OIL-BASED INKJET INK

Abstract

Provided is an oil-based inkjet ink containing a pigment and a fatty acid ester-based solvent represented by general formula (1) shown below and having at least 18 but not more than 29 carbon atoms per molecule. In general formula (1), R.sup.1 represents an alkyl group of 5 or more carbon atoms, R.sup.2 represents an alkyl group of 6 or more carbon atoms, and at least one of R.sup.1 and R.sup.2 is a branched alkyl group of 9 or more carbon atoms having a side chain of 4 or more carbon atoms.

##STR00001##

Claims

1. An oil-based inkjet ink comprising a pigment and a fatty acid ester-based solvent represented by general formula (1) shown below and having at least 18 but not more than 29 carbon atoms per molecule: ##STR00004## wherein in general formula (1), R.sup.1 represents an alkyl group of 5 or more carbon atoms, R.sup.2 represents an alkyl group of 6 or more carbon atoms, and at least one of R.sup.1 and R.sup.2 is a branched alkyl group of 9 or more carbon atoms having a side chain of 4 or more carbon atoms.

2. The oil-based inkjet ink according to claim 1, wherein at least one of R.sup.1 and R.sup.2 is a branched alkyl group of 13 or more carbon atoms having a side chain of 6 or more carbon atoms.

3. The oil-based inkjet ink according to claim 1, wherein R.sup.1 is an alkyl group of 8 or more carbon atoms and R.sup.2 is an alkyl group of 9 or more carbon atoms.

4. The oil-based inkjet ink according to claim 1, wherein the fatty acid ester-based solvent has 24 or more carbon atoms per molecule.

5. The oil-based inkjet ink according to claim 1, wherein the fatty acid ester-based solvent has 26 or fewer carbon atoms per molecule.

6. The oil-based inkjet ink according to claim 1, wherein R.sup.1 and R.sup.2 are both branched alkyl groups having a side chain of 4 or more carbon atoms.

7. The oil-based inkjet ink according to claim 2, wherein R.sup.1 is an alkyl group of 8 or more carbon atoms and R.sup.2 is an alkyl group of 9 or more carbon atoms.

8. The oil-based inkjet ink according to claim 2, wherein the fatty acid ester-based solvent has 24 or more carbon atoms per molecule.

9. The oil-based inkjet ink according to claim 3, wherein the fatty acid ester-based solvent has 24 or more carbon atoms per molecule.

10. The oil-based inkjet ink according to claim 2, wherein the fatty acid ester-based solvent has 26 or fewer carbon atoms per molecule.

11. The oil-based inkjet ink according to claim 3, wherein the fatty acid ester-based solvent has 26 or fewer carbon atoms per molecule.

12. The oil-based inkjet ink according to claim 4, wherein the fatty acid ester-based solvent has 26 or fewer carbon atoms per molecule.

13. The oil-based inkjet ink according to claim 2, wherein R.sup.1 and R.sup.2 are both branched alkyl groups having a side chain of 4 or more carbon atoms.

14. The oil-based inkjet ink according to claim 3, wherein R.sup.1 and R.sup.2 are both branched alkyl groups having a side chain of 4 or more carbon atoms.

15. The oil-based inkjet ink according to claim 4, wherein R.sup.1 and R.sup.2 are both branched alkyl groups having a side chain of 4 or more carbon atoms.

16. The oil-based inkjet ink according to claim 5, wherein R.sup.1 and R.sup.2 are both branched alkyl groups having a side chain of 4 or more carbon atoms.

17. The oil-based inkjet ink according to claim 3, wherein the fatty acid ester-based solvent has 24 or more carbon atoms per molecule, and the fatty acid ester-based solvent has 26 or fewer carbon atoms per molecule.

18. The oil-based inkjet ink according to claim 3, wherein the fatty acid ester-based solvent has 24 or more carbon atoms per molecule, and R.sup.1 and R.sup.2 are both branched alkyl groups having a side chain of 4 or more carbon atoms.

19. The oil-based inkjet ink according to claim 3, wherein the fatty acid ester-based solvent has 26 or fewer carbon atoms per molecule, and R.sup.1 and R.sup.2 are both branched alkyl groups having a side chain of 4 or more carbon atoms.

20. The oil-based inkjet ink according to claim 4, wherein the fatty acid ester-based solvent has 26 or fewer carbon atoms per molecule, and R.sup.1 and R.sup.2 are both branched alkyl groups having a side chain of 4 or more carbon atoms.

Description

EXAMPLES

[0109] The present invention is described below in further detail using a series of examples. However, the present invention is in no way limited by the following examples.

[Synthesis of Fatty Acid Esters]

[0110] Formulations of fatty acid esters are shown in Table 1.

[0111] A fatty acid and an alcohol were placed in a four-neck flask in accordance with the formulation shown in Table 1 and mixed together to obtain a uniform solution. The four-neck flask was fitted with a Dean-Stark apparatus to enable removal of the water that was generated as the raw materials reacted. An appropriate amount of sulfuric acid was added as a catalyst to the four-neck flask containing the uniform solution, and the entire system was then heated. The heating temperature was set within a range from 80 C. to 230 C. in accordance with the types of fatty acid and alcohol. The heated reaction time was set within a range from 1 to 48 hours. Following reaction, in order to remove any unreacted raw materials and impurities, the obtained solution was distilled under reduced pressure to obtain the target fatty acid ester. The fatty acid and the alcohol were mixed in a molar ratio of 1:1. The fatty acids and the alcohols can be obtained from Tokyo Chemical Industry Co., Ltd., FUJIFILM Wako Pure Chemical Corporation, and Sasol Group.

TABLE-US-00001 TABLE 1 No. Fatty acid ester Fatty acid Alcohol 1 2-butyloctyl heptanoate heptanoic acid 2-butyloctanol 2 2-butyloctyl 2-ethylhexanoate 2-ethylhexanoic acid 2-butyloctanol 3 octyl 2-butyloctanoate 2-butyloctanoic acid octanol 4 hexyl 2-hexyldecanoate 2-hexyldecanoic acid hexanol 5 2-hexyldecyl 2-ethylhexanoate 2-ethylhexanoic acid 2-hexyldecanol 6 octyl 2-hexyldecanoate 2-hexyldecanoic acid octanol 7 dodecyl 2-butyloctanoate 2-butyloctanoic acid dodecanol 8 2-butyloctyl 2-butyloctanoate 2-butyloctanoic acid 2-butyloctanol 9 nonyl 2-hexyldecanoate 2-hexyldecanoic acid nonanol 10 2-hexyldecyl nonanoate nonanoic acid 2-hexyldecanol 11 tetradecyl 2-butyloctanoate 2-butyloctanoic acid tetradecanol 12 2-butyloctyl tetradecanoate tetradecanoic acid 2-butyloctanol 13 2-hexyldecyl dodecanoate dodecanoic acid 2-hexyldecanol 14 2-octyldodecyl octanoate octanoic acid 2-octyldodecanol 15 hexyl undecanoate undecanoic acid hexanol 16 11-methyldodecyl 3,5,5-trimethylhexanoate 3,5,5-trimethylhexanoic acid 11-methyldodecanol 17 butyl 2-hexyldecanoate 2-hexyldecanoic acid butanol 18 2-ethvlhexyl hexadecanoate hexadecanoic acid 2-ethylhexanol 19 2-octyldodecyl pivalate pivalic acid 2-octyldodecanol 20 octadecyl 2-butyloctanoate 2-butyloctanoic acid octadecanol 21 2-octyldodecyl neodecanoate neodecanoic acid 2-octyldodecanol

[Preparation of Inks]

[0112] Ink formulations are shown in Table 2, Table 3 and Table 4. The number of carbon atoms per molecule of the fatty acid ester, and the number of carbon atoms, the number of side chains and the number of carbon atoms in each side chain for each of R.sup.1 and R.sup.2 are also shown in each table.

[0113] The pigments, pigment dispersants, and solvents were mixed together in accordance with the amounts shown in each table, and the pigment was dispersed thoroughly using a beads mill (Dyno-Mill KDL-A, manufactured by Shinmaru Enterprises Corporation) under conditions including a residence time of 15 minutes. Subsequently, coarse particles were removed with a membrane filter to obtain the ink.

[0114] The components used were as follows.

(Pigments)

[0115] Carbon black: MA77, manufactured by Mitsubishi Chemical Corporation.

[0116] Copper phthalocyanine blue: FASTOGEN Blue LA5380, manufactured by DIC Corporation.

