JP6257526B2 - Paper base - Google Patents

Description

  The present invention relates to a paper substrate containing oxidized pulp.

  Functional sheets with a functional agent added to a breathable sheet base material are deodorizing materials, fragrance materials, oil absorbing materials, water absorbing materials, masks, bedding (pillow covers, etc.), packaging materials, building materials (shoji paper, etc.) (Patent document 1, patent document 2).

  As the base material of these functional sheets, a synthetic resin base material or a paper base material is generally used. However, many synthetic resin base materials are not decomposed by microorganisms, are stable in air and water, and remain semipermanently, so that they are not suitable for landfill disposal. Moreover, since it becomes high temperature when burned, there are problems such as damaging the incinerator and generating toxic gas.

  For this reason, as interest in environmental problems increases, paper bases that are decomposed into microorganisms, dissolved or decomposed in air or water, and that do not generate toxic gas during combustion have been attracting attention.

JP 2001-172896 A JP 2002-266297 A

  The paper base material is an aggregate of pulp fibers and has air permeability, but further improvement in air permeability is required. By improving the air permeability of the paper substrate, for example, when the paper substrate is used as a shoji paper, there is an advantage that sufficient ventilation can be performed without opening the shoji window. In addition, in a three-layer structure mask composed of an outer layer, an inner layer, and a mouth layer, when a highly air-permeable paper base material is used as an outer layer for preventing the entry of large dust from the outside, breathing difficulty can be reduced. There are merits such as. In order to improve the air permeability of the paper base material without making a hole, a method of lowering the basis weight of the paper base material, in other words, a method of thinning the paper base material is common.

  However, when the basis weight of the paper base material is lowered in order to improve the air permeability of the paper base material, the strength and stiffness (rigidity) of the paper base material are usually reduced. For this reason, the shoji paper using the low base weight paper base material with improved air permeability usually has a problem that it is easy to tear and is difficult to be pasted because it is not broken. In addition, when a paper base material with reduced strength and stiffness is used for the outer layer of the mask, the outer layer can be easily torn and cannot prevent the entry of large dust, and the stiffness of the outer layer is insufficient. There arises a problem that it becomes difficult to maintain the shape.

  Therefore, an object of the present invention is to provide a paper base material having excellent strength and stiffness even if it is thin (that is, even if it has a low basis weight).

As a result of intensive studies, the present inventors have made the pulp constituting the paper base material contain a pulp that has been oxidized so as to have a carboxyl group in a specific range, compared with a case where no oxidized pulp is contained. It was found that the strength and stiffness of the paper substrate were improved. In addition, since the paper base material thus obtained has high strength and stiffness, even if it is thin (that is, even when the basis weight is low), it is difficult to break and easy to maintain its shape. It was found that there are advantages such as. That is, the present invention includes, but is not limited to, the following [1] to [6].
[1] A paper base containing oxidized pulp, wherein the amount of carboxyl groups of the oxidized pulp is 1.0 mmol / g to 2.0 mmol / g with respect to the absolutely dry mass of the oxidized pulp. Wood.
[2] The paper base material according to [1], wherein the content of the oxidized pulp is 10% by mass or more based on the absolute dry mass of all pulps constituting the paper base material.
[3] In the presence of a compound selected from the group consisting of (a1) an N-oxyl compound and (a2) bromide, iodide, or a mixture thereof, The paper base material according to [1] or [2], which is obtained by oxidation using an acid.
[4] The paper substrate according to any one of [1] to [3], wherein the basis weight of the paper substrate is 30 g / m ² or less.
[5] A deodorizing material comprising the paper base material according to any one of [1] to [4].
[6] A mask comprising the paper substrate according to any one of [1] to [4].

  According to the present invention, it is possible to provide a paper base material having excellent strength and stiffness even with a low basis weight.

  The present invention relates to a paper substrate containing oxidized pulp having a carboxyl group content of 1.0 mmol / g to 2.0 mmol / g with respect to the absolutely dry mass of oxidized pulp.

The reason why the paper base material of the present invention exhibits an excellent effect as compared with the conventional paper base material is presumed as follows:
By the oxidation reaction, the primary hydroxyl group at the 6-position of cellulose in the pulp is converted to a carboxyl group, and one oxygen atom is introduced. This increases the number of access points for hydrogen bonds between molecules and intramolecular positively-charged hydrogen, making the network structure between celluloses denser and exhibiting superior strength as a paper substrate. it is conceivable that.

<Manufacture of oxidized pulp>
In this invention, the quantity of the carboxyl group of oxidized pulp is 1.0 mmol / g-2.0 mmol / g with respect to the absolute dry mass of oxidized pulp. The method for producing oxidized pulp is not particularly limited, but as an example, the cellulosic material is selected from the group consisting of (a1) N-oxyl compound and (a2) bromide, iodide or a mixture thereof. (A3) A method of oxidizing using an oxidizing agent in the presence of

(1) Cellulose-based raw material The cellulose-based raw material used in the present invention is not particularly limited, and various wood-derived kraft pulp or sulfite pulp can be used. In addition, non-wood pulp derived from plants such as kenaf, hemp, rice, bacus, and bamboo can also be used. It is preferable to use bleached kraft pulp or bleached sulfite pulp having a whiteness (ISO 2470) of 80% or more.

(2) N-oxyl compound (a1)
An N-oxyl compound is a compound capable of generating a nitroxy radical. As the N-oxyl compound, any compound can be used as long as it promotes the target oxidation reaction. For example, the compound shown by the following general formula (Formula 1) is mentioned.

（式１中、Ｒ¹〜Ｒ⁴は同一又は異なる炭素数１〜４程度のアルキル基を示す。）

(In Formula 1, R ^{1 to} R ⁴ represent the same or different alkyl groups having about 1 to 4 carbon atoms.)

  Of the substances represented by Formula 1, 2,2,6,6-tetramethyl-1-piperidine-oxy radical (hereinafter referred to as TEMPO) is preferable. Further, the N-oxyl compound represented by any one of the following formulas 2 to 5, that is, the hydroxyl group of 4-hydroxy TEMPO was etherified with alcohol or esterified with carboxylic acid or sulfonic acid to impart moderate hydrophobicity. A 4-hydroxy TEMPO derivative or 4-acetamido TEMPO to which an amino group of 4-amino TEMPO is acetylated and imparted moderate hydrophobicity is preferable because it is inexpensive and can provide a uniform oxidized pulp.

（式２〜５中、Ｒは炭素数４以下の直鎖又は分岐状炭素鎖である。）

(In formulas 2 to 5, R is a linear or branched carbon chain having 4 or less carbon atoms.)

  Furthermore, an N-oxyl compound represented by the following formula 6, that is, an azaadamantane-type nitroxy radical, is preferable because it can efficiently oxidize a cellulose-based raw material in a short time and is less likely to break the cellulose chain.

（式６中、Ｒ₅及びＲ₆は、同一又は異なる水素又はＣ₁〜Ｃ₆の直鎖若しくは分岐鎖アルキル基を示す。）

(In Formula 6, R ₅ and R ₆ represent the same or different hydrogen or a C _{1 to} C ₆ linear or branched alkyl group.)

  The amount of the N-oxyl compound used is not particularly limited as long as it can promote a desired oxidation reaction. For example, 0.01 to 10 mmol is preferable, 0.01 to 1 mmol is more preferable, and 0.05 to 0.5 mmol is more preferable with respect to 1 g of the absolutely dry cellulosic material.

(3) Bromide or iodide (a2)
Bromide is a compound containing bromine, examples of which include alkali metal bromides that can dissociate and ionize in water. Further, an iodide is a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide used can be selected as long as the oxidation reaction can be promoted. The total amount of bromide and iodide is, for example, preferably from 0.1 to 100 mmol, more preferably from 0.1 to 10 mmol, and even more preferably from 0.5 to 5 mmol, based on 1 g of the cellulosic raw material.

(4) Oxidizing agent (a3)
As the oxidizing agent used in the oxidation of the cellulosic material, known ones can be used, for example, halogen, hypohalous acid, halous acid, perhalogen acid or salts thereof, halogen oxide, peroxide, etc. Can be used. Of these, sodium hypochlorite is preferable because it is inexpensive and has a low environmental impact. The appropriate amount of the oxidizing agent used varies depending on the type of cellulosic raw material used, but is preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, for example, with respect to 1 g of cellulosic raw material. 2.5 to 25 mmol is more preferable, and 5 to 20 mmol is most preferable.

(5) Oxidation reaction conditions This oxidation reaction proceeds efficiently even under relatively mild conditions. Therefore, the temperature during the oxidation reaction may be a room temperature of about 15 to 30 ° C. As the reaction proceeds, a carboxyl group is generated in the cellulose, so that the pH of the reaction solution is reduced. In order to advance the oxidation reaction efficiently, it is preferable to add an alkaline solution such as an aqueous sodium hydroxide solution to maintain the pH of the reaction solution at about 9 to 12, preferably about 10 to 11. The reaction medium is preferably water because it is easy to handle and hardly causes side reactions.

