JPH0850366A - Recording paper - Google Patents

Abstract

PURPOSE:To make it possible to use an acrylonitrile-acrylic ester 8 copolymer for both of electrophotographic transfer paper and ink jet recording paper by using the copolymer in the form of an emulsion. CONSTITUTION:Neutral paper contg. pulp fibers, a filler and an internal sizing agent is coated with a surface sizing agent. This surface sizing agent is an emulsion of an acrylonitrile-acrylic ester copolymer obtd. by emulsion- polymerizing 20-80wt.% (meth)acrylonitrile (a), 20-70wt.% alkyl (meth)acrylate (b) and 0-40wt.% ethylenically unsatd. monomer (c) copolymerizable with the monomers (a), (b) in the presence of an emulsifying agent.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to recording paper. More specifically, it relates to a recording paper that can be used as both electrophotographic transfer paper and inkjet recording paper.

[0002]

2. Description of the Related Art In recent years, with the spread of electrophotographic copying machines, electrophotographic transfer paper has been widely used as recording paper for general office paper and printing paper. Conventionally, acid paper has been the mainstream of such electrophotographic transfer paper, but from the viewpoints of storability, image suitability, etc., and in consideration of energy saving and productivity improvement in paper manufacturing, it is used as a filler. A neutral paper is used in which a so-called neutral sizing agent such as an alkyl ketene dimer is internally added using calcium carbonate. In addition to the electrophotographic copying machine, an inkjet recording method using a water-based ink is also adopted because it has the advantages that noise during recording is small and a high-resolution image can be obtained at high speed. There is. In order to improve the absorbability and dryness of the water-based ink, non-size paper based on acidic paper or recording paper provided with an absorbent coating layer such as silica is used for such inkjet recording paper. There is.

However, since electrophotographic transfer paper and ink jet recording paper have been developed suitable for their respective uses, the electrophotographic transfer paper and ink jet recording paper cannot be diverted to each other. There wasn't. That is, when an inkjet recording paper is used as a transfer paper for electrophotography, it has a coating layer containing silica as a main component on the surface, so that it not only damages the photosensitive drum, but also the fixing property of the toner and the running light of a copying machine. There was almost no suitability for electrophotography such as sex. On the other hand, when electrophotographic transfer paper is used for ink jet recording paper, the ink absorbency is poor and the ink remains on the paper surface for a long time after printing, and the printed image is disturbed when it is touched by hand or the recording paper is rubbed. There is a problem that stains and the like on the recording paper are likely to occur, and a whisker-like bleeding called feathering occurs.

Further, the neutral paper used for the electrophotographic transfer paper, when alkenyl succinic anhydride or alkyl ketene dimer is used as a neutral sizing agent, stains during paper making; If it is used, the friction coefficient of the paper is low and it is slippery; if a hydrophobically modified rosin emulsion is used, it foams in a white water system; I have a problem. Therefore, a small amount of internally added sizing agent is used as the surface sizing agent and anionic styrene-
A transfer paper for electrophotography has been proposed in which an aqueous solution of an acrylic copolymer or an aqueous solution of an anionic styrene-acrylonitrile copolymer is applied to improve the size effect. The recording paper having the surface size of the neutral paper has excellent suitability for electrophotography and also has inkjet suitability such that the penetration of the aqueous ink into the paper layer can be suppressed to some extent and the printing density can be increased. That is, when a conventionally known surface sizing agent is applied by a size press or the like, it penetrates into the paper to improve the sizing property in the Z-axis direction (Steckigt sizing degree) and suppresses the penetration of ink to reduce the print density. Will be higher. However, since all of the conventionally known surface sizing agents are aqueous solutions, the lateral sizing property of the surface is weak and the feathering suitable for inkjet is not sufficiently satisfied.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a recording paper which can be used as both electrophotographic transfer paper and ink jet recording paper. In particular, it is an object of the present invention to provide a recording paper having high printing density, good feathering, and excellent resolution as an inkjet recording paper.

