JP3213637B2 - Desensitizing ink - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a desensitizing ink excellent in various printing properties, and more particularly to a desensitizing ink suitable for pressure-sensitive copying paper.

[0002]

2. Description of the Related Art A carbonless pressure-sensitive copying paper is basically composed of an upper paper coated with a microcapsule containing an electron-donating colorless dye and a lower paper coated with an electron-accepting developer. The colorless dye in the microcapsules of the upper sheet is released by the pressure, and the color is formed by reacting with the developer on the lower sheet to obtain a visible copy image.

[0003] The desensitizing ink has been developed for the purpose of disabling color development by applying it to the color-unnecessary portions of the above-mentioned developer-coated layer, and includes offset printing, flexo / gravure printing, letterpress printing, silk screen printing. Used in etc. For this reason, the desensitizing ink must have, in addition to the function of preventing color formation, printability in accordance with various printing methods.

[0004] The desensitizing ink generally comprises components such as a desensitizing agent, a white pigment, and a vehicle. In particular, regarding white pigments, titanium oxide is mainly used because of its whiteness, opacity, and the like.In producing a desensitizing ink, titanium oxide is used in a vehicle, a desensitizing agent, and an ink solvent by any method. Or they must be dispersed in a mixture of these.

[0005] In general, titanium oxide has a surface derived from its production method, and its surface is covered with a hydrophilic group such as a hydroxyl group. Therefore, titanium oxide has a poor affinity for such an organic medium, and it is extremely difficult to disperse it in this state. Conventionally, in order to disperse such titanium oxide in ink, the surface of titanium oxide particles is subjected to a surface treatment with an organic substance such as a surfactant. However, when the titanium oxide surface-treated by the above method is used, the surface treatment agent such as a surfactant present on the titanium oxide surface breaks the hydrophilic-hydrophobic balance of the desensitizing ink, and the actual printing is performed. In many cases, various problems such as background fouling, emulsification, generation of ink mist, and the like occur, and the influence of such a surface treatment agent itself on the physical properties of the ink has become a problem.

Further, even when titanium oxide is subjected to various surface treatments and supplied in the form of powder, it is unavoidable to generate agglomerates, so that such agglomerates are greatly crushed and dispersed in the desensitizing ink production process. It required heat and mechanical energy. Therefore, there is an urgent need for an effective and simple method of introducing titanium oxide into the ink for the production and quality improvement of the actual desensitizing ink, and the development of a titanium oxide surface treatment agent for improving printability. Is the current situation.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a desensitizing ink which is free from troubles such as background stain, emulsification, ink mist and the like in actual printing, and which has a remarkably excellent printability. .

[0008]

The above objects are achieved by the present invention described below. That is, when a resin (particles) dissolved or dispersed as an additive is added to a desensitizing ink to form an ink, the resin is made of the following polymer (S)
It has been found that the above-mentioned object is achieved by a desensitizing ink, which is a resin obtained by polymerizing at least the following monomer (A) in the presence of: Polymer (S): soluble in aliphatic hydrocarbon medium,
A polymer having a polymerizable double bond group at a terminal or a side chain of the polymer. Monomer (A): a monomer that is soluble in an aliphatic hydrocarbon medium and insoluble by polymerization.

As the polymer having a polymerizable double bond at the terminal of the polymer, a so-called macromonomer can be used. As one method of synthesizing a macromonomer, for example, a vinyl monomer is polymerized using a chain transfer agent such as thioglycolic acid or iodoacetic acid to obtain a polymer having a carboxyl group at only one end, for example, By adding a monomer having an epoxy group such as glycidyl methacrylate to a terminal carboxyl group, a polymer having a polymerizable double bond at only one terminal can be obtained. For the synthesis method of such a macromonomer and its application, for example, see “Y. Yamashita, J. A.
ppl. Polym. Sci., Appl. Polym. Symp., 36, 193 (198
1) '' and `` Complehensive Polymer Science, vol.6, Ch.
apter 9, V. Percec and C. Pugh, "Macromonomers, Ol
igomers and Telechelic Polymers ", Pergamon Press
(1989). As for the method of synthesizing a macromonomer having a polymerizable double bond only at one end, in addition to the method using the radical polymerization method as described above, there is also a method using a living anion polymerization method, a living cation polymerization method, or the like, An optimal synthesis method may be employed depending on the structure or use of the target polymer.

As a method for synthesizing a polymer having a polymerizable double bond in the side chain of the polymer, for example, the literature “KEJ Barrett”
Ed., "Dispersion Polymerization in Organic Medi
a ", Wiley (1975), p.", for example, a polymer having a carboxyl group in the side chain obtained by copolymerizing a monomer having a carboxyl group such as methacrylic acid with another monomer. Then, a polymer having a polymerizable double bond in a target side chain is synthesized by adding a monomer having an epoxy group such as glycidyl methacrylate.

The polymer (S) used in the present invention includes:
It is a polymer having a polymerizable double bond in the terminal or side chain as described above, more preferably a polymer having solubility in an aliphatic hydrocarbon medium, the polymer composition for this at least the following It is necessary to include at least a monomer represented by Chemical formula 1 or Chemical formula 2 as a component.

[0012]

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In Chemical Formula 1, R ₁ represents a hydrogen atom or a methyl group, and R ₂ represents an alkyl group having 8 to 30 carbon atoms. Further, the linking group T represents a -COO- group or a -CONH- group.

[0014]

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In the chemical formula 2, R ₃ represents an alkyl group having 8 to 30 carbon atoms.

In order to obtain a polymer (S) having a terminal double bond by using at least the monomer represented by the above formula (1) or (2), as described above, thioglycolic acid, thiomalic acid Synthesis of a polymer having a carboxyl group at a terminal using a chain transfer agent such as iodoacetic acid,
It can also be obtained by adding glycidyl methacrylate. Various monomers may be introduced as a copolymer component together with Chemical formula 1 or Chemical formula 2, but as long as the solubility of the polymer in an aliphatic hydrocarbon medium is not impaired, the chemical formula 1 or Chemical formula 2 It is preferable to secure at least 50% by weight as a composition.

In order to obtain a polymer having a polymerizable double bond in the side chain by using at least the monomer represented by the above formula (1) or (2), a monomer having a carboxy group, a hydroxyl group, an amino group or the like is copolymerized. Then, the desired polymer can be obtained by adding glycidyl (meth) acrylate to the obtained polymer. Alternatively, glycidyl (meth) acrylate is copolymerized with the monomer of formula 1 or 2, and the obtained copolymer has a monomer such as (meth) acrylic acid, maleic anhydride, or a hydroxyl group or an amino group in the molecule. It can also be easily obtained by adding a monomer or the like.

A solvent is not necessarily required for synthesizing the resin obtained in the present invention. However, the hydrophobic polymer (S) is preferably made of an aliphatic hydrocarbon in order to control heat generation due to heat of polymerization and to obtain a reproducible result. Is preferably used as a polymerization solvent. Further, since it is necessary to use a solvent having no problem even if it is contained together with the resin in the desensitizing ink, the aliphatic hydrocarbon medium used in the present invention may be a normal paraffin-based medium. Examples thereof include hydrocarbons, isoparaffinic hydrocarbons, alicyclic hydrocarbons, and halogenated aliphatic hydrocarbons. From the viewpoint of safety, volatility, and the like, it is practically preferable to use shell sol 71 (shell petroleum) which is an isoparaffinic hydrocarbon. ), Isopar H, Isopar K, Isopar L, Isopar G (Isopor is a trade name of Exxon) and Solvent (manufactured by Idemitsu Petrochemical), and the like can be used.

The molecular weight of the polymer (S) referred to in the present invention is preferably in the range of 1,000 to 500,000. If the molecular weight is less than this, the effect of stabilizing the dispersion of the white pigment particles is hardly exhibited. If it is, the viscosity of the dispersion increases, which is not preferable.

