Pulp and sheet

Abstract

To provide pulp capable of imparting transparency and hydrophobicity to a sheet.SOLUTION: Pulp of the present invention is characterized in that amin having 9 or more with straight chain carbon atoms is supported on pulp in which at least a part of a hydroxy group of cellulose is substituted with a sulfuric ester group, a cellulose I crystal structure is provided as a crystal structure, and a crystallinity is 76% or less and a mean fiber length is 0.3 mm or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to pulp and sheets. [Background technology]

[0002] A hydrophobic sheet has been proposed that has enhanced transparency and improved hydrophobicity, and is made by mixing defibrated anion-modified cellulose fibers with a water-soluble polymer (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6828759 Summary of the Invention [Problem to be solved by the invention]

[0004] As mentioned above, the sheet described in Patent Document 1 is a hydrophobic sheet in which defibrated anion-modified cellulose fibers and a water-soluble polymer are mixed. In contrast, it would be convenient if there was a pulp that could impart transparency and hydrophobicity to a sheet without the need for defibration treatment or mixing with a water-soluble polymer.

[0005] Therefore, an object of the present invention is to provide pulp that can impart transparency and hydrophobicity to a sheet without the need for defibration treatment or mixing with a water-soluble polymer, and a sheet containing the pulp. [Means for solving the problem]

[0006] In order to achieve the above object, the pulp of the present invention is The pulp is characterized in that at least a portion of the hydroxyl groups of cellulose have been substituted with sulfate ester groups (hereinafter referred to as "sulfate ester group-introduced pulp"), and an amine having a linear carbon number of 9 or more is supported on the pulp; the cellulose has a cellulose type I crystal structure, a degree of crystallinity of 76% or less, and an average fiber length of 0.3 mm or more.

[0007] The sheet of the present invention is The present invention is characterized by comprising the pulp of the present invention. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide pulp that can impart transparency and hydrophobicity to a sheet without carrying out defibration treatment or mixing with a water-soluble polymer, and a sheet containing the pulp. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram showing a method for supporting an amine on sulfate ester group-introduced pulp. [Figure 2] FIG. 1 is a table and graph showing experimental results, and is a diagram showing the crystallinity. [Figure 3] FIG. 1 is a graph showing experimental results, illustrating the crystalline structure of amine-loaded pulp. [Figure 4] FIG. 1 is a table and graph showing experimental results, showing average fiber lengths. [Figure 5] 1 is a table and a graph showing experimental results, and is a diagram showing water retention. [Figure 6] 10 is a table and a graph showing experimental results, illustrating the total light transmittance of the sheet. FIG. [Figure 7] 10 is a table and a graph showing experimental results, illustrating the water absorption rate of the sheet. [Figure 8] 10 is a table and photographs showing experimental results, and a diagram showing the contact angle of the sheet. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Pulp> The pulp of the present invention is a pulp into which a sulfate ester group has been introduced and which has supported thereon an amine having a linear carbon number of 9 or more. Hereinafter, the pulp of the present invention may be referred to as "amine-supported pulp."

[0011] <Sulfate ester group-introduced pulp> The sulfate ester group-introduced pulp is a fibrous material composed of a plurality of cellulose fibers, in which at least a portion of the hydroxyl groups (-OH groups) of the cellulose (a chain polymer in which D-glucose is linked via β(1→4) glycosidic bonds) constituting the cellulose fibers contained therein have been substituted with sulfate ester groups represented by formula (1).

[0012] (-OSO3 - ) r Z r+ (1) In formula (1), r is an independent natural number between 1 and 7, Z r+ When r=1, is at least one selected from the group consisting of hydrogen ions, alkali metal ions, monovalent transition metal ions, ammonium ions, aliphatic ammonium ions, aromatic ammonium ions, and cationic polymers, and when r=2 or more, is at least one selected from the group consisting of alkaline earth metal ions, polyvalent metal ions, and compounds containing two or more cationic functional groups (e.g., diamines) in the molecule.

[0013] <amine> The amine may be an amine compound having a linear carbon number of 9 or more, for example, an aliphatic amine having a carbon number of 9 or more and no branched chain. n H 2n+1 NH2: (n is a natural number of 9 or more) and aliphatic amines having a linear branched chain with 9 or more carbon atoms. The amine may further include a special functional group, molecular structure, or polymer structure, as long as it is an amine compound having a linear carbon number of 9 or more. Furthermore, from the viewpoint of producing highly hydrophobic pulp, it is preferable that the amine is a monoamine having no hydrophilic groups other than amino groups.

[0014] <Amine-loaded pulp> In the present invention, "supported" means a state in which the sulfate ester group and the amine are ionic bonded. That is, Z of the sulfate ester group represented by formula (1) in the sulfate ester group-introduced pulp r+The aforementioned linear amine having 9 or more carbon atoms is supported on the carrier.

[0015] The amine is formed by cationizing the amino group (-NH2) in the molecule to form an ammonium ion (-NH3 + ) through electrostatic interaction with the sulfate ester groups. That is, in the amine-loaded pulp, the amine becomes an ammonium ion with respect to the sulfate ester groups of the sulfate ester group-introduced pulp, forming a complex through electrostatic interaction (sulfate ester group-introduced pulp-OSO3 - + The formation of a complex through electrostatic interaction can be determined, for example, by observing the infrared absorption spectrum using an infrared spectrophotometer.

[0016] <Physical properties of amine-loaded pulp> The physical properties of the amine-loaded pulp are as follows:

[0017] <Crystallinity> The amine-supported pulp has a cellulose type I crystal structure as its crystalline structure, and its crystallinity is 76% or less. The crystallinity may be, for example, 70% or less, 60% or less, or 50% or less. From the viewpoint of maintaining the fiber shape, the crystallinity of the amine-supported pulp is preferably 30% or more.

[0018] <Method for measuring crystallinity> The crystallinity of the amine-loaded pulp can be measured, for example, using an X-ray diffraction device.

[0019] <Average fiber length> The average fiber length of the amine-carrying pulp is 0.3 mm or more, and may be, for example, 0.3 mm to 2 mm, 0.3 mm to 1.8 mm, 0.3 mm to 1.5 mm, or 0.3 mm to 1 mm.

[0020] <Method for measuring average fiber length> The average fiber length of the amine-loaded pulp can be measured using, for example, a fiber tester or fiber length distribution measuring instrument manufactured by Lorentzen & Wettley in accordance with ISO 16065-2:2007.