[0006]

Means for Solving the Problems The inventors of the present invention have made extensive studies as to a surface sizing agent to be coated on neutral paper in order to solve the above-mentioned problems of the prior art, and as a result, acrylonitrile-acrylic acid ester-based It was found that the above problems can be solved by using the copolymer in the form of emulsion. The present invention has been completed based on this new finding.

That is, the present invention provides a neutral paper containing pulp fibers, a filler and an internally added sizing agent with acrylonitrile-
The present invention relates to a recording paper coated with a surface sizing agent containing an acrylic acid ester copolymer emulsion as a main component.

The surface sizing agent used in the present invention is an emulsion of an acrylonitrile-acrylic acid ester copolymer as described above. The emulsion of the copolymer of the present invention specifically includes (1) 20 to 80% by weight of (meth) acrylonitrile, (2) 20 to 70% by weight of (meth) acrylic acid alkyl ester, and optionally (3). ) It is obtained by emulsion polymerization of 0 to 40% by weight of an ethylenically unsaturated monomer copolymerizable with the above (1) and (2) in the presence of an emulsifier.

(1) (Meth) acrylonitrile means acrylonitrile and / or methacrylonitrile. The amount of such (meth) acrylonitrile used is 20 to 80% by weight, preferably 30 to 70% by weight of the obtained copolymer.
% By weight. When the amount of the (meth) acrylonitrile used is outside the above range, the size property in the Z-axis direction (Stecht sizing degree) is lowered, the ink absorbency is increased, and the printing density is lowered, which is not preferable.

(2) What is a (meth) acrylic acid ester?
It means acrylic acid ester and / or methacrylic acid ester, and these can use 1 type (s) or 2 or more types.
Examples of the ester substituent of the (meth) acrylic acid ester include a linear or branched alkyl group having 1 to 18 carbon atoms, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and an n-butyl group. Group, isobutyl group,
Examples thereof include t-butyl group, neopentyl group, n-hexyl group, cyclohexyl group, 2-ethylhexyl group, decyl group, palmityl group and stearyl group. Other ester substituents include hydroxyalkyl groups such as 2-hydroxyethyl group and 2-hydroxypropyl group, N, N
Examples thereof include aminoalkyl groups such as -dimethylaminoethyl group and N, N-diethylaminoethyl group, as well as benzyl group and allyl group. Among these ester substituents, the carbon number is 1 to 1 in consideration of the fact that a sticky substance is generated during coating when the film-forming temperature of the resulting copolymer is low.
2 alkyl groups are preferred. The amount of such (meth) acrylic acid ester used is 20 to 70% by weight, preferably 30 to 60% by weight, of the copolymer obtained. When the amount of the (meth) acrylic acid ester used is outside the above range,
It is not preferable because the size property in the Z-axis direction (Steckigt sizing degree) decreases, the ink absorbency increases, and the print density tends to decrease.

In the present invention, if necessary, (3) the above (1)
The ethylenically unsaturated monomer copolymerizable with (2) and (2) can be used as long as the resulting copolymer does not deviate from the object of the present invention and can retain its effect. Examples of the (3) ethylenically unsaturated monomer that can be used as necessary include styrenes such as styrene, α-methylstyrene and vinyltoluene; (meth) acrylamide; vinyl esters such as vinyl acetate and vinyl propionate;
C6 to C22 α-olefins, C1 to C22 alkyl vinyl ethers, nonionic unsaturated monomers such as vinylpyrrolidone, acrylic acid, methacrylic acid, maleic acid (or its half ester), itaconic acid, Examples thereof include anionic unsaturated monomers such as vinyl sulfonic acid, 2-acrylamidopropane sulfonic acid or alkali salts thereof. The amount used is 0 to 0 for the copolymer obtained.
It is 40% by weight, preferably 0 to 20% by weight. For example, when the amount of water-soluble monomer such as acrylamide or acrylic acid exceeds 40% by weight, the viscosity of the obtained emulsion becomes high and the workability is deteriorated. If the amount exceeds 40% by weight, a large amount of an emulsifier is required because the generation of aggregates increases during polymerization, and foaming in the coating solution becomes a problem. If the amount of olefin used exceeds 40% by weight. The fixability of the toner deteriorates.

