JPH01150577A - Processing agent for thermal recording paper - Google Patents

Abstract

PURPOSE:To make the pot life of the title processing agent excellent and to improve the printability, plasticizer resistance and water resistance of thermal recording paper, by preparing the processing agent from an aqueous solution containing a polyvinyl alcohol PVA resin containing an acetoacetate AA group and a zirconium salt. CONSTITUTION:A zirconium salt is used in a processing agent for thermal recording paper as a crosslinking agent together used along with PVA containing an acetoacetate group (acetoacetylated PVA). As a result, all of pot life, printing density, plasticizer resistance and water resistance can be satisfied. The acetoacetilated PVA to be used is obtained by introducing the acetoacetate (AA) group through the reaction of PVA with diketene. The content of the AA-group can be set to a range from 0.05mol.% to the max. concn. showing solubility with respect to PVA. As the zirconium salt, chloride, nitrate, sulfate and acetate show effect. The zirconium salt is used in an amount of about 0.2-10pts.wt. per 100pts.wt. of the acetoacetylated PVA resin. When the zirconium salt is 0.2pts.wt. or less, the effect imparting printing developed color density, plasticizer resistance and water resistance is insufficient and, when said salt is used in an amount of 10pts.wt. or more, pot life becomes short and the effect in printing developed color density, plasticizer and water resistance is not increased too much.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention has excellent pot life and is suitable for improving the printability, plasticizer resistance, water resistance, etc. of the obtained thermosensitive recording paper. It provides paper processing agents used.

[Prior Art] In recent years, thermal recording methods that use heat have achieved the major advantage of being able to easily obtain records without the need for processes such as phenomenon and fixing or replenishment materials that are required for conventional print recording methods. Due to its advantages, its uses are becoming increasingly widespread. Particularly, among these methods, a method in which a color-forming substance such as crystal violet lactone and a color developer such as a phenol compound are heated and reacted to form a color has been highly evaluated and has been put into practical use. Conventionally, polyvinyl alcohol (hereinafter abbreviated as PVA) has been frequently used in the production of such recording paper, but due to problems mainly with water resistance, PVA containing an acetoacetate group (hereinafter abbreviated as AA-PVA) has been widely used. )-based resins are being considered. for example,
JP-A-58-181687 proposes its use as a binder, and JP-A-59-106995 proposes its use as a protective film on a heat coloring layer. In addition, in order to further improve water resistance, the combination of the AA-PVA resin and crosslinking agents, such as various metals and metal compounds such as AI, Fe, Cu, Si, Ti, etc., has been studied. Publication No. 51-106995 discloses zirconium, 'A
An alkoxide, zirconium ammonium carbonate, has been proposed.

[Problems to be solved by the invention] However, when AA-PVA resins and metals or metal compounds are used together, which has been studied in the past, there are problems with the pot life of the coating liquid, the printing density of thermal recording paper, and the plasticizer resistance. It was difficult to satisfy both properties such as durability and water resistance at the same time.

In addition, when zirconium ammonium alkoxycarbonate was used in combination with AA-PVA resin, the present inventors found that there was no problem in terms of pot life, but the plasticity resistance was low, probably because the bifold co-crosslinking reaction was not promoted. No effect was shown on either agent properties or water resistance.

[Means for Solving the Problems] As a result of extensive research in order to solve the above-mentioned problems, the present inventors have developed a process for heat-sensitive recording paper made of an aqueous solution containing an AA-PVA resin and a zirconium salt. The present inventors have discovered that the above-mentioned objective can be achieved by the above-mentioned agent, and have completed the present invention.

A feature of the present invention is that a zirconium salt is used as a crosslinking agent in combination with the above-mentioned AA-PVA resin.

As a result, it has become possible to satisfy all of pot life, print density, plasticizer resistance, and water resistance at the same time.

The AA-PVA used in the present invention is typically PVA
It is obtained by reacting A with diketene or the like to introduce an acetoacetate group (hereinafter abbreviated as AA group) into PVA.