[0021] The physical properties of the amine-carrying pulp, excluding the above-mentioned crystal structure, degree of crystallinity and average fiber length, are not particularly limited, but are, for example, as follows.

[0022] <Amount of sulfate ester groups introduced> The amount of sulfate ester groups introduced per 1 g (solid mass) of amine-supported pulp is preferably adjusted to, for example, 0.6 mmol / g or more, 0.8 mmol / g or more, 1 mmol / g or more, or 1.2 mmol / g or more.

[0023] Although there is no particular upper limit, from the viewpoint of suppressing fiber collapse and cost increases due to decreased crystallinity, for example, the amount of sulfate ester groups introduced per 1 g (solid mass) of amine-supported pulp is 9.9 mmol / g or less, or 5 mmol / g or less.

[0024] <Method for measuring the amount of sulfate ester groups introduced> The amount of sulfate ester groups introduced into the amine-supported pulp can be evaluated by the amount of sulfur introduced due to the sulfate ester groups or by directly measuring the sulfate ester groups. For example, the amount of sulfate ester groups introduced into the amine-supported pulp can be measured using a CHNS / O elemental analyzer. The amount of sulfate ester groups introduced into the amine-supported pulp can also be calculated by measuring electrical conductivity.

[0025] <Short fiber rate (%)> The amine-supported pulp may also contain pulp with short fiber lengths as follows. Examples of pulp with short fiber lengths (hereinafter referred to as "short fibers") include pulp with a fiber length distribution of 0.04 mm or more and 0.2 mm or less. The short fiber content (%) in the amine-supported pulp (i.e., short fiber ratio (%)) is, for example, 10% or more, 15% or more.

[0026] From the viewpoint of handleability, the amine-supported pulp has a short fiber content (%) (i.e., short fiber ratio (%)) of, for example, 10% to 70%, 10% to 60%, 10% to 50%, 10% to 45%, or 15% to 45% in terms of fiber length distribution.

[0027] <Average fiber width> The average fiber width of the amine-supported pulp is not particularly limited, and is, for example, 5 μm to 100 μm, 10 μm to 50 μm, 20 μm to 40 μm, or 20 μm to 30 μm.

[0028] <Method for measuring average fiber width and fiber distribution> The average fiber width of the amine-loaded pulp can be measured, for example, using a fiber tester or fiber length distribution analyzer manufactured by Lorentzen & Wettley in accordance with ISO 16065-2: 2007. The fiber length distribution and fiber width distribution of the amine-loaded pulp can be measured, for example, using a fiber length distribution analyzer in accordance with ISO 16065-2: 2007.

[0029] <Water retention> The amine-loaded pulp was 3000g (3000 × 9.81m / s 2 ) for 15 minutes, the water retention is, for example, 5000% or less, 3000% or less, or 1000% or less. The water retention of amine-supported pulp tends to decrease as the number of carbon atoms in the linear amine chain increases.

[0030] <Method for measuring water retention> The water retention of the amine-loaded pulp can be calculated using the following formula: Water retention (%) = 100 × (mass of amine-loaded pulp after centrifugation (g) - mass of amine-loaded pulp dried after centrifugation (g)) / mass of amine-loaded pulp dried after centrifugation (g)

[0031] The mass (g) of the amine-supported pulp after centrifugation in the above formula refers to the mass of the amine-supported pulp that has been centrifuged. Specifically, a dispersion liquid obtained by dispersing the amine-supported pulp in water to a solid content of 1.0% by mass was centrifuged at 3000 g (3000 × 9.81 m / s).2 ) for 15 minutes and then measure the mass.

[0032] In the above formula, the mass (g) of the amine-loaded pulp dried after centrifugation refers to the dry mass of the amine-loaded pulp after centrifugation. Specifically, this refers to the dry mass of the amine-loaded pulp prepared by drying it to a constant weight using a dryer or other device. For example, the amine-loaded pulp after centrifugation is placed in a dryer and dried under specified drying conditions (e.g., 105°C for 2 hours). The mass can then be measured to calculate the mass of the dried amine-loaded pulp after moisture removal. The term "constant mass" refers to a state in which the moisture in the atmosphere of the treatment facility and the moisture in the amine-loaded pulp no longer appear to move in or out. Specifically, this refers to a state in which the change in mass between two consecutive measurements after drying for a certain period of time (e.g., 2 hours) is within 1% of the mass at the start of drying (however, the second mass measurement must be performed for at least half the drying time required for the first measurement).

[0033] The amine-carrying pulp can be obtained by, for example, the method shown below, but is not limited to this method.

[0034] This method involves chemically treating cellulose-containing pulp (e.g., wood-based pulp (hereinafter simply referred to as "wood pulp")) to prepare sulfate ester group-introduced pulp, followed by loading an amine onto the pulp. This chemical treatment step involves contacting the pulp with a sulfate ester group-donating compound (described below) and at least one of urea and a urea derivative (hereinafter referred to as "urea, etc." Examples of the urea derivative include thiourea, biuret, phenylurea, benzylurea, dimethylurea, diethylurea, tetramethylurea, benzoleinurea, and hydantoin, which may be used alone or in combination). This contact step involves heating the pulp to replace some of the hydroxyl groups of the cellulose with sulfate ester groups, and an amine loading step involves loading an amine having a linear chain of 9 or more carbon atoms onto the sulfate ester groups.

[0035] In this specification, pulp refers to a fibrous material composed of a plurality of cellulose fibers. These cellulose fibers are composed of a plurality of fine fibers (e.g., microfibrils). These fine fibers are composed of a plurality of cellulose molecules (hereinafter simply referred to as "cellulose"), which are chain-like polymers in which D-glucose is linked via β(1→4) glucoside bonds. It is preferable to wash the pulp beforehand. For example, filtration and dehydration using water on a 200-mesh or 235-mesh sieve can remove excessively fine fibers and debris, which is desirable because it improves handling during preparation. In other words, pulp is composed of a collection of cellulose fibers of a size that can become residue on a 200-mesh or 235-mesh sieve. The water may be tap water, but ion-exchanged water or pure water is preferred, as will be the case hereinafter.