As the emulsifier used for producing the emulsion of the copolymer of the present invention, various nonionic surfactants,
Anionic surfactants, various modified starches, and decomposed starches can be used.

Examples of the nonionic surfactant include polyethylene glycol, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether and the like. As the anionic surfactant, for example, alkyl sulfate, alkylbenzene sulfonate,
Examples thereof include polyoxyethylene alkyl ether sulfate, polyoxyethylene alkylphenyl ether sulfate, alkyl sulfonate, polyoxyethylene alkyl ether sulfosuccinate, and polyoxyethylene alkyl ether phosphate ester. Examples of modified starch include starch obtained by chemically modifying starch such as wheat, rice, tapioca, potato or corn with an aminoalkyl group which is hydroxyethylated, hydroxypropylated or quaternized. As decomposed starch,
Starch that has been subjected to oxidative, thermal, acidic hydrolysis or enzymatic decomposition is included.

When a nonionic surfactant and / or an anionic surfactant is used as an emulsifier,
0.1 to 20 relative to the total amount of the monomers (1) to (3)
%, Preferably 0.5-10% by weight is used. If the amount is less than 0.1% by weight, agglomerates are generated during emulsion polymerization, and if the amount is more than 20% by weight, there is a problem of foaming when used as a coating liquid. When modified starch and / or decomposed starch is used as the emulsifier, it is 10 to 200% by weight, preferably 2 to the total amount of the monomers (1) to (3).
It is preferable to use 0 to 150% by weight. If the amount is less than 10% by weight, agglomerates may be generated during emulsion polymerization.
If it exceeds 0% by weight, the sizing property is deteriorated, which is not preferable in any case.

The emulsion of the copolymer of the present invention may be produced by a known emulsion polymerization method. For example, a method may be used in which the monomer, the emulsifier, water, and the radical polymerization initiator are added to a predetermined reaction container, and the mixture is heated with stirring. The dropping method of the monomer or the like may be batch charging or divided dropping, and the monomer and the radical polymerization initiator may be dropped in the presence of an emulsifier and water. The concentration of the monomer mixture in the reaction system is usually 5 to 50% by weight.
About 40 to 110 ° C., preferably 50
The temperature is -100 ° C, and the reaction may be performed for about 1-10 hours.

Examples of the radical polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, hydrogen peroxide, water-soluble radical polymerization initiators such as aqueous azo initiators, and the above-mentioned persulfates. Examples thereof include redox-based polymerization initiators in the form of a combination with a reducing agent such as sodium hydrogen sulfite and sodium thiosulfate. The amount of the initiator used is about 0.05 to 5% by weight, preferably 0.1 to 3% by weight, based on the total amount of the monomer mixture. In addition, the molecular weight of the copolymer can be adjusted by using a molecular weight regulator such as dodecyl mercaptan, 2-mercaptobenzothiazole and bromotrichloromethane.

The molecular weight of the obtained copolymer is usually 1000.
~ 1,000,000, preferably 2000-5000
00. When the molecular weight is less than 1000, a sufficient size effect cannot be obtained, and when the molecular weight exceeds 1,000,000, the viscosity of the emulsion tends to be high and the workability tends to be poor. The viscosity of the obtained copolymer emulsion is usually 100 cp at a concentration of 20% at 25 ° C.
It should be s or less.

The recording paper of the present invention is a neutral paper coated with an emulsion of the above copolymer as a surface sizing agent. As the neutral paper, known paper containing pulp fiber, internally added sizing agent, and filler can be used.

Pulp fibers include NBKP and LBK
Besides P, LBSP, GP, TMP, etc., DIP can also be used.

As the filler, calcium carbonate, calc,
Inorganic and organic fillers such as kaolin, titanium dioxide and clay can be used. Among these, calcium carbonate, when considering the prevention of drum stains when used as electrophotographic transfer paper and the prevention of dot spread and feathering when used as inkjet recording paper, Kaolin is preferred. As the calcium carbonate, various known ones such as heavy calcium carbonate and precipitated calcium carbonate can be used.

As the internally added sizing agent, various sizing agents generally called neutral sizing agents can be used without particular limitation. Examples of the neutral sizing agent include alkenyl succinic anhydride, alkyl ketene dimer, and hydrophobized modified rosin. These are usually used in the form of an aqueous emulsion. The hydrophobized rosin is a rosin substance containing an rosin ester, a polyhydric alcohol, and, if necessary, an α, β-unsaturated carboxylic acid modified rosin ester formed from an α, β-unsaturated carboxylic acid derivative as a main component. Say.

For the neutral paper, a filler and an internal sizing agent are added to pulp fibers, and an aluminum compound such as aluminum sulfate is used so that the papermaking pH becomes 6 to 9, preferably 6.5 to 8.5. Is adjusted and papermaking is performed. Specifically, the sizing agent is usually added to the pulp in an amount of about 0.01 to 2.0% by weight, and the filler is usually added to the pulp in an amount of about 2 to 20% by weight. In addition, various additives that can be usually used for papermaking, such as dyes, size fixing agents, retention aids, various paper strength enhancers, etc., can be used.

For coating the emulsion of the above-mentioned copolymer as a surface sizing agent on such neutral paper, an on-machine coating treatment apparatus such as a size press or a gate roll coater can be appropriately selected and used. The coating solution may be prepared by adding an emulsion of the above-mentioned copolymer to a surface paper quality improving agent such as starch, polyvinyl alcohol, polyacrylamide, etc. to have a concentration suitable for surface coating. Generally, the concentration of the coating liquid is about 0.5 to 25% by weight, although it depends on the type of coating treatment apparatus and the surface paper quality improving agent. The concentration of the copolymer emulsion in the coating liquid was 0.0
It is about 1 to 2% by weight. The coating amount on the neutral paper depends on the size of the base paper, but the solid content of the emulsion of the copolymer is usually 0.002 to 1% by weight based on the dry fiber.
(0.002-0.5g / m ^{2 on} both sides per area of paper)
Degree.

Furthermore, the emulsion of the copolymer as a surface sizing agent contains sodium chloride, potassium chloride,
A conductive agent such as a salt of a strong base such as a quaternary ammonium salt, an antifoaming agent, a latex, a dye or the like can also be used in combination.

[0025]

According to the present invention, it is possible to provide a recording paper which can be used as both electrophotographic transfer paper and ink jet recording paper. In particular, it is possible to provide a recording paper having high printing density, good feathering, and excellent ink jet characteristics as compared with conventionally known recording papers.

[0026]

The present invention will be described in more detail below with reference to Reference Examples, Examples and Comparative Examples, but the present invention is not limited to these Examples. In the examples, parts and% are based on weight.

Reference Example 1 150 parts of water was added to a reaction vessel equipped with a stirrer, a dropping funnel and a reflux condenser, and heated while stirring to raise the temperature to 80 ° C. To this, acrylonitrile 65
Part, 35 parts of methyl methacrylate, 5 parts of sodium dodecylbenzenesulfonate and 95 parts of water were mixed and stirred, and 1 part of 2,2′-azobis (2-methylpropionamidine) dihydrochloride was added to water. The radical polymerization initiator aqueous solution dissolved in 50 parts was dropped completely from the dropping funnel in 2 hours and then aged for 2 hours to complete the reaction. After that, the emulsion of the copolymer was diluted with water to a concentration of 20%, and the viscosity at 25 ° C was 5c.
An emulsion type surface sizing agent (A) of ps was obtained.

Reference Example 2 A reaction was carried out in the same manner as in Reference Example 1 except that the monomer composition was changed to 50 parts of methacrylonitrile, 40 parts of butyl acrylate and 10 parts of methacrylic acid. Polymer emulsion concentration 20%, viscosity at 25 ℃ 7
An cps emulsion type surface sizing agent (B) was obtained.

