JPH061091A - Compressive rubber blanket and manufacture thereof - Google Patents

Abstract

PURPOSE:To constitute a cell by micro balloon even when it is a final product, without necessitating specific process or complicated equipment. CONSTITUTION:In a compressive rubber blanket containing at least 1 reinforced layer, a compressive layer 2 made of oil resistant rubber mixture in which micro balloon 11 having a thermal deformation temperature of 120 deg.C or higher and a pressure proof of 40Kg/cm<2> is contained and a surface rubber layer 4 provided on the compressive layer 2 are provided. For the material of the micro balloon 11, copolymer of matacrylonitrile and acrylonitrile is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressible rubber blanket and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, as a compressible rubber blanket, for example, New Develoments in Offset Blanket.
s. Prof. Print. , Vol. twenty two. no. 6, Nov. / D
ec. 1978, pp2-7 (prior art 1) is known.
This compressible rubber blanket is manufactured by N.P. G. Chamerlain
It was developed to improve smash resistance, and functionally causes vertical compression when rotating in contact with the plate cylinder or impression cylinder of the printing machine, and It states that no uplift will occur. The method for forming the compression layer of the compressible rubber blanket includes (1) a method using impregnated paper, (2) a salt elution method, (3) a foaming agent method, and (4)
There are four types of microballoon methods.

Japanese Patent Publication No. 52-7371 (British Patent 132
No. 7758) (Prior Art 2) describes the formation of substantially completely closed cells, that is, closed cells, by incorporating microballoons that exhibit elasticity and / or collapsibility to pressure in an elastic polymer. A method of doing so is disclosed. The publication discloses that glass, phenolic resin, carbon or a thermoplastic material, particularly a copolymer of acrylonitrile and vinylidene chloride, is suitable as the microballoon. Further, the above-mentioned publication discloses that a blanket is made by vulcanizing at 140 ° C. for 90 minutes.

Japanese Patent Publication No. 61-52800 (Prior Art 3) discloses the use of a copolymer of acrylonitrile and vinylidene chloride. As an improvement method, an unvulcanized compressible rubber sheet is irradiated with an electron beam of about 9 mega rad or less to incompletely vulcanize and fix a microballoon, and then wound around a drum, pressurized and heated. A two-step vulcanization method of vulcanizing is proposed.

US Pat. No. 4,770,928 (Prior Art 4) discloses a compression layer intermediate obtained by mixing a microballoon made of a copolymer of acrylonitrile and vinylidene chloride in an elastomer material, that is, at a temperature at which the microballoon does not melt. About 110F (43 ℃) -170F (77 ℃)
It is disclosed that the microballoons are fixed in the elastomer material by vulcanization for 1 to 12 hours. In the case of the above publication, it is essential to use a special super vulcanization accelerator, dithiocarbamate, for vulcanization at a low temperature. Further, in the above-mentioned publication, after the vulcanized compression layer intermediate body is further provided with a cloth and a surface rubber layer, the main vulcanization is performed at 132 ° C to
It is characterized in that it is carried out at a temperature of 160 ° C. to obtain the final product, that is, it has two steps.

[0006]

However, according to the above-mentioned prior art, there are the following problems.

(A) Prior art 1: The blanket produced by the above methods (1) and (2) has a structure having continuous pores. Therefore, the dampening water and the cleaning agent used during printing permeate into the compressed layer of the blanket, and the portion becomes thicker and becomes overpressure, which causes printing troubles such as tearing and thickening of the dot of the printed matter.

The production of the compression layer by the method (3) is carried out by mixing an unvulcanized rubber compound with an organic foaming agent to form a sheet and heating it at a constant temperature to vulcanize and foam the rubber (form a sponge). ) Is a way to do. The disadvantage of this method is that the vulcanization and foaming of rubber proceed at the same time by heating, resulting in variations in the size of bubbles, resulting in variations in compressibility of the blanket. Further, when wound around a drum and heated to cause vulcanization and foaming, a difference occurs in winding pressure between the lower winding portion and the upper winding portion. In particular, since the lower winding portion has a high pressure, foaming hardly occurs, and it is difficult to obtain sufficient compressibility. On the contrary, since the upper winding part does not receive sufficient pressure, bubbles grow faster, resulting in coarse bubbles.
The compressibility is so great that the printing pressure will be insufficient when the product is mounted on a printing machine and printed.

(B) Prior art 2: The microballoons are melted and destroyed during the process of being wound on a vulcanizing drum and being heated and vulcanized, resulting in variations in the thickness of the compression layer, resulting in large variations in printability. Cause.

(C) Prior art 3: Microballoons composed of a copolymer of acrylonitrile and vinylidene chloride are melted and destroyed at a normal vulcanization temperature. Therefore, a rubber sheet in an unvulcanized state is about 5 megarads. The following electron beams are irradiated to incompletely vulcanize and fix the microballoons. After that, it is a two-step method in which it is wound around a drum and vulcanized again. Therefore, it is a method that requires special equipment which is expensive and dangerous while being uneconomical in two steps.

(E) Prior art 4: A microballoon made of a copolymer of acrylonitrile and vinylidene chloride is
Since it is melted at a usual vulcanization temperature of 120 to 150 ° C., its manufacturing method is divided into two steps. Therefore, the process is complicated and the cost is increased. Also,
This technique is a method of vulcanizing and immobilizing rubber at a temperature at which the microballoons do not melt using dithiocarbamate, which is a supervulcanization accelerator. Means stable. That is, there is a risk of premature vulcanization during production and storage of the rubber paste.

The present invention has been made in view of the above circumstances, and provides a compressible blanket in which cells can be constituted by microballoons even in a final product without requiring a special process or complicated equipment, and a manufacturing method thereof. The purpose is to do.

[0013]

Means for Solving the Problems The first invention of the present application is
For a compressible rubber blanket containing at least one reinforcement layer
And the oil-resistant rubber compound has a heat distortion temperature of 120 ° C or higher.
And 40 kg / cm² Microvalu with pressure resistance
And a compression layer formed by enclosing
And a surface rubber layer, and the material of the microballoon
Is a copolymer of methacrylonitrile and acrylonitrile
It is a compressible rubber blanket characterized by
It

The second invention of the present application is a method for manufacturing a compressible rubber blanket including at least one reinforcing layer,
Oil-resistant rubber compound with heat distortion temperature of 120 ° C or higher and 4
0 kg / cm ² After being integrated with the compression layer and the surface rubber layer, which have microballoons made of a copolymer of methacrylonitrile and acrylonitrile, the compression layer and the surface rubber layer are integrated at a temperature of 120 ° C. or higher. It is a method for producing a compressible rubber blanket characterized by vulcanizing at once.

In the present invention, the amount of the microballoons added to the oil-resistant rubber to be the compression layer varies depending on the type of printing machine and the printed matter, but is preferably 5 to 40 parts by weight, preferably 100 parts by weight of the oil-resistant rubber. Is 10 to 30 parts by weight. Here, the amount of microballoons mixed in affects the performance of the finished blanket, particularly the compressibility. That is, when the amount is small, the porosity is small and the compressibility is small. Conversely, the compressibility increases as the amount increases.

In the present invention, the diameter of the microballoon is preferably 30 to 100 μm. Here, the diameter of the microballoon also affects the compressibility of the blanket. That is, if it is too fine, the thickness of the wall forming the cell becomes large, and the compressibility becomes insufficient. On the other hand, if it is too large, the wall becomes thin and the compressibility is excessive (too soft).
Becomes

In the present invention, the material for forming the microballoon is most preferably a copolymer of methacrylonitrile and acrylonitrile. The inventors conducted the following comparative test in selecting this material. That is, first, a microballoon made of three kinds of materials (a) a copolymer of vinylidene chloride and acrylonitrile, (b) a copolymer of methylmethacrylate and acrylonitrile, and (c) a copolymer of methacrylonitrile and acrylonitrile is prepared. did. All of these materials contain isobutane or isopentane as an expanding agent. Next, 80 of these three types of microballoons are used.
℃, 90 ℃, 110 ℃, 120 ℃, 130 ℃, 140
1 in an oven whose temperature is adjusted to ℃, 150 ℃, 160 ℃
After leaving it for a while, it was observed with a microscope to see if the microballoons were melted, destroyed, or abnormal.
As a result, the data shown in the following "Table 1" were obtained.

[0018]

[Table 1]

From Table 1 above, the microballoons made of the materials (a) and (b) are stable up to 100 ° C., but at 110 ° C., the microballoons are partially melted and destroyed. It is clear that it is completely melted and destroyed at higher temperatures. This is a commonly used rubber vulcanization temperature of 120 to
When vulcanized at 150 ° C, the microballoons melt,
It means destroying it. On the other hand, it has been found that the microballoons made of the material (c) have extremely high heat stability and can sufficiently withstand the vulcanization temperature generally used.

Incidentally, the microballoon made of the material (a) has a heat distortion temperature of 100 ° C. or lower. For this reason, it is necessary to vulcanize once at a temperature not higher than the heat deformation temperature and fix the microballoons in the rubber. Then, the surface rubber layer and the like are formed again, and this time, vulcanization is performed at a higher temperature.
However, when vulcanized at a high temperature, the microballoons are melted and eventually the microballoons do not remain in the cells. Therefore, the cell of the compression layer using the material (a) or the material (b) is finally formed by the rubber film.

On the other hand, the compressible rubber blanket using the compression layer containing the microballoons made of the material (c) has a high thermal deformation temperature of the microballoons and does not melt at the vulcanization temperature of the rubber. In the product, the cells will be formed by microballoons.

The above difference appears as a difference in pressure resistance. Actually, two types of compressible blankets were made using the microballoons made of the material (a) and the microballoons made of the material (c), and a printing test was performed to compare the pressure resistance. That is, the printing pressure is set to 0.1 mm and the thickness is 0.05
Paper having a width of 1 cm and a thickness of 0.25 mm was attached to a printing paper having a size of mm, and an overpressure portion was partially provided for printing.

As a result, a recess was formed at the portion of overpressure, and the ink density at that portion decreased. Then, the normal thickness of 0.
Printing was continued with 05 mm paper, and it was examined on what number of sheets it returned to normal density. As a result, the blanket formed by the microballoon made of the material (a) had a normal ink density on the 20th printing. On the other hand, the blanket made of the material (c) made of microballoons returned to the normal ink density on the fifth sheet. That is, it was revealed that the blanket according to the present invention has extremely excellent cell recoverability. This is probably because the wall of the microballoon is not melted by vulcanization and remains.
Next, the pressure resistance of the microballoon will be described.

Generally, in offset printing, the blanket is subjected to a compression of 0.1 mm to 0.15 mm with respect to its original thickness and is rotated at high speed in contact with the plate cylinder and the impression cylinder. Here, the stress when compressing a blanket having a thickness of 1.9 mm by 0.1 mm with Tensilon (compression tester manufactured by Orientec Co., Ltd.) is generally 3 to 5 kg / cm ^2. Is. Also,
The stress when compressed by 0.15 mm is 5 to 10 kg / cm.
² Is. These stresses differ depending on the blanket type. By the way, the blanket sometimes becomes very overpressure due to the paper being cut off during printing and winding around the blanket cylinder. In such a case, probably 40 Kg / cm ² You will receive some stress. In such a case, for example, a glass balloon having no pressure resistance is easily broken, and even the rubber surrounding the balloon is broken. In such a glass balloon having poor pressure resistance, when excessive pressure is applied, a permanent dent is formed in that portion and it is not restored, and unevenness occurs in the printed matter, resulting in a defect.

To produce a blanket, ink-resistant rubber is thoroughly mixed with sulfur, a vulcanization accelerator, a reinforcing agent, a softening agent, a processing aid and the like with a kneading roll, and then a good solvent for the rubber is used. It is necessary to dissolve in A rubber balloon is mixed with a microballoon, and coated on a woven fabric with a spreader (size-applying machine). The most common rubber having ink resistance includes, for example, NBR (acrylnitl butadiene rubber) and chloroprene rubber. Examples of common solvents for these rubbers include M.I. E. K
(Methyl ethyl ketone). Therefore, the microballoons forming the compressed layer must withstand this solvent. Therefore, the materials (a), (b), and (c) described above are M. E. When it was immersed in K for 4 hours, it dissolved except for the material (c). This means that the microballoons are dissolved in the rubber paste and bubbles are not formed. Therefore, it was found that only microballoons made of the above material (c) can form pores.

From the above, as a result of verifying the requirements for making a compressible blanket and the performance as a compressible blanket, it is found that only a compressible blanket having a compression layer of microballoons of the above-mentioned material (c) satisfies the following requirements. found. (1) Solvent resistance of microballoons for stable formation of bubbles (2) Thermal deformation temperature with respect to the temperature at which the blanket is vulcanized (3) Pressure resistance during printing Next, we will explain the method for manufacturing compressible blankets. To do. FIG. 1 shows a schematic sectional view of a compressible rubber blanket.

(1) First, a rubber compound to be the compression layer 2 is applied onto the first cotton cloth 1a, and the second cotton cloth 1b is attached thereto. When the compression layer 2 is a salt elution method, a certain amount of ground salt is put in the rubber compound. (2) Then, put it in a vulcanizer at 120 ° C to 150 ° C and heat for about 4 hours to vulcanize the rubber. (3) Then, soak in warm water to elute the salt and dry. (4) Next, the first adhesive rubber 3a is used to bond the third cotton cloth 1c. (5) Next, the second adhesive rubber 3b is used to bond the fourth cotton cloth 1d to the fourth cotton cloth 1d. (6) Next, the surface rubber layer 4 is coated via the third adhesive rubber 3c.

(7) Finally, the blanket material thus formed is wrapped around a drum together with release paper, introduced into a vulcanization can, and heated again at 120 to 150 ° C. to complete vulcanization.

[0029]

According to the present invention, a microballoon made of a copolymer of methacrylonitrile and acrylonitrile is not melted or destroyed at a usual vulcanization temperature of 120 to 150 ° C., and therefore, the microballoon is added to a rubber compound to be a compression layer. After forming a blanket by mixing with, the formation of the compression layer and the vulcanization of the surface rubber layer and the like can be performed in a single vulcanization step at a normal vulcanization temperature. Therefore, the deterioration of the cotton cloth due to heat can be prevented.

[0030]

EXAMPLES Examples of the present invention will be described below. (Example 1)

First, medium-high nitrile rubber (NBR) 100
In parts by weight, sulfur, vulcanization accelerator, antioxidant, reinforcing agent,
A plasticizer was mixed and dissolved in methyl ethyl ketone to obtain a rubber paste. Next, 20 parts by weight of microballoons (trade name: Expancel 091DE, manufactured by Nobel Industry Co., Ltd.), which is a copolymer of methacrylonitrile and acrylonitrile, are added to this rubber paste to prepare a rubber paste. Here, the microballoon used was one which was heated in advance and expanded to a diameter of about 60 μm. The vulcanization accelerator is
D. Very common ones such as M (dibenzothiazol.disulfide) and M (2-mercaptobenzothiazole) were used. By vulcanizing the rubber paste, a compressed layer having a large cushioning property containing a large number of microballoons is formed. Next, the first cotton cloth 1 having a thickness of about 0.4 mm
The rubber paste is coated on a in a thickness of 0.35 mm. Then, the second cotton cloth 1b is attached. After that,
The third cotton cloth 1c and the fourth cotton cloth 1d are respectively provided with an adhesive rubber 3
It attaches via a and 3b. Finally, the adhesive rubber 3c is applied on the second cotton cloth 1b that is in contact with the rubber layer to be the compression layer, and then the nitrile rubber compound is laminated as a sheet as the surface rubber layer 4. The total thickness is about 2.1m
Move to m.

