JP2003103957A - Blanket for offset printing and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate occurrence of bulge and to prevent permeation of a cleaning liquid. SOLUTION: This blanket for offset printing has a reinforcing layer and a first base cloth layer, a compressive layer, a second base cloth layer and a surface rubber layer which are provided sequentially on the reinforcing layer. The compressive layer is a foamed sponge rubber layer constituted by a method wherein an acrylonitrile-butadiene rubber compound is blended with an organic foaming agent of 1-40 pts.wt. and kneaded together and also a spheric hollow particle or a spheric particle of 1-200 μm is mixed therein by 1-30 pts.wt. and foamed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an offset printing blanket having a compressible layer having a microsponge layer structure and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, the structure of a blanket for offset printing is generally a structure as shown in FIG. That is, reference numeral 1 in the drawing is a surface rubber layer which plays a role of receiving ink and transferring it to an object. A first base cloth layer 2, a sponge layer 3 as a compressible layer, a second base cloth layer 4, and a reinforcing layer 5 are sequentially formed on the lower side of the surface rubber layer 1, and the entire thickness of the blanket. Is 1.9 to 2.1 mm. The first and second base fabric layers are composed of 3 to 4 plies in terms of the number of plies of the base fabric. Further, the reinforcing layer 5 is formed by alternately arranging the base cloth layers 5a and the rubber layers 5b to form a reinforcing layer as a whole.

Here, the main role of the sponge layer 3 is to absorb shock during printing, but it is also very useful for adjusting the printing pressure. That is, if the printing pressure becomes overpressure, it may cause shock and may cause thickening of dots and plate wear. If the printing pressure is insufficient, the ink transfer amount in the solid portion may be insufficient and may be blurred. It becomes printed matter. These printing pressures are controlled by the sponge layer 3
It is said that it bears a lot because of its hardness.

By the way, as the compressible layer of the blanket for offset printing, the following 1) to 4) have been developed, and each of them exhibits its characteristics and is put to practical use. 1) JP-A-42-38275, JP-A-63-2052
Rubber foaming method using an organic foaming agent as disclosed in JP-A No. 94, etc. 2) A soluble compound is previously mixed with a rubber compound disclosed in JP-A-9-14995, and the salt is added after vulcanization. Extraction method of extracting with hot water to form a sponge, 3) JP-A-2-20392 and JP-A-3-24459
5, as disclosed in JP-A-6-1091,
A microballoon method in which a rubber compound is mixed with a microballoon made of vinylidene chloride, an acrylic resin or the like and vulcanized in the state as it is to form a sponge, 4) JP-A-34-32139, JP-A-38-7761 An impregnated non-woven fabric method disclosed in U.S. Pat.

These sponges are roughly classified into a single-cell sponge having a structure in which cells are arranged independently and an open-cell sponge having a structure in which cells are connected to each other. Figure 2
(A) is an example of a single-cell sponge, and FIG. 2 (B) is a schematic diagram of an open-cell sponge. In addition, reference numerals 6 and 7 in FIG.
Indicates cells forming the sponge layer 3. Also, FIG.
(C) shows an example of a sponge partially forming an open cell structure.

In the compressible layer, the rubber foaming method using an organic foaming agent and the microballoon method are basically single bubbles, and the extraction method forms a tunnel-shaped passage at the stage of extracting soluble salts. Therefore, it is an open cell, and since the impregnated non-woven fabric method impregnates an elastomer in an open cell shape in which fibers are bonded with a resin, this is also an open cell.

Generally, in the case of a single-foam sponge, the cell wall tends to be thick and becomes a hard sponge, whereas in the continuous-foam sponge, the cell wall is thin and becomes a soft sponge.

In the foaming method, a large amount of an organic foaming agent is mixed, or the vulcanization temperature and the vulcanization rate are adjusted to reduce the viscosity of the rubber compound when gas is generated, thereby increasing the foaming ratio and increasing the cell wall. It's not that we can't make it thin.
However, rupture of single bubbles, irregular cells, cell connection, etc. occur, resulting in a lack of homogeneity in the sponge, and the process itself becomes very unstable.

Also in the case of the microballoon method, a large amount of microballoons are intentionally expanded and ruptured at the time of vulcanization so that a part of the single bubbles is made into an open cell to form a soft sponge. However, it is not a practical method because the cell structure varies widely.

In the case of a sponge as the compressible layer, whether it is a single foam or an open foam has a great significance as described below in terms of the effect on the performance of the offset printing blanket. .

The basic role of the offset printing blanket is to receive the ink from the plate and transfer it to paper, film, metal plate or can. Here, in order to guarantee the good adhesion of the transferred ink, it is more advantageous to use a harder single-foam sponge that is difficult to deform and to which printing pressure is applied, and stabilizes the shape of the dot and the image length of the printed matter. In order to control the paper feeding characteristics of the printing paper, the open-cell sponge is more advantageous than the single-cell foam.

Factors controlling these printing characteristics include the compounding and hardness of the surface rubber and the elongation characteristics of the base cloth, but most of them are carried by the compressive layer. Also, in order to prevent the image length from increasing and to stabilize the paper feed characteristics, the sponge cell does not generate a bulge (a phenomenon that the side under pressure swells) when it is rotated under printing pressure. Open cells are favored to ensure a smooth air movement between them.

In order to explain the reason, first, a situation in which a bulge is generated is shown in FIGS. Here, FIG. 3 is a cross-sectional view of a blanket including a single-foam sponge as a compressible layer, and FIG. 4 is a cross-section of a blanket including an open-cell sponge as a compressible layer. As can be seen from FIG. 3, in the single bubble, the cells are independent and there is no air flow between the cells, so that when compressed, the volume moves immediately beside it and a bulge occurs. Further, as can be seen from FIG. 4, in the continuous bubble, the continuous bubble cells are connected and the air is moved quickly, so that the volume of the compressed part is reduced and the occurrence of bulge is suppressed.

[0014]

Since the offset printing blanket using the open-cell sponge as the compressible layer has the function of suppressing the occurrence of bulging, it is excellent in the reproducibility of the dot and the paper feeding characteristic is stable. There are advantages. But,
On the other hand, since the sponge is an open-cell foam, the cleaning liquid permeates the sponge layer when the blanket is applied to the automatic cleaning machine, impairing the compressibility of that part and making it harder. As a result, the sponge layer becomes thin and it is difficult to recover.

On the other hand, an offset printing blanket having a single-foam sponge as a compressible layer has no risk of penetrating the cleaning liquid, but has the above-mentioned bulge and has a serious drawback that the rate of increase in circumference will be increased. is there.

The present invention has been made in consideration of the above circumstances, and it has no bulge and no permeation of the cleaning liquid. Specifically, it is a single-foam sponge but has the characteristics of an open-cell sponge. Another object of the present invention is to provide an offset printing blanket having a sponge layer which has the advantages of both open and closed cells, which are also called open cells, and a method for producing the blanket.

[0017]

[Means for Solving the Problems] As described above, the open-cell sponge has a drawback that the cleaning liquid for the blanket permeates. As a countermeasure against this, an attempt has been made to prevent the permeation of the cleaning liquid by sealing the both ends of the blanket. However,
As a result, it was impossible to completely prevent the invasion of the cleaning liquid. The best solution is to use a single foam sponge,
The problem of bulging remains in the closed-cell sponge.

The most homogeneous method for forming a single-cell sponge is a method in which expanded microballoons are mixed and vulcanized in that state, but this type of sponge is stable because of its stability. In addition, it is difficult to give an open-celled character with the technique of mixing microballoons alone.

Further, in the foaming method which is another means for forming a single foam sponge, it is difficult to stably control the vulcanization rate, the timing of gas generation and the amount of gas generated,
Experience has shown that it is extremely difficult to find conditions under which cells become homogeneous, and conditions under which cells of the same level can always be stably formed.

