JP2907695B2 - Printing blanket - 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 for an offset printing machine, and more particularly to a printing blanket excellent in durability against repeated compression.

[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. Therefore, if the blanket mounted on the blanket cylinder is loosened or misaligned during operation, the printed image is also shifted. For this reason, the printing blanket must not only be easily mounted on the blanket cylinder, but also must be securely fixed after mounting. Generally, a printing blanket used in an offset printing machine includes a reinforcing layer of a plurality of woven fabrics and a surface layer serving as a printing surface. The printing blanket includes a compressible printing blanket having a compressible layer and an incompressible printing blanket having no compressible layer.

A compressible printing blanket is, for example, shown in FIG.
As shown in FIG. 1, a compressible layer 5 which is a foam layer is formed on the lower surface side of a surface layer 1 serving as a printing surface via a support layer 3 made of one layer of woven fabric. The cloth 7 is supported by a support layer 9 formed by laminating three layers. The blanket woven fabric constituting the support 9 includes:
In order to obtain shape stability after the blanket is attached to the blanket cylinder, a woven fabric made of cotton yarn that has been subjected to a stretching process and has a small residual elongation has been used. For the support layer 3 close to the surface layer, a woven fabric having a certain residual elongation is used in consideration of ease of mounting on a blanket cylinder. However, since various tensions are applied to the yarn and the woven fabric during the blending process and the weaving process, the residual elongation of the woven fabric varies. A stretching process is required as a post-process to make the residual elongation of the woven fabric uniform, and the woven fabric used for the support layer 3 is subjected to a low-load stretch process to leave the residual elongation. . A woven fabric made of cotton yarn alone, a blend of cotton yarn and rayon yarn, rayon yarn alone, or the like is used for the support near the surface layer in consideration of the adhesiveness to the surface layer.

[0004]

However, the conventional printing blanket has the following problems. That is, as the speed of the printing press increases, the frequency of the repetitive compressive stress applied to the blanket increases, and the degree of fatigue near the surface layer and the lower surface thereof increases. When the degree of fatigue increases, first, the support layer 3 adjacent to the surface layer 1 breaks, and the surface layer 1 further breaks due to the breakage of the support layer 3. In particular, in order to mount a blanket, both ends are inserted into a slit provided in the blanket cylinder and fixed by a mounting bar, so that the corner of the slit is bent at an acute angle and the compressive stress is concentrated. Further, when the printing paper passes, the compressive stress is concentrated at the boundary portions on both sides of the printing paper. Therefore, the blanket was often broken at the slit of the blanket cylinder and at the boundary of the printing paper.

[0005] If such a breakage of the blanket occurs, it is necessary to replace the blanket, and the printing efficiency (productivity).
Greatly worsens. However, conventionally used woven fabrics made of cotton or rayon have insufficient fatigue resistance against repeated compression, and have a problem in durability against repeated compression during high-speed printing. Therefore, it has been proposed to use a woven fabric using polyester (PET) yarn having high durability against compressive stress for the support layer close to the surface layer. However, the woven fabric of polyester yarn has extremely poor adhesion to the surface layer and the rubber serving as a binder, and the surface layer may peel off from the woven fabric as a support during printing.

Therefore, when a woven fabric made of polyester yarn is used as a support, it is necessary to improve the adhesiveness. To improve the adhesion, as is known as a method of bonding a polyester cord for a tire, RF
It is necessary to apply an adhesive treatment such as L (resorcinol / formalin / latex) treatment to the polyester yarn. Further, in order to further increase the adhesive strength, it is necessary to coat an adhesive (a rubber solution for bonding or the like) on the polyester woven fabric which has been subjected to the adhesive treatment, and then laminate a surface layer or a binder. Therefore, the use of a polyester woven fabric as the support layer of the blanket has a problem that the number of steps for the bonding treatment is increased, and the productivity is reduced and the cost is increased.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a printing blanket having sufficient durability against repeated compression even in high-speed printing.

[0008]

The present invention has the following configuration to achieve the above object. That is, in a printing blanket formed by a support layer and a surface layer made of a plurality of woven fabrics, at least the woven fabric that is close to the surface layer among the woven fabrics that form the support layer is rotated in the rotation direction of the blanket cylinder. Characterized in that the warp yarn is formed of a woven fabric using a polyester blended yarn. In order to obtain sufficient durability against compression fatigue, it is preferable that the blend ratio of the polyester yarn is 30% or more, and in order to obtain sufficient adhesive strength with the surface layer and the binder, cotton yarn and rayon yarn are used. It is preferable that the blending ratio of a yarn having high adhesiveness such as that described above is 20% or more. Therefore, the blending ratio of the polyester yarn is preferably 30% to 80%. The longitudinal elongation of the woven fabric is preferably 20% or more.

[0009] The polyester blended yarn according to the present invention is used for the warp which is the direction of rotation of the blanket cylinder when the blanket is used. This is because there is no particular problem regarding the compressive stress and the adhesive strength in the axial direction of the blanket cylinder.
By making the warp yarn a blended yarn, high durability against compressive stress can be maintained by the polyester, while high adhesiveness to the surface layer or the binder can be obtained by the cotton or rayon. Further, by using a blended yarn, the surface becomes uneven and the contact area increases. Therefore, the adhesive force with the surface layer and the binder is increased. As described above, the polyester blended yarn can satisfy both the durability and the adhesiveness, which have been issues.

[0010] The surface layer of the blanket according to the present invention comprises:
Oil-resistant polymers are used in consideration of printing inks, ink cleaning agents, etc., for example, chloroprene rubber (CR), polysulfide rubber (T), polyacrylonitrile-butadiene rubber (NBR), fluoro rubber (FKM), silicon rubber (Q) and the like. Such an oil-resistant polymer may be one to which one or more of a vulcanizing agent, a vulcanization accelerator, a reinforcing agent, an antioxidant and the like are added.

[0011]

By using a polyester blended yarn, it is possible to combine high durability with polyester and high adhesiveness of cotton yarn and the like.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A specific embodiment of the present invention will be described.
First, as the blanket, a blanket having a normal structure shown in FIG. 1 is manufactured, and the woven fabric forming the support layer 3 adjacent to the surface layer 1 is made of a woof of 30th cotton yarn and a warp yarn of 60th yarn. The blending ratio was changed. In addition, the load during the stretching process was controlled by fixing the blend ratio, and the residual elongation in the longitudinal direction of the woven fabric was changed. The warp material, blend ratio and residual elongation are as shown in Tables 1, 2 and 3.

[0013]

[Table 1]

[0014]

[Table 2]

[0015]

[Table 3]

The repeated compression fatigue evaluation of the blanket having the above configuration was performed as follows. First, as shown in FIG. 2, a compression / rotation test machine (bearer contact system) in which the impression cylinder and blanket cylinder units of a printing press were modified was used as the compression fatigue test machine. That is, the body diameter is 340 m
m, an impression cylinder 10 having a surface length of 1170 mm, and a blanket cylinder 11 were attached to bearers 13 and 15, respectively.
When the bearer 13 and the bearer 15 are abutted, the gap between the impression cylinder 10 and the blanket cylinder 11 is 2 mm.
It was configured to be.

The test method using the above tester was performed as follows. First, the blanket 17 was mounted on the blanket cylinder 11 using an underlay so that the amount of compression of the blanket 17 at the nip was 0.25 mm. At this time, the underlay was stuck with a constant torque (200 kgf-cm) so as to come into contact with the cylinder surface, rotated for several minutes with the blanket attached, and then tightened again. Next, one sheet of paper 19 having a thickness of 0.1 mm is attached to the surface of the blanket to form a bearer 13.
And the bearer 15 were abutted and rotated at a rotation speed of 600 rpm. After one hour, the rotation was stopped and the blanket surface was observed. If there are no breaks or cracks on the blanket surface, a second sheet of paper is placed on top of the bearer 1
3 and the bearer 15 and the rotation speed is also 600
Rotated at rpm for 1 hour. The surface of the blanket was observed, and if there was no abnormality, a third sheet was further stacked and rotated under the same conditions. In the same manner, the observation of the blanket surface was continued while successively stacking the sheets. However, the number of sheets to be stuck on the blanket was limited to 10 in consideration of the damage of the testing machine. The test results are as shown in Tables 4 and 5.

[0018]

[Table 4]

[0019]

[Table 5]

In the above test, the total compression amount of the ten sheets pasted together is 1 m when combined with the initial set compression amount.
m or more. Usually, the amount of compression of the blanket during printing is about 0.15 mm, so that it is possible to determine that the compression fatigue resistance is sufficient if ten blanks are adhered and no abnormalities such as breakage occur in the blanket. Judging from this viewpoint, it is preferable that the blend ratio of the polyester yarn is 30% or more in order to obtain a sufficient resistance to compression fatigue.

Next, the evaluation of the adhesive strength was performed as follows. First, the test method was based on JIS K6256 "Peeling test of cloth and vulcanized rubber". The blanket test piece had a width of 25 mm and a length of 150 mm, and the portion for measuring the adhesive strength was measured between the surface layer and the woven fabric adjacent thereto. The peeling speed was 50 mm / min. The test results are as shown in Tables 6 and 7.

[0022]

[Table 6]

[0023]

[Table 7]

The examples and comparative examples shown in Table 3 were evaluated by the above-described compression / rotation tester. The test results are as shown in Table 8.

[0025]

[Table 8]

Judging from the test results, it is desirable that the residual elongation in the longitudinal direction of the woven fabric is 20% or more in order to obtain a sufficient resistance to compression resistance.

Looking at the test results, Examples 2 to 5
In Examples 7 to 10 and Comparative Examples 2 and 3, the surface layer was broken. This indicates that the adhesive strength between the woven fabric and the surface layer is higher than the strength of the surface layer,
The bonding strength is satisfactory. On the other hand, in Comparative Example 1, Example 1, and Example 6, peeling occurred at the interface between the surface layer and the woven fabric. This indicates that the adhesive strength is clearly lower than the strength of the surface layer. From the above results, in order to obtain a sufficient adhesive strength, it is preferable that the blend ratio of a material having high adhesiveness such as cotton yarn or rayon yarn is 20% or more.

[0028]

As described above in detail, the present invention is excellent in the compression fatigue property and the adhesiveness of the surface layer and the support layer adjacent thereto even at the time of high-speed printing.

[Brief description of the drawings]

FIG. 1 is an enlarged cross-sectional view illustrating an example of a blanket.

FIG. 2 is an explanatory plan view showing a method of a compression fatigue test.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Surface layer 3 Support layer 5 Compressible layer 7 Woven cloth 9 Support layer 10 Impression cylinder 11 Blanket cylinder 13 Bearer 17 Blanket 19 Paper

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B41N 10/00

Claims (2)

(57) [Claims] 1. A printing blanket formed by a support layer made of a plurality of woven fabrics and a surface layer, wherein a woven fabric that is close to at least the surface layer of the woven fabric forming the support layer is placed on a blanket cylinder. The polyester yarn is formed by woven fabric in which the warp in the rotating direction is a polyester blended yarn.
The blended yarn has a polyester blending ratio of 30 to 80%.
A printing blanket having a residual elongation in the warp direction of 20% or more . 2. The polyester blended yarn is mixed with a cotton yarn.
2. The printing blanket according to claim 1, wherein the printing blanket is spinning .