JPS597840B2 - Transparent paper manufacturing method - Google Patents

Description

Detailed Description of the Invention The present invention involves adding a cationic synthetic resin latex to an aqueous dispersion of cellulose pulp (hereinafter abbreviated as pulp slurry), adsorbing the latex to the cellulose pulp, and then producing paper. This invention relates to a new transparent paper obtained by drying and controlling the moisture content in the paper, followed by heat-pressure treatment.

Its uses are mainly tracing paper used for design drawings and copying, copy paper, and also diazo method,
The present invention relates to a method for producing transparent paper that has excellent suitability as a second source paper for use in combination with known copying methods such as the silver halide method and the electrophotographic method.

Conventionally, the materials used for these purposes are a) tracing paper made by highly beating cellulose pulp (tracing paper obtained by impregnating a relatively opaque paper other than tracing paper with a clarifying agent); Impregnated type transparent paper G--→ There is transparent paper obtained by mixing thermoplastic resin-based synthetic pulp with cellulose-based pulp and subjecting it to heat-pressure treatment at a temperature equal to or higher than the melting point of the synthetic pulp.

The transparent paper obtained by the method (2) is the most widely used, but it is extremely sensitive to moisture, has poor dimensional stability, and has very large curls.

In addition, copying by electrophotography, which has become extremely popular in recent years, has a fatal drawback in that it has poor heat resistance and cannot be used as a second original paper. Furthermore, since the beating is advanced to a high degree, the water resistance is poor and the paper making speed is therefore slow. (Although the transparent paper produced by the method of Kang is superior in dimensional stability, curling, and heat resistance compared to l-(), it requires processing equipment for impregnation, and in addition, if the solvent is an organic solvent, The costs of fire and explosion-proof equipment, environmental hygiene equipment, and pollution control equipment will be enormous.The transparent paper produced by the method ←→ eliminates the quality defects such as (a) and (■), but The production cost is extremely high, as synthetic pulp is very expensive, requires special crushing/beating equipment to evenly and finely disperse it with cellulose pulp, and requires heat-pressure equipment that requires high temperatures. Furthermore, as the synthetic pulp and cellulose pulp are not sufficiently dispersed at present, it is not possible to obtain a uniform transparent paper after heat-pressure transparency, and the paper only has the appearance of being sprinkled with opaque spots. As a result of various studies in order to eliminate the above-mentioned quality defects and obtain transparent paper efficiently and at low cost, the present inventors have taken the idea (c) one step further, and have developed a method for producing transparent paper using expensive synthetic pulp. Instead, the present invention was completed by applying an inexpensive synthetic resin latex and solving the newly occurring problems in papermaking.

The advantages in the application of synthetic resin latex are enormous.

First, it has become possible to significantly reduce the price of the resin used. In other words, various methods for producing synthetic pulp and the process leading to paper making have been proposed, but to summarize, polymer synthesis → spinning → (stretching) → cutting → fibrillation/beating (special beating machine) → cellulose pulp. mixing → paper making, and on the other hand, the process for manufacturing synthetic resin latex and paper making according to the present invention is polymer synthesis (emulsion polymerization) → mixing with cellulose pulp → paper making. It is obvious that In the method of the present invention, that is, the latex beater addition method, the yield was conventionally low and it was not possible to incorporate a large amount of synthetic resin latex. However, the present inventor has solved this difficulty by developing a cationic latex. The second advantage is that synthetic resin latex is extremely uniformly dispersed in cellulose pulp compared to synthetic pulp.
When moisture is used as a temporary plasticizer during heat-pressure transparentization for adsorption, the effect is significantly higher, making it possible to perform the transparentization treatment at a low temperature of less than 100℃, and in the case of synthetic pulp. has significant manufacturing and quality advantages, including the absence of unavoidable opaque spots. These advantages will be discussed in more detail below. Regarding beater addition of latex, various methods have been proposed in the past, mainly for synthetic rubber latex.

