JPS6231118B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing paper using anionic polyacrylamide (hereinafter abbreviated as anionic PAA),
In particular, it relates to a paper manufacturing method characterized by using anionic PAA and producing paper in a neutral environment. Normally, paper has a basic composition of pulp, a paper strength agent, a sizing agent, and a fixing agent, and fillers, dyes, wet strength agents, etc. are used as appropriate depending on the required quality of the paper. However, in actual papermaking, these additives and auxiliary agents rarely exhibit their properties immediately if they are simply added to the paper stock; It is a frequently observed phenomenon that agents, auxiliary agents, etc. interact with each other and inhibit the properties of each. For example, with regard to PAA, conventional acidic paper involves adding anionic PAA to the pulp slurry, which is then fixed by adding an aluminum salt such as aluminum sulfate or aluminum chloride.
When making paper using a hand paper machine such as the one described in the TAPP1 standard T2050S, the pH after adding aluminum salt is important, and paper strength increases when the pH is closer to 4.0 than when the pH is 4.5. . In other words, the yield of PAA increases. This trend is reflected in high speed paper, i.e. PAA
This becomes noticeable when the amount of addition exceeds 1 in terms of weight percent of the pulp. However, when such optimal conditions are applied to an actual paper machine, the pH of the paper stock will be less than 4.0, and the paper strength will not be as high as in the case of hand-made paper. The decrease in pH is due to the fact that in actual paper machines, water dehydrated on the wire (hereinafter referred to as white water) is reused as dilution water. For this reason, the amount of aluminum salt added is reduced compared to the case of hand papermaking depending on the actual operating conditions such as water balance, but in this case, in addition to aluminum salt, the white water contains aluminum, PAA, fine fiber complexes, and In normal cases, other additives are also included, so the paper strength that can be obtained by adding the optimum amount of aluminum salt at once cannot be achieved. In this way, anionic PAA is difficult to use especially for making high-strength paper. In the case of acid-free paper, cationic PAA is generally used, and since it is self-fixing, it does not suffer from the above-mentioned drawbacks, but cationic PAA is expensive, and even if the same amount of anionic PAA is used, the same paper It has drawbacks such as not being able to gain power. The first object of the present invention is to provide a paper manufacturing method in which a sufficient amount of aluminum salt is added at once when anionic PAA is used, and the yield of PAA does not decrease. Second, the cheap and high-performance anionic
An object of the present invention is to provide a method for producing acid-free paper using PAA. The third object is to provide a method for producing high-strength paper suitable for use as printing paper, copying paper, and photographic paper. The present inventors studied anionic PAA in order to improve the various drawbacks mentioned above, and found that
After preparing paper stock using the usual system in paper making, that is, anionic PAA-fixing agent,
Add an alkaline substance such as NaOH to lower the pH of the system.
The present invention was completed based on the surprising discovery that by adjusting the ratio to 6.5 to 8, an effect that further exceeds the paper strength enhancing effect obtained with the acidic side can be obtained. The present invention provides anionic material in pulp slurry.
After adding PAA and aluminum salt, the pH is raised to 6.5 to 8 by adding an alkaline substance, and the paper is formed by a normal wet paper making method without the need for any special equipment. To provide a paper manufacturing method which can obtain a paper strength enhancing effect superior to that of anionic PAA on the acidic side, and which can obtain neutral paper without using anionic PAA, which is expensive and less effective. That is, in the present invention, in a method for producing paper from a stock containing a paper strength agent, a sizing agent, and an aluminum salt, the paper strength agent is anionic polyacrylamide, the sizing agent is an alkyl ketene dimer, and the cationic sizing agent is , substituted cyclic dicarboxylic acid anhydrides and stearic acid soaps.
At least one type of sizing agent having a sizing effect in a neutral system with a pH of 6.5 to 8, and an aluminum salt in an amount sufficient to fix the anionic polyacrylamide after adding the anionic polyacrylamide to the paper stock. In order to precipitate excess aluminum ions, the pH of the paper stock is adjusted to 6.5 to 8 with an alkaline substance, and paper is made in a neutral system to obtain paper with high paper strength and high size properties. I can do it. It is preferable to adjust the pH of the paper stock to 4.0 to 4.5 after adding the aluminum salt. The anionic PAA used in the present invention is not particularly limited. For example, Polyacrylon ST-13 manufactured by Hamano Chemical Industry, Polystron manufactured by Arakawa Chemical Industry
117, etc. are available. Although the amount added cannot be absolutely determined depending on the required strength of the paper, it is usually 0.1 to 4.0%, preferably 0.5 to 3.0%, based on the weight of the pulp. The sizing agent used in the present invention is at least one type of sizing agent that is neutral and has a large size effect, selected from the group of alkyl ketene dimers, cationic sizing agents, substituted cyclic dicarboxylic acid anhydrides, and stearic acid soaps. . These sizing agents include Pearl Gum CS manufactured by Seiko Kagaku and GZ- manufactured by Mitsubishi Kasei.
1200 is given. When these sizing agents are used, paper having high paper strength and high sizing properties can be obtained. Particularly preferred are alkyl ketene dimers and cationic sizing agents. As a cationic sizing agent,
Examples include cationic sizing agents obtained by reacting fatty acids, aromatic or petroleum resin carboxylic acids with, for example, polyvalent amines. When at least one sizing agent selected from the group of alkyl ketene dimers, cationic sizing agents, and substituted cyclic dicarboxylic acid anhydrides is used as the sizing agent, the sizing agent has a pH of 6.5 when the paper stock is an alkaline substance. It is added after adjusting to ~8. When stearic acid soap is used as a sizing agent, the sizing agent is added before the stock is adjusted to pH 6.5-8 with an alkaline substance.
Rosin sizing agents, which are most commonly used as paper sizing agents, cannot be used at pH values of 6 or higher, particularly 6.5 or higher, as the sizing effect is extremely poor. The reason why the paper-making system is a neutral system with a pH of 6.5 to 8 is that an excellent paper strength enhancement effect can be obtained with a neutral system. In the present invention, the alkaline substances used to raise the pH of the paper stock to 6.5 to 8 include NaOH, KOH,
Na ₂ CO ₃ , sodium aluminate, etc. are used, but NaOH is particularly preferred in consideration of cost. The pH after addition of alkali is 6.5-8. If it is less than 6.5, the effect is insufficient, and if it exceeds 8, the paper strength will obviously decrease. The main raw materials for the paper stock used in the present invention are pulp, chemical fibers, synthetic fibers, etc., and there is no problem in adding inorganic fibers such as glass fibers and rock wool to the extent that the properties are not impaired. . In addition, starch, natural gums, various natural and synthetic resins, fillers, dyes, fluorescent brighteners, and other so-called papermaking additives and auxiliaries may be added as appropriate depending on the quality of paper required. There is no problem in including it. In addition, starch, PVA, gelatin,
Various synthetic resins, dyes, fluorescent brighteners, etc. may be applied to the surface. In the present invention, when PAA is applied at a pH of 6.5 to 8, an excellent paper strength enhancement effect can be obtained.
A particularly favorable paper strength enhancing effect can be obtained by using PAA in combination with a plant gum such as mannangalactan plant gum (for example, Mayhole Chemical's Maproid gum). The blending ratio of PAA and vegetable gum is 4:6 by weight.
8:2 is preferred. Vegetable gum is an alkaline substance and is added before adjusting the stock to 6.5-8.
Further, when a polyamide polyamine epichlorohydrin resin (for example, Epinox or Kaimen manufactured by Deutsche Hercules) is added as a wet paper strength enhancer, the wet paper strength is significantly increased. Paper produced by the method of the invention is particularly suitable for use as photographic paper. Here, photographic paper refers to paper on which a photographic emulsion is applied directly, or paper on which a so-called baryta coating layer, mainly composed of barium sulfate and gelatin, is applied, or a photographic emulsion applied on one side. Examples include those in which synthetic resin layers such as polyolefin are applied on both sides by extrusion melt coating or lamination, and photographic emulsions are coated on both sides, and photographic packaging materials for diffusion transfer or in direct contact with them. It will be done. In addition, it is of course used for printing paper such as general paper and coated paper, and is particularly useful in special fields such as label paper, poster paper, map paper, and wet diazo photosensitive paper. According to the present invention, the optimum amount of aluminum salt, which is a fixing agent for anionic PAA, can be added at once;
As a result, the yield of PAA is increased, and paper strength does not deteriorate even when white water is circulated. 2 Anionic with excellent characteristics at low cost
Acid-free paper can be produced using conventional acid paper systems using PAA and aluminum salts. 3 As a result, synthetic sizing agents such as alkyl ketene dimers that exhibit alkali resistance and alcohol resistance that cannot be obtained with rosin-based sizing agents used in the field of acidic paper (this product has the highest (Provides strong size characteristics)
By using this, it becomes possible to produce paper with high alkali and alcohol resistance and high paper strength. 4. Therefore, when processed into waterproof photographic paper that is coated with synthetic resin such as polyolefin by extrusion melt coating on both sides of the paper, high paper strength,
Because of its size, it is possible to prevent photographic processing liquid from penetrating through the cut. As a result, it is possible to eliminate edge stains (referred to as edge stains) caused by penetration of photographic processing liquid through the cut edges, and to significantly increase commercial value. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples, but these are not intended to limit the present invention. Parts and % described in Examples and Comparative Examples
are all based on weight. Example 1 Paper of 150 g/m ² was made using the following recipe. The pulp slurry concentration when adding chemicals is 3%, and when hand-papering
Diluted to 0.075%. 1:1 mixture of bleached hardwood kraft pulp and bleached softwood sulfite pulp (beaten to Canadian Standard Freeness 310ml) 100 parts Sodium stearate 1.5 parts Polyacrylamide (Polyacrylamide manufactured by Hamano Industries)
ST-13) 0.3, 0.6, 1.0, 2.0, 3.0 Aluminum chloride Adjusted to PH4.2 NaOH Adjusted to PH6.8 Polyamide polyamine epichlorohydrin resin (Epinox manufactured by Deik Hercules) 0.5 The obtained wet paper was heated on a heating plate at 120℃. It was dried and supercalendered at a linear pressure of 90 kg/cm. These samples are given the following sample numbers depending on the amount of PAA added.

