JP2838639B2 - Blanket for offset printing - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing blanket used in an offset printing machine, and more particularly, to an offset printing blanket which enhances the durability of an uppermost surface layer and has high printing durability.

[0002]

2. Description of the Related Art In offset printing, an image is transferred from a printing plate to a blanket once, and the image transferred to the blanket is printed on paper. Plates conventionally used for offset printing have low durability, and so-called “printing plate”
Sometimes occurred. The printing plate is generated because the printing plate and the blanket come into contact with each other at the time of printing and the printing plate is worn. For this reason, at least the uppermost layer of the surface layer of the blanket which comes into contact with the printing plate has been required to have low abrasion resistance. However, in recent years, the durability of a printing plate has been dramatically improved due to improvements in plate materials and plate making techniques.

[0003] On the other hand, in the conventional blanket cleaning, the surface of the blanket is manually wiped with a cleaning agent in a rag or the like to remove ink, paper powder, and the like. Such hand-wiping cleaning is a dangerous and time-consuming operation, and has to be performed under bad conditions such as odor and stains of the cleaning agent. For this reason, in recent years, automatic blanket washing machines have been used in order to save labor in printing work. As one of the automatic blanket washing machines, for example,
There is a method in which a cleaning liquid is sprayed to press a wet cleaning cloth (nonwoven fabric) against a blanket of a blanket cylinder, and then the blanket cylinder is rotated to scrape off ink and paper powder. Thus, in the method of rubbing while pressing the blanket surface, a high load is applied to the blanket surface. Therefore, if the pressing force on the surface of the blanket becomes excessive, or if the cleaning conditions are inappropriate such as the amount of the cleaning liquid supplied to the cleaning cloth (nonwoven fabric) is insufficient, the surface of the blanket is worn in a short time. Become. In addition, the load on the blanket has increased with the speeding up of the printing press, and the frequency of replacement due to wear of the blanket has also increased.

[0004] Therefore, as the printing durability of the printing plate is improved, there is now a demand for a highly durable blanket having enhanced rubber strength, particularly abrasion resistance, for forming the surface layer of the blanket. As a method of improving rubber strength, a method of filling a large amount of a reinforcing filler such as hydrated silica, a method of adding a large amount of hydrated silica, and a method of adding a coupling such as a silane coupling agent are known. .

[0005]

However, in order to greatly improve the rubber strength by adding a coupling agent, a large amount of a reinforcing filler must be filled. Increasing the filling amount of the reinforcing filler also increases the hardness of the rubber. When the hardness of the rubber in the surface layer of the blanket increases, so-called "image fatness" occurs. That is, a phenomenon occurs in which the image transferred from the blanket to the sheet becomes larger than the image on the original printing plate, and the gradation of printing is significantly impaired. From these facts, it is considered that the hardness of the rubber material used for the surface layer of the blanket is preferably about 50 according to a JIS A hardness meter. Therefore, the conventional method of filling the reinforcing filler in a large amount cannot be applied to the rubber material of the surface layer of the blanket because the hardness cannot be suppressed to the above-mentioned value. Therefore, it is required to increase the strength of the rubber without increasing the hardness of the rubber.

The invention described in Japanese Patent Application Laid-Open No. Hei 5-77578 discloses a hydrogenated acrylonitrile-butadiene copolymer rubber (having a surface layer thereof) for the purpose of improving the paper discharge property of the blanket, that is, the ease of separation of the paper from the blanket. Hereinafter, simply referred to as water-added NBR), or the above-mentioned water-added NBR and ordinary acrylonitrile-butadiene copolymer rubber (hereinafter, referred to as
(Hereinafter simply referred to as NBR). In order to achieve the above object, the hydrogenation rate of the water-added NBR used is limited to 90% or more. Water-added NBR has higher strength in the polymer itself than ordinary NBR. By using water-added NBR, it is possible to increase the strength of rubber without increasing the hardness of the rubber as well as the paper discharging property. It is possible.

