JP7412148B2 - industrial belt - Google Patents

Description

The present invention relates to industrial belts.

In the drying section of a paper machine in the papermaking process, wet paper is placed on a papermaking dryer canvas (hereinafter also simply referred to as "canvas") and heated and dried while being conveyed. At this time, adhesive substances (gummy pitch) contained in papermaking raw materials, chemicals such as sizing liquid and coating liquid used in papermaking, or inorganic substances such as aluminum hydroxide and talc become stains. Adheres to the surface of the canvas. If this dirt adheres to the wet paper, it will be a disadvantage. Furthermore, if the above-mentioned dirt accumulates on the canvas, it will cause clogging of the canvas, causing separation of the paper sheet from the canvas and uneven drying, which will eventually lead to a significant decrease in air permeability and loss of drying ability. Therefore, dirt adhering to the canvas has been considered a major problem for some time.

As a measure against the adhesion of dirt to a canvas, a method is known in which the surface of the canvas is coated with a resin containing an antifouling agent (antifouling resin) that prevents dirt from adhering to the canvas to form a film. For example, in Patent Document 1 below, antifouling performance is improved by applying a mixture containing silicone oil, acrylic resin, epoxy resin, and imidazole curing agent to the surface of a canvas to form a resin film. ing.

Japanese Patent Application Publication No. 2004-360102

However, since the canvas is repeatedly washed to remove the above-mentioned stains, the antifouling resin coating may peel off from the canvas surface. In particular, in recent years, many canvas cleaning devices spray water at higher pressures, which has led to an increasing number of cases in which the antifouling resin coating on the canvas surface peels off, causing problems with its sustainability.

The above problems can occur not only in canvases but also in industrial belts whose surfaces are coated with an antifouling resin film.

Therefore, an object of the present invention is to improve the sustainability of the effect of the antifouling resin film coated on the surface of an industrial belt.

In order to solve the above problems, the present invention provides an industrial belt comprising a belt main body made of synthetic fiber and an antifouling resin coating coated on the surface of the belt main body, wherein the antifouling resin coating is An industrial belt containing cellulose nanofibers is provided.

As mentioned above, by adding cellulose nanofibers (hereinafter also referred to as "CNF") to the antifouling resin coating, the strength of the antifouling resin coating is increased and the antifouling resin coating becomes difficult to peel off from the belt body. This improves the sustainability of the antifouling effect.

In the present invention, CNF is a fine fiber with an average fiber diameter of about 2 to 500 nm and an aspect ratio of 100 or more, and is a cellulose raw material such as pulp, or carboxylated (also called oxidized), carboxymethylated, phosphoric acid It can be obtained by applying mechanical force to a cellulose raw material that has been chemically modified such as esterification or cationization (chemically modified cellulose raw material) to defibrate it. The average fiber diameter and average fiber length of CNF are calculated from the average values of the fiber diameter and fiber length obtained from the results of observing each fiber using an atomic force microscope (AFM) or a transmission electron microscope (TEM). You can get it by doing this. Further, the aspect ratio can be calculated by dividing the average fiber length by the average fiber diameter.

CNF itself has low antifouling properties and is susceptible to dirt, so if the proportion of CNF in the antifouling resin film is too high, the antifouling properties will decrease. Therefore, the proportion of CNF in the antifouling resin film is preferably 20 mass% or less.

The antifouling resin film is formed by applying a mixed solution containing an antifouling agent, a resin component, and CNF to the surface of the belt body, but if the CNF fiber diameter is large, CNF will precipitate in the mixed solution. This makes it difficult to apply to the belt body. Therefore, the average fiber diameter of CNF is preferably 2 to 500 nm, more preferably 2 to 100 nm, even more preferably 2 to 10 nm.

When CNF is blended into the antifouling resin coating as described above, it is thought that the longer the fiber length of the CNF is, the easier the CNFs are to bond with each other, so that the strength of the antifouling resin coating becomes higher. However, if the CNF fiber length is too long, the CNFs tend to approach each other and bond together in the mixed solution, making it easy for CNF lumps to form in the mixed solution. If such a liquid mixture is applied to the surface of the belt body, there is a risk that the gaps between the fibers of the belt body will be clogged with lumps, resulting in insufficient air permeability. Therefore, in order to suppress the decrease in air permeability of the belt body, the average fiber length of the CNF is preferably 50 μm or less, more preferably 10 μm or less, even more preferably 1 μm or less, even more preferably 600 nm or less, and even more preferably 450 nm or less.

