Fibrous material for thermoforming and composite material for thermoforming

Abstract

To provide a fibrous material for thermoforming and a composite material for thermoforming including anionically modified pulp having thermoformability.SOLUTION: A fibrous material for thermoforming according to an embodiment includes anionically modified pulp in which 45 mol% or more of anionic groups are onium salts. A composite material for thermoforming according to an embodiment includes anionically modified pulp in which 45 mol% or more of anionic groups are onium salts, and a thermoplastic resin.SELECTED DRAWING: None

Description

Technical Field

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

Background Art

[0002] In recent years, from the perspective of sustainability, materials using cellulose fibers, which are biomass abundantly present in nature, have attracted attention. For example, Patent Document 1 describes a fiber-reinforced resin composition containing chemically modified cellulose nanofibers and a thermoplastic resin. As an example, it is described that a chemically modified pulp is defibrated by kneading the chemically modified pulp and the thermoplastic resin to obtain a resin composition containing chemically modified cellulose nanofibers and the thermoplastic resin.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

[0005] An embodiment of the present invention aims to provide a novel fibrous material for thermoforming and a composite material for thermoforming, each containing an anion-modified pulp having thermoformability.

Means for Solving the Problems

[0006] The present invention includes the embodiments shown below. [1] A fibrous material for thermoforming, comprising an anion-modified pulp in which 45 mol% or more of anionic groups are onium salts. [2] The fibrous material for thermoforming according to [1], wherein the melting point of the modifier for converting the anionic group into an onium salt is 150°C or lower. [3] The fibrous material for thermoforming according to [1] or [2], wherein the onium salt is a quaternary onium salt. [4] The fibrous material for thermoforming according to any one of [1] to [3], wherein the anion-modified pulp has an amount of anionic groups measured with all the anionic groups in 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 [1] to [4].

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

[0008] According to the embodiments of the present invention, it is possible to provide a novel fibrous material for thermoforming and a composite material for thermoforming, which contain an anion-modified pulp having thermoformability. [Modes for Carrying Out the Invention]

[0009] [Fibrous Material for Thermoforming] The fibrous material for thermoforming according to this embodiment contains an anionic-modified pulp in which 45 mol% or more of anionic groups are onium salts. Here, the "fibrous material for thermoforming" refers to a material used for thermoforming and having a fibrous form. "Thermoforming" refers to a forming method in which a material is softened by heating, formed into a predetermined shape, and then hardened by cooling, and includes, for example, hot press forming, vacuum forming, pressure air forming, etc. Note that the softening here does not necessarily mean that the pulp (cellulose fiber) melts, but rather means that the fiber becomes more fluid by heating, and it is considered that the fibers adhere to each other by thermoforming, solidify in that state by cooling, and can maintain a certain shape. "Fibrous" refers to something having a fibrous form, which may be a collection of fibers, such as a fiber sheet like paper or non-woven fabric, or may be cotton-like.

[0010] The anionic-modified pulp is a pulp into which anionic groups are introduced and can be obtained by chemically modifying unmodified pulp. "Pulp" refers to cellulose fibers extracted by mechanically and / or chemically treating plant bodies such as wood. The anionic groups are preferably introduced at least on the fiber surface of the pulp.

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

[0012] Examples of the anionic group include at least one selected from the group consisting of a carboxy group, a phosphoric acid group, a sulfuric acid group, a sulfonic acid group, a nitric acid group, and a boric acid group. Among these, at least one selected from the group consisting of a carboxy group, a phosphoric acid group, and a sulfuric acid group is preferable. These anionic groups may be directly bonded to the glucose unit which is a constituent unit of the cellulose molecule, or may be indirectly bonded. In the case of indirect bonding, an alkylene group having 1 to 4 carbon atoms may be present between the glucose unit and the anionic group. The anionic group may be bonded to one or more of all the glucose units constituting the cellulose molecule, or may be bonded to one or more of a part of the glucose units constituting the cellulose molecule.

[0013] In one embodiment, examples of the anion-modified pulp include oxidized cellulose fibers obtained by oxidizing the hydroxyl group of the glucose unit in the cellulose molecule, and carboxymethylated cellulose fibers obtained by carboxymethylating the hydroxyl group of the glucose unit in the cellulose molecule. Examples of the 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 and modified to a carboxy group. The oxidized cellulose fibers can be obtained by oxidizing natural cellulose such as wood pulp in the presence of an N-oxyl compound using a co-oxidant. As the N-oxyl compound, a compound having a nitroxyl radical generally used as an oxidation catalyst is used, for example, a piperidine nitroxyl radical, and particularly 2,2,6,6-tetramethylpiperidinooxy radical (TEMPO) or 4-acetamido-TEMPO is preferable. The anion-modified cellulose fiber according to a preferred embodiment is a TEMPO-oxidized cellulose fiber oxidized using TEMPO.