The PVA includes not only partially saponified polyvinyl acetate or completely saponified polyvinyl acetate, but also vinyl esters and monomers copolymerizable therewith, such as ethylene, propylene, isobutylene, α-octene, α-dodecene, and α-occudecene. olefins such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid or their salts or mono- or dialkyl esters, nitriles such as acrylonitrile and methacrylonitrile, acrylamide, Amides such as methacrylamide, ethylene sulfonic acid, allyl sulfonic acid, methalylsulfonic acid and its salts, alkyl vinyl ethers, N-acrylamide methyl trimethyl ammonium chloride, allyl small methyl ammonium chloride, dimethyl Compounds with cationic groups such as allyl ammonium chloride,
Examples include saponified copolymers with vinyl ketone, N-vinylpyrrolidone, vinyl chloride, vinylidene chloride, etc.
It is not necessarily limited to this.

The average degree of saponification of PVA is 70-100 mol%, preferably 85-99 mol%, and the average degree of polymerization is 300-3,000.
, preferably from 500 to 2,000.

Any method can be used to incorporate the AA group into the PVA, but preferred methods include adding diketene to the PVA or transesterifying it with acetoacetate. The content of AA groups is
It is possible to use O in a water-soluble range of 0.05 mol % or more based on A, but it is usually selected from the range of 1 to 10 mol %, especially 0.5 to 10 mol %. If the content of AA groups is too small, it is difficult to obtain the effects of the present invention, and conversely, if the content is more than necessary, the expected effects cannot be obtained considering the amount used.

Next, as the zirconium salt used in combination, chloride, nitrate, sulfate, and acetate are effective. Zirconium chloride here includes not only dichloride, trichloride, and tetrachloride, but also zirconium acid chloride. Similarly, zirconium nitrate, zirconium sulfate, and zirconium acetate are also zirconium nitrate. , zirconyl sulfate, and zirconyl acetate. These can be used alone or in combination.

It is advantageous to use such a zirconium salt in an amount of about 0.2 to 10 parts by weight per 100 parts by weight of the AA-PVA resin. If it is less than 0.2 parts by weight, the effect of imparting printing color density, plasticizer resistance, water resistance, etc. will not be sufficient, and if it is used more than 10 parts by weight, there will be a problem that the pot life will be shortened. In terms of color density, plasticizer resistance, and water resistance, the effects do not increase that much considering the amount used, which is also economically disadvantageous.

In the paper processing agent of the present application, the pH of the system is also an important point; if the pH is 9 or higher, the AA group may decompose, so the pH is preferably 9 or lower. Normally, it can be controlled by adjusting the amount of zirconium salt added, but if there is a possibility that the pH will exceed 9, it is necessary to adjust the pH to 9 or lower using an appropriate buffer.

When applying the paper processing agent of the present invention to thermal recording paper,
Composed of a color-forming substance, a color developer, and a binder: Either a method of coating the processing agent as a protective film on the heat-sensitive color-forming layer or a method of using it as a binder component of the heat-sensitive color-forming layer is possible, but the former method is possible. This method is more efficient in obtaining the effects of the present invention.

The former method will be specifically explained.

First, in preparing a coloring liquid for forming a heat-sensitive coloring layer, an aqueous dispersion of a coloring substance and an aqueous dispersion of a color developer are prepared separately, and they are thoroughly stirred and pulverized. A uniformly dispersed coloring liquid can be obtained by simply mixing and stirring both liquids.

The binder component is added to at least one of the aqueous dispersion of the color-forming substance and the aqueous dispersion of the color developer. The binder component is suitably 10 to 200% by weight based on the total amount of the color forming substance and color developer. The solid content concentration of the coloring liquid is selected from the range of 10 to 40% in consideration of workability. As the binder, for example, PVA, modified PVA such as carboxyl group-containing PVA, 5AA converted PVA, methylcellulose, carboquine methylcellulose, starches, latexes, or the same paper processing agent as the protective layer of the present invention can be used.

Examples of color-forming substances include 3,3-bis(P-dimethylaminophenyl)-phthalide, 3,3-his(P-dimethylaminophenyl)-6-dimethylaminophthalide C
crystal violet lactone], 3,3-bis(P
-dimethylaminophenyl)-6-dimethylaminophenyl, 3.3-bis(P-dimethylaminophenyl)-
6-chlorophthalide, 3-dimethylamino-6-medoquinofluorane, 7-acetamino-3-diethylaminofluorane, 3-diethylamino-5,7-tumethylfluorane, 3-dinithylamino-5,7-dimethylfluorane, Examples include leuco forms of triphenylmethane dyes such as 3,6-his-β-methoxyethoxyfluoran and 3,6-bis-β-cyanoethoxyfluoran.

The color developer is one that reacts with the color-forming substance when heated and is liquefied or vaporized at room temperature or higher, preferably 70°C or higher, such as phenol, P-methylphenol, P-tert-butylphenol, P' - phenylphenol, α-naphthol, β-naphthol,
4.4′-isopropylidene diphenol [hisphenol A], 4,4′-secondary butylidene diphenol, 4.4′-sochlorohexylidene phenol, 4
．． 4'-isopropylidene bis(2-tert-butylphenol), 4.4'' (+-methyl-n-hexylidene) diphenol, 4.4°-isopropylidene dicatechol, 4,4°-benzylidene diphenol, 4,
4-isopropylidene bis(2-chlorophenol),
Phenyl-4-hydroquine benzoate, salicylic acid,
3-phenylsalicylic acid, 5-methylsalicylic acid, 3,
5-di-tert-butylsalicylic acid, 1-oxy-
Examples include 2-naphthoic acid, m-oxybenzoic acid, 4-oxyphthalic acid, gallic acid, etc., but neither the color forming substance nor the color developer is limited to these.

There is no particular restriction on the paper on which the coloring liquid is applied, and any paper can be used.

For coating, any known method such as a roll coater method, an air doctor method, a blade coater method, etc. may be employed. However, the coating amount of the coloring liquid is 1~20~7m.
In particular, it is appropriate to set it to about 3 to 10 g/m''.

The paper processing agent of the present invention is coated on the heat-sensitive recording layer thus obtained.

Coating can be done by any means. The concentration of the coating liquid is suitably about 1 to IO% by weight in consideration of coatability and the like. The coating amount is preferably about 0.5 to 5 g/m'. After coating, the desired coating layer is formed by air drying or mild heat treatment.

Coating can be carried out by any method such as a roll coater method, an air doctor method, or a blade coater method.

Next, the case where the paper processing agent of the present invention is used as a binder component in a heat-sensitive layer for a heat-sensitive recording paper will be explained. Technically speaking, the content of the step of forming the heat-sensitive recording layer in the explanation of the method for forming the protective layer is explained below. is almost the same as

Although it is repetitive, I will explain it in detail again.

When preparing a coating composition using the above binder, an aqueous dispersion of a color-forming substance and an aqueous dispersion of a color developer are prepared separately, and after stirring them thoroughly and pulverizing them, A uniform dispersion coloring liquid can be obtained simply by mixing and stirring both liquids. AA PVA and zirconium salt are water A, which is a color-forming substance.
A-PVA contains 10% of the total amount of color-forming substances and color developers.
~200% by weight is suitable. The solid content concentration of the coloring liquid is selected from the range of 10 to 40% by weight in consideration of workability.

As a binder, a binder other than AA-modified PVA, for example, modified PVA such as PVA and carboxyl group-containing PVA.

Methylcellulose, carboquine methylcellulose, starches, latexes, etc. can also be used in combination.

There is no particular restriction on the paper on which the coloring liquid is applied, and any paper can be used.

For coating, any known method such as a roll coater method, an air doctor method, a blade coater method, etc. may be employed. However, the coating amount of the coloring liquid is 1 to 20 g/m
! Above all, it is appropriate to set it to about 3 to IOg/m'.

