JPH07278343A - Porous polyvinyl acetal resin and its production - Google Patents

Abstract

PURPOSE:To easily produce a porous polyvinyl acetate resin having excellent water-absorptivity in dry state and capable of quickly varying from dry state to wet state by including or attaching a surfactant to a polyvinyl acetal resin using a specific method. CONSTITUTION:This porous material containing a surfactant included in or attached to a polyvinyl acetal resin is produced by adding and mixing e.g. 0.005-0.01W/V% of a surfactant to a reaction liquid composed of a PVA (preferably having an average polymerization degree of 1,500-3,800), a pore-forming material (preferably starch grain extracted from plant), a crosslinking agent (e.g. formaldehyde) and a crosslinking catalyst (usually sulfuric acid), subjecting the reaction liquid to crosslinking reaction and finally removing the pore-forming material. The surfactant is preferably an alkylbenzene sulfonic acid salt, sulfosuccinic acid dioctyl ester, etc., e.g. to prevent the shrinkage of the reaction product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl acetal resin porous body, and more specifically, a polyvinyl acetal having excellent water absorption performance (hereinafter abbreviated as "PVAt").
-Based resin porous body and a method for producing the same.

[0002]

2. Description of the Related Art A porous PVAt resin body is known as a material having excellent water absorbency and water content as well as preferable flexibility and impact resilience when wet. The PVAt-based resin porous body is widely used for cleaning tools, wiping materials, puffs for makeup, etc. by utilizing such properties. By the way, PVA
The t-based resin porous material has a problem that mold tends to be generated when it is stored for a long time in a wet state. For this reason, it is desirable to store the PVAt-based resin porous body in a dry state, absorb water during use, and make it a wet state before use. However,
The water absorption rate of the PVAt resin porous body has a large difference between the dry state and the wet state, and the water absorption rate in the dry state is significantly slower than that in the wet state. Therefore, it takes some time to bring the dry PVAt resin porous body into the wet state. Therefore, it is very practically preferable that the PVAt-based resin porous body has a high water absorption rate in a dry state and rapidly shifts to a wet state.

It is known that the water absorption rate of the PVAt resin porous body in a dry state is affected by the degree of acetalization of the PVAt resin and the size of pores. That is, since the higher the degree of acetalization of the PVAt resin porous body, the higher the hydrophobicity thereof, the lower the degree of acetalization is, the better the water absorption is. However, it is not easy to control the degree of acetalization in the manufacturing process, and PVAt resins having a low degree of acetalization tend to have low mechanical strength.

On the other hand, it is known that the water absorption rate becomes slow when the pore size is too large or too small, but the relationship between the pore size and the water absorption is complicatedly related to other factors such as the degree of acetalization. Therefore, it is extremely difficult to find the optimal pore size for obtaining excellent water absorption and control the pore size. Further, the improvement in water absorption obtained by controlling the pore diameter is not so great.

[0005]

DISCLOSURE OF THE INVENTION As a result of intensive studies conducted by the present inventors in view of the above circumstances, the water absorption rate of a PVAt resin porous body is increased by adding a surfactant to the PVAt resin. The present invention has been completed, and the object of the present invention is to provide a PVAt that excels in water absorption performance in a dry state and rapidly transitions from a dry state to a wet state.
A resin-based porous body and a method for producing the same.

[0006]

The above object of the present invention is to provide P
This is achieved by a porous PVAt resin body characterized by containing or adhering a surfactant to the VAt resin.

In the first method of the present invention, a reaction liquid comprising polyvinyl alcohol, a pore-forming material, a cross-linking agent and a cross-linking catalyst is cross-linked, and then the pore-forming material is removed to remove P.
In producing the VAt resin porous body, a surfactant is added to and mixed with the reaction solution.

The second method of the present invention is characterized in that an aqueous solution containing a surfactant is applied to the polyvinyl acetal resin porous body obtained in advance and then dried.

Examples of the surfactant used in the present invention include anionic surfactants such as alkyl sulfonates and alkyl sulfates, cationic surfactants such as amine salts and quaternary ammonium salts, polyoxyethylene alkyl ethers,
Examples thereof include nonionic surfactants such as polyethylene glycol fatty acid ester and sorbitan fatty acid ester, and amphoteric surfactants such as carboxylic acid type and sulfonic acid type.

The degree of acetalization of the PVAt resin porous body of the present invention is not particularly limited, but 70 mol%
In the above cases, the effect of the present invention becomes remarkable. Generally, the smaller the degree of acetalization, the better the water absorption and the weaker the mechanical strength.

The content of the surfactant used in the first method of the present invention in the reaction solution is, for example, 0.005 to 0.01.
% (Weight / volume), and the effect can be obtained even with such a small amount. When the acid concentration of the reaction solution is high, it is preferable to use a cationic surfactant. When a nonionic surfactant is used, it is preferable that the cloud point of the surfactant used is higher than the temperature at which the crosslinking reaction occurs. When the reaction solution becomes cloudy, it becomes difficult to uniformly contain the surfactant in the obtained PVAt resin.

Further, in the first method of the present invention, when alkylbenzene sulfonate or dioctyl sulfosuccinate is used as the surfactant, the reaction product does not shrink and is difficult to peel from the mold. It is suitable in terms of points.

The reaction liquid used in the method of the present invention is a dispersion aqueous solution containing polyvinyl alcohol (hereinafter abbreviated as "PVA"), a pore-forming material, a crosslinking agent and a crosslinking catalyst,
The above-mentioned surfactant is added and mixed. PVA used in the above reaction solution preferably has an average degree of polymerization of 1500 to
3800, which may be completely saponified or partially saponified.

The pore-forming material used in the method of the present invention is
It suffices to appropriately select from conventionally known ones, and fine powders of starch and other organic substances can be used, but starch granules extracted from plants are preferable. Examples of plants from which starch granules are derived include grains such as rice, wheat and corn,
Examples include potatoes such as potatoes, sweet potatoes, and taros. Since the particle size of starch granules varies depending on the type of plant, the kind of starch used may be appropriately selected according to the desired pore size. Further, when it is desired to obtain a particularly large pore size, a processed starch obtained by drying the starch once gelatinized and then pulverizing and classifying the starch can be used. The pore diameter and porosity of the porous body can be adjusted by changing the type and amount of the pore forming material.

The cross-linking agent used in the reaction solution is an aldehyde, for example, an aliphatic aldehyde such as formaldehyde, acetaldehyde, butyraldehyde, acrylaldehyde, an aliphatic dialdehyde such as glyoxal, and an aromatic aldehyde such as benzaldehyde. Etc. can be mentioned.

The crosslinking catalyst used in the above reaction solution is an acid, and examples thereof include inorganic acids and organic acids such as sulfuric acid, hydrochloric acid, phosphoric acid and maleic acid, and sulfuric acid is usually used.

Further, in the second method of the present invention, an aqueous solution of the above surfactant is applied to a PVAt resin porous body produced in advance and then dried, and the surfactant is attached to the PVAt resin porous body. It is the one to be confused. Here, the concentration of the surfactant contained in the aqueous solution is, for example, 0.005 to 0.
It is adjusted to about 01% (weight / volume).

In the above method, the method of applying the aqueous solution of the surfactant to the PVAt resin porous body is not particularly limited as long as it is a method of impregnating and adhering the aqueous solution into the PVAt resin porous body. It may be performed by a known appropriate method. As such a method, a method of immersing a PVAt resin porous body in an aqueous solution is preferable because it can be uniformly impregnated and adhered in a short time, but other methods such as PVAt
A method of spraying an aqueous solution on the surface of the porous resin body by a spray or the like to impregnate it, a method of applying the aqueous solution to the surface of the porous PVAt resin body and impregnating the same may be used.

The surfactant used here is PVA.
Those that do not easily fall off from the t-based resin are preferable, and it is generally preferable to use a cationic surfactant that strongly adsorbs to the PVAt-based resin. For example, for applications in which the wet state and the dry state are frequently repeated, it is preferable to use a cationic surfactant because the PVAt resin has a hydroxyl group which is an anionic species in the constituent molecule,
This is because when the surfactant in contact with this is a cation, it is chemically strongly adsorbed.

On the other hand, cationic surfactants are preferable for those mainly used for absorbing acidic liquids, and anionic surfactants for those mainly used for absorbing alkaline liquids. Is preferred. This is due to the stability of the surfactant at the respective pH.

The PVAt resin porous body impregnated with the aqueous solution of the surfactant is dried after removing the excess aqueous solution by squeezing if necessary. The drying condition may be a temperature at which the PVAt resin is not modified, for example, a temperature of 50 to 70.
It can be performed at ° C.

[0022]

[Function] The surfactant contained in the PVAt resin is PV
To improve the hydrophilicity by modifying the surface of At resin, P
The water absorption performance of the VAt resin porous body is improved, and the water absorption rate in the dry state is increased.

[0023]

The present invention will be specifically described with reference to the following examples. Before that, a method of measuring the water absorption rate in the present specification will be described.

<Water Absorption Rate> A sheet of PVAt type resin porous material (thickness 2 mm) is cut into a triangle having a base of 9 mm and a height of 17 mm to obtain a sample for measurement. The sample is dried at 60 ° C. for 2 hours and then left at room temperature for 1 hour. Next, the top 4 mm of this sample is immersed in water having a water temperature of 19 ° C., and the time until the water spreads over the entire sample is measured.

Example 1 Partially saponified PVA having an average degree of polymerization of 1400 was added to water to make the total amount 600 ml. Next, this liquid was heated to around 100 ° C. and stirred sufficiently to completely dissolve PVA, and then water was added to bring the total amount to 730 ml. This solution was cooled to 78 ° C. with stirring, and then 28 g of corn starch was dispersed in water to make a total amount of 90 ml, and the anionic surfactant dioctyl sulfosuccinate ester (trade name: Aerosol-OT, American Cyanamid Co., Ltd. 0.1 g) was added and uniformly mixed with stirring. Then, 82 ml of 50% sulfuric acid and 98 ml of 37% aqueous formaldehyde solution were successively added, and the mixture was rapidly and uniformly stirred to obtain a reaction solution.

The obtained reaction solution was poured into a vinyl chloride container having an internal volume of 1000 ml and reacted at 60 ° C. for 18 hours, and then the reaction product was taken out from the container and washed to form a pore-forming material and unreacted crosslinking. The agent and the like were extracted and removed to obtain a PVAt-based resin porous body.

The obtained PVAt resin porous body was dried and then sliced to a thickness of 2 mm to obtain a sheet of the PVAt resin porous body. The results of the obtained PVAt resin porous body are as shown in Table 1.

Example 2 Instead of the surfactant used in Example 1, anionic surfactant sodium dodecylbenzenesulfonate (S
PVA in the same manner as in Example 1 except that DBS) was used.
A sheet of porous t-based resin was obtained. When the reaction solution was subjected to a crosslinking reaction, there was no phenomenon such that the reaction product contracted and separated from the mold. The results of the obtained PVAt resin porous body are as shown in Table 1.

Example 3 In place of the surfactant used in Example 1, a cationic surfactant quaternary ammonium salt (trade name: Eretat, produced by Yatasha Yushi Kogyo Co., Ltd.) was used. In the same manner as described above, a sheet of a PVAt resin porous body was obtained. The results of the obtained PVAt resin porous body are as shown in Table 1.

Example 4 Example 4 was repeated except that a cationic surfactant polyoxyethylene alkylamine salt (trade name: bisnol, produced by Yatasha Yushi Kogyo Co., Ltd.) was used in place of the surfactant used in Example 1. In the same manner as in 1, a sheet of a PVAt resin porous body was obtained. The results of the obtained PVAt resin porous body are as shown in Table 1.

Example 5 In place of the surfactant used in Example 1, an ethylene oxide condensate of nonionic surfactant sorbitan monooleate (trade name: Tween 80, manufactured by Atlas Powder Co.) was used. PV as in Example 1
A sheet of porous At resin was obtained. PV obtained
The results of the At resin porous body were as shown in Table 1.

Comparative Example 1 A sheet of a PVAt-based resin porous body was obtained in the same manner as in Example 1 except that the surfactant used in Example 1 was not added to and mixed with the reaction solution. The results of the obtained PVAt resin porous body are as shown in Table 1.

[0033]

[Table 1]

Example 6 0.01 wt / vol of anionic surfactant dioctyl sulfosuccinate ester (trade name: Aerosol-OT)
% Solution was prepared, and a PVAt-based resin porous body having an average pore diameter of 200 μ and a porosity of 90% prepared in advance and prepared was immersed in this solution to sufficiently impregnate the inside of the pores with the solution. Then, excess solution is squeezed from the PVAt resin porous body impregnated with the solution, dried at 60 ° C., and then cut into a thickness of 2 mm to obtain a sheet-shaped PVAt resin porous body. It was The results of the obtained PVAt resin porous body are as shown in Table 2.

Example 7 Example 6 was repeated except that a cationic surfactant quaternary ammonium salt (trade name: Eletat, manufactured by Yatasha Yushi Kogyo Co., Ltd.) was used in place of the surfactant used in Example 6. In the same manner as described above, a sheet-like PVAt resin porous body was obtained. The results of the obtained PVAt resin porous body are as shown in Table 2.

Example 8 Instead of the surfactant used in Example 6, anionic surfactant sodium dodecylbenzenesulfonate (S
A sheet-like PVAt resin porous body was obtained in the same manner as in Example 6 except that DBS) was used. Obtained PVA
The results of the t-based resin porous body were as shown in Table 2.

Example 9 Example except that the surfactant used in Example 6 was replaced with a cationic surfactant polyoxyethylene alkylamine salt (trade name: bisnol, manufactured by Yatasha Yushi Kogyo Co., Ltd.). In the same manner as in 6, a sheet-shaped PVAt resin porous body was obtained. The results of the obtained PVAt resin porous body are as shown in Table 2.

Example 10 In place of the surfactant used in Example 6, an ethylene oxide condensate of nonionic surfactant sorbitan monooleate (trade name: Tween 80, manufactured by Atlas Powder Co.) was used. In the same manner as in Example 6, a sheet-shaped PVAt resin porous body was obtained. PV obtained
The results of the At resin porous body were as shown in Table 2.

Comparative Example 2 The water absorption performance of the PVAt resin porous material used in Example 6 was evaluated without treatment with a surfactant. The results are shown in Table 2.

[0040]

[Table 2]

[0041]

The PVAt resin porous body of the present invention has P
Since the VAt-based resin contains or adheres a surfactant, the hydrophilicity of the PVAt-based resin is improved, the water absorption rate during drying is significantly improved, and the water absorption performance is extremely excellent. Therefore, the PVAt-based resin porous body of the present invention can be rapidly changed from a dry state to a wet state, which is extremely useful in practice.

According to the method of the present invention, a PVAt resin porous body having the above-mentioned performance can be easily produced.

Claims (3)

[Claims] 1. A polyvinyl acetal resin porous body comprising a polyvinyl acetal resin containing or adhering a surfactant. 2. A reaction liquid comprising a polyvinyl alcohol, a pore-forming material, a cross-linking agent and a cross-linking catalyst is cross-linked, and then the pore-forming material is removed to produce a polyvinyl acetal resin porous body. A method for producing a polyvinyl acetal-based resin porous body, comprising adding a surfactant to and mixing the same. 3. A method for producing a polyvinyl acetal resin porous body, which comprises applying an aqueous solution containing a surfactant to the polyvinyl acetal resin porous body and then drying the same.