JPH05214166A - Color-developing agent composition for pressure-sensitive copying paper - Google Patents

Abstract

PURPOSE:To provide the subject composition containing a pigment, a color- developing agent and a specific copolymer latex as a binder and capable of giving a color-developing paper for pressure-sensitive copying paper having excellent color-developing performance, especially a low-temperature initial color-developing performance and a print strength. CONSTITUTION:The objective composition contains a copolymer latex produced by the emulsion polymerization of (A) a pigment, (B) a color-developing agent and (C) a binder consisting of (i) 20-60wt.% of an aliphatic conjugated diene monomer (preferably 1,3-butadiene), (ii) 0-20wt.% of a vinyl cyanide monomer (preferably acrylonitrile), (iii) 1-20wt.% of an ethylenically unsaturated carboxylic acid monomer (e.g. acrylic acid) and (iv) 0-79wt.% of other monomer copolymerizable with the components (i) to (iii) in the presence of (D) a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring (preferably cyclopentene, etc.).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a color developer composition for pressure-sensitive copying paper. More specifically, the present invention relates to a developer composition which gives a developer for pressure-sensitive copying paper, which is excellent in color development and printing strength.

[0002]

2. Description of the Related Art Generally, a pressure-sensitive copying paper is composed of an upper paper coated with fine capsules containing an electron-donating colorless or light-colored leuco dye dissolved in an organic solvent (capsule oil) on the back surface and an electron-accepting paper. Consisting of a lower sheet of paper with a color developing layer containing a color developing agent on the surface, and applying pressure with a ballpoint pen or typewriter, etc. The capsules in the other part are destroyed, and the capsule oil containing the leuco dye is transferred to the color developing layer to cause a color reaction, whereby a printed record can be obtained.

Such pressure-sensitive copying paper has become widespread because it is more aesthetically pleasing than conventional copying methods using carbon paper and does not stain clothes or hands. Due to its characteristics, pressure-sensitive copying paper is most widely used as slip paper, but in this case, several copies may be required at one time. In such a case, it is common practice to insert one to several sheets of so-called middle paper, which has a color-developing layer on the front surface and capsules on the back surface, between the upper and lower paper sheets. However, there is a problem in that the more the medium paper is inserted, the lower the printing pressure and the writing pressure transmitted to the lower paper and the lower the color developability.

Further, such a pressure-sensitive paper is often used outdoors, but there is a problem that the so-called low temperature initial color development immediately after copying is inferior especially in a cold region in winter. On the other hand, offset printing is often performed on the developer layers of the middle and lower sheets, and if the adhesive strength of the developer layers is low, there is a problem that waste of paper and powder drop occur during printing. In order to solve these problems, JP-A-60-249
92 and Japanese Patent Application Laid-Open No. 61-83093,
Attempts have been made to use specific latexes or pigments with specific particle sizes. However, it was hard to say that the low temperature initial color development was sufficiently improved even by these methods.

[0005]

[Means for Solving the Problems] As a result of earnest studies on the above problems, the present inventors have found that a copolymer latex obtained by emulsion polymerization in the presence of a specific compound is used as a binder. The inventors have found that the developer composition for pressure-sensitive copying paper has excellent performance, and completed the present invention.

That is, the present invention provides a developer composition for pressure-sensitive copying paper containing a pigment, a developer and a copolymer latex as a binder, wherein the copolymer latex is an aliphatic conjugated diene-based monomer. 20 to 60% by weight, vinyl cyanide-based monomer 0 to 20% by weight, ethylenically unsaturated carboxylic acid monomer 1 to 20% by weight, and other monomer copolymerizable with these 0 to 79% by weight % Is a copolymer latex obtained by emulsion polymerization in the presence of a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring, and a developer composition for pressure-sensitive copying paper, characterized in that Is provided.

The present invention will be described in detail below.

Examples of the aliphatic conjugated diene-based monomer in the present invention include 1,3-butadiene and 2-methyl-1,3-
Butadiene, 2,3-dimethyl-1,3 butadiene, 2
-Chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes and the like can be mentioned, and one or more kinds can be used. Particularly, 1,3-butadiene is preferable.

Examples of vinyl cyanide-based monomers include acrylonitrile, methacrylonitrile, α-chloroacrylonitrile and α-ethylacrylonitrile, and one or more of them can be used. Acrylonitrile is particularly preferable.

Examples of the ethylenically unsaturated carboxylic acid monomer include mono- or dicarboxylic acids (anhydrides) such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid.

Other monomers copolymerizable with these monomers include alkenyl aromatic monomers, unsaturated carboxylic acid alkyl ester monomers and hydroxyalkyl group-containing unsaturated monomers. And unsaturated carboxylic acid amide monomers.

As the alkenyl aromatic monomer, styrene, α-methylstyrene, methyl α-methylstyrene,
Vinyltoluene and divinylbenzene and the like,
One kind or two or more kinds can be used. Particularly preferred is styrene.

The unsaturated carboxylic acid alkyl ester monomers include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, glycidyl methacrylate, dimethyl fumarate, diethyl fumarate, dimethyl maleate, diethyl malate, dimethyl. Itaconate, monomethyl fumarate, monoethyl fumarate, 2-ethylhexyl acrylate and the like can be mentioned, and one kind or two or more kinds can be used. Methyl methacrylate is particularly preferable.

Examples of unsaturated monomers containing a hydroxyalkyl group include β-hydroxyethyl acrylate and β-hydroxyethyl acrylate.
-Hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate,
Hydroxybutyl acrylate, hydroxybutyl methacrylate, 3-chloro-2-hydroxypropyl methacrylate, di- (ethylene glycol) maleate,
Di- (ethylene glycol) itaconate, 2-hydroxyethyl maleate, bis (2-hydroxyethyl)
Maleate, 2-hydroxyethylmethyl fumarate and the like can be mentioned, and one kind or two or more kinds can be used. In particular, β-hydroxyethyl acrylate is preferable.

As the unsaturated carboxylic acid amide monomer,
Acrylamide, methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N,
N-dimethylacrylamide and the like can be mentioned, and one kind or two or more kinds can be used. Particularly preferred is acrylamide.

The above monomer composition is such that 20 to 60% by weight of the aliphatic conjugated diene-based monomer and the vinyl cyanide-based monomer 0 to
20% by weight, ethylenically unsaturated carboxylic acid monomers 1-2
0% by weight and 0 to 7 other monomers copolymerizable therewith
It is 9% by weight.

If the amount of the aliphatic conjugated diene-based monomer is less than 20% by weight, the printing strength is high, and if it is more than 60% by weight, the color developability is poor, which is not preferable. When the amount of the vinyl cyanide-based monomer exceeds 20% by weight, the printing strength becomes poor, which is not preferable. When the content of the ethylenically unsaturated carboxylic acid monomer is less than 1% by weight, mechanical stability is poor, and when it exceeds 20% by weight, printing strength is poor, which is not preferable. If the amount of the other copolymerizable monomer exceeds 79% by weight, the printing strength becomes poor, which is not preferable.

The gel content of the copolymer latex is not particularly limited, but it is 50 from the viewpoint of color developability and printability.
It is preferably in the range of -100%.

Emulsion polymerization is carried out using these monomers,
In order to obtain the copolymer latex, it is essential to use a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring (hereinafter, simply referred to as unsaturated hydrocarbon).

Most of the unsaturated hydrocarbons used in the present invention remain unreacted after the completion of the polymerization, and the unreacted substances need to be recovered. preferable. Specific examples include cyclopentene, cyclohexene, cycloheptene, 4-methylcyclohexene, 1-methylcyclohexene and the like.

The amount of the above compound used in the present invention is 0.1 to 30 parts by weight based on 100 parts by weight of the monomer mixture. If the amount is less than 0.1 parts by weight, the effect of the present invention is not sufficiently exhibited, and if the amount exceeds 30 parts by weight, the amount of the compound remaining as an unreacted product relatively increases, and the energy required for recovery thereof is increased. It is not preferable because it becomes large. It is preferably 0.5 to 15 parts by weight.

Further, since the unsaturated hydrocarbon used in the production process is unfavorable in terms of work environment hygiene in the end use, in the present invention, after the copolymer latex is polymerized by the production method, unreacted. The compound remaining as a substance is substantially removed (0.5 parts by weight or less, more preferably 0.1 parts by weight or less based on 100 parts by weight of the copolymer latex (solid content)).

