JP7008450B2 - Method for manufacturing powdered synthetic pulp - Google Patents

Description

The present invention relates to a method for producing powdered synthetic pulp.

Pulp-like products manufactured from thermoplastic resins, so-called synthetic pulps, are processed into non-woven fabrics and used as synthetic papers for use as various wrapping papers, filters, etc., and additives added to paints and inks. It is used as.

Conventionally, synthetic pulp produced from a thermoplastic resin has a problem that it has poor infiltration property when dried and is difficult to disperse in water. As a method for improving the dispersibility of synthetic pulp, for example, a method of surface-treating synthetic pulp with polyvinyl alcohol is known. In addition, polyvinyl alcohol used as a suspending agent in the production of synthetic pulp may remain on the surface of synthetic pulp. It is known that synthetic pulp having polyvinyl alcohol adhered to its surface exhibits good dispersibility when immersed in water, but exhibits water repellency and low water absorption in a dry state. Therefore, an efficient production method that has high water dispersibility and infiltration into synthetic pulp even when dried is desired.

For example, Patent Document 1 describes synthetic pulp having improved hydrophilicity by adhering polypropylene glycol to a pulp-like material of a thermoplastic resin. In the embodiment of Patent Document 1, a pulp-like substance is added to water, polypropylene glycol is added thereto, and the mixture is vigorously stirred to obtain a slurry in which polypropylene glycol is adhered to the surface of the pulp-like substance. Further, a slurry of pulp-like material to which polypropylene glycol is attached is dehydrated and made into a sheet and dried to obtain a dried sheet, and the obtained dried sheet is crushed to obtain a powder-like synthetic pulp.

Japanese Unexamined Patent Publication No. 63-66380

Similar to the production method described in Patent Document 1, the present inventors have adhered polypropylene glycol to a pulp-like material of a thermoplastic resin, dehydrated it and processed it into a sheet, which is used for dehydration papermaking. The processed sheet sometimes adhered to the wire mesh of the equipment that was used. In addition, when the processed sheet was cut, the edge of the sheet sometimes collapsed. Collapse of the seat edge leads to a decrease in work efficiency and yield. Because of these problems, it has been found that further improvement in the production efficiency of synthetic pulp is desired.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for efficiently producing a powdery synthetic pulp having infiltration property even when dried.

The present invention is the following method for producing powdered synthetic pulp.
[1] A method for producing powdered synthetic pulp.
A water-containing sheet composed of a pulp-like material containing polyvinyl alcohol and a thermoplastic resin other than polyvinyl alcohol, and the content of the polyvinyl alcohol is 0.1% by mass or more and 10% by mass or less with respect to the total mass of the pulp-like material. And the process of providing raw material
A pulverization step of pulverizing the raw material under the condition that the water content is 400 parts by mass or less with respect to 100 parts by mass of the pulp-like material.
An attachment step of attaching a nonionic surfactant to the raw material, and
It includes a drying step of drying the raw material to which the nonionic surfactant is attached.
Before the drying step or at the same time as the drying step, the adhesion step is performed using the nonionic surfactant of 0.1% by mass or more and 10% by mass or less with respect to the total mass of the pulp-like material of the raw material. A method for producing a powdered synthetic pulp to be carried out.
[2] The method for producing powdered synthetic pulp according to [1], wherein the thermoplastic resin is a crystalline polyolefin.
[3] The method for producing powdered synthetic pulp according to [1] or [2], wherein the nonionic surfactant is polypropylene glycol having a weight average molecular weight of 200 or more and 10,000 or less.
[4] The powder according to any one of [1] to [3], wherein at least the crushing step is carried out with a mixer having stirring blades installed in two upper and lower stages of the lower blade and the upper blade in a stirring container. A method for producing synthetic pulp.
[5] The method for producing powdered synthetic pulp according to any one of [1] to [3], wherein at least the crushing step and the drying step are carried out in a continuous apparatus.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a method for efficiently producing powdered synthetic pulp having infiltration property even when dried.

As a result of diligent research in view of the above problems, the present inventors have infiltrated when a nonionic surfactant such as polypropylene further adheres to a thermoplastic resin pulp-like material to which polyvinyl alcohol adheres to the surface. Was found to improve, but the cohesive force decreased. When a pulp-like material to which polyvinyl alcohol and a nonionic surfactant are attached is formed into a sheet due to a decrease in cohesive force, the sheet is brittle and easily loses its shape, and adheres to equipment or at the edge of the sheet when the sheet is cut. It is thought that problems such as collapse will occur.

Therefore, in the production method of the present invention, a water-containing sheet made of a pulp-like material, which has polyvinyl alcohol attached but does not substantially contain a nonionic surfactant, is provided as a raw material, and the water-containing sheet is provided. Then, a pulverization step, a nonionic surfactant adhesion step, and a drying step are carried out to produce a powdery synthetic pulp. By doing so, it is possible to prevent problems such as adhesion of the water-containing sheet to equipment such as wire mesh and collapse of the sheet edge when cutting the water-containing sheet, which may occur when processing pulp-like material into a water-containing sheet. It has become possible to increase efficiency. Further, the powdery synthetic pulp obtained by such a production method has excellent infiltration property equivalent to that of the powdery synthetic pulp produced by the conventional method.

Hereinafter, the present invention will be described with reference to exemplary embodiments, but the present invention is not limited to the following embodiments.

The present invention is a production method including the following steps for producing powdered synthetic pulp.
It is composed of a pulp-like material containing polyvinyl alcohol (PVA) and a thermoplastic resin other than PVA, and the content of the PVA is 0.1% by mass or more and 10% by mass or less with respect to the total mass of the pulp-like material. A process of providing a sheet (hereinafter, sometimes abbreviated as "PVA-adhered water-containing sheet") as a raw material, and
A crushing step of crushing the raw material in an environment with a water content within a predetermined range, and
An attachment step of attaching a nonionic surfactant to the raw material, and
A drying step of drying the raw material to which the nonionic surfactant is attached.

First, a process of providing the PVA-adhered water-containing sheet as a raw material will be described.

The pulp-like material containing PVA and a thermoplastic resin other than PVA is a fiber having a structure in which a plurality of fine fibers substantially made of the thermoplastic resin are entangled to form a thicker fiber having a branched structure (a fiber having a structure of forming a thicker fiber having a branched structure. It is also simply referred to as "microfibril fiber", and such a structure is also simply referred to as "microfibril structure"), which is a fiber aggregate formed by not aligning in a specific direction as a whole, and PVA is contained in the fiber. It is attached.