Reference Example 3 A copolymer was prepared in the same manner as in Reference Example 1, except that the composition of the monomer was changed to 45 parts of acrylonitrile, 50 parts of 2-ethylhexyl acrylate and 5 parts of acrylamide. Emulsion type surface sizing agent (C) with a concentration of 20% and a viscosity at 25 ° C of 75 cps
I got

Reference Example 4 Reference Example 1 except that 5 parts of sodium dodecylbenzenesulfonate as an emulsifier was replaced with 60 parts of dextrin (decomposed starch) and 95 parts of water was replaced with 300 parts of water.
The reaction is performed in the same manner as above, and the emulsion concentration of the copolymer is 2
An emulsion type surface sizing agent (D) having a viscosity of 0% and a viscosity at 25 ° C. of 15 cps was obtained.

Reference Example 5 In Reference Example 2, 5 parts of sodium dodecylbenzenesulfonate as an emulsifier was replaced with 30 parts of Amikol No6 (enzyme-modified starch, manufactured by Nippon Starch Chemical Co., Ltd.), and 95 parts of water was replaced with 200 parts of water. Other than that, the reaction was performed in the same manner as in Reference Example 1,
An emulsion type surface sizing agent (E) having a copolymer emulsion concentration of 20% and a viscosity at 25 ° C. of 8 cps was obtained.

Reference Example 6 100 parts of water and 75 parts of isopropyl alcohol were charged into a reaction vessel similar to that of Reference Example 1 and heated with stirring to raise the temperature to 85 ° C. To this, methacrylic acid 5
5 parts, isopropyl acrylate 15 parts and styrene 3
The reaction was completed after dropping all the monomer mixture liquid in which 0 parts were mixed and the radical polymerization initiator aqueous solution in which 5 parts of potassium persulfate was dissolved in 120 parts of water in 3 hours from the dropping funnel. Then, isopropyl alcohol was distilled off,
After cooling, 27 parts of 28% aqueous ammonia solution was added, and further diluted with water so that the concentration of the copolymer was 20%, and the temperature was 25 ° C.
Aqueous surface sizing agent with a viscosity of 1200 cps (F)
I got

Reference Example 7 Acrylonitrile 25 was placed in the same reaction vessel as in Reference Example 1.
Parts, 30 parts of methacrylic acid and 45 parts of butyl acrylate were added and heated with stirring to raise the temperature to 45 ° C. To this, an aqueous radical polymerization initiator solution prepared by dissolving 0.5 part of ammonium persulfate in 9.5 parts of water was added. The temperature rose to 80 ° C. due to the heat generation, and the reaction was completed by aging at 80 ° C. for 3 hours. After cooling, 10 parts of monoethanolamine was added, and further diluted with water so that the concentration of the copolymer was 20% to obtain an aqueous surface sizing agent (G) having a viscosity of 3000 cps at 25 ° C.

Reference Example 8 The reaction was carried out in the same manner as in Reference Example 6 except that the composition of the monomer was changed to 30 parts of acrylonitrile, 25 parts of styrene and 45 parts of methacrylic acid, and the concentration of the copolymer was changed. An aqueous surface sizing agent (H) having a viscosity of 20% and a viscosity at 25 ° C. of 1800 cps was obtained.

Example 1 (1) Manufacture of Neutral Paper Using a slurry having the following composition, a neutral paper having a basis weight of 65 g / m ² was produced.

The slurry is L-BKP (freeness 360 m).
lCSF) 65 parts, B-BLP (freeness 400 mlC
SF) 35 parts, calcium carbonate (Okutama Kogyo Co., Ltd. Tama Pearl 121) 10 parts, alkyl ketene dimer sizing agent (Arakawa Chemical Co., Ltd. Size Pine K)
903) 0.5 part, aluminum sulfate 1 part, cationic starch (Cato F manufactured by Oji National Co., Ltd.) 1 part, and a retention aid (Percoll 47 manufactured by Allied Colloid Co., Ltd.) 0.03 part were mixed and prepared.

