JP3026365B2 - Base paper for pressure-sensitive copying paper - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base paper for pressure-sensitive copying paper having excellent size and printability.

[0002]

2. Description of the Related Art In recent years, the production of neutral base paper for pressure-sensitive copying paper for the purpose of improving whiteness and opacity by using calcium carbonate, improving storage stability of paper, and the like has been increasing. When producing paper with neutrality, a rosin sizing agent that performs in an acidic atmosphere and in the presence of a sulfate band cannot be used, and a neutral sizing agent is used instead.

[0003] As the neutral sizing agent, alkyl ketene dimer (hereinafter abbreviated as AKD) or alkenyl succinic anhydride (hereinafter abbreviated as ASA) is used as a neutral sizing agent because of its easy handling and excellent sizing obtained with a small amount of addition. (Abbreviated)
Aqueous dispersions are most often used. In addition, a cationic polymer type neutral sizing agent is also known.
If the amount of addition is the same as that of ASA, paper having a sufficient size cannot be obtained.

AKD is used as a sizing agent for base paper for pressure-sensitive copying paper.
Alternatively, when ASA is used, increasing the amount of sizing agent to obtain the required high sizing degree lowers the surface energy of the paper, and performs multicolor printing on the pressure-sensitive copying paper or base paper after applying the pressure-sensitive coating liquid. In this case, the ink setting of the second and third colors tends to deteriorate.

As a result, blanket contamination of the printing press occurs in the second and subsequent colors.

As countermeasures against this, attempts have been made to reduce the amount of AKD or ASA added, use other neutral sizing agents, increase the amount of surface-sized starch applied, and the like.

[0007]

The techniques which can be applied to obtain a base paper for pressure-sensitive copying paper having excellent size and ink setting properties include reduction of the amount of AKD and ASA added as described above, and other neutral properties. There is an application of sizing agents and an increase in the amount of surface size starch applied.

However, when the amount of added AKD is reduced or other sizing agent is used, the ink setting property is good, but a paper having a sufficient sizing degree cannot be obtained. In any case, it was not possible to obtain sufficient quality pressure-sensitive copy paper base paper.

That is, an object of the present invention is to provide a base paper for pressure-sensitive copying paper which is excellent in size and ink setting in multicolor printing.

[0010]

The present inventors have studied the use of a surface sizing agent whose main component is a styrene-acrylic acid copolymer in order to solve the above-mentioned problems. A surface sizing agent having a styrene weight ratio of 0.30 or more and 0.60 or less among the surface sizing agents of the copolymer is applied to the paper surface together with oxidized starch by a size press or a gate roll coater (hereinafter abbreviated as GRC). It has been found that the adverse effect of the internal sizing agent on the ink setting property can be particularly reduced.

Meanwhile, styrene weight ratio to Table Men'e energy decreases when exceeding 0.60, the size of the improvement can not be expected in the ink set of the improvement of what can be expected.

Further, the styrene content ratio is 0.3% by weight.
0 to 0.60 surface sizing agent
It has been found that the effect of improving the sizing property and the ink setting property becomes even more remarkable when applied in an amount of from 0.1 g / m ^{2 to} 0.1 g / m ^2, thereby completing the present invention.

[0013] As the reason, the table Men'e energy by covering the covered surface with a sizing at a rate less surface sizing agent of hydrophobic groups occupying in the molecule small hydrophobic group increases, the ink pigment and a solvent It is conceivable that the penetration of (a drying oil or the like) becomes faster and the ink setting property is improved.

The base paper for pressure-sensitive copying paper in the present invention is "upper paper" having a layer coated with microcapsules containing an electron-donating dye on one side, and is colored by contact reaction with the electron-donating dye. "Lower paper" with a layer coated with an electron-accepting compound (developing agent), "middle paper" coated with a microcapsule on one side and a developer on the other, and microcapsules on the same side of the base paper And a developer used as a base paper for pressure-sensitive copying paper such as "self-coloring paper".

The coating liquid containing microcapsules is lactone,
Dissolve basic dyes such as spiropyran, diphenylmethane, fluoran and azines in solvents consisting of synthetic oils such as alkylated diphenyl, alkylated diphenylmethane, alkylated naphthalene and alkylated terphenyl, vegetable oils, animal oils and mineral oils or mixtures thereof. In general, it is prepared by a method in which a basic dye is contained in microcapsules by various encapsulation methods such as a lake acervation method, an in-situ method, and an interfacial polymerization method, and dispersed in a binder.

Further, the developer-containing coating solution may be an inorganic developer such as attapulgite, acid clay, activated clay, or various aliphatic carboxylic acids, phthalic acid, salicylic acid, benzoic acid, p
-Tert-butylbenzoic acid, 3-phenylsalicylic acid, 3-isopropylsalicylic acid, 3-cyclohexylsalicylic acid, 3,5-di-tert-butylsalicylic acid, 3-methyl-5-benzylsalicylic acid, 3-phenyl-5- (α , Α-dimethylbenzyl) salicylic acid,
Aromatic carboxylic acids such as 3,5-di- (α-methylbenzyl) salicylic acid and organic developers such as p-phenylphenol-formalin resin and p-butylphenol-acetylene resin, and the above organic developers And various developers which are salts with polyvalent metals such as zinc, calcium, aluminum, titanium, manganese, tin and nickel are dispersed in a binder by a sand grinding mill or the like.

As the binder, starches, celluloses, proteins, polyvinyl alcohol, gum arabic,
Styrene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, polyacrylate, styrene-butadiene copolymer emulsion and the like are used.

There are no particular restrictions on the method of applying the microcapsule-containing coating liquid and the developer-containing coating liquid. Each coating liquid is an on-machine coater having a coater head such as a blade coater, an air knife coater, a curtain coater, and a rod coater. Alternatively, it is applied and dried by an off-machine coater.

The pulp used in the base paper of the present invention includes NBKP, LBKP, NBSP, LBSP, GP,
TMP, DIP and the like. In use,
These are mixed and used in proportions depending on the purpose.

The surface sizing agent whose main component is a styrene-acrylic copolymer used in the present invention is described, for example, in JP-A-55-99909 and JP-A-57-24363.
It is a surface sizing agent containing a copolymer of styrene and acrylic as a main component as described in Japanese Patent Application Laid-Open Publication No. H10-163, etc.

The amount of the surface sizing agent applied is 0.01 g / m ^2.
If it is less than the above, sufficient improvement in size and ink setting property cannot be obtained. Further, even if the coating is performed in excess of 0.1 g / m ² , the ink setting property is not further improved.

The base paper for pressure-sensitive copying of the present invention contains, if necessary, dyes, fillers, sizing agents, fixing agents, dry paper strength enhancers, etc., which are usually used in papermaking. The surface sizing agent of the present invention is prepared by applying a size press and GR
C can be applied, and it does not matter whether it is used by mixing with starch or alone.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to embodiments. The present invention is not limited to the embodiments. All parts and percentages in the following are by weight. The value indicating the amount of smear is the weight after drying unless otherwise specified.

Preparation Example 1 Styrene monomer and acrylic monomer used in Examples
A method for preparing a surface sizing agent obtained by copolymerization of

In a four-necked flask equipped with a stirrer, a thermometer and a reflux condenser, 6.9 parts of styrene, 39 parts of N, N-dimethylaminopropylacrylamide and 50 parts of toluene were charged, and azobisisopropane was used as a polymerization initiator. 3.3 parts of butyronitrile was added, and a polymerization reaction was carried out at a reaction temperature of 90 ° C. for 4 hours. The toluene was distilled off under reduced pressure, and the polymer was neutralized with sodium hydroxide and aqueous ammonia to obtain a styrene / acrylic acid copolymer having a styrene weight ratio of 0.15.

[0026] In Preparation Example 2-5 Preparation Example 1 was charged amount 16.7 parts of styrene, 3
Various surface sizing agents which react in the same manner except that the weight ratio of styrene is changed to 0.30, 0.45, 0.60 and 0.75 by changing to 4 levels of 2 parts, 58.5 parts and 117 parts. I got These are referred to as Preparation Examples 2, 3, 4, and 5, respectively.

Preparation Example 6 A method for preparing a coating liquid containing microcapsules used in Examples is described. 4 parts of crystal violet lactone was added to a diarylethane solvent (trade name: Hisol SASN-296)
A solution dissolved in 96 parts of Nippon Petrochemical Co., Ltd.) was prepared.
To 180 parts of a 5% aqueous solution of styrene-maleic anhydride copolymer (manufactured by Arakawa Chemical Co., Ltd.), 220 parts of the above-mentioned hydrophobic liquid was gradually added under vigorous stirring, so that the 50% value of the volume average diameter by the Coulter counter method became 3 μm. Stirring was continued until an emulsion was obtained. Separately, 11 parts of melamine, 21.2 parts of a 37% formaldehyde aqueous solution, and 28.2 parts of water were heated and dissolved, and an aqueous solution of a melamine-formaldehyde precondensate was added during the emulsification, and the mixture was stirred at 70 ° C. for 2 hours. Thus, a microcapsule solution was obtained.

Preparation Example 7 A method for preparing a developer-containing coating liquid used in the examples is described. Developer 3, 10 parts of 5-di-α-methylbenzyl salicylic acid and 10% polyvinyl alcohol (PVA117, trade name)
3 parts of Kuraray Co., Ltd.) and 22.5 parts of water were dispersed by a sand grinding mill to obtain a developer dispersion.

Example 1 Freeness of 380 ml c. s. f. LBKP beaten up to 450 ml c. s. f. NB beaten up to
7 parts of light calcium carbonate (TP121, manufactured by Okutama Kogyo Co., Ltd.) and alkyl ketene dimer sizing agent (Size Pine K903, manufactured by Arakawa Chemical Co., Ltd.) are based on 100 parts of pulp obtained by mixing KP at a weight ratio of 7: 3. 0.1 part as an alkyl ketene dimer, amphoteric starch (Cato3
210, manufactured by Oji National Co., Ltd.) to prepare a handsheet having a basis weight of 60 g / m ² .

The sheet was dried at 90 ° C. for 5 minutes. Then, the surface sizing agent having a weight ratio of styrene of Preparation Example 1, 2, 3, 4, or 5 different from that of the above five sheets together with the oxidized starch by a size press is applied to these sheets at a coating amount of 0.05 g / m ^2. And machine calendering was performed so that the Beck smoothness became 80 seconds to obtain a base paper for pressure-sensitive copying paper.

The coating liquid of Preparation Example 6 was applied to these base papers at 5 g / m
^A pressure-sensitive copying paper comprising ^two smeared upper papers and a lower paper smeared with 5 g / m ² of the coating solution of Preparation Example 7 was prepared.

These samples are referred to as sample 1-1, sample 1-2, sample 1-3, sample 1-4, and sample 1-5 in order from the one having the smallest weight ratio of styrene.

Comparative Example 1 A sample was prepared in the same manner as in Example 1, except that nothing was smeared with the size press, and only the oxidized starch was smeared with the size press. These samples are referred to as Sample 2-1 and Sample 2-2, respectively. The results are summarized in Table 1 below.

[0034]

[Table 1]

Evaluation criteria ◎: extremely good, ：: good, ×: bad

In order to evaluate the ink setting property, 0.3 g of red ink (trade name: New Prous-G, manufactured by Dainippon Ink Co., Ltd.) is kneaded with an RI tester (manufactured by Mei Seisakusho) and then printed on a sample.

After one hour has passed to the printed portion where the optical density of the printed portion (using a Macbeth reflection densitometer) is about 1.2, a commercially available 18 mm wide adhesive tape (cellophane tape,
(Manufactured by Nichiban Co., Ltd.) was applied, and the print density of the portion where the cellophane tape was peeled off by hand was measured.

As an index for evaluating the ink setting property, the following printing density ratio (hereinafter abbreviated as OD ratio) was used. OD ratio = print density after peeling / print density before peeling

As the uncoated printing paper, the OD ratio is 0.8
An ink setting property of 0 or more is required.

In the color development test, the upper paper and the lower paper are overlapped so that the capsule-coated surface of the upper paper and the developer-coated surface of the lower paper face each other, and a load of 600 kg / cm ² is applied. The density of the obtained color image was measured with a Macbeth reflection densitometer.

The sizing degree was measured by the Steckicht method according to JISP8122. Similarly to high quality paper, the base paper for pressure-sensitive copying paper is required to have a size of 18 seconds or more when the basis weight is 60 g / m ² .

From Table 1, it can be seen that by applying a surface sizing agent having a styrene content ratio of not more than 60% by weight on the paper surface to the paper surface, pressure-sensitive copying excellent in ink setting properties, sizing properties and coloring properties can be obtained. It is clear that paper base paper can be obtained.

Example 2 Using a surface sizing agent having a weight ratio of styrene of 0.5 to paper hand-made in the same manner as in Example 1, the amount applied by a size press was 0.005, 0.01. , 0.05, 0.1
A sample was prepared in the same manner as in Example 1 except that the amount of coating was changed to five levels of 0.15 g / m ² and 0.15 g / m ² .

These samples are referred to as sample 3-1, sample 3-2, sample 3-3, sample 3-4, and sample 3-5 in the order from the smallest smear. Table 2 summarizes the above results.

[0045]

[Table 2]

As is clear from the table, if the amount is less than 0.01 g / m ² , a sufficient effect of improving the ink setting property cannot be obtained.
Even when the amount exceeds 0.1 g / m ² , the ink setting property is hardly improved, which is uneconomical.

[0047]

As described above, the surface sizing agent whose main component is a styrene-acrylic acid copolymer was applied to the surface of the base paper for pressure-sensitive copying paper of the present invention, that is, the paper containing AKD or ASA. The base paper for pressure-sensitive copying paper is
It became clear that the ink setting property and the coloring property were excellent.

Claims (2)

(57) [Claims] 1. A filler containing calcium carbonate as a filler,
In pressure-sensitive copying paper containing an alkyl ketene dimer or alkenyl succinic anhydride as an internal sizing agent, a surface sizing agent whose main component is a styrene-acrylic acid copolymer is applied to the surface. Base paper for pressure-sensitive copying paper. 2. A method according to claim 1 Symbol placement of pressure-sensitive copying paper base paper is in a range amount of 0.01 g / m ² or more 0.1 g / m ² or less of the surface sizing agent applied to the paper surface.