JP2023008139A - water supply roll - Google Patents

Abstract

To provide a water supply roll capable of maintaining hydrophilicity over a long term, made of a rubber vulcanizate whose material itself is hydrophilic, and used for offset printing.SOLUTION: A water supply roll is incorporated into an offset printing press, and comprises a support and one or more elastic layers arranged on the surface of the support. The elastic layer located on the outermost surface is a rubber vulcanizate containing modified rubber and cellulose nanofibers. The cellulose nanofiber is included in 0.5 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the modified rubber.SELECTED DRAWING: Figure 1

Description

The present invention relates to a water supply roll for offset printing.

Offset printing is a printing method that utilizes the repelling properties of oil (ink) and water. This printing method is currently the mainstream printing technology and is used for printing newspapers, magazines and the like.

Offset printing is performed by the following procedure. First, an image area (ink-philic (lipophilic) resin layer) and a non-image area (hydrophilic aluminum layer) are formed in advance on a plate mounted on a printing cylinder. Then, dampening water is applied to the non-image area by a dampening water device. Subsequently, the image area is inked by an inking device, and the ink image is transferred to a rubber blanket that rotates in contact with the plate. Then, an object to be printed such as paper is passed between the rubber blanket and the rotating impression cylinder, and the ink image on the rubber blanket is transferred to perform printing.

A dampening water device used in offset printing includes, for example, a water boat containing dampening water, and a metal water source roll partly immersed in the dampening water in the water boat and plated with chromium on the surface. , a metering roll having a rubber layer on the surface that rotates in contact with the water source roll, a metal transfer roll that rotates in contact with the metering roll, and water that rotates in contact with the transfer roll Comes with a wearing roll. In the dampening water apparatus of such construction, the dampening water in the water boat is drawn up by the water source roll and transferred to the metering roll. After the dampening solution on the metering roll is transferred from the transfer roll to the dampening roll, it is supplied to the non-image area of the plate mounted on the plate cylinder to dampen the plate surface. In addition, as another dampening water device, a water source roll having a rubber layer on the surface is used instead of the water source roll whose surface is plated with chromium, and the surface is chromium plated instead of the metering roll and the transfer roll. There is a form that uses a metal water leveling roll that has been subjected to These rolls have hydrophilic surfaces and are collectively called water supply rolls.

In offset printing, if the dampening water supplied to the plate by the water supply roll is insufficient, the ink adheres to the non-image areas of the plate, and the ink is transferred to the printed matter, resulting in a defective printed matter. On the other hand, if the amount of dampening water is excessive, the dampening water will also adhere to the image area on the plate, and the amount of ink transferred to the image area will be insufficient, resulting in insufficient ink density on the printed matter.

In rolls having a rubber layer on their surface, the rubber material used for the rubber layer is generally often hydrophobic. However, the surface of the water supply roll is desired to be hydrophilic in order to supply an appropriate amount of dampening water to the plate.

Techniques for imparting hydrophilicity to the surface of a rubber roll are disclosed in Patent Documents 1 and 2, for example. Patent Literature 1 discloses a non-porous metal leveling roll coated with a hydrophilic metal layer.

Patent Literature 2 discloses a wet dampening roll in which the surface of a rubber roll is treated with an organic halogen compound to impart hydrophilicity to the surface.

JP-A-7-186568 JP-A-2000-158842

However, the leveling roll described in Patent Document 1 is different from the roll whose outermost surface is coated with a metal layer and whose outermost surface is a rubber layer.

The dampening roll described in Patent Document 2 is hydrophilized only in the vicinity of the surface due to surface treatment with an organic halogen compound. Therefore, when the surface of the wet dampening roll wears out due to use, the hydrophilic function decreases or disappears, causing poor printing. In addition, when the hydrophilicity of the surface is lowered, ink tends to adhere to the surface, making it difficult to clean the surface after printing. Furthermore, in order to impart a hydrophilic function, it is necessary to re-treat the surface with an organic halogen compound, which is costly and labor intensive.

An object of the present invention is to provide a water supply roll for offset printing, which is made of a rubber vulcanizate having hydrophilic properties and has an elastic layer capable of maintaining hydrophilic properties over a long period of time.

In order to solve the above problems, the water supply roll of the present invention comprises a support and one or more elastic layers disposed on the surface of the support, wherein the elastic layer located on the outermost surface comprises a modified rubber and It is a rubber vulcanizate containing cellulose nanofibers, and the cellulose nanofibers are contained in an amount of 0.5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the modified rubber.

FIG. 1 is a schematic cross-sectional view showing an example of a water supply roll according to an embodiment. FIG. 2 is a schematic cross-sectional view showing an example of the water supply roll according to the embodiment. FIG. 3 is a schematic diagram showing an example of a printing press equipped with a dampening device to which the water supply roll according to the embodiment is applied. FIG. 4 is a schematic diagram showing an example of another printing press equipped with a dampening device to which the water supply roll according to the embodiment is applied.

A water supply roll according to an embodiment of the present invention will be described below.

(First embodiment)
A water supply roll according to the first embodiment is provided for an offset printing press. As shown in FIG. 1 , the water supply roll 1 has a support 2 . One or more (for example, one) elastic layer 3 is provided on the surface of the support.

FIG. 2 is a schematic cross-sectional view showing another form of the water supply roll 1. As shown in FIG. The water supply roll 1 is provided with two elastic layers consisting of an outermost elastic layer 3 on the surface of the support 2 and an elastic layer 4 positioned inside the elastic layer 3 (lower elastic layer).

(support)
The support is, for example, a cylindrical cored bar. As the support, for example, a known rigid support such as a metal such as iron, aluminum, or stainless steel, or a carbon fiber reinforced plastic can be used. The support may be a cylindrical cored bar. Furthermore, a configuration in which shafts are pressed against both ends of a cylindrical core bar may be used.

(elastic layer)
The elastic layer is composed of one or more layers, and at least the outermost elastic layer is a rubber vulcanizate containing modified rubber and cellulose nanofibers (hereinafter sometimes referred to as outermost rubber vulcanizate). The elastic layer may have a single-layer structure or a multi-layer structure. When the elastic layer has a single layer structure, it is composed only of the rubber vulcanizate for the outermost surface. When the elastic layer has a multi-layer structure, the elastic layer below the outermost elastic layer is composed of a rubber vulcanizate (hereinafter sometimes referred to as a rubber vulcanizate for the lower layer). This rubber vulcanizate is not particularly limited, and is appropriately selected according to the use conditions of the water supply roll. However, the underlayer rubber vulcanizate may or may not contain cellulose nanofibers. Incidentally, the lower elastic layer may be two or more layers.

