JPS6366677B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing clay paper for pressure-sensitive copying paper, which improves discoloration or fading of copied images. Pressure-sensitive copying paper that utilizes a coloring reaction between an electron-donating coloring agent and an electron-accepting clay is already well known. As the clay used for this pressure-sensitive copying paper, for example, acid clay, activated clay, attapulgite, zeolite, bentonite, etc. are introduced in many literatures. However, with clay paper made from these clays, reproduced images change color or fade over time, and furthermore, the activity of the clay paper decreases when it comes into contact with the atmosphere, resulting in a deterioration of its suitability for copying. There are drawbacks. The present invention aims to improve this drawback of clay paper. A prior art technique for improving clay paper involves adding a water-dispersible emulsion of an oily substance to a water-dispersible coating liquid (hereinafter referred to as "coating liquid") made of clay and a binder. (Special Publication No. 46-13165).
According to this method, it is said that the reduction in the activity of clay paper and the discoloration or fading of copied images can be improved, but as the amount of water-dispersible emulsion of oily substance added is increased, part of the emulsion is gradually broken down. This causes giant oil droplets to form, which tends to cause a phenomenon of partial repellency (generally referred to as "bird's eye" or "flash eye") when the coating liquid is applied to the base paper. The problem arises that the appearance and suitability of copying are seriously impaired. Therefore, in the method of the prior art, the amount of water-dispersible emulsion of oil-based substance added to the coating liquid is 10% of the clay.
There is a practical restriction that it must be kept within. Therefore, there is a problem in that the effects are not always sufficient, especially with regard to discoloration or fading of the copied images. Therefore, the present inventors investigated a method of adding more oil-based substances to the coating solution without causing the repelling phenomenon, and found that if the oil-based substances were added in microcapsule form, it would be possible to add 10% of the oil-based substances to the clay. It was confirmed that the repelling phenomenon did not occur even if the amount was added in excess of the above amount, resulting in the present invention. The structure of the present invention is a clay paper manufacturing method in which an oily substance is contained in a water-dispersible coating liquid mainly composed of electron-accepting clay and an adhesive. This is a method for producing clay paper for pressure-sensitive copying paper, which is characterized by incorporating the clay paper into a dispersible coating liquid. With this configuration, the oily substance exists in the form of being included in individual microcapsules, so that it can be dispersed in the coating liquid without coalescing with each other. Therefore, the amount of oily substance added to the coating solution can be freely selected as required, even if it exceeds 10% of the clay. In the structure of the present invention, the oily substances that are liquid at room temperature include vegetable oils, animal oils, mineral oils, and synthetic oils. Incidentally, vegetable oils include olive oil, castor oil, cottonseed oil, lemon oil, and corn oil; animal oils include fish oil and whale oil; mineral oils include various paraffin oils, kerosene, and petroleum naphtha; and synthetic oils include alkylated oils. Biphenyl, alkylated terphenyl, alkylated naphthalene, diarylethane, triarylmethane, diphenylalkane, di-n-butyl adipate, di-adipate
Examples include octyl, di-n-butyl phthalate, dioctyl phthalate, tricresyl phosphate, silicone oil, fluorine oil, and oligomers with a molecular weight of 5000 or less such as polybutene, polybutadiene, and polypentadiene. The microencapsulation method for this oil-based substance includes the coacervation method, interfacial polymerization method, in-situ polymerization method, which is already known in the field of pressure-sensitive copying paper, etc.
