JPS5813573B2 - I want to know how to use it. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a porous sheet that is free of folds, is strong, and has excellent flexibility.

One way to produce a fiber-bonded sheet that is more flexible than before is to provide flexibility by creating voids between the fibers and the binder in the sheet structure so that the fibers themselves can move to some extent. There are many technical ideas, and many techniques have been proposed, for example, in Japanese Patent Publications No. 44-21835, No. 45-1943, No. 47-21275, No. 48-28043.

That is, these are achieved by pre-treating the fibrous base material with a water-soluble polymer, then applying a binder, coagulating or drying, and then extracting the water-soluble polymer.

In these conventional methods, water-soluble polymers such as polyvinyl alcohol, carboxymethyl cellulose, polyethylene oxide, and polyacrylamide are used as extraction substances, while the main binders are polyurethane, synthetic rubber, In most cases, it is a solution in a water-miscible organic solvent such as polyacrylate.

The reason for this is that the extracted substance is water-soluble, so if a water-based binder is used, the water-soluble polymers that have been attached in advance during the impregnation process will be easily dissolved by the water in the binder solution and bonded from the fiber surface. This is because the binder is dispersed in the agent solution, which not only increases the viscosity of the binder and causes trouble during impregnation, but also does not achieve the desired purpose at all.

Therefore, when using an aqueous binder, the extracted substances are:
A synthetic resin that is insoluble in water and soluble in an organic solvent, such as polyvinyl acetate or polyvinyl chloride, is used for post-treatment by extraction with an organic solvent such as methanol or ethyl acetate.

However, since these processes require organic solvents, special care is required in handling them due to their toxicity, flammability, etc., and therefore there are difficulties in workability and productivity.

On the other hand, in order to increase the pore-forming effect of such extraction, a considerably large amount of extracted material is required, and it is usually applied at a weight of about 15% to 30% of the weight of the fibrous base material. Not only is this economically disadvantageous, but the permeability of the substrate treated with a large amount of extracted substances is significantly inhibited during the subsequent binder impregnation step, and the final extraction step is extremely difficult. Since it requires a long time, it causes a decrease in productivity.

Therefore, as a result of intensive research on extracted substances in this technology, the present inventor found that an aqueous solution of water-soluble alginate or carboxyalkyl cellulose salt (hereinafter sometimes referred to as jelly polymer), etc. Producing polymer jelly that is insoluble in water and almost any organic solvent by instantaneously causing a cation exchange reaction with an electrolyte solution such as a valent metal salt, and this insoluble polymer jelly and products further dried. (Hereinafter, this will be referred to as polymer xerogel.

Furthermore, the polymer jelly and polymer xerogel may be collectively referred to as insoluble polymer.

), by skillfully utilizing the fact that it can be replaced with the original water-soluble polymer again through a cation exchange reaction, it solves all of the drawbacks of the above-mentioned conventional technology, and also has many other advantages. What we found, quality,
The present invention provides a method for manufacturing a flexible porous sheet that satisfies all aspects such as productivity, workability, and economy.

That is, the present invention involves the first step of impregnating a dilute aqueous solution of a water-soluble alginate or carboxyalkylcellulose salt into a fibrous base material, and instantly converting the applied aqueous polymer solution into a water-insoluble polymer jelly. a second step of converting the insoluble polymer into a xerogel, further drying it if necessary to transform it into an insoluble polymer xerogel; a third step of further impregnating it with a binder and fixing it; This method is characterized by comprising a step of extracting and removing the , and a fourth step.

In the present invention, the soluble and insoluble reversible polymer jelly used as the extraction substance is represented by, for example, agar, gelatin, etc. Like 97~9
It is a solid substance containing 9% water, and in other words, it is a solid substance with a huge volume even at an extremely low concentration.

Furthermore, the volume of the polymer xerogel obtained by drying this polymer jelly is much larger than that of the conventional polymer aqueous solution simply dried without turning it into a jelly, and this is also the source of agar. This is obvious when considering the dry matter.

The insoluble polymer jelly used as the extract material in the present invention can be produced, for example, as follows.

In other words, a dilute aqueous solution of alginic acid soda salt or ammonium salt is treated by immersion or spraying in an electrolyte solution such as a dilute acid aqueous solution such as sulfuric acid or hydrochloric acid or a polyvalent metal salt aqueous solution such as calcium chloride, zinc sulfate, or aluminum sulfate. By carrying out this process, a polymer jelly that is insoluble in water and almost all organic solvents can be obtained instantly and easily.

Similarly, carboxyalkylcellulose salts, e.g.
In the case of soda salts such as carboxymethyl cellulose and carboxyethyl cellulose, it is preferable to use mainly trivalent metal salt aqueous solutions such as aluminum sulfate and aluminum nitrate as the treatment electrolyte solution.

Both of these jelly-forming reactions are so-called cation exchange reactions of metal ions in carboxyl groups, and in the above polymer aqueous solution, the polymer becomes three-dimensional when it comes into contact with hydrogen ions or polyvalent metal ions, and this It is thought that water is trapped within the three-dimensional network and becomes solid phase water (jelly).

Therefore, it is completely different from dehydration coagulation of polyvinyl alcohol aqueous solution or viscose alkali aqueous solution with mirabilite aqueous solution, trivalent salt coagulation of polyacrylic acid soda, etc., and the present invention will not be achieved at all even if these are used as extraction substances. It is something.

On the other hand, the insoluble polymer in the present invention can be treated with an aqueous solution containing alkali metal ions such as sodium or potassium, or ammonium ions, to perform a cation exchange reaction, which is the reverse of the previous jelly formation reaction, or A complex ion formation reaction occurs instantly, making it water-soluble again, and it can be easily extracted and removed by washing with water.

Specifically, for example, an insoluble polymer called calcium alginate is treated with a 5 to 10% aqueous solution of sodium carbonate, and by ion exchange between calcium and soda, it is converted into a water-soluble polymer called sodium alginate. .

As described above, the present invention has many advantages as follows, since it uses a soluble and insoluble reversible polymer jelly or polymer xerogel as an extraction substance.

First of all, the insoluble polymer that is the extracted substance of the present invention is
Even though the solid content is extremely small, its volume is very large, so
In the first step, only a very small amount is required to adhere to the fibrous base material, which is economical.

Second, the polymer jelly, which is the extracted substance, is instantly and firmly fixed within the fibrous base material in the second step, and the water in the jelly does not leak out at all, so it is not necessary to wait until the fourth step. No deformation occurs even when the base material is subjected to stress during post-processes such as squeezing and impregnation, contributing to improved workability and quality reproducibility.

Furthermore, when this is further dried to form a polymer xerogel, it is clear that migration cannot occur during drying.

Thirdly, since the extracted substances, polymer jelly and polymer xerogel, are insoluble in water and almost all organic solvents, the organic solvents conventionally used as the fiber binder to be impregnated in the third step are Not only binders, but also water-based binders such as latex and emulsion types, which have rarely been used until now, can be widely used, which greatly improves productivity, workability, and economic efficiency. It becomes possible to manufacture a wide variety of products.

Fourthly, the fibrous base material to which the polymer xerogel adhered obtained by drying in the second step has a microporous property due to the three-dimensional network molecular structure of the polymer xerogel itself, and a polymer xerogel and constituent fibers. Due to the synergistic effect with the so-called macroporous property due to the capillary structure formed between the two, the liquid absorption property is significantly improved, and the permeability of the binder and processing liquid in the third step into the base material is greatly increased.

In this case, the binder penetrates into the microporous of the polymer xerogel, and when the final product after extraction is observed, the binder forms a fine mesh around the fibers compared to a product extracted as a polymer jelly. It becomes a porous sheet with extremely fine voids.

Fifth, and this is extremely important in the present invention, since the polymer jelly that is the extracted material usually contains a large amount of water, 95% or more, the binder solution applied in the third step does not contain water. When a non-solvent is used, the binder impregnated into the fibrous base material comes into contact with the polymer jelly that has already adhered, and is coagulated near the surface of the polymer jelly by the moisture.

In this case, the coagulation of the binder occurs over time after the binder is completely impregnated into the substrate, since the water in the polymer jelly cannot flow out under mechanical stress.

This means that solidification never occurs before the binder penetrates into the substrate.

On the other hand, such polymer jelly and polymer xerogel contain polyvalent metals in their molecules, as described above, and easily cause an ion exchange reaction.

For example, if an anionic latex or emulsion containing alkali metal ions such as sodium or potassium is used as a binder, after being impregnated in the same way as before, it will bind to the polyvalent metal of the insoluble polymer already attached. A cation exchange reaction occurs with the alkali metal in the agent, and polyvalent metal ions are liberated, causing coagulation of the binder latex or emulsion.

In this way, in the former case, the binder can be coagulated by solvent-non-solvent substitution, and in the latter case, it is possible to coagulate the binder by ion exchange reaction, so the coagulation process of the binder is not necessarily necessary in the third step, and it can be dried as it is. However, no binder migration occurs.

Furthermore, the coagulation of this binder weakens the adhesion between the binder and the insoluble polymer or constituent fibers, improving the ability to extract the insoluble polymer in the fourth step, and at the same time, the resulting fibrous sheet has excellent flexibility. It becomes something.

Next, the present invention will be explained step by step.

First, in the first step, the fibrous base material that is the raw material layer is a woven fabric, knitted fabric, felt made of natural fibers, synthetic fibers, or mixed fibers thereof, or a nonwoven fabric made by a card method, an air-lay method, etc. Fleece etc. are used.

First, a dilute aqueous solution of a jelly-formed polymer such as sodium alginate or carboxymethyl cellulose as described above is impregnated or sprayed onto a fibrous base material in liquid or foam form. ,
The particles may be distributed uniformly within the fibrous base material, or may be distributed more on one or both sides of the base material with a density gradient.

In the former case, the binder distribution in the resulting porous sheet is uniform throughout, while in the latter case, the binder is distributed on one side or inside the base material, resulting in a wide variety of porosity. A sheet product is obtained.

The aqueous solution of the jelly-formed polymer is usually used at a concentration of 0.5% to 5%, but it is adjusted as appropriate depending on the viscosity of the solution and the amount of adhesion.

Furthermore, in the past, a large amount of about 15% to 40% of the solid content was usually required as the amount of adhesion to the fibrous base material, but in the present invention, about 0.2% to 15% is sufficient and preferably. is 1
A range of % to 10% is preferable.

In the second step, the aqueous solution of the gelatinized polymer previously applied to the fibrous base material is turned into a jelly.
It is instantly transformed into an insoluble jelly by immersing or spraying it in a % aqueous solution, squeezing out excess electrolyte solution, and then washing with water if necessary.

As for the jelly-forming treatment time, although it is effective even if it is only a few seconds, in consideration of quality stabilization, productivity, etc., a period of about 10 to 50 seconds is appropriate.

If necessary, this can be further dried to obtain a fibrous base material to which the polymeric clasp gel is attached, but in this case, it is more preferable because the permeability of the binder in the third step is improved. .

Next, in the first step of the third step, a binder that is the main binder of the fibrous base material is impregnated, but unless the binder itself is extremely hard, most of the binders normally used for nonwoven fabrics are used. Which bonding agent is applied.

For example, solvent solution types such as natural rubber, chloroprene, NBR, SBR, ethylene-vinyl acetate copolymer, polyacrylate, plasticized polyvinyl chloride, polyamide, polyurethane, etc., or aqueous dispersion types such as latex and dispersion of these materials are used. Ru.

Now, in the second step, the required amount of the binder is attached to the fibrous base material by a conventionally known method such as impregnation, spraying, or coating, and then it is fixed. There are two methods: drying and once coagulating the binder.

Methods for coagulating the binder include well-known heat-sensitive coagulation methods, wet coagulation methods, and the like, and can be appropriately selected depending on the type of binder.

As mentioned above, if the binder coagulates due to the insoluble polymer used as the extracted substance, it is possible to obtain a product that is quite satisfactory in terms of quality even if it is dried as is. It is even better to go through the solidification process.
A flexible sheet can be obtained.

Now, in the fourth and final step, the fibrous base material to which the insoluble polymer substance and binder are fixed is treated with a solubilizing liquid that is inert to the constituent fibers and binder but makes the insoluble polymer soluble in water. The purpose is to extract and remove this from the base material by washing with water or hot water while squeezing after treatment, and to create many voids inside the base material.

For example, a 5% to 10% aqueous solution of common salt, soda carbonate, sodium citrate, ammonia, etc. is suitable for the solubilization treatment, and is achieved by impregnating or spraying the substrate with these solubilizing solutions.

The processing time is the second step of jelly. The time is approximately the same as the unification time, but preferably about 15 seconds to 1 minute.

Moreover, as an advantageous method, when the binder coagulation step is performed in the third step, the above-mentioned solubilizing liquid is mixed into the binder coagulation bath, so that the coagulation of the binder and the solubilization of the insoluble polymer are carried out. It is preferable to do it simultaneously.

In this case, the third step and the first step of the fourth step are performed simultaneously in one step.

The fibrous sheet obtained through the above process has almost no direct bond between the fibers and the binder, and has many voids inside the sheet, so it is extremely flexible and has excellent breathability and moisture absorption. This is a strong porous structure that is ideal as a base fabric for cloths such as wiping cloths and tablecloths, or as a base fabric for artificial leathers and synthetic leathers such as shoe bags and furniture.

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

Example 1 A random fleece made of nylon stable fibers having a length of 3 denier and 51 mm was subjected to 21 dollar punching at a needle density of 200 needles/cm to obtain a 21 dollar felt with a weight of 200 g/d.

Next, sodium alginate (Datsukalgin NSPH2)
A 1% aqueous solution of .

This impregnated base material was immersed in a 5% aqueous solution of calcium chloride for 30 seconds, and the adhering aqueous sodium alginate solution was immediately converted into calcium alginate jelly, which was fixed to the fibers.

After washing with water and squeezing, it was immediately impregnated with a heat-sensitive composition of NBR latex without drying, and the fiber/binder ratio was adjusted to 60/40 in terms of solid content.

This was placed in an oven at 150°C to thermally solidify the binder for 1 minute, and then immersed in an 8% aqueous solution of sodium carbonate for 1 minute to replace the calcium alginate component in the base material with sodium alginate. Complete extraction and removal was carried out by squeezing with hot water at ℃.

The thus obtained nonwoven fabric sheet had an air permeable porous structure with almost no substantial bonding between the fibers and the binder, and had an extremely soft texture.

Example 2 Twenty-one dollar felt with the same composition as Example 1 (weight: 150
Zinc alginate jelly was fixed inside the 21-dol felt by uniformly impregnating it with a 1% sodium alginate aqueous solution and then spraying a 5% lead nitrate aqueous solution.

When this was washed with water and dried, it was found that 8% lead alginate was attached to the needle felt.

Next, the fibers were impregnated with a binder latex mixture having the following composition so that the fiber/binder ratio was 55/45.

After immediately drying this at 150°C for 5 minutes, the alginic acid was extracted and removed in the same manner as in Example 1. As a result, the resulting nonwoven fabric sheet was First, there was no migration phenomenon of the binder at all, the sheet was uniformly colored, and the sheet was a flexible porous sheet with adhesive and weldability.

Example 3 60% nylon fiber of 1.5 denier 51 mm length and 3
A fiber fleece made of 40% polyester fibers having a length of 64 mm was subjected to 21-dringing at a needle density of 180/crA to obtain a needle felt with a weight of 180 g/m2.

In addition, carboxymethylcellulose (Celogen PR・
...A 2% aqueous solution of Daiichi Kogyo Seiyaku Co., Ltd.) was applied to one side of the above-mentioned 21 Dorfelt to impregnate it so that more of it was applied to one side, and then a 3% aqueous solution of aluminum nitrate was applied from both sides. It was sprayed and immediately transformed into carboxymethyl cellulose aluminum jelly.

Next, after squeezing this, it was impregnated with a 12% dimethylformamide solution of one-component polyurethane (Crysbon 7667EL, manufactured by Dainippon Ink Co., Ltd.) as a binder, so that the fiber/binder ratio was 65/35. And so.

Further, this was immersed in a 10% aqueous solution of soda carbonate to coagulate the polyurethane binder and solubilize the extracted material at the same time, and then thoroughly washed with water to completely extract and remove DMF and the extracted material.

After drying, the surface on which more extracted substances were deposited in the first step was buffed to obtain a soft and tough raised porous sheet.

Claims (1)

[Claims] 1. A step of impregnating a fibrous base material with an aqueous solution of a water-soluble polymer that becomes jelly-like upon insolubilization, a step of changing the applied aqueous polymer solution into a water-insoluble polymer jelly,
A process of impregnating a binder and fixing it, converting the water-insoluble polymer into a water-soluble polymer again, and extracting the water-soluble polymer. A method for producing a flexible porous sheet, comprising the steps of: removing the sheet.