JPH0281664A - Pressure-sensitive copying paper - Google Patents

Abstract

PURPOSE:To obtain a paper support body having a required resistance to oil and improved catching efficiency of a dye by employing a paper support body which is sized at the surface thereof by a synthetic sizing agent which is a water-soluble polymer containing polycarbonic acid and/or its derivative as a monomer component and having the penetrating speed of diisopropylnaphthalene not higher than 35mm. CONSTITUTION:For polycarbonic acid and/or its derivative as a monomer component of a synthetic sizing agent, at least one of maleic anhydride, maleic acid and their partially esterified substance (A) is preferably employed. Diisopropylnaphthalene (referred to as an oil hereinafter) penetrates at the speed not higher than 35mm. If the penetrating speed of the oil exceeds 35mm, an oil moving in a paper support body cannot be sufficiently suppressed, causing insufficient catch of the dye. The above synthetic sizing agent is superior in water proof property. Therefore, the paper support body the surface of which is sized by the above synthetic sizing agent is effective to suppress the penetration of a color developing agent application liquid or capsule application liquid thereinside.

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to pressure-sensitive copying paper, and in particular, oil in microcapsules destroyed by undesired pressure migrates through the paper support to form a color developer. This invention relates to pressure-sensitive copying paper that effectively prevents the phenomenon of reaching the coated surface and causing unnecessary color development without reducing the color development ability.

"Prior Art" Pressure-sensitive copying paper is described in, for example, U.S. Pat. No. 2,711,375, U.S. Pat. These include "upper paper," which has a layer containing microcapsules containing an electron-donating dye on one side of base paper, and an electron-accepting compound (color developer) that develops color by contact with the electron-donating dye. ``Lower paper'' has a layer containing microcapsules on one side of the base paper and a layer containing a color developer on the other side. "Self-coloring paper" which is a layered or mixed layer of microfoble and a color developer is known, and these are used in appropriate combinations.

``Problems to be Solved by the Invention'' However, there is still room for improvement in practical aspects of these pressure-sensitive copying papers. For example, in medium-sized paper, the microcapsules are destroyed by unintentional bending, impact, etc., or by printing pressure during printing, and the oil containing the dye in the capsules migrates through the paper support, causing the color development on the opposite side. It may reach the surface to which the agent is applied, causing unnecessary color development and fogging. In addition, when printing a roll of paper, a large amount of the ink vehicle used in the solid printing area applied to the developer-coated surface migrates through the paper support and is slightly destroyed by the printing pressure. This may cause unnecessary coloring on other developer-coated surfaces that are in contact with the oil in the capsules, or the oil in the capsules may be slightly destroyed on the capsule-coated surface that has come into contact with the above-mentioned solid printing area. is extracted in the same way, causing unnecessary color development on the developer-coated surface on the opposite side of the paper support.

This phenomenon tends to occur when neutral paper is used as a paper support or when an organic color developer such as a polyvalent metal salt of an aromatic carboxylic acid is used as a color developer, and improvement is desirable. It is rare.

Therefore, by increasing the amount of binder in the capsule layer,
Methods of reducing the amount of coloring agent or oil have also been proposed, but these methods reduce the ability to develop color, so satisfactory results have not been obtained. In addition, methods of surface sizing paper supports with water-soluble polymers such as oxidized starch, polyvinyl alcohol, modified polyvinyl alcohol, and carboxymethyl cellulose have been used, but sufficient effects cannot be obtained even if the amount applied is considerably large. Therefore, it is not necessarily practical in terms of operability, cost, etc. Furthermore, JP-A-48-98913
No. 52-125019, etc., propose a method of treating a paper support with a specific fluorine compound.
Industrially, this is still not practical because the cost is too high. In addition, JP-A No. 58-220789 proposes a method using alkenylsuccinic acid or alkylsuccinic acid as an internal sizing agent, but the effect is not sufficient, especially when using neutral paper as a paper support. At present, when using this method, almost no practical effect is obtained.

In view of the current situation, the inventors of the present invention have conducted extensive research into improving the above-mentioned difficulties, and have found that the fogging and unnecessary coloring that occur in the inner paper, as well as the phenomena that are exacerbated by the printing ink vehicle, have been investigated. It was discovered that this is not simply due to the lack of oil resistance of the paper support, but is also greatly affected by the ability of the paper support to capture dyes contained in oil.

Based on this knowledge, and as a result of intensive research, it was found that surface sizing of a paper support with a synthetic sizing agent containing polycarboxylic acid and/or its derivatives as a monomer component and having a specific oil penetration rate can achieve the desired oil resistance. The present inventors have discovered that it is possible to obtain a paper support that has excellent properties and has significantly improved dye-trapping ability, leading to the completion of the present invention.

"Means for Solving the Problems" The present invention is a synthetic sizing agent which is a water-soluble polymer containing polycarboxylic acid and/or its derivative as a monomer component and has a diisopropylnaphthalene permeation rate of 35ff111 or less, and which is suitable for surface sizing. This is a pressure-sensitive copying paper characterized by using a paper support made of

"Effect" The permeation rate of diisopropylnaphthalene (hereinafter referred to as oil) as used in the present invention is measured by the following method.

That is, a 120 g/rdO size filter paper was immersed for 1 minute in a 10% diluted synthetic sizing agent solution (impregnated liquid 220 g/I±), dried in a hot air dryer at 105°C, and then cut into strips (151 m 1301m). The end of this strip is placed vertically in the oil, and after 30 minutes, the distance of oil penetration is measured and determined as the penetration rate.

The ability to capture the dye can be determined by coating a portion of the strip impregnated with a synthetic sizing agent with a solution of the color developer, and standing the end of the strip vertically in oil containing the dye, until the dye develops color. This is confirmed by measuring the distance traveled. In samples with dye capture ability, the dye migration distance is extremely short compared to the oil penetration rate.

The pressure-sensitive copying paper of the present invention is a water-soluble polymer containing polycarboxylic acid and/or its derivative as a monomer component, and has an oil penetration rate of 35% as measured by the above-mentioned method.
A synthetic sizing agent having a size of 1 mm or less is selectively used.

If the oil permeation speed exceeds 35 mm, the oil migration through the paper support cannot be sufficiently suppressed and the dye will not be captured sufficiently, making it impossible to obtain the desired effects of the present invention. In addition, synthetic sizing agents that do not contain polycarboxylic acids and/or their derivatives as monomer components have insufficient ability to capture dyes, and the dyes reach the surface coated with the color developer together with oil, causing unnecessary color development. It ends up.

Examples of polycarboxylic acids and/or derivatives thereof which are monomer components constituting the synthetic sizing agent include maleic anhydride, maleic acid, and partial esters thereof (A).
At least one of these is preferably used. In the pressure-sensitive copying paper of the present invention, a water-soluble copolymer obtained by copolymerizing these monomer components with diisobutylene (B) is particularly preferably used. Furthermore, a water-soluble copolymer obtained by copolymerizing an α-olefin CC) having 10 to 18 carbon atoms is also preferable, and specific examples of α-olefins having 10 to 18 carbon atoms include 1-dodecene, 1-pentadecene, etc. ,
Examples include 1-hexadecene, 1-octadecene, etc., but it may also be a mixture of α-olefins having 10 to 18 carbon atoms; A mixture or the like is preferably used.

Note that, if necessary, it is also possible to further copolymerize an ester of acrylic acid or methacrylic acid (D) to change other properties of the resulting synthetic sizing agent.

The preferred blending ratio of monomer components constituting the water-soluble copolymer is (A): (B): (C): (D)=
45-50: 20-50: 0-30: 0-10 mol%.

