JPH0839927A - Surface coating agent of paper - Google Patents

Abstract

PURPOSE:To enhance the color developability, resolving power, water resistance, light fastness, setting properties and strength of ink by adding six kinds of repeating units respectively represented by specific formulae in specific ratios and specifying a value of reduced viscosity. CONSTITUTION:Repeating units respectively represented by first and second formulae are respectively added in a ratio of 20-90mol% and a repeating unit represented by third formula is added in a ratio of 0-40mol% and a repeating unit represented by fourth formula is added in a ratio of 0-70mol% and a repeating unit represented by fifth formula is added in a ratio of 0-70mol% and a repeating unit represented by sixth formula is added in a ratio of 0-20mol%. A value of reduced viscosity measured with respect to a soln. of 0.1g/dl in a 1N saline soln. at 25 deg.C is specified to 0.1-10dl/g. In the formulae, R<1> and R<2> are a hydrogen atom or a methyl group, R<3> is a 1-4C alkyl group, R<4> is a hydrogen atom and others, X<-1> is an anion, Y is COOM and others and M is a cation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper surface coating agent for improving the surface paper quality. More specifically, by applying a water-soluble polymer having an amidine structural unit on the paper surface after paper making, the color development of the ink is excellent, the resolution is high, the water resistance is high, and the light resistance is also improved. The present invention relates to a paper surface coating agent that improves ink setting properties, surface strength and internal strength.

[0002]

2. Description of the Related Art Ink jet recording is a system in which minute droplets of ink are generated and ejected according to various operating principles and adhered to a recording material such as paper for recording. This method produces little noise and is rapidly spreading as a recording method capable of high-speed printing and multicolor printing. As a recording material used in this ink jet recording method, general paper has been used. However, with the improvement of the performance of the device such as the speeding up of recording or multi-coloring and the expansion of applications,
Higher characteristics have also been required for inkjet recording materials.

That is, as a recording material for obtaining a recorded image of high resolution and high quality comparable to that of a color photograph, (1) rapid absorption of ink. (2) When ink dots overlap, the ink that adheres later does not flow out to the previous dot. (3) The shape of the ink dot is close to a perfect circle, and the surrounding area is smooth. (4) The diameter of the ink dot should not become larger than necessary. (5) The density of ink dots is high and the area around the dots is not blurred. (6) The color development of the ink is excellent. It is necessary to meet various requirements such as. Water resistance,
Light resistance is also required at the same time. However, a recording material satisfying all of these requirements has not yet been found.

For example, a urea-formaldehyde resin is contained in the coating layer in order to improve the ink absorption (Japanese Patent Laid-Open No. 53-49113), and non-colloidal silica powder is used as a pigment in the coating layer. (JP-A-55-51583)
Gazette) is disclosed. Although ink absorption is improved by these methods, there is a big problem that the recorded image lacks water resistance. In order to improve the water resistance of recorded images, a method of incorporating a cationic polymer in the coating layer is adopted. For example, polyethyleneimine (JP-A-56-
No. 84992), organic acid salts of polyethyleneimine (JP-A-59-198186), dimethyldiallylammonium chloride (JP-A-59-20696), polyallylamine hydrochloride (JP-A-62-174).
184), polyvinylamine homopolymer (Japanese Patent Laid-Open No. 64-8085), and the like. However, although these polymer compounds improve water resistance to some extent, improvement in light resistance is still insufficient, and in some cases, light resistance is decreased.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to develop a recording material which has excellent color developability of ink, high resolution, high water resistance and improved light resistance.

[0006]

Means for Solving the Problems As a result of intensive studies by the present inventors in order to achieve the above-mentioned object, as a result of coating a specific water-soluble polymer having an amidine structure in or on a substrate. It has been found that a recording material which forms a recorded image having water resistance and light resistance can be obtained by incorporating it in the working layer, and the present invention has been completed.

