JPS6224560B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing paper using pulp slurry in an approximately neutral range, in place of the acidic paper making that is currently widely practiced industrially, and in particular, it relates to a method for producing paper using a pulp slurry in an approximately neutral range, and in particular, contains an alkaline filler of 20% or more by weight in the filler. In addition, a cationic paper strength enhancer and a water-soluble aluminum salt are added to this filler to improve the papermaking pH.
It is characterized by paper making using pulp slurry adjusted to 6.5 to 8.5, and provides advantages such as improved dry paper strength and reduced wastewater load. Currently, in the papermaking method most commonly carried out on an industrial scale in the paper industry, sizing agents, fillers, dyes, etc. are added to an aqueous slurry of fibrous pulp.
Additives such as paper strength enhancers are added, and aluminum sulfate (band) is added as a fixing agent to adjust the pH of the slurry to acidic. Aluminum sulfate hydrolyzes in water to form an alumina complex with a cationic charge, which, when attracted to the anionically charged pulp fibers, simultaneously attracts and fixes the additives. Paper is made using the pulp slurry that has undergone such adjustment, and this paper making method is usually called acid paper making. Since this method requires the use of aluminum sulfate, the resulting paper is acidic and suffers from problems such as decreased paper strength, discoloration, and decreased printability during long-term storage. There are also disadvantages such as the inability to use alkaline pigments, drainage problems, and corrosion of the paper machine. In order to avoid the above-mentioned difficulties in acidic paper making, so-called neutral paper making methods without adding aluminum sulfate or without pH adjustment are known, but there are also drawbacks.
It has only been put into practical use to a very limited extent. As mentioned above, cellulose fiber has an anionic charge in water, and it is widely known that if a cationic substance is added to it, it will adsorb well. Various types of cationic polymers that are not required have been proposed, but they are still insufficient for practical use. For example, polyamide polyamine resin
3547), polyethyleneimine (Special Publication 1979-
18401), polyethyleneimine-epichlorohydrin adduct (Japanese Patent Publication No. 43-14165), copolymer of acrylamide and dimethylaminoethyl methacrylate (US Patent No. 2838397), copolymer of acrylamide and cationic monomer, and polymerization Cationic acrylamide resins (Japanese Unexamined Patent Application Publication No. 155706/1983) have been proposed, which are produced by reacting with polyalkyleneimine having a degree of 20 or more and deammonizing the resin, but all of them have poor drainage properties, filler retention effects, wet strength, It is said that there are drawbacks related to various performances such as dry strength. Today, resource saving, energy saving, environmental improvement, etc. are the biggest issues, and it is important to use raw materials effectively and commercialize products in the most efficient way and maximize their functionality. is necessary. For example, as the raw wood situation has worsened in recent years, the range of options for using various tree species has become narrower, and it is now desirable to effectively utilize even pulp that has little paper strength, which has not been widely used in the past. In addition, it is also attracting attention to save the thermal energy consumed in drying by omitting the size press step using starch, etc., which is carried out as an auxiliary means for imparting paper strength. To meet these demands, the challenge is to develop an appropriate paper strength enhancer to ensure paper strength. In addition, wastewater standards are becoming increasingly strict, and quantitative restrictions are being placed on water and wastewater for papermaking, and there is a trend toward a high degree of recovery and reuse of papermaking white water. ,
As a result, COD and BOD components in white water increase, making wastewater treatment more difficult. Therefore, reducing the amount of unadsorbed content in white water has become an imperative issue not only from the standpoint of effective use of raw materials, but also from the standpoint of facilitating wastewater treatment and reducing treatment costs. A first object of the present invention is to provide a paper strength enhancer that is further improved over conventional methods. Furthermore, the second objective is to reduce the COD and BOD loads in wastewater. Furthermore, a third object of the present invention is to contribute to cost reduction by widening the selection range of paper strength enhancers. Furthermore, other objects of the present invention will be understood from the following description. The above object of the present invention is to produce pulp fibers by adding (b) a cationic tertiary amine-based polyacrylamide paper strength enhancer to (a) a filler containing 20% or more of an alkaline filler by weight. They have discovered that this can be achieved by preparing an aqueous slurry, further impregnating (c) a water-soluble aluminum salt, and adjusting the papermaking pH of the slurry to 6.5 to 8.5 before making paper. As mentioned above, the essential structural conditions of the present invention are:
A filler containing at least 20% alkaline filler by weight should be used. Conventionally, various pigments have been used as fillers for papermaking, but in the present invention, it is essential to include an alkaline filler among them, and a representative example thereof is heavy calcium carbonate. , light calcium carbonate, aluminum hydroxide, alumina, zinc oxide, calcium hydroxide, zinc hydroxide, magnesium hydroxide, and the like. In order to include such an alkaline filler in the pulp slurry, it is not only necessary to add the fresh powder thereof to the slurry, but other sources can also be used. For example, waste paper from art paper and coated paper is unavoidably generated in various processes such as paper making machines, coating machines, cutters, supercalenders, and sorting, but these waste papers are collected within the manufacturing factory. It is defibrated again in a pulper, mixed with virgin pulp slurry, and used again in the papermaking process. art paper,
Alkaline pigments are commonly used as coating materials in coated paper, so if this is collected as waste paper and reused in the papermaking process,
Such pigments will be effectively utilized as paper-making fillers. Generally, the amount of filler used is about 15% based on the dry weight of the pulp, but the amount used varies from low ash to high ash depending on the desired paper properties. Further, in the present invention,
The alkaline filler is not limited to the use alone, and fillers other than alkaline pigments such as kaolin, clay, talc, and titanium oxide may be used in combination. In that case, in order to exhibit the desired effect of the present invention, the proportion of the alkaline filler and other fillers should be in the range of 100:0 to 20:80 by weight, as is clear from the data below. is desirable. In the present invention, as a result of attempting to improve the method of using the filler, it has been confirmed that an effect can be obtained from the viewpoint of reducing the abrasion of the wire. As is well known, the filler contained in the pulp slurry wears out the wire to a greater or lesser extent during the paper forming process on the wire of a paper machine. This wire abrasion has a large effect on papermaking efficiency and paper quality, so the degree of abrasion is strictly checked and the wire is replaced as necessary, but the paper machine is completely stopped during the wire replacement period. The impact on production costs is significant. Therefore, if efforts were made to reduce wire wear as much as possible and reduce the frequency of wire replacement, this would have great industrial value. In the process of completing the present invention, we also investigated the degree of wire abrasion due to the filler, and found that if the filler was wet-pulverized in advance and added to the pulp slurry, it would have the effect of reducing wire abrasion. Accompanied. For example, commercially available heavy calcium carbonate is dry-pulverized and then classified, and this is used as a starting material, or dry-crushed raw stone is used as a starting material and wet-pulverized. Various types of crushers were tried, including a sand grinder, ball mill, attritor, and K-day mill, but the sand grinder was the most effective. The sand grinder itself is well known; a cell equipped with stirring blades inside is filled with microparticles of glass, metal, ceramic, etc., and the slurry of the material to be processed is passed through the cell to perform the grinding process. I am starting to receive this. Wet grinding of filler improves wire abrasion because, for example, sand grinding selectively grinds coarse particles that have a greater effect on wire abrasion, resulting in uniform particle size. This is thought to be mainly due to the progress of atomization and the change in the particle shape of the filler to a desirable shape that reduces the influence on wire wear. Furthermore, when heavy calcium carbonate is used as the alkaline filler, it is the most excellent material because it can be procured at a low cost from a place with abundant domestic resources and is highly effective in reducing wire wear. It can be said. Another essential material in the present invention is a cationic tertiary amine-based polyacrylamide paper strength agent, that is, a water-soluble tertiary amine-based cationic polymer. Examples of such tertiary amine-based cationic polymers include the following. For example, copolymers of dialkylaminoalkyl (meth)acrylate, vinylpyridine, etc. and acrylamide, water-soluble copolymers of these copolymers with vinyl monomers that can be further copolymerized, and homopolymers of acrylamide and methacrylamide. Typical examples include Mannitz compounds, which are water-soluble copolymers of vinyl monomers copolymerizable with these compounds. Cationic polymers are generally classified into quaternary ammonium-based, tertiary amine-based, and secondary amine-based based on their cationic characteristics. Traditionally, quaternary ammonium systems have no PH dependence and are recommended for use alone, but tertiary amine systems have no PH dependence.
It is usually used on the acidic side of around 5.5, and paper strength tends to decrease as it moves to the alkaline side. Furthermore, according to measurements using colloid titration, when the pulp slurry becomes alkaline with a pH of about 8.5 or higher, it shows almost no cationic properties, making it extremely difficult to fix onto pulp fibers, which is a practical problem for neutral paper making. However, according to the present invention, even the cationic tertiary amine type polyacrylamide exhibits fixing properties almost equivalent to that of the quaternary ammonium type, and can be used alone. Furthermore, tertiary amine-based cationic polymers have the advantage of being relatively inexpensive compared to quaternary ammonium-based polymers. Among the various tertiary amine-based cationic polymers listed above, dialkylaminoalkyl (meth)acrylate and the like are preferred from the viewpoints of increasing paper strength, redisintegration property of broken paper for reuse, and long-term stability of the polymer. and acrylamide are most preferred. Quaternary ammonium-based cationic polymers such as copolymers of trialkylaminoalkyl (meth)acrylate and acrylamide have a pH of 8.0.
It is unstable under alkaline conditions exceeding 100 ml, and has the property of emitting a foul odor such as trimethylamine odor due to alkali decomposition.
When applying an alkaline paint with a pH of 8 or higher, a cationic tertiary amine polymer such as a copolymer of dialkylaminoalkyl (meth)acrylate and acrylamide is selectively used as a paper strength enhancer as in the present invention. By doing so, it is possible to obtain an excellent base paper suitable for such coated paper. In the present invention, the amount of the tertiary amine-based cationic polymer used is not particularly limited, but if the desired paper strength enhancement effect, economic efficiency, etc. It is preferable to use within the range. Of course, if it is desired to further increase the paper strength, an anionic paper strength enhancer and a general fixing agent may be added in combination to an extent that does not impede the effects of the present invention, or starch, polyvinyl There is no hindrance to adding a size press means using a water-soluble polymer such as alcohol. The third essential component in the present invention is a water-soluble aluminum salt. Examples include aluminum sulfate (band), aluminum nitrate, aluminum chloride, potassium alum, and polyaluminum chloride. In the present invention, a water-soluble aluminum salt is added to a pulp slurry containing an alkaline filler and a cationic paper strength agent so as to adjust the pH of the pulp slurry immediately before paper making to a range of 6.5 to 8.5. For example, for a slurry whose pH exceeds 8.5 due to the inclusion of an alkaline filler, the content of water-soluble aluminum salt is determined so that the pH falls within the range of 8.5 or lower and 6.5 or higher. Further, even if the PH of the pulp slurry before including the water-soluble aluminum salt is within the range of 6.5 to 8.5, the PH is lowered by the water-soluble aluminum salt within that range. In any case, if paper is made using a pulp slurry with a pH of 8.5 or higher after containing a water-soluble aluminum salt, it will have little effect on increasing the desired paper strength.
Furthermore, if the pH is less than 6.5, it is not preferable because foaming problems due to the decomposition of the alkaline filler and free aluminum ions hinder the fixation of the cationic paper strength agent to the pulp. Most preferably, pulp slurry
It is preferable to include a water-soluble aluminum salt so that the pH can be adjusted within the range of 7.0 to 8.0. The effect of adding a water-soluble aluminum salt in the specific pH range of the present invention is that the alumina complex produced by the reaction of the acidic aluminum salt with the alkaline filler first aggregates the filler and fine fibers, and then deposits them into the paper in a flocculated state. This is thought to be due to the fact that the flocs can be kept at a low temperature, and that these flocs are then further strengthened in aggregation by the cationic paper strength enhancer. Even if the pH is adjusted to a specific region using a general acid such as sulfuric acid, it is ineffective because no alumina complex is generated. In addition, when no alkaline filler is present, the aluminum salt is fixed to the pulp and inhibits the fixation of the cationic paper strength enhancer to the pulp, resulting in a decrease in paper strength. When preparing a pulp slurry, the order in which the above three essential components are added is not particularly limited; however, in the case of industrial implementation, an alkaline filler is first added to an aqueous dispersion of pulp fibers ( It is easiest to add the alkaline pigment derived from recycled waste paper (as described above), followed by the water-soluble aluminum salt and the cationic paper strength agent in this order. Such pulp slurry contains various known additives, such as anionic rosin size, petroleum resin size, alkyl ketene dimer,
Paper is made by optionally adding sizing agents such as acid anhydrides, dyes, etc. Conventionally, an example of using a paper strength agent made of a cationic polymer in a pulp slurry containing calcium carbonate is described in Test Example 1 of JP-A-155706, mentioned above. The present invention was the first to discover a method for making paper by further including a water-soluble aluminum salt in an amount necessary to adjust the pH of the slurry to 6.5 to 8.5 in a pulp slurry containing a filler and a cationic paper strength enhancer. The advantages brought about by this will be more clearly understood from the following examples. In the following Examples and Comparative Examples, the amount (parts) of each material added indicates parts by weight in solid terms. Example 1-1 to 1-7 80 copies of LBKP (CSF 500c.c.), NBKP (CSF
500c.c.) 20 parts of various alkaline fillers as shown in Table 1 were added to the pulp slurry in which 100 parts of pulp was dispersed, and stirring was continued. Add sulfuric acid at the same amount as added, then add 0.6 part of a copolymer of dimethylaminoethyl acrylate and acrylamide (KW-615 manufactured by Arakawa Chemical Co., Ltd.) as a cationic paper strength enhancer and continue stirring for 3 minutes. A pulp slurry was prepared. Using each pulp slurry obtained as above,
Paper with a weight of 60 g/m ² was made using a TAPPI standard hand paper machine. The PH of the pulp slurry during paper making, the paper strength of the obtained paper, and other results are shown in Table 1. Comparative Example 1-1 to 1-4 In Example 1-1, the amount of sulfuric acid added was 0 and 5.0 parts, and sulfuric acid was added in place of sulfuric acid 0.5 parts.
