JP2011074535A - Oil-resistant paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide oil-resistant paper having oilproof property to prevent an oil from leaking out and spreading on a surface of the oil-resistant paper and to make oil stain inconspicuous, while having water-vapor permeability, opacity, safety and disintegration property (recyclability) to enable reuse of the material. <P>SOLUTION: The oil-resistant paper has a coating layer composed of cellulose nanofibers on at least one surface of a base paper. The cellulose nanofiber preferably has a viscosity of 500-2,000 mPa s measured by a Brookfield viscometer (60 rpm, 20°C) in the form of an aqueous solution having a concentration of 2 mass%. The cellulose nanofiber is preferably produced into nanofiber by adding an oxidizing agent to a cellulosic raw material in the presence of an N-oxyl compound and a bromide, an iodide or their mixture, treating the cellulosic raw material in water to prepare oxidized cellulose, and finely pulverizing the oxidized cellulose in wet state. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to oil-resistant paper, and more specifically, is a sheet that comes into contact with foods containing a lot of oil, and has good oil resistance and water vapor permeability, opaqueness that makes it difficult to see the contents, and harmful substances The present invention relates to food packaging paper that has no safety and resource reusability (recyclability).

  When packaging cooked foods such as sugar beet and fast foods such as hamburgers at stores, packaging materials in the form of oil-resistant paper having oil resistance and water vapor permeability have been used.

If a laminated film made of plastic film or plastic film and paper is used as the packaging material, the air permeability of the packaging material is poor. For example, a normal laminated paper having a polyethylene layer of 14 to 20 μm has a moisture permeability of about 50 g / m. because it is ² · 24 hr or less, and when packaged fried acids or fried chicken and the like, such as tempura, when heated packaged them in thermal insulation devices and microwave oven, steam emanating from the food filled therein bag The clothes such as fried foods contain moisture and become too soft, and the taste is significantly impaired.

Therefore, plastic film-paper laminated paper and synthetic resin-coated paper are rarely used as oil-resistant paper having oil resistance and water vapor permeability, and are exclusively polyacrylates or phosphate esters having perfluoroalkyl groups. The thing using fluorine-type compounds, such as, has been used.

  Fluorine-based compounds with perfluoroalkyl groups used in these oil-resistant papers have phosphoric acid ester groups fixed to the paper due to their hydrophilicity, and the perfluoroalkyl groups are oriented outward on the paper surface and processed. When the surface tension of the treated surface is lower than the surface tension of the oily substance, oil resistance based on oil repellency is exhibited. Accordingly, the surface of the processed paper using the fluorine-based compound does not have a barrier layer that prevents the permeation of water vapor, and thus an oil-resistant paper having both oil resistance and water vapor permeability can be obtained.

  However, processed paper using a fluorine-based compound repels printing ink due to the high oil repellency of the fluorine-based compound. Therefore, problems such as white spots occurring in solid print portions when gravure printing is performed. There is.

  In addition, fluorine-based compounds having a perfluoroalkyl group generate hydrogen fluoride, which is a toxic substance during combustion, and in recent years, perfluorooctane sulfonic acids produced in the fluorine-based compound production process by electrolytic polymerization have been used in humans and animals. Perfluoroalcohol, which is widely accumulated in the environment such as blood and seawater, and is highly environmentally accumulative when heated to 100 ° C or higher regardless of the production method for fluorine compounds produced by electrolytic polymerization or telomerization In addition, other low-molecular fluorine compounds are generally hardly decomposable, so that in food packaging applications, oil resistance and water vapor permeability can be achieved without using fluorine compounds. An oil-resistant paper is also desired.

  The oil resistance required for oil wrapping paper for food packaging is that it has an oil barrier property that prevents oil from passing through the paper and leaking to the opposite side. It refers to characteristics such as not exhibiting such an appearance. In addition, other functions required for oil-resistant paper for food packaging include the water vapor permeability described above, the contents are difficult to see from the outside when packaging food, no harmful substances, and disaggregation (recyclability). And the resources can be reused.

