JP2599114B2 - Polyvinyl acetal porous sheet with excellent water absorption rate - Google Patents

Description

The present invention relates to an improved polyvinyl acetal (hereinafter abbreviated as PVAt) -based porous sheet used as an industrial or household wiping material. The present invention relates to a wiping sheet having an excellent water absorption rate.

(Prior art) Conventionally, car bodies, glass and plastic molded products,
Towels, rags, and porous sheets of PVAt-based materials have been frequently used as a material for wiping water droplets adhered to the surface of a metal, a human face, a body, and the like. PVAt porous material has good hydrophilicity,
It has been widely used as a material having excellent performance for such purposes because of its excellent water absorbing power and low pollution and low dust generation. Also, hydrophobic synthetic fibers such as nylon, polyester, and vinylon have been used as a fiber structure as a reinforcing material for a PVAt-based porous material. However, while the PVAt porous material has the above excellent properties when wet,
When the water content falls below a certain level, the state changes drastically and becomes a hardened state and cannot be used for such purpose. Nylon, polyester, vinylon, etc. as a reinforcing material are hydrophobic as is well known, and do not have a complicated structure as seen in a natural fiber even from the viewpoint of a fine structure, and are completely hydrophilic and have a water absorbing capacity. Lacking.

Therefore, when the PVAt-based porous material is dried and hardened, it is necessary to immerse the material in water or slightly warm water to make it wet and return to a wet soft state. However, such an operation is not useful in an emergency, and has a disadvantage that the range of application is significantly limited.

In order to compensate for such a drawback, it is effective to store in a special storage case in a wet state, but there is a problem in simplicity.

(Problems to be Solved by the Invention) In view of the above-mentioned problems, the present inventors have conducted intensive studies, and as a result, as a interlining used for the purpose of reinforcing a PVAt-based porous sheet, a material having an excellent water absorbing power It has been found that the use of a compound increases the water absorption rate from a dry state to a wet state, and has completed the present invention. The object of the present invention is to
An object of the present invention is to provide a PVAt-based porous sheet having an excellent water absorption rate (water permeability) from a dry hardened state to a wet softened state. Other objects and advantages will be apparent from the following description.

(Means for Solving the Problems) The above-described object is to provide a polyvinyl acetal-based porous sheet obtained by laminating and integrating at least two or more polyvinyl acetal-based porous sheet materials and a fiber structure. The fibrous structure is achieved by a polyvinyl acetal-based porous sheet excellent in water absorption rate, characterized by being a fibrous structure composed of acrylic fibers having a large number of voids, and the fibrous structure is a fabric or This is achieved by being a woven fabric. Further, the average pore diameter of the polyvinyl acetal-based porous sheet material is 30 to 300
It is achieved by setting it to μm.

The acrylic fiber having a large number of voids according to the present invention is obtained by a known method described in JP-B-60-11124. Acrylic copolymer 70-98
%, And 30 to 2% by weight of cellulose acetate, and contains macrovoids in which the presence of microvoids is suppressed.

A sheet in which a PVAt-based porous sheet material and a fiber structure are laminated and integrated is disclosed in, for example, JP-B-36-17284 and JP-B-48.
It can be easily obtained by selecting an appropriate method from known methods described in -38630 and the like.

A specific example is as follows. For example, completely or partially saponified polyvinyl alcohol having an average degree of polymerization of 300 to 3000 is dissolved in water, and a necessary amount of a crosslinking agent such as an aldehyde, a catalyst such as a mineral acid, and further a starch as a pore-forming agent are added thereto. After the reaction solution is prepared, it is poured into a predetermined mold. Subsequently, the acrylic fiber structure is placed on the reaction solution, and the same amount of the reaction solution is poured thereon. Next, release paper is placed on this liquid. Further, the next reaction liquid is flowed on the surface of the release paper, and the same overlapping operation of reaction liquid-interlining-reaction liquid-release paper-reaction liquid is repeated, and when about 20 layers are formed, the lid is put on the mold. Then, react at a temperature of 50 to 100 degrees for 10 to 24 hours. By doing so, the PVAt-based porous body generated after the reaction is completed adheres to the interlining, and the paper loosens the fiber binding and adheres to the PVAt-based porous body surface, which can be easily peeled off from this surface. A large number of PVAt porous sheets using fibers as interlining can be obtained. This can be washed with water and deoxidized, and the paper fibers adhering to the surface can be removed to obtain a product. The pore size depends on the type of starch used, but if it is less than 30 μm, the elasticity tends to decrease, while if it exceeds 300 μm, the water absorption tends to decrease. Therefore, as the PVAt-based porous material used in the present invention, those having an average pore diameter of 30 to 300 μm are particularly suitable.