However, water-added NBR having a hydrogenation rate of 90% or more has the following problems. First,
The vulcanization method used in ordinary blanket production involves winding the blanket sheet around a metal drum while simultaneously sandwiching vulcanized paper, and then vulcanizing the vulcanized paper by placing it in a dry heat vulcanizer. ing. In such a vulcanization method, the vulcanization temperature cannot be set high because steam is used as a heat source from the viewpoint of economy. Usually, vulcanization is 13
It is performed at a temperature of 5 to 150 ° C. Also, because the blanket sheet is wrapped around the drum many times,
The temperature rise rate differs between the outside of the surface layer portion and the inside of the drum side due to the effect of heat conduction. In order to reduce the temperature difference between the outside and the inside, vulcanization must be performed at a low temperature for a long time. On the other hand, in a water-added NBR having a hydrogenation rate of 90% or more as disclosed in Japanese Patent Application Laid-Open No. Hei 5-77578, double bonds contributing to the vulcanization reaction are extremely small. 16
A temperature of 0 ° C. or higher is required, which is usually 15
If vulcanization is carried out at a low temperature of 0 ° C. or lower, there is a problem that a sufficient crosslink density cannot be achieved and original physical properties cannot be obtained.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and can increase the strength of rubber without increasing the hardness of the rubber. It is an object of the present invention to provide a blanket for offset printing manufactured with a compounded rubber capable of obtaining a sufficient crosslinking density even at a temperature of (° C.).

[0009]

The present invention has the following configuration to achieve the above object. That is, in a printing blanket comprising a support layer made of one or a plurality of woven fabrics and a surface layer laminated thereon, at least the uppermost layer of the surface layers is made of water having a hydrogenation rate of 73% to 87%. It is characterized by being formed of added NBR alone or a mixed rubber of the water-added NBR and another rubber. By setting the hydrogenation rate of the water-added NBR to 73% or more, sufficient abrasion resistance can be obtained. Further, by setting the hydrogenation rate of the water addition rate NBR to 87% or less, the vulcanization temperature usually used (135 to 150 ° C.)
However, a sufficient crosslinking density can be obtained.

Further, NBR or acrylonitrile butadiene-isoprene terpolymer rubber (hereinafter simply referred to as NBIR) is used as another rubber mixed with water-added NBR having a hydrogenation ratio of 73 to 87% to form a surface layer of a blanket. ) Can be used. The NBR and NBIR
Can be mixed alone or simultaneously with the water-added NBR. In the mixing of the water-added NBR and the NBR, the mixing ratio of the water-added NBR is desirably 40% or more in the polymer component. In addition, in the mixing of the water-added NBR and the NBR, the mixing ratio of the water-added NBR is desirably 20% or more in the polymer component. Further, when the uppermost layer in the surface layer is formed of the rubber mixture of the water-added NBR and NBR and NBR, the mixing ratio of the water-added NBR is desirably 30% or more in the polymer component. One or more kinds of commonly used vulcanizing agents, vulcanization accelerators, reinforcing agents, antioxidants and the like can be added to the rubber compounding.

[0011]

Function: Water-added NBR having a hydrogenation rate of 73 to 87%
Therefore, the strength can be increased without increasing the hardness of the rubber itself. By setting the hydrogenation rate to 73% or more, the abrasion resistance is improved, and by setting the hydrogenation rate to 87% or less, vulcanization at a practical level of vulcanization temperature is possible.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described.
First, as a blanket to be used, a compressible blanket made of a normal abrasive was prepared, and only the composition of the surface layer was changed. The composition of the surface layer is as shown in Tables 1 to 4. Table 1 shows the case where water-added NBR with a different hydrogenation rate was used alone as the compounded rubber, and Table 2 shows the case where water-added NBR and NBR were mixed as the compounded rubber. Table 3 shows water-containing NBR and NBI as compounded rubber.
Table 4 shows that water-added NBR and NB
This is the case where R and NBIR are mixed.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

[0016]

[Table 4]

In Tables 1 to 4, the vulcanization conditions are as follows:
This is the case where the blanket sheet was wound around a drum and put in a dry heat vulcanization can at 145 ° C. for 10 hours. The vulcanization condition is a case where after vulcanizing under dry conditions under vulcanization conditions, cut into a predetermined size, put in a 160 ° C. electric heating oven and post-vulcanize for 3 hours.

The abrasion resistance of the blanket vulcanized under the above conditions was evaluated as follows. The wear tester is AS
Based on TM D1630 NBS abrasion tester. That is, as shown in FIG. 5, the abrasion tester wraps a cleaning cloth (nonwoven fabric) 11 around an iron drum 10 having a diameter of 150 mm, and the surface layer of the blanket 15 is
Attach so that it contacts 1. The sample holder 13
Is rotatably supported by a support 16 and has a weight 1 at its tip.
7 to attach the blanket to the iron drum 10
Is pressed. The blanket was worn by rotation of the iron drum 10 and the amount of wear was measured with a dial gauge 19.

