Pulp sheets for fluff pulp, fluff pulp, and products containing fluff pulp

Abstract

The present invention provides a pulp sheet for producing fluff pulp that has excellent deodorizing properties, good crushability, and easily recovers its bulk after compression. [Solution] A pulp sheet for producing fluff pulp is prepared by blending (A) softener kraft pulp, (B) metal ion-containing cellulose fibers having ionic substituents and containing ions of one or more metal elements selected from Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, or Cu, and (C) softener, such that (C) is 0.1 to 50 parts by mass per 100 parts by mass of the total of (A) and (B).

Description

[Technical Field]

[0001] The present invention relates to a pulp sheet for fluff pulp, fluff pulp obtained therefrom, and products containing fluff pulp. More specifically, it relates to a pulp sheet for fluff pulp containing metal ion-containing cellulose fibers, fluff pulp obtained therefrom, and products containing fluff pulp. [Background technology]

[0002] Fluff pulp is generally a material made by crushing plant-derived pulp sheets into cotton-like fibrous masses. Its water absorption and bulkiness are utilized in the manufacture of absorbent components for absorbent products such as disposable diapers, as well as sound-absorbing materials. For the production of fluff pulp, pulp derived from coniferous trees, which has good bulkiness, water absorption, and crushability, is widely used.

[0003] Meanwhile, research is being conducted to impart various functionalities to cellulose fibers obtained from plants. For example, Patent Document 1 describes that metal ion-containing cellulose fibers, which are oxidized cellulose fibers in which carboxyl groups are introduced on the surface of the cellulose fibers and contain ions of one or more metal elements selected from the group consisting of Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, and Cu, have excellent deodorizing effects. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] International Publication No. 2017 / 014255 [Overview of the project] [Problems that the invention aims to solve]

[0005] While cellulose fibers containing metal ions have excellent deodorizing properties, when used as pulp sheets, the metal ions tend to cause the fibers to aggregate and become densely packed. Therefore, when the pulp sheets are crushed, the pulp fibers are difficult to separate, leaving large clumps, making it difficult to crush them into a cotton-like consistency to produce fluff pulp. Furthermore, continued crushing tends to break the clumps into shorter pieces, resulting in a mixture of finely fragmented clumps and fine powder (Figure 1). In short, although pulp sheets containing metal ions have excellent deodorizing properties, they are unsuitable for use as pulp sheets for producing fluff pulp.

[0006] Furthermore, while fluff pulp is generally used in applications where its bulkiness is a factor, fluff pulp manufactured from pulp sheets made of metal ion-containing cellulose fibers has a problem in that, when removed after being packed into bags or other containers, it does not recover its volume well from its compressed state, making it difficult to restore its characteristic fluffy shape and bulkiness.

[0007] The present invention aims to provide a pulp sheet for producing fluff pulp that has excellent deodorizing effects, good crushability, and easily recovers its bulk after compression. [Means for solving the problem]

[0008] As a result of diligent research, the inventors have discovered that by mixing metal ion-containing cellulose fibers with coniferous kraft pulp when manufacturing pulp sheets for fluff pulp, it is possible to obtain fluff pulp that is less prone to clumping and powdering when crushed, and that exhibits excellent deodorizing effect and bulk recovery. Furthermore, they have discovered that by using a softening agent in combination during the manufacturing of the pulp sheet, the aggregation of metal ion-containing cellulose fibers can be suppressed, further improving the crushability. The present invention includes the following: (1)(A) Coniferous kraft pulp, (B) A cellulose fiber having an ionic substituent, comprising a metal ion-containing cellulose fiber containing ions of one or more metal elements selected from Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, or Cu. (C) Fabric softener It contains, A pulp sheet for fluff pulp, wherein the content of (C) softener is 0.1 to 50 parts by mass per 100 parts by mass of the total of (A) and (B). (2) The fluff pulp sheet according to (1), wherein the content of (B) metal ion-containing cellulose fibers is 1 to 60 parts by mass per 100 parts by mass of (A) coniferous kraft pulp. (3) The cellulose fiber having the ionic substituent is a cellulose fiber having one or more groups selected from carboxylic acid-derived groups, phosphoric acid-derived groups, or sulfuric acid-derived groups as ionic substituents, according to (1) or (2). (4) The cellulose fiber having the ionic substituent is an oxidized cellulose fiber, The amount of carboxyl groups in the cellulose fibers having the ionic substituent is 0.2 to 2.2 mmol / g, a pulp sheet for fluff pulp according to any one of (1) to (3). (5) A pulp sheet for fluff pulp according to any one of (1) to (4), wherein the content of the metal ions relative to the oven-dry mass of the metal ion-containing cellulose fibers is 20 to 60 mg / g. (6) Fluff pulp using a pulp sheet for fluff pulp as described in any one of (1) to (5). (7) A product containing the fluff pulp described in (6), which is selected from absorbent materials, sound-absorbing materials, pillows, surgical sheets, shock-absorbing materials, or cushioning materials. [Effects of the Invention]

[0009] The present invention provides a pulp sheet for producing fluff pulp that has excellent deodorizing properties, good crushability, and easily recovers its bulk after compression. The pulp sheet for fluff pulp of the present invention has the characteristic of not easily forming clumps when crushed. Furthermore, the fluff pulp obtained by crushing the pulp sheet for fluff pulp of the present invention has excellent deodorizing properties. In addition, the fluff pulp obtained by crushing the pulp sheet for fluff pulp of the present invention has good volume recovery (recovery of bulk) after compression and also possesses the water absorption and water retention properties generally required for fluff pulp.

[0010] The fluff pulp obtained by crushing the pulp sheet for fluff pulp of the present invention can be used in a variety of applications, such as absorbent materials for absorbing moisture and odors, sound-absorbing materials, pillows, surgical sheets, shock absorbers, and cushioning materials, due to its high deodorizing properties, bulkiness, water absorption, and water retention. [Brief explanation of the drawing]

[0011] [Figure 1] This is a photograph of the crushed pulp sheet from Comparative Example 1. [Modes for carrying out the invention]

[0012] <Pulp sheet for fluff pulp> Fluff pulp is generally a material obtained by crushing plant-derived pulp sheets into cottony fiber lumps. The pulp sheet for fluff pulp of the present invention is a pulp sheet used for crushing into fluff pulp. The pulp sheet for fluff pulp can generally be obtained by papermaking a pulp slurry containing raw material pulp or cellulose fibers into a sheet shape. The pulp sheet for fluff pulp of the present invention contains (A) softwood kraft pulp and (B) metal ion-containing cellulose fibers in which metal ions are bonded / coordinated to cellulose fibers having ionic substituents as raw materials, and further contains (C) a softener. By combining these, the pulp sheet for fluff pulp of the present invention has the advantage that no lumps occur when crushing to produce fluff pulp. Furthermore, the fluff pulp obtained by crushing has water absorption and water retention properties, and not only has good volume recovery (recovery of bulkiness) after compression, but also has the advantage of excellent deodorizing properties.

[0013] <Softwood kraft pulp> Softwood kraft pulp is used as one of the raw materials in the pulp sheet for fluff pulp of the present invention. Any softwood kraft pulp can be used as long as it is generally used for manufacturing pulp sheets for fluff pulp, and its tree species, manufacturing method, etc. are not particularly limited.

[0014] <Metal ion-containing cellulose fiber> Metal ion-containing cellulose fibers are used as one of the raw materials in the pulp sheet for fluff pulp of the present invention. Specifically, metal ion-containing cellulose fibers are fibers to which ions of one or more metal elements selected from Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, or Cu are added to cellulose fibers having ionic substituents. In the metal ion-containing cellulose fibers, the ions of the above metal elements are usually in a bonded or coordinated state to the cellulose fibers having ionic substituents.

[0015] Cellulose fibers having an ionic substituent as a raw material for metal ion-containing cellulose fibers can be obtained by subjecting a cellulose raw material to a treatment for imparting an ionic substituent. The type of the cellulose raw material is not particularly limited. Cellulose is a polysaccharide having a structure in which D-glucopyranose (simply referred to as "glucose residue" or "anhydrous glucose") is linked by β-1,4 bonds. Generally, depending on the origin, production method, etc., it is classified into natural cellulose, regenerated cellulose, microcrystalline cellulose, microcrystalline cellulose excluding the amorphous region, etc. In the present invention, any of these celluloses can be used as a raw material for cellulose fibers having an ionic substituent. From the viewpoint of cost, it is preferable to use pulp derived from wood as the cellulose raw material. Examples of wood pulp include, but are not limited to, mechanical pulp (thermomechanical pulp (TMP), groundwood pulp) used as pulp for papermaking, chemical pulp (sulfite pulp such as softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP); kraft pulp such as softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), etc.).

[0016] Any ionic substituent can be used in the cellulose fibers having an ionic substituent as long as it can carry a metal ion. Examples of the ionic substituent include, but are not limited to, a group derived from carboxylic acid, a group derived from phosphoric acid, or a group derived from sulfuric acid.

[0017] Examples of the group derived from carboxylic acid include a carboxy group (-COOH, -COO - ) or a carboxymethyl group (-CH2COOH, -CH2COO -Examples include: Cellulose fibers having carboxyl groups can be obtained by oxidizing cellulose raw materials, as described later, and the resulting fibers are also called oxidized cellulose fibers. Cellulose fibers having carboxymethyl groups (carboxymethylated cellulose fibers) can be obtained by a known method in which cellulose raw materials are mercerized and then etherified using a carboxymethylating agent.

[0018] Examples of phosphoric acid-derived groups include phosphoric acid, polyphosphoric acid, phosphorous acid, phosphonic acid, and polyphosphonic acid-derived groups. Cellulose fibers having phosphoric acid-derived groups as ionic substituents can be obtained using known methods that involve mixing a powder or aqueous solution of compounds having these phosphoric acid-based groups with a cellulose raw material and esterifying the cellulose with the phosphoric acid-based groups.

[0019] Cellulose fibers having sulfuric acid-derived groups as ionic substituents can be obtained using known methods that involve mixing an aqueous solution of a compound having a sulfuric acid-based group, such as sulfuric acid, sulfamic acid, chlorosulfonic acid, sulfur trioxide, or esters or salts thereof, with a cellulose raw material to esterify the cellulose and the sulfuric acid-based group.

[0020] In cellulose fibers having ionic substituents, the ionic substituents are, among the above, carboxyl groups (-COOH, -COO - It is particularly preferable that the cellulose fibers have carboxyl groups. As mentioned above, cellulose fibers having carboxyl groups are also called oxidized cellulose fibers. Oxidized cellulose fibers can be obtained by methods such as oxidizing cellulose fibers in water using an oxidizing agent in the presence of an N-oxyl compound and a substance selected from the group consisting of bromide, iodide, or a mixture thereof, or by contacting cellulose fibers with a gas containing ozone. In oxidized cellulose fibers obtained by these methods, some of the hydroxyl groups of the cellulose fibers are converted to carboxyl groups.

[0021] N-oxyl compounds are compounds that can generate nitroxyl radicals, such as 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) and its derivatives. Bromides are alkali metal bromides that can dissociate and ionize in water, such as sodium bromide. Iodides are alkali metal iodides that can dissociate and ionize in water, such as sodium iodide. Oxidizing agents include halogens, hypohalous acids, halogenous acids, perhalous acids, their salts, halogen oxides, and peroxides, among which hypohalous acids or their salts are preferred due to their low cost and environmental impact, and sodium hypochlorite is particularly preferred. By mixing the above-mentioned N-oxyl compound, bromide and / or iodide, and oxidizing agent with an aqueous slurry in which cellulose raw material is suspended, a portion of the hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface can be selectively oxidized and converted to a carboxyl group. The oxidation reaction can proceed at room temperature, for example, around 4-40°C or 15-30°C. The pH of the reaction solution during the oxidation reaction is preferably around 8-12, and more preferably around 10-11. The reaction time is typically 0.5-6 hours, for example, 0.5-4 hours.

[0022] When oxidizing cellulose fibers using a gas containing ozone, the concentration of ozone in the gas is 50-250 g / m³. 3 Preferably, it is 50-220 g / m² 3 It is more preferable that the cellulose fibers are brought into contact with a gas containing ozone. Some of the hydroxyl groups in the cellulose fibers can be oxidized and converted to carboxyl groups. The result obtained after ozone treatment may be further treated with an oxidizing agent. Examples of oxidizing agents used in the further treatment include chlorine compounds such as chlorine dioxide and sodium chlorite, as well as oxygen, hydrogen peroxide, persulfuric acid, and peracetic acid. A method for the further treatment may be to dissolve these oxidizing agents in water or a polar organic solvent such as alcohol to create an oxidizing agent solution, and then immerse the cellulose fibers in the oxidizing agent solution.

[0023] The amount of carboxyl groups in oxidized cellulose fibers is preferably about 0.2 to 2.2 mmol / g, considering the subsequent inclusion of metal ions. The amount of carboxyl groups in cellulose fibers can be adjusted by controlling oxidation conditions such as the amount of oxidizing agent added and the reaction time.

[0024] The amount of carboxyl groups in oxidized cellulose fibers can be measured, for example, by the following method: Prepare 60 ml of a 0.5% by mass slurry (aqueous dispersion) of oxidized cellulose fibers. Add 0.1 M hydrochloric acid aqueous solution to adjust the pH to 2.5. Then, add 0.05 N sodium hydroxide aqueous solution dropwise until the pH reaches 11. Measure the electrical conductivity and determine the amount of sodium hydroxide consumed during the neutralization stage of the weak acid, where the change in electrical conductivity is gradual (a). Next, calculate the amount of carboxyl groups [mmol / g] in the oxidized cellulose fibers using the following formula. Amount of carboxyl groups [mmol / g] = a [ml] × 0.05 / Mass of oxidized cellulose fibers [g] Metal ion-containing cellulose fibers can be obtained by contacting cellulose fibers having ionic substituents with an aqueous solution of a compound containing one or more metal elements selected from Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, or Cu. In metal ion-containing cellulose fibers, it is presumed that metal ions derived from the metal compound form ionic bonds with or coordinate to the ionic substituents.

[0025] The aqueous solution of the compound containing the metal element may be an aqueous solution of the metal salt. Examples of metal salts include the above-mentioned metal complexes (complex ions), halides, nitrates, sulfates, and acetates. The concentration of the aqueous solution of the compound containing the metal element is not particularly limited, but is preferably 10 to 80 parts by mass, and more preferably 30 to 60 parts by mass, per 100 parts by mass of cellulose fibers having ionic substituents. The contact time of the aqueous solution with the cellulose fibers may be adjusted as appropriate. For example, it may be 3 minutes to 3 hours, preferably 20 minutes to 1 hour. During contact, it is preferable to continue stirring for the above contact time. The temperature during contact is not particularly limited, but is preferably 20 to 40°C. The pH of the solution during contact is not particularly limited, but is preferably 7 to 13, and particularly preferably 8 to 12, because if the pH is low, it becomes difficult for metal ions to bind to the ionic substituents.

[0026] The presence of metal ions in cellulose fibers with ionic substituents can be confirmed by scanning electron microscopy and / or ICP emission spectroscopy of an extract with a strong acid. While the presence of metal ions cannot be confirmed by scanning electron microscopy alone, it can be confirmed by combining scanning electron microscopy with elemental mapping, or by using ICP emission spectroscopy. Furthermore, if the metal ions are reduced and exist as metal particles, these metal particles can also be confirmed by scanning electron microscopy.

[0027] Metal ions do not need to be bonded to all ionic substituents; they only need to be bonded to some of them. The ion content of metal elements in metal ion-containing cellulose fibers is preferably 20 to 60 mg / g relative to the oven-dry mass of the metal ion-containing cellulose fibers. More preferably, it is 22 to 55 mg / g, even more preferably 25 to 50 mg / g, and even more preferably 30 to 45 mg / g. By supporting this amount, the deodorizing effect can be enhanced.

[0028] The ion content of metal elements in metal ion-containing cellulose fibers can be measured, for example, by the following methods: 0.04 g of metal ion-containing cellulose fiber is collected by oven-dry weight and extracted using 10 ml of concentrated nitric acid. The extract is diluted 10-fold, and the metal ion content is measured using ICP emission spectrometry (ICP-OES, Shimadzu Corporation: ICPE-9000).

[0029] The Canadian standard filtration efficiency (CSF) of metal ion-containing cellulose fibers is preferably 500 to 800 ml. More preferably, it is 550 to 750 ml, and even more preferably, 600 to 700 ml. Metal ion-containing cellulose fibers having such a filtration efficiency have good dewatering properties, allowing for papermaking without dewatering problems during the papermaking process.

[0030] The average fiber length of metal ion-containing cellulose fibers is preferably about 0.5 to 2.5 mm. Furthermore, an average fiber diameter of about 10 to 40 μm is preferable because it allows for good dispersion when mixed with coniferous kraft pulp. Generally, the average fiber diameter of metal ion-containing cellulose fibers is about the same as the average fiber diameter of cellulose fibers with ionic substituents before the metal ion is added. The average fiber length and average fiber diameter can be determined by calculating the length-weighted average fiber length and length-weighted average fiber diameter using a Fiber Tester manufactured by Lorentzen & Wettre.

[0031] <Fabric softener> In manufacturing the pulp sheet for fluff pulp according to the present invention, a softener is used in addition to the above-mentioned coniferous kraft pulp and metal ion-containing cellulose fibers. The softener penetrates between the cellulose fiber bundles and weakens the bonds between the cellulose fibers through its hydrophobic and steric hindrance effects. Examples of softeners include surfactants, paraffinic waxes, silicone waxes, and polysiloxane compounds. Among these, surfactants are preferred.

[0032] Examples of surfactants that can be used as fabric softeners include cationic surfactants, anionic surfactants, amphoteric surfactants, and nonionic surfactants. Among these, cationic surfactants are preferred. Examples of cationic surfactants include aliphatic amine salts, aliphatic quaternary ammonium salts, benzalkonium salts, benzethonium chloride salts, pyridinium salts, imidazolium salts, and polyamide derivatives. Specifically, examples include lauryltrimethylammonium salt, cetyltrimethylammonium salt, tetradecyldimethylbenzylammonium salt, stearyltrimethylammonium salt, trioctylmethylammonium salt, dimethyldistearylammonium salt, dimethyloleyllinolylammonium salt, trimethylmonobehenylammonium salt, methyltrilaurylammonium salt, laurylpyridinium salt, cetylpyridinium salt, benzalkonium salt, benzethonium salt, methylbenzethonium salt, laurylphenoxyethyldimethylammonium salt, laurylisoquinolinium salt, laurylnicotinium salt, and laurylquinaldinium salt. Cationic surfactants are preferably fatty acid derivatives. Furthermore, the pH of the cationic surfactant is preferably 3 to 6, and more preferably 3 to 5. It is believed that a lower pH increases the stability of the cationic moiety in the surfactant, which in turn increases its adsorption capacity to the anionic moiety in the cellulose fiber, thereby improving flexibility.

[0033] Examples of polysiloxane compounds that can be used as fabric softeners include amino-functional polydimethylpolysiloxane compounds. Examples of substituents other than amino functional groups include carboxyl groups, hydroxyl groups, ether groups, polyether groups, aldehyde groups, ketone groups, amide groups, ester groups, and thiol groups.

[0034] <Manufacturing of pulp sheets for fluff pulp> A pulp sheet for fluff pulp can be manufactured by papermaking using a pulp slurry containing coniferous kraft pulp and metal ion-containing cellulose fibers. A softening agent is used in combination during this process.

[0035] The amount of (B) metal ion-containing cellulose fibers in the pulp sheet for fluff pulp is preferably 1 to 250 parts by mass per 100 parts by mass of (A) softwood kraft pulp. If the content of (B) is less than 1 part by mass per 100 parts by mass of (A), a sufficient deodorizing effect may not be obtained. Also, if the content of (B) exceeds 250 parts by mass per 100 parts by mass of (A), the disintegrability of the pulp sheet may decrease. The content of (B) is more preferably 1 to 150 parts by mass, even more preferably 1 to 60 parts by mass, even more preferably 6 to 50 parts by mass, even more preferably 7 to 40 parts by mass, even more preferably 8 to 35 parts by mass, and even more preferably 10 to 30 parts by mass per 100 parts by mass of (A).

[0036] Softeners are used in the manufacture of pulp sheets for fluff pulp. The softener may be incorporated into the pulp sheet by adding it to the pulp slurry, or it may be incorporated into the pulp sheet by impregnating the pulp sheet in an aqueous solution of the softener after manufacture, or the softener may be applied to the surface of the pulp sheet by coating it with an aqueous solution of the softener after manufacture. The softener may be added as is or after dilution.

[0037] The content of (C) softener in the pulp sheet for fluff pulp is 0.1 to 50 parts by mass when the total content of (A) softwood kraft pulp and (B) metal ion-containing cellulose fibers is 100 parts by mass. By including such an amount of softener, the disintegrability of the pulp sheet can be improved. The content of (C) is more preferably 0.3 to 20 parts by mass, and even more preferably 0.3 to 10 parts by mass, relative to 100 parts by mass of the total of (A) and (B).

[0038] Pulp sheets for fluff pulp may or may not contain other additives as needed. When additives are included, for example, fillers, pigments, sizing agents, coagulants, oil resistant agents, aluminum sulfate, yield improvers, water drainage improvers, dry strength enhancers, wet strength enhancers, coloring pigments, water-resistant agents, etc., may be used individually or in combination as needed.

[0039] The papermaking method for producing pulp sheets for fluff pulp is not particularly limited, and the sheets can be made using known methods. The resulting pulp sheets for fluff pulp may be rolled up after drying and stored, although this is not limited to these methods.

[0040] The pulp sheets for fluff pulp have a density of 0.30 to 0.70 g / cm³. 3 It is preferable that the concentration be around 0.30 to 0.60 g / cm³. 3 It is even more preferable that the concentration be around 0.35-0.55 g / cm³. 3 It is even more preferable if the density is within this range. When the density is within this range, it is easier to break down and less likely to form clumps.

[0041] <Crushing of pulp sheets for fluff pulp> Fluff pulp can be obtained by crushing a pulp sheet for fluff pulp. Fluff pulp is a material obtained by crushing a pulp sheet into cotton-like fibers. The pulp sheet for fluff pulp of the present invention has excellent crushability and has the advantage of not easily forming clumps (aggregates of pulp that remain unbroken) during crushing.

[0042] The method for crushing the pulp sheet for fluff pulp is not particularly limited, and known crushing methods used in the production of ordinary fluff pulp can be used. The crushing machine is not limited to these, but for example, hammer type, impact type, roll type, and jet stream type crushers can be used. The average fiber diameter of the fluff pulp after crushing is not particularly limited, but when measured by the method described in the examples below, it is preferably 15.0 to 35.0 μm, more preferably 20.0 to 30.0 μm, which tends to result in cotton-like fibers.

[0043] The fluff pulp obtained from the pulp sheet for fluff pulp of the present invention preferably has an average fiber length of 1.00 mm or more when measured by the method described in the examples below. More preferably, it has an average fiber length of 1.50 mm or more. Furthermore, the fluff pulp obtained from the pulp sheet for fluff pulp of the present invention preferably has a fineness ratio of 10.0% or less when measured by the method described in the examples below. More preferably, it has a fineness ratio of 9.0% or less. The fineness ratio is the percentage (based on the number) of fibers with a fiber length of 0.1 mm or less. The pulp sheet for fluff pulp of the present invention has excellent crushability, and is less prone to excessive cutting of fibers during crushing, resulting in a cotton-like fluff pulp that maintains an appropriate fiber length.

[0044] <Uses of fluff pulp> The fluff pulp obtained from the pulp sheet for fluff pulp of the present invention has a high deodorizing effect due to the inclusion of metal ion-containing cellulose fibers. Furthermore, by containing coniferous kraft pulp and a softener, it maintains a cotton-like form without clumping despite containing metal ion-containing cellulose fibers, and exhibits good water absorption, water retention, and recovery of bulk after compression.

[0045] The fluff pulp obtained from the pulp sheet for fluff pulp of the present invention has the water absorption, water retention, and bulkiness characteristics expected of ordinary fluff pulp, and can therefore be used in the same applications as ordinary fluff pulp. For example, it can be used in various applications such as absorbent materials for absorbing moisture, sound absorbing materials, shock absorbing materials, and cushioning materials. The fluff pulp obtained by the present invention contains metal ion-containing cellulose fibers, and therefore has a deodorizing effect not seen in ordinary fluff pulp made only from coniferous kraft pulp, making it particularly suitable for use in applications where a deodorizing effect is expected. Such applications include, but are not limited to, absorbent materials in disposable diapers, urine pads, light incontinence pads, sanitary napkins, pillows, surgical sheets, and shock absorbing materials, cushioning materials, and sound absorbing materials for holding materials that have an odor. [Examples]

[0046] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. <Manufacturing of metal ion-containing cellulose fibers (copper ion-containing cellulose fibers)> 50 g (bone dry) of cellulose raw material (bleached unbeaten kraft pulp derived from softwood) was added to 50 ml of an aqueous solution in which 172 mg of TEMPO (Sigma Aldrich) and 5.145 g of sodium bromide were dissolved, and the mixture was stirred until the pulp was uniformly dispersed. An aqueous sodium hypochlorite solution was added to the reaction system to a concentration of 5.2 mmol / g to initiate the oxidation reaction. During the reaction, the pH of the system decreased, but 3M aqueous sodium hydroxide solution was sequentially added to adjust the pH to 10. The reaction was terminated when sodium hypochlorite was consumed and the pH in the system no longer changed. After the reaction, the mixture was filtered through a glass filter to separate the pulp and washed with water to obtain oxidized cellulose fibers with a carboxyl group content of 1.42 mmol / g. The obtained oxidized cellulose fibers were suspended in water, adjusted to pH 9 using an aqueous sodium hydroxide solution, and 1.5 mmol of metal salt (CuSO4) per 1 g of oxidized cellulose fibers was added and stirred. After incorporating Cu ions into the oxidized cellulose fibers, they were washed to remove unreacted metal salts. The metal ion content of the obtained metal ion-containing cellulose fibers (copper ion-containing cellulose fibers) was 44 mg / g.

[0047] <Example 1> Softwood kraft pulp (NBKP) and the metal ion-containing cellulose fibers (copper ion-containing cellulose fibers) produced above were added to water at a mass ratio of NBKP: copper ion-containing cellulose fibers = 90:10 to produce a 1 mass% slurry. Here, 0.3 parts by mass of a softening agent (cationic surfactant (fatty acid derivative), trade name: Neo Softter SOFT-CAT-1, manufactured by Nisshin Chemical Laboratory) was added to and mixed with a total of 100 parts by mass of NBKP and copper ion-containing cellulose fibers.

[0048] 1372 g of the obtained pulp slurry was weighed and put into a standard round hand-sheet making machine, and hand-sheet making was carried out according to JIS P8222:2015. The obtained hand-sheet was dried with a cylinder dryer at 105 °C to produce a pulp sheet for fluff pulp. The density of the obtained pulp sheet was 0.47 g / cm 3 It was.

[0049] Next, the obtained pulp sheet was torn into pieces approximately 1 cm square, 1 g was measured out and placed in a mixer (Iwatani Corporation, Silent Millser IFM-S10G), and crushed at 20,000 rpm for 20 seconds to produce fluff pulp.

[0050] <Evaluation of disintegration properties> The fluff pulp obtained by crushing was visually inspected and evaluated for the presence of clumps according to the following criteria. The evaluation results are shown in Table 1. When the crushing performance is good, no clumps are formed, but when the crushing performance is poor, it becomes difficult to break down the pulp sheet into cotton-like fibers, and clumps, which are aggregates of pulp, are formed. A: There are absolutely no clumps. B: There are some clumps. C: There are a lot of clumps.

[0051] <Measurement of fiber morphology> Water was added to 0.15 g of the obtained fluff pulp (oven-dry mass) to a total volume of 300 g. The mixture was stirred in a homodisper at 3000 rpm for 2 minutes, then stirred and dissociated with 300 mL of water. The average fiber length, average fiber diameter, and fineness ratio of the pulp fibers in the fluff pulp were measured using a Lorentzen & Wettre Fiber Tester. The average fiber length is the length-weighted average fiber length based on ISO 16065, and the average fiber diameter is the length-weighted average fiber diameter. The fineness ratio is the percentage of fibers (based on the number of fibers) with a fiber length of 0.1 mm or less. Measurements were performed until the measurement time reached 300 seconds or the number of measured fibers (number of detected fibers) reached 100,000. The results are shown in Table 1. With this device, fibers with a fiber width of 4 μm or more are detected. Also, lumps larger than 7.5 mm are not recognized as fibers.

[0052] <Measurement of water absorption and water retention> Approximately 1 g of fluff pulp was weighed by its oven-dry mass and placed in a 250-mesh nylon tea bag. This was then immersed in 200 ml of pure water (room temperature) in a tall beaker for 10 minutes, suspended from a support with a clip for 5 minutes to drain, and its mass (b) was measured. The drained sample, still in the tea bag, was placed in a centrifuge (Kokusan H-103N, rotor: RF-10, bucket: MF-110 (inner diameter 40 mm)) and centrifuged and dehydrated at 915 rpm for 1 minute. The mass (d) of the sample removed from the centrifuge was measured. The pulp remaining in the tea bag was also collected, dried, and its mass (x) was measured using a weighing bottle.

[0053] As a blank test, the same procedure was performed with empty tea bags, and the mass after draining (a) and after centrifugation (c) was measured. N=2 measurements were taken for each sample, and the average of the water absorption and retention amounts was calculated using the following formula. The results are shown in Table 1. Water absorption = (ba) / x Water retention amount = (dc) / x b: Mass (g) of (tea bag + pulp) after draining a: Mass of the tea bag after draining in the blank test (g) x: Absolute dry mass (g) of weighed fluff pulp d: Mass (g) of (tea bag + pulp) after centrifugation c: Weight of the tea bag after centrifugation in the blank test (g).

[0054] <Measurement of post-compression recovery rate> 0.5g of fluff pulp was measured and placed in a 25ml syringe. The syringe piston was pushed down to the 3ml mark and held for 5 seconds. The piston was then pulled back to the 25ml mark, and the height of the fluff pulp in the syringe was taken as the scale mark (ml) after compression and restoration. The post-compression and restoration rate of the fluff pulp was calculated using the following formula. If the height was less than 3ml when 0.5g of fluff pulp was added, measurement was deemed impossible. The results are shown in Table 1. Post-compression and restoration rate (%) = Scale mark (ml) after compression and restoration / 3 (ml) × 100.

[0055] <Evaluation of deodorizing properties> 3g of fluff pulp was placed in a 600ml lidded plastic container. Three sprays of 1% ammonia solution were then added using a commercially available spray bottle. For comparison, a sample was also prepared in which ammonia solution was sprayed without any pulp. After spraying with ammonia solution, the lid was closed, and after 3 minutes, the lid was opened. A rating of ○ was given if the ammonia odor was weaker compared to the sample without pulp, and a rating of × if the ammonia odor was the same. The results are shown in Table 1.

[0056] <Example 2> A pulp sheet for fluff pulp and fluff pulp were manufactured and evaluated in the same manner as in Example 1, except that the amount of softener was changed. The results are shown in Table 1.

[0057] <Comparative Example 1> A pulp sheet for fluff pulp and fluff pulp were manufactured and evaluated in the same manner as in Example 1, except that softwood kraft pulp was not used and no softening agent was used. The results are shown in Table 1.

[0058] <Comparative Example 2> A pulp sheet for fluff pulp and fluff pulp were manufactured and evaluated in the same manner as in Example 2, except that softwood kraft pulp was not used. The results are shown in Table 1.

[0059] <Comparative Example 3> A pulp sheet for fluff pulp and fluff pulp were manufactured and evaluated in the same manner as in Example 1, except that a softening agent was not added. The results are shown in Table 1.

[0060] <Reference example 1> A pulp sheet for fluff pulp and fluff pulp were manufactured and evaluated in the same manner as in Example 1, except that metal ion-containing cellulose fibers and softeners were not used. The results are shown in Table 1.

[0061] <Reference example 2> A pulp sheet for fluff pulp and fluff pulp were manufactured and evaluated in the same manner as in Example 1, except that metal ion-containing cellulose fibers were not used. The results are shown in Table 1.

[0062] <Examples 3, 5, 7> A pulp sheet for fluff pulp and fluff pulp were manufactured and evaluated in the same manner as in Example 1, except that the mass ratio of coniferous kraft pulp and metal ion-containing cellulose fibers was changed as shown in Table 2. The results are shown in Table 2.

[0063] <Examples 4, 6, 8> A pulp sheet for fluff pulp and fluff pulp were manufactured and evaluated in the same manner as in Example 2, except that the mass ratio of coniferous kraft pulp and metal ion-containing cellulose fibers was changed as shown in Table 2. The results are shown in Table 2.

[0064] <Comparative Examples 4-6> Except for the absence of a softening agent, pulp sheets for fluff pulp and fluff pulp were manufactured and evaluated in the same manner as in Examples 3, 5, and 7. The results are shown in Table 2.

[0065] [Table 1]

[0066] [Table 2]

[0067] Pulp sheets for fluff pulp manufactured using only metal ion-containing cellulose fibers without using coniferous kraft pulp (Comparative Examples 1 and 2) exhibited poor disintegration properties and could not be broken down into cotton-like fibers (Evaluation: C). The pulp after disintegration formed into small clumps, and some powdery material was also observed. Figure 1 shows a photograph of the pulp after disintegration obtained in Comparative Example 1. In contrast, pulp sheets for fluff pulp manufactured by mixing metal ion-containing cellulose fibers with coniferous kraft pulp showed improved disintegration properties (Evaluation: A or B) (Examples 1-8, Comparative Examples 3-6). Furthermore, when a softening agent was added (Examples 1-8), the disintegration properties were very good (Evaluation: A), and no clumping was observed. Furthermore, the fluff pulp obtained from the pulp sheets for fluff pulp in Examples 1 and 2 had water absorption and water retention capacities equivalent to conventional fluff pulp made solely from coniferous kraft pulp (Reference Examples 1 and 2), and also exhibited a good recovery rate after compression (recovery of bulk). Examples 3 to 8, in which the amount of metal ion-containing cellulose fibers was changed, also tended to exhibit good water absorption, water retention, and recovery rate after compression compared to the corresponding Comparative Examples 4 to 6. Moreover, the fluff pulp obtained from the pulp sheets for fluff pulp in Examples 1 to 8 possessed deodorizing properties not seen in conventional fluff pulp made solely from coniferous kraft pulp (Reference Examples 1 and 2).

[0068] <Reference example 3> The inhibition of aggregation of metal ion-containing cellulose fibers by using them in combination with a softener was evaluated. To 150 L of a 1.7% by mass slurry of the metal ion-containing cellulose fibers prepared above, 1.5 parts by mass of the softener from Example 1 was added per 100 parts by mass of metal ion-containing cellulose fibers. The mixture was stirred for 30 minutes, and then dewatered using a screw press. The solid content concentration after dewatering was 37% by mass. The mixture was then diluted to a 1.5% by mass slurry of metal ion-containing cellulose fibers and stirred at 3000 rpm for 60 minutes to dissociate the fibers. Next, the dissociated slurry was further diluted to 0.1% by mass, 50 mL was placed in a glass tube, and the number of fiber clumps visible to the naked eye was measured by shaking the tube up and down. This procedure was repeated three times. The results are shown in Table 3.

[0069] <Reference example 4> The procedure was carried out in the same manner as in Reference Example 3, except that no fabric softener was added. The results are shown in Table 3.

[0070] [Table 3]

[0071] The results in Table 3 show that using metal ion-containing cellulose fibers in combination with a fabric softener suppresses the aggregation of the metal ion-containing cellulose fibers.

Claims

1. (A) Coniferous wood kraft pulp, (B) A metal ion-containing cellulose fiber having an ionic substituent, wherein the cellulose fiber contains ions of one or more metal elements selected from Ag, Au, Pt, Pd, Ni, Mn, Fe, Ti, Al, Zn, or Cu. (C) Fabric softener It contains, A pulp sheet for fluff pulp, wherein the content of (C) softener is 0.1 to 50 parts by mass per 100 parts by mass of the total of (A) and (B).

2. The fluff pulp sheet according to claim 1, wherein the content of (B) metal ion-containing cellulose fibers is 1 to 60 parts by mass per 100 parts by mass of (A) coniferous kraft pulp.

3. The cellulose fiber having the ionic substituent is a cellulose fiber having one or more groups selected from carboxylic acid-derived groups, phosphoric acid-derived groups, or sulfuric acid-derived groups as ionic substituents, according to claim 1 or 2.

4. The cellulose fiber having the ionic substituent is an oxidized cellulose fiber, The pulp sheet for fluff pulp according to claim 1 or 2, wherein the amount of carboxyl groups in the cellulose fibers having the ionic substituent is 0.2 to 2.2 mmol / g.

5. The pulp sheet for fluff pulp according to claim 1 or 2, wherein the content of the metal ions relative to the oven-dry mass of the metal ion-containing cellulose fibers is 20 to 60 mg / g.

6. A fluff pulp using the fluff pulp sheet described in claim 1 or 2.

7. A product containing the fluff pulp described in claim 5, wherein the product is selected from an absorbent member, a sound-absorbing material, a pillow, a surgical sheet, a shock-absorbing material, or a cushioning material.

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