JPS59122519A - Manufacture of water-absorbing sheet and water-absorbing composite material - Google Patents

Abstract

PURPOSE:To manufacture a sheet having high water absorption, economically in an industrial scale, by compounding vinyl chloride resin powder, a plasticizer and a water-absorbing resin powder at specific ratios, applying the obtained resin powder to a substrate, and heating, melting and cooling the coating layer. CONSTITUTION:The objective water-absorbing sheet can be manufactured by (1) dryblending (A) 100pts.wt. of powder of a vinyl chloride resin (e.g. polyvinyl chloride) with (B) 20-80pts.wt. of a plasticizer (e.g. dioctyl phthalate), (C) 5- 40pts.wt. of the powder of a water-absorbing resin (e.g. starch-based resin) and if necessary (D) a resin stabilizer, a UV-absorber, a filler, a colorant, etc. to obtain resin powder having a bulk density of >=0.25 and an angle of repose of <=40 deg., (2) applying the resin powder to a releasable substrate (e.g. thin metal plate), and (3) heating, melting and cooling the coating layer at about room temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a water absorbent sheet and a water absorbent composite material. More specifically, the present invention relates to a method for producing sheets and composite materials that are soft and have excellent water absorption properties using a vinyl chloride resin as a binder.

Conventionally, hydrophilic acrylic resins containing pulp hydroxyethyl methacrylate as a main component have been known as water-absorbing materials, but all of them have had the problem of low water-absorbing ability. Recently, superabsorbent polymer materials such as starch-acrylic acid ground polymers have been proposed and are used in sanitary products, absorbents for disposable diapers, additives for gel fragrances, and the like.

Most of these water-absorbing resins are obtained in powder form, but they do not melt like normal thermoplastic resins when heated, and cannot be formed into films, sheets, or other molded products by themselves. There is a drawback. In order to eliminate such drawbacks, (a) a method of adding and kneading a water-absorbing resin to a normal thermoplastic resin and molding this mixture into films, sheets, and other molded products in accordance with thermoplastic resin molding technology; (B)
Utilization techniques have been proposed, such as a method of covering a water-absorbing resin with a base material having ventilation holes, such as cloth or nonwoven fabric, to obtain an object.

However, when using method (a) above, molded products such as films and sheets have poor water absorption properties, so if a large amount of sound-absorbing resin is blended, the molded products will become brittle. On the other hand, when using the method (b) above, the water-absorbing resin absorbs water until it reaches its maximum water absorption value and swells, so there is a drawback that the shape of the molded product, such as a film or sheet, is no longer maintained.

Under such circumstances, the present inventors aimed to provide an industrially advantageous method for producing water-absorbing sheets and water-absorbing composites without sacrificing the excellent water-absorbing properties of water-absorbing resins. As a result of intensive study, the present invention has been completed.

Therefore, the gist of the present invention is that 20-g0 parts by weight of plasticizer,
Water-absorbing resin powder &-40 parts by weight, further tri-blended with other resin compounding agents if necessary, with a bulk specific gravity of 0.2.5
- The above is characterized in that a resin powder with an angle of repose of 90 degrees or less is used, this resin powder is applied to a base material with surface releasability to form a coating film, and then this coating film is heated, melted, and then cooled. A method for manufacturing a water-absorbent sheet with
invention). Furthermore, there is a method in which a base material having ventilation holes is attached to one or both sides of the water-absorbing sheet obtained by the above method (Kiko invention).

The present invention will be explained in detail below.

In the present invention, the vinyl chloride resin refers to polyvinyl chloride and a copolymer mainly composed of vinyl chloride. Monomers copolymerizable with vinyl chloride include vinyl esters, vinyl ethers, acrylic acid or methacrylic acid and their esters, maleic acid or fumaric acid and their esters, maleic anhydride, and aromatic vinyl compounds. , halogenated vinylidene compounds, acrylonitrile, methacrylonitrile, ethylene, propylene, etc. These monomers may be partially crosslinked by adding a trace amount of a polyfunctional group-containing compound.

The above-mentioned vinyl chloride resin may be in the form of particles produced by a conventionally known method such as a suspension polymerization method, a microsuspension polymerization method, or an emulsion polymerization method. The diameter is preferably in the range of 20 to 00 microns, and the average degree of polymerization is preferably in the range of SOO to 2000.

The base vinyl chloride resin can be used as a single resin (homopolymer), as a copolymer, as a combination of these, or even as an average polymerization degree, depending on the thickness, strength, feel, etc. of the final water absorbent sheet. The same resin type or a combination of two or more types can be used.

According to the present invention, the vinyl chloride resin is triblended with a plasticizer and a water-absorbing resin, along with other additives if necessary.

Plasticizers that can be used include phthalate esters such as dioctyl phthalate, dibenzyl phthalate, butylbenzyl phthalate, diisodecyl phthalate, didodecyl phthalate, and diisodecyl phthalate; dioctyl adipate, di-n-butyl adipate,
Aliphatic dibasic acid esters such as diptyl sebacate; glycol esters such as pentaerythritol ester and diethylene glycol dibenzoate; fatty acid esters such as methyl acetyl ricinoleate; phosphorus such as tricresyl phosphate and triphenyl phosphate Acid esters; Epoxidized oils such as epoxidized soybean oil and epoxidized linseed oil; Citric acid esters such as acetyl tributyl citrate, acetyl trioctyl citrate, tri-n-butyl citrate; trialkyl trimellitate , tetra-n-octylpyromellitate, polypropylene adipate, and other polyester plasticizers.

These plasticizers may be used alone or in combination of two or more. The amount of plasticizer is the vinyl chloride resin io
It can be selected within the range of -0 to go parts by weight relative to o parts by weight. If the amount of plasticizer is less than 20 parts by weight, a breathable film with excellent flexibility cannot be obtained. vice versa,
If the amount of plasticizer is more than go parts by weight, it becomes too soft, which is not preferable.

Typical examples of water-absorbing resins that can be used in the present invention include starch-based resins, cellulose-based resins, and other water-absorbing resins.

The outline of the method for synthesizing these water-absorbing resins is illustrated below.

Cross-linking] Taichiun Ryobanka Fibrous (3) Regenerated cellulose + sodium polyacrylate → spinning → coagulation → drying → fibrous 3 ・Water-absorbing resins other than the above (1) Acrylic acid metal salt polylune cross-linked The above examples of the types and synthesis methods of the agent (metal ion, Borievo water-absorbing resin) are not intended to limit the present invention.

A powdered water-absorbing resin is used. The shape of the powder may be spherical, flat, or cylindrical, and the average particle size is /θ
A range of ~xoo microns is preferred.

The amount of the water-absorbing resin is S-70 parts by weight based on 700 parts by weight of the base vinyl chloride resin.

If it is less than 5 parts by weight, the water absorbency of the final product '9 cannot be expected, and if it exceeds q and o parts by weight, the amount of water absorbed becomes too large and the sheet form cannot be maintained, which is not preferable. 10-2 from the viewpoint of water absorption and product shape maintenance, etc.
A range of 0 parts by weight is particularly preferred.

When dispersing plasticizers and water-absorbing resins in vinyl chloride resin, small amounts of other resin compounding agents, such as resin stabilizers, ultraviolet absorbers, fillers, dyes, pigments, flame retardants, colorants, etc., may be added. Can be mixed.

According to the present invention, the polyvinyl chloride resin, plasticizer, water-absorbing resin, and if necessary other resin compounding agents are tri-blended, and the bulk specific gravity (according to J Engineering 5K4727 method) is 0.25 or more. The angle (according to the injection method) is a resin powder with a qo degree or less.

If the bulk specific gravity of the resin powder is less than 0.25 and the angle of repose is greater than 'IQ degrees, the resin powder will aggregate, and when it is applied to a base material to form a coating film, the thickness of the coating film will be It becomes difficult to prepare.

In order to adjust the bulk specific gravity and angle of repose of the resin powder, it is preferable to use a base vinyl chloride resin having a large particle size and a base vinyl chloride resin having a small particle size.

In order to adjust the bulk specific gravity and angle of repose of the resin powder, a small amount of vinyl chloride resin having a small average particle size may be added in addition to the resin compounding agent.

The vinyl chloride resin is triblended with a plasticizer and a water-absorbing resin, along with other resin compounding agents if necessary. The triblend operation is performed to make the vinyl chloride resin absorb the plasticizer and uniformly disperse the water absorbent resin.

This triblending operation is preferably carried out while heating at a temperature of 70 to 730°C until the entire amount of plasticizer is absorbed into the resin powder. The tri-blend operation involves combining the above ingredients with
It is preferable to use a Henschel mixer, a sieve machine, a rotary cone mixer, a rotary mixer, a ribbon blender, etc.

According to the present invention, the resin powder prepared by the above method is
Apply to substrates with surface releasability! This base material functions to support a coating film based on resin powder. The base material is preferably composed of a thin metal plate, paper, or a thin heat-resistant resin plate. The surface of this base material on which the coating film will be formed is given surface releasability by applying a release agent, etc., so that the water absorbent sheet obtained after heating and melting the coating film can be easily peeled off. . According to the present invention, since it is necessary to pressurize the coating film formed on the surface of the base material, it is preferable to support the base material with an endless metal belt or the like. An endless metal belt may be used as the base material.