(Pigment Dispersants)

[0117] Solsperse 13940: manufactured by The Lubrizol Corporation, non-volatile fraction: 40% by mass.

[0118] Solsperse 18000: manufactured by The Lubrizol Corporation, non-volatile fraction: 100% by mass.

(Hydrocarbon Solvent)

[0119] Hydrocarbon solvent Exxsol D110: manufactured by Exxon Mobil Corporation

[Evaluations]

[0120] The inks from each of the examples and comparative examples described above were evaluated using the methods described below. The evaluation results are shown in Table 2, Table 3 and Table 4.

(Vinyl Chloride Tube Swelling Characteristics)

[0121] A vinyl chloride tube having an inner diameter of 2.38 mm and an external diameter of 4.76 mm was cut to lengths of 5 cm to prepare test pieces. One of these test piece was immersed in each ink, and stored at room temperature for one week. Using the values for the mass a of the test piece prior to storage and the mass b of the test piece following storage, the change in mass [(ba)/a100] was determined.

[0122] AA: less than +3.0%

[0123] A: at least +3.0%, but less than +5.0%

[0124] B: at least +5.0% but less than +10.0%

[0125] C: +10.0% or greater

(Roller Transfer Contamination)

[0126] A nitrile rubber (NBR) transport roller was fitted in the transport path of an inkjet printer ORPHIS EX9050 (manufactured by RISO KAGAKU CORPORATION) in a position that faced and made contact with the printed surface of printed items at a location downstream from the inkjet head in the printed item transport direction. Each of the inks was loaded into the inkjet printer, and a solid image was printed using a plain paper RISO Paper Thin Type (manufactured by RISO KAGAKU CORPORATION) as the recording medium. One hundred copies of the image were printed continuously, and the level of roller transfer contamination on the 100th printed item was evaluated visually against the following criteria.

[0127] A: no contamination is noticeable on the printed item

[0128] B: the printed item seems contaminated

[0129] C: the printed item is clearly contaminated

(Ink Odor)

[0130] The ink odor was evaluated using the following criteria. The odor evaluation was performed by having 10 panelists smell the ink directly and perform a sensory evaluation against the following criteria. The evaluation result was recorded as the average of the evaluation results from the 10 panelists.

[0131] A: odor is of a level that is almost undetectable

[0132] B: odor is of a level that is slightly noticeable

[0133] C: odor is of a noticeable level

[0134] Although a detailed description is not provided here, printing using the inks of each of the examples was able to produce printed items of satisfactory image density. Further, the viscosity of the ink from each example was also appropriate.

TABLE-US-00002 TABLE 2 Ink formulations and evaluation results R.sup.1 R.sup.2 Number of Number Number of Number Number of carbon of Number carbon of Number carbon atoms per carbon of side atoms in carbon of side atoms in Example Example Units: % by mass molecule atoms chains side chain atoms chains side chain 1 2 Pigments Carbon black 5.0 5.0 Copper phthalocyanine blue Pigment Solsperse 13940 5.0 5.0 dispersants (Active (2.0) (2.0) component: 40%) Solsperse 18000 Fatty acid (1) 2-butyloctyl 19 6 0 0 12 1 4 80.0 esters heptanoate (2) 2-butyloctyl 20 7 1 2 12 1 4 80.0 2-ethylhexanoate (3) octyl 20 11 1 4 8 0 0 2-butyloctanoate (4) hexyl 22 15 1 6 6 0 0 2-hexyldecanoate (5) 2-hexyldecyl 24 7 1 2 16 1 6 2-ethylhexanoate (6) octyl 24 15 1 6 8 0 0 2-hexyldecanoate (7) dodecyl 24 11 1 4 12 0 0 2-butyloctanoate (8) 2-butyloctyl 24 11 1 4 12 1 4 2-butyloctanoate Hydrocarbon 10.0 10.0 solvent Exxsol D110 Total (% by mass) 100.0 100.0 Vinyl chloride tube B B swelling characteristics Roller transfer contamination A A Ink odor B B Example Example Example Example Example Example 3 4 5 6 7 8 Pigments Carbon black 5.0 5.0 5.0 5.0 5.0 5.0 Copper phthalocyanine blue Pigment Solsperse 13940 5.0 5.0 5.0 5.0 5.0 5.0 dispersants (Active (2.0) (2.0) (2.0) (2.0) (2.0) (2.0) component: 40%) Solsperse 18000 Fatty acid (1) 2-butyloctyl esters heptanoate (2) 2-butyloctyl 2-ethylhexanoate (3) octyl 80.0 2-butyloctanoate (4) hexyl 80.0 2-hexyldecanoate (5) 2-hexyldecyl 80.0 2-ethylhexanoate (6) octyl 80.0 2-hexyldecanoate (7) dodecyl 80.0 2-butyloctanoate (8) 2-butyloctyl 80.0 2-butyloctanoate Hydrocarbon 10.0 10.0 10.0 10.0 10.0 10.0 solvent Exxsol D110 Total (% by mass) 100.0 100.0 100.0 100.0 100.0 100.0 Vinyl chloride tube B A A A B B swelling characteristics Roller transfer contamination A A A A A A Ink odor B B A A A A