The invention according to claim 1 of the present invention comprises 20 to 9 repeating units represented by the following (1) and / or (2).
0 mol%, 0 to 4 repeating units represented by the following (3)
0 mol%, 0 to 7 repeating units represented by the following (4)
0 mol%, 0 to 7 repeating units represented by the following (5)
0 mol%, 0 to 2 repeating units represented by the following (6)
It contains 0 mol% and has a reduced viscosity value of 0.1 to 10 measured at 25 ° C. as a solution of 0.1 g / dl in 1 N saline.
It is a paper surface coating agent comprising a water-soluble polymer, which is characterized in that it is dl / g.

[0008]

[Chemical 7]

[0009]

Embedded image

[0010]

[Chemical 9]

[0011]

[Chemical 10]

[0012]

[Chemical 11]

[0013]

[Chemical 12]

(Wherein R ¹ and R ² are hydrogen atoms or a methyl group, R ³ is an alkyl group having 1 to 4 carbon atoms, R ⁴ is a hydrogen atom, a methyl group or a carboxymethyl group, X ⁻ is an anion, and Y is Y. Is COOM, C ₆ H ₄ SO ₃ M, CH ₂ SO _{3
M, CONHC (CH 3) 2} CH 2 SO 3 M, M represents respectively a cation. )

The invention according to claim 2 of the present invention is the paper surface coating agent according to claim 1, characterized in that the repeating units (1) and / or (2) are 40 to 80 mol%.

The invention of claim 3 of the present invention comprises an acid hydrolyzate of a copolymer of N-vinylformamide and acrylonitrile, and a paper surface coating agent according to claim 1 or 2. Is.

The invention according to claim 4 of the present invention is the paper surface coating agent according to any one of claims 1 to 3, which improves printability.

The invention according to claim 5 of the present invention is the surface coating agent for paper according to any one of claims 1 to 3, which is used for recording paper for ink jet.

The invention according to claim 6 of the present invention is the surface coating agent for paper according to any one of claims 1 to 3, which is used as an agent for improving ink setting properties.

The invention according to claim 7 of the present invention is characterized in that the surface strength of paper is improved.
The above-mentioned paper surface coating agent.

The invention according to claim 8 of the present invention is characterized in that the internal strength of the paper is improved.
The above-mentioned paper surface coating agent.

The amidine unit represented by the above (1) and (2) has an amidine structure consisting of a five-membered ring, and nuclear magnetic resonance spectroscopy (NMR), infrared spectroscopy (IR), etc. Is usually equivalently observed in the analysis of (1)
And (2) is quantified as the total amount. However, as shown in the conceptual diagram below, when considering the repeating unit of the polymer produced in the amidation reaction of the polymer described later,
Two types of repeating units represented by (1) and (2) must be considered. In the conceptual diagram below, the CN group and NH ₂ group represent a cyano group unit and an amino group unit that were not involved in the amidation reaction.

[0023]

[Chemical 13]

The method for producing the above water-soluble polymer having an amidine structure is not particularly limited, but generally, a primary amino group or a substituted amino group capable of forming a primary amino group by a conversion reaction is used. It can be obtained by producing a copolymer of an ethylenically unsaturated monomer having an acrylonitrile or a nitrile of methacrylonitrile, and further reacting a cyano group and a primary amino group in the copolymer to form an amidine. .

The above-mentioned ethylenically unsaturated monomer has the general formula

Embedded image A compound represented by CH ₂ ═CR ² —NHCOR ³ (wherein R ² represents a hydrogen atom or a methyl group, and R ³ represents an alkyl group having 1 to 4 carbon atoms or a hydrogen atom). preferable.

In the copolymer, the substituted amino group derived from such a compound is easily converted into a primary amino group by hydrolysis or alcoholysis. Furthermore this 1
The primary amino group reacts with an adjacent cyano group to form an amidine. Examples of the compound include N-vinylformamide (R
^{2 = H, R 3 = H} ), N- vinylacetamide (R ² =
H, R ³ = CH ₃ ) and the like are exemplified.

The molar ratio of copolymerization of these ethylenically unsaturated monomers and nitriles is usually 20:80 to 80: 2.
0, but if desired a polymerization molar ratio outside this range,
For example, it is also possible to employ a polymerization mole having a larger proportion of ethylenically unsaturated monomers. Considering the application as a surface coating agent, the performance is higher when the proportion of amidine units in the cationic polymer is higher. Further, it is considered that the amine unit also contributes to the performance as the surface coating agent. Therefore, the copolymerization molar ratio of the ethylenically unsaturated monomer and the nitriles, which gives a copolymer suitable as a coating agent, is generally 20:80 to 80:20, particularly preferably 40:
60 to 60:40.

