JP2684505B2 - Washi Reinforcing Agent - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to papermaking of natural fibers such as Kozo, Mitsumata and Manila hemp, or a part of these natural fibers made of polypropylene, vinylon, polyester, nylon,
The present invention relates to a Washi paper reinforcing agent that imparts excellent dry paper strengthening properties and wet paper strength enhancing properties to a Washi paper obtained by mixing and making synthetic fibers such as rayon by impregnation, and in particular, a resin laminated with a polyester film. It is suitable as a Washi paper reinforcing agent for heat-sensitive stencil printer master paper, which provides wet ultra-thin Japanese paper with adhesiveness and printing durability and is subjected to a plate making method using a writing perforation method with a thermal head.

[0002]

2. Description of the Related Art Conventional paper strengthening agents include polyvinyl alcohol resins, polyacrylamides and starches as dry paper strengthening agents, and urea formaldehyde resins, melamine formaldehyde resins as wet strength agents.
Dialdehyde starch, glyoxal modified polyacrylamide, polyamide polyamine epichlorohydrin, etc. have been used as internal additives during the papermaking process. As the impregnating agent, resin type latex such as SBR latex, chloroprene latex, NBR latex, vinyl acetate latex, acrylate latex, vinyl chloride latex and vinylidene chloride latex is used as a dry paper strength enhancer and a wet paper strength enhancer. Has been used.

In particular, with respect to a heat-sensitive stencil printing press master paper obtained by laminating a polyester film on a natural fiber type ultra-thin Japanese paper, when the plate is perforated and printed by a thermal head, the ink permeability is good, but the water resistance is small.
Printing durability is insufficient when continuously printed by using water-based ink, and in order to use ultra-thin Japanese paper as a master paper for heat-sensitive stencil printing machine, it has excellent wet adhesion to polyester film and conventional No wet paper strength is required.

However, the internal additives used in the papermaking process not only have problems in work environment and work safety due to generation of formalin, but also have insufficient wet paper strength.
In addition, even resin-based latex that has been conventionally used as an impregnating agent has poor adhesiveness when wet with a polyester film,
Wet paper strength is not satisfied, and the use of these conventional internal additives and impregnating agents as reinforcing agents for Japanese paper for heat sensitive stencil printing press master papers has the drawback that printing durability is insufficient and printing bleeding occurs during continuous printing. It was

More recently, in order to improve image clarity, Japanese paper for heat sensitive stencil printer master paper includes kozo, mitsumata and some natural fibers such as manila hemp and polypropylene, vinylon, polyester, nylon and rayon. Therefore, there is a growing demand for a Washi paper reinforcing agent for a heat sensitive stencil printing press master paper, which enhances the wet adhesion with a polyester film and the wet paper strength because it tends to be mixed with synthetic fibers.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a Japanese paper reinforcing agent which is excellent in dry paper strength and wet paper strength by impregnating Japanese paper, and a polyester film. The laminated resin processed ultra-thin Japanese paper has excellent adhesiveness when wet,
Further, it is an object of the present invention to provide a Japanese paper reinforcing agent for a heat sensitive stencil printing machine master paper for providing a master paper for a heat sensitive stencil printing machine which is excellent in printing durability and does not cause bleeding of printing during continuous printing.

[0007]

Means for Solving the Problems As a result of earnest research for solving the above problems, the present inventors have achieved the present invention by overcoming the above problems by using a specific water-based polyurethane resin as a Washi reinforcing agent. . That is, it is a water-based polyurethane resin containing a urethane prepolymer, a salt forming agent and a chain extender as essential components, and the acid value of the carboxyl group in the water-based polyurethane resin is 13 relative to the solid content.
KOH mg / g or more, glass transition temperature is 20 ° C. or more, the urethane prepolymer has a [A] average molecular weight of 62 to 5,000, and a polyol compound having two or more hydroxyl groups in the molecule ( Hereinafter referred to as compound [A]),
[B] An organic polyisocyanate having two or more isocyanate groups in the molecule (hereinafter referred to as compound [B]) and [C] a compound having a hydroxyl group or an amino group and a carboxyl group in the molecule (hereinafter, compound [C]) And the salt-forming agent is a salt-forming agent corresponding to the compound [C].

The Washi reinforcing agent of the present invention has at least three glycidyl groups in the molecule on average with respect to the water-based polyurethane resin, and has an epoxy equivalent of 200 (wpe) or less based on the solid content. , And the water solubility is 70
% Or more of an epoxy cross-linking agent and / or a water-soluble or water-dispersible melamine cross-linking agent (hereinafter referred to as a cross-linking agent) in a solid content ratio of 40% by weight or less is further suitable as a Washi reinforcing agent. is there.

Particularly when the water-based polyurethane resin or the water-based polyurethane resin and the cross-linking agent are used as a reinforcing agent for Japanese paper for master paper of a heat sensitive stencil printer, excellent performance can be provided.

(Requirements Constituting Means) The main items relating to the structure of the invention will be described below item by item.

[Water-based polyurethane resin] As the water-based polyurethane resin, as described above, a urethane prepolymer,
Prepared from salt formers and chain extenders.

(1) Urethane Prepolymer The urethane prepolymer is composed of the following compounds A, B and C.

Compound [A] As the polyol compound used as the compound [A] and having an average molecular weight of 62 to 5,000 and two or more hydroxyl groups in the molecule, ethylene glycol, diethylene glycol,
Butanediol, propylene glycol, polypropylene glycol, hexanediol, bisphenol A, bisphenol S, hydrogenated bisphenol A, dibromobisphenol A, 3-methyl-1,5-pentanediol,
1,4-cyclohexanedimethanol, dihydroxyethyl terephthalate, hydroquinone dihydroxyethyl ether, trimethylolpropane, glycerin, polyhydric alcohols such as pentaerythritol, their alkylene derivatives or their polyhydric alcohols or alkylene derivatives and polycarboxylic acids, Polycarboxylic acid anhydride,
Alternatively, esterified products from polyvalent carboxylic acid esters, polybutylene adipate, polycarbonate polyols, polytetramethylene glycol, polycaprolactone polyols, polybutadiene polyols, polythioether polyols, polyacetal polyols, castor oil polyols, and other polyols. And the like.

When the average molecular weight of the compound A exceeds 5,000, the viscosity of the urethane prepolymer produced is remarkably increased, which is not preferable.

Compound [B] As the compound [B] of the present invention, an organic polyisocyanate having two or more isocyanate groups in the molecule is used.
Specific organic polyisocyanates include tolylene diisocyanate, diphenylmethane diisocyanate,
Xylylene diisocyanate, naphthylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, hydrogenated diphenylmethane diisocyanate, hydrogenated toluene diisocyanate, tetramethylene xylylene diisocyanate And burettes and isocyanurates of these isocyanates, and all conventionally used aromatic, aliphatic or alicyclic isocyanates alone or as a mixture.

Compound [C] The compound [C] of the present invention is a compound having a hydroxyl group or an amino group and a carboxyl group in the molecule, which is a compound having a salt-forming carboxyl group, such as glycolic acid, Malic acid, glycine, aminobenzoic acid,
Alanine, hydroxy acids such as dimethylolpropionic acid, aminocarboxylic acids, polyhydric hydroxy acids and half-ester compounds that have stopped the reaction in the course of the synthesis of the ester compound, etc., but especially the use of dimethylolpropionic acid preferable.

(2) Salt forming agent corresponding to the compound [C] Examples of the salt forming agent corresponding to the compound [C] include monovalent metal hydroxides such as sodium hydroxide and potassium hydroxide and ammonia, Examples include tertiary amine compounds such as trimethylamine, triethylamine and dimethylaminoethanol.

(3) Chain extender As the chain extender used in the present invention, a compound having two or more amino groups is used, and examples thereof include ethylenediamine, propylenediamine, diethylenetriamine, hexylenediamine, triethylenetetramine and tetraethylenediamine. Examples thereof include ethylene pentamine, isophorone diamine, xylylene diamine, diphenyl methane diamine, hydrogenated diphenyl methane diamine and the like. Water also plays a role as a chain extender. The amount of the chain extender added is compound [A],
An equivalent amount or less is preferable with respect to the isocyanate group of the isocyanate-terminated urethane prepolymer obtained from [B] and [C].

(4) Acid Value Due to Carboxyl Group in Water-Based Polyurethane Resin In producing the water-based polyurethane resin of the present invention, the acid value due to the carboxyl group is 13 KOH mg / g or more, preferably 17 to 45 KOH mg per solid content of the water-based polyurethane resin.
It must be / g.

When the amount of carboxyl group is less than 13 KOH mg / g, not only the particle size of the resulting aqueous polyurethane resin becomes coarse but also the crosslinkability with the crosslinking agent is insufficient. When impregnated into
Since a sufficient paper strength-enhancing effect cannot be obtained and the wet paper strength is particularly inferior, when used as a master paper for a heat-sensitive stencil printing machine, printing bleeding occurs during continuous printing.

(5) Glass transition temperature in water-based polyurethane resin Glass transition temperature (Tg) of water-based polyurethane resin of the present invention
Needs to be 20 ° C or higher, preferably 35 ° C to 80 ° C. If the glass transition temperature (Tg) is less than 20 ℃,
The water-based polyurethane resin obtained is soft, and when Japanese paper is impregnated with such a water-based polyurethane resin, a sufficient paper-strengthening effect cannot be obtained, and wet paper-strength strength is also poor.

(6) Production of Aqueous Polyurethane Resin As a production method of the aqueous polyurethane resin of the present invention, an isocyanate-terminated urethane prepolymer obtained from compound [A], compound [B] and compound [C] is used as compound [C]. By using a salt-forming agent corresponding to the above-mentioned (1), it can be obtained by emulsifying in water by a known method and then extending the chain with water or a chain extender having two or more amino groups. At this time, an organic solvent which does not react with an isocyanate group is optionally reacted with an isocyanate-terminated urethane prepolymer in a reaction step,
Alternatively, emulsification can be facilitated by adding after the reaction. In this case, if necessary, the organic solvent can be distilled off under reduced pressure to obtain a solventless water-based polyurethane resin. It is also possible to add an anionic or nonionic surface active agent during the emulsification to facilitate the emulsification.

[Epoxy type cross-linking agent] The epoxy type cross-linking agent used in the present invention has at least 3 or more glycidyl groups in the molecule on average, and the epoxy equivalent is 2 with respect to the solid content.
It is an epoxy compound having a water solubility of not more than 00 (wpe) and not less than 70%, and examples thereof include sorbitol polyglycidyl ether, polyglycerol polyglycidyl ether, diglycerol polyglycidyl ether, glycerol polyglycidyl ether, resorcin diglycidyl. There is ether etc.

When the average number of glycidyl groups in the molecule is less than 3, the effect of crosslinking with the water-based polyurethane resin is insufficient, and when impregnated into Japanese paper, sufficient wet paper strengthening effect cannot be obtained. The epoxy equivalent is 20 with respect to the solid content.
When it exceeds 0 (wpe), the crosslinking effect with the water-based polyurethane resin is insufficient, and when the Japanese paper is impregnated, it becomes difficult to obtain a sufficient wet paper strength enhancing effect. Next, if the water content is less than 70%, the compatibility with the water-based polyurethane resin tends to be poor, and not only the crosslinking effect becomes insufficient, but also the workability when impregnating the Japanese paper is poor, and the processing machine is also poor. It can also become a cause of dirt.

