JPH07216785A - Neutral base paper for pressure sensitive paper - Google Patents

Abstract

PURPOSE:To provide neutral base paper for pressure sensitive paper having little migration of a desensitizing ink even when preserved for a long period of time. CONSTITUTION:Neutral base paper for pressure sensitive paper having >=20-sec. Gurley air permeability made by coating base paper of pressure sensitive paper with surface size starch to >=0.5g/m<2> using an emulsion type neutral sizing agent as an interior sizing agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a neutral base paper for pressure-sensitive copying paper. More specifically, a neutral rosin sizing agent is used as an internal sizing agent, and by combination with the coating amount of the surface sizing agent of the base paper, the transfer of the desensitizing ink to the base paper is prevented, and the phenomenon of color deterioration during long-term storage is prevented. The present invention relates to a base paper for neutral pressure-sensitive copying paper which prevents

[0002]

2. Description of the Related Art It has been known for a long time that a color image can be obtained by a contact reaction between an electron-donating, almost colorless organic compound (hereinafter referred to as a color former) and an electron-accepting compound (hereinafter referred to as a color developer). ing. Pressure-sensitive copying papers that specifically utilize this phenomenon are disclosed, for example, in U.S. Pat. Nos. 2,71,375 and 2,730,457, and JP-B-47-20972.
It is described in Japanese Patent Publication and is widely put into practical use. These are a paper on which a layer containing microcapsules containing an electrophilic dye is formed on one side of a support, a layer containing an electron-accepting compound (developing agent) that develops a color by contacting with an electron-donating dye. The lower paper on which the microcapsules are formed, the support is coated with a layer containing microcapsules on one side, and the other surface is formed with a layer containing the color developer, and the microcapsules and the developer are coated on the same surface of the support. Laminated or mixed self-coloring paper is known,
They are used in appropriate combinations.

The coating solution for the color-developing layer for making middle-use and lower-quality papers is generally alkaline, but when the pH of the coating base paper is low, the coating layer pH of the color-developing layer is lowered and the color developability is lowered. Therefore, a pressure-sensitive copying paper using a reactive neutral sizing agent such as an alkyl ketene dimer or alkenyl succinic anhydride as a base paper or a neutral paper containing calcium carbonate internally (for example, Japanese Patent Publication No. 52-6645). , Using a base paper made by a sizing method so as to obtain an extraction pH close to neutrality (for example, JP-A-52-86807), and providing a layer containing an alkaline substance between the developer and the base paper. Tamono (Japanese Patent Publication Sho 52
No. 29649) is known. Furthermore, it is also known to use a calcium carbonate pigment having a specific oil absorption amount in the developer layer in order to prevent stains due to transfer of the desensitizing ink, which is excellent in color development (Japanese Patent Laid-Open No. 4-193581). ).

However, these pressure-sensitive copying papers still have room for improvement in practical use. For example, desensitizing printing with desensitizing ink on areas where color development is not required on the surface coated with the developer, and leaving it for a long time, the desensitizing ink migrates through the base paper, and areas where color development is required occur. The solution to the phenomenon of desensitization is still insufficient.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems by using a neutral rosin sizing agent as an internal sizing agent and combining the amount of the surface sizing agent with the coating amount of the surface sizing agent to form a color with a desensitizing ink. It is an object of the present invention to provide a base paper for pressure-sensitive copying paper in which the phenomenon of insufficient color development at a portion is improved.

[0006]

According to the present invention, as a neutral base paper for pressure-sensitive copying paper, an emulsion type neutral rosin sizing agent is contained as an internal sizing agent, and a surface sized starch is used.
These problems are solved by applying 5 g / m ² or more and setting the Gurley air permeability to 20 sec or more.

