JPS6071797A - Production of water absorbable 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 Applicability] The present invention provides a method for applying 5. It relates to a method of continuously imparting water absorbency in a very short period of time (several minutes).

[Prior art]

Cellulose - Water-bathable carboxymethylcellulose obtained by etherifying pulp with monochloroacetic acid, caustic soda, etc., is crosslinked with epichlorohydrin, etc., but it absorbs water, but at least a large portion of it is insoluble in water. It is already known that pulp can be obtained. For example, according to the method described in JP-A-50-80!176, cellulose is mixed with aqueous ingropanol solvent (
'87%) under strong stirring at 20°C for 45 minutes, then a crosslinking agent was added and the mixture was heated at 50°C for 1 hour.
time and then add monochloroacetic acid to 70°C.
There is a problem in that it takes a very long time, as it states that the treatment is carried out for one hour.

In addition, there is a continuous production method for fast-dissolving paper described in Japanese Patent Publication No. 42-2925 as a method for etherifying the paper state, but the purpose of this proposal is to provide a method for producing water-soluble paper. In particular, it is completely different from the method of the present inventors for producing water-absorbing paper, and the etherification reaction is also characterized by the use of reaction heat, and the reaction time is 40 minutes. There is a problem in that it takes a long time, up to 90 minutes.

In addition, as is well known, starch-based, synthetic polymer-based, cellulose-based, and other superabsorbent resins are commercially available. Fixed in a sandwich shape, dispersed on the surface of paper,
The conventional method of adhesive processing has problems such as problems with the adhesive processing method, uneven adhesion of the adhesive resin, and falling off of the resin.

[Purpose of the invention]

The purpose of the present invention is to solve the above-mentioned problems, and to provide a method for continuously and quickly imparting water absorbency to paper whose main component is wood pulp while still in the paper state. be.

[Structure of the invention]

The present invention is characterized by impregnating paper whose main component is wood pulp with an etherifying agent, an alkaline agent, and a polyfunctional reactant (crosslinking agent) as a water-containing methanol solution, and then subjecting it to a heating reaction for a short period of time. This is a method for producing water-absorbent paper.

In order to solve the above-mentioned problems, the present inventors have conducted intensive research on a method for continuously and quickly imparting water absorbency to paper whose main component is wood pulp, and have developed the present invention. reached.

In other words, paper whose main component is wood pulp, such as high-quality paper, tissue paper, etc. made from BKP (bleached kraft pulp), which has a relatively low lignin content, and GP (ground wood pulp), which has a high lignin content. ), TM
Newspaper and medium-quality paper whose main ingredients are P (thermomechanical pulp), RGP (refined ground wood pulp), and D-P (recovered paper pulp) have a methanol content of 60%.
The cellulose content in the paper is etherified by immersing it in ~70% water-containing methanol solvent monochloroacetic acid, monochloroacetic acid sodium solution, and caustic soda solution to attach chemicals, and then heating to cause a rapid reaction. , and by crosslinking this, it was discovered that water absorbency could be continuously imparted in a short period of time (several minutes), and the present invention was completed.

Conventionally, hydrous isopropanol (87%) has been used as a solvent for the carboxymethylation reaction of cellulose, but when monochloroacetic acid or caustic soda is dissolved, it separates into two layers, which requires stirring the liquid, which is not desirable. do not have. On the other hand, the water-containing methanol solvent used in the present invention does not have the problem of two-layer separation as described above, and is extremely effective when paper is immersed in 6"1 treatment. Furthermore, regarding the ratio of methanol and water, monochloroacetic acid Although it depends on the concentration of the caustic soda solution, water-containing methanol with a methanol content of 60 to 70 g is desirable.

Furthermore, when methanol is used as a solvent, there is an advantage that it can be easily recovered at the same time as methanol, which can be used in the subsequent washing process. As the etherification agent, either monochloroacetic acid or sodium monochloroacetate can be used, but monochloroacetic acid is preferably used.

The strained etherification agent can have a concentration in the range of 50 to 701F/100-hydrous alcohol, and the alkali agent can have a concentration in the range of IO to sot/+ogo hydroalcohol. good.

We also carefully considered the order of dipping the etherification agent and the alkali agent, but we found that monochloroacetic acid and caustic soda were uniformly applied in the specified manner.
It has been found that it is desirable to immerse the material in an etherifying agent solution and then in a caustic powder solution in order to make it adhere. The immersion time in the etherification agent may be instantaneous, but for alkaline solutions it is necessary to immerse the material in the alkali solution for at least 50 seconds, preferably for at least 1 minute.

Further, it is necessary to heat the paper impregnated with a predetermined amount of an etherifying agent, caustic soda, etc. at a temperature of 100° C. or higher.

In order to carry out the reaction continuously and to easily control the temperature, it is preferable to bring the paper to which a predetermined amount of the etherifying agent and caustic soda are attached to a rotating heated roll having a surface temperature of 100° C. or higher. At this temperature, a short reaction time of 2 to 5 minutes is sufficient.

The adhesion rate of the etherifying agent (monochloroacetic acid) to paper should be in the range of 20 to 60%, preferably 25 to 45%, and the adhesion rate of caustic soda should be in the range of 10 to 60%, preferably 15 to 55%. It is necessary to attach it so that it exists. The adhesion rate is, for example, 35% when monochloroacetic acid 35F adheres to 100 f of paper.

A polyfunctional reactant (crosslinking agent) can be used to insolubilize the cellulose ether in paper, such as epichlorohydrin, polyhydric alcohol diglycidyl ether M (2-ethyl hexyl・Glycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, etc.) can be used. The crosslinking agent can be added by immersing the paper after etherification in a solution of the crosslinking agent dissolved in methanol and heating +=1-l treatment, by adding it to the raw material before paper making, or by adding it to the raw material before papermaking. A method of coexisting in an alkaline agent or an alkaline agent is conceivable, but from the point of view of imparting water absorbency in a short time, which is the objective of the present invention, it was found that it is best to have it coexist in an alkaline agent.

The concentration of the crosslinking agent used may be in the range of 3 to 20 y/Io o -hydrated methanol.

It is also easily possible to repeat immersion in an etherifying agent, immersion in an alkali agent containing a crosslinking agent, and heating roll treatment many times.

Furthermore, the method of the present invention will be specifically explained based on FIG.

In No. 1, the paper △ 1 mainly composed of wood pulp is introduced into a water-containing methanol solution tank 2 of monochlorosodium acetate, passed through a press roll 6, coated with a predetermined amount of monochloroacetate soda, and then treated with caustic soda. and a crosslinking agent into a mixed water-containing methanol solution tank 4, and then pressed with a press roll 5 to adhere a predetermined amount of caustic soda and the crosslinking agent, and then heated in contact with a heating roll 6 having a surface temperature of 100° C. or more. After reacting the paper with the above-mentioned chemical, the paper is passed through a water-containing methanol liquid bath 7 containing acetic acid and the like, a press 8, and dried by a drying roll 9, thereby obtaining water-absorbing paper 10. Note that the methanol solvent can be recovered into the tube 11 by sealing the entire system and using heat treatment and drying heat.

The absorbent paper obtained by the method of the present invention has a wide variety of uses, such as sanitary products, sanitary materials such as disposable diapers, medical materials,
It can be used as paper to prevent condensation.

The present invention will be explained in more detail with reference to Examples below.

I asked for it.

Example-1 A piece of paper with a basis weight of 17,017 m'' was immersed in a reaction solution (50 f / 100 ml) in which monochloroacetic acid was dissolved in a water-containing methanol solvent with a methanol content of 70% by weight, and further dissolved in caustic soda and ethylene glycol diglyclycetic acid.・After immersing in a water-containing methanol reaction solution (NaOH22t/1o ant, diglycidyl ether sr/+ooy) containing 70% by weight of methanol containing dielether for different immersion times to adhere a predetermined amount of chemicals, The paper was reacted by contacting it with a rotary dryer for photographic drying (diameter 55 cm x 60 ml, rotation speed 2 minutes 50 seconds/time, surface temperature 125 U).The paper was washed with 70% methanol and 100% methanol, The water absorption rate was measured after drying under reduced pressure.The immersion time in monochloroacetic acid had almost no effect, so it was set at 30 seconds in this test.The results are shown in Table 1. Table 1 shows that time is important and 30 seconds or more is required. Table -
Shown in 2. The immersion time in the caustic soda solution was 1 minute.