[0014] In this embodiment, as the anionic modified pulp, a pulp in which 45 mol% or more of its anionic groups are onium salts is used. That is, 45 mol% or more of the anionic groups have onium ions as counterions. By introducing 45 mol% or more of the onium salt, thermoformability (also referred to as thermoplastic softening characteristics) can be imparted to the anionic modified pulp, and thermoforming becomes possible even without containing a resin such as a thermoplastic resin. The introduction rate of the onium salt 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 still more preferably 100 mol%.

[0015] The introduction rate of the onium salt is calculated, for example, when the anionic group is a carboxy group, from the absorption peak area derived from the onium salt and the absorption peak area derived from the anionic group in the acid form using FT-IR. In that case, when a metal salt is included as another salt, it is calculated by measuring the metal content together with an ICP emission spectrometer. When the anionic group is a phosphate group or a sulfate group, the introduction rate of the onium salt is calculated by measuring the nitrogen content with a total nitrogen analyzer. Regarding the introduction rate of the onium salt, specifically, it is as described in the column of the examples.

[0016] The "onium salt" referred to here is a broad sense onium salt that includes not only a salt containing an onium ion generated by protonation of a hydride but also a salt containing a cation in which some or all of the protons of the onium ion are substituted with an alkyl group or an arene group. Examples of the onium salt include ammonium salts, phosphonium salts, sulfonium salts, oxonium salts, and the like. Among these, ammonium salts and phosphonium salts are preferred. Any one of these may be used, or two or more of them may be used in combination. Here, the arene group refers to a monovalent hydrocarbon group having an aromatic ring, and examples include aryl groups and aralkyl groups.

[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, didodecyldimethylammonium salt, etc., ammonium salts containing an arene group such as benzyltributylammonium salt, benzyltripropylammonium salt, benzyltriethylammonium salt, benzyltrimethylammonium salt, benzyldimethyldodecylammonium salt, benzyldimethyltetradecylammonium salt, benzyldimethyloctadecylammonium salt, etc., heterocyclic quaternary ammonium salts such as 1-ethyl-3-methylimidazolium salt, dodecylpyridinium salt, 1-allyl-3-methylimidazolium salt, 1-butylpyridinium salt, 1-butyl-4-methylpyridinium salt), tertiary ammonium salts (e.g., trialkylammonium salts such as trioctylammonium salt, trihexylammonium salt), secondary ammonium salts (e.g., dialkylammonium salts such as dioctylammonium salt, dibutylammonium salt, dihexylammonium salt, didodecylammonium salt, distearylammonium salt), and primary ammonium salts (e.g., alkylammonium salts such as dodecylammonium salt, oleylammonium salt, stearylammonium salt, alkanolammonium salts such as diethylene glycol ammonium 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, tetraoctylphosphonium salt, tetraphenylphosphonium salt, benzyltriphenylphosphonium salt, methyltriphenylphosphonium salt, ethyltriphenylphosphonium salt, butyltriphenylphosphonium salt, tetradecyltriphenylphosphonium salt, etc., and phosphonium salts containing an arene group).

[0019] In addition, any one of the above-listed onium salts may be used, or two or more of them may be used in combination.

[0020] As the onium salt, those having a modifier melting point of 150°C or lower for forming an anionic group into an onium salt are preferred. By having a modifier melting point of 150°C or lower, the thermoformability can be further improved. The melting point of the modifier is more preferably 100°C or lower, more preferably 50°C or lower, and still more preferably 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 modifier refers to a compound that forms an onium salt together with an acid-type anionic group. However, when the modifier is a quaternary onium salt, the "melting point" is the melting point measured for the acetate in which the anion forming a salt with the onium ion is replaced with an acetate ion. The melting point is determined as the temperature at which the modifier melts by gradually raising the temperature of the modifier using a melting point measuring device, and specifically, it is as described in the Examples section.

[0022] As the onium salt, it is preferable that it is a quaternary onium salt in order to further improve the thermoformability. As the quaternary onium salt, for example, the above-mentioned quaternary ammonium salt and / or quaternary phosphonium salt 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 anionic modified pulp preferably has an amount of anionic groups measured with all anionic groups in the acid form of 0.5 to 3.0 mmol / g, more preferably 1.0 to 2.8 mmol / g, and still more preferably 1.5 to 2.5 mmol / g. Since the anionic modified pulp according to the embodiment as described above is a salt-type anionic modified pulp containing an onium salt, when measuring the amount of anionic groups, all anionic groups are converted to the acid form and then measured. The amount of anionic groups is the amount of substance (mmol) of anionic groups per dry mass of the acid-form anionic modified pulp, and can be measured by a known method. Specifically, it can be measured by the method described in the Examples section. In this specification, the "dry mass" refers to the mass after drying at 140°C until the mass change rate per minute becomes 0.05% or less.

