JPS6137095B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a plastic film with remarkable water absorption capacity and a method for producing the same. In general, superabsorbent resins can be broadly divided into three types: starch-based, cellulose-based, and synthetic resin-based, and each type is being used in a variety of water-related fields, taking advantage of the characteristics of each. In particular, synthetic resin-based superabsorbent resins are attracting attention due to their high water absorption capacity and extremely high water absorption rate, but their shape is powder-like.
Since it does not melt even when heated, it has the disadvantage that it cannot be molded like general plastic films and sheets, and this seems to be hindering the development of applications. At present, synthetic resin-based superabsorbent resins can be used in powdered form in some applications, such as industrial dehydration agents and soil water retention agents, but in other applications, they can be mixed into absorbent cotton or used in tea bags. Or,
It is incorporated into paper or pulp to make final products and is used for napkins, disposable diapers, underpants, etc. However, the process of producing such a final product is complicated, and there are restrictions on application development, such as the inability to use it in applications that require greater strength. In other words, if superabsorbent resins can be processed into films, sheets, or molded products like ordinary plastics, their uses will expand dramatically. Although there have been attempts to contain it, this method has not been put to practical use because cellophane cannot be sealed. The present inventors successfully incorporated this superabsorbent resin into a general moldable plastic, and
As a result of various studies to find a way to improve water absorption performance from the surface, we found that polyolefin resin with a fibrous structure could be produced by foaming extrusion molding or foaming stretch extrusion molding of polyolefin resin mixed with super absorbent resin powder. The inventors have discovered that a film can be created in which super absorbent resin particles are interspersed, and that a film that effectively absorbs water from the surface can be created.Further studies have led to the completion of the present invention. An object of the present invention is to provide a superabsorbent resin having a remarkable water absorption capacity and a high water absorption rate in the form of molded articles, mainly films and sheets, which can be applied in a wide range of applications, without substantially impairing its performance. Furthermore, the second object of the present invention is to laminate such a super-absorbent film with a general plastic film in two layers, so that one side is super-absorbent and
A special film whose other side is hydrophobic,
Another object of the present invention is to provide films in various forms, such as a multilayer film in which a hydrophobic film is sandwiched between two super absorbent films. The super-absorbent plastic film of the present invention is a single-layer or multi-layer plastic film, in which at least one layer is foamed or foam-stretched, and the foamed resin layer has a ratio of 1% to 100 parts by weight of polyolefin. The foamed resin layer is composed of ~50 parts by weight of a water-absorbing resin and 0.1-2.0 parts by weight of a surfactant, and the foamed resin layer has a fine fibrous structure in which the water-absorbing resin is scattered. It is characterized by If a super-absorbent resin is simply kneaded with polyolefin and formed into a film, most of it will be buried in the polyolefin and will not appear on the surface, and therefore will have almost no water-absorbing ability (Figure 1). However, by adding a foaming agent to polyolefin and foaming it until the cells are destroyed during extrusion molding, or by foaming and stretching to make the foam layer into a fibrous structure, the surface of the polyolefin layer can be improved. It was discovered that most of the superabsorbent resin particles have a structure with their heads sticking out (Figure 2), and that water absorption occurs quickly upon contact with water. FIG. 1 is a cross-sectional view of a film obtained by kneading a super absorbent resin with polyolefin and extruding the same. In the figure, 1 indicates a polyolefin resin layer and 2 indicates particles of a super absorbent resin. Second
The figure is a cross-sectional view of a film made by kneading polyolefin with a foaming agent and a superabsorbent resin and then extruded. In the figure, 3 indicates a foamed polyolefin resin layer, and 4 indicates particles of the superabsorbent resin. In the super-absorbent film of the present invention, super-absorbent resins made from synthetic resins include polyvinyl alcohol-based resins such as cross-linked polyvinyl alcohol, polyethylene oxide-based resins such as cross-linked polyoxyethylene,
There are polyacrylate-based materials such as sodium polyacrylate, and polyacrylate-based materials are particularly preferred because of their excellent water-absorbing ability. High water absorption performance is polyolefin
1 to 50 parts by weight per 100 parts by weight, preferably
Add 10 to 30 parts by weight. Further, as the polyolefin resin, polypropylene, polyethylene, ethylene-vinyl acetate copolymer, etc. are preferable, but ionomer resin, which is a metal ion crosslinked product of ethylene/methacrylic acid copolymer which is easily compatible with polyacrylate, is most preferable. Furthermore, the surfactant to be used is added mainly for the purpose of preventing the superabsorbent resin particles from agglomerating in the foam layer and uniformly dispersing them in the polyolefin, and is not particularly limited. Stearic acid monoglyceride, stearic acid amide, etc. are preferred, and the amount added depends on the polyolefin.
It is preferably 0.1 to 2.0 parts by weight per 100 parts by weight.
The blowing agent to be used is not particularly limited, but azodicarbonamide, sodium bicarbonate, p-toluenesulfonyl semicarbazide, trihydrazinotriazine, etc. are preferred, and the amount added is preferably 0.5 to 2.0 parts by weight per 100 parts by weight of the polyolefin resin. . A foamed or foamed stretched film containing a superabsorbent resin and a surfactant in a polyolefin resin provides a good superabsorbent film, but in addition, acetylene alcohol and/or acetylene glycol with low surface tension is added to the foam layer. By adding and melt-extruding the film or impregnating it after film molding, the resin surface of the fibrous structure of the foam layer becomes hydrophilic, and water quickly flows into the super absorbent resin inside the fibrous structure. , and the initial water absorption rate can be further improved. When adding acetylene alcohol and/or acetylene glycol during film melt extrusion molding, the amount is 0.1 to 100 parts by weight of polyolefin.
It is preferable to add 2.0 parts by weight. When impregnating the film after molding, it is preferable to impregnate the film with 5.0 to 20.0 ml of a 1 to 50 weight percent solution of acetylene alcohol and/or acetylene glycol in an organic solvent such as methanol per ^square meter of the film, and then dry the film. Furthermore, in addition to chemical treatment with acetylene alcohol, plasma surface treatment, corona discharge treatment,
It is preferable to perform physical treatment such as ultraviolet irradiation treatment, particularly plasma surface treatment. By such physical treatment, the resin surface of the fibrous structure of the super absorbent plastic film of the present invention becomes hydrophilic, and the initial water absorption rate can be further improved. The superabsorbent plastic film of the present invention can be generally produced by a method similar to that used for molding thermoplastic resin films. For example, it can be manufactured by the T-die method or the inflation method, but if the proportion of super absorbent resin in the raw material is 20 parts by weight or more per 100 parts by weight of polyolefin, a master batch must be made in advance. is preferable. In addition, the super-absorbent film of the present invention can be extruded in at least one direction, either vertically or horizontally, by extruding a single foam layer containing a super-absorbent resin or a multi-layered thermoplastic resin layer without using a foaming agent.
It is preferable to produce the film by stretching it 2.0 to 5.0 times during the cooling process. The purpose of stretching is to make the polyolefin layer containing the super absorbent resin into a fibrous structure and to expose the heads of the super absorbent resin particles to the surface as much as possible, and the effect is even greater than just foaming. When the super absorbent film of the present invention is formed into a film using only a foam layer, pinholes and film breakage are particularly likely to occur. Therefore, it is preferable to form the film with at least two layers of other thermoplastic resin. When trying to obtain a super-absorbent film with only a layer, it is coextruded and molded with a thermoplastic resin that does not adhere to the layer, and after molding, it is peeled off to obtain a single-layer super-absorbent film with only a foam layer. is preferred. The following layer structure can be considered for the super absorbent film of the present invention. Here, is a foamed or foamed stretched layer containing a superabsorbent resin, is a non-foamed layer that does not contain a superabsorbent resin, and is a foamed or foamed stretched layer that does not contain a high-grade aqueous resin.A, A/B , C/A/B, A/B/A, B/A/B, C/A/B/A/C, C/A/C/A/C, and the like are preferred. Alternatively, it may be formed by multilayer extrusion, or each film may be laminated, but lamination conditions must be selected so that the fibrous structure of the foam layer is not crushed during lamination. In addition, providing a foamed or foamed stretched layer that does not contain a superabsorbent resin as the outermost layer, as shown in .