Any method may be used. As the wall material for the microcapsules, known materials can be used, but among them, urea-formalin resin capsules and melamine-formalin resin capsules allow the capsule dispersion to be adjusted to a high concentration, and the membrane material is inexpensive. This is particularly preferable. Regarding the particle size of microcapsules and the thickness of the wall film, it is not possible to specify them uniformly because the film strength varies depending on the film forming material used, but it is possible to apply a clay coating liquid containing microcapsules to base paper. death,
Ideally, the material should be of such a degree that it can be easily destroyed by super calendering after drying or by copying pressure. The amount of microcapsules to be added to the clay coating liquid should be in an appropriate amount considering that the main substance forming the copied image is clay, and should be in the range of 1 to 50 parts by weight per 100 parts by weight of viscosity. most preferably between 10 and 20 parts by weight. Incidentally 1
If the amount is less than 50 parts by weight, the desired effect will be poor;
If the amount is more than 1 part by weight, the absolute amount of clay, which is the main color forming agent, decreases, so that the copyability tends to deteriorate. In addition, in the structure of the present invention, the microcapsules added to the clay coating liquid contain only an oil-based substance and do not contain an electron-donating coloring agent, which is different from so-called single coloring paper. Furthermore, in the present invention, in order to improve various properties of the clay coating liquid such as whiteness, color development, and physical properties of the coating liquid,
Inorganic materials such as oxides, hydroxides, carbonates, silicates, formates, acetates, phosphates, nitrates, sulfates, and halogen salts of aluminum, cobalt, nickel, titanium, magnesium, and calcium. It is also possible to use them together, and when dispersing these inorganic pigments and the above-mentioned clays, the dispersibility can be improved by using a suitable pigment dispersant such as polyphosphate or sodium polyacrylate. You can get good paint. Furthermore, in the present invention, phenolic compounds, phenolic resins, aromatic carboxylic acids and other electron-accepting substances such as polyvalent metal salts thereof, ultraviolet absorbers, fluorescent whitening agents, and oxidizing agents are added to the clay coating solution. Inhibitors and the like can also be included. In addition, as the adhesive constituting the clay coating liquid in the structure of the present invention, styrene-butadiene latex,
The target materials include latexes such as acrylic ester copolymer latex, vinyl acetate latex, and vinyl acetate-acrylic ester copolymer latex, and water-soluble polymers such as polyvinyl alcohol, starch, casein, and sodium acrylate. The clay coating solution thus obtained is applied to base paper by any known coating method, such as coating with an air knife coater, roll coater, blade coater, size press coater, curtain coater, bill blade coater, or by spot printing with a printing machine. It will be applied. In addition, this clay coating liquid can be finished not only as clay paper, but also as middle paper (also called CFB paper).
It is also possible to use it in combination with other microcapsules containing a dissolved color former to create a single colored paper. Therefore, the clay paper for pressure-sensitive copying obtained from the structure of the present invention can significantly increase the content of an oily substance compared to the prior art in which a water-dispersible emulsion of an oily substance is added to a clay coating liquid. As a result, the effect of preventing discoloration or fading of copied images can be significantly improved, and the activity ability of clay paper can also be improved, so that the effect of improving copying suitability can also be obtained. The present invention will be explained in more detail with reference to examples below, but it is of course not limited thereto. still,
In the examples, "parts" and "%" indicate "parts by weight" and "% by weight," respectively. Example 1 A 10% EMA-31 (ethylene-maleic anhydride copolymer, manufactured by Monsanto Chemical Co., Ltd.) aqueous solution was added to an aqueous solution in which 10 parts of urea and 1 part of resorcin were dissolved in 200 parts of water.
After adding 100 parts, adjust the pH to around 3.4 with a 20% caustic soda aqueous solution. Add 300 parts of liquid paraffin to this, and use a homomixer to reduce the average particle size.
It was emulsified to a thickness of 7.0μ. Next, 25 parts of a 37% formaldehyde aqueous solution was added to this system, and the temperature was raised to 75° C. with stirring, and the mixture was stirred under these conditions for 3 hours to prepare a capsule dispersion. Next, 6 parts of polyphosphate and 2700 parts of active whiteness were added to 9000 parts of water and dispersed under strong stirring.A 20% aqueous sodium hydroxide solution was added to adjust the pH of the system to 9.5. Liquid paraffin-containing microcapsules were added to this, and styrene-butadiene copolymer latex (solid content) was added.
50%) was added and mixed with stirring to obtain a paint.