In view of the above, the present invention provides a compressible sponge layer having a single-cell structure and no bulging, by combining the foaming method, which is a means for forming the single-cell structure, with the microballoon method. . That is, by introducing a vulcanizable compressible sponge layer obtained by mixing substantially spherical hollow particles or substantially spherical particles in a sponge formulation with an organic foaming agent, achieving homogenization of compressibility and single continuous foaming, It is intended to obtain an offset printing blanket with a small increase in the circumference and in which the cleaning liquid from the automatic cleaning machine hardly penetrates.

The blanket for offset printing according to the first invention of the present application comprises a reinforcing layer, a first base cloth layer, a compressive layer, a second base cloth layer and a surface rubber layer which are sequentially provided on the reinforcing layer. A blanket for offset printing comprising:
The compressive layer is formed by adding 1 to 40 parts by weight of an organic foaming agent to acrylonitrile-butadiene rubber compound, kneading the mixture, and mixing 1 to 30 parts by weight of spherical hollow particles or spherical particles of 1 to 200 μm to foam. It is a foamed rubber sponge layer formed by

A method of manufacturing a blanket for offset printing according to a second aspect of the present invention is directed to a reinforcing layer, a first base cloth layer, a compressive layer, a second base cloth layer, and a second base cloth layer which are sequentially provided on the reinforcing layer. In the method for producing a blanket for offset printing having a surface rubber layer, a rubber paste prepared by dissolving acrylonitrile-butadiene rubber compound in a solvent is coated on the first base fabric layer, and a second base fabric layer is formed. A step of coating a rubber paste prepared by dissolving an acrylonitrile-butadiene rubber compound in a solvent, and a step of bonding the first base fabric layer and the second base fabric layer with the compound positioned inside, and After vulcanization, a step of attaching a reinforcing layer,
The step of coating or laminating a surface rubber layer on one side of the base fabric layer and then vulcanizing the same.

A method of manufacturing a blanket for offset printing according to a third aspect of the present invention comprises a reinforcing layer, a first base cloth layer, a compressive layer, a second base cloth layer and a base cloth layer which are sequentially provided on the reinforcing layer. In the method for producing a blanket for offset printing having a surface rubber layer, a rubber paste prepared by dissolving acrylonitrile-butadiene rubber compound in a solvent is coated on the first base fabric layer, and a second base fabric layer is formed. A step of coating a rubber paste prepared by dissolving an acrylonitrile-butadiene rubber compound in a solvent, and a step of bonding the first base fabric layer and the second base fabric layer with the compound positioned inside A step of adhering a reinforcing layer in a vulcanized state, and a step of coating or adhering a surface rubber layer on one surface of the first base cloth layer and then vulcanizing it at once. Characterized by comprising and.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. In the blanket for offset printing of the present invention, the compressive layer, which is one of the constituents of the blanket, is added to an ordinary acrylonitrile-butadiene rubber (NBR) compound with 1 to 40 parts by weight of an organic foaming agent and a spherical hollow body or spherical shape of 1 to 200 μm. It is produced by mixing 1 to 30 parts by weight of body particles and molding and vulcanizing it by a usual method. Here, the organic foaming agent is set in the above range because the amount of gas generated is less than 1 part by weight and does not remain in the rubber, and when it exceeds 40 parts by weight, the amount of gas generated is too large. This is because there is no place to go and the rubber breaks. The organic foaming agent is preferably in the range of 5 to 20 parts by weight.

The same applies to the spherical hollow particles or the spherical particles, and if the particles are smaller than 1 μm or less than 1 part by weight, the number of cells is small and they do not contribute to the compressibility. Further, if the size exceeds 200 μm or exceeds 30 parts by weight, the cells become too soft because of too many cells, the printing pressure becomes ineffective, and the strength of the sponge rubber becomes insufficient.
It cannot be put to practical use. It should be noted that preferably used is 10 to 50 μm and 5 to 15 parts by weight.

Here, the role of the spherical hollow body or spherical body particles (hereinafter collectively referred to as spherical body particles) is to uniformly disperse the gas generated from the organic foaming agent. Since the spherical particles have a spherical shape, they can be easily dispersed uniformly in the rubber, and the gas generated from the organic blowing agent diffuses along the surface of the spherical particles to form a gas passage. As a result, a homogeneous foam structure is obtained.

