Thermoforming Fibrous Material] The thermoforming fibrous material according to this embodiment includes anion-modified pulp in which at least 45 mol% of the anionic groups are onium salts. Here, "thermoforming fibrous material" refers to a fibrous material used for thermoforming. "Thermoforming" refers to a molding method in which the pulp (cellulose fiber) is softened by heating, molded into a desired shape, and then hardened by cooling, including, for example, heat press molding, vacuum molding, and pressure molding. Note that "softening" here does not necessarily mean that the pulp (cellulose fiber) melts, but refers to the fibers becoming more fluid upon heating. It is believed that the fibers bond together during thermoforming, solidify in that state upon cooling, and maintain a certain shape. "Fibrous" refers to a material having a fibrous form, and may be a collection of fibers, such as a fiber sheet like paper or nonwoven fabric, or a cotton-like material.

[0010] Anionically modified pulp is pulp into which anionic groups have been introduced and is obtained by chemically modifying unmodified pulp. "Pulp" refers to cellulose fibers extracted by mechanically and / or chemically treating plants such as wood. The anionic groups are preferably introduced at least onto the fiber surface of the pulp.

[0011] Examples of plant-derived pulps include unbleached softwood kraft pulp (NUKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), bleached hardwood kraft pulp (LBKP), unbleached softwood sulfite pulp (NUSP), bleached softwood sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, and recycled paper pulp. Any of these may be used alone or in combination of two or more.

[0012] Examples of anionic groups include at least one selected from the group consisting of a carboxyl group, a phosphate group, a sulfate group, a sulfonate group, a nitrate group, and a borate group. Among these, at least one selected from the group consisting of a carboxyl group, a phosphate group, and a sulfate group is preferred. These anionic groups may be directly or indirectly bonded to glucose units, which are structural units of cellulose molecules. When indirectly bonded, for example, an alkylene group having 1 to 4 carbon atoms may be present between the glucose unit and the anionic group. One or more anionic groups may be bonded to all glucose units constituting the cellulose molecule, or one or more anionic groups may be bonded to a portion of the glucose units constituting the cellulose molecule.

[0013] In one embodiment, examples of anion-modified pulp include oxidized cellulose fibers obtained by oxidizing the hydroxyl groups of glucose units in cellulose molecules, and carboxymethylated cellulose fibers obtained by carboxymethylating the hydroxyl groups of glucose units in cellulose molecules. Oxidized cellulose fibers include those in which the hydroxyl group at the C6 position of the glucose unit in the cellulose molecule is selectively oxidized to a carboxyl group. Oxidized cellulose fibers are obtained by oxidizing natural cellulose, such as wood pulp, using a co-oxidant in the presence of an N-oxyl compound. The N-oxyl compound used is a compound containing a nitroxy radical, which is commonly used as an oxidation catalyst. For example, a piperidine nitroxyoxy radical is used, and 2,2,6,6-tetramethylpiperidinoxy radical (TEMPO) or 4-acetamido-TEMPO is particularly preferred. Anion-modified cellulose fibers according to a preferred embodiment are TEMPO-oxidized cellulose fibers oxidized using TEMPO.

[0014] In this embodiment, the anion-modified pulp used has 45 mol% or more of its anionic groups being onium salts. That is, 45 mol% or more of the anionic groups have onium ions as counterions. By incorporating 45 mol% or more of onium salts, the anion-modified pulp can be endowed with thermoformability (also known as heat-softening properties), making it possible to thermoform even without the inclusion of a resin such as a thermoplastic resin. The onium salt introduction rate is preferably 50 mol% or more of the anionic groups, more preferably 70 mol% or more, more preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 100 mol%.

[0015] For example, when the anionic group is a carboxy group, the onium salt introduction rate is calculated using FT-IR from the absorption peak area derived from the onium salt and the absorption peak area derived from the acid-type anionic group. In this case, when a metal salt is contained as another salt, the metal content is also measured using an ICP atomic emission spectrometer to calculate the onium salt introduction rate. When the anionic group is a phosphate group or a sulfate group, the nitrogen content is measured using a total nitrogen analyzer to calculate the onium salt introduction rate. Details of the onium salt introduction rate are as described in the Examples section.

[0016] The term "onium salt" as used herein refers to a broad onium salt that encompasses not only salts containing onium ions generated by protonation of hydrides, but also salts containing cations in which some or all of the protons of the onium ion have been replaced with alkyl groups, arene groups, or the like. Examples of onium salts include ammonium salts, phosphonium salts, sulfonium salts, and oxonium salts. Among these, ammonium salts and phosphonium salts are preferred. Any one of these may be used alone, or two or more may be used in combination. Here, the arene group refers to a monovalent hydrocarbon group having an aromatic ring, and examples thereof include an aryl group and an aralkyl group.

