JP2015196918A - Base paper for mold press molding processing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base paper for mold press molding processing excellent in mold press molding property and capable of manufacturing a molded body excellent in mechanical physical properties such as strength and elastic modulus.SOLUTION: The base paper for mold press molding processing contains a fine cellulose fiber having an average fiber width of 2 to 1000 nm and density of 0.01 to 0.9 g/cm.

Description

  The present invention relates to a base paper to be die-molded.

As a method for producing a molded body made of paper such as a packaging container, a method of press-molding a base paper composed of general pulp with a pair of concave and convex molds under heating (hereinafter referred to as “mold press molding”). It has been known. This method of producing a molded product has the advantage of high productivity. However, unlike resin and metal, paper has poor stretchability and stretchability and has low mold press moldability, which may cause molding failure. It was. For example, if you try to make a molded body with a certain depth, the base paper cannot withstand stretching during molding, breaks, cracks or distortion occurs on the surface of the molded body, and irregularities occur in the folded wrinkles There was also. For this reason, in the conventional press molding of base paper, only a molded body having a very small depth such as a paper plate or the like was obtained. Moreover, the obtained molded body was not high in mechanical properties such as strength and elastic modulus.
In addition, as a method for producing a paper molded body, a method in which a base paper containing microfibrillated fibers is press-molded is also known (Patent Document 1).

JP 2003-201695 A

However, when the present inventors confirmed about the method of patent document 1, it was confirmed that press formability is inferior depending on the papermaking product.
An object of the present invention is to provide a mold press molding base paper that is excellent in mold press moldability and capable of producing a molded article having excellent mechanical properties such as strength and elastic modulus.

The present invention has the following aspects.
[1] The mold press molding base paper of the present invention contains fine cellulose fibers having an average fiber width of 2 to 1000 nm and a density of 0.01 to 0.9 g / cm ³ .
[2] It is more preferable that the base paper for mold press molding processing according to the present invention has an aspect ratio of fine cellulose fibers of 20 to 10,000.

  The base paper for mold press molding processing of the present invention is excellent in mold press moldability, and can produce a molded body excellent in mechanical properties such as strength and elastic modulus.

Hereinafter, the base paper for die press molding processing of the present invention will be described in detail.
In the present specification, a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

<Fine cellulose fiber>
The base paper for die press molding processing of the present invention (hereinafter referred to as “base paper”) contains fine cellulose fibers. When the base paper contains fine cellulose fibers, the density increases and mechanical properties such as strength and elastic modulus are improved.
The fine cellulose fibers are cellulose fibers or rod-like particles having a type I crystal structure that is much finer and shorter than pulp fibers usually used in papermaking applications.
The fact that the fine cellulose fiber has a type I crystal structure is that 2θ = 14 to 17 ° in a diffraction profile obtained from a wide-angle X-ray diffraction photograph using CuKα (λ = 1.5418４) monochromatized with graphite. It can be identified by having typical peaks in the vicinity and two positions near 2θ = 22 to 23 °.
The degree of crystallinity of fine cellulose fibers determined by the X-ray diffraction method is preferably 60% or more, more preferably 65% or more, and further preferably 70% or more. If the degree of crystallinity is not less than the lower limit, further excellent performance can be expected in terms of heat resistance and low linear thermal expansion. The degree of crystallinity can be obtained by measuring an X-ray diffraction profile and using a conventional method (Segal et al., Textile Research Journal, 29, 786, 1959).

(Fiber width)
The fine cellulose fiber is cellulose having an average fiber width of 2 to 1000 nm determined by observation with an electron microscope. The average fiber width of the fine cellulose fibers is preferably 2 to 1000 nm, more preferably 2 to 700 nm, and particularly preferably 2 to 500 nm. When the average fiber width of the fine cellulose fiber exceeds the upper limit, it becomes a cellulose fiber that is not different from the non-fine cellulose fiber, and it is difficult to obtain characteristics (high strength, high rigidity, high dimensional stability) as the fine cellulose fiber. become. If the average fiber width of the fine cellulose fibers is less than the lower limit value, the cellulose molecules are dissolved in the dispersion medium, so that characteristics (high strength, high rigidity, high dimensional stability) as fine cellulose fibers can be obtained. It becomes difficult.

Measurement of the average fiber width by observation with an electron microscope of fine cellulose fibers is performed as follows. A slurry containing fine cellulose fibers is prepared, and the slurry is cast on a carbon film-coated grid that has been subjected to a hydrophilization treatment to obtain a transmission electron microscope (TEM) observation sample. When wide fibers are included, a scanning electron microscope (SEM) image of the surface cast on glass may be observed. Observation by an electron microscope image is performed at any magnification of 1000 times, 5000 times, 10000 times, 20000 times, 50000 times or 100,000 times depending on the width of the constituent fibers. However, the sample, observation conditions, and magnification are adjusted to satisfy the following conditions.
(1) One straight line X is drawn at an arbitrary location in the observation image, and 20 or more fibers intersect the straight line X.
(2) A straight line Y perpendicularly intersecting the straight line X is drawn in the same image, and 20 or more fibers intersect the straight line Y.
For the electron microscope observation image as described above, the width (minor axis of the fiber) of at least 20 fibers (that is, at least 40 in total) is read for each of the fibers intersecting with the straight line X and the fibers intersecting with the straight line Y. . In this way, at least three or more sets of electron microscope images as described above are observed, and the fiber width of at least 40 × 3 sets (that is, at least 120 sets) is read. The fiber widths thus read are averaged to obtain the average fiber width. This average fiber width is equal to the number average fiber width.

(Fiber length)
0.1-700 micrometers is preferable, as for the average fiber length of a fine cellulose fiber, it is more preferable that it is 0.5-700 micrometers, and it is further more preferable that it is 1-700 micrometers. If the average fiber length of the fine cellulose fibers is not less than the lower limit, the mold press moldability is higher, and if it is not more than the upper limit, the mechanical properties of the base paper are higher.
The average fiber length is determined by measuring the length-weighted average fiber length using a Kajaani fiber length measuring device (FS-200 type) manufactured by Kajaani Automation.
In addition, as the miniaturization progresses, fibers having a narrow width and a short length may not be measured with a Kajaani fiber length measuring instrument. Therefore, an optical microscope, a scanning microscope (SEM), and a transmission electron microscope (TEM) are appropriately selected according to the length of the fiber, and the fiber length is observed and measured. The fiber length is measured by selecting 20 or more fibers from the obtained photograph.

