JPH05246016A - Printing rubber roll - Google Patents

Abstract

PURPOSE:To make a rubber roll superior in stability to ultraviolet-curing ink and usable over a long period, by a method wherein a printing rubber roll is constituted of a mixture of silicone rubber and oil-resistant rubber. CONSTITUTION:Millable silicone rubber is used preferably as silicone rubber for a rubber roll, this rubber consists mainly of polyorganosiloxane which has a straight-chain and high polymerization degree and supplied as a rubber compound obtained by compounding the same with a reinforcement filler for an increase in quantity and dispersion accelerator. Then acrylonitrile-butadiene rubber is mentioned as oil-resistant rubber and it is preferable that because of equilibrium between the oil resistance and ink transfer properties, a matter having at least 30% of acrylonitrile is used mainly for the rubber. Then a matter whose compounding ratio of the silicone rubber to oil-resistant rubber is within a range of 20/80-60/40 by a weight ratio is preferable since it is superior in durability to ultraviolet-curing ink and strength of the rubber and the transfer properties of the ink also become favorable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber roll for printing, which is particularly applied to an offset printing machine using an ultraviolet curable ink.

[0002]

2. Description of the Related Art Recently, in offset printing, from the viewpoint of preventing the deterioration of the working environment due to the solvent component evaporated from the ink, speeding up the printing work and improving the efficiency. The use of UV curable ink (UV ink) is increasing. In particular, the demand for UV-curable inks is increasing due to food packaging that dislikes the odor of printed matter and diversification of printed materials (particularly plastics).

In commercial offset printing, as shown in FIG. 4, an ink transfer roll 5a, an ink kneading roll 5b, and an inking roll 5c are installed from an ink tank 6 to a plate cylinder 7, and the plate is kneaded while kneading the ink. Torso 7
Is being supplied to. These rubber rolls 5a, 5b, 5
c is usually an acrylonitrile-butadiene copolymer rubber (NB) in consideration of affinity with oil-based ink and strength.
R), oil-resistant rubber such as urethane rubber and plastics such as polyvinyl chloride were mainly used.

However, when an ultraviolet-curable ink is used in an offset printing machine using such oil-resistant rubber,
Swelling or rubber rolls 5a, 5b, 5
Additives such as plasticizers contained in c are eluted and the outer diameter is reduced, which is a disadvantage. As a result, the rubber rolls 5a, 5b, 5c became unusable in a short period of time and had to be replaced frequently.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a printing rubber roll which is excellent in stability against an ultraviolet curable ink and can be used for a long period of time.

[0006]

The rubber roll for printing of the present invention has been made to solve the above-mentioned problems and is characterized in that it is made of a mixture of silicone rubber and oil resistant rubber. The present inventors have conducted various studies on rubber materials having excellent stability with respect to UV-curable ink, and have found that silicone rubber has excellent durability with respect to UV-curable ink.
Since the rubber strength is low and the affinity for the ink is extremely low, the kneading of the ink and the ink transferability, which are the purpose of the rubber roll, are insufficient. That is, as described above, in offset printing, a large number of rubber rolls are arranged between the ink tank and the plate cylinder, and the ink is passed between the rolls to knead the ink to form a uniform ink film. If a rubber material that is formed but has insufficient rubber strength such as tensile strength is used, the rolls cannot be sufficiently clamped, and the ink cannot be sufficiently kneaded. Further, the transferability of ink is a problem in transfer of ink from the rubber roll to the surface of the plate cylinder. In any case, the print quality is deteriorated such that the print is faint.

Further, since silicone rubber is poor in oil resistance, it is easily deteriorated and swelled by an ordinary oil-based ink or a solvent for cleaning the ink. Therefore, when a conventional oil-based ink is used for a roll made of silicone rubber, There was also a problem that the print was distorted. On the other hand, ordinary oil-resistant rubbers such as acrylonitrile-butadiene copolymer rubber are inferior in durability to UV curable ink, but are excellent in rubber strength, and are excellent in kneading and ink transfer properties of ink which is the purpose of a rubber roll. ing.

Then, as a result of further investigation, when a rubber roll made of a mixture of the above-mentioned silicone rubber and oil-resistant rubber is used, it is excellent in durability against ultraviolet curable ink and also has good rubber strength and ink transferability. I found that. Also, by mixing oil-resistant rubber and silicone rubber, even when used in ordinary oil-based ink, it is possible to prevent the rubber roll from deteriorating or swelling due to the oil-based ink or the solvent for cleaning the ink. You can

As the silicone rubber used in the rubber roll of the present invention, among various conventionally known silicone rubbers, a millable type silicone rubber which can be handled in the same manner as an ordinary rubber material is preferably used. This millable type silicone rubber is mainly composed of a linear polyorganosiloxane (silicone gum) having a high degree of polymerization (6000 to 10000), and a silica-based reinforcing filler, an expanding filler, a dispersion accelerator, etc. It is supplied as a rubber compound containing As the above-mentioned silicone gum, methyl vinyl silicone [(CH ₂ = C
H) (CH ₃ ) SiO] is most commonly used, but in order to improve the physical properties of rubber, for example, (CH ₃ )
_{2 SiO, (CF 3 CH 2} CH 2) Si O, (C 6 H 5) 2
Polyorganaxane in which polymerized units such as SiO are introduced in a straight chain is also used.

Examples of the oil resistant rubber include acrylic rubber and acrylonitrile-butadiene rubber (NBR). Although various grades of acrylonitrile-butadiene rubber are commercially available depending on the amount of acrylonitrile used and the difference in molecular weight, the acrylonitrile amount is 30% or more, mainly because of the balance between oil resistance and ink transfer property.
It is suitable to use one having a content of about 40 to 50%.

The mixing ratio of silicone rubber and oil resistant rubber is 20/80 by weight ratio of silicone rubber / oil resistant rubber.
It is preferably in the range of 60/40 because it has excellent durability to the ultraviolet curable ink and also has good rubber strength and ink transferability. That is, when the compounding amount of the silicone rubber exceeds 60% by weight, the durability to the ultraviolet curable ink is improved, but the rubber strength is decreased, the kneading and transferability of the ink is decreased, and further the oil resistance is decreased. Swelling or the like is likely to occur in the oil-based ink.
On the other hand, when the addition amount of the silicone rubber is less than 20% by weight, the durability against the ultraviolet curable ink is lowered, and when the ultraviolet curable ink is used, the swelling of the rubber roll and the elution of the additive occur. ..

The rubber roll for printing of the present invention is a mixture of the above silicone rubber and oil resistant rubber with various additives such as a vulcanizing agent, a vulcanization accelerator, a vulcanization accelerating aid, a filler and a plasticizer. It is formed by molding rubber into the shape of a rubber roll and then vulcanizing it by a conventional method. Examples of the vulcanizing agent contained in the compounded rubber include tetramethylthiuram disulfide (TMTD), organic sulfur-containing compounds such as N, N'-dithiobismorpholine, and sulfur. Also,
As the vulcanizing agent, an organic peroxide-based crosslinking agent can also be used. The organic peroxide-based crosslinking agent, te
rt-Butyl hydroperoxide, di-tert-butyl peroxide, dicumyl peroxide, tert-butyl cumyl peroxide, 1,1-bis (tert-butylperoxy) cyclododecane, 2,2-bis (tert-butylperoxy) octane , 2,5-dimethyl-2,5 di (tert
-Butylperoxy) hexane, 1,3-bis (tert-
Butylperoxyisopropyl) benzene, n-butyl-4,4-bis (tert-butylperoxy) valerate, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, and tert-butylperoxybenzoate.

As the vulcanization accelerator, dibenzothiazyl disulfide (MBTS), N-oxydiethylene-2-benzothiazyl sulfenamide (OBS), N
Thiazoles such as -cyclohexyl-2-benzothiazylsulfenamide (CBS) and N-tert-butyl-2-benzothiazylsulfenamide (TBBS) are listed as main accelerators, and if necessary, 1 , 3-diphenylguanidine (DPG), tetramethylthiuram monosulfide (TMTM), zinc dimethyldithiocarbamate (ZnMDC), zinc ethylphenyldithiocarbamate (ZnEPDC), and tetramethylthiuram listed under vulcanizing agents Disulfide (TMTD) etc. 2
It can also be appropriately blended as a next accelerator.

As the filler, inorganic fillers such as calcium carbonate, hard clay, soft clay, hydrous silicic acid, silicic acid anhydride, barium sulfate, diatomaceous earth, talc, mica, asbestos, graphite and pumice stone; regenerated rubber, powdered rubber, asphalt And organic fillers such as styrene resin and glue. The printing rubber roll of the present invention is an ink transfer roll 5a, an ink kneading roll 5b, an inking roll 5 as shown in FIG. 4 except for an offset blanket.
It means an ink roll such as c.

[0015]

Example: Examination of compounding ratio of rubber material Millable silicone rubber (trade name KE manufactured by Shin-Etsu Chemical Co., Ltd.
8751-U) and an acrylonitrile-butadiene copolymer rubber (trade name Clinac 803 manufactured by Polycer Co., Ltd.) (hereinafter, referred to as NBR) which is an oil resistant rubber, are mixed in white by adding 100 parts by weight of raw material rubber. Filler 3
0 parts by weight, dioctyl phthalate 30 parts by weight, zinc oxide 5 parts by weight, stearic acid 0.5 parts by weight, AccTT1.
5 parts by weight and 2.5 parts by weight of AccMOR were compounded to produce compounded rubbers having different compounding ratios of silicone rubber and NBR. (1) Ink resistance test Molding the above compounded rubber and vulcanizing it, 1mm × 2cm × 2cm
The block was prepared by immersing the block in an oil-based ink kept at 40 ° C., and the volume after 24 hours was measured, and the volume increase rate due to swelling was calculated from the volume before immersion and the volume after immersion. ΔV (%) was calculated. The oil-based ink used is a product name "Mark V" manufactured by Toyo Ink Co., Ltd.

Each block produced in the same manner as described above was dipped in an ultraviolet-curable ink kept at 40 ° C., the volume after 24 hours was measured, and swelling was performed in the same manner as described above. The volume increase rate ΔV (%) was calculated. The UV curable ink used is the product name "Best Cure" manufactured by Toka Color Chemical Co., Ltd. Figure 1 shows the results of these tests.
Shown in. From FIG. 1, it was found that the lower the blending ratio of silicone rubber, the higher the oil resistance, whereas the lower the blending ratio of NBR, the higher the durability to the ultraviolet curable ink. (2) Rubber strength test JIS Dumbbell 3
No. 4 test piece was prepared, and the tensile strength of this test piece was measured. The test was performed under the conditions of JIS 6302.

The test results are shown in FIG. From FIG. 2, it is understood that the strength decreases as the blending ratio of silicone rubber increases. Example 1 Millable silicone rubber (trade name KE manufactured by Shin-Etsu Chemical Co., Ltd.
8751-U) and NBR (commercial name Clinac 803 manufactured by Polycer Co., Ltd.), which is an oil resistant rubber, in a weight ratio of 100 parts by weight of raw material rubber, white rubber. 30 parts by weight of a filler, 30 parts by weight of dioctyl phthalate, 5 parts by weight of zinc oxide, 0.5 parts by weight of stearic acid, 1.5 parts by weight of AccTT and 2.5 parts by weight of AccMOR were blended to obtain a compounded rubber.

Each of the compounded rubbers was molded and vulcanized to have a length of 5
00mm, 200mm in length that is externally inserted to the shaft core with an outer diameter of 10mm,
A rubber roll having an outer diameter of 50 mm was produced. Comparative Example A rubber roll was prepared in the same manner as in Example 1 except that only NBR was used as the raw material rubber. (Evaluation test) Each of the rubber rolls was immersed in an ultraviolet curable ink containing an acrylic monomer (trade name "Best Cure" manufactured by Toka Dye Kagaku Co., Ltd.), and the change in outer diameter with time was observed. The ink was maintained at 40 ° C. during the test. The test results are shown in FIG.

From FIG. 3, it can be seen that in the comparative example of the conventional rubber roll, the outer diameter of the roll swelled to nearly 100 mm in about 30 days, and thereafter the plasticizer was extracted to cause the decrease of the outer diameter. Recognize. On the other hand, in Example 1, the swelling rate was reduced to about 1/3 of that in Comparative Example. From this, the rolls of the examples have been used for about three times longer than the comparative examples. Example 2 A rubber roll was produced in the same manner as in Example 1 except that the mixing ratio of the silicone rubber / acrylonitrile-butadiene copolymer rubber was 60/40 by weight.

The durability of this rubber roll against ultraviolet curable ink was almost the same as in Example 1.

[0021]

As described above, the rubber roll of the present invention has the following features.
Since it is formed from a mixture of silicone rubber, which has excellent durability against UV-curable ink, and oil-resistant rubber, which has excellent rubber strength and ink transfer properties, even when used for printing using UV-curable ink, There is an effect that it can be used for a long period of time while maintaining high print quality.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the compounding ratio of silicone rubber and NBR and the volume increase rate due to swelling.

FIG. 2 is a graph showing the relationship between the compounding ratio of silicone rubber and NBR and the tensile strength.

FIG. 3 is a graph showing changes over time in the outer diameter of each rubber roll obtained in Example 1 and Comparative Example.

FIG. 4 is a schematic view showing a usage state of a rubber roll in a normal offset printing machine. 5a: Ink transfer roll 5b: Ink kneading roll 5c: Inking roll 6: Ink tank 7: Plate cylinder

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Nishi Futami, Futami-cho, Akashi-shi, Hyogo 2001-18-C 709 Yasuhiko Kondo

Claims (2)

[Claims] 1. A printing rubber roll comprising a mixture of silicone rubber and oil resistant rubber. 2. The printing rubber roll according to claim 1, wherein the oil resistant rubber is acrylic rubber or acrylonitrile-butadiene rubber. 3. The printing rubber roll according to claim 1, wherein the silicone rubber and the oil resistant rubber are mixed in a weight ratio of 60:40 to 20:80.