[0017] Examples of ammonium salts include quaternary ammonium salts (e.g., tetraalkylammonium salts such as tetramethylammonium salt, tetrabutylammonium salt, tetraoctylammonium salt, hexadecyltrimethylammonium salt, methyltrioctylammonium salt, tetradecylammonium salt, trimethyldodecylammonium salt, trimethyltetradecylammonium salt, trimethyloctadecylammonium salt, tributyldodecylammonium salt, trioctylmethylammonium salt, tetradodecylammonium salt, octyldimethylethylammonium salt, dodecyldimethylethylammonium salt, and didecyldimethylammonium salt), benzyltributylammonium salt, benzyltripropylammonium salt, benzyltriethylammonium salt, benzyltrimethylammonium salt, benzyldimethyldodecylammonium salt, and benzyldimethyltetradecylammonium salt). ammonium salts containing an arene group such as benzyldimethyloctadecylammonium salt; heterocyclic quaternary ammonium salts such as 1-ethyl-3-methylimidazolium salt, dodecylpyridinium salt, 1-allyl-3-methylimidazolium salt, 1-butylpyridinium salt, and 1-butyl-4-methylpyridinium salt); tertiary ammonium salts (for example, trialkylammonium salts such as trioctylammonium salt and trihexylammonium salt); secondary ammonium salts (for example, dialkylammonium salts such as dioctylammonium salt, dibutylammonium salt, dihexylammonium salt, didodecylammonium salt, and distearylammonium salt); primary ammonium salts (for example, alkylammonium salts such as dodecylammonium salt, oleylammonium salt, and stearylammonium salt; and alkanolammonium salts such as diethylene glycolammonium salt).

[0018] Examples of the phosphonium salt include quaternary phosphonium salts (for example, tetraalkylphosphonium salts such as tributylmethylphosphonium salt, tributyldodecylphosphonium salt, tributyltetradecylphosphonium salt, tributylhexadecylphosphonium salt, trihexyl(tetradecyl)phosphonium salt, tetraethylphosphonium salt, tetrabutylphosphonium salt, and tetraoctylphosphonium salt; and phosphonium salts containing an arene group such as tetraphenylphosphonium salt, benzyltriphenylphosphonium salt, methyltriphenylphosphonium salt, ethyltriphenylphosphonium salt, butyltriphenylphosphonium salt, and tetradecyltriphenylphosphonium salt).

[0019] The onium salts listed above may be used alone or in combination of two or more.

[0020] As the onium salt, a modifying agent for converting an anionic group into an onium salt preferably has a melting point of 150°C or less. A modifying agent having a melting point of 150°C or less can further improve thermoformability. The modifying agent more preferably has a melting point of 100°C or less, more preferably 50°C or less, and even more preferably is liquid at room temperature (25°C). The lower limit of the melting point is not particularly limited, and may be, for example, -50°C.

[0021] Here, the modifying agent refers to a compound that forms an onium salt together with an acid-type anionic group. However, when the modifying agent is a quaternary onium salt, the "melting point" refers to the melting point measured for an acetate salt in which the anion that forms a salt with the onium ion is replaced with an acetate ion. The melting point is determined as the temperature at which the modifying agent melts when the temperature of the modifying agent is gradually increased using a melting point measuring device, as described in detail in the Examples section.

[0022] The onium salt is preferably a quaternary onium salt in order to further improve thermoformability. As the quaternary onium salt, for example, the above-mentioned quaternary ammonium salts and / or quaternary phosphonium salts are preferably used, and more preferably at least one selected from the group consisting of tetraalkylammonium salts, aralkyltrialkylammonium salts, and tetraalkylphosphonium salts is used.

[0023] The amount of anionic groups in the anion-modified pulp, measured after converting all anionic groups to the acid form, is preferably 0.5 to 3.0 mmol / g, more preferably 1.0 to 2.8 mmol / g, and even more preferably 1.5 to 2.5 mmol / g. As described above, the anion-modified pulp according to the embodiment is a salt-type anion-modified pulp containing an onium salt. Therefore, when measuring the amount of anionic groups, all anionic groups are converted to the acid form before measurement. The amount of anionic groups is the amount of substance (mmol) of anionic groups per dry mass of the acid-type anion-modified pulp and can be measured by known methods, specifically the method described in the Examples section. In this specification, the term "dry mass" refers to the mass after drying at 140°C until the mass change rate per minute is 0.05% or less.

[0024] In the anion-modified pulp of this embodiment, the anionic group may be only an onium salt, or may contain other salts together with the onium salt. The other salts are not particularly limited, and examples thereof include alkali metal salts such as sodium salts and potassium salts, and alkaline earth metal salts such as magnesium salts and calcium salts. In addition, the anionic groups do not all have to be salt types (for example, in the case of a carboxyl group, -COOX (where X is a cation that forms a salt with a carboxylic acid)), and may be acid types (where the counter ion is H) together with salt types including the onium salt. ＋ and is also called H-type. For example, in the case of a carboxy group, it may contain —COOH.

[0025] As described above, anionically modified pulp is obtained by chemically modifying unmodified pulp and is not defibrated. In this respect, it is distinguished from cellulose nanofibers, which are made by defibrating pulp. The fiber diameter of anionically modified pulp is equivalent to the fiber diameter of untreated pulp and, although it varies depending on the raw material pulp, is usually several tens of μm. Specifically, the number average fiber width of anionically modified pulp is preferably 5 to 100 μm, more preferably 10 to 60 μm, and may be 20 to 40 μm.