(aspect ratio)
In the fine cellulose fiber, the aspect ratio obtained from (average fiber length / average fiber width) is preferably 20 to 10000, more preferably 50 to 5000, and more preferably 100 to 2000. If the aspect ratio of the fine cellulose fiber is equal to or higher than the lower limit, the mold press moldability is higher, and if the aspect ratio is lower than the upper limit, the mechanical properties of the base paper are higher.

(Anionic group)
The fine cellulose fiber may have an anion group and a negative surface charge.
When the fine cellulose fiber has an anionic group, its content is preferably 0.1 to 2.0 mmol / g, more preferably 0.1 to 1.5 mmol / g, 0.2 to More preferably, it is 1.2 mmol / g. If content of an anionic group is the said range, the hydration property of a fine cellulose fiber will not become high too much, and the viscosity at the time of slurrying will become low. If the content of the anionic group exceeds the upper limit, the hydration property becomes too high and the fine cellulose fibers may be dissolved.
Note that cellulose has a small amount (specifically, less than 0.1 mmol / g) of carboxy groups even without a treatment for introducing carboxy groups.

Examples of the anionic group include a carboxy group, a phosphoric acid group, and a sulfonic acid group.
The content of the anionic group is determined using a method of “Test Method T237 cm-08 (2008): Carboxyl Content of pull” of TAPPI, USA. In order to make it possible to measure the content of anionic groups over a wider range, among the test solutions used in the test method, sodium bicarbonate (NaHCO ₃ ) / sodium chloride (NaCl) = 0.84 g / 5.85 g was distilled water. According to TAPPI T237 cm-08 (2008), except that the test solution dissolved and diluted in 1000 ml was changed to 1.60 g of sodium hydroxide so that the concentration of the test solution was substantially 4-fold. Moreover, when an anion group is introduced, the difference in the measured value in the cellulose fiber before and after the introduction of the anion group is regarded as a substantial anion group content. In addition, the absolutely dry cellulose fiber used as a measurement sample is one obtained by freeze-drying in order to avoid alteration of cellulose that may occur due to heating during heat drying.
Since the anion group content measurement method is a measurement method for a monovalent anion group (carboxy group), when the anion group to be quantified is multivalent, it is obtained as the monovalent anion group content. A value obtained by dividing the obtained value by the acid number is defined as an anion group content.

(Method for producing fine cellulose fiber)
As a raw material for fine cellulose fibers (hereinafter sometimes referred to as “cellulose raw material”), a normal pulp raw material such as wood can be used. Specific pulp raw materials include bleached or unbleached sulfite pulp obtained from conifers or hardwoods, kraft pulp, groundwood pulp, explosive pulp, dissolved pulp, thermomechanical pulp (TMP), chemical thermomechanical pulp (CTMP), etc. One selected or a mixture of two or more can be used. Moreover, when the molded object produced from this base paper is used for uses other than foodstuffs, recycled paper recycled pulps, such as a deinked pulp (DIP), may be used as a pulp.
In addition, as raw materials for fine cellulose fibers, non-wood fibers such as hemp, cotton-based pulp such as cotton linter and cotton lint, hemp, straw, bamboo, kenaf, bagasse, shiogusa, esparto, persimmon, three bases, crust, ramie, etc. Non-wood pulp may be used. In addition, microorganism-produced cellulose, valonia cellulose, squirt cellulose and the like can be used. Among these, wood-based paper pulp and non-wood-based pulp are preferable in terms of easy availability.

Examples of the method for producing fine cellulose include a method in which pulp fibers are beaten and a mechanical external force is applied to the pulp fibers to fibrillate a part of the cell walls of the fibers. In this case, it is necessary to strengthen beating. As the degree of beating, for example, in the case of chemical pulp, the freeness (Tappi T-227 Canadian standard type) is preferably 100 ml or less, in the case of mechanical pulp, 70 ml or less, and in the case of waste paper pulp, it is preferably 50 ml or less. A beater, a conical refiner, a drum refiner, a disc refiner, or the like is used for beating the pulp fiber.
As a method for producing fine cellulose fibers having a finer fiber width, there is a method in which an aqueous suspension of cellulose fibers is passed through a small-diameter orifice at a high speed with a pressure difference of at least 3000 psi. For example, a method of treating an aqueous suspension of cellulose fibers with a high-pressure homogenizer (high-pressure homogenizer) (see Japanese Patent Publication Nos. 60-19921 and 63-44763) can be mentioned.
Moreover, as a manufacturing method of a fine cellulose fiber, the method (refer Unexamined-Japanese-Patent No. 4-18186) which processes a cellulose fiber aqueous suspension lightly with a sand mill is mentioned.
Furthermore, there is a wet pulverization method in which the pulverization is performed by a shearing action and an impact action that occur between the pulverization media (beads or balls) of the vibration mill pulverizer and between the pulverization container walls. As a pulverizer, a circular vibration mill, a rotational vibration mill, a centrifugal mill, or the like can be used as a vibration mill pulverizer.

In order to obtain fine cellulose fibers, a method of mechanically pulverizing the cellulose fiber raw material after chemical treatment may be applied.
The chemical treatment is at least one of the following (a) to (e).
(A) Treatment with a carboxylic acid compound (b) Treatment with an oxo acid containing a phosphorus atom or a salt thereof (c) Treatment with ozone (d) Treatment with an enzyme (e) 2,2,6,6-tetramethylpiperidi Treatment with Nooxy Radical (hereinafter referred to as “TEMPO”) The cellulose fiber raw material can be efficiently pulverized by the chemical treatment.