  In general, food packaging paper that is used in contact with food is rarely collected and reused after use from the viewpoint of hygiene, and so disintegration (recyclability) in the present invention is the process for producing oil-resistant paper. This means that the generated product cutting waste can be disaggregated in water to make it usable as a papermaking raw material.

  Glassine paper, tracing paper, base paper for release paper, parchment paper, etc. have high barrier properties against oil, and have been diverted as oil-resistant paper to applications that require oil resistance before the advent of fluorine compounds. These papers are made from highly beaten raw materials and used in combination with super calendering to form a paper layer structure with few voids, or the paper layer surface is dissolved in sulfuric acid to form a film to reduce the voids. Therefore, although the permeation of oil can be suppressed to some extent, it is difficult to eliminate oil stains because the oil penetrates into the voids slightly remaining in the paper layer.

  Furthermore, because the raw material is highly beaten, the transparency of the paper layer is high, so that the contents covered with oil can be seen from the outside, the oil attached to the oil resistant paper shows through the paper further, as if the oil is paper Since it permeates and permeates, there is a problem that the appearance is deteriorated.

  In JP-A-8-188980 (Patent Document 1), 50% by mass or more of finely pulverized pulp in which cellulose fibers are highly beaten is blended so that the fibers are brought into close contact with each other. A transparent paper having a barrier property against an oily substance by reducing the amount is disclosed. However, a special beating machine such as a vibration mill is required for the production of fine fiberized pulp, and there is a problem that the production efficiency is lowered.

In order to improve oil resistance by applying a material having a high film forming property, synthetic resins such as wax and acrylic, and water-soluble polymer materials such as starch and polyvinyl alcohol are generally used. In JP-A-4-2900 (Patent Document 2), 0.5 to 5 g / m ^{2 of} starch is coated on glassine paper having an air resistance of 200 seconds, and further subjected to super calendering to provide an air resistance of 7 A barrier paper is described in which the oil-based magic ink does not pass through for more than 10,000 seconds.

However, when a base paper having an air resistance of about 5 to 1,000 seconds is used, it is necessary to apply 5 g / m ² or more on one side to obtain a sufficient barrier property using a water-soluble polymer such as starch. is there. As a result, such paper becomes sticky on the paper surface, so there is no problem when used as a release paper base paper with a release agent covering the surface, but when used as an oil-resistant paper for food packaging, Since it is sticky, the feeling of use is bad, and food sticking occurs, which is not preferable. Further, when the coating amount of the water-soluble polymer solution is increased, the drying load is large and the productivity is inferior.

  Polyvinyl alcohol-based resins have high film-forming properties, and barrier properties can be obtained by coating in a smaller amount than starch and the like. JP-A-4-2900 (Patent Document 2) describes an example of blending with starch. Further, JP-A-7-60905 (Patent Document 3) describes glassine paper coated with a polyvinyl alcohol resin alone.

  However, polyvinyl alcohol-based resins are easy to foam during coating, and in order to eliminate pinholes on the coating surface, various devices are required on the equipment, and the contact angle with oil becomes small, and the paper surface There is a drawback that the oil adhering to the spread spreads and the appearance becomes poor. Accordingly, polyvinyl alcohol resins are not preferred when used for wrapping paper such as fried foods using edible oils such as olive oil because the oil attached to the surface appears to leak.

JP-A-8-188980 JP-A-4-2900 Japanese Patent Laid-Open No. 7-60905

As described above, no oil-resistant paper having oil resistance and water vapor permeability suitable for food packaging applications, as well as opacity, safety, and disaggregation (recyclability) has been found so far.
The problem to be solved by the present invention is that when oil comes into contact with oil-based food, the oil does not leak through the paper and leak to the opposite surface, and the attached oil is difficult to spread on the surface of the oil-resistant paper, and the appearance of the oil soaked It has oil resistance that doesn't show up, has water vapor permeability that allows water vapor to permeate from the fried food immediately after heating, opaque that the contents are difficult to see from the outside, safety that does not contain harmful substances, and reusable resources It is to provide an oil-resistant paper having both good disaggregation (recyclability).

  The present inventors have found that by providing a coating layer containing cellulose nanofibers, the oil resistance and air permeability resistance are improved, and an oil resistant paper having excellent water vapor permeability can be obtained. It came to be accomplished.

Accordingly, the present invention is an oil-resistant paper in which a coating layer made of cellulose nanofibers is provided on at least one side of the base paper. Furthermore, the cellulose nanofibers preferably have a B-type viscosity (60 rpm, 20 ° C.) of 500 to 2000 mPa · s when the concentration of the aqueous solution is 2% by mass. The cellulose nanofiber is oxidized by adding an oxidizing agent to a cellulose-based raw material in the presence of an N-oxyl compound and bromide, iodide or a mixture thereof, and treating the cellulose-based raw material in water. It is preferable that the prepared cellulose is prepared and the oxidized cellulose is subjected to a wet atomization treatment to form a nanofiber. The base paper is a paper having a basis weight of 30 to 60 g / m ² , which is made with natural fibers for papermaking having a shopper freeness of 85 to 90 ° SR. It is preferably coated at ² g / m ² or more, and the air resistance of the oil-resistant paper is preferably 45,000 seconds or more and the moisture permeability is 2,000 g / m ² · 24 hours or more.

  The present invention does not produce condensed water that does not leak or spread even when foods containing a lot of oil are packaged, has good oil resistance that hardly causes oil stains, and excessively softens the clothes of fried food. It has the effect of providing oil-resistant paper that is inexpensive and highly safe, having water vapor permeability and opaqueness that makes it difficult to see the contents from the outside.

  The cellulose nanofiber, which is the papermaking additive of the present invention, becomes a transparent liquid when dispersed in water and exhibits an appropriate viscosity, so that it can be suitably used as a paint simply by adjusting to a desired concentration. Preferably, when the aqueous solution concentration is 2% by mass, the B-type viscosity (60 rpm, 20 ° C.) is preferably 500 to 2000 mPa · s. Such cellulose nanofibers were oxidized by, for example, treating the cellulosic raw material with the addition of an oxidizing agent in the presence of the N-oxyl compound and the bromide, iodide or mixture of the cellulosic raw material. It can be produced by preparing cellulose, and further subjecting the oxidized cellulose to wet atomization to form nanofibers.

  As the N-oxyl compound used in the present invention, 2,2,6,6-tetramethyl-1-piperidine-N-oxy radical (hereinafter referred to as TEMPO) and 4-hydroxy TEMPO derivative are preferable. As the 4-hydroxy TEMPO derivative, use a 4-hydroxy TEMPO hydroxyl group etherified with an alcohol having a linear or branched carbon chain having 4 or less carbon atoms or esterified with a carboxylic acid or a sulfonic acid. Is preferred. In particular, if the number of carbon atoms is 4 or less, it becomes water-soluble regardless of the presence or absence of saturated or unsaturated bonds, and functions as an oxidation catalyst. However, when the number of carbon atoms is 5 or more, the hydrophobicity is remarkably improved and becomes insoluble in water, so that the function as an oxidation catalyst is lost.

  The usage-amount of 4-hydroxy TEMPO derivative will not be restrict | limited especially if it is the catalyst amount which can make a cellulose raw material into nanofiber. For example, it is 0.01 to 10 mmol, preferably 0.01 to 1 mmol, and more preferably 0.05 to 0.5 mmol, with respect to 1 g of cellulosic raw material.

  The method for oxidizing a cellulose-based raw material of the present invention is carried out in water using an oxidizing agent in the presence of the 4-hydroxy TEMPO derivative and a compound selected from the group consisting of bromide, iodide and a mixture thereof. It is a characteristic, and the oxidized cellulose-based raw material thus obtained can be efficiently converted into nanofibers. As the bromide or iodide, a compound that can be dissociated and ionized in water, such as an alkali metal bromide or an alkali metal iodide, can be used. The amount of bromide or iodide used can be selected as long as the oxidation reaction can be promoted. For example, it is about 0.1 to 100 mmol, preferably 0.1 to 10 mmol, and more preferably about 0.5 to 5 mmol with respect to 1 g of cellulosic raw material.