As the cleaning cloth 11, a cleaning cloth manufactured by Nippon Baldwin Co., Ltd. is used.
5,000 rpm. The weight 17 was set so that a load of 4 N was applied to the blanket, and a blanket sample of 25 mm square was used. In addition, ASTM
D1630 specifies that a load of 22 N should be applied, but when this load is applied, the cleaning cloth 11
In this test, the load applied to the sample was set to 4N because the cleaning cloth was cut off from the seam at the time of winding.

The results of the abrasion test by the above method are shown in Tables 5 to 8. Table 5 shows the amount of wear of the blanket according to the composition shown in Table 1, Table 6 shows the amount of wear of the blanket according to the composition shown in Table 2, Table 7 shows the amount of wear of the blanket according to the composition shown in Table 3, and Table 8 Indicates the wear amount of the blanket according to the composition shown in Table 4.

[0021]

[Table 5]

[0022]

[Table 6]

[0023]

[Table 7]

[0024]

[Table 8]

The test results in Table 1 are shown in Table 5 and FIG.
Is obvious. Under vulcanization conditions, if the hydrogenation rate of the water-added NBR is less than 73%, sufficient abrasion resistance could not be obtained. On the other hand, when the hydrogenation rate exceeds 87%, a sufficient crosslinking density is obtained by performing post-vulcanization at a high temperature such as under vulcanization conditions, and the abrasion resistance is improved. However, under ordinary vulcanization conditions in consideration of productivity, the crosslinking density is insufficient, and the original abrasion resistance cannot be obtained. Therefore, from the above results, the water-added N
The hydrogenation rate of BR is desirably 73 to 87%.

In addition, in the case of mixing the water-added NBR with the NBR, as is clear from Table 6 and FIG. 2, an effect was obtained when the mixing ratio of the water-added NBR was 40% or more. Further, when water-added NBR is mixed with NBIR, as shown in Table 7 and FIG.
The effect was observed when the mixing ratio was 20% or more.
Furthermore, when water-added NBR is simultaneously mixed with NBR and NBR, as is clear from Table 8 and FIG.
The effect was observed when the mixing ratio of the water-added NBR was 30% or more.

[0027]

As described above in detail, according to the present invention, at least the uppermost layer of the surface layer of the blanket is formed of water-added NBR having a hydrogenation rate of 73 to 87%, so that the hardness of the rubber is kept constant. While increasing the strength of the rubber while performing vulcanization at a normal vulcanization temperature, post-vulcanization is unnecessary and productivity can be improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of a wear test of a surface layer using water-added NBR with a different hydrogenation rate.

FIG. 2 is a graph showing the results of a wear test of a surface layer obtained by mixing water-added NBR and NBR.

FIG. 3 is a graph showing the results of a wear test of a surface layer obtained by mixing water-added NBR and NBIR.

FIG. 4 is a graph showing the results of a wear test of a surface layer formed by mixing water-added NBR with NBR and NBIR.

FIG. 5 is an explanatory front view of the abrasion tester.

[Explanation of symbols]

 Reference Signs List 10 iron drum 11 cleaning cloth 13 sample holder 15 sample blanket 17 weight 19 dial gauge

Claims (4)

(57) [Claims] 1. A printing blanket comprising a support layer comprising one or more woven fabrics and a surface layer laminated thereon, wherein at least the uppermost layer of the surface layers has a hydrogenation rate of 73% to 87%. % Hydrogenated acrylonitrile butadiene copolymer rubber alone or 73% hydrogenated
A blanket for offset printing, which is formed from a mixed rubber of a hydrogenated acrylonitrile-butadiene copolymer rubber of up to 87% and another rubber. 2. The other rubber is an acrylonitrile butadiene copolymer rubber having a hydrogenation rate of 73% to 87%.
2. The blanket for offset printing according to claim 1, wherein the hydrogenated acrylonitrile-butadiene copolymer rubber is mixed in an amount of 40% or more of the polymer component. 3. The other rubber is an acrylonitrile-butadiene-isoprene terpolymer rubber, and a hydrogenated acrylonitrile-butadiene copolymer rubber having a hydrogenation rate of 73% to 87% is contained in an amount of 20% or more of a polymer component. 2. The blanket for offset printing according to claim 1, wherein the blanket is mixed in a ratio. 4. The other rubber is an acrylonitrile-butadiene copolymer rubber or an acrylonitrile-butadiene-isoprene terpolymer rubber having a hydrogenation rate of 73%.
2. A blanket for offset printing according to claim 1, wherein a hydrogenated acrylonitrile-butadiene copolymer rubber of from about 87% to about 30% of the polymer component is mixed.