In order to apply the resin powder prepared by the above method to a base material, it is preferable to use an apparatus as shown in FIG. 1 as a side view of the main part. That is, resin powder is stored in a hopper,
From the lower side of the hopper, a fixed amount of resin powder is supplied in layers onto the base material 3 having peelability. The coating film made of resin powder supplied from the hopper is transported in a fixed direction by a metal endless belt 5 installed under the base material 3. The thickness of the coating film II formed on the base material 3 is adjusted by scraping off part of the resin powder by the thickness adjustment plate B. The resin powder scraped off by the thickness adjustment plate B is collected and circulated to the hopper for use. After adjusting the thickness, the coating film is then pressed down with a pressing device such as an endless metal belt.
It is preferable to make the thickness and density of the coating film q uniform. The thickness of this coating film is preferably adjusted so that the thickness of the water absorbent sheet 9 obtained after the subsequent heating and melting process is in the range of 0.2 to -1 mm.

According to the present invention, the coating film formed by the above method is sent to a heating furnace g, the surfaces of the resin particles are melted, and the surfaces of adjacent particles are adhered to each other.

If the heating temperature at this time is too low, the surface of the resin particles will not melt even if heated for a long time, so a water absorbent sheet with excellent strength will not be obtained, which is not preferable.

The heating temperature can be selected depending on the average degree of polymerization of the vinyl chloride resin, the average particle diameter, the number of parts of the plasticizer added, the number of parts of the water absorbent resin added, the thickness of the water absorbent sheet to be finally obtained, etc. can.

It is preferable to select temperature conditions such that the water-absorbing resin powder is uniformly dispersed between the vinyl chloride resin particles, and the surfaces of the vinyl chloride resin particles adhere to each other to form a breathable sheet.

According to the present invention, the water absorbent sheet obtained after the heating and melting operations as described above is cooled to around room temperature, and the water absorbent sheet is peeled from a base material having surface releasability or Roll the material into a roll. The figure shows an example in which the water absorbent sheet 9 is peeled off from the base material 3.

The water-absorbing sheet obtained according to the first aspect of the present invention can be subjected to secondary processing such as adhesion, like ordinary soft synthetic resin sheets.

The water-absorbent sheet obtained according to the first invention of the present invention has a base material having ventilation holes attached to one or both sides thereof (the second invention).
invention) and have excellent strength. Substrates that can be used as substrates with ventilation holes include felt-like sheets, woven or knitted textile products, non-woven fabrics, paper,
Examples include synthetic resin sheets with a large number of pores. When attaching a breathable base material, it may be attached to one side or both sides. The textile product may be woven in any of plain weave, twill weave, satin weave, twill weave, gauze weave, and thin weave. The knitting method may be stockinette knitting, lace knitting, etc. The raw material for the fibers may be not only vegetable fibers but also animal fibers, synthetic fibers, and mixtures thereof.

To attach the water absorbent sheet and the breathable base material,
A thermal bonding method or a method using an adhesive may be used.

The water-absorbing sheets and water-absorbing composites obtained by the method of the present invention can be used in applications such as wallpaper, fresh food packaging materials, soil water-retaining sheets, dehydration sheets, sanitary products, etc. that utilize water-absorbing and water-retaining functions.

The method of the present invention has particularly remarkable effects as described below, and its industrial utility value is extremely significant.

(1) The tooth of the present invention/When according to the invention, it has excellent water absorbency,
In addition, a vinyl chloride resin sheet with excellent flexibility can be easily produced.

(2) When according to the invention of the present invention, it has excellent water absorbency,
A vinyl chloride resin composite material with excellent flexibility and strength can be easily produced.

(3) When using the method of the present invention, the surface area (exposed surface @ ) can be adjusted. Therefore, it is possible to adjust the water absorption amount of the entire product, and it is possible to manufacture a molded product whose form does not change even after water absorption.

Hereinafter, the present invention will be explained in detail based on examples.
The present invention is not limited to the following examples unless it exceeds the gist thereof.

Examples/~ Polyvinyl chloride powder ('P) produced by suspension polymerization method
=/300. Average particle size/so micro 7) 100 parts by weight of dioctyl phthalate s.

parts by weight, and water-absorbing resin powder (manufactured by Seitetsu Kagaku ■, Aqua Keep AK-I's, average particle size of about 10 microns),
17 Each was added in the proportions shown in Table 17. These were heated to 710° C. and stirred for S minutes using a super mixer (manufactured by Kakuda Seisakusho) to absorb the plasticizer into the polyvinyl chloride powder and uniformly disperse the water absorbent resin. To each of the resulting mixtures, parts by weight of polyvinyl chloride powder with an average degree of polymerization/100 and an average particle size of 2 microns were added,
Mixed.

The bulk specific gravity of the four types of resin powder obtained was
47,! The angle of repose was measured according to the injection method. The results are shown in Table 7.

After removing large particle size aggregates from the resin powder using a go mesh sieve, it was fed into a hopper of an apparatus as shown in the figure.

The resin powder was formed as a coating film with a thickness of 2.5 mm on a stainless steel endless belt (in this example, the endless belt was used as the base material), and the upper side of the resin powder was coated with a thickness adjustment plate B. was scraped off to obtain a coating film with a thickness of 2 mm.

This coating film is applied at room temperature by a pressing tool 6 made of an endless belt made of stainless steel. The thickness and density of the coated film were made uniform.

Thereafter, the coating film was sent to a heating furnace and heated at a temperature of 2 j-0''C for 70 minutes to melt the resin particles.

After the above heating and melting operations were completed, the sheet was cooled to obtain a water-absorbing sheet with an average thickness of about 0, gm, B.

For the obtained water absorbent sheet, the temperature was 20°C and the relative humidity was
The moisture absorbency of the water absorbent sheet was measured after placing it in a constant temperature and humidity chamber for qoo hours. The results are shown in Table 17.

Comparative example/Polyvinyl chloride powder produced by suspension polymerization method (p=
30 parts by weight of dioctyl phthalate and 15 parts by weight of a water-absorbing resin (Aqua Keep AK-1IS) were added to 100 parts by weight of i3oθ, average particle size 15o micro7). These were stirred for 5 minutes while being heated to 770°C using a super mixer to absorb the plasticizer into the polyvinyl chloride powder and uniformly disperse the water absorbent resin.

An attempt was made to form a uniform coating film with a thickness of 2, t mm on a stainless steel endless belt using the above resin powder in the same manner as in the example, but the resin powder agglomerated. However, it was not possible to form a coating film with a uniform thickness.

The resin powder prepared as above was heated to 100°C for 9
The mixture was kneaded for 7 minutes on an inch mill roll to form a 2 mm sheet.

The moisture absorption rate of the obtained sheet was measured in the same manner as in the examples. The results are shown in Table 17.

Comparative Example-~S Polyvinyl chloride powder ('F
-t3oo, average particle size 750 microns), 50 parts by weight of dioctyl phthalate and water absorbent resin (
Aqua Keep AK-'@S) was added in the proportions shown in Table 4-7. These were heated to 710° C. and stirred for 5 minutes using a super mixer to absorb the plasticizer into the resin powder and uniformly disperse the water absorbent resin.

An attempt was made to form a coating film with a uniform thickness of approximately 5 mm on a stainless steel endless belt using the seven types of resin powders described above in the same manner as in the example, but the resin powders did not aggregate. However, it was not possible to form a coating film with a uniform thickness.

One type of resin powder prepared as above was kneaded in a qoB extruder with the cylinder temperature adjusted to about 150°C, and extruded into a sheet from a T-die to obtain a sheet with a thickness of about / mm. Ta.

The moisture absorption rate of the obtained tough sheet was measured in the same manner as in the examples. From the results shown in Examples and Comparative Examples, the following is clear.

(1) The water-absorbing sheet obtained by the method of the present invention exhibits high hygroscopicity even if the amount of water-absorbing resin blended is small.

(2) When using the method of the present invention, it is easy to produce sheets with different water absorption amounts.

(3) When the electric ratio and the angle of repose of the resin powder obtained by tri-blending are within the claimed range, it is easy to adjust the thickness of the coating film; This is difficult when outside.

[Brief explanation of the drawing]

FIG. 17 shows a side view of main parts showing an embodiment of the present invention. In the figure, / is the resin powder, xd hopper, 3- is the substrate, ) is the coating film, 5 is the endless belt, O is the thickness adjustment plate, 7
indicates a pressing tool, g indicates a heating furnace, and ri indicates a water absorbent sheet. Flute 1 diagram

Claims (1)

[Claims] (1) In producing the water-absorbing sort, 100 parts by weight of the vinyl chloride resin powder, ○~go parts by weight of plasticizer, and 5~q parts by weight of the water-absorbing resin powder. parts by weight, and if necessary, tri-blend with other resin compounding agents to obtain a bulk specific gravity of 0. ．． A resin powder having an angle of repose of 23 or more and a repose angle of 1Io or less is applied to a base material having surface releasability to form a coating film, and then this coating film is heated, melted, and then cooled. A method of manufacturing a water absorbent sheet characterized by: f2+ When producing a water-absorbing composite material, 20~goz plasticizer is added to 10θ weight parts of vinyl chloride resin powder.
part by weight, water-absorbing resin powder 5-4' 0 part by weight, further tri-blended with other resin compounding agents if necessary, so that the bulk specific gravity is 0. ．． 2! As described above, a resin powder with an angle of repose of lol is used, this resin powder is applied to a base material with surface releasability to form a coating film, and this coating film is then heated, melted, and then cooled to make it absorbent. A method for producing a water-absorbing composite material, which is used as a notebook, and the method comprises attaching a base material having ventilation holes to one or both sides of the water-absorbing sheet.