The content of PVA is 0.1% by mass to 10% by mass with respect to the total mass of the pulp-like material. When the PVA content is within the above range, the pulp-like material exhibits good dispersibility in water. PVA is derived from the suspending agent used in the production of pulp-like material, or is used for surface treatment for improving dispersibility. The content of PVA can be measured by a Fourier transform infrared spectrophotometer (FT-IR). Specifically, the pulp-like material is formed into a film by hot pressing, the absorption spectrum is measured by FT-IR, and the amount of PVA adhered can be obtained from the obtained peak intensity near the wavelength of 3370 nm.

The water-containing sheet made of a pulp-like material is a non-woven fabric made of the pulp-like material and water, and the water content with respect to the mass thereof is 25% by mass or more and 70% by mass or less, preferably 30% by mass or more and 60% by mass or less. It is a thing. The phrase "consisting of the pulpy substance and water" means that PVA, a thermoplastic resin and other components other than water may be present, but the content of the other components is 5% by mass or less. It means that it is preferably 1% by mass or less.

The water content is a value measured by a change in weight before and after drying. More specifically, it is a value measured by an infrared moisture meter.

The PVA-adhered water-containing sheet does not substantially contain the nonionic surfactant described later. Here, "substantially free of nonionic surfactant" means that the presence of a trace amount of nonionic surfactant that does not reduce the cohesive force is permissible. Specifically, "substantially free" means that the content of the nonionic surfactant is 0.01% by mass or less, preferably 0.001% by mass or less, based on the total mass of the water-containing sheet. It is preferably below the detection limit. Examples of nonionic surfactants are as described below.

The content of the nonionic surfactant in the PVA-adhered water-containing sheet can be measured by a Fourier transform infrared spectrophotometer (FT-IR). Specifically, for example, when polypropylene glycol is used as a nonionic surfactant, the synthetic pulp is formed into a film by hot pressing, the absorption spectrum is measured by FT-IR, and the obtained peak intensity near the wavelength of 1100 nm is obtained. The amount of polypropylene glycol attached can be obtained from. For other nonionic surfactants, the wavelength to be confirmed may be changed according to the type of the nonionic surfactant.

The PVA-adhered water-impregnated sheet can be obtained by producing a pulp-like material containing PVA and a thermoplastic resin other than PVA, and processing the produced pulp-like material into a sheet shape. Further, a water-containing sheet having a desired PVA content and water content may be produced by adhering PVA to commercially available synthetic pulp, if necessary, and then making paper. Further, the PVA content and the water content of a commercially available sheet-shaped synthetic pulp (for example, synthetic paper) can be adjusted and used as a PVA-adhered water-containing sheet.

Examples of the synthetic pulp that can be used in the present invention include polyolefin synthetic pulp SWP, ESS-5 and SWP, ESS-2 manufactured by Mitsui Chemicals, Inc.

The thermoplastic resin constituting the PVA-adhered water-containing sheet is not particularly limited as long as it is a thermoplastic resin other than PVA, but a polyolefin is more preferable. Examples of the polyolefin include homopolymers and copolymers of α-olefins having 2 to 6 carbon atoms. The above-mentioned copolymer may be a copolymer of two or more kinds of α-olefins having 2 to 6 carbon atoms, or may be a copolymer of an α-olefin having 2 to 6 carbon atoms and another polymerizable compound. Examples of the above other polymerizable compounds include olefins other than α-olefins having 2 to 6 carbon atoms, unsaturated carboxylic acids containing acrylic acid and methacrylic acid, acrylic acid esters, methacrylic acid esters, and vinyl acetate. included. The above-mentioned copolymer may be a graft copolymer obtained by grafting an unsaturated carboxylic acid monomer with a peroxide on the above-mentioned homopolymer or copolymer. The homopolymer or copolymer is preferably crystalline.

Preferred examples of the α-olefin having 2 to 6 carbon atoms include ethylene, propylene, 1-butene, 3-methyl-1-butene and 4-methyl-1-butene. Examples of crystalline homopolymers or copolymers produced from these materials containing α-olefins having 2 to 6 carbon atoms include linear low-density polyethylene and elastomers (ethylene-α-olefin copolymers). Low density polyethylene, medium density polyethylene, high density polyethylene, ultrahigh molecular weight polyethylene, ethylene-methacrylic acid copolymer, acid-modified polyethylene with maleic acid or acrylic acid, polypropylene, polybutene, poly3-methylbutene, and poly 4 -Includes methylbutene, as well as mixtures thereof.

The thermoplastic resin preferably has a molecular weight distribution (Mw / Mn) (value calculated using the polystyrene-equivalent molecular weight by the GPC method using a TSKgel column) of 1.5 or more and 3.5 or more. Further, the thermoplastic resin preferably has a melt flow rate (MFR: a value measured by ASTMD1238 at 190 ° C. and a weight of 2.16 kg) of 0.1 g / 10 min or more and 200 g / 10 min or less, preferably 5.0 g /. It is more preferably 10 min or more and 150 g / 10 min or less. Further, the upper limit is preferably 110 g / 10 min or less, and particularly preferably 100 g / 10 min or less.

The thermoplastic resin is preferably made of polyethylene, and more preferably polyethylene having a melt flow rate of 5.0 g / 10 min or more and 150 g / 10 min or less.

The method for producing a pulp-like material containing a thermoplastic resin is not particularly limited, but it can usually be produced by a flash method. In the flash method, a high-pressure resin solution in which a resin is dissolved in a solvent is ejected under reduced pressure to volatilize the solvent to form fibers made of the resin, and if necessary, a waring blender or a descriptor. It is a method of cutting and beating the formed fibers by the above. The flash method is preferable because a pulpy substance having high strength can be obtained when it is formed into a sheet. In particular, the method of flushing a polyolefin solution dispersed in an aqueous medium in the presence of a suspending agent, as described in JP-A-48-44523, is fibrous having a randomly branched shape. It is preferable because a pulpy substance having the above resin can be obtained.

The flash method is a step of dissolving a thermoplastic resin which is a material of a microfibril resin constituting a pulp-like substance and adding a suspending agent and water to form an emulsion, and ejecting (flashing) the emulsion under reduced pressure. At the same time, it includes a step of vaporizing the solvent.