This is because the generated gas mainly gathers on the surface of the spherical particles and forms a gas layer on the surface of the spherical particles, but the surplus gas connects the gas layers on the surface of the spherical particles with each other by a tunnel, It is estimated that continuous foaming will occur.
5 and 6 schematically show this mechanism.

FIG. 5 shows that the gas generated from the organic foaming agent is
The figure shows how cells 11 are formed in a circle around the foaming agent itself. When the spherical particles 12 are mixed with this as shown in FIG. 6, the gas generated from the organic foaming agent 13 and filling the peripheral surface of the organic foaming agent 13 starts further diffusion,
The spherical particles 12 penetrate the soft rubber layer, reach the spherical particles 12, and then proceed to lick the peripheral surface of the spherical particles 12, and reach another spherical particle through the next rubber layer. When the gas completely covers the peripheral surface of the spherical particles, it starts diffusing into the next rubber layer again. Proceed along the sphere. By repeating this cycle, it is estimated that the shape shown in FIG. 6 is obtained.

Although not all of the gas on the peripheral surface of the spherical particles is actually connected to each other, depending on the amount of generated gas, the whole does not become open cells, and normally only a part of open cells is formed. ing.

This phenomenon occurs because the particles to be mixed are substantially spherical. Therefore, when the particles to be mixed are non-spherical like the usual filler for rubber, the gas itself does not progress smoothly and at the same time the gas does not spread uniformly. On the other hand, when the particles to be mixed are flat particles, the gas stops advancing there, and in the case of needle-shaped particles, the gas advancing direction is biased, and the homogeneity of the sponge layer is not desired.

In the present invention, the organic foaming agent refers to a chemical for compounding rubber, plastic or the like to produce a sponge product. There were times when inorganic foaming agents such as baking soda and ammonium carbonate that generate carbon dioxide were used, but recently, organic compounds that generate nitrogen gas, which is easy to control cell size and the like, have become the mainstream in sponge production. The organic foaming agents are classified into nitroso compounds, azo compounds, sulfonyl hydrazides, etc., and neocervone N-1000M used in Examples and Comparative Examples of the present invention belongs to benzenesulfonyl hydrazides.

[0032]

EXAMPLES (Examples 1 to 4) A sponge layer portion having a partially open-cell structure shown in FIG. First of all, in carrying out the preparation of comparative samples, a raw rubber, a vulcanizing agent, a vulcanization accelerator, a reinforcing agent, a plasticizer, as a basic rubber compound common to each compound,
Basic compound with fillers (total 185g)
Was prepared and mixed with a foaming agent and spherical particles to prepare a comparative sample.

The above basic rubber compound has the following composition. That is, 2 parts of sulfur as a vulcanizing agent is added to 100 parts by weight of an acrylonitrile-butadiene copolymer.
Parts by weight, 5 parts by weight of a metal oxide such as zinc oxide as a vulcanization aid, 3 parts by weight of a vulcanization accelerator, 15 parts by weight of a carbon-based reinforcing agent, 45 parts by weight of a calcium carbonate-based filler, and a viscosity adjusting and plasticizing agent. A mixture of 15 parts by weight of DOP as an agent was used.

Next, a rubber compound shown in the following Table 1 containing 5 parts by weight or 20 parts by weight of an organic foaming agent (trade name: Neocerbon N1000M, Eiwa Kasei) was dissolved in a toluene solvent to prepare a rubber paste. Subsequently, a sponge rubber paste prepared by mixing an appropriate amount of a spherical hollow body (trade name: EXPANCEL 091DE, Nippon Philite Co., Ltd.) with this rubber paste was used to form a sponge rubber paste in the first base cloth layer by a conventional doctor coating method in an amount of about 0. 1
Coating was performed to a thickness of 5 mm, and the toluene solvent was volatilized. Similarly, the second base cloth layer is similarly coated, the sponge rubber layer is combined to give a thickness of 0.3 mm, and the two pieces are stuck together, and then wound on a vulcanizing drum,
It was vulcanized by the usual hot air vulcanization method.

[0035]

[Table 1]

(Examples 5 to 8) First, 5 parts by weight or 20 parts by weight of an organic foaming agent (trade name: Neocerbon N1000M, Eiwa Kasei) was added to a basic rubber compound,
Spherical porous nylon (trade name: ORGASOL 2002ES3, ELF
Examples 1 to 4 were prepared by dissolving a rubber compound containing ATOKEM (manufactured by ATOKEM) in an appropriate amount shown in Table 1 above in a toluene solvent.
The same operation was performed to obtain a sponge layer portion having a partially open-cell structure shown in FIG. 2 (C). The basic rubber compound, Neocerbon N100M and 2002 in Examples 5 to 8 above.
The mixing ratio of ES3 is shown in Table 2 below.

[0037]

[Table 2]

Comparative Example 1 A basic rubber compound prepared by mixing 20 parts by weight of the above organic foaming agent (Neocerbon N1000M) was dissolved in a toluene solvent to prepare a rubber paste, and the same operation as in Example 1 was carried out. A single-cell sponge layer corresponding to A) was obtained.

(Comparative Example 2) A rubber compound prepared by mixing 10 parts by weight of the spherical hollow body (Expansel 091DE) was dissolved in a toluene solvent to prepare a rubber paste, and the same operation as in Example 1 was carried out. A sponge layer was obtained.

Comparative Example 3 Salt was crushed, and a rubber compound prepared by mixing 200 parts by weight of this with a basic compound was dissolved in a toluene solvent to form a rubber paste, and the same operation as in Example 1 was carried out to obtain a compressed product. The organic layer was dipped in warm water to wash out the salt to obtain an open cell sponge layer corresponding to FIG. 2 (B).

Rubber compounds, Neocerbon N100M and Expancel 091DE in Comparative Examples 1 to 3 above.
The compounding ratio of is as shown in Table 3 below.

[0042]

[Table 3]

Offset printing of the structure shown in FIG. 1 having a thickness of 2.05 mm was performed using the sponge layers prepared in Examples 1 to 8 and Comparative Examples 1 to 3 under the same conditions except for the sponge layer such as surface rubber. Offset blanket was manufactured. Using each blanket, we conducted a market evaluation at a newspaper printing company where paper feeding characteristics are important. The results are shown in Table 4 below.

[0044]

[Table 4]

Regarding the paper feeding characteristics, a test machine having two pressure cylinders and a blanket cylinder in a laboratory,
The blanket cylinder is rotated under the condition that m printing pressure is applied, and the numerical value measured by the circumference increase rate tester, in which the rotation circumference length of the impression cylinder is expressed as a percentage with respect to the rotation circumference length, Penetration of the cleaning liquid into the blanket on the machine is shown in Table 5 below as numerical values corresponding to the above symbols.

[0046]

[Table 5]

According to Table 4 above, in Examples 1 to 8, peeling was different between the sponge layers, although the peeling conditions were different. However, the delamination was not as clear as that of Comparative Example 3, and some parts showed delamination and one part had one-sided delamination. It seems that these are partially open cells and partially closed cells when viewed microscopically.

Further, in Example 4, the amount of the foaming agent and the microballoons was large, so that it became soft and a spotted pattern was generated on the printed surface. In Comparative Example 1, the foaming state was not good, and even the single cells were flat cells, and the overall finish was firm. As a result, the solid was good, but the circumferential increase rate was the maximum. In Comparative Example 2, the overall balance was good, but the circumferential increase rate was rather large. Comparative Example 3
Then, the overall balance was good, but the penetration of the cleaning liquid was intense.

What can be seen from these is that the spherical hollow body and the foaming agent alone cannot obtain sufficient compressibility and the paper feeding property is not good. In addition, when a foaming agent and a spherical body (preferably a microballoon) are combined,
It was confirmed that they complement each other's drawbacks.

In Comparative Examples 1 and 2, when the sponge layer was peeled off, the sponge layers were not peeled off, and the sponge layers were adhered to either side of the cloth, and it was confirmed that they were single bubbles. Was peeled between the sponge layers, and it was confirmed that the cells were open cells.

[0051]

As described in detail above, according to the present invention, no bulge is generated and no permeation of the cleaning liquid occurs. Specifically, although it is a single-foam sponge, it has the characteristics of an open-foam sponge. In other words, it is possible to provide an offset printing blanket having a sponge layer having the advantages of open cells and closed cells, which should be called open cells, and a method for producing the blanket.

[Brief description of drawings]

FIG. 1 is a sectional view of a blanket for offset printing.

FIG. 2 is a schematic diagram when the compressible layer, which is one component of the blanket of FIG. 1, is composed of a single-cell sponge, an open-cell sponge, and a partial open-cell structure.

FIG. 3 is an explanatory diagram of a bulge generation state in an offset printing blanket including a single-foam sponge as a compressible layer.

FIG. 4 is an explanatory view of a bulge generation state in an offset printing blanket having an open cell sponge as a compressible layer.

FIG. 5 is an explanatory view showing how the gas generated from the foaming agent forms independent cells.

FIG. 6 is an explanatory diagram showing a state in which a gas generated from a foaming agent surrounds spherical particles.

[Explanation of symbols]

1 ... Surface rubber layer, 2 ... the first base fabric layer, 3 ... sponge layer (compressible layer), 4 ... the second base fabric layer, 5 ... Reinforcing layer, 6, 11 ... cells, 12 ... Spherical particles, 13 ... Organic foaming agent,

Claims (5)

[Claims] 1. A blanket for offset printing, comprising: a reinforcing layer; and a first base cloth layer, a compressible layer, a second base cloth layer and a surface rubber layer which are sequentially provided on the reinforcing layer, The compressive layer is formed by adding 1 to 40 parts by weight of an organic foaming agent to acrylonitrile-butadiene rubber compound, kneading the mixture, and mixing 1 to 30 parts by weight of spherical hollow particles or spherical particles of 1 to 200 μm to foam. A blanket for offset printing, characterized in that it is a foamed rubber sponge layer. 2. The spherical hollow particles are selected from vinylidene chloride balloons, shirasu balloons, glass balloons, phenol resin balloons and acrylic resin balloons.
The blanket for offset printing according to claim 1, wherein the blanket for offset printing is one kind or plural kinds. 3. The spherical particles are selected from polymethylmethacrylate beads, polystyrene resin beads, polyethylene resin beads, nylon resin beads, cellulose beads, carbon beads, acrylic resin beads, melamine resin beads, epoxy resin beads, and silica beads. Chosen 1
The blanket for offset printing according to claim 1, wherein the blanket for offset printing is one kind or plural kinds. 4. A blanket for offset printing comprising a reinforcing layer, a first base cloth layer, a compressive layer, a second base cloth layer and a surface rubber layer, which are sequentially provided on the reinforcing layer, is manufactured. In the method, a rubber paste prepared by dissolving acrylonitrile-butadiene rubber compound in a solvent is coated on the first base cloth layer, and a rubber paste prepared by dissolving acrylonitrile-butadiene rubber compound in a solvent is formed on the second base cloth layer. Coating step, and the first base cloth layer and the second
A step of attaching the base fabric layer in the state where the compound is positioned inside, a step of attaching a reinforcing layer after vulcanization once, and a step of coating a surface rubber layer on one side of the first base fabric layer or A method of manufacturing a blanket for offset printing, comprising a step of vulcanizing after bonding. 5. A blanket for offset printing comprising a reinforcing layer and a first base cloth layer, a compressible layer, a second base cloth layer and a surface rubber layer, which are sequentially provided on the reinforcing layer, are manufactured. In the method, a rubber paste prepared by dissolving acrylonitrile-butadiene rubber compound in a solvent is coated on the first base cloth layer, and a rubber paste prepared by dissolving acrylonitrile-butadiene rubber compound in a solvent is formed on the second base cloth layer. Coating step, and the first base cloth layer and the second
A step of attaching the base fabric layer in the state where the compound is positioned inside, a step of attaching a reinforcing layer in an unvulcanized state, and a surface rubber layer on one surface of the first base fabric layer. A method of manufacturing a blanket for offset printing, comprising a step of vulcanizing at once after pasting.