As a method for removing the compound, a known method,
For example, it can be removed by steam distillation, vacuum distillation, blowing of an inert gas, or the like.

In emulsion-polymerizing the copolymer latex of the present invention, usual emulsifiers, polymerization initiators, electrolytes,
Chain transfer agents, polymerization accelerators, chelating agents and the like can be used.

The method of adding various components in the present invention is not particularly limited, and any of a batch addition method, a divided addition method and a continuous addition method can be adopted.

Further, in the present invention, any one-step polymerization, two-step polymerization, multi-step polymerization or the like can be employed, but emulsion polymerization is particularly preferred by the following method.

That is, in the first stage, 3 to 40% by weight, preferably 5 to 30% by weight of the monomers are polymerized with respect to all the monomers, and the polymerization conversion rate in the first stage is 50% or more. Preferably, the remaining monomer is polymerized at the time when it reaches 70% or more to substantially complete the polymerization.

As the emulsifier, a sulfuric acid ester salt of a higher alcohol, an alkylbenzene sulfonate, an alkyldiphenyl ether sulfonate, an aliphatic sulfonate, an aliphatic carboxylate, an anionic surfactant such as a sulfuric acid ester salt of a nonionic surfactant is used. Surfactants or nonionic surfactants such as alkyl ester type of polyethylene glycol, alkyl phenyl ether type, alkyl ether type and the like are used in one kind or in two or more kinds.

As the initiator, a water-soluble initiator such as potassium persulfate, ammonium persulfate or sodium persulfate, a redox initiator or an oil-soluble initiator such as benzoyl peroxide can be used.

The chain transfer agent used in the present invention includes
Alkyl mercaptans such as n-hexyl mercaptan, n-octyl mercaptan, t-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-stearyl mercaptan, xanthogen compounds such as dimethylxanthogen disulfide, diisopropylxanthogen disulfide, α- Methylstyrene dimer, terpinolene, tetramethylthiuram disulfide, tetraethylthiuram disulfide,
Thiuram-based compounds such as tetramethylthiuram monosulfide, 2,6-di-t-butyl-4-methylphenol, phenol-based compounds such as styrenated phenol, allyl compounds such as allyl alcohol, dichloromethane, dibromomethane and carbon tetrachloride. , Halogenated hydrocarbon compounds such as carbon tetrabromide, α-benzyloxystyrene, α-benzyloxyacrylonitrile, vinyl ethers such as α-benzyloxyacrylamide, triphenylethane, pentaphenylethane, acrolein, methacrolein, thioglycolic acid , Thiomalic acid, 2-ethylhexyl thioglycolate and the like, and one or more of them can be used.

The amount of the chain transfer agent used is not particularly limited and can be appropriately adjusted depending on the performance required for the copolymer latex, but preferably 0.1 to 100 parts by weight of the monomer mixture. It is from 05 to 10 parts by weight.

The color developer composition for pressure-sensitive copying paper in the present invention is prepared by blending the above-mentioned copolymer latex with a pigment, a color developer and, if necessary, other thickeners, auxiliaries and the like. ..

As the pigment, it is used for general coated paper such as heavy calcium carbonate, light calcium carbonate, kaolin, calcined kaolin, aluminum hydroxide, talc, silica powder, barium sulfate, titanium oxide, satin white and plastic pigment. These are used alone or in combination of two or more.

Examples of developers include acid clay, activated clay, attapulgite, zeolite, bentonite,
All color developers currently in use can be used, such as clay substances such as kaolin, metal salts of aromatic carboxylic acids and phenolic resins.

Other thickeners and binders include, for example, proteins (gelatin, albumin, casein, etc.), starches (cereal grains, pregelatinized starch, oxidized starch, etherified starch, esterified starch, etc.), Water-soluble natural polymer compounds such as cellulose derivatives (carboxymethyl cellulose, hydroxypropyl cellulose, methyl cellulose, etc.), water-soluble such as polyvinyl alcohol, acrylamide modified polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, polyacrylamide, maleic acid copolymers, etc. Synthetic polymer compounds are used.

Other auxiliaries include pH adjusters, emulsifiers, stabilizers, mold release agents, antioxidants, dispersants, defoamers, preservatives, colorants, cross-linking agents and cross-linking auxiliaries which are generally added. Agents and the like.

