JPH0147315B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a binder for thermal recording paper, and in particular, at least one of A) 70 to 95% by weight of acrylic acid amide or methacrylic acid amide and B) hydroxyalkyl ester of acrylic acid or methacrylic acid or methylol acrylic amide. 5～30
It is an object of the present invention to provide a binder for heat-sensitive recording paper comprising an aqueous solution of a water-soluble copolymer with % by weight. In recent years, the development and practical application of magnetic recording methods and thermal recording methods have been actively progressing, and among them, thermal recording methods () do not require a developing process because they develop primary color;
() Easy to assemble and maintain the device; () The heat-sensitive recording sheet has a feel similar to plain paper and is relatively inexpensive;
For this reason, it has been put to practical use in the fields of computer output, printers such as calculators, recorders of medical measuring machines, facsimile machines, automatic ticket vending machines, thermal copying, etc. The thermal recording paper used in this thermal recording method is
It is usually produced in the same way as so-called general coated papers such as art paper and coated paper. i.e. art paper,
In the production of coated paper, etc., inorganic pigments such as barium sulfate, titanium oxide, calcium carbonate, satin white, clay, and kaolin are added to base paper in the form of rolls or sheets, together with various binders such as casein, starch, or synthetic latex. It is applied using a coating liquid dispersed in water and then dried. Furthermore, mechanical processing such as supercalendering is performed. Generally, these binders also have the function of uniformly dispersing the pigment in the coating liquid, but a dispersant may be used separately. Similarly, for thermal recording paper, a coating solution in which leuco dye-based coloring components such as leucolactone compounds and spiropyran compounds and reactive agents such as phenol compounds and organic acids are uniformly dispersed in water together with a binder is applied to the paper substrate. (In addition to wood pulp paper, this also includes synthetic pulp paper and synthetic paper). These binders for heat-sensitive recording paper must have good dispersibility and adhesion of coating materials such as pigments, dyes, and various other additives, provide a homogeneous and strong coating film, and have good water resistance. It is desired that the binder satisfies various requirements such as having good viscosity stability, excellent workability, and being economically inexpensive. It is required to have good thermal response and not cause fogging, thermal head fusion, thermal head deterioration, etc. Conventionally known binders for thermal recording paper include:
For example, polyvinyl alcohol, starch and its modified products, casein, gelatin, soybean protein, carpoxymethylcellulose, gum arabic, methylcellulose, hydroxyethylcellulose, sodium alginate, polyacrylamide, sodium polyacrylate, styrene-maleic anhydride copolymer Water-soluble substances such as alkali-modified substances, styrene/butadiene copolymer, styrene/butadiene/acrylonitrile copolymer, ethylene vinyl acetate copolymer, vinylitene chloride/acrylic acid ester copolymer, vinylitene chloride/acrylonitrile copolymer, Aqueous emulsions such as acrylonitrile/acrylic acid ester copolymer, polyurethane resin, chlorinated polypropylene resin, butadiene/acrylonitrile copolymer, vinyl acetate resin, and the like are known. However, water-soluble substances such as those mentioned above, except for styrene-maleic anhydride alkali-modified substances, have poor water resistance, and therefore, a water-resisting agent is usually used in combination, but there are various drawbacks, and the results are not always satisfactory for practical purposes. Hard to get. On the other hand, styrene
Alkali-modified maleic anhydride gives good results in terms of water resistance, but when used as a binder for the above-mentioned heat-sensitive recording paper, it has the disadvantage of easily causing thermal head deterioration. Similarly, aqueous emulsions made from synthetic resins have high water resistance, but they also have drawbacks such as fogging the skin and causing thermal head fusion, so they cannot be said to be sufficient for practical use. hard. The present inventors have developed a practically excellent binder for leuco dye-based thermal recording paper that satisfies the above-mentioned requirements such as good water resistance, high binding strength, and excellent thermal response. As a result of various studies for the purpose of The invention was completed. The base polymer in the binder for thermal recording paper of the present invention contains A) 70 to 95% by weight of acrylic acid amide or methacrylic acid amide and B) hydroxyalkyl ester of acrylic acid or methacrylic acid or methylol acrylic acid as copolymerized components. It is a water-soluble copolymer containing 5 to 30% by weight of at least one type of amide, and specific examples of the hydroxyalkyl group include hydroxyethyl, hydroxypropyl, and the like. That is, in order to satisfy the above-mentioned requirements as a binder for thermal recording paper, the present inventors have found that the base polymer must have an affinity with paper and have a high bonding strength, and must also be water-soluble. However, the molecular design was based on the idea that it should not be unnecessarily easily soluble and should be difficult to dissolve in water after being applied to paper and dried, and the polymer composition should be acrylic acid or methacrylic acid amide. Since a stand-alone system has low water resistance and binding properties and is of little practical use, it is necessary to copolymerize this with other structurally and physically similar monomers that have an alkyl group to introduce an alkyl group into the polymer side chain. In order to improve water resistance, we introduced groups with hydroxyl groups instead of simple alkyl groups, which not only improved water resistance but also increased affinity and bonding strength with paper, as well as paper as a binder, leuco dyes, and dyes. It has improved binding properties with color-forming components such as coloring agents. Furthermore, this makes it possible to lower the mixing ratio of the binder and color-forming components such as leuco dyes, improve thermal response, and maintain the above-mentioned binding strength at the required level. Regarding the weight ratio of each monomer in the copolymer, for the purpose of improving water resistance and binding properties, it is sufficient to increase the ratio of component B) monomer, but if component B) is increased by more than 30% by weight, the copolymer Cross-linking occurs between them, resulting in a high viscosity ratio, gelation, or loss of water solubility, which is inconvenient for use as a binder. A copolymer containing component B) less than 5% by weight will not be able to sufficiently improve water resistance and binding properties. Although there are no particular restrictions on the production of the copolymer of the present invention, it is usually prepared, for example, by the following method. However, of course, it may be manufactured by other methods. That is, a persulfate or a redox system of persulfate and amine or sulfite is added as a catalyst to an aqueous solution having a monomer concentration of 10 to 30% by weight, preferably 15 to 25% by weight, which is the sum of components A) and B). In addition, the mixture is allowed to react at about room temperature (5 to 30°C) for about 0.5 to 2 hours. As persulfates and sulfites used as catalysts, water-soluble salts such as sodium, potassium, and ammonium salts are suitable, and as amines, for example, monoethanolamine, hexamethylene diamine, aniline, etc. primary amines, secondary amines such as diethanolamine and monomethylaniline, and tertiary amines such as triethanolamine, dimethylaniline, pyridine, and picoline. Among these, a redox catalyst using a combination of ammonium persulfate and triethanolamine is particularly preferred as it is the most effective. There is no particular restriction on the amount of catalyst used, but it is usually 0.1 persulfate per monomer.
It is desirable to use about 2.0% by weight and 0.5 to 20% by weight of amine. The polymerization temperature is initially carried out at room temperature, but increases as the polymerization begins, and usually reaches a final temperature of about 70°C. Cooling is not necessary unless there is localized overheating. In order for the polymer film formed on the paper coated as a base polymer for the coating solution to have sufficient strength, it is better to have a high polymer molecular weight, but on the other hand, if the molecular weight of the coating solution itself is too high, the viscosity will be low. It becomes expensive and the workability becomes poor. Examples of copolymer liquids with relatively high film strength and good workability include
The appropriate viscosity of the 20% aqueous solution is about 2,000 to 60,000 CP, and in order to prepare the copolymer aqueous solution within this range, the amount of catalyst used must be within the above range.
