JP2014008665A - Humectant for lithographic printing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a humectant for a lithographic printing plate excellent in dynamic surface tension reduction property, having low foaming property, and not causing plate off.SOLUTION: A humectant for a lithographic printing plate is provided by adding 8 to 500 pts.wt. of a compatibilizing agent represented by the formula (2) to 1 pts.wt. of a humectant represented by the formula (1). RO-(EO)-(PO)-H (1) where Ris a 3,5,5-trimethyl-1-hexyl group, EO is an oxyethylene group, PO is an oxypropylene group, a is an average addition mole number of oxyethylene group and a=3 to 6, b is the average addition mole number of oxypropylene group and b=2 to 4, a/b=1.0 to 1.7. RO-(AO)-H (2) where Ris H or an alkyl group having 1 to 4 carbon atoms, AO is an oxyalkylene group having 2 or 3 carbon atoms, c is the average addition mole number of oxyalkylene group having 2 or 3 carbon atoms and c=1 to 3.

Description

  The present invention relates to a wetting agent for a lithographic printing plate capable of obtaining a good printed matter in lithographic printing.

  Lithographic printing is a printing method that utilizes the property that water and oil are not essentially mixed, and is a method of obtaining a printed matter by repulsion between oil-based ink and aqueous dampening water. For this reason, it is important to obtain a printed matter having good performance of dampening water as well as ink.

  The performance required for fountain solution is excellent in dynamic surface tension reducing ability and low in order to supply fountain solution quickly and uniformly to fine non-image areas on a rotating printing plate attached to a roller. It is mentioned that it is foamy. Furthermore, it is also required not to cause plate tray, which is a phenomenon in which an image area to which ink is supplied on a printing plate is eroded and peeled off. When plate tray occurs, dampening water is supplied to the area to be the image area, and a good printed matter cannot be obtained. These dynamic surface tension lowering ability, low-foaming property, and plate tray prevention ability are all necessary for obtaining a good printed matter, and if any one of them is inferior, a good printed matter cannot be obtained. For this reason, it is difficult to use water having a high surface tension as the dampening water as it is.

  Therefore, an isopropyl alcohol aqueous solution has been conventionally used as a fountain solution that has excellent dynamic surface tension lowering ability, low foaming property, and does not cause plate tray. However, since isopropyl alcohol is easily volatilized, isopropyl alcohol volatilizes even when dampening water is supplied onto the roller or the printing plate, and it is not possible to exert a sufficient effect as dampening water. It has been a problem that it is difficult to obtain a printed matter and that a special device is required to keep the isopropyl alcohol concentration in the dampening water constant. In addition, there are concerns about the impact on the environment and the human body, and there has been a shift to dampening water that does not use isopropyl alcohol.

  Therefore, a dampening solution containing a surfactant called a wetting agent, a glycol-based compatibilizing component, etc., which is a component that has excellent dynamic surface tension lowering ability and is less volatile than isopropyl alcohol, is used. It became so.

  In recent years, as an improvement in productivity, it has been required to perform higher-speed printing without impairing the quality of printed matter. As the printing speed increases, the printing plate will rotate at a higher speed, so that the dampening water performance will not cause plate trays, but will be even more quickly and uniformly on the non-image area on the printing plate. It is necessary to be able to supply dampening water. Therefore, there is a need for a dampening solution that is more excellent in dynamic surface tension lowering ability and low foaming than before, but in general, the dynamic surface of the dampening solution is increased by increasing the amount of wetting agent added. Tension decreases.

  However, the fountain solution is usually distributed and stored as a concentrated solution, and is diluted 50 to 100 times with tap water or the like when used. When the addition amount of the wetting agent is increased, the compatibility with the glycol-based compatibilizing component and water is lowered, so that there is also a problem that the components blended during storage of the concentrated liquid are likely to precipitate. For this reason, it has been difficult to obtain a fountain solution compatible with high-speed printing simply by increasing the addition amount of the wetting agent.

Heretofore, it has been proposed to use the following compounds as wetting agents.
For example, various anionic surfactants typified by alkyl sulfosuccinate have been used as a wetting agent having excellent dynamic surface tension reducing ability. However, anionic surfactants are excellent in dynamic surface tension lowering ability but have high foaming ability. Therefore, increasing the amount added to reduce dynamic surface tension makes foaming easier. There was a problem. Accordingly, various nonionic surfactants typified by alkylene oxide derivatives, which have low foaming properties compared to anionic surfactants, have been proposed and used.