The copolymer latex in the present invention is usually used in an amount of 5 to 40 parts by weight based on 100 parts by weight of the pigment.

The color developing agent is usually 5 per 100 parts by weight of the pigment.
~ 40 parts by weight are used. Further, a color developer such as a metal salt of an aromatic carboxylic acid or a phenol resin is used in a ball mill,
It is preferable to preliminarily mix it as an aqueous dispersion with a sand mill or the like.

The developer composition thus prepared is
It is coated on a suitable base material such as paper, synthetic paper, synthetic film by a commonly used coating machine such as a blade coater, a roll coater, a bar coater, an air knife coater and a curtain coater.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples as long as the gist thereof is not exceeded. In the examples, parts and percentages are by weight. The physical properties in the examples were measured by the following methods.

A latex film is prepared by drying the gel content at room temperature. After accurately weighing about 1.0 g of latex film, put it in 400 cc of toluene, leave it for 48 hours to dissolve it, filter through a 300-mesh wire net, dry it, and weigh the toluene insoluble content (gel) on the wire net to calculate the gel content. To do.

The degree of picking when printed with dampening water on the RI Wet Pick RI printing machine is judged with the naked eye, and grade 1 to grade 5 (best)
It was evaluated by the five-level method of the grade (the worst one). The average value of 6 times is shown.

Evaluation was performed in the same manner as in the above-mentioned RI Wet Pick, except that RI Dry Pick dampening water was not used.

Color development In the atmosphere of 5 ° C., a commercially available top sheet and the bottom sheet prepared in the present invention are superposed, and the entire surface is developed with a super calender pressure to measure the change in whiteness with time. The lower the number, the better the color development.

Polymerization of Copolymer Latex In a 20 liter autoclave, 100 parts by weight of water, 0.4 part of sodium dodecylbenzene sulfonate, 0.3 part of sodium hydrogen carbonate, 1.0 part of potassium persulfate and Table-1 are shown. The first-stage monomer mixture, chain transfer agent, and unsaturated hydrocarbon shown in Table 2 were charged and the first-stage polymerization was carried out at 70 ° C. When the conversion of the first-stage emulsion polymerization reached 70%, the second-stage monomer mixture, chain transfer agent and unsaturated hydrocarbon were continuously added for 6 hours to carry out the second-stage polymerization. .. Then, in order to complete the polymerization, the polymerization was further continued, and the polymerization was completed at a conversion of 97%. After adjusting the obtained copolymer latex to pH 5 with sodium hydroxide,
Unsaturated hydrocarbons remaining as unreacted monomers and unreacted substances are removed by steam distillation to obtain a copolymer latex a.
got j.

In the table, the amount on the left side is the first step and the amount on the right side is the second step across "/".

[0047]

[Table 1]

[0048]

[Table 2]

Preparation of color developer composition A color developer composition was prepared according to the following formulation.
The developer (phenolic resin) used was previously treated with a ball mill for 24 hours. Heavy calcium carbonate 100 Dry weight part Developer (phenolic resin) 20 PVA 5 Oxidized starch 10 Latex 10 Solid content 50%

Preparation of Lower Paper 7 g of the above-mentioned developer composition was put on a commercially available high-quality paper (64 g / m ² ).
One side was coated with a wire bar so that the pressure would be / cm ² and immediately dried in an oven at 100 ° C. The coated paper was conditioned overnight to prepare a lower paper. Color development, RIDry Pick and RI Wet of the obtained lower paper
Pick was evaluated. The results are shown in Table-3.

[0051]

[Table 3]

Claims (1)

[Claims] 1. A developer composition for pressure-sensitive copying paper containing a pigment, a developer and a copolymer latex as a binder, wherein the copolymer latex comprises an aliphatic conjugated diene monomer 20 to 60% by weight, vinyl cyanide-based monomer 0 to 20% by weight, ethylenically unsaturated carboxylic acid monomer 1
~ 20% by weight and other monomers copolymerizable therewith 0
A color developer for pressure-sensitive copying paper, characterized in that it is a copolymer latex obtained by emulsion polymerization of about 79% by weight in the presence of a cyclic unsaturated hydrocarbon having one unsaturated bond in the ring. Agent composition.