[Treatment with carboxylic acid compound]
In the treatment with the carboxylic acid compound, the hydroxy group of the cellulose molecule and the carboxylic acid compound undergo a dehydration reaction to form a polar group (—COO ⁻ ). Thereby, the bond strength between the cellulose fibers is weakened, and the defibration property is improved.
Examples of the method for treating the cellulose raw material with the carboxylic acid compound include a method of mixing the gasified carboxylic acid compound with the cellulose raw material, and a method of adding the carboxylic acid compound to the dispersion of the cellulose raw material. Among these, a method of mixing a gasified carboxylic acid compound with a cellulose raw material is preferable because the process is simple and the efficiency of introducing a carboxy group is high. Examples of the method for gasifying the carboxylic acid compound include a method for heating the carboxylic acid compound.

The carboxylic acid compound used in this treatment is at least one selected from the group consisting of a compound having two carboxy groups, an acid anhydride of a compound having two carboxy groups, and derivatives thereof. Of the compounds having two carboxy groups, compounds having two carboxy groups (dicarboxylic acid compounds) are preferred.
The compounds having two carboxy groups include propanedioic acid (malonic acid), butanedioic acid (succinic acid), pentanedioic acid (glutaric acid), hexanedioic acid (adipic acid), 2-methylpropanedioic acid, 2 -Methylbutanedioic acid, 2-methylpentanedioic acid, 1,2-cyclohexanedicarboxylic acid, 2-butenedioic acid (maleic acid, fumaric acid), 2-pentenedioic acid, 2,4-hexadienedioic acid, 2-methyl 2-butenedioic acid, 2-methyl-2-pentenedioic acid, 2-methylidenebutanedioic acid (itaconic acid), benzene-1,2-dicarboxylic acid (phthalic acid), benzene-1,3-dicarboxylic acid (isophthalic acid) ), Benzene-1,4-dicarboxylic acid (terephthalic acid), ethanedioic acid (oxalic acid), and the like.
Acid anhydrides of compounds having two carboxy groups include maleic anhydride, succinic anhydride, phthalic anhydride, glutaric anhydride, adipic anhydride, itaconic anhydride, pyromellitic anhydride, 1,2-cyclohexanedicarboxylic anhydride Examples thereof include acid anhydrides of dicarboxylic acid compounds such as acids and compounds containing a plurality of carboxy groups.
The acid anhydride derivative of the compound having two carboxy groups includes at least a part of the acid anhydride of the compound having a carboxy group, such as dimethylmaleic anhydride, diethylmaleic anhydride, and diphenylmaleic anhydride. The hydrogen atom is substituted with a substituent (for example, an alkyl group, a phenyl group, etc.).
Of these, maleic anhydride, succinic anhydride, and phthalic anhydride are preferred because they are industrially applicable and easily gasified.

  The mass ratio of the carboxylic acid compound to the cellulose raw material is preferably 0.1 to 500 parts by mass, and more preferably 10 to 200 parts by mass with respect to 100 parts by mass of the cellulose raw material. . If the ratio of a carboxylic acid type compound is more than the said lower limit, the yield of a fine cellulose fiber can be improved more. However, even if the upper limit is exceeded, the effect of improving the yield reaches its peak, and the carboxylic acid compound is merely used in vain.

  Although it does not specifically limit as an apparatus used in this process, For example, the uniaxial mixer which has a heating reaction container and a rotary heating reaction container which have a stirring blade, a pressure container and a rotary pressure container which have a heating jacket, a heating jacket, and A kneading apparatus having a heating device such as a twin screw mixer or a twin screw extruder, a multi-screw kneading extruder, a pressure kneader, or a double arm kneader may be used.

The treatment temperature is preferably 250 ° C. or less from the viewpoint of the thermal decomposition temperature of cellulose.
Furthermore, when water is contained in the treatment, the temperature is preferably 80 to 200 ° C, more preferably 100 to 170 ° C.

  In this treatment, a catalyst can be used as necessary. As the catalyst, it is preferable to use a basic catalyst such as pyridine, triethylamine, sodium hydroxide or sodium acetate, or an acidic catalyst such as acetic acid, sulfuric acid or perchloric acid.

After the treatment with the carboxylic acid compound, the cellulose dispersion obtained by the treatment is preferably subjected to an alkali treatment with an alkali solution.
Although it does not specifically limit as a method of an alkali treatment, For example, the method of immersing the processed cellulose in an alkaline solution is mentioned.
The alkali compound contained in the alkali solution may be an inorganic alkali compound or an organic alkali compound. Inorganic alkali compounds include alkali metal hydroxides or alkaline earth metal hydroxides, alkali metal carbonates or alkaline earth metal carbonates, alkali metal phosphates or alkaline earth metal phosphates Salt. Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide, and examples of the alkaline earth metal hydroxide include calcium hydroxide.
Examples of the alkali metal carbonate include lithium carbonate, lithium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, sodium carbonate, and sodium hydrogen carbonate. Examples of the alkaline earth metal carbonate include calcium carbonate.
Examples of the alkali metal phosphate include lithium phosphate, potassium phosphate, trisodium phosphate, and disodium hydrogen phosphate. Examples of alkaline earth metal phosphates include calcium phosphate and calcium hydrogen phosphate.
Examples of the organic alkali compounds include ammonia, aliphatic amines, aromatic amines, aliphatic ammoniums, aromatic ammoniums, heterocyclic compounds and their hydroxides, carbonates, and phosphates.
For example, ammonia, hydrazine, methylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, butylamine, diaminoethane, diaminopropane, diaminobutane, diaminopentane, diaminohexane, cyclohexylamine, aniline, tetramethylammonium hydroxide, Tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, benzyltrimethylammonium hydroxide, pyridine, N, N-dimethyl-4-aminopyridine, ammonium carbonate, ammonium hydrogen carbonate, diammonium hydrogen phosphate, etc. Can be mentioned.
The said alkali compound may be single 1 type, and may combine 2 or more types.

The solvent in the alkaline solution may be either water or an organic solvent, but a polar solvent (polar organic solvent such as water or alcohol) is preferred, and an aqueous solvent containing at least water is more preferred.
Among alkaline solutions, a sodium hydroxide aqueous solution, a potassium hydroxide aqueous solution and an ammonia aqueous solution are particularly preferred because of their high versatility.

  The pH at 25 ° C. of the alkaline solution in which cellulose is immersed is preferably 9 or more, more preferably 10 or more, and even more preferably 11-14. If the pH of the alkaline solution is at least the lower limit, the yield of fine cellulose fibers will be higher. However, when pH exceeds 14, the handleability of an alkaline solution will fall.

[Treatment with oxo acid containing phosphorus atom or salt thereof]
In the treatment with an oxo acid containing a phosphorus atom (hereinafter referred to as “phosphoro oxo acid”) or a salt thereof, a hydroxy group of the cellulose molecule and a phosphorus oxo acid having at least (HPO ₄ ) ^{2 —} or a salt thereof undergo a dehydration reaction. Thus, a polar group (—O—PO ₃ ²⁻ ) is formed as shown in the following reaction formula (A). Thereby, the bond strength between the cellulose fibers is weakened, and the defibration property is improved.
—OH + HPO ₄ ²⁻ → —O—PO ₃ ²⁻ + H ₂ O (A)

Examples of the phosphorus oxo acid include phosphoric acid, metaphosphoric acid, polyphosphoric acid and the like.
Examples of the salt of phosphorus oxo acid include phosphoric acid, metaphosphoric acid, lithium salt of polyphosphoric acid, sodium salt, potassium salt, calcium salt, ammonium salt, and organic alkali salt.
Phosphooxo acids or salts thereof may be used alone or in combination of two or more.
Among these, phosphoric acid and / or sodium salt and potassium salt of phosphoric acid are preferable because they are easy to handle at low cost and increase the efficiency of introducing phosphoric acid groups.

  The mass proportion of the phosphorus oxo acid or salt thereof relative to the cellulose raw material is preferably 0.2 to 500 parts by mass, more preferably 1 to 400 parts by mass as the phosphorus element amount of the phosphorus oxo acid or salt thereof relative to 100 parts by mass of the cellulose raw material. 2 to 200 parts by mass is most preferable. If the ratio of the phosphorus oxoacid or its salt is more than the said lower limit, the yield of a fine cellulose fiber can be improved more. However, even if it exceeds the upper limit, the effect of improving the yield reaches its peak, and it is merely uselessly the phosphorus oxo acid or its salt.

  It is preferable that the heat processing temperature is 250 degrees C or less from the point of the thermal decomposition temperature of a cellulose. Moreover, it is preferable that the heat processing temperature is 100-170 degreeC from a viewpoint of suppressing hydrolysis of a cellulose. Furthermore, regarding the heating while water is contained in the system to which phosphorus oxo acid or a salt thereof is added during the heat treatment, it is preferably 130 ° C. or less, more preferably 110 ° C. or less to sufficiently remove water. It is good to dry. After that, it is preferable to heat-process at 100-170 degreeC. Further, when removing moisture, a vacuum dryer may be used.

  After the treatment with the phosphorus oxoacid or a salt thereof, an alkali treatment may be performed in the same manner as the treatment with the carboxylic acid compound.

[Treatment with ozone]
In the treatment with ozone, some hydroxyl groups of cellulose are replaced with carbonyl groups or carboxy groups. Thereby, the bond strength between the cellulose fibers is weakened, and the defibration property is improved.
Ozone can be generated by supplying an oxygen-containing gas such as air, oxygen gas, or oxygen-added air to a known ozone generator.

The treatment with ozone is performed by exposing the cellulose raw material to a closed space / atmosphere where ozone is present.
If the ozone concentration in the gas containing ozone is 250 g / m ³ or more, there is a risk of explosion, so it is necessary to be less than 250 g / m ³ . However, if the concentration is low, the amount of ozone used is increased, and therefore it is preferably 50 to 215 g / m ³ . If the ozone concentration is equal to or higher than the lower limit, the handling of ozone is easy, and the effect of improving the yield of fine cellulose fibers in the pulverization treatment is further increased.

  The amount of ozone added to the cellulose raw material is not particularly limited, but is preferably 5 to 30 parts by mass with respect to 100 parts by mass of the solid content of the cellulose raw material. If the amount of ozone added is equal to or more than the lower limit, the effect of improving the yield of fine fibrous cellulose in the pulverization process becomes higher. However, exceeding the upper limit causes a decrease in yield before and after the ozone treatment and a deterioration in dewaterability. In addition, in the pulverization treatment, the yield improvement effect of fine fibrous cellulose reaches its peak.

  The ozone treatment temperature is not particularly limited, and is appropriately adjusted within a range of 0 to 50 ° C. Further, the ozone treatment time is not particularly limited, and is appropriately adjusted within a range of 1 to 180 minutes.

In addition, you may give an additional oxidation process after performing ozone treatment to a cellulose raw material. Examples of the oxidizing agent used for the additional oxidation treatment include chlorine compounds such as chlorine dioxide and sodium chlorite.
Further, after the ozone treatment, an alkali treatment may be performed in the same manner as the treatment with the carboxylic acid compound.

[Enzyme treatment]
In the treatment with an enzyme, cellulose can be decomposed by the enzyme.
The cellulolytic enzyme used in the enzyme treatment is an enzyme collectively called cellulase having cellobiohydrolase activity, endoglucanase activity, and betaglucosidase activity.
The cellulolytic enzyme used in the enzyme treatment may be prepared by mixing various cellulolytic enzymes with appropriate amounts of enzymes having respective activities, but commercially available cellulase preparations may also be used. Many commercially available cellulase preparations have the above-mentioned various cellulase activities and also have hemicellulase activity.
Commercial cellulase preparations include Trichoderma, Acremonium, Aspergillus, Phanerocheet, Trametes, Humicola, and Humicola. There are cellulase preparations derived from the above. Commercially available products of such cellulase preparations are all trade names, for example, cellulosin T2 (manufactured by HIPI), mecerase (manufactured by Meiji Seika), Novozyme 188 (manufactured by Novozyme), multifect CX10L (manufactured by Genencor) ) And the like.

  In the enzyme treatment, in addition to cellulase, a hemicellulase-based enzyme may be used alone or as a mixture. Among hemicellulase-based enzymes, it is preferable to use xylanase which is an enzyme that degrades xylan, mannase that is an enzyme that degrades mannan, and arabanase that is an enzyme that degrades araban. In addition, pectinase, which is an enzyme that degrades pectin, can also be used as a hemicellulase-based enzyme.

The pH of the dispersion during the enzyme treatment is preferably maintained in a range where the activity of the enzyme used is high. For example, in the case of a commercially available enzyme derived from Trichoderma, the pH is preferably between 4-8.
Further, the temperature of the dispersion during the enzyme treatment is preferably maintained within a range in which the activity of the enzyme used is increased. For example, in the case of a commercially available enzyme derived from Trichoderma, the temperature is preferably 40 ° C to 60 ° C. If the temperature is less than the lower limit, the enzyme activity decreases and the treatment time becomes longer. If the temperature exceeds the upper limit, the enzyme may be deactivated.
The treatment time for the enzyme treatment is preferably in the range of 10 minutes to 24 hours. If it is less than 10 minutes, the effect of the enzyme treatment is hardly exhibited. If it exceeds 24 hours, the decomposition of the cellulose fiber is too advanced by the enzyme, and the average fiber length of the resulting fine fiber may be too short.

  It should be noted that when the enzyme remains active for a predetermined time or longer, the decomposition of cellulose proceeds excessively as described above. Therefore, when the predetermined enzyme treatment is completed, it is preferable to perform an enzyme reaction stop process. . The enzyme reaction is stopped by washing the enzyme-treated dispersion with water, removing the enzyme, adding sodium hydroxide to the enzyme-treated dispersion to a pH of about 12, and then adding the enzyme. Examples thereof include a method for inactivation and a method for inactivating the enzyme by raising the temperature of the dispersion treated with the enzyme to a temperature of 90 ° C.

[Processing by TEMPO]
In the treatment with TEMPO, the cellulose raw material is reacted with an oxidizing agent in the presence of TEMPO and an alkali halide to change a part of the hydroxyl groups of cellulose to carboxy groups. Thereby, the bond strength between the cellulose fibers is weakened, and the defibration property is improved.

The alkali halide used as an oxidation catalyst together with TEMPO is not particularly limited, and alkali iodide, alkali bromide, alkali chloride, alkali fluoride and the like can be appropriately selected and used.
The oxidizing agent is not particularly limited, and sodium hypochlorite, sodium chlorite, sodium hypobromite, sodium bromite and the like can be appropriately selected and used.

  Although the usage-amount of TEMPO and an alkali halide is not restrict | limited in particular, It is preferable that it is 0.1-15 mass parts with respect to 100 mass parts of solid content of a cellulose raw material, respectively. If the addition amount of TEMPO and an alkali halide is each more than the said lower limit, the yield improvement effect of the fine cellulose fiber in a grinding | pulverization process will become higher. However, when the upper limit is exceeded, the yield improvement effect of fine cellulose fibers in the pulverization process may reach a peak.

  The amount of the oxidizing agent used is not particularly limited, but is preferably 1 to 80 parts by mass with respect to 100 parts by mass of the solid content of the cellulose raw material.

  The pH of the dispersion when the dispersion containing the cellulose raw material is treated with TEMPO is appropriately adjusted according to the type of oxidizing agent used. The pH of the cellulose raw material dispersion is adjusted by appropriately adding a basic substance such as potassium hydroxide or ammonia or an acidic substance such as acetic acid or oxalic acid.

The treatment temperature for treating the cellulose raw material with TEMPO is preferably in the range of 20 to 100 ° C., and the treatment time is preferably 0.5 to 4 hours.
Moreover, in order to perform the process by TEMPO uniformly, it is preferable to process, stirring with various stirring apparatuses.

[Crushing process]
In the pulverization process, a fine processing apparatus is usually used. High-speed rotary defibrator, grinder (stone mill type grinder), high-pressure homogenizer and ultra-high pressure homogenizer, high-pressure collision type grinder, ball mill, bead mill, disk type refiner, conical refiner, twin-screw kneader, vibration A wet pulverizing apparatus such as a mill, a homomixer under high-speed rotation, an ultrasonic disperser, or a beater can be used as appropriate. These may be used alone, a plurality of the same devices may be used, or different types of devices may be combined. When combining different types of apparatuses, it is preferable to combine any two of a refiner, a high-pressure homogenizer, and a high-speed rotary defibrator.

<Density>
It base paper of the present invention, density of 0.01~0.9g / cm ^3, is preferably 0.05~0.8g / cm ^3, a 0.1~0.7g / cm ³ Is more preferable. When the density of the base paper is less than the lower limit value, mechanical properties such as strength and elastic modulus may be lowered, and when the upper limit value is exceeded, the die press moldability may be lowered.

(Density adjustment method)
Usually, when fine cellulose fibers are contained, the density of the base paper increases, but the base paper of the present invention has a slightly lower density as described above.
As a method of reducing the density while containing fine cellulose fibers, a method of adding one or more of a bulking agent and a foaming agent to an aqueous dispersion containing fine cellulose fibers, which is used as a raw material for base paper, A wet sheet made of fiber cellulose is replaced with an organic solvent (solvent replacement) and then dried.
As another method of reducing the density while containing fine cellulose fibers, in the production of the base paper described later, a method of reducing the press pressure (press linear pressure) in the press dewatering section, a calendar pressure (calendar linear pressure) in the finishing section ).
The density of the base paper can be adjusted by the average fiber width of the fine cellulose fibers, the average fiber length of the fine cellulose fibers, the aspect ratio of the fine cellulose fibers, and the content of the fine cellulose fibers relative to the total cellulose fibers. Specifically, as the average fiber width of the fine cellulose fibers is increased, the average fiber length of the fine cellulose fibers is increased, the aspect ratio of the fine cellulose fibers is decreased, and the content of fine cellulose fibers relative to the total cellulose fibers is decreased. The lower the density, the lower the density of the base paper. Preferred embodiments of the average fiber width of the fine cellulose fibers, the average fiber length of the fine cellulose fibers, the aspect ratio of the fine cellulose fibers, and the content of the fine cellulose fibers relative to the total cellulose fibers are as described above.

[Bulky agent]
Examples of bulking agents include agents that inhibit the binding between cellulose fibers, for example, ester compounds of polyhydric alcohols and fatty acids, polyoxyalkylene compounds of polyhydric alcohols and fatty acid ester compounds, fatty acid polyamidoamines, polyhydric alcohol surfactants, Examples thereof include oil-based nonionic surfactants.
In order to make the density of the base paper within the above range, the content of the bulking agent in the base paper is preferably 0.05 to 20% by weight, more preferably 0.1 to 15% by weight, More preferably, it is 10 mass%.