Among these monomer components, polycarboxylic acid and/or its derivatives have excellent dye capture performance and control dye migration, while diisobutylene and α-olefin are lipophilic and easily capture oil, so they It is presumed that it works to suppress the penetration rate.

The above-mentioned synthetic sizing agent used in the present invention also has excellent water resistance, and the paper support surface-sized with this agent suppresses penetration of the developer coating liquid and capsule coating liquid into the interior. . Therefore, a uniform color developer layer and capsule layer are formed, and as a result, a pressure-sensitive copying paper with high color density can be obtained. Moreover, since the paper support maintains a sufficient distance between the developer layer and the capsule layer in the case of medium paper, unnecessary colored stains can be more effectively prevented from occurring.

In the present invention, the method of sizing the synthetic sizing agent onto the surface of the paper support is not particularly limited, and various methods such as size press, gate roll, and spray may be appropriately selected and used. The amount of synthetic sizing agent applied was 0.01
~2.0g/rrf is preferable, and 0.01g/rd
If the amount is less than 2.0 g/+d, the effect of improving the oil resistance, dye trapping ability, and water resistance of the paper support will be insufficient, and if the amount exceeds 2.0 g/+d, it will be disadvantageous in terms of cost.

Synthetic sizing agents may be used alone, but if necessary, they may be used in combination with water-soluble polymers such as starch, polyvinyl alcohol, carboxymethyl cellulose, polyacrylamide, acrylic esters, pigments, and other auxiliary agents. Good too.

By the way, in general acidic paper, a combination of rosin and band is often used as an internal sizing agent, but because the amount of rosin and band added is large, it is possible to obtain a certain degree of oil resistance and dye capture ability even with the addition of rosin. However, it does not have sufficient performance as the paper support used in the present invention. Furthermore, in neutral paper, alkyl ketene dimers and the like are used as internal sizing agents, but these alkyl ketene dimers have strong lipophilic properties and tend to accelerate the transfer rate of oil. Moreover, calcium carbonate, especially heavy calcium carbonate, which is commonly used as a filler for acid-free paper, has a lower oil absorption and dye-trapping ability than talc. Compared to paper, it has a much stronger tendency to cause unnecessary coloring and fogging as described above. Therefore, the specific synthetic sizing agent of the present invention exhibits extremely remarkable effects on such neutral paper.

The thus obtained paper support is coated with a color developer coating liquid or a capsule coating liquid, and the color developer coating liquid generally contains an inorganic color developer such as acid clay, activated clay, attapulgide, etc. Various aliphatic carboxylic acids, benzoic acid, p-tert-butylbenzoic acid, phthalic acid, gallic acid, salicylic acid, 3-isopropylsalicylic acid, 3-phenylsalicylic acid, 3-cyclohexylsalicylic acid, 3.5-di-tert-butyl Salicylic acid, 3-methyl-benzyl salicylic acid, 3-phenyl-5-(α,α-dimethylbenzyl) salicylic acid,
Aromatic carboxylic acids such as 3,5-di(α-methylbenzyl)salicylic acid and 2-hydroxy-nibenzyl-3-naphthoic acid, p-phenylphenol-formalin resin,
Organic color developers such as phenolic resins such as p-butylphenol-acetylene resin, and salts of these organic color developers with polyvalent metals such as zinc, magnesium, aluminum, calcium, titanium, manganese, tin, and nickel. It is prepared by dispersing various color developers such as in a binder.

In addition, examples of the binder include starch, cellulose, proteins, gum arabic, polyvinyl alcohol,
Styrene-maleic anhydride n-co-m combination salts, styrene-butadiene copolymer emulsion, vinyl acetate-maleic anhydride copolymer salts, polyacrylates, and the like are appropriately selected and used. In addition, various auxiliary agents such as pigments, dyes, water-resistant agents, water-retaining agents, and antifoaming agents are also appropriately selected and blended as needed.

Capsule coating liquids are generally made by mixing basic dyes such as triarylmethane lactones, spiropyrans, fluorans, diphenylmethanes, and azines with alkylated naphthalenes, alkylated diphenyls, alkylated diphenylmethanes, alkylated terphenyls, etc. It is dissolved in a solvent consisting of synthetic oil, cotton oil, vegetable oil such as castor oil, animal oil, mineral oil, or a mixture thereof, and then subjected to various encapsulation methods such as coacervation method, interfacial polymerization method, and 1n-situ method. It is prepared by including it in microcapsules and dispersing it in a binder. Of course, a stilt agent and various other auxiliary agents can be added as appropriate.

For pressure-sensitive copying paper, see, for example, U.S. Pat. No. 2,505.
No. 470, No. 2,505,471, No. 2,505,4
No. 89, No. 2.548,366, No. 2,712,50
No. 7, No. 2,730.456, No. 2,730,457
No. 3,418,250, No. 3,924.027, No. 4,010,038, etc.
There are various forms of pressure-sensitive copying paper, and the present invention can be applied to these various forms of pressure-sensitive copying paper.

"Example" The present invention will be described in more detail with reference to Examples below, but it is of course not limited to these. Further, "parts" and "%" in the examples indicate "parts by weight" and "% by weight", respectively, unless otherwise specified.

Example 1 Canadian Standard Freeness 450cc NB
A paper stock prepared by adding 5 parts of talc, 1 part of rosin size, and 3 parts of sulfuric acid per pulp to a valve slurry of 20 parts of KP and 80 parts of LBKP was made into a paper stock of 40 g/m on a Fourdrinier paper machine.
Acidic paper is made so that RD is obtained, and using a size press, various synthetic sizing agents 1 to 4 listed in Table 1 are used in combination with oxidized starch, so that the adhesion amount of the synthetic sizing agent is 0.02 g/solid content.
n? The surface was sized so that the amount of oxidized starch attached was 1.5 g/rrr in terms of solid content.

Example 2 Canadian Standard Freeness 450cc NB
To the pulp slurry of 20 parts of KP and 80 parts of LBKP, 5 parts of heavy calcium carbonate, 0.1 part of alkyl ketene dimer sizing agent, 0.5 part of cationic starch,
A paper stock to which 0.02 part of a cationic retention aid has been added is made into neutral paper using a Fourdrinier paper machine to give a paper weight of 40 g/d, and then using a size press to form papers 1 to 4 listed in Table 1. Using various synthetic sizing agents in combination with oxidized starch, surface sizing is performed so that the amount of synthetic sizing agent adhered is 0.2 g/cd in solid content, and the amount of oxidized starch adhered is 1.5 g/rd in solid content. did.

Comparative Example 1 As the synthetic sizing agent, various synthetic sizing agents 5 to 7 listed in Table 1 were used, or oxidized starch 8 was used instead of the synthetic sizing agent, but in the same manner as in Example 1, The surface sizing was carried out in the same manner as in Example 1 on acidic paper of 40 g 1rd square meter.

Comparative Example 2 As the synthetic sizing agent, various synthetic sizing agents 5 to 7 listed in Table 1 were used, or oxidized starch 8 was used instead of the synthetic sizing agent, but in the same manner as in Example 2, The same 40 g/rd neutral paper as in Example 2 was subjected to surface sizing in the same manner.

Table 1 (Note) Penetration rate The penetration rate of Nioil is shown. (Tsuru) Capture ability Indicates the capture ability of crab dye. (1 m) The developer coating liquid and capsule coating liquid shown below were applied to the paper support with the 16 types of surface sizing obtained in this way, and the coating amount after drying with an air knife coater was 5 g/n? and 4g/rd
A middle leaf paper was obtained by smearing it so that it became .

[Developer coating liquid]

65 parts of aluminum hydroxide, 20 parts of zinc oxide, 3.5-
Mixture of zinc di(α-methylbenzyl)salicylate and α-methylstyrene/styrene copolymer (melt ratio 80/
20) Add 20 parts (solid content) of carboxy-modified styrene-butadiene copolymer latex to a dispersion obtained by milling 15 parts of polyvinyl alcohol aqueous solution (solid content) and 300 parts of water in a ball mill for 24 hours. A color coating solution was prepared.

C capsule coating liquid] 112.5 parts of water is added to 37.5 parts of a 20% aqueous solution of a copolymer consisting of 15 mol% vinyl sulfonic acid, 5 mol% styrene, 70 mol% acrylic acid, and 1θ mol% ethyl acrylate.
20% aqueous sodium hydroxide solution to adjust the pH to 4.6, which was used as an aqueous medium for capsule production. to this,
Add 105 parts of diisopropylnaphthalene (trade name: K-113, manufactured by Kureha Chemical Co., Ltd.) in which 5 parts of crystal violet lactone has been dissolved and emulsify and disperse the mixture so that the average particle size becomes 5 μm, and then reduce the temperature of the emulsion to 70°C. The temperature rose to .

Next, the methylated methylolmelamine initial condensate (
Add 20 parts of Beckamine APM (trade name: 80% concentration, manufactured by Dainippon Ink Chemical Co., Ltd.), maintain the temperature of the system at 70°C for 1 hour while continuing to stir, and then cool to obtain a milky white capsule dispersion. Ta. A capsule coating solution was prepared by adding 70 parts of wheat starch and 20 parts of dissolved oxidized starch (solid content) to this capsule dispersion.

The performance comparison tests described below were conducted on the 16 types of medium paper thus obtained, and the results are listed in Table 2.

[Color development test] Layer two sheets of inner paper so that the capsule coated side and the color developer coated side face each other, and measure the density of the colored image formed by applying a load of 600 kg/c (Macbeth densitometer). (RD-
914 model, visual filter).

[Print color stain test]

Business form printing machine (Mei Seisakusho, 17Bll)
Then, printing was performed on the developer-coated side of the inner leaf paper using the wet offset printing method, and a 300ζ-thick roll was obtained.

After the printed roll was left at 50° C. for 3 days, the state of dirt on the developer-coated surface at about 100 g from the core was visually determined.

〔Evaluation criteria〕

◎ is hardly dirty (colored).

△ Slightly dirty (colored).

× It is extremely dirty (colored).

[Dry color stain test]

Place a piece of high-quality paper on the developer-coated side of the inner leaf paper, print the type using an electric typewriter, sandwich it between polyester films, leave it at 100℃ for 2 days, and apply the developer. Visual judgment was made based on the degree of coloration of the printed portion on the surface.

〔Evaluation criteria〕

◎ is hardly dirty (colored).

△ Slightly dirty (colored).

X: Extremely dirty (colored).

Table 2 As is clear from the results in Tables 1 and 2, the pressure-sensitive copying paper obtained in the examples of the present invention has improved coloring ability and coloring stain in an extremely well-balanced manner, and has excellent handling properties and Printability was also good.

Patent applicant: Kanzaki Paper Co., Ltd. [Result J

Claims (3)

[Claims] (1) Use of a surface-sized paper support with a synthetic sizing agent that is a water-soluble polymer containing polycarboxylic acid and/or its derivatives as a monomer component and has a diisopropylnaphthalene penetration rate of 35 mm or less. Features pressure-sensitive copying paper. (2) The pressure-sensitive copying paper according to claim (1), wherein the synthetic sizing agent is a water-soluble polymer containing at least one of maleic anhydride, maleic acid, or a partial ester thereof and diisobutylene as monomer components. . (3) The pressure-sensitive copying paper according to claim (2), wherein the synthetic sizing agent is a water-soluble polymer further containing an α-olefin having 10 to 18 carbon atoms as a monomer component.