As a method for copolymerizing the ethylenically unsaturated monomer and the nitriles, a usual radical polymerization method is used, and any of bulk polymerization, aqueous solution precipitation polymerization, suspension polymerization, emulsion polymerization and the like can be used. . When the polymerization is carried out in a solvent, the raw material monomer concentration is usually 5 to 80% by weight, preferably 20 to 60% by weight. A general radical polymerization initiator can be used as the polymerization initiator, but an azo compound is preferable, and 2,2′-azobis-2-
Examples include amidinopropane hydrochloride and the like. The polymerization reaction is generally carried out at a temperature of 30 to 100 ° C. under an inert gas stream. The obtained copolymer can be used as it is or after being diluted, that is, in the form of a solution or a suspension for the amidination reaction. Alternatively, the solvent may be desolvated and dried by a known method to separate the copolymer as a solid, and then the solid may be subjected to an amidation reaction.

In the amidation reaction, when the N-vinylamide compound represented by the above general formula is used as the ethylenically unsaturated monomer, the substituted amino group of the copolymer is converted into a primary amino group, and then the primary amino group formed is produced. The water-soluble polymer according to the present invention can be produced by a two-step reaction in which an amino group and an adjacent cyano group are reacted to generate an amidine structure. Then, preferably, the copolymer is heated in a water or alcohol solution in the presence of a strong acid or a strong base to form an amidine structure in one step. Also in this case, it is considered that the primary amino group is first formed as an intermediate structure.

The specific conditions for the reaction are, for example, usually 0.9 to 0.9 with respect to the substituted amino group of the copolymer.
Add 5.0 times, preferably 1.0 to 3.0 times equivalent of strong acid, preferably hydrochloric acid, and heat at a temperature of usually 80 to 150 ° C, preferably 90 to 120 ° C, usually for 0.5 to 50 hours. As a result, a cationic polymer having an amidine unit can be obtained. In general, the larger the equivalent ratio of the strong acid to the substituted amino group and the higher the reaction temperature, the more the amidinization proceeds. In addition, upon amidation, 10% by weight or more, preferably 20% by weight of water is usually present in the reaction system with respect to the copolymer used in the reaction.

The surface coating agent comprising a water-soluble polymer according to the present invention, most typically according to what has been described above,
Produced by copolymerizing N-vinylformamide and acrylonitrile and heating the resulting copolymer in the presence of hydrochloric acid as an aqueous suspension to form an amidine unit from a cyano group adjacent to a substituted amino group. To be done. Then, by selecting the molar ratio of N-vinylformamide and acrylonitrile used for the copolymerization and the amidation conditions of the copolymer, it is possible to produce a surface coating agent composed of a water-soluble polymer having various compositions.

One of the typical surface coating agents comprising a water-soluble polymer according to the present invention comprises 20 to 90 mol% of the repeating unit represented by the above (1) and / or (2),
0 to 20 mol% of the repeating unit represented by the above (3),
0 to 70 mol% of the repeating unit represented by the above (4) and 0 to 70 mol% of the repeating unit represented by the above (5)
It has a reduced viscosity of 0.1 to 10 dl / g. In the present invention, the reduced viscosity shall be measured at 25 ° C. as a solution of 0.1 dl / g in 1N saline. In the above-mentioned surface coating agent, it is considered that the amidine unit greatly contributes to the performance of the fixing agent.

As the proportion of amidine units increases, the performance as a surface coating agent generally tends to improve. However, it is difficult to produce an amidine unit having a ratio of more than 90 mol% by heating the above copolymer in an aqueous hydrochloric acid solution. Therefore, the proportion of amidine units in the surface coating agent is usually preferably 20 to 85 mol%.