This paint was coated on one side of base paper with a dry weight of 5 g/m ² using an air knife coater to obtain a colored paper ^. Example 2 A 5% aqueous solution with a pH of 5 prepared by dissolving Scriptset 520 (styrene maleic anhydride copolymer, manufactured by Monsanto) with a small amount of sodium hydroxide.
Add 300 parts of polybutene oligomer (LV-50 manufactured by Nippon Petrochemicals Co., Ltd.) to 100 parts and emulsify it to determine the average particle size.
It was set to 9.8μ. Next, 10 parts of melamine and 25 parts of a 37% formalin aqueous solution were added to 65 parts of water, the pH was adjusted to 9 with sodium hydroxide, and the emulsion was added to the melamine-formalin initial condensate obtained by heating at 80 ° C. for 15 minutes. Thereafter, the mixture was stirred for 1 hour at a liquid temperature of 75°C to obtain a capsule dispersion. Then add 6 polyphosphates to 4500 parts of water.
300 parts of calcium carbonate, 300 parts of zinc oxide, and 2100 parts of active whiteness were added to the system and dispersed with strong stirring to give a 20%
Add potassium hydroxide aqueous solution to bring the pH of the system to 9.0.
Then, the above polybutadiene oligomer-containing microcapsules were added thereto, and 900 parts of styrene-butadiene copolymer latex was further added and mixed with stirring to obtain a paint. Next, this paint was applied to one side of a base paper having a basis weight of 40 g/m ² using a blade coater to give a dry weight of 5 g/m ² to obtain colored paper. Example 3 150 parts of liquid paraffin and 150 parts of alkylnaphthalene in 600 parts of 2% polyvinyl alcohol aqueous solution
After emulsifying by adding a mixture of 30 parts of ethyl acetate, 6 parts of aliphatic polyvalent isocyanate (Sumitomo-Bayer TPL-2291) to give an average particle size of 9.0, the system was heated at 80°C. A capsule dispersion was obtained by reacting for 4 hours. Next, colored paper was obtained in exactly the same manner as in Example 1 except that this capsule dispersion was used. Example 4 300 parts of liquid paraffin was added to 300 parts of a 5% aqueous solution of acid-treated gelatin having an isoelectric point of 8.0 and emulsified at 50°C to give an average particle size of 10 μm. Next, 1000 parts of a 0.15% aqueous solution of carboxymethyl cellulose (average degree of polymerization 160, degree of substitution 0.6) at 50°C was added to this system under strong stirring, and after adjusting the pH to 5.0 with a 5% aqueous sodium hydroxide solution, the liquid The temperature was cooled to 10°C. Further, 2 parts of a 50% aqueous solution of glutaraldehyde and a 5% aqueous sodium hydroxide solution were added to this system to adjust the pH of the system to 7.0, and stirring was continued for 8 hours to complete the hardening of the capsules. Next, colored paper was obtained in exactly the same manner as in Example 1 except that this capsule dispersion was used. Comparative Example 1 6 parts of polyphosphate and 3000 parts of activated clay were added to 9000 parts of water and dispersed under strong stirring. 20% sodium hydroxide was added to bring the pH of the system to 9.5, and then styrene-butadiene was added. Add 900 parts of polymerized latex,
Got the paint. This paint was coated on one side of base paper with a dry weight of 5 g/m ² using an air knife coater to obtain a colored paper ^. Comparative Example 2 Add liquid paraffin to 300 parts of 3% EMA-31 aqueous solution
Add 300 parts and use a homomixer to reduce the average particle size.
It was emulsified to a thickness of 7.0μ. Next, 9000 parts of water, 6 parts of polyphosphate, and 2700 parts of activated clay.
20% sodium hydroxide aqueous solution was added to the dispersed system under strong stirring to adjust the pH of the system to 9.5, and the liquid paraffin emulsion described above was added thereto, followed by a styrene-butadiene copolymer latex.
900 parts were added and mixed with stirring to obtain a paint. Apply this paint to one side of base paper with a dry weight of 40g/ ^m2 .