[0026] The number average fiber width of anion-modified pulp is measured as follows: an aqueous suspension of anion-modified pulp diluted to 0.01% by mass is photographed using an optical microscope, 10 images are taken, 25 fibers are selected from the images, the fiber widths (diameters) are measured, and the arithmetic mean is calculated.

[0027] The thermoforming fibrous material according to this embodiment may consist solely of the anion-modified pulp, or may contain additives as optional components in addition to the anion-modified pulp. Examples of additives include colorants such as pigments and dyes, water-resistant agents, flame retardants, plasticizers, antioxidants, light stabilizers, fillers, and antistatic agents. As described above, the anion-modified pulp according to this embodiment has thermoformability, and therefore can be thermoformed by itself. Therefore, it is preferable that the thermoforming fibrous material does not contain a resin such as a thermoplastic resin, and can be subjected to thermoforming directly without the addition of a resin.

[0028] The form of the thermoforming fibrous material according to this embodiment is not particularly limited, and may be, for example, a fiber sheet such as paper or nonwoven fabric, as described above, or may be in a cotton-like form.

[0029] When forming a fiber sheet, for example, paper may be produced by papermaking using a suspension containing anion-modified pulp as a stock. Papermaking is a process in which the stock is dehydrated by filtration to form a sheet, which is then pressed and dried to produce paper. For papermaking, known papermaking machines, such as a Fourdrinier wet papermaking machine, a twin-wire papermaking machine, a Yankee papermaking machine, a cylinder papermaking machine, or a cylinder / short-wire combination papermaking machine, may be used. Alternatively, for example, a suspension containing anion-modified pulp may be filtered under reduced pressure to form a sheet, which is then dried and pressed to produce a fiber sheet. These pressing and drying steps are preferably performed at a temperature at which the anion-modified pulp does not plasticize. The thickness of the fiber sheet is not particularly limited and may be, for example, 0.001 to 50 mm or 0.01 to 5 mm. In this specification, the terms "sheet" and "sheet-like" encompass the concepts of "film" and "film-like," respectively.

[0030] A molded article is obtained by thermoforming the thermoforming fibrous material. As described above, thermoforming refers to softening (plasticizing) the thermoforming fibrous material by heating to form it into a predetermined shape, which is then hardened by cooling. Examples of such methods include heat press molding, vacuum molding, and pressure molding. The shape of the molded article is not particularly limited, and various shapes such as sheet-like, plate-like, and three-dimensional structures can be mentioned. Specific examples of molded articles include sheets, packaging materials, tableware (cups, plates, etc.), and containers (bottles, trays, etc.).

[0031] Generally, paper made from pulp has voids between the pulp particles, which makes it opaque. In the case of the thermoforming fibrous material according to the present embodiment, for example, by heat press molding, the fibers adhere closely to each other without any gaps, eliminating the voids and making the paper transparent.

[0032] Furthermore, although multiple sheets of paper made from ordinary pulp do not adhere to each other even when stacked together and heat-pressed, when multiple sheets of the fiber sheet made from the thermoforming fibrous material according to the present embodiment are stacked together and at least a portion of the sheets is heat-press molded, the fiber sheets can be bonded together at the thermoformed portions, making heat-sealable. Therefore, a heat-sealable fiber sheet can be provided.

[0033] [Thermoforming Composite Material] The thermoforming composite material according to this embodiment comprises an anion-modified pulp in which at least 45 mol% of the anionic groups are onium salts, and a thermoplastic resin. The anion-modified pulp softens and flows easily when heated due to the presence of the onium salt, making it easier to mix with the heated and melted thermoplastic resin. This reduces the formation of agglomerates of the anion-modified pulp. This allows for the production of molded articles with excellent surface appearance and excellent thermoformability.

[0034] The thermoplastic resin is not particularly limited, and examples thereof include polyethylene (PE), polypropylene (PP), polyvinyl chloride, polystyrene, polyvinylidene chloride, fluororesin, (meth)acrylic resin, polyamide resin, polyester resin, polylactic acid, polycaprolactone, ABS resin, polycarbonate resin, polyphenylene oxide, polyurethane, polyacetal, vinyl ether resin, and polysulfone resin, and any one of these may be used alone or in combination of two or more.

[0035] The amount of anion-modified pulp in the thermoforming composite material is not particularly limited. For example, when the anion-modified pulp is used as a reinforcing material for a thermoplastic resin, it is preferable that the thermoplastic resin be the main component of the matrix, and the amount of the anion-modified pulp may be 0.5 to 50% by mass, or 1 to 30% by mass. In this case, the amount of the thermoplastic resin may be 50 to 99.5% by mass, or 70 to 99% by mass.

[0036] The thermoforming composite material may contain additives as optional components in addition to the anion-modified pulp and the thermoplastic resin, such as colorants such as pigments and dyes, water-resistant agents, flame retardants, plasticizers, antioxidants, light stabilizers, fillers, and antistatic agents.