(Effect of the Invention) The PVAt-based porous sheet of the present invention obtained as described above exhibits excellent water absorption even in a dry-cured state.

A PVAt porous material originally has a large number of residual hydroxyl groups in its molecular structure, is extremely hydrophilic, and has an infinite number of three-dimensionally continuous fine pores. It has the excellent feature that it has an ability to suck up water and has a water retention ability having an amount corresponding to approximately its volume. However, this material dries and releases its moisture. Specifically, when the moisture content falls below about 50 wt% of the material, the residual hydroxyl groups form strong hydrogen bonds and harden as a condition. In addition, it loses flexibility and aggressively loses the ability to absorb moisture. That is, the performance as a wiping material is completely lost. Since such a state change proceeds reversibly depending on the amount of water,
The dried and cured material can be returned to the original wet softened state by providing the necessary moisture. However, a state change requires time.

The essence of the present invention is to shorten the time required for the above-mentioned state change.In general, the interlining used as a reinforcing material of the PVAt-based porous sheet has a water absorbing property, and the PVAt-based porous sheet is used. Water, that is, the time required for the state change to be reduced.

In the PVAt-based porous sheet according to the present invention, since the single fibers constituting the yarn each have a porous void structure, continuous voids actively absorb moisture and permeate moisture. Is to promote. In the state of complete loss of moisture and drying and curing, the PVAt porous body forms strong hydrogen bonds as described above, so it is necessary to relax the hydrogen bonds at the initial stage, so the penetration of moisture is poor, It takes time for flexibility. However, since the interlining according to the present invention does not have this, it is possible to rapidly absorb and suck up moisture even in the early stage. Therefore, the water absorption speed of the sheet is promoted as a whole.

With the PVAt-based porous sheet according to the present invention, the drawbacks of products that have been pointed out as poor water return and trouble have been pointed out, the storage complexity has been improved to some extent, and it has to be stored in a constantly wet state. Obstacles due to not being able to grow
The generation of offensive odor has been eliminated.

 Hereinafter, the present invention will be described with reference to examples.

Example The material of the interlining is an acrylic modified fiber, which is made of a cold gauze using Akwalon WM2 manufactured by Kanebo Co., Ltd., which has many voids communicating with the outside in the fiber, and a regular polyester short fiber as a comparative example. I prepared cold gauze.

A sheet obtained by laminating and integrating the above two types of interlining and a PVAT-based porous sheet was produced according to a known method, and had an average pore diameter of 60%.
μm, a porosity of 88% and a thickness of 1.6 mm were obtained. This was cut into a strip-shaped test piece of 100 mm in length and 20 mm in width, and it was put into a ventilation dryer at 80 ° C. to reach a dry and hardened state. The upper end of this test piece was gripped, and the lower end 10 mm was immersed in 25 ° C. water and the rise time of water was measured.The time required to rise 20 mm was 8.5 seconds for the sheet according to the present invention and 15.5 seconds for the comparative example. Met.

Separately, when this was actually used for car washing, the feeling of use and performance did not change at all, and the time from dry to wet softness was short and good.

Claims (3)

(57) [Claims] 1. A polyvinyl acetal-based porous sheet obtained by laminating and integrating at least two or more polyvinyl acetal-based porous sheets and a fibrous structure, wherein the fibrous structure comprises a large number of voids. A polyvinyl acetal-based porous sheet having an excellent water absorption rate, characterized in that the sheet is a fibrous structure made of acrylic fibers. 2. The polyvinyl acetal-based porous sheet excellent in water absorption rate according to claim 1, wherein the fiber structure made of the acrylic fiber is a fabric or a non-woven fabric. 3. The polyvinyl acetal porous sheet excellent in water absorption rate according to claim 1, wherein the average pore diameter of the polyvinyl acetal porous sheet is 30 to 300 μm.