A colored paper was obtained by coating with an air knife coater to give a coating weight of g/m ² . Comparative Example 3 300 parts of polybutene oligomer was added to 300 parts of a 2.0% aqueous solution of PH5 prepared by dissolving Scriptset 520 with a small amount of sodium hydroxide and emulsified.
The average particle size was set to 9.0, and then 6 parts of polyphosphate, 300 parts of calcium carbonate, 300 parts of zinc chloride, and 2100 parts of activated clay were added to 4500 parts of water and dispersed with strong stirring.
Adjust the pH of the system by adding % potassium hydroxide aqueous solution.
9.0, the above-mentioned polybutadiene oligomer emulsion was added thereto, and 900 parts of styrene-butadiene copolymer latex was further stirred and mixed to obtain a paint. Next, this paint was applied to one side of a base paper having a basis weight of 40 g/m ² using a blade coater to give a dry weight of 5 g/m ² to obtain colored paper. Comparative Example 4 A mixed solution of 150 parts of liquid paraffin and 150 parts of alkylnaphthalene was added to 600 parts of a 2% aqueous polyvinyl alcohol solution to obtain an emulsion with an average particle size of 9.0.
Next, colored paper was obtained in exactly the same manner as in Comparative Example 2 except that this emulsion was used. Preparation of standard top paper Preparation of standard capsule coated paper (standard top paper) 1000 parts of alkylnaphthalene at 60℃ containing 30 parts of crystal violet lactone and 10 parts of benzoyl leucomethylene blue was added to 10% of acid-treated gelatin with an isoelectric point of 8.0. It was emulsified in 2000 parts of an aqueous solution using a homomixer so that the average particle size was 3.0μ. Next, 4900 parts of 5.5℃ warm water and 5%
Add 50 parts of aqueous sodium hydroxide solution, add the above emulsified dispersion to this liquid, and while stirring at 100 rpm, add 400 parts of a 5% aqueous solution of carboxymethylcellulose (average degree of polymerization 160, degree of substitution 0.6). Ta. Next, while maintaining the liquid temperature at 50°C, 5% acetic acid aqueous solution was added dropwise to adjust the pH of the system to 5.2.
While stirring, the liquid temperature was continuously lowered to 10°C with a cooling temperature gradient of -1°C/3 minutes. When the liquid temperature drops to 10℃, switch to strong stirring, add 30 parts of a 50% aqueous solution of glutaraldehyde and 5% aqueous sodium hydroxide solution to the system.
The pH was adjusted to 8.0, and stirring was continued for 3 hours to complete the hardening of the capsules. The capsules thus obtained had an average particle size of 9.0μ. Next, 300 parts of pulp powder and 2000 parts of a 10% starch aqueous solution were added to the capsule dispersion thus obtained to obtain a capsule coating liquid, and the coating liquid was applied to one side of a 40 g/m ² base paper with a dry weight of 4 g/m2. It was coated with an air knife coater to give a standard paper size of m ² . Performance Comparison Test (a) The capsule surface of the standard paper and the coated surface of the colored paper obtained in each Example and Comparative Example were placed one on top of the other so that they faced each other, and a pressure of 160 kg/cm ² was applied using a press to create a colored image. I got it. Next, this colored paper was left in a room away from direct sunlight for 24 hours, and the color change and deterioration of the density of the colored image were visually observed. (b) The capsule surface of the standard paper and the coated surface of the colored paper obtained in each Example and Comparative Example were stacked so as to face each other, and a pressure of 160 kg/cm ² was applied using a press to obtain a colored image. Observe this colored area and notice if the applied surface is partially repelled (birth eye or fissure).
Visual observation was made to see if there were any uncolored areas. The results of the above performance test were as follows.

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Claims (1)

[Claims] 1. In a clay paper manufacturing method in which an oily substance is contained in a water-dispersible coating liquid mainly composed of electron-accepting clay and an adhesive, an oily substance that is liquid at room temperature is microencapsulated and contained in the water-dispersible coating liquid. A method for producing clay paper for pressure-sensitive copying paper, characterized by: