JPS6219317B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resin composition for surface treatment of offset printing blankets, which improves the ink transfer properties of offset printing blankets. In offset printing, printing is performed by first transferring the ink on the printing plate to a blanket, and then transferring it from the blanket to the printing paper. Essentially, the surface of the blanket must be smooth and have excellent ink receptivity. However, chloroprene rubber,
Conventional blankets made of nitrile rubber, thiokol, etc. do not necessarily have sufficient ink receptivity on the surface, and when the surface is smoothed to improve ink receptivity, paper curling during printing becomes worse. When the paper becomes bad, the paper is compressed between the blanket and the impression cylinder, and then when it is pulled by the nails, the paper sticks to the blanket, and when the paper is pulled with the nails in an attempt to forcefully peel it off, the paper stretches. As a result, misregistration, duplication, etc. occur, and in order to avoid this, it is necessary to frequently make fine adjustments to the printing press, which significantly impedes printing work efficiency. For this reason, a method is generally used to improve paper curl by roughening the blanket surface, but in this case, the ink transfer from the blanket to the paper deteriorates and the outline of the printed image, especially the halftone dots, becomes unclear. become. In offset printing, subtle changes in the area of the halftone dots express changes in the shading of the image, so if the outline of the halftone dots becomes unclear, the finished print will become unclear, resulting in blurry prints that lack a sense of volume. . For this reason, there is a limit to the improvement of paper thinning by roughening the surface. As described above, conventional blankets have contradictory properties in that it is difficult to achieve both ink transferability and paper deterioration, and if one is emphasized, the other must be sacrificed. Therefore, in view of the above points, the present inventors
The present invention was completed as a result of intensive research with the aim of providing a blanket for offset printing that is excellent in both ink transferability and paper vanity. That is, the present invention comprises (A) a linear polyester containing hydroxyl groups at both terminals, (B) an organic polyisocyanate compound,
Surface treatment of a printing blanket containing as a main component an unsaturated urethane resin obtained by reacting (C) an ethylenically unsaturated compound having an active hydrogen atom capable of reacting with an isocyanate group and (D) a polyhydric alcohol. By applying this composition to the surface of a blanket for offset printing and curing it, the ink transfer properties are dramatically improved compared to conventional blankets, and the printed lines of printed matter printed with this blanket are improved. The filling of the solid part of
Compared to conventional blankets, it is extremely uniform and smooth, and the contours of halftone dots are clear and reproduced exactly as per pixel.Furthermore, even though the blanket surface is smooth, it is excellent against paper curling, and there is no problem when printing. This makes it possible to manufacture blankets without any problems. The linear polyester containing hydroxyl groups at both ends of the component (A) used in the present invention is one or two of aromatic dibasic acids, cyclic aliphatic dibasic acids, and acyclic aliphatic dibasic acids.
It can be produced by reacting one or more acid components with a dihydric alcohol which may contain an ether bond in its molecule. Aromatic dibasic acids such as phthalic acid, phthalic anhydride, terephthalic acid and isophthalic acid; cyclic aliphatic dibasic acids such as tetrahydrophthalic anhydride; acyclic aliphatic dibasic acids such as succinic acid and adipine; Acids such as pimelic acid, sebacic acid, azelaic acid, maleic acid, their anhydrides, fumaric acid, citraconic acid, itaconic acid, and dihydric alcohols such as ethylene glycol, propylene glycol,
Diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 1,4-butanediol, 1,6-hexanediol, 2,2-diethylpropanediol, neopentyl glycol, diethylene glycol, triethylene glycol, butenediol, 1 -3-butylene glycol, 2,3-butylene glycol, etc. are listed. To produce component (A), a linear polyester containing hydroxyl groups at both ends,
A type of dihydric alcohol containing ether bonds in 12 molecules can be used as the dihydric alcohol, but if the concentration of ether bonds contained in the unsaturated urethane resin according to the present invention exceeds a certain concentration as described below, Blankets surface treated with such resins tend to cause ink piling during printing. What is ink piling?
During printing, paper powder, dust, spray powder to prevent set-off, etc. that adhere to the plate surface do not separate from the plate surface and transfer to the paper, and eventually form clumps and leave traces on the printing paper, seriously damaging the printed image. This is a troublesome phenomenon that causes damage to blankets, and it always occurs to varying degrees in commonly used blankets. Therefore, it is necessary to prevent such piling of the ink. To do this, a dihydric alcohol that does not have an ether bond is used as the alcohol component of the polyester, or even if it does have an ether bond, the number of bonds is 1. It is preferred to use dihydric alcohols having two or less alcohols in the molecule. The linear polyester containing hydroxyl groups at both ends of component (A) obtained using the above raw materials has a number average molecular weight of 500 to 500.
4000 is preferred. This polyester may be manufactured according to a conventional method for manufacturing polyester resins. Examples of the organic polyisocyanate of component (B) include 2,4-tolylene diisocyanate, 2,6-
Tolylene diisocyanate, mixtures of these isomers, p-xylylene diisocyanate, 4.
4'-diphenylmethane diisocyanate, 1.5
- Aromatic diisocyanates such as naphthalene diisocyanate, cycloaliphatic such as cyclohexane-1,3 (or 1,4)-diisocyanate, 1-isocyanate-3-isocyanatomethyl-3,5,5-trimethylcyclohexane, isophorone diisocyanate Examples include acyclic aliphatic diisocyanates such as diisocyanate, tetramethylene diisocyanate, and hexamethylene diisocyanate. As the addition polymerizable ethylenically unsaturated compound having an active hydrogen atom capable of reacting with the isocyanate group of component (C), for example, 2-hydroxyethyl (meth)
Acrylate, 2-hydroxypropyl (meth)
Acrylate, 2-hydroxybutyl (meth)acrylate, diethylene glycol mono(meth)
Acrylate, triethylene glycol mono(meth)acrylate, trimethylolpropane di(meth)acrylate, pentaerythritol tri(meth)acrylate, N-methylol(meth)acrylamide, acrylamide, glycidyl(meth)acrylate and fatty acid or the above dibasic acid Examples include hydroxyl group-containing compounds obtained by reaction with. Examples of the polyhydric alcohol of component (D) include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 1,4-butanediol, 1,6-hexanediol, 2,2- diethylpropanediol,
Neopentyl glycol, diethylene glycol, triethylene glycol, butenediol,
Dihydric alcohols such as 1,3-butylene glycol and 2,3-butylene glycol, glycerin,
Trimethylolpropane, 1,2,6-hexanetriol, 3-methylpentane, 1,3,5-
Examples include trihydric alcohols such as triol, and tetrahydric alcohols such as pentaerythritol. A polyhydric alcohol containing ether bonds in the molecule can be used as component (D), but if the concentration of ether bonds contained in the resulting unsaturated urethane resin exceeds a certain concentration, the above-mentioned piling of the ink will occur. There is a tendency to Therefore, it is preferable to use a polyhydric alcohol that does not have an ether bond as component (D), or a polyhydric alcohol that has an ether bond, but the number of such bonds is 2 or less per molecule. In any case, the concentration of ether bonds contained in the unsaturated urethane resin obtained by reacting the components (A), (B), (C) and (D) is 1.4×10 ^-3 mol/g (resin It is extremely effective to prevent ink piling if the number of -0-bond molecules contained in 1 g is as follows. When producing the unsaturated urethane resin of the present invention by reacting each of the above components, the resulting resin contains:
The ring structure content concentration and the addition-polymerizable unsaturated bond content concentration, like the ether bond content concentration, are important factors that affect the durability, printability, etc. of the blanket surface-treated with this resin.
That is, the ring structure content concentration (number of monocyclic or condensed polycyclic molecules contained in 1 g of resin) is preferably 0.5×
^10-3 to 3.0× ^10-3 mol/g, preferably 1.5×
A range of 10 ^-3 to 2.5×10 ^-3 mol/g is appropriate;
If it is less than 0.5×10 ^-3 mol/g, ink piling tends to occur during printing, and 3.0×10 ^-3 mol/g.
If it exceeds g, cracking of the treated film during printing or thickening of halftone dots will occur, which tends to cause a decrease in the quality of the printed image. Further, the addition polymerizable unsaturated bond content concentration (the number of molecules of unsaturated bonds contained in 1 g of resin) is preferably 0.5×10 ^-3 to 2.0×10 ^-3 mol/g, more preferably 0.5×10 ^-3 to A range of 1.0 x 10 ^-3 mol/g is appropriate; if it is less than 0.5 x 10 ^-3 mol/g, the hardening rate will be slow, and the crosslinking density will be too low, resulting in a soft coating, and the ink will deteriorate during printing. If it exceeds 2.0×10 ^-3 mol/g, the crosslinking density is too high, which tends to cause cracks in the coating film or thickening of halftone dots.
An example of a method for producing an unsaturated urethane resin of the present invention in which the ring structure, ether bond, and addition-polymerizable unsaturated bond content falls within the above-mentioned preferred ranges is a cyclic dibasic acid/acyclic aliphatic acid. The acid component has a molar ratio of group dibasic acids in the range of 10/90 to 50/50,
The number of ether bonds contained in the molecule is as follows:
The number average molecular weight is 500 by reacting the alcohol component.
A linear polyester containing hydroxyl groups at both terminals of ~4000 is produced, 1 equivalent of this polyester is reacted with 2 equivalents of the organic isocyanate having one ring structure, and then this is reacted with the above-mentioned active hydrogen atom-containing addition polymerizable unsaturation. It can be produced by reacting 1/2 equivalent of a compound and further reacting 1/2 equivalent of the above-mentioned polyhydric alcohol containing 2 or less ether bonds in the molecule. The number average molecular weight of the unsaturated urethane resin used in the present invention is preferably in the range of 4,000 to 17,000. During production, a known catalyst may be added as necessary. Examples of the catalysts used include dibutyltin dilaurate, dibutyltin oxide, acetylacetone iron salt, triethylamine tributylamine, sodium acetate, lithium acetate, and the like. Further, a polymerization inhibitor may be added to suppress thermal polymerization during the reaction or dark reaction during storage of the obtained resin. Examples of polymerization inhibitors include hydroquinone, tert-butylhydroquinone, benzoquinone, 2,4-tert-butylhydroxytoluene, N,N-diphenylnitrosamine, 2,6-di-tert-butyl-p-cresol, hydroxyanisole, etc. can be mentioned. If the viscosity of the reaction system increases during the reaction, adjust the viscosity of the reaction system by gradually adding acetone, a ketone such as methyl ethyl ketone, or an ester solvent such as ethyl acetate as necessary. Good too. The composition obtained by the above method is uniformly applied to the surface of an offset printing blanket and cured. Curing methods include thermal curing using infrared rays, etc.
A curing method using high-energy rays such as actinic rays and electron beams can be used. A polymerization initiator is used as necessary during curing. In the case of thermal curing, for example, benzoyl peroxide, kyumene hydroperoxide, t-butyl hydroperoxide, azobisisobutyronitrile, etc. can be used as a thermal polymerization initiator, and in the case of curing with actinic rays, for example, Benzoyl as a photoinitiator,
Acilloin, benzoin methyl ether, benzoin isopropyl ether, naphthoquinone, anthraquinone, benzophenone, acetophenone,
2-hydroxy-2-methylpropiophenone,
Michler's ketone, p-dimethylaminobenzaldehyde, p-dimethylaminoacetophenone,
Azobisisobutyronitrile and the like can be used. When applying the composition of the present invention to the blanket surface, the above-mentioned suitable polymerization initiator is mixed with the composition as necessary, and the composition is dissolved in an appropriate solvent to adjust the viscosity to be easy to apply. It may be applied uniformly to the blanket surface by a method such as spin coating, roll coating, doctor coating, or spray coating, and the solvent may be volatilized. The appropriate thickness of the surface coating film is approximately 5 to 40 microns.
As the solvent used for the above purpose, ester-based solvents such as ethyl acetate, and ketone-based solvents such as acetone and methyl ethyl ketone are suitable. For curing the coating film thus obtained, heat or high-energy radiation can be used as described above. In the case of thermosetting, suitable curing conditions are a heating temperature of 50 to 150°C and a heating time of 1 to 20 hours. When using active light, the wavelength range is 250 ~
It is desirable to use a 700 nm light source. For example, a low pressure mercury lamp, a high pressure mercury lamp, a fluorescent lamp, a xenon lamp, a carbon arc lamp, a tungsten incandescent lamp, etc. can be used. The irradiation time depends on the type and output of the light source, the irradiation distance, etc., but is within a few seconds to 10 minutes. Electron accelerators used for curing with electron beams include Kotscroft type, Kotscroft-Walton type, Vandegraak type, resonant transformer type, insulated core transformer type, dynamitron type, high frequency type, etc. The paint film is irradiated with an electron beam with an acceleration energy of 100 to 200 keV. EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the scope of the present invention is not limited thereby. Production example 1 219.2 parts of adipic acid, 222.2 parts of phthalic anhydride,
355 parts of 1,6-hexanediol and 62 parts of ethylene glycol were placed in a reaction vessel, and the temperature was raised to 240°C.
The temperature was gradually raised over a period of time, and the reaction proceeded while removing water generated as the condensation reaction progressed from the system. After raising the temperature to 240°C, the reaction was continued for another 1 hour, and then under reduced pressure of 160 mmHg for another 1 hour. After confirming that the acid value was 1, the reaction was stopped, and the number average molecular weight was 770 after being cooled. Polyester () was obtained. Production Example 2 438.4 parts of adipic acid, 355 parts of 1,6-hexanediol, and 62 parts of ethylene glycol were placed in a reaction vessel, and the temperature was gradually raised to 240°C over about 3 hours. The reaction proceeded while removing the water from the system. After raising the temperature to 240℃, reacting for another hour, and then under reduced pressure of 160 mmHg for another hour, and confirming that the acid value was 1, the reaction was stopped and cooled to prepare a polyester with a number average molecular weight of 750. I got it. Production example 3 277.7 parts of adipic acid, 1,4-butanediol
108.1 parts of ethylene glycol and 62 parts of ethylene glycol were placed in a reaction vessel and the temperature was gradually raised to 240°C over a period of about 3 hours, and the reaction proceeded while removing water generated as the condensation proceeded from the system. After raising the temperature to 240°C and reacting for another 1 hour, the reaction was carried out for 2 hours under a reduced pressure of 10 mmHg. After confirming that the acid value was 1, the reaction was stopped and cooled to form a polyester with a number average molecular weight of 2100. I got it. Example 1 233 parts of polyester-() obtained in Production Example 1 and 133 parts of isophorone diisocyanate were placed in a reaction vessel and reacted at 80°C for 2 hours, then hydroquinone
0.3 parts of 2-hydroxyethyl acrylate and 38 parts of 2-hydroxyethyl acrylate were added, the temperature was raised to 100°C, and the reaction was continued for an additional 1.5 hours while blowing air. Next, 13.4 parts of 3-methylpentane 1,3,5-triol was added and kept at 100°C, and as the viscosity of the reaction system increased as the reaction progressed, 15 parts of ethyl acetate was mixed and the reaction was carried out for 4 hours while adjusting the viscosity. The reaction was terminated when the remaining amount of NCO groups reached 0.06%, and after cooling, 120 parts of methyl ethyl ketone was added. The obtained resin had a number average molecular weight (Mn) = 4200 and a ring structure content concentration (R) = 2.5.
×10 ^-3 mol/g, ether bond content concentration (E) =
The concentration of additional polymerizable unsaturated bonds (U) was 0.7× ^{10 −3 mol} /g. 100 parts of the resin solution thus obtained, 4 parts of benzophenone
parts, 4 parts of p-dimethylaminobenzaldehyde,
A solution prepared by mixing 5 parts of 2-hydroxy-2-methylpropiophenone (Darquiure 1173, manufactured by Merck & Co., Ltd., West Germany) with 500 parts of methyl ethyl ketone was uniformly applied to a commercially available blanket for offset printing by a spin coating method. The solvent was evaporated by heating at 90°C for 20 minutes. The coating thickness was 12μ.
This was irradiated with light for 20 seconds from a distance of 12 cm using a high-pressure mercury lamp with an output of 80 W/cm ² manufactured by Hanovia Inc. in the United States, to obtain a surface-treated blanket. Example 2 93 parts of the polyester () obtained in Production Example 1, 180 parts of the polyester () obtained in Production Example 2, and 160 parts of isophorone diisocyanate were placed in a reaction vessel, and
℃ for 3 hours, then hydroquinone 0.3
1 part and 46 parts of 2-hydroxyethyl acrylate were added, the temperature was raised to 100°C, and the mixture was allowed to react for 2 hours while blowing air. Then 3-methylpentane-1.3.
16.2 parts of 5-triol was added and kept at 100°C. 4
After some time, the reaction was terminated when the remaining amount of NCO groups reached 0.03%, and after cooling, 154 parts of methyl ethyl ketone was added. The obtained resin has Mn=4100, R=1.8×
10 ^-3 mol/g, E=0 mol/g, U=0.7× ^{10 -3}
It was mol/g. 100 parts of the resin solution thus obtained, 4 parts of benzophenone, 4 parts of p-dimethylaminoacetophenone
A solution of 5 parts of 2-hydroxy-2-methyl-propiophenone mixed with 500 parts of methyl ethyl ketone was uniformly applied to a commercially available offset printing blanket by a spin coating method.
The solvent was evaporated by heating at 90°C for 20 minutes. The coating thickness is
It was 10μ. In addition to this, 80w/cm ² made by Hanobia in the US
A surface-treated blanket was obtained by irradiating it with light for 20 seconds from a distance of 12 cm using a high-power mercury lamp. Example 3 155 parts of the polyester obtained in Production Example 1, 210 parts of the polyester obtained in Production Example 3, and 133 parts of isophorone diisocyanate were placed in a reaction vessel.
React at 80℃ for 1.5 hours, then add hydroquinone
0.3 parts, 2-hydroxyethyl acrylate 38.3
The mixture was heated to 100°C and reacted for 1.5 hours while blowing air. Then 13.4 parts of trimethylolpropane, dibutyltin dilaurate
0.1 part was added and kept at 100℃. After 4 hours, the reaction was terminated when the remaining amount of NCO groups reached 0.05%, and after cooling, 174 parts of methyl ethyl ketone was added to obtain a resin solution. The obtained resin has Mn=5600, R=1.69×
10 ^-3 mol/g, E=0 mol/g, U=0.56× ^{10 -3}
It was mol/g. A solution obtained by mixing 100 parts of the resin solution thus obtained, 4 parts of benzophenone, 4 parts of p-dimethylaminobenzaldehyde, and 5 parts of 2-hydroxy-2methylpropionphenone in 500 parts of methyl ethyl ketone was mixed with a commonly available commercially available solution. Apply it evenly to a printing blanket using the spin coating method and heat it for 20 minutes at 90°C.
The solvent was evaporated by heating for 1 minute. The coating thickness was 12μ. This was irradiated with light for 20 seconds from a distance of 12 cm using a high-pressure mercury lamp with an output of 80 W/cm ² manufactured by Hanovia in the United States to obtain a surface-treated blanket. Example 4 A solution prepared by mixing 100 parts of the resin solution obtained in Example 3 and 0.7 parts of azobisisobutyronitrile in 500 parts of methyl ethyl ketone was spin-coated onto a blanket for offset printing, and left at room temperature for 24 hours to remove the solvent. was vaporized. The coating thickness was 10μ. This was heated in an open setting at 100° C. for 2 hours to cure it and obtain a surface treated blanket. Example 5 A solution prepared by mixing 100 parts of the resin solution obtained in Example 3 with 500 parts of methyl ethyl ketone was uniformly applied to a commercially available blanket for offset printing using a spin coating method, and the mixture was heated at 90°C for 20 minutes. The solvent was evaporated by heating. The coating thickness was 14μ.
A transformer electron accelerator is used to generate electron beam energy.
A surface-treated blanket was obtained by irradiating an electron beam with a 300 kV electron beam current of 45 mA and a dose of 10 Mrad. The surface treated blankets obtained in the examples and the untreated blankets used as comparative examples were
Roland offset printing machine, Favorit
I attached it to the RF-01 and performed offset printing as usual. The ink used was New Champion Super APEL Red manufactured by Dainippon Ink and Chemicals Co., Ltd. The results of this printing are shown in the table below. The printing results were evaluated using the following items. (1) Ink receptivity (smoothness, uniformity) of solid areas on coated paper (2) Ink receptivity (smoothness, uniformity) of solid areas on high-quality paper
(3) Reproducibility of halftone dots on coated paper (outline of halftone dots, reproducibility of pixels) (4) Reproducibility of halftone dots on high-quality paper (outline of halftone dots,
Pixel reproducibility) (5) Ink piling on the blanket (ink piling condition) (6) Paper curliness (degree of paper curl) [Table]

Claims (1)

[Scope of Claims] 1 (A) a linear polyester containing hydroxyl groups at both terminals, (B) an organic polyisocyanate compound, (C) an addition-polymerizable unsaturated compound having an active hydrogen atom capable of reacting with isocyanate groups, and (D) A resin composition for surface treatment of printing blankets containing as a main component an unsaturated urethane resin obtained by reacting a polyhydric alcohol. 2. The concentration of cyclic structures contained in the molecules of unsaturated urethane resin is 0.5×10 ^-3 to 3.0×10 ^-3 mol/g.
The composition according to claim 1. 3. The concentration of addition polymerizable unsaturated bonds contained in the molecules of unsaturated urethane resin is 0.5×10 ^-3 to 2.0×
10 ^-3 mol/g of the composition according to claim 1. 4. The composition according to claim 1, wherein the concentration of ether bonds contained in the molecules of the unsaturated urethane resin is 0 to 1.4 x 10 ^-3 mol/g. 5 The number average molecular weight of the linear polyester containing hydroxyl groups at both ends is 500 to 4000, and the number average molecular weight of the unsaturated polyester urethane resin obtained using this is
4,000 to 17,000. The composition according to claim 1.