  The oxidizing agent may be any oxidizing agent that can promote the target oxidation reaction, such as halogen, hypohalous acid, halous acid, perhalogen acid or salts thereof, halogen oxide, and peroxide. Agents can also be used. From the viewpoint of production cost, sodium hypochlorite, which is the most widely used oxidant in industrial processes at present and is low in environmental load, is suitable. The amount of the oxidizing agent used can be selected within a range that can promote the oxidation reaction. For example, it is 0.5 to 500 mmol, preferably 0.5 to 50 mmol, and more preferably about 2.5 to 25 mmol with respect to 1 g of cellulosic raw material.

  The cellulose-based raw material used in the present invention is not particularly limited, and it is purified by chemical treatment such as kraft pulp or sulfite pulp derived from various woods, powdered cellulose obtained by pulverizing them with a high-pressure homogenizer or a mill, or acid hydrolysis. The microcrystalline cellulose powder can be used.

  The method of the present invention is characterized in that the oxidation reaction can proceed smoothly even under mild conditions. Therefore, even if the reaction temperature is about 15 to 30 ° C., the cellulosic material can be oxidized efficiently. In addition, a carboxyl group produces | generates in a cellulose with progress of reaction, and the pH fall of a reaction liquid is recognized. Therefore, in order to advance the oxidation reaction efficiently, it is desirable to maintain the pH of the reaction solution at about 9 to 12, preferably about 10 to 11.

  The cellulose nanofiber of the present invention can be produced by subjecting the above-mentioned oxidized cellulose to wet atomization and defibrating. As a method of performing the wet atomization treatment, for example, cellulose nanofibers can be formed by treating known mixing / stirring / emulsifying / dispersing devices such as a high-speed shear mixer and a high-pressure homogenizer singly or in combination of two or more kinds as necessary. be able to. As the wet atomization processing apparatus, it is preferable to use a high-pressure homogenizer that enables a pumping pressure of 100 MPa or more.

  The cellulose nanofiber of the present invention is a cellulose single microfibril having a width of 2 to 5 nm and a length of about 1 to 5 μm. Further, the carboxyl group amount is preferably 0.5 mmol / g or more. When this cellulose nanofiber is applied to paper, the air resistance can be improved, and functions such as oil permeation suppression and barrier property improvement can be imparted.

  The cellulose nanofibers described above may be added internally to the base paper, or may be externally added (coated on the surface), but the external addition may cause more cellulose nanofibers to be present near the paper surface. It is possible and preferable in terms of improving the barrier property. For this reason, in this invention, after apply | coating the coating liquid containing a cellulose nanofiber on the base paper surface, it dries with a dryer etc. and provides the coating layer containing a cellulose nanofiber on the base paper surface. As a method of applying a coating solution containing cellulose nanofiber, a two-roll size press coater, a gate roll coater, a blade metalling coater, a rod metalling coater, a blade coater, an air knife coater, a roll coater, a brush coater, a kiss coater, Known coating machines such as squeeze coaters, curtain coaters, die coaters, bar coaters, and gravure coaters can be used.

In this invention, the preferable coating amount of a cellulose nanofiber is 0.2 g / m < ² > or more as a coating amount per one side, Preferably it is 0.5 g / m < ² > or more. When the coating amount of cellulose nanofiber is small, the above-described effect tends to be small. As the coating amount increases, the oil permeation suppression and barrier properties improve, but the flexibility of the oil-resistant paper tends to be impaired.

  In addition, the coating layer made of cellulose nanofibers may contain chemicals such as a water-soluble resin, a resin emulsion, a sizing agent, a water-resistant agent, a water-repellent agent, and a filler as necessary so as not to impair the effects of the present invention. Can be mixed and used.

