JPS63211397A - Production of neutral paper - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for producing acid-free paper.

More specifically, the present invention is capable of keeping the papermaking system clean even when various chemicals are added at a high rate, and producing neutral paper with less reduction in whiteness. This paper relates to a method for producing acid-free paper.

[Conventional technology]

Generally, the papermaking process is carried out using a weakly acidic valve slurry, but it is also known to produce paper used for special purposes using a neutral valve slurry.

Acidic paper manufactured from acidic valve slurry as described above contains sulfuric acid radicals, so during long-term storage or use,
It is known that paper deteriorates, and for this reason, there has been a strong desire in recent years to improve the shelf life of paper. In addition, there are various demands such as reducing wastewater treatment in paper mills, improving the basic unit of chemicals used, and closing the white water system for paper making. In order to meet these demands, papermaking systems have been neutralized, and methods for producing general paper under such neutral papermaking conditions are becoming increasingly common.

The neutral paper manufacturing method has a problem in that the calcium carbonate added as a filler to the papermaking slurry accelerates the wear of the plastic wire of the paper machine. However, in general, the most important problems in neutral papermaking are fixation of neutral sizing agents and improvement of the retention of fillers and short pulp fibers. If the fixation yield of the sizing agent is insufficient, an excessive amount of the sizing agent will be wastefully circulated within the white water system. Also,
The sizing agent is selectively fixed on the short fibers of the pulp over the long fibers. Therefore, if the papermaking yield of short fibers is poor, a portion of the sizing agent will wastefully circulate in the white water system together with the short fibers. During long-term circulation, these hydrolyze and change in quality, forming colored substances and aggregates, which adhere to and contaminate paper, papermaking felt, press rolls, and the like. As a result, the whiteness of the resulting paper decreases, and sometimes stains occur.Furthermore, aggregates adhering to felt and press rolls cause paper breakage, leading to a decrease in productivity in the papermaking process.

In order to solve the above-mentioned problems in neutral paper manufacturing, the following improvements and developments are underway.

(b) Improvement of neutral sizing agents for papermaking and development of new products (b) Development of auxiliary agents effective in improving the fixing properties of sizing agents and the papermaking yield of short pulp fibers (c) New development of the above auxiliary agents and sizing agents (d) Development of a dry/wet paper strength enhancer with good fixing properties and a method for using the same. However, improving the sizing agent alone is insufficient to improve the fixation of the sizing agent and the papermaking yield of short fibers. The effects are still unsatisfactory, and there are still many problems with various additives that have not been fully elucidated regarding how to use them.

[Problem that the invention seeks to solve]

As mentioned above, when a large amount of additives such as sizing agents, paper strength enhancers, retention aids, and fillers are added to the white water system in the production of neutral paper, these additives are Due to poor fixation, poor papermaking yield of short fibers, etc., additives that remain and circulate in the white water system for a long period of time can reduce the whiteness of manufactured paper, cause stains, and cause damage to papermaking equipment. This causes negative effects such as the generation of dirt.

The present invention aims to solve the above-mentioned problems and provide a method for producing neutral paper that maintains the interior of the white thread system clean even in the presence of a large amount of additives and reduces the decrease in whiteness. It is.

[Means for Solving the Problems and Their Effects] The method of the present invention is characterized in that neutral paper is produced by papermaking from a neutral aqueous slurry containing pulp and a chelating agent.

It is known that in the production of special purpose papers that require specific electrical properties, such as insulating paper, conductive metal ions in paper forming materials are sequestered using metal ion sequestering agents (chelating agents). There is. However, the use of a chelating agent to improve the whiteness of ship-neutral paper and to prevent a decrease in whiteness is a new technical idea proposed by the present inventors for the first time in the present invention.

That is, the present inventors made paper from a valve slurry containing a sizing agent, a dry/wet paper strength enhancer, etc.
We have discovered that it is possible to prevent a decrease in the whiteness of neutral paper obtained by carrying out the process in the presence of a metal ion sequestering agent),
This completes the present invention.

In the method of the present invention, the whiteness of the paper is prevented from decreasing.

The reason for this effect is still not fully clear. However, while sizing agents and paper strength agents are retained and circulated in the white water system in neutral papermaking, they are hydrolyzed, producing colored substances and forming aggregates. Ions are involved in some way, and by sequestering these metal ions with a chelating agent (metal ion sequestering agent), the formation of colored substances and aggregates as described above can be prevented, and these can also be prevented. It is thought that this can prevent aggregation using metal ions as nuclei.

Regarding the type and amount of chelating agent used in the present invention, as long as it reacts with metal ions and exhibits the desired effect, the type and amount of various additives contained in the pulp slurry will be taken into consideration. may be determined as appropriate. Generally, the chelating agents used in the method of the invention include ethylenediaminetetraacetic acid (EDTA), N-hydroxyethyl-ethylenediamine-N,N'N'-triacetic acid (HE
EDTA), diethylenetriaminepentaacetic acid (DTPA)
, nitrilotriacetic acid (NTA), N,N,N'N'-tetrakis(2-hydroxypropyl)-ethylenediamine (THPED), trans-1,2-cyclohexanediamine-N,N,N'N'-tetraacetic acid (CyDTA)
, N-(2-hydroxyethyl)-iminodiacetic acid (H
IOA), 3°6-dioxa-1,8-octanediamine-N.

N,N'N'-tetraacetic acid (GEDTA), ethylenediamine-N,N'-diacetic acid (EDDA), 1-hydroxyethylidene-1,1-diphosphoric acid, triethylenetetramine-N, N/, Nll, N11l , N
At least one selected from IIJ-hexaacetic acid, uramil diacetic acid M ([IDA), dimethylglyoxime, phytic acid, water-soluble salts of these acids (e.g., alkali metal salts or ammonium salts), potassium sodium tartrate, etc. Preferably, it consists of

The amount of chelating agent added to the bulb is preferably 0.05 to 1.0% by weight based on the weight of the bulb, and
．． More preferably, it is 2 to 0.5% by weight. If the amount added is less than 0.05% by weight, a sufficient effect of improving base paper whiteness and preventing a decrease in whiteness cannot be obtained, and even if the amount added is more than 1.0% by weight, the effect is no longer achieved. No improvement observed.

In addition, the addition of a chelating agent is effective before, during, and after beating the bulb, but it is particularly effective when added to the bulb before beating, and when the bulb is beaten in the presence of a sequestering agent. It is most effective when used.

The pH range of the valve slurry used in the method of the present invention is in the neutral range, that is, in the range of 6.0 to 9.0;
It is preferable that it is in the range of ~8.5, and in this range, the whiteness improving effect of the chelating agent is fully exhibited. Therefore, it is sufficient to beat the bulb using ordinary neutral paper-based white water and then perform papermaking in the above pH range.

If necessary, an aqueous solution of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium aluminate, etc. is used to adjust the pH, but it is not preferable to use a pH adjusting solution containing a large amount of aluminum ions.

The valve used in the method of the present invention is a chemical wood valve, a mechanical wood valve, or a living body, but may also contain organic fibers, such as synthetic fibers, and/or non-mta fibers (such as glass fibers). . Further, the pulp slurry used in the method of the present invention may contain dyes, pigments, optical brighteners, fillers, sizing materials, paper strength agents, fixing agents, etc. as additives. However, the use of aluminum salts should be avoided.

Examples of fillers include fillers that are also used in acid paper making, such as kaolin, clay, talc, baryta, zinc white,
Titanium, aluminum hydroxide, magnesium hydroxide, silicates, etc. can be used, and calcium carbonate used in neutral paper making, chalk, etc. can also be used. These fillers may be used alone or
Alternatively, two or more types may be used in combination.

The sizing agent that can be used in the method of the present invention is selected from neutral reactive sizing agents for papermaking, cationic sizing agents, and the like. For example, fatty acid salts, rosin, rosin derivatives such as maleated rosin, dialkylketene dimers, alkenyl or alkyl succinates, multi-I! Similar esters are used.

The paper strength enhancer can also be selected from conventionally used ones. For example, cationized starch, cationized polyacrylamide, anionized polyacrylamide, carboxy-modified polyvinyl alcohol, etc. are used as the dry paper strength enhancer.

Further, as a wet paper strength enhancer, melamine resin, urea resin, epoxidized polyamide resin, etc. are used. As the fixing agent, a cationized polymer such as cationized starch is used.

The method of the present invention is characterized in that the neutral papermaking step is carried out using a pulp slurry containing a chelating agent,
Manufacture of general quality paper with internal addition of calcium carbonate as a filler, medium and low grade paper containing mechanical pulp (CP), coated base paper including the use of waste paper recovered pulp from coated paper, and neutral paper for special purposes. Applicable to manufacturing such as. In particular, the method of the present invention
It is extremely effective in the production of neutral paper containing a large amount of chemicals, such as release paper for process use, base paper for water-resistant processing, base paper for photographic paper, base paper for labels, etc.

〔Example〕

The method of the present invention will be further illustrated by examples.

1 to 3, and 6 l Neutral paper of 127.9 g/rd was made under the paper making conditions shown in Table 1. Incidentally, the amount of chemicals added is expressed in weight % with respect to the raw material pulp. The whiteness (measured according to the method of JIS P8123) and the sizing degree (measured according to the Steckcht method) were measured for the raw material pulp and the obtained product, and the results are shown in Table 2.

As is clear from Table 2, the whiteness of the product with the chelating agent decreased less than that of the product with no other chelating agent added. It was confirmed that the drop in energy levels was significantly reduced, and the effect was significant.

〔Effect of the invention〕

The present invention has made it possible to produce acid-free paper that has high whiteness without reducing sizing. In addition, since the decrease in whiteness was reduced, it is thought that contamination in the papermaking system was reduced, and in the case of long-time papermaking, it was possible to improve the degree of sizing, improve the unit consumption of sizing agents and other chemicals, and improve papermaking efficiency. We can expect improvement.

Claims (1)

[Claims] 1. A method for producing neutral paper from a neutral aqueous slurry containing pulp and a chelating agent. 2. The method according to claim 1, wherein the pulp is prepared by beating in the presence of a chelating agent. 3. The method according to claim 1, wherein the content of the chelating agent is within the range of 0.05 to 1.0% based on the dry weight of the pulp. 4. The chelating agent is ethylenediaminetetraacetic acid (E
DTA), N-hydroxyethyl-ethylenediamine-
ME-N,N',N'-triacetic acid (HEEDTA), diethylenetriaminepentaacetic acid (DTPA), nitrilotriacetic acid (N
TA), N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine (THPED), trans-1,2-cyclohexanediamine-N,N,N'
, N'-tetraacetic acid (CyDTA), N-(2-hydroxyethyl)iminodiacetic acid (HIDA), 3,6-dioxa-1,8-octanediamine-N,N,N',N'-tetraacetic acid (GEDTA), ethylenediamine-N,N'-diacetic acid (EDDA), 1-hydroxyethylidene-1,1
-Diphosphoric acid, triethylenetetramine-N, N, N', N
″,N′″,N′″-hexaacetic acid, uramyl diacetic acid (UDA
), dimethylglyoxime, phytic acid, a water-soluble salt of the above acid, and potassium sodium tartrate.