The monomer concentration is selected from the above range from the viewpoint of adjusting the viscosity of the copolymer aqueous solution obtained as a result of polymerization to a suitable range. The binder for thermal recording paper of the present invention is particularly excellent in practical use for leuco dye-based thermal recording paper, and in this use, it strengthens the binding of color former components, color developer components, fillers, etc. to the base paper. The color-forming compounds serving as color-forming agent components are leucolactone compounds and spirobilane compounds, and representative examples thereof are as follows. However, these specific examples do not limit the present invention. As the coloring component, a leuco form of a triphenylmethane dye represented by the following general formula () or a leuco form of a fluoran dye represented by the following formula (2) can generally be used alone or in combination. Rx, Ry, and Rz are hydrogen, hydroxyl group, halogen, alkyl group, nitro group, amino group, dialkylamino group, monoalkylamino group, and allyl group; Z is an atom necessary to form a heterocyclic ring; show. Compound belonging to formula () 3,3-bis(P-dimethylaminophenyl)
-Phthalide 3,3-bis(P-dimethylaminophenyl)
-6-dimethylaminophthalide (crystal violet lactone) 3,3-bis(P-dimethylaminophenyl)
-6-aminophthalide 3,3-bis(P-dimethylaminophenyl)
-6-nitrophthalide 3,3-bis(P-dibutylaminophenyl)
-Phthalide 3,3-bis(P-dimethylaminophel)-
Compounds belonging to the formula 4,5,6,7-tetrachlorophthalide () 3-dimethylamino-6-methoxyfluoran 7-acetamino-3-dimethylaminofluoran 3-dimethylamino-5,7-dimethylfluoran 3-diethylamino-5,7-dimethylfluorane 3,3-bis-β-methoxyethoxyfluorane 3,6-bis-β-cyanoethoxyfluorane 3-diethylamino-6-methyl 7-P-butylanilino Fluoran 3-diethylamino-6-methyl-7-chlorofluoran Also, effective color developer components that react with the above dyes to develop color include phenolic compounds or organic acids. It is desirable that the material is solid and has the property of liquefying or vaporizing at 50°C or higher. Phenol compounds include 4,4'-isobropylidene diphenol (bisphenol A) 4-tert-butylphenol 4-tert-octylphenol 4-tert-amylphenol P-phenylphenol 2,2-bis(P- hydroxyphenyl)butane 2,2-bis(P-hydroxyphenyl)isohexane Organic acids include stearic acid, benzoic acid, salicylic acid, succinic acid, gallic acid, and organic acids such as acrylic acid, methacrylic acid, and itaconic acid. Examples include homopolymerization oligomers of acid monomers and copolymerization oligomers thereof with styrene, acrylamide, and the like. The above-mentioned color forming agent component and color developing agent component can be used alone or, if necessary, two or more kinds can be used in an appropriate mixture. Examples of the filler include inorganic substances such as calcium carbonate, talc, titanium oxide, clay, and kaolin, and synthetic resins such as polystyrene. These can be used alone or in combination of two or more. The appropriate mixing weight ratio of the color former, color developer, and filler to the binder is 1:0.1 to 1:0.3; if the binder is less than this ratio, the binding force will be weak and the performance as a binder will be lost. Moreover, if there is a large amount of binder, the color development sensitivity will decrease. In producing the heat-sensitive coating composition, in addition to the above-mentioned color forming agent, developer, filler binder, wax or the like may be added to prevent heat adhesion if necessary. As described above, the present invention particularly provides a leuco dye-based binder for heat-sensitive recording paper, in which a water-soluble copolymer with at least one of A) acrylic acid amide and B) hydroxyalkyl ester of acrylic acid or methacrylic acid or methylol acryl amide is used. This method uses an aqueous solution of a polymer to provide a practically excellent thermal recording paper, and can be used in combination with other water-soluble or water-dispersible binders, so its range of applications is wide. The present invention will be specifically explained below using examples. Example 1 a Method for manufacturing binder 85 parts of acrylamide, 15 parts of euhydroxypropyl methacrylate, and 400 parts of water were charged into a three-necked flask equipped with a thermometer and a nitrogen inlet tube, and after nitrogen bubbling for 1 hour, The temperature of the solution was adjusted to 20°C, and 8 parts of triethanolamine and 0.8 parts of ammonium persulfate were added as an aqueous solution to initiate polymerization. Polymerization was continued for 1 hour after reaching the maximum temperature to obtain a 20% aqueous solution of the copolymer. The viscosity of this copolymer aqueous solution is 20°C.
It was 50000CP. Dilute this with water to make the concentration
An aqueous solution adjusted to 10% was used as a binder. B. Preparation of heat-sensitive coating liquid A solution consisting of 4 parts of crystal violet lactone, 20 parts of binder, 26 parts of water, 16 parts of bisphenol A, 20 parts of binder, 3 parts of calcium carbonate, and 11 parts of water was heated separately in a ball mill for 3 hours. Mix to make a dispersion liquid, and when using, stir and mix them together to make a thermal coating liquid (A).Also, change the binder in ) to 13 parts and water to 33 parts, and add the binder in ). A heat-sensitive coating liquid (A') was prepared in the same manner as in () and () except that 13 parts and 18 parts of water were used, respectively. Similarly) 4 parts of 3-dimethylamino-5,7-dimethylfluorane, 20 parts of binder, 26 parts of water and) 16 parts of p-phenylphenol, 20 parts of binder, 3 parts of talc,
Thermal coating liquid (B) is prepared by mixing a dispersion consisting of 11 parts of water.
Thermal coating liquid (B ′) was obtained. For comparison, the preparation of the heat-sensitive coating liquids (A) and (A') was repeated in the same manner as above, except that the copolymer aqueous solutions of Comparative Examples 1 and 2 were used instead of the copolymer aqueous solution of the present invention as a binder. Heat-sensitive coating liquids (C) and (C') were obtained, respectively. (c) Manufacturing and testing of recording paper Heat-sensitive coating liquids (A), (A'), (B), (B') and (C), (C') obtained in (b) were each used at 60 g/ ^m2 of fine quality. Thermal recording paper (A), (A'), (B), (B') coated on the paper surface with a wire bar and dried with a coating weight of 4.0 g/m2 ^.
and (C) and (C′) were obtained. These thermal recording papers are 130
The print density, water resistance, and binding properties were tested by printing at ℃, and the results shown in Table 1 were obtained. It was found that the binding property was excellent when the printing density was high with low addition. Comparative Examples 1 to 3 1 10% aqueous solution of polyacrylic acid amide (concentration 20
% aqueous solution temperature 20℃ viscosity 23000cp). 2 Acrylic acid amide 96 parts/methacrylic acid 2-
10% aqueous solution of 4-part hydroxypropyl copolymer (viscosity 23000 cp at temperature 20°C of a 20% aqueous solution): A copolymer that has the same components as the copolymer of the present invention, but the proportion of component B) is lower than its lower limit. Combined. 3 Acrylic acid amide 60 parts/methacrylic acid 2-
Hydroxyethyl 40 parts copolymer (20% concentration aqueous solution could not be used due to gelation of the copolymer): Same components as the copolymer of the present invention, but the proportion of component B) is below its upper limit. High copolymer.

[Table] Examples 2 to 6 Similar tests were conducted on the various binder liquids shown below with the same composition, and it was found that all of them had excellent performance almost equivalent to the above. 2 Acrylic acid amide 80 parts/methacrylic acid 2-
10% aqueous solution of 20 parts hydroxypropyl copolymer (viscosity 30000CP at 20°C temperature of 20% aqueous solution) 3 85 parts of acrylamide/15 parts of methylolacrylamide copolymer (temperature of 20% aqueous solution)
10% aqueous solution 4 of acrylic acid amide 90 parts/hydroxyethyl methacrylate 10 parts copolymer (20% concentration aqueous solution, viscosity 30000 CP at 20°C) 10% aqueous solution 5 Methacrylic acid amide 85 part/acrylic acid 2-
10% aqueous solution of 15 parts hydroxypropyl copolymer (viscosity 35000CP at 20% aqueous solution temperature 20°C) 6 90 parts methacrylic acid amide/10 parts hydroxyethyl methacrylate copolymer (20% aqueous solution temperature 20°C) 10% aqueous solution with viscosity 35000CP).

Claims (1)

[Scope of Claims] 1 A: 70 to 95% by weight of acrylic acid amide or methacrylic acid amide; and B: 5 to 30% by weight of at least one of hydroxyalkyl esters of acrylic acid or methacrylic acid or methylolacrylamide. A binder for thermal recording paper consisting of an aqueous solution of a water-soluble copolymer.