JPH0818466B2 - Wax for thermal transfer ink - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel wax for heat-sensitive transfer ink used for a heat-sensitive transfer recording medium.

[Conventional technology]

In recent years, thermal printers and thermal facsimiles have made remarkable progress due to their advantages such as easy handling and low cost.

In such a thermal printer or thermal facsimile, a ribbon- or sheet-shaped thermal transfer recording medium is generally used in which a substrate is coated with a thermal transfer ink mainly composed of wax and a colorant.

The thermal transfer recording medium is a system in which the thermal transfer ink layer is recorded by being melt-transferred onto plain paper in the form of a printed image by printing with a heating body such as a thermal head. The properties of the wax, which is the main constituent, have a very large effect on the performance of the recording system.

As the wax, conventionally, carnauba wax,
Natural waxes such as candelilla wax, montan wax, wood wax, beeswax, ceresin wax, whale wax;
Synthetic waxes such as petroleum wax, low molecular weight polyethylene, and oxidized wax are used.

[Problems to be Solved by the Invention]

However, in conventional thermal transfer inks using these waxes, the dispersibility of the pigment is not sufficient, the melt viscosity of the ink is high, and a uniform ink application surface cannot be obtained, resulting in poor printing quality. Had. The present inventors have previously found that a copolymer of α-olefin and maleic anhydride is useful as a wax for heat-sensitive transfer ink due to such a drawback (Japanese Patent Laid-Open No. 60-198292).
However, the copolymer of α-olefin and maleic anhydride has a high reactivity of the portion derived from maleic anhydride, and therefore changes in physical properties due to ring opening by moisture absorption, and foaming due to water released by dehydration ring closure during heating. In addition, since it reacts with the maleic anhydride portion, there is a problem that there are dispersible media and dispersoids that cannot be used.

[Means for solving the problem]

The present inventors have completed the present invention as a result of extensive studies to provide a wax suitable for a thermal transfer ink that does not have such a defect.

That is, the present invention comprises an α-olefin having an average number of carbon atoms of 16 to 60 and a compound represented by the general formula (I): (In the formula, R represents a hydrogen atom or an optionally substituted hydrocarbon group), and a maleimide compound represented by the following formula:
A wax for thermal transfer ink, comprising a compound having a structure of a reaction product having a weight average degree of polymerization of 1 to 100,
It is the gist.

 The present invention will be described in more detail below.

The wax for thermal transfer ink of the present invention comprises an α-olefin having an average carbon number of 16 to 60, and a general formula (I): (In the formula, R represents a hydrogen atom or an optionally substituted hydrocarbon group), and a maleimide compound represented by the following formula:
It is characterized by comprising a compound having a structure of a reaction product having a weight average degree of polymerization of 1 to 100 (hereinafter referred to as "AOMI compound").

The α-olefin has an average carbon atom number of 16 to 60,
Preferably, an olefinically unsaturated compound having an average carbon number of 22 to 46 and having a double bond at the α-position is used. These α-olefins may be a single product or a mixture of a plurality of α-olefins having a simple number of carbon atoms.

When an α-olefin having an average number of carbon atoms of 15 or less is used, the obtained product has poor wax-like properties, and when it exceeds 60, the melting point is too high. Is not suitable.

In the maleimide compound represented by the general formula (I), R represents a hydrogen atom or an optionally substituted hydrocarbon group.

Among these, R in the general formula (I) is a hydrogen atom or a carbon atom number of 1 or more, and among them, 1 to 18 aliphatic hydrocarbon groups, alicyclic hydrocarbon groups and aromatic groups which may be substituted. Those which are a group hydrocarbon group or a heterocyclic group are preferable.

Further, among them, R in the general formula (I) is an aliphatic hydrocarbon group, an alicyclic hydrocarbon group or a heterocyclic group each containing a secondary or tertiary amino group, or a primary, Those which are aromatic hydrocarbon groups containing a secondary or tertiary amino group are preferred. Specifically, for example, a hydrogen atom; methyl, ethyl, butyl, 2-ethylhexyl,
Lauryl, stearyl, hydroxyethyl, hydroxypropyl, 3- (N, N-dimethylamino) propyl, 3
Optionally substituted aliphatic hydrocarbon group such as-(N, N-diethylamino) propyl, 2- (N, N-diethylamino) ethyl, 3- (N, N-dibutylamino) propyl; cyclohexyl, methylcyclohexyl Optionally substituted alicyclic hydrocarbon group; phenyl, tolyl, naphthyl, 4-hydroxyphenyl, 4-carboxyphenyl, 2-methoxyphenyl, 4-chlorophenyl, 4-
(4-aminophenylmethyl) phenyl, 4- (4-aminophenyloxy) phenyl, 4- (4-aminophenylsulfonyl) phenyl, 4-aminophenyl, 4-
Examples of the optionally substituted aromatic hydrocarbon group such as (N, N-diethylamino) phenyl; and optionally substituted heterocyclic group such as 2-pyridyl and 2-pyrrolyl.