(2) Production of recording paper To a reactor equipped with a stirrer and a reflux condenser, 10 parts of oxidized starch (Oji Ace manufactured by Oji Corn Starch Co., Ltd.) and 90 parts of water were added, and heated while stirring. Was raised to 95 ° C. Gelatinization was carried out at 95 ° C for 30 minutes to obtain an aqueous starch solution having a concentration of 10%. The following coating liquid was size-pressed with the coating amount shown in Table 1 on the neutral paper prepared in (1) above to obtain a recording paper.

The size press coating liquid was 30 parts of 10% starch paste liquid, and emulsion type surface sizing agent (A) 1.5.
Parts, 0.1 part of sodium chloride and 68.4 parts of water were mixed and prepared.

Examples 2 to 5 and Comparative Examples 1 to 2 Recording sheets were prepared in the same manner as in Example 1 except that the type of surface sizing agent and the coating amount were changed as shown in Table 1. Obtained.

(Test Example) The recording papers obtained in the examples and comparative examples were cut into A4 size sheets, conditioned at 20 ° C. and 65% RH for 24 hours, and then subjected to the following tests. Table 1 shows the evaluation results.

(1) Stoeckigt sizing degree According to JIS P-8122.

(2) Inkjet Suitability: An inkjet printer (BJ-10v) manufactured by Canon was used. 1. Solid density: A solid printing portion printed on two upper and lower sides and three left and right sides of A4 size paper was measured with a Sakura digital densitometer (PDA-65, manufactured by Konishi Rokusha Co., Ltd.) at 12 points, and the average value was determined. The concentration was used. An optical density of 1.25 or higher is required for inkjet recording paper. 2. Feathering: A horizontal ruled line pattern is printed on A4 size paper and the degree of blurring is determined by a pen writing size test (J. Tapp.
i No. According to 12), it was evaluated on a scale of 7 from 0 to 6. At least 5 is required as a recording sheet for inkjet.

(3) Suitability for electrophotography This was carried out using an electrophotographic copying machine (NP6150) manufactured by Canon Inc., using the same recording sheet cut to A4 size as above. 1. Toner fixability: 3 mm of 18 mm width cellophane tape was applied to the image area with optical density of about 1.4, which was copied by the above copying machine.
It was evaluated by the ratio of the image density after peeling to the image density before peeling (image density after peeling / image density before peeling) when the tape was stuck at a linear pressure of 00 g / cm and peeled at a speed of 1 cm / sec. . A Sakura Digital Densitometer (PDA-65, manufactured by Konishi Roku Co., Ltd.) was used to measure the image density. For electrophotographic transfer paper, the above ratio needs to be 0.8 or more. 2. Curl: After passing the recording paper in the CD direction to make a single-sided copy, place it on a flat table with the curl side facing up, measure the highest value of the four corners above the surface of the table, and average 10 sheets. It was evaluated by. The transfer paper for electrophotography is preferably 3 mm or less.

[0044]

[Table 1]

Claims (6)

[Claims] 1. A recording paper obtained by applying a surface sizing agent containing an emulsion of an acrylonitrile-acrylic acid ester copolymer as a main component to a neutral paper containing pulp fibers, a filler and an internally added sizing agent. . 2. An emulsion of an acrylonitrile-acrylic acid ester copolymer comprises (1) (meth) acrylonitrile 20 to 80% by weight, (2) (meth) acrylic acid ester 20 to 70% by weight, and optionally ( 3) An emulsion obtained by emulsion polymerization of 0 to 40% by weight of an ethylenically unsaturated monomer copolymerizable with (1) and (2) in the presence of an emulsifier. Paper. 3. A nonionic surfactant and / or an anionic surfactant is used as an emulsifier in (1) to (3).
The recording paper according to claim 2, wherein the recording paper is used in an amount of 0.1 to 20% by weight based on the total amount of the above monomers. 4. The recording according to claim 2, wherein modified starch and / or decomposed starch is used as an emulsifier in an amount of 10 to 200% by weight based on the total amount of the monomers (1) to (3). Paper. 5. The recording paper according to claim 1, wherein the filler is calcium carbonate and / or kaolin. 6. The recording paper according to claim 1, wherein the internally added sizing agent is at least one selected from alkenyl succinic anhydride, alkyl ketene dimer and hydrophobized modified rosin.