TABLE-US-00003 TABLE 3 Ink formulations and evaluation results R.sup.1 R.sup.2 Number Number Number of of Number of carbon Number Number carbon of Number carbon atoms per of carbon of side atoms in carbon of side atoms in Example Example Units: % by mass molecule atoms chains side chain atoms chains side chain 9 10 Pigments Carbon black 5.0 5.0 Copper phthalocyanine blue Pigment Solsperse 13940 5.0 5.0 dispersants (Active (2.0) (2.0) component: 40%) Solsperse 18000 Fatty acid (9) nonyl 25 15 1 6 9 0 0 80.0 esters 2-hexyldecanoate (10) 2-hexyldecyl 25 8 0 0 16 1 6 80.0 nonanoate (11) tetradecyl 26 11 1 4 14 0 0 2-butyloctanoate (12) 2-butyloctyl 26 13 0 0 12 1 4 tetradecanoate (13) 2-hexyldecyl 28 11 0 0 16 1 6 dodecanoate (14) 2-octyldodecyl 28 7 0 0 20 1 8 octanoate Hydrocarbon solvent 10.0 10.0 Exxsol D110 Total (% by mass) 100.0 100.0 Vinyl chloride tube swelling AA AA characteristics Roller transfer contamination A A Ink odor A A Example Example Example Example Example Example Example Units: % by mass 11 12 13 14 15 16 17 Pigments Carbon black 5.0 5.0 5.0 5.0 5.0 5.0 Copper 4.0 phthalocyanine blue Pigment Solsperse 13940 5.0 5.0 5.0 5.0 5.0 5.0 dispersants (Active (2.0) (2.0) (2.0) (2.0) (2.0) (2.0) component: 40%) Solsperse 18000 3.5 Fatty acid (9) nonyl 82.5 40.0 30.0 esters 2-hexyldecanoate (10) 2-hexyldecyl 40.0 nonanoate (11) tetradecyl 80.0 2-butyloctanoate (12) 2-butyloctyl 80.0 tetradecanoate (13) 2-hexyldecyl 80.0 dodecanoate (14) 2-octyldodecyl 80.0 octanoate Hydrocarbon solvent 10.0 10.0 10.0 10.0 10.0 10.0 60.0 Exxsol D110 Total (% by mass) 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Vinyl chloride tube swelling B B AA AA AA AA B characteristics Roller transfer contamination A A B B A A A Ink odor A A A A A A A