The repeating unit (3) is derived from an N-vinyl compound which is more expensive than acrylonitrile, but its presence does not seem to contribute to the performance as a coating agent. If the number of repeating units (3) increases, the water resistance of the surface coating agent may decrease. However, when the proportion of amidine units is 50 mol% or more, the surface coating agent has excellent performance even if a large amount of repeating units (3) are present. Since the water-soluble polymer that is formed generally has poor stability as it is, it is necessary to add a strong acid to completely neutralize the cationic units of repeating units (1), (2) and (5). preferable.

Although the effect of the repeating unit (4) on the performance as a surface coating agent is not clear, it is presumed that the repeating unit (4) slightly affects the water resistance and light resistance of the recorded image, and at least has no adverse effect. it is conceivable that. The repeating unit (4) is present in the polymer in an amount of 0 to 70 mol%,
Since nitrile is an inexpensive monomer, the presence of the repeating unit (4) is effective in reducing the manufacturing cost of the surface coating agent and improving the performance advantage with respect to the cost. The suitable abundance ratio of the repeating unit (4) is 5 to 60 mol%, particularly 5 to 50 mol%.

In the surface coating agent according to the present invention, the molar ratio of repeating unit (4) to amidine unit [(1) +
(2) / (4)] should generally be in the range of 0.5 to 10.0. This is because it is generally considered that the larger the number of amidine units, the better the surface paper quality improving function.

The repeating unit (5) is cationic,
Like the amidine unit, it is considered that it effectively acts to improve the surface paper quality. The repeating unit (5) is present in the coating composition in an amount of 0 to 70 mol%, preferably 5 to 60 mol%. Repeating units (1), (2) and (5) are all derived from repeating unit (3). Therefore, it is generally preferred that as many repeating units (3) as possible have been converted to repeating units (1), (2) or (5). The total of the repeating units (1), (2) and (5) in the surface coating agent is generally 30 mol%.
The above is preferably 40 to 95 mol%.

This means that, of the repeating units constituting the polymer, most of the repeating units considered to contribute to the function of the surface coating agent are advantageous. In addition,
In the surface coating agent according to the present invention, the molar ratio of the repeating unit (5) and the amidine unit [(1) + (2) / (5)].
Is generally in the range of 0.5 to 10.0. It is considered that the amidine unit more effectively acts on the performance of the coating agent than the repeating unit (5), so that [(1) + (2) /
(5)] is more preferably in the range of 1.0 to 5.0.

The surface coating agent according to the present invention contains an anionic repeating unit such as the repeating unit (6). For example, a carboxyl group represented by the following repeating unit (7) is generally produced in an amount of 0 to 5 mol% by hydrolysis of the repeating unit (4). However, in the case of producing an amphoteric polymer, acrylic acid or methacrylic acid is used. It is more convenient to copolymerize anionic monomers such as acids, allyl sulfonic acids, styrene sulfonic acids, 2-acrylamido-2-methylpropane sulfonic acid, itaconic acid. Generally, 0 to 20 mol% is preferable, but 0 to 10 mol% is more preferable.
When it is 20 mol% or more, the anionic property becomes too strong and the characteristics of the amidine structure are not expressed, which is not practical. The surface coating agent according to the present invention may further contain other repeating units in addition to the above repeating units. However, the total of the above-mentioned repeating units (1) to (6) should account for 90 mol% or more. The following repeating units (8) to (10) can be mentioned as other repeating units that can be contained in the surface cloth preparation of the present invention. The repeating unit (8) is produced by hydrolysis of the repeating unit (4) and is usually in the range of 0 to 5 mol%. The repeating units (9) and (10) are formed by the repeating unit (5) and the repeating unit (8), and usually 0 to 5 mol%.

[0040]

[Chemical 15]

[0041]

Embedded image

[0042]

[Chemical 17]

[0043]

Embedded image

The reduced viscosity of the surface coating agent comprising the water-soluble polymer according to the present invention is usually 0.1 to 10 dl / as described above.
g, preferably in the range of 0.5 to 7.0 dl / g. The reason for this is that if the viscosity is too high, it will hinder the process of surface coating on paper and the handling will be poor. On the other hand, if the viscosity is too low, the surface strength improving effect and water resistance are deteriorated, which is not practical.