In the first step of the flash method, the thermoplastic resin is dissolved in a solvent capable of dissolving the thermoplastic resin, and a suspending agent and water are added to form an emulsion.

Examples of the above solvents include saturated hydrocarbon solvents including butane, pentane, hexane, heptane, octane and cyclohexane, aromatic solvents including benzene and toluene, halogens including methylene chloride, chloroform and carbon tetrachloride. Includes carbon tetrachloride. From these solvents, a solvent that dissolves the thermoplastic resin that is the material of the microfibril resin that constitutes the pulp-like material to be produced and that does not easily remain in the aggregate of fibers obtained by volatilization during flashing is appropriately selected. do it.

Examples of the suspending agent include hydrophilic resins containing polyvinyl alcohol (PVA), polyacrylates, gelatin, tragacant rubber, starch, methyl cellulose, carboxymethyl cellulose and the like. Further, the above hydrophilic resin can also be used in combination with a general cationic surfactant or anionic surfactant. Since the suspending agent uniformly mixes the thermoplastic resin, the solvent and water, the emulsion can be stabilized, and the fibers can be cut and beaten after flushing stably even in water.

PVA is preferable as the suspending agent from the viewpoint of further improving the infiltration property and production efficiency of the powdered synthetic pulp.

The amount of the suspending agent added is preferably 0.1% by weight or more and 10% by weight or less in the fiber. It is preferable to adjust the amount of the suspending agent as appropriate, such as adding a large amount when the operation is such that a part of the added suspending agent is removed in the manufacturing process. As a guideline for the amount to be added, the amount may be 0.1 part by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the thermoplastic resin.

When various compounds other than microfibril fibers (hereinafter, also simply referred to as "other compounds") are added to the pulp-like substance, it is preferable to add them to the above emulsion. By doing so, the other compounds are sufficiently dispersed in the pulp-like substance, and the effects of the other compounds can be maintained for a long period of time. Other compounds that can be added to pulps include antibacterial agents, heat-resistant stabilizers, weather-resistant stabilizers, various stabilizers, antioxidants, dispersants, antistatic agents, slip agents, anti-blocking agents, antifogging agents, etc. Examples include known compounds as lubricants, dyes, pigments, natural oils, synthetic oils, waxes, fillers and the like. The pulpy substance may contain a plurality of kinds of these compounds, and the content thereof can be appropriately selected depending on the purpose of containing these compounds.

In the second step of the flash method, the emulsion obtained in the first step is heated so that the temperature is 100 ° C. or higher and 200 ° C. or lower, preferably 130 ° C. or higher and 150 ° C. or lower, and the pressure is 0.1 MPa. The pressure is set to 5.0 MPa or less, preferably 0.5 MPa or more and 1.5 MPa or less. Then, the heated and pressurized emulsion is ejected (flashed) from the nozzle into a space depressurized, and at the same time, the solvent is vaporized and volatilized. The pressure of the depressurized space is preferably 1 kPa or more and 95 kPa or less. Further, the decompressed space is preferably an inert atmosphere such as a nitrogen atmosphere. In the present invention, "pressure" means absolute pressure.

By the above steps, microfibril fibers having an indefinite length having a branched structure, which are made of a thermoplastic resin as a raw material, can be obtained. It is preferable that the microfibril fibers thus obtained are further cut and beaten with a waring blender or a discifier so that the average fiber length becomes a desired range. At this time, it is preferable to dissolve or disperse the microfibril fibers in water to form a water slurry having a concentration of 0.5 g / L or more and 5.0 g / L, and perform the cutting and beating.

At this time, for example, the fiber diameter of the microfibril resin can be adjusted to a desired degree by selecting, for example, the type of blade of the disc refiner, the number of rotations, the diameter of the screen, and the like according to predetermined conditions.

The average fiber length of the microfibril fiber (the average value of the distance between the ends set to be the longest among the distances between the ends of one fiber) is not particularly limited, but is 0.01 mm or more and 50 mm. It is preferably 0.05 mm or more, and more preferably 10 mm or less. When the average fiber length is in this range, it is preferable because it has an appropriate bulkiness when it is made into a pulp-like material and has a sufficient restoring force when a pressure is applied.

The average fiber length can be obtained by the following procedure.

The microfibril fibers constituting the pulp-like material are classified every 0.05 mm using the above-mentioned longest length. Then, the measured fiber length of the microfibril fibers contained in each class (length) and the number of microfibril fibers contained in each class are measured. The measurement may be performed on 12,000 to 13,000 fibers. Then, from the above measurement results, the number average fiber length Ln (mm) of each class is obtained by the following formula.

Ln = ΣL / N
L: Measured fiber length (mm) of microfibril fibers contained in one class
N: Number of microfibril fibers contained in one class

Then, the average fiber length (mm) of the microfibril fibers constituting the pulp-like material is obtained by the following formula.

Average fiber length = Σ (Nn × Ln ³ ) / Σ (Nn × Ln ² )
Nn: Number of microfibril fibers contained in each class

The measured fiber length is, for example, an automatic fiber measuring machine manufactured by Mezzo Automation Co., Ltd. (product name: FiberLab-3.5) in which pulp-like material is dispersed in water so as to have a concentration of 0.02% by mass. It can be obtained by measuring the length of each fiber constituting the synthetic pulp. In the measuring machine, xenon lamp light is irradiated to the fibers flowing in the capillary, a video signal is collected by a CCD (charge-coupled device) sensor, and image analysis is performed.

Further, the microfibril fiber preferably has a minimum diameter (hereinafter, also simply referred to as “fiber diameter”) of 0.5 μm or more, and preferably a maximum fiber diameter of 50 μm or less. The average fiber diameter is more preferably 15 μm or more, and more preferably 35 μm or less. When the fiber diameter is in this range, it is preferable because it has an appropriate bulkiness when the fibers are aggregated and has a sufficient restoring force when a pressure is applied.

The fiber diameter can be measured by observing each fiber with a microscope such as an optical microscope and an electron microscope.

Specifically, the maximum value and the minimum value of the fiber diameter can be measured as follows.

Synthetic pulp is observed at a magnification of 100 times with a digital HF microscope VH8000 manufactured by KEYENCE, and 100 microfibril fibers observed to have a fiber diameter of 10 μm or more are randomly selected. The fiber diameter of the selected microfibril fiber is measured, and the maximum value among the measured values is defined as the "maximum value of the fiber diameter".

Observe the pulp-like material at a magnification of 3000 times with a scanning electron microscope JSM6480 manufactured by JEOL Ltd., and randomly select 100 microfibril fibers observed to have a fiber diameter of less than 10 μm. The fiber diameter of the selected microfibril fiber is measured, and the smallest value among the measured values is defined as the "minimum value of the fiber diameter".

Further, the average fiber diameter can be measured using a fiber image analyzer such as Valmet FS5 manufactured by Valmet Automation.

The microfibril resin obtained by the above-mentioned flash method can be dried and then opened with a mixer or the like to obtain a pulp-like substance.

Next, a specific water-containing sheet is produced using a pulp-like material containing a thermoplastic resin or a commercially available synthetic pulp. The method for producing the water-containing sheet is not particularly limited, and for example, it can be produced by a method for producing a wet nonwoven fabric.

A pulp containing a thermoplastic resin or a commercially available synthetic pulp is suspended in water to obtain a slurry. For example, when the commercially available synthetic pulp is in the form of a sheet, a slurry of the synthetic pulp can be obtained by vigorously stirring with water using a pulper.

Next, when the PVA content of the pulp-like material containing the thermoplastic resin or the commercially available synthetic pulp is low, PVA is added and mixed with the slurry of the synthetic pulp, and the PVA content of the synthetic pulp is the synthetic pulp. PVA is attached so as to be 0.1% by mass or more and 10% by mass or less with respect to the total mass of.

Next, the obtained slurry is uniformly placed on a net or the like and dehydrated by pressure or heat to form a water-containing sheet. Examples of the device for molding a sheet from the slurry include a sheet machine, a long net paper machine, a circular net paper machine, a circular net short net combination paper machine, and an inclined wire type paper machine.

The sheet molded by a paper machine or the like is dried so as to have a desired water content. The drying temperature is preferably a temperature equal to or lower than the melting point of the pulpy product. Examples of the drying device include a dryer such as a Yankee dryer, an air through dryer, and a drum type dryer.

The water-containing sheet obtained by the above method can be cut into a desired size. The size of the water-containing sheet is not particularly limited and can be appropriately selected in consideration of the capacity of the device used in the next step, and is usually 400 cm ² or more and 14400 cm ² or less, preferably 1600 cm ² or more and 8100 cm ² or less. Cut. The length of one side of the water-containing sheet is usually 20 cm or more and 120 cm or less, preferably 40 cm or more and 90 cm or less.

When a commercially available sheet-shaped synthetic pulp (for example, synthetic paper) is used as a PVA-adhered water-containing sheet, the PVA content and the water content of the sheet-shaped synthetic pulp should be within the desired ranges, if necessary. Use after adjusting. The sheet-shaped synthetic pulp may contain PVA of 0.1% by mass or more and 10% by mass or less with respect to the total mass, but when the PVA content is less than 0.1% by mass, it may contain PVA. For example, the PVA content can be increased by spraying a solution of PVA on a sheet of synthetic pulp. The method for increasing the water content of the sheet-shaped synthetic pulp is not particularly limited, and for example, the sheet-shaped synthetic pulp can be immersed in water. Further, in order to reduce the water content, it may be dried using a dryer as described above.

Next, a crushing step of crushing the raw material using a PVA-adhered water-impregnated sheet as a raw material, an adhesion step of adhering a nonionic surfactant to the raw material, and a drying step of drying the raw material to which the nonionic surfactant is attached are performed. implement. Either the crushing step or the attaching step may be carried out first. That is, the PVA-adhered water-impregnated sheet may be crushed as in Example 1 of the present application, and then the nonionic surfactant may be attached to the pulverized product, or the PVA-adhered water-impregnated sheet may be attached as in Example 2. After adhering the nonionic surfactant, the PVA-adhered water-containing sheet may be pulverized. Further, the pulverization step and the adhesion step may be performed simultaneously in one device.

However, the adhesion step is carried out before the drying step or at the same time as the drying step. Therefore, when the crushing step and the bonding step are performed at the same time, the three steps of the crushing step, the bonding step and the drying step may be performed simultaneously in one device. For example, in Example 3, the adhesion step, the crushing step, and the drying step were carried out simultaneously in one device.

In the pulverization step, the raw material, that is, the PVA-adhered water-impregnated sheet itself or the PVA-adhered water-impregnated sheet to which the nonionic surfactant is attached is pulverized. The pulverization step is performed under the condition that the water content with respect to 100 parts by mass of the pulp-like material is 400 parts by mass or less. If the water content exceeds 400 parts by mass, the paper must be dehydrated and made into a sheet again, resulting in inferior production efficiency. Further, from the viewpoint of further improving the production efficiency, the water content is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, based on 100 parts by mass of the pulp-like material.

The pulverization step can be carried out before the drying step, after the drying step or at the same time as the drying step, but from the viewpoint of production efficiency, it is preferably carried out before the drying step or at the same time as the drying step. When the pulverization step is carried out before the drying step or at the same time as the drying step, the water content with respect to 100 parts by mass of the pulp-like material is increased from the viewpoint of efficiently adhering the nonionic surfactant to the pulp-like material in the adhesion step. It is preferably performed under the condition of 33 parts by mass or more, more preferably 43 parts by mass or more, and further preferably 54 parts by mass or more. The water content when the crushing step and the drying step are carried out at the same time is the water content at the time of starting the crushing step.

The pulverization step may be carried out so that the raw material has a desired size. The size of the crushed material can be selected according to the intended use of the final powdery synthetic pulp, but usually, the size of the crushed material is preferably 0.04 cm ² or less, and the number of fibers is one by one. The separated state is more preferable.

The average fiber length of the pulp-like microfibril fibers in the pulverized material (the average value of the distance between the ends set to be the longest among the ends of one fiber) is not particularly limited. However, it is preferably 0.01 mm or more and 50 mm or less, and more preferably 0.05 mm or more and 10 mm or less. When the average fiber length is in this range, it is preferable because it has an appropriate bulkiness when it is made into a powdery synthetic pulp and has a sufficient restoring force when a pressure is applied.

The method for crushing the raw material is not particularly limited, and a crusher used for producing pulp in the art can be used. Specific examples of the crusher include a knife mill, a cutting mill, a hammer mill, a roller mill, a ball mill, a sand mill and the like. Further, it can also be pulverized by using a single disc refiner, a double disc refiner or the like used for beating the pulp. Further, the crushing step may be carried out by a batch type or continuous type crushing / mixing dryer as described later, which can carry out all three steps of crushing the raw material, adhering the nonionic surfactant, and drying. ..

In the attachment step, the nonionic surfactant is attached to the raw material, that is, the water-containing sheet itself or the pulverized product of the water-containing sheet.

The nonionic surfactant used in the adhesion step is not particularly limited, but its HLB value is preferably 4 or more and 9 or less, and more preferably 5 or more and 8 or less. The HLB value is Hydrophile-Lipophile-Balance, hydrophilicity-lipophilicity-balance, and is a value indicating the magnitude of hydrophilicity or lipophilicity of the compound. The smaller the HLB value, the higher the lipophilicity, and the larger the value, the higher the hydrophilicity.

By using a nonionic surfactant having an HLB of 4 or more, it is possible to impart sufficient infiltration property to the powdery synthetic pulp. Further, by using a nonionic surfactant having an HLB of 9 or less, foaming that may occur when the synthetic pulp is infiltrated can be suppressed.

Examples of the type of nonionic surfactant used in the adhesion step include nonionic surfactants such as EO / PO block copolymer type, alkyl ether type, ester type, amide type, and polyalkylene glycol type. Among them, a polyalkylene glycol type nonionic surfactant is preferable, and polypropylene glycol is particularly preferable, from the viewpoint of further suppressing foaming that may occur when the synthetic pulp is moistened and further improving the infiltration property.

Polypropylene glycol used as a nonionic surfactant in the present invention is obtained by polymerizing propylene oxide by a conventional method, and has a molecular weight of 200 to 10,000, preferably 400 to 6,000. be.

Here, the molecular weight of polypropylene glycol (PPG) is a value determined by gel permeation chromatography (GPC) and is calculated from the comparison of the OH value between a standard PPG having a known OH value and a sample PPG. If the molecular weight of polypropylene glycol is out of the above range and is too small, the adhesion to the pulp-like substance is lowered, and if it is too large, the hydrophilicity-imparting effect is lowered.

As a method of adhering a nonionic surfactant to a raw material (a water-containing sheet or a pulverized product thereof), a method of spraying a nonionic surfactant or an aqueous solution thereof or an aqueous dispersion onto a water-containing sheet, or an aqueous slurry of a pulverized product. A method of adding and mixing a nonionic surfactant, a method of adding and mixing a pulverized product to a nonionic surfactant or an aqueous solution thereof or an aqueous dispersion, and a method of mixing a nonionic surfactant with another synthetic pulp in advance. Examples thereof include a method of mixing this mixture with a pulverized product. A method of spraying a nonionic surfactant or an aqueous solution thereof or an aqueous dispersion on a water-containing sheet is preferable because it increases the degree of freedom in the design of the apparatus used in the subsequent crushing step and drying step.

Further, the method of mixing the nonionic surfactant with other synthetic pulp in advance is preferable in that the nonionic surfactant can be handled as a powder and the nonionic surfactant can be easily handled. .. In this case, as the other synthetic pulp, pre-crushed synthetic pulp is used. The type of other synthetic pulp to be mixed with the nonionic surfactant in advance is not particularly limited as long as it does not affect the physical properties of the finally obtained powdery synthetic pulp, but constitutes a water-containing sheet. It is preferably the same as the pulpy material. In addition, the amount of other synthetic pulp used (other synthetic pulp / nonionic surfactant) with respect to the total mass of the nonionic surfactant when mixed with other synthetic pulp in advance is based on the mass. , 1/5 to 20/1, and preferably 1/3 to 10/1.

The amount of the nonionic surfactant used in the adhesion step is 0.1% by mass with respect to the total mass of the pulp-like material in the water-containing sheet of the raw material (that is, with respect to the total mass of the water-containing sheet excluding water). It is 10% by mass or less, preferably 0.2% by mass or more and 8% by mass or less, and more preferably 0.4% by mass or more and 6% by mass or less. When the amount of the nonionic surfactant used is 0.1% by mass or more, the effect of improving the hydrophilicity of the pulp-like material is achieved. Further, if it is 10% by mass or less, there is little concern that the performance of the pulp-like product as a synthetic pulp is deteriorated.

From the viewpoint of efficiently adhering the nonionic surfactant to the pulp-like material, the adhesion step is preferably performed under the condition that the water content with respect to 100 parts by mass of the pulp-like material is 33 parts by mass or more and 400 parts by mass or less. .. From the same viewpoint, the water content in the adhesion step is more preferably 43 parts by mass or more and 300 parts by mass or less, and further preferably 54 parts by mass or more and 200 parts by mass or less.

The adhesion step may generally be carried out at 0 to 90 ° C., and it is convenient to carry out the adhesion step at room temperature.

Further, a drying step of drying the raw material to which the nonionic surfactant is attached is carried out. The drying method carried out in the drying step is not particularly limited, and a method conventionally used for drying synthetic pulp or the like can be used. In general, a method of heating under reduced pressure, a method of ventilating hot air into the device, and the like can be mentioned. Further, as the drying device, a dryer such as a Yankee dryer, an air through dryer, or a drum type dryer can be used.

In the batch-type manufacturing method, the drying method is preferably a method of heating under reduced pressure. On the other hand, in the continuous manufacturing method, a method of ventilating hot air into the apparatus is more convenient and preferable.

The drying step is carried out until the water content of the powdered synthetic pulp, which is the final product, is 4% by mass or less, preferably 2% by mass or less, and more preferably 1% by mass or less. The water content of the powdered synthetic pulp can be measured in the same manner as the water content of the water-containing sheet described above.

The conditions for carrying out the drying step are not particularly limited as long as there is no risk of denaturation of the pulp-like material and the water content of the powdered synthetic pulp as the final product is equal to or less than the above value. The drying temperature and the temperature of the hot air are preferably 50 ° C. or higher and 100 ° C. or lower, and more preferably 60 ° C. or higher and 90 ° C. or lower. The pressure inside the device when depressurizing is preferably −150 KPa or more and −20 KPa or less, and more preferably −100 KPa or more and −50 KPa or less. In the present invention, "pressure" means absolute pressure.