Its purpose was to produce pseudo-leather paper with a highly flexible, water-resistant, and strong film; there has never been an example of this being done for the purpose of producing transparent paper. The reason is that it has not been possible to manufacture transparent paper using this method using conventional techniques. That is, the key point of beater addition is to uniformly fix the latex on the surface of the cellulose pulp and to produce paper with a good yield. The method currently practiced industrially is to add an anionic synthetic rubber latex to a cellulose pulp slurry and deposit it on the cellulose pulp with a cationic substance such as clay or melamine acid colloid. Although this method has been practiced industrially, it has the drawbacks of poor deposition, release of latex agglomerates, and extremely poor yield. Furthermore, troubles on the paper machine due to poor yield are constant. Therefore, the resin content in the paper produced by this method is generally low and is mostly 15% by weight or less. On the other hand, the transparent paper that is the object of the present invention is not sufficient unless it contains at least 15% by weight of synthetic resin, and therefore cannot be achieved by this method. Attempts have been made to apply cationic latex to the beater addition method for a long time.

However, although the adsorption of latex to cellulose pulp is very good, it has not been put to practical use because its strength is inferior to that of anionic latexes. Therefore, there have been no attempts in the past to produce transparent paper using this method. As a result of various studies, the present inventors found that
By applying heat-pressure treatment to paper obtained by beater addition of cationic latex, which has good adsorption to cellulose pulp, after conditioning the humidity, it is possible to obtain very uniform transparent paper. As a result, the physical strength has been improved, and it has become possible to manufacture transparent paper that can sufficiently withstand the purpose of the present invention, leading to the completion of the present invention. That is, in a mixed system of cellulose pulp and thermoplastic synthetic resin, a cationic synthetic resin latex is mixed in an aqueous medium in an amount of at least 15% by weight based on the weight of cellulose pulp, and the latex is added to the cellulose pulp. After adsorption, the paper is made and dried, and the water content in the paper is adjusted to between 15#) and 30(:f), and then the linear pressure is 100k9/C77 between pressure rolls whose roll temperature is less than 1-00℃! The above is a method for producing transparent paper characterized by passing the paper through and making it transparent.

Examples of the cellulosic pulp used in the present invention include those commonly used as wood pulp, such as kraft pulp, sulfite pulp, semi-chemical pulp, and soda pulp. Kozo, mitsumata, which are the base papers for Japanese paper,
Hemp can also be used, as well as rag pulp and linter pulp. In addition to these main fibers, a small amount of recycled fibers, synthetic fibers, etc. may be added as needed. Next, cationic synthetic resin latex is made by dispersing cationically charged synthetic resin particles in an aqueous medium, and the monomers used for its preparation are those used in ordinary emulsion polymerization reactions. Ethylenically unsaturated compounds capable of radical polymerization or radical copolymerization, such as vinyl esters such as vinyl acetate and vinyl propionate, and acrylic esters such as methyl acrylate, ethyl acrylate, propyl arylate, and butyl acrylate. , methyl methacrylate, ethyl methacrylate, propyl methacrylate,
Methacrylic acid esters such as butyl methacrylate, unsaturated hydrocarbons such as ethylene and propylene, diene compounds such as butadiene and isoprene, halogenated unsaturated compounds such as vinyl chloride, vinyl fluoride, and vinylidene chloride, acrylonitrile, and methacrylate. Unsaturated nitrites such as nitrile, aromatic unsaturated compounds such as styrene, vinyltoluene, and α-methylstyrene, vinyl ethers such as methyl vinyl ether and lauryl vinyl ether,
Allyl alcohol, allyl chloride, allyl compounds such as diallylphthalacetate, ethylene glycol monoacrylate, ethylene glycol monomethacrylate,
Unsaturated alcohols such as propylene glycol monomethacrylate, unsaturated amides such as acrylamide and methacrylamide, ethoxyethyl acrylate, ethoxyethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, methylol acrylamide, dimethylaminoethyl methacrylate, butylaminoethyl These include methacrylate, vinylpyridine, vinylimidazole, and vinylpyrrolidone.

The emulsifiers used in the preparation of cationic synthetic resin latexes are those known as cationic surfactants, such as quaternary ammonium salt types such as lauryltrimethylammonium chloride, primary, secondary, and These include tertiary amine salt type, pyridinium salt type such as cetyloxymethylpyridinium chloride, tertiary sulfonium type or quaternary phosphonium type cationic surfactants.

In addition, if necessary, nonionic surfactants such as polyoxyethylene alkyl ether type, polyoxyethylene alkyl phenol type, polyoxyethylene alkyl acrylic ether type, polyoxyethylene alkyl thioether type, polyoxyethylene alkyl ester type are used. ,
Polyoxyethylene sorbitan alkyl ester type, sorbitan alkyl ester type, polyoxyethylene alkyl amide type, polyoxyethylene polypropylene glycol ester type, pentaerythritol ester type,
Fatty acid ethanolamide type, oxymethylethanolamide type, *adducts of alkylamines and alkylene oxides, *adducts of alkylene diamines and alkylene oxides, etc. are used in combination. However, those marked with * may be used alone. Furthermore, cationic polymeric protective colloids such as polyethyleneimine, polyvinylpyridine, and polydimethylaminoethyl methacrylate can also be used. Examples of radical polymerization initiators used to prepare cationic synthetic resin latex include potassium persulfate,
Persulfates such as ammonium persulfate, perborates such as sodium perborate, hydrogen persulfide, organic hydroperoxides such as tertiary butyl peroxide, cumene hydroperoxide, tertiary butyl perbenzoate, etc. organic peroxides or with them sodium metabisulfite, aqueous thiosulfate and sulfates of metals which may be present in one or more valences such as cobalt, nickel, iron, copper, ascorbic acid, amines, combinations with reducing agents such as alkylanilines, azo compounds such as azobisisobutyronitrile, 2,2'-azobisisobutyramidine hydrochloride, etc.

Furthermore, high-energy ionizing radiation such as alpha rays, beta radiation, electron beams, and X-rays can also be used. Emulsion polymerization is carried out by a known method, for example, as follows. A flask equipped with a thermometer, stirrer, condenser and monomer dropping device is charged with a predetermined amount of water and one or more surfactants. When the inside of the flask reaches a predetermined temperature, a predetermined amount of a reaction initiator is added, and then a monomer is added dropwise over a period of 1 to 2 hours. After the monomer dropwise addition is completed, the reaction temperature is maintained for an additional 0.5 to 1 hour to complete the polymerization reaction, and then the mixture is cooled. Of course, a portion of the above monomer may be added into the flask in advance, or the monomer may be emulsified in advance and then added into the flask. When emulsion polymerization is carried out by irradiation with high-energy ionizing radiation, a polymer latex can also be obtained by charging all the raw materials into a flask and irradiating the flask with high-energy ionizing radiation. The method of the present invention is carried out, for example, as follows.

A cationic synthetic resin latex is added to a slurry having a cellulosic pulp concentration of 1(f) in an amount of at least 15% by weight based on the weight of the pulp, and the synthetic resin is adsorbed onto the cellulose pulp by stirring. Note that the adsorption rate varies slightly depending on the slurry, temperature, stirring conditions, etc., and also varies depending on the cationic synthetic resin latex used, so it is recommended to test and determine the optimal conditions for each in advance. preferable. If necessary, other additives such as antifoaming agents, mold release agents, antistatic agents, etc. may be added to the slurry, and external plasticizers may also be added to the latex. The slurry thus prepared is made into paper using a conventional paper making method and dried. Then, the sheet is processed so that the paper moisture content is 15 (f) or more and 30
After adjusting the humidity to below %, the roll temperature is 100'
The transparent paper of the present invention is obtained by applying a linear pressure of 100 k9 or more in a thermopressure device at a temperature of less than C, preferably 80 to 95 degrees Celsius, to obtain the transparent paper of the present invention. If necessary, a surface treatment such as a surface sizing agent, an antistatic agent, a mold release agent, etc. may be applied to the sheet before the heat-pressing treatment, or it may be subjected to surface treatment after the transparentization treatment.

The advantages of the present invention are as described above, but the advantages of transparent processing will be explained in more detail.
In other words, in the method (c) above, although the synthetic pulp is defibrated and beaten, the cationic synthetic resin latex is extremely large compared to the state adsorbed on the surface of the cellulose pulp, and therefore the synthetic pulp is The dispersion of the bulbs is microscopically non-uniform. Therefore, in order to make it transparent, it is necessary to maintain the roll temperature above the temperature at which the synthetic pulp sufficiently softens or melts. However, the temperature must be at least 12σ°C or higher. Japanese Patent Application Publication No. 1973-
In No. 32803, water is used as a temporary plasticizer, but for the reasons mentioned above, it has little effect on synthetic pulp and requires a roll surface temperature of at least 130°C.

On the other hand, according to the present invention, as described above, the synthetic resin is uniformly and slowly adsorbed on the surface of the cellulose fibers, and the plasticizing effect with water is as high as that of the cellulose fibers.