  For example, it has been proposed to use a nonionic surfactant obtained by adding an alkylene oxide to a branched aliphatic alcohol as a wetting agent (Patent Document 1).

  Further, a nonionic surfactant has been proposed in which ethylene oxide and butylene oxide are added in block order in this order to an alcohol having 9 or more side chains and having 9 carbon atoms (Patent Document 2). When this surfactant is used as a humectant for fountain solution, it does not easily cause plate trays.

  Furthermore, a concentrated fountain solution composition for lithographic printing containing an acetylene glycol ethylene oxide adduct has been proposed (Patent Document 3). This acetylene glycol ethylene oxide adduct is less likely to cause plate training and is excellent in dynamic surface tension lowering ability.

JP 2004-91686 A JP2007-91624 JP2007-176085

  However, the surfactant described in Patent Document 1 is prone to plate trays in addition to insufficient dynamic surface tension reducing ability and low foamability.

  The surfactant described in Patent Document 2 does not have sufficient dynamic surface tension lowering ability and low foamability.

  In the thing of patent document 3, low-foam property is not enough.

  Therefore, a dampening solution for a lithographic printing plate capable of performing further high-speed printing without impairing the printing quality has been desired.

  An object of the present invention is to provide a lithographic printing plate that is capable of withstanding high-speed printing more than ever without deteriorating the printing quality, has excellent dynamic surface tension lowering ability, has low foaming properties, and does not cause plate training. Is to provide an agent.

  As a result of intensive studies to achieve the above object, by using a compound having a structure in which an oxyethylene group or an oxypropylene group is added to a specific alcohol in a specific ratio, the dynamic surface tension reducing ability is excellent. It has been found that a fountain solution having a low foaming property and causing no plate tray is obtained, and the present invention has been achieved.

（式（３）中、ＥＯはオキシエチレン基、ｄ及びｅはそれぞれオキシエチレン基の平均付加モル数、ｄ＋ｅ＝１〜１０である。） That is, the present invention is characterized in that 8 to 500 parts by weight of the compatibilizing component represented by the formula (2) is added to 1 part by weight of the wet component represented by the formula (1). It relates to a lithographic printing plate wetting agent.

R ¹ O— (EO) _a — (PO) _b —H (1)

(In the formula (1), R ¹ is a 3,5,5-trimethyl-1-hexyl group, EO is an oxyethylene group, PO is an oxypropylene group, and a is an average addition mole number of the oxyethylene group, where a = 3. -6 and b are average addition mole number of an oxypropylene group, b = 2-4, a / b = 1.0-1.7.)

_{^{R 2 O- (AO) c -H}} (2)

(In Formula (2), R ² is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, AO is an oxyalkylene group having 2 or 3 carbon atoms, and c is an average added mole number of an oxyalkylene group having 2 or 3 carbon atoms. And c = 1 to 3.)
This composition may contain 0.3-3 weight part of compounds represented by Formula (3).

(In Formula (3), EO is an oxyethylene group, d and e are the average added moles of oxyethylene group, and d + e = 1 to 10).

  According to the present invention, it is possible to provide a fountain solution that can be printed at a higher speed without impairing the printing quality.

(Wet component represented by Formula (1))
By using the wet component represented by the formula (1), it is possible to impart low foaming properties and plate tray prevention properties and to improve the dynamic surface tension lowering ability. The present invention has a remarkable feature in using a wet component represented by the formula (1).

R ¹ is a residue obtained by removing a hydroxyl group from 3,5,5-trimethyl-1-hexanol, that is, a 3,5,5-trimethyl-1-hexyl group. When R ¹ is an alkyl group having 8 or less carbon atoms, the dynamic surface tension lowering ability and low foamability are inferior, and when it is an alkyl group having 10 or more carbon atoms, plate training is likely to occur. Moreover, among the alcohols having 9 carbon atoms, 3,5,5-trimethyl-1-hexyl group having 3 methyl branches is excellent from the viewpoint of dynamic surface tension lowering ability, low foamability, and plate tray prevention. I found that.

  EO is an oxyethylene group. a is the average number of moles of oxyethylene group added, and is 3-6. When a is smaller than 3, the solubility in the compatibilizing component represented by the formula (2) and water is lowered, so that precipitation or separation occurs during use or storage of the concentrated liquid, or plate tray is caused. Therefore, it is not preferable. From this viewpoint, a is more preferably 4 or more. Moreover, when a is larger than 6, it is not preferable because the hydrophilicity becomes too strong, resulting in poor dynamic surface tension reducing ability and low foamability. From this viewpoint, a is more preferably 5 or less.

  PO is an oxypropylene group, preferably an oxypropylene group (methyloxyethylene group) derived from propylene oxide. b is the average addition mole number of an oxypropylene group, 2-4 are preferable and 3-4 are more preferable. When b is smaller than 2, it is not preferable because of low foamability. If b is greater than 4, the solubility of the compound represented by formula (2) or water decreases, so that the components may precipitate or separate during use or storage of the concentrated solution, or plate trays may be caused. This is not preferable.

  a / b is a ratio of the average added mole number a of oxyethylene groups to the average added mole number b of oxypropylene groups, and is set to 1.0 to 1.7. When this is smaller than 1.0, the solubility with the compatibilizing component represented by the formula (2) and water is lowered, and it is likely to precipitate during use or storage of the concentrated liquid. From this viewpoint, a / b is more preferably 1.1 or more. Moreover, when a / b is larger than 1.7, it becomes inferior to dynamic surface tension lowering ability and low-foaming property because hydrophilicity becomes too strong. From this viewpoint, a / b is more preferably 1.6 or less.

(Compatibilizing component represented by formula (2))
The compatibilizing component represented by the formula (2) is for preventing separation of the wet component represented by the formula (1) and obtaining a transparent concentrated solution and a fountain solution. In addition, plate tray prevention is imparted, and the dynamic surface tension lowering ability can be improved.

R ² is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Specific examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, and tert-butyl group.

  AO is an oxyalkylene group having 2 or 3 carbon atoms, specifically an oxyethylene group or an oxypropylene group. The oxypropylene group is derived from propylene oxide, preferably an oxyethylene group.

  c is the average number of added moles of an oxyalkylene group having 2 or 3 carbon atoms, and when AO is 2 or more, the total number of added moles. The range of c is preferably 1 to 3, more preferably 1 to 2, and still more preferably 1. When c is larger than 3, foaming tends to occur or the viscosity becomes too high.

Preferred specific examples of the compatibilizing component represented by the formula (2) include the following.
Ethylene glycol and its ether (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-sec-butyl ether, ethylene glycol monoisobutyl ether Ethylene glycol mono-tert-butyl ether);
Diethylene glycol and its ether (diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monopropyl ether, diethylene glycol monoisopropyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-sec-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol mono-tert-butyl ether) ;
Triethylene glycol and its ether (triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monopropyl ether, triethylene glycol monoisopropyl ether, triethylene glycol mono-n-butyl ether, triethylene glycol mono-sec- Butyl ether, triethylene glycol monoisobutyl ether, triethylene glycol mono-tert-butyl ether);
Propylene glycol and its ether (propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monoisopropyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-sec-butyl ether, propylene glycol monoisobutyl ether , Propylene glycol mono-tert-butyl ether);
Dipropylene glycol and its ether (dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoisopropyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol mono-sec- Butyl ether, dipropylene glycol monoisobutyl ether, dipropylene glycol mono-tert-butyl ether);
Tripropylene glycol and its ether (tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether, tripropylene glycol monopropyl ether, tripropylene glycol monoisopropyl ether, tripropylene glycol mono-n-butyl ether, tripropylene glycol mono-sec- Butyl ether, tripropylene glycol monoisobutyl ether, tripropylene glycol mono-tert-butyl ether).

  Among these, ethers of ethylene glycol (especially ethylene glycol mono-n-butyl ether, ethylene glycol mono-sec-butyl ether, ethylene glycol monoisobutyl ether, ethylene glycol mono-tert-butyl ether), propylene glycol ethers (particularly propylene glycol monomethyl) Ether) and ether of dipropylene glycol (particularly dipropylene glycol monomethyl ether) are more preferred, and ethylene glycol mono-tert-butyl ether is most preferred. These may be used alone or in combination of two or more.

(Compound represented by Formula (3))
The wetting agent of the present invention preferably further uses a compound represented by the formula (3) in combination. By using the compound represented by the formula (3) in combination, it is possible to further improve the dynamic surface tension reducing ability while maintaining the low foaming property and the plate tray prevention property.

  d and e are the average addition mole numbers of an oxyethylene group, respectively, and d + e = 1-10 is preferable. When d + e is smaller than 1, the hydrophilicity is lowered, so that the solubility in the compound represented by the formula (2) and water is lowered, and it is easy to precipitate or separate during use or storage of the concentrated liquid. From this viewpoint, d + e is more preferably 3 or more. On the other hand, when d + e is larger than 10, it is not preferable because the hydrophilicity becomes too strong, resulting in poor dynamic surface tension reducing ability and low foamability. From this viewpoint, d + e is more preferably 4 or less.

  In addition, the compound represented by Formula (3) is marketed as the Surfynol series by Air Products and Chemicals, Olfin series by Nissin Chemical Industry Co., Ltd., and the acetylenol series by Kawaken Fine Chemical Co., Ltd. .

(Wetting agent for lithographic printing plates)
The wetting agent of the present invention includes a wetting component represented by formula (1), a compatibilizing component represented by formula (2), and a compound represented by formula (3) as necessary, The suitable compounding example of a component is as follows.

  The compound represented by the formula (2) is a compound represented by the formula (1) from the viewpoints of the compatibility with the wet component represented by the formula (1) and water, the ability to reduce the dynamic surface tension, the foaming property, the plate tray prevention, and the viscosity. The amount is preferably 8 to 500 parts by weight, more preferably 8 to 40 parts by weight, still more preferably 9 to 25 parts by weight, and most preferably 9 to 15 parts by weight with respect to 1 part by weight of the wet component represented by 1).

  When the compound represented by the formula (3) is used in combination, the blending amount thereof is the compatibility with the compatibilizing component represented by the formula (2) and water, the ability to reduce the dynamic surface tension, the foaming property, the plate tray. From the viewpoint of prevention and viscosity, 0.3 to 3 parts by weight is preferable, 0.4 to 2 parts by weight is more preferable, and 0.4 to 1 part by weight with respect to 1 part by weight of the compound represented by Formula (1). 3 parts by weight is more preferable, and 0.4 to 1.0 part by weight is most preferable.

(Dampening water concentrate)
Since the fountain solution for lithographic printing plates is bulky, it is usually distributed and stored as a concentrated liquid. That is, to the wetting agent of the present invention, other additives are added as necessary, diluted with water to obtain a concentrated solution for storage and distribution. In the concentrate, it is preferable to dilute the wetting agent comprising the wetting component of formula (1), the compatibilizing component of formula (2) and the additive of formula (3) 2 to 6 times by weight.

  And a concentrate is diluted 50-100 times with water, such as a tap water, at the time of use, and expresses the function as a dampening water at this time.

  In addition, other additives can be further added to the concentrate. Such additives include cationic, anionic and nonionic surfactants, gum arabic, starch derivatives, water-soluble polymer compounds such as carboxymethyl cellulose, hydroxyethyl cellulose, organic acids, inorganic acids, and these PH adjusters such as salts of the above, bromonitroalcohol compounds, preservatives such as 1,2-benzisothiazolin-3-one compounds, chelating agents such as ethylenediaminetetraacetic acid and its salts, rust inhibitors such as benzotriazole, Examples include antifoaming agents such as silicone compounds.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Synthesis examples of the compounds according to the present invention are shown below. The structure of the synthesized compound was identified by ¹ H NMR analysis. Table 1 shows the synthesized compounds.

(Synthesis Example 1: Synthesis of Compound 1)
Into a 5 L autoclave, 433 g (3 mol) of 3,5,5-trimethyl-1-hexanol (trade name: Nonanol, manufactured by KH Neochem Co., Ltd.) and 5 g of potassium hydroxide were charged. The temperature rose. Next, 529 g (12 mol) of ethylene oxide was added dropwise by a dropping device and reacted for 1 hour. Subsequently, 523 g (9 mol) of propylene oxide was dropped with a dropping device and reacted for 2 hours. Thereafter, the reaction product is taken out from the autoclave, neutralized with hydrochloric acid to pH 6-7, and subjected to reduced pressure treatment at 100 ° C. for 1 hour to remove the contained water, and finally the salt is removed by filtration. 1410 g of Compound 1 was obtained.

(Synthesis of compounds 2 and 5)
In accordance with Synthesis Example 1, compounds 2 and 5 shown in Table 1 below were synthesized.

(Synthesis Example 2: Synthesis of Compound 3)
In Synthesis Example 1, 433 g (3 mol) of isononanol (trade name: Oxocol 900, number of branches: 1.3, manufactured by KH Neochem) was used instead of 3,5,5-trimethyl-1-hexanol. In the same manner, 1390 g of compound 3 was obtained.

(Synthesis of Compound 4)
In accordance with Synthesis Example 2 described above, Compound 4 shown in Table 1 below was synthesized.

(Synthesis Example 3: Synthesis of Compound 6)
Into a 5 L autoclave, 433 g (3 mol) of 3,5,5-trimethyl-1-hexanol (trade name: Nonanol, manufactured by KH Neochem Co., Ltd.) and 5 g of potassium hydroxide were charged. The temperature rose. Next, 529 g (12 mol) of ethylene oxide was added dropwise by a dropping device and reacted for 1 hour. Thereafter, the reaction product is taken out from the autoclave, neutralized with hydrochloric acid to pH 6-7, and subjected to reduced pressure treatment at 100 ° C. for 1 hour to remove the contained water, and finally the salt is removed by filtration. As a result, 914 g of Compound 6 was obtained.

(Synthesis Example 4: Synthesis of Compound 7)
Into a 5 L autoclave, 433 g (3 mol) of 3,5,5-trimethyl-1-hexanol (trade name: Nonanol, manufactured by KH Neochem Co., Ltd.) and 5 g of potassium hydroxide were charged. The temperature rose. Next, 529 g (12 mol) of ethylene oxide was added dropwise by a dropping device and reacted for 1 hour. Subsequently, 649 g (9 mol) of butylene oxide was added dropwise by a dropping device and reacted for 2 hours. Thereafter, the reaction product is taken out from the autoclave, neutralized with hydrochloric acid to pH 6-7, and subjected to reduced pressure treatment at 100 ° C. for 1 hour to remove the contained water, and finally the salt is removed by filtration. 1520 g of compound 7 was obtained.

(Synthesis Example 5: Synthesis of Compound 8)
Into a 5 L autoclave were charged 391 g (3 mol) of 2-ethyl-1-hexanol (trade name: octanol, manufactured by KH Neochem) and 5 g of potassium hydroxide, and the temperature was raised to 120 ° C. with stirring after nitrogen substitution. Next, 661 g (15 mol) of ethylene oxide was dropped by a dropping device and reacted for 1 hour. Subsequently, 523 g (9 mol) of propylene oxide was dropped with a dropping device and reacted for 2 hours. Thereafter, the reaction product is taken out from the autoclave, neutralized with hydrochloric acid to pH 6-7, and subjected to reduced pressure treatment at 100 ° C. for 1 hour to remove the contained water, and finally the salt is removed by filtration. 1490 g of compound 8 was obtained.

(Synthesis Example 6: Synthesis of Compound 9)
1880 g of compound 9 was obtained in the same manner as in Synthesis Example 1 except that 805 g (3 mol) of oleyl alcohol (trade name: HD Ocenol 90/95 V, manufactured by Cognis) was used instead of octanol.

(Solution preparation and dynamic surface tension measurement)
The following components were mixed in parts by weight shown in Tables 2 and 3.

Each compound shown in Table 1 Compound of formula (2): Ethylene glycol mono-tert-butyl ether (trade name: SWASOLVE ETB, manufactured by Maruzen Petrochemical Co., Ltd.)
Compound of formula (3): 2,4,7,9-tetramethyl-5-decyne-4,7-dioldi (polyoxyethylene (3.5)) ether (trade name: Surfynol 440, Air Products and Chemicals) (Made by company)

  The above-mentioned composition was diluted 4 to 4.5 times with ion-exchanged water to obtain a concentrated solution, the appearance at room temperature was observed, and the results are shown in Tables 2 and 3.

Next, each prepared concentrated solution was further diluted 50 times with ion-exchanged water to obtain a fountain solution.
For each adjusted fountain solution, dynamic surface tension was measured as an index of ease of supply to a fine non-image area during printing. Using a KRUSS bubble pressure type dynamic surface tension meter Cruz BP-2, the test solution surface tension at 25 ° C. at 10 ° C. and the test solution at 100 ms was measured. The results are shown in Tables 2 and 3.

(Test 1: Foam test)
About each adjusted dampening water, the foaming test was done in the following way as a model means to confirm foaming property at the time of printing. In consideration of the fact that a new interface is always formed during printing, the foaming test was carried out by a method of measuring the volume of foam generated after a certain period of time using a diffuser stone.

200 g of each fountain solution prepared was placed in a 1 liter tall measuring cylinder, and a blowing tube with a diffuser stone attached to the tip was set and held at 25 ° C. for 10 minutes. Then, using a flow meter, air was blown from the diffuser stone at a rate of 300 mL per minute, the scale on the top surface of the foam at each time was measured, and the difference between the foam and the control in which the compound shown in Table 1 was not added was measured. Volume. In addition, when foaming property is recognized, the volume of foam becomes larger than 0 cm < ³ >, and it shows that it is not preferable.

(Test 2: Printing plate immersion test)
About each adjusted dampening solution, the printing plate immersion test was done in the following way as a parameter | index which confirms the presence or absence of plate tray at the time of printing.

  40 g of each fountain solution adjusted to a 50 mL screw tube is put, and a test piece of thermal CTP plate (Exthermo TP-W manufactured by Kodak Co., Ltd.) cut to 15 mm × 70 mm is immersed, sealed, and kept in a constant temperature bath at 40 ° C. for 2 hours. After standing, the test piece was taken out and visually checked for the presence of peeling (plate tray). The evaluation results are shown in Tables 2 and 3 as “◯” when there is no plate training, and “×” when the plate training is confirmed.

  In Examples 1 to 3, in which the wet component of the formula (1) was used in combination with the compatibilizing component of the formula (2), a clear concentrated solution was obtained, and no plate tray was generated. It exhibits low foaming and dynamic surface tension lowering ability.

In Comparative Example 1, since the alkyl group of the wet component was not a 3,5,5-trimethyl-1-hexyl group, the low foaming property was inferior, and plate tray was confirmed.
In Comparative Example 2, since the alkyl group of the wet component is not 3,5,5-trimethyl-1-hexyl group and the average added mole number of the oxyethylene group of the wet component is large, the low foam property is inferior, confirmed.

In Comparative Example 3, the average added mole number of the oxyethylene group of the wet component was large, and the low foaming property was poor.
In Comparative Example 4, since the oxypropylene group was not added to the wet component, the low foamability was poor.

In Comparative Example 5, since an oxybutylene group was introduced instead of the oxypropylene group of the wet component, a transparent concentrate was not obtained, and in addition, plate tray was confirmed.
In Comparative Example 6, since the alkyl group of the wet component was not a 3,5,5-trimethyl-1-hexyl group, the foamability was poor.

In Comparative Example 7, since the alkyl group of the wet component was not a 3,5,5-trimethyl-1-hexyl group, a plate concentrate was confirmed in addition to the fact that a transparent concentrate was not obtained.
In Comparative Example 8, the compatibility of the formula (1) was insufficient, and plate tray was confirmed.
In Comparative Example 9, since no wet component was used, the low foamability was poor.
In Comparative Example 10, the plate tray was confirmed because there are few compatibilizing components of the formula (2).

Claims (2)

A lithographic printing plate comprising 8 to 500 parts by weight of a compatibilizing component represented by formula (2) per 1 part by weight of a wet component for printing represented by formula (1) Wetting agent.

R ¹ O— (EO) _a — (PO) _b —H (1)

(In the formula (1), R ¹ is a 3,5,5-trimethyl-1-hexyl group, EO is an oxyethylene group, PO is an oxypropylene group, a is an average addition mole number of the oxyethylene group, and a = 3 6 and b are the average added moles of oxypropylene groups, and b = 2 to 4 and a / b = 1.0 to 1.7.)

_{^{R 2 O- (AO) c -H}} (2)

(In Formula (2), R ² is a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, AO is an oxyalkylene group having 2 or 3 carbon atoms, and c is an average added mole number of an oxyalkylene group having 2 or 3 carbon atoms. And c = 1 to 3.) The lithographic printing plate wetting agent according to claim 1, comprising 0.3 to 3 parts by weight of the compound represented by formula (3).

(In Formula (3), EO is an oxyethylene group, d and e are the average added moles of oxyethylene group, and d + e = 1 to 10).