[0024] In the anionic modified pulp of the present embodiment, the anionic groups may be only the onium salt, or may contain other salts together with the onium salt. The other salts are not particularly limited, and examples include alkali metal salts such as sodium salts and potassium salts, and alkaline earth metal salts such as magnesium salts and calcium salts. Also, not all of the anionic groups have to be in the salt form (for example, in the case of a carboxy group, -COOX (where X is a cation forming a salt with a carboxylic acid)), and may contain an acid form (the counter ion is H + and is also referred to as the H form. For example, in the case of a carboxy group, -COOH) together with the salt form containing the onium salt.

[0025] Anionic modified pulp is obtained by chemically modifying unmodified pulp as described above and is not defibrated. In this regard, it is distinguished from cellulose nanofibers obtained by defibrating pulp to make it finer. The fiber diameter of anionic modified pulp is equivalent to that of untreated pulp and varies depending on the raw material pulp, but is usually several tens of μm. Specifically, the number average fiber width of anionic modified pulp is preferably 5 to 100 μm, more preferably 10 to 60 μm, and may also be 20 to 40 μm.

[0026] The number average fiber width of anionic modified pulp is measured as follows. For an aqueous suspension of anionic modified pulp diluted to 0.01 mass%, 10 images are taken using an optical microscope, 25 fibers are selected from them, the width (diameter) of the fibers is measured, and the arithmetic mean is calculated to obtain it.

[0027] The fibrous material for thermoforming according to this embodiment may consist only of the above anionic modified pulp, or may contain an additive as an optional component together with the above anionic modified pulp. Examples of the additive include colorants such as pigments and dyes, water resistance agents, flame retardants, plasticizers, antioxidants, light stabilizers, fillers, antistatic agents, and the like. Since the anionic modified pulp according to this embodiment has thermoformability as described above, it can be thermoformed alone with the anionic modified pulp. Therefore, it is preferable that the fibrous material for thermoforming does not contain a resin such as a thermoplastic resin, and can be directly used for thermoforming without adding a resin.

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

[0029] When forming a fiber sheet, for example, paper may be produced by papermaking using a suspension containing anionic modified pulp as a furnish. Papermaking is a process of dehydrating the furnish by filtration to form a sheet, followed by pressing and drying 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, a cylinder Fourdrinier combination papermaking machine, etc. may be used. Also, for example, a suspension containing anionic modified pulp may be vacuum-filtered to form a sheet, dried, and then pressed to produce a fiber sheet. These pressing and drying are preferably carried out at a temperature at which the anionic modified pulp does not become plasticized. The thickness of the fiber sheet is not particularly limited and may be, for example, 0.001 to 50 mm, or may be 0.01 to 5 mm. In this specification, "sheet" and "sheet-like" are concepts that respectively include "film" and "film-like".

[0030] By thermoforming the fibrous material for thermoforming, a molded body is obtained. Thermoforming, as described above, refers to softening (plasticizing) the fibrous material for thermoforming by heating and molding it into a predetermined shape, and then curing it by cooling. Examples include thermo-press molding, vacuum molding, pressure-air molding, etc. The shape of the molded body is not particularly limited, and various shapes such as sheet-like, plate-like, and three-dimensional structures can be mentioned. Specific molded bodies include, for example, sheets, packaging materials, tableware (cups, plates, etc.), containers (bottles, trays, etc.).

[0031] Generally, paper made from pulp has voids between the pulps and is therefore opaque. When it is a fibrous material for thermoforming according to this embodiment, for example, by thermo-press molding, the fibers adhere closely without gaps, eliminating voids and enabling transparency.

[0032] In addition, while papers made from ordinary pulp do not adhere even when multiple sheets are stacked and heat-pressed, in the case of a fiber sheet made of the fibrous material for thermoforming according to the present embodiment, by stacking multiple sheets and thermoforming at least a part thereof by heat-pressing, it is possible to adhere between the fiber sheets at the thermoformed part, and heat sealing is possible. Therefore, a fiber sheet capable of heat sealing can be provided.

[0033] [Composite Material for Thermoforming] The composite material for thermoforming according to the present embodiment contains an anionic modified pulp in which 45 mol% or more of the above-described anionic groups are onium salts, and a thermoplastic resin. Since the anionic modified pulp has an onium salt and becomes soft and easy to flow by heating, it is easy to mix with the heat-melted thermoplastic resin, and thus it is difficult to form agglomerates of the anionic modified pulp. Therefore, a molded body with excellent surface appearance can be obtained, and it has excellent thermoformability.

[0034] The thermoplastic resin is not particularly limited. For example, 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, polysulfone resin, etc. may be mentioned, and any one of these may be used alone or two or more of them may be used in combination.