[Foaming agent]
As the foaming agent, a thermally expandable microcapsule in which a low boiling point solvent is enclosed in the microcapsule can be used. These capsules are particles having an average particle diameter of 10 to 30 μm that expands to a diameter of about 4 to 5 times and a volume of 50 to 100 times by heating for a short time at a relatively low temperature of 80 to 200 ° C.
Examples of the low boiling point solvent include volatile organic solvents such as isobutane, pentane, petroleum ether, hexane, low boiling point halogenated hydrocarbon, and methylsilane.
Examples of the microcapsules include thermoplastic resins obtained by polymerizing or copolymerizing monomers such as vinylidene chloride, acrylonitrile, and acrylate esters.
The foaming of the foaming agent is caused by the polymer softening when the polymer forming the microcapsule is heated above the softening point by passing through hot water or drying during base paper manufacture, and the vapor pressure of the solvent in the foaming agent is increased. It is caused by expansion due to the rise of the.
In order to make the density of the base paper within the above range, the content of the foaming agent in the base paper is preferably 1 to 30% by weight, more preferably 2 to 20% by weight, and 5 to 15% by weight. More preferably.

  The bulking agent and the foaming agent can be used alone or in combination.

[Solvent substitution]
Examples of the method for carrying out the solvent replacement include a method of impregnating a wet sheet of fine fiber cellulose with an organic solvent, or a method of applying an organic solvent to a wet sheet of fine fiber cellulose and performing suction dehydration. Examples of the organic solvent include alcohol, ketone, ether, ester, aromatic compound, hydrocarbon, cyclic hydrocarbon, and cyclic hydrocarbon derivative.
Examples of alcohol include methanol, ethanol, propanol, isopropanol, n-butanol, t-butanol, n-pentanol, n-hexanol, n-heptanol, n-octanol, 2-ethyl-1-hexanol, benzyl alcohol, phenol and the like Monohydric alcohols, 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,5-pentanediol, 1,6-hexanediol, triethylene Dihydric alcohols such as glycol, 1,2-hexanediol, 1,2-octanediol, dipropylene glycol methyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol monoe Glycol ethers such as ether, diethylene glycol monoethyl ether acetate, ethylene glycol monomethyl ether acetate, polyethylene glycol, polypropylene glycol and glycerin.
Ethers include diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol diethyl ether, ethylene glycol diethyl ether, ethylene glycol dimethyl ether, diethylene glycol isopropyl methyl ether and other glymes, 1,4-dioxane, tetrahydrofuran And anisole.
Examples of the ketone include acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, t-butyl methyl ketone, diisopropyl ketone, butyl isopropyl ketone, isobutyl isopropyl ketone, diisobutyl ketone, 3-methyl-2-pentanone, 4-methyl-2- Examples include pentanone, 3-methyl-2-hexanone, 5-methyl-3-heptanone, 2-decanone, 3-decanone, 4-decanone, and 5-decanone.
Esters include methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, butyl acetoacetate, amyl acetate, amyl acetoacetate, hexyl acetate, hexyl acetoacetate, heptyl acetate, aceto Heptyl acetate, octyl acetate, octyl acetoacetate, methyl propionate, ethyl propionate, ethyl 2-hydroxypropionate, methyl butyrate, ethyl butyrate, methyl valerate, ethyl valerate, methyl hexanoate, ethyl hexanoate, methyl heptanoate , Ethyl heptanoate, methyl octanoate, ethyl octanoate, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, butyl (meth) acrylate, oxalic acid Dimethyl, oxalic acid Ethyl, dimethyl malonate, diethyl malonate, dimethyl succinate, diethyl succinate, dimethyl maleate, fatty acid esters such as diethyl maleate, methyl benzoate, and aromatic esters such as ethyl benzoate.
Aromatic compounds include benzene, toluene, xylene, ethylbenzene and the like.
Examples of the hydrocarbon include n-hexane, n-heptane, and n-octane.
Examples of the cyclic hydrocarbon include cyclopentane, cyclohexane, and terpene.
Examples of the cyclic hydrocarbon derivative include cyclopentanol, cyclopentanone, cyclopentyl methyl ether, cyclohexanol, cyclohexanone, cyclohexanone dimethyl acetal, terpinolene, terpineol and the like.

  Two or more organic solvents may be mixed and used in combination. Moreover, when mixing and using it, the ratio of the organic solvent which occupies in a mixed solution becomes like this. Preferably it is 40 mass% or more, More preferably, it is 60 mass% or more, More preferably, it is 70 mass% or more. The upper limit of the ratio of the organic solvent is not particularly limited. Two or more organic solvents in the mixed solution may be used. Further, the organic solvent is preferably dissolved in water, but an organic solvent that does not dissolve in water may be emulsified and used as an emulsion.

<Thickness>
The thickness of the base paper is preferably 10 to 700 μm, more preferably 10 to 500 μm, and still more preferably 10 to 150 μm. When the thickness of the base paper is equal to or greater than the lower limit, sufficient mechanical properties can be obtained, and when the thickness is equal to or lower than the upper limit, dewaterability during base paper manufacture is increased, and productivity is increased.

<Basis weight>
Preferably the basis weight of the base paper is 10 to 300 g / ^{m 2,} and more preferably 10 to 200 g / ^{m 2.} If the basis weight of the base paper is equal to or higher than the lower limit value, sufficient mechanical properties can be obtained, and if it is equal to or lower than the upper limit value, dewaterability at the time of base paper manufacture increases and productivity increases.

<Manufacturing method of base paper>
A method for producing a base paper is a method in which an aqueous dispersion containing fine cellulose fibers is cast on a long net, a circular net, an inclined wire, etc., dehydrated, further squeezed and dehydrated by a press, and then dried (so-called papermaking method). Is mentioned.
In this specification, in order to avoid confusion, a press using a mold at the time of manufacturing a molded body is referred to as a “mold press” one by one, and a press of a pressing and dewatering unit in the paper making method is not attached one by one.