CNF is a cellulose raw material such as pulp, or a cellulose raw material that has been chemically modified such as carboxylation (also called oxidation), carboxymethylation, phosphoric acid esterification, phosphorous acid esterification, or cationization (chemically modified cellulose raw material). It can be obtained by defibrating it by applying mechanical force to it. Among these, from the viewpoint of excellent compatibility and dispersibility in the mixed solution applied to the belt body, the chemical modifications applied to the cellulose raw material of CNF include anionic modification, carboxylation, carboxymethylation, and phosphate ester. Chemical modification by carboxylation and phosphite esterification is preferred, and chemical modification by carboxylation (also called oxidation) is particularly preferred. In particular, the oxidation method using a TEMPO catalyst is most preferable, and the TEMPO-oxidized CNF produced using the catalyst is easily dispersed in the mixed liquid, so it is advantageous in that it can suppress the decrease in air permeability of the belt body. It is.

The above industrial belt can be suitably used as a papermaking dryer canvas used in the drying section of a papermaking machine.

As described above, by blending CNF into the antifouling resin coating, the strength of the antifouling resin coating is increased and its adhesion to the belt body is increased, so that the sustainability of the antifouling effect is improved.

1 is a longitudinal sectional view (MD) of an industrial belt (papermaking dryer canvas) according to an embodiment of the present invention. FIG. 3 is a side view of a testing machine that reproduces the long-term use condition of canvas. FIG. 2 is a side view of a testing machine that performs a tape peel strength test of an antifouling resin coating. It is a graph showing the results of a tape peel strength test of an antifouling resin film.

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a papermaking dryer canvas 1 as an industrial belt according to an embodiment of the present invention. The canvas 1 includes a canvas body 10 as a belt body, and an antifouling resin film 20 coated on the surface of the canvas body 10.

The canvas main body 10 is made of synthetic fibers, and in this embodiment is made of a woven fabric formed by weaving warps 11 and wefts 12 made of synthetic fiber monofilaments. In addition to polyester, which has traditionally been commonly used as a canvas material, the synthetic fibers can include polyamide, acrylic, polyphenylene sulfide, and the like. As the warp yarns 11 and the weft yarns 12, for example, monofilaments having a circular, oval, or flat cross section can be used. In FIG. 1, the weft 12 on the side facing the paper (upper side in the figure) has a smaller diameter than the weft 12 on the opposite side (lower side in the figure), but the diameter is not limited to this. For example, both wefts may have the same diameter. You can also use it as

The texture of the fabric constituting the canvas body 10 is not particularly limited, and may be a double weave as shown in FIG. 1, a single weave, or a triple weave. Furthermore, the synthetic fibers forming the woven fabric are not limited to monofilaments as described above, but multifilaments and spun staples may also be used. In addition, the canvas body 10 is not limited to a fabric in which the warp and weft are woven as described above, but may also be a fabric using a synthetic fiber spiral coil, or a synthetic fiber web laminated on a woven base fabric and bonded by needle punching. It may also be made of non-woven fabric.

The antifouling resin film 20 is coated on at least the surface of the canvas body 10 on the paper-contacting surface side. Specifically, the antifouling resin film 20 is coated on the portions of the warp 11 and weft 12 constituting the canvas body 10 that are exposed on the surface facing the paper. The antifouling resin coating 20 is provided, for example, in an area of 1/2 or less of the thickness of the canvas body 10 from the paper-contacting surface of the canvas body 10 (see the shaded area in FIG. 1). In the illustrated example, the antifouling resin coating 20 extends from the surface of the canvas 1 on the paper-contacting surface side to the weft yarn 12 on the paper-contacting surface side. In addition, the antifouling resin coating 20 may be formed so as to extend from the surface of the canvas 1 on the side facing the paper to the weft 12 on the side opposite to the surface, or may be formed so as to reach the surface of the canvas 1 on the side opposite to the surface. You can also Note that the antifouling resin coating 20 is not formed to fill the gaps in the canvas body 10, but in reality, the antifouling resin coating 20 is coated on the surface of each warp 11 and weft 12 of the canvas body 10. The gap formed between the warp yarns 11 and the weft yarns 12 is maintained, and the breathability of the canvas 1 is ensured.

As shown in an enlarged view in FIG. 1, the antifouling resin coating 20 includes a resin portion 21 containing an antifouling agent and CNF. The resin portion 21 of the antifouling resin coating 20 includes, for example, an antifouling agent and a resin component (for example, an acrylic ester copolymer) for fixing the antifouling agent to the canvas body 10. Consists only of staining agent and acrylic ester copolymer. The antifouling agent is made of a material that has lower dirt adhesion than the canvas body 10 (that is, a material that has a lower surface energy than the synthetic resin that makes up the canvas body 10), and specifically, for example, fluorine resin or silicone. It consists of an oil component obtained by heating (heat treatment) an aqueous emulsion. The acrylic ester copolymer is a solid component obtained by heating (heat treatment) an acrylic ester copolymer emulsion, and contributes to improving the strength of the antifouling resin coating 20 and the like. For example, the antifouling agent is mixed in an amount of 40 mass% or more with respect to the resin portion 21 of the antifouling resin coating 20. In this embodiment, both the antifouling agent and the acrylic ester copolymer are blended in an amount of 40 mass% or more with respect to the resin portion 21.

Hereinafter, CNF will be explained in detail.

(cellulose raw material)
Cellulose raw materials include plants (e.g., wood, bamboo, hemp, jute, kenaf, agricultural residues, cloth, pulps (softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp ( LUKP), hardwood bleached kraft pulp (LBKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (e.g. ascidians), Cellulose fibers originating from algae, microorganisms (for example, acetic acid bacteria), microbial products, etc. are known, and any of them can be used in the present invention.Preferably, cellulose fibers derived from plants or microorganisms are used. Cellulose fibers derived from plants are preferred.The cellulose raw material may be chemically modified as described below.

(carboxymethylation)
When carboxymethylated cellulose is used as the chemically modified cellulose, the carboxymethylated cellulose may be obtained by carboxymethylating the above-mentioned cellulose raw material by a known method, or a commercially available product may be used. In either case, the cellulose preferably has a degree of substitution of carboxymethyl groups per anhydroglucose unit of 0.01 to 0.50.

An example of a method for producing such carboxymethylated cellulose is the following method. Cellulose is used as the base material, and as a solvent 3 to 20 times the weight of water and/or lower alcohol, specifically water, methanol, ethanol, N-propyl alcohol, isopropyl alcohol, N-butanol, isobutanol, tertiary alcohol. A single medium such as butanol or a mixture of two or more types is used. Note that when lower alcohols are mixed, the mixing ratio of lower alcohols is 60 to 95% by weight. As the mercerization agent, alkali metal hydroxide, specifically sodium hydroxide and potassium hydroxide, is used in an amount of 0.5 to 20 times the mole per anhydroglucose residue in the bottom starting material. The bottom starting material, a solvent, and a mercerization agent are mixed, and mercerization treatment is performed at a reaction temperature of 0 to 70°C, preferably 10 to 60°C, and a reaction time of 15 minutes to 8 hours, preferably 30 minutes to 7 hours. Thereafter, a carboxymethylating agent is added 0.05 to 10.0 times in mole per glucose residue, and the reaction temperature is 30 to 90°C, preferably 40 to 80°C, and the reaction time is 30 minutes to 10 hours, preferably 1 hour. The etherification reaction is carried out for ~4 hours.

(carboxylation)
When using carboxylated (oxidized) cellulose as the chemically modified cellulose, carboxylated cellulose (also referred to as oxidized cellulose) can be obtained by carboxylating (oxidized) the above cellulose raw material by a known method. Although not particularly limited, during carboxylation, the amount of carboxyl groups should be adjusted to 0.6 to 3.0 mmol/g based on the absolute dry weight of the anion-modified cellulose nanofiber. is preferable, and more preferably adjusted to 1.0 mmol/g to 2.0 mmol/g.

As an example of a carboxylation (oxidation) method, a cellulose feedstock is oxidized in water with an oxidizing agent in the presence of an N-oxyl compound and a compound selected from the group consisting of bromides, iodides or mixtures thereof. Here are some methods. Through this oxidation reaction, the primary hydroxyl group at the C6 position of the glucopyranose ring on the cellulose surface is selectively oxidized, resulting in cellulose fibers having an aldehyde group and a carboxyl group (-COOH) or a carboxylate group (-COO-) on the surface. can be obtained. The concentration of cellulose during the reaction is not particularly limited, but is preferably 5% by weight or less.

The N-oxyl compound refers to a compound capable of generating nitroxy radicals. As the N-oxyl compound, any compound can be used as long as it promotes the desired oxidation reaction. Examples include 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO) and its derivatives (eg, 4-hydroxyTEMPO). The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount that can oxidize cellulose as a raw material. For example, it is preferably 0.01 to 10 mmol, more preferably 0.01 to 1 mmol, and even more preferably 0.05 to 0.5 mmol, per 1 g of bone dry cellulose. Further, it is preferably about 0.1 to 4 mmol/L to the reaction system.

Bromide is a compound containing bromine, examples of which include alkali metal bromides that can be dissociated and ionized in water. Moreover, iodide is a compound containing iodine, and examples thereof include alkali metal iodide. The amount of bromide or iodide to be used can be selected within a range that can promote the oxidation reaction. The total amount of bromide and iodide is, for example, preferably 0.1 to 100 mmol, more preferably 0.1 to 10 mmol, and even more preferably 0.5 to 5 mmol, per 1 g of bone dry cellulose.

As the oxidizing agent, known ones can be used, such as halogen, hypohalous acid, halous acid, perhalogenic acid, salts thereof, halogen oxides, peroxides, and the like. Among these, sodium hypochlorite is preferred because it is inexpensive and has a low environmental impact. The appropriate amount of the oxidizing agent to be used is, for example, preferably 0.5 to 500 mmol, more preferably 0.5 to 50 mmol, even more preferably 1 to 25 mmol, and most preferably 3 to 10 mmol, per 1 g of bone dry cellulose. . Further, for example, it is preferably 1 to 40 mol per 1 mol of the N-oxyl compound.

In the cellulose oxidation process, the reaction can proceed efficiently even under relatively mild conditions. Therefore, the reaction temperature is preferably 4 to 40°C, and may be room temperature of about 15 to 30°C. As the reaction progresses, carboxyl groups are generated in the cellulose, so a decrease in the pH of the reaction solution is observed. In order for the oxidation reaction to proceed 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 8 to 12, preferably about 10 to 11. Water is preferred as the reaction medium because of its ease of handling and the fact that side reactions are less likely to occur.

The reaction time in the oxidation reaction can be appropriately set according to the degree of progress of the oxidation, and is usually about 0.5 to 6 hours, for example about 0.5 to 4 hours. Further, the oxidation reaction may be carried out in two stages. For example, by oxidizing the oxidized cellulose obtained by filtration after the completion of the first-stage reaction again under the same or different reaction conditions, the efficiency can be improved without being inhibited by the salt produced as a by-product in the first-stage reaction. Can be oxidized well.

Another example of the carboxylation (oxidation) method is a method of oxidizing a cellulose raw material by bringing it into contact with a gas containing ozone. This oxidation reaction oxidizes the hydroxyl groups at at least the 2- and 6-positions of the glucopyranose ring and causes decomposition of the cellulose chain.

The ozone concentration in the ozone-containing gas is preferably 50 to 250 g/m ³ , more preferably 50 to 220 g/m ³ . The amount of ozone added to the cellulose raw material is preferably 0.1 to 30 parts by weight, more preferably 5 to 30 parts by weight, when the solid content of the cellulose raw material is 100 parts by weight. The ozone treatment temperature is preferably 0 to 50°C, more preferably 20 to 50°C. The ozone treatment time is not particularly limited, but is about 1 to 360 minutes, preferably about 30 to 360 minutes. When the ozone treatment conditions are within these ranges, excessive oxidation and decomposition of cellulose can be prevented, resulting in a good yield of oxidized cellulose.

After the ozone treatment, additional oxidation treatment may be performed using an oxidizing agent. The oxidizing agent used in the additional oxidation treatment is not particularly limited, but examples thereof include chlorine-based compounds such as chlorine dioxide and sodium chlorite, oxygen, hydrogen peroxide, persulfuric acid, and peracetic acid. For example, the additional oxidation treatment can be performed by dissolving these oxidizing agents in water or a polar organic solvent such as alcohol to prepare an oxidizing agent solution, and immersing the cellulose raw material in the solution.

The amount of carboxyl groups in the oxidized cellulose can be adjusted by controlling reaction conditions such as the amount of the oxidizing agent added and the reaction time.

(cationization)
When carboxylated (oxidized) cellulose is used as chemically modified cellulose, the above cellulose raw material is treated with a cationizing agent such as glycidyltrimethylammonium chloride, 3-chloro-2hydroxypropyltrialkylammonium hydrite, or its halohydrin type, and a catalyst. Cationically modified cellulose can be obtained by reacting a certain alkali metal hydroxide (sodium hydroxide, potassium hydroxide, etc.) in the presence of water and/or an alcohol having 1 to 4 carbon atoms. In addition, in this method, the degree of cation substitution per glucose unit of the obtained cation-modified cellulose can be controlled by controlling the amount of the cationizing agent to be reacted and the composition ratio of water and/or alcohol having 1 to 4 carbon atoms. It can be adjusted by.

The degree of cation substitution per glucose unit of the cation-modified cellulose is preferably 0.02 to 0.50. By introducing cationic substituents into cellulose, the cells electrically repel each other. Therefore, cellulose into which cationic substituents have been introduced can be easily nano-fibrillated. Note that if the degree of cation substitution per glucose unit is less than 0.02, sufficient nanofibrillation cannot be achieved. On the other hand, if the degree of cation substitution per glucose unit is greater than 0.50, the nanofibers may not be obtained due to swelling or dissolution. In order to efficiently perform fibrillation, the oxidized cellulose-based raw material obtained above is preferably washed.

(esterification)
When using cellulose into which phosphate groups have been introduced as chemically modified cellulose, compounds having phosphate groups in the cellulose raw material include phosphoric acid, sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, pyrroline. Sodium acid, sodium metaphosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tripotassium phosphate, potassium pyrophosphate, potassium metaphosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, pyrroline Examples include ammonium acid and ammonium metaphosphate. A phosphoric acid group can be introduced using one type or a combination of two or more types of these. The ratio of the compound having a phosphoric acid group to the cellulose raw material is preferably 0.1 to 500 parts by weight, calculated as elemental phosphorus, per 100 parts by weight of the solid content of the cellulose raw material, and 1 to 400 parts by weight. 1 part by weight, and even more preferably 2 to 200 parts by weight.

(defibration)
The defibrating device is not particularly limited, but it is preferable to apply a strong shearing force to the aqueous dispersion using a device such as a high-speed rotation type, a colloid mill type, a high pressure type, a roll mill type, or an ultrasonic type. In particular, for efficient fibrillation, it is preferable to use a wet high pressure or ultra-high pressure homogenizer that can apply a pressure of 50 MPa or more to the aqueous dispersion and a strong shearing force. The pressure is more preferably 100 MPa or more, and still more preferably 140 MPa or more. Additionally, prior to defibration and dispersion treatment using a high-pressure homogenizer, it is also possible to pre-process the above CNF using a known mixing, stirring, emulsifying, and dispersing device such as a high-speed shear mixer, if necessary. It is.

By blending the above CNFs into the antifouling resin coating 20, the CNFs hydrogen bond with each other to form a network structure, and this network structure and the resin portion 21 are integrated. As a result, the strength (durability) of the antifouling resin coating 20 is improved, so that the sustainability of the antifouling effect of the antifouling resin coating 20 is improved, and antifouling properties can be obtained over a long period of time.

The blending amount of CNF in the antifouling resin coating 20 is set so as to impart desired durability to the antifouling resin coating 20, and is preferably 0.5 mass% or more based on the entire antifouling resin coating 20. is set to be 1 mass% or more. Further, the ratio of CNF to the entire antifouling resin coating 20 is, for example, 20 mass% or less, preferably 10 mass% or less. This suppresses the proportion of CNF exposed on the surface of the antifouling resin coating 20, thereby suppressing deterioration in antifouling properties due to the addition of CNF.