The base paper of the present invention is produced by a known paper machine using natural fibers for paper making such as wood pulp, but the paper making conditions are not particularly defined. Examples of natural fibers for papermaking include wood pulp such as softwood pulp and hardwood pulp, non-wood pulp such as manila hemp pulp, sisal hemp pulp and flax pulp, and pulp obtained by chemically modifying these pulps. As the types of pulp, chemical pulp, ground pulp, chemiground pulp, thermomechanical pulp, etc. by sulfate cooking method, acidic / neutral / alkaline sulfite cooking method, soda salt cooking method and the like can be used.
As the paper machine, a long net paper machine, a twin wire paper machine or the like is used. In order to manufacture multilayer paper and paperboard, a circular net type paper machine is used.

  Moreover, it is preferable that the base paper of the oil-resistant paper of the present invention is manufactured using natural fibers for papermaking beaten to a shopper freeness of 85 to 90 ° SR. The above natural fiber for papermaking is beaten to a freeness of 85 to 90 ° SR with a known device such as an ordinary refiner or beater, but if the freeness is less than 85 ° SR, the required oil resistance is obtained. There is a risk of not being able to. In addition, general papermaking chemicals, such as a sizing agent, a dry paper strength agent, and a wet paper strength agent, can be added to the natural fiber for papermaking as necessary.

The basis weight of the base paper is not particularly limited, but usually 30 to 60 g / m ² , preferably 30 to 40 g / m ² is used. When the basis weight is less than 30 g / m ² , the paper has many pinholes and sufficient oil resistance cannot be obtained, and the strength required for use as oil resistant paper may not be obtained. On the other hand, if the basis weight exceeds 60 g / m ² , dehydration on the paper machine wire and drying with a dryer are slowed, so productivity is lowered and cost tends to increase.

  The oil resistant paper of the present invention is required to have an air resistance of 45,000 seconds or more. When the air resistance is low, it is considered that the inter-fiber gap in the paper layer is large, and oil easily penetrates into the paper layer by capillary action. Moreover, it is thought that the space | gap has increased in the coating layer which consists of a cellulose nanofiber apply | coated to the base paper surface, and the effect which suppresses oil resistance, especially the spread of oil falls.

  When oil adheres to the oil-resistant paper, the oil penetrates into the surface of the paper in contact with the oil to increase transparency, and it looks as if the oil has permeated through the paper. For this reason, a filler can be internally added to the base paper as required. As filler, inorganic fine particles and organic fine particles that are usually used in papermaking can be used as appropriate, but in order to increase the opacity of oil-resistant paper, the refractive index to light is 1.8 to 3.0 and the particle size is It is preferable to add a small filler internally. Examples of fillers include inorganic materials such as rutile titanium dioxide (refractive index 2.76), anatase titanium dioxide (refractive index 2.52), zircon oxide (refractive index 2.40), and zinc oxide (refractive index 2.01). Examples thereof include composite pigments such as pigments, titanium dioxide-coated mica (refractive index 2.3), iron oxide-coated mica (refractive index 2.9), titanium dioxide-coated silica, and titanium dioxide-coated glass flakes. These fillers are added in an amount of 2 to 10% by mass, preferably 3 to 7% by mass, based on natural fibers for papermaking. If it is less than 2% by mass, the required opacity and the effect of suppressing the decrease in opacity cannot be obtained, and if it exceeds 10% by mass, the air resistance of the base paper is lowered and the oil barrier property may be lowered.

Thus, a base paper used for the oil-resistant paper of the present invention is obtained. Thereafter, the cellulose is used to form a coating layer that fills voids existing in the paper layer structure and covers the paper surface. A coating layer mainly composed of nanofibers is applied.
In addition, the coated paper can be improved in oil resistance, smoothness, and printability by performing super calendering as necessary.

The moisture permeability of the oil-resistant paper of the present invention is 2,000 g / m ² · 24 hr or more. If the moisture permeability is less than 2,000 g / m ² · 24 hr, when the deep-fried food is put in the oil-resistant paper bag and sealed, dew condensation occurs in the bag, and the clothes become excessively soft with moisture. , Taste is significantly impaired.

  Examples of the present invention will be described in more detail below, but the present invention is not limited to these. In Examples and Comparative Examples, “mass%” indicates “solid mass%”. Moreover, the value which shows a coating amount shows the solid content mass after drying, unless there is a notice.

[Example 1]
Cellulose nanofiber dispersion prepared as follows is applied to a paper with a basis weight of 30 g / m ² using softwood kraft pulp beaten to a freeness of 90 ° SR. after coating such that m ^2, and dried to obtain a sheet.

(Production of cellulose nanofiber dispersion)
Powdered cellulose (Nippon Paper Chemical Co., Ltd., particle size 24 μm) 15 g (absolutely dry) was added to 500 ml of an aqueous solution in which 78 mg (0.5 mmol) of TEMPO (Sigma Aldrich) and 755 mg (5 mmol) of sodium bromide were dissolved. Was stirred until uniformly dispersed. After adding 50 ml of an aqueous sodium hypochlorite solution (effective chlorine 5%) to the reaction system, the pH was adjusted to 10.3 with an aqueous 0.5N hydrochloric acid solution to initiate the oxidation reaction. 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, oxidized powdered cellulose was separated by centrifugal operation (6000 rpm, 30 minutes, 20 ° C.) and sufficiently washed with water to obtain oxidized powdered cellulose. A 2% (w / v) slurry of oxidized powdered cellulose was treated with a mixer at 12,000 rpm for 15 minutes, and the powdered cellulose slurry was further treated with an ultra-high pressure homogenizer five times at a shipping pressure of 140 MPa to obtain a transparent gel-like dispersion. A liquid was obtained. The B-type viscosity (60 rpm, 20 ° C.) of the obtained 2% (w / v) cellulose nanofiber dispersion was 890 mPa · s.

[Example 2]
With respect to paper having a grammage of 40 g / m ² using softwood kraft pulp beaten to a freeness of 90 ° SR, the above cellulose nanofiber dispersion is coated on both sides to a total of 0.24 g / m ² by bar coating. After coating, the sheet was dried to obtain a sheet.

[Example 3]
Cellulose nanofibers are coated with 0.56 g / m ^{2 on} both sides by bar coating on paper with a grammage of 40 g / m ² using softwood kraft pulp beaten to a freeness of 90 ° SR, and then dried. To obtain a sheet.

[Comparative Example 1]
Relative basis weight 30 g / m ² paper with softwood kraft pulp beaten to a freeness of 90 ° SR, was 30.0 g / m ² coated as a double-sided total net water in the bar coating of pure water And dried to obtain a sheet.

[Comparative Example 2]
Relative basis weight 40 g / m ² paper with softwood kraft pulp beaten to a freeness of 90 ° SR, was 30.0 g / m ² coated as a double-sided total net water in the bar coating of pure water And dried to obtain a sheet.

[Comparative Example 3]
After applying a phosphate esterified starch on both sides of 0.60 g / m ^{2 in} total to a paper with a grammage of 40 g / m ² using softwood kraft pulp beaten to a freeness of 90 ° SR And dried to obtain a sheet.

[Comparative Example 4]
Composition of pure white roll paper / polyethylene layer / rayon mixed paper in which polyethylene is melt-extruded to a thickness of 15 μm between 30 g / m ² pure white roll paper and 22 g / m ² rayon mixed paper as oil-resistant paper laminated with polyethylene Laminated oil resistant paper was prepared. The oil paper basis weight 68 g / ^{m 2,} air resistance 280,000 seconds was moisture permeability ^45g / m 2 · 24hr.