  The concentration of the aqueous dispersion containing fine cellulose fibers is preferably 5% by mass or less, more preferably 0.1 to 4.0% by mass, and 0.2 to 0.4% by mass. Further preferred. If the concentration of the aqueous dispersion containing fine cellulose fibers is not more than the above upper limit, casting can be easily performed.

A porous substrate is used as the wire during dehydration. As the porous substrate, a metal wire made of stainless steel, bronze or the like, or a plastic wire made of polyester, polyamide, polypropylene, polyvinylidene fluoride or the like can be used. Moreover, you may use membrane filters, such as a cellulose acetate base material, as a wire.
The opening of the wire is preferably 0.02 to 200 μm, more preferably 0.04 to 100 μm. If the mesh opening is equal to or greater than the lower limit, the dehydrating property is increased, and if the mesh is equal to or smaller than the upper limit, the yield of fine cellulose fibers on the wire is increased.

In the squeezing and dewatering section, usually, at least two roll nip presses are performed in the flow direction, and the present invention is no exception. The types of press include straight through press, reverse press, straight through press with suction pickup device, invar press with suction pickup device, twin bar press with suction pickup device, trinip press, tiger event press, tandem shoe press A publicly known format such as can be used. In the present invention, the first press is referred to as a first press, and the second and subsequent presses are referred to as a second press, a third press, and a fourth press.
In the present invention, in order to reduce the density of the base paper while containing fine cellulose fibers, the linear pressure of the first press is preferably 10 to 70 kN / m, and more preferably 15 to 60 kN / m. Preferably, it is 20-50 kN / m. This is because the linear pressure of the first press has a large influence on the density of the base paper compared to the linear pressure after the second press, and if the linear pressure of the first press is equal to or higher than the lower limit value, By reducing moisture unevenness in the width direction of the base paper, it becomes easy to obtain uniform mechanical properties, and if it is equal to or less than the upper limit value, it is not excessively compressed, and the density of the base paper is specified in the present invention. Easy to adjust.

  For drying, a publicly known drying apparatus such as a cylinder dryer, a Yankee dryer, a hot air dryer, or an infrared heater can be used.

Before drying or after drying, starch, polyvinyl alcohol, various surface sizing agents, pigments, and the like may be applied to the surface of the base paper by a coating method such as a size press or a gate roll.
If necessary, in order to impart water resistance to the surface of the base paper, as water-resistant paints, emulsions of waxes such as microcrystalline wax and paraffin wax, latexes such as SBR latex and polyvinylidene chloride latex, acrylic emulsion Synthetic resin emulsions such as self-emulsifying polyolefins and polyethylene copolymer resin emulsions may be applied. The coating apparatus for the water-resistant paint is not particularly limited, and a bar coater, an air knife coater, a roll coater, a blade coater, a gate roll, a size press and the like can be used.

The obtained base paper can be subjected to a surface finishing treatment using a calendar device.
The calender device may be a hard nip calender composed only of metal rolls or a soft nip calender composed of metal rolls and elastic rolls, but without excessively increasing the density of the base paper. It is preferable to select a soft nip calender in that the thickness in the width direction can be made uniform.
When a soft nip calender is selected, the calendar arrangement is preferably a two-stack two-stage one-nip.
The calendar linear pressure is preferably 5 to 40 kN / m, and more preferably 10 to 30 kN / m. If the calender linear pressure is equal to or higher than the lower limit value, uniform thickness in the width direction of the base paper can be easily obtained, and if it is equal to or lower than the upper limit value, the density of the base paper is determined in the present invention. It becomes easy to adjust to the specified range.

<Effect>
Since the base paper of the present invention described above contains fine cellulose fibers, mechanical properties such as tensile strength, tear strength, and elastic modulus are high. Moreover, dimensional stability is also high because the base paper contains fine cellulose fibers.
Usually, when fine cellulose fibers are contained, the density is increased, but the base paper of the present invention has a slightly lower density within the above range, so that the mechanical properties are enhanced, but the moldability is enhanced. For this reason, it is possible to suppress the occurrence of breakage, cracks, distortions, and irregularities in the folded wrinkles when the base paper is press-molded. Therefore, according to the base paper of the present invention, so-called deep drawing die press molding can be performed, a molded product having a depth can be produced, and the restriction on the shape of the molded product can be reduced.

<Method for producing molded body>
A molded body can be obtained by press-molding the base paper.
In mold press molding, a base sheet is usually punched into a predetermined shape before molding to form a molding sheet. The molded sheet is obtained by press molding the molding sheet. When the molded body has a curved surface, a streak-like cut may be formed in advance on the surface of the base paper.
Although it does not specifically limit as a metal mold press molding apparatus used by metal mold press molding, The metal metal mold | die provided with the male type | mold and female type | mold used for general metal mold press molding can be used.
In mold press molding, the metal mold for molding is usually heated from the viewpoint of improving moldability. Examples of the means for heating the metal mold for molding include an electric heater heating method, a steam heating method, a hot air heating method, and an oil circulation method. The electric heater heating method is preferable because the apparatus is simple.
The mold press molding temperature is preferably in the range of 100 to 200 ° C., more preferably in the range of 110 to 150 ° C., from the viewpoints of moldability and degradation of cellulose fibers. If the molding temperature is equal to or higher than the lower limit value, the base paper is sufficiently softened to improve the moldability, and if it is equal to or lower than the upper limit value, the cellulose fibers can be prevented from deteriorating.
The die press pressure is preferably in the range of 1 to 10 MPa (gauge pressure). If the pressing pressure is equal to or higher than the lower limit value, sufficient molding can be performed, and if the pressing pressure is equal to or lower than the upper limit value, it is possible to prevent the fibers from peeling and causing cracks and breaks.
The mold press molding time is preferably in the range of 2 to 10 seconds from the viewpoint of moldability and workability.
Before the die press molding, the water content of the base paper is preferably 10 to 20% by mass, more preferably 11 to 18% by mass, and even more preferably 12 to 15% by mass. It is especially preferable to set it to -14.5 mass%. If the moisture content of the base paper is less than or equal to the above upper limit value, the base paper can be prevented from being destroyed during press molding, and the mechanical properties (particularly rigidity) of the molded body can be prevented from being lowered. On the other hand, if the moisture content of the base paper is less than or equal to the above upper limit value, it is possible to prevent the fibers from being peeled during the die press molding process, and to prevent the appearance and mechanical properties of the molded body from being lowered. Moreover, the drying time of a molded object can be shortened and productivity can be improved.
As a humidity control method of the base paper, any method such as a method of spraying or coating water on the base paper or a method of spraying as water vapor can be applied. In addition, humidity control may be performed immediately before mold press molding, during base paper manufacture, when the base paper is wound on a roll, or after punching out the base paper.