(Rubber vulcanizate for outermost surface)
The modified rubber has a polar group introduced into its molecular skeleton. The polar group has the effect of improving the affinity with the cellulose nanofibers, suppressing the aggregation of the cellulose nanofibers, and enhancing the dispersibility of the cellulose nanofibers, as will be described later. Examples of the polar group include a carboxyl group, an acid anhydride group, a hydroxyl group, an epoxy group, and the like. Among them, a modified rubber into which a carboxyl group or an acid anhydride group has been introduced is preferable in terms of easy availability. A plurality of types of polar groups may be introduced.

Modified rubbers include, for example, butadiene rubbers, nitrile rubbers (NBR), rubbers modified from styrene-butadiene rubbers, and rubbers modified from partially hydrogenated rubbers thereof. Specifically, carboxyl group-containing butadiene rubber, carboxyl group-containing nitrile rubber, carboxyl group-containing hydrogenated nitrile rubber, carboxyl group-containing styrene-butadiene rubber, carboxyl group-containing hydrogenated styrene-butadiene rubber, acid anhydride-modified butadiene rubber, acid anhydride One or a mixture of two or more selected from poly-modified nitrile rubber, acid anhydride-modified hydrogenated nitrile rubber, acid anhydride-modified styrene-butadiene rubber, and acid anhydride-modified hydrogenated styrene-butadiene rubber can be used.

Modified rubber may be used by mixing two or more modified rubbers.

In recent years, the cellulose nanofiber has attracted attention as a reinforcing material for rubber because of its light weight, high elastic modulus, and low environmental load. However, the inventors focused on the fact that cellulose nanofibers have hydrophilicity, and found that adding them to the rubber vulcanizate forming the elastic layer on the outermost surface can impart hydrophilicity to the elastic layer. . The cellulose nanofiber preferably has a diameter of 1 nm or more and 1,000 nm or less and a length of 10 times or more and 1,000 times or less of the diameter. Cellulose nanofibers preferably have a diameter of 1 nm or more and 50 nm or less, and a length of 10 times or more and 1,000 times or less the diameter, and still more preferably the same diameter and a length of 50 times or more and 1,000 times or less the diameter. is.

Cellulose nanofibers are dispersed in the range of 0.5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the modified rubber in the rubber vulcanizate. The cellulose nanofiber is more preferably 1 part by mass or more and 10 parts by mass or less, still more preferably 2 parts by mass or more and 10 parts by mass or less. If the amount of cellulose nanofibers dispersed is less than 0.5 parts by mass, the rubber vulcanizate cannot be imparted with sufficient hydrophilicity, making it difficult to obtain a rubber vulcanizate having the desired properties. If the amount of cellulose nanofibers added exceeds 20 parts by mass, the cellulose nanofibers tend to agglomerate with each other, and aggregates may form in the rubber vulcanizate. When aggregates of cellulose nanofibers are generated in the rubber vulcanizate, only those portions are locally swollen, and the smoothness of the outermost elastic layer is impaired. In addition, since the material price of cellulose nanofibers is higher than that of general rubber compounding agents, an excessive increase in the amount added is not preferable from an economic point of view.

(Rubber vulcanizate for lower layer)
The rubber vulcanizate for the lower layer is not particularly limited, and may be selected based on properties such as hardness and liquid resistance according to the usage environment of the water supply roll. For example, a rubber vulcanizate similar to the rubber vulcanizate for the outermost surface may be used, a rubber vulcanizate of modified rubber alone, a vulcanizate of a raw material rubber described in the second embodiment described later, or a modified rubber vulcanizate. A rubber vulcanizate of a mixture of a high molecular weight polymer and a raw material rubber may be used.

In the water supply roll according to the first embodiment, when the amount of cellulose nanofiber added in the rubber vulcanizate for the outermost surface is relatively large within the above range, the rubber vulcanizate for the outermost surface is formed from The elastic layer on the outermost surface swells due to water absorption during use and increases in thickness. Therefore, from the viewpoint of increasing the accuracy of the outer diameter, it is preferable to reduce the thickness of the outermost elastic layer. However, if the thickness of the elastic layer on the outermost surface is reduced, the strength of the elastic layer itself may be lowered. In order to deal with this, it is preferable to arrange one or more elastic layers containing no cellulose nanofibers under the outermost elastic layer to form a multi-layered structure.

On the other hand, when the amount of cellulose nanofiber added to the rubber vulcanizate for the outermost surface is relatively small within the above range, the outermost elastic layer formed from the rubber vulcanizate for the outermost surface is used. It is possible to suppress swelling due to water absorption at times. Therefore, the thickness of the outermost elastic layer can be increased, and the elastic layer coated on the support can have a single-layer structure of the outermost elastic layer.

Cellulose nanofibers are more expensive than general rubber compounding agents. By forming a multi-layered structure of rubber vulcanizates that do not contain, the amount of cellulose nanofibers used can be reduced, which is also preferable from an economical point of view.

When the water supply roll according to the first embodiment has a structure of two or more layers, at least the outermost elastic layer preferably does not contain a plasticizer. If a large amount of plasticizer is added to adjust the elastic layer to a desired hardness, the plasticizer may be gradually extracted during use, resulting in changes in hardness and shrinkage of the outer diameter of the water supply roll. As a result, the contact width (nip width) between the water supply roll and the opposing member rotating in contact with the water supply roll changes, making it difficult to uniformly adjust the water supply amount.

According to the first embodiment, at least the outermost elastic layer is composed of a rubber vulcanizate containing modified rubber and a specific amount of cellulose nanofibers, thereby maintaining hydrophilicity for a long period of time. A water roll can be provided.

When the water supply roll according to the first embodiment has a structure of two or more layers, the elastic layer positioned below the outermost elastic layer has a hardness of 10 to 30 to maintain a desired nip width. Below (type A) (according to JIS K6253), it is preferably formed of a rubber vulcanizate having a hardness of 10 or more and 25 or less (type A). If the hardness exceeds 30 (Type A), it becomes difficult to adjust the desired nip width. On the other hand, if the hardness is less than 10 (Type A), the viscosity of the rubber composition is too low, making it difficult to mold it into a roll shape.

In the water supply roll according to the first embodiment, when it has a structure of two or more layers, the thickness of the outermost elastic layer is preferably 0.1 mm or more and 4.0 mm or less, more preferably 0.3 mm or more. 3.0 mm or less, more preferably 0.5 mm or more and 2.0 mm or less. At this time, the thickness of the elastic layer formed of the rubber vulcanizate having a hardness of 10 or more and 30 or less (type A) located on the lower layer side (inner side) of the outermost surface is adjusted so that the desired nip width can be obtained. should be adjusted accordingly. If the thickness of the elastic layer on the outermost surface exceeds 4.0 mm, there is a risk of impairing the accuracy of the outer diameter of the rubber roll due to swelling during absorption of water. On the other hand, if the thickness of the outermost elastic layer is less than 0.1 mm, the outermost elastic layer may be damaged during polishing.