TABLE-US-00004 TABLE 4 Ink formulations and evaluation results R.sup.1 R.sup.2 Number of Number of Number of Com- carbon Number of Number carbon Number of Number carbon parative atoms per carbon of side atoms in carbon of side atoms in Example Units: % by mass molecule atoms chains side chains atoms chains side chain 1 Pigments Carbon black 5.0 Copper phthalocyanine blue Pigment Solsperse 13940 5.0 dispersants (Active (2.0) component: 40%) Solsperse 18000 Comparative (15) hexyl 17 10 0 0 6 0 0 80.0 fatty acid undecanoate esters (16) 11- methyldodecyl 3,5,5- 22 8 3 1, 1, 1 13 1 1 trimethylhexanoate (17) butyl 20 15 1 6 4 0 0 2-hexyldecanoate (18) 2-ethylhexyl 24 15 0 0 8 1 2 hexadecanoate (19) 2-octyldodecyl 25 4 3 1, 1, 1 20 1 8 pivalate (20) octadecyl 30 11 1 4 18 0 0 2-butyloctanoate (21) 2-octyldodecyl 30 9 3 1, 1, 1 20 1 8 neodecanoate Hydrocarbon solvent Exxsol D110 10.0 Total (% by mass) 100.0 Vinyl chloride tube swelling C characteristics Roller transfer contamination A Ink odor C Com- Com- Com- Com- Com- Com- Com- parative parative parative parative parative parative parative Example Example Example Example Example Example Example Units: % by mass 2 3 4 5 6 7 8 Pigments Carbon black 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Copper phthalocyanine blue Pigment Solsperse 13940 5.0 5.0 5.0 5.0 5.0 5.0 5.0 dispersants (Active (2.0) (2.0) (2.0) (2.0) (2.0) (2.0) (2.0) component: 40%) Solsperse 18000 Comparative (15) hexyl fatty acid undecanoate esters (16) 11- methyldodecyl 3,5,5- 80.0 trimethylhexanoate (17) butyl 80.0 2-hexyldecanoate (18) 2-ethylhexyl 80.0 hexadecanoate (19) 2-octyldodecyl 80.0 pivalate (20) octadecyl 80.0 2-butyloctanoate (21) 2-octyldodecyl 80.0 neodecanoate Hydrocarbon solvent Exxsol D110 10.0 10.0 10.0 10.0 10.0 10.0 90.0 Total (% by mass) 100.0 100.0 100.0 100.0 100.0 100.0 100.0 Vinyl chloride tube swelling C C C C B A C characteristics Roller transfer contamination A A A A C C A Ink odor B C A C A A A

[0135] As shown in the tables, with the inks of each of the examples, vinyl chloride tube swelling and roller transfer contamination were able to be prevented, and ink odor was also able to be prevented.

[0136] The examples revealed that by ensuring the number of carbon atoms in the side chain of R.sup.1 or the side chain of R.sup.2 was at least 4, and particularly 6 or more, vinyl chloride tube swelling was able to be better prevented.

[0137] Further, by ensuring that the number of carbon atoms in R.sup.1 was at least 5, and particularly 8 or more, and the number of carbon atoms in R.sup.2 was at least 6, and particularly 9 or more, vinyl chloride tube swelling was able to be better prevented.

[0138] Furthermore, when the number of carbon atoms per molecule of the fatty acid ester was not more than 29, and particularly 26 or fewer, roller transfer contamination was able to be better prevented.

[0139] Further, when the number of carbon atoms per molecule of the fatty acid ester was at least 18, and particularly 24 or more, vinyl chloride tube swelling was able to be better prevented, and ink odor was also able to be better prevented.

[0140] Example 15 was an example in which the type of pigment and pigment dispersant were altered, and favorable results were able to be obtained.

[0141] Example 16 was an example in which two types of fatty acid ester were used, and favorable results were able to be obtained.

[0142] Example 17 was an example in which a fatty acid ester and a hydrocarbon solvent were combined, and although the proportion of the hydrocarbon solvent was high, favorable results were able to be obtained.

[0143] The fatty acid ester of Comparative Example 1 had 17 carbon atoms per molecule and R.sup.1 and R.sup.2 were both linear alkyl groups, and vinyl chloride tube swelling occurred.

[0144] The fatty acid esters of Comparative Examples 2 and 4 were examples in which a side chain of 4 or more carbon atoms was not included in either of R.sup.1 and R.sup.2, and vinyl chloride tube swelling occurred.

[0145] In the fatty acid ester of Comparative Example 3, the number of carbon atoms in R.sup.2 was a small value of 4, and vinyl chloride tube swelling occurred.

[0146] In the fatty acid ester of Comparative Example 5, the number of carbon atoms in R.sup.1 was 4, and vinyl chloride tube swelling occurred.

[0147] The fatty acid esters of Comparative Examples 6 and 7 each had 30 carbon atoms per molecule, and roller transfer contamination occurred.

[0148] Comparative Example 8 did not use a fatty acid ester, and used only a hydrocarbon solvent, and vinyl chloride tube swelling occurred.

[0149] Based on the examples and comparative examples, it was evident that as the number of carbon atoms per molecule of the fatty acid ester was reduced, an odor tended to develop. Further, it was also evident that as the numbers of carbon atoms in R.sup.1 and R.sup.2 of the fatty acid ester were reduced, odors tended to develop.