[0037] The method for producing the thermoforming composite material is not particularly limited, and examples thereof include a method of mixing a thermoplastic resin and anion-modified pulp at a temperature at which the thermoplastic resin melts. The form of the thermoforming composite material is not particularly limited, and examples thereof include a sheet, plate, pellet, powder, filament, etc.

[0038] A molded article is obtained by thermoforming the thermoforming composite material. Thermoforming refers to softening the thermoforming composite material by heating, molding it into a predetermined shape, and then hardening it by cooling. Examples of thermoforming include heat press molding, vacuum molding, pressure molding, injection molding, extrusion molding, and FDM 3D printers. The shape of the molded article is not particularly limited, and various shapes such as sheet shapes, plate shapes, and three-dimensional structures can be mentioned. Specific examples of molded articles include sheets, packaging materials, tableware (cups, plates, etc.), and containers (bottles, trays, etc.).

[0039] Examples will be described in detail below along with comparative examples, but the present invention is not limited to these examples.

[0040] The methods for measuring the various physical properties in the examples and comparative examples are as follows.

[0041] [Amount of Anionic Groups (Amount of Carboxy Groups)] A 50 mL aqueous suspension of acid-type anion-modified pulp with a pulp concentration of 0.1% by mass was prepared, and the pH was adjusted to approximately 2.5 with a 0.1 mol / L aqueous hydrochloric acid solution. Next, a 0.05 mol / L aqueous sodium hydroxide solution was added dropwise to the aqueous suspension, and electrical conductivity measurements were performed until the pH reached approximately 11. The amount of carboxy groups was calculated from the amount of sodium hydroxide (V) consumed in the neutralization stage of weak acid, where the change in electrical conductivity was gradual, according to the following formula: Amount of Carboxy Groups (mmol / g) = V (mL) × [0.05 / Mass of Acid-Type Anion-Modified Pulp (g)]

[0042] Anionic Group Amount (Phosphate Group Amount) An aqueous suspension prepared by diluting anion-modified pulp with ion-exchange water to a content of 0.2% by mass was treated with ion exchange resin to produce an acidic anion-modified pulp, followed by alkali titration. The ion-exchange resin treatment was performed by adding 1 / 10 by volume of a strongly acidic ion-exchange resin (Amberjet 1024; Organo Corporation, conditioned) to the aqueous suspension, shaking for 1 hour, and then pouring the suspension onto a 90 μm mesh to separate the ion-exchange resin from the aqueous suspension. Alkaline titration was performed by adding 50 μL of 0.1 mol / L sodium hydroxide aqueous solution to the aqueous suspension after ion-exchange resin treatment every 30 seconds, while measuring the change in the electrical conductivity of the aqueous suspension. The phosphate group amount (mmol / g) was calculated by dividing the amount of alkali (mmol) required in the region corresponding to the first region of the measurement results by the solids content (g) in the aqueous suspension being titrated.

[0043] [Amount of Anionic Groups (Amount of Sulfate Groups)] A predetermined amount of acid-type anion-modified pulp was combusted, and the sulfur content in the combustion product was measured using a combustion ion chromatograph according to a method in accordance with IEC 62321, and the amount was converted into the amount of sulfate groups.

[0044] [Introducing rate of onium salt] The sheets as thermoforming fibrous materials obtained in Examples 1 to 18 and Comparative Examples 1 to 4 were measured by FT-IR. The absorption peak area (1720 cm) derived from carboxylic acid, as shown in the following formula, was －１ ), and the absorption peak area due to carboxylate (1600 cm －１ ) was used to calculate the onium salt introduction rate. When a metal salt is contained as another salt, the absorption peaks of the metal salt and the onium salt appear at the same location, so the metal content was also measured using an ICP atomic emission spectrometer to calculate the metal content. Onium salt introduction rate [mol %] = {absorption peak area derived from carboxylate salt / (absorption peak area derived from carboxylate salt + absorption peak area derived from carboxylic acid)} × 100 For the thermoforming fibrous materials obtained in Examples 19 and 20, the onium salt introduction rate was calculated by measuring the nitrogen content using a total nitrogen analyzer.

[0045] [Melting Point of Modifier] A modifier that is not liquid at room temperature (such as an amine, phosphine, ammonium salt, or phosphonium salt) was finely ground in a mortar and packed into a melting point tube. The melting point tube was set in a depression on the aluminum plate of a melting point measurement device, and a glass cover was placed on top of it. The temperature of the melting point measurement device was raised from 25°C at a rate of 5°C / min, and the temperature at which the modifier melted was taken as the melting point. For quaternary onium salt modifiers, measurements were taken of acetate salts in which the anion that forms a salt with the onium ion was replaced with acetate ion.

[0046] [Moldability] The sheets of thermoforming fibrous materials obtained in Examples 1 to 20 and Comparative Examples 1 to 4 were cut into 3 cm length x 3 cm width to prepare test specimens. The test specimens were clamped in a drawing mold and pressed at 100°C and 0.4 MPa using a hot press. The obtained molded bodies were observed and evaluated according to the following criteria. A: A molded body without wrinkles or cracks was obtained when the pressing time was 10 seconds or less. B: A molded body without wrinkles or cracks was obtained when the pressing time was 11 to 60 seconds. C: A molded body without wrinkles or cracks was obtained when the pressing time was 61 to 180 seconds. D: The sheet cracked during pressing, and no molded body was obtained.

[0047] [Heat sealability] The sheets of thermoforming fibrous materials obtained in Examples 1 to 20 and Comparative Examples 1 to 4 were cut into 100 mm length x 15 mm width to prepare test specimens. Two test specimens were stacked on top of each other, and an area of ​​10 mm length x 15 mm width was pressed at 100°C and 0.1 MPa using a heat press. Using a tensile tester, both unpressed ends were gripped and T-peel was performed at a tensile speed of 300 mm / min, and the maximum value was recorded as the heat seal strength. The evaluation criteria for heat sealability are as follows: A: Pressing time 10 seconds or less, heat seal strength 0.1 N / 15 mm or more B: Pressing time 11 to 60 seconds, heat seal strength 0.1 N / 15 mm or more C: Pressing time 61 to 180 seconds, heat seal strength 0.1 N / 15 mm or more D: Pressing time 180 seconds, heat seal strength less than 0.1 N / 15 mm, or no adhesion

[0048] [Transparency] Test specimens were prepared by cutting the sheets of thermoforming fibrous materials obtained in Examples 1 to 20 and Comparative Examples 1 to 4 into pieces measuring 3 cm length x 3 cm width. The test specimens were sandwiched between polyimide films and pressed using a heat press at 100°C and 0.4 MPa for 5 minutes. After pressing, the area of ​​the transparent portion of the test specimen was measured using image analysis software. The transparency evaluation criteria are as follows: A: 50% or more of the entire specimen became transparent B: 5% or more but less than 50% of the entire specimen became transparent C: The transparent portion was less than 5% of the entire specimen

[0049] [Surface Appearance of Molded Article] The thermoforming composite materials obtained in Examples 21 and 22 and Comparative Example 5 were pressed at 200°C using a hot press machine and cut to produce films measuring 5 cm in length, 5 cm in width, and 1 mm in thickness. The judging criteria for the surface appearance of the obtained films are as follows: ∘: Fewer than 5 agglomerates of anion-modified pulp ×: 5 or more agglomerates of anion-modified pulp

[0050] [Preparation of Anion-Modified Pulps A1 to A5] Prior to producing the thermoforming materials of the Examples and Comparative Examples, acid-type anion-modified pulps A1 to A5 to be used therein were prepared according to the following Production Examples 1 to 5.

[0051] [Manufacturing Example 1: Preparation of Anion-Modified Pulp A1 (TEMPO-Oxidized Cellulose Fiber)] 2 g of softwood pulp was mixed with 150 mL of water, 0.25 g of sodium bromide, and 0.025 g of TEMPO, thoroughly stirred to disperse the mixture. A 13% by mass aqueous solution of sodium hypochlorite (co-oxidant) was then added to 1.0 g of pulp to achieve a sodium hypochlorite concentration of 10.0 mmol / g, thereby initiating the reaction. As the reaction progressed, the pH decreased. A 0.5 mol / L aqueous solution of sodium hydroxide was added dropwise to maintain the pH at 10-11, and the reaction was continued until no further change in pH was observed (reaction time: 120 minutes). After completion of the reaction, 0.1 mol / L hydrochloric acid was added to adjust the pH to 2.0. The mixture was then purified by repeated filtration and washing with water to obtain cellulose fibers with oxidized fiber surfaces. This was then diluted with purified water to a cellulose fiber concentration of 4% by mass to prepare a TEMPO-oxidized cellulose fiber suspension. The pH of the slurry was then adjusted to 10 with a 24% by mass aqueous solution of sodium hydroxide, and sodium borohydride was added at 0.2 mmol / g relative to the cellulose fibers to initiate the reaction. The reaction was allowed to proceed for 2 hours for reduction treatment. After the reaction, 0.1 mol / L hydrochloric acid was added to adjust the pH to 2.0, and the mixture was purified by repeated filtration and washing with water to obtain anion-modified pulp A1 in which the carboxyl groups were in the acid form.

[0052] [Production Example 2: Preparation of anion-modified pulp A2 (TEMPO-oxidized cellulose fiber)] Anion-modified pulp A2, in which the carboxyl groups were in the acid form, was obtained in the same manner as in the preparation of anion-modified pulp A1, except that the amount of sodium hypochlorite solution added was 6.0 mmol / g per 1.0 g of softwood pulp.

[0053] [Manufacturing Example 3: Preparation of anion-modified pulp A3 (TEMPO-oxidized cellulose fiber)] Anion-modified pulp A3, in which the carboxyl groups are in the acid form, was obtained in the same manner as the preparation method for anion-modified pulp A1, except that the amount of sodium hypochlorite aqueous solution added was 4.0 mmol / g per 1.0 g of softwood pulp.

[0054] [Production Example 4: Preparation of Anion-Modified Pulp A4 (Phosphate-Esterified Cellulose Fiber)] A mixed aqueous solution of ammonium dihydrogen phosphate and urea was added to 100 parts by mass (bone dry mass) of softwood kraft pulp to adjust the total weight to 45 parts by mass of ammonium dihydrogen phosphate, 120 parts by mass of urea, and 150 parts by mass of water, to obtain a chemical-impregnated pulp. The obtained chemical-impregnated pulp was then heated in a hot air dryer at 165°C for 200 seconds to introduce phosphate groups into the cellulose in the pulp, thereby obtaining a phosphoric acid-esterified cellulose fiber. After the reaction, 0.1 mol / L hydrochloric acid was added to adjust the pH to 1.0, and the fiber surface was purified by repeated filtration and washing with water to obtain anion-modified pulp A4 in which the phosphate groups were in the acid form.

[0055] [Production Example 5: Preparation of Anion-Modified Pulp A5 (Sulfate-Esterified Cellulose Fiber)] 2 g of softwood kraft pulp, 20 g of sulfamic acid, 50 g of urea, and 100 g of ion-exchanged water were mixed and stirred for 10 minutes using a stirrer. After stirring, the slurry was suction filtered using filter paper (No. 2). Suction filtration was continued until the solution stopped dripping. After suction filtration, the pulp was peeled from the filter paper and placed in a dryer with a thermostatic bath set to 50°C for 6 hours to react. After the reaction, 0.1 mol / L hydrochloric acid was added to adjust the pH to 1.0, and then filtration and washing with water were repeated to purify the fiber surface, yielding anion-modified pulp A5 in which the sulfate groups were in the acid form.

[0056] [Example 1] (Preparation of modifying agent) Tetrabutylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in ethanol to a concentration of 0.1 N, and then an ion exchange resin (manufactured by Tokyo Chemical Industry Co., Ltd., Amberlite IRN78) in an amount five times the amount of tetrabutylammonium bromide was added, followed by stirring overnight in a shaker. The ion exchange resin was then removed by filtration, yielding a 0.1 N tetrabutylammonium hydroxide ethanol solution.

[0057] (Introduction of onium salt) Anion-modified pulp A1 was diluted with ethanol to 0.2% by mass, and then a 0.1 N tetrabutylammonium hydroxide ethanol solution in an amount equimolar to the amount of carboxyl groups in anion-modified pulp A1 was added and stirred at room temperature for 2 hours. The mixture was filtered through a nylon mesh filter with a mesh size of 59 μm, and the residue remaining on the filter was diluted with ethanol and filtered three times to obtain anion-modified pulp B1.

[0058] (Preparation of Sheet) The anion-modified pulp B1 obtained was diluted to 0.2% by mass with ethanol, and then filtered under reduced pressure through a nylon mesh filter with a mesh size of 59 μm to obtain a sheet-like wet deposit. After air-drying at room temperature, the resulting mixture was sandwiched between polyimide films and pressed at 20° C. for 5 minutes at 0.1 MPa using a heat press to obtain a 100 μm-thick sheet (fibrous material for thermoforming) of Example 1.

[0059] [Example 2] Anion-modified pulp B2 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 1, except that tetraoctylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) was used. Using the obtained anion-modified pulp B2, a sheet was prepared in the same manner as in Example 1, to obtain the sheet of Example 2.

[0060] [Example 3] Anion-modified pulp B3 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 1, except that benzyltributylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) was used. Using the obtained anion-modified pulp B3, a sheet was prepared in the same manner as in Example 1, to obtain the sheet of Example 3.

[0061] [Example 4] Anion-modified pulp B4 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 1, except that hexadecyltrimethylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) was used. Using the obtained anion-modified pulp B4, a sheet was prepared in the same manner as in Example 1, to obtain the sheet of Example 4.

[0062] [Example 5] Anion-modified pulp B5 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 1, except that trihexyl(tetradecyl)phosphonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) was used. Using the obtained anion-modified pulp B5, a sheet was prepared in the same manner as in Example 1, to obtain the sheet of Example 5.

[0063] [Example 6] Anion-modified pulp B6 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 1, except that tetraoctylphosphonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) was used. Using the obtained anion-modified pulp B6, a sheet was prepared in the same manner as in Example 1, to obtain the sheet of Example 6.

[0064] [Example 7] (Introduction of onium salt) Anion-modified pulp A1 was diluted with ethanol to 0.2% by mass, and then trioctylamine in an amount equimolar to the amount of carboxyl groups in anion-modified pulp A1 was added and stirred at room temperature for 2 hours. The mixture was filtered through a nylon mesh filter with an opening of 59 μm to obtain anion-modified pulp B7.

[0065] (Preparation of Sheet) The obtained anion-modified pulp B7 was diluted with ethanol to 0.2% by mass, and then filtered under reduced pressure through a nylon mesh filter with a mesh size of 59 μm to obtain a sheet-like wet deposit. After air-drying at room temperature, the resulting sheet was sandwiched between polyimide films and pressed at 20° C. for 5 minutes at 0.1 MPa using a heat press to obtain a 100 μm-thick sheet (fibrous material for thermoforming) of Example 7.

[0066] [Example 8] Anion-modified pulp B8 was obtained by introducing an onium salt in the same manner as in Example 7, except that dioctylamine was used. Using the obtained anion-modified pulp B8, a sheet was prepared in the same manner as in Example 7, to obtain the sheet of Example 8.

[0067] [Example 9] Anion-modified pulp B9 was obtained by introducing an onium salt in the same manner as in Example 7, except that diethylene glycol amine (i.e., 2-(2-aminoethoxy)ethanol) was used. Using the obtained anion-modified pulp B9, a sheet was prepared in the same manner as in Example 7, to obtain the sheet of Example 9.

[0068] [Example 10] Anion-modified pulp B10 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 1, except that 1-ethyl-3-methylimidazolium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) was used. Using the obtained anion-modified pulp B10, a sheet was prepared in the same manner as in Example 1, to obtain the sheet of Example 10.

[0069] [Example 11] Except for using anion-modified pulp A2, the preparation of the modifier and the introduction of the onium salt were carried out in the same manner as in Example 2 to obtain anion-modified pulp B11. Using the obtained anion-modified pulp B11, a sheet was prepared in the same manner as in Example 2 to obtain the sheet of Example 11.

[0070] [Example 12] Anion-modified pulp B12 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 2, except that anion-modified pulp A3 was used. A sheet was prepared using the obtained anion-modified pulp B12 in the same manner as in Example 2, to obtain the sheet of Example 12.

[0071] [Example 13] Anion-modified pulp B13 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 2, except that a 0.9-fold molar amount of 0.1 N tetraoctylammonium hydroxide ethanol solution was added to the anion-modified pulp A1. A sheet was prepared using the obtained anion-modified pulp B13 in the same manner as in Example 2, to obtain the sheet of Example 13.

[0072] [Example 14] Anion-modified pulp B14 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 2, except that a 0.75-fold molar amount of 0.1 N tetraoctylammonium hydroxide ethanol solution was added to the anion-modified pulp A1. A sheet was prepared using the obtained anion-modified pulp B14 in the same manner as in Example 2, to obtain the sheet of Example 14.

[0073] [Example 15] Anion-modified pulp B15 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 2, except that a 0.5-fold molar amount of 0.1 N tetraoctylammonium hydroxide ethanol solution was added to the anion-modified pulp A1. A sheet was prepared using the obtained anion-modified pulp B15 in the same manner as in Example 2, to obtain the sheet of Example 15.

[0074] [Example 16] Anion-modified pulp B16 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 2, except that a 0.1 N tetraoctylammonium hydroxide ethanol solution in an amount 0.5 times the molar amount of the carboxyl group in anion-modified pulp A1 and a 0.1 N sodium hydroxide aqueous solution in an amount 0.5 times the molar amount of the carboxyl group in anion-modified pulp A1 were added. A sheet was prepared using the obtained anion-modified pulp B16 in the same manner as in Example 2, to obtain the sheet of Example 16.

[0075] [Example 17] Anion-modified pulp B17 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 2, except that a 0.1 N tetraoctylammonium hydroxide ethanol solution in an amount 0.5 times the molar amount of the carboxyl group in anion-modified pulp A1 and a 0.1 N benzyltributylammonium hydroxide ethanol solution (see Example 3) in an amount 0.5 times the molar amount of the carboxyl group in anion-modified pulp A1 were added. A sheet was prepared using the obtained anion-modified pulp B17 in the same manner as in Example 2, to obtain the sheet of Example 17.

[0076] [Example 18] Anion-modified pulp B18 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 2, except that a 0.1 N tetraoctylammonium hydroxide ethanol solution in an amount 0.5 times the molar amount of the carboxyl group in anion-modified pulp A1 and a 0.1 N hexadecyltrimethylammonium hydroxide ethanol solution (see Example 4) in an amount 0.5 times the molar amount of the carboxyl group in anion-modified pulp A1 were added. A sheet was prepared using the obtained anion-modified pulp B18 in the same manner as in Example 2, to obtain the sheet of Example 18.

[0077] [Example 19] Anion-modified pulp B19 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 2, except that anion-modified pulp A4 was used. A sheet was prepared using the obtained anion-modified pulp B19 in the same manner as in Example 2, to obtain the sheet of Example 19.

[0078] [Example 20] Anion-modified pulp B20 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 2, except that anion-modified pulp A5 was used. A sheet was prepared using the obtained anion-modified pulp B20 in the same manner as in Example 2, to obtain the sheet of Example 20.

[0079] [Comparative Example 1] Anion-modified pulp A1 was diluted to 0.2% by mass with ion-exchanged water, and then filtered under reduced pressure through a nylon mesh filter with a mesh size of 59 μm to obtain a sheet-like wet deposit. After air-drying at room temperature, the resulting deposit was sandwiched between polyimide films and pressed at 20°C for 5 minutes at 0.1 MPa using a heat press to obtain a sheet of Comparative Example 1 having a thickness of 100 μm.

[0080] [Comparative Example 2] Anion-modified pulp A1 was diluted to 0.2% by mass with ion-exchanged water and then neutralized with 0.1N aqueous sodium hydroxide to a pH (25 ° C) of 7.0. This was filtered through a nylon mesh filter with a mesh size of 59 μm to obtain anion-modified pulp C2 in the form of a salt containing sodium salt. The resulting anion-modified pulp C2 was diluted to 0.2% by mass with ethanol and then filtered under reduced pressure through a nylon mesh filter with a mesh size of 59 μm to obtain a sheet-like wet deposit. After air-drying at room temperature, the pulp was sandwiched between polyimide films and pressed at 20 ° C for 5 minutes at 0.1 MPa using a heat press to obtain a 100 μm-thick sheet of Comparative Example 2.

[0081] [Comparative Example 3] Anion-modified pulp C3 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 2, except that a 0.1 N tetraoctylammonium hydroxide ethanol solution in an amount 0.4 times the molar amount of the carboxyl group in anion-modified pulp A1 and a 0.1 N sodium hydroxide aqueous solution in an amount 0.6 times the molar amount of the carboxyl group in anion-modified pulp A1 were added. A sheet was prepared using the obtained anion-modified pulp C3 in the same manner as in Example 2, to obtain the sheet of Comparative Example 3.

[0082] [Comparative Example 4] Anion-modified pulp C4 was obtained by preparing a modifier and introducing an onium salt in the same manner as in Example 2, except that a 0.4-fold molar amount of 0.1 N tetraoctylammonium hydroxide ethanol solution was added as the carboxyl group amount of anion-modified pulp A1. A sheet was prepared using the obtained anion-modified pulp C4 in the same manner as in Example 2, to obtain the sheet of Comparative Example 4.

[0083] The onium salt introduction rate was measured and moldability, heat sealability, and transparency were evaluated for the sheets prepared above in Examples 1 to 20 and Comparative Examples 1 to 4. The results are shown in Table 1.

[0084]

[0085] As shown in Table 1, in Comparative Examples 1 and 2, in which no onium salt was introduced, and in Comparative Examples 3 and 4, in which the onium salt introduction rate was low, the anion-modified pulp lacked thermoformability, and therefore exhibited poor moldability, heat-sealability, and transparency. In contrast, Examples 1 to 20, in which a predetermined amount of onium salt was introduced, exhibited moldability by thermoforming as well as heat-sealability, enabling the sheet to be made transparent. The higher the onium salt introduction rate, the better the moldability, heat-sealability, and transparency. Furthermore, the lower the melting point of the modifier, the better these properties were, and furthermore, quaternary onium salts were superior to primary to tertiary onium salts in these properties.

[0086] [Example 21] 100 parts by mass of polycaprolactone and 2 parts by mass of bone-dried anion-modified pulp B2 were kneaded at 200°C and 100 rpm for 10 minutes using a Laboplastomill (manufactured by Toyo Seiki Seisaku-sho, Ltd.) to produce a thermoforming composite material of Example 21.

[0087] Example 21 A composite material for thermoforming of Example 21 was produced in the same manner as in Example 21, except that polylactic acid was used instead of polycaprolactone.

[0088] Comparative Example 5 A thermoforming composite material of Comparative Example 5 was prepared by kneading 100 parts by mass of polycaprolactone and 2 parts by mass of bone-dried anion-modified pulp A1 at 200°C and 100 rpm for 10 minutes using a Laboplastomill (manufactured by Toyo Seiki Seisaku-sho, Ltd.).

[0089] The surface appearance of the molded articles was evaluated for the thermoforming composite materials prepared above in Examples 21 and 22 and Comparative Example 5. The results are shown in Table 1.

[0090]

[0091] As shown in Table 2, the thermoforming composite material of Comparative Example 5 contained anion-modified pulp without onium salt introduction, and therefore many agglomerates were observed on the surface of the thermoformed molded article. In contrast, the thermoforming composite materials of Examples 21 and 22 contained anion-modified pulp to which thermoformability had been imparted by the introduction of onium salt, and therefore the surface appearance of the thermoformed molded article was excellent.

[0092] The various numerical ranges described in this specification can be arbitrarily combined with their respective upper and lower limit values, and all such combinations are considered to be preferred numerical ranges described in this specification. Furthermore, a numerical range described as "X to Y" means from X to Y.

[0093] Although several embodiments of the present invention have been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their omissions, substitutions, modifications, etc. are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents.

Claims

1. A fibrous material for thermoforming comprising an anionically modified pulp in which at least 45 mol % of the anionic groups are onium salts.

2. The thermoforming fibrous material according to claim 1, wherein the melting point of the modifying agent for converting the anionic group into an onium salt is 150°C or lower.

3. The thermoforming fibrous material of claim 1, wherein the onium salt is a quaternary onium salt.

4. The fibrous material for thermoforming according to claim 1, wherein the anion-modified pulp has an amount of anionic groups, measured after all of the anionic groups are in the acid form, of 0.5 to 3.0 mmol / g.

5. A molded article obtained by thermoforming the fibrous material for thermoforming according to any one of claims 1 to 4.

6. A composite material for thermoforming comprising an anion-modified pulp in which 45 mol % or more of the anionic groups are onium salts, and a thermoplastic resin.

7. A molded article obtained by thermoforming the composite material for thermoforming according to claim 6.

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