  The reaction time in the oxidation reaction can be appropriately set according to the degree of progress of oxidation, and is not particularly limited. For example, it is 0.5 to 6 hours, preferably 2 to 6 hours, and more preferably about 4 to 6 hours. The oxidation reaction may be performed in two stages. For example, oxidized pulp obtained by filtration after the completion of the first-stage reaction is oxidized again under the same or different reaction conditions, so that the cellulose is not subject to reaction inhibition by the salt produced as a by-product in the first-stage reaction. The carboxyl group can be efficiently introduced into the system material, and the oxidation of the cellulosic material can be promoted.

  The amount of carboxyl groups in the oxidized cellulose raw material is preferably 1.0 mmol / g to 2.0 mmol / g with respect to the absolute dry mass of the cellulose raw material. The amount of the carboxyl group can be adjusted by adjusting the oxidation reaction time, adjusting the oxidation reaction temperature, adjusting the pH during the oxidation reaction, adjusting the addition amount of the N-oxyl compound, bromide, iodide, or oxidizing agent.

(6) Others In the present invention, it is possible to carry a functional chemical on the oxidized pulp. There are no particular limitations on the type and carrying method of the functional chemical. As an example, as disclosed in WO 2010/095574, a method of supporting metal nanoparticles on oxidized pulp by adding a reducing agent after immersing oxidized pulp in a metal ion aqueous solution can be exemplified.

  Although oxidized pulp can be converted into nanofibers by defibration, in the present invention, it is possible to use oxidized pulp that has not been defibrated (that is, not converted into nanofibers). From the viewpoint of strength.

<Paper base material>
A paper base material is prepared using the obtained oxidized pulp. The paper base material is a material formed from a plant pulp such as wood pulp as a main component and formed into a sheet (papermaking). The paper base material of the present invention preferably contains 50% by mass or more, more preferably 70% by mass or more, and more preferably 90% by mass or more, of pulp-derived components with respect to the absolute dry mass of the paper base material. Including. You may form a sheet | seat only from the component derived from a pulp (namely, 100 mass%). Examples of materials other than pulp considered to be contained in the paper base material include fillers such as calcium carbonate, binders, yield improvers, paper strength improvers, and metal nanoparticles. Moreover, you may contain the fiber manufactured from the synthetic resin in the range which does not affect the problem with respect to an environment.

  The paper base material of the present invention preferably contains 10% by mass or more of oxidized pulp, more preferably 50% by mass or more, and still more preferably 90% with respect to the absolute dry mass of the total pulp constituting the paper base material. That's it. When the content of the oxidized pulp is 10% by mass or less, there is almost no effect of improving the strength and stiffness of the paper substrate.

  The paper substrate can be produced by a known papermaking technique. As the paper machine, a circular net type paper machine, a slanted short net type paper machine, a long net type paper machine, a twin wire type paper machine, or the like can be used. Moreover, according to the quality requested | required, it is preferable to adjust suitably the freeness of the pulp containing an oxidized pulp, and it is also possible to add various chemicals.

Usually, paper with a low basis weight (i.e., thin paper) is highly breathable but is easily torn and has no stiffness (rigidity or "strain"). However, the paper base material containing the oxidized pulp of the present invention has a feature that it exhibits excellent strength and stiffness even at a low basis weight. Therefore, it can be said that the paper base material of the present invention is particularly suitable for applications that require strength while having a low basis weight. Such a low basis weight is preferably 50 g / m ² or less, more preferably 5 to 30 g / m ² , and still more preferably 5 to 15 g / m ² . When the paper base has a low basis weight, there are advantages such as improved air permeability and light weight. If the basis weight of the paper substrate exceeds 50 g / m ² , the air permeability may be poor.

  Since the paper base material of the present invention exhibits excellent strength and stiffness even with a low basis weight, it is said that it is easy to maintain its shape while being breathable (despite having a low basis weight) and not easily torn. , It has characteristics not found in conventional paper base materials. Therefore, it is suitable for applications that require air permeability, such as deodorizing materials, masks, bedding (such as pillow covers), packaging materials, building materials (such as shoji paper), and the like. Moreover, since it is lightweight (it is low basic weight), it is hard to tear and it is easy to maintain a shape, Therefore It is suitable also as base materials, such as an aromatic material, an oil absorbing material, and a water absorbing material.

  For example, when the paper base material of the present invention is used as an outer layer of a mask (for example, an influenza mask, a cold mask, a surgical mask, etc.), it is not breathing (good breathability) and is lightweight (low basis weight). Advantages such as being hard to break (high strength) and easy to maintain the shape (high stiffness) are obtained. In addition, the present inventors have found that the paper base material of the present invention has a characteristic that it is easy to crease even if it is thin because of its high rigidity. Usually, thin, soft paper is easy to return to its original shape even if it is folded, and it is difficult to crease. However, since the paper base material of the present invention is stiff, it is easy to maintain the folded state. This is suitable for manufacturing a pleated mask.

  Further, the present inventors have found that the paper base material of the present invention itself has a deodorizing effect. Therefore, it can be applied to a deodorizing material having a high deodorizing effect in addition to the effects of high air permeability, light weight, hardly torn, and easy to maintain the shape. The reason why the paper base material of the present invention has a deodorizing effect is not clear, but the present inventors presume that the odor component is neutralized by the carboxyl group in the oxidized pulp contained in the paper base material. doing.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited to this.

<Manufacture of oxidized pulp 1>
5 g (absolutely dried) of bleached softwood unbeaten pulp (made by Nippon Paper Industries Co., Ltd.) was added to 500 ml of an aqueous solution in which 78 mg (0.5 mmol) of TEMPO (Sigma Aldrich) and 754 mg (7.4 mmol) of sodium bromide were dissolved. Stir until evenly dispersed. After adding 16 ml of a 2M aqueous sodium hypochlorite solution to the reaction system, the pH was adjusted to 10.3 with a 0.5N aqueous hydrochloric acid solution to initiate an oxidation reaction (oxidation treatment). During the reaction, the pH in the system was lowered, but a 0.5N aqueous sodium hydroxide solution was successively added to adjust the pH to 10. After reacting for 2 hours, the mixture was filtered through a glass filter and sufficiently washed with water to obtain oxidized pulp having a carboxyl group content of 1.6 mmol / g.

(Measurement of carboxyl group content of oxidized pulp)
Prepare 60 ml of 0.5% by weight slurry of oxidized pulp, add 0.1 M hydrochloric acid aqueous solution to pH 2.5, then add 0.05 N aqueous sodium hydroxide solution dropwise until the pH is 11 Was calculated from the amount (a) of sodium hydroxide consumed in the neutralization step of the weak acid where the change in electrical conductivity was gradual, using the following equation.
Amount of carboxyl group [mmol / g pulp] = a [ml] × 0.05 / oxidized pulp mass [g].

<Manufacture of oxidized pulp 2>
An oxidized pulp having a carboxyl group content of 1.0 mmol / g was obtained in the same manner as in Production 1 except that the amount of the 2M sodium hypochlorite aqueous solution was changed to 10 ml.

<Manufacture of oxidized pulp 3>
An oxidized pulp having a carboxyl group amount of 2.0 mmol / g was obtained in the same manner as in Production 1 except that the amount of the 2M sodium hypochlorite aqueous solution was changed to 20 ml.

<Manufacture of oxidized pulp 4>
An oxidized pulp having a carboxyl group content of 0.6 mmol / g was obtained in the same manner as in Production 1 except that the amount of the 2M sodium hypochlorite aqueous solution was changed to 6 ml.

Effect of Basis Weight and Amount of Carboxyl Group <Example 1>
A wet sheet of oxidized pulp having a basis weight of 5 g / m ² is obtained with a round hand mill (manufactured by Tozai Seiki Co., Ltd.) using a raw material obtained by diluting the oxidized pulp obtained in Production 1 to 0.1% with tap water. Created. The basis weight was measured according to the test method of JIS P8223 Pulp-Test handsheet-Physical properties. The wet pulp sheet was dried with a blow dryer (50 ° C.) to prepare a paper substrate. Table 1 shows the results of measuring the tensile strength, air resistance, and stiffness (rigidity) of the paper substrate.

(Tensile strength)
The paper base was processed into a strip-like sheet having a width of 15 mm, and the tensile strength was measured using a tensile strength measuring instrument (manufactured by ABB).

(Air permeability resistance)
The air resistance was measured using a digital Oken type air permeability smoothness measuring device (Asahi Seiko Co., Ltd.).

(Stiffness)
The paper base was processed into a strip-like sheet having a width of 15 mm. The sheet was fixed to a table having a height of 10 cm or more so that one end of the sheet protruded 5 cm outward from the table, and the lower end of the protruding sheet was measured with respect to the horizontal surface of the table. . The smaller the value, the better the suitability for maintaining the shape.

<Example 2>
A paper base was prepared in the same manner as in Example 1 except that the basis weight was changed to 10 g / m ² .

<Example 3>
A paper substrate was prepared in the same manner as in Example 1 except that the basis weight was changed to 15 g / m ² .