Among the aromatic hydrocarbon groups which may be substituted, those having a primary amino group as a substituent and those having a secondary or tertiary amino group are preferable.

The AOMI compound includes a copolymer, a one-to-one addition product of an α-olefin and a maleimide compound, and a mixture thereof.

First, the copolymer can be produced by solution polymerization or solventless (bulk) polymerization of an α-olefin and a maleimide compound in the presence of a radical catalyst according to a conventional method.

It can also be produced by polymerizing α-olefin and maleic anhydride in the presence of a radical catalyst, adding a primary amine compound thereto, dehydrating and imidizing.

As the radical catalyst, an ordinary radical generator may be used, and a peroxide such as di-t-butyl peroxide,
Usually, t-butyl hydroperoxide or the like is added in the range of 0.001 to 0.1 mol with respect to 1 mol of the α-olefin at the time of charging.

In the solution polymerization method by radical polymerization of an α-olefin and a maleimide compound, xylene, toluene, benzene or the like is suitable as a solvent, and the polymerization conditions are 60 to 140 ° C. and 3 to 8 hours. After the completion of the polymerization reaction, the target copolymer can be easily obtained by separating the solvent, the unreacted α-olefin and the maleimide compound from the reaction mixture by a distillation method.

On the other hand, in order to improve the productivity, a solventless copolymerization method is advantageous, but for this purpose, it is necessary to appropriately control the degree of polymerization by using an appropriate radical transfer agent in combination or by increasing the polymerization temperature. is there.

As the radical transfer agent, lauryl mercaptan, stearyl mercaptan, pt-butylphenol and the like are effective, and 1/100 to 1/10 mol is appropriately added to 1 mol of the maleimide compound.

Further, simply by increasing the polymerization temperature to 160 to 200 ° C, a copolymer having an appropriate degree of polymerization can be obtained without using these radical transfer agents.

On the other hand, in the method of radically polymerizing an α-olefin and maleic anhydride, and imidizing the same with a primary amine compound, the radical polymerization is the same as in the case of the radical polymerization of the α-olefin and the maleimide compound described above. To do. Appropriate reaction conditions are 60 to 140 ° C. and 3 to 8 hours. The imidization reaction uses xylene as a solvent,
Toluene, benzene, etc. are suitable, and in these solvents,
The copolymer of α-olefin and maleic anhydride is dissolved, the temperature of reflux of the solvent is maintained, then the primary amine compound is gradually added, and the water produced by the imidization reaction is azeotropically distilled with the above solvent. While removing to outside the system. After completion of the reaction, the solvent can be distilled off to produce the desired copolymer.

When a compound containing two or more primary amines in the molecule is used, if the weight average polymerization degree is high, crosslinking occurs during the imidization reaction, and the viscosity tends to increase. Therefore, in this case, the weight average degree of polymerization is usually 1 to 10, preferably 1
~ 5 AOMI compound.

The above-mentioned adduct corresponding to a polymerization degree of 1 is
160-2 with α-olefin and maleic anhydride without solvent
60 ℃, preferably 180 ~ 250 ℃, more preferably 190 ~ 230
It is obtained by heating to 0 ° C. to produce a 1: 1 thermal adduct of an α-olefin with maleic anhydride and then imidizing it with a primary amine compound. Alternatively, the α-olefin and the maleimide compound can be heated to 160 to 260 ° C, preferably 180 to 250 ° C, more preferably 190 to 230 ° C in the absence of a solvent to obtain a 1: 1 thermal adduct. .

Further, the mixture of the copolymer of α-olefin and maleimide compound and the one-to-one addition product is obtained by subjecting α-olefin and maleic anhydride to a thermal addition reaction, and then adding a peroxide to obtain an unreacted product. It can be produced by subjecting an olefin and maleic anhydride to a radical polymerization reaction as described above to a dehydration imidization by adding a primary amine compound as described above. The temperature of the heat addition reaction is usually 16
0-260 ° C, preferably 180-250 ° C, more preferably 190
~ 230 ° C. The reaction time is usually 30 minutes to 24 hours, preferably 2 to 12 hours. The charge molar ratio of α-olefin to maleic anhydride is usually 1: 0.5 to 1: 2, preferably 1: 1 to.
1: 2 is suitable. The reaction is usually carried out without solvent, until 95 mol% or less of maleic anhydride, preferably 30 to 95 mol%, particularly preferably about 60 to 90 mol%, is reacted,
Therefore, the reaction system is cooled to terminate the heat addition reaction. Then, peroxide is added and the unreacted maleic anhydride is radically reacted. The peroxide added to the final product of the heat addition reaction is
A usual radical generator may be used. For example, 0.001 to 0.1 mol of di-t-butyl peroxide, t-butyl hydroperoxide or the like is added to 1 mol of α-olefin at the time of charging.

The temperature for radical reaction of maleic anhydride remaining by adding peroxide is usually 100 to 260 ° C, preferably 130 to 2
Unreacted maleic anhydride is substantially reacted at 00 ° C for usually 30 minutes to 10 hours. The reaction product thus obtained is generally composed of a mixture of a one-to-one addition product of α-olefin and maleic anhydride and a copolymer thereof, and the ratio thereof is a ratio of a thermal addition reaction rate and a radical reaction rate. Almost corresponds to the ratio. Then, as described above, by adding a primary amine compound and subjecting to dehydration imidization, a mixture of a copolymer of α-olefin and a maleimide compound and a 1: 1 adduct can be obtained.

The structural formula of the copolymer of the α-olefin and the maleimide compound described above is represented by the following formula (A) when the copolymerization reaction of the α-olefin and the maleimide compound is taken as an example (wherein R ₁ is It is an alkyl group having an average number of carbon atoms of 13 to 57, and m ≧ 1.).

In addition, the structural formula of the above-mentioned one-to-one addition product of α-olefin and maleimide compound, that is, the one corresponding to the weight average polymerization degree of 1, is the copolymerization reaction of α-olefin and maleimide compound. For example, the following equation (B)
(Wherein R ₁ is the same as above).

In addition, when R has a structure of R'-NH ₂ containing a primary amino group (R 'represents an optionally substituted hydrocarbon group), Or a copolymer having a crosslinked structure In some cases, a compound having a structure of an adduct having a crosslinked structure is formed.

In the AOMI compound, the constituent molar ratio of the α-olefin and the maleimide compound is usually in the range of 1: 1 to 1: 2,
Any of these can be used.

Further, in the present invention, among the above AOMI compounds, those having a weight average degree of polymerization of 1 to 100 are required. If the weight average polymerization degree is too high, the melt viscosity becomes too high and good printing characteristics cannot be obtained. Therefore, the weight average degree of polymerization is in the range of 1 to 100, preferably 4 to 40.

The weight average degree of polymerization is measured by the following method.

Method for measuring weight average degree of polymerization (Pw) The degree of polymerization is calculated by gel permeation chromatography (GPC) using a calibration curve of standard polystyrene, and the weight average degree of polymerization is calculated by the following formula.

However The wax for heat-sensitive transfer ink of the present invention obtained as described above is used as a heat-sensitive transfer ink by blending a colorant and an appropriate softening agent in the same manner as a usual wax.

The wax for heat-sensitive transfer ink of the present invention has excellent properties as a wax for heat-sensitive transfer ink, which was previously found by the present inventors and is a copolymer of α-olefin and maleic anhydride (JP-A-60-198292). No.), that is, it can be chemically stabilized by imidizing the portion derived from maleic anhydride without impairing the pigment dispersibility, low heat of fusion, low heat shrinkage, etc. The thermal transfer ink has no change in physical properties due to the above, and can be used for a dispersion medium and a dispersoid having active hydrogen, and further contains an imide portion to further enhance the pigment dispersibility. The properties as a wax for use are remarkably improved.

Needless to say, when preparing a heat-sensitive transfer ink using the wax of the present invention, waxes that have been conventionally used can be appropriately used in combination as long as the characteristics of the wax of the present invention are not impaired. In that case, the wax of the present invention is usually 5% by weight or more, preferably 10 to 70% by weight, and more preferably 20 to
It is preferably 50% by weight.

〔Example〕

Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist.

The weight average degree of polymerization, melting point, viscosity and penetration were measured by the following methods.

(1) Weight average degree of polymerization (Pw) The degree of polymerization was measured by gel permeation chromatography (GPC) using a standard polystyrene inspection line, and the weight average degree of polymerization was calculated by the following formula.

However, Pw: weight-average degree of polymerization Ni: number of molecules of a molecule of Pi: degree of polymerization of a molecule of Pi: i The measurement of the degree of polymerization distribution, Toyo Soda Co., Ltd., using a high-performance liquid chromatograph HLC-802UR, It carried out on condition of the following.

Solvent: THF Column: TSKgelG2000H ₆ × 2, TSKgelG3000H ₆ , TSKgelG400
0H ₆ (manufactured by Toyo Soda Kogyo Co., Ltd.) Temperature: 40 ° C. Flow rate: 1.2 ml / min (2) Melting point Measured using a trace melting point measuring device (Mitamura Riken Kogyo Co., Ltd.).

(3) Viscosity 100 using a B-type viscometer (manufactured by Tokyo Keiki Seisakusho Co., Ltd.)
It was measured at ° C.

(4) Penetration Measured at 25 ° C according to ASTM-D-1321-6 / T.

Production Example 1 (Production of α-Olefin-Maleic Anhydride Copolymer) α-Olefin having 30 to 60 carbon atoms (Mitsubishi Kasei Co., Ltd.)
1200g of linear α-olefin obtained by the polymerization reaction of ethylene) was charged in a flask and, after sufficiently replacing with nitrogen gas, heated to 185 ° C and stirred to give anhydrous maleic anhydride. 180g acid and di-t
4.55 g of -butyl peroxide were simultaneously fed and polymerized for 2 hours. After further aging for 1 hour, cool and α-
Olefin-maleic anhydride copolymer (copolymer A) 13
I got 70g. The physical properties are shown in Table 2.

Production Example 2 (Production of α-olefin-maleic anhydride adduct) α-olefin having 30 to 60 carbon atoms (“Dialene 30”) 1
After charging 200 g to a flask and sufficiently replacing it with nitrogen gas, 180 g of maleic anhydride was charged, and a heat addition reaction was carried out at a temperature of 200 ° C. for 6 hours and further at a temperature of 220 ° C. for 2 hours. Subsequently, the pressure was reduced to distill off the residual maleic anhydride to obtain 1360 g of an α-olefin-maleic anhydride adduct, that is, an alkenylsuccinic anhydride (adduct A). Show its physical properties
It is shown in FIG. Production Example 3 (Production of α-Olefin-Maleic Anhydride Copolymer) α-Olefin having 20 to 28 carbon atoms (Mitsubishi Kasei Co., Ltd.)
Made; registered trademark: Dialene 208) 1000 g was charged into a flask, and after being sufficiently replaced with nitrogen gas, heated to 185 ° C., and while being stirred, maleic anhydride 350 g and di-t-butyl peroxide 12 g were taken for 2 hours. And simultaneously supplied and polymerized. After further aging for 1 hour, the mixture was cooled to obtain 1350 g of an α-olefin-maleic anhydride copolymer (copolymer B). The physical properties are shown in Table 2.

Production Example 4 (Production of a mixture of an adduct of α-olefin and maleic anhydride and a copolymer) 650 g (1 mol) of a mixture of α-olefin having 30 to 60 carbon atoms (“dialene 30”) and maleic anhydride Acid 98g (1
(Mol) was charged in a flask and sufficiently replaced with nitrogen gas, and then reacted at a temperature of 200 ° C. for 4 hours. At this time, the reaction rate of maleic anhydride was 70%. Then, this was gradually cooled and at a temperature of 170 ° C., 1.46 g (0.01 g of di-t-butyl peroxide) was added.
Mol) was added, and then the mixture was kept at 170 ° C. for 1 hour for copolymerization to obtain a mixture containing alkenyl succinic anhydride (mixture A). The reaction rate of maleic anhydride at this time is 99.
% Or more. The physical properties are shown in Table 2.

Production Example 5 (Production of Copolymer of α-Olefin and Maleimide Compound) α-Olefin having 30 to 60 carbon atoms (“Dialene 30”) 1
After charging 200 g to a flask and thoroughly replacing it with nitrogen gas, the mixture was heated to 185 ° C., and 320 g of N-phenylmaleimide and 4.55 g of di-t-butylperoxide were added thereto while stirring.
Were simultaneously fed and polymerized for 2 hours. After further aging for 1 hour, the mixture was cooled to obtain 1520 g of an α-olefin-N-phenylmaleimide copolymer (imidized product A). The physical properties are shown in Table 2.

Production Example 6 (Production of Reaction Product of α-Olefin and Maleimide Compound) Copolymer A1200g and xylene 400ml were charged into a flask, and after nitrogen substitution, it was heated and dissolved to bring xylene to a reflux state.