The following measurements were performed using the sheets prepared in Examples and Comparative Examples, and the results are shown in Tables 1 and 2. The test method is shown below.
(1) Air permeability resistance: Measured by Oken type (2) smoothness air permeability tester according to Japan TAAPI paper pulp test method No.5-2: 2000.
(3) Moisture permeability: Measured according to JISK7129, using a moisture permeability meter (Dr. Lyssy, L80-4000) under conditions of a temperature of 40 ± 0.5 ° C. and a relative humidity of 90 ± 2%.
(4) JIS oil resistance: The paper oil resistance test method described in JIS 8146-1976 was followed.
(5) Opacity: It was measured using a whiteness meter (Murakami Color Co., Ltd., CMS-35SPX).
(6) Opacity after suitable oil: 1 ml of olive oil was dropped on the paper prepared in Examples and Comparative Examples, and the olive oil was wiped off after standing for 1 hour in a 60 ° C. dryer, and the opacity was measured.
(7) Occurrence of dew condensation when fried food was put: The fried food was put into the obtained sheet in a bag shape, and the state of dew condensation was visually observed.

  When comparing oil resistance, Comparative Examples 1 and 2 were values below the lower limit of measurement, whereas Examples 1, 2, and 3 increased the oil resistance by applying cellulose nanofibers. As the amount increased, the oil resistance improved. Further, when Example 3 and Comparative Example 3 were compared, it was found that the increase in oil resistance was greater when cellulose nanofibers were applied than when starch was applied, despite the almost same coating amount.

When Example 1 and Comparative Example 1, and Examples 2 and 3 were compared with Comparative Example 2, respectively, the air resistance was increased by applying cellulose nanofibers. From this, it is considered that by applying cellulose nanofibers to paper, the inter-fiber voids in the paper layer are filled, and the oil resistance is improved. Further, when Example 3 and Comparative Example 3 were compared, it was shown that the increase in air resistance was greater when the cellulose nanofibers were applied than when starch was applied.
Further, in Comparative Example 4 having a polyethylene layer, the moisture permeability was 45 g / m ² · day. When freshly fried food was put in the oil-resistant paper bag and sealed, condensation occurred in the bag. When condensation occurs, the garment becomes excessively soft with moisture, and the taste is significantly impaired. The moisture permeability of the oil-resistant paper of Examples 1, 2, and 3 was 25,575 g / m ² · day or more, and was a value that exceeded the upper limit of the measurement. Therefore, the oil-resistant paper coated with cellulose nanofiber was There was no dew condensation when the fried food was put in without significantly impairing the water vapor permeability.

Moreover, when the opacity after oil dropping of Examples 2 and 3 and Comparative Example 2 was compared, the opacity of Examples 2 and 3 coated with cellulose nanofibers was higher. This suggests that applying nanofibers to paper prevents oil from penetrating into the paper from the deep-fried food and can be used without impairing the appearance.
From the above, the oil-resistant paper of Examples 1 to 3 is a paper coated with cellulose nanofibers, which has improved oil resistance and water vapor permeability that does not generate condensed water that makes the fried clothes excessively soft. It has been shown to prevent oil penetration from the contents.

Claims (4)

  An oil-resistant paper provided with a coating layer made of cellulose nanofibers on at least one side of a base paper.   2. The oil-resistant paper according to claim 1, wherein the cellulose nanofiber has a B-type viscosity (60 rpm, 20 ° C.) of 500 to 2000 mPa · s when the concentration of the aqueous solution is 2 mass%.   The cellulose nanofibers were oxidized by adding an oxidizing agent to the cellulose raw material in the presence of an N-oxyl compound and bromide, iodide or a mixture thereof, and treating the cellulose raw material in water. The oil-resistant paper according to claim 1 or 2, wherein cellulose is prepared, and the oxidized cellulose is subjected to wet atomization treatment to form nanofibers. The base paper is a paper having a basis weight of 30 to 60 g / m ² made of natural fiber for papermaking having a shopper freeness of 85 to 90 ° SR, and the coating amount of the cellulose nanofiber is 0.2 g / m. ^The air permeability resistance is 45,000 seconds or more, and the moisture permeability is 2,000 g / m ² · 24 hr or more. Oil-resistant paper as described.