JPS6225799B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides microcapsule-containing paper which is produced by making paper using one or more types of microcapsules together with papermaking fibers in a multi-cylindrical cylinder paper machine that uses two or more cylinder meshes and two or more plow tanks. In particular, the present invention relates to a method for producing microcapsule-containing paper, characterized in that the microcapsules contain a liquid core substance and have a melamine-formaldehyde polycondensation resin as a membrane material. Conventionally, known methods for producing paper containing microcapsules include fixing them with cellulose fibers during the papermaking process and making paper using a fourdrinier machine under normal conditions, or using a so-called wet-end papermaking method. Methods include adding capsules alone or a cellulose fiber slurry containing capsules to paper. Regarding the encapsulation method of microcapsules used for these and the manufacturing method of capsule-containing paper, see the example of urea-formalin capsules in Japanese Patent Publication No. 44-3495,
Example of capsules produced by gelatin-gum arabic complex coacervation method of No. 14602,
etc. are known. In addition to the method of incorporating capsules into a fiber sheet on a paper machine, methods for manufacturing capsule-applied sheets include coating on general paper, etc. using a coater, or methods of providing capsules on the surface of paper by printing with a printing machine. etc. are widely known, but it is better to make capsules on a paper machine.
Since the capsules are not on the surface of the paper, but are protected by cellulose fibers inside, they have the essential advantage of being extremely unlikely to break during normal handling. Of course, the advantage of reducing the number of coating steps is important in various industrial respects. Furthermore, in a method for manufacturing microcapsule-containing paper using a multi-cylindrical cylinder paper machine in which two or more circular meshes and two or more plow tanks are arranged, microcapsules can be contained in any paper layer, e.g. By containing microcapsules only in the uppermost layer, the microcapsule-containing pressure-sensitive recording paper produced by this production method can be expected to have good coloring efficiency on the surface since there is a large difference between the front and back sides. In other words, regarding the manufacturing method of microcapsule-containing paper, for example, Japanese Patent Publication No. 3495-1986 and Japanese Patent Publication No. 47-1989
A description can be found in Publication No. 10780, but all detailed and specific descriptions are limited to examples of manufacturing using a fourdrinier paper machine (hood linear paper machine), and there is only a slight description of The statement "made into sheet material using a type paper machine" may be related to production using a cylinder paper machine, but the details are unclear. Under these circumstances, the present inventor conducted extensive research in search of a purposeful manufacturing method for microcapsule-containing paper, and as a result of the present invention, a cylinder paper machine, in particular, two or more cylinders and two or more plow tanks each arranged, as in the present invention, was developed. For the first time, the multi-cylindrical cylinder paper machine used, and the use of microcapsules made of melamine-formaldehyde polycondensation resin as a membrane material, can withstand various mechanical stresses and heat during the manufacturing process, and prevent scum and pits from forming on machine parts. The manufacturing process proceeds smoothly without depositing microcapsules, and the microcapsules can be concentrated in the desired area (layer), such as the surface layer or core layer of the paper, or different microcapsules can be created in the surface layer and the back layer. This made it possible to produce a wide variety of paper products. As an example, a multi-layer wet paper is made using a multi-cylindrical cylinder paper machine so that a combination of a colorless electron-donating dye and a color developer used in a carbonless pressure-sensitive recording paper system is microencapsulated and contained only in the surface layer. By combining and drying, it is possible to produce pressure-sensitive recording paper in which only the surface layer develops a deep color. Furthermore, the pressure-sensitive recording paper manufactured in this way has a lower color development per unit area than paper manufactured using a Fourdrinier paper machine or the like in which microencapsulated dyes and color developers are uniformly present in the paper layer. It was found that even if the amount of reagent was the same, the printed color was deep and excellent. Conventional gelatin-gum arabic capsules are widely known and most widely used in applications such as carbonless copying paper, and can be said to be quite excellent in terms of protecting the internal phase. However, the encapsulation process for this capsule is complicated;
Furthermore, since the film is mainly composed of gelatin, it has a serious drawback of poor water resistance. For this reason, when used in a normal papermaking process, there is a fatal drawback that the microcapsules are destroyed during the drying process. On the other hand, capsules made of urea-formalin resin have excellent water resistance, but
Since no dispersants or emulsifiers are used (Special Publication No. 1977-3495)
(No. 1), the capsules cannot be made into a desired particle size, and they are inferior in terms of protecting the internal phase, so when applied to carbonless paper, for example, undesirable colored stains are likely to occur during handling, and the film may be damaged. It has to be made thick, which has the disadvantage that the capsule cannot be sufficiently destroyed even when necessary. Another effective microencapsulation method is the interfacial polymerization method.
No. 27257, Special Publication No. 1971-771, Special Publication No. 18127
(Japanese Patent Publication No. 50-22507) This method is generally used due to the solubility of monomers or prepolymers.
Difficult to control film thickness, highly reactive,
Because it uses toxic monomers, it requires special equipment, and because it uses a reaction with active hydrogen,
Because reactions with water (side reactions, decomposition) occur during emulsification, it is difficult to make the particle size of emulsified particles uniform.
It has various drawbacks such as poor heat resistance compared to urea-formalin resin. Due to the inconvenient properties of these capsules, even though the merits of applying capsules to paper by paper-making are well known, it is currently only being put to practical use in extremely limited fields. It is. An object of the present invention is to produce a microcapsule-containing paper that is excellent in protecting the internal phase. Another object of the present invention is to efficiently produce microcapsule-containing paper. Yet another object of the present invention is to produce a microcapsule-containing paper that has a large difference in microcapsule distribution between the front and back sides, and has excellent color development efficiency, especially in microcapsule-containing pressure-sensitive recording paper. The microcapsules used in the present invention are basically made of a membrane material made of melamine-formalin resin. Melamine-formalin resin has better properties than urea resin, such as higher water resistance, higher heat resistance, higher tensile strength and compressive strength, and resistance to chemicals, weak acids, and weak alkalis. These properties are extremely favorable during the dehydration and drying process when paper is made with cellulose fibers, and it has been found that there is very little destruction of capsules during paper making, and that the subsequent protection of the internal phase is also excellent. Furthermore, it has been found that the melamine-formalin resin capsules of the present invention bond extremely easily to cellulose fibers, so that capsule-containing paper can be easily obtained at a good yield by simply adding them in the same way as fillers for ordinary papermaking. Urea-formalin resin (initial condensate) usually has poor fixation to cellulose fibers, so much so that it is used as a water-proofing agent for paper. It is thought that something similar occurs when it is used as a membrane material for capsules, and in fact it can be fixed at a high yield under normal papermaking conditions. The method for manufacturing melamine-formalin capsules of the present invention is disclosed in Japanese Patent Publication No. 1983-1993, which is filed by the same applicant as the present application.
The method is described in Publication No. 116249 (title of the invention "Microcapsule"). That is, after dispersing and emulsifying a hydrophobic substance (internal phase) in an acidic aqueous solution of a copolymer having maleic anhydride as one constituent unit, a melamine-formalin initial condensate is added and reacted under acidic conditions and heat. By doing so, the melamine-formalin resin is formed as a membrane material. Preferred polymerization conditions include a pH of 4.0 to 6.5 and a temperature of 40°C or higher. The ratio of the internal phase and membrane material of the capsule can be arbitrarily selected depending on the application, but usually the internal phase is 100 (by weight).
It is appropriate to use 5 to 50 parts of the film material per part of the film.
Among the copolymers having maleic anhydride as one constituent unit, the most preferred is a styrene-maleic anhydride copolymer. The capsules thus obtained can be easily fixed on cellulose by adding them to the beaten pulp slurry in the same way as ordinary fillers (clays, etc.). In addition to capsules, the pulp slurry contains conventional known additives (sizing agent, liquid solution,
Bands, clays, starches, latex wet strength improvers, softeners, hardeners, gum retention agents, antifoaming agents) can be added. Further, other characteristics can be imparted by size pressing or coating if necessary. Usually 0.1 to 1 capsule per 100 parts (by weight) of pulp
It is used in an amount of 15 parts (preferably 1 to 10 parts).
The pH at the time of paper making can be acidic, neutral, or alkaline, but perhaps because the capsules are negatively charged due to the anionic (anhydrous) maleic acid, especially when cationic additives are added, the capsules are hardly fixed.
I found out that it is 100%. Suitable additives to anchor this capsule include polyethyleneimine,
(cation-modified) polyamide, polyacrylamide-polyethyleneimine, or epichlorohydrin adducts thereof, cationic starch,
A preferred example is a cation-modified urea resin. The encapsulation using the melamine resin of the present invention has a higher PH (urea resin 3 to 3.5, melamine resin 4.0 to 6.5) than urea resin, so it is difficult to encapsulate acidic and unstable substances. Its usefulness is even more remarkable when making paper. The most typical example of this is the case of carbonless copying paper containing microcapsules containing a solution of a colorless electron-donating dye for carbonless paper. Typical papermaking fibers used in the present invention are various types of wood pulp, but plant fibers other than wood, synthetic pulp made from synthetic resins, cellulose-based chemical fibers, synthetic fibers, glass fibers, and other inorganic fibers can also be used. can. When the present invention is applied to the production of pressure-sensitive recording paper, a solution of a known color former or color developer may be used as the liquid core material of the microcapsules. and,
If at least one of a color forming agent and a color developer is made into a solution and coated with microcapsules and present in paper, it can be used as pressure-sensitive recording paper. Typical coloring agents are lactone dyes such as triphenylmethane phthalide type and xanthene phthalide type, and colorless electron-donating dyes such as lactam dyes and spiropyran type dyes (so-called pressure-sensitive dyes), but metal chelate dyes Various organic ligands may be used to form color-producing systems. As a color developer, phenolic acidic polymers such as acidic (novolac type) polycondensation resins of various phenol derivatives with aldehydes, polyaddition resins with acetylene, salts thereof (metal modified products, etc.), or salicylic acid derivatives and their Salt etc. are suitable. Alternatively, it may be an organometallic compound for a metal chelate coloring system. The novel technology of the present invention is particularly applicable to a method for producing a self-coloring pressure-sensitive recording paper in which both a color forming agent and a color developer are present in the paper layer, and at least one of the two is microencapsulated. usefully applied. This will be explained in detail below using Examples. Example 1 Production of color former capsules (production of melamine-formaldehyde resin capsules) 10g of crystal violet lactone
The above internal phase oil was heated and dissolved in 190 g of KMC-113 (aromatic high boiling point oil manufactured by Kureha Chemical Co., Ltd.) to obtain an internal phase oil, and the above internal phase oil was dissolved in 200 g of a 5% aqueous solution of styrene-maleic anhydride copolymer with a pH of 5.0. emulsify. 10g of melamine, 25g of 37% formalin aqueous solution, 15g of water.
Adjust the pH to 3.5 with NaOH, heat to 60℃, and stir to create a melamine-formalin initial condensate. Add this initial condensate to the above emulsion, adjust the pH to 5.6,
Polymerize by heating at 70℃ for 1.5 hours, then cool and adjust the pH.
Set to 8.0 and finish encapsulation. The average particle size was 5.0μ. Manufacture of color developer capsules P-phenylphenol 850g, P-sec-butylphenol 150g, 37% formalin aqueous solution
302 g and 20 g of oxalic acid as a catalyst were added, and the mixture was allowed to react for 5 hours while heating under reflux, then heated to 130°C and dehydrated. The resin that comes out is slightly brown in color.
mp was 80℃. 40g of this color developer resin was heated and dissolved in 40g of KMC-113 (aromatic high boiling point oil manufactured by Kureha Chemical Co., Ltd.) to obtain an internal phase oil, and the pH was adjusted to 5.4.A 5% aqueous solution of styrene-maleic anhydride copolymer. Emulsify 160 g of the above internal phase oil. 10 g of melamine, 20 g of 37% formalin aqueous solution, and 10 g of water were adjusted to pH 9.0 with NaOH and 70
Heat to ℃ and stir to prepare a melamine-formalin initial condensate. This initial condensate is added to the above emulsion, the pH is adjusted to 5.8, the mixture is polymerized by heating at 70° C. for 3 hours, and then cooled, the pH is adjusted to 9.0, and encapsulation is completed. The average particle diameter was 3.5μ. Example of Paper Making A self-coloring pressure-sensitive recording paper containing microcapsules with two layers was produced having the following structure. The above blending ratio is as follows. Ingredients Parts by Weight (Dry) Pulp 100 Color former capsules 4 Color developer capsules 7 Rosin 1 Sulfuric acid band 2 Cation-modified polyacrylamide 0.5 In other words, LBKP50 beaten with a beater to a mouth water level of 40 degrees SR (Shopper Rigler) department and
To 50 parts of NBKP, add 4 parts of dye capsules (dry basis), 7 parts of developer capsules (dry basis), add sodium salt of rosin, and finally add sulfate and cation-modified polyacrylamide to form an aqueous slurry. The solid content is approximately 0.3%. The lower layer consists of only 50 parts of LBKP and 50 parts of NBKP that have been beaten in a beating machine to a mouth water level of 40 degrees SR (shot par rigler), making the solid content of the aqueous slurry approximately 0.3%. The above paper stocks are combined in a multi-cylindrical cylinder paper machine consisting of two cylinder screens and a plow tank, and the basis weight is 50g/
^m2 of microcapsule-containing paper was produced. The manufacturing process proceeded smoothly and there were no problems such as color stains on the paper or pitch problems in the machine. Example 2 A self-coloring pressure-sensitive recording paper containing two layers of microcapsules having the following structure was produced. The blending ratio of the upper layer is as follows. Ingredients Parts by weight (dry) Pulp 100 Color former capsule of Example 4 Resin 5 Rosin 1 Sulfate band 2 Cationic polyacrylamide 0.5 Other conditions were the same as in Example 1, basis weight 50 g/m ²
A self-coloring pressure-sensitive recording paper containing microcapsules was produced. No problems were observed during the paper manufacturing process. In the above formulation, the resin refers to 100 parts of paraphenylphenol resin (MP87℃) mixed with 100 parts of a 2% styrene maleic anhydride copolymer aqueous solution (PH8).
The mixture was dispersed in 100 ml and ground in a ball mill to an average particle size of 2 to 3 microns, and used as a color developer. Comparative Example 1 Production of color former capsules (capsules using urea-formalin) 10g of crystal violet lactone
It was dissolved in 190 g of KMC-113 to obtain an internal phase oil. Add 10 g of urea, 23 g of 37% formaldehyde, and 17 g of water and react at 70°C for 1 hour to form an initial condensate. Add water to this initial condensate to make a total amount of 250g.
Then, lower the pH to 4 with citric acid, and add the above internal phase oil with vigorous stirring to emulsify. Capsules are formed at 45° C. for 3 hours. Despite vigorous stirring, the average particle size was approximately 50μ. Example of Paper Making The color former capsules of Comparative Example 1 (capsules made of urea-formalin) were used in place of the color former capsules used in Example 2, and the other conditions were the same as in Example 2. 50g/ ^m2
A self-coloring pressure-sensitive recording paper containing microcapsules was produced, but the entire surface was colored blue and no further color development was obtained. This could not be used as a self-coloring pressure-sensitive recording paper. Comparative Example 2 A modified urea-formalin capsule was used as a coloring agent capsule. Internal phase oil similar to Comparative Example 1
200 g was emulsified in 200 g of a 5% aqueous solution of copolyethylene maleic anhydride. The average particle size was approximately 4.5μ. urea 10g, resorcinol 1g, 37% formalin
Add 25g, adjust the pH to 3.5, heat at 60°C for 3 hours to complete encapsulation, and adjust the pH of the capsule to 3.0. When paper was made under the same conditions as in Example 2, except for the capsule, there were fewer blue spots than in Comparative Example 1, but the entire surface had a blue color cast. When the drying temperature was lowered and the paper was taken out in an undried state, there was little color fog, which revealed that the heat during drying destroyed the capsules and caused the color fog. Table 1 below shows the characteristic values obtained in each example and comparative example.

[Table] The self-coloring pressure-sensitive recording paper produced in Examples 1 and 2 and Comparative Example 2 was printed using a ribbonless typewriter, and the reflectance of the blank area and colored area was determined. The results were as follows. That is, it was found that Examples 1 and 2 according to the present invention had high whiteness and deep color density. In particular, Example 1, in which the color developer was microencapsulated with melamine-formaldehyde, which has strong heat and humidity resistance, showed particularly excellent whiteness. On the other hand, in Comparative Example 2, the entire surface was already colored blue, and furthermore, only the type marks were barely visible.

Claims (1)

[Scope of Claims] 1. A micro-capsule paper machine that uses one or more types of microcapsules together with papermaking fibers in a multi-cylindrical cylinder paper machine that uses two or more cylinder screens and two or more plow tanks. A method for producing paper containing capsules, characterized in that the microcapsules contain a liquid core substance and have a membrane material of melamine-formaldehyde polycondensation resin. 2. The method for producing microcapsule-containing paper according to claim 1, wherein the liquid core substance is a solution of a colorless electron-donating dye. 3. The method for producing microcapsule-containing paper according to claim 1, wherein the liquid core material is a solution of a color developer selected from phenolic acidic polymers, salicylic acid derivatives, and salts thereof. 4 Microcapsules and phenolic acidic polymers whose liquid core substance is a solution of a colorless electron-donating dye;
Production of microcapsule-containing paper according to claim 1, which is made by making paper with two types of microcapsules, one being a solution of a color developer selected from salicylic acid derivatives and their salts, together with papermaking fibers. Law. 5. Microcapsules containing a liquid core material having a membrane material of melamine-formaldehyde polycondensation resin are dispersed and emulsified in an aqueous solution of a copolymer having maleic anhydride as one constituent unit, The method for producing microcapsule-containing paper according to claim 1, wherein the microcapsules are made by adding a melamine-formalin initial condensate and reacting under acidic heating. 6. The method for producing microcapsule-containing paper according to claim 5, wherein the copolymer having maleic anhydride as one constituent unit is a styrene-maleic anhydride copolymer.