[0036] Examples of the pulp include, but are not limited to, wood pulp, dissolving pulp, cotton-based pulp such as cotton linter, non-wood pulp such as wheat straw, bagasse, paper mulberry, mitsumata, hemp, kenaf, and fruit, and recycled paper pulp prepared from recycled newspapers, magazines, cardboard, etc. From the viewpoint of availability, wood pulp is easily used as the pulp.

[0037] There are various types of wood pulp, and the use is not particularly limited, and examples thereof include paper pulps such as softwood kraft pulp (NBKP), hardwood kraft pulp (LBKP), thermomechanical pulp (TMP), etc. One type of pulp may be used alone, or two or more types of pulp may be used in combination.

[0038] The sulfate ester group-donating compound is not particularly limited as long as it is a compound capable of donating sulfate ester groups to pulp, and examples thereof include sulfamic acid, sulfamic acid salts, and sulfuryl compounds having a sulfonyl group with two oxygen atoms covalently bonded to sulfur. One of these compounds may be used alone, or two or more may be used in combination. Sulfamic acid is preferred as the sulfate ester group-donating compound because it has lower acidity than sulfuric acid and a higher efficiency of introducing sulfate ester groups, is inexpensive, and is highly safe. Hereinafter, an example will be described in which sulfamic acid is used as the sulfate ester group-donating compound and urea is used as the urea.

[0039] <Contact process> The contacting step is a step of contacting the pulp with sulfamic acid and urea. This contacting step is not particularly limited as long as it is a method capable of inducing the contact. For example, the pulp may be immersed in a reaction solution in which sulfamic acid and urea are dissolved in a solvent, thereby impregnating the pulp with the reaction solution, or the reaction solution may be applied to the pulp. Alternatively, sulfamic acid and urea may be separately applied to, impregnated into, or sprayed onto the pulp. Among these methods, the method of immersing the pulp in the reaction solution to impregnate the pulp with the reaction solution facilitates uniform contact of the pulp with sulfamic acid and urea.

[0040] The solvent for dissolving sulfamic acid and urea is not particularly limited, and examples thereof include protic polar solvents such as water, ethanol, methanol, acetic acid, formic acid, 2-propanol, nitromethane, and aqueous ammonia; aprotic polar solvents such as acetone, ethyl acetate, tetrahydrofuran (THF), dimethylformamide (DMF), acetonitrile, dimethyl sulfoxide (DMSO), dimethyl sulfide (DMS), and dimethylacetamide (DMA); and nonpolar solvents such as diethyl ether, benzene, toluene, hexane, chloroform, and 1,4-dioxane. One of the solvents may be used alone, or two or more may be used in combination. Water is particularly preferred because it easily dissolves sulfamic acid and urea.

[0041] The pulp in this contacting state with sulfamic acid and urea in this contacting step is sometimes called "reaction liquid-impregnated pulp."

[0042] <Contact amount of reaction solution> When the reaction solution is brought into contact with the pulp, it is preferable to adjust the ratio of sulfamic acid and urea in the reaction solution to the pulp to a predetermined ratio. Specifically, the reaction solution is contacted so that the amounts of sulfamic acid and urea in the reaction solution relative to the pulp in the reaction solution-impregnated pulp when subjected to the reaction step are appropriate. More specifically, the contact amount of sulfamic acid relative to the pulp (solid mass, which is the dry mass) in the reaction solution-impregnated pulp immediately before being subjected to the heating reaction in the reaction step is adjusted to be equal to or greater than the contact amount of urea.

[0043] For example, the reaction liquid is prepared so that the mixing ratio of sulfamic acid and urea is such that the value (sulfamic acid / urea) obtained by dividing the parts by mass of sulfamic acid per 100 parts by mass of the solids content of pulp in the reaction liquid-impregnated pulp immediately before being subjected to the heating reaction by the parts by mass of urea per 100 parts by mass of the solids content of pulp in the reaction liquid-impregnated pulp immediately before being subjected to the heating reaction is 0.8 or more, 0.85 or more, or 1 or more.

[0044] Furthermore, for example, the contact amount of sulfamic acid is adjusted to be 70 parts by mass or more, 100 parts by mass or more, or 200 parts by mass or more per 100 parts by mass of the solid content of the pulp in the reaction liquid-impregnated pulp immediately before being subjected to the heating reaction.

[0045] Furthermore, for example, the contact amount of urea, i.e., the contact amount of urea relative to the mass of solids of the pulp in the reaction solution-impregnated pulp immediately before being subjected to the heating reaction, is adjusted to 20 parts by mass or more, 30 parts by mass or more, or 50 parts by mass or more per 100 parts by mass of the solids of the pulp while maintaining the above-mentioned relationship with sulfamic acid. The upper limit of the contact amount of urea is not particularly limited, and is, for example, 350 parts by mass or less, 300 parts by mass or less, or 250 parts by mass or less per 100 parts by mass of the solids of the pulp.

[0046] The contact amounts of sulfamic acid and urea per 100 parts by mass of the solid content of the pulp can be calculated appropriately depending on, for example, the state of the reaction liquid-impregnated pulp to be subjected to the reaction step.

[0047] <State of pulp impregnated with reaction liquid> The state of the reaction liquid-impregnated pulp to be subjected to the above-mentioned next reaction step may be, for example, the reaction liquid-impregnated pulp in its original state, i.e., in a state in which the pulp is in contact with the reaction liquid without actively removing water, or in a state in which the pulp is in contact with the reaction liquid and water has been actively removed.

[0048] The former reaction liquid-impregnated pulp (in a state where water is not actively removed) includes pulp in a state where the pulp is in contact with the reaction liquid (including, for example, a slurry state), and pulp prepared by removing the pulp from a state where the pulp is in contact with the reaction liquid and leaving it to stand.

[0049] On the other hand, the latter reaction liquid impregnated pulp (in a state where water has been actively removed) refers to pulp that has been in contact with the reaction liquid and has had water intentionally removed from the pulp. Examples include pulp that has been prepared by removing the pulp from the reaction liquid and contacting it and then naturally drying it by air drying or the like, pulp that has been in contact with the reaction liquid and then filtered and dehydrated, pulp that has been contacted with the reaction liquid and then further air-dried, pulp that has been filtered and dehydrated and then further dried using a circulating air dryer, pulp that has been filtered and dehydrated and then further dried using a heated dryer, pulp that has been contacted with the reaction liquid and then dried using a circulating air dryer or a heated dryer, and the like.

[0050] Thus, the reaction solution-impregnated pulp to be subjected to the reaction step may be one that has not been subjected to the aforementioned active water removal, or one that has had a certain amount of water removed by active water removal. Furthermore, when removing water by drying, there is no particular problem even if the moisture content after drying is about 1%. In particular, the latter method can reduce the moisture content in the reaction solution-impregnated pulp to be subjected to the reaction step, thereby shortening the reaction time for the heating reaction in the reaction step. This has the advantage of improving pulp productivity. Furthermore, the method of dehydration treatment has the advantage of enabling the preparation of reaction solution-impregnated pulp more efficiently than when treating a large amount of reaction solution.

[0051] When an active drying method is used, the reaction solution-impregnated pulp may be dried until its moisture content reaches about 1%, or the moisture may be removed by drying it until it reaches an absolutely dry state with a moisture content significantly lower than 1%.

[0052] In this specification, the term "wet state" refers to a reaction solution-impregnated pulp that has a moisture content of 1% or more and is not in an absolute dry state. For example, the term "wet state" may refer to pulp that is still impregnated with the reaction solution, pulp that has been dehydrated to a certain extent, or pulp that has been dried to a certain extent.

[0053] In addition, in this specification, bone dry means a state in which the moisture content is reduced to less than 1% by, for example, reducing the pressure in a desiccator containing a desiccant such as calcium chloride or diphosphorus pentoxide, or by performing a long-term heat drying process.

[0054] Therefore, when the latter method (reaction method in a state where active moisture removal is performed) is used in the contact step, a method in which the moisture content of the reaction liquid-impregnated pulp is brought to a non-bone-dry state or a bone-dry state may be used, but it is preferable to use a method in which the moisture content is brought to a non-bone-dry state.

[0055] The moisture content of the reaction liquid-impregnated pulp in this specification is calculated using the following formula. Moisture content of reaction liquid-impregnated pulp (%) = 100 - (mass of solid content of reaction liquid-impregnated pulp (g) / mass of reaction liquid-impregnated pulp at the time of moisture content measurement (g)) × 100 = {(mass of reaction liquid-impregnated pulp at the time of moisture content measurement (g) - mass of solid content of reaction liquid-impregnated pulp (g)) / mass of reaction liquid-impregnated pulp at the time of moisture content measurement (g)} × 100

[0056] The solids mass (g) of the reaction solution-impregnated pulp in the above formula refers to the dry mass of the reaction solution-impregnated pulp. Specifically, it refers to the dry mass adjusted to a constant weight by drying the sample using a dryer or the like. For example, by placing the reaction solution-impregnated pulp in a dryer and drying it under specified drying conditions (e.g., 105°C for 2 hours) and measuring the mass, the mass of the dried reaction solution-impregnated pulp after moisture removal (i.e., the mass of the reaction solution-impregnated pulp that is not removed under the drying conditions, including, for example, the pulp and the reagents in the reaction solution) can be calculated.

[0057] The state of the pulp when it is brought into contact with the reaction liquid is not particularly limited, and may be, for example, in a dry state or a wet state (i.e., a moist state).

[0058] <Pre-drying process in the contact process> In the above example, a method for preparing reaction solution-impregnated pulp in the contacting step was described in which the reaction solution-impregnated pulp was prepared by actively removing moisture. However, when using a method for removing moisture while heating (pre-drying step) in this method (for example, when directly heating and drying pulp in a state where the reaction solution has been contacted, or when heating and drying dehydrated pulp), it is desirable to adjust the heating temperature to a predetermined temperature or lower. The drying temperature in this pre-drying step is not particularly limited, but is preferably adjusted to a temperature that can remove moisture contained in the reaction solution-impregnated pulp and ambient moisture and does not allow the reaction to proceed. For example, the drying temperature in the pre-drying step can be adjusted so that the ambient temperature of the reaction solution-impregnated pulp is 100°C or lower. On the other hand, from the viewpoint of workability, it is preferable to adjust the temperature to 50°C or higher. Therefore, the drying temperature in the pre-drying step in the contacting step is preferably 50°C to 100°C, or 70°C to 100°C.

[0059] <Moisture adjustment process in contact process> The contacting step may include a moisture adjustment step in which the moisture content of the pulp to be contacted with the reaction solution is adjusted to fall within a predetermined range. This moisture adjustment step involves drying or humidifying the pulp so that it has a predetermined moisture content. By including this moisture adjustment step, the moisture content in the pulp when contacted with the reaction solution or the like can be made somewhat uniform, which may improve product stability in continuous operation. In addition, drying the pulp to a certain extent to reduce the moisture content (for example, to a moisture content of 1% to 10%) has the advantage of improving storage stability.

[0060] <Reaction process> As described above, the reaction solution-impregnated pulp prepared in the contacting step is subjected to the next step, the reaction step. This reaction step is a step in which cellulose fibers contained in the reaction solution-impregnated pulp supplied from the contacting step are reacted with sulfamic acid and urea to substitute at least a portion of the hydroxyl groups in the cellulose fibers with sulfate ester groups, thereby introducing sulfate ester groups into the cellulose fibers contained in the pulp. That is, this reaction step is a step in which a reaction is carried out to substitute at least a portion of the hydroxyl groups in the cellulose fibers contained in the reaction solution-impregnated pulp with sulfate ester groups.

[0061] The reaction step is not particularly limited as long as it is a method capable of substituting at least a portion of the hydroxyl groups of the cellulose fibers in the reaction solution-impregnated pulp with sulfate ester groups, and for example, a method of accelerating the reaction by heating the reaction solution-impregnated pulp can be used. Hereinafter, the reaction will be described taking as an example a case where the reaction is carried out by this heating method.

[0062] <Reaction temperature in the reaction process> The reaction temperature in the reaction step is not particularly limited, but is preferably a temperature at which sulfate ester groups can be introduced into the cellulose fibers that make up the pulp while suppressing thermal decomposition and hydrolysis of the fibers. For example, the ambient temperature of the reaction solution-impregnated pulp subjected to the reaction step is adjusted to 100°C to 200°C, 120°C to 200°C, 120°C to 180°C, or 120°C to 160°C. If the ambient temperature during heating is 200°C or less, thermal decomposition and discoloration of the fibers can be suppressed.

[0063] The heater used in the reaction step is not particularly limited, and may be, for example, one that can directly or indirectly heat the reaction solution-impregnated pulp after the contact step while satisfying the above-mentioned requirements, such as a known dryer, reduced pressure dryer, microwave heater, autoclave, infrared heater, or hot press method using a heat press (e.g., AH-2003C manufactured by AS ONE Corporation). In particular, from the viewpoint of operability, it is preferable to use a circulating air dryer because gas may be generated in the reaction step.

[0064] <Reaction time in the reaction process> When the heating method is used as the reaction step, the heating time (i.e., reaction time) is not particularly limited, but is, for example, 1 minute or more, 5 minutes or more, 10 minutes or more, or 15 minutes or more when the reaction temperature is adjusted to be within the above range, and from the viewpoints of operability and cost, it is 5 to 300 minutes, or 5 to 120 minutes.

[0065] By carrying out the above steps, a pulp having sulfate ester groups introduced therein can be prepared.

[0066] <Cleaning process after reaction process> After the reaction step, a washing step may be included in which the sulfate ester group-introduced pulp is washed. The sulfate ester group-introduced pulp has an acidic surface due to the influence of sulfamic acid (a sulfate ester group-donating compound). Furthermore, unreacted reaction liquid is still present. Therefore, by providing a washing step in which the reaction is completely terminated and excess reaction liquid is removed to neutralize the pulp, handling can be improved.

[0067] The washing step is not particularly limited, and may be carried out so long as the sulfate ester group-introduced pulp is substantially neutral. For example, a method of washing the sulfate ester group-introduced pulp with pure water or the like until it becomes neutral may be used. Neutralization washing using an alkaline solution or the like may also be carried out. When such neutralization washing is carried out, examples of the alkaline compound contained in the alkaline solution include inorganic alkaline compounds and organic alkaline compounds. Examples of inorganic alkaline compounds include hydroxides, carbonates, and phosphates of alkali metals. Examples of organic alkaline compounds include ammonia, aliphatic amines, aromatic amines, aliphatic ammonium, aromatic ammonium, heterocyclic compounds, and hydroxides of heterocyclic compounds.

[0068] The method for separating the sulfate ester group-introduced pulp in the washing step is not particularly limited, and may be any method as long as the sulfate ester group-introduced pulp and the wash water can be separated by filtration. For example, the sulfate ester group-introduced pulp after the reaction can be washed using a stainless steel sieve with a mesh size of 243 μm (70 mesh) to 20 μm (635 mesh), 132 μm (120 mesh) to 45 μm (300 mesh), or 75 μm (200 mesh) to 45 μm (300 mesh).

[0069] <Amine Supporting Step> Next, an example of a method for making the sulfate ester group-introduced pulp support a linear amine having 9 or more carbon atoms will be described with reference to FIG. 1, but this step is not limited to this example.

[0070] As shown in Figure 1, an aqueous dispersion of sulfate ester-containing pulp 1 is placed in a container 3, and then an amine solution 2 containing hydrochloric acid is added and mixed for a predetermined period of time to prepare an amine-supported pulp 4. After the mixing, the amine-supported pulp 4 is placed on a 200-mesh sieve 5 and washed with a large amount of water 6 and alcohol 7 to obtain a pulp supported with a linear amine having 9 or more carbon atoms (amine-supported pulp).

[0071] The solvent for the amine solution 2 is not particularly limited, and examples thereof include protic polar solvents such as water, ethanol, methanol, acetic acid, formic acid, 2-propanol, nitromethane, and aqueous ammonia; aprotic polar solvents such as acetone, ethyl acetate, tetrahydrofuran (THF), dimethylformamide (DMF), acetonitrile, dimethyl sulfoxide (DMSO), dimethyl sulfide (DMS), and dimethylacetamide (DMA); and nonpolar solvents such as diethyl ether, benzene, toluene, hexane, chloroform, and 1,4-dioxane. One of the solvents may be used alone, or two or more may be used in combination. Ethanol is particularly preferred because it dissolves amines easily.

[0072] The method for mixing the sulfate ester group-introduced pulp aqueous dispersion 1 and the amine solution 2 is not particularly limited, and they can be mixed, for example, using a device with a stirring or shaking function. Examples of devices that can be used for stirring include a magnetic stirrer, an ultrasonic vibrator, a shaker, and other stirrers with various stirring bars.

[0073] The alcohol used for washing the amine-carrying pulp 4 is not particularly limited as long as it can wash away the amine and the solvent of the amine solution 2. In particular, ethanol is preferred from the viewpoints of ease of handling and cost.

[0074] The concentration of the amine in the amine solution 2 is, for example, 1 g / L to 10 g / L. If an amine solution 2 with a higher concentration is used, the time required for the amine to be supported on the sulfate ester group-introduced pulp can be shortened. On the other hand, if the concentration of the amine solution 2 is increased, it is expected that the amount of amine that is not supported on the sulfate ester group-introduced pulp will increase. Considering the load during wastewater treatment, it is desirable to set the concentration of the amine solution 2 to an appropriate level.

[0075] The ratio of the amount (volume) of the amine solution 2 to the mass of the sulfate ester group-introduced pulp aqueous dispersion 1 to be immersed therein is not particularly limited, but may be, for example, a ratio such that 50 mL of the amine solution 2 is immersed in 1.0 g of sulfate ester group-introduced pulp aqueous dispersion 1 by solids mass.

[0076] The time for stirring the sulfate ester group-introduced pulp aqueous dispersion 1 to which the amine solution 2 has been added is not particularly limited, and may be, for example, 1 minute or more, 5 minutes or more, 10 minutes or more, or 15 minutes or more.

[0077] <Sheet> The sheet of the present invention contains the pulp of the present invention (amine-supported pulp). The sheet containing the amine-supported pulp has transparency and hydrophobicity. The physical properties of the sheet are, for example, as follows.

[0078] <Total light transmittance> The total light transmittance of the sheet is, for example, 60% or more, 70% or more, 80% or more, or 90% or more. The total light transmittance of the sheet can be determined, for example, by measurement using a spectrophotometer in accordance with JIS K 7361.

[0079] <Water absorption rate> The water absorption rate of the sheet when immersed in water for 10 minutes is, for example, 1000% or less, 500% or less, or 300% or less.

[0080] <Method for measuring water absorption> The water absorption rate of the sheet was calculated by measuring the mass of the sheet before and after immersion in water and using the following formula. Water absorption rate (%) = 100 x (mass (g) of sheet with moisture content of 10% or less before immersion - mass (g) of sheet after immersion) / mass (g) of sheet after immersion

[0081] The mass (g) of the sheet after immersion in the above formula refers to the mass of the sheet after immersion in water and wiping off the water droplets. Specifically, the mass was measured after immersing the sheet in water for 10 minutes, removing it from the water, wiping off the water droplets attached to the sheet, and then wiping off the water droplets.

[0082] The moisture content in the above formula can be calculated using the following formula. Moisture content (%) = 100 - (mass of solid content of sheet (g) / mass of sheet at the time of moisture content measurement (g)) x 100 = {(mass of sheet at the time of moisture content measurement (g) - mass of solid content of sheet (g)) / mass of sheet at the time of moisture content measurement (g)} x 100

[0083] The solid mass (g) of the sheet in the above formula refers to the dry mass of the sheet. Specifically, it refers to the dry mass adjusted to a constant weight by drying the sheet using a dryer or the like. For example, by placing the sheet in a dryer and drying it under specified drying conditions (e.g., a temperature of 105°C for 2 hours) and measuring the mass, the mass of the dried sheet after moisture has been removed can be calculated.

[0084] <Contact angle> The sheet has a contact angle with a water droplet 30 seconds after the water droplet is dropped on the sheet of, for example, 90° or more, 100° or more, 110° or more, or 120° or more.

[0085] <Contact angle measurement method> The contact angle of the sheet can be measured, for example, by a drop method.

[0086] <Sheet manufacturing method> The sheet can be produced by, for example, the following two methods, but is not limited to these.

[0087] The first method is to form a dispersion of the amine-carrying pulp into a sheet, air-dry it, and then dry it by a hot press.

[0088] The press used for the heat press is not particularly limited, and for example, a hydraulic press or the like can be used. The temperature during drying by the heat press is not particularly limited as long as it is a temperature at which the sheet-like amine-supported pulp can be dried, and can be adjusted, for example, to 50°C or higher and 120°C or lower. By setting the temperature at 120°C or lower, discoloration of the amino-supported pulp can be suppressed. The drying temperature may also be 80°C or higher and 120°C or lower, or 80°C or higher and 110°C or lower. These points are the same as in the second method described below.

[0089] The second method is to form a dispersion of the amine-loaded pulp into a sheet, dehydrate it, and then dry it by a hot press.

[0090] The dehydration method is not particularly limited as long as it can dehydrate the amine-carrying pulp formed into a sheet. For example, the dehydration method may include a reduced pressure dehydration step and a pressing step.

[0091] <Decompression dehydration process> The strength of the reduced pressure in the reduced pressure dehydration step is not particularly limited as long as it is sufficient to remove moisture contained in the sheet and moisture in the surrounding area, and is, for example, 30 kPa or more, 40 kPa or more, or 50 kPa or more.

[0092] <Pressing process> The pressing step is a step of dewatering the sheet-like amine-supported pulp after reduced pressure dewatering using a press, etc. In addition to the method using a press, various other methods can be used for this dewatering step, such as a method of removing moisture from at least one of the top and bottom of the sheet-like pulp.

[0093] In this manner, the sheet can be produced.

[0094] The amine-carrying pulp of the present invention and a sheet containing the same can be suitably used for many applications in various fields such as industrial, food, medical, and cosmetic fields, and are also suitable for transparent films and the like used in these fields. [Example]

[0095] Example 1 A reaction solution was prepared by completely dissolving 9 g of sulfamic acid and 4.5 g of urea in 30 g of pure water. The reaction solution was uniformly absorbed into 20 g (5 g solids) of bleached softwood kraft pulp (NBKP, hereafter simply referred to as "pulp") placed in a plastic bag (Ziploc®, manufactured by Asahi Kasei Home Products Corporation), then spread thinly on an acrylic board and dried at 85°C for 3 hours. The dried product was then subjected to a heat reaction at 140°C for 30 minutes. The resulting reaction product was neutralized with aqueous sodium bicarbonate solution to convert the counter ions of the sulfate ester groups introduced into the pulp to sodium ions. The pulp was then washed with pure water on a 300-mesh sieve to obtain sulfate ester group-introduced pulp. The amount of sulfate ester groups introduced into this sulfate ester group-introduced pulp was 1.64 mmol / g. The resulting sulfate ester group-introduced pulp was then prepared into a 0.5% by mass aqueous sulfate ester group-introduced pulp dispersion. The softwood bleached kraft pulp (NBKP) used was a product manufactured by Marusumi Paper Co., Ltd. that had never been dried (solid content 25% by mass, the remaining 75% by mass being water), the sulfamic acid used was a product manufactured by Fuso Chemical Co., Ltd. with a purity of 99.8%, the urea used was a product manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. with a purity of 99.0% and model number: special grade, and the sodium bicarbonate used was a product manufactured by Nacalai Tesque, Inc., meeting Nacalai standard grade 1.

[0096] An amine solution was prepared by adding 58.7 mg (0.41 mmol) of nonylamine and 410 μL (0.41 mmol) of hydrochloric acid to a container containing 50 mL of ethanol. The prepared amine solution was added to 50 g of a 0.5% by mass aqueous dispersion of sulfate ester-introduced pulp, stirred for 10 minutes, and washed with a large amount of water and ethanol to obtain the amine-supported pulp of Example 1. Ethanol (special grade, 99.5% purity, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), nonylamine (>98% purity, manufactured by Tokyo Chemical Industry Co., Ltd.), and hydrochloric acid (volumetric grade, 1 M concentration, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were used.

[0097] The resulting amine-loaded pulp (0.27 g solids) was cut into a 7.5 cm diameter sheet and sandwiched between three paper towels (e-Syut®, manufactured by Marusumi Paper Co., Ltd.), a nonwoven fabric (Hirose Paper Co., Ltd., model number 05TH-48), the sheet, the nonwoven fabric, and the three paper towels, in that order, and then air-dried. The air-dried sheet was then heat-pressed at 105°C under 2 MPa for 1 minute and 30 seconds using a small heat press (AS ONE Corporation, model number HC300-05) to obtain a sheet containing amine-loaded pulp.

[0098] Example 2 The amine-supported pulp of Example 2 was obtained in the same manner as that for obtaining the amine-supported pulp of Example 1, except that the amine used was changed to decylamine and 81.6 μL (0.41 mmol) was used. The decylamine used was 90% pure, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0099] The resulting decylamine-loaded amine-loaded pulp (solid content 0.27 g) was added to 700 mL of pure water to prepare a slurry. The prepared slurry was suction filtered using a 7.5 cm nylon mesh (manufactured by AS ONE Corporation, model number: PA-46, mesh size 46 μm). Suction filtration was continued until the solution stopped flowing.

[0100] The amine-loaded pulp after suction filtration was sandwiched between three paper towels (e-Syut (registered trademark), manufactured by Marusumi Paper Co., Ltd.), a nonwoven fabric (manufactured by Hirose Paper Co., Ltd., model number: 05TH-48), the sheet-like amine-loaded pulp obtained by suction filtration (hereinafter referred to as the "sheet"), the nonwoven fabric, and three paper towels, in that order, and dewatered by placing a weight on it according to steps 1 to 3 shown below. Note that the paper towels were replaced with new ones when the weight was replaced. 1: Place a 350g weight on it for 1 minute. 2: Place a 700g weight on it for 2 minutes. 3: Place a 1,400g weight on it for 3 minutes.

[0101] After dehydration using a weight, the sheet was further dehydrated by pressing. Dehydration by pressing was carried out by applying pressure according to steps 1 to 7 shown below. After each pressing, the paper towel was replaced with a new one. 1: Pressed at 0.07 MPa. 2: Pressed at 1.4 MPa. 3: Pressed at 3.0 MPa. 4: Pressed at 4.0 MPa. 5: Pressed at 6.0 MPa. 6: Press at 6.0 MPa for 5 minutes. 7: Press at 6.0 MPa for 2 minutes. After completing steps 1 to 7, the sheet was removed.

[0102] After dehydration by pressing, the sheet was heat-pressed at 105° C. and 2 MPa for 1 minute and 30 seconds to obtain a sheet containing amine-supported pulp.

[0103] Example 3 The amine-supported pulp of Example 3 was obtained in the same manner as the amine-supported pulp of Example 1, except that the amine used was changed to dodecylamine and 88.4 μL (0.41 mmol) was used. Subsequently, a sheet containing the amine-supported pulp of Example 3 was obtained in the same manner as the sheet containing the amine-supported pulp of Example 2. The dodecylamine used was 95% pure, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., model number: Grade 1.

[0104] Example 4 The amine-supported pulp of Example 4 was obtained in the same manner as the amine-supported pulp of Example 1, except that the amine used was changed to tetradecylamine and 87.5 mg (0.41 mmol) was used. Subsequently, a sheet containing the amine-supported pulp of Example 4 was obtained in the same manner as the sheet containing the amine-supported pulp of Example 2. Tetradecylamine with a purity of >96%, manufactured by Tokyo Chemical Industry Co., Ltd., was used.

[0105] Example 5 The amine-supported pulp of Example 5 was obtained in the same manner as the amine-supported pulp of Example 1, except that the amine used was changed to stearylamine and 110.5 mg (0.41 mmol) was used. Subsequently, a sheet containing the amine-supported pulp of Example 5 was obtained in the same manner as the sheet containing the amine-supported pulp of Example 2. The stearylamine used had a purity of >85%, manufactured by Tokyo Chemical Industry Co., Ltd.

[0106] Example 6 The amine-supported pulp of Example 6 was obtained in the same manner as the amine-supported pulp of Example 1, except that the amine used was changed to an aqueous hexadecyltrimethylammonium hydroxide solution (1.2 mL (0.41 mmol)) and hydrochloric acid was not added. Subsequently, a sheet containing the amine-supported pulp of Example 6 was obtained in the same manner as the sheet containing the amine-supported pulp of Example 2. The hexadecyltrimethylammonium hydroxide used had a purity of 10-11%, and was manufactured by Tokyo Chemical Industry Co., Ltd.

[0107] (Comparative Example 1) Sulfate group-introduced pulp in which the counter ion of the sulfate group was sodium was used. Subsequently, in the same manner as in Example 1, a sheet containing the sulfate group-introduced pulp of Comparative Example 1 was obtained.

[0108] (Comparative Example 2) The amine-supported pulp of Comparative Example 2 was obtained in the same manner as the amine-supported pulp of Example 1, except that the amine used was changed to an ethylamine aqueous solution, and 33.3 μL (0.41 mmol) was used. Subsequently, a sheet containing amine-supported pulp of Comparative Example 2 was obtained in the same manner as the sheet containing amine-supported pulp of Example 1. The ethylamine aqueous solution used had a purity of 70%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.

[0109] (Comparative Example 3) The amine-supported pulp of Comparative Example 3 was obtained in the same manner as the amine-supported pulp of Example 1, except that the amine used was changed to hexylamine and 54.4 μL (0.41 mmol) was used. Subsequently, a sheet containing amine-supported pulp of Comparative Example 3 was obtained in the same manner as the sheet containing amine-supported pulp of Example 1. The hexylamine used was 98% pure, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., model number: Grade 1.

[0110] Comparative Example 4 The amine-supported pulp of Comparative Example 4 was obtained in the same manner as the amine-supported pulp of Example 1, except that the amine used was changed to octylamine and 68.1 μL (0.41 mmol) was used. Subsequently, a sheet containing amine-supported pulp of Comparative Example 4 was obtained in the same manner as the sheet containing amine-supported pulp of Example 1. The octylamine used was 98% pure, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., model number: special grade.

[0111] The physical properties of the amine-supported pulp and the sheet containing it in each of the Examples and Comparative Examples (sulfuric acid ester group-introduced pulp and the sheet containing it in Comparative Example 1) were measured by the following methods.

[0112] (Amount of sulfate ester groups introduced) The amount of sulfate ester groups introduced was measured by electrical conductivity. An electrical conductivity meter (water quality meter, manufactured by DKK-TOA Corporation, model number MM-43X) and an electrical conductivity electrode (manufactured by DKK-TOA Corporation, model number CT-58101B) were used for the electrical conductivity measurement. 50 g of a 0.4% by mass aqueous dispersion of protonated sulfate ester group-introduced pulp was used as the measurement solution.

[0113] (crystallinity) The crystallinity of the amine-loaded pulp was measured by XRD. XRD was performed using a multipurpose X-ray diffractometer (Spectris, model number: Panalytical Empyrean) with the measurement sample placed on a non-reflective plate. The measurement conditions were 2θ = 10-30°, Cu kα radiation (λ = 1.54 Å (1.54 × 10 -10The measurement was performed at 45 kV and 40 mV. A freeze-dried sample weighing approximately 0.2 g was placed in a φ14 mm mold (manufactured by AS ONE Corporation) and pressed at 5 MPa for 5 minutes using a small press (manufactured by AS ONE Corporation, model number: HC300-05).

[0114] The degree of crystallinity was evaluated by the intensity (I 22.4 ) and 18.5° (non-crystalline region) intensity (I 18.5 ) was calculated using the following formula: Crystallinity (%)={(I 22.4 -I 18.5 ) / I 22.4}×100

[0115] (Average fiber length and average fiber width of amine-loaded pulp) The average fiber length and average fiber width of the amine-loaded pulp were measured using a fiber length distribution measurement device. The fiber length distribution measurement was performed using a Fiber Tester (manufactured by Valmet Co., Ltd.). The measurement solution was prepared by adding water to the amine-loaded pulp (solid content 0.1 g) to make a total volume of 300 mL.

[0116] (Water retention) The water retention of the amine-supported pulp was measured by centrifuging the measurement solution. The centrifugation was performed using a tabletop centrifuge (manufactured by Kokusan Co., Ltd., model number: H-36α). The measurement solution was prepared by dissolving the amine-supported pulp in pure water to a solids concentration of 1% by mass.

[0117] (Total light transmittance) The total light transmittance of the sheet containing the amine-supported pulp was measured in accordance with JIS K 7161-1 using a spectroscopic haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., model number: SH-7000, Ver. 2.00.02).

[0118] (Water absorption rate) The water absorption rate of the amine-loaded pulp sheet was measured by immersing the test piece in a 15 cm diameter glass dish filled with pure water for 10 minutes. The test piece was prepared by cutting the amine-loaded pulp sheet into a 4 cm x 4 cm piece.

[0119] (contact angle) The contact angle of the sheet containing the amine-supported pulp was measured by the drop method using a drop of pure water. The contact angle was measured using a solid-liquid interface analysis system (manufactured by Kyowa Interface Science Co., Ltd., model number: DROP Master300). Test pieces were prepared by cutting the prepared sheet containing the amine-supported pulp into 4 cm x 4 cm pieces.

[0120] (Measurement results) Figure 2 is a table and graph showing the results of measuring the crystallinity of the amine-supported pulp of each Example and Comparative Example. Figure 3 is a graph showing XRD of the amine-supported pulp of Example 1 and the sulfate ester group-introduced pulp of Comparative Example 1. Figure 4 is a table and graph showing the results of measuring the average fiber length of the amine-supported pulp of each Example and Comparative Example. Figure 5 is a table and graph showing the results of measuring the water retention of the amine-supported pulp of each Example and Comparative Example.

[0121] As shown in Figure 2, the crystallinity of the amine-supported pulp was confirmed to be 76% or less. Furthermore, as shown in Figure 3, the amine-supported pulp was confirmed to have a type I crystal structure. Furthermore, as shown in Figure 4, the amine-supported pulps of Examples 1 to 6 were confirmed to have an average fiber length of 0.3 mm or more.

[0122] As shown in Figure 5, the water retention of the amine-supported pulps of Examples 1 to 6 was confirmed to be 5000% or less. Furthermore, when the number of carbon atoms in the linear amine chain was 8 or less, the water retention value did not decrease compared to Comparative Example 1, which did not support the amine, confirming that the hydrophobic effect is manifested when the number of carbon atoms in the linear amine chain was 9 or more. Furthermore, it was confirmed that the water retention value decreased as the number of carbon atoms in the linear amine chain increased. In other words, it was confirmed that the water retention could be controlled by adjusting the number of carbon atoms in the linear amine chain to 9 or more.

[0123] Figure 6 is a table and graph showing the results of the total light transmittance of sheets containing amine-supported pulp of each Example and Comparative Example. Figure 7 is a table and graph showing the results of the water absorption of sheets containing amine-supported pulp of each Example and Comparative Example. Figure 8 is a table and photograph showing the contact angle 30 seconds after a water droplet was dropped on sheets containing amine-supported pulp of some Examples and Comparative Examples. The left photograph in Figure 8 shows the sheet containing the amine-supported pulp of Example 1, and the right photograph shows the sheet containing the amine-supported pulp of Comparative Example 4.

[0124] As shown in FIG. 6, it was confirmed that the sheet containing the amine-carrying pulp had a total light transmittance of 60% or more.

[0125] As shown in Figure 7, it was confirmed that the sheets containing the amine-supported pulp of Examples 1 to 6 had a water absorption rate of 1000% or less. It was also confirmed that the water absorption rate decreased as the number of carbon atoms in the linear amine chain increased. In other words, it was confirmed that the water absorption rate could be controlled by adjusting the number of carbon atoms in the linear amine chain to 9 or more.

[0126] As shown in Figure 8, the sheets containing the amine-loaded pulp of Examples 1, 2, and 6 were confirmed to have a contact angle of 90° or more 30 seconds after a water droplet was dropped on them. In other words, it was confirmed that the sheets remained hydrophobic, maintaining their water repellency without absorbing water even after a certain period of time had passed.

[0127] Although the present invention has been described above with reference to the embodiments and examples, the present invention is not limited to the above-described embodiments and examples. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

Claims

1. A pulp characterized in that the pulp has a cellulose I type crystal structure, in which at least a portion of the hydroxyl groups of cellulose are substituted with sulfate ester groups, and in which an amine having a linear chain of 9 or more carbon atoms is supported, the pulp has a crystal structure of cellulose I type, a degree of crystallinity of 76% or less, and an average fiber length of 0.3 mm or more.

2. 2. The pulp according to claim 1, wherein the amine is a monoamine having no hydrophilic groups other than amino groups.

3. 3000g (3000 x 9.81m / s ２ 3. The pulp according to claim 1, wherein the water retention after centrifuging for 15 minutes in a centrifuge is 5000% or less.

4. A sheet comprising the pulp according to any one of claims 1 to 3.

5. 5. The sheet according to claim 4, wherein the total light transmittance is 60% or more.

6. 6. The sheet according to claim 4, wherein the water absorption rate when immersed in water for 10 minutes is 1000% or less.

7. 7. The sheet according to claim 4, wherein the contact angle with a water droplet 30 seconds after the drop is applied is 90° or more.

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