  The molded body obtained by the above method is not only used as a container, such as a food packaging container such as a lunch box or a food tray, or an industrial product packaging container such as a CD case or electrical component case, but also an electrical product. It can also be used as a housing or a part of the above.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited to the following examples.
In the following examples, “%” means “% by mass”, and “part” means “part by mass”.
In the following examples, the average fiber width of fine cellulose fibers was measured by the method described in the above paragraph 0009, and the average fiber length was measured by the method described in the above paragraph 0010. Further, the aspect ratio was obtained from the formula of (average fiber length) / (average fiber width). The average fiber width and average fiber length (length-weighted average fiber length) of the non-fine cellulose fibers were determined by measurement using a Kajaani fiber length measuring instrument (FS-200 type) manufactured by Kajaani Automation. The aspect ratio of the non-fine cellulose fibers was determined from the formula (average fiber length) / (average fiber width).
Further, the basis weight of the obtained base paper for die press molding was measured according to JIS P8124, and the density was measured according to JIS P8118.

<Example 1>
<Fine cellulose fiber>
Water was added to a softwood bleached kraft pulp (manufactured by Oji F-Tex Co., Ltd., water 50%, Canadian standard freeness (CSF) 700 ml measured according to JIS P8121) to a concentration of 4%. Next, using a double disc refiner, beat the irregular CSF (plain mesh 80 mesh, according to JIS P8121 except that the amount of pulp collected is 0.3 g) to 250 ml, and the average fiber length to 0.68 mm. Got.
The obtained pulp slurry is diluted with water so that the solid content concentration is 0.5%, and treated with a rotary high-speed homogenizer (CLEAMIX 2.2S manufactured by M Technique Co., Ltd.) at 21500 rpm for 30 minutes to obtain cellulose fibers. Was defibrated.
The fiber width of the fine cellulose fiber thus obtained was 300 nm, the fiber length was 0.45 mm, and the aspect ratio was 1500.
<Preparation of base paper for mold press molding>
A wet sheet was prepared while decompressing the fine cellulose fibers obtained by the above method on a 500 mesh polyester mesh. The solid content of the wet sheet was about 10%. 240 parts of ethylene glycol-tert-butyl ether was applied to 100 parts of the wet sheet on the obtained wet sheet. Further, the pressure was reduced and suction dewatered to form a wet sheet containing water and an organic solvent. The solid content of the wet sheet was about 10%. Subsequently, the wet sheet was covered with filter paper, and dried with a cylinder roll at 120 ° C. for 10 minutes together with a 500 mesh polyester mesh.
The base paper for mold press molding thus obtained had a basis weight of 38.3 g / m ² and a density of 0.47 g / cm ³ .

<Comparative Example 1>
<Preparation of base paper for mold press molding>
A base paper for die press molding was prepared in the same manner as in Example 1, except that ethylene glycol-tert-butyl ether was not applied on the wet sheet.
The obtained base paper for press molding processing had a basis weight of 39.9 g / m ² and a density of 0.95 g / cm ³ .

<Comparative Example 2>
<Non-fine cellulose fiber>
Canadian standard freeness measured according to JIS P8121 with a disc refiner using softwood bleached kraft pulp (manufactured by Oji F-Tex Co., Ltd., water 50%, Canadian standard freeness (CSF) 700 ml measured according to JIS P8121) Beating until (CSF) reached 640 ml.
The thus obtained non-fine cellulose fiber had a fiber width of 20400 nm, a fiber length of 1.34 mm, and an aspect ratio of 66.
<Preparation of base paper for mold press molding>
From the non-fine cellulose fiber obtained by the above method, a base paper for mold press molding was prepared with an experimental hand-making machine.
The obtained base paper for press molding processing had a basis weight of 70.0 g / m ² and a density of 0.45 g / cm ³ .

<Evaluation>
The moldability and the strength of the molded body of the obtained base paper for mold press molding were evaluated by the following methods. The evaluation results are shown in Table 1.

(Evaluation of moldability)
A base sheet for mold press molding was punched into a predetermined shape to produce a molding sheet, and then humidity was adjusted at 40 ° C. and 90% RH using a constant temperature and humidity chamber. Using a test press molding machine (manufactured by Daiichi Koki Co., Ltd.) equipped with male and female concave and convex tray molding molds, the humidity-controlled molding sheet was molded by heating and pressing at 130 ° C. and 3.5 MPa. . As a result, a tray shape having a height of 4 cm, an opening portion having a substantially rectangular shape with a length of 18.6 cm and a width of 12.6 cm, a flange portion with a width of 0.7 cm, and a curved surface from the side wall to the bottom surface. A molded body was obtained.
The moldability at that time was visually evaluated as follows.
◯: Can be easily molded into a bowl shape, and the surface of the molded body is smooth.
X: Although it can be molded into a tray shape, there are large irregularities on the surface of the molded body, particularly on the folded wrinkles.

(Evaluation of molded body strength)
The strength of the molded body obtained at the time of the evaluation of the moldability was evaluated in three stages as follows by tactile sensation.
A: There is a very strong resistance when the molded body is twisted with both hands.
○: Strong resistance is felt when the molded body is twisted with both hands.
X: There is no sense of resistance when the molded body is twisted with both hands.

  From Table 1, the molded article of Example 1 using the mold press molding base paper of the present invention as a molding sheet is excellent in moldability and strength.

Claims (2)

A base paper for die press molding processing containing fine cellulose fibers having an average fiber width of 2 to 1000 nm and a density of 0.01 to 0.9 g / cm ³ .   The base paper for metal mold | die press molding processing of Claim 1 whose aspect-ratio of a fine cellulose fiber is 20-10000.