[Table] Table 1 shows the dry burst strength of each material. Next, use the white water that fell under the wire during paper-making as dilution water to perform the next paper-making process (fill in fresh water to make up for any shortage), and repeat this process 10 times.The sample numbers for the sheets obtained are as follows.

[Table] Sample No.
The respective dry burst strengths are also shown in Table 1.

[Table] As is clear from the table, according to the present invention, even if white water is used as dilution water, no decrease in strength occurs. Comparative Example 1 In Example 1, the addition of NaOH was removed and the pH was adjusted to 4.2 with aluminum chloride instead of fresh water.
Samples were prepared under the same conditions except that dilution water adjusted to The sample number is as follows.

[Table] Table 2 shows the dry burst strength of each sample.

【table】

[Table] As is clear from the table, after adding aluminum chloride
When the PH is not adjusted to near neutrality with NaOH, samples using fresh water with a pH of 4.2 as dilution water are used in Examples 1-1 to 1.
There is no decrease in strength compared to the bursting strength of -5, but
Samples using white water as the dilution water showed a significant decrease in strength. Comparative Example 2 In Example 1, when the amount of PAA added was 1.0 part,
Samples were prepared under the same conditions except that NaOH was not added, the amount of aluminum chloride was reduced, and the pH after adding aluminum chloride was set to 4.7. Table 3 shows the sample number and bursting strength. For reference, the measured values of Sample Nos. 1-3 and 1-3A of Example 1 are also listed.

[Table] Note: Adjusted with aluminum chloride.
As is clear from the table, if the amount of aluminum chloride added is insufficient, the highest strength cannot be obtained. or,
Supplementing this with aluminum chloride in white water still does not give the highest strength. Example 2 A 150 g/m ² paper was made using a conventional Fourdrinier paper machine using the following recipe. The pulp slurry concentration at the time of chemical addition was 3%, and the concentration at the time of flowing onto the wire was 0.3%. 1:1 mixture of bleached hardwood kraft pulp and bleached softwood sulfite pulp (beaten to Canadian Standard Freeness 310ml) 100 parts polyacrylamide (Polyacron manufactured by Hamano Industries)
ST-13) 2.0 Oxidized starch 1.0 Aluminum chloride Adjusted to PH4.0 NaOH PH6.8 〃 Polyamide polyamine epichlorohydrin resin (Epinox manufactured by Deitz Hercules) 0.7 Alkyl ketene dimer (Acopel manufactured by Deitz Hercules) 0.5 Next, this After pre-corona discharge treatment on the back side of the paper, high-density polyethylene (density 0.96 g/cm ² , melt index 5) and low-density polyethylene (density
A 1:1 mixture of 0.92 g/cm ² and melt index 5) was extruded using a melt coating machine at a resin temperature of 330°C.
It was coated to a thickness of 30μ. Next, the opposite side was previously treated with corona discharge, and then low-density polyethylene containing 8% anatase-type titanium oxide (polyethylene before pigment addition had a density of 0.92 g/cm ² and a melt index of 5) was placed at a resin temperature. It was coated at 330°C to a thickness of 30μ.
The linear pressure between the clean roll and press roll during coating is 15Kg/cm, and the coating speed is:
It was 20m/min. After corona discharge treatment is applied to the surface of the titanium oxide-containing polyethylene, a yellow color photographic silver halide gelatin emulsion, a gelatin intermediate layer, a magenta color emulsion, a gelatin intermediate layer, a cyan color emulsion, and a magenta protective layer are coated in order from the bottom. , and dried to obtain color photographic paper. This product was developed using a continuous automatic processor (Color Roll Processor, manufactured by FC Seisakusho). After processing, the depth of liquid penetration from the edges of the photographic paper was read using a magnifying glass. Apart from this, NaOH in added chemicals was used as a comparison sample.
Samples were prepared under the same conditions except for the addition of , and the same tests were conducted. In this case, the main sources of fresh water are dispersion water for dispersing the dry pulp sheet to a concentration of 3%, dilution water for adding chemicals, and spray water sprayed by rifflers (sedimentation type dust removal equipment) and other devices for the purpose of defoaming. , most other dilution water uses white water dehydrated on a wire. The results obtained are shown in Table 4.

[Table] As is clear from the table, although the size of the sample according to the present invention is not significantly different from that of the comparative sample, the paper strength is superior, and therefore, when processed with an emulsion coater, automatic processor, etc., the paper roll As a result of the fact that the bonds between the fibers of the paper layer do not easily loosen when exposed to repeated bending, the penetration of the processing liquid from the edges, which is a practical property, is significantly improved, and as a result, the coloring is considerably lighter. . Example 3 A sample was prepared in the same manner as in Example 1. However, the amount of PAA added was fixed at 1.0, and the pH after addition of NaOH was adjusted to 4.2, 5.0, 6.0, 7.0, 8.0, and 9.0. The numbers of samples using fresh water as dilution water are as follows.

[Table] Also, use the white water that fell under the wire during paper making as dilution water to perform the next paper making process, repeat this process 10 times, and the sample numbers of the sheets obtained are as follows.

【table】 Table 5 shows the dry burst strength of each.

【table】

【table】

[Table] As is clear from the table, a slight effect is recognized at a pH of 5 after addition of NaOH, and the effect becomes obvious at a pH of 6 to 8. Furthermore, increasing the pH is not only disadvantageous in terms of cost, but also changes the texture due to the progress of cellulose deterioration due to alkali.

Claims (1)

[Scope of Claims] 1. A method for producing paper from a stock containing a paper strength agent, a sizing agent, and an aluminum salt, wherein the paper strength agent is anionic polyacrylamide, the sizing agent is an alkyl ketene dimer, and the cationic sizing agent. , substituted cyclic dicarboxylic acid anhydrides, and stearic acid soaps, the sizing agent is at least one type of neutral sizing agent with a pH of 6.5 to 8 and has a large size effect, and anionic polyacrylamide is added to the paper stock. After that, aluminum salt is added in an amount sufficient to fix the anionic polyacrylamide, and then the pH of the stock is adjusted to 6.5 to 6.5 with an alkaline substance in order to precipitate excess aluminum ions.
8, a paper manufacturing method characterized by paper making using a neutral system. 2 The pH of the stock after adding aluminum salt is
4.0 to 4.5, the method for producing paper according to claim 1. 3. The sizing agent is at least one type of sizing agent selected from the group of alkyl ketene dimers, cationic sizing agents, and substituted cyclic dicarboxylic acid anhydrides, and is a neutral sizing agent with a large size effect, and the sizing agent
The method for producing paper according to claim 1, wherein the additive is added after adjusting the pH to 6.5 to 8. 4. The paper manufacturing method according to claim 1, wherein the sizing agent is stearic acid soap and is added before adjusting the pH of the stock to 6.5 to 8 with an alkaline substance. 5 Plant gum uses alkaline substances to adjust the pH of paper stock.
6.5-8. The method for manufacturing paper according to claim 1, wherein the addition is made before adjusting the concentration to 6.5 to 8. 6. The method for producing paper according to claim 5, wherein the plant gum is a mannangalactan plant gum. 7. The paper manufacturing method according to claim 5 or 6, wherein the blending ratio of anionic polyacrylamide and vegetable gum is 4:6 to 8:2 by weight.