The foam layer has a microporous structure in order to prevent the superabsorbent resin that swells upon water absorption from detaching from the surface as much as possible, and since it is necessary to allow water to pass through from the outside. is preferred. More preferably, it is effective to add acetylene alcohol or the like to the foamed layer or to subject it to physical treatment such as plasma surface treatment in order to improve the initial water absorption rate. In this way, the super-absorbent film of the present invention can have a wide range of layer configurations, from single layer to multi-layer. In particular, in the case of multi-layered films, the super-absorbent layer and non-water-absorbent layer can be formed by combining the following resins. A multilayer film consisting of a repeating structure can be obtained, and by water absorption, a film with a special structure consisting of a repeating structure of a water-containing layer and a non-water-containing layer can also be obtained. Furthermore, when the super-absorbent film of the present invention is applied to an impulse sealer, the sealed portion becomes an ordinary unfoamed film.
It also has the feature of disappearing water absorption. Therefore, even if the film surface of this film is divided into several zones by seals and different aqueous solutions are dropped into each zone, they will not mix with each other and each zone will absorb water and swell independently. It is also easy to add the unique property of In this way, the super-absorbent plastic film of the present invention effectively incorporates the super-absorbent resin that does not melt even when heated into the fiber structure of the thermoplastic resin.
The aim is to provide it in the form of a single-layer or multi-layer film without substantially impairing its remarkable water-absorbing ability, and to apply it to a wide range of water-related uses. The effects will be explained below using examples. Example 1 To 100 parts by weight of ionomer resin (Himilan 1707, manufactured by Mitsui Polychemical Co., Ltd.), 15 parts by weight of powdered sodium polyacrylate (manufactured by Steel Chemical Industry Co., Ltd., Aqua Keep 10SH) was added to add surface activity. 0.5 parts by weight of acetylene alcohol (Surf-inol 104, manufactured by Nissin Chemical Co., Ltd.), liquid polybutene (manufactured by Nisseki Chemical Co., Ltd.). , 1.0 parts by weight of Nisseki Polybutene LV-100), a blowing agent (manufactured by Otsuka Chemical Co., Ltd., Uniform)
AZ-L) was added in an amount of 0.8 parts by weight, and the raw materials mixed in a super mixer and a single ionomer resin (Himilan 1707, manufactured by Mitsui Polychemicals Co., Ltd.) were melt-extruded using separate extruders, and then melt-extruded using a two-layer circular die. The resin temperature was set to 200°C in order to maintain the water absorption capacity of the super absorbent resin as low as possible.
℃ or less, and a two-layer film was formed by an air-cooled inflation method at a blow-up ratio of 3.0 and a take-up ratio of 2.0. The foamed layer of the obtained film had a fine fibrous structure, and it was also visually observed that superabsorbent resin particles were scattered therein. These super-absorbent resin particles were fixed without being easily detached even when the film was rubbed by hand. The film was immersed in water for a certain period of time, taken out, lightly drained, and weighed. The water absorption rate relative to the film weight was calculated using the following formula. The results are shown in Table 1. Film water absorption rate (%) = (film weight after water absorption) - (initial film weight) / initial film weight x 100

[Table] Thus, it can be seen that the super absorbent film of the present invention has a higher water absorption capacity and a higher water absorption rate than commercially available filter paper.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a film obtained by kneading a super absorbent resin with polyolefin and extrusion molding, and FIG. 2 is a cross-sectional view of an example of the film of the present invention.

Claims (1)

[Scope of Claims] 1 A single-layer or multi-layer plastic film, at least one of which is a foamed or foam-stretched layer, and the foamed resin layer contains 1 to 50 parts by weight based on 100 parts by weight of polyolefin. super absorbent resin and 0.1~
2.0 parts by weight of a surfactant, the foamed resin layer has a fine fibrous structure, and super absorbent resin particles are scattered in the foamed resin layer. Water absorbent plastic film. 2. The super-absorbent plastic film according to claim 1, wherein the super-absorbent resin is one or more polyacrylate-based resins. 3. The super-absorbent plastic film according to claim 1, wherein the polyolefin of the foamed resin layer is an ionomer resin. 4 1 to 50 per 100 parts by weight of polyolefin
At least two types of raw materials: a foamed resin raw material whose main components are a super absorbent resin of 0.1 part by weight or more, a blowing agent of 0.1 to 2.0 parts by weight, and a surfactant of 0.1 to 2.0 parts by weight, and a polyolefin resin raw material that does not contain a blowing agent. are melt-extruded using separate extruders and extruded from a circular die into a cylindrical shape with at least two layers.During the cooling process, the foamed layer containing super absorbent resin has a fine fibrous structure. 1. A method for producing a super-absorbent plastic film, which comprises stretching the film by at least twice as much in at least one direction.