The time for carrying out the drying step is preferably 10 minutes or more and 180 minutes or less, and more preferably 20 minutes or more and 120 minutes or less.

The pulverization step, the adhesion step, and the drying step in the production method of the present invention may be carried out by using individual devices, or a plurality of steps may be carried out sequentially or simultaneously in one device. In the present invention, it is preferable to carry out at least two of the above three steps in one device from the viewpoint of improving manufacturing efficiency.

According to the production method of the present invention, it is not necessary to re-sheet the water-containing sheet as a raw material after the production. Therefore, there is no possibility that the sheet adheres to the equipment (wire mesh, etc.) used for dehydration papermaking, and the manufacturing efficiency is excellent. The production method of the present invention preferably does not include a sheeting step accompanied by dehydration papermaking. Further, even if the sheet is formed again, by forming the sheet again before the bonding step, there is no possibility that the processed sheet adheres to the device such as the wire mesh used for dehydration papermaking, and the manufacturing efficiency is excellent.

Next, an apparatus capable of carrying out a plurality of steps will be described.

As an example of an apparatus capable of performing the three steps of crushing, adhering, and drying raw materials, there is a mixer having a stirring blade installed in two upper and lower stages of a lower blade and an upper blade in a stirring container. Such a mixer can be used for batch production of powdered synthetic pulp. In the mixer, the raw material (moisture-containing sheet) can be made to flow by the rotational force of the lower blade, and at the same time, the raw material can be crushed by the shearing force of the upper blade.

The peripheral speed of the lower blade when carrying out the pulverization step is preferably 10 m / s or more and 100 m / s or less, and more preferably 20 m / s or more and 80 m / s or less. On the other hand, the rotation speed of the upper blade may be coaxial with the lower blade and may be the same circumferential speed. When the peripheral speed can be changed with the lower blade on two axes or the like, the peripheral speed can be changed within the range of the peripheral speed of the lower blade. The implementation time of the pulverization step is preferably 1 minute or more and 30 minutes or less, and more preferably 2 minutes or more and 20 minutes or less.

Further, when the nonionic surfactant is put into the mixer, the raw material (water-containing sheet and / or its pulverized product) and the nonionic surfactant are made to flow by the rotational force of the lower blade, and at the same time, the shearing force of the upper blade. By stirring and mixing the raw material and the nonionic surfactant, the nonionic surfactant can be attached to the raw material.

Further, by reducing the pressure inside the mixer and heating it, the raw material to which the nonionic surfactant is attached in the mixer can be dried. When the nonionic surfactant is attached by stirring and mixing, the adhesion step and the drying step can be performed at the same time by reducing the pressure and heating the inside of the mixer. Further, after the adhesion step is carried out for a certain period of time, the inside of the mixer is depressurized and heated, so that the drying step can be performed after the adhesion step.

The peripheral speed of the lower blade when carrying out the adhesion step and the drying step is preferably 10 m / s or more and 100 m / s or less, and more preferably 20 m / s or more and 80 m / s or less. On the other hand, the rotation speed of the upper blade may be coaxial with the lower blade and may be the same circumferential speed. When the peripheral speed can be changed with the lower blade on two axes or the like, the peripheral speed can be changed within the range of the peripheral speed of the lower blade. The implementation time of the adhesion step is preferably 3 minutes or more and 30 minutes or less, and more preferably 5 minutes or more and 20 minutes or less. The implementation time of the drying step is preferably 3 minutes or more and 30 minutes or less, and more preferably 5 minutes or more and 20 minutes or less. When the adhesion step and the drying step are performed at the same time, the implementation time is preferably 3 minutes or more and 30 minutes or less, and more preferably 5 minutes or more and 20 minutes or less.

The shearing force and the like can be adjusted by appropriately changing the stirring blade between the crushing step and the adhesion step.

An example of a mixer having stirring blades installed in the upper and lower stages includes a Henschel type mixer. In particular, FM mixers, CP mixers, cyclomix (R) CLX high-speed shear type mixers manufactured by Nippon Coke Industries, etc. are preferable. Among these, an FM mixer manufactured by Nippon Coke Industries Co., Ltd., which can perform shearing and mixing more sufficiently, is preferable.

Another example of an apparatus capable of performing the three steps of crushing, adhering, and drying raw materials includes a continuous mixing and stirring device. Such an apparatus can be used in the case of continuously producing synthetic pulp. As an example of a continuous device, a mixing stirring blade having an input port and an discharging port for mixing the contents from the input port to the discharging port, and a return blade for promoting crushing by the mixing stirring blade. A device having and is mentioned. A specific example is the equipment of the Mazeray series of Kirikawa Bussan Co., Ltd.

As another example of the continuous type device, it has an input port and an discharge port, a mixing stirring blade for mixing the contents from the input port to the discharge port, and the contents are crushed by rotating at high speed. Examples thereof include a device having a crushing blade and a crushing blade. A specific example is the Pam Apex Mixer of Pacific Kiko Co., Ltd.

In any type of continuous device, stirring / mixing and crushing can be performed at the same time. Therefore, by simultaneously charging the water-containing sheet and the nonionic surfactant from the charging port, the crushing process can be performed. The bonding step can be performed at the same time. Further, by allowing hot air to pass through the inside of the apparatus, it is possible to perform the drying step at the same time as the crushing step and the attaching step.

The powdery synthetic pulp obtained by the production method of the present invention can be used for applications in which powdery synthetic pulp has been conventionally used. Specifically, the powdered synthetic pulp alone can be used as an additive as it is, or can be formed into a sheet and used as a single sheet. Further, it can be used as a mixture or mixed extract sheet of powdered synthetic pulp and natural pulp, organic fiber, inorganic fiber, inorganic powder and the like. Further, it can be used in the form of a laminated body of a single sheet or a mixed paper sheet and another sheet.