Since the adhesion rate of monochloroacetic acid was low, the water absorption rate was low, but the surface temperature and contact time of the rotary dryer were set at 100℃ or higher, and the dryer was placed at 125℃ for 2 minutes.
It has been found that a contact time of 0 seconds or more is required.

Table 2 Example 3 An experiment was conducted using the same method as in Example 1 (the immersion time in the caustic soda solution was 1 minute) regarding the order in which paper was immersed in monochloroacetic acid and the caustic soda solution. The results are shown in Table-5. When the sample was immersed in a monochloroacetic acid solution after being immersed in a caustic soda solution, no high water absorption capacity was obtained. On the other hand, if the material is immersed in monochloroacetic acid and then immersed in caustic soda, a high water absorption capacity can be obtained.
A similar test was conducted using sodium monochloroacetate instead of monochloroacetic acid.

A water absorption +rLt with a water absorption capacity of 197 times was obtained with a monochloroacetate sodium adhesion rate of 27% and a caustic soda adhesion rate of 21%.

Example 5 In the same manner as in Example 1, the relationship between the adhesion rate of monochloroacetic acid and caustic soda and the water absorption capacity was tested by changing the adhesion rate. The results are shown in Figure 2 ==.

In FIG. 2, the X mark indicates a water absorption capacity of 5 times or less, the Δ mark indicates a water absorption capacity of 5 to 9 times, the mu mark indicates a water absorption capacity of 10 to 14 times, the O mark indicates a water absorption capacity of 15 to 19 times, and the ◎ mark indicates a water absorption capacity of 20 times or more.

It was found that the adhesion rate of monochloroacetic acid to paper should be 20 to 60%, preferably 25 to 45%, and the adhesion rate of caustic soda should be 10 to 60%, preferably 15 to 65%. .

It can be seen that water absorbent paper with a water absorption capacity of 20 times or more can be obtained by depositing about 55% of monochloroacetic acid and about 30% of caustic soda.

Example-6 Same method as Example-1 (caustic soda immersion time 1 minute)
A test was conducted using epichlorohydrin as the crosslinking agent added to the caustic soda solution. Monochloroacetic acid adhesion rate is 51%, caustic soda adhesion rate is 27%, and water absorption capacity is 21.
An 8 times more absorbent paper was obtained.

Example 7 Various papers were tested in the same manner as in Example 1. The results are shown in Table 4. BKP with low lignin content
Tissue 1 paper (basis weight 5 K G 1)
7m”), one paper used in Example-1 (basis weight 1
7017m''), it was found that a water absorbent paper with a high water absorption capacity could be obtained.

In addition, newspapers and medium-quality paper whose main component is pulp with a high lignin content such as GP, TMP, RGP, and D-sphere are inferior to wood-free paper or have poor water absorbency.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining one embodiment of the present invention, and FIG. 2 is a diagram showing the relationship between the adhesion rate of monochloroacetic acid and caustic soda and the absorption capacity of paper.

Claims (1)

[Claims] 1. Paper mainly composed of wood pulp, an etherification agent,
A method for producing water absorbent paper, which comprises impregnating an alkaline agent and a polyfunctional reactant L (crosslinking agent) as a water-containing methanol solution, and then subjecting the product to a short heating reaction. 2. The method for producing water-absorbing paper according to claim 1, wherein the paper is impregnated with an etherifying agent and then immersed in an alkaline agent solution for 30 seconds or more to adhere the alkaline agent. 5. The method for producing water-absorbing paper according to claim 1 or 2, wherein the etherification agent has an adhesion rate of 20 to 60 cm and the alkali agent has an adhesion rate of 10 to 60 cm. . 4. The method for producing water-absorbing paper according to claim 1 or 2, wherein the etherification agent has an adhesion rate of 25 to 45% and the alkali agent has an adhesion rate of 15 to 55%. . 5. According to any one of claims 1 to 4, the paper impregnated with an etherification agent, an alkaline agent, and a polyfunctional reactant is brought into contact with a roll having a surface temperature of 100° C. or higher and heated. A method for producing absorbent paper. 6. The method for producing water-absorbing paper according to any one of claims 1 to 5, wherein monochloric acid flit or monochloric sodium acetate is used as the etherification agent, and caustic soda is used as the alkali agent. 9. A method for producing water-absorbent paper according to any one of claims 1 to 6, wherein epichlorohydrin or glycyl ethers of polyhydric alcohols are used as the polyfunctional reactant.