JPH03290291A - Manufacture of offset blanket - Google Patents

Abstract

PURPOSE:To obtain effectively an offset blanket having a surface rubber layer which is excellent in ejectability, printability, operating property, etc., by a method wherein an unvulcanized rubber layer in which dextrin powder is mixed in a surface layer part and/or is fixed to its surface is formed on a base material layer, is vulcanized to form a surface rubber layer, and the dextrin powder is removed by washing with water. CONSTITUTION:A base material layer 1 is formed by laminating a plurality of sheets 11, 11... and a compressive layer 12 via a plurality of adhesive layers G, G.... For a surface of the base material layer 1, any one of an unvulcanized rubber layer 21 of which to a surface layer part water soluble dextrin powder D, D... is mixed to be dispersed, an unvulcanized rubber layer 22 of which to a surface dextrin powder D, D... is stuck, or an unvulcanized rubber layer 23 of which to a surface layer part dextrin powder D, D... is mixed to be dispersed and besides is stuck, is formed. When the unvulcanized rubber layer 21, 22 or 23 is vulcanized and the surface rubber layer 2 is washed with water, dextrin powder D, D of the surface rubber layer 2 is eluted into water to be removed, and an offset blanket of which the surface roughness of the surface rubber layer 2 is controlled is completed.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an offset blanket used in offset printing.

<Prior Art> Conventionally, in the offset blanket described above, especially during high-speed printing or when printing on paper with a smooth surface such as coated paper, adhesive force is generated between the paper and the blanket, causing the paper to curl. Problems such as cracking or tearing may occur. This is a phenomenon that occurs due to the so-called poor paper release properties (paper discharge properties), and when such trouble occurs, the productivity of printed matter by the printing machine is greatly reduced.

Therefore, offset blankets are required to have good paper discharge properties.

Offset blankets are usually made by forming an unvulcanized rubber layer on the surface of a support layer consisting of at least one base material, and then vulcanizing this unvulcanized rubber layer to form a surface rubber layer. Manufactured in Usually, the surface of the surface rubber layer after vulcanization is polished with a puff or the like to adjust its surface roughness.

However, with the above-mentioned method of adjusting surface roughness by polishing, the surface roughness is either extremely large or completely smooth, which leads to problems with paper ejection performance, halftone dot reproducibility, etc. It is not possible to achieve both printability and workability such as ink washability after printing.

That is, a surface rubber layer with extremely high surface roughness has excellent paper discharge properties, and is therefore suitable for high-speed printing machines and for printing on paper with a smooth surface. However, there are problems in that halftone dot reproducibility decreases and ink washability after printing decreases.

On the other hand, although a smooth surface rubber layer has excellent halftone dot reproducibility and ink washability, it has high adhesion to paper and deteriorates paper discharge performance.

There is a method in which the surface of the unvulcanized rubber layer is vulcanized with talc powder sprinkled on it, and then the talc is removed to adjust the surface roughness of the vulcanized surface rubber layer. According to this method, since the surface roughness of the surface rubber layer corresponds to the particle size of the talc, it is possible to form a surface rubber layer having a surface roughness that can satisfy the above-mentioned paper discharge properties, printability, and workability. becomes easier.

However, it is difficult to completely remove talc from the surface rubber layer after vulcanization, and there is a problem that talc remaining in the surface rubber layer inhibits ink transfer.

Therefore, a method was proposed in which starch powder was used in place of the talc, and after vulcanization, the starch was dissolved and removed with an aqueous sodium hydroxide solution to improve the surface roughness of the surface rubber layer (Japanese Patent Application Laid-Open No. 1986-1992-1). (See Publication No. 253493).

The reason for using an aqueous sodium hydroxide solution to dissolve starch is as follows.

That is, when water or cold water is used, it takes a long time to completely dissolve the starch, which significantly reduces productivity. On the other hand, when hot water is used, the dissolution rate improves, but the solution becomes pasty, making it difficult to remove from the surface rubber layer, and as a result, high productivity cannot be obtained. On the other hand, when an aqueous sodium hydroxide solution is used, the starch is hydrolyzed and its molecular weight decreases, so that it can be quickly dissolved and removed from the surface rubber layer.

