JPH04255388A - Base paper for pressure sensitive duplicating paper - Google Patents

Abstract

PURPOSE:To provide base paper having excellent color developing properties, size properties and ink setting properties in base paper for pressure sensitive duplicating paper. CONSTITUTION:The base paper is obtained by coating paper, to which internally attached size is executed by an alkylketene dimer and an alkenyl succinic anhydride with a surface sizing agent as a styrene-acrylic copolymer with oxidized starch by a size press and a coater such as a gate roll coater. Since the sizing of the base paper is improved and ink setting properties are also enhanced in addition to excellent color-developing properties as pressure sensitive duplicating paper, no blanket after two colors is generated.

Description

[Detailed description of the invention]

0001

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

0002

BACKGROUND OF THE INVENTION In recent years, base papers for pressure-sensitive copying paper have been increasingly produced in a neutral manner with the aim of improving whiteness and opacity and improving paper shelf life by using calcium carbonate. When producing paper in neutral conditions, rosin sizing agents that perform well in an acidic atmosphere and in the presence of sulfuric acid cannot be used, and neutral sizing agents are used instead.

[0003] As neutral sizing agents, alkyl ketene dimer (hereinafter abbreviated as AKD) and alkenyl succinic anhydride (hereinafter referred to as ASA) are used because they are easy to handle or can provide excellent sizing properties with the addition of a small amount. Aqueous dispersions of (abbreviated) are most commonly used. Cationic polymer type neutral sizing agents are also known, but paper with sufficient sizing properties cannot be obtained when added in the same amount as AKD or ASA.

AKD as a sizing agent for base paper for pressure-sensitive copying paper
Alternatively, when using ASA, increasing the amount of sizing agent added to obtain the required high degree of sizing reduces the surface energy of the paper, resulting in multicolor printing on the pressure-sensitive copying paper or base paper surface after applying the pressure-sensitive coating fluid. In this case, the ink setting properties of the second and third colors tend to deteriorate.

[0005] As a result, printing machine blanket stains occur after the second color.

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

[0007]

[Problems to be Solved by the Invention] Techniques that can be applied to obtain base paper for pressure-sensitive copying paper with excellent size properties and ink setting properties include reducing the amount of AKD and ASA added, as described above, and using other neutral There is an increase in the application of sizing agents and the amount of surface size starch applied.

However, by reducing the amount of AKD added or using other sizing agents, although the ink setting properties are good, paper with sufficient sizing cannot be obtained, and by increasing the amount of starch adhering to the surface size, the curling properties of the paper are reduced. In either case, it was not possible to obtain a base paper for pressure-sensitive copying paper of sufficient quality.

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

0010

[Means for Solving the Problems] In order to solve the above problems, the present inventors investigated the use of a surface sizing agent whose main component is a styrene/acrylic acid copolymer. Among copolymer surface sizing agents, a surface sizing agent having a styrene weight ratio of 0.30 to 0.60 is applied to the paper surface together with oxidized starch using a size press or a gate roll coater (hereinafter abbreviated as GRC). It was discovered that the negative effect of internally added sizing agents on ink setting properties can be particularly reduced.

On the other hand, if the styrene weight ratio exceeds 0.60, the surface free energy decreases, so although an improvement in size properties can be expected, an improvement in ink setting properties cannot be expected much.

Furthermore, the styrene content ratio is 0.3 by weight.
0.01 to 0.60 surface sizing agent to the paper surface
The present inventors have found that the effect of improving size properties and ink setting properties becomes even more remarkable when the coating is applied in a range of 0.1 g/m2 to 0.1 g/m2, leading to the completion of the present invention.

The reason for this is that by covering the surface covered with the sizing agent with a surface sizing agent that has a small hydrophobic group and a small proportion of the hydrophobic group in the molecule, the surface free energy increases, and the ink pigment and solvent ( It is thought that the penetration of drying oil, etc.) becomes faster and the ink setting properties are improved.

[0014] The base paper for pressure-sensitive copying paper in the present invention is a "top paper" having a layer coated with microcapsules containing an electron-donating dye on one side, which develops color by contact with the electron-donating dye. "Lower paper" has a layer coated with an electron-accepting compound (color developer), "middle paper" has microcapsules on one side and a color developer on the other, and microcapsules on the same side of the base paper. This refers to paper used as a base paper for pressure-sensitive copying paper such as ``self-coloring paper'' that is laminated or mixed with color developer and color developer.

[0015] The microcapsule-containing coating liquid contains lactone,
Basic dyes such as spiropyran, diphenylmethane, fluorane and azines are dissolved in solvents consisting of synthetic oils, vegetable oils, animal oils and mineral oils or mixtures thereof, such as alkylated diphenyls, alkylated diphenylmethanes, alkylated naphthalenes and alkylated terphenyls. However, it is generally prepared by including a basic dye in microcapsules using various encapsulation methods such as the lake acervation method, in-situ method, and interfacial polymerization method, and dispersing it in a binder.

The color developer-containing coating solution may also contain inorganic color developers such as attapulgite, acid clay, activated clay, 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, 3,5-
Aromatic carboxylic acids such as di-(α-methylbenzyl)salicylic acid and organic color developers such as p-phenylphenol-formalin resin and p-butylphenol-acetylene resin, as well as the above organic color developers and zinc and calcium. It is prepared by dispersing various color developers, which are salts of polyvalent metals such as aluminum, titanium, manganese, tin, and nickel, into a binder using a sand grinding mill.

As binders, starch, cellulose, proteins, polyvinyl alcohol, gum arabic, styrene-maleic anhydride copolymer, vinyl acetate-maleic anhydride copolymer, polyacrylate, styrene-butadiene copolymer are used. Combined emulsions are used.

[0018] There are no particular restrictions on the coating method for the microcapsule-containing coating liquid and the color developer-containing coating liquid, and each coating liquid can be applied using an on-machine coater having a cotter head such as a blade coater, air knife coater, curtain coater, or rod coater. Alternatively, it is applied and dried using an off-machine coater.

The pulp used for the base paper of the present invention includes NBKP, LBKP, NBSP, LBSP, GP, and T.
Examples include MP and DIP. When using them, they are mixed in a ratio 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.
This refers to a surface sizing agent whose main component is a copolymer of styrene and acrylic, as described in Japanese Patent Publication No.

[0021] The amount of surface sizing agent applied is 0.01 g/m2.
If it is less than that, sufficient improvement in sizing properties and ink setting properties cannot be obtained. Further, even if the amount exceeds 0.1 g/m2, the ink setting property will not be improved any further.

The base paper for pressure-sensitive copying of the present invention contains dyes, fillers, sizing agents, fixing agents, dry paper strength enhancers, etc., which are normally used in paper making, as necessary. The surface sizing agent of the present invention is applied to the surface of the base paper by size press and GR.
It can be applied with C, and it can be used alone or mixed with starch.

[0023]

[Examples] The present invention will be explained in detail below using examples. Note that the present invention is not limited to the examples. All parts and percentages below are by weight. In addition, unless otherwise specified, the values indicating the amount of smearing are the weights after drying.

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

16 parts of styrene, 39 parts of N,N-dimethylaminopropylacrylamide and 50 parts of toluene were charged into a four-necked flask equipped with a stirrer, a thermometer and a reflux condenser, and then azobisisobutylene was added as a polymerization initiator. 3.3 parts of nitrile was added, and a polymerization reaction was carried out at a reaction temperature of 90° C. for 4 hours. 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 with a styrene weight ratio of 0.15.

Preparation Examples 2 to 5 In Preparation Example 1, the amount of styrene charged was changed to four levels: 39 parts, 75 parts, 138 parts, and 267 parts, and the weight ratio of styrene was 0.30, 0.45, and 0.60. and 0.7
Various surface sizing agents were obtained by carrying out the reaction in the same manner as above, except that Example No. 5 was used. These were prepared in Preparation Examples 2, 3, 4 and 5, respectively.
shall be.

Preparation Example 6 A method for preparing the microcapsule-containing coating liquid used in the examples will be described. 4 parts of crystal violet lactone was dissolved in a diarylethane solvent (trade name Hysol SASN-296).
A solution was prepared by dissolving 96 parts of the compound (manufactured by Nippon Petrochemical Co., Ltd.). 220 parts of the above hydrophobic liquid was gradually added to 180 parts of a 5% styrene-maleic anhydride copolymer aqueous solution (manufactured by Arakawa Chemical Co., Ltd.) under strong stirring until the volume average diameter at 50% by the Coulter-Counter method was 3 μm. Stirring was continued until an emulsion was obtained. Separately, a melamine-formaldehyde initial condensate aqueous solution obtained by heating and dissolving 11 parts of melamine, 21.2 parts of a 37% formaldehyde aqueous solution, and 28.2 parts of water was added during emulsification, and stirred at a temperature of 70°C for 2 hours. A microcapsule liquid was obtained.

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

Example 1 PFI mill with freeness of 380 mlc. s. f. LBKP beaten to 450 mlc. s. f. NB improved to
For 100 parts of pulp mixed with KP at a weight ratio of 7:3, 7 parts of light calcium carbonate (TP121, manufactured by Okutama Kogyo Co., Ltd.) and an alkyl ketene dimer sizing agent (Size Pine K903, manufactured by Arakawa Chemical Co., Ltd.) 0.1 part as alkyl ketene dimer, amphoteric starch (Cato3
210 (manufactured by Oji National Co., Ltd.) was added thereto to prepare a handmade sheet with a basis weight of 60 g/m2.

The sheet was dried at 90° C. for 5 minutes. Thereafter, surface sizing agents having different styrene weight ratios of Preparation Examples 1, 2, 3, 4, or 5 were applied to these sheets in a size press together with oxidized starch in an amount of 0.
．． 05g/m2, Beck smoothness is 8.
A base paper for pressure-sensitive copying paper was prepared by machine calendering so that the time was 0 seconds.

[0031] 5 g/m of the coating liquid of Preparation Example 6 was applied to these base papers.
Pressure-sensitive copying paper was prepared, consisting of an upper sheet coated with 5 g/m2 of the coating solution of Preparation Example 7 and a lower sheet coated with 5 g/m2 of the coating solution of Preparation Example 7.

These samples were designated as sample 1-1, sample 1-2, sample 1-3, sample 1-4, and sample 1-5 in descending order of styrene weight ratio.

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

[0034]

[Table 1]

Evaluation criteria ◎: Extremely good, ○: Good, ×: Bad

[0036]
In order to evaluate ink setting properties, 0.3 g of red ink (trade name: New Proas-G, manufactured by Dainippon Ink Co., Ltd.) was kneaded using an RI tester (manufactured by Mei Seisakusho), and then printed on a sample.

After one hour has passed, a commercially available 18 mm wide adhesive tape (cellophane tape, cellophane tape,
(manufactured by Nichiban Co., Ltd.) was attached, and the cellophane tape was peeled off by hand to measure the print density.

The following printing density ratio (hereinafter abbreviated as OD ratio) was used as an index for evaluating the ink set property. OD ratio=Print density after peeling/Print density before peeling

0
[039] Non-coated printing paper is required to have an ink set property with an OD ratio of 0.80 or more.

[0040] In the color development test, the upper and lower sheets were stacked so that the capsule-coated surface of the upper sheet and the color developer-coated surface of the lower sheet faced each other, and a load of 600 kg/cm2 was applied. The density of the colored image was measured using a Macbeth reflection densitometer.

[0041] Further, the degree of size was measured by the Stekicht method according to JISP8122. Similarly to high-quality paper, 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/m2.

From Table 1, pressure-sensitive copying with excellent ink setting properties, sizing properties and coloring properties can be achieved by applying a surface sizing agent containing styrene in the copolymer at a weight ratio of 60% or less to the paper surface. It is clear that paper base paper can be obtained.

Example 2 A surface sizing agent with a weight ratio of styrene of 0.5 was used on paper made by hand in the same manner as in Example 1, and the amounts applied with a size press were 0.005 and 0.01. , 0.05, 0.1
Samples were prepared in the same manner as in Example 1, except that the smear amount was changed to 5 levels of 0.15 g/m2.

These samples were designated as sample 3-1, sample 3-2, sample 3-3, sample 3-4, and sample 3-5 in descending order of smear amount. The above results are summarized in Table 2.

[0045]

[Table 2]

As is clear from the table, if it is less than 0.01 g/m2, a sufficient effect of improving ink setting property cannot be obtained;
Even if the amount exceeds 0.1 g/m2, the ink setting property is hardly improved and it is uneconomical.

[0047]

[Effects of the Invention] From the above examples, it is clear that a 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, paper containing AKD or ASA. The base paper for pressure-sensitive copying paper has size,
It was found that the ink set properties and coloring properties were excellent.

Claims (3)

[Claims] Claim 1: In a pressure-sensitive copying paper containing calcium carbonate as a filler and an alkyl ketene dimer or alkenyl succinic anhydride as an internal sizing agent, the main component on the surface is a styrene-acrylic acid copolymer. A base paper for pressure-sensitive copying paper that is coated with a surface sizing agent. 2. The base paper for pressure-sensitive copying paper according to claim 1, wherein the weight ratio of styrene in the surface sizing agent obtained by copolymerizing a styrene monomer and an acrylic monomer is from 0.3 to 0.6. 3. The base paper for pressure-sensitive copying paper according to claim 1, wherein the amount of the surface sizing agent applied to the paper surface is in the range of 0.01 g/m 2 to 0.1 g/m 2 .