A pulp slurry was prepared in the same manner as in 1 of Example 1, except that 50% of the pulp slurry was used, and paper was obtained. Also, Example 1
A paper was obtained in the same manner except that the addition of sulfuric acid in step 7 was changed to 0. The details of these formulations and the results of paper strength, etc., are also listed in Table 1. Example 2 In Example 1 1 to 1-6, a commercial product with an average particle size of 7μ that was dry-pulverized and classified by elutriation was used as heavy calcium carbonate, but in this example,
This heavy calcium carbonate was wet-pulverized using a sand grinder (manufactured by Igarashi Kikai) to reduce the average particle size to 4 μm. A pulp slurry was obtained in the same manner as in Example 1, 1 to 1, 6, except that this sand grinder-treated heavy calcium carbonate was used. These pulp slurries are 1 to 1 of Example 1.
The effect of further improving the wire abrasion resistance was observed without deteriorating the results of paper strength and paper strength agent yield COD in No. 6. The abrasion properties were measured using a wire abrasion tester (manufactured by Jujo Kikai Co., Ltd.). Example 3 and Comparative Example 2 20 parts of NBKP (CSF 500c.c.), LBKP (CSF
A pulp slurry consisting of 55 parts (500 c.c.) and 25 parts of printing pigment-coated paper waste re-disintegrated in a TAPPI standard disintegrator is mixed with sulfuric acid while stirring.
1.0 part and copolymer of dimethylaminoethyl acrylate and acrylamide (KW- manufactured by Arakawa Chemical)
615) was added to obtain pulp slurry before paper making. This slurry contains 6 parts of heavy calcium carbonate and 6 parts of kaolin as fillers derived from the coated paper waste. Using the pulp slurry obtained as above,
Paper with a weight of 60 g/m ² was obtained using a TAPPI standard hand paper machine. The results of paper strength, etc. of the paper are shown in Table 2. As a comparative example, a pulp slurry was obtained in the same manner as in Example 3 except that the addition of sulfuric acid band was 0,
And finished paper was obtained. The results of paper strength etc. of this paper are also shown.
Also listed in 2. Example 4-1 to 4-3 20 copies of NBKP (CSF 500c.c.), LBKP (CSF
500c.c.) Table-3
Add various fillers as shown and continue stirring.
Furthermore, sulfate was added in the amount shown in Table 3, and then a copolymer of dimethylaminoethyl acrylate and acrylamide (manufactured by Arakawa Chemical Co., Ltd.) was added.
KW-615) was added and stirred for 3 minutes to prepare a pulp slurry before paper making. Using this pulp slurry, paper with a weight of 60 g/m ² was made using a TAPPI standard hand paper machine. The pH of the pulp slurry during paper making, the paper strength of the paper, etc. were as listed in Table 3. Comparative Example 3, 1 to 3, 3 A pulp slurry was prepared in the same manner as in Example 4, 1 to 4, 3, except that the addition of sulfuric acid band in 1 to 4, 3 of Example 4 was set to 0, and I got a finished paper. The pH of the pulp slurry during paper making, the paper strength of the paper, etc. in these comparative examples are also listed in Table 3. Example 5 The formed paper obtained in Example 1-1 was used as a base paper, and one side of it was coated with 50 parts of kaolin, 25 parts of calcium carbonate, 25 parts of aluminum hydroxide, 5 parts of starch, and 12 parts of styrene-putadiene copolymer latex. , PH9.2
A coated paper was obtained by applying the following paint to a coating amount of 15 g/m ² (solid content equivalent) and drying it. The resulting coated paper had no trimethylamine odor at all. Comparative Example 4 In Example 1-3, a copolymer of trimethylaminoethyl acrylate and acrylamide (KW- manufactured by Arakawa Chemical Co., Ltd.) was used as a cationic paper strength enhancer.
A paper was obtained in the same manner as in Example 1-3 except that 613) was used. When the obtained paper was processed into coated paper in the same manner as in Example 5, the obtained coated paper gave off a trimethylamine odor.

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Claims (1)

[Claims] 1. (a) A filler containing at least 20% by weight of an alkaline filler, (b) a cationic tertiary amine-based polyacrylamide paper strength enhancer, and (c) a water-soluble aluminum salt. A method for producing paper, which comprises making paper using a pulp slurry whose paper pH is adjusted to 6.5 to 8.5. 2. The method for producing paper according to claim 1, wherein the alkaline filler is mainly composed of heavy calcium carbonate. 3. The method for producing paper according to claim 2, wherein the heavy calcium carbonate is wet-pulverized. 4. The paper manufacturing method according to claim 3, wherein the wet grinding treatment is performed using a sand grinder.