However, in the above method, the sodium hydroxide remaining in the surface rubber layer after vulcanization must be neutralized and removed, which increases the number of steps and reduces production efficiency. In addition, sodium hydroxide and acid for neutralization may cause problems such as deterioration of the working environment and environmental protection around the factory. Therefore, safety measures, wastewater treatment equipment, etc. are required, which raises the problem of increased manufacturing costs.

Methods using water-soluble organic substances such as sugar, polyvinyl alcohol, gum arabic, gelatin, urea, and carboxymethyl cellulose, which can be dissolved and removed with cold or hot water, or water-soluble inorganic substances such as sodium sulfate, sodium chloride, and ammonium nitrate have also been proposed. (Unexamined Japanese Patent Publication No. 1999)
(Refer to Publication No.-141035).

However, among the above-mentioned organic substances, polyvinyl alcohol has poor water solubility, depending on the degree of polymerization, and requires a long time for washing and removal, making it impossible to improve productivity.

In addition, compounds other than the polyvinyl alcohol mentioned above have excellent water solubility, so they exhibit high hygroscopicity and may deliquesce or
There is a problem that it becomes hydrated. For this reason,
It is difficult to make the above compound into a powder with a particle size of around 20μ, which is suitable for forming a surface rubber layer with excellent printability and washability.
It is not possible to form a surface rubber layer that has a surface condition that is excellent in printability and printability. Furthermore, if a water-containing powder is used, it may adversely affect the vulcanization of the rubber.

This invention was made in view of the above circumstances, and
The object of the present invention is to provide a manufacturing method that can safely, inexpensively, efficiently, and with high productivity manufacture an offset blanket having a surface rubber layer with excellent paper discharge properties, printability, workability, etc.

Means and Effects for Solving the Problems> In order to solve the above problems, the method for producing an offset blanket of the present invention includes mixing dextrin powder into at least the surface layer portion of the support layer and/or adding the dextrin powder to the surface of the support layer. The method is characterized in that after forming an attached unvulcanized rubber layer and vulcanizing the unvulcanized rubber layer to form a surface rubber layer, the dextrin powder is removed by washing with water.

In the method for producing an offset blanket of the present invention having the above configuration, dextrin, which is a starch hydrolysis product and has excellent water solubility, is used.
The unvulcanized rubber layer can be easily removed by washing with water after vulcanization. In addition, the above-mentioned dextrin does not exhibit high hygroscopicity like various water-soluble compounds conventionally used, so it has poor paper discharge properties.
It can be used in the form of a powder having a particle size suitable for forming a surface rubber layer with excellent printability and workability.

Hereinafter, a method for manufacturing an offset blanket according to the present invention will be explained with reference to the drawings.

First, a support layer 1 is prepared (FIG. 1). In the figure,
An adhesive layer G includes a plurality of woven fabrics 11, 11... and a compressible layer 12 made of synthetic resin foam or the like.

Although a support layer 1 for a compressible offset blanket is shown, which is laminated with G..., support layers with other layer configurations can also be used.

Next, an unvulcanized rubber layer is formed on the surface of the support layer 1. The unvulcanized rubber layer is shown in FIG. 2 (as shown in ω, the unvulcanized rubber layer 21 in which water-soluble dextrin powder D1D is mixed and dispersed at least in the surface layer, in FIG. 2) As shown in , the above dextrin powder, D
... or, as shown in FIG. 2(C), water-soluble dextrin powder, D
Mixing and dispersing ... into at least the surface layer, and
Any of the unvulcanized rubber layers 23 having the above-mentioned dextrin powder, D, etc. adhered to the surface can be selected. Although not shown, the unvulcanized rubber layer may include an unvulcanized rubber layer in which water-soluble dextrin powder is mixed and dispersed throughout the layer, or an unvulcanized rubber layer in which water-soluble dextrin powder is further mixed in the entire layer. It is also possible to use an unvulcanized rubber layer in which the dextrin powder is dispersed and the dextrin powder is adhered to the surface thereof.

The unvulcanized rubber layer 21 shown in FIG.
After forming a base layer 21a by laminating a rubber plate containing no D... on the support layer 1, dextrin powder is applied to the surface of the base layer 21a.

The surface layer 21b is formed by applying rubber glue mixed with D....

The unvulcanized rubber layer 22 shown in FIG.
・It is formed by dispersing.

The unvulcanized rubber layer 23 shown in FIG. 2 (C1) is shown in FIG. 2 (al
After forming a base layer 23a not containing dextrin powder, D... and a surface layer 23b containing dextrin powder, D... in the same manner as the unvulcanized rubber layer 21 shown in FIG.
It is formed by scattering dextrin powder, D... on the surface.

Next, when the unvulcanized rubber layer 21, 22 or 23 is vulcanized using a conventionally known rubber vulcanizing device, the unvulcanized rubber layer 21, 22 or 23 is formed on the surface of the support layer 1. Vulcanized.

Thereafter, when the surface rubber layer 2 formed by vulcanization of the unvulcanized rubber layer 21, 22 or 23 is washed with cold water or hot water, the dextrin powder mixed and dispersed in at least the surface layer of the surface rubber layer 2 is removed. , D... and/or dextrin powder, D... attached to the surface are eluted and removed. Then, the dextrin powder, D...
A recess corresponding to the surface is formed, and an offset blanket in which the surface roughness of the surface rubber layer 2 is smoothed is completed (third
figure). Note that the dextrin powder D... has excellent water solubility and dissolves quickly even in cold water or water at room temperature. It is preferable to use cold water or water at room temperature.

The rubber glue used when configuring the unvulcanized rubber layers 21 to 23 is made of raw rubber in an unvulcanized state and mixed with a variety of vulcanizing agents, vulcanization accelerators, vulcanization accelerators, fillers, etc. A liquid or paste-like material dissolved, dispersed, or mixed in a solvent is used together with the additive.

The rubber glue is applied onto the support layer 1 by various conventionally known coating methods such as a barcode method and a roll coating method.

Further, the rubber plate used is one obtained by kneading the above-mentioned components except for the solvent and molding the mixture into a plate shape.

The raw rubber contained in the above rubber glue and rubber plate includes natural rubber latex, styrene-butadiene rubber, nitrile rubber, chloroprene rubber, ethylene propylene rubber, ethylene propylene diene rubber, acrylic rubber, polysulfide rubber, and epichlorohydrin. Examples include rubber, urethane rubber, fluororubber, silicone rubber, butadiene rubber, butyl rubber, isoprene rubber, and the like.

Furthermore, as the dextrin, various conventionally known dextrins can be used, ranging from high molecular weight so-called soluble starch, which is obtained by slightly hydrolyzing starch with dilute acid or heating, to low molecular weight ones that do not exhibit iodine starch reaction. In particular, yellow dextrin produced by a fluidized roasting method or the like is preferably used.

The particle size of the dextrin is determined by the paper discharge properties of the surface rubber layer in the offset blanket manufactured by the present invention,
Considering printability and workability, the thickness is preferably within the range of 1 to 50 μm, and more preferably within the range of 10 to 20 μm. If the particle size of the dextrin powder is less than 1 .mu.m, paper discharge properties may deteriorate, and if it exceeds 50 .mu.m, printability and workability may deteriorate.

When the above-mentioned dextrin powder, D... is mixed and dispersed in rubber glue, the blending ratio of the dextrin powder, D... to the raw rubber should be within the range of 50 to 150% by weight. is preferred. If the blending ratio of dextrin powder, D, etc. to the raw rubber is less than 50% by weight, the surface roughness of the formed surface rubber layer may be insufficient, resulting in poor paper discharge properties. Furthermore, if the blending ratio of dextrin powder, D, etc. to the raw rubber exceeds 150% by weight, the strength of the surface rubber layer may become insufficient.

In addition, when dextrin powder, D... is mixed and dispersed and further sprinkled with dextrin powder, D..., the dextrin powder, D... is added to the raw rubber.
The blending ratio of ... may be less than the above lower limit range.

On the other hand, when the above-mentioned dextrin powder, D... is attached to the surface of the unvulcanized rubber layer, the amount of attachment is 10 to 20 g.
It is preferably within the range of /rrf.

2 Adhesion amount of dextrin powder, D... is 10g/rr
? If it is less than that, the surface roughness of the formed surface rubber layer may be insufficient. Also, dextrin powder.

If the amount of D... exceeds 20g1rd, the thickness may vary due to uneven adhesion of the dextrin powder, which may cause variations in the surface roughness of the surface rubber layer. In addition, when the dextrin powder, D... is mixed and dispersed, and the dextrin powder, D... is further sprinkled, the amount of the dextrin powder, D... attached should be within the above lower limit. It may be less than the range.

Examples of the vulcanizing agent include organic sulfur-containing compounds such as tetramethylthiuram disulfide (TM.TD) and N,N'-dithiobismorpholine, and sulfur.

In addition, as a vulcanization accelerator, dibenzothiazyl disulfide (MBTS), N-cyclohexyl-2-benzothiazyl sulfenamide (CB5), N-oxydiethylene-2-benzothiazyl sulfenamide (, OB
S), N-tert-butyl-2-benzothiazylsulfenamide (TBBS) and other thiazoles are mentioned as main promoters, and if necessary, 1,3-diphenylguanidine (DPG), tetramethyl Thiuram monosulfide (TMTM), zinc dimethyldithiocarbamate (ZnMDC), zinc ethyl phenyldithiocarbamate (ZnEPDC), and tetramethylthiuram disulfide (TMTD) mentioned in the vulcanizing agent section are used as secondary accelerators. They can also be blended as appropriate.

As vulcanization accelerators, zinc oxide, magnesium oxide,
Metal oxides such as lead oxide, zinc carbonate, fatty acids such as stearic acid, oleic acid, cottonseed fatty acid, amines such as dicyclohexylamine and triethanolamine,
Examples include polyhydric alcohols such as diethylene glycol.

Examples of fillers include inorganic fillers such as calcium carbonate, hard plastic soft clay, barium sulfate, diatom, talc, mica, asbestos, graphite, and pumice; recycled rubber;
Examples include organic fillers such as powdered rubber, asphalts, styrene resin, and glue.

The above-mentioned vulcanizing agent, vulcanization accelerator, filler, etc. can be appropriately blended depending on the type of raw material rubber.

<Example> The present invention will be explained below based on Examples.

Example 1 Acrylonitrile butadiene rubber 10 as raw material rubber
Yellow dextrin powder (average degree of polymerization 31,000 to 370
2 parts by weight of sulfur as a vulcanizing agent, 1 part by weight of tetramethylthiuram disulfide (TMTD) as a vulcanization accelerator, and 5 parts by weight of zinc oxide as a vulcanization accelerator. parts by weight and 20 parts by weight of hydrated silicic acid as a filler were added, toluene was added until the viscosity reached 500 cP, and the mixture was uniformly stirred and mixed to prepare a rubber paste.

Next, a nearly rectangular support layer (length: 10 m x width: 13 m
, 1.9 mm thick), the above-mentioned rubber paste is applied thinly to form a surface layer on the surface of an acrylonitrile butadiene rubber base layer (0.5 mm thick), and the above-mentioned base layer and surface layer An unvulcanized rubber layer consisting of and b was formed.

Next, when the surface layer of the unvulcanized rubber layer has dried to some extent, yellow dextrin powder (average degree of polymerization 31,000 to 37,000, particle size 12 to 18 μm) produced from cornstarch by a fluidized roasting method is sprinkled on the unvulcanized rubber layer. It was attached to the surface of the vulcanized rubber layer. The amount of yellow dextrin powder attached is 16 g.
/co? Met.

Next, with a release paper layered on the surface of the unvulcanized rubber layer, the support layer was wound around a drum, and placed in a vulcanization can for 140 minutes.
Vulcanization was carried out for 5 hours at ℃.

After completion of vulcanization, the support layer was unwound from the drum, and the surface rubber layer was hand washed with cold water to remove the yellow dextrin powder to obtain an offset blanket.

When the surface of the obtained offset blanket was observed6, it was found that on the surface layer of the surface rubber layer, there was a porous layer with a thickness of 20 μm, in which many four parts of 12 to 18 μm were formed, which corresponded to the particle size of the yellow dextrin powder. confirmed.

In addition, the surface roughness of this surface rubber layer is 5 on the ten-point average roughness.
The output was ~8μ.

Example 2 An offset blanket was obtained in the same manner as in Example 1, except that 100 parts by weight of yellow dextrin powder was not mixed in as the rubber glue for forming the surface rubber layer.

When the surface of the obtained offset blanket was observed, a porous layer with a thickness of 20 μm in which many concave portions of 12 to 18 μm, which corresponds to the particle size of the yellow dextrin powder, were formed was confirmed on the surface layer of the surface rubber layer. Ta. Moreover, the surface roughness of this surface rubber layer was 5 to 8 μm as a ten-point average roughness.

Example 3 An offset blanket was obtained in the same manner as in Example 1 above, except that the yellow dextrin powder was not sprinkled on the surface layer of the unvulcanized rubber layer.

When the surface of the obtained offset blanket was observed, a porous layer with a thickness of 20 μm in which many concave portions of 12 to 18 μm, which corresponds to the particle size of the yellow dextrin powder, were formed was confirmed on the surface layer of the surface rubber layer. Ta. Moreover, the surface roughness of this surface rubber layer was 5 to 8 μm in ten point average roughness.

Comparative Examples 1 and 2 A rubber paste that does not contain 100 parts by weight of yellow dextrin powder was used as a secondary rubber paste to form the surface layer of the surface rubber layer, and yellow dextrin was added to the surface layer of the formed unvulcanized rubber layer. After producing an offset blanket in the same manner as in Example 1 above, except that no powder was sprinkled, the surface of the surface rubber layer was puff-polished, and its surface roughness (10-point average roughness RZ) was determined as follows: The values were adjusted as shown in Table 1 below.

Table 1 7 8 The following tests were conducted on the offset blankets obtained in the above Examples and Comparative Examples.

Halftone reproducibility test The offset blankets of the above examples and comparative examples were
Load the offset printing machine (manufactured by Ryobi Co., Ltd.) into a halftone original plate [halftone size 150 lines (one halftone dot per 11 nch length)]
50 pieces)] were used to print on coated paper (manufactured by Mitsubishi Paper Mills) under the following conditions, and the state of the printed matter was observed.

・Test conditions Printing speed: 5000 rph Solid Density: 1.5 Temperature: 23°C Room temperature: 23°C Humidity: 55% As a result, the offset of Comparative Example 2 The blanket had the best halftone dot reproducibility, and the offset blankets of Examples 1 to 3 had good gradation reproducibility and good halftone dot shape, although fine non-directional whiskers were observed. . On the other hand, with the off-9 set blanket of Comparative Example 1, whiskers due to the polishing pitch were observed, and the halftone dots also tended to become thicker.

Solid ink receptivity test Using the solid original plate, printing was performed on coated paper (manufactured by Mitsubishi Paper Mills) under the same conditions as above, and the state of the printed matter was observed.

As a result, in the offset blankets of Examples 1 to 3, good printing with little density unevenness was obtained.
In the offset blanket of Comparative Example 2, white spots were noticeable, and in the offset blanket of Comparative Example 1, density unevenness due to the polishing pitch was observed.

Cleanability Test Using the offset blankets of the above Examples and Comparative Examples, 5,000 full-page solid prints were performed with oil-based ink. ) were used to clean the surface of the offset blanket under the same conditions, and the cleanability was observed. As a result, the offset blanket of Comparative Example 2 had the best washability, followed by the offset blankets of Examples 1 to 3. On the other hand, in the offset blanket of Comparative Example 1, residual ink was observed in the polishing pitch portion.

Paper discharge property test Comparison of paper discharge trays when printing with actual machine Example 1
The discharge tray using the offset blanket of No. 3 was the smallest, followed by the offset blanket of Comparative Example 1 and the offset blanket of Comparative Example 2.

In addition, using a solid original plate, the number of prints per hour is 30.
The curl height of 10 sheets of coated paper (manufactured by Mitsubishi Paper Mills) was measured at printing speeds of 00 sheets, 5000 sheets, and 8000 sheets, as shown in Table 2 below. The curl height was lowest when the offset blankets of Examples 1 to 3 were used, followed by the offset blanket of Comparative Example 1 and the offset blanket of Comparative Example 2.

The measured value of the curl height is shown in Table 2 below, along with the evaluation of the halftone dot reproducibility, ink reproducibility, sheet discharge stand, and washability. In addition, in Table 2, ◎ is extremely good, ○
indicates good, △ indicates slightly poor, and × indicates poor.
(The following is a blank space) 2 Comparative Examples 3 to 9 Offset blankets were produced in the same manner as in Example 1, except that the following water-soluble organic substance was used in place of the yellow dextrin powder.

3 Comparative Example 3: Starch (average molecular weight 1000000-5oooooo, particle size 10-60 μm) Comparative Example 4: Sugar (particle size 150-500 μm) Comparative Example 5:
Polyvinyl alcohol (particle size 50-150 μm) Comparative example 6: Gum arabic (particle size 70-150 μm) Comparative example 7: Gelatin (particle size 50-150 μm) Comparative example 8: Urea (particle size 50-100 μm) Comparative example 9: Carboxymethyl cellulose (particle size 100 to 500 μm) Then, using the offset blankets of the above comparative examples, halftone dot reproducibility, solid inking property, paper discharge stand, and washability were evaluated in the same manner as above. The results are shown in Table 3 below, along with the evaluation of Example 1, as well as the water solubility of each compound, the cost required for dissolution and removal, and whether or not wastewater has an impact on the environment. In Table 3, ◎ indicates extremely good, O indicates good, Δ indicates slightly poor, X indicates poor, and - indicates unmeasurable.

(Margin below) 5 6 As is clear from the results in Table 3 above, in Comparative Example 5 using polyvinyl alcohol, the polyvinyl alcohol could not be completely removed by washing with water after vulcanization.
It was not possible to evaluate halftone dot reproducibility, solid ink coverage, paper discharge performance, and washability.

Furthermore, in Comparative Example 3 using starch, it took a long time to wash with water and remove after vulcanization.

Furthermore, in Comparative Example 4 and Comparative Examples 6 to 9, in which organic substances with excellent water solubility were used, since the particle size of these organic substances was large, it was difficult to form a surface rubber layer with surface roughness suitable for printing. could not.

On the other hand, in Example 1, it was found that an offset blanket having a surface rubber layer that is compatible with paper discharge properties, printability, workability, etc. can be produced safely, inexpensively, and efficiently.

<Effects of the Invention> The method for producing an offset blanket of the present invention is configured as described above, and since dextrin, which is a hydrolysis product of starch and has excellent water solubility, is used, The sulfur rubber layer can be easily removed by washing with water after vulcanization. In addition, the above dextrin does not exhibit high hygroscopicity like the various water-soluble compounds conventionally used, so it is suitable for forming a surface rubber layer with excellent paper discharge properties, printability, and workability. It can be used in powder form with a particle size of

Therefore, according to the method for manufacturing an offset blanket of the present invention, an offset blanket having a surface rubber layer with excellent paper discharge properties, printability, workability, etc. can be manufactured safely, inexpensively, efficiently, and with high productivity. be able to.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing an example of a support layer used in the method for producing an offset blanket of the present invention, and FIG.
Figures (a) to (e) are schematic cross-sectional views showing a state in which an unvulcanized rubber layer is formed on the surface of the support layer, and a third
The figure is a schematic cross-sectional view showing an offset blanket completed by vulcanizing the unvulcanized rubber layer and removing the dextrin powder by washing with water. 8 1...Support layer, 2...Surface rubber layer, 21.22.
23... Unvulcanized rubber layer, 21b, 23b... Surface layer, D... Dextrin powder.

Claims (1)

[Claims] 1. On the support layer, form an unvulcanized rubber layer in which dextrin powder is mixed into at least the surface layer portion and/or adhered to the surface, and vulcanize the unvulcanized rubber layer to form a surface rubber layer. A method for producing an offset blanket, which comprises removing the dextrin powder by washing with water after forming the blanket.