The surface roughness of the water supply roll according to the first embodiment (the surface roughness of the outermost elastic layer) is preferably 2 μm or less, more preferably 1 μm in terms of arithmetic mean roughness Ra (according to JIS B0601). .5 μm or less. Surface roughness affects the supply of dampening water. When the water supply roll is used for a long period of time, the surface roughness gradually becomes finer due to the wear of the surface, and the amount of dampening water supplied changes. By finely finishing the initial surface roughness such that the arithmetic mean roughness Ra is 2 μm or less as described above, the change in surface roughness can be reduced, and the initial supply amount of dampening water can be reduced. can be maintained. In addition, in the water supply roll according to the embodiment, the outermost elastic layer composed of the rubber vulcanizate described above exhibits hydrophilicity, and the dependence of the surface roughness on the amount of dampening water supplied is low. Even if the surface roughness changes over time, the initial supply of dampening water can be maintained.

(contact angle)
The elastic layer on the outermost surface of the water supply roll according to the first embodiment preferably has a contact angle with pure water of 100 degrees or less in a water-containing state. That is, since the water supply roll is used while constantly in contact with the dampening water, the outermost elastic layer is impregnated with the dampening water during use. Therefore, in the measurement of the contact angle in the present invention as well, the contact angle with pure water is measured after immersing the measurement sample in pure water in advance to obtain a water-containing state.

By setting the contact angle with pure water in a water-containing state to 100 degrees or less, the dampening water spreads evenly on the surface of the outermost elastic layer of the water supply roll to form a uniform thin film of dampening water. can be done. On the other hand, if the contact angle exceeds 100 degrees, the dampening water becomes uneven on the surface of the water supply roll, which may cause poor printing.

(Thickness change rate of rubber vulcanizate for outermost surface)
In the water supply roll according to the first embodiment, the outermost rubber vulcanizate used for the outermost elastic layer has a thickness change rate of 20% or less in a pure water immersion test (according to JIS K6258). is preferably 10% or less. If the rate of change in thickness exceeds 20%, the outermost elastic layer swells due to water absorption during use, and there is a risk of impairing the accuracy of the outer diameter of the water supply roll.

The rate of change in thickness of the rubber vulcanizate for the outermost surface, excluding the cellulose nanofiber, in a pure water immersion test is preferably 2% or less, more preferably 1% or less, and still more preferably 0. .5% or less. If it exceeds 2%, the water resistance of the elastic layer on the outermost surface is deteriorated, and the deterioration of the elastic layer may be accelerated when used for a long period of time.

A method for manufacturing the water supply roll according to the first embodiment will be described below.

First prepare the support. The surface of the support is blasted, cleaned, and coated with an adhesive.

Next, a rubber composition is prepared. First, an aqueous dispersion of cellulose nanofibers and an aqueous dispersion of modified rubber are mixed and uniformly dispersed. The aqueous dispersion of cellulose nanofibers may be, for example, an aqueous dispersion in which cellulose nanofibers are dispersed in water at a concentration of 0.2% or more and 10% or less, and such dispersions are commercially available. Commercially available rubber latex, for example, may be used as the aqueous dispersion of the modified rubber.

Next, the mixed dispersion is dried to remove moisture to obtain a masterbatch of cellulose nanofibers and modified rubber.

The resulting masterbatch is then kneaded. At the time of kneading, the masterbatch may optionally contain general rubber compounding agents such as vulcanizing agents, vulcanization accelerators, anti-aging agents, processing aids, fillers, or plasticizers. The method of kneading is not particularly limited, but known techniques such as a kneader kneader, Banbury mixer, and open roll may be used.

Next, the rubber composition obtained by kneading is coated on the support to form an elastic layer. The method of forming the elastic layer is not particularly limited, but for example, a method in which the rubber composition is dispensed into a sheet and wound around the surface of the support; The support is coated with the rubber composition by a method such as coating with Next, after heating and vulcanizing, the surface of the cylindrical rubber vulcanizate is polished using a rotating grindstone or the like to form a single elastic layer having a predetermined outer diameter and surface roughness. to manufacture a water supply roll.

In the case of an elastic layer having a multi-layered structure having two or more elastic layers, the lower elastic layer is first formed on the support, vulcanized and polished, and then the outermost elastic layer is formed on the lower elastic layer. do it. Alternatively, after forming the lower elastic layer first, the outermost elastic layer may be formed, vulcanized and polished before vulcanizing the elastic layer. In order to strengthen the adhesion of the outermost elastic layer to the underlying elastic layer, an adhesive may be further applied between the layers. Furthermore, when forming a thin outermost elastic layer, a solvent such as toluene may be added to the outermost rubber composition to form a solution, which may then be molded by coating.

(Second embodiment)
The water supply roll according to the second embodiment has the same structure as shown in FIG. 1 or 2 as described in the first embodiment, that is, a support and one or more layers provided on the surface of the support. and an elastic layer.

(elastic layer)
The elastic layer is composed of one or more layers, and at least the outermost elastic layer is a rubber vulcanizate containing a raw material rubber, a modified polymer, and cellulose nanofibers (hereinafter sometimes referred to as an outermost rubber vulcanizate). There is). The elastic layer may have a single-layer structure or a multi-layer structure. When the elastic layer has a single layer structure, it is composed only of the rubber vulcanizate for the outermost surface. When the elastic layer has a multi-layer structure, the elastic layer below the outermost elastic layer (hereinafter sometimes referred to as the lower layer rubber vulcanizate) is composed of a rubber vulcanizate. This rubber vulcanizate is not particularly limited, and is appropriately selected according to the use conditions of the water supply roll. However, the underlayer rubber vulcanizate may or may not contain cellulose nanofibers. Incidentally, the lower elastic layer may be two or more layers.

(Rubber vulcanizate for outermost surface)
Examples of the raw rubber include natural rubber, isoprene rubber, butadiene rubber, nitrile rubber, hydrogenated nitrile rubber, carboxyl group-containing nitrile rubber, styrene-butadiene rubber, hydrogenated styrene-butadiene rubber, epichlorohydrin rubber, urethane rubber, ethylene propylene rubber ( EPDM) and chloroprene rubber, or mixtures of one or more rubbers may be used.

Among the raw rubbers, polar raw rubbers are, for example, nitrile rubber, epichlorohydrin rubber, urethane rubber, etc., and non-polar raw rubbers are, for example, ethylene propylene rubber, styrene butadiene rubber and the like.

Among them, ethylene propylene rubber is excellent in water resistance, and by using it as the raw material rubber, the durability of the water supply roll can be further enhanced.