[Melamine resin-based cross-linking agent] The melamine resin-based cross-linking agent used in the present invention is a water-soluble or water-dispersible melamine such as methylol melamine, methyl etherified melamine, and methyl / butyl mixed etherified melamine. It is a resin-based crosslinking agent. A melamine resin-based crosslinking agent that is not water-soluble or water-dispersible, such as butyl etherified melamine, is not preferable because it not only has poor workability in mixing with a water-based polyurethane resin but also causes stains on the processing machine.

[Amount of Crosslinking Agent] The crosslinking agent used in the present invention is not always necessary, but when higher wet paper strength is required, it is preferably added to the water-based polyurethane resin of the present invention. . The epoxy crosslinking agent and the melamine resin crosslinking agent may be used alone or in combination. When the above-mentioned cross-linking agent is used in combination, the ratio can be arbitrarily adopted within a range not exceeding 40% by weight.

The amount of the water-based polyurethane resin and the cross-linking agent to be added is preferably 100: 0 to 40, preferably 100: 5 to 30 (weight ratio) in terms of solid content. If the amount of the cross-linking agent is more than 100: 40, the effect of crosslinking with the water-based urethane resin is adversely deteriorated. When impregnated into Japanese paper, not only the sufficient wet paper strengthening effect cannot be obtained, but The workability during the impregnation treatment is poor, and it also causes stains on the processing machine.

[Other Compounds] In the water-based polyurethane resin of the present invention, an anti-skin agent, a leveling agent, an antifoaming agent,
Various additives such as penetrants, film-forming aids, color pigments, thickeners, etc. may be added within the range not deteriorating the performance in order to obtain the desired properties. Further, polyvinyl alcohol resin, S, which has been conventionally used as a paper strengthening agent, within a range that does not deteriorate the performance for the purpose of cost reduction and the like.
Various latexes of water-based resin such as BR latex, chloroprene latex, NBR latex, acrylate latex, vinyl chloride latex and colloidal silica may be mixed.

[Use of Water-Based Polyurethane Resin] The water-based polyurethane resin of the present invention is used for papermaking of natural fibers such as Kozo, Mitsumata and Manila hemp, or synthetic fibers such as polypropylene, vinylon, polyester, nylon and rayon. By targeting a Japanese paper mixed with paper and impregnating it, a resin-processed Japanese paper excellent in dry paper strength and wet paper strength can be obtained. Furthermore, it is a heat sensitive stencil printer that is used in a plate making method that uses a writing perforation method with a thermal head laminated with a polyester film for ultra-thin Japanese paper. Is.

Further, by impregnating the water-based polyurethane resin of the present invention into a paper made of various natural fibers or synthetic fibers, the dry paper strength-enhancing property, the wet paper-strengthening property and the wet adhesiveness with a polyester film are improved. Since it is possible to obtain excellent resin-processed paper, in addition to using it as a Japanese paper reinforcing agent, it is also considered to be used as a secondary processing chemical for printing paper, information paper, electronic paper, filters, medical hygiene paper, household paper, packaging paper, etc. To be

As a method for treating the aqueous polyurethane resin of the present invention on Japanese paper, various treatment methods such as spray treatment, impregnation treatment, brush treatment, roller coater treatment and the like can be mentioned. The treatment amount of the water-based polyurethane resin of the present application to Japanese paper is 0.2 g / m ² or more, preferably 0.5 to 2.0 g.
/ M ² .

[0032]

[Function] The main component of papermaking of natural fibers such as Kozo, Mitsumata and Manila hemp, or Japanese paper made by mixing some of these natural fibers with synthetic fibers such as polypropylene, vinylon, polyester, nylon and rayon is natural cellulose fiber. , Its molecular structure is linear and many -OH groups are densely arranged to form fine crystals, which are exclusive and have poor adhesion to other substances. Further, in Japanese paper in which synthetic fibers are mixed and made, the binding strength of the synthetic fibers is weak, and the paper strength strength when dry and the paper strength strength when wet are extremely reduced. Therefore, polyvinyl alcohol resin, SBR latex, chloroprene latex, which has been conventionally used as a paper strengthening agent,
Various water-based resin latices such as NBR latex, acrylate latex, vinyl chloride latex, ethylene vinyl acetate latex have not only insufficient adhesion to natural cellulose fibers and synthetic fibers, but also resin in the resin treatment drying step. However, the desired paper-strengthening effect, particularly the wet paper-strengthening effect, was inferior.

However, it has been found that the water-based polyurethane resin of the present invention can produce a resin-processed Japanese paper which is excellent not only in dry paper strength but also in wet paper strength and adhesion to a polyester film when wet. This is because the carboxyl group-containing waterborne polyurethane resin emulsified with the volatile tertiary amine compound which is a salt forming agent is hydrophobized when the volatile tertiary amine compound is liberated and volatilized by drying at high temperature. Urethane bond with high cohesion,
Urea bond has adhesion to natural cellulose fiber and synthetic fiber,
Improving the permeability and suppressing the occurrence of migration,
Furthermore, since the carboxyl group-containing waterborne polyurethane resin and the epoxy-based crosslinking agent and / or the melamine resin-based crosslinking agent form a reticulated bond inside the natural cellulose fiber or the synthetic fiber or at the entanglement point, the dry paper strength is not only enhanced. It is thought that a resin-processed Japanese paper having further excellent wet paper strengthening property and wet film adhesiveness with a polyester film can be produced.

[0034]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited to these Examples. Synthetic Examples 1 to 4 and Comparative Synthetic Examples 1 to 2 As shown in Table 1, a polyol compound [A] having two or more hydroxyl groups in the molecule in a methyl ethyl ketone solvent,
After synthesizing an isocyanate-terminated urethane prepolymer from an organic polyisocyanate [B] having two or more isocyanate groups in the molecule, a compound [C] having a hydroxyl group or an amino group and a carboxyl group in the molecule and a salt forming agent corresponding thereto, After emulsifying in water by a known method, water or a milky white or transparent liquid water-based polyurethane resin obtained by chain extension with a chain extender having two or more amino groups is distilled off the methyl ethyl ketone solvent under reduced pressure. As a result, various solventless waterborne polyurethane resins were produced.

[0035]

[Table 1]

The polymer polyol compounds having two or more hydroxyl groups in the molecule shown in Table 1 were as shown below. The numbers in Table 1 indicate parts by weight. Bisphenol A alkylene derivative: Bisphenol A
3 mol adduct of ethylene oxide (average molecular weight 360) Polytetramethylene glycol: Tetrahydrofuran ring-opening polymer (average molecular weight 2000) Phthalic acid polyester: 3-methyl-1,5-pentanediol and terephthalic acid Polyester (average molecular weight 10
00) Polypropylene glycol: 1,4-butanediol 33 mol adduct of propylene oxide (average molecular weight 2000) Polybutylene adipate: Polyester from 1,4-butanediol and adipic acid (average molecular weight 1000)

Examples 1 to 7 Various solventless water-based polyurethane resins obtained in Synthesis Examples 1 to 4 at the ratios shown in Table 2 or those obtained by blending the crosslinking agent shown in Table 2 therein have a solid content of 7%. As mentioned above, after diluting with water, the paper made from Manila hemp is impregnated, passed through a mangle squeezing machine (squeezing pressure 2 Kg / cm ² ), and forcedly dried for 1 minute in an atmosphere of 150 ° C to make resin-treated Japanese paper. did. Next, a solvent-type thermoplastic polyurethane resin was applied onto the polyester film, and then the resin-processed Japanese paper was press-bonded at 180 ° C. for 15 seconds to prepare a heat-sensitive stencil printing press master paper. With respect to the obtained resin-treated Japanese paper and heat-sensitive stencil printing press master paper, various performances of the following items were compared and confirmed. The results are also shown in Table 2.