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

[0036] The composite material for thermoforming may contain an additive as an optional component together with an anionic modified pulp and a thermoplastic resin. Examples of the additive include a colorant such as a pigment or a dye, a water resistance agent, a flame retardant, a plasticizer, an antioxidant, a light stabilizer, a filler, an antistatic agent, and the like.

[0037] The manufacturing method of the composite material for thermoforming is not particularly limited. For example, a method of mixing a thermoplastic resin and an anionic modified pulp at a temperature at which the thermoplastic resin melts can be mentioned. The form of the composite material for thermoforming is not particularly limited, and examples thereof include a sheet form, a plate form, a pellet form, a powder form, a filament, and the like.

[0038] A molded body is obtained by thermoforming the composite material for thermoforming. Thermoforming means softening the composite material for thermoforming by heating and molding it into a predetermined shape, and then curing it by cooling. Examples thereof include hot press molding, vacuum molding, pressure air molding, injection molding, extrusion molding, an FDM method 3D printer, and the like. The shape of the molded body is not particularly limited, and various shapes such as a sheet form, a plate form, and a three-dimensional structure can be mentioned. Specific examples of the molded body include a sheet, a packaging material, tableware (such as a cup and a plate), a container (such as a bottle and a tray), and the like.

Examples

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

[0040] The measurement methods of each physical property in the examples and comparative examples are as follows.

[0041] [Amount of anionic group (amount of carboxy group)] 50 mL of an aqueous suspension of an acid-type anionic 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 hydrochloric acid aqueous solution. Then, a 0.05 mol / L sodium hydroxide aqueous solution was added dropwise to the aqueous suspension, and the electrical conductivity was measured until the pH reached approximately 11. From the amount of sodium hydroxide (V) consumed in the neutralization stage of the weak acid where the change in electrical conductivity was gentle, the amount of carboxyl groups was calculated according to the following formula. Amount of carboxyl groups (mmol / g) = V (mL) × [0.05 / mass of acid-type anionic modified pulp (g)]

[0042] [Amount of anionic groups (phosphate groups)] For an aqueous suspension prepared by diluting an anionic modified pulp with ion-exchanged water to a content of 0.2% by mass, after treatment with an ion-exchange resin to obtain an acid-type anionic modified pulp, titration with an alkali was performed for measurement. The treatment with the ion-exchange resin was carried out by adding a strongly acidic ion-exchange resin (Amberjet 1024; Organo Corporation, conditioned) with a volume of 1 / 10 to the aqueous suspension, performing a shaking treatment for 1 hour, and then pouring it onto a mesh with an opening of 90 μm to separate the ion-exchange resin from the aqueous suspension. Also, the titration with an alkali was performed by measuring the change in the value of the electrical conductivity shown by the aqueous suspension while adding 50 μL of a 0.1 mol / L sodium hydroxide aqueous solution to the aqueous suspension after treatment with the ion-exchange resin, once every 30 seconds. The amount of phosphate groups (mmol / g) was calculated by dividing the amount of alkali (mmol) required in the region corresponding to the first region in the measurement results by the solid content (g) in the aqueous suspension to be titrated.

[0043] [Amount of anionic groups (sulfate groups)] A predetermined amount of the acid-type anionic modified pulp was burned, and the sulfur content contained in the combustion product was measured using a combustion ion chromatograph by a method conforming to IEC 62321, and calculated after conversion to the amount of sulfate groups.

[0044] [Introduction rate of onium salt] The sheets as fibrous materials for thermoforming obtained in Examples 1 to 18 and Comparative Examples 1 to 4 were measured by FT-IR. The absorption peak area derived from carboxylic acid (around 1720 cm -1 ), and the introduction rate of the onium salt was calculated from the absorption peak area derived from carboxylate (1600 cm -1 ). When a metal salt is included as another salt, since the absorption peaks of the metal salt and the onium salt appear at the same position, it was calculated by measuring the metal content together with an ICP emission spectrometer. Introduction rate of onium salt [mol%] = {Absorption peak area derived from carboxylate / (Absorption peak area derived from carboxylate + Absorption peak area derived from carboxylic acid)} × 100 For the fibrous materials for thermoforming obtained in Examples 19 and 20, the introduction rate of the onium salt was calculated by measuring the nitrogen content with a total nitrogen analyzer.

[0045] [Melting point of modifier] Modifiers that are not liquid at room temperature (amines, phosphines, ammonium salts, phosphonium salts, etc.) were finely ground in a mortar and filled into a melting point measuring tube. The melting point measuring tube was set in the depression on the aluminum plate of the melting point measuring device, and a glass cover was placed on it. The temperature of the melting point measuring 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 the modifier of the quaternary onium salt, the acetate in which the anion forming a salt with the onium ion was replaced with an acetate ion was measured.