Said modified macromolecular polymers are for example modified rubbers or resins. A modified rubber or resin has a polar group introduced into its molecular skeleton. The polar group has the effect of improving the affinity with the cellulose nanofibers, suppressing the aggregation of the cellulose nanofibers, and enhancing the dispersibility of the cellulose nanofibers, as will be described later. Examples of the polar group include a carboxyl group, an acid anhydride group, a hydroxyl group, an epoxy group, and the like. Among them, a modified high molecular weight polymer into which a carboxyl group or an acid anhydride group has been introduced is preferable in terms of easy availability. A plurality of types of polar groups may be introduced.

As the modified rubber, the same one as explained in the first embodiment can be used.

Examples of modified resins include modified polyolefin resins. Examples of polyolefin resins include polyethylene, polypropylene, polybutene, ethylene-propylene copolymers, ethylene-butene copolymers, and the like. Those modified with are exemplified.

The modified high molecular weight polymer may be used by mixing two or more modified high molecular weight polymers.

In the second embodiment, the modified high molecular weight polymer has a relatively low melting point, and modified polyethylene, ethylene-propylene copolymer, ethylene-butene copolymer, which improves workability in the kneading step with the raw rubber. It is preferred to use polymers. Furthermore, the modified polyolefin resin is preferable because it has good compatibility with low-polar raw material rubber such as ethylene propylene rubber.

The mixture of raw rubber and modified high molecular weight polymer has the following four forms.
1) A mixture of raw rubber having polarity and modified rubber.
2) A mixture of raw rubber having polarity and modified resin (modified polyolefin).
3) A mixture of non-polar raw rubber and modified rubber.
4) A mixture of a non-polar raw rubber and a modified resin (modified polyolefin).

The inventors have found that the modified polyolefin is compatible with the non-polar raw rubber in the mixture of the form 4). The rubber vulcanizate for the outermost surface containing such a mixture can exhibit high durability in addition to hydrophilicity due to the excellent water resistance of the non-polar raw rubber.

The mixing ratio of the raw material rubber is preferably 1 part by mass or more and 99 parts by mass or less with respect to 100 parts by mass as the total amount of the raw material rubber and the modified polymer. It is more preferably 40 parts by mass or more and 95 parts by mass or less, and still more preferably 60 parts by mass or more and 95 parts by mass or less. If the raw rubber exceeds 99 parts by mass, the cellulose nanofibers may easily aggregate. In addition, since the production cost of the modified high molecular weight polymer is high for masterbatching, it is economically preferable to reduce it as much as possible. is preferred.

The same cellulose nanofibers as those described in the first embodiment can be used. Cellulose nanofibers are preferably dispersed in the range of 0.5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass as the total amount of raw rubber and modified polymer in the rubber vulcanizate. The cellulose nanofiber is more preferably 1 part by mass or more and 10 parts by mass or less, still more preferably 2 parts by mass or more and 10 parts by mass or less. The stipulation of the mixing ratio of the cellulose nanofibers is based on the same reason as explained in the first embodiment.

(Rubber vulcanizate for lower layer)
The rubber vulcanizate for the lower layer is not particularly limited, and may be selected based on properties such as hardness and liquid resistance according to the usage environment of the water supply roll. For example, a rubber vulcanizate similar to the rubber vulcanizate for the outermost surface may be used, a rubber vulcanizate of a raw material rubber, or a rubber vulcanizate of a mixture of a raw rubber and a modified high molecular polymer may be used. good.

According to the second embodiment, at least the outermost elastic layer is composed of a rubber vulcanizate containing a raw material rubber, a modified high molecular weight polymer, and a specific amount of cellulose nanofibers. Similarly, it is possible to provide a water supply roll capable of maintaining hydrophilicity for a long period of time.
Further, according to the second embodiment, since raw rubber is used for the rubber vulcanizate for the outermost surface, it is possible to provide a water supply roll with reduced raw material costs.

Further, according to the water supply roll of the second embodiment, since the water resistance of the raw rubber can be improved, a long-life water supply roll can be provided.

In the water supply roll according to the second embodiment, the hardness of the elastic layer located on the lower layer side of the outermost elastic layer, the thickness of the outermost elastic layer, the surface roughness (surface roughness of the outermost elastic layer ), the contact angle with pure water in the water-containing state of the outermost elastic layer, and the thickness change rate of the outermost rubber vulcanizate are specified to values similar to those described in the first embodiment. is preferred.
A method for manufacturing a water supply roll according to the second embodiment will be described below.

The method for producing a water supply roll according to the second embodiment is substantially the same as the first method except that raw rubber is added to the masterbatch of cellulose nanofibers and modified high molecular weight polymer and kneaded to prepare a rubber composition. It is the same as the manufacturing method of the water supply roll described in the embodiment of .

That is, after obtaining a masterbatch of cellulose nanofibers and a modified high molecular weight polymer, the obtained masterbatch is kneaded with raw rubber to obtain a rubber composition. When kneading, in addition to the masterbatch and raw rubber, vulcanizing agents and vulcanization accelerators are blended, and general rubber such as anti-aging agents, processing aids, fillers, or plasticizers are added as necessary. A compounding agent may be blended. The method of kneading is not particularly limited, but known techniques such as a kneader kneader, Banbury mixer, and open roll may be used.

Then, the obtained rubber composition is coated on a support to form an elastic layer. Then, after vulcanizing by heating to obtain a rubber vulcanizate, the surface of the rubber vulcanizate is polished to produce a water supply roll.

Cellulose nanofibers have poor dispersibility in raw rubber. As in the method for manufacturing a water supply roll of the second embodiment, a masterbatch of cellulose nanofibers and a modified high molecular weight polymer is prepared in advance, and then the raw material rubber is kneaded into the masterbatch, whereby the cellulose nanofibers are well formed. A dispersed rubber composition can be obtained.

Next, application examples of the water supply rolls according to the first and second embodiments will be described with reference to FIG. FIG. 3 is a schematic diagram showing an example of a printing press equipped with a dampening water device to which the water supply rolls according to the first and second embodiments are applied.

A printing cylinder 101 shown in FIG. 3 has a printing plate (not shown) attached to its surface and rotates, for example, counterclockwise. A dampening unit 110 and an inking unit 120 are arranged counterclockwise around the plate cylinder 101 in this order. The dampening system 110 comprises a water boat 111 containing dampening water. A portion of a rotatable water fountain roll 112 is immersed in the dampening water in the water boat 111 . The water source roll 112 has a function of assembling dampening water in the water boat 111 . The water source roll 112 is provided with a metering roll 113 that rotates in contact with the water source roll 112 . The metering roll 113 is configured to be axially reciprocable in order to transfer the dampening water pumped up by the water source roll 112 as a film and spread the dampening water film uniformly. A transfer roll 114 that rotates in contact with the metering roll 113 is arranged on the metering roll 113 . Between the plate cylinder 101 and the transfer roll 114 is disposed a dampening roll 115 that rotates in contact with the plates (not shown) of the plate cylinder 101 and the transfer roll 114 . In the dampening water apparatus 110 having such a configuration, the dampening water in the water boat 111 is drawn up by the water source roll 112 and transferred to the metering roll 113 . Since the metering roll 113 reciprocates in the axial direction, the dampening solution film transferred from the dampening roll 112 is uniformly spread and transferred to the transfer roll 114 and then to the dampening roll 115 . The dampening water transferred to dampening roll 115 is supplied to the non-image portion of the plate (not shown) of plate cylinder 101 to dampen the plate surface.

The inking unit 120 comprises a plurality of, for example three, ink transfer rolls 21 . After the plate (not shown) on the plate cylinder 101 passes through the dampening water device 110, ink is supplied to the image portion by the inking device 120 to form an ink image. The ink image is then transferred to a rubber blanket, not shown, which rotates in contact with the plate.

The water supply rolls according to the first and second embodiments can be applied to the metering roll 113 of the dampening water device 110 shown in FIG. In the water supply rolls according to the first and second embodiments, the outermost elastic layer is a rubber vulcanizate containing cellulose nanofibers, and the surface exhibits excellent hydrophilicity. Therefore, by applying the water supply rolls according to the first and second embodiments to the metering roll 113, the wettability with the dampening water is excellent, so that the dampening water film drawn up by the water source roll 112 can be spread evenly and transferred to the transfer roll 114 .

Further, as described above, since the metering roll 113 reciprocates in the axial direction, it is used under conditions where the surface tends to be worn and the surface roughness tends to change. By applying the water supply rolls according to the first and second embodiments to the metering roll 113, the material of the outermost elastic layer itself has excellent hydrophilicity. The dampening water film drawn up by the original roll 112 can be spread uniformly.

The water supply rolls according to the first and second embodiments can be applied to the dampening roll 115 of the dampening water device 110 shown in FIG. The dampening roll 115 is placed in contact with the plate (not shown) of the plate cylinder 101 and supplies dampening water pumped up from the water boat 111 to the plate. In the water supply rolls according to the first and second embodiments, the elastic layer on the outermost surface is a rubber vulcanizate containing cellulose nanofibers, and the surface exhibits excellent hydrophilicity, so good wettability with dampening water. have As a result, by applying the water supply roll to the dampening roll 115 , the dampening water received from the transfer roll 114 can be maintained in a uniform thin film state and supplied to the plate of the plate cylinder 101 .

In the process of supplying ink to the image portion of the plate on the plate cylinder 101 by the inking device 120 and transferring the ink image to the rubber blanket rotating in contact with the plate, all the ink on the plate surface is transferred to the rubber blanket. Instead, some of the ink remains on the plate surface and comes into contact with the dampening roll 115 again. As a result, the ink remaining on the plate adheres to the dampening roll 115 and prevents the formation of a uniform dampening solution film on the surface of the dampening roll 115, resulting in poor printing.

In the water supply rolls according to the first and second embodiments, the elastic layer on the outermost surface exhibits excellent hydrophilicity as described above. It repels and can suppress adhesion to the dampening roll surface.

In addition, when the ink adheres to the surface of the dampening roll 115, the ink also migrates to the metering roll 113 or the like arranged upstream (on the water boat 111 side), thereby inhibiting the formation of a uniform dampening solution film. there is a possibility. Even in such a case, by applying the water supply rolls according to the first and second embodiments not only to the soaking roll 115 but also to the metering roll 113, adhesion of ink to the surfaces of these rolls can be suppressed and uniform ink can be applied. The effect of maintaining the formation of a dampening water film is obtained.

Furthermore, in general, when ink adheres to the surface of a water supply roll having an elastic layer made of a rubber material on the outermost surface, the ink gradually permeates the inside of the elastic layer. difficult to remove. In the water supply rolls according to the first and second embodiments, the surface (outermost elastic layer) exhibits excellent hydrophilicity and contains water in the vicinity of the surface. to prevent it from penetrating into As a result, there is an effect that the surface of the water supply roll can be easily cleaned.

Next, application examples of the water supply rolls according to the first and second embodiments will be described with reference to FIG. FIG. 4 is a schematic diagram showing an example of another printing press equipped with a dampening water device to which the water supply rolls according to the first and second embodiments are applied. In FIG. 4, members similar to those in FIG. 3 are denoted by the same reference numerals, and descriptions thereof are omitted.

The dampening water device 110 shown in FIG. 4 includes a water boat 111 containing dampening water. A portion of a rotatable water fountain roll 112 is immersed in the dampening water in the water boat 111 . A water leveling roll 116 made of metal plated with chromium, for example, is arranged on the water leveling roll 112 to rotate in contact with the water leveling roll 112 . The leveling roll 116 evenly spreads the dampening water film drawn up by the water source roll 112 at the nip portion between the water source roll 112 and the water source roll 112 . Between the plate cylinder 101 and the leveling roll 116 is disposed a dampening roll 115 that rotates in contact with the plate (not shown) of the plate cylinder 101 and the leveling roll 116 . A water kneading roll 117 that rotates in contact with the dampening roll 115 is arranged on the dampening roll 115 . In the dampening water apparatus 110 having such a configuration, the dampening water in the water boat 111 is drawn up by the water source roll 112 and transferred to the water leveling roll 116 . The dampening roll 116 uniformly spreads the dampening water film transferred from the dampening roll 112 by the nip between the dampening roll 116 and the dampening roll 116 and transfers it to the dampening roll 115 . The dampening water transferred to dampening roll 115 is supplied to the non-image portion of the plate (not shown) of plate cylinder 101 to dampen the plate surface.

The inking device 120 forms an ink image by supplying ink to the image portion after the plate (not shown) of the plate cylinder 101 passes through the dampening water device 110, like the printing machine shown in FIG. The ink image is then transferred to a rubber blanket, not shown, which rotates in contact with the plate.

The water supply rolls according to the first and second embodiments can be applied to the water source roll 112 of the dampening water device 110 shown in FIG. The water supply rolls according to the first and second embodiments have excellent hydrophilicity and good wettability with dampening water. It can be pumped up in the state of a water film, and the dampening water film can be transferred to the leveling roll 116 in a uniform state.

In the water supply rolls according to the first and second embodiments, the elastic layer on the outermost surface has excellent hydrophilicity and good wettability with dampening water. can be applied to the dampening roll 115 of the dampening water device 110 shown in FIG.

In the water supply rolls according to the first and second embodiments, the elastic layer on the outermost surface is a rubber vulcanizate containing cellulose nanofibers, and exhibits high hydrophilicity, so that the hydrophilicity is not lost even when worn. . Therefore, the wet dampening roll 115 applied thereto does not cause poor printing due to long-term use, and the operation cost can be reduced by reducing the work for imparting hydrophilicity again.

[Example]
Examples will be described in detail below.

(Example 1)
(Preparation of masterbatch of cellulose nanofiber and modified rubber)
A carboxyl group-containing nitrile rubber latex (Nipol LX511A, Nippon Zeon Co., Ltd.) was added to 1,000 g of an aqueous dispersion of cellulose nanofibers (Auro Visco, Oji Holdings Co., Ltd., solid content concentration 2.0%). The material was prepared at a ratio of 217 g (product, solid content concentration 46%), mixed using a homogenizer, and dispersed uniformly. A mixture of the obtained aqueous dispersion of cellulose nanofibers and the latex of carboxyl group-containing nitrile rubber was dried in a constant temperature bath at 80°C for 72 hours to prepare a masterbatch containing 20 parts by mass of cellulose nanofibers. .

(Preparation of rubber composition containing cellulose nanofibers)
Next, without using the raw rubber, 120 parts by mass of the above masterbatch, 5 parts by mass of zinc oxide (type 2 zinc oxide, manufactured by Seido Chemical Industry Co., Ltd.) as a vulcanization accelerator, and a processing aid Stearic acid (Lunac S-70V, manufactured by Kao Corporation) 1 part by mass, sulfur for vulcanization (fine powder sulfur, manufactured by Tsurumi Chemical Industry Co., Ltd.) 1.5 parts by mass, CZ as a vulcanization accelerator (N-Cyclohexylbenzothiazole-2-sulfenamide) (Noccellar CZ-G, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.) 1 part by mass was kneaded with an open roll, and A rubber composition for the outermost surface containing 20 parts by mass of cellulose nanofibers (CNF) was produced. After that, it was divided into sheets having a thickness of 0.5 mm by a calender.

(Manufacture of water supply roll)
A rubber composition (lower layer rubber composition) of nitrile rubber having a hardness of 30 (type A) was cut into sheets having a thickness of 0.5 mm.

After blasting the surface of an iron core with a core diameter of 76 mm as a support and applying a rubber adhesive, the sheet of the separated rubber composition for the lower layer is wound around the core and molded, and this is placed in a heating furnace. and vulcanized. After that, the surface was polished with a rotating grindstone to form a lower elastic layer. The outer diameter of the obtained rubber roll was adjusted to 100 mm.

Next, a rubber-based adhesive was applied to the surface of the lower elastic layer, and the separated sheet of the rubber composition for outermost surface was wound around to form a mold. After that, the surface of the vulcanized rubber composition was ground with a rotating grindstone to produce a water supply roll having an outer diameter of 101 mm. The thickness of the entire elastic layer was 12.5 mm, and the thickness of the outermost elastic layer was 0.5 mm. The resulting water supply roll was applied to the dampening roll of the dampening unit of an offset printing press and evaluated.

(Example 2)
A material was prepared at a ratio of 217 g of carboxyl group-containing nitrile rubber latex to 2,500 g of the cellulose nanofiber aqueous dispersion similar to Example 1, and mixed using a homogenizer to uniformly disperse. A mixture of the resulting aqueous dispersion of cellulose nanofibers and the latex of carboxyl group-containing nitrile rubber was dried in a constant temperature bath at 80°C for 72 hours to prepare a masterbatch containing 50 parts by mass of cellulose nanofibers. .

90 parts by mass of nitrile rubber (Nipol DN3350, manufactured by Nippon Zeon Co., Ltd.) as raw rubber, 15 parts by mass of the masterbatch, 5 parts by mass of zinc oxide as in Example 1, 1 part by mass of stearic acid, sulfur 1.5 parts by mass and 1 part by mass of a vulcanization accelerator are kneaded in an open roll, and the maximum amount containing 5 parts by mass of cellulose nanofiber (CNF) is added to the total amount of 100 parts by mass of nitrile rubber and carboxyl group-containing nitrile rubber. A surface rubber composition was prepared. After that, it was divided into sheets having a thickness of 0.5 mm by a calender.

An iron core metal with a core diameter of 60 mm was used as the support, and the surface was blasted and coated with a rubber adhesive. The diameter was adjusted to 83 mm. Next, a water supply roll having an outer diameter of 86 mm and a thickness of the outermost elastic layer of 1.5 mm was adjusted in the same manner as in Example 1, except that the sheet of the rubber composition for the outermost surface was used. was made. The produced water supply roll was applied to the water supply roll of the dampening device of the offset printing press and evaluated.

(Example 3)
At a ratio of 400 g of an aqueous dispersion of modified polyethylene (Arrowbase SB-1200, manufactured by Unitika Ltd., total solid concentration 25%) to 1,250 g of the same aqueous dispersion of cellulose nanofibers as in Example 1 Materials were prepared and mixed using a homogenizer to evenly disperse. A mixture of the obtained aqueous dispersion of cellulose nanofibers and the aqueous dispersion of modified polyethylene was dried in a constant temperature bath at 60°C for 72 hours to obtain a masterbatch containing 25 parts by mass of cellulose nanofibers. made.

80 parts by mass of ethylene propylene rubber (JSR EP342, manufactured by JSR Corporation) as raw material rubber, 25 parts by mass of the masterbatch, 5 parts by mass of zinc oxide as in Example 1, 1 part by mass of stearic acid, and vulcanization 5.4 parts by mass of dicumyl peroxide (Percumyl D-40, manufactured by NOF Corporation) as an organic peroxide for and triallyl isocyanurate (TAIC, manufactured by Mitsubishi Chemical Corporation) as a co-crosslinking agent ) was kneaded with an open roll to prepare a rubber composition for the outermost surface containing 5 parts by mass of cellulose nanofibers (CNF) per 100 parts by mass of the total amount of ethylene propylene rubber and modified polyethylene. After that, it was divided into sheets having a thickness of 0.5 mm by a calender.

Next, a rubber composition (lower layer rubber composition) of ethylene propylene rubber having a hardness of 25 (type A) was calendered into 0.5 mm thick sheets.

An iron core metal with a core diameter of 60 mm was used as a support, the surface was blasted, and after applying a rubber adhesive, it was molded using the separated rubber composition for the lower layer, and the outer diameter of the rubber roll was 83 mm. adjusted to Next, a water supply roll having an outer diameter of 86 mm and a thickness of the outermost elastic layer of 1.5 mm was produced in the same manner as in Example 1, except that the rubber composition for the outermost surface was used. . The produced water supply roll was applied to a metering roll of a dampening water device of an offset printing press and evaluated.