Comparative Examples 1 and 2 Comparative Synthesis Examples 1 and 2 Other than solvent-free water-based polyurethane resins obtained were diluted with water to a solid content of 7% and then impregnated into Japanese paper made from Manila hemp. In the same manner as in Examples 1 to 7, the obtained resin-processed Japanese paper and heat-sensitive stencil printing master paper were compared and confirmed for various performances for each item.

Comparative Examples 3 to 6 Commercially available polyvinyl alcohol resin, SBR latex,
Acrylate latex, vinylidene chloride latex
After diluting with water to have a solid content of 7%, and impregnating the Japanese paper made from Manila hemp in the same manner as in Examples 1 to 7,
With respect to the obtained resin-processed Japanese paper and heat-sensitive stencil printing press master paper, the performance of each item was compared and confirmed.

Comparative Example 7 Next, a solvent-type thermoplastic polyurethane resin was applied on a polyester film and then pressure-bonded to raw Washi paper at 180 ° C. for 15 seconds to prepare a heat-sensitive stencil printing press master paper. With respect to the unprocessed Japanese paper and the obtained heat-sensitive stencil printing press master paper, various performances of respective items were compared and confirmed in the same manner as in Examples 1 to 7. Table 3 shows the results of comparative confirmation tests of these various performances.
Shown in

[0041]

[Table 2]

[0042]

[Table 3]

Each performance test method is shown below. Dry paper strength: Measure the strength of dry paper cut with a width of 15 mm on a resin-processed Japanese paper using a tensile tester. Wet paper strength: Dip the cut paper with a width of 15 mm on water for 30 seconds and wet it with a tensile tester. Paper strength was measured Adhesion when wet: Heat-sensitive stencil printing press master paper cut into a square of 5 cm on each side was immersed in water for 120 seconds and then taken out to visually evaluate the adhesion between the polyester film and the resin-treated Japanese paper. Printing durability: Using a thermal stencil printer, punching was performed with a thermal head, printing was performed up to 5000 sheets, and it was visually confirmed whether or not bleeding occurred in the printing.

[0044]

EFFECTS OF THE INVENTION With the Washi reinforcing agent of the present invention, papermaking Japanese paper made of natural fibers such as Kozo, Mitsumata and Manila hemp, and synthetic paper such as polypropylene, vinylon, nylon, polyester and rayon are partially mixed with these natural fibers. When used on Japanese paper, it can give excellent dry and wet paper strength, and can also give excellent wet adhesion and printing durability to heat sensitive stencil printing press master paper laminated with polyester film. .

Claims (4)

(57) [Claims] 1. A water-based polyurethane resin comprising a urethane prepolymer, a salt-forming agent and a chain extender as essential components, wherein the acid value of the carboxyl group in the water-based polyurethane resin is 13 KOH mg / g or more based on the solid content. And the glass transition temperature is 20 ° C. or higher, the urethane prepolymer has an [A] average molecular weight of 62 to 5,000,
A polyol compound having two or more hydroxyl groups in the molecule,
[B] an organic polyisocyanate having two or more isocyanate groups in the molecule and [C] a compound having a hydroxyl group or an amino group and a carboxyl group in the molecule (hereinafter referred to as compound [C]), and forming the salt. A Japanese paper reinforcing agent containing an aqueous polyurethane resin, which is a salt-forming agent corresponding to the compound [C]. 2. The water-based polyurethane resin according to claim 1, further having at least an average of 3 glycidyl groups in the molecule.
More than one, the epoxy equivalent is 200 (w
pe) or less and a water-soluble rate of 70% or more and an epoxy-based crosslinking agent and / or a water-soluble or water-dispersible melamine resin-based crosslinking agent are blended in a solid content ratio of 40% by weight or less, and a Washi reinforcing agent. . 3. A Japanese paper reinforcing agent for a heat sensitive stencil printing press master paper, which comprises the Japanese paper reinforcing agent according to claim 1 or 2. 4. A thermal stencil printing press master paper treated with the reinforcing agent according to claim 3.