[0046] [Formability] The sheets as fibrous materials for thermoforming obtained in Examples 1 to 20 and Comparative Examples 1 to 4 were cut into test pieces measuring 3 cm in length and 3 cm in width. The test pieces were sandwiched in a drawing die and pressed at 100°C and 0.4 MPa using a hot press device. The obtained molded bodies were observed and evaluated according to the following criteria. A: A molded body without wrinkles or cracks can be obtained with a pressing time of 10 seconds or less. B: A molded body without wrinkles or cracks can be obtained with a pressing time of 11 seconds or more and 60 seconds or less. C: A molded body without wrinkles or cracks can be obtained with a pressing time of 61 seconds or more and 180 seconds or less. D: The sheet cracks under pressure and no molded body can be obtained.

[0047] [Heat sealability] The sheets as fibrous materials for thermoforming obtained in Examples 1 to 20 and Comparative Examples 1 to 4 were cut into pieces 100 mm long and 15 mm wide to prepare test pieces. Two test pieces were stacked, and a range of 10 mm long and 15 mm wide was pressed at 100 °C and 0.1 MPa using a hot press device. Using a tensile testing machine, the two unpressed ends were grasped and T-peel separation was performed at a tensile speed of 300 mm / min, and the maximum value was taken as the heat seal strength. The criteria for judging heat sealability are shown below. A: Those with a heat seal strength of 0.1 N / 15 mm or more and a pressing time of 10 seconds or less B: Those with a heat seal strength of 0.1 N / 15 mm or more and a pressing time of 11 seconds or more and 60 seconds or less C: Those with a heat seal strength of 0.1 N / 15 mm or more and a pressing time of 61 seconds or more and 180 seconds or less D: Those with a heat seal strength of less than 0.1 N / 15 mm or non-adhesive at a pressing time of 180 seconds

[0048] [Transparency] The sheets as fibrous materials for thermoforming obtained in Examples 1 to 20 and Comparative Examples 1 to 4 were cut into pieces 3 cm long and 3 cm wide to prepare test pieces. The test pieces were sandwiched between polyimide films and pressed at 100 °C, 0.4 MPa for 5 minutes using a hot press device. For the test pieces after pressing, the area of the transparent portion was measured using image analysis software. The criteria for judging transparency are shown below. A: Those in which 50% or more of the whole is transparent B: Those in which 5% or more and less than 50% of the whole is transparent C: Those in which the transparent portion is less than 5% of the whole

[0049] [Appearance of the surface of the molded body] The composite materials for thermoforming obtained in Examples 21 to 22 and Comparative Example 5 were pressed at 200 °C using a hot press apparatus and then cut to produce films measuring 5 cm in length × 5 cm in width × 1 mm in thickness. The criteria for determining the surface appearance of the obtained films are shown below. 〇: Less than 5 agglomerates of anionic modified pulp ×: 5 or more agglomerates of anionic modified pulp

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

[0051] [Production Example 1: Preparation of Anionic Modified Pulp A1 (TEMPO-Oxidized Cellulose Fibers)] To 2 g of softwood pulp, 150 mL of water, 0.25 g of sodium bromide, and 0.025 g of TEMPO were added, and after thoroughly stirring and dispersing, an aqueous solution of 13% by mass sodium hypochlorite (co-oxidizing agent) was added such that the amount of sodium hypochlorite was 10.0 mmol / g with respect to 1.0 g of the above pulp, and the reaction was initiated. Since the pH decreased as the reaction proceeded, a 0.5 mol / L aqueous sodium hydroxide solution was added dropwise to maintain the pH at 10 to 11, and the reaction was carried out until no 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, followed by repeated filtration and washing with water for purification to obtain cellulose fibers with oxidized fiber surfaces. Pure water was added thereto and diluted to a cellulose fiber concentration of 4% by mass to prepare a TEMPO-oxidized cellulose fiber suspension. Thereafter, after adjusting the pH of the slurry to 10 with a 24% by mass aqueous sodium hydroxide solution, sodium borohydride was added at 0.2 mmol / g with respect to the cellulose fibers, and the reaction was initiated. The reduction treatment was carried out by reacting for 2 hours. After the reaction, 0.1 mol / L hydrochloric acid was added to adjust the pH to 2.0, followed by repeated filtration and washing with water for purification to obtain anionic modified pulp A1 in which the carboxyl groups are in the acid form.

[0052] [Production Example 2: Preparation of Anionic Modified Pulp A2 (TEMPO Oxidized Cellulose Fiber)] An anionic modified pulp A2 with carboxyl groups in acid form was obtained in the same manner as the preparation method of anionic modified pulp A1, except that the addition amount of the aqueous sodium hypochlorite solution was 6.0 mmol / g with respect to 1.0 g of softwood pulp.

[0053] [Production Example 3: Preparation of Anionic Modified Pulp A3 (TEMPO Oxidized Cellulose Fiber)] An anionic modified pulp A3 with carboxyl groups in acid form was obtained in the same manner as the preparation method of anionic modified pulp A1, except that the addition amount of the aqueous sodium hypochlorite solution was 4.0 mmol / g with respect to 1.0 g of softwood pulp.