The polymer (S) obtained by the above method
The monomer to be polymerized in the presence of is not particularly limited, but particularly when a monomer (A) which is soluble in a medium and insolubilized by polymerization is used, the polymer (S) is polymerized by polymerization.
Is formed on the surface of the white pigment particles, and acts as an effective dispersion stabilizer for stabilizing the dispersion of the white pigment in the ink.

The monomer (A) referred to in the present invention is not particularly limited as long as it is soluble in the medium in the state of the monomer and becomes insoluble in the medium by polymerization. Vinyl esters of aliphatic carboxylic acids having 1 to 6 carbon atoms such as vinyl propionate and vinyl chloroacetate, vinyl benzoate, or acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid and the like. Alkyl esters or amides having 1 to 6 carbon atoms, ethylene glycol di (meth) acrylate, methylene bisacrylamide, styrene and derivatives thereof, divinylbenzene, or N-vinyl-2-pyrrolidone;
N-vinylpyridine, N-vinylimidazole, N, N
N-containing dialkylaminoethyl (meth) acrylate
Vinyl ethers having 1 to 6 carbon atoms, such as vinyl monomers,
Alternatively, examples of the monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and polyethylene glycol mono (meth) acrylate.

Further, as a monomer other than the monomer (A) to be polymerized in the presence of the polymer (S), a monomer component which is soluble in the medium in a monomer state and further gives a soluble polymer by polymerization ( B) may be used together with the monomer (A). In this case, the substituent by the monomer component (B) appears on the surface of the white pigment particles, so that the dispersion stability of the pigment particles can be further enhanced.

Examples of such a monomer (B) include:
Esters, amides or vinyl esters and vinyl ethers of (meth) acrylic acid having an alkyl group having 8 or more carbon atoms as a substituent as shown in Chemical formula 1 or Chemical formula 2 are preferable, and the ratio to the monomer (A) is preferred. Is preferably used in an amount not exceeding 100% by weight with respect to (A). At a ratio higher than this, the adsorptivity to the pigment particles in the ink is impaired, resulting in poor pigment dispersibility and improved ink performance. May not be effective.

The ratio of the polymer (S) to the total amount of the monomers (A) and (B) can be used in an amount of 0.2% by weight or more, below which the solubility or dispersibility of the resin in the ink is reduced. And the effect of stabilizing the dispersion of the white pigment particles is lost. By using the polymer (S) and polymerizing a small amount (for example, several percent based on the polymer (S)) of the monomer (A) or a mixed monomer of (A) and (B), the resulting resin can be used in the ink. Can be preferably used because they have a sufficient solubility and a small amount of the adsorption point for a white pigment is sufficiently effective.

The resin according to the present invention has a function of improving the dispersion stability of the white pigment in the ink, and also has an important function of improving the printability of the ink. , Emulsification and prevention of generation of ink mist and the like.

There are various possible mechanisms for the above-described problems in actual printing. In reality, the mechanism is a combination of complicated factors. However, the amount of water in the ink and its distribution may cause various troubles. Often become. For example, when a hydrophilic substance such as a surfactant is present in the ink at a ratio of several percent or more, a large amount of water is contained in the ink in, for example, actual offset printing, and a disadvantage that the ink is easily emulsified occurs. Conversely, if some amount of water cannot be absorbed into the ink, the occurrence of background fouling often becomes a problem, so controlling the water in the ink is an important issue.

In the present invention, titanium oxide is preferably used as a white pigment. However, irrespective of titanium oxide, since many white inorganic metal oxides are covered with hydrophilic groups, water is applied to the particle surface. Since the ink has a characteristic of being easily adsorbed, this essentially renders the ink itself hydrophilic, which is likely to cause troubles such as emulsification.

The above resin disclosed in the present invention can control the degree of hydrophilicity of the pigment surface and improve the dispersion stability of the pigment particles in the ink by effectively adsorbing on the surface of the white pigment. In addition, since the resin itself is a graft copolymer composed of two types of polymers having different degrees of hydrophobicity and hydrophilicity, since the polarity of the ink itself is controlled in the ink, the water content of the ink is controlled. It also works effectively as a control agent.

For example, the polymer (S) soluble in an aliphatic hydrocarbon solvent is hydrophobic, and as a monomer unit (A) added as a graft copolymer to the polymer (S), for example, 2-hydroxyethyl (meth) acrylate By using a monomer having a hydroxyl group such as a monomer or a monomer having a carboxyl group such as (meth) acrylic acid (salt), and a nitrogen-containing basic monomer such as N-vinylpyrrolidone, an amphiphilic property can be obtained. A graft polymer is formed, and the degree of hydrophobicity / hydrophilicity of the resin itself can be controlled by changing the ratio or composition of these two components. Alternatively, if the ink itself is already hydrophilic to some extent, it may be preferable to use a hydrophobic monomer such as styrene or vinyl acetate as the monomer (A) for the purpose of increasing the hydrophobicity of the ink.

Since an actual desensitizing ink contains a desensitizing agent, a vehicle and the like in addition to the resin, the optimum composition of the resin for controlling the amount of water in the ink and improving printability is based on the above-mentioned concept. Adjustments must be made appropriately within the range. Furthermore, since the composition of the resin exhibiting the optimum dispersing effect generally differs depending on the type of the white pigment used, the actual optimum composition is determined in such a manner as to balance such pigment dispersibility and printability.

The amount of the resin having the above function is preferably in the range of 1 to 10% by weight based on the amount of the white pigment in the ink. Addition of more than this is not preferable because it is difficult to balance physical properties such as tackiness of the ink itself.

As described above, titanium oxide is preferably used as the white pigment according to the present invention. Further, titanium oxide surface-treated with aluminum or silica, rutile type, or anatase type may be used. Can be done.
In addition, inorganic pigments such as zinc oxide, silicon dioxide, barium sulfate, barium carbonate, talc, and kaolin, or fine particles (plastic pigment) such as urea resin, melamine resin, styrene resin, and acrylic resin can be used. Various titanium oxides are most preferably used because of their concealing properties and the like. The mixing ratio of such a white pigment in the ink is preferably in the range of 15 to 35% by weight based on the ink, but is not limited to this range.

As the ink solvent, in addition to the above, for example, aromatic compounds such as benzene and xylene, high-boiling alcohols, linseed oil, tung oil, soybean oil and the like can be used as required.

The vehicle is usually composed of a solvent and / or a resin, and the above-mentioned ink solvent, alkyd resin, maleic acid resin, rosin-modified phenol resin, vinyl resin and the like are used. In addition, when a general ultraviolet-curable vehicle is used, an ultraviolet-curable desensitizing ink is produced.

As a desensitizer, a desensitizer which acts on a color developer and hinders color formation by reaction with a color former is disclosed in US Pat.
No. 7780, Japanese Patent Publication No. 44-27255, No. 45
As described in JP-A-214448 and JP-A-63-56877, quaternary ammonium salts such as dodecyltrimethylammonium chloride, amines such as dodecylamine, and 2,4,4-trimethyl-2-oxazoline. Substituted oxazoline, xylene diamine, a reaction product of a diamine or polyamine derivative having a cyclic structure in the molecule such as N-aminopropylpiperidine and an alkylene oxide, polyoxyethylene alkylamine,
Various compounds such as polyoxyethylene alkyl ether and polyoxyethylene alkyl phenyl ether can be used.

As the components in the desensitizing ink, various additives such as antioxidants, desiccants, waxes and the like may be introduced as necessary.

The object of the present invention can be achieved by the above constitution, but the performance of the desensitizing ink is further improved by pre-treating the white pigment with the resin obtained in the present invention in the step of ink formation. Can be done. That is, by adding a white pigment together with the resin to an ink solvent and / or a desensitizer and treating the pigment surface with the resin, the dispersibility of the pigment in the ink is improved, and the resin is effectively used as a pigment. The performance of the ink itself is improved by adsorbing the ink. Furthermore, when adding the white pigment,
Using a dispersing machine such as a homomixer and mixing under high-speed shearing enables quick and effective surface treatment and dispersion. In this way, a dispersion containing a white pigment is prepared in advance, and then simply mixed with a vehicle and kneaded, whereby a target desensitizing ink can be easily produced. This eliminates the need for the steps of pulverizing and dispersing the pigment.

[0038]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples as well as the effects.

Synthesis Example 1 300 g of n-dodecyl methacrylate and 5 g of thioglycolic acid were placed in a one-liter four-necked flask equipped with a stirrer, a thermometer, a nitrogen inlet tube and a reflux condenser tube by IP Solvent (manufactured by Idemitsu Petrochemical Co., Ltd.). , IP-1620) 3
Then, 3 g of AIBN was added at 70 ° C., and the mixture was heated and stirred for 12 hours. Then, hydroquinone 0.5
Grams, 15 grams of glycidyl methacrylate,
Heat stirring was further performed at 120 ° C. for 12 hours. After cooling the solution to room temperature, the whole was added to 2 liters of acetone,
The precipitated polymer was separated by decantation, and further thoroughly washed with methanol. The molecular weight of the produced polymer was measured by GPC-LALLS (light scattering method) and found to be a number average molecular weight of 6,500.

After 100 g of the polymer (S) obtained as described above was dissolved in 100 g of IP solvent, 20 g of acrylic acid was added thereto, and 0.3 g of AIBN was further added at 75 ° C. The second-stage polymerization was performed to obtain a stable resin dispersion dispersed in white.

Synthesis Example 2 Polymerization was carried out using 2-ethylhexyl methacrylate instead of n-dodecyl methacrylate in exactly the same manner as in Synthesis Example 1, and glycidyl methacrylate was added in the same manner. However, the number average molecular weight is 70
00 polymer was obtained. Subsequently, the obtained polymer 10
0 g is dissolved in 100 g of IP Solvent,
Further, 50 g of N-vinyl-2-pyrrolidone was added,
The second-stage polymerization was carried out by adding 0.5 g of AIBN at 75 ° C., to obtain a white and stably dispersed resin dispersion.

Synthesis Example 3 As in Synthesis Example 1, 300 g of stearyl methacrylate and 5 g of methacrylic acid were added to IP Solvent 35.
0 g and 2,2′-azobis (4
3 g of (cyanovaleric acid) was added and the mixture was heated and stirred for 8 hours.
Thereafter, 0.5 g of hydroquinone and 15 g of glycidyl methacrylate were added, and the mixture was heated and stirred at 120 ° C. for 12 hours. After cooling the solution to room temperature, the whole was added to 2 liters of acetone, and the precipitated precipitate was purified by filtration.
A polymer having a number average molecular weight of 150,000 was obtained.

100 g of the obtained polymer was dissolved in 100 g of IP solvent, 50 g of 2-hydroxyethyl acrylate and 10 g of 2-ethylhexyl acrylate were added, and 0.5 g of AIBN was added at 75 ° C. to prepare a second step. Was carried out to obtain a resin dispersion which was stably dispersed.

Synthesis Example 4 n-Dodecyl methacrylate 270 was prepared in the same manner as in Synthesis Example 3.
Gram and 4 grams of acrylic acid are dissolved in 100 grams of xylene and azobisisobutyronitrile (AIBN)
3.0 g was added, and the mixture was heated and stirred at 70 ° C. for 9 hours.
In the same manner as in Synthesis Example 3, 0.5 g of hydroquinone and 10 g of glycidyl methacrylate were added, and the mixture was reacted under heating and refluxing for 12 hours.
A polymer having a number average molecular weight of 100,000 was obtained.

100 g of the obtained polymer was dissolved in 100 g of IP Solvent, and styrene 3
0 g and 5 g of n-butyl acrylate were added.
0.5 g of AIBN was added at 5 ° C., and the second stage of polymerization was carried out to obtain a suspended semi-dissolved resin solution.

Synthesis Example 5 The polymer (S) obtained in Synthesis Example 1 was used.
0 g was dissolved in the same amount of IP solvent, and 70 g of vinyl acetate was added thereto.
The second stage polymerization is carried out by adding 0.7 g of BN,
A stably dispersed resin dispersion was obtained.

Synthesis Example 6 100 g of the polymer (S) obtained in Synthesis Example 1 was
This was dissolved in 100 g of IP solvent, 80 g of 2-hydroxyethyl acrylate was added thereto, and 0.5 g of AIBN was added at 70 ° C. to obtain a resin dispersion which was stably dispersed.

Example 1-6 The resin dispersion obtained in Synthesis Example 1-6 was weighed so as to have a solid content of 5 g, and each was used as a desensitizer to add 8 mol of butylene oxide to ethylenediamine. Added to 1000 grams and heat mixed to 100 ° C. Using a homomixer as a high-speed shear disperser, 600 grams of titanium oxide was gradually added to the desensitizer solution containing each of the above resins at a stirring speed of 5000 rpm over 30 minutes. Further stirring was continued at 100 ° C. for 1 hour to obtain a titanium oxide dispersion uniformly dispersed in the desensitizer.

For each of the obtained titanium oxide dispersions,
A rosin-modified phenolic resin (Tamanol 350, manufactured by Arakawa Chemical Industry Co., Ltd.) and 500 g of a vehicle containing linseed oil as main components were added, uniformly mixed at 130 ° C., and further milled with a three-roller mill to obtain a desensitized ink. .

For each of the six desensitizing inks thus obtained, a commercially available paper containing no carbon pressure-sensitive copying paper (N-40, the developing layer containing a para-phenylphenol formalin resin) was used on a form printing machine manufactured by Miyakoshi Kikai Seisakusho. Offset printing was performed on the developing surface. The printing plate is PS plate S made by Fuji Photo Film
Using G-II, printing was performed at a speed of 100 m / min, and a test was performed. H-liquid NO. 4 was used as a 1% aqueous solution. At the time of the test, the water supply amount of the humidifier was changed to evaluate the background contamination on the printed material under the condition where the amount of the humidifier was small. By evaluating the presence or absence, the water width of each desensitizing ink, that is, the latitude width depending on the printing conditions was evaluated.

As a comparison, when the desensitizing ink containing no resin according to the present invention was used, good printing results were obtained only in a narrow range of the supply amount, centering on the appropriate supply amount of the humidifier. If the amount is reduced, background soiling will be noticeable,
Further, when the supply amount was set to be large, emulsification occurred, and the latitude of printing conditions for obtaining a good printed matter was narrow. All of the desensitizing inks obtained as described above under the same conditions are hardly soiled and emulsified,
Good printed matter was obtained in a wide range of the supply amount of the humidifier.
Furthermore, no ink mist was generated during printing,
It turned out to be a good ink.

[0052]

In the printing using the desensitizing ink obtained by the present invention, since the water width of the desensitizing ink is wide,
Good printed matter can be obtained regardless of printing conditions. Further, there is an effect that the step of dispersing the white pigment (such as titanium oxide) in the desensitizing ink is greatly simplified.

Claims (3)

(57) [Claims] 1. A desensitizing ink for pressure-sensitive copying paper containing at least a white pigment, a vehicle, and a desensitizing agent, comprising a resin (particle) dissolved or dispersed as an additive, wherein the resin is formed of the following polymer ( A desensitizing ink for pressure-sensitive copying paper, which is a resin obtained by polymerizing at least the following monomer (A) in the presence of S). Polymer (S): a polymer that is soluble in an aliphatic hydrocarbon medium and has a polymerizable double bond group at a terminal or side chain of the polymer. Monomer (A): a monomer that is soluble in an aliphatic hydrocarbon medium and insoluble by polymerization. 2. The desensitizing ink for pressure-sensitive copying paper according to claim 1, wherein the resin is a resin obtained by copolymerizing a monomer (B) in addition to the monomer (A). Monomer (B): A monomer that is soluble in an aliphatic hydrocarbon medium and forms a polymer that is soluble even when polymerized. 3. The method according to claim 1, further comprising, together with the resin, a white pigment dispersion obtained by mixing and dispersing a white pigment in an organic solvent and / or a desensitizer under high-speed shearing. Desensitizing ink for pressure-sensitive copying paper.