In the manufacturing process of the canvas 1 described above, first, the warp 11 and the weft 12 are woven to form the canvas body 10. Thereafter, the antifouling agent, acrylic ester copolymer emulsion, CNF, and water are mixed to create a mixed solution. The canvas 1 is completed by applying this liquid mixture to the paper-contacting surface of the canvas body 10 and then drying it to remove moisture.

At this time, by using CNF with a small fiber diameter as described above as the CNF added to the mixed liquid, it becomes difficult for CNF to precipitate in the mixed liquid, so it is possible to uniformly disperse CNF in the mixed liquid. can. By applying this liquid mixture to the surface of the canvas body 10, CNF can be uniformly distributed on the surface of the canvas body 10.

Further, by using CNF having a short fiber length as described above as the CNF added to the mixed liquid, it becomes difficult for CNF to aggregate in the mixed liquid. Moreover, by using TEMPO-oxidized CNF as CNF added to the mixed liquid, CNF becomes more difficult to aggregate in the mixed liquid. This makes it difficult for aggregated CNF lumps to be formed in the mixed liquid, so it is possible to prevent the air permeability of the canvas 1 from decreasing due to CNF lumps clogging the gaps in the canvas body 10.

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

<Production of cellulose nanofiber A>
5.00 g (absolutely dry) of bleached unbeaten kraft pulp (whiteness 85%) derived from conifers, 39 mg of TEMPO (Sigma Aldrich) (0.05 mmol per 1 g of absolutely dry cellulose) and 514 mg of sodium bromide (absolutely dry) 1.0 mmol per 1 g of cellulose) was added to 500 ml of an aqueous solution and stirred until the pulp was uniformly dispersed. An aqueous sodium hypochlorite solution was added to the reaction system so that the sodium hypochlorite concentration was 6.0 mmol/g, and the oxidation reaction was started. During the reaction, the pH in the system decreased, but the pH was adjusted to 10 by successively adding a 3M aqueous sodium hydroxide solution. The reaction was terminated when the sodium hypochlorite was consumed and the pH within the system stopped changing. The mixture after the reaction was filtered through a glass filter to separate the pulp, and the pulp was sufficiently washed with water to obtain oxidized pulp (carboxylated cellulose). The pulp yield at this time was 90%, the time required for the oxidation reaction was 90 minutes, and the amount of carboxyl groups was 1.6 mmol/g. This was adjusted to 1.0% (w/v) with water and treated with an ultra-high pressure homogenizer (20° C., 150 MPa) three times to obtain a dispersion of cellulose nanofibers A. The average fiber diameter was 3 nm, and the average fiber length was 700 nm.

The amount of carboxyl groups in the obtained oxidized cellulose was measured as follows. Prepare 60ml of 0.5% by mass slurry of oxidized cellulose, add 0.1M hydrochloric acid aqueous solution to adjust the pH to 2.5, and then dropwise add 0.05N sodium hydroxide aqueous solution until the pH reaches 11.Electrical conductivity was measured and calculated using the following formula from the amount of sodium hydroxide (a) consumed in the neutralization stage of the weak acid where the change in electrical conductivity is gradual.
Amount of carboxyl group [mmol/g pulp] = a [ml] x 0.05/mass of oxidized cellulose [g].

<Production of cellulose nanofiber B>
5 g (absolutely dry) of bleached conifer-derived DKP (manufactured by Bakkai) was added to 500 ml of an aqueous solution containing 78 mg (0.5 mmol) of TEMPO (Sigma Aldrich) and 755 mg (7.4 mmol) of sodium bromide, until the pulp was uniform. Stir until dispersed. After adding 16 ml of 2M aqueous sodium hypochlorite solution to the reaction system, the pH was adjusted to 10.3 with 0.5N aqueous hydrochloric acid solution to start the oxidation reaction (oxidation treatment). During the reaction, the pH in the system decreased, but the pH was adjusted to 10 by successively adding 0.5N aqueous sodium hydroxide solution. After reacting for 2 hours, oxidized cellulose was obtained by filtering with a glass filter and thoroughly washing with water. The amount of carboxyl groups in the obtained oxidized cellulose was 1.7 mmol/g. This was adjusted to 1.0% (w/v) with water and treated 10 times with an ultra-high pressure homogenizer (20° C., 140 MPa) (fibrillation and dispersion treatment) to obtain a dispersion of cellulose nanofibers B. The average fiber diameter was 3 nm, and the average fiber length was 350 nm.

[Tape peel strength test]
Comparative Example 1 in which no antifouling resin coating was formed on the surface of the canvas body shown in Table 1 below, and Comparative Example 2 and Examples 1 to 4 in which an antifouling resin coating was formed on the surface of the same canvas body were prepared. . The specifications of Comparative Examples 1 and 2 and Examples 1 to 4 are shown in Table 2 below. The antifouling resin film was formed from an antifouling agent, an acrylic ester copolymer, and CNF. As the antifouling agent in the antifouling resin film, SG3 manufactured by Parker Corporation, which is a silicone water-based emulsion, was used. As the CNF, the above cellulose nanofiber A and cellulose nanofiber B were used.

Then, in order to reproduce the long-term usage condition, as shown in FIG. The roll 30 and the canvas C were rotated while being pressed with a load F. Then, the tape peel strength was measured at predetermined time intervals using the apparatus shown in FIG. Specifically, a tape 51 is pasted on the paper-contacting surface of the canvas C (the surface on which the antifouling resin film is formed), and the tape 51 is pulled in a predetermined direction with a predetermined force via a load cell 52 to remove the canvas. The tape was peeled off from C, and the load (tape peel strength) indicated by the load cell 52 at this time was measured.

As a result, as shown in FIG. 4, Comparative Example 2 and Examples 1 to 5, in which an antifouling resin coating was formed, had lower tape peel strength than Comparative Example 1, which did not have an antifouling resin coating (i.e., an antifouling resin coating). high quality). In addition, in Examples 1 to 5 in which an antifouling resin film containing CNF was formed, compared to Comparative Example 2 in which an antifouling resin film not containing CNF was formed, when the friction time with the brush elapsed (after 9 hours) ) had low tape peel strength. These results show that the antifouling property of the antifouling resin coating decreases as the friction time with the brush passes, but the extent to which the antifouling property decreases (the degree of increase in tape peel strength) is greater than that in Comparative Example 2. It was confirmed that Examples 1 to 4 were higher. This confirmed that the sustainability of the antifouling effect was improved by incorporating CNF into the antifouling resin film.

[Breathability test]
For Comparative Example 2 and Examples 1 to 4 in Table 2, the air permeability before and after forming the antifouling resin film was measured by the Frazier test method (see JIS L 1096:2010 8.26.1). As a result, as shown in Table 3 below, in Example 1 in which the CNF fiber length was relatively long, the air permeability was significantly lower than before the antifouling resin coating was formed. On the other hand, in Comparative Example 2, which did not contain CNF, and Examples 2 to 4, in which the CNF fiber length was relatively short, the air permeability was almost the same as before the antifouling resin coating was formed. From the above, it was confirmed that by incorporating CNF with a relatively short fiber length (specifically 600 nm or less) into the antifouling resin film, the decrease in air permeability of the canvas body due to the formation of the antifouling resin film can be suppressed. It was done.

1 Dryer canvas for papermaking (industrial belt)
10 Canvas body (belt body)
11 Warp 12 Weft 20 Antifouling resin coating 21 Resin part 30 Roll 40 Brush 51 Tape 52 Load cell

Claims (5)

An industrial belt comprising a belt body made of a woven or nonwoven fabric made of synthetic fibers, and an antifouling resin coating coated on the surface of the belt body,
The antifouling resin coating contains cellulose nanofibers,
An industrial belt , wherein the average fiber length of the cellulose nanofibers is 600 nm or less . The industrial belt according to claim 1, wherein the proportion of cellulose nanofibers in the antifouling resin coating is 20 mass% or less. The industrial belt according to claim 1 or 2, wherein the cellulose nanofibers are anion-modified cellulose nanofibers. The industrial belt according to claim 3, wherein the anion-modified cellulose nanofiber is a TEMPO-oxidized cellulose nanofiber. The industrial belt according to any one of claims 1 to 4, which is used as a dryer canvas for papermaking.