The use of the powdered synthetic pulp obtained by the production method of the present invention is not limited in any way, but more specifically, it can be used for the following uses.
(1) Make a sheet by itself to make heat-sealed paper used for manufacturing battery separators, molded boards, tea bag paper, sterilized paper, desiccant packaging bags, and the like.
(2) As an additive alone, it is used as a thickening additive such as a paint sagging preventive agent, a sealer, a sealant, a caulking material, and an adhesive.
(3) Mix with natural pulp such as wood pulp to make label paper, tissue paper, towel paper, wipe and other water resistant paper.
(4) Mix with other synthetic fibers to make synthetic paper or in-mold label paper.
(5) After mixing with crushed pulp or the like, the mat is formed into a water-absorbing sheet or a water-absorbing mat that absorbs water, oil, solvent, urine, and the like.
(6) Mix with other crushed fibers to make a dry binder for electric wire cable covering materials, insulating paper, book covers, etc.
(7) Use as a cement additive such as fiber cement.
(8) Use as a filter material such as a gas filter, a liquid filter, a mask, and ceramic paper.
(9) In addition, it is used as molded paperboard such as paper plates, wallpaper, cushion floor lining material, wall material reinforcing fiber, tile grout, filtration aid, etc.

Hereinafter, the present invention will be described in more detail with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

(Example 1)
Using commercially available synthetic pulp, a PVA-adhered water-containing sheet was prepared as follows.
100 g of a pulp-like product (manufactured by Mitsui Chemicals, Inc., registered trademark SWP, ESS-5) manufactured from polyethylene is added to 10 L of water and vigorously stirred with a pulper at room temperature for 30 seconds to obtain a slurry of synthetic pulp. rice field. This slurry was dehydrated and made by a 25 × 25 cm square sheet machine, and further dehydrated by a hand press to prepare a water-containing sheet having a water content of 50% by weight and an absolute dry weighing of 1500 g / m ² .

The polyvinyl alcohol (PVA) content of the obtained water-containing sheet was measured by a Fourier transform infrared spectrophotometer (FT-IR). Specifically, the water-containing sheet was formed into a film by hot pressing, the absorption spectrum was measured by FT-IR, and the amount of PVA adhered was determined from the obtained peak intensity near the wavelength of 3370 nm.
As a result, the PVA content of the water-containing sheet was 0.5% by mass.

When the wire mesh of the sheet / machine was visually confirmed, there was little adhesion of the sheet. Moreover, although the water-containing sheet was cut with a water cutter, no collapse was observed at the end of the water-containing sheet.

The water-containing sheet prepared above was used as a raw material PVA-adhered water-containing sheet, placed in a crushing / mixing dryer (FM 20C / I, FM mixer manufactured by Nippon Coke Industries, Ltd.), and crushed at a peripheral speed of 20 m / s for 4 minutes. Then, 1.0 g of polypropylene glycol having a molecular weight of 2000 (P-2000 manufactured by ADEKA) was added and mixed for 10 minutes. Further, the jacket was heated with warm water at 80 ° C. and dried with stirring under a reduced pressure of −80 KPa for 1 hour to obtain a powdery synthetic pulp in an absolutely dry state.

The stirring blade of the pulverizing mixer was changed as necessary. A0 / Z0 was used as the stirring blade.

When water at 20 ± 2 ° C. was dropped on the surface of the obtained powdery synthetic pulp, the water was immediately absorbed by the synthetic pulp. Further, powdery synthetic pulp was added to water at 20 ± 2 ° C. to a concentration of 10 g / L and gently stirred to obtain a uniform slurry. When the lumps were further separated from this slurry by an 8-cut screen, the amount was 10 ppm or less, and it was found that the slurry was in a good dispersed state.

(Example 2)
Using commercially available synthetic pulp, a PVA-adhered water-containing sheet was prepared as follows.
100 g of a pulp-like product (manufactured by Mitsui Chemicals, Inc., registered trademark SWP, ESS-5) manufactured from polyethylene is added to 10 L of water and vigorously stirred with a pulper at room temperature for 30 seconds to obtain a slurry of synthetic pulp. rice field. This slurry was dehydrated and made by a 25 × 25 cm square sheet machine, and further dehydrated by a hand press to prepare a water-containing sheet having a water content of 50% by weight and an absolute dry weighing of 1500 g / m ² . When the PVA content of the obtained water-containing sheet was measured by the above-mentioned method, it was 0.5% by mass.

When the wire mesh of the sheet / machine was visually confirmed, there was little adhesion of the sheet. Moreover, although the water-containing sheet was cut with a water cutter, no collapse was observed at the end of the water-containing sheet.

100 g of a pulp-like product (manufactured by Mitsui Chemicals, Inc., registered trademark SWP, ESS-5) manufactured from polyethylene is crushed, and 100 g of polypropylene glycol (P-2000 manufactured by Adeka Corporation) having a molecular weight of 2000 is preliminarily added. Mixing gave a polypropylene glycol mixture. 2.0 g of the obtained mixture and the PVA-adhered water-impregnated sheet as a raw material prepared above were put into a continuous pulverizing / mixing / drying machine (manufactured by Nippon Coke Industries, continuous FM mixer FM-C type) in the apparatus. The water-containing sheet was crushed, stirred and mixed with the polypropylene glycol mixture, and dried continuously while passing hot air at 90 ° C. to obtain a powdery synthetic pulp in an absolutely dry state.

When water at 20 ± 2 ° C. was dropped on the surface of the obtained powdery synthetic pulp, the water was immediately absorbed by the synthetic pulp. Further, powdery synthetic pulp was added to water at 20 ± 2 ° C. to a concentration of 10 g / L and gently stirred to obtain a uniform slurry. When the lumps were further separated from this slurry by an 8-cut screen, the amount was 10 ppm or less, and it was found that the slurry was in a good dispersed state.

(Example 3)
Using commercially available synthetic pulp, a PVA-adhered water-containing sheet was prepared as follows.
100 g of a pulp-like product (manufactured by Mitsui Chemicals, Inc., registered trademark SWP, ESS-5) manufactured from polyethylene is added to 10 L of water and vigorously stirred with a pulper at room temperature for 30 seconds to obtain a slurry of synthetic pulp. rice field. This slurry was dehydrated and made by a 25 × 25 cm square sheet machine, and further dehydrated by a hand press to prepare a water-containing sheet having a water content of 50% by weight and an absolute dry weighing of 1500 g / m ² . When the PVA content of the obtained water-containing sheet was measured by the above-mentioned method, it was 0.5% by mass.

When the wire mesh of the sheet / machine was visually confirmed, there was little sheet adhesion. Moreover, although the water-containing sheet was cut with a water cutter, no collapse was observed at the end of the water-containing sheet.