For this reason, it has become possible to achieve maximum transparency by keeping the surface temperature of the hot press roll at a temperature below 100°C, preferably between 80°C and 95°C. When the surface temperature of the roll exceeds 100℃, water boils,
It is difficult to contain a large amount of water, and unless it is at most 15% or less, paper with uniform transparency cannot be stably obtained.
Therefore, water cannot be effectively used as a plasticizer. If you attempt to make the roll transparent by heat and pressure with a roll surface temperature of 1000C or higher with a water content of 15% or more, blisters or large spots of non-uniform transparency will easily occur, which will cause operational problems. It is self-evident that there are many difficulties involved. The moisture content in paper referred to here is a value obtained by the following calculation formula. In other words, water content in paper (%) - (weight of water content in paper/weight of paper in wet state) x 1000.Then, the pressure during heat pressure transparency is at least 100k9/CTI.
A linear pressure of I is necessary, and if it is less than this, sufficient transparency cannot be obtained.

Regarding the heat-pressure device for making transparent paper, the method for producing transparent paper using the method described above requires a special device because it requires a high temperature of at least 12°C or more, but the method of the present invention requires a special device. The method is advantageous in that existing machine calendars and supercalendars can be used.

Of course, it is sufficient to have at least one pair of hot pressure roll devices, and the present invention is not limited to the above devices. The roll may have a mirror surface, a rough surface, or a patterned roll, or may be a roll that is partially transparentized by heat and pressure. It is not limited to this.

Example 1 NBKP:LBKP-3:7, finished water level 450m1C. S
．． F. (Canadian Standard Freeness),
Polysol 2380 [cationic synthetic resin latex, composition: styrene-acrylic acid ester copolymer, MFT (minimum film forming temperature) 0°C, concentration 30% by weight, manufactured by Showa Kobunshi Co., Ltd., was added to 1000 kg of pulp slurry with a concentration of 1% by weight. ] 8
, 33 kg (solid content 2.5 kg) were added and mixed.

Note that the water temperature at this time was maintained at about 20°C, or around neutrality. Five minutes after the addition, the latex had been completely adsorbed to the pulp, and the liquid was completely clear.

This was made into paper by a conventional method, dried, and the basis weight was 699/Trl.
Obtained an opaque paper. Next, after adjusting the moisture in the paper to 25% using a humidifier, the surface temperature of the tilt roll of the super calendar was maintained at 85°C, and the linear pressure was 150k9/c:
A transparent paper according to the present invention was obtained. The properties of the obtained transparent paper are as shown in Table 1, and it had very uniform transparency, excellent dimensional stability, and sufficient paper strength.

Furthermore, when used as a second original paper for electrophotography, a very good second original paper was obtained, with excellent toner fixation and no blistering as seen in tracing paper.

Example 2 Pulp slurry similar to Example 1 Polysol 2385 [cationic synthetic resin latex,
Composition: Styrene-acrylic acid ester copolymer, MFT
45°C, concentration 30% by weight, manufactured by Showa Kobunshi Co., Ltd.] at 14.3
kg (solid content: 4.3 kg) and stirred to mix.

The water temperature at this time was kept at about 35 degrees Celsius and the water temperature was kept around neutral. Five minutes after the end of the addition, the latex had been completely adsorbed to the pulp, and the liquid was completely clear.

This is then made into paper with a basis weight of 759/m'' and dried, and then starch and an antistatic agent are applied to the surface using a size press device located at the dryer outlet of the paper machine. The paper is dried using an after-dryer to reduce the moisture content to 20 (:
Cm) and wound it up with one reeler. The properties of the obtained transparent paper are as shown in Table 1, and it had very uniform transparency, excellent dimensional stability, and sufficient paper strength.

Claims (1)

[Claims] 1. In a mixed system of cellulose pulp and thermoplastic synthetic resin, at least 15% by weight of cationic synthetic resin latex is mixed in an aqueous medium based on the weight of cellulose pulp, and the latex is adsorbed onto the cellulose pulp. After drying the paper and adjusting the water content in the paper to 15% to 30%, the paper is passed between pressure rolls with a roll temperature of 70°C to less than 100°C at a linear pressure of 100 kg/cm or more to make it transparent. A method for manufacturing transparent paper, characterized by: