JP2546816B2 - Method for producing polyvinyl acetal-based porous body - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyvinyl acetal-based porous body having an improved surface texture and feel, and more specifically, a polyvinyl acetal-based porous body suitable for a body-wiping sheet or the like. The present invention relates to a method for manufacturing a body.

[0002]

2. Description of the Related Art Conventionally, a sheet of a polyvinyl acetal type porous body or a sheet of a polyvinyl acetal type porous body in which reinforcing cloths are inserted and compositely integrated is Is used as a wiping material for wiping off and removing water droplets, dust, etc. on the surface of an article having a good absorption ability and a relatively high smoothness. For example, it is commercially available as a sheet for removing water drops on the surface of a vehicle body after car washing, a waste cloth for cleaning the surface of precision machinery, parts, instruments and the like.

Further, in recent years, due to its flexibility, good texture and high water absorption, it is often applied to sports, and above all, it is used as a wet body wipe for swimming and a sweat wipe. It is increasing rapidly.

As described above, the use for sports is increasing, in addition to having a stronger water absorption force than a normal towel, it also has an action of positively sucking it up, so that it comes into contact with a water drop portion. This is because it is possible to quickly remove water only by itself, and it is not necessary to rub it like a towel when wiping the body, and it is sufficient to just press it. That is, it is possible to avoid friction between the towel and the skin.

For example, in repeated use such as swimming and diving, it is particularly preferably used because excessive irritation and friction to the skin can be avoided.

However, since the surface shape of the above-mentioned polyvinyl acetal-based porous body is relatively dense, when it is used as a body-wiping sheet, it is cold when it first comes into contact with the skin. The feeling is unavoidable, and some people perceive it as an unpleasant sensation and may complain of poor usability.

In particular, most of the polyvinyl acetal type porous bodies used as sports towels are of a type in which a reinforcing cloth is inserted so as to withstand repeated use. This type is generally manufactured by layering several sheets by partitioning with paper, so that the surface of the paper itself has the precise and smooth shape of the paper transferred to it. The badness is especially remarkable.

In order to overcome such drawbacks, a method has been proposed in which a pattern of fine irregularities is placed on the surface to reduce the coefficient of friction, but this has the effect of eliminating the squeaky feeling during use and improving the feeling of use. However, it was intended only for articles, and the effect of eliminating the feeling of coldness and discomfort to the body was not recognized.

There has also been an attempt to remove the dense skin layer on the surface and change the surface texture by a sanding method performed on leather or woven or knitted fabrics, but the processing method does not fit well and the finished surface is also It is not so good, and because the skin layer is removed, the overall strength
There was also a drawback that it deteriorated the durability.

[0010]

The inventors of the present invention have completed the present invention as a result of intensive studies in view of the above-mentioned problems, and the object of the present invention is to provide a surface-modified poly It is to provide a method for stably and efficiently producing a vinyl acetal-based porous body.

[0011]

The above-described object is to react carbon dioxide gas by reacting at least a part of the surface with the acid when reacting a reaction stock solution containing polyvinyl alcohol, aldehydes, acids, and a pore-forming material. Reacting in the state of contacting the paper to which carbonate or hydrogencarbonate that generates hydrogen is contacted, and after the reaction is completed, unreacted aldehydes, acids, and pore-forming material are removed, and at the same time, the paper is removed. And a method for producing a polyvinyl acetal-based porous body.

The polyvinyl alcohol used in the present invention is a completely or partially saponified one having a degree of polymerization of 300 to 2000, and may be one in which a part of the hydroxyl groups is substituted with some other functional group. These can be used alone or in combination.

The aldehyde used in the present invention is a cross-linking agent for converting polyvinyl alcohol into polyvinyl acetal, which is aliphatic or aromatic and may be monovalent or polyvalent. It may be one. In particular, formaldehyde and acetaldehyde are suitable for exhibiting the physical properties of the polyvinyl acetal-based porous material.

The acids used in the present invention are those which act as a catalyst, and are composed of, for example, inorganic acids such as hydrochloric acid, sulfuric acid and nitric acid, organic acids such as oxalic acid, citric acid and maleic acid, or strong acids and weak bases. Salts that exhibit acidity in an aqueous solution can also be used.

The pore-forming material used in the present invention may be a fine powder of starch or other organic substances, but is preferably starch granules extracted from plants. Examples of the plant from which it is derived include grains such as rice, wheat and corn, and potatoes such as potato, sweet potato and taro. Since the starch granules have different particle diameters depending on the type of plant, they may be appropriately selected according to the target pore diameter. Also, so-called modified starch obtained by introducing a hydrophobic functional group into the hydroxyl group of these starch granules and modifying it may be used. Further, in order to obtain a large pore size, it is also possible to use a processed starch in which the starch is once gelatinized, dried, pulverized and then classified if necessary.

The pore diameter and the porosity can be adjusted by changing the kind and the addition amount of the pore forming material.

The paper used in the present invention is used as a so-called separator and is completely loosened and removed after the reaction. Therefore, the paper does not contain a binder, does not contain additives, and has a low beating degree. It is preferable to use the one having a property almost similar to pulp.

The carbonate or hydrogen carbonate used in the present invention is a compound which reacts with the above-mentioned acids to generate carbon dioxide gas, and is an alkali metal hydrogen carbonate compound, or an alkali metal or alkaline earth metal carbonate. Examples of the salt compound include sodium hydrogen carbonate, potassium hydrogen carbonate, and sodium carbonate. In the present invention, the above carbonates or hydrogen carbonates are used alone or in combination.

The method of applying the above-mentioned carbonate or hydrogencarbonate to the surface of the above-mentioned paper is not particularly limited, and for example, a binder containing a carbonate or hydrogencarbonate is applied to the paper by a printing method. Examples thereof include a method of adhering to and immobilizing it on the surface, a method of applying a thin aqueous solution of carbonate or hydrogencarbonate to the surface of paper and drying.

When it is applied as a fine powder, it is preferable that it is as fine as possible so that a uniform foaming effect can be obtained. If it is too large, the reaction with acids will be too concentrated to obtain a good surface. In particular, since the reaction between the carbonate or hydrogen carbonate and the acid proceeds rapidly and instantaneously, it is desirable to coat with a binder or the like to suppress the reaction and to make it slow.

When the carbonate or hydrogencarbonate is applied as a dilute aqueous solution, it is preferable in that the concentration can be adjusted appropriately, but it may penetrate into the paper and the effect may be insufficient. The method of applying to the paper using the binder described above is preferable.

As a method for applying a binder containing a carbonate or a hydrogen carbonate dispersed therein to a paper, a print printing method is suitable. According to this method, a desired design such as a design or a character can be extremely efficiently produced. It can be formed on the surface of paper.

As the type of binder used at this time, polyvinyl alcohol or acrylic type is preferable because it is easily fixed. If the amount of the carbonate or hydrogen carbonate to be applied is too small, there is no effect. On the contrary, if the amount is too large, fine bubbles are more concentrated and become large bubbles, which is not preferable. Unless a special effect is aimed at, it is preferable to apply the composition as thinly as possible and the application amount is preferably about 10 to 200 mg per 1 m ² .

In order to produce a polyvinyl acetal type porous body by the method of the present invention, for example, the following may be carried out.

That is, first, polyvinyl alcohol is dissolved in warm water to prepare a polyvinyl alcohol aqueous solution of about 5 to 15% by weight. A liquid in which fine starch powder as a pore-forming material is dispersed in water is put therein, and an aqueous solution of sulfuric acid and formaldehyde is further added, followed by sufficient stirring and mixing to form a uniform slurry-like stock solution.

The stock solution is heated to a temperature near the temperature at which the previously added fine starch powder is converted into α and poured into a predetermined mold in a predetermined amount. A paper on which a binder containing a fine powder of a carbonate or a hydrogen carbonate is dispersed by print printing is placed thereon, and then a predetermined amount of the stock solution is poured again. Further, when the placing of the paper and the casting of the undiluted solution are alternately repeated in the same manner, the separated layers on the paper as the separator are stacked in multiple layers.

The reaction is carried out as it is at about 60 ° C. for 10 hours or more, and after the reaction is completed, the unreacted aldehydes, acids and starch are removed by squeezing and washing with water, and at the same time, the paper is peeled off. A polyvinyl acetal-based porous body can be manufactured.

Further, when the cloth is placed after casting the stock solution and the stock solution is poured again, the product can be obtained by sandwiching the cloth as a reinforcing material. The cloth used at that time is preferably cloth having a coarse mesh and capable of integrating the polyvinyl acetal-based porous bodies on both sides, such as a ginseng cloth.

[0029]

The carbonate or hydrogen carbonate immobilized on the surface of the paper reacts with the acids in the reaction stock solution to generate carbon dioxide gas. Diffusion of generated carbon dioxide is prevented by the presence of paper, and it collects on the surface of the paper as a group of minute bubbles, and the surface of the PVAt-based porous body that is the reaction product has a fine and smooth surface to a slight roughness. The surface is modified.

Examples of the gas that reacts with acids to generate gas include metals having a higher ionization tendency than hydrogen. However, the gas generated in this case is hydrogen gas, and when a large amount is generated, there is a risk of ignition, explosion, and the like. In the method of the present invention, the gas generated is carbon dioxide, and there is no fear of ignition or explosion.

In the present invention, if the carbonate or hydrogen carbonate to be applied to the paper is fixed to a desired design shape such as a design, pattern, character, logo, etc., it is desired on the surface of the polyvinyl acetal type porous body. A design can be formed.

[0032]

EXAMPLES The method of the present invention will be described in detail below with reference to examples.

Acrylic resin emulsion (Brand name: Binder HK, manufactured by Dainippon Ink and Chemicals, concentration 50%)
A fine powder of 5 g of sodium hydrogencarbonate was added to 1 kg and sufficiently mixed to prepare a paste-like liquid. After printing this paste-like liquid on paper in the same manner as screen printing,
It was dried and fixed to form a paper for a separator. The pattern printed was a striped pattern in which straight lines having a width of 30 mm were obliquely arranged at intervals of 30 mm. The amount of acrylic resin containing sodium hydrogen carbonate applied to paper is 0.6 mg / c.
m ² .

750 g of completely saponified polyvinyl alcohol (trade name: PVA-117, manufactured by Kuraray) was dissolved in warm water to make a total amount of 8 l. Next, 700 g of corn starch was dispersed in water, and this was added to the above polyvinyl alcohol aqueous solution with stirring to make the total amount 10 l.

A mixed solution of 1 l of 37% aqueous formaldehyde and 1 l of 50% sulfuric acid was added to the mixed solution of polyvinyl alcohol and starch to form a homogeneous mixed solution, which was used as a reaction stock solution.

A resin container having a length of 78 cm, a width of 49 cm and a depth of 10 cm was prepared. 300m of reaction stock solution in this
l, then place a reinforcing vinylon gauze on it, then inject 300 ml of the reaction stock solution, and then place a separator paper on it to almost completely separate the layer of the reaction stock solution. I'm sorry. This procedure was repeated many times to form multiple layers. The paper for the separator was placed so that the surface coated with sodium hydrogencarbonate faced the lower surface.

After the lamination was completed, the container was placed in a heat treatment machine adjusted to 60 ° C. and reacted for about 24 hours.

After the reaction was completed, the contents were taken out of the container,
After thoroughly washing with water to remove unreacted formaldehyde, sulfuric acid and starch, the reaction product is further divided with a separator paper portion to obtain a sheet-shaped polyvinyl acetal-based porous body having a thickness of about 1.5 mm. Obtained.

The upper surface of the obtained polyvinyl acetal-based porous material had a surface shape different from the normal surface due to the effect of sodium hydrogencarbonate applied to the separator paper. That is, it was a shape in which an extremely fine and uniform shape of the bubble layer was transferred, and had an appearance and a feeling of touch as if sanded. Moreover, no deterioration or deterioration of the physical properties of the part was observed.

Further, in appearance, a striped pattern is clearly embossed on the surface, which gives a high-class feeling.

[0041]

According to the method of the present invention, it is possible to stably obtain a polyvinyl acetal-based porous body having fine irregularities on its surface. In the method of the present invention, the surface modification does not require secondary processing such as sanding,
It has high production efficiency and is extremely advantageous in industry. Further, since it is not a method of removing the dense skin layer formed on the surface of the polyvinyl acetal-based porous body, the physical strength and durability are not deteriorated at all. In other words, it is possible to obtain a surface having the conventional toughness, softness, and no feeling of coldness and sliminess.

The sheet-shaped polyvinyl acetal-based porous body obtained by the method of the present invention is very suitable as a sheet for wiping a body such as a towel.

Claims (1)

(57) [Claims] 1. A carbonate or carbonic acid which, when reacting a reaction stock solution containing polyvinyl alcohol, aldehydes, acids, and a pore-forming material, produces carbon dioxide gas on at least a part of the surface by reacting with the acids. A polyvinyl acetal system characterized in that it reacts with a paper to which a hydrogen salt has been brought into contact, and after the reaction is completed, unreacted aldehydes, acids and pore-forming materials are removed and the paper is removed. A method for producing a porous body.