The neutral sizing agent used in the present invention has a pH of 6
-9 is an emulsion type rosin sizing agent which is emulsified with various surfactants or water-soluble polymers used in the neutral region. Here, as the rosin substance, gum rosin, wood rosin, tall oil rosin, hydrogenated rosin, disproportionated rosin, polymerized rosin, aldehyde-modified rosin, rosin ester and other rosins, and further rosins and acrylic acid, maleic anhydride. Acid, fumaric acid, it can be exemplified heating reaction product with α, β-unsaturated carboxylic acid such as itaconic acid, polymerization is performed for the purpose of suppressing elution of rosin substance in the neutral region, insolubilization treatment such as water resistance is performed. I can do things. Specifically, the amount of the neutral rosin sizing agent added is 1.0 to 10.0 parts, preferably 3.0 to 7.
The desired result can be obtained by using 0 part.

Regarding the ionicity of the neutral rosin sizing agent, it is possible to select anionic or cationic depending on various surfactants or water-soluble polymers used during emulsification, but the present invention does not matter.

The above-mentioned neutral rosin sizing agent is used for the neutral base paper in the present invention, and other additives such as a defoaming agent,
A slime control agent, a dye, a dry paper strength enhancer, a wet paper strength enhancer, a size fixing agent, a drainage improver, a retention improver and the like can be contained as necessary.

Further, for the purpose of expressing the sizing property of the neutral rosin sizing agent, a polymetal compound of aluminum (for example, a sulfuric acid band, polyaluminum chloride, polyaluminum silicate sulfite, sodium aluminate, etc.)
Needless to say,

The filler used in the present invention includes heavy calcium carbonate, precipitated calcium carbonate, talc, kaolin,
It is possible to use general inorganic pigments such as titanium dioxide,
Two or more of these may be used in combination. Further, these fillers are usually added in an amount of 4 to 17% by weight, preferably 6 to 12% by weight, based on 100 parts by weight of pulp.

Examples of the size press liquid applied to the surface of the neutral raw paper of the present invention include oxidized starch, urea-phosphoric acid esterified starch, and autothermal chemical modified starch, but the kind of starch is not particularly limited. These coating amount preferably used in 0.9~5.0g / m ² at 0.5 g / m ² or more, 0.5
When it is less than g / m ² , the barrier effect due to the surface size is small and the desensitizing ink is more likely to come off. Also 5.0g / m
^{When it is 2} or more, the physical properties are not significantly negative, but the papermaking speed is lowered due to an increase in the drying load. Moreover, since the amount of adhesion is large above all, the cost is increased.

Under the above conditions, the Gurley air permeability of the surface-treated neutral base paper is required to be 20 seconds or more in order to prevent the desensitizing ink from coming off. In addition to increasing the surface size, the degree of freeness of the pulp can be reduced to 20 seconds or more by lowering the freeness of pulp or increasing the density by calendering, and these may be used in combination.

[0014]

As described above, in the pressure-sensitive copying paper using the neutral base paper of the present invention, the movement of the desensitizing ink in the base paper is a problem. By using the agent, the amount of adhesion on the surface size press is set to 0.5 g / m ² or more, and the Gurley air permeability is maintained for 20 seconds or more, so that the movement of the desensitizing ink in the base paper can be reduced.

[0015]

The present invention will be described in detail below with reference to examples of the present invention, but the present invention is not limited to these examples.
The parts and% in the examples are parts by weight and% by weight, respectively, unless otherwise specified.

Example 1 LBKP 100 wt% (csf 350 ml), internal addition size (neutral rosin size Harima Kasei Neu Size 7)
70) was mixed with 5.0% by weight to 100% by weight of pulp, and talc and calcium carbonate as a filler were mixed in a ratio of 7: 3, and added so that the ash content in the paper was 8% by weight.
A neutral base paper of g / m2 was obtained. Next, a surface size starch (MS-3800 manufactured by Nippon Shokuhin Kako Co., Ltd.) was applied by a size press so that the surface size starch would be 2.8 g / m ² . Table 1 shows the results of measuring the air permeability of the obtained neutral base paper with a Gurley air permeability tester.

Example 2 The procedure of Example 1 was repeated, except that the surface-sized starch was applied at a size of 3.5 g / m ² .

Example 3 The procedure of Example 1 was repeated, except that the surface-sized starch was applied in a size press at 0.9 g / m ² .

Example 4 The same procedure as in Example 1 was carried out except that the surface-sized starch was coated at a size of 0.5 g / m ² .

Example 5 The same procedure as in Example 1 was carried out with the internally added size being 3.0% by weight.

Example 6 The same procedure as in Example 1 was carried out with the internally added size being 7.0% by weight.

Comparative Example 1 The procedure of Example 1 was repeated, except that the surface-sized starch was coated at a size of 0.3 g / m ² .

Comparative Example 2 The procedure of Example 1 was repeated, except that the surface-sized starch was applied by a size press to a concentration of 0.1 g / m ² .

Comparative Example 3 The procedure of Example 1 was repeated, except that the freeness of LBKP was 350 → 420 ml and that the surface size starch was 0.3 g / m ² by a size press.

Comparative Example 4 The procedure of Example 1 was repeated, except that the freeness of LBKP was 350 → 500 ml, and the surface-sized starch was coated with a size press at 0.6 g / m ² .

The following color developer coating solutions were applied to the neutral base papers of Examples 1 to 3 and Comparative Examples 1 to 4 so as to have a concentration of 3 g / m ² to obtain lower sheets. (A) 25% developer pulverizing liquid The following mixed liquid was pulverized with a ball mill so that the average particle diameter was 3 μm.・ 3,5 di (4-methylbenzyl) -salicylic acid resin zinc 100 parts ・ 10% polyvinyl alcohol aqueous solution 50 parts ・ Additional water 250 parts (B) Developer coating liquid ・ Kaolin (JM Huber's Hydrasperse) ) 40 parts-Calcium carbonate (ECC, Carbital-90) 60 parts-10% sodium hexametaphosphate aqueous solution 5 parts- (A) 25% developer grinding liquid 60 parts-10% starch aqueous solution ( Nippon Food Processing Co., Ltd., MS-3800) 100 parts 48% styrene butadiene latex (Asahi Dow, L-620) 20 parts Additive water 50 parts

For each sample obtained as described above,
The following residual rate test was conducted in order to evaluate the desensitizing ink removal. The results are shown together as a mark. Residual rate test due to loss of desensitizing ink: The amount of desensitizing ink (Desensitizing ink for Mitsubishi offset (TO-1A) for Mitsubishi offset) deposited on the surface of the lower paper coated with the developer is 3.0 g / m. ^2. Print the bottom paper without desensitization printing on both sides, apply a weight of 10 kg, leave it in a dryer at 60 ° C for 3 days, and expose the bottom paper without the desensitization ink printed. The colorant coated surface is overlaid with the capsule coated surface of the upper paper, and a pressure of 100 kg / cm ² is applied with a calendar so that the density of the color image is Z-.
It was measured with a Σ80 densitometer (manufactured by Nippon Denshoku Co., Ltd.). At the same time, the untested lower paper was also put in a drier and calendered to measure the density of the color image.

[0028]

## EQU1 ## Residual rate = (100-I5 / I6) / (100-
I3 / I4) × 100 I3: Colored image density of processed paper I4: Undeveloped color density of 3 days left I5: Untested colored image density of lower paper I6: Untested lower paper uncolored density

[0029]

[Table 1]

In the table, the degree of color development: the smaller the value, the less the decrease in color density. Omission of desensitizing ink: The higher the value, the less omission. Usage judgment: A grade of Δ or above is passed. ×: Unusable, × to △: Unusable, △: Limited use, ○
Above: Available

[0031]

INDUSTRIAL APPLICABILITY The present invention uses a neutral rosin sizing agent as an internally added sizing agent and has a surface size coating amount of 0.5 g.
By setting the Gurley air permeability to 20 sec or more at / m ² or more, it is possible to obtain a base paper for pressure-sensitive copying paper in which the transfer of the desensitizing ink to the base paper is small even when the desensitizing ink is applied and stored for a long time.

Claims (1)

[Claims] 1. An internal sizing agent containing an emulsion type neutral rosin sizing agent, and surface-sized starch of 0.5 g / m ² or more is applied, and the Gurley air permeability is 20 sec.
The above is the neutral base paper for pressure-sensitive copying paper, which is characterized by the above.