(Example 4)
90 parts by mass of nitrile rubber (Nipol DN3350, manufactured by Nippon Zeon Co., Ltd.) as a raw rubber, 15 parts by mass of the masterbatch prepared in Example 2, and zinc oxide as a vulcanization accelerator (type 2 zinc oxide, identical Kagaku Kogyo Co., Ltd.) 5 parts by mass, stearic acid (Lunac S-70V, Kao Corporation) 1 part by mass as a processing aid, and sulfur for vulcanization (fine powder sulfur, Tsurumi Chemical Industry Co., Ltd. )) and 1.5 parts by mass of CZ (N-cyclohexylbenzothiazole-2-sulfenamide) (Noxera-CZ-G, manufactured by Ouchi Shinko Kagaku Kogyo Co., Ltd.) as a vulcanization accelerator. , 10 parts by mass of silica (Nipsil ER, manufactured by Tosoh Silica Co., Ltd.) as a reinforcing material, 20 parts by mass of clay (Hard Top Clay S, manufactured by Shiraishi Calcium Co., Ltd.) as a filler, and a plasticizer (Mezamol, (manufactured by Lanxess KK) were kneaded with an open roll to prepare a rubber composition for the outermost surface. The rubber composition for the outermost surface contained 5 parts by mass of cellulose nanofibers (CNF) with respect to 100 parts by mass of the total amount of the nitrile rubber and the carboxyl group-containing nitrile rubber. After that, it was divided into sheets having a thickness of 0.5 mm by a calender.

The same procedure as in Example 1 was carried out except that a rubber-based adhesive was applied to a metal core having a core diameter of 60 mm as a support, and a sheet of the separated outermost rubber composition was wound without using the rubber composition for the lower layer. A water supply roll having a single layer structure with an outer diameter of 86 mm and a thickness of the outermost elastic layer of 13 mm was produced by the method. The produced water supply roll was applied to a metering roll of a dampening device of an offset printing press and evaluated.

(Comparative example 1)
50 parts by mass of nitrile rubber (Nipol DN3350, manufactured by Nippon Zeon Co., Ltd.) as raw rubber, 75 parts by mass of the masterbatch prepared in Example 2, the same material as in Example 1 and the same amount of zinc oxide, Stearic acid, sulfur, and a vulcanization accelerator are kneaded in an open roll, and a rubber for the outermost surface containing 25 parts by mass of cellulose nanofiber (CNF) per 100 parts by mass of the total amount of nitrile rubber and carboxyl group-containing nitrile rubber. A composition was made. After that, it was divided into sheets having a thickness of 0.5 mm by a calender. Next, the surface of an iron core metal with a core diameter of 76 mm as a support was blasted, coated with a rubber adhesive, and molded using the same rubber composition for the lower layer as in Example 1, and the outer diameter of the rubber roll was was adjusted to 98 mm. Thereafter, the water supply roll was adjusted to have an outer diameter of 101 mm and a thickness of the outermost elastic layer of 1.5 mm in the same manner as in Example 1, except that the sheet of the rubber composition for the outermost surface was used. was made. The produced water supply roll was applied to a dampening roll of an offset printing press and evaluated.

(Comparative example 2)
98.8 parts by mass of ethylene propylene rubber (JSR EP342, manufactured by JSR Corporation) as raw rubber, 1.5 parts by mass of the masterbatch prepared in Example 3, and the same materials and amounts as in Example 3. Zinc oxide, stearic acid, an organic peroxide, and a co-crosslinking agent are kneaded in an open roll, and 0.3 of cellulose nanofiber (CNF) is added to 100 parts by mass of the total amount of ethylene propylene rubber and modified polyethylene. A rubber composition for the outermost surface containing parts by mass was produced. After that, it was divided into sheets having a thickness of 0.5 mm by a calender. Next, the surface of an iron core metal with a core diameter of 60 mm as a support was blasted, coated with a rubber adhesive, and molded using the same rubber composition for the lower layer as in Example 3, and the outer diameter of the rubber roll was was adjusted to 83 mm. Next, a water supply roll having an outer diameter of 86 mm and a thickness of the outermost elastic layer of 1.5 mm was adjusted in the same manner as in Example 1, except that the sheet of the rubber composition for the outermost surface was used. was made. The produced water supply roll was applied to a metering roll of an offset printing press and evaluated.

(Comparative Example 3)
Without using a masterbatch, 100 parts by mass of nitrile rubber (Nipol DN3350, manufactured by Nippon Zeon Co., Ltd.) as a raw rubber, a vulcanization accelerator in the same amount as in Example 4, a processing aid, A rubber composition for the outermost surface was produced by kneading sulfur, a vulcanization accelerator, a reinforcing material, a filler, and a plasticizer with an open roll. Then, as a support, the surface of an iron core metal with a core diameter of 60 mm was blasted, coated with an adhesive for rubber, and then the sheet of the rubber composition for the outermost surface was used. A single-layer structure water supply roll having an outer diameter of 86 mm and a thickness of the elastic layer on the outermost surface of 13 mm was produced by the above method. Further, the surface of the water supply roll was treated with a chlorine-based compound treatment liquid (Primer M50, manufactured by Shinko Giken Co., Ltd.) to impart hydrophilicity. The produced water supply roll was applied to a metering roll of an offset printing press and evaluated.

The rubber vulcanizate for outermost surface and the water supply roll thus prepared were evaluated by the following methods.

(Evaluation of contact angle)
The prepared rubber composition for outermost surface was press-molded, heated and vulcanized to prepare a sheet having a thickness of 2 mm, which was punched into a size of 10 mm×50 mm. After that, the surface of the punched sheet was ground with a surface grinder to prepare a sample for contact angle measurement.

The obtained sample was immersed in pure water and allowed to stand at room temperature of 25° C. for 7 days. After removing the sample from the pure water and removing excess water droplets on the surface, the contact angle was measured using pure water. The contact angle was measured using a contact angle meter CA-X (Kyowa Interface Science Co., Ltd.) with a droplet volume of 1.8 μL.

(Evaluation of thickness change rate)
Using the rubber compositions for the outermost surface obtained in Examples 1 to 4 and Comparative Examples 1 to 3, rubber sheets with a thickness of 2 mm were prepared in the same manner as used in the measurement of the contact angle.

Further, rubber vulcanizates were prepared by removing the cellulose nanofibers from the outermost rubber vulcanizates obtained in Examples 1 to 4 and Comparative Examples 1 to 3, and rubber sheets having a thickness of 2 mm were prepared in the same manner. . Each obtained rubber sheet was punched into a size of 20 mm×50 mm to obtain a sample.

Each sample was tested according to JIS K6258. The test was conducted by immersing each sample in pure water at a temperature of 40° C. for 28 days.