The water-soluble polymer according to the present invention is used by surface coating. After performing papermaking drying, a size press, a gate roll coater, a coating solution obtained by mixing a single solution of the water-soluble polymer according to the present invention or another coating agent.
It is common to use a blade coater or a calender.

The water-soluble polymer according to the present invention can be used in combination with other coating agents. For example, cationic modified starch, oxidized starch, polyvinyl alcohol, polyacrylamide for surface coating, etc., or a mixed solution with a surface sizing agent can be used for coating. Examples of the coating pigment include finely powdered silicic acid, clay, talc, diatomaceous earth, calcium carbonate, barium sulfate, titanium oxide, zinc oxide, satin white, and aluminum silicate. Other additives such as surface sizing agent, anti-slip agent, antiseptic agent, defoaming agent, viscosity modifier and dye may be used in combination.

The amount of the water-soluble polymer according to the present invention added to these coating layers is usually 0.05 g / m ² -1.
0 g / m ^2, and preferably from ^{0.2g / m 2 ~5g / m 2} . The coating base paper when the water-soluble polymer according to the present invention is used as a surface coating agent is not particularly limited, and includes acid papermaking, neutral papermaking base paper, newsprint paper, printing writing paper, foam paper, PPC paper, etc. It can be applied to each base paper.

[0048]

EXAMPLES In order to further clarify the present invention, a production example of a water-soluble polymer which is a surface coating agent of the present invention will be shown as a reference example, and then a treatment of paper with the coating agent of the present invention and the result thereof will be described. An example of is shown. The examples are representative examples, and the present invention is not limited to the examples. In addition,
In the examples, "%" means "% by weight" unless otherwise specified.

(Production Example of Water-Soluble Polymer) A reactor equipped with a stirrer, a nitrogen inlet tube, and a condenser was charged with 20 g of a monomer having the composition shown in Table 1 and 133.1 g of demineralized water. In a nitrogen gas stream, the temperature was raised to 60 ° C. and maintained for 30 minutes, then, 0.19 g of a 10% aqueous solution of 2,2′-azobisamidinopropane dihydrochloride was added, and the mixture was maintained at 60 ° C. for 4 hours with stirring. A suspension in which the polymer was precipitated in water was obtained. 2-mercaptoethanol was added as a chain transfer agent to control the degree of polymerization. 1 and NO. 2 is 0.8% of monomer, N
O. 3 and NO. 4 and NO. 7 to NO. 10 is 0.
2%, NO. 5 and NO. 6 was 0.05% and was added at the time of polymerization. In addition, NO. 7 and NO. No. 8 is a copolymer of acrylic acid and NO. 9 and NO. 10 is an N-vinylformamide homopolymer. After the polymerization, the suspension was added with an equivalent amount of hydrochloric acid as shown in Table 1 with respect to the formyl group in the polymer and stirred at 90 ° C. for 4 hours to amidate the polymer. The polymer solution thus obtained was added to acetone to cause precipitation, and this was dried to obtain solid polymer NO. 1
To NO. Got 10. The polymer NO. 1 to NO. 1
The composition and reduced viscosity were measured by the following method for 0. The results are shown in Table 1.

(Analysis method of composition) The composition of each united body before amidation was calculated from the integral value of absorption spectrum corresponding to each monomer unit of ¹³ C-NMR spectrum ( ¹³ C-nuclear magnetic resonance spectrum). Polymer N after amidation
O. 1 to NO. The composition of 10 was calculated from the integrated value of the absorption peak corresponding to each repeating unit of the ¹³ C-NMR spectrum. It should be noted that the repeating units (1) and (2) were calculated as the total amount without distinction. Repeating unit (9)
(10) was also calculated as the total amount without distinction. Further, the absorption peaks of the repeating units (1) and (2), (8) and (9) and (10) were from 170 ppm to 18 ppm.
Since it was observed at a position near 5 ppm, the structure corresponding to each absorption peak was assigned by the following method. That is, the weight balance is confirmed by the elemental analysis of the polymer and the measurement of the water content, and further the IR spectrum is measured in addition to the ¹³ C-NMR spectrum of the polymer, and the spectrum of the polymer and the amidine group, amide group, lactam group, etc. This method is used to compare and examine the spectrum with a known compound in detail.

(Measurement of Reduced Viscosity) Polymer NO. 1 to N
O. 10 was measured as a solution of 0.1 g / dl in 1 N saline at 25 ° C. using an Ostwald viscometer.

[0052]

[Table 1]

(Examples 1 to 8) (1) Application of water-soluble polymer Using fine wood paper having a basis weight of 70 g / m ² and a Steckigt sizing degree of 25 seconds as a support, 100 g of fine powder silica, 50 g of polyvinyl alcohol, a book 3 g of water-soluble polymer of the invention, 500 g of water
A coating solution was prepared by mixing at a ratio of 1 and the solid content of 18.8 g / m ^{2 was} applied on one side by a test size press (manufactured by Kumagai Riki Co., Ltd.). After printing as described below, an ink fixing test was conducted. (2) Ink fixability test a. Printing: Inkjet printer [BJC-600
J (manufactured by Canon Inc.)] for each color of magenta (M), cyan (C), yellow (Y), and black (B). b. Water resistance: The printed image was allowed to stand in running water of 3 liters / min for 5 minutes, the image density before and after the test was measured with a Macbeth Densidometer RD918, and the degree of residual color was displayed as a percentage. c. Light resistance: The printed image was put into a fade meter, irradiated at 60 ° C. for 24 hours, the image density before and after irradiation was measured by a Macbeth Densidometer, and the degree of residual color was displayed as a percentage. The above results are summarized in Table 2.

Comparative Examples 1 to 5 For comparison, hydrochloric acid hydrolyzate of N-vinylformamide homopolymer (polymer N
O. 9, polymer NO. 10) (Comparative Examples 1 and 2), polyethyleneimine (polymer No. 11) (Comparative Example 3), dicyandiamide-formalin resin (polymer No. 12)
Each polymer of (Comparative Example 4) was also prepared by preparing a dispersion containing the same proportions, and coating and testing. The same test was carried out for the case where no polymer was used (Comparative Example 5). The above results are summarized in Table 2.

[0055]

[Table 2]

(Examples 9 to 16) In the same manner as in Example 1, application of a water-soluble polymer, printing of test pieces after application, and water resistance and light resistance tests were performed. The same base paper as in Example 1 was used as a support for the base paper, 100 g of white carbon for papermaking, 50 g of polyvinyl alcohol, 4.5 g of water-soluble polymer and 500 g of water were mixed in a proportion of 14.0 g / m ^{2 on} one side as a solid content. did. The results are shown in Table 3.

Comparative Examples 6 to 10 Polymer N for comparison
O. 9 (Comparative Example 6), polymer NO. 10 (Comparative Example 7),
Polymer NO. 11 (Comparative Example 8), polymer NO. Tests were carried out in the same manner as in Example 9 using each polymer of No. 12 (Comparative Example 9). The same test was carried out also when the polymer was not used (Comparative Example 10). Table 3 is a summary of the above results.
Shown in

[0058]

[Table 3]

(Examples 17 to 24) In the same manner as in Example 1, application of a water-soluble polymer, printing of test pieces after application, and water resistance and light resistance tests were performed. The same base paper as in Example 1 was used as the base paper, and 100 g of finely divided silica, 45 g of polyvinyl alcohol, 6.0 g of water-soluble polymer and 500 g of water were mixed together, and the solid content was coated on one side at 10.0 g / m ² . . The results are shown in Table 4.

(Comparative Examples 11 to 15) Polymer N for comparison
O. 9 (Comparative Example 11), polymer NO. 10 (Comparative Example 1
2), polymer NO. 11 (Comparative Example 13), polymer NO.
Tests were carried out in the same manner as in Example 17 using each polymer of No. 12 (Comparative Example 14). The same test was carried out when the polymer was not used (Comparative Example 15). The above results are summarized in Table 4.

[0061]

[Table 4]

(Examples 25 to 32) A size press test was conducted using the water-soluble polymer of the present invention. (1) Size Press After diluting the water-soluble polymer (polymer Nos. 1 to 8) of the present invention with water so that the final concentration is 2.5%, a commercial size paper ( The basis weight was 55 g / m ² ) and both sides were coated so that the coating amount was 1.0 g / m ² .
Drying is performed with a drum dryer at 90 ° C. for 1 minute, and after drying, it is left standing for 24 hours under the conditions of 20 ° C. and 65% RH to control the humidity. (2) Paper quality measurement a. Ink T.D. V. 8. Printing was performed with an ink amount of 0.5 ml. b. Ink T.I. using a wet pick RI printing tester. V. 8, ink amount 0.
Printed at 5 ml. In each case, the peeled state after printing is observed, and 5 is evaluated as being excellent and 1 is inferior. c. Ink setting property 0.5 ml of an offset ink for newspapers is used for printing by an RI printability test, and then the ink setting property is judged according to the degree of set-off by press-bonding to an upper coated paper. 5 is excellent and 1
Is evaluated as inferior and evaluated on a scale of five. d. Whiteness The whiteness of the size-pressed paper in (1) was measured according to JIS 8123. e. Opacity The opacity of the paper size-pressed in (1) was measured according to JIS 8138A. The above results are shown in Table 5.

(Comparative Examples 16 to 19) For comparison, N-
Hydrochloric acid hydrolyzate of vinylformamide homopolymer (polymer polymer No. 10 (Comparative Example 16), polyethyleneimine (polymer No. 11) (Comparative Example 17), oxidized starch [Oji Ace A] (polymer No. 13) (Comparative Example 1
8), 90 mol% acrylamide and 10 mol% acrylic acid copolymer [viscosity at 10% concentration is 8500 cp (25
C.)] (Polymer No. 14) (Comparative Example 19). The above results are summarized in Table 5.

[0064]

[Table 5]

(Examples 33 to 40) A size press test was conducted using the water-soluble polymer of the present invention. (1) Size press After diluting the water-soluble polymer (polymer Nos. 1 to 8) of the present invention with water so that the final concentration becomes 1.9%, Hacon S20 as a surface sizing agent was used as a liquid sizing agent. After adding so as to be 11%, a commercially available high-quality paper [basis weight 70 g / m ² ] was used as a base paper by a size press for test, and the coating amount was 0.7.
Both sides were coated so as to have g / m ² . Drying is done with a drum dryer at 90 ° C for 1 minute, and after drying at 20 ° C, 65%
It is left to stand for 24 hours under the condition of RH to control the humidity. (2) Paper quality measurement a. Internal strength The internal bond tester (manufactured by Rigaku Kumagai) was used under the conditions of an adhesive pressure of 1 kg / cm ² and 30 seconds. b. Surface strength Dry pick RI Ink test using an RI printing tester. V. 18, printed with an ink amount of 0.5 ml. Ink T.W. using a wet pick RI printing tester. V. 18, printed with an ink amount of 0.5 ml. In each case, the peeled state after printing is observed, and 5 is evaluated as being excellent and 1 is inferior. c. Sizing degree The sizing degree of the paper size-pressed in (1) was measured according to the Steckigt method JIS 8122. d. Tensile Strength The tensile strength of the paper size-pressed in (1) was measured according to JIS 8113, and the breaking length (Km) was calculated. The above results are shown in Table 6.

(Comparative Examples 20 to 23) For comparison, N-
Hydrochloric acid hydrolyzate of vinylformamide homopolymer (polymer polymer No. 10 (Comparative Example 20), polyethyleneimine (polymer No. 11) (Comparative Example 21), oxidized starch [trade name: Oji Ace A] (heavy) Combined No. 13) (Comparative Example 22), 90 mol% acrylamide and 10 acrylic acid
Mol% copolymer [viscosity at 10% concentration 8500 cp (2
5 ° C.)] (Polymer No. 14) (Comparative Example 23). The above results are summarized in Table 6.

[0067]

[Table 6]

[0068]

INDUSTRIAL APPLICABILITY The present invention relates to a paper surface coating agent, which comprises applying a specific water-soluble polymer having an amidine structural unit on the surface of a paper after paper making It is possible to improve water resistance, light resistance, and fixability of anionic water-based ink. The paper whose surface paper quality is improved by the surface coating agent of the present invention is also preferably used as a recording material from which a recorded image of high resolution and high quality comparable to that of a color photograph can be obtained.

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[Procedure amendment]

[Submission date] March 9, 1995

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0068

[Correction method] Change

[Correction content]

(Examples 41 to 48) In the same manner as in Example 1, a single coating of the water-soluble polymer, printing of test pieces after coating, and water resistance and light resistance tests were performed. The base paper is the same as in Example 1 and the support is used, and 2.5 g of the water-soluble polymer is added to water.
0.4 g of solid content was applied on one side by a solution dissolved in 7.5 g. The results are shown in Table 7. (Comparative Examples 24 to 28) Polymer No. 9, polymer no. 10, polymer no. 11, polymer No. 12 polymers were used and tested in the same manner as in Example 41 (Comparative Examples 24 to 27). In addition, a polymer-uncoated paper was also tested (Comparative Example 28). The above is summarized in Table 7.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0069

[Correction method] Added

[Correction content]

[0069]

[Table 7]

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0070

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(Examples 49 to 57) In the same manner as in Example 41, a water-soluble polymer, a commercial surface strength agent A (polyacrylamide type), a commercial surface strength agent B (polyvinyl alcohol type), and a commercial surface strength agent C ( Each mixed application with oxidized starch) was tested. As the base paper, the same paper as in Example 1 was used as a support, and 2.0 g of a water-soluble polymer and a commercial surface strength agent 4.0 were used.
0.4 g on one side was applied with a solution of g in 94.0 g of water. Table 8 shows the results.

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Comparative Examples 29-37 Polymer N for comparison
o. 10 and polymer no. 12 polymers were used and tested in the same manner as in Example 49 (Comparative Examples 29 to 34).
Further, the paper coated with only the commercial surface strength agent was also tested (Comparative Examples 35 to 37). The above is summarized in Table 8.

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[0072]

[Table 8]

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[0073]

INDUSTRIAL APPLICABILITY The present invention relates to a paper surface coating agent, which comprises applying a specific water-soluble polymer having an amidine structural unit on the surface of a paper after paper making It is possible to improve water resistance, light resistance, and fixability of anionic water-based ink. The paper whose surface paper quality is improved by the surface coating agent of the present invention is also preferably used as a recording material from which a recorded image of high resolution and high quality comparable to that of a color photograph can be obtained.

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Claims (8)

[Claims] 1. A repeating unit represented by the following (1) and / or (2) is 20 to 90 mol%, a repeating unit represented by the following (3) is 0 to 40 mol%, and the following (4) is It contains 0 to 70 mol% of the repeating unit represented by the formula, 0 to 70 mol% of the repeating unit represented by the following (5), and 0 to 20 mol% of the repeating unit represented by the following (6). A paper surface coating agent comprising a water-soluble polymer, which has a reduced viscosity value of 0.1 to 10 dl / g measured at 25 ° C. as a solution of 0.1 g / dl in saline solution. Embedded image Embedded image Embedded image [Chemical 4] Embedded image [Chemical 6] (Wherein R ¹ and R ² are a hydrogen atom or a methyl group, R ³ is an alkyl group having 1 to 4 carbon atoms, R ⁴ is a hydrogen atom, a methyl group or a carboxymethyl group, X ⁻ is an anion, and Y is CO.
OM, C ₆ H ₄ SO ₃ M, CH ₂ SO ₃ M, CONHC
(CH ₃ ) ₂ CH ₂ SO ₃ M and M each represent a cation. ) 2. The paper surface coating agent according to claim 1, wherein the repeating unit (1) and / or (2) is 40 to 80 mol%. 3. The paper surface coating agent according to claim 1, which comprises an acid hydrolyzate of a copolymer of N-vinylformamide and acrylonitrile. 4. The paper surface coating agent according to claim 1, which improves printability. 5. The paper surface coating agent according to claim 1, which is used as a recording paper for ink jet. 6. The paper surface coating agent according to claim 1, which is used as an agent for improving ink setting properties. 7. The paper surface coating agent according to claim 1, which improves the surface strength of the paper. 8. The paper surface coating agent according to claim 1, which improves the internal strength of the paper.