Next, 160 g of N, N-dimethyl-1,3-propanediamine was added to 2
The reaction mixture was added dropwise over a period of time, and the produced water was azeotropically distilled with xylene to separate it out of the system to complete the reaction. Subsequently, xylene was distilled off under reduced pressure to give an imidization reaction product (imidized product B).
I got 1295g. The physical properties are shown in Table 2.

Production Examples 7 to 14 (Production of Reaction Product of α-Olefin and Maleimide-Based Compound) The copolymer A, the copolymer B, the adduct A or the mixture A obtained in Production Examples 1 to 4 shown in Table 1. And a primary amine compound were reacted in the same manner as in Production Example 6 to obtain imidization reaction products (imidized products C to J) in Table 1. The physical properties thereof are shown in Table 2.

Test Example 1 (Stability) Copolymer A, mixture A, imidized product C and imidized product H were crushed, respectively, and sieved to obtain particles having a particle size of 1 to 10 mm. The temperature was 20 ° C and the relative humidity was 60%. Put in constant temperature and humidity,
The change with time of the melt viscosity was traced. The results are shown in Table 3.

The copolymer A and the mixture A containing the acid anhydride have a relatively large change in viscosity with time, whereas the imidized products C and H hardly change.

Further, when the test samples after 80 days were heated to 160 ° C., the copolymer A and the mixture A were foamed by dehydration, but the imidized products C and H were not changed.

From these results, the wax of the present invention containing an imide moiety has stable properties, and as a wax for thermal transfer ink,
It turns out that it is more preferable.

Test Examples 2 to 7 and Comparative Test Examples 2 to 6 (Carbon Black Dispersibility) Each dispersant shown in Table 5 was blended with the composition shown in Table 4 to obtain 95-
The mixture was mixed for 4 hours using a sand mill at a temperature of 100 ° C., and the viscosity of this was measured at 100 ° C. to examine the dispersibility of carbon black. The results are shown in Table 5. It can be seen that when the wax of the present invention is used, the viscosity is low and the dispersing effect is excellent.

Test Examples 8 to 10 and Comparative Test Examples 7 to 9 (Dispersion of Organic Pigment) Each dispersant and organic pigment shown in Table 7 were blended with the composition shown in Table 6, respectively, and the mixture was sand milled at a temperature of 95 to 100 ° C. Was mixed for 4 hours and the dispersibility of the organic pigment was examined. Dispersibility was evaluated by viscosity and stability. The lower the viscosity, the better the dispersibility.

It can be seen that the wax of the present invention has an excellent dispersing effect even for organic pigments, and is particularly excellent for yellow pigments.

Use Example-1 The thermal transfer inks prepared by using the imidized products A to J and having the compositions shown in Table 8 were hot-melt coated with a wire bar on a polyethylene terephthalate film having a thickness of 6 μm to form an ink layer thickness. A thermal transfer recording sheet of 3 to 4 μm was obtained.

The coatability was good in all cases, and a uniform sheet having no coating unevenness was obtained. When these coated sheets were mounted on a thermal printer (a prototype equipped with a thin-film line thermal head with a heating element density of 8 dots / mm) and thermal recording was performed on high-quality paper, clear and good printed images were obtained. Was obtained.

EFFECT OF THE INVENTION The wax of the present invention has extremely useful properties as a wax for heat-sensitive transfer ink, that is, low melting heat, high dispersibility and high stability, and its industrial value is extremely high.

Continuation of the front page (56) Reference JP 61-169287 (JP, A) JP 61-169286 (JP, A) JP 62-104794 (JP, A) JP 60-198292 (JP , A)

Claims (4)

[Claims] 1. An α-olefin having an average carbon number of 16 to 60 and a compound represented by the general formula (I): (In the formula, R represents a hydrogen atom or an optionally substituted hydrocarbon group), and a maleimide compound represented by the following formula:
A wax for thermal transfer ink, comprising a compound having a structure of a reaction product having a weight average polymerization degree of 1 to 100. 2. The wax for heat-sensitive transfer ink according to claim 1, wherein R in the general formula (I) is an optionally substituted aliphatic hydrocarbon group, alicyclic hydrocarbon group or aromatic. Characterized by being a group hydrocarbon group or a heterocyclic group. 3. The wax for thermal transfer ink according to claim 1 or 2, wherein R in the general formula (I) each contains a secondary or tertiary amino group. , An alicyclic hydrocarbon group or a heterocyclic group. 4. The wax for thermal transfer ink according to claim 1 or 2, wherein R in the general formula (I) is an aromatic hydrocarbon group containing a primary, secondary or tertiary amino group. What is characterized by.