The unvulcanized compressible rubber blanket thus prepared was wound around a metal drum and then placed on the outside.
It puts inside the double can which introduce | transduced the steam of 50 degreeC, and heats for 6 hours, and completes vulcanization. After cooling, the surface rubber layer is ground with 240 mesh sandpaper to a thickness of 1.9 mm.

According to the above Example 1, the microballoon 11 made of a copolymer of methacrylonitrile and acrylonitrile was melted at a usual vulcanization temperature of 120 to 150 ° C.
Since it is not destroyed, the microballoons 11 are mixed into the rubber compound forming the compression layer 2 to form a blanket integrally, and then 1 at a normal vulcanization temperature (ie 120 to 150 ° C).
The compression layer 2 can be formed and the surface rubber layer 4 and the like can be vulcanized in one vulcanization step. Therefore, the deterioration of the cotton cloth due to heat can be prevented.

In fact, when observing the cross section of the blanket thus made with a microscope, it is found that the compression layer 2 has a void 13 formed in the wall 12 of the microballoon 11 as shown in FIG. confirmed. In addition, 13 in the figure is a rubber layer. (Example 2)

In Example 1, medium-high nitrile rubber (NBR, acrylonitrile content was used as the oil-resistant synthetic rubber).
33%), but in Example 2, high nitrile rubber (NBR, trade name Nipol 1031, manufactured by Nippon Zeon Co., Ltd., acrylonitrile amount 41%) was used instead.
A compressible rubber blanket was prepared in the same manner as in. Since the high nitrile rubber has strong oil resistance and solvent resistance, it does not dissolve in toluene when forming a rubber paste, and cannot be a rubber paste unless it is a strong solvent such as methyl ethyl ketone (M.E.K.). An advantage of using the high nitrile rubber is that it has a strong resistance to a cleaning agent used for washing out ink when it is attached to a printing machine and subjected to printing.

When the compressible rubber blanket according to Example 2 was used in an offset rotary press, no infiltration of the cleaning agent into the compression layer was observed, and it could be used for a long period of 6 months. On the other hand, the life of the conventional blanket was about one month.

[0037]

As described above in detail, according to the present invention, there is provided a compressible rubber blanket in which cells can be constituted by microballoons even in a final product without requiring a special process or complicated equipment, and a manufacturing method thereof. Can be provided.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a compressible rubber blanket according to a first embodiment of the present invention.

FIG. 2 is a partially enlarged view of a compression layer forming the compressible rubber blanket of FIG.

[Explanation of symbols]

1a, 1b, 1c, 1d ... cotton cloth, 2 ... compression layer, 3a, 3
b ... Adhesive rubber, 4 ... Surface rubber layer.

Claims (2)

[Claims] 1. A compressible rubber blanket comprising at least one reinforcing layer, wherein the oil resistant rubber compound has a heat distortion temperature of 120 ° C. or higher and 40 kg / cm ^2. A compression layer comprising a microballoon having pressure resistance and a surface rubber layer provided on the compression layer, wherein the material of the microballoon is a copolymer of methacrylonitrile and acrylonitrile. Characteristic compressible rubber blanket. 2. A method for producing a compressible rubber blanket containing at least one reinforcing layer, wherein the oil resistant rubber compound has a heat distortion temperature of 120 ° C. or higher and 40 kg / cm ^2. After having integrated the compression layer and the surface rubber layer containing microballoons having a pressure resistance of methacrylonitrile and acrylonitrile copolymer, the compression layer and the surface rubber layer were once integrated at a temperature of 120 ° C or higher. A method for producing a compressible rubber blanket, which comprises vulcanizing into a rubber.