The paper processing agent of the present invention is mainly used for producing heat-sensitive recording paper, but the paper processing agent of the present invention can also be used for information industry paper such as inkinoet recording paper, paperboard such as Manila board, white board, liner, and general high-quality paper. It can be applied to arbitrary materials such as printing paper such as gravure paper.

Moreover, it can be applied not only to paper but also to composite materials with base materials such as films, nonwoven fabrics, and sheets.

, [Function] ゛The heat-sensitive recording paper processing agent made of an aqueous solution containing an AA-PVA resin and a zirconium salt of the present application satisfies all of pot life, print color density, plasticizer resistance, and water resistance at the same time. It has the advantage of being able to

[Example] Hereinafter, the present invention will be explained in more detail by giving examples.

Example I Liquid A and Liquid B (coating liquid) Liquids A and B were separately ground to an average particle size of 2 using a sand grinder.
After grinding to a particle size of about μ, liquid A, liquid B, 50 parts by weight of calcium carbonate, and 250 parts by weight of a 15% aqueous solution of PVA, which is the same as that used in liquids A and B, are mixed to form a coloring liquid. Obtained. The coloring liquid was applied onto a base paper measuring 15,097 m' in area so that the coated amount after drying was 8 Li/m'', and dried at 60°C.

Furthermore, the above liquid C was coated at 5g/by using a Dickson coater.
m2 (net) and dried at 60° C. to obtain thermal recording paper.

The printed color density, plasticizer resistance, and water resistance of the recording paper were evaluated by the following methods.

(1) Print color density thermal gradient tester (manufactured by Toyo Seiki Co., Ltd.) at 120℃, 2K
Print color is developed under the conditions of IJ/cm' for 10 seconds, and the print color density is measured using a Macbeth densitometer (manufactured by Macbeth Co., Ltd., RD-100).
(2) The recording paper on which the plasticizer-resistant barcode was recorded was sandwiched between three upper and lower soft vinyl chloride sheets, a load of 300 g/m2 was applied, and the recording paper was held at a 40° angle.
After 124 hours, the reading rate was measured using a barcode scanner.

(3) Place the recording paper with the water-resistant barcode on it in tap water at 20℃ for 2.1 minutes.
After soaking for a time, the reading rate of the barcode scanner was measured.

(4) Pot life The gelation time of the coating solution was measured in a 30°C constant temperature water bath.

The results are shown in Table 1.

Examples 2 to 4, Comparative Examples 1 to 4 Experiments were conducted according to the method of Example I using the metal salts shown in Table 1. The results are also shown in Table 1.

Example 5 D-liquid E-liquor E-liquid and E-liquid were separately processed with a sand grinder to reduce the average particle size to 2.
It was ground to about μ. These 3 liquids D, E and E
A coloring solution was obtained by mixing the seed solution. The basis weight of the coloring liquid is 50g.
/m2 base paper so that the coated amount after drying was 7.59/m', and dried to obtain heat-sensitive recording paper.

The properties of the obtained recording paper were evaluated in the same manner as in Example 1 and are shown in Table 2.

Control Example 5 An experiment was conducted in the same manner as in Example 5, using titanium chloride (TiC1,) instead of Zircosol ZC used in Example 5. The results are shown in Table 2.

[Effect] As described above, the heat-sensitive recording paper processing agent of the present invention, which is composed of an aqueous solution containing a polyvinyl alcohol resin containing an acetoacetate ester group and a zirconium salt, improves the pot life of the coating solution and improves the heat-sensitive Because it satisfies all of the printing density, plasticizer resistance, and water resistance of recording paper at the same time,
It is extremely useful in industry.

Claims (1)

[Claims] 1. A processing agent for thermal recording paper comprising an aqueous solution containing a polyvinyl alcohol resin containing an acetoacetate group and a zirconium salt. 2. The processing agent for thermal recording paper according to claim 1, wherein the zirconium salt is at least one of zirconium chloride, zirconium acetate, zirconium nitrate, and zirconium sulfate.