[0054] [Production Example 4: Preparation of Anionic Modified Pulp A4 (Phosphoric Esterified Cellulose Fiber)] To 100 parts by mass (dry mass) of softwood kraft pulp, an aqueous mixed solution of ammonium dihydrogen phosphate and urea was added and adjusted to contain 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. Next, the obtained chemical impregnated pulp was heated in a hot air dryer at 165 °C for 200 seconds to introduce phosphate groups into the cellulose in the pulp and obtain phosphoric esterified cellulose fiber. 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 for purification to obtain an anionic modified pulp A4 in which the fiber surface was phosphoric esterified and the phosphate groups were in acid form.

[0055] [Production Example 5: Preparation of Anionic Modified Pulp A5 (Sulfuric 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 using a stirrer for 10 minutes. After stirring, the slurry was suction-filtered using filter paper (No. 2). The suction filtration was carried out until the solution stopped dripping. After suction filtration, the pulp was peeled off from the filter paper, and the pulp was placed in a dryer with the temperature of the constant temperature bath set at 50 °C and reacted for 6 hours. 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 for purification to obtain an anion-modified pulp A5 in which the fiber surface was sulfated and the sulfate group was in the acid form.

[0056] [Example 1] (Preparation of modifier) After dissolving tetrabutylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.) in ethanol to a concentration of 0.1 N, 5 times the amount of ion-exchange resin (Amberlite IRN78, manufactured by Tokyo Chemical Industry Co., Ltd.) of tetrabutylammonium bromide was added, and the mixture was stirred overnight using a shaker. Then, the ion-exchange resin was removed by filtration to obtain a 0.1 N tetrabutylammonium hydroxide ethanol solution.

[0057] (Introduction of onium salt) After diluting anion-modified pulp A1 with ethanol to 0.2% by mass, a 0.1 N tetrabutylammonium hydroxide ethanol solution in an equimolar amount to the amount of carboxyl groups of anion-modified pulp A1 was added, and the mixture was stirred at room temperature for 2 hours. This was filtered through a nylon mesh filter with an aperture of 59 μm, and the residue remaining on the filter was diluted with ethanol and filtered 3 times repeatedly to obtain anion-modified pulp B1.

[0058] (Preparation of sheet) After diluting the obtained anion-modified pulp B1 with ethanol to 0.2% by mass, a sheet-like wet deposit was obtained by vacuum filtration through a nylon mesh filter with an aperture of 59 μm. After air-drying at room temperature, it was sandwiched between polyimide films and pressed at 20 °C for 5 minutes at 0.1 MPa using a hot press apparatus to obtain a sheet of Example 1 with a thickness of 100 μm (fibrous material for thermoforming).

[0059] [Example 2] Except for using tetraoctylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.), the modifier was prepared and the onium salt was introduced in the same manner as in Example 1 to obtain anionic modified pulp B2. Using the obtained anionic 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] Except for using benzyltributylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.), the modifier was prepared and the onium salt was introduced in the same manner as in Example 1 to obtain anionic modified pulp B3. Using the obtained anionic 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] Except for using hexadecyltrimethylammonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.), the modifier was prepared and the onium salt was introduced in the same manner as in Example 1 to obtain anionic modified pulp B4. Using the obtained anionic 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] Except for using trihexyl(tetradecyl)phosphonium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.), the modifier was prepared and the onium salt was introduced in the same manner as in Example 1 to obtain anionic modified pulp B5. Using the obtained anionic 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] Except for using tetraoctylphosphonium bromide (manufactured by Tokyo Chemical Industry Co., Ltd.), the modifier was prepared and the onium salt was introduced in the same manner as in Example 1 to obtain anionic modified pulp B6. Using the obtained anionic 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) After diluting anionic modified pulp A1 to 0.2% by mass with ethanol, an equimolar amount of trioctylamine to the amount of carboxy groups of anionic modified pulp A1 was added, and the mixture was stirred at room temperature for 2 hours. This was filtered through a nylon mesh filter with an aperture of 59 μm to obtain anionic modified pulp B7.

[0065] (Preparation of sheet) After diluting the obtained anionic modified pulp B7 to 0.2% by mass with ethanol, a sheet-like wet deposit was obtained by vacuum filtration through a nylon mesh filter with an aperture of 59 μm. After air-drying at room temperature, it was sandwiched between polyimide films and pressed at 20 °C for 5 minutes at 0.1 MPa using a hot press apparatus to obtain a sheet (fibrous material for thermoforming) of Example 7 with a thickness of 100 μm.

[0066] [Example 8] Introduction of onium salt was carried out in the same manner as in Example 7 except that dioctylamine was used to obtain anionic modified pulp B8. Using the obtained anionic modified pulp B8, a sheet was prepared in the same manner as in Example 7 to obtain a sheet of Example 8.

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

[0068] [Example 10] Except for using 1-ethyl-3-methylimidazolium chloride (manufactured by Tokyo Chemical Industry Co., Ltd.), the preparation of the modifier and the introduction of the onium salt were carried out in the same manner as in Example 1 to obtain anionic modified pulp B10. Using the obtained anionic modified pulp B10, a sheet was prepared in the same manner as in Example 1 to obtain a sheet of Example 10.

[0069] [Example 11] Except for using anionic modified pulp A2, the modifier was prepared and the onium salt was introduced in the same manner as in Example 2 to obtain anionic modified pulp B11. Using the obtained anionic 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] Except for using anionic modified pulp A3, the modifier was prepared and the onium salt was introduced in the same manner as in Example 2 to obtain anionic modified pulp B12. Using the obtained anionic modified pulp B12, a sheet was prepared in the same manner as in Example 2 to obtain the sheet of Example 12.

[0071] [Example 13] Except for adding a 0.1N tetraoctylammonium hydroxide ethanol solution in an amount 0.9 times the molar amount of the carboxy groups of anionic modified pulp A1, the modifier was prepared and the onium salt was introduced in the same manner as in Example 2 to obtain anionic modified pulp B13. Using the obtained anionic modified pulp B13, a sheet was prepared in the same manner as in Example 2 to obtain the sheet of Example 13.

[0072] [Example 14] Except for adding a 0.1N tetraoctylammonium hydroxide ethanol solution in an amount 0.75 times the molar amount of the carboxy groups of anionic modified pulp A1, the modifier was prepared and the onium salt was introduced in the same manner as in Example 2 to obtain anionic modified pulp B14. Using the obtained anionic modified pulp B14, a sheet was prepared in the same manner as in Example 2 to obtain the sheet of Example 14.

[0073] [Example 15] Except for adding a 0.1N tetraoctylammonium hydroxide ethanol solution in an amount of 0.5 times the molar amount of the carboxyl groups of anionic modified pulp A1, the modifier was prepared and the onium salt was introduced in the same manner as in Example 2 to obtain anionic modified pulp B15. Using the obtained anionic modified pulp B15, a sheet was prepared in the same manner as in Example 2 to obtain the sheet of Example 15.

[0074] [Example 16] Except for adding a 0.1N tetraoctylammonium hydroxide ethanol solution in an amount of 0.5 times the molar amount of the carboxyl groups of anionic modified pulp A1 and a 0.1N aqueous sodium hydroxide solution in an amount of 0.5 times the molar amount of the carboxyl groups of anionic modified pulp A1, the modifier was prepared and the onium salt was introduced in the same manner as in Example 2 to obtain anionic modified pulp B16. Using the obtained anionic modified pulp B16, a sheet was prepared in the same manner as in Example 2 to obtain the sheet of Example 16.

[0075] [Example 17] Except for adding a 0.1N tetraoctylammonium hydroxide ethanol solution in an amount of 0.5 times the molar amount of the carboxyl groups of anionic modified pulp A1 and a 0.1N benzyltributylammonium hydroxide ethanol solution (see Example 3) in an amount of 0.5 times the molar amount of the carboxyl groups of anionic modified pulp A1, the modifier was prepared and the onium salt was introduced in the same manner as in Example 2 to obtain anionic modified pulp B17. Using the obtained anionic modified pulp B17, a sheet was prepared in the same manner as in Example 2 to obtain the sheet of Example 17.

[0076] [Example 18] A 0.1N tetraoctylammonium hydroxide ethanol solution in an amount 0.5 times the molar amount of the carboxyl groups of anionic modified pulp A1, and a 0.1N hexadecyltrimethylammonium hydroxide ethanol solution in an amount 0.5 times the molar amount of the carboxyl groups of anionic modified pulp A1 (see Example 4) were added, and then the modifier was prepared and the onium salt was introduced in the same manner as in Example 2 to obtain anionic modified pulp B18. Using the obtained anionic modified pulp B18, a sheet was prepared in the same manner as in Example 2 to obtain the sheet of Example 18.

[0077] [Example 19] Except for using anionic modified pulp A4, the modifier was prepared and the onium salt was introduced in the same manner as in Example 2 to obtain anionic modified pulp B19. Using the obtained anionic modified pulp B19, a sheet was prepared in the same manner as in Example 2 to obtain the sheet of Example 19.

[0078] [Example 20] Except for using anionic modified pulp A5, the modifier was prepared and the onium salt was introduced in the same manner as in Example 2 to obtain anionic modified pulp B20. Using the obtained anionic modified pulp B20, a sheet was prepared in the same manner as in Example 2 to obtain the sheet of Example 20.

[0079] [Comparative Example 1] Anionic modified pulp A1 was diluted to 0.2% by mass with ion-exchanged water, and then a sheet-like wet deposit was obtained by vacuum filtration through a nylon mesh filter with an aperture of 59 μm. After air-drying at room temperature, it was sandwiched between polyimide films and pressed at 20 °C for 5 minutes at 0.1 MPa using a hot press device to obtain the sheet of Comparative Example 1 with a thickness of 100 μm.

[0080] [Comparative Example 2] Anionic modified pulp A1 was diluted to 0.2% by mass with ion-exchanged water and then neutralized with a 0.1N aqueous sodium hydroxide solution to adjust the pH (25°C) to 7.0. This was filtered through a nylon mesh filter with an aperture of 59 μm to obtain anionic modified pulp C2 in the salt form with sodium salt. The obtained anionic modified pulp C3 was diluted to 0.2% by mass with ethanol and then vacuum filtered through a nylon mesh filter with an aperture of 59 μm to obtain a sheet-like wet deposit. After air drying at room temperature, it was sandwiched between polyimide films and pressed at 20°C for 5 minutes at 0.1 MPa using a hot press apparatus to obtain a sheet of Comparative Example 2 with a thickness of 100 μm.

[0081] [Comparative Example 3] Except for adding a 0.1N tetraoctylammonium hydroxide ethanol solution in a molar amount 0.4 times the amount of carboxyl groups in anionic modified pulp A1 and a 0.1N aqueous sodium hydroxide solution in a molar amount 0.6 times the amount of carboxyl groups in anionic modified pulp A1, the modifier was prepared and the onium salt was introduced in the same manner as in Example 2 to obtain anionic modified pulp C3. Using the obtained anionic modified pulp C2, a sheet was prepared in the same manner as in Example 2 to obtain a sheet of Comparative Example 3.

[0082] [Comparative Example 4] Except for adding a 0.1N tetraoctylammonium hydroxide ethanol solution in a molar amount 0.4 times the amount of carboxyl groups in anionic modified pulp A1, the modifier was prepared and the onium salt was introduced in the same manner as in Example 2 to obtain anionic modified pulp C4. Using the obtained anionic modified pulp C4, a sheet was prepared in the same manner as in Example 2 to obtain a sheet of Comparative Example 4.

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

[0084]

Table 1

[0085] As shown in Table 1, in Comparative Examples 1 and 2 where no onium salt was introduced and Comparative Examples 3 and 4 where the introduction rate of the onium salt was low, the anionic modified pulp did not have thermoformability, so the formability, heat sealability, and transparency were inferior. On the other hand, in Examples 1 to 20 where a predetermined amount or more of the onium salt was introduced, it had formability by thermoforming and heat sealability, and the sheet could be made transparent. The formability, heat sealability, and transparency were better as the introduction rate of the onium salt was higher. Also, the lower the melting point of the modifier, the better these performances, and furthermore, the quaternary onium salt was superior to the primary to tertiary ones in these performances.

[0086] [Example 21] For 100 parts by mass of polycaprolactone, 2 parts by mass of absolutely dry anionic modified pulp B2 was kneaded at 200 °C and 100 rpm for 10 minutes using a Laboplastomill (manufactured by Toyo Seiki Seisakusho Co., Ltd.) to produce a composite material for thermoforming 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] For 100 parts by mass of polycaprolactone, 2 parts by mass of absolutely dry anionic modified pulp A1 was kneaded at 200 °C and 100 rpm for 10 minutes using a Laboplastomill (manufactured by Toyo Seiki Seisakusho Co., Ltd.) to produce a composite material for thermoforming of Comparative Example 5.

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

[0090]

Table 2

[0091] As shown in Table 2, the composite material for thermoforming of Comparative Example 5 contains an anion-modified pulp into which an onium salt is not introduced, and thus a large number of agglomerates were observed on the surface of the thermoformed molded body. In contrast, the composite materials for thermoforming of Examples 21 and 22 contain an anion-modified pulp to which thermoformability was imparted by the introduction of an onium salt, and thus the surface appearance of the thermoformed molded body was excellent.

[0092] In addition, the various numerical ranges described in the specification can arbitrarily combine their upper limit values and lower limit values, and all of these combinations are described in this specification as preferred numerical ranges. Also, the description of the numerical range of "X to Y" means X or more and Y or less.

[0093] As described above, some embodiments of the present invention have been described. However, 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, replacements, and changes can be made without departing from the gist of the invention. These embodiments, their omissions, replacements, changes, etc. are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalent scope thereof.

Claims

1. A fibrous material for thermoforming, comprising an anion-modified pulp in which 45 mol% or more of the anionic groups are onium salts.

2. The fibrous material for thermoforming according to Claim 1, wherein the modifier for converting the anionic group into an onium salt has a melting point of 150°C or lower.

3. The fibrous material for thermoforming according to 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 with all the anionic groups 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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