1.0 g of the PVA-adhered water-containing sheet as a raw material and polypropylene glycol (P-2000 manufactured by Adeca Co., Ltd.) having a molecular weight of 2000 prepared above are continuously pulverized and mixed and dried (Mazeray KB3200 manufactured by Kirikawa Bussan). The water-containing sheet was crushed, polypropylene glycol was attached, and dried continuously while allowing hot air at 90 ° C. to pass through the apparatus to obtain a powdery synthetic pulp in an absolutely dry state.

When water at 20 ± 2 ° C. was dropped on the surface of the obtained powdery synthetic pulp, the water was immediately absorbed by the synthetic pulp. Further, powdery synthetic pulp was added to water at 20 ± 2 ° C. to a concentration of 10 g / L and gently stirred to obtain a uniform slurry. When the lumps were further separated from this slurry by an 8-cut screen, the amount was 10 ppm or less, and it was found that the slurry was in a good dispersed state.

(Example 4)
Using commercially available synthetic pulp, a PVA-adhered water-containing sheet was prepared as follows.
A water-containing sheet was produced in the same manner as in Example 1 except that SWP and ESS-2 (manufactured by Mitsui Chemicals, Inc.) were used instead of SWP and ESS-5 as the pulp-like material produced from polyethylene. When the PVA content of the obtained water-containing sheet was measured by the above-mentioned method, it was 0.5% by mass.

When the wire mesh of the sheet / machine was visually confirmed, there was little adhesion of the sheet. Moreover, although the water-containing sheet was cut with a water cutter, no collapse was observed at the end of the water-containing sheet.

Next, the water-containing sheet prepared above was used as a PVA-adhered water-containing sheet as a raw material, and a powdery synthetic pulp in an absolutely dry state was obtained in the same manner as in Example 1.

When water at 20 ± 2 ° C. was dropped on the surface of the obtained powdery synthetic pulp, the water was immediately absorbed by the synthetic pulp. Further, powdery synthetic pulp was added to water at 20 ± 2 ° C. to a concentration of 10 g / L and gently stirred to obtain a uniform slurry. When the lumps were further separated from this slurry by an 8-cut screen, the amount was 10 ppm or less, and it was found that the slurry was in a good dispersed state.

(Comparative Example 1)
A powdery synthetic pulp was obtained by the method described in Example 1 of JP-A-61-209450, which is a conventional technique. Specifically, it is as follows.
100 g of a pulp-like substance (manufactured by Mitsui Chemical Industries, Ltd., registered trademark SWP, ESS-5) manufactured from polyethylene is added to 10 L of water, and polypropylene glycol (reagent manufactured by Wako Pure Chemical Industries, Ltd.) having a molecular weight of 2000 is added. .0 g was added to make a mixture. The obtained mixture was put into a household mixer in several portions and stirred vigorously at room temperature for 30 seconds to obtain a slurry of synthetic pulp.

The obtained slurry was dehydrated and machined using a 25 × 25 cm square sheet machine, and further dehydrated by a hand press to prepare a water-containing sheet having a water content of 50% by weight and an absolute dry weighing of 1500 g / m ² . When the PVA content of the water-containing sheet was measured by the above-mentioned method, it was 0.5% by mass.

The water-containing sheet was dried at 50 ° C. for 8 hours with a circulation type dryer to prepare a dry sheet in an absolutely dry state. This dry sheet was crushed by a hammer mill type crusher to obtain a powdery synthetic pulp in an absolutely dry state.

When the wire mesh of the sheet / machine was visually checked, many sheets were found to adhere. Moreover, when the water-containing sheet was cut with a water cutter, collapse was observed at the end of the water-containing sheet.

According to the methods of Examples 1 to 4, a PVA-adhered water-containing sheet having a PVA content of 0.1% by mass or more and 10% by mass or less with respect to the total mass of the pulp-like material is used as a raw material to form a sheet. It was possible to produce powdered synthetic pulp without performing the above procedure. For this reason, it was possible to avoid problems such as adhesion of the sheet to the equipment during dehydration papermaking and collapse of the sheet edge during sheet cutting. In addition, the obtained powdery synthetic pulp was excellent in infiltration.

On the other hand, polypropylene glycol is attached to a pulp-like material having a PVA content of 0.1% by mass or more and 10% by mass or less, and the sheet is dehydrated and processed into a sheet to obtain a water-containing sheet. In Comparative Example 1 which was dried and crushed, a sheet adhered to the wire mesh used for dehydration papermaking. Further, when the obtained water-containing sheet was cut, the edge of the sheet was found to collapse. It is considered that this is because the method of Comparative Example 1 reduced the cohesive force of the pulp-like material. Therefore, the manufacturing method of Comparative Example 1 was a method having low work efficiency and yield.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for efficiently producing powdered synthetic pulp having infiltration property even when dried. This method is expected to contribute to the further spread of powdered synthetic pulp.

Claims (4)

A method for producing powdered synthetic pulp,
A water-containing sheet composed of a pulp-like material containing polyvinyl alcohol and a thermoplastic resin other than polyvinyl alcohol, and the content of the polyvinyl alcohol is 0.1% by mass or more and 10% by mass or less with respect to the total mass of the pulp-like material. And the process of providing raw material
A pulverization step of pulverizing the raw material under the condition that the water content is 400 parts by mass or less with respect to 100 parts by mass of the pulp-like material.
An attachment step of attaching a nonionic surfactant to the raw material, and
It includes a drying step of drying the raw material to which the nonionic surfactant is attached.
Before the drying step or at the same time as the drying step, the adhesion step is performed using the nonionic surfactant of 0.1% by mass or more and 10% by mass or less with respect to the total mass of the pulp-like material of the raw material. Carry out ,
The nonionic surfactant is polypropylene glycol having a weight average molecular weight of 200 or more and 10,000 or less.
A method for producing powdered synthetic pulp. The method for producing powdered synthetic pulp according to claim 1, wherein the thermoplastic resin is a crystalline polyolefin. The method for producing powdered synthetic pulp according to claim 1 or 2 , wherein at least the crushing step is carried out with a mixer having stirring blades installed in two upper and lower stages of the lower blade and the upper blade in a stirring container. The method for producing powdered synthetic pulp according to claim 1 or 2 , wherein at least the crushing step and the drying step are carried out in a continuous apparatus.