<Example 4>
A paper substrate was prepared in the same manner as in Example 1 except that the basis weight was changed to 20 g / m ² .

<Example 5>
A paper substrate was prepared in the same manner as in Example 1 except that the basis weight was changed to 30 g / m ² .

<Example 6>
A paper substrate was prepared in the same manner as in Example 1 except that the basis weight was changed to 50 g / m ² .

<Example 7>
A paper base was prepared in the same manner as in Example 2 except that the oxidized pulp of Production 2 was used.

<Example 8>
A paper substrate was prepared in the same manner as in Example 2 except that the oxidized pulp of Production 3 was used.

<Comparative Example 1>
Instead of oxidized pulp, an attempt was made to make a paper substrate in the same manner as in Example 1 except that unoxidized bleached softwood unbeaten pulp (manufactured by Nippon Paper Industries) was used. However, the strength of the wet sheet was weak, It could not be peeled off from the round hand mill. For this reason, a paper base material could not be obtained.

<Comparative example 2>
A paper base was prepared in the same manner as in Example 2 except that bleached softwood unbeaten pulp (made by Nippon Paper Industries) that was not oxidized was used instead of oxidized pulp.

<Comparative Example 3>
A paper substrate was prepared in the same manner as in Example 2 except that the oxidized pulp of Production 4 was used.

<Comparative Example 4>
A paper base was prepared in the same manner as in Example 4 except that non-oxidized bleached softwood unbeaten pulp NBKP (manufactured by Nippon Paper Industries Co., Ltd.) was used instead of oxidized pulp.

  The results are shown in Table 1.

As is clear from the results in Table 1, it can be seen that the paper base materials of the present invention (Examples 1 to 8) have high tensile strength even when the basis weight is low. Moreover, even if a paper base material of this invention is a case where basic weight is low, it turns out in a stiffness test that paper does not hang down easily and maintains a shape. For example, it is a very surprising result that a paper having a basis weight equal to or lower than that of tissue paper such as about 10 g / m ² maintains its shape with almost no sagging. On the other hand, the paper base materials of Comparative Examples 1 to 4 were low in strength that could not be measured or less than 0.1 kN / m, and were easily broken. Moreover, the paper base materials of Comparative Examples 1 to 4 showed such low stiffness that most of the paper base materials hang down in the stiffness test. Paper that is too low in this way is inferior in workability such as pleating and cutting.

Effect of blended amount of oxidized pulp <Example 9>
A paper base was prepared in the same manner as in Example 1 except that the oxidized pulp used in Example 1 and the pulp (NBKP) used in Comparative Example 1 were changed to oxidized pulp / NBKP = 10/90. The results are shown in Table 2.

<Example 10>
A paper base was prepared in the same manner as in Example 1 except that the oxidized pulp used in Example 1 and the pulp used in Comparative Example 1 were changed to oxidized pulp / NBKP = 50/50. The results are shown in Table 2.

<Example 11>
A paper base was prepared in the same manner as in Example 1 except that the oxidized pulp used in Example 1 and the pulp used in Comparative Example 1 were changed to oxidized pulp / NBKP = 90/10. The results are shown in Table 2.

Deodorizing effect <Example 12>
The paper substrates of Example 2 and Comparative Example 2 were processed into 5 cm × 5 cm test pieces. A gas sampling bag with a cock was prepared, a cut was made in the side of the bag, four test pieces were added into the bag from the cut, and sealed with aluminum tape. Ammonia gas was fed into the bag with a syringe. Then, 1.5 L of air was filled from the cock with an air pump (ammonia gas concentration in the bag was 80 to 90 ppm). The ammonia gas detector tube was connected to a cock, and the ammonia gas concentration in the bag 60 minutes after sealing was measured. The results are shown in Table 3.

Claims (5)

A paper substrate containing oxidized pulp,
The basis weight of the paper substrate is 30 g / m ² or less,
The amount of the carboxyl group of the acid pulp is Ri 1.0mmol / g~2.0mmol / g der against absolute dry weight of the oxide pulp,
A paper substrate in which the oxidized pulp is not converted to nanofibers.   The paper base material according to claim 1, wherein the content of the oxidized pulp is 10% by mass or more based on the absolute dry mass of all pulps constituting the paper base material.   In the presence of a compound selected from the group consisting of (a1) an N-oxyl compound and (a2) bromide, iodide, or a mixture thereof, the oxidized pulp is obtained by using (a3) an oxidizing agent. The paper substrate according to claim 1 or 2, which is obtained by oxidation. The deodorizing material containing the paper base material of any one of Claims 1-3 . The mask containing the paper base material of any one of Claims 1-3 .