The evaluation was performed by the rate of change in thickness, which was calculated using the following formula (1). Also, changes in appearance after immersion were observed.
Δt ₁₀₀ = (t ₁ -t ₀ )/t ₀ ×100 (1)
Here, Δt ₁₀₀ : thickness change rate (%), t ₀ : thickness before immersion (mm), t ₁ : thickness after immersion (mm).

(Evaluation with offset printing press)
The water supply rolls obtained in Examples 1-4 and Comparative Examples 1-3 were applied to an offset printing press. Example 1 and Comparative Example 1 were applied to wet dampening rolls, Example 2 was applied to water source rolls, and Example 3, Example 4, Comparative Example 2 and Comparative Example 3 were applied to metering rolls. A uniform film of dampening water was formed on the surface of the water supply roll at the time of application, and a good printing performance was judged to be good. On the other hand, when the dampening water film on the surface of the water supply roll was uneven, or the printed matter was stained with ink, it was judged to be defective. Furthermore, durability was evaluated. Durability was rated as ◯ when the device could be used satisfactorily for 3 months or more, ⊚ when it could be used satisfactorily for 6 months or more, and x when a problem occurred before the device could be used for 3 months.

The results of the above evaluation are shown in Tables 1 and 2 below.

As is clear from Tables 1 and 2, when the water supply roll of Example 1 was used as a dampening roll for an offset printing press, the surface was extremely wettable from the initial stage of printing, and the dampening water film was uniform. . Printing was carried out at a speed of 12,000 sheets/hour for 6 hours, but no problems such as ink staining on the printed matter occurred, and good printing results were obtained. Furthermore, even a small amount of ink adhering to the surface of the roll after printing could be easily wiped off with the cleaning liquid. Moreover, the water supply roll of Example 1 could be used satisfactorily for 3 months or more.

When the water supply roll of Example 2 was used as a water source roll for an offset printing press, the surface was extremely wetted with water, and the dampening water film drawn up from the water boat was thin and uniform, similarly to the water supply roll of Example 1. Yes, and good printing was possible. Furthermore, the water supply roll of Example 2 could be used satisfactorily for 3 months or longer.

When the water supply roll of Example 3 was used as a metering roll for an offset printing press, the surface was extremely wetted with water similarly to the water supply roll of Example 1, and the dampening water pumped up from the water source roll was thin and uniform. It was possible to spread it on the roll surface, and good printing could be performed. Furthermore, the water supply roll of Example 3 could be used satisfactorily for 6 months or longer. It is believed that this is because ethylene propylene rubber, which has excellent water resistance, is used as the raw material rubber.

When the water supply roll of Example 4 was used as a metering roll for an offset printing press, the surface was extremely wetted with water similarly to the water supply roll of Example 1, and the dampening water pumped up from the water source roll was thinly and uniformly distributed. It was possible to spread it on the roll surface, and good printing could be performed. Furthermore, the water supply roll of Example 4 could be used satisfactorily for 3 months or more.

On the other hand, when the water supply roll of Comparative Example 1 was used as a dampening roll for an offset printing machine, printing unevenness occurred. Observation of the surface of the roll revealed that unevenness was locally generated due to swelling. Observation of the inside of the uneven rubber with an electron microscope revealed the presence of aggregates of cellulose nanofibers. Thus, the amount of cellulose nanofibers contained in the outermost elastic layer exceeds 20 parts by mass, which is the upper limit of the range of the present invention (0.5 parts by mass or more and 20 parts by mass or less), and is excessive such as 25 parts by mass. This is probably because the cellulose nanofibers tended to aggregate with each other when the amount was too small, and aggregates were generated in the rubber vulcanizate.

When the water supply roll of Comparative Example 2 was used as a metering roll for an offset printing press, the dampening solution film was non-uniform immediately after the start of printing, resulting in density unevenness in the printed matter. As is clear from the comparison with Example 3, the amount of cellulose nanofibers contained in the outermost elastic layer is the lower limit of the range of the present invention (0.5 parts by mass or more and 20 parts by mass or less). Since it is 0.3 parts by mass, which is less than 0.5 parts by mass, it is considered to be the result of insufficient hydrophilicity.

When the water supply roll of Comparative Example 3 was used as a metering roll for an offset printing press, the surface was extremely wet immediately after the start of printing, and dampening water pumped up from the water source roll was spread thinly and evenly over the roll surface. It was possible to perform good printing. However, with use, the dampening water film gradually became non-uniform, and ink stains occurred on printed matter. After one month from the start of use, it became unusable as a metering roll. Observation of the roll after the test showed wear on the surface, presumably due to partial lack of hydrophilicity.

While several embodiments have been described, these embodiments are provided by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.

DESCRIPTION OF SYMBOLS 1... Water supply roll, 2... Support body, 3, 4... Elastic layer, 101... Plate cylinder, 110... Dampening device, 111... Water boat, 112... Mizumoto roll, 113... Metering roll, 114... Transfer roll , 115...Wetting roll, 116...Water leveling roll, 117...Water kneading roll, 120...Inking device.

Claims (8)

A water supply roll incorporated in an offset printing press,
comprising a support and one or more elastic layers disposed on the surface of the support;
The elastic layer located on the outermost surface is a rubber vulcanizate containing modified rubber and cellulose nanofibers,
A water supply roll containing 0.5 parts by mass or more and 20 parts by mass or less of the cellulose nanofiber with respect to 100 parts by mass of the modified rubber. A water supply roll incorporated in an offset printing press,
comprising a support and one or more elastic layers disposed on the surface of the support;
The elastic layer located on the outermost surface is a rubber vulcanizate containing a raw rubber, a modified high molecular weight polymer and cellulose nanofibers,
The water supplying roll, wherein the cellulose nanofiber is contained in an amount of 0.5 parts by mass or more and 20 parts by mass or less with respect to 100 parts by mass of the total amount of the raw material rubber and the modified high molecular weight polymer. 3. The water supply roll according to claim 1, comprising two or more elastic layers, wherein the outermost elastic layer has a thickness of 0.1 mm or more and 4.0 mm or less. 4. The water supply roll according to any one of claims 1 to 3, wherein the elastic layer located on the outermost surface has a contact angle with pure water of 100 degrees or less in a water-containing state. The elastic layer located on the outermost surface has a thickness change rate of 20% or less in a pure water immersion test, and the thickness of the rubber vulcanizate excluding the cellulose nanofiber in a pure water immersion test 5. The water supply roll according to any one of claims 1 to 4, wherein the rate of change is 2% or less. The water supply roll according to any one of claims 2 to 5, wherein the raw material rubber is ethylene propylene rubber. The water supply roll according to any one of claims 2 to 6, wherein the modified high molecular weight polymer is a modified polyolefin resin. The water supply roll according to any one of claims 1 to 7, wherein the elastic layer located inside the outermost elastic layer is made of rubber having a hardness of 30 (type A) or less.

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